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The objective of this study was to evaluate carbon and (C) and nitrogen (N) of the light organic matter in labile and humic fractions of the soil in a chronosequence of clonal Eucalyptus urophylla. The study was carried out on six different sites in the South-Central region of Maranhão state, northeastern Brazil, inserted in the Cerrado biome. Soil was sampled in five clonal Eucalyptus urophylla S.T. Blake stands of different ages and one in the area with old-growth forest (OG), which represents the native vegetation area. Soil samples were collected in the 0–20, 20–40, and 40–60 cm layers to determine textural class, bulk density, C, and N in the light organic matter of labile and humic fractions. Eucalyptus plantations can have great capacity to increase stocks of soil C and N, humic, and labile fractions over the years, presenting results equal or higher than a native Cerrado forest. Thus, Eucalyptus plantations come as an effective lad use to sink C and increase soil nutrient levels. [ABSTRACT FROM AUTHOR]

Understanding the regeneration and succession of belowground communities, particularly in forests, is vital for maintaining ecosystem health. Despite its importance, there is limited knowledge regarding how fungal communities change over time during ecosystem development, especially under different forest restoration strategies. In this study, we focused on two restoration methods used in northern Japan: monoculture planting and natural regeneration. We examined the responses of the fungal community to monoculture plantations (active tree planting) and naturally regenerated (passive regeneration) forests over a 50-year chronosequence, using natural forests as a reference. Based on DNA metabarcoding, we assessed the richness of fungal Operational Taxonomic Units (OTUs) and their dissimilarity. Our findings revealed that soil fungal richness remained stable after natural regeneration but declined in monoculture plantations, from 354 to 247 OTUs. While the compositional dissimilarity of fungal assemblages between monoculture plantations and natural forests remained consistent regardless of the time since tree planting, it significantly decreased after natural regeneration, suggesting recovery to a state close to the reference level. Notably, the composition of key functional fungal groups—saprotrophic and ectomycorrhizal— has increasingly mirrored that of natural forests over time following passive natural regeneration. In summary, our study suggests that monoculture plantations may not be effective for long-term ecosystem function and service recovery because of their limited support for soil fungal diversity. These results underscore the importance of natural regeneration in forest restoration and management strategies. [ABSTRACT FROM AUTHOR]

Peatland margins are a distinct ecotone especially vulnerable to deep smouldering in the Boreal Plains because they can experience greater water table drawdown during dry periods compared to peatland middles. Margin recovery trajectories have potentially important implications for wildfire behaviour as both the rate of vegetation recovery and community composition control fuel load and flammability. We compared peatland margin and middle vegetation trajectories using a chronosequence of time-since-fire in boreal Alberta, Canada. Margins had unique post-fire indicator species, with a higher broadleaf cover and limited Sphagnum moss colonization. Middles and margins became less distinct with greater time-since-fire, where both were dominated by feathermoss as canopy closure increased. High burn severity in margins can expose the seedbank in the underlying mineral soil to favourable conditions, causing rapid accumulation of broadleaf aboveground biomass and limiting Sphagnum establishment. The rapid accumulation of aboveground biomass increases potential fuel load, while exclusion of Sphagnum increases future smouldering potential given the dense peat in the margin ecotone. However, the dominance of deciduous vegetation for several decades post fire would serve to limit wildfire compared to a conifer-dominated system, particularly post leaf-out. Thus, peatland margins could represent a positive feedback to peat carbon loss for early season fires and a negative feedback for post leaf-out fires due to the interplay between fuel load, fire seasonality, and species flammability. Characterization of margins as distinct ecotones with a separate vegetation structure and species composition from peatland middles provides critical insight about wildfire vulnerability and carbon storage in the Boreal Plains. [ABSTRACT FROM AUTHOR]

Drivers of shrub primary production and associated landscape impacts of encroachment are well known in drylands but have not been thoroughly studied in mesic and coastal habitats. The native, nitrogen-fixing shrub, Morella cerifera, has expanded into coastal grassland along the US Atlantic coast due to warming temperatures, but impacts on ecosystem function are not well known. Annual net primary production (ANPP) of Morella cerifera and key environmental drivers were measured long-term (1990 – 2007) across a chronosequence of shrub age on a mid-Atlantic barrier island. Soil and groundwater nutrients were compared with un-encroached grassland soil to evaluate impacts of vegetation on nutrient dynamics. Shrub ANPP declined with age at the same rate among all thickets, but there was variability from year to year. When climate variables were included in models, shrub age, precipitation, and freshwater table depth were consistent predictors of ANPP. Water table depth decreased over time, reducing ANPP. This may be due to rising sea-level, as well as to feedbacks with shrub age and evapotranspiration. Soil N and C increased with shrub age and were higher than adjacent grassland sites; however, there was a significant loss of N and C to groundwater. Our results demonstrate that drivers influencing the encroachment of shrubs in this coastal system (i.e., warming temperature) are not as important in predicting shrub primary production. Rather, interactions between shrub age and hydrological properties impact ANPP, contributing to coastal carbon storage. [ABSTRACT FROM AUTHOR]

Urbanization is homogenizing residential developments and soils across a wide climate gradient of the United States. Land development practices commonly install landscapes on low-quality compacted fill material. While previous research shows that soil quality beneath urban lawns improves over time, studies used golf courses to represent lawns or sampled across variable development and management styles. Limited data on sandy soil quality within residential landscapes in subtropical climate warranted investigation. To evaluate the effect of age on residential soil characteristics, two residential developments from Central and Southwest Florida were selected based on known lot ages up to 31 years. Soil samples (0 to 30 cm) were collected from landscape beds and lawns, along with lawn of common areas, to evaluate bulk density and organic matter over time. Though landscape beds typically require less management, soil characteristics were similar between lawns and landscape beds, suggesting similar processes. Bulk densities decreased by 22–34% and 9–20% within the upper (0–15 cm) and lower (15–30 cm) soil depths, respectively. Upper layer soil carbon accumulation rates ranged from 0.060 to 0.156 kg C m−2 yr−1, comparable to previous studies but did not exceed 0.021 kg C m−2 yr−1 or were not significant for greater depths. The results of this study are representative of past chronosequence studies conducted in cooler climates with fine soil texture. Sandy soil texture and warm climate do not govern carbon sequestration rates, but instead vegetation type and landscape management practices overcome these conditions. Article Highlights: Soil quality improves similarly over time within landscapes on sandy soils in separate developments.1 Bulk densities decrease within the top 30 cm while soil organic matter increases only within upper 15 cm. Results align with similar studies suggesting common drivers across broad spatial scales. [ABSTRACT FROM AUTHOR]

Silicon is an essential or beneficial element in many organisms. Silicon uptake by vegetation strongly influences terrestrial silicon dynamics; however, little is known about the changes in plant silicon cycling during secondary succession. We hypothesized that the community-weighted mean (CWM) leaf silicon concentration changes along a secondary successional gradient because of turnover of species that differ in silicon uptake. We also hypothesized that the concentration of water-soluble soil silicon should increase with silicon input to the upper soil layer by increasing leaf litterfall. This study tested these predictions using chronosequence plots with stand ages of 16–100 years of secondary succession in a cool-temperate forest in Hokkaido, Japan. We measured the levels of leaf silicon in 36 woody species, leaf litter silicon, and water-extractable soil silicon and examined their correlations with stand age. The leaf silicon concentration varied by 17-fold from 0.6 to 10.3 mg Si g−1, with strong phylogenetic signals among woody species. Reflecting the turnover of species and change in their abundance, the CWM leaf and leaf litter silicon concentrations increased with stand age. In contrast, water-extractable soil silicon concentration decreased despite an increase in leaf-litter silicon flux. The water-extractable soil silicon concentration was strongly and positively correlated with the soil carbon concentration, which decreased with stand age. Our results suggest that during secondary succession, forest silicon dynamics are largely associated with changes in the abundance of silicon-accumulating woody plants and soil carbon dynamics, which potentially influences other silicon-dependent organisms in the ecosystem. [ABSTRACT FROM AUTHOR]

Natural reforestation on abandoned arable lands is one of the characteristic processes that trigger the transformation of soil organic matter accompanied by changes in the abundance, biomass, and taxonomic structure of soil macrofauna. The assessment of the time for a potential return of soil properties and macrofauna to their natural state, dynamics of soil organic matter stocks, and the role of macrofauna in this process at different stages of postagrogenic successions is relevant in the context of predicting the changes in ecosystem components and their role in organic carbon sequestration under various land use scenarios. The stock of organic carbon, soil morphological properties, as well as the abundance, biomass, and taxonomic structure of soil macrofauna in arable lands of five stages of pine forest restoration (fallow meadows and pine forests of different ages), and primary forests in the Smolenskoye Poozerye (Smolensk Lakeland) National Park (Smolensk oblast, Russia) have been examined. The soils of 85–100-year-old pine forests retain the lower boundary of the former humus horizon; at the meadow stage, restoration signs appear, namely, a shallow humus horizon pierced with roots and later transformed into a raw-humus horizon in young forests. By the age of 80, the carbon stock in the mineral soil part restores to almost background values. The soil macrofauna composition radically changes with the substitution of meadow communities by forest ones. At the initial stages (in agrocenoses and fallow meadows), the macrofauna of organomineral soil horizons is prevalent, being represented by soil earthworms and larvae of scarab beetles. Further, the macrofauna of organic horizons is restored to contain a high share of saprophages, such as epigeic and epi-endogeic earthworms, which contribute to the differentiation of litter into subhorizons. The biomass of saprophages negatively correlates with the carbon stock in the mineral part of forest soils, its content in the litter, and litter thickness and positively correlates with the share of easily decomposable litter fraction. [ABSTRACT FROM AUTHOR]

Ecosystem C:N:P stoichiometry has implications for biogeochemical cycles and ecosystem functioning. However, variations in ecosystem stoichiometry along a forest succession chronosequence and the underlying mechanisms remain unclear. We quantified the C:N:P stoichiometry of different plant organs (leaves, branches, stems and roots), and different ecosystem components (plant community, litter and soil) at four successional stages of a mixed broadleaved–Korean pine (Pinus koraiensis) forest in northeast China. The C:N:P stoichiometry of plant organs and the plant community varied significantly along the succession chronosequence, with variation mainly driven by changes in tree size and plant diversity. The C:N:P stoichiometry in litter and soil did not change with succession. Furthermore, most allometric exponents of C-N-P scaling relationships did not differ among plant organs and ecosystem components and were equal to 1, indicating strong conservatism of the C-N-P stoichiometry scaling relationship in this ecosystem. Our findings highlight the conservative isometric allocation strategies of elements among different organs and ecosystem components during forest succession. Further, they help improve our understanding of the underlying mechanisms for variations in C:N:P stoichiometry from the plant organ level to the ecosystem level. [ABSTRACT FROM AUTHOR]

Wetlands are valuable ecosystems because they are highly productive, support a wide range of wildlife, and serve as hotspots for biogeochemical cycling. Historically, vast areas of wetlands in the United States (US) were drained and converted to agriculture. Efforts are currently underway to restore wetland and floodplain functioning across the US and elsewhere. Re-wetting historically drained and farmed soils can potentially liberate legacy phosphorus (P) to surface waters as soluble reactive P (SRP), offsetting P retained by sedimentation during floods. A better understanding of the controls on SRP release is needed to estimate net P retention in these settings. Soil P saturation ratio (PSR) and soil P storage capacity (SPSC) are two proxies for SRP runoff risk that have shown promise for characterizing restored wetlands but require further testing. In this study, we examined soils at 42 riparian sites ranging from active farms to mature wetlands in the Vermont portion of the Lake Champlain Basin (USA), where phosphorus load reduction is a critical goal to achieve in-lake water quality targets. We additionally quantified potential SRP release to overlying water using intact soil cores from 20 plots spanning 14 sites. Final SRP concentrations in intact cores spanned two orders of magnitude and were predicted well by SPSC and PSR. SRP release was greatest at more recently and frequently farmed sites. Several soil properties, including PSR and SPSC, were correlated with farming frequency and time since farming, indicating that SRP release could be mapped using existing geodata for soils, hydrology and land use. Our findings confirm that soil SRP release during flooding needs to be considered in estimates of net P balance for restored riparian wetlands in agricultural landscapes. [ABSTRACT FROM AUTHOR]

Aims: Plant community dynamics are influenced by interspecific interactions. Previous studies have shown that soil organisms play a key role in such interactions, but few studies have quantified soil fauna contributions.We investigated the effects of root lesion (RLN) and bacterial feeding (BFN) nematodes on the interaction between seedlings of nitrogen-(N)-fixing tree species of Acacia and non-fixing Banksia from early and late successional stages of a temperate forest in a pot experiment.Nematodes had consistent, albeit minor, negative effects on both N-fixers and non-fixers in the early successional stage scenario. By contrast, BFNs increased biomass production of both species in late-stage monocultures and in Banksia in mixed cultures. Moreover, RLNs negatively affected late-stage Banksia in monocultures but promoted its biomass production when grown with Acacia. Reduced 15N concentration in Banksia indicates that the switch was driven by transfer of N from Acacia facilitated by RLN.Soil nematodes thus moderate interspecific interactions differently in early and late successional stages.Methods: Plant community dynamics are influenced by interspecific interactions. Previous studies have shown that soil organisms play a key role in such interactions, but few studies have quantified soil fauna contributions.We investigated the effects of root lesion (RLN) and bacterial feeding (BFN) nematodes on the interaction between seedlings of nitrogen-(N)-fixing tree species of Acacia and non-fixing Banksia from early and late successional stages of a temperate forest in a pot experiment.Nematodes had consistent, albeit minor, negative effects on both N-fixers and non-fixers in the early successional stage scenario. By contrast, BFNs increased biomass production of both species in late-stage monocultures and in Banksia in mixed cultures. Moreover, RLNs negatively affected late-stage Banksia in monocultures but promoted its biomass production when grown with Acacia. Reduced 15N concentration in Banksia indicates that the switch was driven by transfer of N from Acacia facilitated by RLN.Soil nematodes thus moderate interspecific interactions differently in early and late successional stages.Results: Plant community dynamics are influenced by interspecific interactions. Previous studies have shown that soil organisms play a key role in such interactions, but few studies have quantified soil fauna contributions.We investigated the effects of root lesion (RLN) and bacterial feeding (BFN) nematodes on the interaction between seedlings of nitrogen-(N)-fixing tree species of Acacia and non-fixing Banksia from early and late successional stages of a temperate forest in a pot experiment.Nematodes had consistent, albeit minor, negative effects on both N-fixers and non-fixers in the early successional stage scenario. By contrast, BFNs increased biomass production of both species in late-stage monocultures and in Banksia in mixed cultures. Moreover, RLNs negatively affected late-stage Banksia in monocultures but promoted its biomass production when grown with Acacia. Reduced 15N concentration in Banksia indicates that the switch was driven by transfer of N from Acacia facilitated by RLN.Soil nematodes thus moderate interspecific interactions differently in early and late successional stages.Conclusions: Plant community dynamics are influenced by interspecific interactions. Previous studies have shown that soil organisms play a key role in such interactions, but few studies have quantified soil fauna contributions.We investigated the effects of root lesion (RLN) and bacterial feeding (BFN) nematodes on the interaction between seedlings of nitrogen-(N)-fixing tree species of Acacia and non-fixing Banksia from early and late successional stages of a temperate forest in a pot experiment.Nematodes had consistent, albeit minor, negative effects on both N-fixers and non-fixers in the early successional stage scenario. By contrast, BFNs increased biomass production of both species in late-stage monocultures and in Banksia in mixed cultures. Moreover, RLNs negatively affected late-stage Banksia in monocultures but promoted its biomass production when grown with Acacia. Reduced 15N concentration in Banksia indicates that the switch was driven by transfer of N from Acacia facilitated by RLN.Soil nematodes thus moderate interspecific interactions differently in early and late successional stages. [ABSTRACT FROM AUTHOR]

Background and aims: Natural forest succession may modify soil nitrogen (N) cycling and N gas emissions. However, little is known about how this ecological succession modulates soil N2O and N2 emissions. We focused on three typical succession chronsequences of subtropical forests: the early stage of an Alnus nepalensis forest (~ 60 years), the intermediate stage of a Populus bonatii forest (~ 100 years), and the late stage of an evergreen broad-leaved forest (> 300 years).The acetylene inhibition technique and molecular method were used to investigate the changing patterns of soil N2O and N2 emissions, as well as the key abiotic and biotic factors that regulate gas emissions.The highest rates of soil N2O and N2 emissions were observed in the early-successional stage, which were 10–21 times and 6–12 times higher than those of the intermediate and late stages, respectively. This stimulation in the early stage was mainly related to the pure stands of N-fixing trees, thus amplifying soil inorganic N pools and providing additional substrates for nitrification- and denitrification- driven N2O. Although N2O emissions under denitrifying conditions were 2–131 times higher than those under nitrifying conditions, N2 was the dominant N gas loss in subtropical forests. Changes in nirK-denitrifier abundance with forest succession were closely related to N2O emissions.Our findings suggest that variations in soil active nitrogen pools and nirK abundance associated with subtropical forest succession could reduce N2O and N2 emissions, thus resulting in positive feedbacks for climate change mitigation.Methods: Natural forest succession may modify soil nitrogen (N) cycling and N gas emissions. However, little is known about how this ecological succession modulates soil N2O and N2 emissions. We focused on three typical succession chronsequences of subtropical forests: the early stage of an Alnus nepalensis forest (~ 60 years), the intermediate stage of a Populus bonatii forest (~ 100 years), and the late stage of an evergreen broad-leaved forest (> 300 years).The acetylene inhibition technique and molecular method were used to investigate the changing patterns of soil N2O and N2 emissions, as well as the key abiotic and biotic factors that regulate gas emissions.The highest rates of soil N2O and N2 emissions were observed in the early-successional stage, which were 10–21 times and 6–12 times higher than those of the intermediate and late stages, respectively. This stimulation in the early stage was mainly related to the pure stands of N-fixing trees, thus amplifying soil inorganic N pools and providing additional substrates for nitrification- and denitrification- driven N2O. Although N2O emissions under denitrifying conditions were 2–131 times higher than those under nitrifying conditions, N2 was the dominant N gas loss in subtropical forests. Changes in nirK-denitrifier abundance with forest succession were closely related to N2O emissions.Our findings suggest that variations in soil active nitrogen pools and nirK abundance associated with subtropical forest succession could reduce N2O and N2 emissions, thus resulting in positive feedbacks for climate change mitigation.Results: Natural forest succession may modify soil nitrogen (N) cycling and N gas emissions. However, little is known about how this ecological succession modulates soil N2O and N2 emissions. We focused on three typical succession chronsequences of subtropical forests: the early stage of an Alnus nepalensis forest (~ 60 years), the intermediate stage of a Populus bonatii forest (~ 100 years), and the late stage of an evergreen broad-leaved forest (> 300 years).The acetylene inhibition technique and molecular method were used to investigate the changing patterns of soil N2O and N2 emissions, as well as the key abiotic and biotic factors that regulate gas emissions.The highest rates of soil N2O and N2 emissions were observed in the early-successional stage, which were 10–21 times and 6–12 times higher than those of the intermediate and late stages, respectively. This stimulation in the early stage was mainly related to the pure stands of N-fixing trees, thus amplifying soil inorganic N pools and providing additional substrates for nitrification- and denitrification- driven N2O. Although N2O emissions under denitrifying conditions were 2–131 times higher than those under nitrifying conditions, N2 was the dominant N gas loss in subtropical forests. Changes in nirK-denitrifier abundance with forest succession were closely related to N2O emissions.Our findings suggest that variations in soil active nitrogen pools and nirK abundance associated with subtropical forest succession could reduce N2O and N2 emissions, thus resulting in positive feedbacks for climate change mitigation.Conclusion: Natural forest succession may modify soil nitrogen (N) cycling and N gas emissions. However, little is known about how this ecological succession modulates soil N2O and N2 emissions. We focused on three typical succession chronsequences of subtropical forests: the early stage of an Alnus nepalensis forest (~ 60 years), the intermediate stage of a Populus bonatii forest (~ 100 years), and the late stage of an evergreen broad-leaved forest (> 300 years).The acetylene inhibition technique and molecular method were used to investigate the changing patterns of soil N2O and N2 emissions, as well as the key abiotic and biotic factors that regulate gas emissions.The highest rates of soil N2O and N2 emissions were observed in the early-successional stage, which were 10–21 times and 6–12 times higher than those of the intermediate and late stages, respectively. This stimulation in the early stage was mainly related to the pure stands of N-fixing trees, thus amplifying soil inorganic N pools and providing additional substrates for nitrification- and denitrification- driven N2O. Although N2O emissions under denitrifying conditions were 2–131 times higher than those under nitrifying conditions, N2 was the dominant N gas loss in subtropical forests. Changes in nirK-denitrifier abundance with forest succession were closely related to N2O emissions.Our findings suggest that variations in soil active nitrogen pools and nirK abundance associated with subtropical forest succession could reduce N2O and N2 emissions, thus resulting in positive feedbacks for climate change mitigation. [ABSTRACT FROM AUTHOR]

We studied automorphic forest-steppe Luvic and Haplic Chernozems (Siltic/Clayic, Pachic) of the southern part of the Central Russian Upland (Belgorod region), which were covered with broadleaved forest vegetation at different times (from 25 to 75 years ago). The studies were carried out on an overgrowing fallow and the adjacent maple–ash shelterbelt and on an area of growth of a natural oak forest towards the virgin meadow steppe. The line of effervescence in the soil profiles descended by 12–25 cm during 60–75 years of the growth of forest vegetation on Chernozems. The average rate of carbonate carbon leaching from a 2-m soil layer reached 5 t/ha per decade. The humus horizon thickness increased by 7–13 cm. A decrease in the organic carbon storage was observed in the soil profiles during the first 25–30 years of the development of Chernozems under forest vegetation; in the following decades, the organic carbon storage increased. The soil organic matter in the upper part of the profiles (0–40 cm) was directionally enriched with fulvic acids, while the opposite tendency of an increase in the content of humic acids was observed in the middle part of the profiles (40–80 cm). The clay mobility increased in the Chernozems under forest vegetation, which is proved by an increase in the content of silty infillings in the studied chronosequence of Chernozems under tree stands of different ages (from 25 to 60–75 years) and by the appearance of clay–humus cutans in the soils under forest vegetation. The direction and staging of changes characterize the evolutionary transformation of Chernozems over time under the impact of forest vegetation. Soil changes were caused by changes in vegetation from herbaceous (meadow-steppe) to forest and the resulting changes in the hydrothermal regimes of soil formation. The staging of soil changes could be determined by the vegetation succession changes coupled with corresponding changes in the soil regimes in microclimatic conditions. [ABSTRACT FROM AUTHOR]

Purpose: The objective of this study was to examine the pedogenetic evolution occurring in technic hard materials from an iron mine through the characterization of a chronosequence of 0-, 15-, and 40-year-old Technosols and an older natural soil. Materials and methods: Samples were taken from Technosols of different ages (0, 15, 40 years) which had developed after a layer of crushed conglomerate was placed over the top of the mine tailings, as well as from a natural soil developed on conglomerate which represented the most advanced evolutionary stage in the chronosequence. Analyses of soil micromorphological, physical, chemical, and mineralogical properties included grain size distribution; pH; electric conductivity (EC); organic matter; exchangeable bases; N-NO3; available P, Fe, Zn, Mn, Cu, and B micronutrients; and clay mineralogy (by X-ray diffraction). Results: Results showed that 15- and 40-year-old Technosols already displayed an advanced structural development and nutrient contents comparable to those in the studied natural soil. Such a rapid pedogenesis was due to the high clay content found within the conglomerates which can be easily incorporated into the soil and reordered within the soil groundmass. The tailings were characterized by a neutral pH (6.9) and a high EC (0.188 S m−1), which decreased in the upper horizons of the 15-year-old Technosols, conforming thionic horizons. Generally, similar clay mineral assemblages dominated by smectite were observed in the conglomerate, the natural soil, and the 40-year-old Technosol. Conclusion: This study confirms the possibility of rehabilitating iron mine tailings with a layer of conglomerate, which mitigates against the adverse effects of mining. Results showed that the conglomerate can easily evolve into a soil within a relatively short period. However, the conglomerate cover should be thick enough to avoid acidification of the topsoil. [ABSTRACT FROM AUTHOR]

Aims: Soil nematode community is an important component of the soil food web, which has been widely recognized as a key bio-indicator for assessing the influence of nature restoration on ecological functions. However, the dynamics of the abundance, structure of soil nematode community remain unclear under nature restoration. Methods: The soil nematode community of natural secondary forests was investigated using a chronosequence approach in subtropical forests in China. Six succession stages of nature restoration were sampled to represent forest stand age groups with 4-5, 8-12, 18-22, 25-30, 35-40 and over 100 years. To enhance our understanding of the factors influencing soil nematode communities, we also examined the relationships between plant community, soil microbial community, and soil properties by structural equation modeling. Results: Soil nematode abundance gradually increased with forest stand ages, which reached a peak value (574 individuals 100 g−1 dry soil) in the oldest stands. Soil available nitrogen and phosphorus were key factors influencing soil nematode abundance and diversity during secondary forest succession. The plant parasite index decreased with forest stand ages, which indicated that ecosystem function and health would be improved as nature restoration. The structure of soil nematode community was more sensitive to microbial community compared to plant community. The bottom-up effects of microbial communities on soil nematode communities were important drivers of nematode communities in subtropical forests. Conclusions: This study demonstrates the active responses of soil nematode community to nature restoration and highlights the importance of the above-ground and below-ground interactions to the soil food web. [ABSTRACT FROM AUTHOR]

Background: Phosphorus (P) is the limiting nutrient in many mature tropical forests. The ecological significance of declining P stocks as soils age is exacerbated by much of the remaining P being progressively sequestered. However, the details of how and where P is sequestered during the ageing in tropical forest soils remains unclear. Results: We examined the relationships between various forms of the Fe and Al sesquioxides and the Hedley fractions of P in soils of an incipient ferralitic chronosequence on an altitudinal series of gently sloping benches on Green Island, off the southeastern coast of Taiwan. These soils contain limited amounts of easily exchangeable P. Of the sesquioxide variables, only Fe and Al crystallinities increased significantly with bench altitude/soil age, indicating that the ferralisation trend is weak. The bulk of the soil P was in the NaOH and residual extractable fractions, and of low lability. The P fractions that correlated best with the sesquioxides were the organic components of the NaHCO3 and NaOH extracts. Conclusions: The amorphous sesquioxides, Feo and Alo, were the forms that correlated best with the P fractions. A substantial proportion of the labile P appears to be organic and to be associated with Alo in organic-aluminium complexes. The progression of P sequestration appears to be slightly slower than the chemical and mineralogical indicators of ferralisation. [ABSTRACT FROM AUTHOR]

Aims: The stability of hillslopes is an essential ecosystem service, especially in alpine regions with soils prone to erosion. One key variable controlling hillslope stability is soil aggregate stability. We aimed at identifying dominant controls of vegetation parameters on aggregate stability and analysed their importance for soil aggregate stability during landscape development. Methods: We quantified the aggregate stability coefficient (ASC) and measured plant cover, diversity, root mass and root length, density (RMD, RLD) along two chronosequences with contrasting bedrocks (siliceous, calcareous) in the Swiss Alps. Results: We found that ASC developed slower along the calcareous chronosequence. Furthermore, we observed a significant positive effect of vegetation cover and diversity on ASC that was mediated via root density. These relationships developed in a time-depended manner: At young terrain ages, vegetation parameters had a strong effect on aggregate stability compared to older stages. Moreover, RLD was the most powerful predictor of ASC on young terrain, whereas on older moraines RMD became more important. Conclusions: We highlight that root density plays a major role in governing ASC for soils differing in moraine ages. The changing importances of RLD and RMD for ASC development suggest different mechanistic linkages between vegetation and hillsope stability during landscape development. [ABSTRACT FROM AUTHOR]

Prairies converted from agriculture are known to accumulate carbon (C) and nitrogen (N) and are an important contribution to terrestrial C sequestration. However, estimates of decadal accumulation rates of C and N and their vertical distribution in the soil profile are highly variable among studies, in part due to the lack of repeated inventories of soil C and N stocks over long time periods. We determined the depth profile of soil C and N accumulation and bulk density following the transition from agriculture to planted prairie. Using 13 contiguous plantings with similar land-use histories, planted sequentially from 1995 to 2007, we sampled soil C, N, and bulk density three times over the course of two decades (2000, 2010, and 2019), combining a chronosequence approach with repeated inventories through time. In the top 20 cm of the profile, we found consistent accumulation of C and N, corresponding to 58% (0–10 cm) and 29% (10–20 cm) increases in soil C concentrations and 3.18% (0–10 cm) and 2.7% (10–20 cm) increases in soil N concentration over 19 years. In contrast, we found no change in C or N concentrations at 20–65 cm depth. A chronosequence approach did not detect C or N accumulation in any single sample year. Rather, initial soil C and N content appeared to be the best predictor of final concentrations. Our results suggest that the majority of C and N accumulation is occurring in the top portion of the profile and that restored prairies continue to sequester C two decades after initial planting. [ABSTRACT FROM AUTHOR]

Archeological investigations in one of the most species-rich French Mediterranean dry grasslands (La Crau, Southern France) revealed a dense network of ancient sheep corrals dating from Roman to modern times. By analyzing soil chemistry and vegetation across abandonment dates spanning two millennia, we bring to light a persisting signature of Roman, eighteenth century and modern corrals on present-day ecosystems. Community composition and species-richness reflect time after abandonment of sheep stables and are linked to long-term persistence of eutrophication from historical sheep concentrations. Our data highlight changes in vegetation that persist two millennia after human impacts ceased. Small-scale pastoral legacies from Roman times continue to have significant impacts on present-day herbaceous plant communities. Our findings point to a need for greater consideration of persisting eutrophication in dry grasslands and of the conservation value of these long-term legacies. [ABSTRACT FROM AUTHOR]

Aims: Tea plantation soils have great potential for carbon (C) sequestration because of the perennial nature of tea plants. Long-term tea plantations can lead to soil acidification. However, how the dynamics of soil organic carbon (SOC) stocks and its molecular composition respond to tea plantation establishment remains unclear.Amino sugars and lignin phenols were used as biomarkers for microbial necromass and plant lignin components to investigate the changes in their distribution to SOC across a tea plantation chronosequence (1-, 7-, 16-, 25-, and 42-year old), thus providing a holistic perspective of SOC formation and stabilization.Long-term tea plantation increased SOC content and the levels of amino sugars and lignin phenols, but reduced microbial biomass C despite an increase in dissolved organic C. Comparatively, the contribution of microbial-derived C to SOC was lower than that of plant-derived C. Despite the increased levels of amino sugars over the time-course, the proportion of bacterial-derived C in the SOC decreased, reflecting diluted contributions of bacterial residues to the SOC pool. Further, the decrease in soil pH and microbial biomass C over time resulted in shifts in the contribution of bacterial and fungal residues the pool, with an increase in the contribution of fungal residues.These findings provide new insights into changes in SOC accumulation in long-term tea plantations, highlighting an increase in soil C sequestration associated primarily by the presence of lignin phenols. This build up is affected by abiotic (physical and chemical protection) and biotic factors including increased dominance of fungal residues inputs.Methods: Tea plantation soils have great potential for carbon (C) sequestration because of the perennial nature of tea plants. Long-term tea plantations can lead to soil acidification. However, how the dynamics of soil organic carbon (SOC) stocks and its molecular composition respond to tea plantation establishment remains unclear.Amino sugars and lignin phenols were used as biomarkers for microbial necromass and plant lignin components to investigate the changes in their distribution to SOC across a tea plantation chronosequence (1-, 7-, 16-, 25-, and 42-year old), thus providing a holistic perspective of SOC formation and stabilization.Long-term tea plantation increased SOC content and the levels of amino sugars and lignin phenols, but reduced microbial biomass C despite an increase in dissolved organic C. Comparatively, the contribution of microbial-derived C to SOC was lower than that of plant-derived C. Despite the increased levels of amino sugars over the time-course, the proportion of bacterial-derived C in the SOC decreased, reflecting diluted contributions of bacterial residues to the SOC pool. Further, the decrease in soil pH and microbial biomass C over time resulted in shifts in the contribution of bacterial and fungal residues the pool, with an increase in the contribution of fungal residues.These findings provide new insights into changes in SOC accumulation in long-term tea plantations, highlighting an increase in soil C sequestration associated primarily by the presence of lignin phenols. This build up is affected by abiotic (physical and chemical protection) and biotic factors including increased dominance of fungal residues inputs.Results: Tea plantation soils have great potential for carbon (C) sequestration because of the perennial nature of tea plants. Long-term tea plantations can lead to soil acidification. However, how the dynamics of soil organic carbon (SOC) stocks and its molecular composition respond to tea plantation establishment remains unclear.Amino sugars and lignin phenols were used as biomarkers for microbial necromass and plant lignin components to investigate the changes in their distribution to SOC across a tea plantation chronosequence (1-, 7-, 16-, 25-, and 42-year old), thus providing a holistic perspective of SOC formation and stabilization.Long-term tea plantation increased SOC content and the levels of amino sugars and lignin phenols, but reduced microbial biomass C despite an increase in dissolved organic C. Comparatively, the contribution of microbial-derived C to SOC was lower than that of plant-derived C. Despite the increased levels of amino sugars over the time-course, the proportion of bacterial-derived C in the SOC decreased, reflecting diluted contributions of bacterial residues to the SOC pool. Further, the decrease in soil pH and microbial biomass C over time resulted in shifts in the contribution of bacterial and fungal residues the pool, with an increase in the contribution of fungal residues.These findings provide new insights into changes in SOC accumulation in long-term tea plantations, highlighting an increase in soil C sequestration associated primarily by the presence of lignin phenols. This build up is affected by abiotic (physical and chemical protection) and biotic factors including increased dominance of fungal residues inputs.Conclusions: Tea plantation soils have great potential for carbon (C) sequestration because of the perennial nature of tea plants. Long-term tea plantations can lead to soil acidification. However, how the dynamics of soil organic carbon (SOC) stocks and its molecular composition respond to tea plantation establishment remains unclear.Amino sugars and lignin phenols were used as biomarkers for microbial necromass and plant lignin components to investigate the changes in their distribution to SOC across a tea plantation chronosequence (1-, 7-, 16-, 25-, and 42-year old), thus providing a holistic perspective of SOC formation and stabilization.Long-term tea plantation increased SOC content and the levels of amino sugars and lignin phenols, but reduced microbial biomass C despite an increase in dissolved organic C. Comparatively, the contribution of microbial-derived C to SOC was lower than that of plant-derived C. Despite the increased levels of amino sugars over the time-course, the proportion of bacterial-derived C in the SOC decreased, reflecting diluted contributions of bacterial residues to the SOC pool. Further, the decrease in soil pH and microbial biomass C over time resulted in shifts in the contribution of bacterial and fungal residues the pool, with an increase in the contribution of fungal residues.These findings provide new insights into changes in SOC accumulation in long-term tea plantations, highlighting an increase in soil C sequestration associated primarily by the presence of lignin phenols. This build up is affected by abiotic (physical and chemical protection) and biotic factors including increased dominance of fungal residues inputs. [ABSTRACT FROM AUTHOR]

Despite worldwide efforts to restore degraded mangrove forests in the past decades, defining and tracking restoration success remains a major challenge. In this study, we used a multi-isotope approach to trace ecosystem responses to forest clearing and replanting in a tropical mangrove forest reserve at Matang, Malaysia. We measured δ2H or δD deuterium, δ13C and δ15N (HCN isotopes) in common macroinvertebrate consumers (barnacles, prawns, gastropods, and crabs) across a 70-year chronosequence of mangroves. Functional food web recovery was indicated by a decrease in δ13C and δ15N and increase in δD for gastropod and crab consumers in older forests. Timing of this shift in food web isotopic signals took place between 5 and 15 years post-clearing of mangroves. These changes in food web function paralleled changes in crab community composition, but also reflected changes in physicochemical conditions within the forest, such as increased tree cover and shading, which resulted in a shift of the food web base from microalgal-derived to mangrove-derived organic matter. Prawns and barnacles from tidal waters adjacent to the mangrove forests were estimated to derive 17 to 25% of their nutrition from mangroves, primarily from a microbial loop that was processing localised dissolved and particulate organic matter exported from mangrove marshes. The top-down mixing model approach using combined HCN isotope measurements clearly separated inputs from mangroves versus microalgae for the first time in estuarine food web studies, and tracked ecological mangrove ecosystem recovery. This combination of tracers is recommended for future studies of mangrove conservation and restoration. [ABSTRACT FROM AUTHOR]

Metacommunity theory predicts that the relative importance of regional and local processes structuring communities will change over time since initiation of community assembly. Determining effects of these processes on species and trait diversity over succession remains largely unaddressed in metacommunity ecology to date, yet could confer an improved mechanistic understanding of community assembly. To test theoretical predictions of the increasing importance of local processes in structuring communities over successional stages in metacommunities, we evaluated fish species and trait diversity in three pond metacommunities undergoing secondary succession from beaver (Castor canadensis) disturbance. Processes influencing taxonomic and trait diversity were contrasted across pond communities of different ages and in reference streams. Counter to predictions, the local environment became less important in structuring communities over succession but did exert a stronger effect on trait sorting. Beta diversity and trait richness declined over succession while there was no influence on species richness or trait dispersion. The trait filtering in older habitats was likely a response to the larger and deeper pond ecosystems characteristic of late succession. In contrast to these observed effects in ponds, the local environment primarily structured species and trait diversity in streams. Analyses of the relative importance of regional and local processes in structuring fish assemblages within each pond metacommunity suggests that habitat age and connectivity were more important than the environment in structuring communities but contributions were region and scale-dependent. Together, these findings highlight that regional and local processes can differentially influence taxonomic and trait diversity in successional metacommunity mosaics. [ABSTRACT FROM AUTHOR]

Background: The forelands of retreating glaciers are invaluable natural laboratories in which to explore the processes of primary succession. Numerous studies have been conducted on foreland chronosequences to identify temporal and spatial trends of the successional communities. This study focused on the spatio-temporal distribution of three woody plant species on the foreland of a retreating glacier in southern Iceland where historical observations provide precise age control of the moraines. To evaluate colonization and successional trends, we examined which species increase in abundance with time and tested the role of proximity to a seed source in colonization. Additionally, we quantified the rate at which biomass carbon is added to the landscape. Results: The density of stems of Betula pubescens increases with moraine age across the foreland chronosequence while the density of stems of both Salix lanata and Salix phylicifolia decreases. We found low statistical significance to the relationship between the density of B. pubescens and distance from a forested ridge nor did we find a relationship between the lengths of the stems and the moraine ages. Woody biomass increased fastest during early successional stages and reached a maximum of 28.5 g C m− 2 on the oldest moraine. Conclusions: Early colonization of moraines was controlled by environmental filters which favored both Salix species. Colonization by B. pubescens followed as environmental factors, e.g., favorable soil properties, improved. We found no conclusive evidence that proximity to a potential source of B. pubescens propagules was a significant factor in controlling colonization. The assumption that the abundance of individuals increased with time through later successional stages proved valid for B. pubescens, but not for either species of Salix. These findings are consistent with the classical spatial successional model of community homogenization. Thus, general successional processes at the landscape scale control the temporal dynamics of individual species. [ABSTRACT FROM AUTHOR]

The objectives for this study were to determine changes in soil organic carbon (SOC) components and water-stable aggregates for soil profiles from different ages of plantations of Liriodendron chinense and to clarify which organic carbon component is more closely associated with the formation and stability of soil aggregates. Three layers of soil (depths 0–20 cm, 20–40 cm, 40–60 cm) were collected from young, half-mature and mature stages of L. chinense. SOC, readily oxidizable organic carbon, chemically stable organic carbon and aggregate composition were determined. Intermediate stable organic carbon, the microbial quotient and aggregate stability (mean weight diameter) were calculated. SOC and aggregate stability in the L. chinense plantation did not increase linearly with an increase in L. chinense age; rather, they first decreased, then increased with increasing age of L. chinense. The microbial quotient had a negative effect on the level of organic carbon and the stability of aggregates, while chemically stable organic carbon had a positive effect, which explained 55.0% and 19.3% of the total variation, respectively (P < 0.01). Therefore, more attention should be paid of these two indicators in the future. [ABSTRACT FROM AUTHOR]

Understanding how microclimate and vegetation are associated during secondary succession is of primary importance for plant conservation in the face of the increasing land cover modification. However, these patterns are still unstudied for many plant communities. This study aimed to evaluate the structure (species richness, Shannon's diversity index, Simpson´s dominance index, abundance of each species, average height of species, species cover (%), species composition, and indicator values) of a low thorn forest fragment and to analyze its relation with microclimate along a successional gradient. Four stages of succession were delimited by the analysis of Landsat images, in the state of Tamaulipas, northeast Mexico. Statistical models incorporated species richness, diversity indices, abundance, height, and cover, as variables for searching differences between stages, or to evaluate microclimate associations. A total of 70 species, 54 genera, and 27 families were determined. Height of tree layer was the most important variable for discrimination of the successional stages. Conserved areas differed floristically from other stages, associated mainly with the lowest values of wind speed originated by tree layer characteristics. A significant association between species and microclimate was found, being wind speed and relative humidity the most important variables. Some species, due to their high importance values and their patterns of association with microclimate, may be considered as key taxa for low thorn forest, which is a threatened semitropical community in northeast Mexico. Conserved and late successional areas account for climatic regulation of this plant community, and the importance of these forest patches may be considered when establishing biodiversity protection areas. [ABSTRACT FROM AUTHOR]

In order to understand the management of regional vegetation, numerical classification and ordination are widely used to investigate community distribution and vegetation features. In particular, two-way indicator-species analysis programs (TWINSPAN) classifies plots and species into different groups. De-trended correspondence analysis (DCA) and canonical correspondence analysis (CCA) reflects the relationship between community and site conditions. Afforestation with Larix olgensis Herry. Plantations is a suitable restoration strategy on post-agricultural fields in the Lesser Khingan Mountains. The results of this study show how these plantations develop over time to establish a reliable pathway model by measuring and clarifying the succession process. Twenty-eight L. olgensis plantations along a 48-year chronosequence of afforestation were investigated with a quadrat sampling method. Species composition, community structure attributes of diversity, and site conditions were analyzed. Communities were classified by TWINSPAN into five successional stages: immature, juvenile, mid-aged, near-mature and mature. Classifications were validated by DCA and CCA analysis. Site conditions such as soil and litter thickness, soil organic matter, soil density, and pH were measured. Successional stages varied in community composition and species population, accompanied by time from afforestation and a gradient of site conditions. This gradient showed changes in vegetation occurrence and diversity coinciding with changes in soil conditions. The study showed that L. olgensis plantations had marked predominance in growth and were associated with improved soil fertility and the formation of a stable plant community. [ABSTRACT FROM AUTHOR]

Understanding soil responses to plant colonization is important for managing abandoned lands. We investigated the influence of species colonizing abandoned fields on soil components and properties related to C cycle and limiting nutrients (N, P) over time. A chronosequence was built of vineyards that had been abandoned over the past 50 years. Sixty-nine plots were chosen with different abandonment ages, and the soils in each plot were sampled under the influence of the dominant species in the area present in each one, obtaining a total of 132 samples. Total C and N content and available P content were determined in all these soils. Organic matter was fractionated by acid hydrolysis and three different fractions were differentiated into labile pool I and II and recalcitrant fraction. The soil properties and components with the greatest effect on the stabilization of organic matter were quantified, and the geomorphological factors that may influence these cycles were determined. The abandoned soils accumulated a large amount of C during the secondary post-abandonment succession. The various colonizing species showed differences in the accumulation of C and nutrients in the soils under their influence. Retama sphaerocarpa and Agrostis castellana accumulated more C and N than the rest of the species throughout the chronosequence. Despite the low content of inorganic colloids (clay and free Fe and Mn oxides) in the study soils, minor variations in these contents played a decisive role in stabilizing the organic matter. [ABSTRACT FROM AUTHOR]

Grazing by large herbivorous mammals is still a structuring force in tropical grassy ecosystems, and cattle grazing is one of the main economic activities carried out in these ecosystems in modern times. Therefore, understanding the impacts of cattle grazing removal on biodiversity may be a key step for conservation of this ecosystem. Here, we studied the successional trajectory of dung beetle communities in a tropical grassy ecosystem after cattle removal. For this, we assessed the patterns of dung beetle taxonomic and functional diversity of 14 natural grasslands with distinct cattle grazing removal ages (from 3 months to 22 years) along a chronosequence, applying the space-for-time substitution method. Our results show a strong decrease in dung beetle abundance (93 times) and species richness (6 times) in the first ten years of cattle removal. However, after ten years there is an increase in dung beetle abundance (73 times) and species richness (5 times). Taxonomic composition was also influenced by cattle removal time demonstrating the importance of cattle in the structuring of dung beetle communities in natural grasslands. In contrast, functional composition and diversity were not affected by cattle grazing removal, indicating these metrics are less sensitive to cattle absence than taxonomic diversity and composition. Our results provide evidence that cattle grazing removal, at least in the short term (10 years), may be an inefficient management tool for restoration and conservation of tropical grassy ecosystems. However, we highlight the need to investigate the reintroduction of cattle grazing after different removal times to provide complimentary information to livestock management able to integrate human use and conservation of tropical grassy ecosystems. [ABSTRACT FROM AUTHOR]

Purpose: Phytoliths are siliceous substances that are abundant within intercellular spaces and inside cells of numerous types of plants. During the formation of phytoliths, between 0.2 and 5.8% of organic carbon (C) can be occluded within the phytoliths. Phytolith-occluded C (PhytOC) in terrestrial ecosystems is a stable C sink and can be distributed in organic matter that is not strongly associated with soil minerals (LFOM) or that is strongly associated with mineral particles (forming organo-mineral complexes) (HFOM). We (1) investigated the impact of plantation age and soil depth on the size of the PhytOC pool and its distribution in soil physical fractions in Moso bamboo (Phyllostachys pubescens) forests; and (2) explore the relationship among phytoliths and PhytOC (and their fractions) concentrations and the soil properties. Materials and methods: We used a chronosequence approach by sampling 5-, 10-, 20-, 50-, and 100-year-old Moso bamboo stands to examine the effect of plantation age on PhytOC storage and its distribution between the LFOM and HFOM pools. Results and discussion: Our results showed that PhytOC concentration and the concentration of PhytOC in LFOM and HFOM increased with increasing stand age in the topsoil (0–30 cm) but not in the subsoil (30–100 cm). Long-term planting of Moso bamboo forests increased the soil PhytOC pool size, as well as the LFOM- and HFOM-PhytOC fractions. The LFOM- and HFOM-PhytOC concentrations were positively correlated with soil organic C concentrations. The HFOM-PhytOC concentration was positively correlated with that of water-soluble silicon. Conclusions: We conclude that the increasing bamboo plantation age will promote PhytOC storage in the bulk soil and physical fractions in subtropical China. Management practices that increase PhytOC input and decrease PhytOC output should be developed in the future to increase PhytOC storage in bamboo plantations. [ABSTRACT FROM AUTHOR]

Purpose: Purple paddy soils cover about 66% of the paddy soils in Sichuan Basin. Complex interactions made the effects of potassium fertilizer application on NH4+ adsorption more complicated and the behavior of NH4+ and K+ interaction in purple paddy soils has rarely been evaluated. We hypothesize that correct management of these soils can enhance the efficiency of ammonium and potassium fertilizers. In order to determine correct management methods, it is important to understand the interaction of main nutrient cations NH4+ and K+ and maturation hydroponics in purple paddy soils with different paddy cultivation times. Materials and methods: A purple paddy soil chronosequence with cultivation history from 0 to 300 years was studied to understand the respective effects of SOM and mineralogy on NH4+ and K+ sorption behavior by adsorption experiments using samples both before and after H2O2 oxidation. Results and discussion: The study shows that maturation hydroponics influenced NH4+ and K+ adsorption mainly through changing clay mineralogy and enhancing SOM accumulation. SOM and smectite play positive effects for NH4+ adsorption. The K+ adsorption, however, is mainly affected by the smectite changes. The adsorption percentages are obviously higher at 25–50 mg L−1 for each NH4+ solution and higher at 50–100 mg L−1 for each K+ solution. When ammonium and potassium were applied together, NH4+ and K+ adsorption are mutually weakened. In addition, the percentage of K+ adsorption increased from 49.7–57.7% for the 100 mg L−1 K+ solution to 50.9–58.5% for the 200 mg L−1 K+ solution at 200 mg L−1 of added NH4+. Conclusions: SOM enrichments could be a positive way to improve the ammonium fertilizer utilization efficiency in purple paddy soils. Potassium may be more vulnerable to loss at low K+ concentrations given that ammonium and potassium fertilizers were applied together and it should be separately applied to enhance the utilization efficiency of applied fertilizer. [ABSTRACT FROM AUTHOR]

High-severity wildfires, which can homogenize floral communities, are becoming more common relative to historic mixed-severity fire regimes in the Northern Rockies of the U.S. High-severity wildfire could negatively affect bumble bees, which are typically diet generalists, if floral species of inadequate pollen quality dominate the landscape post-burn. High-severity wildfires often require more time to return to pre-burn vegetation composition, and thus, effects of high-severity burns may persist past initial impacts. We investigated how wildfire severity (mixed- vs. high-severity) and time-since-burn affected available floral pollen quality, corbicular pollen quality, and bumble bee nutrition using percent nitrogen as a proxy for pollen quality and bumble bee nutrition. We found that community-weighted mean floral pollen nitrogen, corbicular pollen nitrogen, and bumble bee nitrogen were greater on average by 0.82%N, 0.60%N, and 1.16%N, respectively, in mixed-severity burns. This pattern of enhanced floral pollen nitrogen in mixed-severity burns was likely driven by the floral community, as community-weighted mean floral pollen percent nitrogen explained 87.4% of deviance in floral community composition. Only bee percent nitrogen varied with time-since-burn, increasing by 0.33%N per year. If these patterns persist across systems, our findings suggest that although wildfire is an essential ecosystem process, there are negative early successional impacts of high-severity wildfires on bumble bees and potentially on other pollen-dependent organisms via reductions in available pollen quality and nutrition. This work examines a previously unexplored pathway for how disturbances can influence native bee success via altering the nutritional landscape of pollen. [ABSTRACT FROM AUTHOR]

In second-growth forest the abundance and diversity of non-native plant species often differ considerably with stand age and the history of disturbance. To understand the role of agricultural history in shaping non-native forest floras, we compared successional trajectories between second-growth stands that were formerly cultivated and pastured, two historically common land uses differing in soil disturbance and vegetation structure. Successional change was inferred from a replicated chronosequence consisting of 40 second-growth stands in southeastern Ohio, USA. The non-native flora was described in terms of community composition and individual species abundance and compared across biotic and abiotic gradients. Abundance of non-native species generally declined through the chronosequence in both land-use categories but was significantly greater in formerly cultivated sites. Non-native richness in the oldest post-agricultural sites was significantly greater than in undisturbed forest, implying that the nonnative flora has not stabilized after 80 years. Species dispersing seeds by ingestion were more abundant in formerly pastured sites; clonal species were more common in cultivated stands. Thus, the non-native forest flora shows a long-lived legacy of variation between stands of different agricultural histories. The distribution of non-native species suggests colonization of established forest as well as relictual survival from the open, agricultural stage. Although non-native abundance declines with successional time, a subset of shade tolerant species should be considered a long-term component of the second-growth flora. [ABSTRACT FROM AUTHOR]

The boreal forest is a globally critical biome for carbon cycling. Its forests are shaped by wildfire events that affect ecosystem properties and climate feedbacks including greenhouse gas (GHG) emissions. Improved understanding of boreal forest floor processes is needed to predict the impacts of anticipated increases in fire frequency, severity, and extent. In this study, we examined relationships between time since last wildfire (TSF), forest floor soil properties, and GHG emissions (CO2, CH4, N2O) along a Pleurozium schreberi-dominated chronosequence in mid- to late succession located in northern Sweden. Over three growing seasons in 2012–2014, GHG flux measurements were made in situ and samples were collected for laboratory analyses. We predicted that P. schreberi-covered forest floor GHG fluxes would be related to distinct trends in the soil properties and microbial community along the wildfire chronosequence. Although we found no overall effect of TSF on GHG emissions, there was evidence that soil C/N, one of the few properties to show a trend with time, was inversely linked to ecosystem respiration. We also found that local microclimatic conditions and site-dependent properties were better predictors of GHG fluxes than TSF. This shows that site-dependent co-variables (that is, forest floor climate and plant-soil properties) need to be considered as well as TSF to predict GHG emissions as wildfires become more frequent, extensive and severe. [ABSTRACT FROM AUTHOR]

Conceptual models of nutrient retention in ecosystems suggest that mature forests receiving chronically elevated atmospheric nitrogen (N) deposition should experience increased nitrate (NO3−) losses to streams. However, at the Hubbard Brook Experimental Forest (New Hampshire, USA), recent stream NO3− concentrations have been unexpectedly low in mature watersheds. Poorly understood retention of NO3−-N in soil organic matter (SOM) may explain this discrepancy. The relative availability of C and N in SOM influences NO3−-N retention and may vary during succession due to processes of N mining and re-accumulation. To evaluate the strength of the SOM sink for NO3−-N, we applied a 15NO3− tracer to the mineral soil in eight stands spanning a forest chronosequence from about 20 years to old growth (≫ 200 years). We tracked 15N recovery in SOM fractions in the upper 10 cm of B horizon over 5 weeks. Overall, forest age did not directly control the 5-week recovery of 15N, but it had an indirect effect via its influence on SOM properties such as C/N. Old-growth forest soils had the lowest C/N, implying closer proximity to effective N saturation. Across sites, both the particulate- and mineral-associated SOM fractions rapidly incorporated 15N, but recovery in each fraction generally declined with time, reflecting the dynamic nature of SOM. These results indicate that mineral horizons can provide an important N sink through the short term in forests of all ages, but that SOM-N remains subject to active cycling and potential loss from the soil pool over the longer term. [ABSTRACT FROM AUTHOR]

Soil quality is widely regarded as an important factor in sustainable agriculture and is often assessed by evaluating the pertinent physical, chemical and biological properties of soils. The aims of this study were to (i) establish a minimum data set (MDS) of soil quality parameters capable of monitoring changes in soil condition and ecosystem functioning in smallholder cocoa production systems on tropical alfisols in southwest Nigeria; and (ii) examine the relationship between selected MDS of soil quality parameters and cocoa yield along a chronosequence of 3-, 7-, 15-, 22-, 30-, 40-, 60- and 80-year-old farm plots. To achieve these aims, five plots were identified for each plantation age group and bulk soil samples were collected at a depth of 0–20 cm. The samples were analysed for a total data set (TDS) of twenty-three separate soil quality parameters. Principal component analysis (PCA) was employed to reduce the dimensionality of the TDS to five principal components. The PCA results showed that five principal components with eigenvalues > 1 explained more than 78% of the variability in the soil properties. Within PC1–PC5, eleven (11) soil quality parameters with high loadings were identified and selected as the MDS. A stepwise multiple regression analysis of cocoa yield and MDS revealed that soil organic matter and cation exchange capacity are the key parameters influencing cocoa yield. To maintain the yield as well as long-term sustainability of smallholder cocoa farming systems, inorganic fertilizer application is needed. Considering the poor transportation system in rural areas and prohibitive costs associated with inorganic fertilizer application in cocoa plantations, it is suggested that organic materials such as cocoa pod husk should be used to improve soil health. Another proposed approach for improving the N content of cocoa soils is to inter-crop nitrogen-fixing legumes. [ABSTRACT FROM AUTHOR]

Disturbance caused by loss of vegetal cover modifies interactions between abiotic environment and species, including phytophagous insects such as leaf beetles (Chrysomelidae: Coleoptera). Furthermore, secondary succession changes both resource availability and microclimatic conditions after disturbance, thus influencing species niche requirements. However, despite this importance, effects of such modifications on phytophagous insects remain almost unknown. Therefore, in this study we compared microclimatic niche parameters of leaf beetle communities in a successional gradient of low thorn forest in northeastern Mexico. A chronosequence of four categories with different succession time was delimited (conserved areas, 31, 17 and 4 years) through the analysis of Landsat satellite images (1973, 1986, 2000, 2005 and 2015). In each category, we systematically sampled leaf beetles (using sweep nets) and recorded seven microclimatic variables monthly, during the wet season of 2016 (May–October). In total, 66 species of Chrysomelidae were found, distributed in the four successional categories. Association between communities and microclimatic variables, as well as the number of species significantly related with these changes, decreased with successional time. Relative humidity, temperature and heat index were variables mainly related to these changes, and their specific contributions changed with time. Results suggest that microclimate influences the structuration of the phytophagous insect community after disturbance, but only in areas of recent succession; thus, other factors are operating in conserved areas. Therefore, secondary vegetation areas of different recovery time constitute unique microclimate niches for leaf beetle species, and as such, these need to be accounted for when delimiting conservation areas. [ABSTRACT FROM AUTHOR]

Afforestation of savannah is suggested as an approach to help addressing climate change mitigation through increased carbon (C) storage. Previous studies in Central Cameroon evidenced farmers' ability to realize afforestation by establishing cocoa-based agroforestry systems (cAFS) on humid savannah. In this forest-savannah transition zone, we studied an 80 years chronosequence of cAFS to assess C dynamics. We selected cAFS established after forest or savannah, and we used local forest and savannah patches as controls. Aboveground carbon (AGC) was highest in the forests (118 Mg C ha−1) and lowest in the savannahs (8 Mg C ha−1). Systems established after forest (F-cAFS) revealed a mean AGC 40% lower than that of forests and did not evolve with time. The AGC of cAFS established after savannah (S-cAFS) increased with time and reached the mean AGC of F-cAFS (72 Mg C ha−1) after ca. 75 years. Soil organic carbon (SOC) concentration depended on clay content (R2 = 0.55, P < 0.001). The SOC concentration of F-cAFS did not evolve with time and revealed no difference with forest. In S-cAFS, considering a time of about 80 years after afforestation, the average annual increase in SOC concentration in the 0–15 cm layer ranged from 7.3‰ in soils with low clay content (10–15%) (R2 = 0.60, P < 0.01) to 9.5‰ in soils with higher clay content (20–25%). No significant change in SOC concentration was found for the 15–30 cm layer. Overall, S-cAFS revealed to store and maintain significant levels of C both in the aboveground biomass and in the soil. Such an afforestation thus appeared as a valuable local strategy to combine cocoa and other perennial plant productions with C storage while avoiding deforestation. [ABSTRACT FROM AUTHOR]

We conducted this study to understand the dynamics of revegetation by examining the levels of mineral nitrogen (NO3− and NH4+) in soil and the capacity of nitrogen use by the principal species growing in secondary forest in central Amazonia. For this, we measured the nitrate and ammonium content of soil, leaves and xylem sap, nitrate reductase activity of the leaves and free amino acid contents of the xylem sap in five tree species (Vismia cayennensis, Vismia japurensis, Bellucia dichotoma, Laetia procera and Goupia glabra) over a chronosequence during recovery after pasture abandonment at two seasons. Soil ammonium was higher in the dry season and nitrate higher in the wet season and increased these with pasture abandonment age. V. japurensis, B. dichotoma and G. glabra decreased foliar ammonium due to pasture abandonment in the dry season and foliar ammonium increased in L. procera in the wet season. V. japurensis and V. cayennensis showed a decrease in nitrate reductase activity, while B. dichotoma and L. procera showed an increase. Xylem nitrate decreased in L. procera and B. dichotoma in the dry and wet seasons, respectively, and ammonium increased only in V. japurensis and V. cayennensis in the wet. Xylem arginine increased in all plant species after a period of pasture abandonment (except B. dichotoma). Tree species growing in pasture abandoned areas didn't show the same pattern of use of nitrogen, and this can be important in order to understand the nitrogen metabolism of trees in the Amazon region during forest restoration. [ABSTRACT FROM AUTHOR]

Fine-scale spatial structure is an essential feature of plant populations, controlling pollination, herbivory, pathogen spread, and resource partitioning. Origins of spatial distribution are often obscure in long-established forests, but successional stands offer insight through their physical and compositional simplicity. We tested the hypothesis that spatial structure in forest herb populations arises through a nucleation process in which colonizing species transition from random to clustered distributions through clonal expansion, seed dispersal, and conformity to environmental gradients. Spatial structure was examined in a chronosequence of 40 s growth stands in southeast Ohio, USA. Herbaceous vegetation was recorded in nested plots to describe the evolution of pattern across multiple scales. Spatial distribution was described as the variance:mean ratio of stem number plot-1, and compared between age classes and functional groups. Environmental influence was assessed as the marginal R2 value of environmental models predicting stem number. Herb species responded individualistically to stand age and environmental gradients, although all were to some degree clustered across age classes. Dispersal-limited, non-clonal, and annual species were most strongly clustered, suggesting the importance of seed dispersal range and population growth rate in determining spatial structure. Spatial distribution was weakly related to environmental variables. Clustered distributions established early in succession and remained stable for at least 80 years. Pattern formation can be interpreted in terms of nucleation, as we hypothesized, but clusters form earlier than expected. The spatial structure of herb populations in deciduous forests appears to be governed by patterns established during colonization; environmental filtering appears to play a minor role. [ABSTRACT FROM AUTHOR]

Purpose: Purple paddy soils are important for food production. Their potassium (K) supply capacity affects rice yields through its effect on nutrient availability. We hypothesize that changes in soil mineralogy can influence the K supply capacity and the efficiency of K fertilizer. Designing management practices that optimize crop yield while minimizing environmental impacts is a major challenge in agriculture. For this, it is necessary to understand the evolution of, and interaction of, minerals and different chemical forms of K in the soil system.Materials and methods: Taking advantage of the long-term paddy cultivation history in China, two purple paddy soil chronosequences, one in Guang'an, Sichuan Province (P sequence) and the other in Longsheng, Guangxi Autonomous Region (PS sequence) in Southwest China, were investigated.Results and discussion: Depotassification is prevalent in both paddy soil chronosequences, which is consistent with the decrease of illite and K-feldspar in the P sequence and with the decrease of muscovite in the PS sequence. K-bearing primary minerals are the long-term stable source of non-exchangeable K (interlayer K) in both chronosequences. Illite in clay fractions acts as the main sources of non-exchangeable K in the P sequence. In contrast, clay minerals derived from muscovite are the main sources of non-exchangeable K in the PS sequence. Clay mineral authigenesis is an important process in the purple paddy soils rich in K-bearing minerals.Conclusions: The changes in mineralogy of purple paddy soils do not conform to the usual sequence found in the well-drained natural soils. Artificial submergence promotes the conversion of mineral K (lattice-bound K) to non-exchangeable K and enhances the availability of mineral K. The disintegration of K-bearing primary minerals thus controls the K supply capacity in purple paddy soils. [ABSTRACT FROM AUTHOR]

Aims: We examined how legacies of afforestation affect soil food webs using the composition, structure, and diversity of soil nematode communities along a prairie restoration chronosequence.Methods: Vegetation and soil nematode surveys were conducted across a restoration chronosequence of tree removal (2, 5, and 20 years) in a former plantation in Riding Mountain National Park, Canada, established on a Great Plains rough fescue prairie. Nematodes were extracted using sugar-gradient centrifugation, counted and assigned to feeding groups.Results: Remaining plantation and recently restored prairies were characterized by bacterial feeding nematodes whereas the oldest restored prairie and control prairie were dominated by plant-root feeders. Nematode diversity did not reach the level observed in the prairie even 20 years following the removal of trees. Nematode community diversity and structure was strongly correlated with the composition of restored plant communities. Invasion of restored prairies by exotic grasses corresponded with a strong decline in the diversity of plant-root feeders.Conclusions: Legacies of afforestation can impact prairie soils years after trees have been removed and can lead to shifts in feeding structure and a loss of diversity in the soil food web. As grasslands continue to decline globally, considering soil faunal communities may help evaluate the outcomes of ecosystem restoration and maintain their key functions. [ABSTRACT FROM AUTHOR]

Wildfire is the primary abiotic disturbance in the boreal forest, and its long-term absence can lead to large changes in ecosystem properties, including the availability and cycling of nutrients. These effects are, however, often confounded with the effects of successional changes in vegetation toward nutrient-conservative species. We studied a system of boreal forested lake islands in eastern Canada, where time since last fire ranged from 50 to 1500 years, and where the relative abundance of the most nutrient-conservative tree species, black spruce, was largely independent of time since last fire. This allowed us to disentangle the effects of time since fire and the dominant vegetation on ecosystem properties, including nutrient stocks and concentrations. Effects of time since fire independent of vegetation composition mostly involved an increase in the thickness of the organic layer and in nitrogen concentration in both soil and leaves. Domination by black spruce had strong negative effects on nutrient concentrations and was associated with a shift toward more fungi and Gram-positive bacteria in the soil microbial community. Path modeling showed that phosphorus concentration was inversely related to organic layer thickness, which was in turn related to both time since fire and black spruce abundance, while nitrogen was more directly related to time since fire and the composition of the overstory. We conclude that discriminating between the effects of vegetation and time since fire is necessary for better understanding and predicting the long-term changes that occur in forest nutrient availability and ecosystem properties. [ABSTRACT FROM AUTHOR]

Proteinaceous compounds are critical in soil organic matter (SOM) formation and persistence, but the partitioning into mineral-associated and organic forms during hundreds and thousands of years of pedogenesis are poorly understood across multiple climates and vegetation types. We investigated the partitioning of amino acids (AA) into mineral-bound (MB) and non-mineral associated organic (NMO) soil fractions to discern whether consistent patterns during ecosystem development were observed across two different climates (cool temperate continental, USA; and moist oceanic forests, New Zealand). Although each ecosystem retained unique soil AA signatures, consistent patterns in both systems were observed with three main findings. (1) Regardless of differences in climate and vegetation between the two ecosystems, AA consistently partitioned in similar ways into MB and NMO soil fractions. For example, Thr, Ser, and Asx were relatively more dominant in the NMO fraction while Arg, Lys, Cys, and Met were relatively more dominant in the MB soil fraction. (2) AA change, showed similar trends related to chemical groupings of positively-charged, polar aromatic, sulfur containing, and non-polar AAs across both ecosystems consistent with changing patterns of soil Fe and Al bearing minerals, such as an increasing weathering index (WI; Fe dithionite/total Fe) and losses of Fe and Al from surface soils during ecosystem development. (3) The pedogenic patterns of AA change, in each system paralleled biological transitions in bacterial communities, suggesting a linkage between the AA sources and the soil sink that contributes to soil organic N. This latter point contrasts with the potential for complete change in soil AA composition that could occur upon processing and binding in soil. Overall, the consistency in the types of AAs that partition into either MB or NMO soil fractions across locations provide evidence of similar processes that contribute to soil organic N accrual across soils. Some AA also appeared to be retained in soil by electrostatic forces, and AA-organic matter interactions, that need further study. Mineral-metal complexation of AAs with sulfur side chain groups, and non-polar interactions, respectively, provide examples of these potential mechanisms for study. The results not only support mechanisms of soil proteinacous organic matter chemistry being driven by the interactions with the soil matrix, acting as a "sink", but also draw attention to the sources of organic matter (microbes, plants) in determining the composition of organic N in soil during pedogenesis. [ABSTRACT FROM AUTHOR]

Canopy structure and tree species diversity, shaped by succession, disturbance, and community composition, are linked to numerous ecosystem functions, including net primary production (NPP). Understanding of how ecosystem structural metrics are interrelated and mechanistically link to NPP, however, is incomplete. We characterized leaf area index (LAI), Simpson’s index of Diversity (D′, a measure of species diversity), and canopy rugosity (Rc, a measure of canopy physical complexity) in 11 forest stands comprising two chronosequences varying in establishing disturbance, and in three late successional communities. We related LAI, D′, and Rc to wood NPP (NPPw), and examined whether absorption of photosynthetically active radiation and light use-efficiency (LUE) link NPPw with ecosystem structure. We found that recovery of LAI and D′ was delayed following more severe establishing disturbances, but that the development of Rc was strikingly conserved regardless of disturbance, converging on a common mean value in late-successional stands irrespective of differences in leaf area index and species diversity. LAI was significantly correlated with NPPw in each stage of ecosystem development, but NPPw was only correlated with Rc in early successional stages and with D′ in late successional stages. Across all stands, NPPw was coupled with LAI and Rc, (but not D′) through positive relationships with light absorption and LUE. We conclude by advocating for better integration of ecological disciplines investigating structure-function interactions, suggesting that improved understanding of such relationships will require ecologists to traverse disciplinary boundaries. [ABSTRACT FROM AUTHOR]

Urban lawn ecosystems are widespread across the United States, with fertilization rates commonly exceeding plant nitrogen (N) uptake rates. While urban soils have been shown to accumulate C and N over time, the long-term balance of N inputs and losses from lawn soils remains largely uncertain. We sampled residential lawn soils aged 7-100 years in the Salt Lake City metropolitan area as a means of inferring changes in total nitrogen (TN) content, organic carbon (OC) content, C:N ratio, and δ15N of bulk soil over time. Core-integrated (0-40 cm) TN and OC stocks increased linearly by 2.39 g N m−2 year−1 and 29.8 g OC m−2 year−1 over the 100-year chronosequence. TN and OC percent were also negatively correlated with elevation. Multiple linear regression models including housing age and elevation as covariates, explained 68 and 62% of variability in TN and OC stocks respectively. δ15N increased with housing age, soil depth, and clay content, suggesting N removal over time, especially in poorly drained soils. We quantified potential hydrologic and gaseous N losses over time by comparing observed N accumulation to different historic fertilization scenarios. Modeling and isotopic results suggest that, while soil N has accumulated over time, the majority of N added to lawns in the Salt Lake Valley over 50 years of fertilization was likely lost from surface soils via denitrification or leaching. [ABSTRACT FROM AUTHOR]

Methane production by methanogens in wetland is recognized as a significant contributor to global warming. Spartina alterniflora (S. alterniflora), which is an invasion plant in China’s wetland, was reported to have enormous effects on methane production. But studies on shifts in the methanogen community in response to S. alterniflora invasion at temporal and spatial scales in the initial invasion years are rare. Sediments derived from the invasive species S. alterniflora and the native species Phragmites australis (P. australis) in pairwise sites and an invasion chronosequence patch (4 years) were analyzed to investigate the abundance and community structure of methanogens using quantitative real-time PCR (qPCR) and Denaturing gradient gel electrophoresis (DGGE) cloning of the methyl-coenzyme M reductase A (mcrA) gene. For the pairwise sites, the abundance of methanogens in S. alterniflora soils was lower than that of P. australis soils. For the chronosequence patch, the abundance and diversity of methanogens was highest in the soil subjected to two years invasion, in which we detected some rare groups including Methanocellales and Methanococcales. These results indicated a priming effect at the initial invasion stages of S. alterniflora for microorganisms in the soil, which was also supported by the diverse root exudates. The shifts of methanogen communities after S. alterniflora invasion were due to changes in pH, salinity and sulfate. The results indicate that root exudates from S. alterniflora have a priming effect on methanogens in the initial years after invasion, and the predominate methylotrophic groups (Methanosarcinales) may adapt to the availability of diverse substrates and reflects the potential for high methane production after invasion by S. alterniflora. [ABSTRACT FROM AUTHOR]

Aims: Human activities can dramatically alter natural plant communities which, after disturbance cessation, undergo secondary succession. In arid environments plant succession is quite slow, and its link to the carbon (C) cycle is not well known. We assessed changes in C balance on a semiarid plant community along a chronosequence spanning ca. 100 years after land abandonment in an arid environment in SE Spain to examine temporal changes in C following human disturbance.Methods: We selected 5 individuals of the dominant plant species along five plant community stages differing in the time since land abandonment occurred, and we used a closed-chamber infrared gas analyzer method to estimate the contribution of whole plants and bare soil to community C exchange. We estimated CO2 fluxes for each plant community stage and calculated temporal differences along the chronosequence.Results: Plant community composition and plant cover changed throughout the chronosequence. Carbon balance was related to changes in plant photosynthesis and plant and soil respiration along the chronosequence. Overall, community C exchange shifted from source to sink as plant colonization progressed. It took 65 years for the system to recover the equivalent C sink capacity of the undisturbed site.Conclusions: Recovery of arid plant communities after land abandonment may enhance long-term C sequestration and significantly contribute to C balance at the global level. [ABSTRACT FROM AUTHOR]

Background and aims: Soil development follows a predictable pattern of nutrient availability over hundreds to thousands of years, which drives changes in the composition and productivity of associated plant communities. However, our understanding of the influence of soil forming factors such as parent material on ecosystem development is constrained by the scarcity of appropriate chronosequences.Methods: We studied a chronosequence of coastal beach ridges at the mouth of the Arawhata River in Westland, New Zealand. The Arawhata chronosequence is formed of coarse gravel, so comparison with the nearby Haast chronosequence, formed of sand of the same lithological origin, presents a rare opportunity to isolate the influence of the physical nature of the parent material on ecosystem development.Results: Soils at Arawhata are Entisols with a shallow organic horizon over unconsolidated rounded coarse gravel, although old soils demonstrate features of podsolization and are morphologically similar to Spodosols. The fine earth fraction is a small proportion of the total volume, but increased in surface mineral soils from 5% to 20% over approximately 2000 years of pedogenesis. Corresponding soil phosphorus concentrations in the fine-earth fraction declined markedly, from >900 mg P kg−1 in young soils to 135 mg P kg−1 in older soils. However, on a profile basis the fine-earth fraction at Arawhata contained little phosphorus (10 g P m−2 on a 300-year-old soil) compared to the same-aged soil at Haast (253 g P m−2). Total nitrogen concentrations declined in surface mineral soil but not in the organic horizon, so nitrogen to phosphorus ratios increased with pedogenesis only in the organic horizon. Tree basal area at Arawhata was lower than on similar-aged soils at Haast, and the tree community on the youngest undisturbed ridge at Arawhata included Nothofagus menziesii, an ectomycorrhizal species that appears only on old infertile soils at Haast. Similarly, tree ferns were rare on the youngest soil at Arawhata and became more abundant along the chronosequence, yet at Haast they were most abundant on the phosphorus-rich young soils and decreased with soil age.Conclusions: Collectively, these results suggest that ecosystem development along the Arawhata chronosequence represents ‘backward succession’, because phosphorus stocks in the fine earth increase during the early stages of pedogenesis, even as mass-based concentrations decline. We conclude that the nature of the parent material plays a key role in determining the basal area and composition of tree communities during succession in the region, although further studies are required to isolate the relative importance of chemical and physical characteristics of the substrate. [ABSTRACT FROM AUTHOR]

Purpose: Numerous studies have investigated rhizosphere soil microbial communities. However, the question on how composition and diversity of rhizosphere communities shift with plant age has received far less attention. Materials and methods: We collected rhizosphere and bulk soils from replicated plots representing 1, 8, 14, 31, and 40-year-old stands of the leguminous perennial shrub Caragana liouana at a research site in Shanxi, China. The bulk soils were used to analyze physicochemical properties. The rhizosphere soils were used to analyze the diversity and structure of rhizosphere bacteria communities by using barcoded pyrosequencing of the 16S rRNA gene. Results and discussion: We found that different stages of plant development harbored unique rhizosphere bacterial communities. The α-diversity showed a significantly positive correlation with stand age suggesting that the rhizosphere bacterial community benefits from the establishment and development of C. liouana. We also found that the composition of the bacterial community was shaped primarily by stand age. The bacterial rhizosphere community composition did not change much from 8- to 31-year-old stands, but then dramatically changed at the 40-year-old stand. Further, we found a negative correlation between stand age and the abundance of Proteobacteria, while the abundances of Chloroflexi were positively correlated with age. Conclusion: Our results indicated that stand age exerted strong influences on the composition of the rhizosphere bacterial community explaining almost 30% of community variances among samples. These results shed new light on the dynamic interactions between long-lived plants and rhizosphere bacteria under field conditions. [ABSTRACT FROM AUTHOR]

Ecosystem restoration provides unique opportunities to study community dynamics under succession and can reveal how consumer communities re-assemble and respond to successional changes. Studying community dynamics from both taxonomic and functional trait perspectives also may provide more robust assessments of restoration progress or success and allow cross-system comparisons. We studied ground beetle (Coleoptera: Carabidae) communities for three years in a restored grassland chronosequence with sites from 0 to 28 years old. We measured traditional community metrics (abundance, richness, Shannon diversity) and functional trait metrics based on species' body length, wing morphology, activity time, phenology, and diet. Communities had high species richness and abundance in early successional stages, but these declined in later stages to low levels comparable to an adjacent grassland remnant. Species composition also shifted with time, converging with the remnant. Although functional richness, like species richness, declined as succession progressed, functional divergence quickly increased and was maintained over time, suggesting niche differentiation in established communities. Young sites were typified by small, macropterous, phytophagous species, while older sites contained larger species more likely to be flightless and carnivorous. Prescribed burns also affected traits, decreasing prevalence of larger species. This study demonstrates that functionally diverse consumer communities can self-assemble under restoration practices. In a relatively short amount of time both morphological and trophic level diversity are established. However, prescribed fire intended to control non-desirable plants may also shape beetle community functional composition, and restoration managers should consider if plant community benefits of fire outweigh potential declines in consumer function. [ABSTRACT FROM AUTHOR]