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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. 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. 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. 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.

Soil properties play key roles in ecosystem recovery at the landscape scale and are regulated by a complex interplay between abiotic and biotic factors. Our study aimed to identify the potential drivers of post-fire changes in mineral soil in the larch forest of southeastern Siberia. We established a 28-year fire chronosequence with 80 sites over a small region of the Greater Khingan Range. At each site, we measured topographic factors, arboreal variables, and ten physical and chemical attributes of surface mineral soils. We used the hierarchical clustering analysis, distance-based redundancy analysis, variation partitioning analysis, Random Forest analysis, and structural equation modeling to disentangle the drivers for the coupled and decoupled patterns in soil properties. The results showed that time since fire is an ecological predictor that cannot be completely discarded for the soil property prediction model. Wildfires altered the effects of topography and arbors on soil properties. Compared with the unburned area, the soil properties of the burned area were associated more with explanatory variables. Here, altitude was a powerful topographic factor that positively correlated with soil properties, whereas slope position, gradient, and aspect had more negative and less positive effects on soil fertility and exhibited similar patterns, of which slope position and gradient exerted stronger influences than aspect. The importance ranking of average tree size was not significantly changed by fires though its relationship with the soil was obviously changed. In boreal larch forest, wildfires enhance the impact of topography on soil properties while decreasing the impact of arbors on soil properties. Although the arbors are not as critical as topography to the change of soil properties in a few decades after fire, the importance of arbors tends to gradually increase over many years. Consequently, wildfires can cause an on-going shift in the importance and the relative importance of topography and arbors on soil properties in boreal larch forest.

Wood decomposition in tropical forests is strongly linked to the terrestrial carbon cycle. Our understanding of the successional changes in wood decomposition in diverse tropical forests is still limited. In this study, we tested the hypothesis that fine wood decomposition rates decline with the increasing age of successional forests due to the interspecific variation in wood density and changes in species composition. We studied fine wood decomposition in a chronosequence of tropical forests representing four successional phases in southern Mexico. Wood segments (1–7.5 cm diameter) from 30 dominant species (wood density range 0.34–0.83 g cm−3) were left on the ground for decomposition, and samples were recollected at different time intervals for three years. We used a modified negative exponential model by introducing the power parameter (p) that allowed for a time-dependent decomposition rate (k). Average k within a successional phase ranged from 0.22 to 0.39 yr−1 and declined gradually with the increase in forest age. We found a significant negative correlation between wood density and decomposition rate constants. The kspecies ranged from 0.07 to 1.11 yr−1, whereas p-parameters varied between 0.65 and 1.42. Trees such as Bursera simaruba, and Cascabela gaumeri decomposed faster, while Eugenia ibarrae, and Pouteria reticulata decomposed slower. Average fine woody debris inputs ranged from 1.2 to 3.7 Mg ha−1 yr−1 which increased with forest age. Increasing production and declining decomposition rates during succession contribute to the higher accumulation of deadwood in primary forests. The results on generalized, age- and species-specific wood decay parameters have important implications in simulating carbon dynamics of the changing tropical forests.

Bacterial communities have been identified as functional key members in soil ecology. A deep relation with these communities maintains forest coverture. Trees harbor particular bacteriomes in the rhizosphere, endosphere, or phyllosphere, different from bulk-soil representatives. Moreover, the plant microbiome appears to be specific for the plant-hosting species, varies through season, and responsive to several environmental factors. This work reports the changes in bacterial communities associated with dominant pioneer trees [Tabebuia rosea and Handroanthus chrysanthus [(Bignoniaceae)] during tropical forest recovery chronosequence in the Mayan forest in Campeche, Mexico. Massive 16S sequencing approach leads to identifying phylotypes associated with rhizosphere, bulk-soil, or recovery stage. Lotka-Volterra interactome modeling suggests the presence of putative regulatory roles of some phylotypes over the rest of the community. Our results may indicate that bacterial communities associated with pioneer trees may establish more complex regulatory networks than those found in bulk-soil. Moreover, modeled regulatory networks predicted from rhizosphere samples resulted in a higher number of nodes and interactions than those found in the analysis of bulk-soil samples.

Freeze–thaw (FT) events exert a great physiological stress on the soil microbial community and thus significantly impact soil biogeochemical processes. Studies often show ambiguous and contradicting results, because a multitude of environmental factors affect biogeochemical responses to FT. Thus, a better understanding of the factors driving and regulating microbial responses to FT events is required. Soil chronosequences allow more focused comparisons among soils with initially similar start conditions. We therefore exposed four soils with contrasting organic carbon contents and opposing soil age (i.e., years after restoration) from a postmining agricultural chronosequence to three consecutive FT events and evaluated soil biochgeoemical responses after thawing. The major microbial biomass carbon losses occurred after the first FT event, while microbial biomass N decreased more steadily with subsequent FT cycles. This led to an immediate and lasting decoupling of microbial biomass carbon:nitrogen stoichiometry. After the first FT event, basal respiration and the metabolic quotient (i.e., respiration per microbial biomass unit) were above pre-freezing values and thereafter decreased with subsequent FT cycles, demonstrating initially high dissimilatory carbon losses and less and less microbial metabolic activity with each iterative FT cycle. As a consequence, dissolved organic carbon and total dissolved nitrogen increased in soil solution after the first FT event, while a substantial part of the liberated nitrogen was likely lost through gaseous emissions. Overall, high-carbon soils were more vulnerable to microbial biomass losses than low-carbon soils. Surprisingly, soil age explained more variation in soil chemical and microbial responses than soil organic carbon content. Further studies are needed to dissect the factors associated with soil age and its influence on soil biochemical responses to FT events.

Plant–soil feedbacks (PSFs) are often involved in fundamental ecological processes such as plant succession and species coexistence. After a plant initiating PSFs dies, legacies of PSFs occurring as soil signatures that influence subsequent plants could persist for an unknown duration. Altered resource environments following plant death (especially light availability) could affect whether legacy effects manifest and persist. To evaluate PSFs and their legacies, we obtained soils from a chronosequence of Prunus serotina harvests. In a greenhouse experiment, we planted conspecific seedlings under two light levels in these soils of varying time since the influence of live Prunus serotina, and compared seed/seedling survival in soils from live trees, stumps, and surrounding forest matrix within each site and across the chronosequence. PSF legacies were measured as the difference between seedling performance in live tree and stump soils within a site. Negative PSF legacies of P. serotina were short-lived, lasting up to 0.5 years after tree removal. These effects occurred under 5% but not 30% full sun. PSFs and their legacies manifested in seed/seedling survival, but not biomass. Though restricted to low light, short-lived legacies of P. serotina PSFs could have lasting impacts on plant community dynamics during post-disturbance regeneration by disfavoring P. serotina regeneration in small tree-fall gaps.

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.

The recovery of tree species composition after disturbance depends on dispersal either from nearby forests or from surviving individuals within the disturbed area. Understanding the influence of proximity to mature forests on species composition of regenerating secondary forests can help in predicting the trajectory of recovery from anthropogenic disturbances. Using forest inventory data from a chronosequence of regenerating secondary forests in the Atlantic Forest of southern Bahia, whereby transects were arranged from the edge of mature forest 100 m into the regenerating area, we calculated community weighted means (CWMs) for traits and the natural distribution ranges of species. We used Generalized Linear Mixed Models to investigate whether site characteristics such as forest age, distance from mature forest edge, soil chemical and physical properties, and canopy openness influence traits and natural distribution of regenerating secondary forest tree species. Results show that species traits were associated with regenerating forest age while the proportion of endemic and widespread species was associated with distance from mature forest and regenerating forest age. Irrespective of distance from mature forest, regenerating secondary forests recruit species with heavy and recalcitrant seeds, but this increased with regenerating forest age. Our results contribute to understanding the effects of forest fragmentation and in restoring forests after deforestation.

Mangrove plantations exhibit a high potential for biomass carbon sequestration, however, their effects on soil organic carbon (SOC) accumulation remains unclear. We examined the dynamics of community structure and ecosystem carbon accumulation along a chronosequence of Sonneratia apetala plantations on Qi’ao Island, China. To reveal the self-thinning pattern of S. apetala plantations, 114 quadrats were randomly established in the S. apetala plantations. Four quadrats were selected for soil sampling from differently-aged (4, 9, and 15 years) S. apetala plantations, a 15-year-old S. apetala + Bruguiera gymnorrhiza plantation and a 40-year-old mature Kandelia obovate community. We found that the self-thinning process happened in these S. apetala plantations. The vegetation biomass was found to significantly increase with forest age and the 15-year-old S. apetala and 15-year-old S. apetala + Bruguiera gymnorrhiza plantations had similar total biomass as the 40-year-old K. obovate community. Notably, SOC content and stocks only showed a minor increment along the chronosequence of S. apetala plantations, and SOC stock of the 15-year-old S. apetala community was less than 60% of that of the 40-year-old K. obovate community. The 15-year-old S. apetala + B. gymnorrhiza community had a similar biomass value as the 15-year-old S. apetala community, but the former community had a significant higher SOC stock than the latter. Biomass increment and SOC accumulation are unsynchronized with mangrove plantation development, and monospecific mangrove plantations may not be able to significantly accelerate SOC sequestration in the early plantation stage. Multi-specific plantations may facilitate SOC accumulation more than monospecific plantations.

Tropical dry forests (TDFs) usually occur as mosaics at different stages of natural regeneration, along which variations in soil attributes (fertility and texture) can affect plant growth and leaf traits and, consequently, leaf herbivory. In the present study, we used a chronosequence approach to determine the variations in plant growth, leaf defense, and insect herbivory in different successional species groups, following the predictions of the resource availability hypothesis: plants at early successional stages would grow faster, have lower specific leaf mass (SLM), and suffer higher herbivore damage than late successional plants. For this purpose, we measured plant diameter and collected leaves at the end of the rainy season (April) during three consecutive years in three different successional stages (early, intermediate, and late). In total, we sampled 38 plant species, from which 31 species were exclusive to a single successional stage (10 early, 13 intermediate, and eight late species). Our results did not conform to the resource availability hypothesis, as plants growing in early successional stages had higher growth rates and SLM, and lower leaf damage by herbivores. Soil fertility and texture did not affect plant growth or SLM, but leaf damage was negatively affected by SLM. Apart from being a defensive trait, SLM is also involved in the conservation of water and nutrients and photoprotection, and its variation along successional gradients in TDFs conforms to a continuum from conservative traits in hot and dry, early successional stages, to acquisitive traits in more humid late stages. Although other plant defenses must be considered, our three-year study indicates that the resource availability hypothesis, which was formulated for wet forests, should be adapted to deciduous TDFs where water availability is the main environmental filter along succession.

Nitrogen (N) and phosphorus (P) availabilities limit plant productivity, especially in primary succession; however, our understanding of species-specific strategies regarding their allocation and coordination with other functional traits remains limited. Community-weighted mean traits were compared to decipher the ecophysiological mechanisms of forest succession in nine dominant species along 120-y successional stages across a glacier-retreating chronosequence. High foliar N and P concentrations in N2-fixing plants on a 12-year-old surface did not result in high photosynthetic capacity due to the inefficient allocation, as indicated by their low photosynthetic N- and P-use efficiencies. On a 40-year-old surface, exploitative strategies, manifested in a higher specific leaf area and greater N allocation to Rubisco, as well as quick-return energy economics, helped deciduous forests dominate. When P availability decreased on a 120-year-old surface, evergreens maintained high photosynthetic P-use efficiency, by reducing overall P concentration and its allocation to structural fraction. Efficient P allocation and a higher ratio of leaf lifespan to payback time facilitated the dominance of evergreens in low P-sites. Optimizing allocation of limiting N or P among foliar fractions and fast–slow economic strategies drive primary succession after glacier retreat. Integrating the above- and below-ground subsystems through food webs will provide further insights into ecosystem dynamics.

Soil microbial C:N:P stoichiometry and microbial maintenance respiration (i.e. metabolic quotient, qCO2) were monitored along a nutrient gradient in soils from a 52-year space-for-time chronosequence of reclaimed agricultural land after brown-coal mining. Land reclamation produced loess soils of initially low (0.2%) SOC. Consecutive agricultural land management led to a gradual recovery of SOC contents. Our data revealed sudden shifts in microbial stoichiometry and metabolic quotient with increasing SOC at a critical value of 1% SOC. As SOC increased, accrual rate of C into microbial biomass decreased, whereas microbial N increased. Simultaneously, metabolic quotient strongly decreased with increasing SOC until the same critical value of 1% SOC and remained at a constant low thereafter. The microbial fractions of the soil in samples containing

Microorganisms have a major influence on soil biogeochemical processes and vegetation establishment. However, their long-term succession patterns and short-term turnover are not well-understood in artificial forest ecosystems. The aim of the present study was to investigate the effects of stand ages and seasons on soil bacterial community in a chronosequence of Chinese Pinus massoniana plantations, in 3, 19, and 58-year-old plots. Soil physicochemical properties were measured in three stand ages between two seasons (dry-rainy). The soil bacterial community composition was determined by 16S rRNA Illumina HiSeq sequencing. The results showed that soil bacterial community diversity and structure significantly differed among three stand ages, but was not different between two seasons. The diversity of soil bacterial community increased with an increase in stand age. Proteobacteria, Acidobacteria, and Actinobacteria were the dominant phyla in the three stands. The soil bacterial community structure in all the stands was influenced by soil pH, available phosphorus content, and litter phosphorus content. With the accumulation of available phosphorus, the relative abundance of Acidobacteria decreased, while that of Proteobacteria increased. These shifts suggested that dominant microbial communities transitioned from oligotrophic to copiotrophic with increasing stand age. Extending rotation periods could increase soil bacterial diversity, and in turn help improving soil quality of P. massoniana plantations.

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.

The decomposition of coarse woody debris (CWD) affects the energy flow and nutrient cycling in forest ecosystems. Previous studies on CWD have focused on the input, decomposition, reserve dynamics, and CWD functions, but coarse woody debris decomposition is complex and the results from different regions vary considerably. It is not clear which factors affect decay rate (k), especially at different decomposition stages. In this study, a single-exponential decay model was used to analyze the characteristics of CWD decomposition in Larix gmelinii forests over the 33 years following a fire in the Greater Khingan Mountains. The results show that the decay rate of coarse woody debris was positively correlated to decay class. The average decomposition rate was 0.019, and 41 years and 176 years are needed for a 50% and 95% mass loss, respectively. CWD nutrient content, density, and water content could explain the variance in the decay rate (~ 42%) of the decay factors such as amount of leaching, degree of fragmentation, respiration of the debris, and biotransformation, and varied significantly between different decay classes. Using the space–time substitution method, this study arranged the coarse woody debris of different mortality times to form a 33 year chronosequence which revealed the decomposition process. It was concluded that the decay rate was mainly explained by structural component of the debris and its nitrogen and water contents. This paper quantifies the indicators affecting CWD decay to explain the decomposition process.

In recent decades, riparian floodplains have undergone intensive reclamation worldwide, which has potential to influence soil carbon (C) accumulation. Such influence generally varies based on reclamation duration. Therefore, a study on changes in soil C stock along the reclamation chronosequence can help reveal the impact of reclamation on terrestrial C cycling. We chose natural floodplains (as the control) and croplands reclaimed for 13, 24, and 33 years in the lower reaches of the Yellow River and determined soil organic C (SOC) and soil inorganic C (SIC) contents at different depths and the stocks in 0–100 cm profiles. The SOC and SIC stocks generally increased at average rates of 2.73 and 5.54 Mg C ha−1 yr−1, respectively, and the SIC stock was closely related with the SOC stock across the reclamation chronosequence. The SOC content increased more at 0–20 cm depth in the profile along the reclamation chronosequence, but the SIC content often had a higher rate of increase in the deep soil layers. Significantly, the contents of SOC and SIC were both positively correlated with the proportion of silt fractions. Our findings suggest that reclaimed croplands from riparian floodplain play an important role in C accumulation, highlighting the importance of soil inorganic C in C budget. Moreover, soil C accumulation relates closely to soil texture, which changes continuously along the reclamation chronosequence and often varies due to spatial heterogeneity.

Soil carbon (C), nitrogen (N) and phosphorus (P) concentrations and stoichiometries can be used to evaluate the success indicators to the effects of wetland restoration and reflect ecosystem function. Restoration of inland soda saline-alkali wetlands is widespread, however, the soil nutrition changes that follow restoration are unclear. We quantified the recovery trajectories of soil physicochemical properties, including soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) pools, for a chronosequence of three restored wetlands (7 yr, 12 yr and 21 yr) and compared these properties to those of degraded and natural wetlands in the western Songnen Plain, Northeast China. Wetland degradation lead to the loss of soil nutrients. Relative to natural wetlands, the mean reductions of in SOC, TN, and TP concentrations were 89.6%, 65.5% and 52.5%, respectively. Nutrients recovered as years passed after restoration. The SOC, TN, and TP concentrations increased by 2.36 times, 1.15 times, and 0.83 times, respectively in degraded wetlands that had been restored for 21 yr, but remained 29.2%, 17.3%, and 12.8% lower, respectively, than those in natural wetlands. The soil C:N (RCN), C:P (RCP), and N:P (RNP) ratios increased from 5.92 to 8.81, 45.36 to 79.19, and 7.67 to 8.71, respectively in the wetland that had been restored for 12 yr. These results were similar to those from the natural wetland and the wetland that had been restored for 21 yr (P > 0.05). Soil nutrients changes occurred mainly in the upper layers (≤ 30 cm), and no significant differences were found in deeper soils (> 30 cm). Based on this, we inferred that it would take at least 34 yr for SOC, TN, and TP concentrations and 12 yr for RCN, RCP, and RNP in the top soils of degraded wetlands to recover to levels of natural wetlands. Soil salinity negatively influenced SOC (r =.0.704, P < 0.01), TN (r =.0.722, P < 0.01), and TP (r =.0.882, P < 0.01) concentrations during wetland restoration, which indicates that reducing salinity is beneficial to SOC, TN, and TP recovery. Moreover, plants were an important source of soil nutrients and vegetation restoration was conducive to soil nutrient accumulation. In brief, wetland restoration increased the accumulation of soil biogenic elements, which indicated that positive ecosystem functions changes had occurred.

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.

Reclamation of abandoned mines to grassland may benefit non-target wildlife like pollinators by providing conservation habitat. Co-colonization of wildflowers and pollinators has been used to measure ecological recovery in other disturbed herbaceous habitats. Revegetated surface coal mines in eastern North America are a unique system in which to study re-establishment of plant–pollinator interactions because they are field islands isolated by forest. Using a time series of 10 grassland-reclaimed mines (aged 20 years) in Ohio, USA, we evaluate whether former mines provide habitat for bees, seek insights into species accumulation as sites mature, and examine the consequences for bee conservation and plant–pollinator interactions. In 120 h of netting over two consecutive years, we documented 7749 bees of 139 species visiting 117 wildflower species. Bee richness did not differ between young and mature sites, suggesting that diverse communities established rapidly following reclamation and persisted. Bee species assemblage, however, differed between sites 10 years post-reclamation, and was influenced by vegetation and the amount of nearby forest. Plant–bee networks on sites > 10 years old had more links per species and greater network nestedness than new reclamations, suggesting the development of a core community of interacting species that stabilize pollination services over time. Reclamation grasslands are not typically considered high-quality pollinator conservation habitat, but we found that they harbor a diverse bee fauna similar to other regional meadow habitats. Reclaimed mines remain undeveloped for many years, and can accumulate pollinator species and export bees to the surrounding landscape.

The present study aimed to assess the diversity of saprobic fungi associated with three decompositional stages of Hevea brasiliensis (Wild. ex Juss.) Mull. Arg. leaves along a chronosequence of plantations. The modified surface disinfection culture method was followed for isolation of saprobic fungi from three different phases (G1, G2 and G3) of decomposing leaves. The result revealed 51 species of fungi isolated from three plantations. There was an increasing trend of number of species along a chronosequence of plantations. Cladosporium sp. was isolated from all the phases of decomposition from all the three plantations. There is an increasing trend in diversity and a decreasing trend in dominance of fungi along a chronosequence of plantations. Overall, higher number of species and maximum diversity was recorded in G2 (Hʹ = 3.61) among the decompositional phases. The study suggests increase in diversity along a chronosequence of plantations and the similarity index suggests distinct fungal occurrence pattern in the leaf litter along a chronosequence of plantations.

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.

We examined how restoration affects the structure and function of grasslands belowground by relating changes in the morphology and architecture of root systems of dominant plants to the structure of soil food webs. We measured changes in root traits of dominant plants (Bouteloua gracilis and Pascopyrum smithii) and related them to the diversity and feeding structure of soil nematodes across a restoration chronosequence in a mixed-grass prairie in Grasslands National Park, Saskatchewan, Canada. Root architecture and morphology of dominant grasses changed with restoration, and soil food webs in recently restored prairies centred around resources provided by roots. In contrast, food webs in a native prairie centred around the decomposition of soil organic matter and plant litter. Our study demonstrates that changes in root traits following restoration can cascade through soil foodwebs, altering the function of restored prairies. Our study also highlights that the diversity and structure of soil nematodes can reflect changes in root traits of dominant plants. However, traits that generalize the whole root system may be insufficient to explain the causal relationship between root feeding nematodes and their resources.

Soils of India are generally deficient in micronutrients. The Fe, Mn, Zn, and Cu are present in different chemical fractions, and the extent to which each fraction is present is sensitive to cultivation and management practices. The inclusion of trees in major cropping systems may ameliorate micronutrient deficiencies to some extent as they increase mobilization of micronutrients in the soils. Depthwise dynamics of total, DTPA-extractable, water-soluble plus exchangeable (WSEX), specifically adsorbed (SpAd), carbonate bound (CARB), Mn-Oxide bound (MnOX), amorphous Fe-Oxides bound (AFeOX), crystalline Fe-Oxides bound (CFeOX), organically bound (OM), and residual (RES) fractions of cationic micronutrients (Fe, Mn, Zn, and Cu) were observed on the sites having poplar (Populus deltoides Bartr.)-based agroforestry system (AFS) for 10, 20, and 30 years, fodder-fodder (F-F) rotation and fallow land (FL). Total and DTPA-extractable micronutrients followed the order AFS > F-F > FL, and in chronosequence of AFS, the total content of Fe, Mn, Zn, and Cu increased by 9.8, 24.8, 50.8, and 9.2%, respectively, in 0–15 cm soil depth on the sites having AFS for 30 years over 10 years of AFS. All the micronutrients were highest in residual fraction than their other fractions in each land use system. Adoption of poplar-based AFS led to buildup of total micronutrients and their various pools in the soil. Chronosequence of AFS resulted in increase and redistribution of micronutrients from unavailable (CARB and CFeOX) to readily available (WSEX) and potentially available (OM, MnOX and AFeOX) forms in the soil.

The impact of mining activities on spider (Araneae) diversity and assemblages was studied in two abandoned mine sites in Sardinia (Italy), where mining activities started in the middle of the nineteenth century and closed down over a century later. Spider community composition was analysed in dumps, undisturbed forests and scrublands which represent the natural chronosequence following the abandonment of the mining district. The identification of spiders was performed at the lowest taxonomic level possible and differences in abundance, species richness (SR), and functional diversity (FD) were analysed. Nonmetric multidimensional scaling (NMDS) and a permutated multivariate analysis of variance (PERMANOVA) routine were conducted to evaluate the relationships of spider assemblages with land cover, and the indicator species analysis was performed to identify the typifying species. During the entire sampling period, 2312 spiders were captured, and approximately 80% of the total were identified at the species level (79 spider species belonging to 28 different families). No differences in abundance and SR were found, whereas FD, which showed the highest values in forests, significantly differed among sites. A distinct separation among assemblages and a significant effect of the land use on spider assemblages were found (PERMANOVA, R2 = 0.59, p

Tea (Camellia sinensis) is often grown under a canopy of trees forming a distinctive agroforestry system covering an estimated area of 3.94 million ha of land globally. Although, tea is a major commercial crop in many countries in tropical and sub-tropical regions, including China, India and Sri Lanka, tea agroforestry systems (TAFS) have remained little studied for their role in carbon management and climate change adaptation/mitigation actions. We, therefore, undertook a detailed study on the storage of organic carbon in above- and below-ground vegetation and soil under age chronosequence of TAFS in North East India. The specific aim of this study was to quantify variations in soil physical and chemical properties, carbon storage in shade trees and tea bushes, and ecosystem carbon stocks under the chronosequence of TAFS. This study has established significant variations in soil properties and carbon storage in different aged TAFS. One of the salient findings is the decrease in soil bulk density and increase in water holding capacity with the age of TAFS in the 0–50 cm depth. The total vegetation C stock (shade trees + tea bushes + litter biomass) increased with increase in the age of TAFS, and the increase was as high as 25% in > 20 years compared to younger (

Seagrass meadows are carbon (C) sinks and nitrogen (N)-limited ecosystems that experience degradation from climate change and anthropogenic stressors, including prop-scarring disturbances by boating vessels. To better understand the variability in C and N pools of undisturbed seagrass soils and the recovery of these pools following boat propeller scarring, we quantified organic carbon (Corg) and N pools within the top 1 m of soils in undisturbed Thalassia testudinum seagrass beds of the Lower Laguna Madre (LLM), Texas, USA—a sub-tropical, uniquely hypersaline, and heavily used recreational boating lagoon—and used a chronosequence approach to compare these undisturbed soil pools to those in different aged prop scars (1–3, 4–6, 7–9, and 10+ years). We found that undisturbed soils stored 108.41 ± 2.93 and 6.65 ± 0.26 Mg (megagram) ha−1 of Corg and N, respectively, in the top 1 m, with ~ 30% of these pools stored within the top 20 cm. Scarring impacted these shallow, organic-rich pools, exposing higher bulk density (BD) mineral soils with lower %Corg and %N. Consequently, young scars (1–3 years) had significantly lower %Corg and %N values in the top 20 cm of soil compared with undisturbed soils, but the greater BD offset these changes, leading to no differences in total Corg and N pools in the top 1 m between scarred and undisturbed soils. Scars 10+ years had similar %Corg, %N, and BD soil characteristics to undisturbed soils, producing similar Corg and N pools in both upper and lower soil horizons. These findings indicate that recovery of Corg and N pools of prop-scarred seagrass soils within T. testudinum beds of the LLM will likely recover a decade or more post-disturbance. Our findings contribute to the growing global database on seagrass C and N storage and demonstrate the rate at which seagrass meadows recover post-disturbance.

We tested the hypothesis that benthic fluxes will increase spatially in a coastal deltaic floodplain as sediment organic matter increases in response to developing hydrogeomorphic zones along a chronosequence of the active Mississippi River Delta. A continuous flow-through core system was used to incubate intact sediment cores from three hydrogeomorphic zones along a chronosequence in the emerging Wax Lake Delta (WLD). Organic matter content increased from younger to older deltaic sediments from subtidal to supratidal hydrogeomorphic zones, which were coupled with increasing benthic oxygen and nitrogen fluxes. Mean net denitrification rate in spring was 100 µmol N2–N m−2 h−1 with significantly lower rates occurring in the younger intertidal zones (T4 transect, − 22 µmol N2–N m−2 h−1) and higher rates occurring in the older supratidal zones (T2 and T1 transects, 330 and 262 µmol N2–N m−2 h−1, respectively). Mean net denitrification rate in summer was 397 µmol N2–N m−2 h−1 without significant site-to-site variability except for the supratidal-T2 site (911 µmol N2–N m−2 h−1) showing higher denitrification rate than the other sites. Based on seasonal temperature and inundation time, annual rates of benthic NO3− removal varied from − 0.5 to − 3.4 mol m−2 y−1 and N2–N production rates varied from 1.0 to 3.2 mol N m−2 y−1 across WLD. The subtidal zone had the lowest fluxes associated with lower organic matter content, but was the hydrogeomorphic zone with the largest area and longest flood duration, and therefore contributed over half of N removal in WLD. The estimated annual NO3− removal of 896 Mg N y−1 in WLD accounts for 10 to 27% of total NO3− load to WLD, most of which is converted to N2 through denitrification. As a small prograding coastal deltaic floodplain under early stages of delta development, WLD is a continuously emerging ecosystem where the capacity of N removal increases by 0.2 to 2% per year prior to riverine NO3− is export to coastal ocean. These results highlight the contribution of the coastal deltaic floodplain in an active coastal basin in processing elevated riverine NO3− at continental margins with coastal ocean. The potential loss of this ecosystem service in N removal may increase in global significance as delta areas decline as result of accelerated relative sea level rise and decreased sediment loading in major river basins around the world.

Carbon accumulation in agroecosystems is regulated to a major extent by the variability of C:N:P stoichiometry. To understand the impact of C:N:P ratios and the cycling of limiting nutrients in the leaf–litter–aggregate continuum on soil C sequestration following afforesxtation, we assessed the contribution of aggregate-associated organic carbon (OC) to bulk soil OC accumulation, and examined the C, N, and P concentrations in leaves, litter, aggregates, and their stoichiometric couplings along an afforestation chronosequence. Averaged across the entire chronosequence, bulk soil OC stocks increased at the rate of 12.3 g m−2 year−1 at the 0–0.4-m depth, and significantly correlated with macroaggregates-associated OC stocks which increased on average by 114.5% with increasing stand age at soil depth of 0.4 m. Moreover, the C:P and N:P ratios of litter decreased by 19.7–33.0% and 7.6–26.8%, respectively, with increasing stand age, and were significantly associated with aggregate-associated C:P and N:P ratios. Both C:P and N:P ratios in microaggregates and clay-plus-silt fractions were, respectively, 18.0%, 13.3%, and 23.0%, 19.7% lower than those in macroaggregates, indicating a higher P availability in fine fractions. Macroaggregate-associated C:P and N:P ratios increased by 29.5 and 26.3%, respectively, at the 0–0.4-m depth with plantation age and were linked to the increased macroaggregate-associated OC stocks. Collectively, our results suggest that C:P and N:P ratios are good indicators of P cycling in ecosystem, and that P status under the control of aggregates may be an important factor for the sustainable accumulation of OC during afforestation.

Global warming leads to deglaciations in high-elevation regions, which exposes deglaciated soils to microbial colonization. Disparity in year-to-year successional patterns of bacterial community and influencing factors in freshly deglaciated soils remain unclear.We explored the abundance of bacterial 16S rRNA gene and community succession in deglaciated soils along a 14-year chronosequence after deglaciation using qPCR and Illumina sequencing on the Tibetan Plateau. The results showed that the abundance of bacterial 16S rRNA gene gradually increased with increasing deglaciation age. Soil bacterial community succession was clustered into three deglaciation stages, which were the early (zero-year old), transitional (1–7 years old) and late (8–14 years old) stages. A significantly abrupt bacterial community succession occurred from the early to the transitional stage (P < 0.01), while a mild succession (P = 0.078) occurred from the transitional to the late stage. The bacterial community at the early and transitional stages were dominated by Proteobacteria, while the late stage was dominated by Actinobacteria. Less abundant ( < 10%) Acidobacteria, Gemmatimonadetes, Verrucomicrobia, Chloroflexi, Planctomycetes, unclassified bacteria dominantly occurred in the transition and late stage and Cyanobacteria in the early stage. Total organic carbon (24.7%), post deglaciation age (21%), pH (16.5%) and moisture (10.1%) significantly contributed (P < 0.05) to the variation of bacterial community succession. Our findings provided a new insight that short time-scale chronosequence is a good model to study yearly resolution of microbial community succession.

Coastal wetlands can sequester large amounts of organic carbon (OC), providing an additional motivation for the preservation and restoration of these ecosystems. In Tampa Bay (Florida, USA), created coastal wetlands are initially planted with Spartina spp., but nearly all sites naturally transition into mangrove forests. It was hypothesized that carbon storage in the created wetlands would increase with site age due to the accumulation of soil organic carbon and replacement of salt marsh vegetation with mangrove forests. Mature, mangrove-dominated sites had higher total organic carbon stocks (138.7 ± 13.8 Mg C ha−1) than middle-aged transitional sites (85.6 ± 25.5 Mg C ha−1) or young salt marshes (34.5 ± 7.7 Mg C ha−1). Mature sites consisted of tall trees (> 130 cm tall) and scarce salt marsh vegetation. Transitional sites contained mangrove scrubs (30–130 cm tall) and seedlings (

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

The Walker and Syers model predict that phosphorus (P) availability decreases with time leading to a final stage known as retrogression. We tested the validity of the Walker and Syers model in the Canary Islands, a soil chronosequence ranging from 300 years to 11 million years under recurrent episodes of atmospheric dust-containing P inputs. In particular, we compared our results with those from the volcanic soil chronosequences described in the Hawaii Islands and in Arizona, as they share key biological and/or geological characteristics. In three islands of the Canarian Archipelago, we selected 18 independent sites dominated by mature Pinus canariensis forests and grouped them into six age classes. For each site, soil samples were analyzed for known proxies of soil nitrogen (N), P and cations availability. We also analyzed the P. canariensis needles for N, P and cation contents. We found tendencies similar to those observed in other soil chronosequences: maximum N and P concentrations at intermediate ages and lower P concentrations in the older soils. The nutrient dynamics suggested that the older sites may indeed be approaching the retrogression stage but at lower rates than in other similar chronosequences. Differences from other chronosequences are likely due to the drier Canarian climate, the higher P deposition rates originating from the nearby Sahara Desert and the top soil horizon studied. Our results confirm the validity of the Walker and Syers model for the Canary Islands despite the influence that the high P deposition rates and the seasonally dry climate may have on soil development and P pools in P. canariensis ecosystems.

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. 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. 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. 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.

Wetland restoration had been implemented for more than two decades in Sanjiang Plain, Northeast China. To assess the restoration efficiency of wetland vegetation, we investigated plants composition of community, plant species diversity and aboveground biomass of restored sites in a chronosequence of restoration (1, 2, 3, 6, 8, 11, 15 and 25 years) in the Sanjiang Nature Reserve. As comparison, we also investigated the same factors in a cropland and a natural marsh adjacent to the restored sites. The results showed that wetland plant species can invade quickly after croplands were abandoned when there were suitable hydrology conditions. On the early stage of the restoration, weeds were main plant species in the restored sites. Wetland species appeared at the same time but differed from the dominant species from the adjacent natural marshes. Common native wetland species could dominance the community after 3-year restoration. Species richness and diversity increased on the early stage, and then decreased to the similar level of the natural marsh with the extension of restoration. Plant biomass could restore easier than the species composition and diversity. Our results indicated that plant species composition and diversity of abandoned reclaimed wetlands can restore gradually by natural succession in Sanjiang Plain. However, 25-year restoration site had similarity index of only 56% with the natural marsh, which revealed that two decades are not enough for complete restoration of vegetation.

Natural regeneration is important in the context of the strategies to recover native vegetation in Brazil and of the international commitments of forest restoration undertaken by the country. However, trajectories of recovery can be highly variable and context-dependent, demanding studies to foster the use of secondary forests in restoration. Here, we describe the natural recovery of plant diversity in a chronosequence (5–21 years old) and how it is influenced by age of the regenerating forests. For this, we sampled the floristic composition and structure in 20 fragments of secondary forest in Southeast Para in 2014 and 2015. Transects of either 10 × 250 m or 20 × 125 m (0.25 ha) were delimited in each forest fragment, and subdivided into 25 subplots of 10 × 10 m, where plants of the upper stratum (DBH ≥ 10 cm) were sampled. The lower stratum (DBH

Silicon (Si) in plants confers a number of benefits, including resistance to herbivores and water or nutrient stress. However, the dynamics of Si during long-term ecosystem development remain poorly documented, especially the changes in soils in terms of plant availability. We studied a 2-million-year soil chronosequence to examine how long-term changes in soil properties influence soil Si pools. The chronosequence exhibits extreme mineralogical changes—from carbonate-rich to quartz-rich soils—where a carbonate weathering domain is succeeded by a silicate weathering domain. Plant-available Si concentrations were lowest in young soils (Holocene

While the effects of destocking on soil nutrient and plant productivity are known, the effect on functional groups of fungi has received less attention. The objective of this study was to evaluate the effect of long-term destocking on fungal functional guilds and their association with plants and soil. We characterized the changes in five fungal functional guilds, including plant pathogens, animal pathogens, wood saprotrophs, dung saprotrophs, and arbuscular mycorrhizal fungi (AMF), along a 35-year chronosequence following destocking at 0–60 cm soil depths on the Chinese Loess Plateau. Fungal community composition was assigned by comparing with the FUNGuild database. After 35 years of destocking, diversities of plant pathogens, wood saprotrophs, and AMF increased, while that of animal pathogens and dung saprotrophs decreased. Destocking had a greater effect in the near-surface layers (0–10 and 10–20 cm) owing to the greater influence of plant biomass and soil nutrients. Among the above- and belowground drivers, plant pathogen diversity was largely associated with plant diversity, while animal pathogens, dung saprotrophs, and wood saprotrophs were associated with aboveground biomass, AMF were responsive to soil conditions (e.g., organic C, NO3−-N, C:N ratio, and moisture). Long-term destocking can be considered to be an important predictor of fungal functional guilds, and changes in these microorganisms were associated with cessation-induced shifts in plants and soil by grazing. Our findings provide insights into the duration of destocking necessary to benefit fungal communities, and how this varies according to soil depth.

Despite considerable efforts to restore coastal wetlands, the ecological mechanisms contributing to the success or failure of restoration are rarely assessed. Accumulation of hydrogen sulfide in sediments may accelerate rates of marsh loss in eutrophic estuaries and is likely driven by complex feedbacks between wetland plant growth and microbial redox reactions. We used a chronosequence of restored marshes in urbanized and eutrophic Jamaica Bay (New York City, USA) to assess how sediment redox conditions change among seasons and over the lifetime of restored marshes. We also compared a stable extant marsh to one that has deteriorated over the past 50 years. We collected seasonal sediment cores from each marsh, and used a motorized microprofiling system to measure the vertical distribution of oxygen and sulfide. We fit a logistic function to each profile to estimate (1) maximum concentrations, (2) rates of increase/decline, and (3) depths of maximum increase/decline. We quantified sediment density, porosity, organic content, and belowground plant biomass, and estimated differences in daily tidal inundation among sites using water-level loggers. We found that minimum oxygen and maximum sulfide concentrations occur during summer. Sulfide concentrations were highest in sites that experienced the longest daily tidal inundation, including the degraded extant marsh and the oldest restored marsh. Spatial patterns in oxygen and sulfide were related to belowground plant biomass, supporting our hypothesis that root growth increases sediment oxygen and partially alleviates sulfide stress. Our data support the growing body of evidence that belowground plant growth may enhance the resilience of marshes to sea-level rise by increasing marsh elevation and facilitating oxygen diffusion into marsh sediments.

This study aimed to determine the responses of soil bacteria and fungi to plant species diversity and plant family composition (PFC) following secondary succession on former farmland (FL). Illumina sequencing of 16S rRNA and ITS genes was used to determine soil microbial communities along a chronosequence of FL left abandoned for 0, 10, 20, 30, 40, and 50 years on the Loess Plateau. Soil properties, plant diversity, and PFC were also investigated. Fungal communities were dominated by Ascomycota and Basidiomycota. Fungal diversity and Ascomycota abundance increased with time, while Basidiomycota abundance decreased. The fungal diversity and dominant phyla were related to the increasing levels of plant species diversity and evenness with succession. Bacterial diversity first increased and then decreased as succession proceeded, peaking at 30 years. Bacterial communities transitioned from Actinobacteria to Proteobacteria dominance during the first 30 years, after which Actinobacteria was dominant. Plant family composition exerted indirect effects on the diversity and dominant phyla of bacterial communities, mainly through direct effects on soil organic carbon and total nitrogen content. Bacterial diversity and Proteobacteria abundance were higher at Leguminosae- and Gramineae-dominant succession stages, but lower in Compositae-dominant plots; Actinobacteria showed the opposite result. Plant species diversity and evenness might be the key drivers for shaping fungal communities, but bacteria are influenced more by changes in PFC and abiotic soil nutrient levels during succession.

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.

Biological soil crusts (BSCs) are widely considered critical for soil fertility in arid ecosystems. However, how microbial communities regulate the C and N cycles during BSC succession is not well understood. We utilized GeoChip 5.0 to analyze the functional potential of bacteria and fungi involved in the C and N cycles of BSCs along a 61-year revegetation chronosequence. The normalized average signal intensities of different functional genes involved in C and N metabolism in 61-year-old BSCs were significantly different from those in younger BSCs and most functional gene subcategories and the corresponding dominant functional populations were derived from bacterial rather than fungal communities. Most C degradation genes (dominated by the starch-degrading gene amyA) were derived from Actinobacteria (mainly Streptomyces) in bacteria, but Ascomycota (mainly Aspergillus) was the key population for lignin degradation (dominated by the phenol oxidase gene) during BSC succession. N cycle genes involved in denitrification (such as narG, nirK/S, and nosZ) and N fixation (nifH) were mainly derived from Unclassified Bacteria, whereas genes involved in ammonification (ureC) were mainly derived from Streptomyces. Moreover, redundancy analysis showed that soil biogeochemical properties were closely related to bacterial and fungal functional gene structures during BSC succession. These findings indicate that bacteria play a crucial role in the regulation of C and N cycles during BSC succession in arid ecosystems, while fungi perform supplementary degradation of lignin, and these communities can successfully stimulate an increase in C and N metabolism in soil during the later successional stages of BSCs.

Climate change is melting glaciers and altering watershed biogeochemistry across the globe, particularly in regions dominated by mountain glaciers, such as southeast Alaska. Glacier dominated watersheds exhibit distinct dissolved organic matter (DOM) characteristics compared to forested and vegetated watersheds. However, there is a paucity of information on how stream DOM composition changes as glaciers retreat and terrestrial ecosystem succession ensues. Importantly, it is unclear over what timescales these transformations occur. Here, we used bulk, isotopic and ultrahigh resolution molecular-level techniques to assess how streamwater DOM composition evolves in response to glacier retreat and subsequent terrestrial ecosystem succession. For this, water samples were collected from eleven streams across a chronosequence spanning a temporal gradient 0 to ~1,400 years since glacier retreat in coastal, southeast Alaska. During the first ~200 years since glacier retreat, stream DOM showed marked and consistent changes in bulk, isotopic, and molecular-level composition. In particular, there was a decreased abundance of ancient, energy-rich (e.g., elevated aliphatic contribution), low aromaticity (e.g., low SUVA 254 and AI mod ) DOM and an increased abundance of soil and vegetation derived aromatic DOM (e.g., more depleted d 13 C, elevated condensed aromatic and polyphenolic contribution) that had a modern radiocarbon age. After ~200 years of ecosystem development, DOM composition was comparable to that observed for other temperate and arctic forested watersheds without permafrost influence. These results underscore the timelines on which glacier retreat may have substantial impacts on watershed biogeochemistry and coastal ecosystems that receive DOM subsidies from these rapidly changing landscapes.

We aimed to quantify the pool size of soil microbial biomass P (Pmic) during the early stage of soil development up to 125 years after glacial retreat in the Gongga Mountains, China and relate the pool size of Pmic to the plant P (Pplant) pools in the ecosystem. We determined the pool sizes of P in soil microbes, plants and soils and the P fluxes with plant uptake and litterfall in successional ecosystems at five study sites along the 125-year Hailuogou glacial retreat chronosequence. Moreover, we estimated the flux of P cycled through microbial biomass (Pmic cycling) based on literature data. We also approached the likelihood of P competition between plants and soil microbes based on the P status of the plants, soils and soil microbes. The size of the Pmic pools (0.2–8.3 g m−2) in the organic layer and top 10 cm of the mineral soils was comparable to that of the Pplant pools (0.3–9.1 g m−2) at all study sites along the Hailuogou chronosequence. Based on the literature, the Pmic cycling at our study site (0.3–13.5 g m−2 year−1 if estimated based on temporal fluctuations of Pmic, 5.2–268 g m−2 year−1 if estimated based on the isotope dilution method) was at least one order of magnitude larger than the Pplant uptake (not detected-0.36 g m−2 year−1) and the Pplant return by litterfall (not detected-0.16 g m−2 year−1). Although Pmic became a major pool of biological P, we did not find indications of P competition between plants and soil microbes as indicated by the positive relationships between the concentrations of Pmic and plant-available P in soils and the P-rich status of plants and soil microbes. Soil microbial biomass already becomes a major P pool in the early stage of soil development. Our estimations based on the literature suggest that Pmic cycling is probably the largest P flux in the studied up to 125-year ecosystems. Plants likely did not suffer P competition with microbes, in part due to the preferential decomposition of the P-rich compounds from dead microbial biomass which led to net P mineralization.

Restoration interventions such as revegetation are globally-important to combat biodiversity declines and land degradation. However, restoration projects are generally poorly monitored because current approaches to monitoring are limited in their ability to assess important components of biodiversity, such as belowground microbial diversity. Since soil bacterial communities mediate many belowground ecosystems processes and represent substantial biodiversity in their own right, bacteria are important components to monitor during ecosystem restoration. High-throughput amplicon sequencing (DNA metabarcoding) has been put forward as a potential cost-effective, scalable and easy-to-standardise partial solution to restoration’s monitoring problem. However, its application to restoration projects has to date been limited. Here, we used DNA metabarcoding of bacterial 16S rRNA gene from soil DNA to explore community differences across a 16-year restoration chronosequence. The bacterial composition in the oldest revegetation sites was comparable to the remnant sites. Proteobacteria and Acidobacteria were significantly higher in relative sequence abundance, while Actinobacteria was significantly lower, with time since revegetation. Classes Alphaproteobacteria and Acidobacteria were indicative of remnant and the oldest revegetation sites, while Deltaproteobacteria and Rubrobacteria were characteristic of younger revegetation sites. Changes in the soil physical and chemical characteristics associated with revegetation appear to shape bacterial community structure and composition. These findings provide evidence that revegetation can have positive effects on belowground microbial communities, and help demonstrate that the soil bacterial community can be restored towards its native state by revegetation, which may be useful in restoration monitoring.

Phosphorus (P) is a limiting nutrient for plant growth in most forest ecosystems. In response to P deficiency, plants alter root exudates (organic acids, phosphatases, and protons) to increase P bioavailability in soils. However, little is known about how bioavailable P pools (soluble-P, exchangeable-P, hydrolysable-P, and ligand-P extracted by CaCl2, citric acid, enzyme mixture, and HCl solution, respectively) change with stand age, especially for plantation forests. We selected a chronosequence of second-generation Chinese fir [Cunninghamia lanceolata (Lamb.) Hook., Taxodiaceae] plantations with increasing age including 3, 8–11, 16, 20, 25, 29, and 32 years. We measured total P and four bioavailable P pools in organic (O) and mineral horizons, and rhizosphere soil, as well as root exudates in the rhizosphere, litter biomass on the forest floor, and annual P uptake. Soluble-P, exchangeable-P, and ligand-P in the O horizon increased with stand age due to litter accumulation. Exchangeable-P and ligand-P in mineral soil decreased with stand age because of the increasing annual P uptake that depleted inorganic P. Exchangeable-P and ligand-P in the rhizosphere increased with stand age because the decrease in pH and citric acid concentration led to phosphate being more strongly bound to Fe and Al oxyhydroxides. Consequently, the trees’ ability for P mobilization decreased with stand age, but the P recycling within the tree increased. Continuous mineralization of hydrolysable-P by acid phosphatase replenished inorganic P pools, especially in solution. The progressive incorporation of P in the biological cycle with increasing tree age indicates that extending rotation periods might be an appropriate measure to increase P supply.

Whether wind pollination in trees can offset the negative genetic consequences of anthropogenic forest fragmentation is not clearly established. To answer this question, we examined the demographic genetics of Quercus bambusifolia over a 70-year recovery period in highly fragmented forests in Hong Kong. We sampled 1138 individuals from 37 locations, and genetically analysed the chronosequence through the classification of tree diameters from the same populations using 13 microsatellite markers. Our study reveals that severe fragmentation caused a significant genetic bottleneck with very few remaining but genetically diverse individuals. We observed an enhanced genetic diversity during demographic recovery. We found full-sibs within populations and half-sibs across the study range. This reflects a limited seed dispersal and extensive pollen flow. Despite reduced genetic structure both among and within populations, overall a strong persisting genetic differentiation (F′(ST) = 0.240, P

Our goal was to better understand tree growth and photosynthetic responses to variations in plant available water and elucidate the role of the inverse texture effect in snow dominated montane forests. We measured tree ring carbon isotope composition and annual growth over a 31-year record for lodgepole pine (Pinus contorta Douglas ex Loudon) growing on three different-aged glacial till surfaces in Wyoming, USA. Soils of different ages developed on till surfaces from three separate glaciation events were significantly different in clay content and distribution with depth; maximum clay content at depth ranged from 19 to 20% on the two youngest till surfaces, but was as high as 36% on the oldest till surface. Ring growth was lowest at the youngest till sites, and only on these coarse-textured soils was growth positively correlated with annual maximum snow water equivalent (SWEmax). Δ13C was highest for trees at these young till sites, suggesting that hydraulic conductivity and stomatal conductance is comparatively high during growth periods on these coarse-textured soils. Taken together, we found that age of glacial till and related soil texture differences strongly influenced tree-ring growth and Δ13C response of lodgepole pine to interannual variation in precipitation and drought severity, but responses did not support an inverse texture effect in these semi-arid forest systems.

Agricultural abandonment has been taken as one of the most widely used strategies for ecological restoration. Abandoned croplands expanded worldwide since the middle of the twentieth century and will increase considerably in the future. Whether agricultural abandonment alters the abundances of soil carbon (C) and nitrogen (N) mineralization genes, and whether these functional genes are linked to alterations in C and N mineralization rates remain unknown. We took advantage of a well-established chronosequence of nature restoration sites on abandoned croplands which represent a century of vegetation succession in China’s Qinling Mountains, to determine soil C and N mineralization rates, and their relationships with vegetation succession, edaphic characteristics, soil microbial communities, and functional genes based on GeoChip 5.0. We found that soil C and N mineralization rates, microbial biomass and composition, and the number and abundances of functional genes were significantly affected by vegetation succession following agricultural abandonment. Soil C and N mineralization rates increased by sixfold and threefold, respectively, along the cropland to forest successional gradient. The NO3-N, NH4-N and soil available phosphorus (P) concentrations were important factors associated with the C and N mineralization genes. The shifts in edaphic environments (i.e., soil moisture, cation exchange capacity, and C/P ratio), vegetation-derived substrates (i.e., soil organic C and N), and soil microbial composition (i.e., Fungi/Bacteria ratio, amounts of Gram-negative bacteria, Actinomycetes, and arbuscular mycorrhizal fungi), rather than the abundances of functional genes involved in mineralization processes, controlled soil C and N mineralization rates along the long-term vegetation successional gradient. Abandoning cropland for natural succession could facilitate the recuperation of soil C and N processes and alter soil microbial composition and functional genes. The abundances of microbial functional genes are less important than previously expected in regulating soil C and N mineralization rates.

Invasion of Spartina alterniflora has been reported to modify carbon (C) cycling processes and pools of the native salt marsh ecosystems. However, it remains unclear how the invasion age and expansion direction of S. alterniflora impact the soil organic carbon (SOC) dynamics. In this study, by considering the continuous invasion of S. alterniflora into mudflat (seaward) and native species Suaeda salsa (landward) salt marshes over a period of 20 years chronosequence, we quantify their impacts on SOC dynamics along the coastal salt marshes of Yancheng National Nature Reserve of China, based on the extensive field sampling and remote sensing data. The results showed that (1) S. alterniflora invasion increased SOC concentration and density, which averaged 8.39 g C kg−1 and 0.0085 g C cm−3 seaward and 6.26 g C kg−1 and 0.0065 g C cm−3 landward, respectively; (2) soil organic carbon showed a significantly positive relationship with total nitrogen (TN), salinity, and water content and a negative relationship with pH and bulk density for S. alterniflora landward expansion. For seaward expansion, it showed a similar relationship, but there are higher correlations with soil properties except an insignificant relationship with pH; and (3) soil organic carbon and carbon accumulation rate are significantly higher in seaward than in landward. However, for landward expansion, soil organic carbon concentration keeps increasing linearly with invasion time, while for seaward expansion, it increased to a maximum in 11 years of invasion and then decreased. Our results showed that it is very important to assess the effects of invasion on SOC dynamics in salt marsh ecosystems by considering both the expansion direction and invasion age.