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Litter-derived dissolved organic matter (DOM) plays an essential role in biogeochemical cycles. In wetlands, species relative abundance and its change have great influences on input features of litter-derived DOM, including chemical characteristics per se and functional diversity of chemical characteristics. Functional diversity is an important factor controlling organic matter biodegradation, but little is known in terms of the DOM. We mixed litter leachates of four macrophytes with a constant concentration (20 mg DOC L−1) but varying dominant species and volume ratios, i.e. 15:1:1:1 (low-evenness), 5:1:1:1 (mid-evenness), and 2:1:1:1 (high-evenness), generating a gradient of chemical characteristics and functional diversity (represented by functional dispersion index FDis). Based on a 42-d incubation, we measured degradation dynamics of these DOM mixtures, and analyzed potential determinants. After 42 days of incubation, the high-evenness treatments, along with mid-evenness treatments sometimes, had most degradation, while the low-evenness treatments always had least degradation. The degradation of mixtures related significantly to not only the volume-weighted mean chemical characteristics but also FDis. Furthermore, the FDis even explained more variation of degradation. The non-additive mixing effects, synergistic effects (faster degradation than predicted) in particular, on degradation of DOM mixtures were rather common, especially in the high- and mid-evenness treatments. Remarkably, the mixing effects increased linearly with the FDis values (r2adj. = 0.426). This study highlights the critical role of functional diversity in regulating degradation of mixed litter-derived DOM. Resulting changes in chemistry and composition of litter leachates due to plant community succession may exert substantial influences on biogeochemical cycling. [ABSTRACT FROM AUTHOR]

Warming drives material cycling in terrestrial ecosystems by affecting litter decomposition, as it can alter litter yield, quality and decomposer composition and activity. The effect of warming on the decomposition of mixed litter in arid and semi-arid zones remains unknown. We investigated the mass loss and nutrient release dynamics during 450 days of decomposition of Artemisia ordosica, Leymus secalinus, and their mixture in Mu Us Desert by open-top chambers and litter bags. The results showed interspecific differences in the responses to warming, in that warming promoted mass loss and N and p release from L. secalinus and inhibited mass loss and p but promoting N release from A. ordosica. Mixing of A. ordosica and L. secalinus litter inhibited decomposition. Warming enhanced the antagonistic effects of mixed decomposition. The total mass loss of mixed litter was decreased by 9%, and the release of N and P was decreased by 4.9% and 12.6%, respectively. The antagonistic effects of mixed litter mass loss and p release under the warming treatment gradually strengthened with time, with N release changing from a synergistic to an antagonistic effect at 150 d. The non-additive effects produced by the mixed decomposition of A. ordosica and L. secalinus litter were jointly regulated by temperature and time. Future research on mixed litter decomposition should consider the interaction between temperature and time. [ABSTRACT FROM AUTHOR]

What is the effect of phyllosphere microorganisms on litter decomposition in the absence of colonization by soil microorganisms? Here, we simulated the litter standing decomposition stage in the field to study the differences in the composition and structure of the phyllosphere microbial community after the mixed decomposition of Populus × canadensis and Pinus sylvestris var. mongolica litter. After 15 months of mixed decomposition, we discovered that litters that were not in contact with soil had an antagonistic effect (the actual decomposition rate was 18.18%, which is lower than the expected decomposition rate) and the difference between the litters themselves resulted in a negative response to litter decomposition. In addition, there was no significant difference in bacterial and fungal community diversity after litter decomposition. The litter bacterial community was negatively responsive to litter properties and positively responsive to the fungal community. Importantly, we found that bacterial communities had a greater impact on litter decomposition than fungi. This study has enriched our understanding of the decomposition of litter itself and provided a theoretical basis for further exploring the "additive and non-additive effects" of litter decomposition and the mechanism of microbial drive. IMPORTANCE The study of litter decomposition mechanism plays an important role in the material circulation of the global ecosystem. However, previous studies have often looked at contact with soil as the starting point for decomposition. But actually, standing litter is very common in forest ecosystems. Therefore, we used field simulation experiments to simulate the decomposition of litters without contact with soil for 15 months, to explore the combined and non-added benefits of the decomposition of mixed litters, and to study the influence of microbial community composition on the decomposition rate while comparing the differences of microbial communities. [ABSTRACT FROM AUTHOR]

Copyright of Acta Agriculturae Zhejiangensis is the property of Acta Agriculturae Zhejiangensis Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In grassland ecosystems, the decomposition of litter serves as a vital conduit for nutrient transfer between plants and soil. The aim of this study was to depict the dynamic process of grass litter decomposition and explore its major driver. Three typical grasses [Stipa bungeana Trin (St. B), Artemisia sacrorun Ledeb (Ar. S), and Thymus mongolicus Ronniger (Th. M)] were selected for long-term litter decomposition. Experiments were conducted using three single litters, namely, St. B, Ar. S, and Th. M, and four different compositions of mixed litter: ML1 (55% St. B and 45% Th. M), ML2 (55% St. B and 45% Ar. S), ML3 (75% St. B and 25% Th. M), and ML4 (75% St. B and 25% Ar. S). The dynamic patterns of mass and microelements (Ca, Mg, Fe, Mn, Cu, and Zn) within different litter groups were analyzed. Our findings indicated that, after 1035 days of decomposition, the proportion of residual mass for the single litters was as follows: Th. M (60.6%) > St. B (47.3%) > Ar. S (44.3%), and for the mixed groups it was ML1 (48.0%) > ML3 (41.6%) > ML2 (40.9) > ML4 (38.4%). Mixed cultivation of the different litter groups accelerated the decomposition process, indicating that the mixture of litters had a synergistic effect on litter decomposition. The microelements of the litter exhibited an initial short-term increase followed by long-term decay. After 1035 days of decomposition, the microelements released from the litter were, in descending order, Mg > Ca > Fe > Cu > Mn > Zn. Compared to the separately decomposed St. B litter, mixing led to an inhibition of the release of Ca (antagonistic effect), while it promoted the release of Mg, Cu, and Zn (synergistic effect). For the single litter, the stepwise regression analysis showed that Ca was the dominant factor determining early litter decomposition. Mg, Mn, and Cu were the dominant factors regulating later litter decomposition. For the mixed litter groups, Ca, Mn, and Mg were the dominant factors closely related to early decomposition, and TN emerged as a key factor regulating the mass loss of mixtures during later decomposition. In summary, nitrogen and microelements co-drive the decomposition of typical grass litter. Our study underscores that, in the succession process of grassland, the presence of multiple co-existing species led to a faster loss of plant-derived materials (litter mass and internal elements), which was primarily modulated by species identity and uniformity. [ABSTRACT FROM AUTHOR]

Copyright of Agronomía Colombiana is the property of Universidad Nacional de Colombia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Litter decomposition is a key step in global biogeochemical cycling. In forest ecosystems, litter from different tree spec1ies often decompose together. Although species diversity is widely acknowledged to accelerate decomposition through the regulation of nutrient transfer between litter and decomposer communities, the underlying mechanism remains unclear. To explore the association between the bacterial community and mixed-litter chemical transformation, we conducted a one-year litter mixing decomposition experiment using leaf litter from four dominant tree species in Mount Tai (Eastern China), Robinia pseudoacacia, Quercus acutissima, Pinus tabulaeformis, and Pinus densiflora. Our results showed that: 1) Mass loss of leaf litter mixtures was significantly faster than that of leaf litter monocultures, except for R. pseudoacacia. Litter mixtures without R. pseudoacacia showed non-additive synergistic effects, whereas litter mixtures with R. pseudoacacia exerted additive effects; 2) Litter species in the absence of R. pseudoacacia significantly decreased the nutrient retention rates of litter mixtures compared to those of monocultures; 3) Litter mixtures with or without R. pseudoacacia showing additive and non-additive effects in monocultures had a distinct bacterial community structure; 4) Bacterial community structure was also modified by initial litter traits; carbon (C), nitrogen (N), and phosphorus (P) concentrations in monocultures; N/P and C/N ratios of mixtures with R. pseudoacacia; and the lignin/N ratio of mixtures without R. pseudoacacia. Overall, these findings indicate that tree species diversity controls decomposition and nutrient cycling, implying that an appropriate species community composition is beneficial to maintaining forest ecosystems.

In grassland ecosystems, the decomposition of litter serves as a vital conduit for nutrient transfer between plants and soil. The aim of this study was to depict the dynamic process of grass litter decomposition and explore its major driver. Three typical grasses [Stipa bungeana Trin (St. B), Artemisia sacrorun Ledeb (Ar. S), and Thymus mongolicus Ronniger (Th. M)] were selected for long-term litter decomposition. Experiments were conducted using three single litters, namely, St. B, Ar. S, and Th. M, and four different compositions of mixed litter: ML1 (55% St. B and 45% Th. M), ML2 (55% St. B and 45% Ar. S), ML3 (75% St. B and 25% Th. M), and ML4 (75% St. B and 25% Ar. S). The dynamic patterns of mass and microelements (Ca, Mg, Fe, Mn, Cu, and Zn) within different litter groups were analyzed. Our findings indicated that, after 1035 days of decomposition, the proportion of residual mass for the single litters was as follows: Th. M (60.6%) > St. B (47.3%) > Ar. S (44.3%), and for the mixed groups it was ML1 (48.0%) > ML3 (41.6%) > ML2 (40.9) > ML4 (38.4%). Mixed cultivation of the different litter groups accelerated the decomposition process, indicating that the mixture of litters had a synergistic effect on litter decomposition. The microelements of the litter exhibited an initial short-term increase followed by long-term decay. After 1035 days of decomposition, the microelements released from the litter were, in descending order, Mg > Ca > Fe > Cu > Mn > Zn. Compared to the separately decomposed St. B litter, mixing led to an inhibition of the release of Ca (antagonistic effect), while it promoted the release of Mg, Cu, and Zn (synergistic effect). For the single litter, the stepwise regression analysis showed that Ca was the dominant factor determining early litter decomposition. Mg, Mn, and Cu were the dominant factors regulating later litter decomposition. For the mixed litter groups, Ca, Mn, and Mg were the dominant factors closely related to early decomposition, and TN emerged as a key factor regulating the mass loss of mixtures during later decomposition. In summary, nitrogen and microelements co-drive the decomposition of typical grass litter. Our study underscores that, in the succession process of grassland, the presence of multiple co-existing species led to a faster loss of plant-derived materials (litter mass and internal elements), which was primarily modulated by species identity and uniformity.

The decomposition of plant litter and animal dung is the key processes of nutrient cycling and has been studied in a wide range of grassland ecosystems. However, most studies focus on the separate processes of either plant litter or animal dung decomposition, while the interactions between these two processes, which occur in grazed grassland ecosystems, are rarely studied. We conducted an experiment in a semi-arid grassland in Central Inner Mongolia, to examine the mass loss rates and chemical composition changes of two plant litter species and three herbivore dung types separately or in combination over a 2-year period. Twenty litterbag treatments were used to represent 2 treatments of plant litter only, 6 treatments of herbivore dung only at two addition levels, and 12 treatments of litter and dung combinations. We found that horse dung had the biggest mass loss rate, followed by cattle dung and sheep dung, either separately or mixed with plant litter. Dung addition promoted the mass loss, nitrogen release and fiber fraction (hemicellulose, cellulose and lignin) loss of plant litter, and the promotion was strongest for cattle dung, weakest for sheep dung, and stronger at high dung addition levels and in the early stages. However, the effect of litter addition on dung decomposition, a negative effect, was significant only when the dung proportion was low in the litter and dung mixture (that is, in the treatment of 10 g litter + 6 g dung). Furthermore, a significant positive non-additive effect of mixing litter and dung on their total mass loss was detected for the mixture at a litter:dung ratio of 10:6, the ratio in the major grazing area of the grassland. Our findings suggest that mixture of herbivore dung with plant litter, as in actual grassland ecosystems, promotes litter decomposition, and the composition of the litter and dung in mixture, though it may inhibit dung decomposition, due to the changes in chemical stoichiometry of decomposing materials and biophysical microenvironment by the mixing. It is necessary to incorporate the non-additive effect of litter and dung mixture in modeling carbon and nutrient cycling of grassland ecosystems. [ABSTRACT FROM AUTHOR]

Genetically diverse bell pepper cultivars and their 30 F1 hybrids were developed by means of diallel mating system including reciprocals. Variance analysis illustrated considerable disparity among newly developed bacterial wilt resistant hybrid lines for all the studied traits. General Combining ability (gca) effects were more pronounced than specific combining ability effects (sca). The gca effects were high with parents DPBWRC-6-1, EC-464107, EC-464115 and DPBWRC-39 for fruit yield and yield-enhancing traits. Further, reciprocal effects influenced all parameters except fruit width, TSS and lobes per fruit. Among the additive and non-additive genetic variance, the latter had a more significant influence on the inheritance of all studied characters except for fruit width and pericarp thickness. Based on sca analysis, three cross-combinations viz., DPBWRC-29×EC-464107, DPBWRC-39× DPBWRC-1 and EC-464115 × DPBWRC-29 were found to be good specific combiners for the majority of traits and can further be utilized to isolate superior segregates or released as hybrids.

Coastal wetlands are among the most carbon-rich ecosystems in the world. Litter decomposition is a major process controlling soil carbon input. Non-additive effect of litter mixture on decomposition has been observed in many terrestrial plants but rarely tested in coastal species. We selected three common mangrove species and one saltmarsh species co-occurring in subtropical coasts to test whether the non-additive effect occurs when their litters mixed together, and how the nutrients release into water are impacted consequently. A litter-bag experiment was carried out in a glasshouse with single and mixed leaf litters. Non-additive effects were observed in the litter mixtures of mangrove species Aegiceras corniculatum vs. Kandelia obovata (antagonistic) and A. corniculatum vs. Avicennia marina (synergistic), but not in the litter mixtures of A. corniculatum (mangrove species) vs. Spartina alterniflora (saltmarsh species). The strength of the non-additive effect was unrelated to the initial trait dissimilarity of litters. Instead, the decomposition rate and mass remaining of litter mixtures were strongly related to the carbon concentrations in litter mixtures. Nutrient content in waters was dependent on the decomposition rate of litter mixtures but not on the initial nutrient concentrations in litters. Despite the behind mechanisms were not yet revealed by the current study, our findings have improved the understanding of the litter decomposition of coastal species and the consequent nutrient release. [ABSTRACT FROM AUTHOR]

Background: In boreal peatlands, climate warming and associated soil drying facilitate the growth of vascular plants at the cost of moss species, resulting in an alteration of species dominance in plant communities. However, how altered dominant species and evenness affect litter mixture decomposition is still unclear in these ecosystems. Methods: We collected fresh litter from Larix gmelinii (tree), Betula fruticosa (shrub), Eriophorum vaginatum (sedge), and Sphagnum magellanicum (moss), and determined mass loss and nitrogen (N) release of four-species mixtures with varying dominant species and evenness at 10 and 20 oC during 360-day decomposition. Results: Irrespective of the incubation temperature, B. fruticosa-dominated litter mixtures had greatest mass loss and N release throughout decomposition, while S. magellanicum-dominated litter mixtures had lowest values. Moreover, mass loss and N release of B. fruticosa-dominated litter mixtures decreased with elevating evenness after 360 days of decomposition, but the opposite trends were observed for litter mixtures dominated by the other three species. Increasing incubation temperature facilitated decomposition of all litter mixtures, with the lowest magnitude for S. magellanicum-dominated mixtures. Non-additive effects, especially positive effects, on mass loss and N release were common, which played a key role in enhancing the influences of dominant species and evenness on litter mixture decomposition. Moreover, the incidence of positive non-additive effects on mass loss decreased at 20 oC as litter decomposition proceeded. Conclusions: Warming-induced increased dominance of vascular plants, especially shrubs, will amplify the warming effect on litter decomposition and N availability in boreal peatlands, thus generating positive feedback to climate warming. [ABSTRACT FROM AUTHOR]

Heatwaves under global warming have negative impacts on ecosystem primary producers. This warming effect may be synergized or antagonized by local environments such as light and nutrient availability. However, little is known about the interactive effects of warming, irradiance, and nutrients on physiology of marine macroalgae, which are dominant in coastal ecosystems. The present study examined the combined effects of warming (23 and 26 °C), irradiance (30 and 150 µmol photon m−2 s−1), and nutrients (enriched and non-enriched) on specific growth rate (SGR) and biochemical compositions of the canopy-forming marine macroalga Sargassum fusiforme. The negative effect of warming on SGR and ratio of chlorophyll (Chl) c to Chl a was antagonized by decreased irradiance. Moreover, the negative effect of temperature elevation on carbon content was antagonized by nutrient enrichment. These results suggest that the effect of warming on the growth and carbon accumulation of this species can be mitigated by decreased irradiance and nutrient enrichment. [ABSTRACT FROM AUTHOR]

Genome-wide prediction is a promising approach to boost selection gain in hybrid breeding. Our main objective was to evaluate the potential and limits of genome-wide prediction to identify superior hybrid combinations adapted to Northwest China. A total of 490 hybrids derived from crosses among 119 inbred lines from the Shaan A and Shaan B heterotic pattern were used for genome-wide prediction of ten agronomic traits. We tested eight different statistical prediction models considering additive (A) effects and in addition evaluated the impact of dominance (D) and epistasis (E) on the prediction ability. Employing five-fold cross validation, we show that the average prediction ability ranged from 0.386 to 0.794 across traits and models. Six parametric methods, i.e. ridge regression, LASSO, Elastic Net, Bayes B, Bayes C and reproducing kernel Hilbert space (RKHS) approach, displayed a very similar prediction ability for each trait and two non-parametric methods (random forest and support vector machine) had a higher prediction performance for the trait rind penetrometer resistance of the third internode above ground (RPR_TIAG). The models of A + D RKHS and A + D + E RKHS were slightly better for predicting traits with a relatively high non-additive variance. Integrating trait-specific markers into the A + D RKHS model improved the prediction ability of grain yield by 3%, from 0.528 to 0.558. Of all 6328 potential hybrids, selection of the top 44 hybrids would lead to a 6% increase in grain yield compared with Zhengdan 958, a commercially successful hybrid variety. In conclusion, our results substantiate the value of genome-wide prediction for hybrid breeding and suggest dozens of promising single crosses for developing high-yielding hybrids for Northwest China.

Litter decomposition was a key ecological process of nutrient cycling in the forest ecosystem,which played an important role in the terrestrial ecosystem and was an important part of the global carbon budget.Litter decomposition rate controlled the nutrient cycling and energy flow,and then regulated the carbon emission in the atmosphere,the composition of soil organic matters and the nutrient availability.The chemical properties of litters,environmental climate,root system and microbial community composition regulated the decomposition rate of litter.By systematically summarizing the basic theory of litter decomposition,the role and regulation mechanism of root system during the root and litter decomposition,and the research progress on the non-additive effects of the decomposition of mixed litters,the complex regulation mechanism involved by multiple factors in the process of litter decomposition was discussed,and the future research direction was prospected. [ABSTRACT FROM AUTHOR]

Background: Attempts to restore degraded highlands by tree planting are common in East Africa. However, up till now, little attention has been given to effects of tree species choice on litter decomposition and nutrient recycling. Method: In this study, three indigenous and two exotic tree species were selected for a litter decomposition study. The objective was to identify optimal tree species combinations and tree diversity levels for the restoration of degraded land via enhanced litter turnover. Litterbags were installed in June 2019 into potential restoration sites (disturbed natural forest and forest plantation) and compared to intact natural forest. The tested tree leaf litters included five monospecific litters, ten mixtures of three species and one mixture of five species. Standard green and rooibos tea were used for comparison. A total of 1,033 litters were retrieved for weight loss analysis after one, three, six, and twelve months of incubation. Results: The finding indicates a significant effect of both litter quality and litter diversity on litter decomposition. The nitrogen-fixing native tree Millettia ferruginea showed a comparable decomposition rate as the fast decomposing green tea. The exotic conifer Cupressus lusitanica and the native recalcitrant Syzygium guineense have even a lower decomposition rate than the slowly decomposing rooibos tea. A significant correlation was observed between litter mass loss and initial leaf litter chemical composition. Moreover, we found positive non-additive effects for litter mixtures including nutrient-rich and negative non-additive effects for litter mixtures including poor leaf litters respectively. Conclusion: These findings suggest that both litter quality and litter diversity play an important role in decomposition processes and therefore in the restoration of degraded tropical moist evergreen forest [ABSTRACT FROM AUTHOR]

Warming drives material cycling in terrestrial ecosystems by affecting litter decomposition, as it can alter litter yield, quality and decomposer composition and activity. The effect of warming on the decomposition of mixed litter in arid and semi-arid zones remains unknown. We investigated the mass loss and nutrient release dynamics during 450 days of decomposition of Artemisia ordosica , Leymus secalinus , and their mixture in Mu Us Desert by open-top chambers and litter bags. The results showed interspecific differences in the responses to warming, in that warming promoted mass loss and N and P release from L. secalinus and inhibited mass loss and P but promoting N release from A. ordosica . Mixing of A. ordosica and L. secalinus litter inhibited decomposition. Warming enhanced the antagonistic effects of mixed decomposition. The total mass loss of mixed litter was decreased by 9%, and the release of N and P was decreased by 4.9% and 12.6%, respectively. The antagonistic effects of mixed litter mass loss and P release under the warming treatment gradually strengthened with time, with N release changing from a synergistic to an antagonistic effect at 150 d. The non-additive effects produced by the mixed decomposition of A. ordosica and L. secalinus litter were jointly regulated by temperature and time. Future research on mixed litter decomposition should consider the interaction between temperature and time.

Heat stress is known to induce photoinhibition, leaf senescence, and nutrient remobilization in terrestrial plants with apical growth, however, its effect on blade erosion and associated-changes in chemical compositions has rarely been studied in marine macroalgae with intercalary growth such as kelp. The present study examined the combined effects of ocean warming (23 and 26°C), irradiance (30 and 180 μmol m–2 s–1), and nutrient enrichment (enriched and non-enriched) on photosystem II maximum efficiency (Fv/Fm) in the kelp Eisenia bicyclis. It also investigated the effect of ocean warming on the kelp’s relative growth rates based on five morphological parameters and three chemical compositions (carbon, nitrogen, and phlorotannnins). A warming effect on photoinhibition (i.e., decline in Fv/Fm) was only detected under the higher irradiance combined with nutrient-enrichment condition. Under this condition, elevated temperature decreased relative growth rates to negative values, indicating occurrence of apical blade erosion. Temperature elevation also caused increases in nitrogen and phlorotannin contents within the whole body, but not carbon content. Moreover, nitrogen content in the meristems at 26°C was higher than that at 23°C, although such a difference was not observed with phlorotannin content. These results suggested that heat-induced apical blade erosion promoted nitrogen accumulation in the meristems, located in the lower part of the blade, in E. bicyclis.

Heatwaves under global warming have negative impacts on ecosystem primary producers. This warming effect may be synergized or antagonized by local environments such as light and nutrient availability. However, little is known about the interactive effects of warming, irradiance, and nutrients on physiology of marine macroalgae, which are dominant in coastal ecosystems. The present study examined the combined effects of warming (23 and 26 °C), irradiance (30 and 150 µmol photon m−2 s−1), and nutrients (enriched and non-enriched) on specific growth rate (SGR) and biochemical compositions of the canopy-forming marine macroalga Sargassum fusiforme. The negative effect of warming on SGR and ratio of chlorophyll (Chl) c to Chl a was antagonized by decreased irradiance. Moreover, the negative effect of temperature elevation on carbon content was antagonized by nutrient enrichment. These results suggest that the effect of warming on the growth and carbon accumulation of this species can be mitigated by decreased irradiance and nutrient enrichment.

Litter decomposition plays a critical role in both nutrient cycling and the interspecific relationships between tree species. In this study, leaf litter from Robinia pseudoacacia was mixed with litter from 10 other species, this mixture was then ground and incubated in soil. The soil indexes (i.e., quantity of microbes, activities of enzymes, and chemical properties) were analyzed to study the effects of litter decomposition on soil properties and the interaction between the litters. If mixed separately with Larix principis-rupprechtii or Betula platyphylla, R. pseudoacacia litter exerted synergistic effects on the activities of most enzymes. The mixed litters of R. pseudoacacia and Pinus sylvestris var. mongolica or Ulmus pumila exerted synergistic effects on the soil available P. With regard to the soil properties as a whole, the mixed litters of R. pseudoacacia and B. platyphylla, Pinus tabulaeformis, P. sylvestris var. mongolica, or L. principis-rupprechtii exerted synergistic effects on soil during their decomposition. However, the mixed litters of R. pseudoacacia and Populus simonii, Quercus liaotungensis, U. pumila, or Caragana microphylla did not. This indicated that R. pseudoacacia mixed with the litter of other needle-leaf tree species benefits the development and regeneration of soil and thus can be used for sustainable forest management. [ABSTRACT FROM AUTHOR]

Aims The conifer litter is fairly recalcitrant and nutrient poor, and broadleaved litter promotes coniferous litter decomposition by increasing degradable nutrients and promoting microbial metabolism. Mixing Pinus massoniana litter and three broadleaved litters may increase the diversity and abundance of fungal decomposers compared with those in P. massoniana litter and vary depending on the number and proportion of broadleaved species included. Methods We analysed the composition and diversity of fungal communities during mixed litter decomposition in southwestern China with 35 treatments (P. massoniana , Toona sinensis , Cinnamomum camphora and Sassafras tzumu litter) using Illumina high-throughput sequencing. Important Findings The mixed litters increased fungal diversity and richness compared with those in the single-species litter, except in the following treatments: P. massoniana litter accounting for 70%–80% in the P. massoniana + T. sinensis , P. massoniana + S. tzumu + T. sinensis and P. massoniana + S. tzumu + C. camphora combinations, and P. massoniana + S. tzumu + C. camphora + T. sinensis combination with small proportion of T. sinensis litter. The diversity and richness of the 7:1:2 combination of P. massoniana + C. camphora + T. sinensis were significantly higher than those in the other treatments. Ascomycota and Basidiomycota were the dominant phyla, and Aspergillus was the most abundant genus. The decomposition of litters from one needleleaf and one broadleaved species (6:4) and one needleleaf species and two broadleaved species (broadleaved litter accounting for 30%–40%) exhibited synergistic interactions throughout the decomposition process, and the relative abundance of fungi that decompose refractory substances increased. The P. massoniana + C. camphora + T. sinensis combination and a 30%–40% broadleaf litter proportion increased fungal diversity and accelerated the decomposition of recalcitrant coniferous litter. Therefore, C. camphora and T. sinensis are a potential candidate species for mixed planting with P. massoniana. [ABSTRACT FROM AUTHOR]

Aims: Larix kaempferi planting with broad-leaved trees can increase production and alleviate soil degradation; however, the mechanism is unclear, especially on large scales and in different climate regions. This paper attempts to explain the underlying mechanism in a temperate region and northern subtropical alpine region of China. Methods: Litter decomposition rates, nutrient release, enzyme activity and microbial community composition were determined in conifer litter, broad-leaved litter and mixed litter by the litterbag method during about 500 days in the two regions. Results: Decomposition rate was increased by 4.00% in temperate region and 3.38% in the subtropical region after litter mixing and the synergistic effect increased with decomposition progress. However, nutrients release was not always enhanced, and enzyme activities were enhanced at the most of decomposition time and higher in the subtropical region. After litter mixing, a few new dominant taxa emerged, and the microbial gene quantities were increased in the temperate region, but not in the subtropical region. The dominant bacterial taxa were similar, while most of the dominant fungal taxa shifted with decomposition. In addition, the dominant fungi completely differed between the two regions. The environmental variables with greater influence on microbial community were similar in the two regions, including C:N, C:P and pH. Conclusions: After mixing with broad-leaved litter, the decomposition of Larix kaempferi was enhanced by increasing enzyme activities and microbial quantities in the temperate region, but the mechanisms were not clear in the subtropical region. [ABSTRACT FROM AUTHOR]

Litter decomposition, an important component of nutrient cycling, is often one of the limiting factors for the development of monoculture tree plantations for restoration, and how to improve the litter decomposition rate remains as a major challenge. To help resolve this issue, we developed a mixed-litter transplantation approach to improve the litter decomposition and nutrient cycling in Schima superba, Cunninghamia lanceolata, Eucalyptus urophylla, and Acacia mangium monoculture plantations in China. The monospecific leaf litters of the four species were collected and their possible two-, three- and four-species combinations were transplanted between plantations. We examined the influences of home/away field, litter species richness, and litter composition on litter decomposition during 24 months treatment. A significant effect of litter composition on litter decomposition (Duration × Composition effect) was detected in E. urophylla plantation. The influence of litter richness on litter decomposition was significant in A. mangium plantation (Duration × Richness effect). The litter of C. lanceolata and A. mangium had a distinct home-field advantage, while the litter of S. superba had a distinct away-field advantage in decomposition. We observed a positive relationship between richness and litter decomposition in C. lanceolate plantation. The effect of Duration × Species Interaction on litter decomposition, was significant in E. urophylla plantation, indicating a non-additive effect. Litter decomposition in E. urophylla plantation could be explained by idiosyncratic model, and the rivet model may be appropriate to illustrate the litter decomposition in A. mangium plantation. Finally, since the litter decomposition in degraded A. mangium plantations had a distinct home-field advantage and was significantly affected by litter richness, transplanting mixed litters of neighboring plantations may be beneficial to improve its litter decomposition rate. Transplanting of S. superba litters due to the distinct home-field advantage to neighboring plantations such as E. urophylla plantation whose litter decomposition is significantly affected by litter composition, may be an effective management method for improving litters decomposition. [ABSTRACT FROM AUTHOR]

Ocean warming and the associated changes in fish herbivory have caused polarward distributional shifts in the majority of canopy-forming macroalgae that are dominant in temperate Japan, but have little effect on the alga Sargassum fusiforme. The regeneration ability of new shoots from holdfasts in this species may be advantageous in highly grazed environments. However, little is known about the factors regulating this in Sargassum species. Moreover, holdfast tolerance to high-temperature and nutrient-poor conditions during summer has rarely been evaluated. In the present study, S. fusiforme holdfast responses to the combined effects of temperature and nutrient availability were compared to those of sexually reproduced propagules. The combined effects of holdfast fragmentation and irradiance on regeneration were also evaluated. Propagule growth rate values changed from positive to negative under the combination of elevated temperature (20 °C–30 °C) and reduced nutrient availability, whereas holdfasts exhibited a positive growth rate even at 32 °C in nutrient-poor conditions. The regeneration rate increased with holdfast fragmentation (1 mm segments), but was unaffected by decreased irradiance. These results suggest that S. fusiforme holdfasts have a higher tolerance to high-temperature and nutrient-poor conditions during summer than propagules, and regenerate new shoots even if 1-mm segments remain in shaded refuges for fish herbivory avoidance.

Durian (Durio zibethinus Murr.) seed flour (DSF) has very soft gel with high syneresis. Blending it with cassava starch (CS) could deliver strongly advantageous effects. The objective of this work was to investigate the functional and physicochemical properties of blends of CS and DSF. Experimentally, commercial cassava starch CS (18.18 ± 0.11% amylose) was blended with DSF (containing 55.44 ± 4.93% gum and 14.62 ± 0.07% amylose) in various CS/DSF ratios: 100/0, 90/10, 80/20, 70/30, 60/40, 50/50, 40/60, 30/70, 20/80, 10/90, and 0/100 by dry weight. The key properties of those blends were investigated, namely swelling power (SP), solubility, pasting properties by the Rapid Visco Analyzer (RVA), gelatinization temperature, and gel texture and syneresis. CS showed lower SP at 60 °C, but higher SP at 75 and 90 °C than DSF, while DSF had higher solubility than CS at all temperatures tested. The blends had SP and solubility between these extremes. RVA viscosities for all ratios of the CS/DSF blends were often below those of the individual components, with DSF influencing more than expected from its proportion. The peak viscosity (PV) of CS was significantly higher than that of DSF (3955 ± 37 vs. 1918 ± 17 mPa.s). The PV of CS/DSF blends with 10/90–60/40 ratios was slightly different from that of DSF, but increased strongly for the 70/30- 90/10 ratios. As regards gelatinization, CS had lower temperature range (62.66 ± 0.13–72.06 ± 0.21 °C,) than DSF (67.50 ± 0.55–79.35 ± 0.16 °C), while its enthalpy was higher (12.83 ± 0.81 vs. 5.38 ± 0.16 J/g). All the blends showed higher gelatinization temperature than CS but lower than DSF and their enthalpies had the opposite trend. Regarding the gel properties, gel hardness of CS was about five-fold higher than that of DSF (50.9 ± 30.27 vs. 9.59 ± 0.67, p < 0.05), while syneresis of CS was much lower (1.61 ± 0.33 vs. 58.30 ± 0.44%, p < 0.05) than of DSF. For their blends, it turned out that gel hardness increased and syneresis decreased with CS content in the blend. The gel hardness was synergistic for 90/10 and 80/20 ratios with about 50% increase over the pure components, and simultaneously the syneresis relative to plain DSF was reduced by over 50%. The results suggested that improved DSF properties can be achieved by blending with CS, and also a small amount of DSF (10–20%) has synergistic effect on gel hardness of the blend. Gum in the DSF plays an important role in the continuous phase of the paste and the gel. [ABSTRACT FROM AUTHOR]

Little is known about the effect of woody plant expansion on decomposition of root mixtures in grass-dominant temperate wetlands. Here, we collected fine roots (< 1 mm) of Deyeuxia angustifolia (grass) and Betula fruticosa (shrub) from a freshwater wetland in the Sanjiang Plain, Northeast China, and decomposition rates of their monocultures and mixtures (with 2:1 and 1:2 mass ratios) were determined by measuring carbon (C) mineralization and mass loss with a 365 days incubation experiment. Meanwhile, litter mixing effects were assessed by the differences in observed decomposition rates of root mixtures and predicted values based on the performance of component species decomposing alone. Betula fruticosa fine roots had higher N, total polyphenol, and condensed tannin concentrations than D. angustifolia fine roots. By the end of incubation, B. fruticosa fine roots generally had greater C mineralization rate and mass loss than the other three root treatments. Notably, both C mineralization rate and mass loss were lower than the expected values in the B. fruticosa-dominant mixture, whereas there were no significant differences between observed and expected values in the D. angustifolia-dominant mixture. Our findings imply that the increase in woody plant abundance will exert influences on fine root decomposition rates through altered substrate quality and litter mixing effects in grass-dominated temperate wetlands. [ABSTRACT FROM AUTHOR]

Aims: Improvement cutting or harvesting can change the coverage of understory vegetation, which can significantly influence the litter decomposition process in plantations. However, difference in potential non-additive mass loss in response to understory vegetation changes is poorly studied. Methods: A field litterbag experiment involving various litter types and treatments with no understory vegetation removal, shrub removal, herb removal and whole-understory vegetation removal was conducted to examine non-additive mass loss. Results: During approximately 2 years of decomposition, the decomposition rate of shrub and herb components was accelerated in the mixed litter with full understory vegetation. There was significant non-additive mass loss during decomposition in the plots with trees, shrubs and herbs, while the incidence of non-additive mass loss was lower in the plots with understory vegetation removal. Statistical analysis revealed a significant difference between the expected mass loss calculated with the data from the corresponding decomposition plots and that calculated with the data from the plots with whole-understory vegetation removal. Conclusions: Our results show that understory vegetation removal can inhibit litter decomposition in Masson pine plantation ecosystems in subtropical China. We highlight that non-additive litter decomposition should be assessed on the basis of litter species composition and decomposition microenvironments in situ. [ABSTRACT FROM AUTHOR]

Abstract Starches from different origins are often blended with the aim of lowering cost and modulating product texture. However, the law governing the blending consequence is not well established. To this end, the pastes, fresh and dried gels from the blends of sweet potato starch (SPS) with cassava starch (CS) at different ratios were investigated. The results revealed that SPS and CS largely differ in terms of pasting behavior, rheological properties of hot and cooled paste as well as the textural parameters of fresh and dried gels. Generally, there are two categories, namely additive and non-additive for the blending effects of different starches. The present study shows that the blending effect of SPS and CS highly depends on the ratios of individual components and is also property specific. The pasting behavior during peak viscosity development is of non-additive nature but the remaining part is governed by an additive law. In hot and cooled blend pastes, the individual starches behave independently in steady shear measurements while they interact more or less in dynamic oscillatory shear measurements, thus demonstrating additive and non-additive effects, respectively. As for fresh and dried blend gels, additive effects were concluded for most tested textural parameters and physicochemical properties except for the enthalpy of dried ones and the elasticity of the cooked ones. This study provides basis to formulate the blend of SPS and CS with particular functionalities. Graphical abstract Image 1 Highlights • Sweet potato starch (SPS) differs from cassava starch (CS) in diverse functionalities. • A non-additive pasting behavior was observed for the blends before peak development. • Both hot and cooled blend pastes non-additively behavior in steady shear measurements. • The blending effects in paste viscoelasticity are parameter and blending ratio specific. • The blends show additive effects in most textural parameters of fresh and dried gels. [ABSTRACT FROM AUTHOR]

Sweetpotato (Ipomoea batatas L. (Lam)) is a nutritious food security crop for most tropical households, but its utilisation is very low in Ghana compared to the other root and tuber crops due to lack of end-user-preferred cultivars. Knowledge on the genetic control of important traits such as dry matter, starch and sugar content of sweetpotato storage roots in a breeding population is critical for making breeding progress in developing sweetpotato varieties preferred by farmers and consumers. This study used diallel mating design to elucidate general combining ability and specific combining ability, to determine the gene action controlling storage root dry matter, starch and sugar content in sweetpotato and the heterotic potential of the traits to facilitate the crop’s improvement for increased utilisation. A general model for estimating genetic effects, GEAN II, was used to analyse the data. Genetic variability was seen for dry matter, starch and sugar content of sweetpotato and much of this genetic variation was additive in nature. The study also revealed significant heterosis in sweetpotato which offers opportunity for breeding non-sweet, high dry matter sweetpotato varieties that are preferred by farmers and consumers in Ghana.

Forest litter is a fuel component that is important for the propagation of fire. Data describing fuel load, structure and fuel condition were gathered for two sites of Sydney Coastal Dry Sclerophyll Forest, a common vegetation type in the Sydney Basin, Australia. Surface litter from the sites was sorted into its constituent components and used to establish which component or mixture of components were the most flammable using several metrics. A general blending model was used to estimate the effect the different mixtures had on the response of the flammability metrics and identify non-additive effects. Optimisation methods were applied to the models to determine the mixture compositions that were the most or least flammable. Differences in the flammability of the two sites were significant and were driven by Allocasuarina littoralis. The presence of A. littoralis in litter mixtures caused non-additive effects, increasing the rate of flame spread and flame height non-linearly. We discuss how land managers could use these models as a tool to assist in prioritising areas for hazard reduction burns and how the methodology can be extended to other fuel conditions or forest types.

[Display omitted] • Mixed residues decomposition exhibited a positive non-additive effect in mass loss. • Mixing increased the recalcitrant carbon content during residue decomposition. • Bacterial community mediated chemical structure of carbon in decomposed residue. Microbe-regulated organic residue decomposition is a central hub of carbon (C) cycling in ecosystems. However, little is known about the changes in organic C composition and its microbial mechanisms during mixed crop residue decomposition in agroecosystems. We conducted a field litterbag experiment to explore the changes in organic C chemical structure and their associations with microbial communities during mixed (1:1 maize:potato residues based on dry matter mass) and single-species residue decomposition in agricultural soils. Compared with single-species residues, mixed residues exhibited a positive non-additive effect, specifically higher mass loss, and more recalcitrant organic C composition. Structural equation modelling combined with network analysis suggested that residues mixing modified bacterial keystone taxa, augmented the activity of C-degrading enzymes such as β-glucosidase, and increased stable C content during mixed residues decomposition. Thus, this study highlights the potential advantages of applying residue mixtures to agri-cropping soils to increase the relative amount of persistent aromatic compounds derived from their decomposition and the importance of bacterial keystone taxa during residue decomposition. [ABSTRACT FROM AUTHOR]

Key message: This study compares five models of GWAS, to show the added value of non-additive modeling of allelic effects to identify genomic regions controlling flowering time of sunflower hybrids. Abstract: Genome-wide association studies are a powerful and widely used tool to decipher the genetic control of complex traits. One of the main challenges for hybrid crops, such as maize or sunflower, is to model the hybrid vigor in the linear mixed models, considering the relatedness between individuals. Here, we compared two additive and three non-additive association models for their ability to identify genomic regions associated with flowering time in sunflower hybrids. A panel of 452 sunflower hybrids, corresponding to incomplete crossing between 36 male lines and 36 female lines, was phenotyped in five environments and genotyped for 2,204,423 SNPs. Intra-locus effects were estimated in multi-locus models to detect genomic regions associated with flowering time using the different models. Thirteen quantitative trait loci were identified in total, two with both model categories and one with only non-additive models. A quantitative trait loci on LG09, detected by both the additive and non-additive models, is located near a GAI homolog and is presented in detail. Overall, this study shows the added value of non-additive modeling of allelic effects for identifying genomic regions that control traits of interest and that could participate in the heterosis observed in hybrids. [ABSTRACT FROM AUTHOR]

The structural properties of blends of waxy corn starch and potato starch at different proportions were evaluated at 20% solids content. The results from differential scanning calorimetry, wide-angle X-ray scattering, and small-angle X-ray scattering of the starch blends indicated that each starch gelatinized completely and independently. The setback viscosity values were higher in the blends compared with native starches, which suggested that the granular interactions had an important effect. The presence of waxy corn starch granules could have reinforced the network formed by amylose leached from potato starch granules. The intrinsic characteristics of waxy corn starch and potato starch determined the type of granular and molecular interactions that could be carried out during the processes of gelatinization and gel formation in starch blends. [ABSTRACT FROM AUTHOR]

Background and aims: Leaf litters commonly interact during decomposition in ways that can synergistically increases rates of decay. These interactions have been linked to moisture availability, suggesting that drought could slow decomposition rates by disrupting litter interactions. Slowed decomposition may reduce competitive ability of exotic species that exploit rapid decomposition rates as part of niche construction mechanisms. Here, we evaluated the impacts of drought on interactions between native and exotic species' litter decomposition. Methods: We considered litter mixtures of Lupinus polyphyllus (exotic N-fixing forb) , Trifolium pratense (native N-fixing forb), Senecio inaequidens (exotic non-N-fixing forb) , and Senecio jacobaea (native non-N-fixing forb) with the native grass Alopecurus pratensis and evaluated the difference between the observed rate of decay and the one expected based on species decomposing in monocultures. Litters were deployed in Belgium and Germany and exposed to a 56 day drought, which resembled local millennium drought (statistical recurrence of duration in local precipitation series >1000 years). Results: Litter interactions reduced mass remaining by 81% in Belgium and 15% in Germany, averaged across mixtures. Similarly, litter interactions reduced N remaining by 93% in Belgium and 14% in Germany. Drought consistently removed these interactions and resulted in additive litter decay. Litters of native and exotic species did not differ in their response to drought. Conclusions: These findings support moisture availability as a key regulator of interactions between litters during decomposition. Thus, increasing frequency of drought may slow nutrient cycling to a greater extent than previously thought. [ABSTRACT FROM AUTHOR]

SUMMARY Previous experiments with a factorial design have revealed the effects of several environmental factors on species performance and their interactions, which indicate synergistic or antagonistic effects. Temperature, nutrient availability, and irradiance are well-known environmental factors that affect the growth and chemical composition of brown algae. However, relatively few studies have tested their combined effect on brown algal growth and chemical composition using a three-way factorial design. We conducted a culture experiment to test the combined effects of elevated summer temperatures (23 and 26°C), irradiance (180 and 30 μmol photon m−2 s−1), and nutrient availability (enriched and non-enriched seawater) on four relative growth rates ( RGRs; based on wet weight, blade width, length, and area) and three chemical compositions (including carbon, nitrogen, and phlorotannin content) in juvenile sporophytes of the kelp Eisenia bicyclis. RGR based on blade width was the most sensitive to abiotic factors among all RGRs. A significant interaction between temperature and nutrient availability on this RGR suggested that the negative effect of elevated temperature was antagonized by a reduction in nutrient availability. Similarly, the positive effect of elevated irradiance on carbon content was synergized by reduced nutrient availability. Moreover, the negative effect of increased irradiance on nitrogen content was antagonized by elevated temperature in nutrient-enriched treatments, but not in non-enriched treatments. The content of carbon-based phlorotannins increased with reduced nutrient availability but not with elevated irradiance. These results suggest that these abiotic factors have complex interactions on the growth and chemical composition of this species. [ABSTRACT FROM AUTHOR]

Sweetpotato (Ipomoea batatasL. (Lam)) is a nutritious food security crop for most tropical households, but its utilisation is very low in Ghana compared to the other root and tuber crops due to lack of end-user-preferred cultivars. Knowledge on the genetic control of important traits such as dry matter, starch and sugar content of sweetpotato storage roots in a breeding population is critical for making breeding progress in developing sweetpotato varieties preferred by farmers and consumers. This study used diallel mating design to elucidate general combining ability and specific combining ability, to determine the gene action controlling storage root dry matter, starch and sugar content in sweetpotato and the heterotic potential of the traits to facilitate the crop’s improvement for increased utilisation. A general model for estimating genetic effects, GEAN II, was used to analyse the data. Genetic variability was seen for dry matter, starch and sugar content of sweetpotato and much of this genetic variation was additive in nature. The study also revealed significant heterosis in sweetpotato which offers opportunity for breeding non-sweet, high dry matter sweetpotato varieties that are preferred by farmers and consumers in Ghana. [ABSTRACT FROM AUTHOR]

Foram utilizados dados de 62.985 animais das raças Nelore, Hereford, Angus e produtos de cruzamentos Nelore × Angus e Nelore × Hereford de rebanhos comerciais a fim de estimar os efeitos de heterose materna e individual para o ganho médio diário no período pré-desmama (GMD). Os valores obtidos de heterose individual e materna considerando-se o valor médio de GMD da população representam um acréscimo de 6,2% e 11,2% no GMD para os animais F1 e filhos de vacas F1, respectivamente. A heterose materna correspondeu a 64,5% da heterose total. Animais cruzados Bos taurus × Bos indicus obtêm GMD maior do que o dos animais das raças puras.Data on 62.985 Nellore, Hereford, Angus and Nellore × Angus and Nellore × Hereford crossbred calves were analyzed to estimate maternal and individual heterosis for preweaning daily weight gain (PWD). The individual and maternal heterosis of average daily weight gain showed improvements of 6.2 and 11.2% for PWD of F1 calves and for calves borne from F1 dams. Maternal heterosis corresponded to 64.5% of total heterosis. Bos taurus × Bos indicus crossbred cattle have a PWD larger than the average of purebred cattle.

Prediction of complex trait phenotypes in the presence of unknown gene action is an ongoing challenge in animals, plants, and humans. Development of flexible predictive models that perform well irrespective of genetic and environmental architectures is desirable. Methods that can address non-additive variation in a non-explicit manner are gaining attention for this purpose and, in particular, semi-parametric kernel-based methods have been applied to diverse datasets, mostly providing encouraging results. On the other hand, the gains obtained from these methods have been smaller when smoothed values such as estimated breeding value (EBV) have been used as response variables. However, less emphasis has been placed on the choice of phenotypes to be used in kernel-based whole-genome prediction. This study aimed to evaluate differences between semi-parametric and parametric approaches using two types of response variables and molecular markers as inputs. Pre-corrected phenotypes (PCP) and EBV obtained for dairy cow health traits were used for this comparison. We observed that non-additive genetic variances were major contributors to total genetic variances in PCP, whereas additivity was the largest contributor to variability of EBV, as expected. Within the kernels evaluated, non-parametric methods yielded slightly better predictive performance across traits relative to their additive counterparts regardless of the type of response variable used. This reinforces the view that non-parametric kernels aiming to capture non-linear relationships between a panel of SNPs and phenotypes are appealing for complex trait prediction. However, like past studies, the gain in predictive correlation was not large for either PCP or EBV. We conclude that capturing non-additive genetic variation, especially epistatic variation, in a cross-validation framework remains a significant challenge even when it is important, as seems to be the case for health traits in dairy cows.

Background: Litter decomposition is a fundamental process of biogeochemical cycles, and there is a strong consensus that litter mixture interactions are one of the factors driving the decomposition process. A better understanding of how climate change can alter interactions between species and the litter decomposition process could facilitate projections of ecosystem functioning into the future. Methods: A 24-month litterbag decomposition experiment was carried out in a Mediterranean forest to analyze the effects of climate and species diversity changes on litter mixture interactions and the decomposition process. Results: In the control plot, synergistic interactions increased with time and species diversity in litter mixtures, leading to more efficient litter decomposition. Drier conditions obtained in the field with a rain exclusion device decreased decomposition rates, resulting in three-fold less synergistic interactions and five-fold more antagonistic interactions during the decomposition process. Furthermore, synergistic interactions were better preserved in the drought conditions with increasing number of species. Conclusions: Our findings underline how a longer drought season could strongly affect the relationship between biodiversity and ecosystem functioning. Drier climate led to slower mass loss rates and a strong shift in the litter mixture interactions, with fewer synergistic interactions and more antagonistic interactions. [ABSTRACT FROM AUTHOR]

To examine the potential impact of plant species richness on ecosystems, we studied non-additive effects of different plant litters on the biodegradation rate of dissolved organic matter (DOM) when mixing plant leaf-derived DOM derived from different plant species. A full factorial biodegradation experiment (31 possible singular and multiple combinations of five litter type-derived DOM sources) was conducted using plant litters from the five most abundant plant species in a subtropical watershed ecosystem, from which dissolved organic carbon (DOC) disappearance was measured. Loss of DOC over time was considered biodegradable DOC. We tested whether DOM diversity, measured as source species richness and composition, would affect biodegradation rates. Overall, we found significant non-additive (synergistic) effects of DOM diversity on biodegradation rates of DOM, which were explained both by plant species richness and composition. Across all treatments, a significantly higher biodegradation rate was correlated with the presence of DOM from higher nitrogen (N) containing plant litters; conversely, the presence of lower N decreased these rates. The N content and chemical characteristic of DOM might influence the magnitude of the synergistic effect. Our results suggest that loss of plant litter species diversity would not affect DOC biodegradation rate, provided that at least two species are conserved. However, the variability in DOC biodegradation rate across the treatments decreased with increased DOM diversity at three incubation time points. Our results also indicate that in an ecosystem with low plant biodiversity, loss of key species such as Lophostemon confertus could reduce the synergistic effects on DOC biodegradation rate. [ABSTRACT FROM AUTHOR]

SPMD-based virtual organisms (VOs) were deployed at five to eight sites in the Three Gorges Reservoir (TGR), China for five periods in 2008, 2009 and 2011. The water exposure of aryl hydrocarbon receptor (AhR) agonists was assessed by the VOs. The chosen bioassay response for the extracts of the VOs, the induction of 7-ethoxyresorufin-O-deethylase (EROD) was assayed using a rat hepatoma cell line (H4IIE). The results show that the extracts from the VOs could induce AhR activity significantly, whereas the chemically derived 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) equivalent (TEQ cal ) accounted for < 11% of the observed AhR responses (TEQ bio ). Unidentified AhR-active compounds represented a greater proportion of the TCDD equivalent in VOs from TGR. High TEQ bio value in diluted extract and low TEQ bio in concentrated extract of the same sample was observed suggesting potential non-additive effects in the mixture. The levels of AhR agonists in VOs from upstream TGR were in general higher than those from downstream reservoir, indicating urbanization effect on AhR agonist pollution. The temporal variation showed that levels of AhR agonists in 2009 and 2011 were higher than those in 2008, and the potential non-additive effects in the area close to the dam were also obviously higher in 2009 and 2011 than in 2008, indicating big changes in the composition of pollutants in the area after water level reached a maximum of 175 m. Although the aqueous concentration of AhR agonists of 0.8–4.8 pg TCDD L − 1 in TGR was not alarming, the tendency of accumulating high concentration of AhR agonists in VO lipid and existence of possible synergism or antagonism in the water may exhibit a potential hazard to local biota being exposed to AhR agonists. [ABSTRACT FROM AUTHOR]

Purpose: The rate of litter decomposition can be affected by a suite of factors, including the diversity of litter type in the environment. The effect of mixing different litter types on decomposition rates is increasingly being studied but is still poorly understood. We investigated the effect of mixing either litter material with high nitrogen (N) and phosphorus (P) concentrations or those with low N and P concentrations on litter decomposition and nutrient release in the context of agroforestry systems. Materials and methods: Poplar leaf litter, wheat straw, peanut leaf, peanut straw, and mixtures of poplar leaf litter-wheat straw, poplar leaf litter-peanut leaf, and poplar leaf litter-peanut straw litter samples were placed in litter bags, and their rates of decomposition and changes in nutrient concentrations were studied for 12 months in poplar-based agroforestry systems at two sites with contrasting soil textures (clay loam vs silt loam). Results and discussion: Mixing of different litter types increased the decomposition rate of litter, more so for the site with a clay loam soil texture, representing site differences, and in mixtures that included litter with high N and P concentrations (i.e., peanut leaf). The decomposition rate was highest in the peanut leaf that had the highest N and P concentrations among the tested litter materials. Initial N and P immobilization may have occurred in litter of high carbon (C) to N or C to P ratios, with net mineralization occurring in the later stage of the decomposition process. For litter materials with a low C to N or P ratios, net mineralization and nutrient release may occur quickly over the course of the litter decomposition. Conclusions: Non-additive effects were clearly demonstrated for decomposition rates and nutrient release when different types of litter were mixed, and such effects were moderated by site differences. The implications from this study are that it may be possible to manage plant species composition to affect litter decomposition and nutrient biogeochemistry; mixed species agroforestry systems can be used to enhance nutrient cycling, soil fertility, and site productivity in land-use systems. [ABSTRACT FROM AUTHOR]

Aims We explored the decomposition rates of single- and mixed-species litter, the litter-mixing effect and the effect of component litters in a mixture on decomposition. Methods In a litter bag experiment, shoot litters from two dominant grasses (Leymus chinensis and Stipa baicalensis) and one legume (Melissitus ruthenica) were decomposed separately and as a mixture from May 2010 to September 2011 in the Hulun Buir meadow steppe of Inner Mongolia, China. We separated the litter mixture into its individual component litters (i.e. the different single-species litters) and analyzed the changes in litter mass remaining and litter nitrogen (N) remaining during single- and mixed-species litter decomposition. Important Findings (i) Litter mixing had significant positive effects on litter decomposition. The litter-mixing effect was strongest for the mixture of S. baicalensis and L. chinensis litters, followed by the mixture of S. baicalensis and M. ruthenica litters. (ii) Single-species component litters decomposed faster in the mixtures than separately (positive effect), but these effects were not significant for legume species M. ruthenica litter. Relative to single-species litter decomposition, the decomposition rates of the two grass (S. baicalensis and L. chinensis) litters significantly increased when they were mixed with each other or with M. ruthenica litter. (iii) For each species litter type, the percentage of litter N remaining during decomposition (NR) differed between the single-species litter and mixed litter treatments. The NR of S. baicalensis litter was higher when it was decomposed in the mixture than in isolation. However, the NR of L. chinensis litter was lowest in its mixture with M. ruthenica among the treatments. Regardless of its decomposition in the mixture or in isolation, the NR of M. ruthenica litter varied little among treatments. There was a significant positive relationship between the NR and percentage of initial litter mass remaining in both the single litter and mixed litter treatments. These results suggest that N transfer may happen among component litters in mixture and further affect the decomposition. [ABSTRACT FROM PUBLISHER]