Litter Mass Loss Research Articles

The role of Collembola for litter decomposition under minimum and conventional tillage

AbstractBackgroundThe role of soil mesofauna in decomposition processes still is debated and this applies in particular to arable systems.AimThis study investigates the role of Collembola in decomposition processes of crop residues in two different tillage systems.MethodsWe conducted a litterbag experiment in a long‐term field site in Germany managed by conventional tillage (CT; mouldboard ploughing) and minimum tillage (MT). Litterbags filled with maize leaf litter of two mesh sizes (2 mm and 48 μm) were used. Litterbags were buried at 23 cm (CT) and 5–8 cm (MT), and retrieved after 2, 5 and 7 months. Litter mass, concentrations of carbon and nitrogen, litter C/N ratio as well as the abundance and community structure of Collembola and the incorporation of maize‐derived carbon into Collembola were investigated.ResultsMesofauna enhanced the loss of litter carbon, while litter mass loss was reduced. Litter C/N ratio in MT was generally lower than that in CT and decreased faster in litterbags with coarse mesh size. Abundance of Collembola in litterbags in CT exceeded that in MT, but species composition remained unaffected by tillage. Overall, Collembola effectively colonised the litter irrespective of tillage system, but benefited in particular from translocation deeper into the soil by conventional tillage.ConclusionsMesofauna accelerates litter carbon loss and increases litter nitrogen accumulation irrespective of tillage system. This may reduce nitrogen losses due to leaching in winter and facilitate nitrogen capture from decomposing litter material by crops in the following season, thereby contributing to the sustainable management of arable systems.

UV radiation doubles microbial degradation of standing litter in a subtropical forest

Abstract UV radiation has been recognized as a direct driver of litter decomposition by photodegrading organic matter in dryland ecosystems. However, the importance and mechanism of UV radiation on litter decomposition, especially on standing litter, in humid forest ecosystems remain unclear. We conducted a factorial experiment in a humid subtropical forest gap, manipulating the effects of UV radiation on the decomposition of standing litter under different microbial conditions. After 366 days of standing incubation, under normal conditions (UV pass with microorganisms), up to 40.63% of the litter mass was lost. However, under a UV pass without microorganisms, litter mass loss was only 16.30%. Under a UV block, the mass loss of litter with microorganisms was 27.68% and that of litter without microorganisms was 15.54%. Without microorganisms, UV radiation had no significant effect on the mass loss of litter carbon. However, UV radiation increased the DOC concentration of litter. And in the presence of microorganisms, UV radiation contributed to an increased mass loss of lignin by 16.72% and of cellulose by 14.75%. No negative effects of UV radiation on microorganisms were observed. These results suggest that UV radiation increased the net mass loss of litter by 106.67%, and this doubling promotion was achieved through microbial degradation. Synthesis. The increase in microbial degradation under UV radiation may be linked to the increased degradability of lignin and cellulose caused by photodegradation. Our study indicates that direct photodegradation by UV radiation could be weak in subtropical forests, but UV photofacilitation generates rapid turnover of carbon in this system.

Global Patterns and Drivers of Litter Decomposition Under Nitrogen Enrichment: A Meta-Analysis

Nitrogen (N) enrichment has substantially altered patterns of terrestrial litter decomposition, with positive, neutral, and negative effects. However, the general response patterns and drivers of litter decomposition to N enrichment rates are poorly understood, and how litter decomposition has changed under the N enrichment rate, especially in different ecosystems, still requires further study. We reviewed 118 published papers dealing with litter mass remaining after N enrichment to assess the influences of various environmental and experimental factors on the relationships between N enrichment and litter decomposition in grasslands, forests, and wetland ecosystems. The results indicated that N enrichment had an insignificant effect on litter decomposition globally. However, the effects varied greatly among ecosystem types, with an increase in litter decomposition of 3.91% in grasslands and 1.82% in wetlands and a decrease of 1.23% in forests. When forests were subdivided into plantations, primary, and secondary forests, the results showed that N enrichment significantly slowed litter decomposition rate by 2.96% in plantations but had no significant influence in primary and secondary forests. However, litter decomposition was significantly influenced by the level of N addition in plantations and secondary forests, with an increase in litter mass loss at low N addition (50 kg N ha–1 year–1) and a decrease in litter mass loss at high N addition (>50 kg N ha–1 year–1). The magnitude and direction of the N effect are affected by experimental and environmental factors. Specifically, mixed N enrichment (for example, urea and glycine) exerted a stronger effect on litter decomposition compared with an N fertilizer alone. Our findings indicated the different effects of N on litter decomposition in forests and grasslands and knowledge which will greatly advance our ability to accurately evaluate and predict global C cycling under increased N deposition, which should improve future models of global biogeochemical cycling.

Trait relationships of fungal decomposers in response to drought using a dual field and laboratory approach

AbstractDecomposer fungi play a fundamental role in terrestrial ecosystem dynamics. In the southwestern United States, climate change is causing more frequent and severe droughts, which may alter fungal community composition and activity. Investigating relationships between fungal traits may improve the prediction of fungal responses to drought. In this dual field and laboratory experiment, we examine whether trade‐offs occur between traits associated with drought. Specifically, we test the hypothesis that fungi sort into lifestyles specializing in growthyield, resourceacquisition, and droughtstress tolerance (“YAS” framework). For the field experiment, we constructed microbial “cages” containing sterilized litter and 1 of 10 fungal isolates. These cages were placed in long‐term drought and control plots in a southern Californian grassland for 6 and 12 months. We measured fungal hyphal length per unit litter mass loss for growth yield, the potential activities of four extracellular enzymes for resource acquisition, and the ability to grow in the drought versus control plots for drought stress tolerance. We compared these results with a laboratory microcosm experiment constructed with the same fungal isolates and that measured the same fungal traits. The field experiment corroborated our laboratory results, in that no trade‐offs were observed between growth yield and resource acquisition traits. However, in contrast to the laboratory experiment, drought tolerance was negatively related to extracellular enzyme activity and growth yield in the field, implying a trade‐off. Despite this observed trade‐off in the field, growth yield was not hindered by drought. We propose a modification to the YAS framework, by combining the growth yield and resource acquisition lifestyles, which may be more appropriate for this arid system. This joint laboratory and field approach contextualizes a theoretical framework in microbial ecology and improves understanding of fungal community response to climate change.

Canopy opening increases leaf‐shredding arthropods and nutrient mineralization but not mass loss in wet tropical forest

AbstractHurricanes alter forest habitat by opening the canopy and depositing fresh wood and leaves. The objectives of this study were to evaluate the effects of hurricane and drought‐driven changes to forests on green litter decomposition, invertebrate communities, and nutrient mineralization over a short period (6 months) after disturbance. We used three complete replicated blocks with two canopy treatments: control and trim + detritus. Green leaves were enclosed in litterbags of three different mesh sizes to determine the effect of soil fauna of varying body sizes. Litterbags were retrieved from the field after 21, 35, 84, and 168 days and transported to the laboratory in individually sealed plastic bags. We extracted and identified invertebrates, measured leached and mineralized litter nutrients using ion resin membranes placed for 1 week under the leaves inside the litterbags, and determined litter mass loss. Additional resin membranes were placed in the lowest litter layer above the mineral soil. The number of arthropod taxonomic groups and nutrient mineralization differed significantly between control and trim + detritus. Regardless of mesh size, bags in control plots had consistently higher invertebrate richness than in trim + detritus plots. Nitrogen mineralization and phosphorous mineralization were significantly higher in trim + detritus in large mesh size, and decomposer arthropod abundance was highest in large‐sized mesh bags. These data suggest that within functional categories, variations in feeding behavior among arthropod orders may affect the release of nutrients from organic matter. Percent mass loss did not differ between canopy treatments or litterbag mesh sizes, but instead decreased during drought. Invertebrate composition, but not abundance, differed significantly between canopy treatments with greater dominance by shredders (Lepidoptera and Diptera larvae) in trim + detritus, which corresponded to higher rates of nutrient mineralization from green leaves. These results suggest that regional drought dominated the mesoclimate surpassing any microclimate variation in response to canopy treatments. Since mass loss did not differ between canopy treatments or litterbag mesh sizes, our results suggest that differences in short‐term nutrient fluxes from green litter are mostly related to changes in the litter invertebrate food web rather than rates of decomposition.

Evaluating Litter Decomposition Rate of Five Tropical Trees using Litter Bag Technique

Replenishment of soil nutrients and organic matter is a serious concern in sustaining livelihood securitywhich is favoured by cycling of nutrients through litter addition. The chief objective of the investigationwas, to inspect the decomposition rate of leaf litter of five tropical trees using evaluation tools like massloss, decomposition rate, and relative decomposition rate. The study was carried out at the tree plantationsof Agricultural College and Research Institute, Tamil Nadu Agricultural University, Madurai-625104, Indiaduring summer 2019-2020 for eight weeks. Litter Decomposition of legume and non legume trees viz.,Peltophorumferrugineum, Pongamia glabra, Albizia lebbek and Delonix regia along with a non-legume, Azadirachtaindica was evaluated through litter bag technique. The soil moisture, soil temperature, litter moisture content,mass loss, decomposition rate and relative decomposition rate were studied. The study revealed that Pongamiaglabra litter showed 70 % mass loss in 8 weeks time with maximum decomposition rate. It was closelyfollowed by Azadirachta indica. As Pongamia glabra litter is fast decaying, it can help in improvement of soilhealth through enhancing carbon level, organic matter and also microbial activity.

Soil warming did not enhance leaf litter decomposition in two subtropical forests

Climate warming is expected to increase leaf litter decomposition rates. However, higher temperature may not uniformly affect the factors that influence decomposition, resulting in unexpected decomposition patterns. Over a period of two years, we studied litter decomposition in response to soil warming in a native Castanopsis kawakamii forest and a Cunninghamia lanceolata (Chinese fir) plantation. Our study aimed to determine how soil warming affects litter mass loss, extracellular enzymatic activities (EEAs), litter chemistry, and microbial biomass. In the C. kawakamii forest, soil warming caused variation in litter mass loss with time but had no net effect on the litter decomposition constant. In the Chinese fir forest, however, soil warming had a consistent negative effect on litter mass loss, leading to a significant decrease in the decomposition constant by the end of the study. Additionally, there was a significantly slower mass loss of the acid-insoluble C fraction in Chinese fir litter in response to warming. Soil warming did not affect the microbial biomass of either litter, and its effect on EEAs varied with time. Litter moisture was significantly reduced by soil warming, with a greater reduction in Chinese fir litter (−9.2%) than in C. kawakamii litter (−4.1%). Applying an ANCOVA model, we found a significant correlation between litter mass loss rate and litter moisture, but not with other litter characteristics. Our results suggest that litter drying in soil warming does not affect microbial activities or litter microbial decomposition, but may diminish the physical leaching of soluble compounds from the litter into the underlying soil horizons. This may be a mechanism that explains the soil warming effect on litter decomposition in subtropical forests.

The amounts and ratio of nitrogen and phosphorus addition drive the rate of litter decomposition in a subtropical forest

Nitrogen (N) and phosphorus (P) control biogeochemical cycling in terrestrial ecosystems. However, N and P addition effects on litter decomposition, especially biological pathways in subtropical forests, remain unclear. Here, a two-year field litterbag experiment was employed in a subtropical forest in southwestern China to examine N and P addition effects on litter biological decomposition with nine treatments: low and high N- and P-only addition (LN, HN, LP, and HP), NP coaddition (LNLP, LNHP, HNLP, and HNHP), and a control (CK). The results showed that the decomposition coefficient (k) was higher in NP coaddition treatments (P < 0.05), and lower in N- and P-only addition treatments than in CK (P < 0.05). The highest k was observed with LNLP (P < 0.05). The N- and P-only addition treatments decreased the losses of litter mass, lignin, cellulose, and condensed tannins, litter microbial biomass carbon (MBC), litter cellulase, and soil pH (P < 0.05). The NP coaddition treatments increased the losses of litter mass, lignin, and cellulose, MBC concentration, litter invertase, urease, cellulase, and catalase activities, soil arthropod diversity (S) in litterbags, and soil pH (P < 0.05). Litter acid phosphatase activity and N:P ratio were lower in N-only addition treatments but higher in P-only addition and NP coaddition treatments than in CK (P < 0.05). Structural equation model showed that litter MBC, S, cellulase, acid phosphatase, and polyphenol oxidase contributed to the loss of litter mass (P < 0.05). The litter N:P ratio was negatively logarithmically correlated with mass loss (P < 0.01). In conclusion, the negative effect of N addition on litter decomposition was reversed when P was added by increasing decomposed litter soil arthropod diversity, MBC concentration, and invertase and cellulase activities. Finally, the results highlighted the important role of the N:P ratio in litter decomposition.

Temperature and precipitation affect seasonal changes in mite communities (Acari: Mesostigmata) in decomposing litter of broadleaved and coniferous temperate tree species

Key messageWe identified the effect of microclimatic conditions on soil mite communities (Mesostigmata) during the decomposition of broadleaved and coniferous litter. The abundance, species richness, and diversity of mite communities decreased from spring to autumn regardless of litter quality and was related to changes in temperature and precipitation.ContextLitter decomposition is one of the fundamental soil-supporting processes in terrestrial ecosystems. However, there is still a lack of knowledge on some general patterns of the relationships between litter quality (tree species), microclimate, and structure of soil mite assemblages.AimsThe study aimed to analyze the impact of climatic conditions (temperature and precipitation) on mesostigmatid mite communities in the litter of 11 tree species through the vegetation season.MethodsThe experiment tested litter decomposition of 11 different tree species (693 litterbags), for seven consecutive months (April-October) under homogenous Scots pine (Pinus sylvestris L.) canopy monocultures in common garden conditions. Soil mites were extracted in Tullgren funnels.ResultsMesostigmatid mite abundance was positively correlated with the temperature of the sampling month and negatively with the temperature of the previous month. Species richness depended on the sampling month temperature. Changes in litter mass loss in late autumn (after litterfall) and overwinter were important for colonization of litterbags by soil mesostigmatid mites in the following spring.ConclusionsChanges in climatic conditions, i.e., temperature and precipitation between the sampling months (during the following vegetation period), may cause significant changes in mesostigmatid mite abundance and thus may impact ecosystem functions. The winter period is important for mesostigmatid mite abundance in the following vegetation period.

Transient Flooding and Soil Covering Interfere with Decomposition Dynamics of Populus euphratica Leaf Litter: Changes of Mass Loss and Stoichiometry of C, N, P, and K

Litter decomposition plays a critical role in carbon and nutrient cycling in terrestrial and aquatic ecosystems. However, the effects transient flooding and soil covering have on leaf litter decomposition remain unclear. The changes of litter mass loss and stoichiometric ratio of C:N (the ratio of carbon to nitrogen), C:K (the ratio of carbon to potassium), C:P (the ratio of carbon to phosphorus), N:P (the ratio of nitrogen to phosphorus), and N:K (the ratio of nitrogen to potassium) of fresh Populus euphratica (P. euphratica) leaves in surface, transient flooding, and soil covering treatments were studied using litterbags in a desert riparian forest in a field decomposition experiment for a period of 640 d. The results showed that there was a significant influence of disturbance type and incubation time on litter mass loss rate and stoichiometric ratios of C:N, C:K, C:P, N:P, and N:K of fresh P. euphratica leaves, but no significant influence of the interaction between disturbance type and incubation time on leaf litter mass loss. In three treatments, five sequential phases of leaf litter mass loss rate and different temporal change patterns of stoichiometric ratio were identified within 640 d. Transient flooding was shown to affect P. euphratica leaf litter mass loss phases compared to that in no-disturbance conditions, and especially promote leaf litter mass loss within 0–173 d of incubation time. It was also demonstrated that transient flooding and soil covering can influence leaf litter decomposition, which led to the leaf litter mass loss rate and the stoichiometric ratios of C:N, C:K, C:P, N:P, and N:K exhibiting varied patterns and phases in different treatments during decay.

Seasonal variation in the coupling of microbial activity and leaf litter decomposition in a boreal stream network

Abstract Most stream networks are characterised by spatial and temporal variability in the physico‐chemical conditions that regulate microbial processing of particulate organic matter. How these patterns control the turnover of particulate organic matter via altered activity of leaf‐associated microbes has rarely been studied in high‐latitude landscapes, particularly throughout long (i.e., up to 6 months) ice‐ and snow‐covered periods. We investigated development of fungal biomass, enzyme activity, microbial respiration, and birch leaf litter decomposition from autumn to early summer in 11 nested streams in a boreal catchment that encompass a gradient in wetland (mire) cover. We observed relatively low variability in decomposition rates across the network, despite differences in key physical and chemical variables (e.g. temperature, pH, and dissolved organic carbon [DOC] concentrations) over time and space. Microbial enzymatic activity and respiration were positively related to leaf litter decomposition rates during early stages of decomposition (i.e., up to c. 30% loss of initial ash‐free dry mass). Thereafter, variation in microbial activity and respiration was decoupled from leaf litter mass loss, as enzymatic activity and respiration instead became positively related to DOC concentrations and upstream mire (wetland) cover among streams. Our results suggest that leaf‐associated microbes increase their reliance on external sources of energy over time. This switch in resource use was more evident in streams with higher DOC concentration, which in boreal landscapes is largely determined by mire cover. Hence, variation in DOC concentration, linked to landscape configuration, or from intensified land use and climate change, could affect how different carbon sources are used by stream microbial communities, with consequences for overall carbon cycling in boreal headwaters.

Soil fauna drives vertical redistribution of soil organic carbon in a long-term irrigated dry pine forest.

Summer droughts strongly affect soil organic carbon (SOC) cycling, but net effects on SOC storage are unclear as drought affects both C inputs and outputs from soils. Here, we explored the overlooked role of soil fauna on SOC storage in forests, hypothesizing that soil faunal activity is particularly drought‐sensitive, thereby reducing litter incorporation into the mineral soil and, eventually, long‐term SOC storage.In a drought‐prone pine forest (Switzerland), we performed a large‐scale irrigation experiment for 17 years and assessed its impact on vertical SOC distribution and composition. We also examined litter mass loss of dominant tree species using different mesh‐size litterbags and determined soil fauna abundance and community composition.The 17‐year‐long irrigation resulted in a C loss in the organic layers (−1.0 kg C m−2) and a comparable C gain in the mineral soil (+0.8 kg C m−2) and thus did not affect total SOC stocks. Irrigation increased the mass loss of Quercus pubescens and Viburnum lantana leaf litter, with greater effect sizes when meso‐ and macrofauna were included (+215%) than when excluded (+44%). The enhanced faunal‐mediated litter mass loss was paralleled by a many‐fold increase in the abundance of meso‐ and macrofauna during irrigation. Moreover, Acari and Collembola community composition shifted, with a higher presence of drought‐sensitive species in irrigated soils. In comparison, microbial SOC mineralization was less sensitive to soil moisture. Our results suggest that the vertical redistribution of SOC with irrigation was mainly driven by faunal‐mediated litter incorporation, together with increased root C inputs.Our study shows that soil fauna is highly sensitive to natural drought, which leads to a reduced C transfer from organic layers to the mineral soil. In the longer term, this potentially affects SOC storage and, therefore, soil fauna plays a key but so far largely overlooked role in shaping SOC responses to drought.

Predominant role of air warming in regulating litter decomposition in a Tibetan alpine meadow: A multi-factor global change experiment

Alpine ecosystems worldwide are experiencing multi-faceted climate changes, but the interactive effects of these drivers on litter decomposition are poorly understood. Here, we examined the effects of air warming, nitrogen (N) addition and altered precipitation, and their interactions on litter decomposition originating from four species (Elymus nutans, Kobresia capillifolia, Thermopsis lanceolata, Saussurea nigrescens) in a Tibetan alpine meadow. Among the three factors, air warming by open top chambers (OTCs) significantly decreased all litter decomposition except for K. capillifolia with the highest C:N ratio over one-year field decomposition. The reduced litter mass loss in the chambered plots was mainly attributed to OTC-induced decrease in soil temperature, with more negative effects of OTC on litter decomposition in winter and spring than in summer. However, N addition offset the negative effects of OTC on litter mass loss of K. capillifolia, likely by alleviating N limitation to this poor-quality litter decomposition. In addition, simulated precipitation increase promoted decomposition of high-quality litter (T. lanceolata and S. nigrescens) in the dry winter, likely by alleviating water stress. Together, our findings highlight the predominant role of climate in controlling litter decomposition in alpine ecosystems.

Response of litter decomposition and the soil environment to one-year nitrogen addition in a Schrenk spruce forest in the Tianshan Mountains, China

Human activities have increased the input of nitrogen (N) to forest ecosystems and have greatly affected litter decomposition and the soil environment. But differences in forests with different nitrogen deposition backgrounds. To better understand the response of litter decomposition and soil environment of N-limited forest to nitrogen deposition. We established an in situ experiment to simulate the effects of N deposition on soil and litter ecosystem processes in a Picea schrenkiana forest in the Tianshan Mountains, China. This study included four N treatments: control (no N addition), low N addition (LN: 5 kg N ha−1 a−1), medium N addition (MN: 10 kg N ha−1 a−1) and high N addition (HN: 20 kg N ha−1 a−1). Our results showed that N addition had a significant effect on litter decomposition and the soil environment. Litter mass loss in the LN treatment and in the MN treatment was significantly higher than that in the control treatment. In contrast, the amount of litter lost in the HN treatment was significantly lower than the other treatments. N application inhibited the degradation of lignin but promoted the breakdown of cellulose. The carbon (C), N, and phosphorus (P) contents of litter did not differ significantly among the treatments, but LN promoted the release of C and P. Our results also showed that soil pH decreased with increasing nitrogen application rates, while soil enzyme activity showed the opposite trend. In addition, the results of redundancy analysis (RDA) and correlation analyses showed that the soil environment was closely related to litter decomposition. Soil enzymes had a positive effect on litter decomposition rates, and N addition amplified these correlations. Our study confirmed that N application had effects on litter decomposition and the soil environment in a N-limited P. schrenkiana forest. LN had a strong positive effect on litter decomposition and the soil environment, while HN was significantly negative. Therefore, increased N deposition may have a negative effect on material cycling of similar forest ecosystems in the near future.

Impact of tree litter identity, litter diversity and habitat quality on litter decomposition rates in tropical moist evergreen forest

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. 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. 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. 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.

典型冷暖季沉水植物凋落物分解特性及沉积物微生物群落变化

PDF HTML阅读 XML下载 导出引用 引用提醒 典型冷暖季沉水植物凋落物分解特性及沉积物微生物群落变化 DOI: 10.5846/stxb202106281715 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家水体污染控制与治理科技重大专项（2018ZX07110003）；国家自然科学基金项目（31670467） Decomposition characteristics of typical warm season and cold season submerged plant litters and change of microbial community in sediment Author: Affiliation: Fund Project: National Major Science and Technology Program-“Water Body Pollution Control and Remediation” (2018ZX07110003), National Natural Science Foundation of China (31670467) 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为研究湿地沉水植物腐败分解对水体的污染状况，选择典型沉水植物金鱼藻（暖季植物）和菹草（冷季植物）进行了为期60 d的凋落物分解实验。结果表明金鱼藻和菹草凋落物分解规律相似，0-15 d快速分解，15-60 d缓慢分解，60 d凋落物失重率分别达到60.43%和66.72%。菹草的有机物释放量明显高于金鱼藻，N和P释放量相反，分解释放的N主要是NH+4-N和有机氮。三维荧光光谱（EEMs）结合平行因子分析法解析出一种类色氨酸物质C2和3种类腐殖质物质C1、C3、C4，易降解的类色氨酸有机物先增加后减少，难降解的类富里酸和类腐殖酸有机物逐渐增加。EEMs和四种组分的最大荧光强度百分比表明，溶解性有机物（DOM）在0-15 d以易降解有机物为主，15-60 d以难降解有机物为主。两种植物凋落物分解释放的DOM含量及特性不同，整体上呈低腐殖化特征，可能是水中难降解DOM的一个重要来源。植物凋落物的分解促进了沉积物中微生物的丰富度，降低了微生物的多样性；参与分解的主要微生物包括4 d时的Pseudomonas属（26%-35%）、15 d和30 d时的Malikia属（>8%）和Bacillus属（2.6%-9%），分解难降解有机物的微生物逐渐增加，如Flavobacterium属；沉积物中微生物群落结构的变化受营养物质可利用性变化的影响。分析发现植物凋落物分解对水质的影响具有阶段性，0-15 d，N和P释放量增加暂时导致了水质恶化；15-60 d，N和P释放量降低，难降解有机物含量逐渐增加，可能会加剧水体甚至是沉积物的腐殖化程度。因此，在植物衰亡期应及时打捞或者做好植物平衡收割管理，避免因植物大量腐败导致水质恶化。 Abstract:In order to study the pollution of submerged plant litter decomposition in wetland, a 60-days litter decomposition experiment was carried out with typical submerged plants, including Ceratophyllum demersum L. (warm season plant) and Potamogeton crispus L. (cold season plant). The results showed that decomposition process of both plant litters was similar, a fast decomposition from 0 to 15 d followed by slow decomposition from 15 to 60 d. The mass loss of plant litters on 60 d reached 60.43% and 66.72%, respectively. More organic matters were obviously released from Potamogeton crispus L. than those from Ceratophyllum demersum L., while nitrogen and phosphorus release was the opposite. The nitrogen released was mainly ammonia nitrogen and organic nitrogen. Excitation emission matrix parallel factor analysis identified four kinds of fluorescence components:tryptophan-like C2, and three kinds of humus-like C1, C3, C4. The easily biodegradable tryptophan-like organic matters increased first and then decreased, while the difficult biodegradable fulvic acid-like and humic acid-like organic matters increased gradually. Three-dimensional fluorescence spectra and the maximum fluorescence intensity percentages of the four components showed that dissolved organic matter (DOM) was dominated by easily degradable organic compounds during 0-15 d and by refractory organic compounds during 15-60 d. The contents and characteristics of DOM released during the decomposition of plant litters were different, showing a low humification feature on the whole, which may be an important endogenous source of difficult biodegradable DOM in water. The decomposition of plant litters improved the microbial richness and decreased the microbial diversity in sediments. The main microorganisms included Pseudomonas (26%-35%) at 4 d, Malikia (>8%) and Bacillus (2.6%-9%) at 15 d and 30 d for decomposition, while the microorganisms that decomposed the refractory organic matter increased gradually, such as Flavobacterium. Changes in microbial community structure in sediments were influenced by changes in the availability of nutrients. The results showed that the effects of plant litter decomposition on water quality were phased. The release nitrogen and phosphorus increased during 0-15 d, which led to the deterioration of water quality temporarily; during 15-60 d, nitrogen and phosphorus release decreased, while refractory organic matter content increased gradually, which may exacerbate the humification degree of water and even sediment. Therefore, in the decay period of plant litters, it is necessary to salvage plant litters in time or manage plant harvesting rationally to avoid the deterioration of water quality caused by plant litter decay. 参考文献 相似文献 引证文献

Intra-annual colonization of Chironomidae on leaf litter in a Brazilian Cerrado stream

In low-order streams, the processing of allochthonous leaf litter is essential in the carbon/energy flow dynamics. Benthic macroinvertebrates, such as chironomids, play critical roles in the breakdown of allochthonous materials, because their larvae take part in intricate trophic networks and have varied trophic ecologies. We evaluated the effects of intra-annual variability on the input of allochthonous leaf litter, and the interactions of leaf-detritus on the succession of Chironomidae assemblages in the dry, rainy, and transition seasons (rainy-dry and dry-rainy). The study took place in a stream in the Brazilian Cerrado. Leaves were incubated in the stream to ascertain the colonization process by Chironomidae and the loss of leaf litter mass after 90 days. Functional feeding groups (FFG) were less rich and less abundant in the dry and dry-rainy seasons, than in the other seasons. The FFG composition of Chironomidae demonstrated that temporal variation between seasons was affected by the exposure time of the leaf-detritus in the stream, and there was more segregation during the dry and rainy seasons. In conclusion, the colonization of leaf-detritus by Chironomidae larvae depended on how long allochthonous plant material remained in the stream, and the variability of the organic matter dynamics input into the stream.

Tree Diversity, Initial Litter Quality, and Site Conditions Drive Early-Stage Fine-Root Decomposition in European Forests

Decomposition of dead fine roots contributes significantly to nutrient cycling and soil organic matter stabilization. Most knowledge of tree fine-root decomposition stems from studies in monospecific stands or single-species litter, although most forests are mixed. Therefore, we assessed how tree species mixing affects fine-root litter mass loss and which role initial litter quality and environmental factors play. For this purpose, we determined fine-root decomposition of 13 common tree species in four European forest types ranging from boreal to Mediterranean climates. Litter incubations in 315 tree neighborhoods allowed for separating the effects of litter species from environmental influences and litter mixing (direct) from tree diversity (indirect). On average, mass loss of mixed-species litter was higher than those of single-species litter in monospecific neighborhoods. This was mainly attributable to indirect diversity effects, that is, alterations in microenvironmental conditions as a result of tree species mixing, rather than direct diversity effects, that is, litter mixing itself. Tree species mixing effects were relatively weak, and initial litter quality and environmental conditions were more important predictors of fine-root litter mass loss than tree diversity. We showed that tree species mixing can alter fine-root litter mass loss across large environmental gradients, but these effects are context-dependent and of moderate importance compared to environmental influences. Interactions between species identity and site conditions need to be considered to explain diversity effects on fine-root decomposition.

Effect of metal pollution from mining on litter decomposition in streams

Litter decomposition is critical to stream biogeochemical cycles. Metal pollution from past or present mining activities seriously threatens stream ecosystems. However, its effects on litter decomposition in streams remain unclear. A field litterbag experiment was conducted to determine the direct (i.e., via changes in stream water quality: a mine-affected vs. forest stream) and indirect (i.e., via changes in litter traits: polluted vs. non-polluted litter) effects of metal pollution from mining activities on leaf litter decomposition (total vs. microbial-driven) and the associated microbial activity and community composition in streams. Platanus acerifolia leaf litter collected from a polluted and a non-polluted site was enclosed in fine and coarse mesh bags and incubated in a mine-affected stream and a forest stream. The litter from the polluted site had a higher Pb, Zn, Cd, N, soluble sugar concentrations, specific leaf area and pH, and lower leaf toughness and lignin concentration than the litter from the non-polluted site. After incubation in situ, litter mass loss did not significantly differ between streams, but the mine-affected stream had a greater impact on total-driven decomposition rates than microbial-driven decomposition rates. Polluted litter had a significantly higher decomposition rate than non-polluted litter. The decomposition potential of polluted litter produces faster nutrient cycling and supports higher microbial colonization. Litter traits and decomposer community type modulate the influence of metal pollution on litter decomposition. The results suggest that the indirect effects of mining activities on litter decomposition were stronger than the direct effects.

Role of soil fauna to litter decomposition in pine stands under Atlantic Forest biome

Litter production and its decomposition play an important role in the terrestrial carbon cycle and soil quality, being a crucial process involved in ecosystem productivity and functioning. Understanding this process under pine commercial stands or pine invasions is crucial to design forest management or ecosystems restoration. We conducted a study in a commercial pine plantation (Pinus taeda L.) under Atlantic Forest biome to investigate (1) the contribution of soil fauna to pine litter mass loss; (2) the litter fauna feeding activity within seasons. Litter bags with pine needles (5 g dry weight) were prepared as exclusion treatments for different sized soil fauna by varying mesh size (2 mm and 0.06 mm). Litter bags were removed after 60, 120, 180, 240, 300, and 365 days to estimate the decomposition rates. Bait lamina sticks were exposed seasonally and horizontally in soil surface to determine the fauna feeding activity on litter. We found: (1) no differences in litter mass loss and decomposition rate when soil macrofauna and most of the mesofauna were excluded; (2) feeding activity of litter organisms was higher in the summer, probably stimulated by a combination of high temperature and rainfall. In commercial pine stands, we can conclude that the nutrient cycling is slower than in natural areas, related to litter traits, as described in the scientific literature. Our results indicated that soil macro and mesofauna play a low role in the pine litter decomposition, where the organic material decomposition is more related to microorganism’s activity.