Litter Decomposition Experiment Research Articles

A Case Study Demonstrates That the Litter of the Rare Species Cinnamomum migao Composed of Different Tissues Can Affect the Chemical Properties and Microbial Community Diversity in Topsoil

The decomposition of litter plays an important role in the return of forest soil nutrients, as well as the growth and productivity of plants. With this study, we aimed to determine the impact of litter mulching on different tissues of Cinnamomum migao, a rare Chinese endemic species. In particular, seeds and pericarp are easily overlooked components of C. migao litter. In this study, we tested control (uncovered litter) and litter (leaf, branch, seed, and pericarp) mulching conditions and conducted a one-year litter decomposition experiment. The enzyme activities of urease enzyme (UE) and invertase enzyme (INV) were significantly improved by litter mulching. Catalase (CAT) enzyme activities in leaf, branch, and seed litter mulching were lower than in the control, whereas CAT activity in pericarp mulching was significantly higher than in the control. Although Mortierella, Cladophialophora, Acidothermus, Sphingomonas, and Burkholderia were the dominant microbes of topsoil in different mulching treatments, there were differences in the number and connectivity of microbial communities, and this change was correlated with soil organic carbon (SOC) and CAT enzyme activity. Compared with leaves and branches, seeds and pericarp as litter are also very important for nutrient return and affect topsoil microbes in C. migao forest, which may be of significance for the growth feedback of C. migao in biennial bearing.

Tree species identity and mixing ratio affected the release of several metallic elements from mixed litter in coniferous-broadleaf plantations in subtropical China

Planting broadleaf trees in coniferous forests has been shown to promote biogeochemical cycling in plantations; however, how species mixing influences litter decomposition and release of metallic elements from mixed coniferous-broadleaf litter remains unclear. An in situ litter decomposition experiment was conducted to examine the effect of 1) a mixture from coniferous litter (Pinus massoniana) with different individual broadleaved litter (Bretschneidera sinensis, Manglietia chingii, Cercidiphyllum japonicum, Michelia maudiae, Camellia oleifera) and 2) their mixing ratio (mass ratios of coniferous and broadleaf litter of 5:5, 6:4 and 7:3) on the release of metallic elements [calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), manganese (Mn), iron (Fe), copper (Cu) and zinc (Zn)] during litter decomposition. We found that the identity of the broadleaf tree species in the mixed litter and the mixing ratio affected the release rates of metallic elements (p < 0.05). After one year of decomposition, K, Mg, Mn and Zn were released, while Na, Ca, Fe and Cu accumulated in the mixed litter. Mixing increased the release of K, Ca, Na, Mg, Fe, Mn, Cu and Zn in more than one-third of the samples, but inhibited the release of K, Fe and Mn in less than 14% of the samples. Increasing the mixing ratio of coniferous to broadleaf litter enhanced the release of Na, Fe, Mn and Zn but decreased the release of Ca and Mg. Overall, these results highlight that mixed litter, particularly tree species identity and mixing ratio, can alter the release and enrichment of metallic elements during litter decomposition, thereby affecting the cycling of metallic elements in plantations with different species compositions.

Home-Field Advantage of Litter Decomposition Faded 8 Years after Spruce Forest Clearcutting in Western Germany

Home-field advantage (HFA) encompasses all the processes leading to faster litter decomposition in the ‘home’ environment compared to that of ‘away’ environments. To determine the occurrence of HFA in a forest and adjacent clear-cut, we set up a reciprocal litter decomposition experiment within the forest and clear-cut for two soil types (Cambisols and Gleysols) in temperate Germany. The forest was dominated by Norway spruce (Picea abies), whereas forest regeneration of European Beech (Fagus sylvatica) after clearcutting was encouraged. Our observation that Norway spruce decomposed faster than European beech in 70-yr-old spruce forest was most likely related to specialized litter-soil interaction under existing spruce, leading to an HFA. Elevated soil moisture and temperature, and promoted litter N release, indicated the rapid change of soil-litter affinity of the original spruce forest even after a short-term regeneration following clearcutting, resulting in faster beech decomposition, particularly in moisture- and nutrient-deficient Cambisols. The divergence between forest and clear-cut in the Cambisol of their litter δ15N values beyond nine months implied litter N decomposition was only initially independent of soil and residual C status. We conclude that clearcutting modifies the litter-field affinity and helps promote the establishment or regeneration of European beech in this and similar forest mountain upland areas.

Decreased ultraviolet radiation and decomposer biodiversity inhibit litter decomposition under continuous nitrogen inputs

Abstract Atmospheric nitrogen (N) deposition has altered biogeochemical cycles and ecosystem functioning. As a key process involved in carbon and nutrient cycles in terrestrial ecosystems, litter decomposition is sensitive to external N inputs. However, it remains unclear how the interactions of ultraviolet (UV) radiation, soil biodiversity (bacteria, fungi and invertebrates) and conventional drivers (e.g. litter chemistry and microbial activities) regulate the responses of litter decomposition to continuous N inputs. Based on a multilevel N addition experimental platform, we conducted a 2‐year litter decomposition experiment to examine the relative importance of N‐induced changes in biotic and abiotic factors in mediating changes in the decomposition rates of four litter types (three representative species and their mixture) along an experimental N gradient in a Tibetan alpine steppe. Our results showed that litter decomposition rates exhibited a consistent decrease in response to N enrichment among all species and their mixture. The slowed decomposition rates with increasing N addition were associated with N‐induced reductions in UV radiation and soil bacterial diversity. An additional UV radiation manipulative experiment further confirmed that photodegradation had strong effects on plant litter decomposition at our study site. These results demonstrated that N‐induced declines in UV radiation and soil bacterial diversity inhibited litter decomposition, challenging the traditional view that changes in litter chemistry and microbial activities determine the responses of litter decomposition to external N inputs. Read the free Plain Language Summary for this article on the Journal blog.

Influence of rhizosphere activity on litter decomposition in subtropical forest: implications of estimating soil organic matter contributions to soil respiration

AbstractLitter decomposition plays an important role in the carbon cycle and is affected by many factors in forest ecosystems. This study aimed to quantify the rhizosphere priming effect on litter decomposition in subtropical forest southwestern China. A litter decomposition experiment including control and trenching treatments was conducted using the litter bag method, and the litter decomposition rate was calculated by litter dry mass loss. Trenching did not change soil temperature, but increased the soil water content by 14.5%. In this study, the interaction of soil temperature and soil water content controlled the litter decomposition rate, and explained 87.4 and 85.5% of the variation in litter decomposition in the control and trenching treatments, respectively. Considering changes in soil environmental factors due to trenching, the litter decomposition rates were corrected by regression models. After correction, the litter decomposition rates of the control and trenching treatments were 32.47 ± 3.15 and 25.71 ± 2.72% year–1, respectively, in the 2-year period. Rhizosphere activity significantly primed litter decomposition by 26.3%. Our study suggested a priming effect of rhizosphere activity on litter decomposition in the subtropical forest. Combining previous interaction effect results, we estimated the contributions of total soil organic matter (SOM) decomposition, total litter decomposition, and root respiration to soil respiration in the subtropical forest, and our new method of estimating the components of soil respiration provided basic theory for SOM decomposition research.

The afterlife of herbaceous plant species: A litter decomposition experiment in a temperate oak-hornbeam forest

Understanding the mechanisms of singular species and their traits impacts on ecosystem functions, is crucial in the era of unprecedented anthropogenic changes of the environment, e.g. to predict changes in carbon and nutrient cycling connected with species shifts. It may allow us to take protective measurements and mitigate the negative effects of global changes. Litter decomposition is a crucial process shaping nutrient cycling in ecosystems. Studies on decomposition in forest ecosystems are mainly limited to foliar litter. In contrast to woody plant species, our knowledge of decomposition of herbaceous plants is scarce. Thus, unanswered questions remain about the model that best describes the decomposition process of herbaceous plants. The relationship of decomposition rate to functional traits is unknown for this species pool. We used the litter bag method to determine the decomposition rate of 13 herbaceous plant species and four overstory tree species growing in a temperate oak-hornbeam forest. We showed that the litter decomposition rate and C and N release were higher in spring ephemerals than summer green herbaceous species, as the plants with small total individual aboveground biomass (TAB) and small total leaf area (TLA) decomposed the fastest. Our results demonstrate that in this generally acquisitive group of plants, size traits have a stronger impact on decomposition than economic traits. For almost all species, the two-phase exponential decay model explains the course of herbaceous species litter decomposition only slightly better than the single exponential model.

Stronger effect of litter quality than micro‐organisms on leaf and root litter C and N loss at different decomposition stages following a subtropical land use change

Abstract Litter decomposition contributes largely to global carbon (C) and nitrogen (N) cycling, and it is strongly determined by litter quality and microbial community composition in ways that are poorly understood. Here, we conducted a 2‐year field litter decomposition experiment by collecting leaf and root litter of crops (from cropland), shrubs (from shrubland) and wood (from woodland) and placing samples for decomposition in woodland soil in central China to investigate the effects of litter quality and microbial community composition on C and N losses of leaf and root litter of three species under different decomposition stages. Our results showed that the leaf litter C and N losses of shrubs were significantly higher than those of crops and wood, whereas the root litter C and N losses of crops were significantly higher than those of shrubs and wood. Generally, the leaf litter C and N losses of the three species were higher on average than those of fine root litter during the whole decomposition period. For the C loss of the three species, litter lignin and phosphorus as well as initial litter quality were predominant drivers of root litter decomposition, while litter lignin, cellulose and hemicellulose concentrations were dominant for leaf litter decomposition. For N loss, litter stoichiometry and litter quality directly governed leaf and root litter N loss, and the initial litter quality largely regulated N loss at the late decomposition stage. Unexpectedly, the effect of microbial community composition on litter C and N losses was relatively weak and only exhibited an effect on litter C and N losses during the early stage of decomposition. Thus, our results revealed the huge disparity in C and N loss of plant species and litter types at different decomposition stages, which should be considered jointly when evaluating their roles in plant–soil feedbacks under global land use change. A free Plain Language Summary can be found within the Supporting Information of this article.

长白山苔原带凋落物生态化学计量特征及其对模拟氮沉降的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 长白山苔原带凋落物生态化学计量特征及其对模拟氮沉降的响应 DOI: 10.5846/stxb202110212976 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（41571078） Response of chemical composition and ecological stoichiometric characteristics of three types of litter to simulated nitrogen deposition in the Changbai Mountain tundra Author: Affiliation: Fund Project: The National Natural Science Foundation of China (General Program, Key Program, Major Research Plan) 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:长白山苔原是我国乃至欧亚大陆东部独有的高山苔原，根据前人调查植被以灌木苔原为主要类型。在全球变暖背景下，近30年来，长白山岳桦林下的草本植物侵入苔原带，原生灌木苔原分化为灌木苔原、灌草苔原和草本苔原，形成了灌木、灌草混合和草本3种不同类型的凋落物，凋落物数量和质量发生显著改变。与此同时长白山苔原氮沉降量也在逐年增加，导致了土壤中氮的累积，势必影响凋落物的分解。凋落物作为连接植物和土壤的纽带，其分解过程中碳（C）、氮（N）、磷（P）等化学组分和化学计量比的变化直接和间接影响着土壤养分有效性和植物养分利用策略。为揭示氮沉降增加对长白山苔原带不同类型凋落物化学组分及生态化学计量特征早期变化的影响，开展了为期8个月的模拟氮沉降室内凋落物分解实验。在苔原带采集灌木优势种牛皮杜鹃和草本优势种小叶章的凋落物带回实验室，模拟灌木牛皮杜鹃群落、灌草混合的牛皮杜鹃-小叶章群落和草本小叶章群落的3种不同类型凋落物，设置三个施氮处理：对照（CK，0 g N m-2 a-1）、低氮（LN，10 g N m-2 a-1）、高氮（HN，20 g N m-2 a-1）。研究表明：（1）不施氮处理时，3种凋落物的C、P均呈释放状态，木质素（Li）呈先累积再略有降解趋势；牛皮杜鹃凋落物的N元素富集而其余两种凋落物N元素呈释放状态；灌草混合和草本凋落物比原生的灌木凋落物C和N元素释放快、Li累积少；而灌木凋落物的P释放略快于灌草和草本凋落物。3种植被类型凋落物的C/N、C/P、Li/N大小表现为：牛皮杜鹃凋落物>牛皮杜鹃-小叶章混生群落凋落物>小叶章凋落物；N/P表现为：小叶章凋落物>牛皮杜鹃凋落物>牛皮杜鹃-小叶章混生群落凋落物。（2）氮沉降促进3种类型凋落物分解过程中C、N和P化学组分的释放，且氮浓度越高促进作用越显著。在牛皮杜鹃凋落物分解过程中，氮素添加到达某一阈值后，其C/N、C/P、N/P、Li/N的降幅最大，后续若再增加氮素，其对化学计量比的影响均会减弱；本实验中的氮素添加量增加促进了小叶章凋落物的C/N、Li/N下降。（3）草本植物入侵引起凋落物类型的变化带来凋落物分解加快，将导致长白山苔原带养分循环的变化；氮沉降增加对小叶章凋落物化学组分的释放及C/N、Li/N的下降更为促进，小叶章凋落物内难分解化合物减少，分解受到促进。高氮沉降加快了小叶章凋落物与土壤、草本植物之间的养分循环。因此，随着未来苔原带氮沉降量的增加，将更有利于小叶章在与牛皮杜鹃的竞争中获胜，使苔原带呈现草甸化趋势。 Abstract:The Changbai Mountain tundra is the only typical alpine tundra of eastern China and eastern Eurasia. In the recent 30 years, herbaceous plants have invaded from low altitude to the alpine tundra, which transformed shrub tundra to shrub-herb-mixed tundra and herb tundra, causing significant changes to the litter components. To understand the response of chemical composition and ecological stoichiometric characteristics of three types of litter to simulated nitrogen deposition in the Changbai Mountain tundra, an artificial simulated litter decomposition experiment was designed and conducted. Rhododendron aureum (native dominant shrub species) litter, Deyeuxia angustifolia (invasion herb species) litter and Rhododendron aureum-Deyeuxia angustifolia-mixed litter collected from the Changbai alpine tundra were used to set up nitrogen addition experiment at three levels under laboratory condition:control group (CK:without nitrogen addition), low N level group (LN:10 g N m-2 a-1)), and high N level group (HN:20 g N m-2 a-1)). Then we collected litter after decomposition and measured the content of C, N, P and lignin (Li), aiming to study the differences of chemical composition and ecological stoichiometric characteristics of the litter with different components and nitrogen addition levels. The results showed that:(1) Without nitrogen addition, the content of C and P in the litter reduced significantly while the content of Li increased at the beginning and then reduced; the content of N in the R. aureum litter increased significantly while the content of N in the R. aureum litter and the mixed litter reduced. C/N, C/P, Li/N of the litter of three types decreased by R. aureum>R. aureum-D. angustifolia-mixed>D. angustifolia; N/P of the litter of three types decreased by D. angustifolia>R. aureum> R. aureum-D. angustifolia-mixed. (2) The simulated nitrogen deposition promoted the release of nutrients during decomposition process and the promoting effects of high nitrogen addition turned out to be more significant. C/N, C/P, N/P, Li/N of the R. aureum litter decreased rapidly at a certain nitrogen addition threshold then the effects on ecological stoichiometric characteristics would be weakened if more nitrogen was added. In our study, high nitrogen addition promoted the decline of C/N and Li/N of the D. angustifolia litter. (3) Change of litter components caused by herbaceous species invasion would promote the decomposition of litter and affect the nutrient cycle mechanisms of Changbai Mountain alpine tundra. As nitrogen deposition increased, the contents of C, N, P, Li and C/N, Li/N of the D. angustifolia litter decreased further and refractory compounds decreased. Nitrogen deposition accelerated nutrients cycle between the D. angustifolia litter, soils and herbaceous plants. Thus, we suggest that the increase of nitrogen deposition will be more favorable to the win of D. angustifolia in the competition with R. aureum, which will impulse meadowization trend in the Changbai Mountain alpine tundra. 参考文献 相似文献 引证文献

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

Litter decomposition rates across tropical montane and lowland forests are controlled foremost by climate

AbstractThe “hierarchy of factors” hypothesis states that decomposition rates are controlled primarily by climatic, followed by biological and soil variables. Tropical montane forests (TMF) are globally important ecosystems, yet there have been limited efforts to provide a biome‐scale characterization of litter decomposition. We designed a common litter decomposition experiment replicated in 23 tropical montane sites across the Americas, Asia, and Africa and combined these results with a previous study of 23 sites in tropical lowland forests (TLF). Specifically, we investigated (1) spatial heterogeneity in decomposition, (2) the relative importance of biological factors that affect leaf and wood decomposition in TMF, and (3) the role of climate in determining leaf litter decomposition rates within and across the TMF and TLF biomes. Litterbags of two mesh sizes containing Laurus nobilis leaves or birchwood popsicle sticks were spatially dispersed and incubated in TMF sites, for 3 and 7 months on the soil surface and at 10–15 cm depth. The within‐site replication demonstrated spatial variability in mass loss. Within TMF, litter type was the predominant biological factor influencing decomposition (leaves &gt; wood), with mesh and burial effects playing a minor role. When comparing across TMF and TLF, climate was the predominant control over decomposition, but the Yasso07 global model (based on mean annual temperature and precipitation) only modestly predicted decomposition rate. Differences in controlling factors between biomes suggest that TMF, with their high rates of carbon storage, must be explicitly considered when developing theory and models to elucidate carbon cycling rates in the tropics.Abstract in Spanish is available with online material.

No Difference in Instream Decomposition Among Upland Agricultural and Forested Streams in Kenya

Expansion of agriculture is particularly worrying in tropical regions of the world, where native forests have been replaced by croplands and grasslands, with severe consequences for biodiversity conservation and ecosystem functioning. However, limited data exist on the effects of agriculture on the functioning of tropical streams. We conducted a leaf litter decomposition experiment in coarse- and fine-mesh litterbags using the three species of leaves (Eucalyptus globulus [non-native], Vernonia myriantha, and Syzygium cordatum [indigenous]) in three forested and agricultural streams to determine the effect of agriculture on instream leaf litter decomposition in headwater stream sites. We also examined the functional composition of macroinvertebrates in the streams through the contents of benthic kick samples. Agricultural streams had a less dense riparian canopy and smaller abundance of coarse organic particulate matter, and higher electric conductivity and suspended solids than forested streams. In terms of the effects of litter quality on decomposition rates, Vernonia had the fastest decomposition rates while Eucalyptus had the slowest in both forested and agricultural sites. Shredder invertebrates were less abundant in agricultural streams, and in both stream types, they were less diverse and abundant than other functional groups. Overall, leaf litter decomposition rates did not respond to agricultural land-use. The hypothesized negative effects of agriculture on organic matter processing were minimal and likely modulated by intact riparian zones along agricultural streams.

Effects of temperature increase and nitrogen addition on the early litter decomposition in permafrost peatlands

As one kind of the most important carbon (C) sink in the world, peatlands are sensitive to climate change. The decomposition of litter plays an important role in C fixation and nutrient utilization in peatlands. To reveal the mechanism of response of the litter decomposition to climate warming and the addition of nitrogen (N) in permafrostpeatlands, we selected two typical plants, Eriophorumvaginatum and Sphagnumpalustre, in the permafrost peatland of Da Xing’anling Mountains, China, as the research objects and conducted a 54-day litter decomposition experiment at 10 ℃ and 20 ℃. Three N addition treatments (CK: 0 mg N g−1, N1: 2.5 mg N g−1, and N2: 5 mg N g−1) were established. Our results showed that the E. vaginatum litter decomposed more quickly than that of Sphagnum, and an increase in temperature significantly promoted the litter decomposition and CO2 emission of E. vaginatum and Sphagnum. The addition of N promoted the decomposition of E. vaginatum litter, whereas the decomposition of Sphagnum litter was promoted by the N1 treatment but was inhibited by the N2 treatment. The enzyme activity in both types of litter was inhibited with the increase in temperature. The abundances of bacteria and fungi positively correlated with the decomposition constant and mean CO2 release rate by E. vaginatum and Sphagnum litter, indicating that the effects of temperature and N addition on the decomposition of plant litter were primarily regulated by microorganisms. This study provides a theoretical basis to understand and predict the effects of global climate change on the decomposition of plant litter in boreal peatlands.

Forest soil acidification consistently reduces litter decomposition irrespective of nutrient availability and litter type

Abstract Nitrogen (N), phosphorus (P) and acid deposition are co‐occurring in many ecosystems, likely with complex interactive effects on litter decomposition. Few studies have been conducted to distinguish the interactive effects of these three factors on forest litter decomposition. Thus, we performed a 5‐year litter decomposition experiment with N, P, acid addition in a temperate forest of Changbai Mountain in China, including four litter types from Pinus koraiensis, Quercus mongolica, Tilia amurensis and their mixtures. Our results showed that acid addition consistently reduced litter decomposition rate, irrespective of nutrient addition or litter types. In contrast, N and P addition had less impact on litter decomposition. Litter decomposition rate linearly reduced with decreasing soil pH, but positively increased with soil N availability. No relationship was found between soil P availability and litter decomposition. Soil enzyme activity played a key role in regulating litter decomposition response, such as acid phosphatase, xylosidase, N‐cacetyl‐b‐D‐glucosaminidase and α‐1,4 glucosidase. Besides, low‐quality litter (i.e. high C concentration, C:N and C:P ratio) amplified the negative effect of soil acidification on litter decomposition. This study suggests that soil acidification consistently decelerates litter decomposition in temperate forests, which is independent of soil nutrient availability and litter types. The intensifying soil acidification with continuous N deposition in the future will greatly reduce litter nutrient return to soil, increasing the risk of multiple soil nutrient limitation. A free Plain Language Summary can be found within the Supporting Information of this article.

Effects of exogenous N and endogenous nutrients on alpine tundra litter decomposition in an area of high nitrogen deposition

The effects of N deposition on the C and N cycles via altered litter decomposition rates are an important aspect of global environmental change. The Changbai Mountain region experienced a high N deposition (2.7 g·m−2·year−1 in 2015) and corresponding expansion of Deyeuxia purpurea into the alpine tundra, resulting in changes in endogenous nutrients. However, the relative contributions of the N deposition and endogenous litter nutrients to litter decompositions remain unclear. Therefore, a 5-year N addition and 2-year litter decomposition experiments were conducted. Exogenous N reduced the remaining litter mass of Rhododendron aureum at the early stage (30–240 d) by promoting soluble sugar release, and increased it at the late stage (360–720 d) by suppressing lignin release and decreasing soil microbial community and enzyme activity. A higher proportion of D. purpurea litter (representing higher N, lower lignin, and C:N ratio) decreased remaining litter mass and increased net N release. Exogenous N decreased decomposition rate from 0.32 to 0.21 and net N release from 34% to 24%, whereas litter compositions increased decomposition rates from 0.32 to 0.69 and net litter N release from 34% to 69%. Endogenous litter nutrients directly explained 62% and 40% of the litter decomposition and net N release variables, respectively, whereas exogenous N indirectly explained 12% and 9%, respectively. Thus, we infer that the reductions in C and N storage following D. purpurea expansion may offset the increases of C and N storage under N deposition and the expansion of D. purpurea has a potential long-term negative impact on the ability of tundra plants to sequester C and N in the alpine tundra of the Changbai Mountains. These findings highlight how shifting plant expansion, through changes endogenous nutrients, can influence tundra litter decomposition and C and N storage responses to N deposition.

Soil fauna modulates the effect of experimental drought on litter decomposition in forests invaded by an exotic pathogen

Abstract Litter decomposition is a fundamental process for nutrient cycling and C fluxes between terrestrial ecosystems and the atmosphere. Multiple factors such as environmental conditions, litter quality and decomposer organisms are known to influence this ecological process in direct and indirect ways. However, it remains poorly understood to what extent this entangled bank of complex interactions can be disrupted by several global change drivers such as climate change and invasive species. Here we reported main findings from a litter decomposition experiment conducted in a natural mixed forest invaded by Phytophthora cinnamomi, an exotic oomycete well known for causing tree disease and forest decline. In two Mediterranean forest types (namely woodland and closed forest), we first built a rainfall exclusion infrastructure to reduce natural precipitation by 30%. Then, we followed the spatial variation in C and N leaf litter dynamics as well as the abundance of the exotic oomycete P. cinnamomi for 18 months under both control and rainfall exclusion conditions using a litter bag methodology with different mesh sizes to further evaluate the indirect role of mesofauna abundance and diversity in litter C and N temporal dynamics. Significant reductions in soil moisture produced by the experimental rainfall exclusion increased C litter loss with time directly, and indirectly via increases in overall mesofauna abundance and changes in the ratio between predators and decomposers. N litter dynamics were in contrast modulated mainly by initial litter quality. Surprisingly, P. cinnamomi abundance did not correlate with variation in initial litter quality as previously suggested, but we found that the exotic oomycete was negatively correlated with both decomposer and predator abundances. These results suggest it might participate indirectly in litter decomposition dynamics through the biotic soil component. Synthesis. Contrary to expected, our results show that a moderate but realistic rainfall reduction can accelerate the litter decomposition process. It also points out to litter fauna as a key component modulating the indirect impacts of global change drivers on litter decomposition.

Visualizing the transfer of organic matter from decaying plant residues to soil mineral surfaces controlled by microorganisms

The interface between decaying plant residues and soil minerals represents an essential soil microenvironment at which soil organic matter forms. The high amount of microbial products and residues within this hot spot of microbial activity fosters the formation of mineral-associated organic matter. Besides classical quantitative analyses, our understanding of processes controlling soil organic matter formation greatly benefits from microscopic observations and measurements, which provide spatially resolved information at a meaningful scale for microbial processes and for the association between organic and mineral particles. We studied carbon and nitrogen transfer from fresh-plant residues to the mineral soil, through a litter decomposition experiment in an artificial soil mixture. Needles of Norway spruce (Picea abies L.) were placed in microbatch containers filled with an artificial soil mixture free of soil organic matter. Containers were buried in fresh organic layer material from a Norway spruce stand and incubated for 14 and 42 days. We applied nanoscale secondary ion mass spectroscopy (NanoSIMS) to investigate the spatial distribution of mineral and organic compounds at the needle vicinity and into the mineral soil (0–550 μm from the needle). After 14 days, we depicted the formation of mineral-associated organic matter in the surrounding of the decaying needles. After 42 days, we observed substantial colonization of the needles and the detritusphere by saprotrophic fungi. The fungal hyphae extended into the mineral matrix of the artificial soil acting as vectors for the transfer of litter-derived carbon and nitrogen into the bulk soil. This resulted in an increase of the area covered by organic matter in the detritusphere, with up to 10% of the total investigated area classified as organic matter closely associated with mineral surfaces. Our results provide evidence that the carbon and nitrogen derived from litter decomposition transformed by microorganisms is transferred as mineral-associated organic matter, heterogeneously distributed from the litter source, and still detected 550 μm away from the latter. The close association of newly formed soil organic matter and fine sized minerals suggests that the formation of mineral-associated OM and likely also microaggregates is directly driven by microbial activity in the vicinity of hot spots for plant carbon input (e.g. the detritusphere).

Volatilome of Aleppo Pine litter over decomposition process.

Biogenic Volatile Organic Compounds (BVOC) are largely accepted to contribute to both atmospheric chemistry and ecosystem functioning. While the forest canopy is recognized as a major source of BVOC, emissions from plant litter have scarcely been explored with just a couple of studies being focused on emission patterns over litter decomposition process. The aim of this study was to quantitatively and qualitatively characterize BVOC emissions (C1–C15) from Pinus halepensis litter, one of the major Mediterranean conifer species, over a 15‐month litter decomposition experiment. Senescent needles of P. halepensis were collected and placed in 42 litterbags where they underwent in situ decomposition. Litterbags were collected every 3 months and litter BVOC emissions were studied in vitro using both online (PTR‐ToF‐MS) and offline analyses (GC‐MS). Results showed a large diversity of BVOC (58 compounds detected), with a strong variation over time. Maximum total BVOC emissions were observed after 3 months of decomposition with 9.18 µg gDM −1 hr−1 mainly composed by terpene emissions (e.g., α‐pinene, terpinolene, β‐caryophyllene). At this stage, methanol, acetone, and acetic acid were the most important nonterpenic volatiles representing, respectively, up to 26%, 10%, and 26% of total emissions. This study gives an overview of the evolution of BVOC emissions from litter along with decomposition process and will thus contribute to better understand the dynamics and sources of BVOC emission in Mediterranean pine forests.

Network analysis and subsequent culturing reveal keystone taxa involved in microbial litter decomposition dynamics

Plant litter decomposition in the soil is governed by microorganisms such as bacteria and fungi that colonize lignocellulose residues during the decomposition process, and thus, the interplay of bacterial and fungal communities can yield insight into the lignocellulose decomposition dynamics. Previous studies have mainly investigated litter decomposing communities in microcosms or ex-situ conditions or at a single soil ecosystem. Here we conducted a 12 week-long litter decomposition experiment to explore how the temporal dynamics of soil enzyme activities and microbial communities are linked to litter decomposition under three different land use sites (forestland, farmland, and abandoned farmland) in Nanjing, China. We found that litter decomposition in the forestland was the highest among the three land use sites. Then, using a multifactorial approach, we showed that this higher decomposition rate in forest soils is determined by microbial communities with higher ligninolytic enzyme activities, higher diversity, and a less complex but more specialized network. Chryseobacterium in bacteria, and Fusarium, Aspergillus and Penicillium in fungi were the keystone taxa in networks across three land use types. We conducted subsequent culturing that further confirmed the strong decomposition ability and enzyme activities of these taxa, indicating their importance for microbial litter decomposition. As such, this is one of the first studies to validate the role of keystone taxa for litter decomposition, and it demonstrates that co-occurrence network scores can be used for statistical identification of putative keystone taxa for further screening and linking to microbiome functioning. Overall, we show that land use alters the composition and network structure of soil microbiota that determine the litter decomposition. Our study also reveals that specialized keystone taxa are involved in the decomposition dynamics, and highlights an opportunity of harnessing such taxa for manipulating lignocellulose decomposition in soil ecosystems.

Litter decomposition in European coniferous and broadleaf forests under experimentally elevated acidity and nitrogen addition

Atmospheric sulfur (S) and nitrogen (N) deposition has impacted many regions across the Northern Hemisphere inducing acidification and eutrophication of terrestrial ecosystems. However, acidification and eutrophication processes may differently impact litter decomposition and thus soil carbon (C) dynamics. We performed a field soil chemistry manipulation in two mountainous temperate forest stands (Picea abies and Fagus sylvatica) historically affected by acid (S and N) deposition. In each stand, four treatments were established: control, acid addition (H2SO4 – 50 kg S·ha− 1·year− 1), N addition (NH4NO3 – 50 kg N·ha− 1·year− 1) and their combination. In fourth year of manipulation, we established litter decomposition experiment. Litter bags of contrasting quality and origin (green tea, rooibos tea, spruce needles and beech leaves), in total 1536 samples, were buried below the organic layer and left to decompose up to 24 months. Retrieved samples were analysed for mass loss, C/N, and concentration of CuO oxidation lignin. Data were complemented by monitoring soil water pH and soil CO2 efflux. Acid additions decreased soil water pH, soil respiration and suppressed decomposition of the high-quality litter (green tea) in both stands, whereas mass loss of remaining litter was reduced only in the spruce stand. Nitrogen treatments, when coupled with decreasing soil water pH, constrained needle decomposition in the naturally more acidic spruce stand. Our study demonstrates a suppressing effect of soil acidity on decomposition processes and soil C dynamics. The effect of N addition, as a nutrient, was insignificant, likely because of previous ecosystem adaptation to historical N loadings.

The decomposition rates of leaf litter and fine root and their temperature sensitivities are influenced differently by biotic factors

Determining the temperature sensitivities of the decomposition rates of leaf litter and fine root is important for predicting the impact of climate warming on above- and belowground carbon (C) cycles in forest ecosystems. However, the responses of leaf and root decomposition rates to temperature have rarely been examined together. Here, we present the results of paired leaf litter and fine root decomposition experiments at four forest sites spanning 32° latitude in eastern China. The mean annual soil temperature explained the variances of the decomposition rates of the leaf litter (kLeaf, R2 = 0.95) and fine root (kFine root, R2 = 0.86) across the different biomes well and exerted a positive effect on the kLeaf: kFine root ratio. As a result, the sensitivity of the decomposition rate to temperature was significantly higher in the leaf litter (Q10 = 2.17 ± 0.07) than in the fine root (Q10 = 1.40 ± 0.06). The results of structural equation models indicated that the initial C:nitrogen (C:N) ratio exhibited negative effects, and phosphorus (P) cycling related enzymes activity exhibited positive effects on the kFine root when the effects of temperature were controlled. Even when the variables of these biotic factors were added, the soil temperature still exerted a dominant effect on the kLeaf. Our results suggest that temperature directly influences the kLeaf but indirectly affects the kFine root through litter quality and soil decomposers.