Litter Manipulation Research Articles

Urea addition and litter manipulation alter plant community and soil microbial community composition in a Kobresia humilis meadow

Overgrazing and climate change strongly affect alpine meadows by decreasing the plant community biomass and deteriorating the soil environment. To understand how the plant community and soil microbial community structure respond to grazing and N deposition, we conducted an experiment to remove or maintain the plant litter under the chronic addition of N in the Haibei Alpine Meadow in 2005. The experiment included four treatments: added N (+N, 20 g m−2) with the litter removed (LR), +N with the litter left intact (LI), LI without N addition (−N), and LR with −N. Soil samples were collected at depths of 0–10 and 10–20 cm, and the following parameters were measured: 1) aboveground biomass (AGB) and litter biomass and 2) microbial community composition and content. Overall, the AGB and litter biomass significantly increased by 45.85% and 50.42% in response to N addition, whereas litter removal increased the AGB by 52.96%. The addition of urea N significantly decreased the PLFA content of the bacterial, gram-positive (G+), gram-negative (G−) at a soil of 0–10 cm in the LI and LR treatments by 64.87%, 61.82%, 76.07% and 64.86%, 53.02%, 51.44%, respectively. However, the PLFA content of the bacterial increased from 37.09 to 53.54 nmol g−1 and from 37.09 to 62.05 nmol g−1 at a depth of 10–20 cm for the +N + LI and +N + LR treatments compare to the LR+(−)N treatment, respectively. In addition, the total PLFAs in the LR+(−)N treatment significantly increased by 50.61% at a depth of 0–10 cm but decreased from 121.62 to 42.31 nmol g−1 at a depth of 10–20 cm relative to the LI+(−)N treatment. Using PLFA as a biomarker, we detected that G− bacteria and total PLFA generally increased with increasing soil depth in the +N plots. However, the content of G− was the highest at a depth of 0–10 cm and the lowest at a depth of 10–20 cm in the LR plots. The modification of soil microbial biomass at a depth of 0–10 cm was induced by the bottom-up effect of changes in soil nutrient contents and using ability, which were driven by N addition and litter manipulation. Thus, different soil depths with different soil nutrient conditions resulted in a strong microbial community composition gradient.

Oxygen isotope ratios of plant available phosphate in lowland tropical forest soils

Phosphorus (P) cycles rapidly in lowland tropical forest soils, but the process have been proven difficult to quantify. Recently it was demonstrated that valuable data on soil P transformations can be derived from the natural abundance of stable oxygen isotopes in phosphate (δ18OP). Here, we measured the δ18OP of soils that had received long-term nutrient additions (P, nitrogen, and potassium) or litter manipulations in lowland tropical forest in Panama and performed controlled incubations of fresh soils amended with a single pulse of P. To detect whether δ18OP values measured in the incubations apply also for soils in the field, we examined the δ18OP values after rewetting dry soils. In the incubations, resin-P δ18OP values converged to ∼3.5‰ above the expected isotopic equilibrium with soil water. This contrasts with extra-tropical soils in which the δ18OP of resin-P matches the expected equilibrium with soil water. Identical above-equilibrium resin-P δ18OP values were also found in field soils that did not receive P additions or extra litter. We suggest that the 3.5‰ above-equilibrium δ18OP values reflect a steady state between microbial uptake of phosphate (which enriches the remaining phosphate with the heavier isotopologues) and the release of isotopically equilibrated cell internal phosphate back to the soil. We also found that soil nutrient status affected the microbial turnover rate because in soils that had received chronic P addition, the original δ18OP signature of the fertilizer was preserved for at least eight weeks, indicating that the off-equilibrium δ18OP values produced during microbial phosphate turnover was not imprinted in these soils. Overall, our results demonstrate that ongoing microbial turnover of phosphate mediates its biological availability in lowland tropical soils.

Soil extracellular enzyme activities are sensitive indicators of detrital inputs and carbon availability

In a litter manipulation experiment in a temperate deciduous oak forest in Central Europe, we examined soil carbon contents and density fractions, as well as β-glucosidase and polyphenol oxidase enzyme activities, which play central roles in the degradation of litter and soil organic matter. Our measurements were taken in the DIRT (detritus input and removal treatments) plots, where manipulations include doubling of leaf litter or woody debris inputs, as well as removal of litter, trenching to prevent root inputs, and removal of all litter inputs. After 10 years of manipulation, soil C content did not vary predictably among plots, although the amount of light fraction material was greater in control and litter addition plots compared to litter removal plots. Even after 10 years of litter addition, there were no significant differences in activities of either enzyme in double litter plots compared to control plots, a result consistent with other observed measures of microbial activity. However, removal of roots and litter caused significant decreases in β-glucosidase activities very quickly, and these differences increased over time. However, polyphenol oxidase activities were not significant different among treatments. Enzyme activities were not correlated with total soil carbon contents, but activities of both enzymes were significantly and positively related to the amount of light fraction carbon, suggesting that enzymes respond to increases in labile carbon availability.

Strong stoichiometric resilience after litter manipulation experiments; a case study in a Chinese grassland

Abstract. Global climate change has generally modified net primary production (NPP) which leads to increasing litter inputs in some ecosystems. Therefore, assessing the impacts of increasing litter inputs on soil nutrients, plant growth and ecological carbon (C) : nitrogen (N) : phosphorus (P) stoichiometry is critical for an understanding of C, N and P cycling and their feedback processes to climate change. In this study, we added plant above-ground litter, harvested near the experimental plots, to the 10–20 cm subsoil layer of a steppe community at rates equivalent to annual litter input of 0, 15, 30, 60 and 120%, respectively, covering the entire range of the expected NPP increases in this region due to climate change (10–60%). We measured the resulting C, N and P content of different pools (above- and below-ground plant biomass, litter, microbial biomass). Small litter additions, which are more plausible compared to the expected increase predicted by Earth system models, had no effect on the variables examined. Nevertheless, high litter addition (120% of the annual litter inputs) significantly increased soil inorganic N and available P, above-ground biomass, below-ground biomass and litter. Our results suggest that while very high litter addition can strongly affect C : N : P stoichiometry, the grassland studied here is resilient to more plausible inputs in terms of stoichiometric functioning.

Effects of long-term litter manipulation on soil carbon, nitrogen, and phosphorus in a temperate deciduous forest

Changes in above-ground litterfall can influence below-ground biogeochemical processes in forests. In order to examine how above-ground litter inputs affect soil carbon (C), nitrogen (N) and phosphorus (P) in a temperate deciduous forest, we studied a 14-year-old small-scale litter manipulation experiment that included control, litter exclusion, and doubled litter addition at a mature Fagus sylvatica L. site. Total organic C (TOC), total N (TN) and total P (TP), total organic P (TOP), bioavailable inorganic P (Pi), microbial C, N and P, soil respiration and fine root biomass were analyzed in the A and in two B horizons. Our results showed that litter manipulation had no significant effect on TOC in the mineral soil. Litter addition increased the bioavailable Pi in the A horizon but had no significant effect on N in the mineral soil. Litter exclusion decreased TN and TP in the B horizon to a depth of 10 cm. In the A horizon of the litter exclusion treatment, TP, TOP and bioavailable Pi were increased, which is most likely due to the higher root biomass in this treatment. The high fine root biomass seems to have counteracted the effects of the excluded aboveground litter. In conclusion, our study indicates that aboveground litter is not an important source for C in the mineral soil and that P recycling from root litter might be more important than from above-ground litter.

Priming of soil organic matter decomposition scales linearly with microbial biomass response to litter input in steppe vegetation

Fresh plant litter inputs accelerate soil organic matter (SOM) decomposition through a ubiquitous mechanism called priming. Insufficient priming has been suggested as a stabilization mechanism of SOM at depth, as well as the long‐term persistence of some highly degradable organic compounds in soils. Priming therefore plays a crucial, albeit unquantified and commonly neglected, role in the global carbon cycle. Because priming intensity is likely to be altered by global change‐induced changes in net primary productivity, it casts substantial uncertainty to future projections of the climate‐carbon cycle feedback. Using results from a large field litter manipulation experiment in Mongolian steppe, we here show that priming intensifies with increasing litter inputs, but at a decreasing efficiency: the stimulation per unit litter added declines with increasing litter inputs. This non‐linear behavior originates from two antagonistic responses to fresh litter inputs: a stimulation of microbial activity versus a shift in microbial community composition (more fungi) associated to substrate shift from SOM to litter. Despite all complexity, however, the priming effect on SOM decomposition scaled linearly with the response of microbial biomass across the entire range of plant litter addition (60–480 g C m−2), suggesting that priming could be modeled effectively as a function of the response of microbial biomass to litter inputs. Incorporating the priming mechanism in Earth System models will improve their estimates of the SOM‐climate feedback and appears to be best addressed by explicitly representing microbial biomass in the models.

Increasing Red Maple Leaf Litter Alters Decomposition Rates and Nitrogen Cycling in Historically Oak-Dominated Forests of the Eastern U.S.

Without canopy-opening fire disturbances, shade-tolerant, fire-sensitive species like red maple (Acer rubrum L.) proliferate in many historically oak-dominated forests of the eastern U.S. Here, we evaluate potential implications of increased red maple dominance in upland oak forests of Kentucky on rates of leaf litter decomposition and nitrogen (N) cycling. Over 5 years, we evaluated mass loss of leaf litter and changes in total N and carbon (C) within six leaf litter treatments comprised of scarlet oak, chestnut oak, and red maple, and three mixed treatments of increasing red maple contribution to the leaf litter pool (25, 50, and 75% red maple). Over a 1.5-year period, we conducted a plot-level leaf litter manipulation study using the same treatments plus a control and assessed changes in net nitrification, ammonification, and N mineralization within leaf litter and upper (0–5 cm depth) mineral soil horizons. Red maple leaf litter contained more “fast” decomposing material and initially lost mass faster than either oak species. All litter treatments immobilized N during initial stages of decomposition, but the degree of immobilization decreased with decreasing red maple contribution. The leaf litter plot-level experiment confirmed slower N mineralization rates for red maple only plots compared to chestnut oak plots. As red maple increases, initial leaf litter decomposition rates will increase, leading to lower fuel loads and more N immobilization from the surrounding environment. These changes may reduce forest flammability and resource availability and promote red maple expansion and thereby the “mesophication” of eastern forests of the U.S.

Effects of litter manipulation in a tropical Eucalyptus plantation on leaching of mineral nutrients, dissolved organic nitrogen and dissolved organic carbon

Although many studies have shown that soil solution chemistry can be a reliable indicator of biogeochemical cycling in forest ecosystems, the effects of litter manipulations on the fluxes of dissolved elements in gravitational soil solutions have rarely been investigated. We estimated the fluxes of NH4-N, NO3-N, K, Ca, Mg, Na, Cl, dissolved organic nitrogen (DON) and dissolved organic carbon (DOC) over the first two years after re-planting Eucalyptus trees in the coastal area of Congo. Two treatments were replicated in two blocks after clear-cutting 7-year-old stands: in treatment R, all the litter above the mineral soil was removed before planting, and in a double slash (DS) treatment, the amount of harvest residues was doubled. The soil solutions were sampled down to a depth of 4m and the water fluxes were estimated using the Hydrus 1D model parameterized from soil moisture measurements in 4 plots. Isotopic and spectroscopic analytical techniques were used to assess the changes in dissolved organic matter (DOM) properties throughout the transfer in the soil. The first year after planting, the fluxes of NH4-N, K, Ca, Mg, Na, Cl and DOC in the topsoil of the DS treatment were 2–5 times higher than in R, which showed that litter was a major source of dissolved nutrients. Nutrient fluxes in gravitational solutions decreased sharply in the second year after planting, irrespective of the soil depth, as a result of intense nutrient uptake by Eucalyptus trees. Losses of dissolved nutrients were noticeably low in these Eucalyptus plantations despite a low cation exchange capacity, a coarse soil texture and large amounts of harvest residues left on-site at the clear cut in the DS treatment. All together, these results clarified the strong effect of litter manipulation observed on eucalypt growth in Congolese sandy soils. DOM fluxes, as well as changes in δ13C, C:N and aromaticity of DOM throughout the soil profile showed that the organic compounds produced in the litter layer were mainly consumed by microorganisms or retained in the topsoil. Below a depth of 15cm, most of the DOC and the DON originated from the first 2cm of the soil and the exchanges between soil solutions and soil organic matter were low.

Effects of litter manipulation on litter decomposition in a successional gradients of tropical forests in southern China.

Global changes such as increasing CO2, rising temperature, and land-use change are likely to drive shifts in litter inputs to forest floors, but the effects of such changes on litter decomposition remain largely unknown. We initiated a litter manipulation experiment to test the response of litter decomposition to litter removal/addition in three successional forests in southern China, namely masson pine forest (MPF), mixed coniferous and broadleaved forest (MF) and monsoon evergreen broadleaved forest (MEBF). Results showed that litter removal decreased litter decomposition rates by 27%, 10% and 8% and litter addition increased litter decomposition rates by 55%, 36% and 14% in MEBF, MF and MPF, respectively. The magnitudes of changes in litter decomposition were more significant in MEBF forest and less significant in MF, but not significant in MPF. Our results suggest that change in litter quantity can affect litter decomposition, and this impact may become stronger with forest succession in tropical forest ecosystem.

Combined effects of nitrogen addition and litter manipulation on nutrient resorption of Leymus chinensis in a semi‐arid grassland of northern China

Plant growth in semi-arid ecosystems is usually severely limited by soil nutrient availability. Alleviation of these resource stresses by fertiliser application and aboveground litter input may affect plant internal nutrient cycling in such regions. We conducted a 4-year field experiment to investigate the effects of nitrogen (N) addition (10 g N·m(-2) ·year(-1)) and plant litter manipulation on nutrient resorption of Leymus chinensis, the dominant native grass in a semi-arid grassland in northern China. Although N addition had no clear effects on N and phosphorus (P) resorption efficiencies in leaves and culms, N fertilisation generally decreased leaf N resorption proficiency by 54%, culm N resorption proficiency by 65%. Moreover, N fertilisation increased leaf P resorption proficiency by 13%, culm P resorption proficiency by 20%. Under ambient or enriched N conditions, litter addition reduced N and P resorption proficiencies in both leaves and culms. The response of P resorption proficiency to litter manipulation was more sensitive than N resorption proficiency: P resorption proficiency in leaves and culms decreased strongly with increasing litter amount under both ambient and enriched N conditions. In contrast, N resorption proficiency was not significantly affected by litter addition, except for leaf N resorption proficiency under ambient N conditions. Furthermore, although litter addition caused a general decrease of leaf and culm nutrient resorption efficiencies under both ambient and enriched N conditions, litter addition effects on nutrient resorption efficiency were much weaker than the effects of litter addition on nutrient resorption proficiency. Taken together, our results show that leaf and non-leaf organs of L. chinensis respond consistently to altered soil N availability. Our study confirms the strong effects of N addition on plant nutrient resorption processes and the potential role of aboveground litter, the most important natural fertiliser in terrestrial ecosystems, in influencing plant internal nutrient cycling.

Changes to particulate versus mineral-associated soil carbon after 50 years of litter manipulation in forest and prairie experimental ecosystems

Models of ecosystem carbon (C) balance generally assume a strong relationship between NPP, litter inputs, and soil C accumulation, but there is little direct evidence for such a coupled relationship. Using a unique 50-year detrital manipulation experiment in a mixed deciduous forest and in restored prairie grasslands in Wisconsin, combined with sequential density fractionation, isotopic analysis, and short-term incubation, we examined the effects of detrital inputs and removals on soil C stabilization, destabilization, and quality. Both forested sites showed greater decline in bulk soil C content in litter removal plots (55 and 66 %) compared to increases in litter addition plots (27 and 38 % increase in surface soils compared to controls). No accumulation in the mineral fraction C was observed after 50 years of litter addition of the two forested plots, thus increases in the light density fraction pool drove patterns in total C content. Litter removal across both ecosystem types resulted in a decline in both free light fraction and mineral C content, with an overall 51 % decline in mineral-associated carbon in the intermediate (1.85–2.4 g cm−3) density pool; isotopic data suggest that it was preferentially younger C that was lost. In contrast to results from other, but younger litter manipulation sites, there was with no evidence of priming even in soils collected after 28 years of treatment. In prairie soils, aboveground litter exclusion had an effect on C levels similar to that of root exclusion, thus we did not see evidence that root-derived C is more critical to soil C sequestration. There was no clear evidence that soil C quality changed in litter addition plots in the forested sites; δ13C and Δ14C values, and incubation estimates of labile C were similar between control and litter addition soils. C quality appeared to change in litter removal plots; soils with litter excluded had Δ14C values indicative of longer mean residence times, δ13C values indicative of loss of fresh plant-derived C, and decreases in all light fraction C pools, although incubation estimates of labile C did not change. In prairie soils, δ13C values suggest a loss of recent C4-derived soil C in litter removal plots along with significant increases in mean residence time, especially in plots with removal of roots. Our results suggest surface mineral soils may be vulnerable to significant C loss in association with disturbance, land use change, or perhaps even climate change over century–decadal timescales, and also highlight the need for longer-term experimental manipulations to study soil organic matter dynamics.

Plant litter effects on soil nutrient availability and vegetation dynamics: changes that occur when annual grasses invade shrub-steppe communities

Changes in the quantity and quality of plant litter occur in many ecosystems as they are invaded by exotic species, which impact soil nutrient cycling and plant community composition. Such changes in sagebrush-steppe communities are occurring with invasion of annual grasses (AG) into a perennial grass (PG) dominated system. We conducted a 5-year litter manipulation study located in the northern Great Basin, USA. Springtime litter was partially or completely removed in three communities with differing levels of invasion (invaded, mixed, and native) to determine how litter removal and litter biomass affected plant-available soil N and plant community composition. Litter biomass (prior to the removal treatment) was negatively correlated with plant-available N in the invaded community, but was positively correlated in the native community. Plant-available N had greater intra- and inter-annual fluctuations in the invaded compared to the mixed or native communities, but was not generally affected by removal treatments. Litter removal had negative effects on AG cover during a warm/dry year and negative effects on PG cover during a cool/wet year in the mixed community. Overall, the effectiveness of springtime litter manipulations on plant-available N were limited and weather dependent, and only removal treatments >75 % had effects on the plant community. Our study demonstrates how communities invaded by AGs have significantly increased temporal variability in nutrient cycling, which may decrease ecosystem stability. Further, we found that the ecological impacts from litter manipulation on sagebrush communities were dependent on the extent of AG invasion, the timing of removal, and seasonal precipitation.

亚热带杉木和米老排人工林土壤呼吸对凋落物去除和交换的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 亚热带杉木和米老排人工林土壤呼吸对凋落物去除和交换的响应 DOI: 10.5846/stxb201309092240 作者: 作者单位: 湿润亚热带山地生态国家重点实验室培育基地;福建师范大学地理科学学院,湿润亚热带山地生态国家重点实验室培育基地;福建师范大学地理科学学院,湿润亚热带山地生态国家重点实验室培育基地;福建师范大学地理科学学院,湿润亚热带山地生态国家重点实验室培育基地;福建师范大学地理科学学院,湿润亚热带山地生态国家重点实验室培育基地;福建师范大学地理科学学院,湿润亚热带山地生态国家重点实验室培育基地;福建师范大学地理科学学院,福建农林大学林学院,湿润亚热带山地生态国家重点实验室培育基地;福建师范大学地理科学学院 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（41371269）；教育部新世纪优秀人才支持计划（DB-168）；福建省杰出青年科学基金项目（2060203） Contrasting responses of soil respiration to litter manipulation in subtropical Mytilaria laosensis and Cunninghamia lanceolata plantations Author: Affiliation: College of Geographical Science, Fujian Normal University,College of Geographical Science, Fujian Normal University,,,,,, Fund Project: 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:在我国亚热带地区米老排（Mytilaria laosensis）和杉木（Cunninghamia lanceolata）人工林中设置去除凋落物、交换凋落物和对照3种处理，利用LI-8100对不同处理土壤呼吸速率进行为期14个月的连续观测。结果表明：与对照相比，去除和交换凋落物导致米老排人工林CO2年排放量显著减少29.8%和14.2%，杉木人工林则分别减少6.1%和增加37.8%。两种林分交换凋落物处理产生了不同程度的激发效应，米老排凋落物相对于杉木凋落物具有更大的激发效应。不同处理土壤呼吸速率均与土壤温度呈显著指数关系，与土壤含水量呈负相关，土壤温度和含水量的回归模型可以分别解释米老排人工林中去除、交换和对照处理土壤呼吸速率的68.9%、77.0%和69.6%，杉木人工林的53.0%、36.2%和63.8%。两种林分不同处理土壤呼吸速率与土壤可溶性有机碳含量、微生物生物量碳含量以及主要微生物种群生物量显著相关。米老排人工林去除和交换凋落物处理均降低了土壤呼吸的温度敏感性Q10值，而杉木林中仅去除凋落物降低了Q10值。研究表明，土壤呼吸对凋落物输入方式改变的响应因树种而异，这种差异与凋落物输入的数量和质量及其对土壤易变性有机碳含量和微生物生物量的影响有关。 Abstract:Future climate change is expected to alter the primary productivity of forest ecosystems, and thus potentially change the quality and quantity of aboveground litter inputs which could affect soil carbon emission and sequestration. A litter manipulation experiment was carried out in 19-year-old Mytilaria laosensis and Cunninghamia lanceolata plantations replanted in C.lanceolata woodland in subtropical China between January 2012 and February 2013. Three treatments including litter exclusion, reciprocal litter transplant and control were conducted within 2 m ×2 m plots in randomized block design. Soil respiration rate (Rs) were measured monthly by Li-Cor 8100 and soil temperature and soil moisture were also monitored. The results showed that Rs subject to three treatments exhibited similar seasonal patterns in M.laosensis and C.lanceolata plots. The average Rs in litter exclusion, litter transplant and control treatments were 1.79, 2.18, 2.45μmol CO2 m-2 s-1 in M.laosensis plots and 1.77, 2.29, 1.90μmol CO2 m-2 s-1 in C.lanceolata plots, respectively. Overall, litter exclusion and transplant significantly decreased the annual fluxes under M.laosensis plots by 29.8% and 14.2%, respectively. Litter exclusion caused a slight decline in annual flux but litter transplant markedly increased the annual flux by 37.8% in C.lanceolata plots. Using the decay constants of the two litter species in a reciprocal litter transplant decomposition experiment, priming effects were calculated as the amount of litter-derived respiration minus decomposed carbon from litter. Results showed that M.laosensis litter aroused higher priming effect than C.lanceolata litter, suggesting that the quantity and quality of litter input caused by different tree species could result in different below-ground responses. Correlations showed that Rs were exponentially correlated with the soil temperature and negatively correlated with the soil moisture under both M.laosensis and C.lanceolata plots. Non-liner regressions of soil temperature and soil moisture together accounted for 68.9%-77.0% and 36.2%-63.8% of monthly variation in soil respiration in M.laosensis and C.lanceolata plots, respectively, indicating that other factors were responsible for interpreting variations in Rs. The average Rs was significantly correlated to soil dissolved organic carbon concentration (P=0.019) and microbial biomass carbon concentration (P=0.037), which suggests that litter manipulation induced changes in soil labile carbon caused significant effects on Rs. A one time-point measured soil PLFA profiles showed that the average Rs was significantly correlated with the biomass of main signature PLFAs such as fungi (18:1 w9c, 18:2 w6,9c), which may imply that the high quality of litter input could alter soil microbial biomass and thus affect Rs. The temperature sensitivity (Q10) of Rs decreased to 1.86 and 2.05 in the litter exclusion and transplant plots compared to 2.14 in the control plots under M.laosensis plantations. However, the Q10 in the litter exclusion, litter transplanting and control plots were 1.40, 1.52 and 1.52 in C.lanceolata plantations, respectively, which are lower than other studies in subtropical China. In summary, we concluded that the effects of litter manipulation on Rs were dependent on tree species, the contributions of litter toRs. can be attributed to the quantity and quality of litter input, the changes in soil labile carbon and soil microbial biomass in subtropical forest plantations. 参考文献 相似文献 引证文献

Dehydrogenase Activity in a Litter Manipulation Experiment in Temperate Forest Soil

Abstract Soil enzyme activities are “sensors” of soil organic matter (SOM) decomposition since they integrate information about microbial status and physico-chemical condition of soils. We measured dehydrogenase enzyme activity in a deciduous temperate oak forest in Hungary under litter manipulation treatments. The Síkfőkút Detritus Input and Removal Treatments (DIRT) Project includes treatments with doubling of leaf litter and woody debris inputs as well as removal of leaf litter and trenching to prevent root inputs. We hypothesized that increased detrital inputs increase labile carbon substrates to soils and would increase enzyme activities particularly that of dehydrogenase, which has been used as an indicator of soil microbial activity. We also hypothesized that enzyme activities would decrease with detritus removal plots and decrease labile carbon inputs to soil. After ten years of treatments, litter removal had a stronger effect on soil dehydrogenase activity than did litter additions. These results showed that in this forest ecosystem the changed litter production affected soil microbial activity: reduced litter production decreased the soil dehydrogenase activity; increased litter production had no significant effect on the enzyme activity.

Do litter manipulations affect leaf functional traits of savanna woody plants?

Plant litter is the layer composed of dead plant material that covers soil surfaces in terrestrial ecosystems. It is an important pool of essential nutrients for soil and plants, serving also as a protective layer on the soil surface. In this study, we investigated the effects of litter addition and removal on leaf functional traits of woody Neotropical savanna trees. We measured maximum photosynthesis (A max), stomatal conductance (g s), leaf transpiration (E), intrinsic water use efficiency (IWUE), specific leaf area (SLA), and chlorophyll content (CCI) in 15 species belonging to three different phenological groups (evergreen, briefly deciduous, and deciduous species) that were subjected to three distinct litter availability treatments (addition, removal, and control plots) in a Neotropical Savanna site in Brazil. Although SLA and CCI differed among phenology groups, they were not affected by the litter treatments. In contrast, when considered at the community level, we found that the availability of litter affected the leaf traits linked with the water status of the plants (E, g s and IWUE). Plants in the litter removal plots exhibited lower g s and E (25 % of reduction in comparison with control group) but higher IWUE, while plants in the litter addition plots had a 10 % decrease in IWUE but a 12 % increase in g s and E compared with plants in control plots. Savanna woody plants responded promptly to litter manipulation by adjusting leaf water loss, which suggests that in the short term, changes in the amount of litter in Cerrado ecosystems can affect the soil water availability to the plant community.

Variability of above-ground litter inputs alters soil physicochemical and biological processes: a meta-analysis of litterfall-manipulation experiments

Abstract. Global change has been shown to alter the amount of above-ground litter inputs to soil greatly, which could cause substantial cascading effects on below-ground biogeochemical cycling. Despite extensive study, there is uncertainty about how changes in above-ground litter inputs affect soil carbon and nutrient turnover and transformation. Here, we conducted a meta-analysis on 70 litter-manipulation experiments in order to assess how changes in above-ground litter inputs alter soil physicochemical properties, carbon dynamics and nutrient cycles. Our results demonstrated that litter removal decreased soil respiration by 34%, microbial biomass carbon in the mineral soil by 39% and total carbon in the mineral soil by 10%, whereas litter addition increased them by 31, 26 and 10%, respectively. This suggests that greater litter inputs increase the soil carbon sink despite higher rates of carbon release and transformation. Total nitrogen and extractable inorganic nitrogen in the mineral soil decreased by 17 and 30%, respectively, under litter removal, but were not altered by litter addition. Overall, litter manipulation had a significant impact upon soil temperature and moisture, but not soil pH; litter inputs were more crucial in buffering soil temperature and moisture fluctuations in grassland than in forest. Compared to other ecosystems, tropical and subtropical forests were more sensitive to variation in litter inputs, as altered litter inputs affected the turnover and accumulation of soil carbon and nutrients more substantially over a shorter time period. Our study demonstrates that although the magnitude of responses differed greatly among ecosystems, the direction of the responses was very similar across different ecosystems. Interactions between plant productivity and below-ground biogeochemical cycling need to be taken into account to predict ecosystem responses to environmental change.

Responses of litter invertebrate communities to litter manipulation in a Japanese conifer plantation

We examined how the litter invertebrate communities were affected by the temporal changes in the mass and structural complexity of the litter resources by adding and removing litter on the forest floor of a temperate conifer plantation (Cryptomeria japonica) in Japan. We showed that litter mass and depth in the litter-addition (L+) plots changed rapidly into a steady-state condition similar to those in the control plots, mainly due to accelerated decomposition processes during the rainy season. Higher area-based densities of litter invertebrates in the L+ plots, similar mass-based densities between the L+ and control plots, and significant positive correlations between litter mass and the number of individuals implied that the abundance of litter invertebrates would be governed by litter mass rather than by the litter depth. Many litter invertebrates including detritivores were collected even in the litter-removal (L−) area. The relative abundances of invertebrate predators collecting pitfall traps were higher in the L− plots and lower in the L+ plots compared to those in the control plots, whereas those collecting Tullgren funnels were higher in the L+ plots than in the control plots. In the L+ plots, the range of variation in the community compositions among the samples decreased significantly over time in response to a drastic decrease in litter mass, in contrast to the control plots, which showed a relatively constant community composition during the study period. Our litter manipulation experiment reveals some of the mechanisms responsible for maintaining an equilibrium state of forest-floor litter mass and for the responses of litter invertebrate communities to temporal changes in the litter.

Soil microbial biomass, community composition and soil nitrogen cycling in relation to tree species in subtropical China

We investigated microbial biomass and composition (lipid profile), mineral N pools and soil physicochemical parameters in the top 5-cm soils 19 years after reforestation of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) woodland with itself or a native broadleaf species, Mytilaria laosensis. The results suggested that tree species transition had a large impact on microbial biomass and a small impact on the composition of the microbial community as indicated by the relative abundance of individual lipid biomarkers. Between November 2011 and October 2012, there was on average 50% greater microbial biomass carbon (C) measured by the fumigation extraction procedure under M. laosensis than under C. lanceolata. A one-time measurement of phospholipid fatty acids in soil samples collected in May 2012 suggested M. laosensis plots had greater content of individual lipid biomarkers than C. lanceolata plots. Using a litter manipulation experiment, we found that the increases in content of lipid biomarkers under M. laosensis can be attributed to changed litter chemistry. Analysis of soil mineral N pools indicated that there were significantly lower NH4+ and NO3− pools as well as potential net N mineralization rates in M. laosensis soil than in C. lanceolata soil. The relationships among N dynamics, soil chemistry and microbial properties were analysed. The results suggested tree species induced differences in soil N mineralization rates and mineral N pools were related to labile C availability, soil C:N ratio and the composition of the microbial community. Our data of mineral N pools and soil δ15N implied that the transition of land use from C. lanceolata to M. laosensis leads to an enhanced N retention in the plantation.

Litter manipulation and the soil arthropod community in a lowland tropical rainforest

Tropical soil arthropod communities are highly diverse and provide a number of important ecosystem services, including the maintenance of soil structure, regulation of hydrological processes, nutrient cycling and decomposition. Experiments in temperate regions suggest that litter dynamics are important in determining the abundance, richness and community composition of soil fauna, but there is little information for lowland tropical forests. We used a long-term litter manipulation experiment (removing, doubling and control) in a neotropical forest to investigate the consequences of changing litter dynamics on the soil arthropod community. The abundance and biomass of arthropods were reduced significantly by the removal of litter, but not affected by litter addition. Litter manipulation had no effect on simple measures of taxonomic richness or diversity, but multivariate ordination techniques revealed a significant shift in arthropod community composition with the removal, but not addition, of litter. This suggests the overall importance of top-down controls on the arthropod community in this ecosystem, with bottom-up influences only important following the removal of large quantities of litter. Of the parameters measured, the faunal composition of experimental plots was best predicted by litter depth and the concentrations of total carbon and readily-exchangeable phosphorus (in order of importance), highlighting the influential role of soil chemical properties, in addition to the physical properties of litter, in shaping soil arthropod communities. Comparison with the results of a previous study of litter-dwelling fauna in the same litter manipulation experiment suggested that the soil and litter arthropod communities are influenced by different parameters: total carbon and litter depth for the soil community, but sodium and calcium for the litter community, although phosphorus was important in both environments. We conclude that arthropod community composition is controlled by different factors in the soil than in the litter and is affected by decreasing, but not increasing, depth of litter.

Impacts of changed litter inputs on soil CO2 efflux in three forest types in central south China

Climate change is expected to cause the alteration of litter production in forests, which may result in substantial changes in soil CO2 efflux (FCO2) process as litter represents a major pathway of carbon from vegetation to the soils. In this study, we conducted an aboveground litter manipulation experiment to examine the influence of litter addition and exclusion on soil FCO2 in Camphor tree, Masson pine, and mixed Camphor tree and Masson pine forests in central south China. Litter input manipulation included three treatments: non-litter input (litter exclusion), double litter input (litter addition), and natural litter input (control). On average, litter exclusion significantly reduced soil FCO2 rate by approximately 39%, 24% and 22% in Camphor tree forests, the Mixed forests, and Masson pine forests, respectively. On a yearly basis, double litter addition significantly increased soil CO2 by 12% in the Mixed forests (P=0.02) but not in both Camphor tree and Masson pine forests (P>0.05), when compared with their corresponding control treatments. However, litter addition increased soil FCO2 rates in the months of June-August in Camphor tree and Masson pine forests, coinciding with high soil temperature of summer conditions. Litter exclusion reduced soil FCO2 more than litter addition increased it in the study sites. Responses of soil respiration to litter input treatments varied with forest types. Litter input treatments did not alter the seasonal patterns of soil temperature and soil water content. Our results indicated that changes in aboveground litter as a result of global climate change and/or forest management have a great potential to alter soil respiration and soil carbon balance in forest ecosystems.