杉木凋落物及其生物炭对土壤微生物群落结构的影响

以福建建瓯万木林自然保护区内的杉木人工林土壤为研究对象,设置单独添加生物炭、单独添加凋落物以及混合添加凋落物和生物炭处理,进行一年的室内培养实验,研究不同添加物处理对土壤性质及微生物群落结构的影响。结果表明:与对照(S)相比,单独添加凋落物与混合添加凋落物和生物炭均使土壤磷脂脂肪酸(PLFA)总量、真菌丰度以及真菌/细菌比值显著增加;单独添加生物炭与混合添加凋落物和生物炭均使革兰氏阳性细菌/革兰氏阴性细菌比值显著增加。混合添加凋落物和生物炭处理的放线菌丰度显著高于单独添加凋落物处理的。主成分分析表明,不同添加物处理的土壤微生物群落结构存在显著差异;典范对应分析表明,不同添加物处理通过改变土壤p H、全碳、全氮、C/N、可溶性有机碳(DOC)和可溶性有机氮(DON)等性质,进而影响土壤微生物群落结构。     

模拟氮沉降对森林土壤酚类物质和可溶性糖含量的影响

采用野外原位试验模拟氮沉降,研究其对福建建瓯万木林自然保护区杉木林(CUL)、浙江桂(CIC)和罗浮栲林(CAF)3种林分土壤多酚、单宁和可溶性糖含量的影响。每个林分设置对照(CK,0 kg/(hm2·a))、低氮(LN,30 kg/(hm2·a))和高氮(HN,100 kg/(hm2·a))3个处理。结果表明:针叶杉木林土壤多酚含量最高,单宁和可溶性糖含量最低,且均与另两个阔叶树种林分差异显著。杉木和罗浮栲林土壤多酚含量随着氮添加量的增加而显著降低,浙江桂多酚受HN处理影响不大,仅LN处理显著降低49.4%。氮沉降主要表现为降低土壤单宁含量,LN处理分别显著降低杉木林、浙江桂和罗浮栲林单宁含量43.5%、70.0%和79.5%;而HN处理仅降低阔叶林土壤单宁含量。然而,氮沉降增加土壤可溶性糖含量,与对照处理相比,LN处理分别显著增加杉木、浙江桂和罗浮栲林土壤可溶性糖48.8%、19.2%和19.8%。各林分凋落物中多酚、单宁和可溶性糖含量受氮沉降的影响不显著。     

不同凋落物质量对杉木人工林土壤微生物群落结构的影响

凋落物是森林生态系统的重要组成部分。对福建南平峡阳林场7年生二代杉木人工林生态系统进行添加8种不同凋落物处理3年后,分析不同质量凋落物对土壤微生物群落组成的影响。结果表明:(1)添加高质量的桉树凋落物会使土壤磷脂脂肪酸总量、革兰氏阳性、阴性细菌生物量比添加杉木凋落物分别增加了27%、35%和19%,而添加低质量的樟树凋落物使得土壤磷脂脂肪酸总量和革兰氏阴性细菌较杉木显著降低29%和10%。(2)桉树凋落物添加下土壤真菌/细菌比(0.14)显著高于其他凋落物添加的比值,樟树凋落物添加下土壤的革兰氏阳性细菌/革兰氏阴性细菌比(1.64)显著高于其他凋落物添加处理的比值。(3)不同质量凋落物添加处理对土壤pH和碳氮比无显著影响。毛竹凋落物添加下土壤中硝态氮含量最高。(4)相关性分析表明,凋落物碳含量与土壤中脂肪酸总量、革兰氏阳性细菌、革兰氏阴性细菌、真菌和菌根真菌具有正相关关系。烷基碳(Alkyl C)与脂肪酸总量、革兰氏阳性、阴性细菌、细菌、真菌及真菌细菌比均有正相关性。甲氧基碳(N-alkyl C)、氧烷基碳(O-alkylC)和芳碳(ArylC)与革兰氏阳性阴性细菌比呈显著正相关。冗余分析表明,烷基碳(AlkylC)与16︰1ω7c、18︰1ω7c、18︰2ω6c、18︰1ω9显著正相关,对土壤微生物群落结构有显著影响。可见,不同树种之间凋落物烷基碳组分的差异是影响土壤微生物生物量和群落组成的重要指标。     

不同凋落物质量对杉木人工林土壤微生物群落结构的影响

凋落物是森林生态系统的重要组成部分。对福建南平峡阳林场7年生二代杉木人工林生态系统进行添加8种不同凋落物处理3年后，分析不同质量凋落物对土壤微生物群落组成的影响。结果表明：(1) 添加高质量的桉树凋落物会使土壤磷脂脂肪酸总量、革兰氏阳性、阴性细菌生物量比添加杉木凋落物分别增加了27%、35%和19%，而添加低质量的樟树凋落物使得土壤磷脂脂肪酸总量和革兰氏阴性细菌较杉木显著降低29%和10%。(2) 桉树凋落物添加下土壤真菌/细菌比(0.14)显著高于其他凋落物添加的比值，樟树凋落物添加下土壤的革兰氏阳性细菌/革兰氏阴性细菌比(1.64)显著高于其他凋落物添加处理的比值。(3) 不同质量凋落物添加处理对土壤pH和碳氮比无显著影响。毛竹凋落物添加下土壤中硝态氮含量最高。(4) 相关性分析表明，凋落物碳含量与土壤中脂肪酸总量、革兰氏阳性细菌、革兰氏阴性细菌、真菌和菌根真菌具有正相关关系。烷基碳(Alkyl C)与脂肪酸总量、革兰氏阳性、阴性细菌、细菌、真菌及真菌细菌比均有正相关性。甲氧基碳(N-alkyl C)、氧烷基碳(O-alkyl C)和芳碳(Aryl C)与革兰氏阳性阴性细菌比呈显著正相关。冗余分析表明，烷基碳(Alkyl C) 与16:1ω7c,18:1ω7c ,18:2ω6c,18:1ω9显著正相关，对土壤微生物群落结构有显著影响。可见，不同树种之间凋落物烷基碳组分的差异是影响土壤微生物生物量和群落组成的重要指标。     

凋落物及氮添加对针阔叶林土壤氮和水解氨基酸的影响

为探究凋落物对森林土壤氮的影响及氮沉降的调节，本研究以亚热带天然阔叶林(罗浮栲林)和人工针叶林(杉木林)2种林型土壤和凋落物为对象，分别设置土壤(对照)、土壤+凋落物(3倍添加)、土壤+氮(120 mg/kg)、土壤+凋落物(3倍添加)+氮(120 mg/kg) 4种处理，每种处理设置3个重复，进行为期一年的室内模拟淋溶试验，分析土壤可溶性氮和物理分级后各粒径土壤水解氨基酸变化。结果表明：与对照比较，阔叶林土壤添加凋落物处理增加土壤铵态氮和游离氨基酸，而降低硝态氮含量；氮添加降低针叶林土壤氨态氮，增加硝态氮含量，但是增加阔叶林土壤铵态氮和游离氨基酸；凋落物添加的情况下，氮添加显著增加阔叶林土壤硝态氮含量。土壤的各粒径组分分布比例差异显著，氮添加倾向于降低针叶林土壤大粒径、增加小粒径分配比例，而阔叶林相反。针叶林土壤添加凋落物显著增加土壤粒径组分2 000 ~ 250 μm、20 ~ 2 μm、<2 μm水解氨基酸含量；氮添加增加针叶林全土、2 000 ~ 250 μm和20 ~ 2 μm粒径水解氨基酸含量；在凋落物添加或氮添加情况下，氮添加或凋落物显著降低全土、250 ~ 53 μm、53 ~ 20 μm粒径水解氨基酸含量。而凋落物和氮添加对阔叶林土壤水解氨基酸含量的影响基本上相反。可见，不同土壤粒径组分水解氨基酸(作为可矿化氮)响应凋落物和氮添加处理的差异，有望作为揭示针阔叶林可溶性氮变化的指标。     

杉木人工林凋落物添加与去除对土壤碳氮及酶活性的影响

为了解未来气候变化过程中森林生产力增加的背景下,凋落物增加如何影响土壤碳氮过程,在杉木人工林中通过模拟实验研究凋落物添加(一倍)与去除对土壤中碳氮、碳氮同位素(δ~(13)C、δ~(15)N)、微生物生物量碳氮(MBC、MBN)及酶活性的影响。结果表明:凋落物添加后土壤中氮获得酶(β-N-乙酰氨基葡萄糖苷酶)活性显著上升,加速对土壤中有机质的分解获取氮素;凋落物添加与去除处理对土壤碳的影响较小,土壤有机碳(SOC)与可溶性有机碳(DOC)均未发生显著变化;土壤中δ~(13)C丰度与凋落物处理之间未呈现出相关规律性,而δ~(15)N丰度在凋落物添加处理后显著上升。这些结果说明,凋落物处理对杉木林土壤中氮的影响较为敏感,对土壤碳的影响较小。因此,未来气候变化导致森林生产力提高、凋落物输入增加,可能会导致土壤中氮素的损失,迫使土壤微生物分泌更多的氮获得酶同植物竞争土壤氮,最终可能会造成土壤碳氮循环的不平衡,对整个生态系统造成严重影响。     

去除凋落物和草毡层对寒温带典型森林土壤活性有机碳的短期影响

[目的]探究去除凋落物和草毡层对寒温带森林土壤活性有机碳的影响，为我国寒温带森林土壤碳循环的研究提供科学参考。[方法]以大兴安岭北部3种典型森林(白桦林、樟子松林和兴安落叶松林)为研究对象，在3种林型中设置对照、去除凋落物、去除草毡层以及去除凋落物和草毡层4种处理，于2021年9月对各处理不同土层(0—10 cm和10—20 cm)土壤进行取样，研究其土壤活性有机碳组分及其影响因子。[结果]在0—10 cm土层，与对照相比，去除凋落物后土壤可溶性有机碳和易氧化有机碳含量在白桦林和樟子松林中无显著变化，而在兴安落叶松林中显著降低了25.49%和39.40%;土壤微生物量碳含量在白桦林和兴安落叶松林中显著降低了19.26%和18.86%,而在樟子松林中无显著变化。去除草毡层后土壤可溶性有机碳和易氧化有机碳含量在白桦林和樟子松林中显著降低了16.08%,60.69%和17.38%,17.33%,而在兴安落叶松林中的变化不显著；土壤微生物量碳含量在3种林型中显著降低了19.47%～42.02%。同时去除凋落物和草毡层后3种林型土壤微生物量碳和易氧化有机碳含量极显著降低了22.03%～27.01...     

杉木人工林凋落物添加与去除对土壤碳氮及酶活性的影响

为了解未来气候变化过程中森林生产力增加的背景下，凋落物增加如何影响土壤碳氮过程，本研究在杉木人工林中通过模拟实验研究了凋落物添加（Litter addition）（一倍）与去除(Litter exclusion)对土壤中碳氮、碳氮同位素（δ13C、δ15N）、微生物量碳氮（MBC、MBN）、及酶活性的影响。研究结果表明，凋落物添加后导致土壤中氮获得酶（β-N-乙酰氨基葡萄糖苷酶）活性显著上升，加速对土壤中有机质的分解获取氮素，这可能是由于凋落物添加后导致植物细根生物量增加，增强了植物吸收氮素的能力，从而使土壤中可溶性有机氮（DON）、铵态氮、硝态氮含量下降，迫使微生物分泌更多的氮获得酶去获取氮素；凋落物添加与去除处理对土壤碳的影响较小，土壤中SOC、DOC均未发生显著变化；土壤中δ13C丰度与凋落物处理之间未呈现出相关规律性，而δ15N丰度在凋落物添加处理后显著上升。这些结果说明，凋落物处理对杉木林土壤中氮的影响较为敏感，对土壤碳的影响较小。因此，未来气候变化导致森林生产力提高、凋落物输入增加，可能会导致土壤中氮素的损失，迫使土壤微生物分泌更多的氮获得酶同植物竞争土壤氮，最终可能会造成土壤碳氮循环的不平衡，对整个生态系统造成严重影响。     

杉木和米槠人工林土壤可溶性碳组分动态及其对凋落叶输入的响应

可溶性碳组分是土壤有机碳库中最活跃的部分,作为土壤碳周转初期变化的敏感指标,其含量受到凋落叶等植物残体输入、森林类型及季节性水热变化的共同调节。采用土壤原位培养法,以亚热带米槠(Castanopsis carlesii)人工林与杉木(Cunninghamia lanceolata)人工林为对象,分析生长季内土壤可溶性碳(DOC)与热水溶性碳(HWSC)含量动态变化及其对凋落叶输入的响应趋势。结果表明,凋落叶输入、森林类型和培养月份均极显著影响土壤可溶性碳组分含量(p<0.001)。杉木人工林土壤DOC与HWSC含量整体较高,分别高出米槠人工林15.09%和13.06%,但后者的土壤可溶性有机质芳香化程度更高。经过1个生长季的培养,2种人工林土壤DOC与HWSC含量均明显增加。凋落叶增加生长季米槠人工林土壤DOC与HWSC的含量,但对杉木人工林的影响具有季节差异。研究结果表明杉木人工林土壤DOC与HWSC含量更高,但凋落叶输入促进米槠人工林DOC与HWSC含量,更易于随淋溶过程流失。     

黄土丘陵区沙棘混交林叶片、凋落物、土壤碳氮磷化学计量特征

以黄土丘陵区沙棘(Hippophae rhamnoides)+油松(Pinus tabuliformis)、沙棘(H.rhamnoides)+刺槐(Robinia pseudoacacia)混交林(H_rP_t、H_rR_p)及油松(P_t)和刺槐(R_p)纯林为对象,测定叶片、凋落物和0—100 cm土壤C、N、P含量及其化学计量比,探究混交造林对不同组分间养分协同变化规律的影响。结果表明:(1)相比P_t,H_rP_t中油松叶片C、N、P含量(p0.05)及N∶P(p0.05)增加,C∶N和C∶P降低(p0.05),表明H_rP_t有助于缓解N限制,加快其生长速率;相比R_p,H_rR_p中刺槐叶片C、N含量及C∶P和N∶P降低,P含量及C∶N增加(p0.05),表明H_rR_p增强刺槐对P的吸收,但降低其对C和N的固存;(2)相比P_t,H_rP_t凋落物C、N、P含量及N∶P增加,C∶N和C∶P降低(p0.05),表明H_rP_t有助于加快凋落物分解,促进养分归还;相比R_p,H_rR_p凋落物C、N、P含量及其计量比均有所增加(p0.05),表明H_rR_p对凋落物分解无显著作用;(3)相比P_t和R_p,H_rP_t和H_rR_p土壤C、N、P含量增加,但C∶N和C∶P降低(p0.05),表明H_rP_t和H_rR_p均有助于提高N和P利用效率,改善土壤养分状况;(4)叶片、凋落物化学计量指标间具有较强协同效应,且N、P相比C在不同组分间的相关性更明显。综上,相比H_rR_p,H_rP_t更有助于改善养分限制因子供给,加快组分间养分转化。研究结果对于揭示黄土高原地区人工混交林生态系统养分供应潜力及合理制定营林规划具有重要意义。     

Effects of tree species and topography on soil chemistry, litter quality, and decomposition in Northeast Turkey

Leaf litters from beech (Fagus orientalis Lipsky.) and oak (Quercus robur L.), and needle litters from fir (Abies nordmanniana Spach.) and pine (Pinus sylvestris L.) trees were collected from north-facing site and south-facing site and at three slope positions (top, middle and bottom) on each aspect that varied in soil chemical characteristics (soil pH, cation exchange capacity and base saturation). The litters were analysed for initial total carbon, nitrogen, acid detergent fibre, lignin and cellulose concentrations. Nitrogen, acid detergent fibre and lignin concentrations and carbon:nitrogen and lignin:nitrogen ratios varied significantly within and between species according to soil chemical characteristics on aspects and slope positions. Litter decomposition was studied in the field using the litterbag technique. The litters were placed on two aspects and at three slopes on each aspect in October 2001, and were sampled every 6-month for 2 years. The main effects of aspect, species and slope position on decomposition rates were all statistically significant. Oak leaf litter showed highest decomposition rates, followed by pine, fir and beech litter, and the litters placed on north-facing site decomposed faster than those on the south-facing site. The litters placed at the top slope position decomposed slower than at those at either the bottom or middle positions. Initial lignin concentrations explained most of the variation in decomposition rates between species, and within species for the aspects and the slope positions, but the explained variance showed differences between aspects and slope positions. This result illustrates the important point that litter quality may define the potential rates of microbial decomposition but these are significantly influenced by the biotic and abiotic environment in which decomposition takes place.     

西藏原始暗针叶林凋落物有机碳释放特征与土壤有机碳库关系研究

结合野外凋落物分解袋法和室内分析试验,对藏东南2种典型暗针叶林—急尖长苞冷杉(Abies georgei var.Smithii)和林芝云杉(Picea likiangensis var.linzhiensis)凋落物的分解和有机碳释放特征进行研究,分析了2种亚高山暗针叶林凋落物有机碳释放速率与土壤有机碳及其组分之间的关系。结果表明:藏东南2种原始暗针叶林凋落物分解均呈现出雨季分解快(4—9月)、旱季分解慢(10—翌年3月),前期分解快(3—9月)、后期分解慢(10—翌年2月)的特征,且冷杉(PLLF)分解速率大于云杉(AGSF),Olson指数衰减模型能够较好地模拟2种暗针叶林凋落物的分解,冷杉(PLLF)和云杉(AGSF)凋落物半分解时间为2.11,2.52年;分解95%时间为8.96,10.84年;2种暗针叶林凋落物中有机碳含量表现出先上升后下降,再平稳降低的趋势,而2种暗针叶林凋落物中有机碳释放速率表现出先短暂富集再释放的模式;2种暗针叶林土壤总有机碳(TOC)及其活性组分(MBC、POC、LOC)含量都具有明显的表聚性(p<0.01),且同一土壤层次内TOC、MBC、POC、LOC互相之间均呈极显著正相关关系(p<0.01);2种暗针叶林凋落物分解进程中有机碳的释放速率与表层土(0—10 cm)中TOC、MBC、POC、LOC含量、10—20 cm土层中的TOC、MBC含量以及20—40 cm土层中MBC含量之间呈现显著的正相关(p<0.05)。     

Predicting soil fauna effect on plant litter decomposition by using boosted regression trees

Extensive studies have been conducted to evaluate the effect of soil fauna on plant litter decomposition in terrestrial ecosystems. However, scholars have reported inconsistent results on the direction and magnitude of the soil fauna effect. We present a global synthesis of 75 papers that cover 197 plant species with 543 cases of plant litter decomposition experiments and soil fauna effects on plant litter decomposition. By using a boosted regression tree model (BRT), we aim to provide a synthesis of existing data that comprehensively and quantitatively evaluates how climate, plant litter quality, and study methods interact with soil fauna in affecting plant litter decomposition. Global average effect size (ES) is −0.426, which indicates a 35% lower decomposition rate when soil fauna is excluded by physical or chemical exclusion techniques. The final model explains 32.3% of the variation in ES. The predictors that substantially account for the explained variation include mean annual temperature (MAT, 37.1%), mean annual precipitation (MAP, 9.7%), phosphorus (12.4%), nitrogen (5.6%), and lignin content (5.5%). By contrast, the heterogeneity of the study duration and soil fauna exclusion technique have negligible contributions (each <5%). Log effect size strongly decreases with both MAT and MAP. Plant litters with high quality have stronger soil fauna effect because the log effect size is negatively related to nitrogen and phosphorus content and positively related to lignin content. Our analysis demonstrates the critical role of climate and plant litter quality in determining the soil fauna effect on plant litter decomposition in terrestrial ecosystems. However, the large unexplained variation (67.7%) in ES in the BRT model indicates undiscovered mechanisms underlying the soil fauna effect in our analysis. We call for further studies on this topic in the future.     

荒漠草原4种主要植物群落枯落物层水土保持功能

枯落物层是草地除冠层外,大气与矿质土壤层、植物根系层进行物质与能量交换的重要介质,在生态学中起着不可替代的作用。通过研究荒漠草原4种主要植物群落(蒙古冰草群落、甘草群落、赖草群落和沙蒿群落)水土保持功能,结果表明:荒漠草原4种植物群落枯落物层年截留率在4.58%～5.61%,截留量为22.77～27.87mm,且枯落物对降雨的截留量随降雨量增加而增大,而截留率随降雨量增加而减小,当降雨等级在0～2mm时,截留率为100%,当降雨等级高于2mm时,截留率随1次降雨降雨量的增加而减少。枯落物层抑制土壤蒸发的效应与枯落物层厚度的增加呈正相关,有枯落物层比无枯落物层覆盖的土壤蒸发量减少了19.25%～76.82%,但当土壤含水量升高为田间持水量的3/4时,不同植物群落枯落物减少土壤水分蒸发的效应有所不同。围封内枯落物对土壤风蚀的抑制显著低于围封外,枯落物对风蚀的抑制作用与枯落物的蓄积量呈正相关。     

Increased total nitrogen content of poultry manure by decreasing water content through composting processes

Microbial mineralization of urea and uric acid in poultry litter can lead to loss of nitrogen (N) content and its value as a fertilizer. To minimize the loss of N in the composting processes, controlling the water content in litters is a key to reduce the mineralization processes of N compounds. The N content of litter may be influenced by diets, hen age and the type of poultry houses used. The objectives of the present study were i) to determine the relationship between the water content and the decomposition rate of uric acid in poultry litter and ii) to investigate the effect of hen age and crude protein (CP) percentages in diets on the N content of poultry litter. A layer feeding trial was conducted in two poultry farms with windowless and open-floor houses. An incubation study of poultry litter was performed under different levels of water content. Our study found that the diet CP percentage (16.5–18%) and the growth stage of laying hens did not have a significant effect on the amount of total N (52–56?g?kg^?1) and uric acid-N (26–31g?kg^?1) in fresh litters. At the 7^th day of litter incubation study, the concentration of uric acid-N was 22 g kg^?1 in litters with a water content of 35%, whereas it further decreased to less than 1.3 g kg^?1 in litters with a water content of 55% and higher levels. The decomposition rate of uric acid-N in litter was 0.3–3.1g?kg^?1?day^?1 in the windowless house and 3.1–7.1g?kg^?1?day^?1 in the open-floor house. Decomposition of uric acid in litters was positively correlated to the litter moisture content that is controlled to be lower in windowless houses (40–50%) than in open-floor houses (55–80%) during the composting period. Our study suggests that the use of windowless houses for layer chicken production is effective for producing poultry manure with a high N content.     

Control of pitch pine seed germination and initial growth exerted by leaf litters and polyphenolic compounds

We investigated the influence of three concentrations of water extracts of three leaf litter species (pitch pine, huckleberry and white oak) and a mixture of all litters on the germination of pitch pine seeds and initial seedling growth in a microcosm experiment. All three plant species are important components of the pine barrens ecosystems in New Jersey, where it has been seen that pine seedling recruitment occurs only after stand replacing fire or in disturbed sites, where surface organic soil horizons and leaf litter have been removed. Leaf litter extracts did not influence seed germination, but significantly reduced seedling growth at high concentrations. There was little difference between the leaf litter species in growth suppression. As charcoal is a natural residue on the forest floor following fire, its influence on growth suppression was examined; it has been shown to immobilize polyphenols. Charcoal removed the inhibitory effect of leaf litter extracts and allowed the fertilizer effect of nutrients leached from the leaves to enhance seedling growth, particularly at the higher concentration of litter extract used. Responses to litter extracts were compared to four pure phenolic compounds, catchecol, p-coumaric acid, p-hydroxybenzoic acid and tannic acid. None of these compounds suppressed pine seedling growth, suggesting that these phenolics are not allelopathic to pine seedlings. The results are discussed in the context of fire as a driving factor in these oligotrophic and seasonally dry ecosystems and the interactions between nutrient supply and allelopathic chemistry of different leaf litters.     

凋落物输入改变对慈竹林土壤有机碳的影响

通过野外试验,研究了凋落物输入改变对慈竹林土壤有机碳的影响。设置10%,50%和70%这3种去除凋落物量和分别添加15%,25%的绵竹、杉木凋落物处理及对照。结果发现,去除凋落后慈竹林土壤有机碳含量明显减少(p<0.05),而且去除量越大,有机碳含量减少越大。添加外源凋落物显著提高了慈竹林土壤有机碳含量(p<0.05),其中,15%的添加比例比25%更有利于土壤有机碳的积累,添加绵竹凋落物对土壤有机碳增加的效应高于添加杉木凋落物。研究表明,选择适合的树种和恰当的混交比例以及加强对凋落物层的保护,对维持慈竹林土壤有机碳具有重要的意义。     

不同生境条件下西藏原始冷杉林凋落物分解特征与土壤养分的关系

[目的]研究不同生境条件下(林内、林外、林缘)藏东南急尖长苞冷杉林(Abies georgei var.smithii)凋落物分解特征与土壤养分特征之间的关系,为深入了解高寒高山森林生态系统物质循环过程提供依据。[方法]采用野外分解袋法和室内分析相结合,在林内、林外、林缘3种不同生境条件下对藏东南急尖长苞冷杉林凋落物进行了原位分解试验。[结果]分解速率总体上呈现出:林内林缘林外的特点,逐月分解率的变异系数表现为:林内(34.83%)林缘(57.35%)林外(72.09%);Olson指数衰减模型的模拟结果显示不同生境条件下(林内、林缘、林外)凋落物分解50%需要的时间为2.11,2.52,2.34 a,分解95%需要的时间为8.96,10.01,10.84 a;3种不同生境土壤养分在空间上差异显著,林内生境中与凋落物分解速率呈现极显著相关的土壤养分因子有土壤总有机碳(TOC)含量、N含量、土壤微生物量碳(SMBC)含量、土壤微生物量氮(SMBN)含量以及W_C∶W_N值;林外、林缘生境中与凋落物分解速率相关性最大的为土壤TOC含量,其次为W_C∶W_N值。[结论]生境条件的差异对凋落物分解速率有显著影响,在不同的生境条件下对凋落物分解影响起主导作用的土壤养分因素不同,凋落物—土壤生物地化循环紧密联系,相互作用关系复杂,生境作用效应突出。     

Legacies of plant litter on carbon and nitrogen dynamics and the role of the soil community

There is increasing awareness of the importance of ecological legacies in contemporary ecosystem processes. Decomposition is regulated by a set of interacting hierarchically organized factors. As spatial and temporal scales decrease, decomposition is largely dependent on the quality of resources and the decomposer community, but whether and how these factors manifest via historical legacy effects is not well understood. We tested whether the history of plant litter inputs had short-term legacy effects on contemporary litter and soil organic matter carbon (C) and nitrogen (N) mineralization. Using a field/laboratory microcosm approach, we exposed soils to two litters of contrasting chemistry and, after adding fresh substrates, we monitored C and N dynamics. In a parallel experiment, we manipulated the soil community to reduce litter-history impacts on its composition and size to investigate whether the soil community could be an important contributor to legacy effects We found strong short-term litter legacy effects on contemporary litter and soil N mineralization, the duration of which was dependent on the contemporary substrate for decomposition. These strong effects were not consistent with the home field advantage phenomenon, as exposure to a specific litter did not favor the decomposition of the same litter when it was applied as a contemporary substrate. Reduction of the litter-history effects on soil biota decreased the impact of litter history on N immobilization, suggesting that plant litter impacts on the soil community may be an important component of plant litter legacies on N decomposition. In contrast to N, litter legacies appeared to be much less important for C decomposition, suggesting that legacy effects might uncouple contemporary C and N dynamics.