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1.
以亚热带常绿阔叶林建群种米槠(Castanopsis carlesii)凋落叶为研究对象,对照地表环境,研究了溪流和间歇性溪流凋落叶分解过程中水溶性有机碳、氮、磷含量变化及其累积损失特征。结果表明:(1)3种生境中凋落叶水溶性有机碳的含量在分解过程中均表现出逐渐降低的趋势,但在溪流中降低程度最大,损失率达92.18%;水溶性氮含量在溪流和间歇性溪流释放时间提前,其变化程度相对较小;相比于地表和间歇性溪流,溪流中的凋落叶水溶性磷含量在分解过程中持续降低,损失率达86.75%。(2)相对于地表,溪流和间歇性溪流显著促进了凋落叶中的水溶性有机碳、氮、磷的释放速率,表明源头溪流持续流动的水体促进凋落叶水溶性组分的释放。(3)尽管3种生境中凋落叶水溶性有机碳、氮、磷元素的损失率共同受到温度、降水、环境中营养元素含量的影响,但源头溪流持续流动的水流和间歇性溪流频繁的干湿交替促进凋落叶水溶性组分的释放。研究结果为揭示亚热带山地森林凋落叶分解过程中水溶性碳氮磷在不同生境中的释放动态提供基础数据。  相似文献   

2.
榕树叶片分解过程物质与能量动态变化研究   总被引：4，自引：0，他引：4  
对榕树叶片分解过程中物质与能量动态变化研究结果表明 ,叶片分解过程中干物质量呈下降趋势 ,半分解期的理论值为 10 1d ,且与实测值十分接近。叶片分解过程中C含量前 5个月变化较小 ,随后呈下降趋势 ;N含量升高 ,C/N值下降。分解初期单宁含量迅速下降 ,而分解后期其含量相对稳定 ;随榕树叶片分解可溶性糖含量下降而粗蛋白质含量呈上升趋势 ;分解过程中可溶性糖含量与单宁含量均遵循指数方程变化 (P <0 .0 1)。榕树落叶分解的前 2个月其干物质量热值略下降 ,之后 2个月其干物质量热值开始上升 ,特别是在分解的第 4个月其干物质量热值迅速上升并达最大值 ,之后干物质量热值开始迅速下降。分解的第 1个月去灰分热值略下降 ,第 2个月开始上升 ,至第 4个月达 (半分解期 )最高值 ,之后去灰分热值呈下降趋势。  相似文献   

3.
以黄土高原的主要人工林树种侧柏为对象,通过采集侧柏及其他拟混交的8个树种的当年枯落叶,以无林荒草地腐殖质层土壤作为分解介质,在室内将侧柏与不同树种枯落叶剪碎后以一定比例混合装入尼龙网袋并埋人盛土培养钵中,进行恒温恒湿下连续345 d分解培养试验,测定分解前后枯落叶质量及养分含量的变化.结果表明:(1)在枯落叶分解释放养分元素中,K最活跃而易于释出,p一般比较迟钝而难以释出,C、N居中并具有一定的释出同步性,且各种养分的周转期约为1～2a.(2)与侧柏枯落叶混合分解后,在对C释放的影响中白榆表现为促进作用,紫穗槐、白桦和辽东栎表现为抑制作用;在对N释放的影响中小叶杨表现为促进作用,白桦、辽东栎和紫穗槐表现为抑制作用;在对P释放的影响中除小叶杨、白榆不明显之外均表现为抑制作用;在对K释放的影响中白榆表现为促进作用,紫穗槐表现为抑制作用.(3)应用主成分分析法分析不同树种枯落叶混合分解对C、N、P、K释放的综合影响结果表明,与侧柏枯落叶混合分解后总体上促进养分释放的树种以白榆、小叶杨最显著,其次为柠条和辽东栎;而总体上抑制养分释放的树种以紫穗槐的作用最强,白桦、沙棘和刺槐的作用较弱.  相似文献   

4.
为探索加快毛白杨落叶分解的途径, 采取室内培养的方法研究了添加铵态氮、硝态氮及混合氮对三倍体毛白杨落叶分解速度和主要营养元素释放的影响。结果表明, 添加氮源对三倍体毛白杨落叶分解有一定的促进作用, 不同氮源之间差异显著。140 d后, 施加铵态氮、混合氮和硝态氮的落叶分解率分别为46.0%、30.0%和28.8%, 而对照为27.4%, 处理间差异显著; Olson指数方程拟合结果表明,施加铵态氮、混合氮和硝态氮后落叶分解50%和95%所需时间分别为175 d、316 d、301 d和781 d、1 238 d、1 627 d,比对照分别缩短49.7%、9.2%、13.5%和52.0%、23.9%、14.1%。同时, 添加氮源后对落叶中N、P、K元素的释放影响有所不同, 其中对K元素的释放基本没有产生影响, 随着分解的进行, 不同处理落叶中K元素浓度逐渐降低。但添加氮源对N、P元素的释放产生了显著影响, 与对照相比, 添加氮源缩短了N、P释放的富集时间, 降低了富集的幅度;N、P的富集时间均从对照的21 d缩短到处理的7 d; N的富集幅度从对照为初始浓度的1.94倍降低到处理为初始浓度的1.32~1.56倍, P的富集幅度从对照为初始浓度的2.98倍降低到处理为初始浓度的1.70~2.26倍。因此添加氮源加快了落叶的分解速度,促进了落叶中N、P的释放, 有利于加快养分循环, 提高立地生产力。  相似文献   

5.
试验以油菜秸秆和紫云英(Astragalus sinicus L.)为研究材料,通过盆栽模拟稻田条件,研究了油菜秸秆、紫云英绿肥及其不同比例混合处理腐解及养分释放动态。结果表明,腐解过程均呈现出前10~20 d分解较快,后期分解较慢并逐渐趋于平稳的规律。不同处理各养分的释放快慢不同,表现为钾磷氮碳,在翻压90d时钾的累积释放率为95.09%~97.17%,磷的累积释放率为62.65%~87.14%,氮的累积释放率为70%~76.48%,碳的累积释放率为39.53%~64.69%。翻压90 d后紫云英腐解率达到60.07%,油菜秸秆仅40.8%,混合紫云英后,混合处理的腐解程度加快,且腐解程度随紫云英量的增加而增加。  相似文献   

6.
基于对伊犁河谷山地北坡垂直地带植被多样性和土壤生境的调查分析数据,采用Pearson相关系数法、主成分法和DCA排序法分析了物种多样性指数与环境因子之间的关系。结果表明:根据其植被带和土壤带沿不同海拔将其分为针叶林、山地草原、落叶阔叶林和荒漠草原;其总的物种丰富度和Simpson指数与海拔呈现先升高后降低,再升高的格局,不同海拔植被群落丰富度指数之间差异均显著(p0.05),Shannon-Wiener指数随海拔的增加呈先增加后降低的趋势,Pielou均匀度指数随海拔的增加呈先降低后增加,然后降低的格局。犁河谷山地北坡土壤有机质和有效氮含量随海拔的增加而增加的趋势,基本表现为针叶林山地草原落叶阔叶林荒漠草原,其中不同海拔植被群落土壤有机质含量之间差异均显著(p0.05),土壤有效磷含量没有明显的垂直变化规律,土壤有效钾含量随海拔的增加呈先增加后降低的趋势,基本表现为山地草原针叶林落叶阔叶林荒漠草原。犁河谷山地北坡土壤pH值随海拔的增加而降低的趋势,基本表现为荒漠草原山地草原落叶阔叶林针叶林,土壤电导率、全盐和总盐含量均随海拔的增加呈先增加后降低的格局,基本表现为山地草原落叶阔叶林荒漠草原针叶林。主成分的结果分析表明,第一主成分负荷值最高的分别为土壤全盐、总盐、电导率,可称为土壤盐分因子;第二主成分负荷值最高的分别为土壤有效氮、有机质和pH值,可称为保肥、供肥因子。DCA排序结果表明,沿着DCA第一轴,随着海拔逐渐降低,土壤有机质、有效氮和有效钾等土壤养分的含量逐渐下降,而pH值和电导率逐渐上升;沿着DCA第二轴,随着海拔逐渐降低,土壤总盐和全盐含量逐渐增加,而土壤有效磷含量却逐渐降低。由此可知,犁河谷山地北坡植物群落多样性的垂直分布格局是由海拔为主的多种环境因子综合作用的结果,而土壤养分和盐分随海拔的变化与植被带不尽一致,可能它们之间的同步变化存在一定的滞后期。  相似文献   

7.
为研究火烧迹地雷竹(Phyllostachys violascens)凋落叶分解过程中土壤动物群落特征,以毗邻雷竹林为对照,采用凋落物袋法研究雷竹凋落叶分解速率及土壤动物群落结构的变化特征。结果显示,两个样地雷竹凋落叶分解过程总体上可以划分为3个阶段,即分解初期(质量损失率较高)、分解中期(凋落叶的质量损失率较上阶段减缓)、分解后期(质量损失率再次上升)。调查共捕获土壤动物824只,其中火烧迹地375只,对照样地449只,以绥螨科、蚁科、线虫纲和等节(虫兆)科为优势类群,所占百分比为49.27%,火烧迹地土壤动物类群数变化幅度较个体数小。统计分析表明,火烧迹地和对照样地凋落叶分解过程中土壤动物类群数无显著差异(P0.05)。两个样地土壤动物均匀度指数、多样性指数和丰富度指数均呈上升趋势,而优势度指数则逐渐降低,凋落叶分解过程中土壤动物个体数、类群数均与降水量存在显著相关关系(P0.05)。主坐标分析(PCoA)表明,凋落叶分解初期受火烧干扰较大,后期受分解时间累积效应影响较大。试验表明,火烧干扰延缓了雷竹凋落叶的分解速率,但随着时间的延续,火烧迹地雷竹叶分解速率则迅速提升,土壤动物群落也得到恢复。  相似文献   

8.
[目的]研究喀斯特森林生态系统凋落叶分解特征,为喀斯特森林区石漠化防治及水土保持提供科学依据。[方法]采用1 mm网孔孔径分解袋,对茂兰喀斯特森林自然保护区不同树种凋落叶(落叶和常绿叶)在不同坡位的分解状况进行为期18个月的观测研究。研究茂兰喀斯特森林自然保护区凋落叶失重率和干重残留率动态变化、分解速率及养分释放特征。[结果]凋落叶分解过程呈现"快—慢—快"的周期变化,春夏季分解速度快于秋冬季,落叶树种凋落叶分解速度快于常绿树种凋落叶,不同坡位凋落叶的分解速度表现为:下坡中坡上坡。利用Olson模型对凋落叶分解50%和95%所需时间进行估测,发现落叶树种凋落叶分解50%和95%所需时间分别为0.95～1.66 a和4.13～7.19 a,常绿树种凋落叶分解50%和95%所需时间分别为1.14～1.69 a和4.92～7.30 a,二者无显著性差异。凋落叶分解速率低于中亚热带东部常绿阔叶林和常绿落叶阔叶混交林,但比同区域喀斯特次生林与人工林高。落叶树种凋落叶和常绿树种凋落叶的N元素释放模式为富集—释放模式,C含量随分解时间的波动差异显著,总体在不断减少,而C/N比呈逐步下降的趋势。[结论]由于不同树种凋落叶初始养分含量和叶片理化结构的差异,落叶比常绿叶具有更快的分解速率和养分释放速率,对促进喀斯特森林生态系统物质循环起着积极作用。  相似文献   

9.
通过油松及其他10个树种枯落叶单独和混合分解试验,探讨了油松与其他树种枯落叶混合分解对土壤性质的影响及在对土壤性质影响中是否存在相互促进或抑制作用。结果表明:11种枯落叶单独分解均明显提高了土壤脲酶、脱氢酶、磷酸酶活性和有机质、碱解氮含量,但在对土壤速效磷含量和CEC的影响中存在较大差异。油松分别与侧柏、小叶杨、刺槐和白榆枯落叶混合分解对土壤微生物总量的影响存在明显的相互促进作用;油松与沙棘枯落叶混合分解对土壤磷酸酶活性的影响存在相互促进作用,而与侧柏、白桦和白榆枯落叶混合分解对土壤磷酸酶活性的影响存在相互抑制作用;油松与大部分树种枯落叶混合分解对土壤速效钾的影响存在相互促进作用,而对土壤速效磷的影响存在相互抑制作用;油松分别与小叶杨、沙棘、紫穗槐枯落叶混合分解对土壤有机质的影响存在相互促进作用。就土壤性质总体而言,油松与沙棘、刺槐、小叶杨和紫穗槐枯落叶成对混合分解对土壤性质综合表现为相互促进,而与侧柏、辽东栎、白桦、落叶松和柠条枯落叶成对混合分解对土壤性质综合表现为相互抑制。  相似文献   

10.
冬油菜叶片的物质及养分积累与转移特性研究   总被引：7，自引：0，他引：7  
为优化当季和下季作物的养分管理,采用田间试验研究了冬油菜品种:华双5号与中油杂12号叶片的干物质及氮、磷、钾的积累及转移规律,并比较了品种间的异同。结果表明,两个油菜品种的绿叶干物质量在苗后期基本达最大值,花后期迅速降低;苗期的落叶干物质量较小,蕾薹期后直线增加;叶片总干物质先增后减,花期达最大值。中油杂12号的落叶及叶片总干物质均高于华双5号,差异随生育期的推进逐渐明显。绿叶氮含量出苗后逐渐降低,后因越冬肥的施用又略有升高,蕾薹期后便迅速下降;落叶氮含量持续降低,苗后期降至最低点,其后一直保持稳定。绿叶磷含量在苗期缓慢增加,蕾薹期达到最大值,而后迅速下降;苗期落叶的磷含量逐渐降低,蕾薹期降至最低值,角果期后又略有升高。出苗50d后绿叶钾含量快速下降,70d达到最低值,其后保持稳定;落叶钾含量在蕾薹期达到最低值,其后波动较大。两品种叶片养分含量的变化趋势相似,但无论绿叶还是落叶,华双5号的养分含量总体略低于中油杂12号。绿叶的养分与叶片总养分积累的变化规律一致,即氮、磷、钾积累量均先增加后降低,分别在蕾薹期、苗后期和花期达到最高值。落叶的养分积累量在抽薹后迅速增加,收获期达最大值。华双5号叶片的干物质、N、P2O5、K2O转移率分别为25.5%、82.9%、75.4%、45.8%;中油杂12号则分别为8.4%、76.0%、60.2%、38.8%,品种间差异显著。  相似文献   

11.
Predicting litter decay rates in arid systems has proved elusive and sunlight (photodegradation) is a potentially important but poorly understood driver of litter decay in these systems. We placed three litter types (Cynodon dactylon, Larrea tridentata leaves, and L. tridentata twigs) in envelopes whose tops either transmitted all solar radiation, filtered UV-B, filtered all UV, or filtered all UV and visible solar radiation, on the soil surface of the Sonoran Desert and assessed mass loss over 14 months. Regardless of treatment, final mass loss was greatest in C. dactylon litter and least in L. tridentata twig litter, consistent with initial litter characteristics of presumed litter quality; C. dactylon had the lowest lignin concentration and lignin:N, and the highest cellulose:lignin and area:mass. Compared to litter in sunlight, excluding solar UV, or UV-B, slowed mass loss of all 3 litter types, and UV-B appeared more effective than UV-A in photodegradation. The relative contribution of UV photodegradation to mass loss increased with litter age. After 14 months, litter exposed to solar UV lost 1.2 (C. dactylon), 1.3 (L. tridentata twigs) and 1.4 (L. tridentata leaves) times as much mass as litter not exposed to UV radiation. The relative contribution of UV photodegradation to mass loss increased with the initial C:N ratio of litter, but was not related to initial lignin concentration or optical properties (i.e. UV and visible absorbance and transmittance) of litter. Within all litter type by treatment combinations, there was a strong positive correlation between litter mass loss and ash concentration. In some cases, a discontinuity in this relationship was detected, suggesting a threshold ash concentration, above which further mass loss was negligible. We expected these thresholds to be most prevalent in sunlight, because soil films could prevent sunlight from reaching litter and thereby minimize photodegradation. Contrary to expectations, thresholds were more common in shade or UV filter treatments, suggesting that reductions in photodegradation attributable to soil films were not typically responsible. The effect of shading, which likely enhanced microbial degradation via higher relative humidity due to lower temperatures, depended on litter type and time. Compared to litter in sunlight, mass loss of shaded litter was greater over the initial 3 months in all litter types, illustrating that microbial degradation in shade was greater than photodegradation in sunlight. These differences in mass loss between shaded and sunlit litter increased over the 14 month experiment in L. tridentata twigs, declined in L. tridentata leaves, and disappeared within 6 months in C. dactylon, illustrating that the timing of this shift in the dominance of photodegradation versus microbial degradation was highly dependent on litter type. In a second experiment, we reduced microclimate differences among sun and shade treatments, pre-sterilized litter to reduce microbial degradation, and examined the mass loss of young and old and L. tridentata leaf litter after 53 days outdoors. Consistent with our first experiment, mass loss attributable to photodegradation was greater in old than young litter. Unsterilized litter exposed to sunlight (UV and visible) lost 1.3 (young) and 1.5 (old) times as much mass as shaded litter. Pre-sterilized litter exposed to sunlight lost 11.4 (young litter) and 45.9 (old litter) times as much mass as shaded litter. These large differences in pre-sterilized litter were the result of the very small mass loss of shaded litter (≤0.2%), together with modest losses of sunlit litter (<5%). Taken together, our findings suggest that as litter aged, microbial degradation became a weaker driver of mass loss, while photodegradation became stronger.  相似文献   

12.
Litter decomposition is a major fundamental ecological process that regulates nutrient cycling, thereby affecting net ecosystem carbon (C) storage as well as primary productivity in forest ecosystems. Litter decomposes in its home environment faster than in any other environment. However, evidence for this phenomenon, which is called the home-field advantage (HFA), has not been universal. We provide the first HFA quantification of litter decomposition and nutrient release through meta-analysis of published data in global forest ecosystems. Litter mass loss was 4.2 % faster on average, whereas nitrogen (N) release was 1.7 % lower at the home environment than in another environment. However, no HFA of phosphorus (P) release was observed. Broadleaf litter (4.4 %) had a higher litter mass loss HFA than coniferous litter (1.0 %). The positive HFA of N release was found in the coniferous litter. Mass loss HFA was significantly and negatively correlated with the initial lignin:N litter ratio. The litter decomposition and N release HFAs were obtained when mesh size ranged from 0.15 mm to 2.0 mm. The HFA of litter decomposition increased with decomposition duration during the early decomposition stage. The HFA of N release was well correlated with mass loss, and the greatest HFA was at mass loss less than 20 %. Our results suggest that the litter decomposition and N release HFAs are widespread in forest ecosystems. Furthermore, soil mesofauna is significantly involved in the HFA of litter decomposition.  相似文献   

13.
Litter is one of the main sources of dissolved organic carbon (DOC) in forest soils and litter decomposition is an important control of carbon storage and DOC dynamics. The aim of our study was to evaluate (i) effects of tree species on DOC production and (ii) relationships between litter decomposition and the amount and quality of DOC. Five different types of leaves and needles were exposed in litterbags at two neighboring forest sites. Within 12 months we sampled the litterbags five times and leached aliquots of field moist litter in the laboratory. In the collected litter percolates we measured DOC concentrations and recorded UV and fluorescence spectra in order to estimate the aromaticity and complexity of the organic molecules. Furthermore, we investigated the biodegradability of DOC from fresh and decomposed litter during 6 weeks incubations. Fresh sycamore maple litter released the largest amounts of DOC reaching about 6.2% of litter C after applying precipitation of 94 mm. We leached 3.9, 1.6, 1.0 and 3.3% carbon from fresh mountain ash, beech, spruce and pine litter, respectively. In the initial phase of litter decomposition significantly decreasing DOC amounts were released with increasing litter mass loss. However, after mass loss exceeds 20% DOC production from needle litter tended to increase. UV and fluorescence spectra of percolates from pine and spruce litter indicated an increasing degree of aromaticity and complexity with increasing mass loss as often described for decomposing litter. However, for deciduous litter the relationship was less obvious. We assume that during litter decomposition the source of produced DOC in coniferous litter tended toward a larger contribution from lignin-derived compounds. Biodegradability of DOC from fresh litter was very high, ranging from 30 to 95% mineralized C. DOC from degraded litter was on average 34% less mineralizable than DOC from fresh litter. Taking into account the large DOC production from decomposed needles we can assume there is an important role for DOC in the accumulation of organic matter in soils during litter decomposition particularly in coniferous forests.  相似文献   

14.
应用开顶式生长室（OTC, Open Top Chamber）模拟增温,以自然状态为对照,设增温(W)、增水（P）和增温+增水（WP）3个处理,对克氏针茅草原主要物种克氏针茅(Stipa krylovii)、糙隐子草(Cleistogenes squarrosa)、冷蒿（Artemisia frigida）以及群落凋落物的分解速率进行试验研究。结果表明：(1)经过1a的分解,W处理下各物种凋落物质量残余率高于CK,即增温减缓了凋落物的分解;WP处理对凋落物质量残余率的影响与W处理一致,但其增温的影响程度更大;P处理下凋落物残余率与CK无显著差异。(2) 增温对不同种类凋落物分解进程无显著影响;而增水明显加快了糙隐子草的分解进程;增温+增水对冷蒿的分解进程影响较大,但最终各物种凋落物残余率差异不显著。(3)对残余率变化动态的方差分析表明,增温增水对凋落物分解的影响主要与凋落物种类以及分解时间的长短有关。(4)采用Olso负指数模型模拟凋落物质量损失变化过程,增温条件下,除冷蒿外,其它各种凋落物的k值（表征分解速率）均低于CK;增水条件下,克氏针茅和糙隐子草的k值低于CK,而冷蒿和群落凋落物的k值高于CK;增温+增水条件下,不同种类凋落物k值的变化与W处理一致,但整体上WP处理下凋落物的k值高于W处理。根据研究结果可以推断出,未来气候变化下内蒙古克氏针茅草原凋落物的分解将趋于减缓。  相似文献   

15.
In a litterbag study in a tropical montane rainforest in Ecuador we assessed the impact of leaf litter species identity and richness on decomposition. We incubated leaf litter of six native tree species in monocultures and all possible two and four species combinations and analysed mass loss over a period of 24 months. Mass loss in monocultures averaged 30.7% after 6 month and differed significantly between species with variations being closely related to initial concentrations of lignin, Mg and P. At later harvests mass loss in monocultures averaged 54.5% but did not vary among leaf litter species and, unexpectedly, did not increase between 12 and 24 months suggesting that litter converged towards an extremely poor common quality retarding decomposition. After 6 months mass loss of leaf litter species was significantly faster in mixtures than in monocultures, resulting in synergistic non-additive mixture effects on decomposition, whereas at later harvests mass loss of component litter species was more variable and leaf litter mixture effects differed with species richness. Mass loss in the two species mixtures did not deviate from those predicted from monocultures, while we found antagonistic non-additive mixture effects in the four species mixtures. This suggests that litter species shared a poor common quality but different chemistry resulting in negative interactions in chemically diverse litter mixtures at later stages of decomposition. Overall, the results suggest that interspecific variations in diversity and composition of structural and secondary litter compounds rather than concentrations of individual litter compounds per se, control long term leaf litter decomposition in tropical montane rainforests. Plant species diversity thus appears to act as a major driver for decomposition processes in tropical montane rainforest ecosystems, highlighting the need for increasing plant conservation efforts to protect ecosystem functioning of this threatened biodiversity hotspot.  相似文献   

16.
Abstract

In a southern boreal aspen forest located in Saskatchewan, Canada, we examined decomposition rates of leaf litter from trembling aspen (Populus tremuloides Michx.), hazel (Corylus cornuta March.), and a mixture of different species over a six‐month period. Mass loss was measured in the field using the litter bag method. The greatest mass losses occurred during the first month regardless of litter type. On average, mass loss during the first 28 days was 3.2 g#lbkg‐1#lbd‐1 for the aspen leaves, 4.4 for hazel leaves and 4.9 for the mixture. The initial rapid loss of weight is attributed to leaching and decomposition of water soluble material. The decomposition rates of the leaf litter were related to water‐soluble organic carbon and nitrogen content, and C:N ratio. Several models were used to describe mass loss of the aspen, hazel, and mixed leaf litter at the early stages of decomposition. A single model was not found to be appropriate to describe decomposition of all leaf‐litter types. A second order model provided the best fit for the aspen litter decomposition, while the logarithmic model best described the decomposition of hazel and mixed leaf litter.  相似文献   

17.
Bamboos are one of the fast-growing and multiple use species in the world, and thus bamboo forests/plantations play an important role in C sequestration at regional and global levels. We studied aboveground litterfall, litter decomposition and nutrient dynamics for two years in two subtropical bamboo ecosystems in Southwest China so as to test the hypothesis that litter quality determine the rate and nutrient dynamics during decomposition of different litter fractions. Mean annual total aboveground litter production ranged from 494 to 434 g m-2 in two bamboo stands （P stand, dominated by Pleioblastus amarus and H stand, hybrid bamboo dominated by Bambusa pervariabilis x Dendrocalamopsis daii）. Bulk （-80%） of litter production was contributed by leaf litter in two stands followed by twigs and sheathes. Different litter fractions represented considerable variations in the rates of mass loss and nutrient release. Variation of the mass remaining after 2 years of decomposition was significantly explained by initial C/N ratio and initial P concentration. Initial concentrations of N, P, Ca, and Mg explained 57.9%, 95.0%, 99.8% and 98.1%, respectively, of the variations of these elements mass remaining after 2 years of decomposition. The patterns of nutrient dynamics and the final amount remaining were mainly determined by their initial litter substrate quality in tl~ese two subtropical bamboo plantations.  相似文献   

18.
Accumulation of soil carbon is mainly controlled by the balance between litter production and litter decomposition. Usually In Mediterranean forests there are contrasting conditions in the distribution of faunal activity and the moss layer that may have different effects on litter decomposition. Decomposition and faunal activity were studied by exposing litter of contrasting quality (Pinus halepensis Mill. and Quercus ilex L.) for 3.5 yr in three Mediterranean pine forests of the eastern Iberian Peninsula. The effects of mosses on decomposition and on faunal activity were studied by exposing P. halepensis litter either on moss patches or directly on the forest floor. Faecal pellet production was used as an indication of faunal activity. Water availability or soil characteristics seem to limit faunal activities in the drier sites. Faecal pellets were not found during the first stages of decomposition and in all sites they appeared when about a 30% of the initial litter had decomposed. Under wet conditions faecal pellet production was very high and a mass balance suggested that soil faunal activity may result in a net flow of organic matter from the lower organic horizons to the surface Oi horizon. Mosses slightly increased mass loss of pine litter probably as a consequence of high potentially mineralizable nitrogen in the Oa horizon of moss patches and also, perhaps, as a consequence of the higher moisture content measured in the Oi horizon needles sampled among the mosses. In contrast, moss patches reduced faunal activity. The effect of litter quality on mass loss was not always significant, suggesting an interaction between litter quality and site conditions. During the first stages of decomposition there was N immobilisation in P. halepensis litter (poorer in N) and N release from Q. ilex litter (richer in N). In conclusion, in these forests soil microclimate and/or N availability appear to be more important controlling litter decomposition than the distribution of faunal activity.  相似文献   

19.
Initial decomposition rates, changes in organic chemical components (acid-insoluble fraction, holocellulose, polyphenols, soluble carbohydrates) and nutrient dynamics (K, Mg, Ca, P, N) were examined for fine roots and leaves of Japanese cypress (Chamaecyparis obtusa). Litterbag experiments designed to evaluate the relative effects of litter type and position of litter supply in the soil were carried out, considering that root and leaf litter typically occupy different locations and have different substrate qualities. Litterbags of roots and leaves were placed at two positions (on the soil surface and in the humus layer), and collected every 3 months over one year. The mass loss rate and N release were slower during root decomposition in the humus layer than during leaf decomposition on the soil surface. These differences between root and leaf decomposition were mainly caused by the litter type, and the effect of the position on decomposition was relatively small. Root litter was less influenced by position related effects, such as differences in humidity, than leaf litter, and this recalcitrant trait to environmental effects may be responsible for the slower mass loss rate and N release in root decomposition. The results of the present study suggest that fine roots are persistent in the soil and serve an important role in N retention in forest ecosystems because of their litter substrate quality.  相似文献   

20.
Investigations on the mass loss of leaf litter were carried out between 1992 and 1994 using litter bags of 0.02 mm and 5 mm mesh sizes in a beech and a mixed forest in northern Germany. The two forests on moder humus differed in soil faunal composition, vegetation type, and nutrient supply. Mass loss and N and C concentrations were determined from the litter at bimonthly intervals. From subsamples macrofauna were sorted by hand and mesofauna was extracted by heat. The biomass and N content of the litter bag fauna was estimated. Mass loss, particularly that attributed to the fauna, was different between the two sites with highest rates in the mixed forest and lowest at the beech site. A significantly higher rate of N release was found for the litter extracted from 5 mm mesh size litter bags in the mixed forest but not in the beech forest. Collembola and Cryptostigmata changed in numbers during litter breakdown. Collembola reached high numbers in the beginning, whereas Cryptostigmata dominated later. The diversity of Cryptostigmata increased at both sites during litter breakdown, whereas collembolan diversity only increased in the beech forest and remained at the same level in the mixed forest. Several species of Collembola and Cryptostigmata occurred earlier in the mixed forest than in the beech forest. Mass loss rate attributable to the fauna did not correspond to total faunal biomass. Only Isopoda, Diplopoda and Cryptostigmata appeared to affect the mass loss positively, whereas the biomass of Lumbricidae was negatively correlated with mass loss, particularly in the beech forest. On the other hand, the release of N attributable to the fauna was positively correlated with the total faunal biomass in the beech forest and Lumbricidae in particular were positively correlated with N-release at both sites.  相似文献   

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