桉-桤混合凋落物分解及其土壤动物群落动态

采用放置不同孔径凋落袋(6目、30目和260目)的方法,研究了四川省乐山市苏稽镇不同比例巨桉(Eucalyptus grandis)与台湾桤木(Alnus formosana)混合凋落物的质量损失率及土壤动物群落结构的变化.结果表明:不同比例桉-桤混合凋落物均表现出前期分解迅速,后期分解较慢的规律.不同孔径凋落物袋中凋落物的分解率表现为6目最大,30目次之,260目最小.同孔径凋落物袋中不同比例桉-桤混合凋落物的分解速率也有不同,6目中各种凋落物分解时长相差较小,而30目和260目中纯巨桉、纯台湾桤木凋落物分解率达95%的时间之差分别为1175 d和908 d.凋落物分解过程中大型土壤动物类群结构发生了明显变化,分解初期主要为啮虫目,中期为后孔寡毛目,后期为鞘翅目,末期为双翅目.这些结果为进一步研究桉桤混交林物质循环提供了重要数据.     

桉-桤不同混合比例凋落物分解过程中 土壤动物群落动态

采用凋落物分解袋法研究了10:0(TⅠ)、7:3(TⅡ)5:5(TⅢ)、3:7(TⅣ)和0:10(TV)巨桉(Eucalyptus grandis)和台湾桤木(Alnus formosana)混合凋落物分解过程中的土壤动物群落特征.从5种类型、3种规格的810只凋落袋中共收集土壤动物75651只,隶属2门10纲20目,其中弹尾目(Collembola)和蜱螨目(Acarina)为优势类群.土壤动物个体数最高是7-8月,大型土壤动物个体数最高是7月,中小型土壤动物个体数最高是7-8月.大型、中小型土壤动物类群数各月间均波动较小.与30目和6目相比,260目网袋中弹尾目和蜱螨目等中小型土壤动物数量更高.相对台湾桤木(TV)而言,巨桉(TⅠ)凋落物中弹尾目数量更多.啮虫目(Psocoptera)在台湾桤木(TV)凋落物中的数量远远高于其它凋落物,后孔寡毛目(Opisthopora)在混合凋落物中数量较高.不同比例的凋落物混合可改变凋落物中土壤动物的数量和组成.桤木、混合凋落物中大型土壤动物的个体数高于巨桉凋落物,而且上述凋落物的分解速率亦明显快于巨桉凋落物,这意味着大型土壤动物的活动可加速凋落物的分解.因此,在巨桉人工纯林中混栽台湾桤木,可显著提高大型土壤动物的数量,促进凋落物的分解.     

青冈林土壤动物群落结构在落叶分解过程中的演替变化

１９９３年５月－１９９５年４月,采用落叶袋法研究了中亚热带青冈（Ｃｙｃｌｏｂａｌａｎｏｐｓｉｓｇｌａｕｃａ）林土壤动物在落叶分离过程中的演替,变化,用多样性指数,演替指数,相似系数分析土壤动物群落结构的季节变化和在落叶分解过程中的演替,分解出现的类群,密度最高的为蜱螨目（Ａｃａｒｉｎａ）其次为弹尾目（Ｃｏｌｌｅｍｂｏｌａ）,二者个体数之和占总数的９２．７％,其他依次为：双翅目（Ｄｉｐｔｅｒａ）膜翅     

四川盆地亚热带常绿阔叶林不同物候期凋落物分解与土壤动物群落结构的关系

为了解植物生长不同物候时期凋落物分解过程中土壤动物群落结构动态及其与凋落物分解的关系,以四川盆地亚热带常绿阔叶林典型人工林树种马尾松和柳杉,次生林树种香樟和麻栎凋落物为研究对象,采用凋落物分解袋试验研究,凋落物分解过程中土壤动物的群落特征。4种凋落物分解袋共获得土壤动物8047只,其中,柳杉(2341只)>香樟(2105只)>马尾松(2046只)>麻栎(1555只)。其中,秋末落叶期、萌动期和展叶期,马尾松凋落物袋中主要以捕食性土壤动物为优势类群,而后以菌食性土壤动物为主;香樟凋落物袋中除秋末落叶期和叶衰期以菌食性土壤动物为主要优势类群外,其他各时期均以捕食性土壤动物为主要优势类群;柳杉凋落物分解各时期均以菌食性土壤动物为主要优势类群;麻栎凋落物分解在前3个时期以菌食性为主,而后以植食性土壤动物为主要优势类群。相关分析表明,在秋末落叶期和萌动期土壤动物的个体密度主要和氮、磷含量及其格局密切相关,叶衰期主要和难分解组分木质素显著相关。除在秋末落叶期土壤动物对凋落物分解的贡献率与土壤动物的个体密度显著相关外,其余主要物候关键时期均与土壤动物的类群密度及其食性显著相关。     

上海宝钢工业区凋落物中土壤动物群落结构及季节变化

为探讨城市工业区凋落物中土壤动物的群落特征, 作者于2005年夏季至2006年春季, 对上海市宝山钢铁公司厂区不同功能区(生产区、过渡区和办公区)凋落物中的土壤动物进行了调查。共捕获土壤动物52,070 只, 分别隶属于3门10纲19目, 优势类群为蜱螨目和弹尾目, 二者共占总数的90.60%; 常见类群为鳞翅目和近孔寡毛目。不同功能区的优势类群相同, 常见类群相异, 且土壤动物总密度随着生产区-过渡区-办公区呈现递减趋势; 不同功能区凋落物和不同绿化类型(乔木和灌木)中的5种指数呈现规律不同: Simpson优势度指数(C)、Margalef丰富度指数(D)为中间过渡区高, 两边区域低; Pielou均匀度指数(E)为生产区>办公区>过渡区; DG指数和Shannon-Wiener多样性指数表现为生产区>过渡区>办公区; 凋落物中土壤动物数量的季节变化为冬季>秋季>夏季>春季, 而类群数量为冬季=秋季>夏季=春季; 不同功能区凋落物pH值、有机碳、总氮和总磷含量不同, 其中pH值、总氮达到显著性差异, 对凋落物中土壤动物有一定影响。     

青冈林土壤跳虫群落结构在落叶分解过程中的变化

1993年5月至1995年4月,用落叶代法研究青冈（Cyclobalanopsis glauca）落叶分解过程中跳虫的群落结构变化。用多样性指数、演替指数、相似系数分析跳虫在落叶分解过程中群落结构及其季节变化特点。青冈落叶分解经淋洗、养分固定 养分活化3个阶段,分解常数分别为k1=9.11,k2=2.57,k3=0.43（百分比／月）。跳中心在落叶分解过程中的集聚型分为3组：A组为落叶分解前期集聚的种类,B组为后期的种类,C组为中期或全过程的种类,分析讨论了落叶分解过程与跳虫功能群及群落结构变化的关系。     

放牧对内蒙古典型草原大针茅凋落物中土壤动物组成及其分解功能的影响

放牧是影响草地生态系统中土壤动物组成和凋落物分解的重要因素.2010—2012年,选择内蒙古锡林郭勒盟白音锡勒牧场境内的禁牧草地、放牧草地和沙地为研究样地,以凋落物袋法研究了大针茅凋落物分解过程中主要理化特性以及其中土壤动物群落的变化特征.共采集到土壤动物67056头52类,隶属于5门8纲,其中螨类23科,昆虫19科.大针茅凋落物的初始有机质含量为92.5%,分解780 d后分别降至40.0%(禁牧草地)和41.3%(放牧草地),差异不显著;凋落物残留率分别降低至50.0%(禁牧草地)和23.0%(放牧草地),差异显著.放牧影响下,大针茅残留凋落物中土壤动物多度显著降低.将大针茅凋落物置入沙地环境,有机质分解速率无显著变化,但凋落物残留率显著降低,螨类群落组成发生显著变化.在内蒙古典型草原环境下,放牧显著改变了植物凋落物中的土壤动物群落组成和多度,但凋落物中有机质分解速率未发生显著变化;半干旱地区土壤动物的凋落物分解功能较为微弱.     

亚热带森林凋落叶分解过程土壤节肢动物群落的变化特征

土壤动物群落结构和多样性可能随凋落物分解进程和基质质量的变化不断改变。为了解亚热带森林凋落叶分解过程中土壤节肢动物群落变化特征,以四川盆地亚热带森林麻栎（Quercus acutissima）和柳杉（Cryptomeria fortunei）凋落叶为对象,于2011-2015年采用分解袋法研究了2种凋落叶分解过程中土壤节肢动物组成、结构和多样性动态变化。整个研究期间,柳杉和麻栎凋落叶分解袋中共捕获土壤节肢动物3855只,分属于16目51科,且均以等节跳科和棘跳科为优势类群;麻栎凋落叶中土壤节肢动物的个体密度随分解进程呈现增加趋势,在分解的1079天达最高值后降低,而柳杉凋落叶则在分解的156天急剧增加后快速降低,2种凋落叶中土壤节肢动物类群数量具有相似的动态变化过程;2种凋落叶中土壤节肢动物总体以菌食性数量比例最高,腐食性最低,且随凋落叶分解进程,植食性土壤节肢动物占比明显下降,菌食性则上升;非度量多维尺度（NMDS）分析显示,2种凋落叶中土壤节肢动物群落组成具有显著差异,聚类分析表明,2种凋落叶土壤节肢动物群落结构相似性随分解进程不断降低。亚热带森林凋落叶分解过程中土壤节肢动物群落组成、结构和多样性受凋落叶类型影响。     

天童常绿阔叶林五个演替阶段凋落物中的土壤动物群落

为探讨森林凋落物中土壤动物群落的结构特征以及土壤动物群落随植被演替而发生的变化 ,于 2 0 0 3年冬季 ,对浙江天童常绿阔叶林 5个演替阶段凋落物中的土壤动物群落 ,按代表不同分解阶段的新鲜凋落物层、腐叶层和腐殖土层进行了调查研究。共获得土壤动物 13381只 ,分别隶属于 2门 8纲 2 0目。优势类群为蜱螨目 (Arcarina)和弹尾目 (Collem bola) ,二者共占总数的 94 .2 4 % ,A/ C为 7.6 6 ;常见类群为双翅目 (Diptera)。研究结果表明 :(1)凋落物中的土壤动物群落存在明显的有别于真土层的垂直分布 ,类群数和个体数总体表现为向下递增的趋势。共有 19类、5 9.0 3%的土壤动物分布在底部腐殖土层 ,仅 8类、5 .35 %的土壤动物分布在新鲜凋落物层 ,其余共 8类分布在中间腐叶层。而且 ,不同类群在各演替阶段的分布表现出一定的差异 ;(2 )凋落物中土壤动物群落随植物群落的演替而发生明显的变化 :个体总数和类群总数在演替顶极阶段最高 ,其次为中期阶段 ,演替初期最低。但是 ,在目这一分类等级上 ,各演替阶段凋落物中土壤动物群落的主要类群基本一致 ,均为蜱螨目、弹尾目、双翅目和鳞翅目 (L epidoptera) ;(3)相似性分析表明 ,演替中期凋落物中土壤动物群落与顶极阶段最为相似 ;但它们的Shannon- Wiener多样性     

凋落物多样性及组成对凋落物分解和土壤微生物群落的影响

凋落物分解是生态系统营养物质循环的核心过程,而土壤微生物群落在凋落物分解过程中扮演着极其重要且不可替代的角色。随着生物多样性的丧失日益严峻,探讨凋落物多样性及组成对凋落物分解和土壤微生物群落的影响,不仅有助于了解凋落物分解的内在机制,而且可为退化草原生态系统的恢复提供参考。以内蒙古呼伦贝尔草原退化恢复群落中的草本植物为研究对象,依据植物多度、盖度、频度和物种的重要值及其在群落中的恢复程度筛选出排序前4的羊草（Leymus chinensis）、茵陈蒿（Artemisia capillaris）、麻花头（Serratula centauroides）、二裂委陵菜（Potentilla bifurca）的凋落物为实验材料,通过设置3种凋落物多样性水平（1,2,4）,包括11种凋落物组合（单物种凋落物共4种,两物种凋落物混合共6种,四物种凋落物混合共1种）,利用磷脂脂肪酸（PLFA）方法来研究分解60 d后凋落物多样性及组成对凋落物分解和土壤微生物群落的影响。结果表明：（1）凋落物物种多样性仅对C残余率具有显著影响,表现在两物种混合凋落物C残余率显著低于单物种凋落物,而凋落物组成对所观测的4个凋落物分解参数（质量、C、N残余率以及C/N）均具有显著影响;（2）凋落物物种多样性对细菌（B）含量具有显著影响,而凋落物组成对真菌（F）含量具有显著影响,两者对F/B以及微生物总量均无显著影响;（3）冗余分析结果表明凋落物组成与凋落物分解相关指标（凋落物质量、C、N残余率及C/N）和土壤微生物（真菌、细菌含量）的相关关系高于凋落物多样性。（4）进一步建立结构方程模型（Structural Equation Model,SEM）发现,凋落物初始C含量对凋落物质量、C、N残余率及C/N有显著正的直接影响;凋落物木质素含量对凋落物质量、C、N残余率有显著正的直接影响;凋落物初始N含量对N残余率有显著正的直接影响,而对C残余率及C/N有显著负的直接影响;凋落物初始C/N对凋落物质量、N残余率有显著正的直接影响,而对C/N有显著负的直接影响。此外,凋落物初始C、N、木质素含量及C/N均对真菌含量具有显著正影响,并可通过真菌对凋落物质量分解产生显著负的间接影响。以上结果表明该退化恢复区域优势种凋落物分解以初始C、木质素为主导,主要通过土壤真菌影响凋落物的分解进程,这将减缓凋落物的分解速率进而减慢草原生态系统的进程。这些结果为凋落物多样性及组成对自身分解和土壤微生物群落的影响提供了实验依据,也为进一步分析凋落物分解内在机制以及草原生态系统的恢复提供了数据参考。     

Leaf Litter Mixtures Alter Microbial Community Development: Mechanisms for Non-Additive Effects in Litter Decomposition

To what extent microbial community composition can explain variability in ecosystem processes remains an open question in ecology. Microbial decomposer communities can change during litter decomposition due to biotic interactions and shifting substrate availability. Though relative abundance of decomposers may change due to mixing leaf litter, linking these shifts to the non-additive patterns often recorded in mixed species litter decomposition rates has been elusive, and links community composition to ecosystem function. We extracted phospholipid fatty acids (PLFAs) from single species and mixed species leaf litterbags after 10 and 27 months of decomposition in a mixed conifer forest. Total PLFA concentrations were 70% higher on litter mixtures than single litter types after 10 months, but were only 20% higher after 27 months. Similarly, fungal-to-bacterial ratios differed between mixed and single litter types after 10 months of decomposition, but equalized over time. Microbial community composition, as indicated by principal components analyses, differed due to both litter mixing and stage of litter decomposition. PLFA biomarkers a15∶0 and cy17∶0, which indicate gram-positive and gram-negative bacteria respectively, in particular drove these shifts. Total PLFA correlated significantly with single litter mass loss early in decomposition but not at later stages. We conclude that litter mixing alters microbial community development, which can contribute to synergisms in litter decomposition. These findings advance our understanding of how changing forest biodiversity can alter microbial communities and the ecosystem processes they mediate.     

Interactions between Litter Lignin and Nitrogenitter Lignin and Soil Nitrogen Availability during Leaf Litter Decomposition in a Hawaiian Montane Forest

Previous work in a young Hawaiian forest has shown that nitrogen (N) limits aboveground net primary production (ANPP) more strongly than it does decomposition, despite low soil N availability. In this study, I determined whether (a) poor litter C quality (that is, high litter lignin) poses an overriding constraint on decomposition, preventing decomposers from responding to added N, or (b) high N levels inhibit lignin degradation, lessening the effects of added N on decomposition overall. I obtained leaf litter from one species, Metrosideros polymorpha, which dominates a range of sites in the Hawaiian Islands and whose litter lignin concentration declines with decreasing precipitation. Litter from three dry sites had lignin concentrations of 12% or less, whereas litter from two wet sites, including the study site, had lignin concentrations of more than 18%. This litter was deployed 2.5 years in a common site in control plots (receiving no added nutrients) and in N-fertilized plots. Nitrogen fertilization stimulated decomposition of the low-lignin litter types more than that of the high-lignin litter types. However, in contrast to results from temperate forests, N did not inhibit lignin decomposition. Rather, lignin decay increased with added N, suggesting that the small effect of N on decomposition at this site results from limitation of decomposition by poor C quality rather than from N inhibition of lignin decay. Even though ANPP is limited by N, decomposers are strongly limited by C quality. My results suggest that anthropogenic N deposition may increase leaf litter decomposition more in ecosystems characterized by low-lignin litter than in those characterized by high-lignin litter. Received 26 October 1999; accepted 2 June 2000.     

Temperature and Moisture Modulate the Contribution of Soil Fauna to Litter Decomposition via Different Pathways

Ecosystems - Soil fauna are crucial decomposers in terrestrial ecosystems, but how the role of soil fauna varies among climatic conditions and litter substrates remains poorly understood. Here, we...     

Effects of Leaf Litter Species on Macroinvertebrate Colonization during Decomposition in a Portuguese Stream

This study evaluated if there are differences in leaf breakdown and invertebrate colonization among tree species differing in quality (toughness), and which factors could influence these differences. Common alder leaves decomposed significantly faster then either sweet chestnut or Spanish oak (k values of –0.0332, –0.0108, and –0.0112, respectively) during the first 2 months. Shredder abundance was highest when leaf mass remaining was 50%, and the samples clustered in mixed groups of sampling dates and leaf species, suggesting that stage of decomposition was an important factor influencing shredder colonization. During the first two months of decomposition, the physicochemical characteristics of leaf litter and the interaction between leaf toughness and the occurrence of frequent spates seemed to be the main factors affecting leaf breakdown rates in the stream. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Disentangling the Litter Quality and Soil Microbial Contribution to Leaf and Fine Root Litter Decomposition Responses to Reduced Rainfall

Climate change-induced rainfall reductions in Mediterranean forests negatively affect the decomposition of plant litter through decreased soil moisture. However, the indirect effects of reduced precipitation on litter decomposition through changes in litter quality and soil microbial communities are poorly studied. This is especially the case for fine root litter, which contributes importantly to forests plant biomass. Here we analyzed the effects of long-term (11 years) rainfall exclusion (29% reduction) on leaf and fine root litter quality, soil microbial biomass, and microbial community-level physiological profiles in a Mediterranean holm oak forest. Additionally, we reciprocally transplanted soils and litter among the control and reduced rainfall treatments in the laboratory, and analyzed litter decomposition and its responses to a simulated extreme drought event. The decreased soil microbial biomass and altered physiological profiles with reduced rainfall promoted lower fine root—but not leaf—litter decomposition. Both leaf and root litter, from the reduced rainfall treatment, decomposed faster than those from the control treatment. The impact of the extreme drought event on fine root litter decomposition was higher in soils from the control treatment compared to soils subjected to long-term rainfall exclusion. Our results suggest contrasting mechanisms driving drought indirect effects on above-(for example, changes in litter quality) and belowground (for example, shifts in soil microbial community) litter decomposition, even within a single tree species. Quantifying the contribution of these mechanisms relative to the direct soil moisture-effect is critical for an accurate integration of litter decomposition into ecosystem carbon dynamics in Mediterranean forests under climate change.     

Leaf Litter Fuels Methanogenesis Throughout Decomposition in a Forested Peatland

Decomposing leaf litter is a large supply of energy and nutrients for soil microorganisms. How long decaying leaves continue to fuel anaerobic microbial activity in wetland ecosystems is poorly understood. Here, we compare leaf litter from 15 tree species with different growth forms (angiosperms and gymnosperms, deciduous, and longer life span), using litterbags positioned for up to 4 years in a forested peatland in New York State. Periodically, we incubated partially decayed residue per species with fresh soil to assess its ability to fuel microbial methane (CH₄) production and concomitant anaerobic carbon dioxide (CO₂) production. Decay rates varied by leaf type: deciduous angiosperm > evergreen gymnosperm > deciduous gymnosperm. Decay rates were slower in leaf litter with a large concentration of lignin. Soil with residue of leaves decomposed for 338 days had greater rates of CH₄ production (5.8 µmol g^?1 dry mass d^?1) than less decomposed (<0.42 µmol g^?1 dry mass d^?1) or more decomposed (2.1 µmol g^?1 dry mass d^?1) leaf residue. Species-driven differences in their ability to fuel CH₄ production were evident throughout the study, whereas concomitant rates of CO₂ production were more similar among species and declined with degree of decomposition. Methane production rates exhibited a positive correlation with pectin and the rate of pectin decomposition. This link between leaf litter decay rates, biochemical components in leaves, and microorganisms producing greenhouse gases should improve predictions of CH₄ production in wetlands.     

Bacterial Diversity in Agricultural Soils during Litter Decomposition

Denaturing gradient gel electrophoresis (DGGE) of amplified fragments of genes coding for 16S rRNA was used to study the development of bacterial communities during decomposition of crop residues in agricultural soils. Ten strains were tested, and eight of these strains produced a single band. Furthermore, a mixture of strains yielded distinguishable bands. Thus, DGGE DNA band patterns were used to estimate bacterial diversity. A field experiment performed with litter in nylon bags was used to evaluate the bacterial diversity during the decomposition of readily degradable rye and more refractory wheat material in comparable luvisols and cambisols in northern, central, and southern Germany. The amount of bacterial DNA in the fresh litter was small. The DNA content increased rapidly after the litter was added to the soil, particularly in the rapidly decomposing rye material. Concurrently, diversity indices, such as the Shannon-Weaver index, evenness, and equitability, which were calculated from the number and relative abundance (intensity) of the bacterial DNA bands amplified from genes coding for 16S rRNA, increased during the course of decomposition. This general trend was not significant for evenness and equitability at any time. The indices were higher for the more degradation-resistant wheat straw than for the more easily decomposed rye grass. Thus, the DNA band patterns indicated that there was increasing bacterial diversity as decomposition proceeded and substrate quality decreased. The bacterial diversity differed for the sites in northern, central, and southern Germany, where the same litter material was buried in the soil. This shows that in addition to litter type climate, vegetation, and indigenous microbes in the surrounding soil affected the development of the bacterial communities in the litter.     

Effect of Temperature on the Taxonomic Structure of Soil Bacterial Communities during Litter Decomposition

Microbiology - Effect of temperature on succession changes of the saprotrophic bacterial community of gray forest soil in the course of decomposition of aspen leaves and branches was studied in...     

Contribution of Fungi and Bacteria to Leaf Litter Decomposition in a Polluted River

The contribution of fungi and bacteria to the decomposition of alder leaves was examined at two reference and two polluted sites in the Ave River (northwestern Portugal). Leaf mass loss, microbial production from incorporation rates of radiolabeled compounds into biomolecules, fungal biomass from ergosterol concentration, sporulation rates, and diversity of aquatic hyphomycetes associated with decomposing leaves were determined. The concentrations of organic nutrients and of inorganic nitrogen and phosphorus in the stream water was elevated and increased at downstream sites. Leaf decomposition rates were high (0.013 day⁻¹ < k < 0.042 day⁻¹), and the highest value was estimated at the most downstream polluted site, where maximum values of microbial production and fungal biomass and sporulation were found. The slowest decomposition occurred at the other polluted site, where, along with the nutrient enrichment, the lowest current velocity and dissolved-oxygen concentration in water were observed. At this site, fungal production, biomass, and sporulation were depressed, suggesting that stimulation of fungal activity by increased nutrient concentrations might be offset by other factors. Although bacterial production was higher at polluted sites, fungi accounted for more than 94% of the total microbial net production. Fungal yield coefficients varied from 10.2 to 13.6%, while those of bacteria were less than 1%. The contribution of fungi to overall leaf carbon loss (29.0 to 38.8%) greatly exceeded that of bacteria (4.2 to 13.9%).     

Fine Scale Patterns in Microbial Extracellular Enzyme Activity during Leaf Litter Decomposition in a Stream and its Floodplain

Microorganisms mediate the decomposition of leaf-litter through the release of extracellular enzymes. The surfaces of decomposing leaves are both chemically and physically heterogeneous, and spatial patterns in microbial enzyme activity on the litter surface should provide insights into fine-scale patterns of leaf-litter decomposition. Platanus occidentalis leaves were collected from the floodplain of a third-order stream in northern Mississippi, enclosed in individual litter bags, and placed in the stream channel and in the floodplain. Replicate leaves were collected approximately monthly over a 9-month period and assayed for spatial variation in microbial extracellular enzyme activity and rates of organic matter (OM) decomposition. Spatial variation in enzyme activity was measured by sampling 96 small discs (5-mm diameter) cut from each leaf. Discs were assayed for the activity of enzymes involved in lignin (oxidative enzymes) and cellulose (β-glucosidase, cellobiohydrolase) degradation. Rates of OM loss were greater in the stream than the floodplain. Activities of all enzymes displayed high variability in both environments, with severalfold differences across individual leaves, and replicate leaves varied greatly in their distribution of activities. Geostatistical analysis revealed no clear patterns in spatial distribution of activity over time or among replicates, and replicate leaves were highly variable. These results show that fine-scale spatial heterogeneity occurs on decomposing leaves, but the level of spatial variability varies among individual leaves at the measured spatial scales. This study is the first to use geostatistical analyses to analyze landscape patterns of microbial activity on decomposing leaf litter and in conjunction with studies of the microbial community composition and/or substrate characteristics, should provide key insights into the function of these processes.