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。     

Genetic parameters for canalisation analysis of litter size and litter weight traits at birth in mice

The aim of this research was to explore the genetic parameters associated with environmental variability for litter size (LS), litter weight (LW) and mean individual birth weight (IW) in mice before canalisation. The analyses were conducted on an experimental mice population designed to reduce environmental variability for LS. The analysed database included 1976 records for LW and IW and 4129 records for LS. The total number of individuals included in the analysed pedigree was 3997. Heritabilities estimated for the traits under an initial exploratory approach varied from 0.099 to 0.101 for LS, from 0.112 to 0.148 for LW and from 0.028 to 0.033 for IW. The means of the posterior distribution of the heritability under a Bayesian approach were the following: 0.10 (LS), 0.13 (LW) and 0.03 (IW). In general, the heritabilities estimated under the initial exploratory approach for the environmental variability of the analysed traits were low. Genetic correlations estimated between the trait and its variability reached values of -0.929 (LS), -0.815 (LW) and 0.969 (IW). The results presented here for the first time in mice may suggest a genetic basis for variability of the evaluated traits, thus opening the possibility to be implemented in selection schemes.     

Effects of grassland-use on soil respiration and litter decomposition

 草地利用方式影响植被群落结构和土壤微环境, 制约草地生态系统碳循环。该文通过测定温带草原在放牧、割草、围封3种利用方式下湿润年(2012年)和干旱年(2011年)的凋落物产量、质量及其分解速率和土壤碳通量, 分析了草地利用方式对土壤呼吸和凋落物的影响, 探讨了凋落物对土壤呼吸的贡献机制。结果表明: 在干旱年份, 放牧样地土壤呼吸最大, 分别达到割草和围封样地的1.5倍和1.29倍; 在湿润年份, 割草样地土壤呼吸最大, 为309 g C·m^–2·a^–1, 明显高于放牧样地和围封样地。不论干旱年还是湿润年, 围封样地凋落物产量都大于放牧样地和割草样地。3种利用方式下湿润年土壤呼吸和凋落物分解均比干旱年增强。因此, 水分是温带草原植物生长和生态系统碳循环的主要限制因子, 草地利用方式则显著影响凋落物生产和分解。进一步分析表明, 经过两年的分解, 同一样地内凋落物质量C:N下降, N含量和木质素:N升高, 土壤呼吸与凋落物产量、凋落物分解速率以及木质素:N正相关, 而与凋落物C:N负相关。     

草地利用方式对土壤呼吸和凋落物分解的影响

草地利用方式影响植被群落结构和土壤微环境, 制约草地生态系统碳循环。该文通过测定温带草原在放牧、割草、围封3种利用方式下湿润年(2012年)和干旱年(2011年)的凋落物产量、质量及其分解速率和土壤碳通量, 分析了草地利用方式对土壤呼吸和凋落物的影响, 探讨了凋落物对土壤呼吸的贡献机制。结果表明: 在干旱年份, 放牧样地土壤呼吸最大, 分别达到割草和围封样地的1.5倍和1.29倍; 在湿润年份, 割草样地土壤呼吸最大, 为309 g C∙m^-2∙a^-1, 明显高于放牧样地和围封样地。不论干旱年还是湿润年, 围封样地凋落物产量都大于放牧样地和割草样地。3种利用方式下湿润年土壤呼吸和凋落物分解均比干旱年增强。因此, 水分是温带草原植物生长和生态系统碳循环的主要限制因子, 草地利用方式则显著影响凋落物生产和分解。进一步分析表明, 经过两年的分解, 同一样地内凋落物质量C:N下降, N含量和木质素:N升高, 土壤呼吸与凋落物产量、凋落物分解速率以及木质素:N正相关, 而与凋落物C:N负相关。     

亚热带3种树种凋落叶厚度对其分解速率及酶活性的影响

对中国亚热带树种杉木(Cunninghamia lanceolata)、香樟(Cinnamomum camphora)、银杏(Ginkgo biloba)3个树种在不同凋落物厚度下凋落物分解速率和分解酶活性进行了探究.利用分解网袋法,根据浙江省的平均酸雨水平,在酸雨(pH4.0)条件下设置了凋落物40g、凋落物20g、凋落物10g 3个梯度.结果表明:凋落物分解速率随厚度的增加呈加快的趋势,杉木凋落物10、20、40g的年分解系数K分别为0.24、0.27、0.34,香樟凋落物10、20、40g的年分解系数K分别为0.25、0.3、0.32,银杏凋落物10、20、40g的年分解系数K分别为0.42、0.5、0.58;脲酶活性表现为:凋落叶40g＞凋落叶20g＞凋落叶10g,纤维素酶活性表现为:凋落叶40g、凋落叶20g＞凋落叶10g,蔗糖酶活性表现为:后期凋落叶40g＞凋落叶20g＞凋落叶10g,凋落物分解过程是多种酶共同作用的结果.     

Temporal dynamics of biotic and abiotic drivers of litter decomposition

Climate, litter quality and decomposers drive litter decomposition. However, little is known about whether their relative contribution changes at different decomposition stages. To fill this gap, we evaluated the relative importance of leaf litter polyphenols, decomposer communities and soil moisture for litter C and N loss at different stages throughout the decomposition process. Although both microbial and nematode communities regulated litter C and N loss in the early decomposition stages, soil moisture and legacy effects of initial differences in litter quality played a major role in the late stages of the process. Our results provide strong evidence for substantial shifts in how biotic and abiotic factors control litter C and N dynamics during decomposition. Taking into account such temporal dynamics will increase the predictive power of decomposition models that are currently limited by a single‐pool approach applying control variables uniformly to the entire decay process.     

凋落物多样性及组成对凋落物分解及土壤微生物群落的影响——二氧化碳倍增条件下

受全球变化的影响生物多样性的丧失日益严重,及时了解凋落物物种多样性及其组成如何直接或者通过调节微生物群落来间接影响凋落物分解已经成为生态学领域的热点问题之一。在呼伦贝尔典型草原区,羊草（Leymus chinensis）为原生群落建群种,茵陈蒿（Artemisia capillaris）、麻花头（Serratula centauroides）、二裂委陵菜（Potentilla bifurca）在退化及恢复群落中的多度均较大,本研究以此4种植物的凋落物为研究对象,在两倍于当前大气CO₂浓度（800 μmol/mol）条件下,通过嵌套实验设计来研究凋落物多样性（凋落物组成）对凋落物质量、C、N残余率和残余C/N的影响,并深入分析凋落物初始性质以及土壤革兰氏阳性菌（G⁺）、革兰氏阴性菌（G^-）、细菌（B）、真菌（F）及土壤总微生物磷脂脂肪酸（Phospholipid Fatty Acid,PLFA）含量和F/B对凋落物分解的影响。结果表明：（1）凋落物多样性及组成对凋落物质量、C、N残余率以及残余C/N均具有显著影响;凋落物组成对G⁺ PLFAs含量具有显著影响;（2）冗余分析（Redundancy Analysis,RDA）结果表明凋落物组成对凋落物分解和土壤微生物群落相关指标的影响高于凋落物多样性;（3）结构方程模型（Structural Equation Model,SEM）结果表明凋落物初始木质素含量和初始C/N均对凋落物分解具有显著影响,其中凋落物初始木质素含量起主导作用,其还可通过对土壤真菌PLFAs含量的影响来间接影响凋落物N残余率和残余C/N。所得结果可为大气CO₂浓度升高条件下退化草原生态系统的物质循环特征的预测乃至草原生态系统功能的合理评估提供数据支持。     

毛竹凋落叶组成对叶凋落物分解的影响

毛竹混交林具有较高的生产力和较好的生态功能,可能与混合凋落物的养分归还特征有关。本研究采用凋落物分解袋法对不同混合比例毛竹凋落叶分解特征进行了为期1年的研究,共设置5个处理,分别为Ⅰ(毛竹纯叶)、Ⅱ(毛竹、楠木叶比例为8:2);Ⅲ(毛竹、杉木叶比例8:2)、Ⅳ(毛竹、楠木叶比例5:5)和Ⅴ(毛竹、杉木叶比例5:5)。结果表明,不同处理凋落物分解速率符合Olson指数分解模型,R2均高于0.92。5个处理分解系数的排列顺序为Ⅱ>Ⅰ>Ⅲ>Ⅴ>Ⅳ,分别为0.68、0.66、0.58、0.55和0.49。处理Ⅰ和Ⅱ的分解速度显著高于其他处理,说明并非所有类型毛竹混合凋落叶均会促进凋落物分解,只有合适的比例和树种会促进凋落物分解。其中,竹阔混合凋落叶的分解速度高于竹针混合凋落叶的分解速度,竹阔混交可能更有利于竹林持续生产力的维持。N、P、K3种元素养分释放模式不同,N元素表现为净富集与净释放交替出现;P元素在经过4个月的快速富集后,4—5个月有短暂的净释放过程,其后呈富集状态;K元素浓度先升高后降低,在放置的前3个月净释放,随后呈富集状态。竹林凋落叶的养分含量对凋落物养分归还有重要影响,尤其是C/N和P可能作为竹林凋落...     

川西高山林线交错带凋落叶分解初期转化酶特征

胞外酶对于有机质的降解具有重要的作用。在凋落物分解过程中,酶活性不仅受到凋落物种类或基质质量的影响,还受到环境因素的影响。转化酶催化蔗糖水解为葡萄糖和果糖,因此在凋落物分解早期,转化酶比降解难分解物质的酶具有更重要的作用。以川西高山林线交错带12种代表性凋落叶为研究对象,对林线交错带不同植被类型下的凋落叶转化酶活性以及物种和环境因子对转化酶活性的影响进行了研究。结果表明:同一植被类型下,12个物种转化酶活性具有极显著差异(P0.01)。物种、环境因子及其交互作用对转化酶活性有极显著的影响(P0.01)。初始纤维素含量与转化酶活性极显著正相关(P0.01)。初始木质素和总酚含量与转化酶活性极显著负相关(P0.01),能够共同解释转化酶活性变异的50.8%。不同植物生活型中,禾草类转化酶活性均为最高,这可能与禾草类较高的初始纤维素含量、较低的木质素和总酚含量有关。多元线性回归分析表明,凋落叶含水量能单独解释转化酶活性变量的62.1%,是环境因子中最重要的变量。从植被类型来看,大多数物种的转化酶活性在针叶林中均极显著高于高山草甸和灌丛(P0.01),这可能与针叶林中凋落叶的含水量最高且雪被最厚有关。历经一个雪被期分解后,凋落叶初始质量与环境因子的综合作用能够解释转化酶活性变异的79.1%,表明川西高山林线交错带凋落叶分解前期转化酶活性主要受初始木质素含量、总酚含量和含水量的调控。在全球气候变化情景下,凋落物水分含量的变化将会强烈的影响凋落叶分解前期的转化酶活性。     

Nitrogen in shoot litter,root litter and root exudates from nitrogen-fixingAlnus incana

Summary A pot experiment withAlnus incana (L.) Moench growing in sand was set up to compare the amounts of nitrogen released from plants shoot litter with that released below ground as root litter and/or root exudation. No nitrogen fixation by free-living microorganisms was found in the sand and the increased nitrogen content of the plant + soil system was therefore due to nitrogen fixation byFrankia in the alder root-nodules. Most of the nitrogen released from the plants was in the nitrogen-rich leaf and other shoot litter. Only small amounts of nitrogen were found in the drainage water from the pots and were recorded as increased nitrogen content of the sand.     

Climate and litter quality differently modulate the effects of soil fauna on litter decomposition across biomes

Climate and litter quality have been identified as major drivers of litter decomposition at large spatial scales. However, the role played by soil fauna remains largely unknown, despite its importance for litter fragmentation and microbial activity. We synthesised litterbag studies to quantify the effect sizes of soil fauna on litter decomposition rates at the global and biome scales, and to assess how climate, litter quality and soil fauna interact to determine such rates. Soil fauna consistently enhanced litter decomposition at both global and biome scales (average increment ~ 27%). However, climate and litter quality differently modulated the effects of soil fauna on decomposition rates between biomes, from climate‐driven biomes to those where climate effects were mediated by changes in litter quality. Our results advocate for the inclusion of biome‐specific soil fauna effects on litter decomposition as a mean to reduce the unexplained variation in large‐scale decomposition models.     

Tree litter functional diversity and nitrogen concentration enhance litter decomposition via changes in earthworm communities

Biodiversity is a major driver of numerous ecosystem functions. However, consequences of changes in forest biodiversity remain difficult to predict because of limited knowledge about how tree diversity influences ecosystem functions. Litter decomposition is a key process affecting nutrient cycling, productivity, and carbon storage and can be influenced by plant biodiversity. Leaf litter species composition, environmental conditions, and the detritivore community are main components of the decomposition process, but their complex interactions are poorly understood. In this study, we tested the effect of tree functional diversity (FD) on litter decomposition in a field experiment manipulating tree diversity and partitioned the effects of litter physiochemical diversity and the detritivore community. We used litterbags with different mesh sizes to separate the effects of microorganisms and microfauna, mesofauna, and macrofauna and monitored soil fauna using pitfall traps and earthworm extractions. We hypothesized that higher tree litter FD accelerates litter decomposition due to the availability of complementary food components and higher activity of detritivores. Although we did not find direct effects of tree FD on litter decomposition, we identified key litter traits and macrodetritivores that explained part of the process. Litter mass loss was found to decrease with an increase in leaf litter carbon:nitrogen ratio. Moreover, litter mass loss increased with an increasing density of epigeic earthworms, with most pronounced effects in litterbags with a smaller mesh size, indicating indirect effects. Higher litter FD and litter nutrient content were found to increase the density of surface‐dwelling macrofauna and epigeic earthworm biomass. Based on structural equation modeling, we conclude that tree FD has a weak positive effect on soil surface litter decomposition by increasing the density of epigeic earthworms and that litter nitrogen‐related traits play a central role in tree composition effects on soil fauna and decomposition.     

Genetic determinism for within-litter birth weight variation and its relationship with litter weight and litter size in the Ripollesa ewe breed

Birth weight plays a central role in lamb survival and growth, and the knowledge of its genetic determinism has become essential in worldwide selection programmes. Within this context, within-litter birth weight variation (BWV) has been suggested as an attractive trait to homogenise litters in prolific species, although it has not been analysed in sheep. The objective of this study was to ascertain whether maternal additive genetic variance exists for BWV in Ripollesa ewes, and to study its genetic, permanent environmental and residual relationships with litter weight (LW) and litter size (LS) at birth. Data were recorded in the Ripollesa experimental flock of the Universitat Autònoma of Barcelona, between 1986 and 2005, and included 1 662 litters from 380 ewes, with 712 records of BWV and 1 530 records of LW. Traits were analysed with a multivariate animal model solved through Bayesian methodologies, and with a threshold characterisation of LS. Additionally, the effect of BWV on lamb survival was studied. Additive genetic variance was observed for BWV (h² = 0.061), as well as for LW (h² = 0.200) and LS (h² = 0.141). Nevertheless, genetic correlations among those traits were not substantial (BWV and LW = 0.151; BWV and LS = − 0.219; LW and LS = − 0.320) and suffered from a high degree of uncertainly, with the null correlation included within the highest posterior interval at 95%. Within-litter birth weight variation and LS showed a negative and large permanent environmental correlation ( − 0.872), and LW and LS were negatively correlated due to residual ( − 0.762) and permanent environmental ( − 0.449) random sources of variation. Within-litter birth weight variation influenced lamb mortality during the first 7 days of life (P < 0.05), increasing and decreasing survivability in heavier and lighter littermates, respectively. Nevertheless, stillbirths and lambs died after the 1st week of life were not affected by BWV (P>0.05). The low heritability found indicates that slow genetic progress may be expected from selecting for BWV. Close to zero genetic correlations suggest that this selection will probably not affect LS and LW, although some significant permanent and residual correlations must be taken into account. Further studies are needed to understand better the genetic architecture among these three reproductive traits.     

降水量变化对蒙古栎落叶分解过程的间接影响

分析了在4种不同降水量条件下蒙古栎叶凋落物基质质量的变化,并应用分解袋法研究其凋落物在蒙古栎次生林内的分解过程.结果表明：与对照相比,降水量减少条件下,蒙古栎叶凋落物的初始N、P、K浓度显著升高,初始木质素浓度显著降低,凋落物分解速率大,N、P、K矿化率高,N和P固持时间缩短;降水量增加情况下,其凋落物初始N浓度显著降低、木质素浓度显著升高,N、P、K矿化率低,N和P固持时间延长.4种类型叶片凋落物的质量损失过程均符合指数降解模型,分解速率可以由凋落物木质素/N来预测.相关性分析显示,木质素浓度高、N浓度低的两种凋落物的分解速率与N浓度相关性最大;而木质素浓度低、N浓度高的两种凋落物的分解速率与木质素浓度相关性最大.说明降水量的变化显著地改变了蒙古栎叶凋落物的基质质量,进而间接地改变了凋落物的分解过程.     

根系在凋落物层中的生长及其对凋落物分解的影响

凋落物分解是生态系统养分循环的重要过程, 直接影响着生态系统功能。植物根系作为重要的生物因子调控着凋落物分解过程, 然而这一重要作用却在凋落物分解的研究中长期被忽视。凋落物中下层养分充足、保水能力强, 为根系生长提供了良好环境; 同时, 生长进入凋落物层的根系通过激发效应、共生真菌、N吸收等方式对分解过程产生了重要影响。该文针对根系生长及其影响因素、根系对凋落物分解的影响及其内在机制等关键方面进行了综述, 并提出了根系生长与凋落物分解之间关系的概念模型, 以期引起大家对这个领域的关注, 并为根系与凋落物分解之间关系的研究提供良好的借鉴。     

Dry matter and nutrient inputs through litter fall in a dry tropical forest of India

The present paper elucidates the pattern of leaf and non-leaf fall and quantifies of the total annual input of litter in a dry tropical forest of India. In addition, concentration of selected nutrients in various litter species and their annual return to the forest floor are examined. Total annual input of litter measured in litter traps ranged between 488.0–671.0 g m^-2 of which 65–72% was leaf litter fall and 28–35% wood litter fall. 73–81% leaves fall during the winter season. Herbaceous litter fall ranged between 80.0–110.0 g m^-2 yr^-1. The annual nutrient return through litter fall amounted (kg ha^-1): 51.6–69.6 N, 3.1–4.3 P, 31.0–40.0 Ca, 14.0–19.0 K and 3.7–5.0 Na, of which 71–77% and 23–29% were contributed by leaf and wood litter fall, respectively for different nutrients. Input of nutrients through herbaceous litter was: 13.0–16.6 for N, 1.0–1.4 for P, 4.0–5.0 for Ca, 7.9–10.5 for K and 0.8–1.0 kg ha^-1 yr^-1 for Na.     

森林凋落物分解重要影响因子及其研究进展

当前 ,森林凋落物分解被放在陆地生态系统碳平衡背景下进行研究 ,认识凋落物分解过程的影响因素和影响机理对理解地表碳平衡具有重要意义。凋落物在分解过程中 ,伴随有养分含量的变化 ,低品质凋落物在分解前期 (可达 2～ 3年 )会从环境中固定养分 ,特别是氮磷养分 ,而在后期则会释放出养分。凋落物本身的养分含量是影响分解速率的重要因素 ,高养分含量的凋落物分解快些 ,阔叶凋落物比针叶凋落物分解快些。有资料显示 ,在总分解率为2 9 4 %的构成中 ,理化因素、微生物因素与土壤动物因素对凋落物分解的贡献率分别为 7 2 %、8 0 %和 14 2 %。不同类型凋落物在分解过程中的土壤动物类群也不同 ,它也是造成凋落物分解速率不同的关键因素 ,通常阔叶树种凋落物分解过程中 ,会有更多的微节肢动物出现。CO2浓度升高将造成植物有机质含碳量与其它养分的比值升高 ,形成低品质的凋落物 ,从而间接影响凋落物分解速率 ,一般认为 ,全球CO2 浓度升高会加强土壤作为碳汇的功能。     

Stronger effects of litter origin on the processing of conifer than broadleaf leaves: A test of home‐field advantage of stream litter breakdown

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Drivers of litter mass loss and faunal composition of detritus patches change over time

Decomposition of vegetal detritus is one of the most fundamental ecosystem processes. In complex landscapes, the fate of litter of terrestrial plants may depend on whether it ends up decomposing in terrestrial or aquatic conditions. However, (1) to what extent decomposition rates are controlled by environmental conditions or by detritus type, and (2) how important the composition of the detritivorous fauna is in mediating decomposition in different habitats, remain as unanswered questions. We incubated two contrasting detritus types in three distinct habitat types in Coastal Georgia, USA, to test the hypotheses that (1) the litter fauna composition depends on the habitat and the litter type available, and (2) litter mass loss (as a proxy for decomposition) depends on environmental conditions (habitat) and the litter type. We found that the abundance of most taxa of the litter fauna depends primarily on habitat. Litter type became a stronger driver for some taxa over time, but the overall faunal composition was only weakly affected by litter type. Decomposition also depends strongly on habitat, with up to ca. 80% of the initial detrital mass lost over 25 months in the marsh and forest habitats, but less than 50% lost in the creek bank habitat. Mass loss rates of oak versus pine litter differed initially but converged within habitat types within 12 months. We conclude that, although the habitat type is the principle driver of the community composition of the litter fauna, litter type is a significant driver of litter mass loss in the early stages of the decomposition process. With time, however, litter types become more and more similar, and habitat becomes the dominating factor in determining decomposition of older litter. Thus, the major driver of litter mass loss changes over time from being the litter type in the early stages to the habitat (environmental conditions) in later stages.     

Dry weight loss and colonization of plant litter by macroinvertebrates: plant species and lake types compared

Rates of dry weight loss and of colonization of litter samples of different plants by macro-invertebrates were estimated using litter bags submerged in different types of lake. Samples of Carex rostrata litter were submerged for 3 months, in summer, in two lakes, one with an acidic and nutrient-poor water and one with near-neutral and nutrient-rich water. More plant litter remained (75%) in the former lake than in the latter (51–62%, varying with the mesh size of the litter bags used). The biomass of invertebrates in the litter samples from the acid lake was about 10 times less than in those from the near-neutral. Oligochaeta and Chironomidae were the dominant taxa found in the litter bags from the acidic lake, whereas Hirudinea and Isopoda predominated in those from the near-neutral lake.Litter samples from four different plants (Carex rostrata, Typha latifolia, Triticum sp. and Phleum pratense) were immersed in litter bags in another near-neutral lake further south for 12 months. When recovered, about 45% of the Triticum litter remained compared with only 7% of the Phleum. The values for Carex and Typha fell between these two extremes. When expressed as per g dry weight of residual plant litter, the greatest biomass of invertebrates was recorded in the Phleum litter samples and the least in the Typha samples. The faunal composition of the invertebrates in the different types of litter was approximately the same, with Isopoda and Hirudinea predominating.