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1.
土壤动物主要生态特征与生态功能研究进展   总被引:27,自引:4,他引:23       下载免费PDF全文
武海涛  吕宪国  杨青  姜明 《土壤学报》2006,43(2):314-323
土壤动物是陆地生态系统重要的组成部分,是物质循环和能量流动正常运行的关键环节。近年来,土壤动物研究越来越受到人们的重视,研究主要包括土壤动物生态特征和生态功能两个方面。本文概括了土壤动物的定义和分类,阐述了土壤动物的数量、种类、分布格局及影响因素等主要生态特征,着重论述了土壤动物的分解、生态指示等功能。认为,目前土壤动物研究发展缓慢,基础研究差,生态特征研究仍处于定性与半定量水平;功能研究单一,缺少土壤动物多样性功能研究。对今后研究提出展望。本文旨在加深对土壤动物的了解,为生物多样性保护、合理开发利用土壤资源、健全生态指标和实现农业、生态可持续发展提供必要的理论支持。  相似文献
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Previous experiments in meadow and forest-floor communities have uncovered a negative indirect effect of spiders and other large epigeic predators on decomposition, presumably through depression of densities of microbi-detritivores. We report the results of a 17-month field experiment in a deciduous forest in which spiders exerted the opposite effect on decomposition. In autumn we collected falling leaves of oak (Quercus), maple (Acer) and hickory (Carya), and placed three bags of mixed litter, and three groups of tethered leaves, in 1-m2 fenced plots. We determined the disappearance rate of these leaves through April of the second year. Spider densities were reduced by >50% in the spider-removal treatment. The rate of leaf-litter disappearance was not higher in spider-removal plots, but instead was ca. 20% lower (P=0.057). Thus, spider predation clearly was not decreasing the rates of litter decomposition in our experiment; on the contrary, the results suggest that spiders were indirectly enhancing decomposition. Possible hypotheses to explain this unexpected result are discussed.  相似文献
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为了系统了解国际上土壤有机碳与微生物多样性的研究进展,基于Web of Science数据源,利用Web of Science数据库分析工具和Thomson Data Analysis(TDA)、社会网络分析与可视化工具Netdraw和Ucinet,从论文年度变化趋势、全球研究实力国家、机构分布和力量比较、基金资助机构和主题分布、机构合作和研究内容等方面,对1992 ~ 2015年的相关论文,尤其是近10年来土壤有机碳及其影响因素的相关文章进行计量分析.结果表明:(1)论文数量呈逐年增长态势,土壤有机碳与土壤微生物多样性研究主要集中在欧美发达国家(地区);美国和德国综合影响力最高,英国、瑞典、瑞士、荷兰论文篇均被引较高,以中国科学院为代表的中国机构在该领域研究增长较快,研究论文最多,但论文整体质量有待提高.(2)中国国家自然基金资助机构产出论文最多;美国国家科学基金会资助论文篇均被引最高,其次是德国研究基金会,中国科学院科学基金名列第3,各国在共同资助的研究主题基础上,各有其特色主题;美国的一些研究机构是全球该领域研究合作交流的中心,其次是德国和中国中科院.(3)土壤有机质、土壤有机碳、凋落物分解、氮、磷、微生物生物量、土壤性质、气候变化、碳固定是该领域10年来的热点研究主题.未来应加强国际合作研究,关注土壤重金属、凋落物分解和微生物呼吸等相关主题,以提高我国研究水平,将相关研究成果及时应用于解决相应的实际问题.  相似文献
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Changes in climate or forest management practices leading to increased litter production will most likely cause increased leaching rates of dissolved organic carbon (DOC) from the O horizon. The rhizosphere is often assumed to have a large carbon flux associated with root turnover and exudation. However, little has been done to quantify the amount of DOC originating from root litter. We studied decomposition of fine root and needle litter of Norway spruce (Picea abies) through a combined incubation and leaching experiment in the laboratory using five different litter types: fresh needle litter, aged needles from the litter layer, fresh and dead roots from mineral soil samples, and seven-year-old roots from a previous litterbag study. After respiration measurements, the samples were percolated with artificial throughfall water and DOC and UV absorbance were measured in the leachate. Mineralisation of dissolved organic matter in the leachate and sorption of DOC to ferrihydrite were determined as a measure of DOC ability to be stabilised by iron (hydr)oxide surfaces.The mineralisation rate and DOC production rate of root samples were always lower than that of needle samples. However, root and needle derived dissolved organic matter (DOM) were similar in terms of aromaticity, as indicated by their specific UV absorbance, and ability to be sorbed by ferrihydrite. For seven-year-old roots, a significantly higher fraction of carbon was lost as DOC (30%) than for younger roots (20%). Furthermore, DOM from old roots bound more strongly to ferrihydrite and is mineralised at a lower rate than DOC from younger roots, suggesting that roots at late stages of decomposition, although a small fraction of total litter, significantly contribute to carbon build-up in mineral soils. The slower decomposition rate of roots compared with needles must be taken into account when modelling litter decomposition.  相似文献
6.
Extracellular enzymes mediate the degradation, transformation and mineralization of soil organic matter. The activity of cellulases, phosphatases and other hydrolases has received extensive study and in many cases stoichiometric relationships and responses to disturbances are well established. In contrast, phenol oxidase and peroxidase activities, which are often uncorrelated with hydrolase activities, have been measured in only a small subset of soil enzyme studies. These enzymes are expressed for a variety of purposes including ontogeny, defense and the acquisition of carbon and nitrogen. Through excretion or lysis, these enzymes enter the environment where their aggegrate activity mediates key ecosystem functions of lignin degradation, humification, carbon mineralization and dissolved organic carbon export. Phenol oxidases and peroxidases are less stable in the environment than extracellular hydrolases, especially when associated with organic particles. Activities are also affected, positively and negatively, by interaction with mineral surfaces. High spatiotemporal variation obscures their relationships with environmental variables and ecological process. Across ecosystems, phenol oxidase and peroxidase activities generally increase with soil pH, a finding not predicted from the pH optima of purified enzymes. Activities associated with plant litter and particulate organic matter often correlate with decomposition rates and potential activities generally increase with the lignin and secondary compound content of the material. At the ecosystem scale, nitrogen amendment alters the expression of phenol oxidase and peroxidase enzymes more broadly than culture studies imply and these responses correlate with positive and negative changes in litter decomposition rates and soil organic matter content. At the global scale, N amendment of basidiomycete-dominated soils of temperate and boreal forest ecoystems often leads to losses of oxidative enzyme activity, while activities in grassland soils dominated by glomeromycota and ascomycetes show little net response. Land use that leads to loss of soil organic matter tends to increase oxidative activities. Across ecosystems, soil organic matter content is not correlated with mean potential phenol oxidase and peroxidase activities. A multiple regression model that includes soil pH, mean annual temperature, mean annual precipitation and potential phenol oxidase activity accounts for 37% of the variation in soil organic matter (SOM) content across ecosystems (n = 63); a similar model for peroxidase activity describes 32% of SOM variance (n = 43). Analysis of residual variation suggest that suites of interacting factors create both positive and negative feedbacks on soil organic matter storage. Soils with high oxygen availability, pH and mineral activity tend to be substrate limited: high in situ oxidative activities limit soil organic matter accumulation. Soils with opposing characteristics are activity limited: low in situ oxidative activities promote soil organic matter storage.  相似文献
7.
Partitioning of the quantities of C lost by leaf litter through decomposition into (i) CO2 efflux to the atmosphere and (ii) C input to soil organic matter (SOM) is essential in order to develop a deeper understanding of the litter-soil biogeochemical continuum. However, this is a challenging task due to the occurrence of many different processes contributing to litter biomass loss. With the aim of quantifying different fluxes of C lost by leaf litter decomposition, a field experiment was performed at a short rotation coppice poplar plantation in central Italy. Populus nigra leaf litter, enriched in 13C (δ13C ∼ +160‰) was placed within collars to decompose in direct contact with the soil (δ13C ∼ −26‰) for 11 months. CO2 efflux from within the collars and its isotopic composition were determined at monthly intervals. After 11 months, remaining litter and soil profiles (0-20 cm) were sampled and analysed for their total C and 13C content. Gas chromatography (GC), GC-mass spectrometry (MS) and GC-combustion-isotope ratio (GC/C/IRMS) were used to analyse phospholipid fatty acids (PLFA) extracted from soil samples to identify the groups of soil micro-organisms that had incorporated litter-derived C and to determine the quantity of C incorporated by the soil microbial biomass (SMB). By the end of the experiment, the litter had lost about 80% of its original weight. The fraction of litter C lost as an input into the soil (67 ± 12% of the total C loss) was found to be twice as much as the fraction released as CO2 to the atmosphere (30 ± 3%), thus demonstrating the importance of quantifying litter-derived C input to soils, in litter decomposition studies. The mean δ13C values of PLFAs in soil (δ13C = −12.5‰) showed sustained incorporation of litter-derived C after one year (7.8 ± 1.6% of total PLFA-C). Thus, through the application of stable 13C isotope analyses, we have quantified two major C fluxes contributing to litter decomposition, at macroscopic and microscopic levels.  相似文献
8.
Soil respiration is the largest terrestrial source of CO2 to the atmosphere. In forests, roughly half of the soil respiration is autotrophic (mainly root respiration) while the remainder is heterotrophic, originating from decomposition of soil organic matter. Decomposition is an important process for cycling of nutrients in forest ecosystems. Hence, tree species induced changes may have a great impact on atmospheric CO2 concentrations. Since studies on the combined effects of beech-spruce mixtures are very rare, we firstly measured CO2 emission rates in three adjacent stands of pure spruce (Picea abies), mixed spruce-beech and pure beech (Fagus sylvatica) on three base-rich sites (Flysch) and three base-poor sites (Molasse; yielding a total of 18 stands) during two summer periods using the closed chamber method. CO2 emissions were higher on the well-aerated sandy soils on Molasse than on the clayey soils on Flysch, characterized by frequent water logging. Mean CO2 effluxes increased from spruce (41) over the mixed (55) to the beech (59) stands on Molasse, while tree species effects were lower on Flysch (30-35, mixed > beech = spruce; all data in mg CO2-C m−2 h−1). Secondly, we studied decomposition after fourfold litter manipulations at the 6 mixed species stands: the Oi - and Oe horizons were removed and replaced by additions of beech -, spruce - and mixed litter of the adjacent pure stands of known chemical quality and one zero addition (blank) in open rings (20 cm inner diameter), which were covered with meshes to exclude fresh litter fall. Mass loss within two years amounted to 61-68% on Flysch and 36-44% on Molasse, indicating non-additive mixed species effects (mixed litter showed highest mass loss). However, base cation release showed a linear response, increasing from the spruce - over the mixed - to the beech litter. The differences in N release (immobilization) resulted in a characteristic converging trend in C/N ratios for all litter compositions on both bedrocks during decomposition. In the summers 2006 and 2007 we measured CO2 efflux from these manipulated areas (a closed chamber fits exactly over such a ring) as field indicator of the microbial activity. Net fluxes (subtracting the so-called blank values) are considered an indicator of litter induced changes only and increased on both bedrocks from the spruce - over the mixed - to the beech litter. According to these measurements, decomposing litter contributed between 22-32% (Flysch) and 11-28% (Molasse) to total soil respiration, strengthening its role within the global carbon cycle.  相似文献
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Total belowground C allocation (TBCA) accounts for a large fraction of gross primary production, it may overtake aboveground net primary production, and contributes to the primary source of detrital C in the mineral soil. Here, we measure soil respiration, water erosion, litterfall and estimate annual changes in C stored in mineral soil, litter and roots, in three representative land uses in a Mediterranean ecosystem (late-successional forest, abandoned agricultural field, rain-fed olive grove), and use two C balance approaches (steady-state and non-steady-state) to estimate TBCA. Both TBCA approaches are compared to assess how different C fluxes (outputs and inputs) affect our estimates of TBCA within each land use. In addition, annual net primary productivity is determined and C allocation patterns are examined for each land use. We hypothesized that changes in C stored in mineral soil, litter and roots will be slight compared to soil respiration, but will still have a significant effect on the estimates of TBCA. Annual net primary productivity was 648 ± 31.5, 541 ± 42.3 and 324 ± 22.3 g C m−2 yr−1 for forest, abandoned agricultural field and olive grove, respectively. Across land uses, more than 60% of the C was allocated belowground. Soil respiration (FS) was the largest component in the TBCA approaches across all land uses. Annual C losses through water erosion were negligible compared to FS (less than 1%) and had little effect on the estimates of TBCA. Annual changes in C stored in the soil, litter layer and roots were low compared to FS (16, 24 and 10% for forest, abandoned agricultural field and olive grove, respectively), but had a significant effect on the estimates of TBCA. In our sites, an assumption that Δ[CS + CR + CL]/Δt = 0 will underestimate TBCA, particularly in the abandoned agricultural field, where soil C storage may be increasing more rapidly. Therefore, the steady-state model is unsuited to these Mediterranean ecosystems and the full model is recommended.  相似文献
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