陆地生态系统混合凋落物分解研究进展

凋落物分解在陆地生态系统养分循环与能量流动中具有重要作用,是碳、氮及其他重要矿质养分在生态系统生命组分间循环与平衡的核心生态过程。自然生态系统中,植物群落大多具有较高的物种丰富度和多样性,其混合凋落物在分解过程中也更有可能发生养分传递、化学抑制等种间互作,形成多样化的分解生境,多样性较高的分解者类群以及复杂的级联效应分解,这些因素和过程均对研究混合凋落物分解过程、揭示其内在机制形成了极大的挑战。从构成混合凋落物物种丰富度和多样性对分解生境、分解者多样性及其营养级联效应的影响等方面,综合阐述混合凋落物对陆地生态系统凋落物分解的影响,探讨生物多样性在凋落物分解中的作用。通过综述近些年的研究发现,有超过60%的混合凋落物对其分解速率的影响存在正向或负向的效应。养分含量有差异的凋落物混合分解过程中,分解者优先利用高质量凋落物,使低质量的凋落物反而具有了较高的养分有效性,引起低质量凋落物分解加快并最终使混合凋落物整体分解速率加快;而凋落物物种丰富度对土壤动物群落总多度有轻微的影响或几乎没有影响,但是对线虫和大型土壤动物的群落组成和多样性有显著影响,并随着分解阶段呈现一定动态变化;混合凋落物改变土壤微生物生存的理化环境,为微生物提供更多丰富的分解底物和养分,优化微生物种群数量和群落结构及其分泌酶的活性,并进一步促进了混合凋落物的分解。这些基于植物-土壤-分解者系统的动态分解过程的研究,表明混合凋落物分解作用不只是经由凋落物自身质量的改变,更会通过逐级影响分解者多样性水平而进一步改变分解速率和养分释放动态,说明生物多样性确实在一定程度上调控凋落物分解及其养分释放过程。     

全球气候变暖对凋落物分解的影响

凋落物分解作为生态系统核心过程,参与生态系统碳的周转与循环,影响生态系统碳的收支平衡,调控生态系统对全球气候变暖的反馈结果。全球气候变暖通过环境因素、凋落物数量和质量以及分解者3个方面,直接或间接地作用于凋落物分解过程,并进一步影响土壤养分周转和碳库动态。气候变暖可通过升高温度和改变实际蒸散量等环境因素直接作用于凋落物分解。气候变暖可引起植物物种短期内碳、氮和木质素等化学性质的改变以及群落中物种组成的长期变化从而改变凋落物质量。在凋落物分解过程中,土壤分解者亚系统作为主要生命组分(土壤动物和微生物)彼此相互作用、相互协调共同参与调节凋落物的分解过程。凋落物分解可以通过改变土壤微生物量、微生物活动和群落结构来加快微生物养分的固定或矿化,以形成新的养分利用模式来改变土壤有机质从而对气候变化做出响应。未来凋落物分解的研究方向应基于大尺度跨区域分解实验和长期实验,关注多个因子交互影响下,分解过程中碳、氮养分释放、地上/地下凋落物分解生物学过程与联系、分解者亚系统营养级联效应等方面。     

森林生态系统凋落物多样性对分解过程和土壤微生物特性影响研究进展

凋落物的分解过程是森林生态系统养分循环的关键环节, 也是林分内植被层可利用养分的重要来源。一般来说, 在自然生态系统中, 地上植被的种类越丰富, 其凋落物的多样性也越高, 多样化的凋落物在混合分解过程中存在的相互作用关系也更为复杂, 对其自身的分解过程、分解生境以及分解者群体也会产生重要影响。文章以凋落物的多样性为着眼点, 综述了凋落物的多样性对其分解过程以及对分解过程中最重要的分解者-土壤微生物特性所产生的影响, 重点阐述了凋落物多样性对分解过程中土壤微生物的生物量、群落结构、多样性以及分解活性的影响, 并对其可能的原因和潜在的机理进行了分析。综述结果表明, 较高的凋落物多样性总体上能够加速凋落物的分解, 提高分解过程中土壤微生物的生物量、多样性及分解活性。在此基础上, 对今后凋落物多样性在分解过程中的效应研究进行了展望, 为人工林可持续经营的混交林营造以及林下植被的科学管理提供理论依据。     

土壤微食物网结构与生态功能

土壤微食物网是碎屑食物网中与土壤生态过程密切相关的一部分,通过取食资源基质直接或间接地参与养分循环过程,影响陆地生态系统功能.本文从土壤微食物网的组成、结构和生态功能等方面综述了近年来土壤微食物网的研究进展.通过对土壤微食物网的能量通道及营养级联效应的介绍,阐述了土壤微食物网在碳(C)、氮(N)转化、凋落物分解和植物生长等方面的重要作用.针对目前的研究现状,提出未来土壤生态学研究应与高通量测序及稳定同位素技术相结合;通过构建模型进一步加强对土壤食物网结构和功能的研究,从而深入揭示地下生态过程及其对地上植物生长的反馈作用机理.     

河口三角洲湿地健康生态圈构建:理论与方法

河口三角洲湿地生态环境保护和区域开发的矛盾突出,对湿地生态圈健康和栖息地生态功能产生直接而强烈的影响.健康的河口三角洲湿地生态圈是由自然过程的连续性、生态系统的连通性、生境的异质性以及食物网的多样性等多种因素共同决定的.本文讨论了健康湿地生态圈构建的基础理论,综述了景观生态网络构建、水文连通性网络构建、食物网构建以及生境异质性栖息地营建的理论与方法.在区域和景观尺度上,以土地利用-生态系统完整性为主线,阐明了湿地破碎化对湿地生态功能的影响,特别强调景观完整性、水文连通性对湿地栖息地的影响;在生态系统和群落尺度上,以食物网-生态系统稳定性为主线,强调食物网多样性、生境异质性对湿地生物圈构建的支撑作用.基于景观完整性、水文连通性、生境异质性和食物网多样性构建健康湿地生态圈,可为湿地生态环境保护和建设提供科学依据和技术支撑.     

不同植物群丛下铜尾矿复垦地土壤线虫的分布特征

对铜陵市凤凰山铜尾矿复垦地禾本科(矛叶荩草AL、白茅IC)和豆科(野豌豆GS)等3类典型植物群丛及外围对照禾本科(毛马唐)植物群丛下的土壤线虫群落进行调查.共分离得到1277 条土壤线虫,隶属于51属,平均密度590条·100 g^-1干土.采用多样性指数和土壤食物网结构指数等分析铜尾矿复垦地土壤线虫群落的分布特征.结果表明： 铜尾矿复垦地3类植物群丛下土壤线虫群落的类群总数和Shannon〖KG-*4〗多样性指数明显小于毛马唐对照组.对比铜尾矿复垦地和邻近自然栖息地不同植物群丛下的土壤线虫群落生态指数,发现野豌豆群丛下土壤食物网结构较成熟,土壤有机质分解以细菌分解通道为主;生态系统较不稳定,低度干扰;表明该豆科植物群丛下的土壤食物网具有较大的发展潜力,从而提高铜尾矿复垦地的生态稳定性.白茅与矛叶荩草群丛下土壤食物网处于结构化状态,土壤有机质分解以真菌分解通道为主;生态系统较稳定,无干扰;表明禾本科植物群丛下的土壤食物网处于较低层次的发展状态.     

土壤微生物对气候变暖和大气N沉降的响应

气候变暖和大气N沉降是近一、二十年来人们非常关注的全球变化现象,它们所带来的一系列生态问题已成为全球变化研究的重要议题。它们不仅影响地上植被生长和群落组成,还直接或间接地影响土壤微生物过程,而土壤微生物对此做出的响应正是生态系统反馈过程中非常重要的环节。该文分别从气候变化对土壤微生物的影响(土壤微生物量、微生物活动和微生物群落结构)和土壤微生物对气候变化的响应(凋落物分解、养分利用与循环以及养分的固持与流失)两个角度,综述近期土壤微生物对气候变暖和大气N沉降响应与适应的研究进展。气候变暖和大气N沉降对土壤微生物的影响更多地反映在微生物群落的结构和功能上,而土壤微生物量、微生物活动和群落结构的变化又会通过改变凋落物分解、养分利用和C、N循环等重要的土壤生态系统功能和过程做出响应,形成正向或负向反馈,加强或削弱气候变化给整个陆地生态系统带来的影响。然而,到目前为止土壤微生物的响应对陆地生态系统产生的最终结果仍是未决的关键性问题。     

下辽河平原农田土壤线虫群落组成的季节变化

下辽河平原农田生态系统在管理过程中频繁的耕作、施肥以及农用化学品施用等引发了一系列问题, 如土壤退化、耕地数量减少以及生产力下降等, 不可避免地对土壤生物健康产生影响。为探究农田土壤人工管理对土壤生物群落动态的影响, 本研究在辽宁沈阳农田生态系统国家野外科学观测研究站开展了农田土壤线虫群落组成的季节变化研究, 对4个季节农田和废弃农田(对照)的土壤线虫群落组成、多度以及多样性等进行了比较分析。研究结果表明, 土壤线虫总多度在废弃农田中显著高于农田, 但季节间差异不显著。季节变化主要显著影响了自由生活线虫的多度, 其在9月达到最高; 季节变化也显著影响了属的数量, 其在非生长季的11月最低。与废弃农田相比, 农田管理显著降低了杂食捕食线虫和食真菌线虫的多度, 土壤食物网结构相对稳定; 而废弃的农田更易受到季节波动的影响, 土壤食物网也受到一定的干扰。     

放牧对草地枯落物分解和土壤动物群落及其相互关系的影响

在草地生态系统中,枯落物作为介导土-草界面过程的重要环节,主要调控地上-地下生态系统物质循环与能量流动,其分解对土壤食物网和土壤生物营养结构具有显著影响。土壤动物是枯落物与土壤之间物质循环与能量流动的重要媒介,是枯落物分解与养分释放过程的主要调节者。近年来,国内外学者对枯落物分解与土壤动物多样性的研究逐步深入,取得大量的研究成果。本文通过综述国内外文献,从放牧对枯落物分解过程的影响、放牧对土壤动物的影响及放牧对枯落物分解与土壤动物关系的影响等三个方面,总结分析了放牧通过采食、践踏和排泄行为改变枯落物分解,间接影响土壤动物多样性,从而降低了土壤微食物网的复杂性。另外,食草动物对草地枯落物分解和土壤动物关系的影响复杂,且这种关系往往对放牧强度、放牧季节、家畜种类等做出响应,进而会影响到整个生态系统的结构和功能。     

土壤微生物分解作用的研究

1教学建议“土壤微生物的分解作用的研究”是新课程标准中设置的一项活动,旨在使学生能从实验的角度去探究土壤中落叶等物质的消失源于土壤微生物的分解作用。但是,以往的研究在设计思路上只要求学生掌握生态系统物质循环中,微生物作为分解者的知识,最     

农田土壤食物网管理的原理与方法

土壤食物网在维持生态系统生产力和健康等方面起着重要作用,但现代农业中,化肥农药等外部投入已经改变或部分替代了土壤食物网的功能,由此也造成一系列的环境问题。为了协调作物高产与环境保护的利益,需要对土壤食物网进行管理,使土壤食物网符合作物生长的需要,即建立健康土壤食物网。管理土壤食物网有两种方式:(1)直接方式,即通过调节食物网各个功能群的组成来管理土壤食物网;(2)间接方式,即根据农田土壤食物网以自下而上调控方式为主、强调低营养阶层的资源限制的原理,通过调节碎屑的数量和质量来管理食物网。在这两种调控方式中,都需要对被管理的食物网进行监测,监测的方式也分两种,一种是直接测定食物网各功能群的数量和生物量,另外一种方式即以线虫为工具来反应土壤食物网的结构。     

Responses of nematode communities to different land uses in an aquic brown soil

An analysis of the seasonal and vertical distri-bution of soil nematode communities under three con-trasting land uses, i.e., cropland, abandoned cropland and woodland was conducted in an aquic brown soil. The results showed that different land-use types affected the spatiotemporal distribution of soil nematodes and their dominant genera, and different dominant genera showed different responses to land use. In the abandoned cropland and woodland, most dominant genera were pre-sent in the 0-20 cm layers and Chiloplacus was mainly distributed in the 5-30 cm layers, while in the cropland, Pratylenchus exhibited an even distribution from the 0-5 cm to the 40-50 cm depth. Soil environmental para-meters under different land use could influence soil nema-todes; soil porosity, total organic C, total N and the C/N ratio could positively influence the abundance of some dominant genera. Faunal profiles revealed that envir-onmental stability and the homeostasis in the abandoned cropland and woodland lead to higher levels of commun-ity structure, and the soil food web tends to succeed to maturity. Nematode faunal analyses are a useful indicator for interpreting the stress and/or nutrient conditions under different land uses.     

汉中盆地秸秆还田撂荒和林地对土壤碳的影响

农业活动是温室气体重要的排放源,土壤碳库[土壤有机碳(SOC)和无机碳(SIC)]稍微变化会对大气CO_2产生很大影响。汉中盆地是南水北调的重要水源涵养地,在该区域秸秆还田、农田撂荒和林地是目前常见土地利用方式,但缺乏不同利用方式对SIC和SOC影响的研究。该研究采集该区域典型样地土壤,用滴定法和有机碳分析仪分别测定其SIC和SOC含量,研究3种土地利用方式对土壤碳库的影响。结果表明:SOC随土层深度最为敏感的是农田,其次是撂荒地,林地最不敏感。0~140 cm土层SOC碳密度,林地最大,是撂荒田的2.26倍,农田是撂荒田的1.37倍。深土层SOC碳密度,林地是撂荒田的2.44倍,农田是撂荒田的1.07倍。撂荒田的SIC密度最大,其次是农田,林地的SIC碳密度最低。在0~140 cm土层中,SIC密度依次为12.37、11.68和9.77 kg·m~2,撂荒田的SIC碳密度是林地的1.27倍。随着我国农村发展,土地利用管理出现新的方式,今后在估算土地利用管理方式对土壤碳影响时还需要综合考虑SOC和SIC。     

Woodland restoration on agricultural land: long‐term impacts on soil quality

Woodland restoration is underway globally to counter the negative soil quality and ecological impacts of agricultural expansion and woodland fragmentation, and restore or enhance biodiversity, ecosystem functions and services. However, we lack information about the long‐term effects of woodland restoration on agricultural soils, particularly at temporal scales meaningful to woodland and soil development. This study utilized soil and earthworm sampling across a chronosequence of sites transitioning from “agricultural land” to “secondary woodland” (50–110 years) and “ancient woodland” (>400 years), with the goal of quantifying the effects of woodland restoration on agricultural land, on key soil quality parameters (soil bulk density, pH, carbon and nitrogen stocks, and earthworm abundance, biomass, species richness and diversity). Broad‐leaved woodland restoration led to significantly greater soil organic carbon (SOC) stocks compared to arable land, and young (50–60 years) secondary woodland increased earthworm species and functional diversity compared to both arable and pasture agricultural land. SOC stocks in secondary broad‐leaved woodlands (50–110 years) were comparable to those found in long‐term ancient woodlands (>400 years). Our findings show that broad‐leaved woodland restoration of agricultural land can lead to meaningful soil ecological improvement and gains in SOC within 50–110 years, and provide intel on how restoration activities may be best targeted to maximize soil quality and functions.     

Patterns of Orthoptera abundance and lesser kestrel conservation in arable landscapes

The lesser kestrel Falco naumanni experienced a marked decline during the second half of the 20th century due to changes in land use that influenced breeding success by reducing the abundance and quality of prey. However, the factors governing spatial and temporal variation of prey abundance around lesser kestrel colonies has not yet been investigated. We sampled Orthoptera abundance in the main crop types and edge habitats surrounding six lesser kestrel colonies in southern Spain. Samplings focused on Orthoptera because they constitute the main prey during the nestling period. Only those Orthoptera species that are known to be preyed by lesser kestrels were considered in this study. We found differences in prey density among localities, and crop types. Semi-natural habitats such as grasslands, fallow land, and field margins held the highest densities. However, prey abundance showed a complex pattern that was not possible to explain solely on the basis of crop composition around colonies. Factors determining productivity in individual fields like soil type and productivity or biocide input, and mean size of agricultural fields contributed to explain this complex pattern of prey abundance. Our results highlight the key role of semi-natural and edge habitats in farmed landscapes as prey reservoirs and corridors. Higher conservation priorities for these habitats are suggested to benefit foraging lesser kestrels, but many other farmland species that also experienced steep population declines due to decreasing food supply resulting from modern agriculture.     

Are grasslands important habitats for soil microarthropod conservation?

Biodiversity has been a focal aim of environmental protection since the Rio conference, but only with the beginning of the new millennium did soil biodiversity become an important aspect of international policy. Edaphic fauna play a key role in many soil functions, such as organic matter decomposition, humus formation and nutrient element cycling; moreover, affect the porosity, aeration, infiltration and distribution of organic matter in soil horizons, modifying soil structure and improving its fertility. The ecosystem services provided by soil animals are becoming progressively lost due to agricultural practice intensification, which causes a reduction in both abundance and taxonomic diversity of soil communities. In the present study, a permanent grassland habitat was studied in order to evaluate its potential as a soil biodiversity reservoir in agroecosystems. Grassland samples were compared with samples from a semi-natural woodland area and an arable land site. Microarthropod abundances, Acari/Collembola ratio (A/C), Shannon diversity index (H′) and evenness index (E) were calculated. QBS-ar index was used in order to evaluate soil biological quality. Microarthropod communities of the three land use typologies differed in both the observed groups and their abundance. Steady soil taxa characterized both woodland and grassland soils, whereas their abundances were significantly higher in woodland soil. Taxon diversity and soil biological quality in the grasslands did not differ from the woodland samples. The microarthropod community in the arable land showed a reduction both in taxa numbers and soil biological quality compared with the other sites. Soil biological quality and edaphic community composition highlighted the importance of grassland habitats in the protection of soil biodiversity.     

Roadside connectivity does not increase reptile abundance or richness in a fragmented mallee landscape

The effect of isolation and the importance of dispersal in establishing and maintaining populations in fragments of remnant habitat remain poorly understood. Nevertheless, environmental connectivity is likely to be important for ensuring the long‐term preservation of biodiversity in extensively cleared landscapes. In this study, we compared reptile communities in large conservation parks with those in small woodland remnants 6.5–12 km from the parks, on the Eyre Peninsula, South Australia, Australia. We assessed the impact of fragmentation on the abundance, richness and habitat preferences of reptiles, and examined whether connection to linear roadside vegetation altered reptile communities in small woodland remnants. Of the 31 reptile species, 12 were restricted to conservation parks and six to habitat fragments in farmland. There was a substantial reduction in reptile species richness and abundance in farmland fragments. Direct connection of remnant vegetation to roadside corridors did not affect abundance of common species in the farmland fragments, although species richness was lower in isolated remnants in one of our two study regions. The habitat preference of the scincid lizard Menetia greyii differed between farmland fragments, where they were regularly found on dunes and roadsides, and conservation parks, where they were rare and not detected on dunes. We suggest that habitat fragmentation may have altered interspecific interactions, enabling an expansion of habitat use in the farming landscape. Significantly lower abundance of four common species in farmland settings compared with reserves indicated that existing corridors and small fragments provide inadequate connectivity over larger distances. To counter this effect, large reserves may need to be less than 10 km apart.     

Modelling carbon dynamics in coniferous forest soils in a temperature gradient

Climate change and changes in land use will alter the stores of carbon and turnover of soil organic matter. We have used a theory for carbon cycles in terrestrial ecosystems to analyse changes in soil organic matter turnover in coniferous forests. The central concepts of the theory are a continuously changing substrate quality, a constant decomposer efficiency and a climatically controlled decomposer growth rate. Measurements on litter production and soil carbon stores from field experiments have been used to successfully validate the model predictions. Measured litter production increased with increasing temperature but the response was not identical for forests of different vegetation types which reflect variations in productivity. The temperature response of needle-litter production and decomposition rate were strongest in the most productive forests and weakest for the low productive forests. Initial decay rates of soil C store from steady state showed the same trend in temperature response as decay of a single litter cohort did, but the absolute values are 16% of the decay rates of a single litter cohort. Predicted soil C ranged from 5 to 9 kg C m^–2. There exists a remarkable variation in forest soil C store response to temperature; the magnitude and even the sign depends on productivity as defined by vegetation type. The assumption that, in general, decomposition rates increase more than NPP with temperature, and consequently, soil C stores should decrease in response to a climate warming, seems therefore too simplistic.