基于土壤生物空间异质性分析的空间土壤生态学研究

土壤生物以不同的方式改变着土壤的物理、化学和生物学特性。了解土壤生物的空间异质性是很关键的。土壤生态学和空间生态学结合的新的研究领域─空间土壤生态学关注空间在土壤生物种群结构及动态中的重要性。本文通过对土壤生物空间异质性的分析,内容包括空间土壤生态学的提出、土壤生物空间异质性研究的意义、研究方法,重点综述了影响土壤生物分布格局的因素、尺度,土壤生物空间分布对植被-土壤系统的影响,土壤生物空间异质性的作用,其中包括土壤生物空间异质性与多样性的关系、土壤生物对局部干扰的响应、土壤生物空间格局对植被的影响。     

Fingerprinting methods to approach multitrophic interactions among microflora and microfauna communities in soil

The soil functioning and the response of the biota to external perturbations such as organic input are based on multitrophic interactions among a wide range of organisms. However, the various components of the soil microflora and microfauna are rarely addressed in ecological studies. We have developed a molecular approach based on terminal restriction fragment length polymorphism (T-RFLP) analysis to assess the community structures of protozoa and nematodes, together with bacteria and fungi that share the same soil environment. Two soils were characterized by a specific fingerprint for each of the four groups of organisms, showing the potential of all T-RFLP procedures to differentiate the community structures. The response of the soil biota to organic inputs was addressed using T-RFLP fingerprints together with physiological profiles of bacteria communities and global microbial activities and densities. Although the impact of compost or manure on the soil biota was only slightly noticeable from the global parameters measured, it was obvious from the community level analyses. However, the different components of the soil biota were altered to various extents, depending on the group of organisms and the soil–organic matter combination. The potential of the T-RFLP strategy to analyze simultaneously different biotic groups from the same soil DNA extract will facilitate the more systematic integration of eukaryotic organisms in ecological studies to investigate multitrophic interactions among the microflora and microfauna in relation with soil processes.     

From peds to paradoxes: Linkages between soil biota and their influences on ecological processes

Soils and their biota have been studied by a variety of observational and experimental methods that have allowed biologists to infer their structural and functional interactions. Viewing progress made over the last 10 years, it is apparent that an increasing diversity of analytical and chemical methods are providing much more detailed information about feeding preferences and niche overlaps of speciose groups such as oribatid mites.Other topics in which considerable progress has been made include new advances in knowledge of root and mycorrhiza production and turnover and their impacts on soil ecosystems; soil biota, exudations and secretions and soil aggregation phenomena; the biology of invasive species in soils; soil biodiversity, legacies and linkages to soil processes; and soil biodiversity and ecosystem functional responses. Throughout the review I suggest ways for new progress to be made in future research.     

Soil microbial activity and free-living nematode community in the upper soil layer of the anticline erosional cirque,Makhtesh Ramon,Israel

The physical–chemical peculiarity of soil rock formations is one of the leading factors determining diversity and abundance of soil biota. The main aim of the present research was to study soil microbial and free-living nematode abundance and diversity on different soil rock formations (basalt, sandstone, limestone, granite and gypsum) of the Makhtesh Ramon erosional cirque. The obtained results showed the strong effect of soil features of different soil formations on microbial biomass and respiration as well as on the soil free-living nematode communities and its trophic and species composition. The Sorenson-Czenkanowski similarity index indicated significant differences between soil properties as well as between soil biota in observed soil formations. The qCO₂, which is known to increase according to the level of environmental stress, reached maximal values in the sandstone soil formation. The values of ecological indices such as Simpson's dominance index, maturity index and modification and species richness pointed to a specific ecological condition in the studied soil formations dependent on low content of an essential soil matter as soil moisture, organic matter and cations.     

Mountainous meadow chernozem-like soils of high mountains in the North Caucasus region

Original and literature data on the soil-forming conditions and the morphology, physicochemical properties, and bulk chemical and mineralogical composition of mountainous meadow chernozem-like soils of the North Caucasus region indicate that these soils are developed from the coarse-textured pebbly colluvium of calcareous bedrock under the impact of humus accumulation and clay formation. The intensity of these processes is directly related to the activity of soil biota. Suggestions aimed at improving the classification of high-mountain soils are discussed.     

Effects of oxamyl and chlordane on the activities of nontarget soil organisms

Summary The effect of two pesticides, oxamyl and chlordane, on nontarget soil biota were examined in microcosms. Neither oxamyl nor chlordane had an effect on rates of litter decomposition or soil and litter respiration. There were differences in numbers of nematodes and protozoans and in biomass of bacteria and fungi in microcosms with and without chlordane on some sampling dates. One of the nematodes, Pelodera sp., died out in all of the microcosms within 30 days. Although the pesticide chlordane had no measurable effect on the activities of the soil biota as measured by respiration and mass loss, it did affect the population sizes and biomass of some grazers of soil biota.     

Soil biological quality after 36 years of ley-arable cropping,permanent grassland and permanent arable cropping

Insight is needed into how management influences soil biota when sustainable grassland systems are developed. A crop rotation of grass and maize can be sustainable in terms of efficient nutrient use. However, there is lack of information on the effect of such a crop rotation on soil biological quality. Earthworms, nematodes, bacteria and fungi were sampled over three years in a 36 years old experiment. Permanent arable land was compared with permanent grassland and with a ley-arable crop rotation. In the rotation, a period of three years of grassland (temporary grassland) was followed by a period of three years of arable land (temporary arable land) and vice versa. In the first year of arable cropping in the rotation, the number of earthworms was already low and not different from continuous cropping. In the three-year grass ley, the abundance of earthworms returned to the level of permanent grassland in the second year. However, the restoration of earthworm biomass took a minimum of three years. Furthermore, the anecic species did not recover the dominance they had in the permanent grassland. The numbers of herbivorous and microbivorous nematodes in the ley-crop rotation reached similar levels to those in the permanent treatments within one to two years. Although the same holds for the nematode genera composition, the Maturity Index and the proportion of omnivorous nematodes in the temporary treatments remained significantly lower than in their permanent counterparts. Differences in recovery were also found among microbial parameters. In the temporary treatments, bacterial growth rate and the capacity to degrade a suite of substrates recovered in the second year. However, the Community-Level Physiological Profiles in the permanent grassland remained different from the other treatments. Our results suggest that many functions of soil biota that are well established in permanent grassland, are restored in a ley-arable crop rotation. However, due to a reduction in certain species, specific functions of these soil biota could be reduced or lost. The ley-arable crop rotations were intermediate to permanent grassland and continuous arable land in terms of functioning of soil biota (e.g., N-mineralization). In terms of the functional aspects of the soil biota, permanent grassland might be preferable wherever possible. For maize cultivation, a ley-arable crop rotation is preferable to continuous arable land. However, a ley-arable crop rotation is only preferable to continuous arable cropping if it is not practised at the expense of permanent grassland at farm level.     

Biological tools for the assessment of contaminated land: applied soil ecotoxicology

Abstract. Chemical analysis alone is inadequate for comprehensively assessing the impact of soil pollution on biota. The term bioavailability can only be applied in a context specific to a target biological receptor or a proven chemical surrogate. Integration of biological and chemical data can often yield significant advances in hazard assessment and act as a suitable baseline for making site-specific risk assessments. Here, the value of biological techniques is discussed and their application described. The relative merit of test selection is considered and the new direction being developed in sublethal assessments. Currently, however, one of the major limitations is the seeming lack of flexibility of many assays in that they are either applicable to agricultural systems or industrial scenarios, but rarely to both. As a consequence, few assays have internationally adopted protocols. The introduction of new methods and the continued improvement and refinement of assays make this area of soil science dynamic and responsive.     

Dissimilar response of plant and soil biota communities to long-term nutrient addition in grasslands

The long-term effect of fertilizers on plant diversity and productivity is well known, but long-term effects on soil biota communities have received relatively little attention. Here, we used an exceptional long-lasting (>40 years) grassland fertilization experiment to investigate the long-term effect of Ca, N, PK, and NPK addition on the productivity and diversity of both vegetation and soil biota. Whereas plant diversity increased by liming and decreased by N and NPK, the diversity of nematodes, collembolans, mites, and enchytraeids increased by N, PK, or NPK. Fertilization with NPK and PK increased plant biomass and biomass of enchytraeids and collembolans. Biomass of nematodes and earthworms increased by liming. Our results suggest that soil diversity might be driven by plant productivity rather than by plant diversity. This may imply that the selection of measures for restoring or conserving plant diversity may decrease soil biota diversity. This needs to be tested in future experiments.     

Plant removal disturbance and replant mitigation effects on the abundance and diversity of low-arctic soil biota

Due to the dependence of soil organisms on plant derived carbon, disturbances in plant cover are thought to be detrimental for the persistence of soil biota. In this work, we studied the disturbance effects of plant removal and soil mixing and the mitigation effects of replanting on soil biota in a low-arctic meadow ecosystem. We set up altogether six replicate blocks, each including three randomized treatment plots, at two distinct fells at Kilpisjärvi, northern Finland. Vegetation was removed in two thirds of the plots: one third was then kept barren (the plant-removal treatment), while the other third was replanted with a local herb Solidago virgaurea. The remaining plots of intact vegetation were used as treatment comparisons. The responses of soil microbes and fauna were examined six years later in the early and late growing season. The biomass of bacteria, non-mycorrhizal fungi and mycorrhizal fungi (estimated using PLFA markers) were on average 74%, 89% and 84% lower in the plant-removal and 64%, 74% and 71% lower in the Solidago replant plots than in the intact meadow. The positive effect of replanting was statistically significant for fungi, but not for bacteria. The PCA of relative PLFA concentrations further showed that the structure of the microbial community differed significantly among all three treatments. The abundance of nematodes and collembolans was on average 82 and 95% lower, but the total number of nematode genera and collembolan taxa only 27 and 7% lower in the plant-removal plots than in the intact meadow soil. Few disturbance effects on soil fauna were significantly mitigated by the Solidago replant (the plant parasitic nematodes being a notable exception) and in the case of the collembolans, the Solidago replant plots had even fewer animals than the plant-removal plots. The response of soil biota also varied with locality: the effects on fungivorous nematodes were found at one site only and the replant effects on the number and diversity of collembolan taxa varied with site. Our results suggest that despite drastic reductions in the abundance of soil biota, the majority of animal taxa can persist for years in disturbed arctic soils in the absence of vegetation. In contrast, the alleviating replant effects on the abundance of soil biota appear weak and may only partially reverse the negative effects of vegetation removal and soil disturbance.     

Characteristics of phosphorus fractions in the soils derived from sedimentary and serpentinite rocks in lowland tropical rain forests,Borneo

ABSTRACT

Soil organic phosphorus (P) is an important P source for biota especially in P-limited forests. Organic P has various chemical formations which differ in bioavailability and these organic P can be degraded by phosphatase enzymes. Here, we report soil P fractions inferred from solution ³¹P-NMR spectroscopy and soil phosphatase activities of two tropical rain forests on contrasting parent materials; sedimentary and ultramafic igneous (serpentinite) rocks. Compared to the sedimentary soils　and previous studies, P fractions of the serpentinite soils have distinctly high proportions of pyrophosphate and scyllo-inositol hexakisphosphate (scyllo-IP₆). The accumulation of pyrophosphate and scyllo-IP₆ may be related to strong sorptive capacity of iron oxides present in the serpentinite soils, which implies a consequent low P availability in the serpentinite soils. Mean value of soil phosphatase activities was higher in the serpentinite soils than in the sedimentary soils, suggesting that biota in these serpentinite forests depend more on soil organic P as a P source.     

Response of collembolan assemblages to plant species successional gradient

It has been acknowledged that soil organisms play a significant role in nutrient cycling and thus may affect productivity and competition within plant assemblages with potential effects on vegetation trajectories. However, few studies have considered a single conceptual framework referring to both above–belowground linkages and plant succession. Consequently, we lack knowledge on the effects of plant successional processes on the dynamics of soil biota. Given this dearth of information, our study aimed to describe the dynamics of a major group of soil fauna, namely collembola, during the secondary succession on chalky slopes edging the Seine River. We selected five different plant assemblages as representative of a chronosequence: short grassland, tall grassland, encroached grassland, shrubland and forest. Our results clearly highlighted a strong response of collembolan assemblages to vegetation gradient. The changes in collembolan diversity were due to a high turnover rate in early successional stages and to nestedness in late successional stages. In addition, each collembolan life form had a specific response to vegetal succession. Euedaphic assemblages increased progressively during the succession while epedaphic did not follow a clear pattern. Our results also indicated a link between the dynamics of collembolan assemblages and plant life forms (e.g. trees and graminoids) rather than plant diversity. A focus on life forms, for plants and soil biota, seems to provide a good framework to study linkages between above and belowground biota.     

干旱地区土壤碳酸钙淀积过程模拟

根据化学热力学过程吧及土壤剖面碳酸钙淀积过程的机理,借鉴前人的建模经验,构建了干旱地区土壤碳酸钙淋溶淀积过程模型ＣＡＥＤＰ,并以晋西北黄土丘陵土壤为例进行了验证。     

土壤—全方位深松机组系统随机振动研究

建立了土壤——全方位深松机非线性系统模型，分析了系统振动减阻的复杂内共振机理、土壤强度分维和负载信号特性，可以通过调整土壤耕作机组固有频率来改善振动减阻性能，以及利用牵引阻力频谱指数来衡量系统振动减阻性能。田间试验数据分析结果与上述结论相符。     

Biochar effects on soil biota - A review

Soil amendment with biochar is evaluated globally as a means to improve soil fertility and to mitigate climate change. However, the effects of biochar on soil biota have received much less attention than its effects on soil chemical properties. A review of the literature reveals a significant number of early studies on biochar-type materials as soil amendments either for managing pathogens, as inoculant carriers or for manipulative experiments to sorb signaling compounds or toxins. However, no studies exist in the soil biology literature that recognize the observed large variations of biochar physico-chemical properties. This shortcoming has hampered insight into mechanisms by which biochar influences soil microorganisms, fauna and plant roots. Additional factors limiting meaningful interpretation of many datasets are the clearly demonstrated sorption properties that interfere with standard extraction procedures for soil microbial biomass or enzyme assays, and the confounding effects of varying amounts of minerals. In most studies, microbial biomass has been found to increase as a result of biochar additions, with significant changes in microbial community composition and enzyme activities that may explain biogeochemical effects of biochar on element cycles, plant pathogens, and crop growth. Yet, very little is known about the mechanisms through which biochar affects microbial abundance and community composition. The effects of biochar on soil fauna are even less understood than its effects on microorganisms, apart from several notable studies on earthworms. It is clear, however, that sorption phenomena, pH and physical properties of biochars such as pore structure, surface area and mineral matter play important roles in determining how different biochars affect soil biota. Observations on microbial dynamics lead to the conclusion of a possible improved resource use due to co-location of various resources in and around biochars. Sorption and thereby inactivation of growth-inhibiting substances likely plays a role for increased abundance of soil biota. No evidence exists so far for direct negative effects of biochars on plant roots. Occasionally observed decreases in abundance of mycorrhizal fungi are likely caused by concomitant increases in nutrient availability, reducing the need for symbionts. In the short term, the release of a variety of organic molecules from fresh biochar may in some cases be responsible for increases or decreases in abundance and activity of soil biota. A road map for future biochar research must include a systematic appreciation of different biochar-types and basic manipulative experiments that unambiguously identify the interactions between biochar and soil biota.     

Soil management for agro-ecosystems

Several problems of soil biotechnology and their relation with global ecological problems are considered. An analysis of the principal opportunities for soil biota management shows that scientific progress in this field is a necessary but insufficient condition for the solution of these global problems.     

Effects of vegetation removal on soil properties and decomposer organisms

The removal of understory vegetation has been a common forest management practice, especially in plantations, but the effects of understory removal on soil physico-chemical properties and decomposer organisms is poorly known. In the present study, the effects of understory vegetation removal and removal of all-plants (i.e. removal of understory vegetation and trees) on soil properties and soil biota were measured in a plantation of mixed native tree species in southern China. During the wet season, understory vegetation removal did not cause significant changes on soil microbial community and major soil faunal groups except for a marked reduction in the density of herbivorous nematodes. However, all-plants removal significantly decreased the fungal biomass, the fungal:bacterial ratio, the density of herbivorous nematodes, the structure of the nematode community, and the density of mites, collembola and total microarthropods. In the dry season, understory vegetation removal resulted in a marked reduction in the density of total and herbivorous nematodes. The effects of plant removal on soil biota were similar to that in dry season. For both seasons, understory removal had no significant effects on soil physico-chemical properties (soil water content, pH, total nitrogen and soil organic carbon) but removal of all-plants significantly decreased soil pH. In general, the effects of understory vegetation removal on soil biota and other soil properties were much less severe than those of all-plants removal. The soil biota did not show significant response to understory removal, suggesting that this part of the vegetation may not be a major governing factor on such biota.     

地上植食性昆虫对土壤生态系统影响的研究进展

地上地下生态系统之间存在着密切的联系,二者相互作用,共同影响陆地生态系统过程。越来越多的研究表明,地上地下之间的相互联系还受到植食性动物取食作用的调节。地上植食性昆虫不仅可以改变地上植物或动物群落,还可以间接地影响土壤生态系统中的生物群落和相关的土壤过程,进而对地上生态系统形成反馈。本文综述了地上植食性昆虫对土壤食物网中不同营养级的生物群落,以及相关土壤过程的影响;在已有研究报道的基础上,分析并归纳了地上植食性昆虫影响土壤生态系统的途径和调控因素等,旨在较为全面地总结地上植食性昆虫对土壤生态系统的间接影响以及相关的影响机制,并对今后的研究方向作了初步展望。     

Quantification of soil fauna metabolites and dead mass as humification sources in forest soils

The analysis of publications on soil food webs (FWs) allowed calculation of the contents of soil fauna metabolites and dead mass, which can serve as materials for humification. Excreta production of FWmicrofauna reaches 570 kg/ha annually, but the liquid excreta of protozoa and nematodes compose about 25%. The soil fauna dead mass can be also maximally about 580 kg/ha per year. However, up to 70% of this material is a dead mass of bacteria, protozoa, and nematodes. The undecomposed forest floor (L) has low values of these metabolites in comparison with the raw humus organic layer (F + H). The mass of these metabolites is twice lower in Ah. Theoretical assessment of earthworms’ role in SOM formation shows that the SOM amount in fresh coprolites can be 1.4 to 4.5-fold higher than SOM in the bulk soil in dependence on food assimilation efficiency, the soil: litter ratio in the earthworms’ ration, and SOM quantity in the bulk soil. Excreta production varies from 0.2 to 1.9% of the total SOM pool annually, including 0.15–1.5% of excrements of arthropods and enchytraeidae, but the amount of arthropods’ dead mass comprises 0.2–0.4%. The calculated values of the SOM increase due to earthworms’ coprolites are of the same order (0.9–2.7% of SOM pool annually). These values of SOM-forming biota metabolites and dead mass are close to the experimental and simulated data on labile and stable SOM fractions decomposition in forest soils (about 2% annually). Therefore, these biota’s products can play a role to restock SOM decrease due to mineralization.     

Direct, positive feedbacks produce instability in models of interrelationships among soil structure, plants and arbuscular mycorrhizal fungi

Current conceptual models of reciprocal interactions linking soil structure, plants and arbuscular mycorrhizal fungi emphasise positive feedbacks among the components of the system. However, dynamical systems with high dimensionality and several positive feedbacks (i.e. mutualism) are prone to instability. Further, organisms such as arbuscular mycorrhizal fungi (AMF) are obligate biotrophs of plants and are considered major biological agents in soil aggregate stabilization. With these considerations in mind, we developed dynamical models of soil ecosystems that reflect the main features of current conceptual models and empirical data, especially positive feedbacks and linear interactions among plants, AMF and the component of soil structure dependent on aggregates. We found that systems become increasingly unstable the more positive effects with Type I functional response (i.e., the growth rate of a mutualist is modified by the density of its partner through linear proportionality) are added to the model, to the point that increasing the realism of models by adding linear effects produces the most unstable systems. The present theoretical analysis thus offers a framework for modelling and suggests new directions for experimental studies on the interrelationship between soil structure, plants and AMF. Non-linearity in functional responses, spatial and temporal heterogeneity, and indirect effects can be invoked on a theoretical basis and experimentally tested in laboratory and field experiments in order to account for and buffer the local instability of the simplest of current scenarios. This first model presented here may generate interest in more explicitly representing the role of biota in soil physical structure, a phenomenon that is typically viewed in a more process- and management-focused context.