Differences in the diversity of oribatid mite communities in forests and agrosystems lands

A field study was conducted in the province of Burgos (Castile, NW of Spain) to assess the role and influence of the different anthropic use of soil on the oribatid mite communities (Acari, Oribatida).Soil samples from 20 representative soil sites of the Castilian upland steppes, with cultured, pastureland or forest soil uses, were taken in spring and autumn 2000. Thereafter, soil samples were analysed in terms of their mesofaunal biodiversity, measured using the real and relative diversity of the oribatid mite communities.Collected individuals were identified to species level, being altogether 111 Oribatid species. Results from communities' ordination analysis showed clear gradients based on community variables. One of these was defined by plots with high values of diversity and species richness which correspond to the less anthropic natural soils, mainly oak forest. In contrast, the most anthropic agrosystems soils, including extensive cereal crops, most of them receiving only mineral fertilisation or having human management, were placed in opposite gradients. Differences in biodiversity between crop lands and natural soils were also confirmed by ANOVA. The seasonality, measured in terms of difference between spring and autumn plots, played a minimum role in explaining differences of diversity. Nevertheless autumn diversity values were slightly higher than those of spring, except for crops.     

Bird communities, roads and development: prospects and constraints of applying empirical models

Our objectives were to explain the prospects and constraints of applying empirical models that relate bird community metrics to broad-scale characteristics of roads and development. We explored the practical value of regression models that were derived for a large protected area in the Chihuahuan Desert. These models related bird species richness, relative abundance, or probability of occurrence to total length of roads within each of two spatial extents (1- and 2-km radii), distance to the nearest road, distance to the nearest development, or the two-way interactions of these variables. Empirical models can be used to inform conservation decisions, to parameterise simulation models for conservation planning, to identify threshold levels of road and development variables, and to determine the focus of management experiments for confirmatory hypothesis testing and improvement of model realism.     

DCA、CCA和DCCA三种排序方法在中国草地植被群落中的应用现状

排序是用来分析植被与环境之间生态关系的重要手段。该文主要是对除趋势对应分析(DCA)、典范对应分析(CCA)和除趋势典范对应分析(DCCA)这三种排序方法进行总结,讨论它们在中国草地植被群落研究中的应用现状,并得出除趋势对应分析与聚类分析结合使用效果比较好,主要是用来揭示群落之间的关系,并且在实际的应用中也比较多,而典范对应分析和除趋势典范对应分析在揭示种与环境关系方面具有明显的优势,但是由于某些条件的限制,在实际研究中应用的比较少。可见这几种排序方法在实际应用中具有一定的优势,所以应该加强这方面的应用,更加深入的研究草地植被群落,以期对草地生态学及草地植被群落生态关系的研究工作发挥重要的借鉴作用。     

Nano-scale secondary ion mass spectrometry — A new analytical tool in biogeochemistry and soil ecology: A review article

Soils are structurally heterogeneous across a wide range of spatio-temporal scales. Consequently, external environmental conditions do not have a uniform effect throughout the soil, resulting in a large diversity of micro-habitats. It has been suggested that soil function can be studied without explicit consideration of such fine detail, but recent research has indicated that the micro-scale distribution of organisms may be of importance for a mechanistic understanding of many soil functions. Current techniques still lack the adequate sensitivity and resolution for data collection at the micro-scale, and the question ‘How important are various soil processes acting at different scales for ecological function?’ is therefore challenging to answer. The nano-scale secondary ion mass spectrometer (NanoSIMS) represents the latest generation of ion microprobes, which link high-resolution microscopy with isotopic analysis. The main advantage of NanoSIMS over other secondary ion mass spectrometers is its ability to operate at high mass resolution, whilst maintaining both excellent signal transmission and spatial resolution (down to 50 nm). NanoSIMS has been used previously in studies focussing on presolar materials from meteorites, in material science, biology, geology and mineralogy. Recently, the potential of NanoSIMS as a new tool in the study of biophysical interfaces in soils has been demonstrated. This paper describes the principles of NanoSIMS and discusses the potential of this tool to contribute to the field of biogeochemistry and soil ecology. Practical considerations (sample size and preparation, simultaneous collection of isotopes, mass resolution, isobaric interference and quantification of the isotopes of interest) are discussed. Adequate sample preparation, avoiding bias due to artefacts, and identification of regions-of-interest will be critical concerns if NanoSIMS is used as a new tool in biogeochemistry and soil ecology. Finally, we review the areas of research most likely to benefit from the high spatial and high mass resolution attainable with this new approach.     

Lakeshore diversity and rarity relationships along interacting disturbance gradients: catchment area, wave action and depth

Diversity patterns of riparian plant communities have been associated with disturbance. Populations of a diversity of Atlantic Coastal Plain plants occur as disjuncts on shores of large catchment area lakes in Nova Scotia. These lakeshore communities contain rare plants with local, national and global rankings. The populations of rare plants are dynamic and their management requires an understanding of the relationship between disturbance and the survival of rare plants. This present study measured (overwinter wooden dowel removal) and observed disturbance along gradients of catchment area (CA), exposure and depth. In three separate experiments ranging from the landscape to the lake, to the single shoreline level, disturbance was linked to lake CA, exposure and depth, respectively. At all scales, disturbance was positively associated with the presence of rare species. The pattern of rare species richness over the river system was complex; at the within-lake level, the frequency of rare species per site was greatest in the intermediate CA lake while the pool of rare species was greatest in the largest CA lake. The findings focus field efforts on wide, exposed shorelines of large CA lakes where new rare plants continue to be discovered. In addition, the discrepancy between highest frequency of rare plants on intermediate CA lakes and highest species pools of rarities on large CA lakes, reinforces the need for larger protected area systems for the most naturally disturbed ecosystems which often support populations having a high turnover rate but a low site to site frequency.     

宁夏荒漠草原植物群落的空间异质性

荒漠草原植被最显著的特点是植物种类贫乏,几乎全部为旱生种类,且空间异质性强,植物与自然环境之间的联系密切,小地形的差异势必会造成植物群落物种多样性的变化及其在不同尺度上的空间异质性。本研究于2011年9月在宁夏盐池县试验区封育10年的荒漠草原围栏内,采用样线取样法在坡面尺度上调查不同坡位上草地群落的空间分异,分析微地形条件对荒漠草原植物群落空间异质性的影响。结果表明,植物群落的空间变异性在不同坡向及不同坡位间存在差异;矮小半灌木功能群在空间上的分布斑块化最明显,多年生草本功能群次之,一年生草本功能群在阴坡上的分布斑块化程度较高,在阳坡上其斑块性明显下降;在草地植物群落恢复演替的进程中,多年生草本植物已发展到相对稳定的程度,矮小半灌木处于增长期,一年生草本植物在阴坡的增长大于阳坡。     

填沙路基边坡不同植物群落生态防护效应与生长动态变化分析

高速公路边坡是高速公路生态最脆弱的部分,其防护和绿化是公路生态建设的重点。研究针对填沙路基边坡,对不同植物群落生态防护效应进行了探讨,同时分析了不同植物群落覆盖度、地上生物量、灌木生长速率的生长动态变化,最后提出了进一步研究中应注意的问题。     

大兴安岭兴安落叶松群落多样性分析

以内蒙古大兴安岭牙克石林管局下属6个林区的兴安落叶松群落为研究对象,通过对群落物种多样性的量化分析,探讨大兴安岭兴安落叶松群落物种多样性分布规律。结果表明：兴安落叶松群落种群物种多样性总数分布范围为0~28种,垂直结构上变化规律明显,草本层物种数最多,其次是灌木层,最小的是乔木层。群落丰富度最大的为阿里河西陵梯林场,主要是灌木层,草本层物种较多。最小的为克一河库亚林场的兴安落叶松群落,该群落草本层物种较小。     

Surface and subsurface organic carbon, microbial biomass and activity in a forest soil sequence

The distribution of organic carbon, microbial biomass and activity, from the surface down to 70 cm, was investigated through three semiarid Mediterranean soils: (1) a Typic Calcixeroll covered with a native pinewood (NP), (2) a Typic Calcixerept under a mature pine plantation (PP) on abandoned agricultural terraces and (3) a Typic Haploxerept under a grassland (GS). NP and GS had the highest and lowest soil organic carbon (SOC) pools, respectively. Both of them had decreasing SOC contents with depth. PP, which held intermediate SOC levels, showed an increase in total organic C and humic substances C with depth due to their mineralization in the anciently ploughed topsoil layer. The soils were similarly ranked as regards their microbial biomass and activity: NP>PP>GS. In general, the microbial communities were less dense and active towards the deeper horizons. More specifically, PP and GS had a very populated and active top 20-cm layer, which was attributed to the dense root system of their grass cover. NP maintained high microbial biomass and activity levels from 0 to 70 cm, progressively diminishing along with shrub root density (e.g. microbial biomass C dropped from 2342 to 394 mg kg⁻¹ soil). The latter soil presented the sharpest drop of its microbial properties with depth, what was considered an indicator of its quality. Generally decreasing patterns of microbial biomass and activity were not always coincident with previously published gradients of microbial metabolic abilities and genetic structure. This reinforces the need of combining biomass, activity and biodiversity measurements if the ecosystem's functioning is to be fully understood and a real monitoring of degradation processes and restoration strategies is to be achieved.     

Effects of single-tree selection harvesting on hymenopteran and saproxylic insect assemblages in the canopy and understory of northern temperate forests

Insects respond to changes in microhabitat caused by canopy disturbance, and thus can be used to examine the ecological impacts of harvesting. Single-tree selection harvesting is the most common silvicultural system used to emulate local small-scale natural disturbance and maintain uneven-aged forest structure in temperate forests. Here, we test for differences in richness, abundance, and composition of hymenopteran and saproxylic insect assemblages at four different taxon levels (selected insect orders; and all hymenopteran families, and braconid subfamilies and morphospecies) between the canopy and understory of unharvested and single-tree selection harvested sites in a northern temperate forest from central Canada. Harvesting had no effect on insect assemblage richness, composition or abundance at the three highest taxon levels (order, family and subfamily). Similarly, richness and abundance at the lowest-taxon level (braconid morphospecies) were similar, although composition differed slightly between unharvested and harvested stands. Insect assemblages were vertically stratified, with generally higher abundance (for Diptera, Hymenoptera, some hymenopteran families and braconid subfamilies) and richness (for braconid morphospecies) in the understory than the canopy. In particular, composition of the braconid morphospecies assemblage showed relatively low similarity between the understory and canopy. Single-tree selection harvesting appears to influ-ence wood-associated insect taxa only subtly through small changes in community composition at the lowest taxon level, and thus is recommended as a conservative approach for managing these northern temperate forests.