Invertebrate biodiversity under hot rocks: habitat use by the fauna of sandstone outcrops in the Sydney region

Loose surface rocks on sandstone outcrops in coastal eastern Australia are subject to high levels of anthropogenic disturbance. The endangered reptiles that use these rocks as shelter-sites have attracted considerable research, but the invertebrate fauna under the same rocks has been neglected. We surveyed four sites in the Sydney region, to record the invertebrate fauna under a total of 240 rocks and quantify habitat associations of these animals. Fauna were present under almost 90% of surveyed rocks, with high overall abundance and species richness (up to seven species per rock). Our sampling regime was inadequate to fully characterise the sandstone invertebrate fauna, and thus substantially underestimates diversity on a broader spatial scale. The taxa covered a broad phylogenetic range, with ants and spiders the most abundant, widespread and species-rich lineages. The assemblage was dominated by predators and opportunistic scavengers, possibly reflecting the characteristic low productivity of these systems. Canonical correspondence analysis identified consistent linkages between specific faunal groups and microhabitat features (mainly substrate, also degree of shading and characteristics of the overlying rock). We conclude that surface rocks on Hawkesbury sandstone outcrops shelter a diverse and abundant invertebrate fauna, that microhabitat features influence faunal composition, and that our ignorance of this component of biodiversity will severely hamper any rational plan to conserve these distinctive and highly threatened ecosystems.     

Disentangling effects of habitat diversity and area on orthopteran species with contrasting mobility

Loss of semi-natural grasslands and reduction of habitat diversity are considered major potential threats to arthropod diversity in agricultural landscapes. The main aim of this study was to investigate how area and habitat diversity, mediated by shrub encroachment after grassland abandonment, affect species richness of orthopterans in island-like grasslands, and how contrasting mobility might alter species richness response to both factors. We selected 35 isolated patches in landscapes dominated by arable land (durum wheat) in order to obtain two statistically uncorrelated gradients: (i) one in habitat area ranging from 0.2 to 55 ha and (ii) one in habitat diversity ranging from patches dominated by one habitat (either open grasslands or shrublands) to patches with a mosaic of different habitats. Habitat loss due to land-use conversion into arable fields was associated with a substantial loss of species with a positive species-area relationship (SAR), with sedentary species having a steeper and stronger SAR than mobile species. Halting habitat loss is, therefore, needed to avoid further species extinctions. Shrub encroachment, triggered by abandonment, presented a hump-shaped relationship with habitat diversity. An increase in habitat diversity enhanced species richness irrespective of patch area and mobility. Maintaining or enhancing habitat diversity, by cutting or burning small sectors and by reintroducing extensive sheep grazing into abandoned grassland, are suggested as complementary strategies to mitigate further decline of orthopteran diversity in the remnant patches. This would be equally important in both small and large patches.     

Bryophytes in a changing landscape: The hierarchical effects of habitat fragmentation on ecological and evolutionary processes

Testing the myriad predictions associated with the community, demographic and genetic impacts of habitat fragmentation remains a high conservation priority. Many bryophyte taxa are ideal model systems for experimentally testing such metapopulation-based and population genetic predictions due to their relatively fast colonisation-extinction rates, high substrate specificity, dominant haploid condition, and diminutive size. Herein, we review the community, demographic and population genetic impacts of habitat fragmentation on bryophytes, highlight the present knowledge gaps, and offer ideas on how experimental studies utilizing bryophytes may be used to address the broader conservation implications associated with fragmented ecosystems. Previous research suggests that dispersal limitation best explains observed patterns of abundance and distribution of bryophytes in some fragmented habitats. However, edge effects influence bryophyte community structure of border habitats especially where abrupt differences in micro-climatic conditions between the matrix and the forest remnant exist, or where the species pool contains members with inherently restricted ecological amplitudes. Existing studies do not agree on the relationship between basic attributes of bryophyte community structure (i.e., species richness and local density), and habitat area and degree of spatial-isolation. Demographic studies are a critical step in structuring conservation strategies, however surprisingly little empirical information exists as to the impacts of habitat fragmentation on plant population dynamics. We propose that bryophytes offer great potential for testing predictions with respect to plant population persistence in spatially-structured landscapes.     

The influence of patch area and connectivity on avian communities in urban revegetation

Landscape restoration through revegetation is being increasingly used in the conservation management of degraded landscapes. To effectively plan restoration programs information is required on how the landscape context of revegetation influences biodiversity gains. Here, we investigate the relative influence of patch area and connectivity on bird species richness and abundance within urban revegetation patches in Brisbane, Australia. We carried out bird surveys at 20 revegetation sites, and used hierarchical partitioning and model selection to test the relative importance of patch area (the area of revegetation including all directly connected remnant vegetation) and landscape connectivity (the vegetated area connected by less than 10 m, 20 m, 30 m, 40 m and 50 m cleared gaps). We controlled for a number of possible confounding variables within the hierarchical partitioning procedure. Both the hierarchical partitioning and model selection procedures indicated that connectivity had an important influence on bird species richness. Patch area in combination with connectivity were important influencing factors on overall bird abundance. We also carried out the hierarchical partitioning procedure for bird abundance data within a range of feeding guilds, yielding results specific to species groups. Overall our data suggest that greater connectivity enhances the habitat area that colonists can arrive from (resulting in greater species richness), whereas increased patch area allows for increased abundance by expanding the habitat available to species already present in a patch. A combined approach where connectivity and overall habitat area is enhanced across the landscape is likely to be necessary to meet long-term conservation objectives.     

The influence of field shape, area and surrounding landscape on plant species richness in grazed ex-fields

Over the past 100 years species-rich semi-natural grasslands have decreased dramatically in Western Europe, where former arable fields (ex-fields) are used instead as pasture. The disappearance of semi-natural grasslands has caused a threat to the biodiversity in agricultural landscapes. Many typical grassland plants are dispersal limited, thus grazed ex-fields can be used to investigate if species spontaneously colonise these new grassland habitats. We examined the relationship between surrounding landscape, field area, shape, distance between edge and centre, and plant species diversity in ex-fields that had been grazed for 15-18 years. The results showed that there were 35% more plant species in fields surrounded by commercial forestry production compared to those surrounded by open agricultural landscape. Area and shape did not influence species richness, although there was increasing number of species in the centre with decreasing distance from the edge. Twenty-five percent of the species where typical grassland species, and ex-fields surrounded by forest had 91% more grassland species compared to those in the open landscape. It is possible to increase grassland plant occurrences by grazing ex-fields surrounded by forest or other grassland remnant habitats, particularly in landscapes where grazed semi-natural grasslands are scarce.     

稀土农用的经济效应和环境生态效应

从农业经济效应和环境生态效应二方面,论述了稀土肥料促进作物生长、发育,提高作物产量,改善作物品质的效应与机理;影响土壤区系中微生物种群数量和土壤脱氢酶、碱性磷酸酶、脲酶及蔗糖酶的功能,继而反馈调节作物生长;缓解酸雨、紫外辐射和重金属伤害作物的生态生理学效应;并以稀土在作物体内分布与富集规律为参考,探讨了稀土农用的安全性。实践证明,稀土农用只要严格控制剂量就能实现增强作物抗逆性和提高作物经济效益的目标。     

The effects of mixed broad-leaved trees on the collembolan community in larch plantations of central Japan

The effects of broad-leaved trees on the collembolan community in larch plantations were investigated at the foot of Mt. Yatsugatake (1200–1400 m a.s.l.) in Japan. The study sites comprised five pure larch plantation plots (larch dominated more than 95% of the area at breast height) and five mixed forest plots (larch dominated between 50% and 80% of the area at breast height). We compared the collembolan community structures between stand types and related them to the plant community composition and soil properties at each plot. Density and species richness of Collembola were not significantly different between pure larch and mixed plots. Using partial redundancy analysis (pRDA), the variance of collembolan species data in the litter layer was explained by the biomass of grass on the forest floor, and the variance in the soil layer was explained by the biomass of total forest floor plants. These results suggest that the biomass or the composition of forest floor plants influence the collembolan community more than the crown trees in this area.     

农田防护林对田间地表节肢动物分布的影响——以昌图县为例

提升农田生物多样性是当前生态农业研究的热点问题。为探讨农田防护林的生物多样性保护功能,本研究在辽宁省昌图县金家镇选取8个农田-防护林单元（每个单元即为1个田块）,使用陷阱法调查了不同类型林带（完整型、残缺型、消亡型）相邻的农田中,距林带不同距离处（0 m、50 m、100 m、150 m、200 m）地表节肢动物的分布情况,同时记录林带内的植被群落特征。采用方差分析以及群落排序的方法,分析了林带类型、距离梯度以及林带植被结构对农田地表节肢动物分布的影响。研究结果表明：1）与消亡型相比,完整型和残缺型林带相邻的农田物种多度显著较高,物种多样性在各类型林带农田间无显著差异,与完整型及残缺型林带相邻的农田维持着区别于消亡型林带的地表节肢动物群落结构。2）完整型和残缺型林带相邻的农田物种多度梯度变化显著,随距林带距离的增加均呈由低到高的变化趋势;不同类型林带农田中,物种多样性随距林带距离的增加逐渐递减,边缘效应显著。3）林带中草本层物种多度和乔木层盖度是影响农田地表节肢动物群落分布的主要因子,共解释了35.4%的节肢动物数量变异;不同节肢动物物种对林带植被结构的响应存在差异,步甲和蜘蛛作为当地农业景观中主要的天敌类群,与上述林带植被结构因子关系密切：林带内较高的草本层物种多度有利于增加农田中某些步甲常见种的多样性,而较高的乔木层盖度有利于增加蜘蛛目常见科的多样性。研究结果表明,农田防护林作为研究区主要的非耕作生境类型,能够显著提升相邻农田中地表节肢动物的多度,对于物种多样性的提升作用则不明显;林带内草本层物种多度以及乔木层盖度对蜘蛛、步甲等多类天敌多样性保护具有积极作用。因此,加强农业景观中现有林地的改造和提升,如营造适宜盖度的上层林木以及丰富的林下植被,能够提升现有林地的生境质量,进一步发挥其对农田生物多样性的保育功能。     

The effects of forest patch size and matrix type on changes in carabid beetle assemblages in an urbanized landscape

In this study we compared ground beetles (Carabidae) from a range of different forest fragments along an urbanization gradient in Brussels, Belgium. We address the following questions: (i) How does the degree of urbanization in the surrounding habitat affect forest beetles, and does it interact with the effects of patch size and distance to forest edge? (ii) Do these factors have a different effect at the level of individual species, habitat affinity groups or total community? During 2002 we sampled 13 forest plots in 10 forest patches, ranging in size from 5.27 to 4383 ha. The beetles were captured using transects of pitfall traps from the edge to a distance of 100 m into each woodland and identified to species level. Effects of urbanization, forest size and forest edge were evaluated on total species number, abundance and habitat affinity groups and ten abundant, widespread model carabid species. Overall, the effects of urbanization, forest size and edge effects slightly influenced total species richness and abundance but appeared to have a major effect on ground beetle assemblages through species specific responses. More urbanized sites had significantly fewer forest specialists and more generalist species. Large forest fragments were favoured by forest specialist species while generalist species and species frequently associated with forest (forest generalists) dominated the smaller forests. Forest edges mainly harboured generalist species while forest specialist species were more frequent into the forests if the forest patches were large enough, otherwise they disappeared due to the destruction or impoverishment of their habitat. Our results show the importance of differentiating between habitat affinity, especially habitat generalists versus specialists, the latter having a higher value in nature conservation, and merely the quantity of species represented in human-dominated areas.