Assessment of DNA fingerprinting for determining genetic diversity in sheep populations

Genomic DNA, prepared from 12 animals from four sheep flocks, was digested with either HaeIII or Hin fI and probed with three DNA fingerprinting probes. Mean DNA fingerprint band sharing and band frequency calculated for each flock were used to estimate genetic diversity. Each of the DNA fingerprinting systems showed the same trend in diversity within the sampled flocks, and greater diversity between the flocks than within the flocks. DNA fingerprinting therefore provides a useful measure of genetic diversity in sheep.     

A global synthesis of the effects of diversified farming systems on arthropod diversity within fields and across agricultural landscapes

Agricultural intensification is a leading cause of global biodiversity loss, which can reduce the provisioning of ecosystem services in managed ecosystems. Organic farming and plant diversification are farm management schemes that may mitigate potential ecological harm by increasing species richness and boosting related ecosystem services to agroecosystems. What remains unclear is the extent to which farm management schemes affect biodiversity components other than species richness, and whether impacts differ across spatial scales and landscape contexts. Using a global metadataset, we quantified the effects of organic farming and plant diversification on abundance, local diversity (communities within fields), and regional diversity (communities across fields) of arthropod pollinators, predators, herbivores, and detritivores. Both organic farming and higher in‐field plant diversity enhanced arthropod abundance, particularly for rare taxa. This resulted in increased richness but decreased evenness. While these responses were stronger at local relative to regional scales, richness and abundance increased at both scales, and richness on farms embedded in complex relative to simple landscapes. Overall, both organic farming and in‐field plant diversification exerted the strongest effects on pollinators and predators, suggesting these management schemes can facilitate ecosystem service providers without augmenting herbivore (pest) populations. Our results suggest that organic farming and plant diversification promote diverse arthropod metacommunities that may provide temporal and spatial stability of ecosystem service provisioning. Conserving diverse plant and arthropod communities in farming systems therefore requires sustainable practices that operate both within fields and across landscapes.     

Notes on compositional diversity

This paper tries to show some ways and means of simple (binary) modelling, whereby diversity can be interconnected with other attributes of a community. A new type of scaling (called characteristic scaling) is introduced for further use.     

小叶锦鸡儿灌丛化对典型草原群落结构与生态系统功能的影响

草原灌丛化是全球干旱半干旱地区面临的重要生态问题。灌丛化对草原生态系统结构与功能的影响较为复杂, 有待于在更广泛的区域开展研究。该研究在内蒙古锡林郭勒典型草原选择轻度、中度和重度灌丛化草地, 通过群落调查, 结合植物功能性状和土壤理化性质观测, 研究了小叶锦鸡儿(Caragana microphylla)灌丛化对草原群落结构(物种多样性、功能多样性和功能群组成)和生态系统功能(初级生产力、植被和土壤养分库)的影响。结果表明: 1)不同程度灌丛化草地的物种丰富度、功能性状多样性和群落加权性状平均值差异显著, 其中, 中度灌丛化草地的物种多样性和功能多样性较高, 表明一定程度的灌丛化有利于生物多样性维持。2)重度灌丛化草地的地上净初级生产力(ANPP)显著高于轻度和中度灌丛化草地, 其原因主要是随着灌丛化程度加剧, 群落内一/二年生草本植物显著增加, 而多年生禾草和多年生杂类草显著减少。三个灌丛化草地的植被叶片和土壤碳、氮库差异均不显著。3)灌丛化对草原生态系统功能包括ANPP、植被和土壤养分库均没有直接的影响, 而是通过影响功能群组成、土壤理化性质和功能多样性, 间接地影响生态系统功能; 灌丛化导致功能群发生替代和土壤旱碱化是最重要的生物和非生物因素。     

Structural diversity indices based on airborne LiDAR as ecological indicators for managing highly dynamic landscapes

An objective, quantifiable index of structural biodiversity that could be rapidly obtained with reduced or no field effort is essential for the use of structure as universal ecological indicator for ecosystem management. Active remote sensing provides a rapid assessment tool to potentially guide land managers in highly dynamic and spatially complex landscapes. These landscapes are often dependent on frequent disturbance regimes and characterized by high endemism.We propose a modified Shannon–Wiener Index and modified Evenness Index as stand structural complexity indices for surrogates of ecosystem health. These structural indices are validated at Tall Timbers Research Station the site of one of the longest running fire ecology studies in southeastern U.S. This site is dominated by highly dynamic pine-grassland woodlands maintained with frequent fire. Once the dominant ecosystem in the Southeast, this woodland complex has been cleared for agriculture or converted to other cover types, and depends on a frequent (1- to 3-year fire return interval) low- to moderate-intensity fire regime to prevent succession to mixed hardwood forests and maintain understory species diversity. Structural evaluation of the impact of multiple disturbance regimes included height profiles and derived metrics for five different fire interval treatments; 1-year, 2-year, 3-year, mixed fire frequency (a combination of 2- and 4-year fire returns), and fire exclusion. The 3-dimensional spatial arrangement of structural elements was used to assess hardwood encroachment and changes in structural complexity. In agreement with other research, 3-year fire return interval was considered to be the best fire interval treatment for maintaining the pine-grassland woodlands, because canopy cover and vertical diversity indices were shown to be statistically higher in fire excluded and less frequently burned plots than in 1- and 2-year fire interval treatments. We developed a LiDAR-derived structural diversity index, LHDI, and propose that an ecosystem-specific threshold target for management intervention can be developed, based on significant shifts in structure and composition using this new index.Structural diversity indices can be valuable surrogates of ecosystem biodiversity, and ecosystem-specific target values can be developed as objective quantifiable goals for conservation and ecosystem integrity, particularly in remote areas.