西藏退化高寒草原土壤团聚体有机碳的变化特征

为进一步了解高寒草原土壤碳动态变化特点与变化过程,采用湿筛法对藏北高原未退化、轻度退化和严重退化高寒草原表层（0~10 cm）、亚表层（>10~20 cm）不同粒级w（SAOC）（SAOC为土壤团聚体有机碳）进行研究.结果表明,与未退化草地相比,不同程度退化草地w（SAOC）均呈下降趋势,但严重退化草地表层、亚表层中w（SAOC）、>0.25 mm粒级w（SAOC）、 < 0.25 mm粒级w（SAOC）降幅均显著低于轻度退化草地;不同程度退化草地表层、亚表层中>0.25、 < 0.25 mm粒级w（SAOC）在总体上趋于下降,且亚表层的降幅明显高于表层的降幅,但退化草地亚表层中w（SAOC）仍高于表层（未退化草地、轻度和严重退化草地亚表层较表层分别增加51.84%、31.34%、6.83%）,w（SAOC）的土层差异随草地退化加剧而大幅缩小;轻度、严重退化草地不同粒级w（SAOC）的土层分布特征仍与未退化草地一致,其表层、亚表层中>0.25 mm粒级w（SAOC）均明显较高;与未退化草地相同,退化草地表层、亚表层w（SAOC）贡献率亦均呈|2~0.25 mm| > | < 0.25~0.053 mm| > | > 2 mm| > | < 0.053 mm|粒级;退化草地环境对团聚体与w（SAOC）,以及w（SOC）（SOC为土壤有机碳）与w（SAOC）间的关系具有重要影响.研究显示,高原冷干环境下不同粒级SAOC及其变化受草地退化程度、土层深度等的深刻影响,需要从影响土壤有机碳形成与转化的土壤机制等方面进行深入研究.      

Phytodiversity of relict steppe enclaves in the Urals: Experience in comparative assessment

Unique mountain-steppe ecosystems in the Southern Urals have retained a high level of species and cenotic diversity, despite fragmentation and isolation. Specific features of these ecosystems are described.     

Prospects for Restoring the Biodiversity of Steppe Vegetation: Sowing of Perennial Grasses

Russian Journal of Ecology -     

Effects of irrigation and landscape heterogeneity on butterfly diversity in Mediterranean farmlands

Irrigation effects on biodiversity are poorly known, particularly in Mediterranean agro-ecosystems. In this study we analyzed irrigation effects on butterfly species richness, abundance and diversity as well as on species composition in a farmed landscape under Mediterranean climate. The study area consisted of four contiguous agricultural sub-areas with a decreasing degree of intensification: irrigated, mixed (dry and irrigated), dry and environmentally protected (i.e. Special Protection Area, SPA) dry farmland. Forty one km-transects (ten per sub-area) were searched for butterflies in 2008 and 2009. Contrary to expectations, species richness (alfa, beta and gamma diversity) was highest in both years in the most intensified sub-area (i.e. irrigated) followed by SPA, dry and mixed sub-areas. Landscape characteristics accounted for most of the between-subareas differences in species richness. Species richness was negatively related to mean field size at the landscape level and positively related to the number of trees and large shrubs along transects. Therefore, the higher number of butterfly species recorded in the irrigated farmland could be due to a more complex landscape. In contrast, butterfly abundance was highest in cereal steppes (i.e. dry and SPA sub-areas), with abundance being negatively affected by mean field size. Inter-annual change in butterfly abundance was much sharper in rainfed (i.e. dry and SPA) than in irrigated (i.e. irrigated and mixed) sub-areas. Irrigated farmland may provide more favorable conditions for butterflies by buffering the (year-to-year and summer) drought periods characterising Mediterranean climate. Species composition differed among sub-areas, with differences being partly explained by field size and number of trees and shrubs along transects. Our study suggest an important role of landscape characteristics in boosting butterfly biodiversity in intensively managed irrigated croplands and emphasizes the importance of encouraging studies on farmland butterfly diversity in different (bioclimatic) regions allowing the design of region-specific agri-environmental schemes.