肃南山地放牧系统四季供需动态模型

通过分析和综合肃南山地放牧系统的四季放牧试验数据,模拟了该系统的牧草供给与家畜需求的季节动态,用模式图反映了放牧系统牧草供需平衡机理。通过分析放牧系统的时间地带性的生态要素,拟合了肃南山地放牧系统的放牧函数,并建立了北半球中纬度地区的一般方程。这些模型数量化地解释了“生物的时间地带性”理论在山地放牧系统牧草供给与家畜需求平衡中的作用,对放牧管理和畜牧业持续发展具有一定的指导作用。

Degradation of High Mountain Ecosystems in Northern Europe

Data material of a long-term high mountain ecosystem research project was used to interpret thegrazing impact of reindeers. In central Norwayinvestigations were conducted to both, areas wherereindeer grazing is excluded, and areas whereintensive pasturing is present for a long period oftime. The comparative analysis of grazing impact was based on similar environmental conditions. Theresults were transposed to northern Norway wheredramatic overgrazing had been exceeding thecarrying capacity. Using landscape ecologicalmappings, especially of vegetation and soils, theimpact of reindeer grazing in different areas becameobvious. Non-grazed lichen-dominated ecosystems of the snow-free locations functioned sensitively nearthe limit of organism survival. These localities weremost influenced by grazing as they offer the winterforage to the reindeers. So, intensive grazing incentral Norway led to landscape degradation bydestruction of the vegetation and superinduced bysoil erosion. Those features were comparable to thesituation in northern Norway, where a broad-scale destruction of the environment combined with adepression of the altitudinal belts had occurred dueto overgrazing. Functioning principles of intact high mountain systems were explained and used to interpret theenvironmental background for the understanding ofdegradation phenomena. Finally, the use of a newmodel calculating the carrying capacity of high mountain landscape was discussed.

Species turnover drives grassland community to phylogenetic clustering over long-term grazing disturbance

Aims Grazing exerts profound effects on grassland ecosystem service and functions by regulating species composition and diversity,and structuring community assembly worldwide.However,adaptions of phylogenetic diversity and phylogenetic community structure to long-term grazing disturbance remain poorly studied,especially for ecosystems distributed in extreme environments.Methods Here,we conducted an experiment with multigrazing intensities to explore the impacts of grazing disturbance on plant phylogenetic diversity and community structure in an alpine grassland of the Tibetan Plateau.Important Findings Grazing disturbance enriched plant species richness(SR),and stimulated species turnover from regional species pool,consequently changing community species composition.Under low intensities,grazing exerted no obvious effects on phylogenetic diversity and community structure,whereas communities changed from overdispersion to clustering under high grazing intensity.High grazing intensity resulted in stronger environmental filtering,which consequently selected those species with high resilience to grazing disturbance.The observed clustering structure was associated with the colonizing species which were closely related to resident species,and locally extinct species,and distantly related to residents.At the plant functional trait level,high grazing intensity increased species colonization largely by altering the effect of root depth on species colonization compared to light grazing.Our results highlight that solely utilization of SR and diversity cannot fully represent grassland communities responses to grazing.The effects of species turnover on community phylogenetic diversity and structure are entailed to be explored in the future grazing studies.