Department of Molecular Biology and Ecology of Plants, Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 69978, Israel.
Glob Chang Biol. 2015 May;21(5):1939-50. doi: 10.1111/gcb.12866. Epub 2015 Feb 18.
A synthesis of a long-term (19 years) study assessing the effects of cattle grazing on the structure and composition of a Mediterranean grassland in north-eastern Israel is presented, with new insights into the response of the vegetation to grazing management and rainfall. We hypothesized that the plant community studied would be resistant to high grazing intensities and rainfall variability considering the combined long history of land-use and unpredictable climatic conditions where this community evolved. Treatments included manipulations of stocking densities (moderate, heavy, and very heavy) and of grazing regimes (continuous vs. seasonal), in a factorial design. The effect of interannual rainfall variation on the expression of grazing impacts on the plant community was minor. The main effects of grazing on relative cover of plant functional groups were related to early vs. late seasonal grazing. Species diversity and equitability were remarkably stable across all grazing treatments. A reduction in tall grass cover at higher stocking densities was correlated with increased cover of less palatable groups such as annual and perennial thistles, as well as shorter and prostrate groups such as short annual grasses. This long-term study shows that interannual fluctuations in plant functional group composition could be partly accounted for by grazing pressure and timing, but not by the measured rainfall variables. Grazing affected the dominance of tall annual grasses. However, the persistence of tall grasses and more palatable species over time, despite large differences in grazing pressure and timing, supports the idea that Mediterranean grasslands are highly resistant to prolonged grazing. Indeed, even under the most extreme grazing conditions applied, there were no signs of deterioration or collapse of the ecosystem. This high resistance to grazing intensity and interannual fluctuation in climatic conditions should favor the persistence of the plant community under forecasted increasing unpredictability due to climate change.
本文综合了一项长达 19 年的研究，评估了在以色列东北部的地中海草原上放牧对其结构和组成的影响，并提供了对植被对放牧管理和降雨响应的新见解。我们假设，考虑到该群落长期的土地利用历史和不可预测的气候条件，研究中的植物群落应该能够抵御高强度的放牧和降雨变化。处理方法包括在一个因子设计中操纵放牧密度（适度、重度和极重度）和放牧制度（连续与季节性）。年际降雨变化对放牧对植物群落影响的表达影响较小。放牧对植物功能群相对盖度的主要影响与早期和晚期季节性放牧有关。在所有放牧处理下，物种多样性和均匀度都非常稳定。在较高放牧密度下，高大草本植物的覆盖度减少与较难消化的植物群，如一年生和多年生蓟，以及较短的匍匐植物群，如短一年生草本植物的覆盖度增加有关。这项长期研究表明，植物功能群组成的年际波动部分可以归因于放牧压力和时间，但不能归因于测量的降雨变量。放牧影响了高大一年生草本植物的优势。然而，尽管放牧压力和时间存在很大差异，但高大草本植物和更可食用物种的持久性随着时间的推移得到了证实，这表明地中海草原对长期放牧具有高度的抵抗力。事实上，即使在应用最极端的放牧条件下，也没有生态系统恶化或崩溃的迹象。这种对放牧强度和年际气候条件波动的高抵抗力，应该有利于在预测到气候变化导致的不可预测性增加的情况下，植物群落的持续存在。
