Long-term impacts of livestock grazing and browsing in the Succulent Karoo: a 20-year study of vegetation change under different grazing regimes in Namaqualand§
Long-term impacts of livestock grazing and browsing in the Succulent Karoo: a 20-year study of vegetation change under different grazing regimes in Namaqualand§
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多汁卡鲁牲畜放牧和浏览的长期影响：纳马夸兰不同放牧制度下植被变化的 20 年研究§
DOI：
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发表时间：
2018
影响因子：
1.4
通讯作者：
M. Hoffman
中科院分区：
文献类型：
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作者：
E. Nenzhelele;S. Todd;M. Hoffman
本研究采用围栏线对比的方法，调查长期的影响，高放牧压力的植被在南非纳马夸兰的一个网站。1996年、2006年和2016年调查了40对永久标记地块。主要目的是调查近20年来几乎连续放牧的公共牧场和相对较少放牧的商业牧场之间植被结构和物种组成的变化。结果显示，与前两个采样期相比，2016年商业和公共牧场的总植被覆盖率下降。这可归因于2016年的降雨量较低，主要是由于年度植物覆盖减少，特别是在公共牧场上。多年生灌木物种提供了一个饲料库，可供牲畜在干旱时期使用，并可缓冲饲料供应的短期短缺。然而，在公共牧场植被中占主导地位的一年生植物并不形成这种饲料库，因此不具有与多年生灌木相同的多年缓冲能力。这提供了一种机制，即长期连续放牧降低了对降雨量波动的恢复力，增加了牲畜的变异性，从而促进了系统中的非平衡型动态。
This study used a fence-line contrast approach to investigate the long-term impact of high grazing pressure on the vegetation at a site in Namaqualand, South Africa. Forty pairs of permanently marked plots were surveyed in 1996, 2006 and 2016. The main objective was to investigate changes in the vegetation structure and species composition between the near-continuously grazed communal rangelands and the relatively lightly grazed commercial rangelands over the 20-year period. The results showed a decline in total vegetation cover in both commercial and communal rangelands in 2016 relative to the two earlier sampling periods. This can be attributed to the low rainfall in 2016 and was due largely to a reduction in annual plant cover, especially on the communal rangeland. Perennial shrub species provide a fodder bank that can be utilised by livestock in times of drought and can buffer short-term deficits in forage supply. However, the annuals that dominate the vegetation of the communal rangeland do not form such fodder banks and consequently do not have the same multi-year buffering capacity as perennial shrubs. This provides the mechanism whereby long-term continuous grazing decreases resilience to rainfall fluctuations and increases livestock variability, thereby promoting non-equilibrium-type dynamics in the system.