Tillage agriculture and afforestation threaten tropical savanna plant communities across a broad rainfall gradient in India

The consequences of land-use change for savanna biodiversity remain undocumented in most regions of tropical Asia. One such region is western Maharashtra, India, where old-growth savannas occupy a broad rainfall gradient and are increasingly rare due to agricultural conversion and afforestation. To understand the consequences of land-use change, we sampled herbaceous plant communities of old-growth savannas and three alternative land-use types: tree plantations, tillage agriculture, and agricultural fallows (n=15 sites per type). Study sites spanned 457 to 1954 mm of mean annual precipitation—corresponding to the typical rainfall range of mesic savannas globally. Across the rainfall gradient, we found consistent declines in old-growth savanna plant communities due to land-use change. Local-scale native species richness dropped from a mean of 12 species/m2 in old-growth savannas to 8, 6, and 3 species/m2 in tree plantations, fallows, and tillage agriculture, respectively. Cover of native...热带亚洲多数区域的土地利用变化对稀树草原（savanna）生物多样性造成的影响，目前仍未得到系统性研究。印度马哈拉施特拉邦西部便是其中之一，该区域的原生稀树草原分布于广阔的降水梯度范围内，且因农业开垦与造林活动而日益稀缺。 为厘清土地利用变化所带来的生态后果，我们针对原生稀树草原与三类替代土地利用类型的草本植物群落开展了采样调查，三类类型分别为人工林、耕作农用地与农业休耕地（每种类型设置15个样地）。研究样地的年平均降水量介于457至1954毫米之间，这一范围与全球中生稀树草原（mesic savanna）的典型降水区间相符。 沿该降水梯度，我们发现土地利用变化导致原生稀树草原植物群落出现了一致性的衰退。样地内本地物种丰富度均值从原生稀树草原的12种/平方米，分别下降至人工林、休耕地与耕作农用地的8种/平方米、6种/平方米与3种/平方米。本地物种的盖度……