Changes in the herbage nutritive value and yield associated with threshold responses of vegetation to grazing in Mongolian rangelands
Changes in the herbage nutritive value and yield associated with threshold responses of vegetation to grazing in Mongolian rangelands
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DOI：
10.1111/j.1365-2494.2012.00862.x
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发表时间：
2012-09-01
影响因子：
2.4
通讯作者：
Takeuchi, K.
中科院分区：
文献类型：
--
作者：
Sasaki, T.;Ohkuro, T.;Takeuchi, K.
我们研究了蒙古牧场多个生态地点牧草的营养价值和产量沿放牧梯度的变化，其中群落组成发生了突变。在草地上，牧草营养价值的变化可以归因于沿着放牧梯度，多年生草本植物或杂草迅速被杂草取代。在接近放牧梯度时，粗蛋白(CP)浓度急剧升高，中性洗涤纤维和代谢能(ME)浓度急剧下降。由于能量可作为牧草营养价值的主要指标，这些结果表明严重放牧对牧草营养价值的总体损失。因此，草地CP和ME产量在梯度源方向上的逐渐增加并不一定意味着草地条件的改善。相比之下，在灌木林地，我们一般不能检测到牧草营养价值的任何显著趋势。能量产量沿梯度源方向逐渐降低，说明在灌丛样地放牧影响牧草产量而不是牧草饲用价值。因此，牧草的营养价值和产量可以随着植被对牲畜放牧的非线性反应而发生很大的变化。
We examined the changes in the nutritive value and yield of herbage along a grazing gradient, where abrupt changes in community composition occurred, at multiple ecological sites in Mongolian rangelands. At grassland sites, changes in the herbage nutritive value could be attributed to rapid replacement of perennial grasses or forbs with weedy annual forbs along a grazing gradient. Crude protein (CP) concentration increased sharply in approaching the source of grazing gradient, whereas neutral detergent fibre and metabolizable energy (ME) concentrations decreased sharply. As ME can be utilized as a main index of herbage nutritive value, these results indicated its overall loss with severe grazing. Consequently, gradual increases in the yields of CP and ME in the direction of the gradient source at the grassland sites did not necessarily indicate the improvement of rangeland condition. In contrast, at shrubland sites, we could not generally detect any significant trends in the herbage nutritive value. The yield of ME gradually decreased in the direction of gradient source, suggesting that grazing affects herbage yield rather than herbage feed value at shrubland sites. Thus, the nutritive value and yield of herbage can be modified greatly in association with nonlinear responses of vegetation to livestock grazing.