牧草如何生长——植物生长与放牧管理之关联(英文)

How grasses grow-how plant growth relates to grazing management

适当管理饲料饲草资源的基本原则是理解多年生牧草如何生长。长期以来 ,对根系生长有了基本的了解 ,对去叶和环境对根系生长的影响也知之甚多。然而 ,对去叶、干旱及其他环境因素对多年生牧草的影响以及这些牧草对去叶的反应缺乏应有的理解。从牧草返青到开花 ,植物处于短枝阶段 ,适度放牧并不对多年生牧草的健康和活力造成危害 ,因为植物会弥补其失去的叶片。然而 ,当牧草从短枝向长枝阶段 (节间伸长和开花期 )转移时 ,碳水化合物主要用于节间伸长和开花过程。在开花后和休眠前期 ,碳水化合物主要向茎基和植物基部转移 ,以供来年新枝条的发育。因此 ,在花后和休眠前期 ,放牧系统必须被调节到“无放牧”状态。“无放牧”状态 ,如休息、轮牧、延迟轮牧和快速轮牧制 ,其价值在于这种定期的禁牧可提高多年生牧草的活力 ,改善草地的健康状况 ,并且在不利的环境条件下 。

A basic tenet to properly managing forage resources is to understand how perennial grasses grow. We have had a basic understanding of root growth and the impact of defoliation and environmental perturbations on root production for many years. But, we have less appreciation for the impact of defoliation, drought, and other environmental perturbations on shoot growth of perennial grasses and their ability to respond to defoliation. From 'green-up' to flowering (while the plants are in the short-shoot stage), proper grazing is not particularly detrimental to the health and vigor of perennial grasses because the plants replace the leaves as they are removed (assuming environmental conditions are conducive for growth). However, as the grasses shift from the short-shoot to the long-shoot (internode and flowering culm elongation) stage, the carbohydrate resources are primarily allocated to the flowering process and internode elongation. After flowering and before dormancy, carbohydrates are allocated to the stem bases and basal crowns from which new tillers will be derived during the subsequent growing season. Therefore, it is imperative that grazing systems be planned to regularly provide 'no-grazing' during the post-flower, pre-dormancy period. Hence, the value of the 'no-grazing' period of rest-rotation, deferred-rotation, and rapid-rotation systems is that periodic 'no grazing' enhances the vigor of perennial grasses and health of pastures and rangelands; and assures their sustained productive following defoliation, even during times of adverse environmental conditions.