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干旱的标志,主要是树木对水分的需要和它从土壤中获得水分之间的不适宜程度。对于林分,干旱威胁取决于两个因素:年降雨量和叶子的数量。在干燥条件下的研究表明,树木潜在死亡的危险,是在干旱时起码的水分条件不能保证累积蒸腾量的要求。针叶的数量,不仅可以评定林分对水分的需要,而且还可以判断以往年份水分供应的情况。在潮湿的年份,针叶的数量随降雨量的增加而增加;在干旱的年份,情况就会变坏,当水分供应降低到一定的临界点时,树木就会死亡。详细观察了环境条件易变的干旱地区的林分和自我调节系统及适应能力后看出,假
Drought signs, mainly the tree’s need for water and its inappropriateness to get moisture from the soil. For stands, the threat of drought depends on two factors: the annual rainfall and the number of leaves. Studies under dry conditions have shown that the risk of potential death of trees is the requirement that the minimum moisture conditions in drought conditions do not guarantee cumulative transpiration. The number of needles can not only assess the need for moisture in stands, but also determine the moisture supply in previous years. In wet years, the number of needles increases with increasing rainfall; in arid years the situation deteriorates, and trees die when the water supply falls below a certain critical point. After observing in detail the stand and self-regulation system and adaptability of arid areas where environmental conditions are variable, we can see that the fake