干旱风沙区绿洲森林覆盖率的非线性生态模型

以甘肃河西走廊绿洲为例,就干旱风沙区绿洲森林覆盖率进行了研究。研究结果表明：①影响干旱风沙区绿洲森林覆盖率高低的因素,主要与最大风速(V)和主林带的有效防护距离(L)有关,有效防护距离又受主林带平均高度和有效防护系数(r,或宽度)的影响。②经反复试算,最大风速和主林带有效防护距离的比值(V/L)大小与森林覆盖率(F)高低之间存在着相一致的规律性,不同比值代表着不同主林带平均高度(i)降低最大风速20%以上所需的最佳防护效益森林覆盖率,依此建立了干旱风沙区绿洲森林覆盖率的非线性生态模型：F=V/L×100%=V/(ri×i)×100%。③用1979—1994年在乌兰布和沙漠东北缘新建防护林体系森林覆盖率的实验数据对模型的预报结果进行适合性检验,结果表明,η=5.2466＜X2 0.05(5)=11.070,差异不显著,因此应用F=V/(ri×i)×100%预报干旱风沙区绿洲的森林覆盖率是可行的。

No-linear Ecological Model of Oasis Forest Coverage in Arid Sandy Areas

Oases in Hexi Corridor was taken as examples for studying the forest coverage of oases in arid sandy area. Results are as follows: ①The oasis forest coverage(F) is mainly determined by the maximum wind velocity(Vmax) and the effective protection distance(L) of key shelterbelt. Also, the effective protection distance of key shelterbelt is controlled by the average height and the protection coefficient of shelterbelt. ②The ratio of V/L has consistency regularity same as distribution of F. Different ratio represents the forest coverage with the optimal protection benefit to reduce above 20% of the maximum wind velocity under different heights of key shelterbelt, based on which a no-linear ecological mode of oasis forest coverage in arid sandy area has been established. ③The model has passed the test of forecasting adaptability by using the data of forest coverage from 1979 to 1994 in a new constructed protective forest system on northeast rim of WulanBuh Desert, which proved that it is possible to apply this mode in actual application.