Water-holding Characteristics of Litter Under Different Forest Types in the Upper Reaches of Tarim River

Water-holding characteristic of litter could be obtained after survey and analysis,and studied the process of water-holding capacity of litter in the 4typical forests(mixed wood,Populus pruinosa forest, Populus euphraticaforest and shrub forest)in the upper reaches of Tarim river.The result showed as the following:(1)The litter amount,maximum water-holding capacity,maximum retaining amount,effective retaining amount and effective retain depth of half-decomposed litter were higher than that of non-decomposed litter.(2)The total litter storages,maximum water-holding capacity,maximum retaining amount,effective retaining amount and effective retain depth in the 4different forests were Populus pruinosa forestshrub forestPopulus euphratica forestmixed wood,the order of each index of litter in Populus pruinosa forest was 5.45t/hm2,7.83t/hm2,10.63t/hm2,8.73t/hm2,0.87mm which showed Populus pruinosa forest had the largest ability of water-holding capacity.(3)The dynamic changes in water-holding capacity, water-absorbent rate and time of forest litters under different forest types were basically similar.The water holding capacity of litter increased with extension of water immersion and being immersed in water for 16h, the forest litter usually reached its maximum water-holding capacity and the water holding capacity had no longer significant changes with further increase in soaking time.In the initial 2h,the water-absorbent rate of non-decomposed and half-decomposed litter was fastest,in 2~8 hafter immersion,the rate rapidly decreased,10hlater,the rate of decline slowed down significantly,and the water-absorbent rates of the two kinds of litters converged.In the initial 2hof water retention capacity of litter,shrub forest had the largest water absorption rate,mixed forest had the lowest water absorption rate.(4)The relationships between water-holding rate and immersion time of whether half-decomposed or non-decomposed litter in 4differentforest types were significantly fitted by Logarithmic equation(Y=aln t+b).The relationships between water absorption speed rate and soaking time were described by power function(V=ktn).In short,the Populus pruinosaforest showed the best water and soil conservation ability than the other forests in Tarim desert area.Consequently,Populus pruinosa should be planted as first-class tree species in future forest optimization management in order to perform better in water conservation.