沙棘林退化对林木根系和土壤抗冲性的影响

Root system distribution and soil anti-scouring capability with Hippophae rhamnoides degradation

近年来,辽宁建平县亚洲最大的人工沙棘Hippophae rhamnoides林呈现大面积死亡的现象.通过标准样地法调查沙棘的死亡程度,测定与对比不同沙棘死亡率下林地的根系密度和土壤抗冲性,研究沙棘林退化对水土流失的影响.结果表明：0～30 cm范围内,直径d＜1 mm的根系密度随深度增大急剧减小,72％～80％根量分布在0～20cm土层;0～30 cm范围内,随着沙棘死亡率的提高,d＜1 mm根密度显著降低（P＜0.05）;随着深度增大,抗冲性也逐步降低,沙棘的死亡率对土壤抗冲性的影响亦达到显著水平（P＜0.05）,这主要是由根系密度的相应变化引起的;经曲线拟合,土壤抗冲性与d＜1mm根密度的关系可用幂函数表示.目前该区主要应通过采取有效措施降低沙棘林退化的生态影响.

In recent years,widespread death has occurred at the largest Asian artificial Sea Buckthorn （Hippophae rhamnoides） forest in Jianping,Liaoning.To evaluate the effects of Sea Buckthorn degradation on soil loss,the death rates of Sea Buckthorn were determined using standard plot methods with five treatments and three replications.Moreover,soil root density and soil anti-scouring capability were measured on site with soil profile methods and soil anti-scouring instruments,respectively.Results showed that soil root density for a root diameter less than 1 mm decreased at P＜0.05 with an increase of soil depth within the 0-30 cm limit with 72％-80％ in 0-20 cm.With a rise in the Sea Buckthorn death rate,the root density decreased significantly at P ＜0.05,and with an increase of soil depth,the soil anti-scouring capability decreased significantly at P＜0.05.The relationship between soil anti-scouring capability and root density were fitted to power functions y =xb.The decrease of root density and soil anti-scouring capability meant damage of soil texture.Conversely,this will accelerate death rate of Sea Buckthorn,and vicious cycle format.Thus,effective measures,such as replanting shrubs,should be taken to reduce the harmful ecological effects of Sea Buckthorn degradation.