植被作用下土壤干化的反馈效应及相关问题讨论

Discussion on Feedback Effect of Soil Desiccation by Vegetation and Related Issues

黄土高原普遍发生的植被作用下的土壤干化现象,从一个独特角度恰当反映了环境对植被的限制作用。由于人工林草植被不同于天然植被,其负反馈调节机制脆弱,这种植物生长用水与环境供水之间的矛盾表现,使人工林草植被生长滞缓,稳定性下降,甚至导致其衰亡,并对后续深根性植物的生长发育一般起到显著的抑制作用。但是,后续天然植被或者浅根性植物却仍然能够继续良好发育。显然,植被作用下的土壤干化,对追求一定的经济目标来说有其不利性,但对于防止土壤侵蚀并不一定就产生负面影响。需要根据经营目标区别对待人工林草植被的稳定性。人工林草植被的自然化过程研究是有关生态恢复的一个有意义的命题。

Owing to vegetation construction in the Loess Plateau, much attention has been paid to soil desiccation by vegetation for many years. Right thinking about soil desiccation by vegetation would conduce to controlling it, and furthering reasonable management and evolution of vegetation. The feedback response of vegetation to soil desiccation by itself is mainly discussed in this paper. We believe that the phenomenon of soil desiccation by vegetation occurring universally in the Loess Plateau just reflects environmental limitation on vegetation from a peculiar angle. Because artificial forest and grass vegetation is weak in the mechanism of negative feedback regulation compared with natural vegetation, the contradictory show between water use by plant growth and water supply by environment constitutes a so serious threat to stability of artificial forest and grass vegetation that it grows slowly and even declines, and commonly takes marked restraining effect on development of follow-up plant rooting deep after vegetation declination. But on the other hand it is noticeable that follow-up natural vegetation or plant rooting superficially still may succeed to grow well. It is obvious that soil desiccation by vegetation isn＇t favorable for seeking economical goal, but it would uncertainly cause a negative effect on protection of soil from erosion. The stability of artificial forest and grass vegetation should be treated respectively according to their managing goals. The research on naturalizing process of artificial forest and grass vegetation would be a significant proposition related to ecological restoration.