施肥干扰对陕北黄土丘陵区三个典型群落结构组成的影响

The effect of disturbence on the structure and form of three typical communities in Loess hilly region of the northern of Shaanxi Province

在陕北黄土丘陵区,为了加快当地植被的恢复速度,结合当地条件,通过小区施肥实验与野外调查,研究了施肥对不同演替阶段的3个典型群落:猪毛蒿(Artemisia scoparia)、长芒草(Stipa bungeana)和铁杆蒿(Artemisia sacrorum)结构组成的影响。结果表明:(1)与对照相比,施肥后3个群落中物种的重要值发生改变。猪毛蒿群落中,1年生植物狗尾草(Setaria viridis)重要值减小,而多年生植物阿尔泰狗哇花(Heteropappus altaicus)、冰草(Agropyron cristatum)等重要值增大,成为群落中的主要物种;长芒草群落,与对照相比,施肥降低了优势种长芒草的重要性,而达乌里胡枝子(Lespedeza dahurica)的重要值明显增大;铁杆蒿群落则随着肥量增加,铁杆蒿的重要值表现为逐渐上升,与对照相比,群落中的伴生种二裂萎陵菜(Potentilla bifurca)、茭蒿(Artemisia giraldii)在处理区的平均重要值有所下降,而演替后期物种达乌里胡枝子的重要值增大。(2)与对照相比,通过施肥,除铁杆蒿群落高肥区密度外,3个群落的高度、生物量和密度均有显著提高,表现为高度和生物量在高肥区达最大,密度在中肥区达最高。3个群落相比,演替前期的猪毛蒿群落提高幅度最大,长芒草次之,铁杆蒿最小。(3)施肥改变了3个群落的物种多样性。群落类型不同,其变化趋势亦不同。猪毛蒿和铁杆蒿群落Patrick丰富度指数在中肥区达最高,随着施肥量的增加,Margalef(Ima)、Shannon-Wiener(Isw)和Pielou(J)指数产生不同程度的下降,而Berger-Parker优势度指数(I)逐渐增大;长芒草群落则随着施肥量的增加,Patrick指数、Ima、Isw和J均有不同程度的上升,而优势度指数I呈下降趋势。

The vegetation restoration was very slow because of water and fertilizer deficiency, which was caused by serious soil erosion on Loess hilly region. So, it was necessary to use artificial disturbance as a way to improve water and nutrientconditions and to accelerate vegetation rehabilitation. Fertilization was one of many ways that artificial disturbance was applied according to the conditions of this area. The influence of fertilization on the structure and form ofArtemisia scoparia, Stipa bungeana and Artemisia sacrorum community was studied using a plot experiment in which different amounts of fertilizer were used. The results showed that： （1） Compared with CK, the important values of species in three communities changed after fertilization. In A. scoparia community, the important values of annual Setaria viridis decreased and became the companion. But the important values of perennial Heteropappus altaicus and Agropyron cristatum etc increased, and they became the main species in the community; In the S. bungeana community, the important values of S. bungeana decreased, but the important values of Lespedeza dahurica increased significantly, and they became main species in this community; The response of A. sacrorum community to fertilization was different, the important values of A. sacrorum increased little by little as the amount of fertilizer increased. Compared with CK, the even important values of companion Potentilla bifurca, Artemisia giraldii decreased in all treatment plots, but that of Lespedeza dahurica increased in the late phase. （2） In the A. sacrorum, fertilization benefits the height, biomass and density of the plant significantly. However, the density of the plants in A. sacrorum did not change when using the highest amount of fertilizer. The height and biomass of plants were the highest in the plot with high fertilizer level among the three communities, but the density was different. The highest density was in the plot with middle fertilizer level. The A. scoparia community showed the biggest change in height, biomass and density in earlier phases of succession, S. bungeana took the second place, A. sacrorum showed the least change. （3） Species diversity was changed with nutrient inputting. Different types of communities had different trends of changing. The results showed that the Patrick richness index was the highest in the plot with intermediate fertilizer level in A. scoparia and A. sacrorum community. With increasing amounts of the fertilizer, Margalef（ IMs）, Shannon-Wiener （Isw） and evenness index decreased in degrees in these two communities, but the dominance index showed the opposite. The Patrick richness index, IMa, Isw and evenness index increase in S. bungeana community, but the dominance index wasopposite.