| Walnut has high economic value as one of main tree species used in low-efficiency and economic forest transformation model in hilly area of Sichuan. Walnut forest covering with mulch can improve biodiversity, modify soil physical and chemical properties, improve the ability of water and soil conservation and increase yield, which is a soil management and control technology. As a soil ecological indicator organism, the soil fauna is not only sensitive to the changing environment, but also plays an important role in ecological restoration. Soil ecological restoration may be different, due to different mulching on the ground of walnut forest, which was planted in cypress forest gap. The low-benefit cypress forest was restored by planting with walnut covering with different mulch on the ground under the forest gap. There were several treatments set to evaluate the ecological effects of these different transforming measures including transforming the low-benefit cypress forest into walnut covering without surface mulch (HT), with white film (HB), with black film (HH), with shady net (HZ), with litter straw (HD), and pure cypress forest (BM). To evaluate the ecological effects of these different transforming measures. The soil fauna was investigated with cypress forest (BM) from June,2013 to June,2015. The meso and micro-soil fauna was caught by wet and dry funnel method, and soil macrofauna was caught by hand. The results showed that:(1) There were 3781 heads of soil fauna including 2109 heads of meso and micro-soil fauna, belonging to 2 phyla,5 classes,21 groups. The other 1672 heads of soil macrofauna, belonging to 3 phyla,7 classes,18 groups.(2) There were effects of walnut covering with mulch on composition of soil macrofauna, meso and micro-soil fauna. The seasonal dynamics of group number and individual density of soil macrofauna community were similar to meso and micro-soil fauna. They both had a certain seasonal variation. There were a large number of community groups and high density in macrofauna, meso and micro-soil fauna, when it was in heavy rainfall and high temperature in summer and fall. Whereas in less rainfall and low temperature of winter and spring, there were less number of community groups and low density.(3) The macrofaunal, meso and micro-soil faunal population quantity, individual density and Shannon index were all significantly increased (P<0.05) by replanting walnut forest with white film (HB), black film (HH), shady net (HZ), litter straw (HD). Moreover, Simpson index of macrofaunal, meso and micro-soil faunal was significantly reduced(P<0.05) by replanting walnut forest covering with white film (HB), black film (HH) and litter straw (HD). Although the macrofaunal Simpson index was significantly improved (P<0.05) by shady net (HZ), there was no significance (P>0.05) between the meso and micro-soil faunal Simpson index of shady net (HZ) and the control. Compared with pure cypress forest (BM), the macrofaunal and meso and micro-soil faunal Pielou index were not significantly different(P>0.05) by hite film (HB) and black film (HH), which were significantly improved (P<0.05) by litter straw (HD). The meso and micro-soil faunal Pielou index were significantly reduced (P<0.05) by shady net (HZ), however, the macrofaunal Pielou index was not significant (P>0.05) as compared to the control. The macrofaunal population quantity and Simpson index, the meso and micro-soil faunal individual density and Simpson index were significantly increased (P<0.05) by replanting walnut forest without surface mulch (HT). And, replanting walnut forest without surface mulch (HT) did not affect (P>0.05) the macrofaunal individual density and Pielou index, the meso and micro-soil faunal population quantity and Pielou index. The macrofaunal and meso and micro-soil faunal population quantity, individual density and Shannon index of the litter straw (HD) were higher than others, and the Simpson index was lower than others. Therefore, transforming the low-benefit cypress forest into walnut covering with litter straw (HD) was the best one.(4) Walnut covering with mulch had different effects on soil faunal spatial distribution of cypress in low-efficiency forest. The macrofaunal and meso and micro-soil faunal spatial distribution of six treatments were different and the spatial distribution of same treatment was also different in the same season of different years. Most of the macrofauna and meso and micro-soil fauna of hite film (HB), black film (HH), litter straw (HD) and pure cypress forest (BM) moved into shallow layer of soil, while the meso and micro-soil fauna of the without surface mulch(HT) and the shady net(HZ) moved into shallow and deep layer of soil.(5) Soil total N, total P and total K content were similar all the year round. The total amount in soil nutrient content was significantly improved(P<0.05) by replanting measure. And. the litter straw (HD) was the best. For example, compared with the control, soil total N. total P and total K content of hite film (HB), black film (HH), shady net(HZ) and litter straw (HD) were significantly promoted (P<0.05). Among them, soil total N and total P content of litter straw (HD) were more than others. The content of soil total N and total P were significantly increased (P<0.05) by the without surface mulch (HT). Compared with the control, the content of total K of the without surface mulch (HT), however, was not significant (P>0.05).(6) Soil available nutrients were largely different all the year round. The content of soil available nutrients was significantly improved (P<0.05) by replanting walnut forest with mulch. And, the litter straw (HD) was the best. Soil available N, P and K of the litter straw (HD), were significantly increased (P<0.05). Soil available P and K were also significantly improved (P<0.05) by the hite film (HB), black film (HH) and shady net (HZ). But, soil available N of the hite film (HB), black film (HH) and shady net (HZ) were not significantly improved(P>0.05). Soil available P of replanting walnut forest without surface mulch (HT) was much more than the blank (P<0.05), though, soil available N and K of the without surface mulch (HT) were similar with (P>0.05) pure cypress forest (BM).(7) In summer and fall, soil organic matter content was relatively high, whereas pH was relatively low. However, the results were counter-productive in winter and spring, soil organic matter content was relatively low, and pH was relatively high. Soil organic matter content and pH of transformation pattern were similar with the blank (P>0.05). Compared with the blank, soil organic matter content of the hite film (HB), black film (HH), shady net (HZ) and litter straw (HD) were increased slightly, and the litter straw (HD) was more than others.(8) There was a positive correlation among macrofauna, meso-micro-soil fauna and soil physico chemical properties. Soil total N, total P, total K, available N, available P, available K, organic matter and pH were related to each other, which worked together to macrofauna and meso and micro-soil fauna.In conclusion, there were rich soil faunal individuals and large population quantity from June,2013 to June,2015. Compared with the blank, the composition proportion and spatial distribution of soil fauna were influenced by replanting walnut forest covering with mulch. Not only the soil faunal population quantity, individual density and Shannon index were increased, but also the soil nutrients content were improved. Among all the transformation pattern, the litter (HD) was relative economic and significantly increased the soil fauna and utrients content, which was the best one. |
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