| Although plantation area of our country is the highest over the world(69.33 million hm~2),there are still some problems existing such as inferior comprehensive quality and ecological function.Canopy density is one of the most important factors reflecting forest structure and environmental conditions.Dense canopy would decrease intensity of sunlight and rainfall,reduce the undergrowth,which significantly affects litter decomposition and soil nutrient element status,and finally change the soil fauna diversity.On the other hand,soil fauna as members of underground food web plays essential ecological functional role in accelerate material and energy flow and soil fertility maintaining.Besides,the soil fauna community can sensitively indicate micro environmental heterogeneity.But unfortunately the effects of plantation canopy density control on soil fauna community is quit lack.Therefore,this research took Pinus massoniana plantation in Gaoxian county of Sichuan as object and five sized canopy densities(0.9/0.8/0.7/0.6/0.5)as control,studied soil fauna species composition,diversity characteristics,individual density,group number,profile distribution,functional groups and their temporal dynamics,and analyzed the relationship between the main soil fauna species and soil environmental factors.The results showed that:(1)Atotal of 10 278 individuals macro fauna were collected,belonging to 3 phyla,12 classes,12 orders and 150 families,with Diptera larvae and Forrmicidae as the dominant species.A total of 59 528 individuals meso/micro fauna were collected,belonging to 5 phyla,11 classes,23 orders and 121 families,with Nemata and Isotomidae as the dominant species.(2)The macro and meso/micro soil faunal individual density and meso/micro group number in 0.5 canopy densitywere no significant differences with the seasons change.The meso/micro group number of 0.5 canopy density was lower significantly than 0.8 canopy density in October,but in April the macro group number was higher than 0.7 and 0.6 canopy density.The macro faunal individual density of 0.7 canopy density was increased significantly than 0.6 in January.In 0.9 canopy density the macro individual density significantly decreased than 0.8/0.5 canopy density in July,and the meso/micro group number was higher significantly than 0.7 canopy density.(3)In 0.5 canopy density,soil macro faunal individual density of 5-10 cm soil layer was increasedsignificantly in July,and was lower than 0.7 canopy density in October.Macro faunal group number of 0.7-0.5 canopy density increased in April litter layer and in July 0-5 cm layer,and in October 5-10 cm layer the 0.9-0.8 canopy density macro group number was higher significantly than 0.7-0.5.In October litter layer the meso/micro faunal individual density increased in 0.9-0.7 and decreased in 0.7-0.5,the maximum value was in 0.7 canopy density,and in 0-5 cm layer it was decreased with canopy density reduce.Meso/micro group number in 0-5 cm layer increased with canopy density reduce in January,and in July the 0.7-0.5 canopy density was lower significantly than other month.In 5-10 cm layer,meso/micro group number showed N type fluctuation change in January,and in July the highest was in 0.9 canopy density.(4)The meso/micro richness index of0.9-0.7 canopy density in October and the meso/micro diversity index of 0.9 canopy density in April were higher relatively,the meso/micro richness index and diversity index of 0.5 canopy density were decreased in October.The macro richness index of 0.7 canopy density was lower than 0.5 in April.The meso/micro soil faunal diversity characteristics were significantly different in 0.9-0.8 canopy density but stable in 0.7-0.5 canopy density with the seasons change.(5)Between the different years,soil macro and meso/micro faunal group number and macro individual density,diversity characteristics of 0.6 canopy density had no significant difference,meso/micro fauna individual density increased significantly in 0.9/0.8/0.6.Macro fauna richness index in 0.9 canopy density,meso/micro richness index in 0.7 canopy density and meso/micro fauna diversity index and evenness index in 0.9-0.7 and 0.5 canopy density decreased relatively.(6)The omnivores and saprophages accounted for the highest percentage of total individuals in different canopy density of a P.massoniana plantation.Meso/micro soil fauna functional group had no significant difference with the canopy density change.Macro phytophagous soil faunal individual decreased in 0.9 canopy density but fungivores individual and percentage increased.The omnivorous individual in 0.5 canopy density was higher significantly than 0.6-0.9,but the saprozoic percentage significantly decreased.(7)Soil pH and organic carbon greatly influenced the macro soil fauna,and soil bulk density greatly influenced the soil meso/micro fauna in P.massoniana plantation.Elipsocidae,Angstidae,Formicidae,Blattidae and Gryllidae prefer to choose the lower canopy density to live,Coleopteralarvae,Diptera larvae,Carabidae and Geophilidaeadapt to higher canopy density and lower soil organic carbon and moisture content.Nothroid mites could tolerate higher bulk density.Formicidaeare suitable for high moisture content and lower soil bulk density.Nemata,Rotifera,Enchytraeidae,Campodeidae,Neanuridae and Termitidae can endure a certain soil acidity,but higher request for soil organic carbon,moisture content and total nitrogen.Diptera larvae,Isotomidae,Oppioid mites and Liacarid mites greatly influenced by soil pH,total phosphorous and moisture content.Galumnoid mites was less affected by soil environmental factors.In conclusion,canopy density control significantly affected the soil fauna community characteristics of a Pinus Massoniana Plantation,the soil macro fauna had fewer interannual variation,and functional group of meso/micro soil fauna was more stable.Relatively speaking,the 0.7-0.6 canopy density has a better undergrowth restoration and forest environmental factors are moderate comparatively,which is advantageous to the soil fauna diversity maintaining and structure stability of plantation ecosystem. |
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