Responses Of The Community Structure And Diversity Of Soil Mites To Climate Change In The Forest

Soil mites play an important role in soil organic matter decomposition and nutrient cycling. Mite responses to climate change directly affect the structure and functions of terrestrial ecosystems. However, mite response to climite change is still poorly understood, limiting ability to predict the consequences of climite change. To address this issue, it is critical to identify mite response to climate change and the key driving factors.In this study, soil samples were transplanted along an elevation gradient from 3200 m to 1600 m with a 400 m interval on the eastern slope of Gongga Mountain to simulate climate warming in December 2013. Two control treatments were used to reduce the disturbances from some unnecessary environmental factors. The first treatment(CT1) is controlling of the precipitation and litter fall to simulate mite responsing to temperature increasing, the second treatment(CT2) is not controlling precipitation and litter fall to simulate mite responsing to change in temperature, precipitation, plant community and other factors. Soil mite communities and soil physico-chemical properties in five transplant gradients for CT1, CT2 and CK(the contrastive forest) were investigated to reveal the machanisms of soil mite community responding to global change. The main finds were the followings.Effects of climate change on soil physical and chemical properties differed between different treatments. The soil pH, organic matter, total phosphorus, total potassium and available nitrogen in CK treatment differed significantly between different altitudes. For CT1 treatment, only soil pH decreased significantly with increasing temperature, For CT2 treatment, organic matter, total nitrogen, available phosphorus, available potassium and total potassium increased significantly with increasing temperature, while soil pH varied among five gradients with the greatest value at gradient of 2400 m. The changes in soil properties indicated that the effects of CT2 treatment(changes in temperature, precipitation, plant community and other factors) on soil physical and chemical properties are stronger than those of CT1 treatment(changes in temperature only).The taxonomic composition of soil mite community differed between three treatments. Tectocepheus was the common dominant genus for three treatments; Erythacidae was the dominant family for CT1 and CT2 treatments. There were, in sequence, 43, 13 and 3 special groups for CK, CT1 and CT2 treatments, respectively. The sequence of total number for three treatments was CK(107)> CT1(63)> CT2(26), and the sequence of individual number was CK(1755)> CT1(1026)> CT2(476). Principal component analysis(PCA) showed that the mite structure in transplanted soil differeed from those in “home” sites in CT1 treatment; whereas the soil mite community structure only at the 2000 m and 1600 m gradients differed clearly from those of “home” sites in CT2 treatment. For CK treatment, the community structure of soil mite differed clearly among the 3200 m, 2800 m, 2000 m and 1600 m gradents. These results indicated that the community structure of soil mite was affected by the changes in temperature, precipitation, litterfall, and other environmental factors.Community density of soil mite increased significantly with increasing temperature in both CT1 and CT2 treatments. For CK treatment, community density of soil mite was significant higher than 3200 m although decreased from 2800 m to 1600 m. The richness(group number) and Shannon-Wiener index of soil mite community increased significantly with increasing temperature in three treatments. The density, richness and Shannon-Wiener index of soil mites for three treatments showed the similar tendency CK > CT1> CT2, while the Pielou index and Simpson index had no obvious change tendency. The results indicated that the climate warming can increase the density and diversity of soil mitesand the effects of increasing temperature on soil mite diversity were stronger than that of changes in temperature, precipitation, vegetation and other environmental factors.Effects of climate change on oribatida, Prostigmata and mesositigmata mites differed between three treatments. For CK treatment, the responses in community structure and diversity to global change were strongest for Mesositimata and weakest for Oribatida; For CT1 treatment, the responses in community structure and diversity to climate change were strongest for Oribatida and weakest for Mesositigmata; For CT2 treatment, the responses in community structure and diversity to climate change were greatest for Oribatida and weakest for Prostigmata. MI index indicated that climate warming could increase the number of K-selection mites(Mesositigmata). The influences of environmental factor on Oribatida were stronger compared to Mesositigmata and Prostigmata in three treatments, indicating that Oribatida can be used as bioindicator for monitoring soil environment.Multiple regression analysis results showed that the effects of environment factors on mites varied between different treatments. For CT1 treatment, soil mite communities were significantly correlated with soil pH, available potassium and temperature; For CT2 treatment, soil pH, total nitrogen, available potassium and total potassium were the main factors affecting the diversity of soil collembola communities; For CK treatment, soil mite communities significantly correlated to soil pH, total nitrogen, total potassium, air humidity and soil temperature. The relationships between soil mites and environmental factors showed that single temperature change or changes of temperature, precipitation, plant community and other changes affect the soil mite communities by changing soil chemical properties.The results showed that the combined effects of temperature, precipitation, plant community and other factors could change the community composition, increase the diversity and density of soil mite communities, and then promote the material cycle in terrestrial ecosystem. Therefore, the climate change would have a greater impact on the structure and function of soil ecosystem according to the finds from our experiments.