Responses Of Soil Microbial Biomass C,N And P In Alpine Forest To The Simulated Temperature Increasing Of Altitude Gradient

Global warming caused the snow line and forest line rising and the structure and function of terrestrial ecosystem deteriorated sharply. It is urgent need to find countermeasures. Subalpine timberline ecotone is the most sensitive area of terrestrial ecosystems to climate change. And soil microbial is more sensitive to the changes of environmental factors than plants. Therefore, Changes in forest ecotone microbial biomass can reacte the alpine ecosystems Responses to climate change. The simulated temperature increasing of altitude gradient provides a basis for the study of soil microbial community after climate changed in alpine forest.Through the temperature monitoring data found in previous years(From November 1,2011 to November 1,2014), The Annual mean soil temperature of timberline (4000m) was higher than dark coniferous forest (3900m), and temperature fluctuation range is larger. The freeze-thaw cycle is more frequent, with obvious seasonal snow cover period. Based on the different temperature of two attitudes, we used PVC tube moved the soil in dark coniferous forest(soil organic layer and soil mineral layer) to the timberline, And sampling at four periods(Initial freezing period, Deep freeze period, Growing season and Freezing and thawing period) from November 14,2014 to January 14, 2016. Studied The effects of simulated warming on soil microbial biomass C, N and P and their ratio. The results are as fallows:(1)The average temperature of the soil organic layer in the alpine timberline was 1.84? higher than that in the coniferous forest, and the average temperature of the soil mineral layer in the alpine timberline was 1.32? higher than that in the coniferous forest. Coniferous forest soil temperature value is mainly concentrated in the -5? to 10?.Alpine timberline soil temperature value is mainly concentrated in the -10? to 20?which is rather scattered. The soil moisture of different attitude is not significantly(P>0.05),But the average soil moisture of the mineral soil layer was significantly lower than that of the soil organic layer(P<0.01);The snow thickness is higher in alpine timberline at the non growing season;The soil Freezing and thawing cycles is more frequent in alpine timberlineare.(2)The response of MBC,MBN and MBP in soil organic layer to temperature increasing are not significant, but the simulated temperature increasing has a certain effect on the microbial biomass carbon, nitrogen and phosphorus in mineral soil layer. The MBC at Freezing and thawing period and MBP at Growing season in soil mineral layer reduced significantly(P<0.05) and MBN at Initial freezing period increased significantly (P<0.05) because of the temperature increasing. What is more. The temperature increasing caused the MBC/MBN reduced(P<0.05)and MBN/MBP increased(P<0.05),But it was no significant effect on MBC/MBP.(3) From the view of seasonal dynamics, It shows that SMBC is Initial freezing period>Growing season>Freezing and thawing period>Deep freeze period, no significant differences; SMBN in the soil organic layer is Deep freeze period> Freezing and thawing period>Growing season>Initial freezing period, The differences are significantly, SMBP in the soil organic layer and the soil mineral layer of coniferous forest is Growing season>Freezing and thawing period>Deep freeze period>Initial freezing period, The differences are significant.(4) From the view of soil layers,The MBC,MBN and MBP of soil organic layer are higher than soil mineral layer(P<0.01),MBC/MBN is lower in soil organic layer(P<0.05).And the MBC/MBP has no significant difference in two soil layers.(5)The results of correlation analysis shows that MBC/MBN and MBC in the soil were significantly affected by the Soil temperature and snow thickness, and The SMBN were significantly affected by the Soil temperature, soil water content and snow thickness. And there has some positive correlation in the soil organic layer such as MBC and soil temperature (P<0.05),MBN and MBC (P<0.01)?MBN and soil water content(P<0.05),MBN and snow thickness(P<0.01);The negative correlation such as MBC and snow thickness(P<0.05),MBC and MBN(P<0.01),MBN and snow thickness(P<0.01),MBN and soil temperature (P<0.01).What is more, There are some positive correlation in the soil mineral layer such as MBC and soil temperature(P<0.05),MBC and MBP(P<0.05),MBN and soil temperature (P<0.05);The negative correlation such as MBC and MBN(P<0.05), MBC and snow thickness (P<0.05),MBN and MBC(P<0.05),MBN and soil temperature(P<0.01),MBN and MBP(P<0.01),MBP and snow thickness(P<0.01)?...