| As one of the important vegetation types in subalpine of western Sichuan,shrubs play an important role in the carbon and nitrogen budget and hydrological ecological effects of the forest ecosystem in this region.So we selected four shrubs of Sibiraea angustata(SA),Salix atopantha-Lonicera rupicola(SL),Sibiraea angusta-Larix kaempferi,(SP),Rhododendron zheguense(RZ)and three shrubs of Quercus aquifolioides(QJ,QM,QS)along different altitudes,according to different soil depths(surface layer 0～15 cm and sublayer 15～30 cm)to explore the response mechanism of soil quality changes under similar climate background and altitude gradients,the results can provide scientific basis for shrub vegetation regeneration,forest ecological restoration,quality improvement,and forest management in this region.The results showed:(1)Under similar climatic background,the species diversity,carbon and nitrogen storage and nutrient contents of SL and SA were higher than SP and RZ;Under different altitudes,soil density,porosity and water-holding capacity of Q.aquifolioides were effectively changed with altitude increasing,and the soil carbon and nitrogen storage and nutrient contents of QM(3000 m)were higher than QJ and QS.With the increase of soil depth,the nutrient contents of soil showed a general downward trend.(2)The Alpha diversity indices of soil microorganisms in SL were lower than other three shrubs;the main dominant bacterial groups at the phylum level were Proteobacteria,Acidobacteria,Verrucomicrobia and Chloroflexbacteria,the dominant fungal groups were Basidio-mycota and Ascomycota.The Alpha diversity indices of bacteria in the QS(3280 m)were the highest,and the Shannon and Simpson indices of fungi in the QM(3000 m)were the highest;At the phylum level,the dominant groups of soil bacterial were Proteobacteria,Acidobacteria and Bacteroidetes,the dominant fungal groups were Basidiomycota and Ascomycota,with the total relative abundance accounting for more than 80%.(3)N-acetyl-β-D-glucosidase(NAG),peroxidase(POD),cellulase(CBH),N:Peea,C:Peea and vector length(VL)of SP and RZ were higher than SA and SL,PPO,ACP,βG and VA of SA were higher than other three shrubs;Soil enzyme activities(NAG,LAP,POD,PPO,βG and ACP)and N:Peea and VA in the QM(3000 m)were the highest.C:Neea,C:Peea and VL showed the opposite trend.(4)Under similar climatic background and different altitudes,soil enzyme activities of shrubs were closely related to the shrub diversity indices and nutrient contents.The bacterial community structure of four shrubs was mainly affected by enzyme activities(PPO,LAP,βG),nutrient contents(exchangeable calcium,SOC,TP)and p H;the main influencing factors of the 0～15cm and 15～30cm soil fungal community structure were C:Neea,Simpson diversity index,max.Water holding capacity and AK,NAG,Pielou evenness index;The main influencing factors of soil bacterial communities in three altitudes shrubs were nitrate nitrogen,POD,C:Peea,available iron,and fungal influencing factors were species diversity(herb Shannon diversity index,shrub Pielou uniformity).Therefore,in the process of shrub vegetation management and restoration in the study area,for shrubs of different communities under similar climatic background,adjuste forest density,increase microbial carbon and phosphorus fertilizers application to promote enzyme activities;For Q.aquifolioides shrubs under different altitudes,we can appropriately adjuste stand density,apply nitrogen fertilizer and litter management and protection.By implementing differentiated ecological restoration and conservation management measures for different shrub communities,the content of soil organic matter in the shrub land can be increased,thereby improving the productivity of the shrub community and its ecosystem service function,and improving the quality of the shrub land. |
