Study On Soil Nutrients And Plant Diversity In Forest Gap Formed By Planting Gastrodia Elata Bi Under Forest

Forest gap is a common medium and small scale disturbance model in forest,and it is one of the important driving forces of stand cycle and succession.It plays a very important role in maintaining the level of species diversity under forest and adjusting stand dynamics and structure.The study on soil nutrients and plant diversity in the gap formed by planting Gastrodia elata BI under the forest helps to clarify the changes of soil nutrient content and forest plant community dynamics in the gap,and has a certain guiding significance for the feasibility of planting Gastrodia elata BI under the forest and the determination of the optimal planting area scale.In this paper,three kinds of forest gaps formed by planting Gastrodia elata BI(G1:0-55m~2,G2:55-100m~2,G3:>100m~2)under oak broad-leaved mixed forest(KH),pine and sequoia coniferous forest(ZY)in Mazongling area of Jinzhai County,Anhui Province were studied,under the forest as the experimental control group(KH is CK-1;ZY is CK-2),the effects of different gap sizes and forest types on soil nutrients,stoichiometric ratio and plant diversity were studied.The main conclusions are as follows:(1)Effects of forest gap size on soil nutrients and their stoichiometric ratio:The gap size of KH and ZY G1-G3 had no significant effect on the release of soil nitrogen(N),phosphorus(P),potassium(K),carbon(C)and soil organic matter(SOM).There was no significant change in soil total nitrogen(TN),hydrolytic nitrogen(AN),total phosphorus(TP),available phosphorus(AP),total potassium(TK),available potassium(AK),SOM,soil organic carbon(SOC)and p H value in the soil layer of 0-15cm and 15-30cm depth compared with CK-1 in the gap of G1,G2 and G3 of KH.The soil TN and AN of G1 and G3 in ZY at the depth of0-15cm were significantly lower(P<0.05)than those in the control group CK-2,The SOC and SOM of G1,G2 and G3 in ZY were significantly lower(P<0.05)than that of CK-2 at the depth of 0-15cm.There was no significant difference in the rest.There was also no significant change in soil C:N,C:P and N:P in the three area grades of KH and ZY.(2)Effects of different forest types on soil nutrients and their stoichiometric ratio in forest gap:At the depth of 0-15cm,the soil TN,AN,TP,AP and TK of KH are lower than that of CK-1,and the values of AP,SOM,SOC and p H of soil are higher than those of CK-1.The soil TN,AN,SOM and SOC of ZY were significantly lower(P<0.05)than those of CK-2,while the values of TP,AP,TK,AK and p H in soil of CK-2 were higher than those of CK-2,and there were significant differences(P<0.05)in AP.At the depth of 15-30cm,the soil TN,AN,SOM and SOC of KH were higher than that of CK-1,while the values of TP,AP,TK,AK and p H were lower than that of CK-1.ZY is higher than CK-2 except that the values of soil AN and p H are lower than that of CK-2.The soil TN,AN,SOM and SOC of KH were significantly higher(P<0.05)than those of ZY at 0-15cm depth,while the AP of KH was significantly lower(P<0.05)than that of ZY at 0-15cm and 15-30cm depth,there was no significant difference in other items.Compared with the control group under the forest,the C:N,C:P and N:P of KH were higher than those of CK-1 and ZY,and there was significant difference(P<0.05)in C:N at the depth of 0-15cms,while ZY showed the opposite change rule.(3)Effects of forest gap size on plant diversity:Through the analysis of the difference of species diversity index between KH and ZY shrub layer and herb layer,it was found that the species diversity index of KH herb layer reached the maximum at G2 area grade,and the shrub layer reached the maximum at G1.The richness index(R),diversity index(H’)and dominance index(D)of ZY herb layer reached the maximum at the area grade of G3,the evenness index reached the maximum at G2,and the shrub layer reached the maximum at G2.(4)Effects of different forest types on plant diversity:Through the analysis of the difference of species diversity index of shrub layer and herb layer between KH and ZY,it was found that the plant diversity index of shrub layer of KH was lower than that of the control group CK-1,and the R,H’and D of herb layer of KH were higher than those of CK1of the control group under forest,while the level of plant diversity of herb layer of KH was higher than that of ZY.