Effect Of Gap Size On Soil Microbial Biomass And Soil Enzyme Activity

In this study, 3 different sizes(S forest gap: the radius is 4m, the M forest gap: 8m radius, L forest gap: 12 m radius) forest gaps andcontrol plots(no gaps) in Platycladus orientalis(L.) Franco plantation in Xuzhou as the object of study, to understanding the diversity of the understory vegetation in the stand in the inside and outside of the gap, the response of soil physical and chemical properties, soil microbial biomass and enzymatic activity inside, edge and outside of different sizes of gaps, the main results are as follows:(1) Margalef index in both shrub layer and herb layer were higher than the control plots. Simpson index and Shannon index in the gap in shrub layer were both higher than the control plots.Maximum values of Simpson index and Shannon index in the herb layer appeared in the S gaps,while Land M gaps were lower than the control plots.Maximum value of Pielou evenness index in the shrub layer appeared in the S gaps,while L and M gaps was lower than the controlplots.Maximum value of Pielou evenness index in the herb layerappeared in the control plots, and with the gap sizes decreases.(2) Compared with the control plots, the effect of forest soil temperature, water content and dissolvable organic carbon(DOC) content were found,however the influence differed with gaps sizes.Among them, the effect of S gaps on soil physicochemical properties was the most obvious.(3) Compared with the control plots, the M gaps significantly improves soil microbial biomass carbon(MBC) content(p<0.05) in spring, field-effect of M and S gaps on the content of soil MBC reached outside position of the gap in the spring. The soil MBC content were positively correlated with soil total organic carbon and the content of DOC(p<0.01), showed a significant negative correlation with pH values(p<0.05), while significantly negatively correlated with soil temperature(p<0.01).The S gaps significantly reduced soil microbial biomass nitrogen(MBN) content(p<0.05) in spring, while the M gap significantly increased the content of soil MBN in summer(p<0.05). The field-effect of L gaps on soil MBN content reached the gap outside position during the spring and summer, while The field-effect of M gaps on soil MBN content reached the position of the edge of forest in winter, and the field-effect S gaps on soil MBN content reached the edge of forest in the winter and the outside position in the spring.The content of soil MBN and soil moisture content, DOC content and MBC content were positively correlated(p<0.01), and significantly positively correlated with soil total carbon(p<0.05).(4) Compared with the control plots, the gap scale significantly influenced 4 kinds of soil enzymatic activity. The field-effect of M gapson soil peroxidase activity reached the gap outside position in winter and spring, while the S gaps reached outside position in the fall. The field-effect of L gaps on soil dehydrogenase activity reached the gap outside position in the spring, while the field-effect of M gaps reached outside position in winter and summer, and the field-effect of S gaps reached outside position in autumn and spring. The field-effect of L gaps on soil urease activityreached the forest outside position in autumn and summer, while the field-effect of the M gaps reached outside position in spring, and the field-effect of the S gaps reached outside position in autumn and summer.The field-effect of L gaps on soil invertase activity reached the gap outside position in spring and summer, while the field-effect of M gaps reached outside position in summer, and the field-effect of S gaps reached outside position in summer.(5)In the study of different sizes gaps of the forest vegetation diversity, soil physicochemical properties, soil microbial biomass and enzymatic activity were affected to varying degrees,namely the field-effect of different sizes gaps were different, different sizes showed that the formation of gap effect on soil nutrient cycling in different range. This research determined the reasonable gap size and provide a scientific basis for effective way to speed up the forest system update rational production practice.