| In order to monitor and analyze the effects of forest thinning on changes in forest resources and forest ecology,optimize forest structure and improve forest quality,comprehensively promote sustainable forest management in Yong’an City,and formulate scientific and reasonable management measures.In Yong’an City,Fujian Province,taking Cunninghamia lanceolata and Pinus massoniana as the research object,8 groups of monitoring plots of forest thinning were set up to investigate the growth status of stands before and after thinning,and 3 of them were set up as the forest environmental monitoring sample plots to record the temperature,relative humidity,rainfall and soil surface runoff of the sample plots.Through statistical comparison of data,the effects of two-year thinning on stands growth,the stands microclimatic factors,and soil surface runoff were analysed.Research indicates:(1)Intermediate and above intensities thinning effectively accelerated the growth of DBH and individual volume,while thinning could not effectively promote tree height,cross-sectional area,and accumulate growth.However,the natural sparse amount of stands can be reduced by thinning.(2)Compared with the control stand,the monthly lowest temperature was lower in the thinning stands,while the monthly highest temperature,monthly temperature range,the monthly average temperature,and the daily average temperature were higher.The monthly maximum relative humidity in the stands all reached 100%,and the monthly minimum relative humidity,the monthly average relative humidity,and the daily average are all relatively smaller,and the monthly relative humidity range is relatively larger.The monthly rainfall in the thinning stands is relatively larger,and the rainfall increases most rapidly from March to July.Extreme intensity thinning tends to increase the monthly highest temperature,monthly temperature range,and monthly relative humidity range,and significantly decreases the monthly minimum relative humidity of the stands,while the intermediate thinning stands of C.lanceolata and P.massoniana have no significant effect on the microclimatic factors.(3)Pearson correlation analysis of the forest’s microclimatic factors showed that the higher the monthly average temperature is,the smaller the monthly temperature range becomes;the smaller the monthly temperature range is,the smaller monthly relative humidity range becomes;the smaller monthly relative humidity is,The greater monthly average relative humidity becomes;the greater monthly average relative humidity is,the greater the rainfall in the forest.The opposite is also true.The analysis also showed that there was no significant difference in the thinning intensity about the correlation among the microclimatic factors,and there was no significant effect of the C.lanceolata and P.massoniana stands on the correlation among the microclimatic factors.(4)Compared with the control stands,the rainfall needed to produce soil surface runoff is smaller in thinning stands,in other words,tending thinning makes it easier for forests to produce soil surface runoff,and the minimumamount of rainfall required to produce soil surface runoff tends to decrease as the forest thinning intensityto increase.When the stands is intermediate rainy or above,all the soil surface runoff occurs.but in light rain conditions,the ratio of runoff to rainfall was 21%.The runoff-to-rain ratios of thinning stands were greater than that of the control stands,and the runoff-to-rain ratios increased with the increase of thinning intensity,while there was no significant difference between the runoff-to-rain ratios ofC.lanceolata and P.massoniana stands.(5)Thinning makes stands soil surface runoff increase,especially in the months with heavy rainfall.Extremely intensity thinning significantly increased soil surface runoff and soil runoff coefficients in the stands,while intermediate thinning of C.lanceolata and P.massoniana standshad no significant effect on them. |
