Effects Of Tending And Thinning On Hydrological And Ecological Functions Of Larch Secondary Forest In Different Succession Stages

In this paper,the natural secondary forest of Larch in the Daxing'an Mountains is taken as the research object,and 16 succession stages(young forest,middle-age forest,near-mature forest,mature forest)with different gradients of different tending and thinning intensities(contrast to low intensity,medium intensity,and high intensity)are used in this study.Observation 17 samples of hydrological and ecological function indicators were constructed in the plot.The change regularity of forest canopy,litter layer and soil layer was analyzed.total of 17 hydrological and ecological function indicators were selected and the principal component analysis method was used to establish a comprehensive evaluation model.The hydrological and ecological functions of the plots with different tending intensities at each succession stage were comprehensively evaluated,and the natural secondary forests of Larix gmelinii in the Daxing'an Mountains were screened for different performances.The best cutting intensity of tending and thinning that has the best effect on promoting hydrological and ecological functions in the replacement stage.(1)In the forest canopy,the amount of penetrating rain and the rate of penetrating rain gradually decrease with the succession,reaching the maximum in young forests and the smallest in mature forests;canopy interception,canopy interception rate,the trunk stem retention and trunk stem retention rate increased gradually,reaching the smallest in young forests and the largest in mature forests;In the four succession stages,with the increasing of tending and thinning intensity,different canopy indexes showed different rules,and medium and high intensity thinning made the canopy indexes reach the maximum majority,but the corresponding plots were basically small.(2)In the litter layer,as the succession progressed,the litter accumulation amount showed a trend of decreasing and then increasing in the control plots,in low,medium,high-intensity thinning plots showed a trend of increasing gradually,and the most in the mature forest.Natural water holdup and maximum water holdup vary with succession progress;the maximum water capacity and effective retention capacity of litter increased gradually,and reached the maximum in mature forests.In the four succession stages,with the increasing of tending and thinning intensity,the indexes of different litter layers showed different rules,and the indexes of different litter layers were maximized by medium intensity thinning.The fitting equation of water holding capacity and soaking time conforms to the logarithmic relation,and the equation form is W=mln(t)+n.(3)In the soil layer,soil bulk density,soil moisture content and soil capillary porosity increased gradually with the succession,reaching the minimum in the young forest and the maximum in the mature forest.Soil non-capillary porosity increased first and then decreased,reaching the minimum in mature forest and the maximum in mid-age forest.The total soil porosity and soil water capacity reached the maximum in mature forest.In the four succession stages,with the increasing of tending and thinning intensity,the indexes of different soil layers showed different rules,medium and low intensity thinning resulted in the maximum index of soil layer.(4)The total water conservation is between 623.25t·hm-2?1121.38t·hm-2,which is the highest among the high-intensity thinning plots in the near-mature forest,and the smallest in the low-intensity thinning plots in the young forest;In addition to medium age forest M2(820.73t·hm-2)>near-mature forest N1(806.49t·hm-2),water conservation in the four succession stages showed the law of mature forest>near-mature forest>middle-age forest>young forest.(5)Principal component analysis was used to evaluate the hydrologic ecological function,and the result was R3(1.318)>N1(1.268)>N0(0.939)>M2(0.904)>M3(0.702)>R1(0.485)>N2(0.408)>N3(0.390)>R2(0.389)>R0(0.134)>M1(0.125)>M0(-0.211)>Y2(-0.679)>Y0(-0.952)>Y3(-0.975)>Y1(-1.089).In the young forests,medium intensity of tending and thinning(25%-30%)is good for their hydrologic ecological function.In middle-age forest,medium intensity of tending and thinning(25%-30%)and high intensity of tending and thinning(35%-40%)can promote its hydrologic ecological function.In the near mature forest,the hydrologic ecological function of the secondary larch forest under low intensity of tending and thinning(15%-20%)was the best.In mature forests,larch secondary forests with high intensity of tending and thinning(35%-40%)had the best hydrologic ecological function.The results can provide reference and basis for the management of larch natural secondary forest at different succession stages in Daxing'an Mountains mountains.