| Larix principis-rupprechtii is an important afforestation tree species with the largest accumulation and the widest distribution in North China(especially the Saihanba area).It has good growth,excellent materials,strong adaptability and long lifespan.In soil and water conservation and sand control,it does play a vital and necessary role.In this study,the Larix principis-rupprechtii(forest age:26a,30a,46a)in the Yinhe branch of Saihanba Mechanical Forest Farm in Hebei Province was taken as an object to study the changes of soil quality indicators such as soil physical,chemical properties and microorganisms after thinning and pruning,to explore the impact of different tending measures on understory soil,the main conclusions are:(1)The changes of soil physical properties of Larix principis-rupprechtii plantation after tending treatment are different.In terms of overall trends,soil water content,bulk density,capillary porosity,and capillary water holding capacity all increased compared with the control.As the soil layer deepens,soil bulk density increases,soil water content and capillary water holding capacity decrease,and the capillary porosity first increases and then decreases.There are significant differences between different soil layers.Different thinning intensity is most obvious with moderate thinning.(2)The changes in soil chemical properties of Larix principis-rupprechtii plantation after tending treatment were different.On the whole,compared with the control,the p H value and the content of available phosphorus decreased,and the organic matter content increased.As the soil layer deepens,the p H value increases,the organic matter content decreases,and the available phosphorus first decreases and then increases,and the difference between different soil layers is significant(P<0.05).(3)The number of soil microorganisms in Larix principis-rupprechtii plantation under tending treatment is complex and changeable.In general,the number of bacteria,fungi,and actinomycetes increased compared with the control group,and the differences between different treatments were significant.Especially in 46a,after heavy thinning and light pruning,the numbers of bacteria and actinomycetes were higher than the control respectively 45.72%and 17.01%.(4)In general,the soil water content,soil bulk density,capillary porosity,and capillary water holding capacity of both the control and the tending treatments are shown in 2011>2019,of which the T2(46.44%)of 26a and 46a T1(43.31%)is higher than the corresponding capillary water holding capacity in 2011.(5)Comparison of soil physical and chemical properties and microbial quantity of different forest ages.The soil p H value,soil bulk density,soil water content and organic matter content were the largest at 30a,which were 6.28,0.990,21.07%,and 51.0419 g/kg respectively;while capillary water holding capacity and capillary porosity were 26a>30a>46a;soil available phosphorus at 26a The highest content is 9.5757mg/kg.The number of bacteria,fungi,and actinomycetes were 26a(50.10×10~5/g),30a(16.84×10~4/g),46a(10.49×10~5/g),respectively.In general,the soil quality of 30a was the best,and the tending effect was the best,followed by 26a.(6)Using the principal component analysis method,the highest comprehensive scores for 26a and30a are T4P1(heavy thinning and moderate pruning)and T0P2(heavy pruning but no thinning).Compared with the control,the soil quality improved after tending,and decreased with the increase of thinning intensity,and increased with the increase of pruning intensity.In 46a T3P0's(heavy thinning but no pruning)score is the highest,followed by T4P2(heavy thinning and heavy pruning).On the whole,heavy thinning>heavy thinning>control>light thinning>moderate thinning. |
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