Effects Of Land Preparation On The Present Situation Of Cunninghamia Lanceolata Stand And Its Geographical Properties In Rocky Desertification Area Of Western Hunan

The ecological environment of rocky desertification area in Western Hunan is fragile,the environmental capacity is small,the bearing capacity of land is very low,and the growth of trees is vulnerable to climate and water.Reasonable land preparation measures are conducive to coordinate soil moisture,heat,nutrients,air and other factors,improve site conditions,and provide good conditions for tree sowing,growth and forest management.However,different land preparation measures have different effects on the growth of plantation.Therefore,in this study,the national long-term scientific research base for the comprehensive control of rocky desertification in Wuling Mountain,Western Hunan,selected the 34 year old Cunninghamia lanceolata Plantation under three land preparation methods(trench preparation,horizontal stage preparation and cave preparation)in the rocky desertification area of Western Hunan as the research object,investigated and analyzed its stand growth status,understory biodiversity,soil water physical properties and soil chemical properties,and used significance test Correlation test and principal component analysis were used to comprehensively evaluate the stand quality under different land preparation measures.This paper discusses the corresponding relationship between different land preparation methods and the growth of Cunninghamia lanceolata plantation in rocky desertification area,and determines the most suitable land preparation measures for Cunninghamia lanceolata plantation,in order to provide a theoretical basis for the sustainable management and ecological restoration of Cunninghamia lanceolata Plantation in rocky desertification area of Western Hunan.The main conclusions are as follows:(1)The average number of total trees in the tree layer of the existing tiaohao land preparation,horizontal step land preparation and hole land preparation are 2638 tree·hm-2,2242 tree·hm-2 and 2192 tree·hm-2 respectively,of which the Cunninghamia lanceolata is 2038 tree·hm-2,1817 tree·hm-2 and 1321 tree·hm-2 respectively.The preservation rate and stand regeneration of the Cunninghamia lanceolata plantation of tiaohao land preparation after many years of growth are the best,and the hole land preparation is relatively poor.The average tree height and DBH of the underground Cunninghamia lanceolata plantation were better than that of the horizontal terrace and the cave.The average important values of Cunninghamia lanceolata under three different land preparation methods were compared:the horizontal terrace(88.8%)>the trench(88.1%)>the cave(78.5%).(2)Under the three land preparation methods,the species richness and shrub and grass coverage of understory vegetation are cave land preparation>trench land preparation>horizontal step land preparation,and the species diversity index of cave land preparation is also higher than that of the other two land preparation methods.The effect of horizontal land preparation on maintaining species diversity of plantation is relatively poor,and cave land preparation is the best.(3)With the deepening of soil layer,the soil density of the three standard plots increased,and the maximum water holding capacity,capillary water holding capacity,minimum water holding capacity,non capillary porosity,total porosity,soil organic carbon,total N,total P,available P and available K decreased.On the whole,the advantages and disadvantages of soil density,maximum water holding capacity,capillary water holding capacity,minimum water holding capacity,non capillary porosity and total porosity are as follows:trench preparation>horizontal step preparation>cave preparation.Trench preparation can significantly improve soil density,soil water holding capacity and soil air permeability.(4)The variation range of soil pH value in the three standard sites is 5.64～6.15;The surface aggregation effect of soil organic carbon,total N,alkali hydrolyzable N and available P is obvious.The contents of soil alkali hydrolyzable N,total K and total P are as follows:trench preparation>horizontal step preparation>hole preparation,while the contents of total N and available K are as follows:hole preparation>horizontal step preparation>trench preparation.Trench preparation will significantly improve the contents of soil alkali hydrolyzable N,total K and total P,but hole preparation is beneficial to available K The improvement of total N and cation exchange capacity is significantly higher than that of trench preparation and horizontal step preparation.(5)Under different land preparation measures,the comprehensive evaluation scores of various indicators of 34 years growth quality are ranked as follows:trench land preparation(0.358)>horizontal order land preparation(0.261)>cave land preparation(0.259).Considering that all factors of stand quality are equally important,the most ideal land preparation method for Cunninghamia lanceolata afforestation in rocky desertification area of Western Hunan is trench land preparation.