重庆缙云山3种典型倒伏树木根土盘特征

Root-soil plate characteristics of three typical lodging trees in Jinyun mountain,Chongqing

根土盘是边坡林木力学分析建模和了解林木倒伏力学机制的重要模块。为实现基于植株地上部分易观测指标对根土盘几何参数的预测,以及分析根土盘形态特征的主要影响因子,对缙云山林地倒伏树木进行野外调查,统计杉木、润楠、大头茶的树高、冠高、冠幅、根土盘的迎风半径、背风半径、横向直径、根土盘深度、根系数量、地形坡度等指标,并对3种植物的根土盘根系抗拉强度进行测定,最终对调查数据进行统计拟合以及PCA分析。结果表明:1)大头茶具有最大的横向直径与最小的根土盘深度且表层根系数量多于杉木和润楠,根土盘整体呈宽浅圆盘状;杉木具有最小的横向直径与最大的根土盘深度且深层根系数量多于大头茶和润楠,根土盘整体呈窄深圆柱状;2)3种树木根土盘的横向直径、迎风半径、背风半径与胸径均呈较强的正相关关系(R^(2)>0.452),根土盘深度与胸径的相关性则较弱(R^(2)<0.047);3)PCA分析结果显示根土盘横向直径与根系数量和地形坡度呈较强正相关关系,根土盘深度与冠幅、冠高比呈较强正相关关系。综合得出:通过胸径可以对横向直径、迎风半径、背风半径这些指标进行相对比较好的预测,对根土盘深度的预测则较差;倒伏株的根土盘形态主要受根土盘根系数量、冠高比等决定,较多的根系数量和较大的地形坡度导致更大的根土盘横向直径,冠高、冠幅比较大的树木,导致更大的根土盘深度。

[Background]Root-soil plate is an important module for mechanical analysis and modeling of slope forest trees and understanding the mechanical mechanism of forest lodging.The purpose of this study is to predict the geometric parameters of root-soil plate based on the easily observed indexes of aboveground parts of plants,and to analyze the main influencing factors of the morphological characteristics of root-soil plate.[Methods]In this study,the field investigation was carried out on the lodging trees in the forest of Jinyun Mountain.The tree height,crown height,crown width,windward radius,leeward radius,lateral diameter,root-soil plate depth,root quantity and topographic slope of Cunninghamia lanceolata,Machilus nanmu and Gordonia acuminata were counted.The root tensile strengths of the root-soil plates of the three tree species were measured.Finally,the survey data were statistically fitted and PCA analysis was carried out.[Results]1)G.acuminata had the largest lateral diameter and the smallest root-soil plate depth,and the number of surface roots was more than that of C.lanceolata and M.nanmu,and the whole root-soil plate of G.acuminata was in the shape of wide and shallow disc.C.lanceolata had the smallest lateral diameter and the largest root-soil plate depth,and the number of deep roots was more than that of G.acuminata and M.nanmu,and the whole root-soil plate of C.lanceolata was in the shape of narrow and deep cylinder.2)The lateral diameter,windward radius and leeward radius of the root-soil plate of the three tree species had a strong positive correlation with the DBH(R^(2)>0.452),while the correlation between the depth of the root-soil plate and the DBH was weak(R^(2)<0.047).3)The results of PCA analysis showed that there was a strong positive correlation between the lateral diameter of root-soil plate and the number of roots and topographic slope,and there was a strong positive correlation between the root-soil plate depth and the crown width and crown height ratio.[Conclusions]The indicators of the lateral diameter,windward radius and leeward radius can be predicted relatively well by the DBH,but the prediction of the depth of the root-soil plate is poor.The shapes of root-soil plates of lodging plants are mainly determined by the number of roots and the crown height ratio.More number of roots and larger topographic slope lead to greater lateral diameter of root-soil plate,and trees with larger crown height and crown width lead to greater root-soil plate depth.