喀斯特地区树根解剖特征与土壤侵蚀

喀斯特石漠化是指土壤严重侵蚀,基岩大面积出露,地表出现类似荒漠景观的土地退化过程.虽然土壤侵蚀只是石漠化过程的一个环节(王世杰,2002),但要清晰了解喀斯特石漠化的发生发展需要有土壤侵蚀过程资料的支撑.石漠化过程分为地质石漠化过程、生态系统石漠化过程和人为加速石漠化过程(李阳兵等,2004).当降雨量小于80mm时,喀斯特地区土壤的主要流失方式是地下漏失(张信宝等,2007),这种情况下发生的土壤侵蚀很难准确监测.目前研究喀斯特土壤侵蚀的方法有遥感技术(安和平等,1994;蓝安军等,2001;万军等,2003)、放射性同位素示踪(白占国等,1997)、修建径流场和沉沙池等(彭建等,2001)、湖泊沉积物分析(王红亚等,2006)、埋钉(桩)(彭建等,2001)和洞穴石笋记录(蔡炳贵等,2005)等,常被限制在短时间内,且很难获取地下土壤丢失数据和过程,无法综合评价喀斯特土壤侵蚀的历史过程,需要寻求一种有效的新方法来准确描述喀斯特土壤侵蚀.

Anatomical Characteristics of Tree Roots and Soil Erosion in Karst Erosion Area

Karst soil erosion process was studied through analyzing the anatomical characteristics of exposed and unexposed tree root and dating exactly exposed times of the tree root which grow in Guizhou Puding karst area.Results show that average sensitivities of tree ring width are larger than 0.2,which means tree ring recorded environmental information.Tree ring widths of unexposed root are not changed from pith to bark,and vessels size is nearly the same and evenly distributed in each ring.Of the same tree the inner tree ring width,vessel lumen area,and fiber lumen area of exposed root are the same with the unexposed ones,while the exterior demonstrates extremely variance,the tree ring width narrower,the vessel and the fibre lumen area smaller,and most of tree roots are eccentricity.The root exposed time could be exactly identified based on all the former changes:the root exposures were happened respectively from 1996 to 2007.Soil erosion amounts of exposed root recorded decline from 2002 to 2007,and average erosion amount is 0.464 t·a-1,that is to say,exposed root well recorded soil erosion process.