黔中山地喀斯特森林的水文学过程和养分动态

NUTRIENT DYNAMICS AND HYDROLOGICAL PROCESS OF KARST FORESTS IN MOUNTAINOUS AREA OF CENTRAL GUIZHOU PROVINCE,CHINA

采用不同林分类型固定样地的定位研究方法，研究了黔中山地喀斯特森林对降水量的分配和随降水流动的主要离子的影响。结果表明，林内外年降水量的变化趋势为：空旷地〉林隙〉乔木层〉灌草层〉地表和壤中流量〉树干径流量。年降水在林内不同层次分配量的变化趋势为：林地蒸发等量〉灌草层降水截留总量〉林冠层降水截留总量。相关水量的月动态趋势以夏季较高，冬季较低。森林最大持水量的变化趋势为土壤层〉植被层。植被层最大持水量的变化趋势为乔木层〉枯落物层〉灌木层〉草本层。喀斯特原生林植被层地上部分最大持水量为28．20mm，是喀斯特次生林的194．48％。喀斯特原生林土壤层最大持水量加权值为19．24mm，是喀斯特次生林的187．89％。喀斯特原生林冠层降水截留总量、灌草层降水截留总量、地表蒸发等量总值占空旷地降水量的比例为97．93％，喀斯特次生林的相应值为97．89％。喀斯特原生林的调水能力大于喀斯特次生林。土壤层最大持水量占植被-土壤系统的95．88％～96．11％，保土可增加蓄水。合理调整森林植被层结构既可防治土壤侵蚀，又可提高森林的最大持水潜力。随降水流动的SO4^2-、Ca^2＋、Mg^2＋、NH4^＋、K^＋、NO3^-、Cl^-、Na^＋月均浓度在不同喀斯特森林类型的林隙、林内和树干径流中的年变化规律明显，夏季浓度较低，冬季浓度较高。固定样地集水区溪流中相关离子月均浓度变化趋势与林隙、林内和树干径流中的不同。喀斯特原生林年随降水输人的相关离子量为430．951kg·hm^-2·a^-1，随地表径流和90cm壤中流的输出量为49．789kg·hm^-2·a^-1，年随降水净增的相关离子量为381．162kg·hm^-2·a^-1；而喀斯特次生林的相应值为304．101、39．216和264．885kg·hm^-2·a^-1。喀斯特原生林N^3-、K^＋、Ca^2＋、Mg^2＋储量高于喀斯特次生林，土壤层储量〉植被层储量，植被层储量中乔木层〉枯落物层〉灌木层〉草本层。年随降水输人喀斯特森林的相关离子量占植被一土壤系统的总量较小、有效性较高，对森林的生长和养分循环有重要的生态学意义。

Aims Karst forest occurs with limestone soil and humid climate. China＇s southern karst region is subtropical and centered in Guizhou Province. Precipitation is high and unequally distributed seasonally. Soil drought is frequent as a result of climatic and edaphie factors. Our objectives were to enhance understanding of karst forest ecology and methods of controlling loss of soil and water as a means of managing karst desertification. Methods For five years, we observed karst natural forest and secondary natural forest in 20 m × 20 m plots and analyzed major precipitation ions by ion chromatography. Main indicators were analyzed by Forest Soil Analyzed Methods and observed by Meteorological Observational at Ground Standards. Important findings Rankings of annual precipitation value regularity were openland 〉 outside karst forest 〉 inside karst forest 〉 under tree and herbaceous layer 〉 nmoff at surface and in 90 em soil 〉 stemflow, and transpiration at forestland and another 〉 total interception in arbuscular and herbaceous layer 〉 total in-terception in arboreal layer. Annual dynamics of these variables were higher in summer and lower in winter. Maximum water holding capacity ranked soil layer 〉 vegetation, and that in arboreal layer 〉 litter layer 〉 tree layer 〉 herbaceous layer. Ion contents in precipitation had obvious month regularity and decreased in spring and increased in autumn and were high in winter and low in summer. Along precipitation flows （outside forest → in forest → surface runoff → runoff in soil → stream）, eight ions were divided into three types： a sustainable rich type included Ca^2＋ and Mg^2＋; a surface rich type included K^＋, Na^＋, Cl^-, NO3^- and NH4^＋ ; and another type included SO4^2-. Ions input by precipitation, output by runoff and retained in karst natural forest were higher than that in karst secondary natural forest.