海南中部丘陵区3种林分根系分布特征

Root distribution characteristics of three forest stands:a hilly area in central Hainan Island,China

研究热带人工林(plantation;以下简称人工林)和热带天然次生林(secondary forest,SF;以下简称次生林)的根系生物量和根长分布特征,可为当地人工林经营和次生林保护、抚育提供理论指导.以海南省枫木实验林场次生林、橡胶(Hevea brasiliensis,HF)和马占相思(Acacia mangium,AF)人工纯林为研究对象,采用样方挖掘法,分土层分径级对根系生物量密度(root biomass density)和根长密度(root length density)进行分析.结果显示:在0-100cm深的土层中,各林分根系生物量密度和根长密度均随土壤深度和根系径级的增加而显著降低;根系生物量密度次生林(913.42±77.31 g/m^(3))>橡胶林(633.57±58.09 g/m^(3))>马占相思林(529.08±23.00 g/m^(3));根长密度次生林为1023.21±127.90 m/m^(3),橡胶林为998.57±66.38 m/m^(3),马占相思林为463.86±45.64 m/m^(3);细根(0-2 mm)的生物量和根长在各林分中均占主要部分.各林分中超过55%的根系生物量分布在0-20 cm深的土壤表层,土壤表层根长分别占总根长的65.73%(次生林)、44.88%(橡胶林)、41.38%(马占相思林);且橡胶和马占相思人工林中超过25%的根长分布在20-40 cm深的土层中.本研究表明热带天然次生林和人工林的根系分布规律在总体上具有相似性,但在不同直径的根系上又具有差异性;0-20 cm深的土壤表层是各林分进行水肥管理的重点区域,且对于人工林而言,为更好地促进林分生长,可考虑向较深土层进行水肥管理.

The study of the root biomass and root length distribution characteristics of a tropical plantation and a tropical natural secondary forest(SF)can provide theoretical guidance for local plantation management and secondary forest protection and tending.This study investigated a secondary forest,Hevea brasiliensis(HF),and an Acacia mangium forest(AF)at the Fengmu Experimental Forest Farm in Hainan Province using sample mining root biomass density analysis,and determined the root length density of different soil layers and different diameters.The results showed that in the 0-100 cm deep soil layer,the root biomass density and root length density of each forest stand significantly decreased with the increase in soil depth and root diameter.The root biomass density for the secondary forest is 913.42±77.31 g/m^(3)>Hevea brasiliensis forest(633.57±58.09 g/m^(3))>Acacia mangium forest(529.08±23.00 g/m^(3)).For the root length density,the tropical natural secondary forest is 1023.21±127.90m/m^(3),the Hevea brasiliensis forest is 998.57±66.38 g/m^(3),and the Acacia mangium forest is 463.86±45.64 m/m^(3).The biomass and root length of fine roots(0-2 mm)account for the main part of each stand type.In each stand type,the ratio of root biomass in the 0-20 cm deep soil layer to the total biomass is greater than 55%,and the ratio of soil surface(0-20 cm)root length to total root length is 65.73%(secondary forest),44.88%(Hevea brasiliensis forest),and 41.38%(Acacia mangium forest).More than 25%of the root length in the Hevea brasiliensis and Acacia mangium plantations is distributed in the 20-40 cm deep soil layer.This study demonstrates that the root distribution of tropical natural secondary forests and plantation forests are generally similar,but they differ in root diameters.The soil surface is the main area for water and fertilizer management in each forest,and to promote better forest growth in plantation forests,water and fertilizer management can be considered in deeper soil layers.