中亚热带细柄阿丁枫和米槠群落细根的生产和死亡动态

采用微根管技术与挖掘法相结合的方式对福建省万木林自然保护区细柄阿丁枫和米槠天然林细根生产和死亡动态进行了为期两年多的观测,分析细根生产和死亡的季节变化、垂直分布及径级和序级分配,并估计细根的年生产量和年死亡量.结果表明:细柄阿丁枫细根年生产量和年死亡量分别为(230.1±162.8) g·m-2·a-1和(188.8±75.5)g·m-2· a-1,均略大于米槠的(214.5±185.8) g·m-2·a-1和(178.8±26.5) g·m-2·a-1,但两种森林群落的细根年生产量和年死亡量均无显著差异(P＞0.05).两森林群落细根生产均在春季达到高峰,其中米槠细根生产与月降水量呈极显著相关(P＜0.01,r=0.566)；细根死亡则呈现季节性地波动,米槠细根死亡峰值主要发生于夏季和秋季,而细柄阿丁枫则出现在秋季.两森林群落细根生产和死亡皆主要集中于土壤表层0-40 cm中,而且不同径级细根生产和死亡集中于0-1 mm细根中,其中0.3-0.6 mm细根的生产和死亡在两森林群落中均最大.两森林群落一级根的生产和死亡均大于高级根.

Estimating fine root production and mortality in subtropical Altingia grlilipes and Castanopsis carlesii forests

The turnover of fine root,the most dynamic component of root system,play an important role in nutrient cycle and energy flow in forest ecosystems.Fine root production and mortality in two subtropical evergreen broadleaved forests,Altingia grlilipes forest and Castanopsis carlesii forest,in Wanmulin Natural Reserve,Jian-ou,Fujian province,were monitored for more than two consecutive years by using both minirhizotrons and the exvacation methods.The objectives of this research were to:(1) analyze the seasonal patterns of fine root production and mortality;(2) to examine the allocation of both root production and mortality among different soil depths,root diameter classes and orders.In order to extract biomass data of individual root from root image,the relationships between root biomass(M) and root diameter(D) and root length(L) were established: M=0.4671 D2L for Altingia grlilipes,and M=0.5869 D2L for Castanopsis carlesii,respectively.Though there were no significant differences(P>0.05),annual fine root production and mortality in Altingia grlilipes((230.1±162.8) g · m-2 · a-1 and(188.8±75.5) g · m-2 · a-1,respectively) were slightly higher than those in Castanopsis carlesii((214.5±185.8) g · m-2 · a-1 and(178.8±26.5) g · m-2 · a-1,respectively).Fine root production reached a peak in the spring,and showed a normal distribution in 2009 in both two communities.There was a significant correlation between fine root production and monthly precipitation(P<0.01,r=0.566) in Castanopsis carlesii.Fine root mortality fluctuated seasonally in these two forests.The peak of fine root mortality occurred mainly in summer and autumn in Castanopsis carlesii and in fall in Altingia grlilipes.The fine root production of these two forest communities appeared mainly in the top soil layer(0—40 cm),accounting for 88.6% and 95.1% of the total production in Altingia grlilipes and Castanopsis carlesii,respectively.Fine root mortality had the same distribution pattern,and made up to 89.7% and 99.2% of total mortality,respectively,in the 0—40 cm layer.In addition,the maximum of fine root production(Altingia grlilipes:(131.7±91.4) g · m-2 · a-1;Castanopsis carlesii :(108.6±100.4) g · m-2 · a-1) and mortality(Altingia grlilipes:(106.4±69.5) g · m-2 · a-1;Castanopsis carlesii :(99.7±2.4) g · m-2 · a-1) of these two forest communities appeared in the 2040 cm soil layer.With the root diameter increases,the number of root growth and death decreased,while fine root production and mortality had no corresponding tendency with diameter.Root production occurred mainly in 0—1mm,which accounts for 90.4% of total production in Altingia grlilipes and 96.1% in Castanopsis carlesii.Furthermore,fine root production in 0.3—0.6 mm was(100.0±44.0) g · m-2 · a-1 in Altingia grlilipes and(94.8±90.4) g · m-2 · a-1 in Castanopsis carlesii,which was the highest among different root diameter classes.Fine root mortality had the same trend with production,which accounted for 95.5% and 100% of the total fine root mortality in 0—1mm in Altingia grlilipes and Castanopsis carlesii,respectively.Root production and mortality of the first root order were much higher than those of the higher order in both two forest communities.