滨海沙地木麻黄(Casuarina equisetifolia)人工林细根养分与能量动态

2005年1月到2005年11月对福建省惠安县赤湖林场不同林龄木麻黄人工林细根养分和能量的季节动态进行了观测,结果表明:(1)6种元素的含量在不同林龄木麻黄细根中都具有明显的季节变化。各林龄细根的N含量一般在冬夏季节较高,且死细根的N浓度高于相同林龄的活细根,除12林龄活细根P浓度在7月份有最大值外,其他各林龄活、死细根在一年中呈波动性下降,K含量在冬季较高,而在其他季节变化幅度不大,除5林龄活细根和18林龄死细根在3月份和7月份有两个峰值外,其他林龄细根Ca含量随季节变化较小,Mg含量随季节变化总体呈下降趋势,而在11月份上升;各林龄C则呈波浪形变化;(2)随着林龄的增大,细根N、P、Mg含量的变化模式相似,都呈先增加,后降低,再增加的趋势,K和Ca含量变化趋势相似,但变动幅度存在差别,C则呈波浪形变化;(3)随着季节的变化,灰分、干重热值和去灰分热值呈"V"形变动,一年中都存在两个峰值,分别在3月份和7月份或9月份;(4)灰分、干重热值和去灰分热值随林龄的增大表现为波浪形增加。由此可见,不同森林类型的细根养分和能量动态具有季节和林龄的特殊性,在进行整个地区森林生态系统物质循环和能量流动研究时,应考虑不同森林类型的特性。

Dynamics of nutrient and energy for fine roots of Casuarina equisetifolia plantations on coastal sandy soil

The seasonal dynamics of nutrient and energy of fine roots in C.equisetifolia plantations of different ages was studied at Chihu forestry farm of Hui'an county,Fujian province from January to November in 2005.We obtained the following results:(1)There was significant seasonal dynamics of six elements in the fine roots of different aged C.equisetifolia plantations.N concentration of dead fine roots was higher than that of living fine roots,and was relatively higher in summer and winter.P concentration of fine roots fluctuated with a decreasing trend except for the living fine roots of 12 year-old plantation.K concentration was higher in winter than in the other seasons.The highest Ca concentration in March and July was found in living fine roots of 5 year-old plantation and dead fine roots of 18 year-old plantation,while Ca concentration remained little change for other aged plantations.Mg concentration decreased from January to September and then increased in November.C content fluctuated with time.(2)The similar trend was found for N,P and Mg;and for K and Ca,respectively;C concentration fluctuated with plantation age.(3)The ash content,gross caloric values and ash free caloric values changed with "V" type,and were relatively high in March and July or September,respectively.(4)The ash content,gross caloric values and ash free caloric values tended to increase with the increasing plantation age.It was concluded that the nutrient and energy dynamics of fine roots varied with seasons and plantation ages.To discuss matter cycling and energy flow of forest ecosystems,we should pay attention to these characteristics of different stands.