巨桉枯落物持水特性、细根生物量及其关系

本试验研究了一个林龄序列的巨桉林地枯落物储量、持水量、吸水率、土壤持水性能等与细根生物量关系,结果表明：（1）枯落物现存量在不同林龄林分中表现为5 a〉6 a〉2 a〉4 a〉1 a〉3 a。不同时期变化趋势为,7—10月凋落量（5.581 t·hm-2）〉1—4月凋落量（1.619 t·hm-2）〉10—1月的凋落量（0.152 t·hm-2）;（2）枯落物持水量的变异性较大,同一个季节不同林龄林分的枯落物持水量差异显著,1~6 a平均持水量分别为：9.804 0、12.821 8、7.7508、5.949 8、17.004 2和14.459 6 t·hm-2。枯落物吸水率与浸泡时间呈现极显著的相关性（P〈0.01）,其季节差异在浸泡的前4~6 h表现很明显,一般为秋〉冬〉夏〉春季;林龄差异表现表现为4年生巨桉林枯落物的吸水率最差,1年生的最好;（3）各林龄林分细根生物量在不同季节的基本趋势是：秋〉夏〉春〉冬季（P〈0.01）。林龄趋势为：6年生细根生物量最大（0.906 3 t·hm-2）,3年生最小（0.537 7 t·hm-2）。巨桉幼龄林（1~2 a）细根生物量与枯落物持水量及其浸泡时间显著相关,随着林龄的增长,这种关系不明显。

Plantation Hydrological Effects and Their Relationships with Fine Root Biomass in an Age Series of Eucalyptus grandis

This research studied the biomass, water holding capacity and water absorption of litter and fine roots（2 mm） for an age series of Eucalyptus grandis representing a complete rotation（ages 1 ~ 6 years） in Danling, Meishan city of Sichuan province. The results showed： litter reserves differed significantly with age and descended in the following sequence： 5-years 6-years 2-years 4-years 1-year 3-years old. The dynamic of litter at different survey times showed the following results： Jul. – Oct. 2006（5.581 t·hm-2） Jan. – Apr. 2007（1.619 t·hm-2） Oct. 2006 – Jul. 2007（0.152 t·hm-2）. The water holding capacity of litter was also found to vary with season, as well as at different ages, from 9.804 0 t·hm-2for that of 1-year-old plantation, 12.821 8 t·hm-2for 2-year-old, 7.750 8 t·hm-2for 3-year-old; 5.949 8 t·hm-2for 4-year-old, 17.004 2 t·hm-2for 5-year-old, and 14.459 6 t·hm-2for 6-year-old plantation. It was found that the fastest water absorption occurred during the first 4 hours. After 8 hours water absorption slowed or ceased completely. A significant（P0.01） relationship was observed between rate of water absorption and immersion time. Seasonal differences were also observed in water absorption during the first 4 hour period with seasonal averages descending in the order of autumn winter summer spring. Across different plantation ages, water absorption was lowest at age 4-years and highest at age 1-year. The fine root biomass in the top 0~50 cm of soil depth（soil core method） varied significantly（P 0.01） with season in descending order of autumn summer winter spring. The highest fine root biomass was observed in the 6-year old plantation（0.906 3 t·hm-2） and the lowest in the 3-year old plantation（0.537 7 t·hm-2）. There were significant positive correlations between fine root biomass and water holding capacity of litter at age 1 to 2-years but the significance of the correlation decreased as plantation age increased.