不同林龄第2代杉木林枝叶凋落前的养分转移特征

利用会同杉木林25年的定位测定的基础数据,探讨了不同林龄杉木(Cunninghamia lanceolata(lamb) Hook)枝叶凋落前的养分转移特征,为人工林经营管理提供科学依据。结果表明:杉木枝叶凋落前年均养分转移量为3.22—31.89 kg hm~(-2) a~(-1),其中,叶占71.31%—94.41%,枝占5.59%—28.69%。枝的养分转移量随林龄增加而增加。林分20年生以前,叶的养分转移量呈上升趋势,20年生以后,呈下降趋势。枝的养分转移率为20.97%—22.59%,叶是22.98%—26.06%,枝和叶的养分转移率都随林龄增加而增大。各林龄段的枝的养分转移率差异不显著(P0.05),叶的养分转移率除1—7年生与其他林龄段的差异显著(P0.05),其余各林龄段之间差异不显著(P0.05)。转移的元素量中,N和K占83.75%—84.25%,P、Ca、Mg占15.75%—16.25%。N、P、K、Ca、Mg的转移率分别为24.59%—34.53%,36.36%—46.64%,42.86%—51.27%,3.68%—7.35%,3.67%—9.56%。养分转移率主要受枝叶凋落前、后的养分浓度差值与枝叶凋落前的养分浓度控制,与凋落物量无关。养分的转移量不仅受枝叶凋落前、后的养分浓度差值的影响外,更多地取决于凋落物量,而且与杉木生长发育特征有很大的关联。

Characteristics of nutrient translocation before branch and leaf abscission in a second-generation Chinese fir plantation at different stand ages

To provide a scientific basis for the sustainable management of plantations, continuously determined basic data of 25 years on the characteristics of Chinese fir plantation, including information on nutrient transfer before branches and leaves wither, were studied, and the changes in nutrient transfer with forest age were discussed. The results showed that the annual average amount of nutrients transferred before the branches and leaves withered was 3.22 to 31.89 kg hm^-2 yr^-1, among which, the leaves accounted for 71.31% to 94.41% and branches for 5.59% to 28.69%. The amount of nutrient transfer in the branches increased with increasing forest age. Before 20 years of forest age, nutrient transfer rate of the leaves increased, and thereafter, it decreased. The nutrient transfer rate of the branches was 20.97% to 22.59%, and that of the leaves was 22.98% to 26.06%, and these increased with increasing forest age. There was no significant difference detected in nutrient resorption rate among the branches in different age groups and leaves older than 7 years (P > 0.05), except in plantations 1 to 7 years old (P < 0.05). Among the elements transferred, N and K accounted for 83.75% to 84.25%, and P, Ca, and Mg accounted for 15.75% to 16.25%. The transfer rates of N, P, K, Ca, and Mg were 24.59% to 34.53%, 36.36% to 46.64%, 42.86% to 51.27%, 3.68% to 7.35%, and 3.67% to 9.56%, respectively. The nutrient resorption rate was mainly controlled by the nutrient concentration differences between before and after leaf litter fall and nutrient concentration before leaf and branch abscission. However, the amount of nutrient translocation is not only affected by differences in nutrient concentration before and after litter fall, but also depends on the amount of litter fall and the growth status of Chinese fir plantations.