东灵山地区辽东栎叶养分的季节动态与回收效率

为探讨辽东栎叶的养分回收对种群的适应能力和生态系统的养分循环的意义，在东灵山地区分析了辽东栎叶中Ｎ、Ｐ、Ｋ、Ｃa、Ｍg、Fe等６种元素的浓度和单位叶面积含量，确定了了辽东栎叶养分的季节动态与回收效率。结果发现：１）６种元素的浓度和单位叶面积含量在叶的生活史中都发生了明显的季节变化，其中Ｎ、Ｐ、Ｋ等３种元素的浓度在展叶初期下降很快，阴后逐渐下降的，但单位叶面积含量是在７月下旬达到最大值；２）Ｃa浓度和单位叶面积含量整个生长季中一直保持上升趋势，Ｍg的季节变化无一定规律；３）Ｎ、Ｐ、Ｋ、Ｍg都有一定程度的回收，其中Ｎ、Ｐ的回收率分别为６７％和８７％，Ｃa、Ｆe在叶有所积累。为探讨叶养分回收效率在常绿和落叶植物中的差异，对栎属植物养分动态进行了比较分析。结果表明：１）落叶植物成熟叶中的Ｎ浓度稍高于常绿植物，但不显著，Ｎ的回收率与成熟叶中的浓度成显著正相关，；２）栎属植物的成熟叶和落叶中的Ｎ、Ｐ浓度间呈显著正相关。

LEAF NUTRIENT DYNAMICS AND RESORPTION EFFICIENCY OF QUERCUS LIAOTUNGENSIS IN THE DONGLING MOUNTAIN REGION

Six elements, N, P, K, Mg, Ca and Fe, were analyzed in leaves of Quercus liaotungensis to evaluate the nutrient resorption efficiency of this species in the Dongling mountain region. The concentrations and storage of all six elements varied greatly in the life history of the leaves. N, P and K contents decreased abruptly at the early stage of leaf expansion, and then gradually thereafter. Their storage peaked in the last ten days of July. The concentration and storage of Ca increased continuously over the growing season, while Mg showed no obvious pattern. Nutrient resorptions were observed in N, P, K and Mg, and the resorption efficiencies of N and P were 67% and 87%, respectively. Ca and Fe accumulated in the leaves of this species. Comparison of leaf nutrient dynamics in some Quercus species indicates that N concentration in mature leaves of deciduous species is slightly, but not significantly higher than that of evergreen species, and that N resorption efficiencies have a significant, positive association with N concentration in mature leaves. The concentrations of N and P were found to be significantly related in both mature and shed leaves of the Quercus species.