Comparative study on ecological chracteristics of seedlings between Fagus crenata and Fagus japonica.

为了解林地被物成苗过程，比较了共生水曲柳(Fagus crenata，FC)和日本水曲柳(Fj)当年苗木的生态特性。调查了不同光照条件下的苗木种群，测定了苗木的生长和光合作用能力。两种树种的丰产年限由树龄和母树年轮的生长方式决定。1.春季树苗有子叶时林地光照条件较好，夏季林地光照条件较差。Fc的苗木成活率高于Fj。不同树种在物候和形态上存在差异，Fj的子叶较大，寿命比FC长一倍以上，Fj的叶片较薄，展开度较高，出苗较晚。在遮荫条件下，两种植物的子叶寿命都较长。…3.在任何光照条件下，树种间总生物量差异不显著。在更有利的光照条件下，FJ向地上部分分配的干物质比FC多。FC的最大光合速率高于Fj，净同化速率高于Fj。这表明不同树种的光能利用呈现出相对的变化趋势，Fc通过提高光合作用能力的灵活性来有效利用不同水平的光资源，而Fj通过更高的形态灵活性来有效利用不同水平的光资源。4.两种植物子叶的光合成特征与典型太阳叶相似，最大光合作用速率与叶片相当。子叶的光合作用生产在Fc的年净生产量中是不可忽略的，在Fj更重要。近25年来，Fc和Fj的大部分年份是Fc的7倍和Fj的6倍，并且种间不同步。两种树种的主干生长量与径向生长量之间存在显著的相关关系，并可从年轮格局中确定过去的主干生长年限。较少

Ecological characteristics of current-year seedlings were compared between co-occurred Fagus crenata (Fc) and F.japonica (Fj) to understand the process of seedling establishment on the forest floor. Seedling populations were censused and growth of the seedlings under different light conditions, and photosynthetic capacity were surveyed. Mast years of both species were determined by age of saplings and growth patterns of annual rings of mother trees.1.Light condition on the forest floor was favorable in spring when the seedlings had cotyledons and severe in summer. Survival of the seedling of Fc was higher than Fj. Mortality of seedlings was in part due to grazing by insects.2.Differences between species in phenology and morphology were observed ; cotyledons of Fj were larger and their longevity was longer (more than twice) than Fc, leaves of Fj were thinner and more spreading and emerged later than Fc. The longevity of the cotyledons was longer in more shaded condition in both species. … More 3.There were not significant differences in total biomass between species in any light conditions. Fj was allocate more dry matter to aerial parts than Fc in more favorable light condition. Maximum photosynthetic rate of Fc was higher and net assimilation rate was higher than Fj. These showed relative trends in light-use of each species ; Fc uses different levels of light resource efficiently by higher flexibility in photosynthetic capacity while Fj by higher morphological flexibility.4.Photosynthetic characteristics of cotyledons were similar to those of typical sun-leaf in both species and maximum photosynthetic rate was comparable to that of leaves. Photosynthetic production by cotyledons was not negligible in annual net production of Fc and more important in Fj.5.Mast years during resent 25 years were 7 times in Fc and 6 times in Fj, and not synchronous between species. Significant correlation between masting and radial growth of trunk was observed in both species, and mast years in the past was capable to be determined from the annual ring patterns. Less