茂兰喀斯特森林林隙幼苗出现的时空格局

通过4次对茂兰自然保护区喀斯特森林林隙内种子的天然萌发情况进行观测,分析了林隙内幼苗的萌发数量、存活率及幼苗出现的时空分布格局。结果发现：林隙中大多数萌发的幼苗存活率均较高,平均存活率达50%以上,林隙的形成,不但提高了喀斯特森林树种的萌发率,也提高了幼苗的存活率。林隙中心、近中心、林隙边缘各区域幼苗的密度存在显著的空间差异,山拐枣（Poliothyrsis sinensis）、多脉榆（Ulmus castaneifolia）等树种在林隙中心幼苗密度最大,圆果化香（Platycarya longipes）、翅荚香槐（Cladrastis platycarpa）、圆叶乌桕（Sapium rotundifolium）、掌叶木（Handeliodendron bodinieri）、黄连木（Pistacia chinen-sis）和云贵鹅耳枥（Carpinus pubescens）等树种在林隙近中心幼苗密度最大,而樟叶槭（Acercinnamomifolium）、球核荚蒾（Viburnumpropinquum）、小叶青冈（Cyclobalanopsis myrsinaefolia）、轮叶木姜子（Litsea verticillata）等则在林隙边缘光照较弱的地方生长良好。幼苗出现的时间分布特征明显,整个观察期幼苗都持续萌发,但大多数树种幼苗出现在第2观测期（3月）,幼苗出现数目从第2次到后面的几次观察期显著下降。林隙3个区域幼苗出现不是同步的,林隙中心的幼苗出现最快,与其它两个部位相比,林隙边缘的幼苗出现有滞后现象。研究结果表明林隙中心的环境条件有利于种子萌发,但林隙近中心却更利于幼苗存活。

The Temporal and Spatial Patterns of Seedling Emergence in Gaps of Karst Forest in Maolan Nature Reserve, Guizhou Province

Seed natural germination in gaps of karst forest in Maolan Nature reserve, Guizhou Province were observed in 4 observation times. Germination number and survival rate of seedlings in gaps, differences in temporal and spatial patterns of seedling emergence were investigated. The results showed that survival rate of seedlings of most species in gaps was high and average survival rate was above 50%. It increased not only the germination rate of tree seeds but also the survival rate of seedlings because of gap formation in karst forest. Seedling density has spatial heterogeneity in different area of gap center, near gap center and gap border. Seedling density of Poliothyrsis sinensis and Ulmus castaneifolia were great in gap center, seedling density of Platycarya longipes, Cladrastis platycarpa, Sapium rotundifolium, Handeliodendron bodinieri, Pistacia chinensis and Carpinus pubescens were great near gap center and seedling density of Acer cinnamomifolium, Viburnum propinquum, Cyclobalanopsis myrsinaefolia and Litsea verticllata were great in gap border where light was shght. Most of seedlings emerged during the second census. Although germination occurred over the entire observing stage, the total number of seedlings decreased distinctively with the second time. Seedling germination differed temporally among three gap areas. Seedling germination was the most quick in gap center, but in gap border seedlings lagged behind the others. The results showed that it was favorable for seed germination in gap center, but was favorable for seedhngs survival near gap center.