黄土高原马栏林区优势种幼苗与其种群径级结构的演替研究

对黄土高原马栏林区几种典型群落类型中优势种辽东栎(Quercus liaotungensis)、油松(Pinus tabulaefor-mis)、白桦(Betula platyphylla)和山杨(Populus davidiana)的幼苗和种群径级结构进行了研究。结果表明:(1)辽东栎幼苗在马栏林区7种典型群落类型中均有分布,且数量充足,实生苗更新良好,辽东栎在不同的群落类型中表现出不同的种群径级结构。在油松 辽东栎混交林和辽东栎林中趋于稳定型;在油松林、油松 白桦混交林、白桦林、山杨林和白桦 山杨混交林中则为增长型;(2)油松幼苗在油松 白桦混交林、油松林和油松 辽东栎混交林中分布较多,但均少于辽东栎幼苗。在这些群落类型中油松种群的径级结构属于稳定型;(3)白桦和山杨幼苗数量较少,无正常更新能力,种群径级结构趋于衰退,以白桦和山杨为主的群落类型将逐渐被以油松和辽东栎为主的群落类型所取代;(4)马栏林区优势种幼苗分布的广度和丰度受到光照、水和灌草层等非生物和生物因素及其相互作用的影响。表明在黄土高原马栏林区以天然恢复为主的辽东栎种群,将在该地植被的自然恢复过程中产生重要作用;油松种群不仅过去而且将来也同样会在该地区的植被恢复中发挥重要作用。

Succession of the Seedlings of Dominant Species and Diameter-class Structures of Their Populations in Malan Forest Region of the Loess Plateau

The seedlings of several dominant species,Quercus liaotungensis,Pinus tabulaeformis,Betula platyphylla and Populus davidiana,and diameterclass structure of their populations in Malan Forest Region in the Loess Plateau was investigated and this showed that(1) in all the seven typical populations in Malan Forest Region,Quercus liaotungensis seedlings distributed in quantities and renewed well by seed seedling,and different Quercus liaotungensis populations presented different diameter-class structures.They belonged to one stable type in Pinus tabulaeformis and Quercus liaotungensis mixed forest,and one growth type in Populus davidiana forest,Populus davidiana and Betula platyphylla mixed forest,Betula platyphylla forest,Populus davidiana forest and Betula platyphylla and Populus davidiana mixed forest;(2) Pinus tabulaeformis seedlings distributed in quantities in Pinus tabulaeformis and Betula platyphylla mixed forest,Pinus tabulaeformis forest,Pinus tabulaeformis and Quercus liaotungensis mixed forest but the numbers of these seedlings was lean than the numbers of Quercus liaotungensis seedlings in these forests.Of the diameter-class structures of these populations,the diameter-class structure of Pinus tabulaeformis populations belonged to one stable type;(3) Betula platyphylla and Populus davidiana seedlings totaled a small number thus not capable of renewing themselves and the communities mainly composed of Betula platyphylla and Populus davidiana would be gradually replaced by the communities mainly composed of Quercus liaotungensis and Pinus tabulaeformis;(4) Abiotic and biotic factors such as sunshine,water and shrub and herb layers as well as their interactions exerted influences on the distribution and abundance of the seedlings of dominant species in Malan Forest Region.It follows that in Malan Forest Region,the natural vegetation recovery was dominated by Quercus liaotungensis populations,which would consequently play an important role in the natural vegetation recovery.Pinus tabulaeformis populations have played and will play an important role in the vegetation recovery of the region.