平原散生楊树生态特性的調查方法

A METHOD OF ECOLOGICAL STUDY OF POPLARS GROWING AS SCATTERED TREES ON THE LEVELLAND

大多数杨树为平地散生树种,一般山地森林土壤与植被的调查方法不完全适用。本文介绍了一种野外调查与分析材料的方法,以及在河南睢杞林埸,试用于美杨(防护林带为主)的结果。调查土壤时,除剖面调查外,并对一些土壤特性,其中包括透水性、容重、土壤水分、地下水(水位与水质)、质地、粘质层(深度与厚度)、pH值、铵态氮、速效P_2O_5进行了野外观测。观测结果采用了两种分析方法:一方面采用相关系数的统计方法,计算结果,地下水位与美杨树高生长的相关显著=0.458,P<0.05),根系集中层容重与美杨树高生长的相关极显著=0.804,P<0.01),其余土壤特性与美杨树高生长的相关均低于统计学上的一般显著标准;另一方面从理论与野外观测的结果,将地下水位分为3级,质地4级,粘质层3级,透水性3级,pH值(根系集中层)3级,容重3级,并分别找出了各级美杨的树高生长情况。植被稠查分估舒描远(质的稠查)与数量航箭二种,前者主要采用法瑞学派的方法,稠查填目舒有:总估舒度、攀度、物候相、生活型、根系、高度等填;后者采用点样法,点样法架用薄木板与铁杆做成,稠查杭舒盖度与频度二稠。美福拿丛按区别种分为二个亚拿丛:印度白茅亚拿丛与中国白茅亚拿丛,后者复分为黄鼠草类型与标准类裂。对于所有区别种与擎落,均采用加权平均方法,爵算出其对土壤特性的数量指标,并圃明其对美格生长的指示意义。根据满查桔果,提出了在稠查地区内美揭适宜生长的土壤条件的数量指标,以及指示植物与攀落。最后甜渝了所用方法的优缺点。

Methods of soil and vegetation survey generally used for forest trees in mountainous areas are considered inapplicable to poplars growing as scattered trees on the levelland. In the present paper, therefore, a method catering for this purpose together with the result of its application to poplar sheltabelts in East Honan is presented. In soil survey, besides detailed profile descriptions, field determinations of important soil properties, including water permeability, volume weight, moisture content, texture, ground water table and composition, thickness and depth of clay layer, pH value, available N and available P have been obtained. All the data are later annalysed and interpreted from two rather different but complementary approaches. On the first hand, by the calculation of correlation coefficient, correlation between height growth of Populus pyramidalis and ground water tables is found to be significant (r=0.458 P<0.05), and correlation between height growth of this species and volume weight of soil at root-concentrating horizon highly significant (r=0.804 P<0.01). But correlation coefficient between height growth of the same species and all other studied soil properties fall below the significant leyel generally adapted i.e. 5% level. Secondly, on the comparative study of field determinations of soil properties and height measurements of this species, ground water tables with reference to tree heights are divided into 3 classes, soil textures 4 classes, pH values (at root-concentrating horizon) 3 classes, and volume weights 3 classes respectively. In vegetation survey, qualitative investigations are carried out following the ZurichMontpellier School's procedures with but a few modifications, and total estimation, sociability, aspect, life form, root system and plant height are recorded. Also, point quadrat method is employed to collect quantitative data such as cover and frequency. Populetum pyramidalise association is classified into two subassociation:P. Pyr. Imperata cylindrica subassociation and P. Pyr. Imperata cylindrica var. major subassociation respectively. The latter is further classified into Lactuca variant and typical variant. To the above-mentioned plant community units and their respective differential species, a weighted mean of the class value with respect to each soil property is calculated separately. On this basis their indicating values to the growth of the tree are interpreted. Meanwhile, quantitative criteria of soil properties and a list of plant indicators (including individual species and community units) for the choice of planting sites of Populus pyramidalis in the studied area are given. Lastly, merits and demerits of the present method are discussed.