吉林蛟河针阔混交林树木生长与生境的关联性

以吉林蛟河21.12 hm2(660 m×320 m)针阔混交林样地为对象,在以海拔、坡度、坡向以及凸凹度为地形变量划分样地生境类型的基础上,利用2009—2014年植被生长数据,研究生境差异对树木生长的影响机制。研究采用生境空间随机(生境CSR)、物种空间随机(物种CSR)以及物种Thomas3种生态学过程零模型,检验树木径向生长与4种生境类型之间的关联性;采用Pearson相关系数计算树木生长与地形变量之间的相关关系,量化地形变量对树木生长的影响。研究结果显示:(1)样地内绝大多数物种(生境CSR过程:86.1%;物种CSR过程:94.4%;物种Thomas过程:61.1%)的径向生长表现出明显的生境关联性。(2)不同生活型物种的生境利用方式不同:灌木和亚乔木具有类似的生境偏好,与海拔相对较低、地势相对平缓的生境型1正关联,与海拔相对较高、坡度相对较大的生境型2和生境型4负关联;乔木在不同生境类型中会同时存在正、负关联性,但更倾向于和生境1发生负关联,而和生境4发生正关联,并且乔木树种的径向生长对地形之间的差异更加敏感;(3)高达86.1%的物种生长与至少一种地形变量显著相关,其中海拔对树木生长影响最大,其次是坡度和凸凹度,坡向的影响则相对最小。上述结果表明,样地内不同物种之间出现了明显的生境利用性分化,生境利用性分化是影响温带针阔混交林树木径向生长的重要因素。

Habitat associations of tree growth in a coniferous and broad-leaved mixed forest in Jiaohe, Jilin Province

The goal of this study was to determine the relative contribution of habitat differentiation on the radial growth of forest trees and to understand some underlying ecological mechanisms that may affect these relationships. Forest growth data for the period 2009 to 2014 were collected in a 21.12 hm² stem-mapped temperate coniferous and broadleaved forest in Jiaohe, Jilin Province. Based on habitat type classifications, three ecological null models, Habitat Complete Spatial Randomness (CSR) Process, Species Complete Spatial Randomness Process and Species Thomas Process were employed to test the significance of radial growth-habitat associations. Furthermore, Pearson correlation analysis was used to explore the influence of topographical variables on radial growth. A total of 36 species were included in the analysis. The following results were obtained: (1) Sixty one percent of radial growth exhibited significant associations with habitat types based on the Species Thomas Process; whereas for the Species CSR Process and the Habitat CSR Process the corresponding percentages were 94.4% and 86.1%, respectively. (2) Comparing the discrepancies among species of different life forms, we found that the habitat preferences of shrubs and small trees were similar, whereas trees had significantly different habitat preferences. The radial growth of shrubs and small trees were positively associated with habitat type 1 at a relatively low altitude and on flat terrain, but were negatively associated with habitat types 2 and 4, which had a relatively high elevation and on steep slopes. Conversely, trees were positively associated with habitat type 4, but negatively associated with habitat type 1. Furthermore, the radial growth of trees was highly sensitive to habitat heterogeneity when compared with that of shrubs and small trees. (3) Pearson correlation analysis indicated that up to 86.1 percent of growth rates were significantly correlated with one or more topographical variables. Among the four topographical variables evaluated, elevation turned out to be the most influential factor for radial growth, followed by slope and convexity, whereas aspect was the least influential. The results of this study suggest that habitat heterogeneity and niche differentiation have a considerable effect on radial growth in the temperate coniferous and broadleaved forest.