ABSTRACT

Topography plays a critical role in the growth, development, and carbon accumulation of Moso bamboo. However, it is still unknown whether the effects of topography on the newly sprouted culms, the diameter at breast height (DBH) and the carbon stocks of newly sprouted culms (called carbon stocks below) vary temporally following Moso bamboo afforestation. In this study, thirty-one 20 × 20 m long-term sample plots were established and the DBH, age, height, and coordination of every newly sprouted culm were measured from 2009 to 2018. Four Moso bamboo expansion periods (rhizome expansion period, early period, middle period, and stable period) were divided according to the patterns of change of newly sprouted culms. Structural equation modeling and univariate analysis were combined to assess the dynamic effects of topographic factors (slope, aspect, slope position, and topographic complexity) and the effect of single topographic factors and their interactions on the carbon stocks during the four expansion periods. The result showed that the leading topographic factors influencing DBH, newly sprouted culms and carbon stocks were depended on the expansion period. Furthermore, the effective degree of leading topographic factor, aspect, decreased from the early period to a stable period. The four topographic factors studied here did not influence carbon stocks and newly sprouted culms during the stable period. The optimal interactions between carbon stocks and slope position and aspect (an east aspect of lower and upper slope positions) were relatively larger than those of a single aspect (east aspect), and significantly decreased in a stable period. Low topographic complexity was beneficial to the carbon accumulation under abrupt slopes but middle topographic complexity was needed under steeper slopes (steep and dangerous slope). Overall, this study offers a greater understanding of the effect of topography on Moso bamboo growth and provides a scientific basis for the selection of suitable afforestation locations for forest management.

摘要

地形对毛竹的生长、发育和碳积累起着至关重要的作用。然而，尚不清楚地形对新发芽的秆、胸高直径（DBH）和新发芽的秆的碳储量（以下称为碳储量）的影响是否在毛竹造林后随时间变化。本研究建立了 31 个 20 × 20 m 的长期样地，测量了 2009 年至 2018 年每根新发芽的竹秆的胸径、年龄、高度和协调度。四个毛竹扩张期（根茎扩张期，早期、中期、稳定期）根据新芽秆的变化规律进行划分。结构方程建模和单变量分析相结合，评估地形因素（坡度、坡向、坡位置和地形复杂性）以及四个扩张期单个地形因素及其相互作用对碳储量的影响。结果表明，影响胸径、新芽秆和碳储量的主要地形因素取决于扩张期。此外，主要地形因素方面的有效程度从早期下降到稳定期。在此研究的四个地形因素在稳定期间不影响碳储量和新发芽的秆。碳储量与坡位和坡向（下坡位和上坡位的东坡）之间的最佳相互作用大于单一坡向（东坡），并且在稳定期显着降低。低地形复杂度有利于陡坡下的碳积累，但在陡坡（陡峭和危险的斜坡）下需要中等地形复杂度。总体而言，本研究加深了对地形对毛竹生长影响的认识，为森林经营选择合适的造林地点提供了科学依据。