沙质海岸黑松分枝格局特征及其抗风折能力分析

沙质海岸空间梯度上环境差异较大, 黑松(Pinus thunbergii)在长期的适应过程中树冠结构变化也很大。为揭示黑松树冠结构与环境间的适应机制, 在山东省胶南市灵山湾国家森林公园距海岸线0-50、200-250和400-450 m梯度内各设置1个样带, 记为带I、带II、带III, 采用枝构型的理论和方法, 对黑松的分枝格局进行了研究, 并采用模拟自然风法测定了黑松枝条的抗风折能力。结果表明: 1)在海岸梯度上黑松分枝格局差异较大, 随着距离海岸越来越远, 黑松各级枝的分枝长度、总体分枝率均逐渐增大, 而枝径比和逐步分枝率逐渐减小, 各级分枝角度表现为带I >带III >带II。2)带I树冠背风面与迎风面相比, 分枝长度、分枝角度、分枝数量、枝条干枯率分别是迎风面的1.62、1.38、2.65和0.59倍, 随着距离海岸越来越远, 这种不对称性逐渐减弱, 至带III树冠基本对称。3)海风是影响带I分枝角度偏转、枝条干枯和冠型不对称现象的主要原因。4)带III枝条的抗风折能力高于带I, 且两个样带模拟风速与枝条所承受的拉力之间的关系均符合逻辑斯蒂方程, 相关系数R²均达0.97以上。该研究揭示了不同海岸梯度上黑松分枝格局的形成机制及其抗风折能力, 可为沿海黑松防护林的合理经营提供科学依据。

Branching pattern characteristics and anti-windbreakage ability of Pinus thunbergii in sandy coast

Aims Environment varies greatly along the sandy coast of China, as does the crown architecture of Pinus thunbergii. Our objective was to determine the adaptive relationship between the two, including the wind-breakage resistance of the branching pattern, in order to provide guidance for managing coastal protective forests.
Methods We studied three belt transects at 0–50, 200–250 and 400–450 m from the coastline (named transect I, II and III, respectively) in P. thunbergii forest in Lingshan Bay National Forest Park in Shandong from May to September 2009. In each belt transect, we used 20 m × 50 m samples to survey the length and angle of bifurcation, numbers of branches and percentage of dry branches. We imitated natural wind to analyze branch wind-breakage resistance in the different transects.
Important findings The branching pattern of P. thunbergii showed strong plasticity under different environment conditions. Crown architecture was asymmetrical in transects I and II due to the direction of prevailing wind. Average length and angle of bifurcation and branching numbers on the windward side in transect I were significantly smaller than those on the leeward side, while percentage of dry branches was significantly higher on the windward side. This trend weakened gradually with increasing distance from the coastline. In transect III, branch distribution was uniform in each quadrant and there was little difference in average length of bifurcation, average angle of bifurcation, branch numbers and percentage of dry branch among quadrants. Wind was the primary factor influencing the deflection of the branching angle, percentage of dry branches and crown asymmetry. In addition, the wind-breakage resistance of P. thunbergii branching in transect III is higher than that in transect I, and the relationship between imitated wind speed and the force needed was logistic.