基于水量平衡的华北落叶松人工林承载密度研究

Carrying density of Larix principis-rupprechtii plantations based on water balance

【目的】研究冀北地区华北落叶松人工林水分平衡规律及其供求关系,准确计算区域不同降水条件下华北落叶松适宜经营密度。【方法】依据水量平衡原理构建包含大气降水土壤入渗分量、林下蒸散发分量和不同胸径华北落叶松单株蒸腾耗水分量的水源承载密度计算公式。通过对小五台山自然保护区华北落叶松人工林树干液流、林下蒸散发、水量再分配特征的长期定位观测,以及胸径与木质部周长关系模型的构建,确定计算参数,计算不同降水条件下华北落叶松人工林各径级可承载密度。【结果】(1)小五台地区华北落叶松生长季6个月,生长季昼间蒸腾平均时长15 h;生长季平均液流速率0.012 kg/(h·cm),除4月、6月较低外,其余各月都达到0.011 kg/(h·cm)以上,尤其以8月最高,达到0.021 kg/(h·cm)。(2)生长季华北落叶松林下平均蒸散发速率1.448 kg/(m^(2)·d),全年平均速率0.833 kg/(m^(2)·d);蒸散发速率4—6月上升较快,6—9月上升缓慢,并在9月达到峰值,10月迅速下降,11月到来年2月处于较低水平。(3)华北落叶松林冠层截留量占降水量的21.22%,穿透雨量占78.10%,树干径流量占0.68%,坡面径流量占1.50%,土壤入渗量占77.28%。(4)华北落叶松胸径与木质部周长呈线性相关关系,R^(2)为0.958。【结论】依据水量平衡原理计算出小五台地区不同降水条件下华北落叶松林各径级可承载密度,对于冀北地区现有林分的科学经营具有重要指导意义。

[Objective]This paper aims to study the water balance law and supply-demand relationship of Larix principis-rupprechtii plantations in the northern Hebei Province region of northern China,and accurately calculate the proper management density of L.principis-rupprechtii plantations under different precipitation conditions in the region.[Method]The calculation parameters were determined through longterm location observation of sap flow,understory evapotranspiration,water redistribution characteristics of L.principis-rupprechtii plantations in Xiaowutai Mountain Nature Reserve,and the construction of relationship model between DBH and xylem perimeter,and the carrying density of each diameter class of L.principis-rupprechti plantation under different precipitation conditions was calculated.[Result](1)The growth season of Larix principis-rupprechtii in the Xiaowutai area was 6 months,with an average diurnal transpiration time of 15 h during the growth season.The average sap flow velocity of L.principisrupprechtii during the growth season was 0.012 kg/(h·cm).Except for lower values in April and June,it reached above 0.011 kg/(h·cm)in all other months,with the highest value reaching 0.021 kg/(h·cm)in August.(2)The average evapotranspiration rate under L.principis-rupprechtii forest during the growth season was 1.448 kg/(m^(2)·d),and the annual average rate was 0.833 kg/(m^(2)·d).The evapotranspiration rate increased rapidly from April to June,slowly increased from June to September,and reached its peak in September,rapidly decreased in October,and remained at a relatively low value from November to February of the followed year.(3)The canopy interception of L.principis-rupprechtii forest accounted for 21.22%of the precipitation,the penetrating precipitation accounted for 78.10%,the trunk runoff accounted for 0.68%,the slope runoff accounted for 1.50%,and the soil infiltration accounted for 77.28%.(4)There was a linear correlation between DBH and xylem perimeter of L.principis-rupprechtii,R^(2) was 0.958.[Conclusion]Based on the principle of water balance,the bearing density of different DBH of L.principisrupprechtii forests under varied precipitation conditions in the Xiaowutai area is calculated,which has important guiding significance for the scientific management of existing forests in the northern Hebei region of northern China.