天山北坡中段云杉林地表水氮磷含量特征

Nitrogen and Phosphorus Contents in Surface Water of Picea schrenkiana Forest in the Middle Zone of the Northern Slope of Tianshan Mountains

森林的结构对地表水的化学成分具有强烈的影响,量化分析森林结构与水质变化的关系很有必要。为探究天山云杉森林地表水的氮磷含量特征及其影响因素,本文在天山北坡中段的板房沟林场按林地类型、林龄、郁闭度、抚育方式的不同分别设置坡面径流观测场共13处,在雨后测定各径流观测场地表水中总氮和总磷含量并分析比较。结果表明:(1)林地类型对天山云杉森林地表水氮磷含量有重要的影响,人工林、灌木林、天然林三种样地的地表水氮磷含量均显著低于裸地(P<0.05);(2)群落发育阶段对地表水氮磷含量也有重要的影响。在天然林系列样地中,郁闭度相同(均为0.6)时,中龄林总氮含量显著高于幼龄林(P<0.05),总磷含量在不同林龄之间差异不显著;林龄相同(中龄林)时,郁闭度为0.6的样地显著高于郁闭度为0.4样地中氮磷含量(P<0.05);(3)人工干扰强度(修枝和间伐两种不同抚育方式)对林地地表水氮磷含量也会有一定的影响但未达到显著水平(P<0.05)。综上可知,云杉森林地表径流中氮磷含量主要来源于土壤,有无植被覆盖对地表水氮磷含量影响显著,森林郁闭度是地表水中氮磷含量关键影响因素。

Forest structure has a strong influence on the chemical composition of surface water, and it is scientifically necessary to quantify the relationship between forest structure and change in water quality. To explore the nitrogen and phosphorus contents and the main factors affecting them in the surface water of a Picea schrenkiana forest,13 runoff observation plots were selected in Banfanggou forest farm on the northern slope of the Tianshan Mountains in terms of forest type,stand age,canopy density,and tending method. The runoff surface water collected after rainfall was used to determine total nitrogen and phosphorus contents. Results showed that：（ 1） forest types had an important influence on the nitrogen and phosphorus contents in the surface water： the runoff from plantation,shrub forest,and natural forest had significantly lower nitrogen and phosphorus contents than those from bare lands（ P〈0. 05）.（ 2） The community development stage also had an important influence on the nitrogen and phosphorus contents in the surface water. In natural forests with the same canopy density（ 0. 6）,middle-age forest had higher nitrogen content than young forest did,whereas no significant differences were observed among different stand ages for phosphorus. When stand age was the same（ middle-aged plots）,nitrogen and phosphorus contents were significantly higher in plots with a canopy density of 0. 6 than 0. 4（ P〈0. 05）.（ 3）Management intensity（ pruning and thinning） in plantation affected the nitrogen and phosphorus contents,but not significantly（ P〈0. 05）. In conclusion,the nitrogen and phosphorus contents in surface water mainly derived from soil and were significantly influenced by vegetation coverage and forest canopy density.