对西藏色季拉山急尖长苞冷杉林生态系统的养分循环进行了研究,结果表明:养分的总存留量为35.41kg·hm-2·a-1,总归还量为54.89kg·hm-2·a-1,年吸收总量为90.3kg·hm-2·a-1。冷杉林分具有养分低循环利用特征。大气降水主要补充N、Ca、Fe等元素,而凋落物主要补充P、K、Fe等元素,其中Fe元素是净增加的。冷杉林生态系统养分年输入量均大于年输出量,说明该森林生态系统处于良好的养分积累阶段。林地土壤(不包括凋落物层)的养分年输出量(除N、Fe、Mg元素外)稍大于年获得量,土壤年净亏损不大,但K的亏损较严重。冷杉林分的养分利用效率以及土壤养分利用指数均表明,林分对N的需求最大,对Fe的需求最少。

Juglans reg ia is an important econom ic tree species. Observation of its stock sap flow w as carried bySF100 heat pulse recorder in dry season( April-July) in area of conversion farm land for forest and surround ing meteorolog ical facto rs such as air temperature, a ir relative hum idity and radiation intensity w ere monitored in-phase. Experimental p lot locates in P ing shan, H ebe.i Th is study w ould o ffer some references for vegetation restoration. Theresu lts show ed that the Jug lans reg ia stock sap flow changed obv iously betw een day and n igh,t w hich follow ed a single peak type curve. Variation amplitude w as b ig in sunny day and little in cloudy day; In Apr il-M ay, sap flow w asbig and little in June-Ju ly because of so ilw ater stress; In fluencing order on stock sap flow flux byme teoro log ica l facto rs w as sun rad iation> a ir temperature> re lative hum id ity respectively.

西藏色季拉山冷杉林生态系统中土壤地表水和土壤渗漏水中离子和元素的输出量占降水养分输入量的比重很小,均不超过1%。地表枯落物和土壤中的SO42-、HCO3-、N被淋溶;K、Zn、P被吸附;土壤总的淋溶量从大到小的顺序为:SO42-Cl-HCO3-CMgNCaFeNaZnPK;土壤总的淋溶系数显示的次序为HCO3-CaSO42-NaCl-NMgCFePKZn。