陕西省3种主要树种叶片、凋落物和土壤N、P化学计量特征

N and P stoichiometric characteristics of leaves,litter,and soil for three dominant tree species in the Shaanxi Province

以陕西省29个县(市)39个样点的刺槐、辽东栎和油松林为研究对象,分析比较不同树种乔木叶片、凋落物与土壤N、P化学计量特征及其与经纬度、海拔、年均温度和年降水等环境因子间关系的异同以及三者之间可能存在的关系,以期为认识陕西省主要森林树种养分限制状况、制定合理的植被管理和恢复措施提供理论依据。结果表明:3树种叶片N、P含量及比值均为刺槐>辽东栎>油松,与叶片相比,凋落物中N、P含量变化幅度较小,为刺槐>辽东栎>油松,N∶P比值为油松>辽东栎>刺槐。10—20 cm与0—10 cm土层相比,3树种中除辽东栎中P含量差异不显著外,其它指标N、P含量及N∶P比值均显著下降(P<0.05)。刺槐、辽东栎和油松叶片N、P含量与土壤N、P含量均没有显著相关性,以刺槐、辽东栎和油松3种植物叶片为总体来说,P含量与土壤P含量显著正相关(P<0.05)。叶片N、P含量均大致表现出随着年均温度和年降水的增加而增加,随着经纬度的增加而降低的趋势,这一点在刺槐叶中最为明显。凋落物N含量随着年均温度和年降水的增加而增加,随着纬度和经度的增加而降低;P含量随着年降水和经度的增加而降低;N∶P比值随着年均温度和年降水的增加而增加,随着纬度的增加而降低。研究区内,土壤N、P含量随着纬度、海拔的增加和年均温度、年降水、经度的降低而增加,N∶P比值则呈相反的趋势。3树种土壤N、P含量及N∶P比值中,P含量比N含量受环境影响更大,且0—10 cm和10—20 cm土层N、P含量及N∶P比值与各环境因子的关系基本一致。

Plant nutrient stoichiometry can be used to distinguish the biological entities based on element composition and responses to environmental factors. We determined the N and P stoichiometry for leaves, litter, and soil associated with 3 dominant tree species： Robinia pseucdoacacia, Quercus liaotungensis, and Pinus tabulaeformis, at 39 sites in 29 countylevel cites of the Shaanxi Province. We aimed to distinguish the differences in leaf, litter, and soil N and P stoichiometry among the different tree species, and their relationships with environmental factors in the Shaanxi Province. Leaf N and P concentrations and their ratios, were Robinia pseucdoacacia 〉 Quercus liaotungensis 〉 Pinus tabulaeformis. Compared with plant leaves, the range and quantity of litter N and P concentration significantly reduced （P〈0.05） , and the order was still Robinia pseucdoacacia 〉 Quercus liaotungensis 〉 Pinus tabulaeformis, while the order for the N ：P ratio was Pinus tabulaeformis 〉 Quercus liaotungensis 〉 Robinia pseucdoacacia. There were no significant correlations （P〈0.05） between Robinia pseucdoacacia, Quercus liaotungensis, and Pinus tabulaeformis leaf N （ or P ） and soil N （ or P ）, indicating that their growth was not limited by N or P. In total, there were significant correlations between leaf P and soil P （P〈0.05） , which indicated that the growth of the plant was limited by P in the Shaanxi Province. Leaf N and t＇ increased with mean annual temperature and precipitation, especially for Robinia pseucdoacacia. The leaf N ： P ratio for the 3 tree species did not clearly correlate with the environmental factors. Litter N increased with mean annual temperature and precipitation, and decreased depending on the latitude and longitude. Although litter P showed no significant relationships with temperature and latitude （P〈0.05）, it declined with precipitation and longitude. Litter N ：P ratio increased with temperature and precipitation and decreased with latitude. Soil N and P increased with latitude and altitude, and decreased with mean annual temperature, mean annual precipitation, and longitude. The soil N ：P ratios demonstrated an opposite trend. Soil P was more closely correlated with environmental factors than N, and the relationship between the 0--10 cm and 10--20 cm N and P stoichiometry in terms of environmental factors was almost the same.