黄土丘陵区森林草原带不同退耕年限植物群落和土壤N,P化学计量特征

以黄土丘陵森林草原区5个退耕阶段的植物群落和土壤为研究对象,通过测定土壤和植物群落叶片、细根全N、全P含量,阐明了不同退耕阶段植物群落和土壤N,P的化学计量特征。结果表明:各土层全N含量及N/P值在不同退耕年限间差异显著(P < 0.05);同一土层中,全N含量和N/P值随着退耕年限的增加呈现出先减少后增加的趋势,大体在第3阶段(退耕16~22年)值最小;在不同退耕年限内,全N、全P、N/P均随土层加深呈现出逐渐减小的趋势。植物群落叶N含量,叶P含量,叶N/P和根P含量在不同退耕年限间差异极显著(P < 0.01);随着退耕年限的增加,叶N含量,叶P含量和根P含量呈现出先减小后增加的趋势,并且在第3阶段值最小;而根P含量在第4阶段(退耕25~30年)达到最小值;叶N/P大于根N/P。植物群落水平的叶片,细根和土壤的N,P及N/P之间存在不同的相关关系。P是黄土丘陵区森林草原带植物群落生物生长和群落演替的限制因素。

Concentration of N,P and Stoichiometry Characteristics of Plant Communities and Soil under Different Restoration Stages at a Forest-steppe Zone in Hilly and Gully Region of the Loess Plateau,China

In this study, we selected five plant communities and soil under different vegetation restoration stages at a forest-steppe zone in hilly and gully region of the Loess Plateau, and measured the concentration of N and P in leaf, fine root and soil at five restoration stages. The aims of this study were to clarify the N, P and N/P stoichiometry characteristics of plant communities and soil. The results showed that the total N concentration and N/P was significantly different (P < 0.05) among vegetation restoration stages in 0~20 cm, 20~40 cm and 40~60 cm soil layers. The total N concentration and N/P decreased first and then increased with increasing vegetation restoration stages, and they reached the lowest value at the third stage (restored 16~22 years). Meanwhile, the total N concentration, P concentration and N/P decreased with the increase of the soil layer depth at any stage. The total N concentration, P concentration and N/P in leaf and P concentration in fine root was significantly different (P < 0.01) among different stages. The total N concentration, P concentration of leaf and P concentration of fine root decreased first and then increased with increasing vegetation restoration stages, and reached the lowest value at the third stage; while P concentration of fine root reached the lowest values in the fourth stage(restored 25~30 years). The N/P of leaf was greater than that of fine root. The total N concentration, total P concentration and the N/P of leaf, fine root and soil had different correlativity. P was the limiting factor of plant growth and communities restoration at the forest-steppe zone in hilly and gully region of the Loess Plateau.