武夷山不同海拔黄山松新叶和老叶氮磷化学计量特征

Nitrogen and phosphorus stoichiometric characteristics of new and old leaves in Pinus taiwanensis at different altitudes in Wuyi Mountain

土壤是植物养分的直接来源,植物叶片的养分特征在一定程度上能反映土壤养分状况。叶片氮磷比(N∶P)被广泛用于指示土壤养分有效性和养分限制性,选择对土壤养分最敏感的叶片来指示土壤养分状况具有重要意义。为比较黄山松新叶和老叶指示土壤养分状况的准确性,在福建武夷山选择了3个海拔(1100、1500和1900 m)的黄山松新叶和老叶作为研究对象,通过测定土壤碳(C)、氮(N)、磷(P)含量,黄山松叶片N、P含量及土壤和叶片15N丰度值,并计算土壤和叶片的化学计量比,从而揭示黄山松新叶和老叶对不同海拔土壤养分状况的敏感性。结果表明:(1)不同海拔土壤氮有效性无显著差异,而土壤和叶片15N丰度值随海拔呈递增趋势,说明土壤氮素对植物的有效性随海拔升高而增加;低海拔(1100 m)土壤总P和有效P含量低于高海拔(1500和1900 m)处,且低海拔叶片P含量也显著低于高海拔;(2)黄山松新叶N、P和N∶P随海拔升高均无显著变化,且新叶N∶P与土壤养分相关性不大;老叶N、P含量与土壤养分相关性较密切,表明黄山松老叶较新叶对不同海拔土壤养分状况响应更敏感,更能指示土壤养分状况。因此,这些研究结果明晰了不同海拔植物新叶和老叶对土壤养分状况的敏感性差异,对于我们进一步了解未来气候变化背景下不同海拔植物生长对土壤养分状况变化的响应具有重要意义。

Foliar nitrogen to phosphorus ratio( N ∶ P) is widely used as an indicator of soil nutrient availability and nutrient limitation. Therefore,it is necessary to determine the most sensitive plant tissue as the indicator of soil nutrient status. Pinus taiwanensis occupies a wide range of habitats in the Wuyi Mountain,China. Here,soil,new and old leaves of P. taiwanensis from three altitudes( 1100,1500,and 1900 m a.l.s.) were sampled in Wuyi Mountain. The concentrations of carbon( C),nitrogen( N) and phosphorus( P) as well as δ15 N values of soil,new and old leaves were measured. The stoichiometric ratios of C,N and P( i. e. C ∶ N,C ∶ P,N ∶ P) in soil and leaves were calculated,respectively. Results showed that there was no significant difference in soil N availability among different altitudes,while the δ15 N of soil and leaves increased with altitude,indicating that N availability for plants increased with elevations. Soil total P and available P concentrations,and P concentration of leaves at 1100 m altitude were lower than those at 1500 and 1900 m altitudes,indicating that the availability of soil N and P may serve as a limiting factor to the growth of P. taiwanensis at low altitude. There was no significant difference in the N and P concentrations and N ∶ P of the new leaves of P. taiwanensis among different altitudes. There was no correlation between N ∶ P in new leaves and soil nutrients. However,the variation patterns of N and P concentrations in old leaves were similar to those in soils,and the N ∶ P ratio in old leaves were closely related to soil nutrients. Our results indicated that old leaves of P. taiwanensis were more sensitive to soil nutrient status than the new leaves along the altitudinal gradient,which is beneficial to exploring the response of plant growth to variation in soil nutrients in the context of future climate change.