科尔沁沙地退耕杨树人工林生态系统C、N、P储量和分配格局

Effects of afforested poplar plantations on the stock and distribution of C,N,P at Keerqin Sandy Lands

土地利用/覆被变化是影响陆地生态系统C、N、P循环过程的重要因素之一。退耕还林作为一种重要的土地利用/覆被变化,受到国内外研究人员的广泛关注。以科尔沁沙地农田、5年生杨树人工林和10年生杨树人工林为研究对象,开展了退耕还林对生态系统C、N、P储量和空间格局影响的研究。结果发现：（1）与农田相比,退耕5年杨树人工林生态系统总的C、N、P储量下降,然而10年生杨树人工林生态系统总的C、N、P储量升高,其中植物生物量的C、N、P储量占生态系统总储量比例随着退耕还林年龄的增加逐渐增大;（2）与5年生杨树人工林相比,退耕还林10年的杨树人工林树叶、树枝、树干、树根和凋落物的C、N、P储量均显著增加（P〈0.05）,不同元素（C、N、P）储量在退耕5和10年的杨树人工林各器官空间分配格局不同;（3）与农田相比较,退耕还林5年杨树人工林土壤C、N、P储量在不同土层（0~10 cm、10~20 cm、20~40 cm和40~60 cm）均表现出下降趋势,而10年生杨树人工林土壤C、N、P储量在不同土层表现出增加趋势,不同生态系统类型（农田、5年杨树人工林和10年杨树人工林）土壤C、N、P储量在各土层分配格局不同。上述结果充分表明,在我国科尔沁沙地将农田退耕为杨树人工林能够显著改变生态系统C、N、P储量和空间分配格局。

In recent decades converting agricultural land to plantation forestry has been one of the major land use/land cover changes in many countries,and such land use/land cover change can affect ecosystem C,N and P cycling.In this paper we investigated the effects of afforestation with poplar（Populus simonii） on the stock and distribution pattern of C,N and P in former agricultural lands.The sites selected were 5-and 10-year-old poplar plantations with adjacent agricultural lands as control.The results showed that：（1） total ecosystem C,N and P stocks decreased in the initial stages of plantation establishment but increased with the stand age and the proportion of biomass C,N and P in total ecosystem storage increased;（2） C,N and P stocks in leaf,branch,stem,root and forest floor in the 10-year-old plantations were significantly higher than in the 5-year-old plantations,and the distribution of C,N and P in different plant components were different between the 5-and 10-year-old plantations;（3） compared with the agricultural land,C,N and P stocks in the mineral soil decreased in the 5-year-old plantation at the different soil depths（0-10 cm、10-20 cm、20-40 cm and 40-60 cm） but increased in the10 year-old plantation.In addition,we found that soil C,N and P distribution patterns among the three ecosystems were different.Our results indicated that agricultural lands afforestation with poplar affected the stock and distribution pattern of C,N,P at Keerqin Sandy Lands.