核桃-小麦复合系统土壤碳密度动态特征

Dynamic Characteristics of Soil Organic Carbon Density in Walnut-wheat Agroforestry System

以渭北黄土区近年来发展迅速的核桃(Juglans regia)-小麦(Triticum aestivum)间作复合系统为研究对象。讨论核桃-小麦复合系统不同土层有机碳(SOC)密度的动态积累特征。结果表明,核桃-小麦复合系统0~100cm土层SOC密度呈逐年增加趋势,第11年时复合系统显著高于小麦单作,但与核桃单作差异不显著。细分各土层,除了20~40cm土层,其他各土层复合系统SOC密度均呈现逐年增加趋势。在浅层土壤(0~20cm)复合系统从第3年开始显著低于核桃单作,从第7年开始显著高于小麦单作;在较深土层(40~60、60~100cm)复合系统从第5年和第7年开始分别显著高于核桃和小麦两单作系统。SOC积累速度方面,复合系统0~100cm土层的SOC密度积累速度呈现逐年增加趋势,11a观测期内的平均积累速度为0.071 1kg·m^(-2)·a^(-1),分别是小麦单作和核桃单作的4.90倍和1.06倍。核桃-小麦复合系统与小麦单作相比可以同时提高浅层土壤(0~20cm)和较深土层(40~60、60~100cm)的SOC密度,与核桃单作相比最大优势是将SOC积累在较深土层。核桃-小麦复合系统与两单作系统相比均有较高的固碳潜力。

The influence of agroforestry system on soil organic carbon（SOC）density was investigated via a walnut（Juglans regia）-wheat（Triticum aestivum）intercropping system,which was a widespread local agroforestry model in northern Wei River of loess area.The results showed that the SOC density of the walnut-wheat intercropping system in 0-100 cm soil layer showed an increased trend gradually,which was significantly higher than that in the wheat monoculture system at the 11 th year,but there was no significant difference with walnut monoculture system.Subdivided each soil layer,except 20-40 cm soil layer,SOC density of the walnut-wheat intercropping system showed an increased trend gradually in all soil layers.In shallow（0-20 cm）soil layer,SOC density of the intercropping system was significantly lower than that in the walnut monoculture system since the 3 rd year,but significantly higher than that in the wheat monoculture system since the 7 th year.In deep（40-60,60-100 cm）soil layers,SOC density of the intercropping system was significantly higher than that in the walnut and wheat monoculture system since the 5 th and 7 thyear,respectively.In SOC density accumulation rate aspect,the SOC density accumulation rate of the intercropping system showed increased trend year by year in 0-100 cm soil layer,which average value during the 11-year observation period was 0.071 1 kg·m-2·a-1,4.90 and 1.06 times than that in the wheat and walnut monoculture system,respectively.Compared with the wheat monoculture system,the walnut-wheat intercropping system could improve SOC density in shallow（0-20 cm）and deep（40-60,60-100 cm）soil layers;compared with the walnut monoculture system,the most advantage of the intercropping system was that the carbon by sequestrated in deep soil layer.The agroforestry system had higher potential for carbon sequestration than the walnut and wheat monoculture systems.