摘要:
该文对科尔沁沙地章古台地区围栏和未围栏的樟子松人工林土壤 NH+4 -N、NO-3 -N、矿质N和微生物体N进行了一个生长季的观测.结果表明,无论围栏还是未围栏林地,土壤NH+4 -N、NO-3 -N和矿质N含量均很低.围栏林地中土壤NH+4 -N和矿质N比未围栏林地高(P＜0.001),土壤NO-3 -N的结果则相反(P＜0.001),而土壤微生物体N差异不明显(P＜0.05).方差分析表明,土壤NH+4 -N、NO-3 -N、矿质N和微生物体N均存在明显的月份之间差异(P＜0.001);土壤NH+4 -N、NO-3 -N和矿质N表现为明显的季节性的单峰变化;土壤微生物体N并不是完全随季节波动,而与土壤含水量存在极强的相关性(P＜0.001).林分和月份对土壤NH+4 -N和矿质N的交互作用十分明显(P＜0.001),对土壤微生物体N作用明显(P＜0.05),而对土壤NO-3 -N作用不明显(P＜0.05).可见,与未围栏相比,围栏对提高樟子松林N养分有效性、林分生产力和稳定性以及保护环境都是有利的.为此,建议对章古台地区的樟子松人工林实行禁牧和禁止凋落物收集等管理措施.
Abstract:
Dynamics of soil NH+4 -N, NO-3 -N, mineral N and microbial biomass N were measured in two management systems (fenced and unfenced) of Pinus sylvestris var. mongolica plantations in Zhanggutai sandy lands, north China. The results show that the contents of soil NH+4 -N, NO-3 -N, mineral N and microbial biomass N are low. Soil NH+4 -N and mineral N are higher in the fenced stands than those in the unfenced stands (P＜0.001), but soil NO-3 -N reverses (P＜0.001), and microbial biomass N is not different (P＜0.001) in both types of stands. Each soil NH+4 -N, NO-3 -N, mineral N and microbial biomass N is distinctly different for months from April to October according to variance analysis(P＜0.001). Soil NH+4 -N, NO-3 -N and mineral N show a normal seasonal change with highest concentrations in August and lowest in April and October. But soil microbial biomass N does not show a seasonal fluctuation, and is strongly correlated with the soil moisture (P＜0.001). The interactions of stands and months on soil NH+4 -N and mineral N are significant (P＜0.001), these interactions on soil microbial biomass N are evident (P＜0.05), and not significant on soil NO-3 -N (P＜0.05). All of these mentioned above demonstrates that it is advantageous to improve soil N availability, stand production and protect environment, when the P. sylvestris var. mongolica stands on sandy soil are intensively managed (from unfenced to fenced). Then authors suggest that the prohibition of grazing and litter raking should be popularized in order to avoid stand decline and to maintain stand stability.
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