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为了解采伐林窗对马尾松人工林土壤有效氮的影响,在长江上游低山丘陵地区,选取人为采伐形成的马尾松(Pinus massoniana)人工林7种不同大小林窗(G1-G7,面积分别为100 m2、225 m2、400 m2、625 m2、900 m2、1 225 m2、1 600 m2)以及林下对照为研究对象,研究林窗中央和边缘铵态氮(NH4+-N)和硝态氮(NO3--N)的生长季变化.结果显示:林窗形成初期,其大小仅对土壤NH4+-N有显著影响,季节变化仅对NO3--N有显著影响,但两者对土壤NH4+-N、NO3--N均有显著的交互作用,林窗中央和边缘间土壤NH4+-N、NO3--N差异均不显著.具体为:(1)林窗土壤NH4+-N含量为4.30-11.99 mg kg-1,NO3--N含量为2.57-10.81 mg kg-1;不同大小林窗间NH4+-N、NO3--N仅在生长季中期总体随林窗增大先升后降;总的来看,面积为100-400 m2的林窗土壤NH4+-N、NO3--N较高.(2)在季节动态上,NH4+-N在生长季中期较低;NO3--N为中高末低.同时,生长季初期和末期NH4+-N高于NO3--N,而中期却相反.(3)较之林下,生长初期及末期部分林窗土壤NH4+-N、NO3--N降低.(4)相关分析表明,NH4+-N与微生物生物量氮(MBN)极显著正相关,NO3--N与土壤温度、MBN和有机质均极显著正相关,但土壤含水量对NH4+-N、NO3--N均无显著影响.因此,林窗对土壤温度及微生物活性的改变可能是影响土壤有效氮含量的主要因素.
In order to understand the effect of cutting transpiration on soil available N in Pinus massoniana plantation, seven different sizes of Gliwice (Pinus massoniana) plantation gaps (G1-G7, 100 m2, 225 m2, 400 m2, 625 m2, 900 m2, 1 225 m2, 1 600 m2) and under-stand control. The effects of NH4 + -N and nitrate nitrogen (NO3 - N). The results showed that, at the initial stage of Gap formation, the size of Gossypium hirsutum had only a significant effect on soil NH4 + -N and the seasonal variation had only significant effect on NO3 - N. However, N and NO3 - N, and there was no significant difference in the soil NH4 + -N and NO3 - N between the center and the margins of the canopy, which were as follows: (1) The content of NH4 + -N in the soil around the gap was 4.30-11.99 the content of NO3 - N was 2.57-10.81 mg kg-1. The NH4 + -N and NO3 - N in different sizes of ghosters increased first and then decreased with the increase of Gap in the middle of growing season. The NH4 + -N and NO3 - N in the alpine meadow with the area of 100-400 m2 is higher. (2) In the seasonal dynamics, NH4 + -N is lower in the middle of the growing season; NO3 - N is middle to high low At the same time, NH4 + -N is high at the beginning and end of the growing season NO3 - N, while the middle stage was the opposite. (3) Compared with undergrowth, NH4 + -N and NO3 - N in some Gap of Gap decreased at the beginning and end of growth. (4) Correlation analysis showed that NH4 + -N and microbial biomass (MBN). NO3 - N was significantly and positively correlated with soil temperature, MBN and organic matter, but soil moisture had no significant effect on NH4 + -N and NO3 - N. Therefore, Changes in temperature and microbial activity may be the main factors affecting soil available N content.