川中丘陵柏木低效林开窗补阔初期土壤养分和酶活性变化

Soil nutrient and enzymatic activity changes amidst the early stage of gap and mixed transformation of low-efficiency Cupressus funebris in the hilly area of the Central Sichuan Basin

以川中丘陵区德阳市旌阳区37年生柏木人工低效林为研究对象,采用不同开窗补阔面积(50、100、150、200m^2)的改造方式,研究该林地土壤养分和酶活性初期变化规律.结果表明:与对照林分相比,开窗补阔之后0-5 cm土层p H值、全磷和速效磷含量均有升高,开窗补阔面积150 m^2时土壤多酚氧化酶和脲酶活性较对照林有显著提高(P<0.05),但同土层全碳含量和碳氮比随开窗补阔面积增大而减少,全氮含量和碱性磷酸酶活性则呈先减少后升高的折线趋势;开窗补阔面积为100 m^2时在5-20 cm土壤中各全量养分在各处理间处于较高水平,β-葡萄糖苷酶/全碳、碱性磷酸酶/全碳、脲酶/全碳和土壤酶/全氮在开窗补阔面积为50 m^2样地的5-20 cm土壤较对照林均有显著升高(P<0.05);土壤全碳、全氮与土壤酶关系密切;各种养分和酶活性的盈缺关系揭示了开窗补阔改造的重要性.综合来看,开窗补阔面积为100 m^2对土壤养分和土壤酶活性影响效果最佳.

In this study, a transformation mode with different gapping and mixed areas （respectively of 50, 100, 150 and 200 m^2） is used in the 37-year old low-efficiency Cupressus funebris plantation, located in Jingyang District, Deyang City, a hilly area of Central Sichuan, to examine change patterns of soil nutrients and enzymatic activity during early stage of the transformation. The results suggest that compared to the control （CK）, the pH value, contents of total phosphorus and available phosphorus in the 0-5 cm layer of soil have all increased following the gap and mixed transformation. When the area for gap and mixed transformation was 150 m^2, the polyphenol oxidase and urea enzyme activity has significantly increased （P 〈 0.05） compared to those of the CK, but the total carbon content and the carbon-nitrogen ratio declined along with the increase of gap and mixed area, while the total nitrogen content and the alkaline phosphatase activity exhibited a first rising and then falling trend. When the gap and mixed area was 100 m^2, total nutrients in the 5-20 cm layer of soil have maintained relatively high levels across all treatment groups; β-glucosidase/total carbon, alkaline phosphatase/ total carbon, urease/total carbon and soil enzyme/total nitrogen in the 5-20 cm^2 have all significantly increased （P 〈 0.05） when the sample area was 50m^2. A close correlation between total carbon, total nitrogen and enzyme of the soil has been demonstrated; the significance of gap and mixed transformation has been revealed by the surplus-deficit relationship between various nutrients and enzyme activity. Comprehensively speaking, an optimal effect on soil nutrients and enzyme activity can be achieved when the gap and mixed area is 100 m^2.