林地覆盖经营对雷竹林土壤氮素形态及硝化-反硝化作用的影响

Effects of Mulching Management on Soil Nitrogen,Nitrification and Denitrification in Phyllostachys praecox Stand

为探讨林地覆盖经营对雷竹林土壤氮素形态和硝化作用、反硝化作用的影响,选择了覆盖11、3、5 a和不覆盖(CK)4种处理的雷竹林,测定0 20 cm土层土壤全氮、铵态氮和硝态氮含量,并采用气压过程分离系统(Ba PS)测定土壤总硝化速率和反硝化速率。结果表明:随着覆盖年限的增加,试验雷竹林0 20 cm土层土壤全氮含量总体呈增加趋势,覆盖雷竹林全氮含量显著高于CK;土壤铵态氮和硝态氮含量均呈倒"N"型变化,覆盖3 a雷竹林的铵态氮和硝态氮含量最高;土壤铵硝比递增,覆盖3 a后显著提高,覆盖5 a后铵态氮是雷竹林土壤无机氮库的主要存在形式;土壤总硝化速率呈下降趋势,总体上与不同形态氮素含量、铵硝比相关性不显著,且相关性强度随覆盖经营年限的增加而减弱。土壤反硝化速率在覆盖3 a及以下年限时基本为0,覆盖5 a时显著提高,达69.53μg·kg-1·h-1。研究表明,林地覆盖经营对雷竹林土壤氮素形态及组分比例的影响较明显,削弱了土壤硝化作用,土壤氮素不是限制硝化作用进行的主要因子,长期覆盖经营会显著提高土壤反硝化作用,增大土壤氮素的损失。在实际生产中建议采用休闲式覆盖方式,连续覆盖时间不超过3 a。

In order to understand the influence of mulching management on soil nitrogen, nitrification and denitrifi- cation of Phyllostachys praecox stands, and furthermore to provide a theoretic reference for the sustainable manage- ment of Ph. praecox, four kinds of Ph. praecox stand were selected, which were under mulching for one year （ 1 a）, three years （3 a）, five years （5 a） and non-mulching （CK）, to measure the total nitrogen, ammonium nitro- gen, and nitrate nitrogen in the soil layer with the depth from 0 -20 cm. The gross nitrification and denitrificafion rates were measured by the barometrical separation technique. The results showed that, compared with the CK, the content of total nitrogen increased with prolonged mulching. The change law of ammonium nitrogen and nitrate nitro- gen in different trial stands followed a curve of high-low-high-low. The ratio of ammonium nitrogen and nitrate nitro- gen increased significantly with the extended response time, as the ratio was the highest in mulching for 3 a. The ammonium nitrate ratio in soil indicated a progressively increase and had a remarkable increase after mulching for 5 a. Ammonium nitrogen is the main form of inorganic nitrogen reservoir in Ph. praecox stand soil. However, thegross nitrification rate decreased gradually over time. There was a significant decrease in mulching for 3 a and 5 a. Generally speaking, the soil nitrification rate was not positively associated with nitrogen or ammonium nitrate ratio, only the soil nitrification rate in the soil types of CK was positively related to the ammonium nitrate content. The denitrification rates greatly increased in the soil mulching for 5 years, reached 69.53 μg·kg^-1·h^-1 , but the others was 0. Research indicated that forest management had a more significant impact on the component types and rates in the proportion of soil nitrogen, and weakened the soil nitrification. Soil nitrogen was not the major factor limiting nitrification. A long-term management will the loss of soil nitrogen. Casual types of mulching of less than 3 years. significantly improve the soil denitrification, which will increase are recommended in actual production, with continuous coverage