黄河三角洲盐碱地刺槐混交林对土壤脲酶活性的影响

以黄河三角洲盐碱地26年生刺槐＋臭椿混交林（RA）、刺槐＋白榆混交林（RU）和刺槐＋白蜡混交林（RF）为研究对象，以刺槐纯林（RP）和无林地（CK）为对照，研究刺槐混交林对土壤脲酶活性的影响。结果表明：1）同一林分中，土壤脲酶活性随土层深度的增加而减小；2）不同林分之间表现为刺槐混交林〉刺槐纯林〉无林地，RP、RU、RF、RA的脲酶活性分别是CK的4．02、4．74、5．08和5．01倍；3）在影响土壤脲酶活性的土壤因子方面，刺槐混交林较其纯林表现为降低了土壤密度、pH值和含盐量，增大了总孔隙度，增强了蓄水性能，增加了全氮、碱解氮和有机质的质量分数，增加了细菌和固氮菌的数量；4）总孔隙度、细菌、固氮菌、全N和有机质等土壤因子对刺槐混交林土壤脲酶活性的影响较大，建议用这些土壤因子作为评价刺槐混交林土壤脲酶活性的主要指标。

Effects of mixed Robinia pseudoacacia plantations on soil urease activities in saline land of the Yellow River Delta

In this paper, the soil urease activity and its influencing factors of mixed forests of Robinia pseudoacacia （R. pseudoacacia ＋ Ailanthus altissima plantation, R. pseudoacacia ＋ Ulmus pumila plantation and R. pseudoacacia ＋ Fraxinus chinensis plantation） at 26 years old were studied in the Yellow River Delta, and R. pseudoacacia plantation and bare land were taken as the contrast. The results showed that the urease activities were decreased with the soil layer deepening, meanwhile, the soil urease activities of four kinds of plantation increased by 4.02, 4.74, 5.08 and 5.01 times respectively, and that of mixed R. pseudoacacia plantation 〉 R. pseudoacacia plantation 〉 CK. In the aspect of soil factors which affect soil urease activity, compared with the R. pseudoacacia plantation, the mixed Robinia pseudoacacia plantations decreased soil density, pH value and salt content, increased the total porosity, enhanced the water storage capacity, increased the content of the total N, available N and organic C, and increased the number of the bacteria and azotobacter. This study found that the soil urease activity was strongly influenced by the total porosity, bacteria, azotobacter, total N and organic C, hence, they could be used as indicators for evaluating soil urease activity.