中文摘要：

以秦岭西部小陇山沙坝林业试验基地为研究点,采用野外调查采样和室内分析相结合的方法,比较了不同发育阶段油松（Pinus tabulaeformis）和日本落叶松（Larix kaempferi）人工林林下凋落物分解层（H层）和表土层（A层）理化性质及酶活性的变化。结果表明,2种林型林下凋落物分解层各项土壤理化性质及酶活性指标均明显高于相应表土层。随着林龄的增加,除了土壤纤维素酶活性按幼龄林→中龄林→近熟林呈先升高后降低的变化趋势外,土壤荧光素二乙酸酯水解酶（FDA水解酶）、脱氢酶、蛋白酶、脲酶、酸性磷酸酶活性,以及有机质、全氮、有效氮、全磷、有效磷含量随林分的发育总体呈现先降低后升高的变化特征。从幼龄林到近熟林的发育过程中,日本落叶松林下各项土壤理化性质及酶活性指标变化波动性比油松大,说明日本落叶松的引进在一定程度上影响了土壤生物化学过程的强度和方向。除土壤脲酶与pH值之间以及酸性磷酶酸与速效氮之间以外,6种土壤酶活性与土壤pH值,有机质、全氮、速效氮、速效磷含量之间均呈在α=0.05或α=0.01水平上相关显著。

英文摘要：

At the Shaba Forest Experimental Station located in Xiaolongshan Mountain in the west of the Qinling Mountains,a study was carried out to compare differences in soil physicochemical properties and soil enzyme activity in the litter decomposing layer（H-horizon） and topsoil（A-horizon） between Pinus tabulaeformis and Larix kaempferi plantation stands at different development stages,by means of field investigation and laboratory analysis.Results show that all related indices were higher in the litter decomposing layer（H-horizon） than in the topsoil（A-horizon） at any development stages regardless of P.tabulaeformis or L.kaempferi;they all decreased first and then increased with development of the stands,except for the activity of soil cellulase,which presented a reverse trend;however,the variation fluctuated more vigorously with the L.kaempferi stands than with the P.tabulaeformis stands from juvenile to near-mature plantation,suggesting that the introduction of L.kaempferi influenced to some extent the intensity and direction of soil biochemical process.The relationships of the activities of all the enzymes with soil pH,organic matter,total nitrogen,available nitrogen and available phosphorus in the soil were positive and significant at α=0.05 or α=0.01,except for that of the activity of urase with pH and the activity of acid phosphatase with readily available N.