Responses of soil enzyme activity to freeze-thaw alternation in Greater Khingan Mountains, China.

We examined the effects of freeze-thaw cycles (0, 1, 3, 5, 7, 15 cycles) on the activities of urease, invertase, and proteinase in the different layers of the soil under the four typical stands in the cold temperate zone, i.e., Pinus pumila stand, Rhododendron-Betula platyphylla stand, Rhododendron-Larix gmelinii stand, Ledum-Larix gmelinii stand, with the indoor freeze-thaw simulation culture method being used. The relationship between soil enzyme activity and multiple physicochemical variables was analyzed during freeze-thaw alternation. The results showed that the activity of soil urease was firstly increased and then inhibited during freeze-thaw alternation. After freeze-thaw, urease activity did not differ from that without freeze-thaw. Invertase activity was firstly inhibited and then increased during freeze-thaw alternation, and was significantly increased by 8.5%-40.3% after freeze-thaw. Proteinase activity was firstly increased and then inhibited during freeze-thaw alternation, and was significantly decreased by 13.8%-68.9% after freeze-thaw. After freezing and thawing, there was significant positive correlation between urease activity and ammonium nitrogen and soil water content in Ledum-L. gmelinii stand and P. pumila stand, respectively, and proteinase activity had significant negative correlation with inorganic nitrogen concentration in P. pumila stand, Rhododendron-B. platyphylla stand, and Ledum-L. gmelinii stand. Invertase activity had significant positive correlation with organic matter in Rhododendron-L. gmelinii stand and Ledum-L. gmelinii stand.以寒温带偃松林、杜鹃-白桦林、杜鹃-落叶松林和杜香-落叶松林4种典型林分下土壤为研究对象,采用室内冻融模拟培养方法,研究冻融循环次数(0、1、3、5、7、15次循环)对各林分不同土层脲酶、蔗糖酶和蛋白酶活性的影响,分析冻融过程中各林分下土壤酶活性与多元理化变量间的相关性。结果表明: 冻融对土壤脲酶活性呈先提高后抑制作用,冻融结束后其活性较未冻融均无显著变化;冻融对蔗糖酶活性呈先抑制后提高作用,冻融结束后蔗糖酶活性显著提高8.5%～40.3%;冻融对蛋白酶活性呈先提高后抑制作用,冻融结束后蛋白酶活性显著降低13.8%～68.9%。冻融结束后,杜香-落叶松林和偃松林下脲酶分别与铵态氮和含水量呈显著正相关,偃松林、杜鹃-白桦林和杜香-落叶松林下蛋白酶与无机氮化合物呈显著负相关。杜鹃-落叶松林和杜香-落叶松林下蔗糖酶与有机质呈显著正相关。.