增温对青藏高原高寒沼泽草甸不同时期土壤酶活性的影响

Effects of experimental warming on soil enzyme activities in different seasons of the alpine swamp meadow ecosystem on the Qinghai-Tibet Plateau

为研究青藏高原多年冻土区土壤酶活性对气候变暖的响应特征,选择北麓河地区高寒沼泽草甸为研究对象,利用开顶式生长室(OTC)进行模拟增温试验,在7月份、12月份分别对增温和对照样地土壤进行分层取样,并对不同深度土壤脲酶、蔗糖酶、过氧化氢酶和磷酸酶的活性进行分析测定。结果表明:在夏季7月份,增温作用下近地表月平均气温升高4.55℃,不同深度的土壤脲酶、蔗糖酶、过氧化氢酶和磷酸酶活性均有降低趋势,但未达到显著水平(P>0.05)。土壤蔗糖酶活性与土壤水分和根系生物量呈显著相关关系;在冬季12月份,增温作用下近地表月平均温度升高6.64℃,不同深度的土壤脲酶、蔗糖酶、过氧化氢酶和磷酸酶活性均有所提高,且在20—50 cm深度的土壤蔗糖酶和磷酸酶活性和40—50cm深度的土壤脲酶和过氧化氢酶活性变化均达到显著水平(P<0.05)。四种土壤酶活性与土壤温度和水分均呈显著相关关系。在深度变化上,夏季增温样地四种土壤酶活性总体随土层深度增加而降低,而冬季随土层深度增加而显著升高(P<0.05)。增温处理下,不同土层深度冬季四种土壤酶的活性总体均大于夏季,且在40—50 cm深度上差异显著(P<0.05)。增温对高寒沼泽草甸土壤酶活性的影响冬季大于夏季。夏季土壤酶活性受土壤水分、根系生物量降低等因素的影响,对增温的响应不显著。冬季土壤酶活性受不同深度土壤水分、温度的影响,在土壤温度、水分含量均较高的土层表现出较高的活性。

In order to study the response characteristics of soil enzyme activities of the alpine swamp meadow ecosystem distributed in permafrost region of the Qinghai-Tibet Plateau to climate warming, an experimental site with alpine swamp meadow ecosystem was selected in the Beiluhe area and an Open Top Chamber(OTC) method was used to conduct a warming experiment. In July and December of 2019, soil samples at the warming and the control plots were collected in soil depths of 0-10 cm, 20-30 cm, and 40-50 cm, respectively, and activities of soil urease, invertase, catalase and phosphatase at the different soil layers were analyzed. The results showed that in July, when the average monthly near-surface air temperature at the warming plots was 4.55 ℃ higher than that at the control plots, the soil urease, invertase, catalase and phosphatase activities of different soil depths had a decreasing tendency, but did not reach a significant level(P>0.05). Soil invertase activity was significantly correlated with soil moisture and root biomass(P<0.05). In December, at the condition that the average monthly near-surface air temperature at the warmed plots was 6.64 ℃ higher than that at the control plots, the activities of soil urease, invertase, catalase and phosphatase at different depths all increased, but only the activities of soil invertase and phosphatase at the depth of 20-50 cm, and the activities of soil urease and catalase at the depth of 40-50 cm reached significant levels(P<0.05). The activities of the four soil enzymes were significantly correlated with soil temperature and moisture(P<0.05). For the changes of enzyme activities in depth, the four soil enzyme activities in summer generally decreased with the increase of soil depth(P<0.05). In winter, the four soil enzyme activities all rose significantly with the increase of soil depth(P<0.05). At the warming plots, the activities of the four soil enzymes in different soil depths in December were generally greater than those in July, and the difference was significant at 40-50 cm depth(P<0.05). The effect of warming on soil enzyme activity in winter was greater than that in summer. In summer, soil enzyme activity was mainly affected by soil moisture and root biomass, and its response to warming was not significant. While in winter, the soil enzyme activities were usually restricted by soil moisture and temperature at different depths, and the soil enzyme activities were higher at the depths with high soil temperature and water content.