Changes of soil enzyme activity and the stoichiometry of carbon,nitrogen,and phosphorus in Larix principis-rupprechtii plantations at different ages
In order to provide theoretical basis for rational management of Larix principis-rupprechtii plantations,physical and chemical properties enzyme activities,and ecological enzyme stoichiometry of soils at different forest ages(15,25,35,45 and 55 years)and two depths(0-15 and 15-30 cm)were determined and their relationships were analyzed.Results showed that:(1)The contents of soil organic carbon and total nitrogen increased with the increase of forest age,while the soil water content,total phosphorus,and total potassium increased at first and then decreased.The soil water content,organic carbon,total nitrogen,and total phosphorus in surface soil(0-15 cm)were significantly higher than those in the deep soil(15-30 cm),while the content of total potassium in soils showed the opposite changes.(2)The activities of β-1,4-lucosidase,β-D-cellobiohydrolase,β-1,4-xylosidase,leucine amino peptidase,β-1,4-N-acetyl-glucosaminidase,and acid phosphatase increased with the increase of forest age and decreased with the deepening of soil depth.(3)The activities of six soil enzymes were positively correlated with soil water content,the content of organic carbon,and total nitrogen(P＜0.05),while negatively correlated with soil pH and the content of total potassium.Based on the results of redundancy analysis and stepwise regression,the primary factors influencing soil enzyme activity were soil pH,soil water content,the ratio of soil nitrogen to phosphorus,and soil nutrient and the primary factors influencing soil enzyme stoichiometry was soil nutrient.(4)The content of soil phosphorus in the study area was extremely poor(all less than 0.2 g/kg).According to the ratio of soil nitrogen to phosphorus,the growth of the 15-35 years L.principis-rupprechtii was limited by nitrogen and phosphorus,and 45 and 55 years L.principis-rupprechtii were mainly limited by the content of soil phosphorus.The degree of nitrogen limitation decreased,while the degree of phosphorus limitation increased with the deepening of soil depth.(5)Soil enzyme stoichiometric nitrogen to phosphorus ratio(0.77-0.84)and enzyme stoichiometric nitrogen to phosphorus ratio(0.84-0.92)were higher than the global average(0.44 and 0.62).The vector angle of enzyme activity was less than 45° and decreased with the deepening of soil depth.The results showed that soil microorganisms were strongly restricted by nitrogen and phosphorus,and the degree of nitrogen limitation increased with the deepening of soil depth.Therefore,the input of exogenous nitrogen and phosphorus should be considered in the management of plantations to alleviate the nutrient limitation of L.principis-rupprechtii plantations.
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