樟子松天然林土壤碳氮含量与水解酶活性坡位差异及月动态

Slope Locational Differences and Monthly Dynamics of Soil Carbon and Nitrogen Contents and Hydrolases Activity in the Natural Forest of Pinus sylvestris var. mongolica

【目的】研究大兴安岭地区樟子松天然林土壤的碳氮含量与水解酶活性的坡位差异和月份动态,探究土壤碳氮含量与水解酶活性的关系,以期为阐明土壤碳氮转化酶学机制及森林土壤可持续利用提供理论依据。【方法】2018年5—10月每月中旬,在大兴安岭漠河地区樟子松天然林坡地设置试验地。分别在试验地上、中、下坡位各设置3块20 m×30 m的樟子松林试验样地,每样地选3个取样点,每取样点清除枯枝落叶层后,记录不同土深(2.5、7.5、15、25 cm)处土壤温度。同时采集每个取样点不同土层(0~5、5~10、10~20和20~30 cm)的土壤样品测定土壤含水率、碳氮含量(有机碳、全氮)及水解酶(脲酶、蛋白酶、蔗糖酶、纤维素酶)活性。【结果】土壤的有机碳及全氮含量随土层加深而降低,随坡位升高而减少,但坡位差异不显著(P>0.05);0~5、5~10、10~20和20~30 cm土层的有机碳含量分别为68.53~80.38、40.28~46.66、15.86~21.08和11.91~13.79 g·kg-1,土壤全氮含量分别为5.34~5.96、2.98~3.68、2.35~2.61和1.54~1.75 g·kg-1;土壤脲酶、蛋白酶、蔗糖酶及纤维素酶活性随土层加深而降低;随坡位降低,土壤脲酶及蔗糖酶活性增高,蛋白酶与纤维素酶活性降低;月动态分析显示,土壤有机碳和全氮含量高峰期均为9月,酶活性高峰期集中在7—8月;相关分析表明,土壤碳氮(有机碳、全氮)含量与水解酶(脲酶、蔗糖酶、纤维素酶、蛋白酶)活性和含水率均极显著正相关(P<0.01),土壤温度与有机碳含量显著正相关(P>0.05)、与全氮含量显著负相关(P<0.05)。【结论】大兴安岭地区樟子松天然林土壤碳氮含量与水解酶活性随土层加深而降低,土壤碳氮含量与酶活性的坡位差异不显著(P>0.05),有机碳和全氮含量高峰期为9月,土壤水解酶活性高峰期集中在7—8月。土壤碳氮含量与水解酶活性极显著相关(P<0.01),土壤温湿度对碳氮含量与酶活性具有显著影响(P<0.05)。

【Objective】The study was conducted to reveal the slope locational differences and monthly dynamics of soil carbon and nitrogen contents and hydrolase activities in natural forest of Pinus sylvestris var.mongolica Litv.The correlation between carbon/nitrogen contents and hydrolase activities,and the effect of soil temperature and moisture.【Method】The study was performed in a natural forest of Pinus sylvestris var.mongolica located in Mohe Town,Daxing’anling Region.In the middle of every month from May to October,2018,three blocks(20 m×30 m)in every slope location(upper slope,middle slope,lower slope)were selected as sample region.Three sampling points were selected in every sample region.Soil temperatures at depths of 2.5 cm,7.5 cm,15 cm,25 cm were measured after removing litters.Soil samples at different depths(0-5,5-10,10-20,and 20-30 cm),on different slope locations,and in different months were collected by excavating soil profiles.Subsequently,the moistures,organic carbon contents,total nitrogen contents,and hydrolase(urease,protease,sucrase,and cellulase)activities of soil samples were determined in laboratory.【Result】Result showed that the contents of carbon and nitrogen were decreased with the increase of soil depth,and increased with the lowering the slope locations,and the highest contents of both were showed in September.The soil organic carbon contents in the soil layers of depth 0-5,5-10,10-20,20-30 cm were 68.53-80.38,40.28-46.66,15.86-21.08,and 1.91-13.79 g·kg-1 respectively,and soil total nitrogen contents in these layers 5.34-5.96,2.98-3.68,2.35-2.61,and 1.54-1.75 g·kg-1 respectively.However,organic carbon contents and total nitrogen contents among slope locations did not show great differencs(P>0.05).Additionally,activities of urease,protease,sucrase,and cellulase were decreased with soil depth,urease and sucrase maintained higher activities in a lower slope location,but the protease,cellulase did the opposite.Furthermore,hydrolases always showed their highest activities in July or August.Finally,the results also indicated that contents of soil carbon and nitrogen were significantly and positively correlated with activities of detected soil hydrolytic enzymes(P<0.01);soil carbon and nitrogen contents were significantly and positively correlated with soil moisture(P<0.01);and soil temperature was significantly and positively correlated with soil carbon content(P>0.05),but negatively correlated with total soil nitrogen content(P<0.05).【Conclusion】The study demonstrated that soil carbon/nitrogen contents and hydrolase activities in P.sylvestris var.mongolica forest maintains a common pattern that 0-5 cm>5-10 cm>10-20 cm>20-30 cm;contents and activities at different slope locations were indistinguishable(P>0.05);the highest soil carbon and nitrogen contents were found in September;and the highest hydrolase activities were found from July to August.It also proved that contents of carbon and nitrogen were significantly correlated with hydrolytic enzyme activities(P<0.01);ant the soil temperature and moisture had significan affects on the carbon and nitrogen contents and hydrolase activities(P<0.05).