武夷山亚热带常绿阔叶林土壤养分及酶活性对氮沉降的响应

Responses of Soil Nutrients and Enzyme Activities to Nitrogen Deposition in Subtropical Evergreen Broad-leaved Forest in Wuyishan Mountain

通过原位进行对照[N_0,0 kg/(hm^2·a)]、低氮[N_1,50 kg/(hm^2·a)]、中氮[N_2,100 kg/(hm^2·a)]和高氮[N_3,150 kg/(hm^2·a)]处理,对武夷山亚热带常绿阔叶林进行了为期12个月的模拟氮沉降试验,研究了土壤养分和酶活性及其对模拟氮沉降的响应。结果表明:(1)氮沉降对常绿阔叶林土壤有机碳、全氮、全钾、有效磷和有效氮含量起到一定的增加作用,对土壤全磷没有显著的影响(p>0.05),而高浓度氮沉降会引起土壤养分的降低,其中土壤有效养分(有效磷和有效氮)对氮浓度的响应较大。(2)土壤微生物量碳和氮随氮浓度的增加呈先增加后降低的趋势,大致表现为:N_2>N_1>N_3>N_0,模拟氮沉降处理下土壤微生物量磷差异均不显著(p>0.05)。(3)氮沉降对常绿阔叶林土壤Bglu活性、Bxyl活性、NAG活性、Phos活性和Pero活性起到一定的增加作用,对对Phox活性没有显著的影响(p>0.05)。(4)相关性分析表明:土壤养分、酶活性与土壤含水量具有一定的相关性,其中0—5 cm土壤含水量相关系数R^2高于5—10 cm土壤含水量相关系数;土壤养分、酶活性与土壤温度具有一定的相关性,其中0—5 cm土壤温度相关系数R^2高于5—10 cm土壤温度相关系数,说明表层(0—5 cm)土壤温度和水分对土壤养分、酶活性的影响较大。

This study was conducted in in a subtropical evergreen broad-leaved forest in Wuyishan Mountain and aimed at measuring soil nutrients and soil enzyme activities and the effects of nitrogen deposition. Nitrogen addition experiments were carried out within the forest selected in 2016. Four N addition treatments with three replicates were established in mature forest: control, no N [N0, 0 kg/(hm2·a)], low N [N1, 50 kg/(hm2·a)], medium N [N2, 100 kg/(hm2·a)] and high N (N3, 150 kg/(hm2·a))The results showed that:(1) the soil temperature and soil moisture content had the consistent change trend with the highest in January and the lowest in August;(2) there was a significant effect of nitrogen deposition on soil nutrients, and then increased soil nutrients, while there was no significant effect of nitrogen deposition on soil total phosphorus(p>0.05);(3) soil microbial biomass carbon and nitrogen increased first and then decreased with the increase of nitrogen concentration, while there was no significant effect of nitrogen deposition on soil microbial biomass phosphorus(p>0.05);(4) soil Bglu, Bxyl, NAG, Phos, Phox, Pero enzyme activity increased first and then decreased with the increase of nitrogen concentration, and then increased soil enzyme activities, while there was no significant effect of nitrogen deposition on soil Phox enzyme activity(p>0.05);(5) correlation analysis showed that correlation coefficient between soil water content and soil nutrients and soil enzyme activity in 0—5 cm layer was higher than correlation coefficient in 5—10 cm layer;similarly, correlation coefficient between soil temperature and soil nutrients and soil enzyme activity in 0—5 cm layer was higher than correlation coefficient in 5—10 cm layer, suggesting that soil nutrients and soil enzyme are more dependent on soil temperature.