湿地松林土壤生化特性和酶活性对模拟硫沉降的响应

Effects of Sulphur Deposition on Soil Biochemical Properties and Enzymes Activities in Pinus elliottii Plantation

以亚热带湿地松人工林为研究对象,通过3种水平(对照CK:pH 6.5;低硫LS:pH 4.5;高硫HS:pH 2.5)的模拟硫沉降控制试验,分析土壤生化特性及酶活性对硫添加的响应。结果表明:(1)硫输入促进了土壤酸化,0—5 cm土层土壤pH在HS处理下显著降低,5—10 cm土层土壤pH在LS和HS处理下显著降低(P<0.05);(2)硫输入对土壤有机碳库存在一定影响,土壤总有机碳(TOC)对硫输入无显著响应,但土层间的差异性显著增加(P<0.05),土壤可溶性有机碳(DOC)受影响有限,5—10 cm土层微生物量碳(MBC)LS显著降低(P<0.05);(3)硫输入对土壤有效氮库影响存在差异,土壤可溶性有机氮(DON)、铵态氮(NH4^+—N)尚未表现出显著变化,土壤硝态氮(NO3^-—N)、土壤微生物量氮(MBN)均在HS处理下显著降低,且硫输入加剧土层间的差异性(P<0.05);(4)硫输入抑制了酶活性,土壤脲酶活性在HS处理下显著降低(P<0.05),土壤蔗糖酶活性无显著变化,但硫输入均弱化了土层间酶活性的差异性。综合分析所有处理下的土壤生化性质和酶活性等指标发现,对硫添加响应敏感的是土壤pH和酶,土层是另外一个主要影响因子,硫添加和土层的交互作用则影响有限。采用Pearson分析得出,硫输入改变了土壤生化特性、酶活性等指标间的相关性程度。可见,酸雨对土壤酸化的影响是一个逐渐累积的过程,外源性硫添加对土壤碳氮及酶活性的影响存在一定差异,这可为硫沉降环境胁迫下森林管理提供科学依据。

Taking the subtropical pine plantation as research object,the soil biochemical properties and enzymes activities were studied using three simulated sulfur deposition experiments with different levels(control treatment,CK:pH 6.5;low sulfur treatment,LS:pH 4.5;high sulfur treatment,HS:pH 2.5).The results showed that:(1)Sulfur input had a significant effect on soil acid,HS significantly reduced the 0—5 cm soil pH,both LS and HS treatments could significantly reduced the 5—10 cm soil pH(P<0.05).(2)Sulfur input had a certain effect on soil organic carbon pool.Soil total organic carbon(TOC)had no significant response to sulfur input,but its differences increased in soil layers(P<0.05).The impact of sulfur input on soil dissolved organic carbon(DOC)was limited.HS significantly decreased soil microbial biomass carbon(MBC)from 5—10 cm soil layer and increased the differences in soil layers(P<0.05).(3)Sulfur input had different effect on soil effective nitrogen pool.Soil dissolved organic nitrogen(DON)and ammonium nitrogen(NH4^+—N)had no significant change.HS treatments significantly decreased soil nitrate nitrogen(NO3^-—N)and soil microbial biomass nitrogen(MBN)and increased the differences in soil layers(P<0.05).(4)Sulfur input inhibited the activity of soil enzyme.HS significantly decreased soil urease activity(P<0.05).Soil invertase activity had no significant changes,but sulfur input reduced the differences of enzymes activities in the two soil layers.The comprehensive analysis of soil biochemical characteristic and enzymes activities indicators from all treatments showed that soil pH and enzymes had sensitive responses to sulfur input.Soil layer was another major impact factor.But the interaction between sulfur addition and soil layer had the limited impact.Through the Pearson method,sulfur input changed the correlation of the soil biochemical properties and enzymes activities.The effect of simulated acid rain on soil acidification was a gradual process of accumulation.The effect of exogenous sulfur addition on soil carbon,nitrogen and enzymes activities was different.The results could provide scientific basis for forest management under environmental stress of sulfur deposition.