模拟酸雨处理下尾巨桉凋落叶pH值及养分元素释放模式

pH Value and Release Pattern of Nutrient Elements in Leaf Litters of Eucalyptus urophylla×E.grandis under Simulated Acid Rains

以广西国有高峰林场6年生尾巨桉(Eucalyptus urophylla×E.grandis)人工林的凋落叶为试验材料,采用随机区组试验设计,以H2SO4和HNO3比为8∶1配制5种pH值(3.0、4.0、5.0、5.6和6.0),模拟不同酸雨溶液对尾巨桉凋落叶进行处理,研究凋落叶养分释放模式。结果表明,不同酸雨处理下的凋落叶pH值和含水率差异显著。相同酸度处理下,凋落叶pH值在5月最高;相同月份下,凋落叶pH值在pH 3.0处理下最低,pH 6.0处理下最高,随酸雨pH值增大而增大。随着时间的推移,凋落叶含水率逐渐增大;同月采集的凋落叶含水率随酸雨的pH值增大而增大。分解过程中,凋落叶氮含量在pH 5.0处理下最低,磷和钾含量随酸雨pH值增大而减少,钙和镁含量随酸雨pH值增大而增大。氮含量随时间推移而增加,钾和钠含量随时间推移而减少,磷含量缓慢增加后降低,钙含量在6月增加后逐渐下降并保持稳定,镁含量呈W形。凋落叶氮、磷、钾、钙、镁和钠含量在不同酸雨处理下差异不显著;在不同处理月份间,除钙含量外均差异显著。模拟酸雨的pH值与凋落叶的pH值呈显著正相关;分解时间与凋落叶pH值、磷和钾含量呈显著负相关,与凋落叶含水率、钙和镁含量呈显著正相关。尾巨桉凋落叶对不同pH值的模拟酸雨有较强的缓冲作用。

Using leaf litters of six-year-old Eucalyptus urophylla×E.grandis plantations in Guangxi state-owned Gaofeng forest farm as experimental material,and preparing five pH levels(3.0,4.0,5.0,5.6 and 6.0)according to ratio of H2SO4 to HNO3 of 8∶1 to simulate treatment of E.urophylla×E.grandis leaf litters with different acid rain solutions by randomized block experimental design,nutrient release pattern of leaf litters was studied.Results showed that pH value and water content of leaf litters under different treatments were significantly different.Under the same acidity treatment,pH value of leaf litters was the highest in May.In the same month,pH value of leaf litters treated with pH 3.0 was the lowest and that of leaf litters treated with pH 6.0 was the highest,which increased with increase of pH value of acid rain.With the passage of time,moisture content of leaf litters increased gradually.Moisture content of leaf litters collected in the same month increased with increase of pH value of acid rain.In the de⁃composition process,N content of leaf litters was the lowest under pH 5.0 treatment.Contents of P and K decreased with increase of pH value of acid rain,while contents of Ca and Mg increased.N content increased with time;contents of K and Na decreased;P content decreased after slow increase;Ca content gradually decreased and remained stable after increasing in June;Mg content showed W shape.Contents of N,P,K,Ca,Mg and Na in leaf litters under different treatments had no significant differences,and were significantly different among different treatment months except for content of Ca.There was significant positive correlation between pH value of simulated acid rain and that of leaf litters.There was significant negative correlation between decomposition time and pH value,contents of P and K of leaf litters,and significant positive correlations between decomposition time and moisture content,contents of Ca and Mg of leaf litters.Leaf litters of E.urophylla×E.grandis had strong buffer effect on simulated acid rain with different pH values.