模拟N沉降下三种林分土壤营养动态分析

通过模拟N沉降实验,设置对照(CK,0 g N m~(-2)a~(-1));低氮(LN,5 g N m~(-2)a~(-1));中氮(MN,10 g N m~(-2)a~(-1));高氮(HN,15 g N m~(-2)a~(-1))4种N处理,以NH_4NO_3为外源N来研究福建省三明格氏栲自然保护区内板栗人工林、观光木人工林及米槠天然林0—10 cm土层养分变化动态。结果表明:N沉降会使板栗人工林土壤显著酸化,P含量降低,在一些时间段内,中高水平的N沉降会显著降低有机C、全N和速效N含量,中或低水平N沉降会显著降低土壤全P和速效P含量,而从第6个月起只有LN处理会显著降低土壤K含量。N沉降总体上会不同程度地提高观光木人工林土壤p H值、有机C、全N和速效N含量,有时影响会达显著或极显著水平;比较而言,LN和HN处理更会造成土壤全P的富集,而MN处理对速效P的影响更显著;LN和HN处理也会显著增加K含量,且以LN处理的效果更稳定。总体上N沉降量越大米槠天然林土壤酸化越显著;N沉降会使其有机C和速效P量显著波动;实验期间,HN处理会显著降低土壤全N和速效N量,而LN与MN处理则会使速效N和K含量增加;在4种处理下全P含量会呈相同趋势波动,差异不显著。

Analysis of the dynamic soil nutrients of a Castanopsis carlesii, Chinese Chestnut & Sightseeing Wood natural forest under simulated nitrogen deposition

In this study, four treatments were installed in Castanopsis carlesii natural forests, a Chinese chestnut plantation and a Sightseeing wood plantation at Sanming City, Fujian Province, China, for a simulated nitrogen deposition experiment:control (CK, 0 g N m^-2 a^-1), low nitrogen (LN, 5 g N m^-2 a^-1), medium nitrogen (MN, 10 g N m^-2 a^-1), and high nitrogen (HN, 15 g N m^-2 a^-1). A solution of NH₄NO₃ was applied as the nitrogen source. The results show that under the experimental conditions, N significantly acidified the soil in the Chinese chestnut plantation, decreasing the mass fraction of P. Over some period, HN treatment can significantly reduce the mass fraction of organic C, total N, and available N; low levels of N deposition can significantly reduce the mass fraction of soil total P and available P; and from six months, only the LN treatment significantly reduced the content of soil K. N settlement generally improved soil pH, organic C, total N, and the available N mass fraction in the Sightseeing wood plantation, and sometimes the impact was significant or extremely significant. In comparison, the LN and HN treatments caused enrichment of the soil total P mass fraction, and the effect of the MN treatment on available P was significant; the LN and HN treatments also significantly increased the mass fraction of K, and the effects of the LN treatment were more stable. With N settlement rose, the acidification of the soil was more significant in the Castanopsis carlesii natural forest; the N settlement of organic C and available P fluctuated significantly. During the experiment, HN treatment significantly reduced the soil total N and available N; LN and MN treatment increased the mass fractions of available N and K. The mass fraction of P showed the same trend of fluctuations in all 4 treatments, and the difference was not significant.