近日，國(guó)際土壤學(xué)刊物Soil Biology and Biochemistry在線刊登了中科院沈陽(yáng)應(yīng)用生態(tài)研究所研究人員的最新研究成果“Effects of NH4+ and NO3− on litter and soil organic carbon decomposition in a Chinese fir plantation forest in South China”,，文章中,，研究人員揭示了在氮素對(duì)凋落物和土壤有機(jī)碳的影響研究中取得的最新進(jìn)展。
凋落物和土壤有機(jī)碳是人工林土壤養(yǎng)分的主要來(lái)源,，其分解過(guò)程對(duì)維持杉木人工林土壤質(zhì)量及肥力具有重要意義,。氮素是影響凋落物及土壤有機(jī)碳分解速率的重要控制因素，以往研究多將凋落物和土壤分開(kāi)考慮,，而凋落物和土壤是一個(gè)不可分割的完整系統(tǒng),，這個(gè)系統(tǒng)如何對(duì)氮素改變做出響應(yīng)仍知之甚少。
中國(guó)科學(xué)院沈陽(yáng)應(yīng)用生態(tài)研究所張偉東博士采用13C穩(wěn)定同位素技術(shù),，對(duì)杉木凋落物-土壤系統(tǒng)分解開(kāi)展了相關(guān)研究,。結(jié)果發(fā)現(xiàn)，杉木凋落物誘導(dǎo)的激發(fā)效應(yīng)至少可以維持87天,，且激發(fā)效應(yīng)隨著培養(yǎng)時(shí)間的延長(zhǎng)而呈下降趨勢(shì),。無(wú)機(jī)氮在培養(yǎng)前期促進(jìn)凋落物分解并誘導(dǎo)更強(qiáng)的正激發(fā)效應(yīng)，在培養(yǎng)后期則對(duì)凋落物分解具有抑制作用,，并誘導(dǎo)出顯著的負(fù)激發(fā)效應(yīng),。
研究還發(fā)現(xiàn)，銨態(tài)氮和硝態(tài)氮對(duì)杉木凋落物和土壤有機(jī)碳分解影響的程度不同,。雖然凋落物在一定時(shí)期促進(jìn)了土壤有機(jī)碳分解,，但在培養(yǎng)結(jié)束時(shí)，土壤仍呈現(xiàn)正的碳平衡,，這主要是因?yàn)楸患ぐl(fā)的碳仍然小于凋落物在土壤中的存留量,；此外，無(wú)機(jī)氮添加進(jìn)一步增加了土壤碳平衡,。
該研究表明施加氮肥不僅可以提高杉木人工林養(yǎng)分,，而且對(duì)維持土壤有機(jī)碳穩(wěn)定性具有重要意義。該項(xiàng)目得到了國(guó)家自然科學(xué)基金的支持,。（生物谷Bioon.com）
doi:10.1016/j.soilbio.2011.12.004
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Effects of NH4+ and NO3− on litter and soil organic carbon decomposition in a Chinese fir plantation forest in South China
Weidong Zhanga, b, Silong Wanga, b
Soil organic carbon (SOC) dynamics and nutrient availability determine the soil quality and fertility in a Chinese fir plantation forest in subtropical China. Uniformly 13C-labeled Chinese fir (Cunninghamia lanceolata) and alder (Alnus cremastogyne) leaf litter with or without 100 mg NH4+ or NO3− were added to the soil. The purpose was to investigate the influence of N availability on the decomposition of the litter and native SOC. The production of CO2, the natural abundance of 13C–CO2, and the inorganic N dynamics were monitored. The results showed that Chinese fir (with a high C:N ratio) and alder (with a low C:N ratio) leaf litter caused significant positive priming effects (PEs) of 24% and 42%, respectively, at the end of the experiment (235 d). The PE dynamics showed that positive PE can last for at least 87 d. However, the possible occurrence of a significant negative PE with a sufficient incubation period is difficult to confirm. The application of both NH4+ and NO3− was found to have a stimulating effect on the decomposition of Chinese fir and alder leaf litter in the early stage (0–15 d) of incubation, but an adverse effect in the late stage. Compared with NO3−, NH4+ caused a greater decrease in the PE induced by both Chinese fir and alder leaf litter. The effects of NH4+ and NO3− on the PE dynamics had different patterns for different incubation stages. This result may indicate that the stability or recalcitrance of SOC, especially in such plantation forest soils, strongly depends on available leaf litter and application of N to the soil.
