杉木人工林土壤可溶性有机质及其与土壤养分的关系

通过在福建省来舟林场对不同栽植代数杉木人工林土壤可溶性有机碳(DOC)和氮(DON)及土壤养分的研究,其结果表明,随着杉木栽植代数的增加林地土壤DOC和DON含量逐渐下降,在0～10cm土层内第3代杉木林土壤DOC和DON含量分别是第1代杉木林的83.9%和87.1%、第2代杉木林的90.6%和96.9%,在10～20cm土层内第3代杉木林土壤DOC和DON含量分别是第1代杉木林的80.2%和81.5%、第2代杉木林的81.8%和90.0%。在不同林地和土层内土壤DOC含量之间的差异性达到了显著或极显著水平,而DON含量之间的差异性不显著。不同栽植代数杉木林土壤养分的变化趋势与DOM一致,随着杉木连栽,土壤养分含量呈下降趋势。在0～10cm土层内第3代杉木林土壤全氮、全钾、铵态氮和速效钾含量分别是第1代杉木林的83.1%、60.4%、68.1%和44.3%,是第2代杉木林的84.6%、68.5%、74.4%和58.7%;在10～20cm土层内第3代杉木林土壤全氮、全钾、铵态氮和速效钾含量分别是第1代杉木林的74.0%、53.4%、57.6%和54.6%,是第2代杉木林的94.8%、59.5%、74.3%和65.5%。经相关性分析,在各土层内土壤DOC和DON含量与土壤全氮、全钾、铵态氮和速效钾等土壤养分含量存在着不同程度的相关性。

A study on dissolved organic carbon and nitrogen nutrients under Chinese fir plantation: Relationships with soil nutrients

Dissolved organic matter (DOM) is a major controlling factor in soil formation, mineral weathering, and pollutant transport, and plays an important role through nutrient dynamics in terrestrial ecosystems. DOM composed mainly dissolved organic carbon, nitrogen and phosphorus (DOC, DON and DOP). DOM can be produced and consumed by micro-organisms or plants and stabilized/solubilized on and off in soil surface. Like other fractions of soil organic matter, some findings suggest that biodegradation of DOM is mediated by aqueous phase. But, the biodegradation mechanism of DOM is not well known. Carbon, nitrogen and phosphorus are the key elements in organic matter. Therefore, dissolved nutrients play an important role in terrestrial C, N and P budgets. Moreover, they (DOC, DON and DOP) play significant roles in the maintenance of nutrient capital in terrestrial ecosystems. However, a number of studies focused on a single element at a time, but few of them have examined the C, N and P content of DOM and evaluated the relative changes of C, N and P with solution movement through ecosystems level or in response to changing nutrient availability simultaneously. The experiments were conducted to investigate changes of DOC, DON and soil nutrients such as total nitrogen (TN), ammonium-N (NH _4-N), total potassium (TK) and available potassium (AK) under different rotation of Chinese fir plantation at Laizhou Forestry Farm in Nanping, Fujian province. The results indicated that DOC, DON and soil nutrients declined with the continuous plantation of Chinese fir. In the 0~10cm soil layer, DOC and DON values in soil at the third plantation of Chinese fir were 16.1 and 22.9% lower than those of the first rotation, 9.4 and 3.1% lower than those of the second rotation, respectively. In 10~20cm soil layer, the contents of DOC and DON in soil from third rotation of Chinese fir were 19.8 and 18.5% lower than those from the first rotation, and 18.2 and 10.0% lower than those from the second rotation, respectively. The differences in contents of DOC among different forest stands and soil layer were significantly different while differences in contents of DON were insignificant. Soil nutrients decreased with the similar trend of DOC and DON. In the whole soil profile, the contents of TN, TK, NH _4-N, AK under the third rotation of Chinese fir were 21.4, 43.1, 37.7 and 50.5% lower than those of the first rotation, and 10.3, 36.0, 25.6 and 37.9% lower than those the second rotation, respectively. DOC and DON in both soil layers have positive correlation to different degree with soil nutrients. So it was concluded that dissolved organic matter controls soil nutrient dynamics and contents of DOC, DON and nutrients decreased with Chinese fir continuously cropping.