天然次生林改造成香榧林对土壤活性有机碳的影响

Effect of Conversion of Natural Secondary Forest into Torreya grandis Plantation on Soil Active Organic Carbon

为探讨天然次生林改造成人工林后对土壤碳库的影响,为人工林的可持续经营与土壤固碳能力的提高提供参考依据。在浙江省诸暨市香榧国家森林公园内采集天然次生林和由天然次生林改造而来并长期进行经营管理的香榧(Torreya grandis)人工林土壤,测定分析了0-20、20-40、40-60 cm土层土壤的总有机碳(TOC)、易氧化碳(ROC)、轻组有机质(LFOM)及土壤养分含量。结果表明:(1)天然次生林改造成香榧林后,各层土壤TOC均显著下降,减少了27.2%-50.5%,0-20 cm土层土壤ROC呈增加趋势,但20-40 cm和40-60 cm土层呈减小趋势,各层土壤LFOM分别增加31.5%、155.5%和184.8%,在20-40 cm和40-60 cm土层差异显著(P<0.05)。(2)天然次生林改造成香榧林后,0-20 cm土层ROC碳素有效率和碳库活度分别显著增加了123.2%和169.2%。(3)TOC、ROC、LFOM与全氮和水解性氮之间的相关性均达到极显著水平,ROC、LFOM与速效钾、有效磷、交换性钙和交换性镁之间的相关性均达到显著或极显著水平。因此,天然次生林改造成香榧林后,不利于土壤有机碳的积累,且降低了土壤碳库的稳定性。

In order to investigate the effect of conversion from natural forest to plantations on the soil carbon(C)pool,and provide a reference for the sustainable management of plantation and the improvement of soil carbon sequestration capacity,soils of the above two types of forests were sampled from Torreya grandis National Forest Park,Zhuji City,Zhejiang Province.We analyzed the total soil organic carbon(TOC),readily oxidizable carbon(ROC),light fraction organic matter(LFOM),and soil nutrient contents in three different soil layers(0.20,20.40,and 40.60 cm).The results suggested that,(1)TOC of each layer significantly decreased by 27.2%.50.5%.ROC increased in 0.20 cm soil layer,while being decreased in 20.40 cm and 40.60 cm soil layer.LFOM of each layer increased by 31.5%,155.5%and 184.8%respectively,and with significant differences between 20.40 cm and 40.60 cm soil layer.(2)The ratio of ROC to TOC and activity of carbon pool in 0.20 cm markedly increased by 123.2%and 169.2%,respectively.And(3)TOC,ROC and LFOM were extremely correlated with total nitrogen,available nitrogen.ROC and LFOM were significantly/extremely correlated with available potassium,available phosphorus,exchangeable calcium and exchangeable magnesium.Therefore,the transformation of natural secondary forest into T.grandis plantation is not conducive to the accumulation of soil organic carbon,and decreases the stability of soil carbon pool.