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选取缙云山阳坡同一海拔处亚热带常绿阔叶林(以下简称林地)、果园、坡耕地和撂荒地这4种不同土地利用类型,在0~60 cm深度内每隔10 cm采集一个土样,测定土壤轻组有机碳氮(LFOC、LFON)和颗粒态有机碳氮(POC、PON)含量,并计算其分配比例和碳氮比.结果表明,在0~60 cm土壤深度范围内,林地转变为坡耕地后,LFOC及LFON含量分别降低了71.42%和38.46%(P<0.05),转变为果园后变化不明显,坡耕地撂荒后其含量分别升高了3.77倍和1.38倍(P<0.05);林地转变为坡耕地或果园后,POC及PON含量均无明显变化,而坡耕地撂荒后其含量分别增加了4.12和1.25倍(P<0.05).林地转变为坡耕地后土壤LFOC及LFON分配比例显著降低,转变为果园后则明显升高,而POC及PON分配比例变化均不明显;坡耕地撂荒后,LFOC、LFON、POC、PON分配比例均显著增加.土壤SOC/TN为撂荒地(12.93)>林地(8.53)>果园(7.52)>坡耕地(4.40),LFOC/LFON为撂荒地(16.32)>林地(14.29)>果园(11.32)>坡耕地(7.60),POC/PON为撂荒地(23.41)>坡耕地(13.85)>林地(10.30)>果园(9.64).以上研究结果表明林地开垦为果园或坡耕地后容易导致土壤轻组有机碳氮的损失,而坡耕地撂荒则有利于土壤活性有机碳氮的积累;林地转变为坡耕地减弱了土壤有机碳氮的活性,而林地转变为果园以及坡耕地撂荒均使土壤有机碳氮活性增强;林地转变为坡耕地和果园加剧了土壤有机质的矿化,相对而言,坡耕地撂荒后有利于土壤有机质的固定.
Select four different types of land use types of subtropical evergreen broad-leaved forest (hereinafter referred to as forest land), orchard, sloping land and fallow land at the same elevation of Jinyun Mountain at the same altitude, collecting one soil sample every 10 cm within the depth of 0-60 cm, The contents of soil organic matter (LFOC, LFON) and particulate organic carbon and nitrogen (POC, PON) in soil were measured and their distribution ratio and C / N ratio were calculated.The results showed that within the depth of 0-60 cm, After slope farmland conversion, LFOC and LFON contents decreased by 71.42% and 38.46% (P <0.05), respectively, and the changes of the LFOC and LFON contents did not change obviously after orchard conversion. The contents of LFOC and LFON increased by 3.77 and 1.38 times (P <0.05) ), POC and PON contents did not change significantly after the conversion of forestland to sloping cropland or orchard, while the content of POC and PON in sloping farmland increased 4.12 and 1.25 times respectively (P <0.05) The distribution ratio of POC and PON significantly decreased after conversion to orchard, but the distribution ratio of POC and PON was not obvious. After the fallow, the distribution ratio of LFOC, LFON, POC and PON increased significantly, and SOC / TN of the soil was abandoned (12.93)> forest land (8.53)> orchard (7.52)> sloping land (4.40) and LFOC / LFON .32)> forest land (14.29)> orchard (11.32)> sloping farmland (7.60), POC / PON was fallow land (23.41)> sloping farmland (13.85)> woodland (10.30)> orchard (9.64) Land reclamation for orchard and slope farmland easily led to the loss of soil organic carbon and nitrogen, while sloping land fallow was conducive to the accumulation of soil active organic carbon and nitrogen; forest land conversion to sloping land weakened the activity of soil organic carbon and nitrogen, and woodland Change into orchard and slope farmland abandonment both increased soil organic carbon and nitrogen activity; conversion of forestland into slope farmland and orchard aggravated the mineralization of soil organic matter, relatively speaking, slope farmland is conducive to the soil organic matter fixation.