为阐明黄土高原典型区域土壤轻组有机碳(LFOC)和重组有机碳(HFOC)含量随土壤类型、土层和土地利用方式的变化规律,分析了从北向南依次分布的干润砂质新成土(神木)、黄土正常新成土(延安)和土垫旱耕人为土(杨凌)等典型土壤剖面(0~200 cm)LFOC和HFOC含量及分布特征。结果表明,从南到北,土壤LFOC和HFOC含量均显著下降 (P<0.05),整体来看,黄土高原典型区域土壤LFOC含量占有机碳比例偏低;LFOC含量及在土壤有机碳中的分配比例随土层加深而递减,其比例变化范围为1%~26%;土地利用方式对浅层土壤LFOC和HFOC含量影响较为显著,草地土壤0~60 cm土层LFOC和HFOC含量均高于同层次农田土壤(P<0.05),60 cm土层以下差异不显著;土壤LFOC和HFOC含量与微生物量碳、微生物量氮含量均呈极显著正相关关系(P<0.01),前者的相关性系数更高,分别为0.841和0.507,表明土壤LFOC与微生物关系非常密切,是土壤微生物重要的碳和能量来源,极易受土地利用方式和微生物活性影响,同时表明用LFOC的变化更能快速有效地说明土壤碳库的变化规律。
In order to evaluate the effects of location, soil depth, and land use on the soil light fraction organic carbon (LFOC) and soil heavy fraction organic carbon (HFOC), we investigated the contents and the distribution characteristics of soil LFOC and HFOC of three types (Ust-Sandiic-Entisols at Shenmu, Los-Orthic-Entisol at Yan’an and Eum-Orthic-Anthrosol at Yangling) soils profiles (0－200 cm) sampled along a north-south gradient on the Loess Plateau. The results indicated that the contents of soil LFOC and HFOC decreased significantly (P<0.05) from south to north. The ratios of LFOC in soil organic carbon ranged from 1% to 26%. LFOC content and the ratios of LFOC in soil organic carbon significantly (P<0.05) decreased with soil depth. Both of them were lower than the previous reports in other regions of China. Land use closely (P<0.05) correlated with the contents of LFOC and HFOC fractions in the upper soil layers.Compared with farmland, the contents of soil LFOC and HFOC in grassland were significantly higher at the 0－60 cm layers, but had no significant difference below 60 cm soil layers. Both soil LFOC and HFOC contents positively correlated with soil microbial biomass nitrogen and carbon contents, the former with a correlation coefficient of 0.841 and 0.507, respectively. This suggested that soil LFOC was one of the most important carbon and energy sources for soil microbial growth and thus more liable to the impacts of microbial activities and land use change. Our results also implied that soil LFOC could more effectively reflect the variation of soil organic carbon pools than HFOC.
[1] Parfitt R L, Yeates G W, Ross D J, et al. Relationships between soil biota, nitrogen and phosphorus availability, and pasture growth under organic and conventional management [J]. Applied Soil Ecology,2005,28:1-13.
[2] Blanco-Canqui H, Lal R. Soil structure and organic carbon relationships following 10 years of wheat straw management in no-till [J]. Soil & Tillage Research,2007,95:240-254.
[3] LIU Xun, LI Feng-min, LIU Da-qian, et al. Soil organic carbon, carbon fractions and nutrients as affected by land use in semi-arid region of Loess Plateau of China [J]. Pedosphere,2010,20(2):146-152.
[4] Biederbeck V O, Janzen H H, Campbell C A, et al. Labile soil organic matter as influenced by cropping practices in an arid environment [J]. Soil Biology and Biochemistry,1994,26:1647-1656.
[5] Gregorich E G, Cater M R, Angers D A, et al. Towards a minimum data set to assess soil organic matter quality in agricultural soils [J]. Canadian Journal of Soil Science,1994,74:367-385.
[6] 李月梅,王跃思,曹广民,等.开垦对高寒草甸土壤有机碳影响的初步研究[J].地理科学进展,2005,24(6):59-65.
[7] Christensen B.T. Physical fractionation of soil and organic matter in primary particle size and density separates [J]. Advances in Soil Sciences, 1992, 20:2-9.
[8] Christensen B T. Physical fractionation of soil and structural in organic matter turnover [J]. European Journal of Soil Science,2001,52: 345-353.
[9] Alvarez R, Alvarez C R, DanielP E, et al. Nitrogen distribution in soil density fractions and its relation to nitrogen mineral station under different tillage systems [J]. Australia Journal of Soil Research,1998,36:247-256.
[10] Barrios E, Kwesiga F, Buresh R J, et al. Light fraction soil organic matter and available nitrogen following trees and maize [J]. Soil Science Society of America Journal,1997,61:826-831.
[11] 张金波,宋长春.土地利用对土壤碳库影响的敏感性评价指标[J].生态环境,2003,12(4):500-504.
[12] Sollins P, Spycher G, Glassman C A. Net nitrogen mineralization from light and heavy-fraction forest soil organic matter [J]. Soil Biology and Biochemistry,1984,16:31-37.
[13] Tan Z, Lal R, Owens L, et al. Distribution of light and heavy fractions of soil organic carbon as related to land use and tillage practice [J]. Soil & Tillage Research,2007,92:53-59.
[14] 杨玉盛,刘艳丽,陈光水,等.格氏栲天然林与人工林土壤非保护性有机碳研究[J].生态学报,2004,24(1):1-8.
[15] 吴建国,张小全,王彦辉,等.土地利用变化对土壤物理组分中有机碳分配的影响[J].林业科学,2002,38(4):146-157.
[16] 鲁如坤.土壤农化分析[M].北京:农业科技出版社,2000.
[17] Spycher G, Sollins P, Rose S. Carbon and nitrogen in the light fraction of afforest soil: Vertical distribution and seasonal patterns [J]. Soil Science, 1993, 135:79-87.
[18] 党亚爱,李世清,王国栋,等.黄土高原南北主要类型土壤有机碳和微生物碳分布特征的研究[J].自然资源学报,2007,22(6):936-945.
[19] 周莉,李保国,周广胜.土壤有机碳的主导影响因子及其研究进展[J].地球科学进展,2005,20(1):99-105.
[20] Dalal R C, Mayer R J. Long-term trends in fertility of soils under continuous cultivation and cereal cropping in southern Queensland VI: Loss of total nitrogen from different particle-size and density fractions [J]. Australian Journal of Soil Research,1987,25:83-93.
[21] Conteh A, Blair G J, Macleod D A, et al. Soil organic carbon changes in cracking clay soils under cotton production as studied by carbon fractionation [J]. Australian Journal of Agricultural Research,1997,48:1049-1058.
[22] Chotte J L, Ladd J N, Amato M. Sites of microbial assimilation and turnover of soluble and particulate 14C-labelled substrates decomposing in a clay soil [J]. Soil Biology and Biochemistry,1998,30:205-218.
