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黄土高原吕梁山不同撂荒年限土壤团聚体稳定性及有机碳分布特征
陈曦1, 王改玲1, 刘焕焕1, 殷海善2, 樊文华1
1.山西农业大学资源环境学院, 山西太谷 030801;2.山西省农业科学院农业资源与经济研究所, 太原 030006
摘要:
为探究不同撂荒年限土壤结构及有机碳分布特征,试验选取黄土高原吕梁山自然撂荒1、2、3、5、10、15、20 a枣园土壤为研究对象,以清耕作业下的枣园土壤为对照(CK),利用干筛和湿筛法测定并分析各样地0~20 cm土层中土壤团聚体稳定性、团聚体有机碳与土壤总有机碳含量及其相关性。结果表明:撂荒初期,土壤团聚体含量呈波动变化趋势,撂荒3 a后土壤水稳性大团聚体含量(>0.25 mm团聚体含量,R>0.25)及团聚体平均重量直径(MWD)、几何平均直径(GMD)随撂荒年限的增加逐步提高。20 a撂荒地土壤水稳性大团聚体含量占团聚体总量的69.6%,较CK提高了55.2个百分点。土壤总有机碳、团聚体有机碳含量随撂荒年限的延长均呈先降低后增加的趋势,撂荒20 a土壤总有机碳含量达最大值7.88 g/kg;团聚体有机碳含量随团聚体粒径的减小呈先增加后降低的特点,主要集中于1~0.25 mm团聚体内。不同撂荒年限土壤中机械稳定性大团聚体有机碳对土壤总有机碳的贡献率为54.3%~82.2%,较CK(29.3%)提高25.0~52.9个百分点;水稳性大团聚体有机碳对土壤总有机碳的贡献率为17.7%~71.8%,除撂荒1 a和3 a土壤外,其他样地均高于CK (21.1%)。水稳性团聚体MWD、R>0.25与土壤总有机碳含量极显著相关(P<0.01);水稳性团聚体GMD与土壤总有机碳含量显著相关(P<0.05);水稳性团聚体R>0.25与2~1、1~0.25和<0.25 mm水稳性团聚体有机碳含量极显著相关(P<0.01),与5~2 mm团聚体有机碳含量显著相关(P<0.05)。可见,撂荒恢复促进了土壤有机碳及水稳性团聚体有机碳含量的提高,从而提高了团聚体的稳定性。
关键词:  撂荒恢复  团聚体稳定性  有机碳分布  吕梁山
DOI:10.13758/j.cnki.tr.2021.02.022
分类号:S157.2
基金项目:山西省自然科学基金项目(201801D121245)资助。
Stability and Organic Carbon Distribution of Soil Aggregates with Different Fallow Years in Lüliang Mountains in Loess Plateau
CHEN Xi1, WANG Gailing1, LIU Huanhuan1, YIN Haishan2, FAN Wenhua1
1.College of Resources and Environment, Shanxi Agricultural University, Taigu, Shanxi 030801, China;2.Institute of Agricultural Resources and Economics, Shanxi Academy of Agricultural Sciences, Taiyuan 030006, China
Abstract:
To explore the characteristics of soil structure and organic carbon distribution in aggregates with fallow year, soils (0-20 cm depth) under 1, 2, 3, 5, 10, 15, 20 fallow years and under clean tillage (as control (CK) were sampled from Lüliang mountains in Loess Plateau, aggregates were separated by dry and wet sieve methods respectively, and then mechanical-stable and water-stable aggregates, organic carbon contents in soils and aggregates were determined and compared. The results showed that within 3a fallow, aggregate content changed irregularly, then the content of water-stable macro-aggregates (>0.25 mm aggregate content, R>0.25), MWD and GMD of aggregates gradually increased with the increase of fallow year, and it accounted for 69.6% of the total aggregate of water-stable macro-aggregates in 20a fallow, 55.2 percent points higher than CK. The contents of organic carbon in soil and aggregates decreased first and then increased with the extension of fallow year, soil total organic carbon (TOC) in 20a fallow reached 7.88 g/kg, organic carbon in aggregates increased first and then decreased with the decrease of aggregate size, mainly concentrated in 1-0.25 mm aggregates. Organic carbon in mechanical-stable macro-aggregates accounted for 54.3%-82.2% of soil TOC, which were 25.0-52.9 percent points higher than CK (29.3%), organic carbon in water-stable macro-aggregates accounted for 17.7%-71.8% to soil TOC, and other plots accounted more than CK (21.1%) except 1a and 3a fallow. MWD and R>0.25 of water stable aggregates were extremely significantly correlated with soil TOC (P<0.01), and GMD of water stable aggregates was significantly correlated with soil TOC (P<0.05). R>0.25 of water-stable aggregates was extremely significantly correlated with organic carbon in 2-1, 1-0.25 and <0.25 mm aggregates (P<0.01), and significantly correlated with organic carbon in 5-2 mm aggregates (P<0.05). In conclusion, natural recovery promotes the increase of organic carbon in soil and in water-stable aggregates, thereby improves the stability of aggregates.
Key words:  Recovery of abandoned soil  Aggregate stability  Organic carbon distribution  Lüliang mountains

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