长期不同植被覆盖对黑土团聚体内有机碳组分的影响

doi:10.17521/cjpe.2019.0028

摘要/Abstract

摘要：

为探究黑土团聚体内土壤有机碳(SOC)的“分馏”特征, 揭示不同植被覆盖下土壤团聚体的固碳机制, 该文以中国科学院海伦农业生态系统国家野外综合研究站内不同植被覆盖(草地、农田和裸地)长期定位实验的土样为研究对象, 利用团聚体湿筛分组、有机碳物理和化学分组相结合的方法, 研究了黑土团聚体及其内部的碳密度和腐殖质组分的碳分配特征。研究发现, 黑土经过不同植被覆盖31年后, 长期草地覆盖使土壤表层SOC、全氮(TN)含量显著增加, 农田和无植被覆盖的裸地SOC含量减少, 且在裸地显著降低。3种处理中, 2-0.25 mm (含2 mm, 下同)粒级团聚体均为优粒级。土壤团聚体的稳定性顺序为草地>农田>裸地。草地覆盖使土壤大团聚体的比例和有机碳库增加, 微团聚体和粉黏粒所占比例和碳库均减少, 说明草地覆盖促进了土壤大团聚体形成, 土壤固碳能力显著增强。而农田和裸地因外源碳投入少, 有机碳含量均是微团聚体>大团聚体>粉黏粒, SOC主要分布在微团聚体中。不同植被覆盖处理对土壤团聚体内密度组分和腐殖质各组分碳的富集“分馏”作用很明显, 与农田和裸地相比, 长期草地植被覆盖处理>2 mm和2-0.25 mm粒级团聚体中轻组碳含量富集的较多, 2-0.25 mm粒级团聚体中富里酸、胡敏酸和胡敏素的碳富集均最高, 而农田和裸地促进了微团聚体内腐殖质碳的富集。草地覆盖显著增加了大团聚体内活性有机碳组分, 来源于植物的碳首先进入到大粒径的团聚体中, 使土壤团聚结构显著改善, 农田和无植被覆盖的裸地土壤中轻组碳含量显著降低, 团聚体内有机碳以重组碳和胡敏素为主, 稳定化程度更高。

关键词: 植被覆盖, 水稳性团聚体, 土壤有机碳, 密度组分, 腐殖酸

Abstract:

Aims Soil aggregate is the main habitat for decomposition and transformation of soil organic carbon (SOC) and is important to regulate SOC sequestration. The mechanisms of the stability of SOC fractions may vary among different aggregate sizes. The aims of this study were to explore the characteristics of SOC “fractionation” in soil aggregates, and to reveal the mechanisms of carbon (C) sequestration in soil aggregates of mollisols after 31-year changes in vegetation cover.
Methods A long-term field experiment with different vegetation cover (grassland, farmland and bareland) was established in National Observation Station of Hailun Agro-ecosystem System. Soil aggregate fractionation, the density and humus fractionation within different aggregate sizes were further carried out.
Important findings The results showed that after 31 years of land cover change, the surface SOC and total nitrogen (TN) contents in grassland with higher C inputs increased significantly with time, while the SOC and TN contents decreased significantly in bareland, but with no statistical significance in farmland. The 2-0.25 mm (include 2 mm, the same below) aggregates was the excellent fraction for SOC sequestration under all three land cover. The stability of soil aggregate was in the order of: grassland > farmland > bareland. The mass proportion of soil aggregate and its associated content were highest in grassland, while the proportion of microaggregate and its carbon allocation rate were lowest in grassland. However, due to the lower C inputs in farmland and bareland, the distribution of aggregates was in the order of microaggregate > macroaggregate > silt-clay fraction under these two types of land cover, and organic carbon (OC) content was highest in microaggregates. Different vegetation cover changed the C “fractionation” of density and humus fractions in aggregates. Compared with farmland and bareland soils, OC contents in light fractions in >2 mm and 2-0.25 mm aggregates were higher in grassland, and the OC contents in furic acid, humic acid and humin were highest in 2-0.25 mm aggregates in grassland, while the humus OC accumulated in microaggregates in farmland and bareland. Our results indicated that the plant-derived C entered macroaggregates first, and long-term grass cover enhanced free and light C fractions in macroaggregate, which consequently improved the stability of soil aggregates and enhanced the “fractionation” effects of large aggregates on the humus fractions. Our results revealed the characteristics of carbon sequestration in soil aggregates under different vegetation cover.

Key words: vegetation cover, water-stable aggregates, soil organic carbon, density fraction, humus

李娜, 张一鹤, 韩晓增, 尤孟阳, 郝翔翔. 长期不同植被覆盖对黑土团聚体内有机碳组分的影响. 植物生态学报, 2019, 43(7): 624-634. DOI: 10.17521/cjpe.2019.0028

LI Na, ZHANG Yi-He, HAN Xiao-Zeng, YOU Meng-Yang, HAO Xiang-Xiang. Effects of long-term vegetation cover changes on the organic carbon fractions in soil aggregates of mollisols. Chinese Journal of Plant Ecology, 2019, 43(7): 624-634. DOI: 10.17521/cjpe.2019.0028

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链接本文: https://www.plant-ecology.com/CN/10.17521/cjpe.2019.0028

https://www.plant-ecology.com/CN/Y2019/V43/I7/624

图/表 6

图1 初始土壤和不同植被覆盖下表层土壤总有机碳和全氮含量(平均值±标准偏差)。不同小写字母表示处理间差异显著(p < 0.05)。BL, 裸地; FL, 农田; GL, 草地。

Fig. 1 Contents of soil organic carbon and total nitrogen in initial soil and soils under different vegetation covers (mean ± SD). Different lowercase letters above the bar differ at 0.05 levels among different vegetation covers. BL, bareland; FL, farmland; GL, grassland.

图2 不同植被覆盖下土壤团聚体粒径分布及平均质量直径(平均值±标准偏差)。不同小写字母表示处理间差异显著(p < 0.05)。

Fig. 2 Distribution of soil aggregates and mean weight diameter (MWD) of aggregates under different vegetation covers (mean ± SD). Different lowercase letters above the bar differ at 0.05 levels among different vegetation covers.

图3 不同植被覆盖下土壤团聚体中有机碳含量(平均值±标准偏差)。不同小写字母表示处理间差异显著(p < 0.05)。

Fig. 3 Contents of organic carbon in soil aggregates fractions under different vegetation covers (mean ± SD). Different lowercase letters above the bar differ at 0.05 levels among different vegetation covers.

图4 不同植被覆盖下土壤团聚体内密度组分有机碳含量(平均值±标准偏差)。不同小写字母表示处理间差异显著(p < 0.05)。

Fig. 4 Organic carbon contents in different density fractions of aggregates under different vegetation covers (mean ± SD). Different lowercase letters above the bar differ at 0.05 levels among different vegetation covers.

图5 不同植被覆盖下表层全土腐殖质组分的碳含量和腐殖化指标(平均值±标准偏差)。FA, 富里酸; HA, 胡敏酸; HU, 胡敏素。不同小写字母表示处理间差异显著(p < 0.05)。

Fig. 5 Contents of organic carbon in humic substances and humification index in bulk soil under different vegetation covers (mean ± SD). FA, fulvic acid; HA, humic acid; HU, humin. Different lowercase letters above the bar differ at 0.05 levels among different vegetation covers.

图6 不同植被覆盖下表层土壤团聚体内腐殖质组分碳含量(平均值±标准偏差)。不同小写字母表示处理间差异显著(p < 0.05)。

Fig. 6 Contents of organic carbon in soil aggregates under different vegetation covers (mean ± SD). Different lowercase letters above the bar differ at 0.05 levels among different vegetation covers.

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