氮添加对内蒙古温带草原土壤活性有机碳的影响

doi:10.17521/cjpe.2023.0148

摘要/Abstract

摘要：

日益加剧的氮沉降不断影响着草地生态系统碳循环过程及碳汇功能, 活性有机碳能够指示土壤碳库变化, 探究氮添加对草地中土壤活性有机碳组分的影响对正确认识碳循环过程并制定合理有效的生态系统管理措施具有重要意义。该研究以内蒙古温带典型草原为研究对象, 设置5个不同氮添加处理, 探讨不同氮添加水平下温带典型草原土壤活性有机碳组分含量的变化特征及影响因子。结果表明: 氮添加减少了可溶性有机碳(DOC)、微生物生物量碳(MBC)和易氧化有机碳(EOC)含量, 且DOC、MBC、EOC含量均随着土壤深度的增加而减少。5 g·m^-2·a^-1氮添加处理显著促进了活性有机碳组分的分解。氮添加对土壤活性有机碳组分的影响受生物因子(微生物生物量、胞外酶活性等)和非生物因子(土壤理化性质、团聚体稳定性等)共同调控。氮添加降低了土壤密度, 提高了大团聚体平均质量直径和占比, 增大了有机质与底物的接触面积, 促进了活性有机碳分解, 减少了DOC和EOC含量。氮添加抑制多酚氧化酶和过氧化物酶活性, 减少了难分解有机质的分解, 降低了EOC和MBC含量。此外, 氮添加提高了β-葡萄糖苷酶和纤维素水解酶活性, 促进了微生物对DOC的利用, 降低了DOC含量。以上结果表明, 氮添加处理通过改变土壤理化性质和微生物胞外酶的分泌影响活性有机碳的分解过程, 促进温带典型草原土壤碳释放, 为今后进一步探究养分添加下草地土壤碳动态提供了理论依据。

关键词: 氮添加, 活性有机碳, 土壤团聚体, 生物因子, 理化性质

Abstract:

Aims Both the carbon cycle and the function of grassland ecosystem as a carbon sink are impacted by the rising nitrogen deposition. Active organic carbon content is an important measure that can reveal changes in soil carbon pool. For a thorough understanding of carbon cycling and the creation of sensible ecosystem management strategies, it is essential to investigate the impacts of nitrogen addition on the active organic carbon fractions of grassland soils.

Methods Five different nitrogen addition treatments were set up in a temperate typical steppe of Nei Mongol. Soil organic carbon fractions content, soil physical and chemical properties, aggregate stability, microbial activities and extracellular enzyme activities were measured. Pearson correlation and structural equation model (SEM) were used to examine the relationships.

Important findings Nitrogen addition reduced the contents of dissolved organic carbon (DOC), microbial biomass carbon (MBC), and easily oxidizable organic carbon (EOC). The contents of DOC, MBC, and EOC all decreased with the increases of soil depth. The treatment of 5 g·m^-2·a^-1 nitrogen addition significantly promoted the decomposition of active organic carbon fractions. The effect of nitrogen addition on soil active organic carbon fractions content was regulated by biotic (microbial biomass, extracellular enzyme activity, etc.) and abiotic (soil physical and chemical properties, aggregate stability, etc.) factors. Nitrogen addition reduced soil density, increased mean mass diameter and the proportion of large aggregates, increased the contact between organic matter and substrate, promoted the decomposition of active organic carbon, and reduced the contents of DOC and EOC. Nitrogen addition inhibited the activities of polyphenol oxidase and peroxidase, reduced the decomposition of difficult-to-decompose organic matter and the contents of EOC and MBC. Nitrogen addition increased the activities of β-glucosidase and cellulose hydrolase, promoted the utilization of DOC by microorganisms, and reduced the content of DOC. Our results indicated that nitrogen addition treatment can affect the decomposition process of active organic carbon by changing soil physicochemical properties and the secretion of extracellular enzymes from microorganisms, promoting the release of carbon in grassland soils. This provided a theoretical basis for further exploration of grassland soil carbon dynamics under nutrient addition in the future.

Key words: nitrogen addition, active organic carbon, soil aggregates, biotic factor, physicochemical properties

颜辰亦, 龚吉蕊, 张斯琦, 张魏圆, 董学德, 胡宇霞, 杨贵森. 氮添加对内蒙古温带草原土壤活性有机碳的影响. 植物生态学报, 2024, 48(2): 229-241. DOI: 10.17521/cjpe.2023.0148

YAN Chen-Yi, GONG Ji-Rui, ZHANG Si-Qi, ZHANG Wei-Yuan, DONG Xue-De, HU Yu-Xia, YANG Gui-Sen. Effects of nitrogen addition on soil active organic carbon in a temperate grassland of Nei Mongol, China. Chinese Journal of Plant Ecology, 2024, 48(2): 229-241. DOI: 10.17521/cjpe.2023.0148

导出引用管理器 EndNote|Ris|BibTeX

链接本文: https://www.plant-ecology.com/CN/10.17521/cjpe.2023.0148

https://www.plant-ecology.com/CN/Y2024/V48/I2/229

图/表 8

图1 不同氮添加对内蒙古温带草原植被地上和地下生物量的影响(平均值±标准误)。不同小写字母表示地下生物量在不同处理间的差异显著(p < 0.05), 不同大写字母表示地上生物量在不同处理间的差异显著(p < 0.05)。N0、N2、N5、N10、N25分别表示氮添加量为0、2、5、10、25 g·m-2·a‒1。

Fig. 1 Effects of different nitrogen addition treatments on aboveground and belowground biomass of vegetation in a temperate grassland of Nei Mongol (mean ± SE). Different lowercase letters indicate significant differences in belowground biomass between different treatments (p < 0.05), different uppercase letters indicate significant differences in aboveground biomass between different treatments (p < 0.05). N0, N2, N5, N10 and N25 indicate nitrogen addition amounts of 0, 2, 5, 10, 25 g·m-2·a-1, respectively.

表1 不同氮添加对内蒙古温带草原土壤理化性质的影响(平均值±标准误)

Table 1 Effect of different nitrogen additions on soil physical and chemical properties in temperate grassland of Nei Mongol (mean ± SE)

处理 Treatment	土层深度 SLD (cm)	土壤pH Soil pH	土壤密度 SD (g·cm^-3)	土壤含水量 SWC (%)	土壤全碳含量 TC content (g·kg^-1)	全氮含量 TN content (g·kg^-1)	微生物生物量氮含量 MBN content (mg·kg^-1)
N0	0-10	8.22 ± 0.01^Ca	1.26 ± 0.02^Aa	18.27 ± 0.10^Ab	18.40 ± 0.17^Cd	1.39 ± 0.09^Ab	45.03 ± 3.55^Aac
	10-20	8.29 ± 0.00^Ba	1.24 ± 0.02^Aa	17.62 ± 0.27^Bc	22.13 ± 0.29^Ab	1.37 ± 0.09^ABa	34.93 ± 0.35^Bab
	20-30	8.47 ± 0.00^Aa	1.13 ± 0.02^Bb	17.06 ± 0.10^Bb	19.63 ± 0.09^Bd	0.92 ± 0.11^Ba	14.36 ± 0.28^Ca
N2	0-10	8.11 ± 0.00^Cb	1.31 ± 0.01^Aa	19.39 ± 0.19^Ba	21.26 ± 0.10^Bb	1.84 ± 0.22^Aa	53.74 ± 3.20^Aa
	10-20	8.16 ± 0.01^Bb	1.09 ± 0.04^Bb	20.45 ± 0.31^Ab	24.77 ± 0.31^Aa	1.44 ± 0.07^Aa	19.13 ± 3.70^Bc
	20-30	8.29 ± 0.01^Ac	1.09 ± 0.01^Bbc	20.36 ± 0.31^Aa	23.60 ± 0.58^Ab	0.94 ± 0.15^Ba	15.00 ± 0.94^Ba
N5	0-10	8.13 ± 0.01^Bb	1.18 ± 0.01^Ab	19.61 ± 0.30^Ba	21.98 ± 0.05^Ba	1.44 ± 0.03^Aab	31.63 ± 2.56^Ab
	10-20	8.15 ± 0.01^Bb	1.19 ± 0.03^Aab	21.42 ± 0.21^Aa	25.25 ± 0.32^Aa	1.43 ± 0.04^Aa	26.17 ± 1.58^Abc
	20-30	8.37 ± 0.01^Ab	1.24 ± 0.04^Aa	19.53 ± 0.52^Ba	25.10 ± 0.16^Aa	1.16 ± 0.10^Ba	14.14 ± 0.24^Ba
N10	0-10	7.97 ± 0.01^Cc	1.15 ± 0.03^Ab	19.26 ± 0.40^Aa	20.28 ± 0.08^Bc	1.65 ± 0.11^Aab	51.99 ± 2.01^Aa
	10-20	8.01 ± 0.01^Bc	1.03 ± 0.04^Bb	18.25 ± 0.38^Ac	22.65 ± 0.23^Ab	1.47 ± 0.11^Aa	41.81 ± 8.46^Aa
	20-30	8.17 ± 0.01^Ad	1.16 ± 0.02^Ab	19.57 ± 0.41^Aa	22.18 ± 0.04^Ac	0.86 ± 0.08^Ba	14.93 ± 1.72^Ba
N25	0-10	7.89 ± 0.01^Cd	1.17 ± 0.01^Ab	19.99 ± 0.12^Aa	21.36 ± 0.13^Bb	1.60 ± 0.16^Aab	38.19 ± 2.72^Abc
	10-20	8.02 ± 0.00^Bc	1.10 ± 0.01^Bb	19.74 ± 0.12^ABb	24.45 ± 0.40^Aa	1.48 ± 0.05^Ba	21.11 ± 1.67^Bc
	20-30	8.12 ± 0.00^Ae	1.03 ± 0.01^Cc	19.33 ± 0.19^Ba	20.39 ± 0.11^Cd	1.07 ± 0.12^Ca	10.97 ± 2.16^Ca

表1 不同氮添加对内蒙古温带草原土壤理化性质的影响(平均值±标准误)

Table 1 Effect of different nitrogen additions on soil physical and chemical properties in temperate grassland of Nei Mongol (mean ± SE)

处理 Treatment	土层深度 SLD (cm)	土壤pH Soil pH	土壤密度 SD (g·cm^-3)	土壤含水量 SWC (%)	土壤全碳含量 TC content (g·kg^-1)	全氮含量 TN content (g·kg^-1)	微生物生物量氮含量 MBN content (mg·kg^-1)
N0	0-10	8.22 ± 0.01^Ca	1.26 ± 0.02^Aa	18.27 ± 0.10^Ab	18.40 ± 0.17^Cd	1.39 ± 0.09^Ab	45.03 ± 3.55^Aac
	10-20	8.29 ± 0.00^Ba	1.24 ± 0.02^Aa	17.62 ± 0.27^Bc	22.13 ± 0.29^Ab	1.37 ± 0.09^ABa	34.93 ± 0.35^Bab
	20-30	8.47 ± 0.00^Aa	1.13 ± 0.02^Bb	17.06 ± 0.10^Bb	19.63 ± 0.09^Bd	0.92 ± 0.11^Ba	14.36 ± 0.28^Ca
N2	0-10	8.11 ± 0.00^Cb	1.31 ± 0.01^Aa	19.39 ± 0.19^Ba	21.26 ± 0.10^Bb	1.84 ± 0.22^Aa	53.74 ± 3.20^Aa
	10-20	8.16 ± 0.01^Bb	1.09 ± 0.04^Bb	20.45 ± 0.31^Ab	24.77 ± 0.31^Aa	1.44 ± 0.07^Aa	19.13 ± 3.70^Bc
	20-30	8.29 ± 0.01^Ac	1.09 ± 0.01^Bbc	20.36 ± 0.31^Aa	23.60 ± 0.58^Ab	0.94 ± 0.15^Ba	15.00 ± 0.94^Ba
N5	0-10	8.13 ± 0.01^Bb	1.18 ± 0.01^Ab	19.61 ± 0.30^Ba	21.98 ± 0.05^Ba	1.44 ± 0.03^Aab	31.63 ± 2.56^Ab
	10-20	8.15 ± 0.01^Bb	1.19 ± 0.03^Aab	21.42 ± 0.21^Aa	25.25 ± 0.32^Aa	1.43 ± 0.04^Aa	26.17 ± 1.58^Abc
	20-30	8.37 ± 0.01^Ab	1.24 ± 0.04^Aa	19.53 ± 0.52^Ba	25.10 ± 0.16^Aa	1.16 ± 0.10^Ba	14.14 ± 0.24^Ba
N10	0-10	7.97 ± 0.01^Cc	1.15 ± 0.03^Ab	19.26 ± 0.40^Aa	20.28 ± 0.08^Bc	1.65 ± 0.11^Aab	51.99 ± 2.01^Aa
	10-20	8.01 ± 0.01^Bc	1.03 ± 0.04^Bb	18.25 ± 0.38^Ac	22.65 ± 0.23^Ab	1.47 ± 0.11^Aa	41.81 ± 8.46^Aa
	20-30	8.17 ± 0.01^Ad	1.16 ± 0.02^Ab	19.57 ± 0.41^Aa	22.18 ± 0.04^Ac	0.86 ± 0.08^Ba	14.93 ± 1.72^Ba
N25	0-10	7.89 ± 0.01^Cd	1.17 ± 0.01^Ab	19.99 ± 0.12^Aa	21.36 ± 0.13^Bb	1.60 ± 0.16^Aab	38.19 ± 2.72^Abc
	10-20	8.02 ± 0.00^Bc	1.10 ± 0.01^Bb	19.74 ± 0.12^ABb	24.45 ± 0.40^Aa	1.48 ± 0.05^Ba	21.11 ± 1.67^Bc
	20-30	8.12 ± 0.00^Ae	1.03 ± 0.01^Cc	19.33 ± 0.19^Ba	20.39 ± 0.11^Cd	1.07 ± 0.12^Ca	10.97 ± 2.16^Ca

图2 不同氮添加对内蒙古温带草原土壤团聚体组成的影响。不同小写字母表示不同添加处理间的差异显著(p < 0.05), 不同大写字母表示不同土层间的差异显著(p < 0.05)。N0、N2、N5、N10、N25分别表示氮添加量为0、2、5、10、25 g·m-2·a‒1。

Fig. 2 Effects of different nitrogen additions on soil aggregate composition in a temperate grassland of Nei Mongol. Different lowercase letters indicate significant differences between different addition treatments, different uppercase letters indicate significant differences between different soil layers (p < 0.05). N0, N2, N5, N10 and N25 indicate nitrogen addition amounts of 0, 2, 5, 10, 25 g·m-2·a-1, respectively.

表2 不同氮添加对内蒙古温带草原土壤团聚体平均质量直径(MMD)和分形维数(D)的影响(平均值±标准误)

Table 2 Effects of different nitrogen additions on mean mass diameter (MMD) and fractal dimension (D) of soil aggregates in a temperate grassland of Nei Mongol (mean ± SE)

处理 Treatment	MMD			D
处理 Treatment	0-10 cm	10-20 cm	20-30 cm	0-10 cm	10-20 cm	20-30 cm
N0	1.453 ± 0.009^Cb	1.631 ± 0.005^Ae	1.548 ± 0.005^Bc	2.690 ± 0.002^Ab	2.597 ± 0.003^Ca	2.662 ± 0.001^Bb
N2	1.334 ± 0.004^Cd	1.673 ± 0.003^Ad	1.541 ± 0.000^Bc	2.677 ± 0.003^Ac	2.586 ± 0.002^Bb	2.675 ± 0.001^Aa
N5	1.670 ± 0.002^Ca	1.764 ± 0.005^Ab	1.689 ± 0.014^Bb	2.595 ± 0.002^Ad	2.500 ± 0.000^Be	2.592 ± 0.002^Ac
N10	1.168 ± 0.007^Ce	1.814 ± 0.003^Aa	1.684 ± 0.002^Bb	2.741 ± 0.001^Aa	2.516 ± 0.002^Cd	2.578 ± 0.002^Bd
N25	1.430 ± 0.007^Cc	1.691 ± 0.009^Bc	1.913 ± 0.001^Aa	2.674 ± 0.004^Ac	2.528 ± 0.002^Bc	2.518 ± 0.001^Ce

图3 内蒙古温带草原不同氮添加对β-葡萄糖苷酶(A)、纤维素水解酶(B)、过氧化物酶(C)、多酚氧化酶(D)活性的影响(平均值±标准误)。不同小写字母表示不同添加处理间的差异显著, 不同大写字母表示不同土层间的差异显著(p < 0.05)。N0、N2、N5、N10、N25分别表示氮添加量为0、2、5、10、25 g·m-2·a‒1。

Fig. 3 Effects of different nitrogen additions on the activities of β-glucosidase (A), cellulose hydrolase (B), peroxidase (C) and polyphenol oxidase (D) in a temperate grassland of Nei Mongol (mean ± SE). Different lowercase letters indicate significant differences between different addition treatments; different uppercase letters indicate significant differences between different soil layers (p < 0.05). N0, N2, N5, N10 and N25 indicate nitrogen addition amounts of 0, 2, 5, 10, 25 g·m-2·a-1, respectively.

图4 内蒙古温带草原不同氮添加对可溶性有机碳(A)、易氧化有机碳(B)、微生物生物量碳(C)含量和土壤活性有机碳几何平均值(GMC) (D)的影响(平均值±标准误)。不同小写字母表示不同添加处理间的差异显著, 不同大写字母表示不同土层间的差异显著(p < 0.05)。N0、N2、N5、N10、N25分别表示氮添加量为0、2、5、10、25 g·m-2·a‒1。

Fig. 4 Effects of different nitrogen additions on dissolved organic carbon (A), easily oxidized organic carbon (B), microbial biomass carbon (C) contents and geometric mean of active organic carbon (GMC) (D) in a temperate grassland of Nei Mongol (mean ± SE). Different lowercase letters indicate significant differences between different addition treatments, different uppercase letters indicate significant differences between different soil layers (p < 0.05). N0, N2, N5, N10 and N25 indicate nitrogen addition amounts of 0, 2, 5, 10, 25 g·m-2·a-1, respectively.

图5 内蒙古温带草原土壤活性有机碳与土壤理化性质、团聚体结构、胞外酶活性间的关系。AGB, 地上生物量; BG, β-葡萄糖苷酶活性; BGB, 地下生物量; CB, 纤维素水解酶活性; D, 分形维数; DOC, 可溶性有机碳含量; EOC, 易氧化有机碳含量; GMC, 活性有机碳几何平均值; MBC, 微生物生物量碳含量; MBN, 微生物生物量氮含量; MMD, 平均质量直径; PER, 过氧化物酶活性; POX, 多酚氧化酶活性; SD, 土壤密度; SLD, 土层深度; SWC, 土壤含水量; TC, 全碳含量; TN, 全氮含量。*, p < 0.05。

Fig. 5 Pearson’s correlations between soil active organic carbon and soil physicochemical properties, aggregate structure, extracellular enzyme activity in a temperate grassland of Nei Mongol. AGB, aboveground biomass; BG, β-glucosidase activity; BGB, belowground biomass; CB, cellulose hydrolase activity; D, fractal dimension; DOC, dissolved organic carbon content; EOC, easily oxidized organic carbon content; GMC, geometric mean of active organic carbon content; MBC, microbial biomass carbon content; MBN, microbial biomass nitrogen content; MMD, mean mass diameter; PER, peroxidase activity; POX, polyphenol oxidase activity; SD, soil density; SLD, soil layer depth; SWC, soil water content; TC, total carbon content; TN, total nitrogen content. *, p < 0.05.

图6 内蒙古温带草原土壤活性有机碳组分的结构方程模型。箭头表示假设的因果关系方向, 箭头旁边的数字是标准化的路径系数, 箭头宽度表示关系强度, 实线箭头表示显著关系(*, p < 0.05; **, p < 0.01), 虚线箭头表示不显著关系(p > 0.05), 矩形框上R2表示由该变量和其他变量的关系来解释该变量的方差比例。BGB, 地下生物量; DOC, 可溶性有机碳含量; EOC, 易氧化有机碳含量; HA, 水解酶活性; MBC, 微生物生物量碳含量; MMD, 平均质量直径; NA, 氮添加; OA, 氧化酶活性; SD, 土壤密度。

Fig. 6 Structural equation model of soil active organic carbon fractions in a temperate grassland of Nei Mongol. The rectangular box indicates the variables contained in the model. The arrow indicates the direction of the assumed causal relationship. The number next to the arrow indicates the standardized path coefficient. The arrow width indicates the relationship strength. The solid arrow indicates a significant relationship (*, p < 0.05; **, p < 0.01). The dashed arrow indicates an insignificant relationship (p > 0.05), and R2 on the rectangular box indicates the variance ratio of the variable explained by its relationship with other variables. BGB, belowground biomass; DOC, dissolved organic carbon content; EOC, easily oxidized organic carbon content; HA, hydrolase activity; MBC, microbial biomass carbon content; MMD, mean mass diameter; NA, nitrogen addition; OA, oxidase activity; SD, soil density.

参考文献 63

[1]	Allison SD, Czimczik CI, Treseder KK (2008). Microbial activity and soil respiration under nitrogen addition in Alaskan boreal forest. Global Change Biology, 14, 1156-1168.
[2]	Blair GJ, Lefroy R, Lisle L (1995). Soil carbon fractions based on their degree of oxidation, and the development of a carbon management index for agricultural systems. Australian Journal of Agricultural Research, 46, 1459. DOI: 10.1071/ar9951459.
[3]	Brookes PC, Landman A, Pruden G, Jenkinson DS (1985). Chloroform fumigation and the release of soil nitrogen: a rapid direct extraction method to measure microbial biomass nitrogen in soil. Soil Biology & Biochemistry, 17, 837-842.
[4]	Chen H, Li D, Gurmesa GA, Yu G, Li L, Zhang W, Fang H, Mo J (2015). Effects of nitrogen deposition on carbon cycle in terrestrial ecosystems of China: a meta-analysis. Environmental Pollution, 206, 352-360. DOI PMID
[5]	Chen JG, Tian DL, Yan WD, Xiang WH, Fang X (2011). Progress on study of carbon sequestration in soil aggregates. Journal of Central South University of Forestry & Technology, 31(5), 74-80.
	[陈建国, 田大伦, 闫文德, 项文化, 方晰 (2011). 土壤团聚体固碳研究进展. 中南林业科技大学学报, 31(5), 74-80.]
[6]	Compton JE, Watrud LS, Arlene Porteous L, DeGrood S (2004). Response of soil microbial biomass and community composition to chronic nitrogen additions at Harvard forest. Forest Ecology and Management, 196, 143-158.
[7]	Fan MZ, Yin C, Fan FL, Song AL, Wang BR, Li DC, Liang YC (2015). Effects of different long-term fertilization on the activities of enzymes related to carbon, nitrogen, and phosphorus cycles in a red soil. Chinese Journal of Applied Ecology, 26, 833-838.
	[范淼珍, 尹昌, 范分良, 宋阿琳, 王伯仁, 李冬初, 梁永超 (2015). 长期不同施肥对红壤碳、氮、磷循环相关酶活性的影响. 应用生态学报, 26, 833-838.]
[8]	Feng Z, Rütting T, Pleijel H, Wallin G, Reich PB, Kammann CI, Newton PCD, Kobayashi K, Luo Y, Uddling J (2015). Constraints to nitrogen acquisition of terrestrial plants under elevated CO₂. Global Change Biology, 21, 3152-3168. DOI PMID
[9]	Giulia B, Else KB, Chidinma UO, Jennifer M, Gerrit G, Rob C, Paul M, Lijbert B, Ron DG (2019). Sensitivity of labile carbon fractions to tillage and organic matter management and their potential as comprehensive soil quality indicators across pedoclimatic conditions in Europe. Ecological Indicators, 99, 38-50.
[10]	Grandy AS, Neff JC, Weintraub MN (2007). Carbon structure and enzyme activities in alpine and forest ecosystems. Soil Biology & Biochemistry, 39, 2701-2711.
[11]	Guo ZM, Zhang XY, Li DD, Dong WT, Li ML (2017). Characteristics of soil organic carbon and related exo- enzyme activities at different altitudes in temperate forests. Chinese Journal of Applied Ecology, 28, 2888-2896.
	[郭志明, 张心昱, 李丹丹, 董文亭, 李美玲 (2017). 温带森林不同海拔土壤有机碳及相关胞外酶活性特征. 应用生态学报, 28, 2888-2896.] DOI
[12]	Haynes RJ (2005). Labile organic matter fractions as central components of the quality of agricultural soils: an overview. Advances in Agronomy, 85, 221-268.
[13]	He YL, Qi YC, Peng Q, Dong YS, Yan ZQ, Li ZL (2018). Effects of exogenous carbon and nitrogen addition on the key process of carbon cycle in grassland ecosystem: a review. China Environmental Science, 38, 1133-1141.
	[贺云龙, 齐玉春, 彭琴, 董云社, 闫钟清, 李兆林 (2018). 外源碳氮添加对草地碳循环关键过程的影响. 中国环境科学, 38, 1133-1141.]
[14]	Howard AL (2013). Handbook of structural equation modeling. Structural Equation Modeling. A Multidisciplinary Journal, 20, 354-360.
[15]	Hu J, Lyu YH, Zhang K, Tao YZ, Li T, Ren YJ (2016). The differences of water conservation function under typical vegetation types in the Pailugou catchment, Qilian Mountain, northwest China. Acta Ecologica Sinica, 36, 3338-3349.
	[胡健, 吕一河, 张琨, 陶蕴之, 李婷, 任艳娇 (2016). 祁连山排露沟流域典型植被类型的水源涵养功能差异. 生态学报, 36, 3338-3349.]
[16]	Hungate AB, Jackson BR, Field BC, Chapin III FS (1995). Detecting changes in soil carbon in CO₂ enrichment experiments. Plant and Soil, 187, 135-145.
[17]	Jia YL, Yu GR, He NP, Zhan XY, Fang HJ, Sheng WP, Zuo Y, Zhang DY, Wang QF (2014). Spatial and decadal variations in inorganic nitrogen wet deposition in China induced by human activity. Scientific Reports, 4, 3763. DOI: 10.1038/srep03763.
[18]	Jian JN, Liu WC, Zhu YF, Li JX, Wen YH, Liu FH, Ren CJ, Han XH (2022). Effects of short-term nitrogen addition on soil organic carbon components in Robinia pseudoacacia plantation. Environmental Science, 44, 2767-2774.
	[简俊楠, 刘伟超, 朱玉帆, 李佳欣, 温宇豪, 刘付和, 任成杰, 韩新辉 (2022). 短期氮添加对黄土高原人工刺槐林土壤有机碳组分的影响. 环境科学, 44, 2767-2774.]
[19]	Kurt SP, Donald RZ, Andrew JB, Jennifer AA, Neil WM (2004). Chronic nitrate additions dramatically increase the export of carbon and nitrogen from northern hardwood ecosystems. Biogeochemistry, 68, 179-197.
[20]	Li HR, Zhu Y, Tian JH, Wei K, Chen ZH, Chen LJ (2018). Effects of carbon and nitrogen additions on soil organic C, N, P contents and their catalyzed enzyme activities in a grassland. Chinese Journal of Applied Ecology, 29, 2470-2476.
	[李焕茹, 朱莹, 田纪辉, 魏锴, 陈振华, 陈利军 (2018). 碳氮添加对草地土壤有机碳氮磷含量及相关酶活性的影响. 应用生态学报, 29, 2470-2476.] DOI
[21]	Li R, Chang RY (2015). Effects of external nitrogen additions on soil organic carbon dynamics and the mechanism. Chinese Journal of Plant Ecology, 39, 1012-1020. DOI
	[李嵘, 常瑞英 (2015). 土壤有机碳对外源氮添加的响应及其机制. 植物生态学报, 39, 1012-1020.] DOI
[22]	Li T, Cui LZ, Liu LL, Wang H, Dong JF, Wang F, Song XF, Che RX, Li CJ, Tang L, Xu ZH, Wang YF, Du JQ, Hao YB, Cui XY (2022). Characteristics of nitrogen deposition research within grassland ecosystems globally and its insight from grassland microbial community changes in China. Frontiers in Plant Science, 13, 947279. DOI: 10.3389/FPLS.2022.947279.
[23]	Ling XL, Shi BK, Cui HY, Song WZ, Sun W (2021). Effects of nitrogen and phosphorus addition on soil aggregates structure and carbon content in Songnen grassland. Chinese Journal of Grassland, 43(2), 54-63.
	[凌小莉, 史宝库, 崔海莹, 宋文政, 孙伟 (2021). 氮磷添加对松嫩草地土壤团聚体结构及其碳含量的影响. 中国草地学报, 43(2), 54-63.]
[24]	Liu XJ, Duan L, Mo JM, Du EZ, Shen JL, Lu XK, Zhang Y, Zhou XB, He CE, Zhang FS (2011). Nitrogen deposition and its ecological impact in China: an overview. Environmental Pollution, 159, 2251-2264. DOI PMID
[25]	Lu X, Hou E, Guo J, Gilliam FS, Li J, Tang S, Kuang Y (2021). Nitrogen addition stimulates soil aggregation and enhances carbon storage in terrestrial ecosystems of China: a meta-analysis. Global Change Biology, 27, 2780-2792. DOI PMID
[26]	Luo QP, Gong JR, Xu S, Baoyin T, Wang YH, Zhai ZW, Pan Y, Liu M, Yang LL (2016). Effects of N and P additions on net nitrogen mineralization in temperate typical grasslands in Nei Mongol, China. Chinese Journal of Plant Ecology, 40, 480-492.
	[罗亲普, 龚吉蕊, 徐沙, 宝音陶格涛, 王忆慧, 翟占伟, 潘琰, 刘敏, 杨丽丽 (2016). 氮磷添加对内蒙古温带典型草原净氮矿化的影响. 植物生态学报, 40, 480-492.] DOI
[27]	Margit VL, Ingrid K, Klemens E, Heinz F, Georg G, Egbert M, Bernd M (2007). SOM fractionation methods: relevance to functional pools and to stabilization mechanisms. Soil Biology & Biochemistry, 39, 2183-2207.
[28]	Martin JC, Mark BD (1996). Temperature and moisture effects on the production of dissolved organic carbon in a Spodosol. Soil Biology & Biochemistry, 28, 1191-1199.
[29]	Mohammat A (2010). Ecosystem carbon stocks and their changes in China’s grasslands. Science China (Life Sciences), 53, 757-765.
[30]	Moore TR, de Souza W, Koprivnjak JF (1992). Controls on the sorption of dissolved organic carbon by soils. Soil Science, 154, 120-129.
[31]	Murphy DV, MacDonald AJ, Stockdale EA, Goulding KT, Fortune S, Gaunt JL, Poulton PR, Wakefield JA, Webster CP, Wilmer WS (2000). Soluble organic nitrogen in agricultural soils. Biology and Fertility of Soils, 30, 374-387.
[32]	Nagamitsu M, Akira W, Makoto K (2004). Chemical characteristics and potential source of fulvic acids leached from the plow layer of paddy soil. Geoderma, 120, 309-323.
[33]	Nahia G, Ander G, Agustín M, Inazio MDA (2009). Soil organic matter in soil physical fractions in adjacent semi-natural and cultivated stands in temperate Atlantic forests. Soil Biology & Biochemistry, 41, 1674-1683.
[34]	Pirmoradian N, Sepaskhah AR, Hajabbasi MA (2005). Application of fractal theory to quantify soil aggregate stability as influenced by tillage treatments. Biosystems Engineering, 90, 227-234.
[35]	Saiya-Cork KR, Sinsabaugh RL, Zak DR (2002). The effects of long term nitrogen deposition on extracellular enzyme activity in an Acer saccharum forest soil. Soil Biology & Biochemistry, 34, 1309-1315.
[36]	Shen H, Cao ZH, Hu ZY (1999). Characteristics and ecological effects of the active organic carbon in soil. Chinese Journal of Ecology, 18, 32-38.
	[沈宏, 曹志洪, 胡正义 (1999). 土壤活性有机碳的表征及其生态效应. 生态学杂志, 18, 32-38.]
[37]	Song KC, Wang X, Xu DM, Li YK, Sa CN, Ma S (2022). Effects of short-term nitrogen addition on soil biological properties in desert steppe. Journal of Soil and Water Conservation, 36, 303-310.
	[宋珂辰, 王星, 许冬梅, 李永康, 撒春宁, 马霜 (2022). 短期氮添加对荒漠草原土壤微生物特征的影响. 水土保持学报, 36, 303-310.]
[38]	Su YJ (2018). Study on Soil Acidification Characteristics and Regulation Mechanism of Tea Gardens in Southern Anhui Province. Master degree dissertation, Zhejiang University, Hangzhou. 59.
	[苏有健 (2018). 皖南茶园土壤酸化特征及其调控机制的研究. 硕士学位论文, 浙江大学, 杭州. 59.]
[39]	Sun X, Zhang YM, Zhang LJ, Hu CS, Dong WX, Li XX, Wang YY, Liu XP, Xing L, Han J (2021). Effects of long-term exogenous organic material addition on the organic carbon composition of soil aggregates in farmlands of North China. Chinese Journal of Eco-Agriculture, 29, 1384-1396.
	[孙雪, 张玉铭, 张丽娟, 胡春胜, 董文旭, 李晓欣, 王玉英, 刘秀萍, 邢力, 韩建 (2021). 长期添加外源有机物料对华北农田土壤团聚体有机碳组分的影响. 中国生态农业学报(中英文), 29, 1384-1396.]
[40]	Suo WK, Yang JH, Hu CY, Feng SS, Tian XM (2023). Effect of nitrogen fertilizer and soil conditioner on soil carbon and nitrogen content, and oat yield. Chinese Journal of Eco-Agriculture, 31, 858-867.
	[索文康, 杨金翰, 胡晨阳, 冯莎莎, 田小明 (2023). 氮肥和调理剂对土壤碳氮含量及莜麦产量的影响. 中国生态农业学报(中英文), 31, 858-867.]
[41]	Tian L, Shi W (2014). Soil peroxidase regulates organic matter decomposition through improving the accessibility of reducing sugars and amino acids. Biology and Fertility of Soils, 50, 785-794.
[42]	Wang GL, Liu F (2014). Carbon allocation of Chinese pine seedlings along a nitrogen addition gradient. Forest Ecology and Management, 334, 114-121.
[43]	Wang JY, Song CC, Wang XW, Song YY (2012). Changes in labile soil organic carbon fractions in wetland ecosystems along a latitudinal gradient in Northeast China. Catena, 96, 83-89.
[44]	Wang W, Yang YS, Chen GS, Guo JF, Qian W (2008). Profile distribution and seasonal variation of soil dissolved organic carbon in natural Castanopsis fabric forest in subtropical China. Chinese Journal of Ecology, 27, 924-928.
	[汪伟, 杨玉盛, 陈光水, 郭剑芬, 钱伟 (2008). 罗浮栲天然林土壤可溶性有机碳的剖面分布及季节变化. 生态学杂志, 27, 924-928.]
[45]	Wu NN, Filley TR, Bai E, Han SJ, Jiang P (2015). Incipient changes of lignin and substituted fatty acids under N addition in a Chinese forest soil. Organic Geochemistry, 79, 14-20.
[46]	Xi D, Weng HD, Hu YL, Wu JP (2021). Effects of canopy nitrogen addition and understory removal on soil organic carbon fractions in a Chinese fir plantation. Acta Ecologica Sinica, 41, 8525-8534.
	[习丹, 翁浩东, 胡亚林, 吴建平 (2021). 林冠氮添加和林下植被去除对杉木林土壤有机碳组分的影响. 生态学报, 41, 8525-8534.]
[47]	Xiao Y, Huang ZG, Wu HT, Lyu XG (2015). Compositions and contents of active organic carbon in different wetland soils in Sanjiang Plain, Northeast China. Acta Ecologica Sinica, 35, 7625-7633.
	[肖烨, 黄志刚, 武海涛, 吕宪国 (2015). 三江平原不同湿地类型土壤活性有机碳组分及含量差异. 生态学报, 35, 7625-7633.]
[48]	Xu MG, Lou YL, Sun XL, Wang W, Baniyamuddin M, Zhao K (2011). Soil organic carbon active fractions as early indicators for total carbon change under straw incorporation. Biology and Fertility of Soils, 47, 745-752.
[49]	Yang PL, Luo YP, Shi YC (1993). Soil fractal characteristics characterized by weight distribution of particle size. Chinese Science Bulletin, 20, 1896-1899.
	[杨培岭, 罗远培, 石元春 (1993). 用粒径的重量分布表征的土壤分形特征. 科学通报, 20, 1896-1899.]
[50]	Yang X, Wang D, Lan Y, Meng J, Jiang LL, Sun Q, Cao DY, Sun YY, Chen WF (2018). Labile organic carbon fractions and carbon pool management index in a 3-year field study with biochar amendment. Journal of Soils and Sediments, 18, 1569-1578.
[51]	Yang YH, Zhang DY, Wei B, Liu Y, Feng XH, Mao C, Xu WJ, He M, Wang L, Zheng ZH, Wang YY, Chen LY, Peng YF (2023). Nonlinear responses of community diversity, carbon and nitrogen cycles of grassland ecosystems to external nitrogen input. Chinese Journal of Plant Ecology, 47, 1-24.
	[杨元合, 张典业, 魏斌, 刘洋, 冯雪徽, 毛超, 徐玮婕, 贺美, 王璐, 郑志虎, 王媛媛, 陈蕾伊, 彭云峰 (2023). 草地群落多样性和生态系统碳氮循环对氮输入的非线性响应及其机制. 植物生态学报, 47, 1-24.]
[52]	Zhang J, Zhou J, Lambers H, Li Y, Li Y, Qin G, Wang M, Wang J, Li Z, Wang F (2022). Nitrogen and phosphorus addition exerted different influences on litter and soil carbon release in a tropical forest. Science of the Total Environment, 832, 155049. DOI: 10.1016/j.scitotenv.2022.155049.
[53]	Zhang X, Ren HY, Kang J, Zhu Y, Li DH, Han GD (2021). Effects of warming and nitrogen addition on soil physical and chemical properties in desert steppe of Inner Mongolia. Chinese Journal of Grassland, 43(6), 17-24.
	[张欣, 任海燕, 康静, 朱毅, 李冬慧, 韩国栋 (2021). 增温和施氮对内蒙古荒漠草原土壤理化性质的影响. 中国草地学报, 43(6), 17-24.]
[54]	Zhang X, Wang Q, Gilliam FS, Bai W, Han X, Li L (2012). Effect of nitrogen fertilization on net nitrogen mineralization in a grassland soil, northern China. Grass and Forage Science, 67, 219-230.
[55]	Zhang XL, Wang FC, Fang XM, He P, Zhang YF, Chen FS, Wang HM (2017). Responses of soil organic carbon and its labile fractions to nitrogen and phosphorus additions in Cunninghamia lanceolata plantations in subtropical China. Chinese Journal of Applied Ecology, 28, 449-455.
	[张秀兰, 王方超, 方向民, 何平, 张宇飞, 陈伏生, 王辉民 (2017). 亚热带杉木林土壤有机碳及其活性组分对氮磷添加的响应. 应用生态学报, 28, 449-455.] DOI
[56]	Zhang YR, An H, Liu BR, Wen ZL, Wu XZ, Li QL, Du ZY (2019). Effects of short-term nitrogen and phosphorus addition on soil labile organic carbon in desert grassland. Acta Prataculturae Sinica, 28, 12-24. DOI
	[张雅柔, 安慧, 刘秉儒, 文志林, 吴秀芝, 李巧玲, 杜忠毓 (2019). 短期氮磷添加对荒漠草原土壤活性有机碳的影响. 草业学报, 28, 12-24.] DOI
[57]	Zhao X, Yu WT, Li JD, Jiang ZS (2006). Research advances in soil organic carbon and its fractions under different management patterns. Chinese Journal of Applied Ecology, 17, 2203-2209. PMID
	[赵鑫, 宇万太, 李建东, 姜子绍 (2006). 不同经营管理条件下土壤有机碳及其组分研究进展. 应用生态学报, 17, 2203-2209.]
[58]	Zheng BZ (2013). Guidelines for Soil Analysis Techniques. China Agricultural Publishing House, Beijing.
	[郑必昭 (2013). 土壤分析技术指南. 中国农业出版社, 北京.]
[59]	Zhong X, Li J, Li X, Ye Y, Liu S, Hallett PD, Ogden MR, Naveed M (2017). Physical protection by soil aggregates stabilizes soil organic carbon under simulated N deposition in a subtropical forest of China. Geoderma, 285, 323-332.
[60]	Zhou GY, Wu YY (2016). Meta-analysis of effects of grazing on carbon pools in grassland ecosystems in different climatic regions. Acta Prataculturae Sinica, 25(10), 1-10.
	[周贵尧, 吴沿友 (2016). 放牧对草原生态系统不同气候区碳库影响的meta分析. 草业学报, 25(10), 1-10.] DOI
[61]	Zhou ZH, Wang CK, Jin Y (2017). Stoichiometric responses of soil microflora to nutrient additions for two temperate forest soils. Biology and Fertility of Soils, 53, 397-406.
[62]	Zhu KH, Duan LX, Li YC, Li ZW (2021). Research progress of organic carbon in soil aggregates. Chinese Agricultural Science Bulletin, 37(21), 86-90. DOI
	[朱锟恒, 段良霞, 李元辰, 李振炜 (2021). 土壤团聚体有机碳研究进展. 中国农学通报, 37(21), 86-90.] DOI
[63]	Zou XM, Ruan HH, Fu Y, Yang XD, Sha LQ (2005). Estimating soil labile organic carbon and potential turnover rates using a sequential fumigation-incubation procedure. Soil Biology & Biochemistry, 37, 1923-1928.