不同土地利用类型对丹江口库区土壤氮矿化的影响

doi:10.3724/SP.J.1258.2012.00530

摘要/Abstract

摘要：

氮(N)素是陆地生态系统净初级生产力的重要限制因子, 土地利用类型的变化对生态系统氮循环过程有着重要的影响。采用PVC顶盖埋管原位培养的方法, 对丹江口库区清塘河流域相邻的侧柏(Platycladus orientalis)人工林、人工种植灌木林地和农田3种土地利用类型的氮素矿化和硝化作用进行了研究。结果表明, 侧柏人工林、灌木林地和农田的NH₄⁺-N浓度(mg·kg^-1)依次为1.33 ± 0.20、1.67 ± 0.17和1.62 ± 0.13, 不同土地利用类型间的NH₄⁺-N浓度无显著性差异; 而3种土地利用类型下土壤NO₃^--N浓度(mg·kg^-1)差异显著, 农田NO₃^--N浓度(9.00 ± 0.73)显著高于侧柏人工林(1.27 ± 0.18)和灌木林地(3.51 ± 0.11)。NO₃^--N在灌木林地和农田中分别占土壤无机氮库的67.8%和84.8%, 是土壤无机氮库的主要存在形式; 而侧柏人工林中NO₃^--N和NH₄⁺-N浓度则基本相等。土壤硝化速率(mg·kg^-1·30 d^-1)从农田(7.13 ± 2.19)、灌木林地(2.56 ± 1.07)到侧柏人工林(0.85 ± 0.10)显著性降低。侧柏人工林、灌木林地和农田的矿化速率(mg·kg^-1·30 d^-1)依次为0.98 ± 0.12、2.52 ± 1.25和6.58 ± 2.29。矿化速率和硝化速率显著正相关, 但是矿化速率在不同的土地利用类型间差异不显著。培养过程中灌木林地和农田NH₄⁺-N的消耗大于积累, 氨化速率为负值, 导致灌木林地和农田矿化速率小于硝化速率。氮素的矿化和硝化作用受土壤含水量和土壤温度的影响, 并对土壤含水量更为敏感。土壤C:N与土壤矿化和硝化速率显著负相关。研究结果表明: 土地利用类型的变化会改变土壤微环境和土壤C:N, 进而会影响到土壤氮循环过程。

关键词: 丹江口水库, 土地利用类型, 净氮矿化速率, 硝化速率, 土壤无机氮

Abstract:

Aims Land use change may alter nitrogen (N) dynamics in terrestrial ecosystems, but its effects remain poorly quantified. Due to reorganization of the land use by government, a large cultivated area has converted to woodland and shrubland plantation since the 1980’s in Danjiangkou Reservoir area, China. Our objective was to investigate effects of agricultural land use change on soil N dynamics in this area.
Methods We conducted in situ close-top tube incubation experiment to determine soil inorganic N (NH₄⁺-N, NO₃^--N), soil net nitrogen mineralization and nitrification in three adjacent land use types (afforestation, shrubland and cropland) in the Qingtang river basin around Danjiangkou Reservoir in Spring of 2011.
Important findings Soil NO₃^--N concentration (mg·kg^-1) was 1.27 ± 0.18, 3.51 ± 0.11 and 9.00 ± 0.73 in afforestation, shrubland and cropland, respectively. Soil NO₃^--N concentration significantly increased from afforestation to shrubland to cropland, whereas NH₄⁺-N concentration (mg·kg^-1) was not significantly different among afforestation (1.33 ± 0.20), shrubland (1.67 ± 0.17) and cropland (1.62 ± 0.13). We found that NO₃^--N was the main form of inorganic N under shrubland and cropland, and the proportion of NO₃^--N to soil inorganic N content was 67.8% and 84.8% in shrubland and cropland, respectively; however, the concentration of NO₃^--N was approximately equal to NH₄⁺-N under afforestation. Soil net N mineralization rate (mg·kg^-1·30 d^-1) were 0.98 ± 0.12, 2.52 ± 1.25 and 6.58 ± 2.29, respectively in afforestation, shrubland to cropland. Soil net N mineralization rate was not significantly different among the land use types, whereas nitrification rate (mg·kg^-1·30 d^-1) was significantly different: cropland (7.13 ± 2.19), shrubland (2.56 ± 1.07) and afforestation (0.85 ± 0.10). Soil net N mineralization rate was positively correlated with nitrification rate. Nitrification rate accounts for approximately 87% of soil mineralization rate in afforestation, whereas nitrification was higher than mineralization rate in shrubland and cropland soil due to the ammonification rate being below zero. Both soil N mineralization and nitrification were regulated by soil water content and soil temperature with more sensitive to soil water content during the incubation period. Additionally, soil N mineralization and nitrification were negatively correlated with soil C:N ratio. Our results suggest that change in soil microclimate and soil C:N ratio under land use change would impact soil N dynamics.

Key words: Danjiangkou Reservoir, land use type, net nitrogen mineralization rate, nitrification rate, soil inorganic nitrogen

李铭, 朱利川, 张全发, 程晓莉. 不同土地利用类型对丹江口库区土壤氮矿化的影响. 植物生态学报, 2012, 36(6): 530-538. DOI: 10.3724/SP.J.1258.2012.00530

LI Ming, ZHU Li-Chuan, ZHANG Quan-Fa, CHENG Xiao-Li. Impacts of different land use types on soil nitrogen mineralization in Danjiangkou Reservoir Area, China. Chinese Journal of Plant Ecology, 2012, 36(6): 530-538. DOI: 10.3724/SP.J.1258.2012.00530

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图/表 5

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理化性质 Physical and chemical properties	人工林 Afforestation	灌木林地 Shrubland	农田 Cropland
有机碳 Organic C (g·kg^-1)	10.43 ±1.41^a	8.70 ± 0.47^ab	4.07 ± 0.15^b
总氮 Total N (g·kg^-1)	6.83 ± 0.78^a	7.53 ± 0.43^a	5.87 ± 0.43^a
C:N	15.21 ± 0.56^a	11.69 ± 1.22^b	7.03 ± 0.67^c
微生物生物量碳 Microbial biomass C (mg·kg^-1)	290.84 ± 37.46^a	291.34 ± 37.64^a	135.02 ± 27.85^a
微生物生物量氮 Microbial biomass N (mg·kg^-1)	48.41 ± 5.76^a	45.49 ± 5.77^a	18.84 ± 0.68^b
土壤含水量 Soil water content (%)	8.66 ± 0.95^b	11.99 ± 1.32^ab	13.84 ± 1.03^a
土壤温度 Soil temperature (℃)	15.2 ± 0.3^b	19.5 ± 0.8^a	19.0 ± 1.0^a
pH	7.57 ± 0.05^b	7.93 ± 0.07^a	8.04 ± 0.04^a
容重 Bulk density (g·cm^-3)	1.42 ± 0.06^a	1.56 ± 0.07^a	1.44 ± 0.02^a

理化性质 Physical and chemical properties	人工林 Afforestation	灌木林地 Shrubland	农田 Cropland
有机碳 Organic C (g·kg^-1)	10.43 ±1.41^a	8.70 ± 0.47^ab	4.07 ± 0.15^b
总氮 Total N (g·kg^-1)	6.83 ± 0.78^a	7.53 ± 0.43^a	5.87 ± 0.43^a
C:N	15.21 ± 0.56^a	11.69 ± 1.22^b	7.03 ± 0.67^c
微生物生物量碳 Microbial biomass C (mg·kg^-1)	290.84 ± 37.46^a	291.34 ± 37.64^a	135.02 ± 27.85^a
微生物生物量氮 Microbial biomass N (mg·kg^-1)	48.41 ± 5.76^a	45.49 ± 5.77^a	18.84 ± 0.68^b
土壤含水量 Soil water content (%)	8.66 ± 0.95^b	11.99 ± 1.32^ab	13.84 ± 1.03^a
土壤温度 Soil temperature (℃)	15.2 ± 0.3^b	19.5 ± 0.8^a	19.0 ± 1.0^a
pH	7.57 ± 0.05^b	7.93 ± 0.07^a	8.04 ± 0.04^a
容重 Bulk density (g·cm^-3)	1.42 ± 0.06^a	1.56 ± 0.07^a	1.44 ± 0.02^a

土壤理化性质 Soil physical and chemical properties	F	p
硝态氮 NO₃^--N (mg·kg^-1)	81.14	<0.001
铵态氮 NH₄⁺-N (mg·kg^-1)	1.16	0.376
无机氮 Inorganic N (mg·kg^-1)	96.38	<0.001
矿化速率 Mineralization rate (mg·kg^-1·30 d^-1)	3.97	0.09
硝化速率 Nitrification rate (mg·kg^-1·30 d^-1)	5.32	0.047
氨化速率 Ammonification rate (mg·kg^-1·30 d^-1)	6.13	0.035
有机碳 Organic C (g·kg^-1)	14.61	0.005
总氮 Total N (g·kg^-1)	1.50	0.296
C:N	22.55	0.002
微生物生物量碳 Microbial biomass C (mg·kg^-1)	3.59	0.094
微生物生物量氮 Microbial biomass N (mg·kg^-1)	7.78	0.022
土壤含水量 Soil water content (%)	5.60	0.042
土壤温度 Soil temperature (℃)	8.93	0.016
pH	18.97	0.03
容重 Bulk density (g·cm^-3)	1.94	0.224

土壤理化性质 Soil physical and chemical properties	F	p
硝态氮 NO₃^--N (mg·kg^-1)	81.14	<0.001
铵态氮 NH₄⁺-N (mg·kg^-1)	1.16	0.376
无机氮 Inorganic N (mg·kg^-1)	96.38	<0.001
矿化速率 Mineralization rate (mg·kg^-1·30 d^-1)	3.97	0.09
硝化速率 Nitrification rate (mg·kg^-1·30 d^-1)	5.32	0.047
氨化速率 Ammonification rate (mg·kg^-1·30 d^-1)	6.13	0.035
有机碳 Organic C (g·kg^-1)	14.61	0.005
总氮 Total N (g·kg^-1)	1.50	0.296
C:N	22.55	0.002
微生物生物量碳 Microbial biomass C (mg·kg^-1)	3.59	0.094
微生物生物量氮 Microbial biomass N (mg·kg^-1)	7.78	0.022
土壤含水量 Soil water content (%)	5.60	0.042
土壤温度 Soil temperature (℃)	8.93	0.016
pH	18.97	0.03
容重 Bulk density (g·cm^-3)	1.94	0.224

	净矿化速率 Net mineralization rate (mg·kg^-1·30 d^-1)	硝化速率 Nitrification rate (mg·kg^-1·30 d^-1)	氨化速率 Ammonification rate (mg·kg^-1·30 d^-1)
硝态氮 NO₃^--N (mg·kg^-1)	0.819^**	0.869^**	-0.784^*
铵态氮 NH₄⁺-N (mg·kg^-1)	0.181	0.201	-0.249
无机氮 Inorganic N (mg·kg^-1)	0.813^**	0.864^**	-0.785^*
有机碳 Organic C (g·kg^-1)	-0.749^*	-0.787^*	0.653
总氮 Total N (g·kg^-1)	-0.200	-0.243	0.493
C:N	-0.828^**	-0.863^**	0.644
微生物生物量碳 Microbial biomass C (mg·kg^-1)	-0.743^*	-0.774^*	0.580
微生物生物量氮 Microbial biomass N (mg·kg^-1)	-0.689^*	-0.738^*	0.732^*
土壤含水量 Soil water content (%)	0.682^*	0.694^*	-0.373
土壤温度 Soil temperature (℃)	0.287	0.316	-0.382
pH	0.619	0.651	-0.534
容重 Bulk density (g·cm^-3)	0.069	0.039	0.265
氨化速率 Ammonification rate (mg·kg^-1·30 d^-1)	-0.337	-0.429
硝化速率 Nitrification rate (mg·kg^-1·30 d^-1)	0.995^**