CO2浓度倍增、高氮沉降和高降雨对南亚热带人工模拟森林生态系统土壤呼吸的影响

doi:10.3773/j.issn.1005-264x.2009.06.002

摘要/Abstract

摘要：

土壤呼吸响应全球气候变化对全球C循环具有重要作用。应用大型开顶箱(Open-top chamber, OTC)人工控制手段, 研究了大气CO₂浓度倍增、高氮沉降和高降雨处理对南亚热带人工森林生态系统土壤呼吸的影响。结果表明: 对照箱、CO₂浓度倍增处理以及高氮沉降处理下土壤呼吸速率都具有明显的季节变化, 雨季(4~9月)的土壤呼吸速率显著高于旱季(10月至次年3月) (p<0.001); 但高降雨处理下无明显的季节差异(p>0.05)。CO₂浓度倍增能显著提高土壤呼吸速率(p<0.05), 其他处理则变化不大。大气CO₂浓度倍增、高氮沉降、高降雨处理和对照箱的土壤呼吸年通量分别为4 241.7、3 400.8、3 432.0和3 308.4 g CO₂·m^-2·a^-1。但在不同季节, 各种处理对土壤呼吸的影响是不同的。在雨季, 大气CO₂浓度倍增和高氮沉降的土壤呼吸速率显著提高(p<0.05), 其他处理无显著变化; 而在旱季, 高降雨的土壤呼吸速率显著高于对照箱(p<0.05), 氮沉降处理则抑制土壤呼吸作用(p<0.05)。各处理的土壤呼吸速率与地下5 cm土壤温度之间具有显著的指数关系(p<0.001); 当土壤湿度低于15%时, 各处理的土壤呼吸速率与地下5 cm土壤湿度具有显著的线性关系(p<0.001)。

关键词: CO₂浓度倍增, 开顶箱(OTC), 氮沉降, 降雨, 土壤呼吸

Abstract:

Aims Responses of soil respiration to global change play an important role in global carbon cycling, but the effects of increasing atmospheric carbon dioxide concentration ([CO₂]), nitrogen (N) deposition and precipitation on soil respiration in subtropical China are unclear. Our objective was to test the effects of increased [CO₂], N deposition and precipitation on soil respiration and to determine how they influence soil respiration in subtropical China.
Methods A model forest ecosystem was constructed of six tree species native to South China. The species were exposed to four experimental treatments in open-top chambers beginning March 2005. Three chambers were used for elevated [CO₂] (CC), two for high N treatment (NN) and the control (CO) and one for elevated precipitation (HR). The CC treatment was achieved by supplying additional CO ₂ from a tank until the chambers had a concentration of (700 ± 20) μmol CO ₂·mol^-1. The NN treatment was achieved by spraying seedlings once a week for a total amount of NH₄NO₃ of 100 kg N·hm^-2·a^-1. The HR treatment was achieved by weekly irrigation with 100 L water.
Important findings For two years, soil respiration displayed strong seasonal patterns with higher values observed in the wet season (April to September) and lower values in the dry season (October to March) in the control chambers (CO) and the CC and NN treatments (p<0.001). There was no seasonal difference in the HR treatment (p>0.05). The CC enrichment affected soil respiration significantly (p<0.05), and there were no significant differences in annual CO₂effluxes between CO and the other two treatments. The annual CO₂ effluxes reached 4 241.7, 3 400.8, 3 432.0 and 3 308.4 g CO₂·m^-2·a^-1 in the CC, NN, HR and CO treatments, respectively. Soil respiration showed diverse responses between dry and wet seasons under different treatments. Higher soil respiration in the CC and NN treatments occurred in the wet season (p<0.05). In the dry season, soil respiration increased in the HR treatment (p<0.05) and decreased in the NN treatment (p<0.05). We found significant exponential relationships between soil respiration rates and soil temperature and significant linear relationships between soil respiration rates and soil moisture (below 15%).

Key words: CO₂ enrichment, open-top chamber (OTC), nitrogen deposition, precipitation, soil respiration

邓琦, 周国逸, 刘菊秀, 刘世忠, 段洪浪, 陈小梅, 张德强. CO₂浓度倍增、高氮沉降和高降雨对南亚热带人工模拟森林生态系统土壤呼吸的影响. 植物生态学报, 2009, 33(6): 1023-1033. DOI: 10.3773/j.issn.1005-264x.2009.06.002

DENG Qi, ZHOU Guo-Yi, LIU Ju-Xiu, LIU Shi-Zhong, DUAN Hong-Lang, CHEN Xiao-Mei, ZHANG De-Qiang. EFFECTS OF CO<sub>2</sub> ENRICHMENT, HIGH NITROGEN DEPOSITION AND HIGH PRECIPITATION ON A MODEL FOREST ECOSYSTEM IN SOUTHERN CHINA. Chinese Journal of Plant Ecology, 2009, 33(6): 1023-1033. DOI: 10.3773/j.issn.1005-264x.2009.06.002

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https://www.plant-ecology.com/CN/Y2009/V33/I6/1023

图/表 5

图1 不同处理下土壤呼吸速率和环境因子的季节动态 CC: CO2浓度倍增((700±20) μmol CO2·mol-1)+背景N沉降 CO2 enrichment ((700±20) μmol CO2·mol-1)+ambient N deposition CO: 背景CO2浓度+背景N沉降 Ambient CO2concentration+ambient N deposition NN: 高N沉降(100 kg N·hm-2·a-1)+背景CO2浓度 High N deposition (100 kg N·hm-2·a-1)+ambient CO2concentration HR: 高降雨 High precipitation (100 L H2O)

Fig. 1 Seasonal dynamics of soil respiration rate and environmental factors under different treatments

表1 土壤呼吸速率和环境因子的处理间差异性(平均值±标准偏差)

Table 1 Differences in soil respiration rates and environmental factors under different treatments (mean±SD)

处理 Treatment	时间 Time	CC	NN	HR	CO
土壤呼吸速率 Soil respiration rate (μmol CO₂·m^-2·s^-1)	雨季 Wet season	3.85±1.00^a*	3.19±0.80^b*	2.66±0.88^c	2.71±0.70^c*
	旱季 Dry season	2.23±0.47^ab*	1.80±0.44^c*	2.32±0.57^a	2.05±0.42^b*
	年平均值 Annual mean value	3.06±1.13^a	2.46±0.91^b	2.49±0.66^b	2.39±0.76^b
土壤温度 Soil temperature (℃)	雨季 Wet season	24.81±2.99^a*	25.10±2.87^a*	25.22±2.71^a*	25.26±2.80^a*
	旱季 Dry season	17.21±4.08^a*	17.70±4.20^a*	17.23±4.03^a*	17.26±4.11^a*
	年平均值 Annual mean value	21.05±5.22^a	21.50±5.44^a	21.16±5.25^a	21.38±5.04^a
土壤湿度 Soil moisture (%)	雨季 Wet season	25.03±4.60^a*	22.26±4.96^b*	25.76±5.16^a*	23.64±4.82^ab*
	旱季 Dry season	19.34±3.64^a*	15.01±3.84^c*	19.75±3.50^a*	17.03±3.95^b*
	年平均值 Annual mean value	22.25±5.03^a	18.71±5.73^c	20.41±5.50^a	22.83±5.34^b

图2 不同处理下土壤呼吸的年通量 (平均值±标准偏差) 不同小写字母表示差异达到p=0.05显著水平 Different lowercase letters indicate significant difference at p=0.05 level CC、CO、NN、HR: 见图1 See Fig. 1

Fig. 2 Annual soil CO2 efflux under different treatments (mean±SD)

图3 不同处理下土壤呼吸速率和土壤温度的相关性 CC、CO、NN、HR: 见图1 See Fig. 1

Fig. 3 Correlations between soil respiration rate and soil temperature under different treatments

图4 不同处理下土壤呼吸速率和土壤湿度(<15%)的相关性 CC、CO、NN、HR: 见图1 See Fig. 1

Fig. 4 Correlations between soil respiration rate and soil moisture (below 15%) under different treatments

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CO₂浓度倍增、高氮沉降和高降雨对南亚热带人工模拟森林生态系统土壤呼吸的影响

EFFECTS OF CO<sub>2</sub> ENRICHMENT, HIGH NITROGEN DEPOSITION AND HIGH PRECIPITATION ON A MODEL FOREST ECOSYSTEM IN SOUTHERN CHINA

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