表层岩溶系统中土-气-水界面碳流通的短尺度效应——以贵州茂兰国家喀斯特森林公园的秋季日动态监测为例
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摘要
在 2 0 0 1年秋季对贵州省荔波县茂兰国家喀斯特森林公园林地、草地植被下土壤CO2 呼吸释放及岩溶表层泉水HCO3 及其δ13 C值的变化进行了日动态的野外监测 ,表明岩溶系统中土 -气 -水界面间存在着碳交换的日动态变化以及所伴随的同位素交换的变化 ,这种变化与土温的日动态有密切的关系。林地植被显示了平抑这种日动态幅度的效应 ,而草地植被则显示响应于温度变化的较灵敏的动态变化。这种短尺度的变化构成了表层岩溶系统对外界条件的灵敏响应 ,进一步揭示了在生物作用下岩溶地质作用在碳循环过程及其同位素交换上的灵敏性和动态性。其不同植被系统下的日动态差异在解释岩溶沉积记录和讨论岩溶作用与碳循环时值得充分注意
Recent studies on karst process and terrestrial carbon cycling have concentrated on dynamics of carbon fluxes among soil, air, and water in association with the carbon isotopic equilibrium. This investigation aims at depicting daily change of such carbon fluxes in epikarst under different vegetations. The authors conducted a whole day onsite monitoring of soil respiration emission of CO 2, bicarbonate discharge of karst water and analysis of δ 13 C composition in a karst terrain of Maolan Karst Reserve, Guizhou, China in autumn of 2001. The main results are as follows: (1) Compared with the significant daily variation of temperature of free air and of surface soil, soil temperature at different depths varies in the range of 22.0~24.3℃ under forest and of 14.5~19.5℃ under grass respectively. More gentle variation of soil temperature is found under forest than that under grass. While variation of soil temperature at 20cm is still prompt to response air temperature under grass, air temperature hardly affects soil temperature at soil depth lower than 10cm. (2) Soil CO 2 fluxes to air by respiration emission varies in the range of 21.21~41.79mg·m -2 ·h -1 and 24.76~51.84 mg·m -2 ·h -1 under forest and grass respectively. The highest emission appears at 4∶00 am under forest and at 6∶00 pm under grass, with the lag effect behind soil temperature at 10cm depth being 10h under forest and only 4 hrs under grass respectively; The δ 13 C values of soil respired CO 2 varies in negative response to soil respiration emission intensity, despite of heavier carbon under grass than under forest by 1.0‰~1.5‰. The range of δ 13 C of soil respired CO 2 in forest is -21.78‰~-19.65‰ and -20.57‰~-18.83‰ in grass respectively. (3) The pattern of HCO - 3 discharge daily dynamics of the associated karst springs differs from that of CO 2 emission both under forest and under grass. While only minor variation of bicarbonate concentration in water can be found in the spring under forest, the HCO - 3 discharge fluctuates under grass and the variation of the δ 13 C values is up to 2‰. (4) Taking into account of the lag effect, both the soil respiration emission intensity and the δ 13 C of respired CO 2 and/or discharged bicarbonate is well correlated to soil temperature at 10cm under forest or at 10cm or deeper under grass. However, the forest vegetation tends to eliminate the magnitude of respiration intensity and the variation of carbon isotopic composition. The heavier carbon both of respired CO 2 and discharged bicarbonate than that reported on Guilin under similar vegetations in summer is attributed to lower temperature herein in autumn. Nevertheless, the soil under grass vegetation is still active in prompt response to daily temperature changes both on CO 2 emission and the isotopic fractioning by the fluxes. In conclusion, there exists daily variation both of carbon fluxes and the isotopic exchange between the interfaces of soil air and water in karst ecosystem even in autumn. This is largely controlled by the soil temperature regimes and soil carbon lability under different vegetation conditions. More significant variation is likely to occur of soil carbon fluxes and the associated isotopic composition under grass due to the sensitivity to temperature changes by the limited vegetation cover and probably the high lability of soil carbon. This illustrates the dynamics of carbon fluxes in the karst system in small time scale (intra year level),which is implicated by the microlamination found in the stalagmites in caves. Again this dynamic nature of soil carbon fluxes reinforces the awareness about sensitivity and kinetics of epikarstification under soil biota in relation to terrestrial carbon cycling.
Recent studies on karst process and terrestrial carbon cycling have concentrated on dynamics of carbon fluxes among soil, air, and water in association with the carbon isotopic equilibrium. This investigation aims at depicting daily change of such carbon fluxes in epikarst under different vegetations. The authors conducted a whole day onsite monitoring of soil respiration emission of CO 2, bicarbonate discharge of karst water and analysis of δ 13 C composition in a karst terrain of Maolan Karst Reserve, Guizhou, China in autumn of 2001. The main results are as follows: (1) Compared with the significant daily variation of temperature of free air and of surface soil, soil temperature at different depths varies in the range of 22.0~24.3℃ under forest and of 14.5~19.5℃ under grass respectively. More gentle variation of soil temperature is found under forest than that under grass. While variation of soil temperature at 20cm is still prompt to response air temperature under grass, air temperature hardly affects soil temperature at soil depth lower than 10cm. (2) Soil CO 2 fluxes to air by respiration emission varies in the range of 21.21~41.79mg·m -2 ·h -1 and 24.76~51.84 mg·m -2 ·h -1 under forest and grass respectively. The highest emission appears at 4∶00 am under forest and at 6∶00 pm under grass, with the lag effect behind soil temperature at 10cm depth being 10h under forest and only 4 hrs under grass respectively; The δ 13 C values of soil respired CO 2 varies in negative response to soil respiration emission intensity, despite of heavier carbon under grass than under forest by 1.0‰~1.5‰. The range of δ 13 C of soil respired CO 2 in forest is -21.78‰~-19.65‰ and -20.57‰~-18.83‰ in grass respectively. (3) The pattern of HCO - 3 discharge daily dynamics of the associated karst springs differs from that of CO 2 emission both under forest and under grass. While only minor variation of bicarbonate concentration in water can be found in the spring under forest, the HCO - 3 discharge fluctuates under grass and the variation of the δ 13 C values is up to 2‰. (4) Taking into account of the lag effect, both the soil respiration emission intensity and the δ 13 C of respired CO 2 and/or discharged bicarbonate is well correlated to soil temperature at 10cm under forest or at 10cm or deeper under grass. However, the forest vegetation tends to eliminate the magnitude of respiration intensity and the variation of carbon isotopic composition. The heavier carbon both of respired CO 2 and discharged bicarbonate than that reported on Guilin under similar vegetations in summer is attributed to lower temperature herein in autumn. Nevertheless, the soil under grass vegetation is still active in prompt response to daily temperature changes both on CO 2 emission and the isotopic fractioning by the fluxes. In conclusion, there exists daily variation both of carbon fluxes and the isotopic exchange between the interfaces of soil air and water in karst ecosystem even in autumn. This is largely controlled by the soil temperature regimes and soil carbon lability under different vegetation conditions. More significant variation is likely to occur of soil carbon fluxes and the associated isotopic composition under grass due to the sensitivity to temperature changes by the limited vegetation cover and probably the high lability of soil carbon. This illustrates the dynamics of carbon fluxes in the karst system in small time scale (intra year level),which is implicated by the microlamination found in the stalagmites in caves. Again this dynamic nature of soil carbon fluxes reinforces the awareness about sensitivity and kinetics of epikarstification under soil biota in relation to terrestrial carbon cycling.
引文
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2 FranceyRJ,AllisonCE ,EtheridgeDMetal.A 1000 yearhighprecisionrecordofδ13CinatmosphericCO2.Tellus,1999,51B :170~193
3 康世昌,秦大河,MayewskiPA等.近2000a来珠穆朗玛峰北坡远东绒布冰芯气候记录.冰川冻土,2000,22(3):211~217
4 潘根兴,曹建华,何师意等.桂林丫吉村岩溶试验场岩溶土壤碳转移与水排碳作用.自然科学进展,2001,11(7):704~709
5 潘根兴,曹建华.表层带岩溶作用———土壤为媒介的地球表层生态系统过程.中国岩溶,1999,18(4):287~296
6 朴河春,洪业汤,袁芷云等.贵州喀斯特地区土壤中微生物量碳的季节性变化.环境科学学报,2000,20(1):106~110
7 曹建华,潘根兴,袁道先.不同植物凋落物对土壤有机碳淋失的影响及岩溶效应.第四纪研究,2000,20(4):359~366
8 何师意,徐胜友,张美良.岩溶土壤中CO2浓度、水化学观测及其与岩溶作用关系.中国岩溶,1997,16(4):319~324
9 谭 明,刘东生,秦小光等.北京石花洞全新世石笋微生长层与稳定同位素气候意义初步研究.中国岩溶,1997,16(1):1~10
10 潘根兴,何师意,曹建华等.桂林丫吉村表层岩溶土壤系统中δ13C值的差异.科学通报,2001,46(22):1919~1922
11 谭 明,秦小光,刘东生.石笋记录的年际、十年、百年尺度气候变化.中国科学(D辑),1998,28(3):272~277
12 谭 明,潘根兴,秦小光等.石笋与环境———石笋纹层形成的环境机理初探.中国岩溶,1999,18(3):197~205
13 潘根兴,孙玉华,腾永忠等.湿润亚热带峰丛洼地岩溶土壤系统中碳分布及其转移.应用生态学报,2000,11(1):69~72
14 曹建华,潘根兴,袁道先等.桂林岩溶洼地生态系统中大气CO2动态及环境意义.地质论评,1999,45(1):105~111
15 TrudingerCM ,EntingIG ,FranceyRJetal.Long termvariabilityintheglobalcarboncycleinferredfromahigh precisionCO2andδ13Cice corerecord.Tellus,1999,51B :233~248
16 KeltingDL ,BurgerJA ,EdwardsGS .Estimatingrootrespiration,microbialrespirationintherhizosphere,androot freesoilrespirationinforestsoils.SoilBiology&Biochemistry,1998,30:961~968
17 潘根兴,曹建华,何师意等.土壤碳作为湿润亚热带表层岩溶作用的动力机制———系统碳库及碳转移特征.南京农业大学学报,1999,22(3):49~52
18 李 彬,袁道先,林玉石等.桂林地区降水、洞穴滴水及现代洞穴碳酸盐氧碳同位素研究及其环境意义.中国科学(D辑),2000,30(1):81~87
19 DudziakA ,HalasS.DiurnalcycleofcarbonisotoperatioinsoilCO2 invariousecosystems.PlantandSoil,1996,183:291~299
2 FranceyRJ,AllisonCE ,EtheridgeDMetal.A 1000 yearhighprecisionrecordofδ13CinatmosphericCO2.Tellus,1999,51B :170~193
3 康世昌,秦大河,MayewskiPA等.近2000a来珠穆朗玛峰北坡远东绒布冰芯气候记录.冰川冻土,2000,22(3):211~217
4 潘根兴,曹建华,何师意等.桂林丫吉村岩溶试验场岩溶土壤碳转移与水排碳作用.自然科学进展,2001,11(7):704~709
5 潘根兴,曹建华.表层带岩溶作用———土壤为媒介的地球表层生态系统过程.中国岩溶,1999,18(4):287~296
6 朴河春,洪业汤,袁芷云等.贵州喀斯特地区土壤中微生物量碳的季节性变化.环境科学学报,2000,20(1):106~110
7 曹建华,潘根兴,袁道先.不同植物凋落物对土壤有机碳淋失的影响及岩溶效应.第四纪研究,2000,20(4):359~366
8 何师意,徐胜友,张美良.岩溶土壤中CO2浓度、水化学观测及其与岩溶作用关系.中国岩溶,1997,16(4):319~324
9 谭 明,刘东生,秦小光等.北京石花洞全新世石笋微生长层与稳定同位素气候意义初步研究.中国岩溶,1997,16(1):1~10
10 潘根兴,何师意,曹建华等.桂林丫吉村表层岩溶土壤系统中δ13C值的差异.科学通报,2001,46(22):1919~1922
11 谭 明,秦小光,刘东生.石笋记录的年际、十年、百年尺度气候变化.中国科学(D辑),1998,28(3):272~277
12 谭 明,潘根兴,秦小光等.石笋与环境———石笋纹层形成的环境机理初探.中国岩溶,1999,18(3):197~205
13 潘根兴,孙玉华,腾永忠等.湿润亚热带峰丛洼地岩溶土壤系统中碳分布及其转移.应用生态学报,2000,11(1):69~72
14 曹建华,潘根兴,袁道先等.桂林岩溶洼地生态系统中大气CO2动态及环境意义.地质论评,1999,45(1):105~111
15 TrudingerCM ,EntingIG ,FranceyRJetal.Long termvariabilityintheglobalcarboncycleinferredfromahigh precisionCO2andδ13Cice corerecord.Tellus,1999,51B :233~248
16 KeltingDL ,BurgerJA ,EdwardsGS .Estimatingrootrespiration,microbialrespirationintherhizosphere,androot freesoilrespirationinforestsoils.SoilBiology&Biochemistry,1998,30:961~968
17 潘根兴,曹建华,何师意等.土壤碳作为湿润亚热带表层岩溶作用的动力机制———系统碳库及碳转移特征.南京农业大学学报,1999,22(3):49~52
18 李 彬,袁道先,林玉石等.桂林地区降水、洞穴滴水及现代洞穴碳酸盐氧碳同位素研究及其环境意义.中国科学(D辑),2000,30(1):81~87
19 DudziakA ,HalasS.DiurnalcycleofcarbonisotoperatioinsoilCO2 invariousecosystems.PlantandSoil,1996,183:291~299
目录