亚热带城市高温对城市生态系统碳通量的抑制作用研究

Study on High Temperature Constraints on Urban Ecosystem Carbon Fluxesin A Subtropical City

全球变暖对生态系统碳循环的影响研究是全球碳循环研究领域的热点话题,但城市热环境变化对城市生态系统碳通量影响的研究案例较少。使用经过参数本地化的植被光合作用与呼吸模型(VPRM,Vegetation Photosynthesis and Respiration Model),分析2018年亚热带城市深圳高温对生态系统碳通量的影响。结果表明,(1)研究区高温对植被生长的抑制作用较为明显。当气温超过31℃或32℃以后,植被总初级生产力(GPP,Gross Primary Production)和净生态系统交换量(NEE,Net Ecosystem Exchange)均出现明显下降趋势。(2)城区站点的高温抑制现象比郊区站点出现更为频繁。2018年城区站点出现植被高温抑制的天数(平均82 d)显著高于郊区站点(平均56 d)。出现高温抑制的时间主要是夏秋季节,冬春季节由于多数情况没有达到热抑制温度阈值,研究区气温升高对植被生长具有促进作用。(3)高温抑制作用对GPP和NEE的季节变化有明显影响,其通量强度季节排序分别为:夏季>春季>秋季>冬季和春季>夏季>秋季>冬季。生态系统呼吸(Reco,Ecosystem Respiration)则表现为随着温度升高而增强,即夏季>秋季>春季>冬季。以上研究结果意味着未来全球变暖将有可能对热带、亚热带地区的生态系统碳通量造成显著影响,导致这些地区生态系统碳汇被削弱。

The effects of global warming on ecosystem carbon fluxes is a hot topic in the study field of global carbon cycle.However,few studies have conducted on the effects of urban thermal environmental change on urban ecosystem carbon fluxes.In this study,we analyzed the effects of high temperature on ecosystem carbon fluxes in the subtropical city Shenzhen for the year 2018,using a locally parametrized Vegetation Photosynthesis and Respiration Model(VPRM).The results showed that:the phenomena that high temperature constraints on vegetation growth in the study area was typical.When the temperature was higher than 31℃or 32℃,both gross primary productivity(GPP)and net ecosystem exchange(NEE)of vegetation showed an obvious decreasing trend.(2)The phenomena of high temperature constraints happened more frequent in the urban study sites than in the suburban study sites.For the year 2018,the days that high temperature constraints happened in the urban study sites(i.e.,on average 82 days)is significantly higher than that in the suburban study sites(i.e.,on average 56 days).High temperature constraints mostly happened in summer and autumn.In winter and spring,high temperature could promote vegetation growth in the study area because the average day temperature did not reach the threshold temperature that can have high temperature constraint effect.And(3)seasonal variations of GPP and NEE were affected remarkably by high temperature constraints,and seasonal sequences of the two types of fluxes were summer>spring>autumn>winter and spring>summer>autumn>winter,respectively.Ecosystem Respiration appeared to increase with temperature rising,i.e.summer>autumn>spring>winter.The above results implied that future global warming may have significant effects on ecosystem carbon fluxes in tropical and subtropical ecosystems and cause the weakening of carbon sequestration in these ecosystems.