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若尔盖高寒湿地-大气间碳交换特征及驱动机制研究

A study on the characteristics and driving mechanism of carbon exchange between the Zoige alpine wetland and atmosphere

  • 摘要: 在全球变暖背景下,高寒湿地生态系统的碳过程是复杂且敏感。然而,高寒湿地生态系统碳收支的长期动态及其驱动机制尚不清楚。本研究利用涡度协方差技术测量的二氧化碳(CO2)通量,分析了若尔盖高寒湿地2017-2021年间的CO2交换通量,以及CO2交换通量的动态变化和驱动机制。结果显示,在植被生长季(6-10月),若尔盖高寒湿地的年均生态系统总初级生产力(Gross Primary Productivity,GPP)和生态系统呼吸(Ecosystem espiration,Re)呈现出单峰型分布,而年均生态系统CO2交换(Net Ecosystem Exchange,NEE)则呈现V型趋势。若尔盖高寒湿地生态系统在生长季节是一个碳汇,即一个吸收比释放更多的陆-气间碳交换过程。多年日平均NEE、GPP和Re分别达到-3.10±4.61、4.78±5.61和1.65±1.56 umol/(m2·s)。在月度尺度上,回归分析了气温(Air Temperature,Ta)、土壤温度(Soil Temperature,Ts)、光合光子通量密度(Photosynthetic Photon Flux Density,PPFD)、降水量(Precipitation,PPT)、空气相对湿度(Air Relative Humidity,RH)和水汽压差(Vapor Pressure Deficit,VPD)分别对NEE、GPP和Re的影响,结果显示,Ts、Ta和VPD是月度NEE变化的主要决定因素,NEE与它们都呈负相关。Ts和Ta在很大程度上决定了每月GPP的变化,GPP与其呈正相关,Ts、Ta和PPT是月度Re变化的主要决定因素,Re与它们都呈正相关。利用分类回归树算法(Classification and Regression Tree,CART)分析了日尺度上各个要素对碳交换通量的影响,结果表明:土壤温度对日GPP和Re具有较大影响,气温是每日NEE的主要控制因素。本研究结果为理解高寒湿地生态系统碳收支提供了重要数据和参考依据。

     

    Abstract: In the context of global warming, the carbon process of alpine wetland ecosystems is complex and sensitive. However, the long-term dynamics and driving mechanisms of carbon balance in alpine wetland ecosystems are still unclear. In this study, the carbon dioxide (CO2) flux measured by eddy covariance technique is used to analyze the CO2 exchange flux of the Zoige alpine wetland from 2017 to 2021, as well as the dynamics and driving mechanisms of CO2 exchange flux. The results showed that during the vegetation growing season (June - October), the annual gross primary productivity (Gross Primary Productivity, GPP) and ecosystem respiration (Ecosystem espiration, Re) of the ecosystem showed an unimodal pattern, while the annual net ecosystem CO2 exchange (Net Ecosystem Exchange, NEE) of the ecosystem showed a V-shaped trend. The Zoige alpine wetland ecosystem is a carbon sink during the growing season, which is a carbon exchange process between land and air that absorbs more than releases. The daily average NEE, GPP, and Re over the years reached -3.10±4.61, 4.78±5.61, and 1.65±1.56 umol(m2·s), respectively. On the monthly scale, the effects of air temperature (Air Temperature, Ta), soil temperature (Soil Temperature, Ts), photosynthetic photon flux density (Photosynthetic Photon Flux Density, PPFD), precipitation (Precipitation, PPT), air relative humidity (Air Relative Humidity, RH) and vapor pressure deficit (Vapor Pressure Deficit, VPD) on NEE, GPP and Re were analyzed by the regression analysis. The results showed that Ta, Ts and PPT were the main determinants of monthly NEE changes, and NEE was negatively correlated with them. Ts and Ta largely determined the monthly variation of GPP, which is positively correlated with it. Ts ,Ta and PPT are the main determinants of monthly Re variation, and Re is positively correlated with them. The Classification and Regression Tree (Classification and Regression Tree, CART) algorithm was used to analyze the effects of various factors on carbon exchange flux in the daily scale. The results showed that soil temperature had a great influence on daily GPP and Re, and temperature is the main controlling factor for daily NEE. The results of this study provide important data and reference for understanding the carbon budget of alpine wetland ecosystems.

     

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