Environmental and Vegetation Drivers of Seasonal CO2 Fluxes in a Sub-arctic Forest-Mire Ecotone
Environmental and Vegetation Drivers of Seasonal CO2 Fluxes in a Sub-arctic Forest-Mire Ecotone
复制标题
亚北极森林-泥沼交错带季节性二氧化碳通量的环境和植被驱动因素
DOI：
10.1007/s10021-013-9728-2
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发表时间：
2013
期刊：
影响因子：
3.7
通讯作者：
Poyatos R
中科院分区：
文献类型：
--
作者：
Poyatos R
揭示高度异质冻原中总初级生产力（GPP）和生态系统呼吸（Reco）的结构和环境驱动因素的作用是北极景观中基于小室的二氧化碳通量升级的一个重大挑战。在山区桦树林地沼泽交错带，我们调查的作用LAI（和NDVI），环境因子（小气候，土壤水分），和微网站类型跨苔原灌木地块（湿丘，干丘，干洼地）和地衣丘，在控制净生态系统CO2交换（NEE）。在生长季节，我们连续测量NEE通量，封闭的动态室，并进行多次拟合（每3天一次）的一个简单的光和温度响应模型，每小时NEE数据。苔原灌木地块主要是CO2汇，而不是地衣地块，虽然通量变化很大，在微型网站类型。对于苔原灌木地块，微立地类型不影响光合参数，但它影响基础（即温度归一化）生态系统呼吸（R 0）。PAR归一化光合速率（P600）随气温升高而升高，随水汽压亏缺的增加而降低; R 0随土壤水分的增加而降低，随温度的升高而明显升高，这可能是GPP与Reco之间存在紧密联系的原因。植被指数能较好地反映灌木样地的叶面积指数、最大P600和最大R 0。累积CO2通量与LAI（NDVI）密切相关，但我们观察到一个相对较低的GPP/LAI在干丘。我们的研究结果大致同意跨苔原植被的功能收敛的报告，但在这里，我们表明，在过渡区的生产力下降的作用和温度和水平衡对季节性CO2通量的影响，在亚北极森林沼泽交错带不能忽视。
Unravelling the role of structural and environmental drivers of gross primary productivity (GPP) and ecosystem respiration (Reco) in highly heterogeneous tundra is a major challenge for the upscaling of chamber-based CO2fluxes in Arctic landscapes. In a mountain birch woodland-mire ecotone, we investigated the role of LAI (and NDVI), environmental factors (microclimate, soil moisture), and microsite type across tundra shrub plots (wet hummocks, dry hummocks, dry hollows) and lichen hummocks, in controlling net ecosystem CO2exchange (NEE). During a growing season, we measured NEE fluxes continuously, with closed dynamic chambers, and performed multiple fits (one for each 3-day period) of a simple light and temperature response model to hourly NEE data. Tundra shrub plots were largely CO2sinks, as opposed to lichen plots, although fluxes were highly variable within microsite type. For tundra shrub plots, microsite type did not influence photosynthetic parameters but it affected basal (that is, temperature-normalized) ecosystem respiration (R0). PAR-normalized photosynthesis (P600) increased with air temperature and declined with increasing vapor pressure deficit.R0declined with soil moisture and showed an apparent increase with temperature, which may underlie a tight link between GPP andReco. NDVI was a good proxy for LAI, maximumP600and maximumR0of shrub plots. Cumulative CO2fluxes were strongly correlated with LAI (NDVI) but we observed a comparatively low GPP/LAI in dry hummocks. Our results broadly agree with the reported functional convergence across tundra vegetation, but here we show that the role of decreased productivity in transition zones and the influence of temperature and water balance on seasonal CO2fluxes in sub-Arctic forest–mire ecotones cannot be overlooked.