Abstract：
Climate change is exposing subarctic ecosystems to higher temperatures, increased nutrient availability, and increasing cloud cover. In this study, we assessed how these factors affect the fluxes of greenhouse gases (GHGs) (i.e., methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2)), and biogenic volatile organic compounds (BVOCs) in a subarctic mesic heath subjected to 34 years of climate change related manipulations of temperature, nutrient availability, and light. GHGs were sampled from static chambers and gases analyzed with gas chromatograph. BVOCs were measured using the push-pull method and gases analyzed with chromatography-mass spectrometry. The soil temperature and moisture content in the warmed and shaded plots did not differ significantly from that in the controls during GHG and BVOC measurements. Also, the enclosure temperatures during BVOC measurements in the warmed and shaded plots did not differ significantly from temperatures in the controls. Hence, this allowed for assessment of long-term effects of the climate treatment manipulations without interference of temperature and moisture differences at the time of measurements. Warming enhanced CH4 uptake and the emissions of CO2, N2O, and isoprene. Increased nutrient availability increased the emissions of CO2 and N2O but caused no significant changes in the fluxes of CH4 and BVOCs. Shading (simulating increased cloudiness) enhanced CH4 uptake but caused no significant changes in the fluxes of other gases compared to the controls. The results show that climate warming and increased cloudiness will enhance CH4 sink strength of subarctic mesic heath ecosystems, providing negative climate feedback, while climate warming and enhanced nutrient availability will provide positive climate feedback through increased emissions of CO2 and N2O. Climate warming will also indirectly, through vegetation changes, increase the amount of carbon lost as isoprene from subarctic ecosystems.
摘要：
气候变化使亚北极生态系统暴露在更高的温度下，增加营养的可用性，增加云层覆盖。在这项研究中,我们评估了这些因素如何影响温室气体(GHG)的通量(即，甲烷(CH4),一氧化二氮（N2O），和二氧化碳(CO2))，和亚北极地区的生物挥发性有机化合物（BVOCs）经历了34年的气候变化相关的温度操纵，营养可用性，和光。温室气体从静态室取样，并用气相色谱仪分析气体。使用推拉法测量BVOCs，并用色谱-质谱分析气体。在GHG和BVOC测量过程中，温暖和阴影地块的土壤温度和水分含量与对照没有显着差异。此外，在加温和阴影地块的BVOC测量过程中，外壳温度与对照温度没有显着差异。因此，这允许评估气候处理操作的长期影响，而不会干扰测量时的温度和湿度差异。变暖增强了CH4的吸收和CO2，N2O的排放，和异戊二烯。养分利用率的增加增加了CO2和N2O的排放量，但没有引起CH4和BVOCs通量的显着变化。与对照相比，阴影（模拟混浊度增加）增强了CH4的吸收，但未引起其他气体通量的显着变化。结果表明，气候变暖和云量增加将增强北极下中部健康生态系统的CH4沉降强度，提供负面的气候反馈，而气候变暖和营养供应的增加将通过增加CO2和N2O的排放提供积极的气候反馈。气候变暖也会间接,通过植被变化，增加亚北极生态系统中作为异戊二烯的碳损失量。
