Department Biology, San Diego State University, San Diego, CA, 92182, USA.
School of Biosciences, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK.
Sci Rep. 2022 Mar 21;12(1):3986. doi: 10.1038/s41598-022-07561-1.
Arctic warming is affecting snow cover and soil hydrology, with consequences for carbon sequestration in tundra ecosystems. The scarcity of observations in the Arctic has limited our understanding of the impact of covarying environmental drivers on the carbon balance of tundra ecosystems. In this study, we address some of these uncertainties through a novel record of 119 site-years of summer data from eddy covariance towers representing dominant tundra vegetation types located on continuous permafrost in the Arctic. Here we found that earlier snowmelt was associated with more tundra net CO sequestration and higher gross primary productivity (GPP) only in June and July, but with lower net carbon sequestration and lower GPP in August. Although higher evapotranspiration (ET) can result in soil drying with the progression of the summer, we did not find significantly lower soil moisture with earlier snowmelt, nor evidence that water stress affected GPP in the late growing season. Our results suggest that the expected increased CO sequestration arising from Arctic warming and the associated increase in growing season length may not materialize if tundra ecosystems are not able to continue sequestering CO later in the season.
北极变暖正在影响积雪和土壤水文学，对苔原生态系统的碳固存产生影响。北极地区观测数据的稀缺限制了我们对共同变化的环境驱动因素对苔原生态系统碳平衡的影响的理解。在这项研究中，我们通过来自涡度相关塔的 119 个站点年夏季数据的新记录来解决其中的一些不确定性，这些数据代表了位于北极连续多年冻土上的主要苔原生态系统植被类型。在这里，我们发现，只有在 6 月和 7 月，融雪时间提前与更多的苔原生态系统净碳固存和更高的总初级生产力（GPP）相关，但在 8 月与更低的净碳固存和更低的 GPP 相关。尽管随着夏季的推进，较高的蒸散量可能导致土壤干燥，但我们没有发现融雪时间提前导致土壤水分显著降低，也没有证据表明水分胁迫会影响生长后期的 GPP。我们的研究结果表明，如果苔原生态系统无法在季节后期继续固碳，那么预计由于北极变暖而增加的碳固存以及与生长季节延长相关的碳固存可能无法实现。
