Kantola Noora, Welker Jeffrey M, Leffler A Joshua, Lämsä Juho, Paavola Riku, Suominen Otso, Väisänen Maria
Ecology and Genetics Research Unit, University of Oulu, Oulu, Finland.
Ecology and Genetics Research Unit, University of Oulu, Oulu, Finland; Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK, USA; University of the Arctic (UArctic), Rovaniemi, Finland.
Sci Total Environ. 2025 Sep 15;995:180089. doi: 10.1016/j.scitotenv.2025.180089. Epub 2025 Jul 21.
In northern regions, the ongoing climate change is altering snow depth with complex consequences for carbon dioxide (CO) exchange and thus, global carbon (C) balance. In addition, ungulate grazers such as reindeer and caribou often alter plant and soil properties that may lead to modifications in the magnitudes and patterns of CO exchange. To understand how reindeer grazing, coupled with changes in snow depth affects CO exchange, we used recent snow treatments (ambient, reduced, and increased snow depth) combined with 25- and 55-year-old reindeer exclusions and the adjacent grazed areas in boreal and subarctic Scots pine forests that are main winter pastures for reindeer/caribou and cover a significant portion of boreal and subarctic landscapes. At both study sites, we measured understory net ecosystem exchange (i.e., NEE), ecosystem respiration (i.e., ER), and gross ecosystem production (i.e., GEP) over two snow-free seasons. We found that 55 years of reindeer exclusion increased C source strength by 136 % under ambient snow depth and 205 % under reduced snow depth in comparison to the grazed area with respective snow conditions. On the contrary, increased snow depth decreased C source strength inside the exclusion offsetting the difference between reindeer grazing treatments. Our results show that grazing may enhance ecosystem stability to winter climate change in comparison to long-term absence of grazing. This highlights the complexity of climate-grazer interactions in functioning of northern ecosystems which are experiencing variations in snow depth.
在北方地区，持续的气候变化正在改变积雪深度，这对二氧化碳（CO）交换产生复杂影响，进而影响全球碳（C）平衡。此外，驯鹿和北美驯鹿等有蹄类食草动物常常改变植物和土壤特性，这可能导致CO交换的幅度和模式发生变化。为了了解驯鹿放牧与积雪深度变化如何影响CO交换，我们采用了近期的积雪处理方式（环境积雪、减少积雪和增加积雪深度），并结合了25年和55年未放牧区域以及相邻的放牧区域，这些区域位于北方和亚北极的苏格兰松林中，是驯鹿/北美驯鹿的主要冬季牧场，覆盖了北方和亚北极景观的很大一部分。在两个研究地点，我们在两个无雪季节测量了林下净生态系统交换量（即NEE）、生态系统呼吸量（即ER）和总生态系统生产量（即GEP）。我们发现，与处于相应积雪条件下的放牧区域相比，55年未放牧使环境积雪深度下的碳源强度增加了136%，在减少积雪深度下增加了205%。相反，增加积雪深度降低了未放牧区域内的碳源强度，抵消了驯鹿放牧处理之间的差异。我们的结果表明，与长期不放牧相比，放牧可能增强生态系统对冬季气候变化的稳定性。这突出了在积雪深度发生变化的北方生态系统功能中，气候 - 食草动物相互作用的复杂性。
