A Topographic Gradient Drives Spatial Variability of Stem CH4 Fluxes in a Temperate Alder Stand

作者：Daniel Köhn, Anke Günther, Marko Smiljanić, Gerald Jurasinski · 发表于：Ecosystems · 年份：2025 · DOI：10.1007/s10021-025-00989-2 · 被引用次数：2 · 研究领域：Atmospheric and Environmental Gas Dynamics、Hydrocarbon exploration and reservoir analysis、Soil Carbon and Nitrogen Dynamics

Abstract Tree stems in both wetland and upland forests are a potentially significant source of the greenhouse gas methane (CH 4 ). Stem CH 4 emissions are assumed to play an important role on a global scale. Yet, uncertainties regarding temporal and spatial variability as well as transport processes of stem emissions remain high. Here, we assess the spatial variability and range of CH 4 egress from 28 black alder ( Alnus glutinosa (L.) Gaertn.) trees based on data we recorded during three measurement campaigns in a mature alder carr in spring 2019. Fluxes varied significantly in time and space. The overall temporal variability during the three campaigns was larger than the spatial variability. The fluxes ranged from less than 1 µg m −2 h −1 to 450 µg m −2 h −1 with an average overall flux of 25 ± 59 µg m −2 h −1 (± SD). Stem CH 4 fluxes were highest (61.6 ± 104.5 µg m −2 h −1 ) during higher soil temperatures in spring, with increasing sap flux density and an intermediate water level just above the surface (+ 2.7 ± 0.3 cm). Morphological properties of the trees, including diameter at breast height, their position on hummocks or hollows and height of the measurement on the stem, largely failed to explain variability in stem CH 4 fluxes. Large-scale topography (overall elevation gradient) within the study site and CO 2 flux were the best predictors of stem CH 4 emissions, but inundation and leaf out also significantly influenced stem CH 4 fluxes. Thus, large-scale factors such ...