The influence of aquaporin (AQP) activity on plant water movement remains unclear, especially in plants subject to unfavorable conditions. We applied a multitiered approach at a range of plant scales to (i) characterize the resistances controlling water transport under drought, flooding, and flooding plus salinity conditions; (ii) quantify the respective effects of AQP activity and xylem structure on root (K_root), stem (K_stem), and leaf (K_leaf) conductances; and (iii) evaluate the impact of AQP-regulated transport capacity on gas exchange. We found that drought, flooding, and flooding plus salinity reduced K_root and root AQP activity in Pinus taeda, whereas K_root of the flood-tolerant Taxodium distichum did not decline under flooding. The extent of the AQP control of transport efficiency varied among organs and species, ranging from 35–55% in K_root to 10–30% in K_stem and K_leaf. In response to treatments, AQP-mediated inhibition of K_root rather than changes in xylem acclimation controlled the fluctuations in K_root. The reduction in stomatal conductance and its sensitivity to vapor pressure deficit were direct responses to decreased whole-plant conductance triggered by lower K_root and larger resistance belowground. Our results provide new mechanistic and functional insights on plant hydraulics that are essential to quantifying the influences of future stress on ecosystem function.

Standing dead trees (snags) are recognized for their influence on methane (CH₄) cycling in coastal wetlands, yet the biogeochemical processes that control the magnitude and direction of fluxes across the snag-atmosphere interface are not fully elucidated. Herein, we analyzed microbial communities and fluxes at one height from ten snags in a ghost forest wetland. Snag-atmosphere CH₄ fluxes were highly variable (− 0.11–0.51 mg CH₄ m⁻² h⁻¹). CH₄ production was measured in three out of ten snags; whereas, CH₄ consumption was measured in two out of ten snags. Potential CH₄ production and oxidation in one core from each snag was assayed in vitro. A single core produced CH₄ under anoxic and oxic conditions, at measured rates of 0.7 and 0.6 ng CH₄ g⁻¹ h⁻¹, respectively. Four cores oxidized CH₄ under oxic conditions, with an average rate of − 1.13 ± 0.31 ng CH₄ g⁻¹ h⁻¹. Illumina sequencing of the V3/V4 region of the 16S rRNA gene sequence revealed diverse microbial communities and indicated oxidative decomposition of deadwood. Methanogens were present in 20% of the snags, with a mean relative abundance of < 0.0001%. Methanotrophs were identified in all snags, with a mean relative abundance of 2% and represented the sole CH₄-cycling communities in 80% of the snags. These data indicate potential for microbial attenuation of CH₄ emissions across the snag-atmosphere interface in ghost forests. A better understanding of the environmental drivers of snag-associated microbial communities is necessary to forecast the response of CH₄ cycling in coastal ghost forest wetlands to a shifting coastal landscape.