In cloud forests, foliar uptake (FU) of water has been reported for numerous species, possibly acting to relieve daily water and carbon stress. While the prevalence of FU seems common, how daily variation in fog timing may affect this process has not been studied. We examined the quantity of FU, water potentials, gas exchange and abiotic variation at the beginning and end of a 9-day exposure to fog in a glasshouse setting. Saplings of Abies fraseri (Pursh) Poir. and Picea rubens Sarg. were exposed to morning (MF), afternoon (AF) or evening fog (EF) regimes to assess the ability to utilize fog water at different times of day and after sustained exposure to simulated fog. The greatest amount of FU occurred during MF (up to 50%), followed by AF (up to 23%) and then EF, which surprisingly had no FU. There was also a positive relationship between leaf conductance and FU, suggesting a role of stomata in FU. Moreover, MF and AF lead to the greatest improvements in daily water balance and carbon gain, respectively. Foliar uptake was important for improving plant ecophysiology but was influenced by diurnal variation in fog. With climate change scenarios predicting changes to cloud patterns and frequency that will likely alter diurnal patterns, cloud forests that rely on this water subsidy could be affected.

In vegetated wetland ecosystems, plants can be a dominant pathway in the atmospheric flux of methane, a potent greenhouse gas. Although the roles of herbaceous vegetation and live woody vegetation in this flux have been established, the role of dead woody vegetation is not yet known. In a restored wetland of North Carolina's coastal plain, static flux chambers were deployed at two heights on standing dead trees to determine if these structures acted as a conduit for methane emissions. Methane fluxes to the atmosphere were measured in five of the chambers, with a mean flux of 0.4±0.1 mg m-2 h-1. Methane consumption was also measured in three of the chambers, with a mean flux of-0.6±0.3 mg m-2 h-1. Standing dead trees were also a source of the flux of CO2 (114.6±23.8 mg m-2 h-1) to the atmosphere. Results confirm that standing dead trees represent a conduit for the atmospheric flux of carbon gases from wetlands. However, several questions remain regarding the ultimate source of these carbon gases, the controls on the magnitude and direction of this flux, the mechanisms that induce this flux, and the importance of this pathway relative to other sources at the landscape level.

10Determining which water sources a plant accesses throughout a year is an important step 11 in understanding how changes in source characteristics affect utilization by plants. Water 12 sources of Acer negundo and Betula nigra of the foothills of the southern Appalachians 13 Mountains were examined during one full year, including the phenological stages of leaf bolt, 14 flowering, and leaf senescence/abscission. Source utilization was monitored, comparing the 15 isotopic composition of water samples from woody tissue to those of possible water sources at 16 the site. Species used deep ground and shallow soil water, with a greater reliance on deeper 17 sources during the late growing season. B. nigra was typically more depleted in δ 2 H than all 18 water sources measured, while values from A. negundo were more variable throughout the study.19

Fog, dew and cloud-borne mist are sources of water to vegetation in many ecosystems. The importance of fog as a water source has been documented well beyond ecosystems where plants experience fog for extensive periods over the course of the day (e.g. cloud forests); however, relatively little is known regarding the roles of fog and foliar water uptake in ecosystems such as coastal freshwater wetlands that do not experience fog for extensive periods over the course of the day. Coastal freshwater wetland ecosystems lie on the forefront of climate change-associated stressors that threaten freshwater supplies to vegetation. Considering the potential impact of climate warming on diminishing coastal fog regimes, an improved understanding of the ecophysiological benefits of fog immersion to the vegetation in these ecosystems is critical for understanding the response of these ecosystems to global climate change. Herein, we investigate the potential for foliar water deposition from fog to act as a direct freshwater subsidy to four tree species (Taxodium distichum (L.) Rich., Nyssa aquatica L., Nyssa biflora Walter and Liquidambar styraciflua L.) that are common in coastal freshwater wetlands. All four species showed the capacity for foliar water uptake across the leaf/needle surface, with a ca. 5-10% increase in leaf water content after a 3-h submersion experiment. Stable isotopes of water provided strong evidence for foliar water uptake in all four species and for bark water uptake in T. distichum after a 24-h fogging experiment. Fog exposure also resulted in several ecophysiological benefits to the saplings, including significant improvements in pre-dawn water status and net photosynthesis. K E Y W O R D S fog, foliar water uptake, leaf gas exchange, plant water status, stable isotopes, Taxodium distichum, wetlands 1 | INTRODUCTION Occult precipitation (e.g. fog, dew and cloud-borne mist; Rutter, 1975) is increasingly being recognized for its importance as a water source for plants across ecosystem types, despite rarely increasing soil moisture content (Berry, Emery, Gotsch, & Goldsmith, 2019). The mechanism for this is primarily through foliar water deposition, which is known to reduce transpiration and even be absorbed directly by the leaf (for a detailed review of this topic, please see Dawson & Goldsmith, 2018, and references therein). This recognition