Plant-mediated CH₄ transport (PMT) is the dominant pathway through which soil-produced CH₄ can escape into the atmosphere and thus plays an important role in controlling ecosystem CH₄ emission. PMT is affected by abiotic and biotic factors simultaneously, and the effects of biotic factors, such as the dominant plant species and their traits, can override the effects of abiotic factors. Increasing evidence shows that plant-mediated CH₄ fluxes include not only PMT, but also within-plant CH₄ production and oxidation due to the detection of methanogens and methanotrophs attached to the shoots. Despite the inter-species and seasonal differences, and the probable contribution of within-plant microbes to total plant-mediated CH₄ exchange (PME), current process-based ecosystem models only estimate PMT based on the bulk biomass or leaf area index of aerenchymatous plants. We highlight five knowledge gaps to which more research efforts should be devoted. First, large between-species variation, even within the same family, complicates general estimation of PMT, and calls for further work on the key dominant species in different types of wetlands. Second, the interface (rhizosphere-root, root-shoot, or leaf-atmosphere) and plant traits controlling PMT remain poorly documented, but would be required for generalizations from species to relevant functional groups. Third, the main environmental controls of PMT across species remain uncertain. Fourth, the role of within-plant CH₄ production and oxidation is poorly quantified. Fifth, the simplistic description of PMT in current process models results in uncertainty and potentially high errors in predictions of the ecosystem CH₄ flux. Our review suggest that flux measurements should be conducted over multiple growing seasons and be paired with trait assessment and microbial analysis, and that trait-based models should be developed. Only then we are capable to accurately estimate plant-mediated CH₄ emissions, and eventually ecosystem total CH₄ emissions at both regional and global scales.

Understanding the response of vegetation and ecosystem resilience to climate variability and drought conditions is essential for ecosystem planning and management. In this study, we assessed the vegetation changes and ecosystem resilience in the Horn of Africa (HOA) since 2000 and detected their drivers based mainly on analysis of the Moderate Resolution Imaging Spectroradiometer (MODIS) products. We found that the annual and seasonal trends of NDVI (Normalized Difference Vegetation Index) generally increased during the last two decades over the Horn of Africa particularly in western parts of Ethiopia and Kenya. The weakest annual and seasonal NDVI trends were observed over the grassland cover and tropical arid agroecological zones. The NDVI variation negatively correlated with Land Surface Temperature (LST) and positively correlated with precipitation at a significant level (p < 0.05) account for 683,197 km² and 533,385 km² area, respectively. The ecosystem Water Use Efficiency (eWUE) showed overall increasing trends with larger values for the grassland biome. The precipitation had the most significant effect on eWUE variation compared to LST and annual SPEI (Standardized Evapotranspiration Index). There were about 54.9% of HOA resilient to drought disturbance, whereas 32.6% was completely not-resilient. The ecosystems in the humid agroecological zones, the cropland, and wetland were slightly not-resilient to severe drought conditions in the region. This study provides useful information for policy makers regarding ecosystem and dryland management in the context of climate change at both national and regional levels.

Background and Aims: Methane (CH₄) fluxes at peatland plant surfaces are net results of transport of soil-produced CH₄ and within-plant CH₄ production and consumption, yet factors and processes controlling these fluxes remain unclear. We aimed to assess the effects of seasonality, environmental variables, and CH₄ cycling microbes on CH₄ fluxes from characteristic fen species. Methods: Four species (Carex rostrata, Menyanthes trifoliata, Betula nana, Salix lapponum) were selected, and their CH₄ fluxes determined in climate-controlled environments with three mesocosms per growing season per species. Microbial genes for CH₄ cycling were analysed to check the potential for within-plant CH₄ production and oxidation. Two extra experiments were conducted: removal of C. rostrata leaves to identify how leaves constrain CH₄ transport, and a labelling experiment with S. lapponum to distinguish between plant-produced and soil-produced CH₄ in the plant flux. Results: All species showed seasonal variability in CH₄ fluxes. Higher porewater CH₄ concentration increased fluxes from C. rostrata and M. trifoliata, decreased fluxes from S. lapponum, and did not affect fluxes from B. nana. Air temperature only and negatively affected CH₄ flux from C. rostrata. Light level did not impact CH₄ fluxes. Both methanogens and methanotrophs were detected in shoots of S. lapponum and M. trifoliata, methanotrophs in B. nana, and neither in C. rostrata. Conclusion: Our study demonstrates that the seasonal phase of the plants regulates the CH₄ fluxes they mediate across species. The detection of methanogens and methanotrophs in herbs and shrubs suggests that microbial processes may contribute to their CH₄ fluxes.

Recent studies have identified the significant role of plants in controlling methane (CH4) emission from peatlands by acting as conduits and further demonstrated that such conduit effect is species-specific. In most studies, species-specific plant-mediated CH4 transport has been estimated indirectly by comparing CH4 flux from surfaces with different plant communities to that from surfaces where plants responsible for CH4 transport are cut, known as the clipping technique. However, the estimation based on the clipping technique has shown large uncertainty due to the plant residual effect. Thus, directly investigating the variation in CH4 transport between different plant species and the factors affecting it is necessary to more precisely assess changes in the CH4 fluxes of peatland ecosystems in a changing environment.We measured CH4 emission directly from shoots of Carex rostrata, Menyanthes trifoliata, Betula nana, and Salix lapponum from the early growing season until the beginning of senescence (June-September 2020 and 2021, three campaigns both years), with three specimens per species and campaign. We also measured CH4 emission from Equisetum fluviatile and Comarum palustre during high summer in 2021 to further shed light on species-specific characteristics of plant-mediated CH4 flux. We monitored abiotic factors such as belowground CH4 concentration, potential CH4 production and oxidation rate, water table level, and peat temperature.During high summer in 2021, C. rostrata had the highest CH4 transport rate per leaf area (6.86 mg m-2 h-1). This value was significantly higher than that from M. trifoliata which was the secondarily important CH4 emitter with the rate of 4.07 mg m-2 h-1. E. fluviatile, C. palustre, B. nana, and S. lapponum had limited CH4 transport rate per leaf area (0.66, 0.02, 0.14, and 0.15 mg m-2 h-1, respectively) and thus were negligible CH4 emitters. CH4 emission from C. rostrata demonstrated the most pronounced seasonal variation (ranging from 0.02 to 24.78 mg m-2 h-1), driven primarily by seasonal vegetation development (phenology) and only secondarily by rhizospheric peat temperature. In contrast, CH4 emission from M. trifoliata, B. nana, and S. lapponum showed little seasonal variation, and no factors that significantly affected the flux from these species were found. Lastly, the sharp decrease in rhizospheric peat CH4 concentration during high summer and the simultaneous increase in emission from C. rostrata, the most dominant species in our site, indicated the conduit effect predominated over the CH4 production and oxidation. The findings highlight the importance of C. rostrata in mediating CH4, which could exacerbate the climatic impact of the thawing permafrost region where C. rostrata can thrive in wet microsites.

Alpine meadows and peatlands on the Qinghai‐Tibetan Plateau, respectively, act as sinks and sources of atmospheric CH ₄ . Yet, little is known about plant‐mediated CH ₄ fluxes in these ecosystems. We measured CH ₄ flux from shoots of plants in both ecosystems (45 and 7 species, respectively) and investigated its response to experimental warming. We further investigated the CH ₄ transport mechanism of key plant species in the peatland through shading and clipping experiments and scanning electron microscope analysis. In the meadow, most plant families showed negative plant CH ₄ flux (CH ₄ uptake), ranging from −0.0005 to −0.04 mg CH ₄ g ⁻¹ g h ⁻¹ . The plant CH ₄ flux in the peatland was positive for all species but showed large between‐species variation, ranging from 0.0006 to 0.167 mg CH ₄ g ⁻¹ g h ⁻¹ . Experimental warming did not affect plant CH ₄ flux in the peatland, while it negatively affected CH ₄ uptake in the meadow. Plant CH ₄ transport mechanisms in the peatland were species‐specific: the dense exodermes of the primary roots restrained transport in Blysmus sinocompressus and Carex myosuroides , while leaves controlled transport in Carex muliensis due to small aerenchyma and limited connectivity. Our findings have important implications for the regional CH ₄ budget and show that species‐level differences should be considered when assessing plant‐mediated CH ₄ emissions. Read the free Plain Language Summary for this article on the Journal blog.