Mangrove forests are highly productive tidal saline wetland ecosystems found along sheltered tropical and subtropical coasts. Ecologists have long assumed that climatic drivers (i.e., temperature and rainfall regimes) govern the global distribution, structure, and function of mangrove forests. However, data constraints have hindered the quantification of direct climate–mangrove linkages in many parts of the world. Recently, the quality and availability of global‐scale climate and mangrove data have been improving. Here, we used these data to better understand the influence of air temperature and rainfall regimes upon the distribution, abundance, and species richness of mangrove forests. Although our analyses identify global‐scale relationships and thresholds, we show that the influence of climatic drivers is best characterized via regional range‐limit‐specific analyses. We quantified climatic controls across targeted gradients in temperature and/or rainfall within 14 mangrove distributional range limits. Climatic thresholds for mangrove presence, abundance, and species richness differed among the 14 studied range limits. We identified minimum temperature‐based thresholds for range limits in eastern North America, eastern Australia, New Zealand, eastern Asia, eastern South America, and southeast Africa. We identified rainfall‐based thresholds for range limits in western North America, western Gulf of Mexico, western South America, western Australia, Middle East, northwest Africa, east central Africa, and west‐central Africa. Our results show that in certain range limits (e.g., eastern North America, western Gulf of Mexico, eastern Asia), winter air temperature extremes play an especially important role. We conclude that rainfall and temperature regimes are both important in western North America, western Gulf of Mexico, and western Australia. With climate change, alterations in temperature and rainfall regimes will affect the global distribution, abundance, and diversity of mangrove forests. In general, warmer winter temperatures are expected to allow mangroves to expand poleward at the expense of salt marshes. However, dispersal and habitat availability constraints may hinder expansion near certain range limits. Along arid and semiarid coasts, decreases or increases in rainfall are expected to lead to mangrove contraction or expansion, respectively. Collectively, our analyses quantify climate–mangrove linkages and improve our understanding of the expected global‐ and regional‐scale effects of climate change upon mangrove forests.

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. 2017. Linear and nonlinear effects of temperature and precipitation on ecosystem properties in tidal saline wetlands. Ecosphere 8(10):e01956. 10. 1002/ecs2.1956 Abstract. Climate greatly influences the structure and functioning of tidal saline wetland ecosystems.However, there is a need to better quantify the effects of climatic drivers on ecosystem properties, particularly near climate-sensitive ecological transition zones. Here, we used climate-and literature-derived ecological data from tidal saline wetlands to test hypotheses regarding the influence of climatic drivers (i.e., temperature and precipitation regimes) on the following six ecosystem properties: canopy height, biomass, productivity, decomposition, soil carbon density, and soil carbon accumulation. Our analyses quantify and elucidate linear and nonlinear effects of climatic drivers. We quantified positive linear relationships between temperature and above-ground productivity and strong positive nonlinear (sigmoidal) relationships between (1) temperature and above-ground biomass and canopy height and (2) precipitation and canopy height. Near temperature-controlled mangrove range limits, small changes in temperature are expected to trigger comparatively large changes in biomass and canopy height, as mangrove forests grow, expand, and, in some cases, replace salt marshes. However, within these same transition zones, temperature-induced changes in productivity are expected to be comparatively small. Interestingly, despite the significant above-ground height, biomass, and productivity relationships across the tropical-temperate mangrove-marsh transition zone, the relationships between temperature and soil carbon density or soil carbon accumulation were not significant. Our literature review identifies several ecosystem properties and many regions of the world for which there are insufficient data to fully evaluate the influence of climatic drivers, and the identified data gaps can be used by scientists to guide future research. Our analyses indicate that near precipitation-controlled transition zones, small changes in precipitation are expected to trigger comparatively large changes in canopy height. However, there are scant data to evaluate the influence of precipitation on other ecosystem properties. There is a need for more decomposition data across climatic gradients, and to advance understanding of the influence of changes in precipitation and freshwater availability, additional ecological data are needed from tidal saline wetlands in arid climates. Collectively, our results can help scientists and managers better anticipate the linear and nonlinear ecological consequences of climate change for coastal wetlands.

While numerous studies have documented patterns of invasion by non-indigenous plant species, few have considered the invasive properties of non-native genotypes of native species. Characteristics associated with specific genotypes, such as tolerance to disturbance, may mistakenly be applied to an entire species in the absence of genetic information, which consequently may affect management decisions. We report here on the incidence and growth of an introduced lineage of Phragmites australis in the Gulf of Mexico coastal zone of Louisiana. P. australis was collected from nine separate locations for inclusion in a series of growth experiments. Chloroplast DNA analysis indicated that specimens collected from four locations in the Mississippi River Delta represented the introduced Eurasian haplotype; the remainder represented the gulf coast haplotype. Three distinct genotypes, or clones, were identified within each haplotype via analysis using amplified fragment length polymorphisms, which also revealed reduced genetic diversity of the gulf coast clones compared to the Eurasian clones. Clones of each haplotype were planted along with three other native macrophytes at similar densities in a restored brackish marsh and monitored for growth. After 14 months, the Eurasian haplotype had spread vegetatively to cover about 82% of the experimental plots, more than four times the coverage (18%) of the gulf coast haplotype. Thus, the use of P. australis plantings for wetland restoration should consider the genetic lineage of plants used since our results indicate the potential of the Eurasian haplotype to grow rapidly at newly restored sites. This rapid growth may limit the establishment of more slowly growing native species.

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The effects of increased salinity on plant growth were examined in a greenhouse experiment with four species common to oligohaline marshes of the northern Gulf of Mexico: Eleocharis palustris, Panicum hemitomon, Sagittaria lancifolia, and Scirpus americanus. Effects of final salinity reached (6 or 12 g/L), salinity influx rate (3 d or 3 wk), and duration of exposure (1, 2, or 3 mo) were investigated. Sagittaria lancifolia was the first species to show visible signs of stress, with browning and curling of older leaf edges. The salt effect was delayed for 6-8 wk in P. hemitomon, but this species had the highest aboveground tissue mortality rate at 12 g/L as exposure continued. Final salt concentration affected all species to a greater degree than did salinity influx rate. No aboveground mortality occurred at 6 g/L, but growth suppression was apparent and varied with species. The magnitude of growth suppression in response to salinity increased for all species as the duration of exposure increased. Overall, we ranked the species as follows, in order from least to most salt tolerant: Panicum hemitomon < Sagittaria lancifolia < Eleocharis palustris < Scirpus americanus. This ranking reflects the field occurrence of these species along a gradient of increasing salinity in northern Gulf of Mexico coastal habitats from freshwater wetlands through oligohaline areas to mesohaline wetlands.