Effects and significance of groundwater for vegetation: A systematic review.

Groundwater represents a critical water source for plants, especially during drought, with continuous groundwater availability widely associated with the presence of ecological refugia and the preservation of biodiversity during periods of adverse conditions. Here, we present a systematic quantitative literature review of global groundwater and ecosystem interactions to synthesise current knowledge and identify key knowledge gaps and research priorities through a management lens. Despite increasing research on groundwater dependent vegetation since the late 1990s, significant geographical and ecological biases are evident with papers focused on arid regions or areas with significant anthropogenic changes. Of the 140 papers reviewed, desert and steepe arid landscapes accounted for 50.7 % and desert and xeric shrublands were represented in 37.9 % of papers. A third of papers (34.4 %) quantified groundwater uptake by ecosystems and groundwater contributions to transpiration, with studies examining the influence of groundwater on vegetation productivity, distribution, and composition also well represented. In contrast, groundwater influences on other ecosystem functions are relatively poorly explored. The research biases introduce uncertainty in the transferability of findings between locations and ecosystems limiting the generality of our current understanding. This synthesis contributes to consolidating a solid knowledge base of the hydrological and ecological interrelationships for managers, planners, and other decision-makers that is relevant to the landscapes and environments they manage, so can more effectively deliver ecological and conservation outcomes.