Revisiting plant hydrological niches: The importance of atmospheric resources for ground-rooted plants

Occult precipitation events (fog, dew and light rain) can alter plant water and nutritional status, both directly through the aerial uptake of surface water and nutrients, and indirectly via redistribution of atmospheric resources to the soil. However, current frameworks that explain niche segregation, species interactions and coexistence still consider that ground-rooted plants obtain resources almost exclusively via root absorption from soil. Here, we expand the plant hydrological niches model to incorporate both soil and atmospheric resource-axes, thus providing a more complete picture of how ground-rooted terrestrial plants obtain, remobilise, share and compete for water and soluble nutrients. First, we describe how plants with different water acquisition strategies access directly or indirectly atmospheric resources. Then, we discuss how the use of such resources may promote spatiotemporal niche segregation, contributing to shape species distribution and abundance within plant communities. We illustrate this argument with examples from arid, mesic and wet vegetation types. Finally, we examine how climate and land-use changes may influence plant hydrological niches, potentially altering community structure. Synthesis. Understanding how available atmospheric resources influences niche segregation in plant communities is a crucial step towards better predictions of species responses (e.g. changes in distribution, abundance and interactions) to climate change.