Climatic, ecophysiological, and phenological controls on plant ecohydrological strategies in seasonally dry ecosystems

Abstract

Large areas in the tropics and at mid‐latitudes experience pronounced seasonality and inter‐annual variability in rainfall and hence water availability. Despite the importance of these seasonally dry ecosystems (SDEs) for the global carbon cycling and in providing ecosystem services, a unifying ecohydrological framework to interpret the effects of climatic variability on SDEs is still lacking. A synthesis of existing data about plant functional adaptations in SDEs, covering some 400 species, shows that leaf phenological variations, rather than physiological traits, provide the dominant control on plant‐water‐carbon interactions. Motivated by this result, the combined implications of leaf phenology and climatic variability on plant water use strategies are here explored with a minimalist model of the coupled soil water and plant carbon balances. The analyses are extended to five locations with different hydroclimatic forcing, spanning seasonally dry tropical climates (without temperature seasonality) and Mediterranean climates (exhibiting out of phase seasonal patterns of rainfall and temperature). The most beneficial leaf phenology in terms of carbon uptake depends on the climatic regime: evergreen species are favoured by short dry seasons or access to persistent water stores, whereas high inter‐annual variability of rainy season duration favours the coexistence of multiple drought‐deciduous phenological strategies. We conclude that drought‐deciduousness may provide a competitive advantage in face of predicted declines in rainfall totals, while reduced seasonality and access to deep water stores may favour evergreen species. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Stochastic soil water balance under seasonal climates

“…Vico et al [4] recently investigated plant water and carbon uptake based on different physiological and phenological strategies in seasonally dry ecosystems using a coupled model of soil water (including deeper, more persistent storage) and plant carbon balances. The versatility of the models introduced here can allow for similar future extensions to account for the role of groundwater dynamics and vegetation water uptake strategies on seasonal and annual water partitioning.…”

“…Furthermore, in some dry climates where rainfall and potential evapotranspiration are in-phase, annual evapotranspiration can be shown to increase because of inter-seasonal soil moisture transfer, highlighting the importance of soil water storage in the seasonal context. plant responses and adaptive strategies [3,4], regional vegetation distribution, carbon fluxes and primary productivity [5][6][7][8], with further implications for agriculture and land management [9]. These scientific emphases on the role of climate seasonality come at a time of discernible climate change.…”

Dynamic interactions of ecohydrological and biogeochemical processes in water‐limited systems

“…Hence understanding the coupled hydrological and biogeochemical processes in drylands is motivated by our increasing need to design novel solutions for water resource management, to explain and predict ecosystem degradation, evaluate degradation control strategies, and to analyze the effect of changing climate and anthropogenic activities on dryland systems. In addition to drylands, the coupling between hydrological and biogeochemical processes also appears evident in areas with strong seasonal precipitation patterns (e.g., Mediterranean and seasonally-dry tropical regions), and in mesic systems during droughts (Lohse et al 2009, Thompson et al 2011, Moyano et al 2013, Vico et al 2014. Therefore, understanding the connections between hydrological and biogeochem-ical processes in water-limited systems can be translated to other systems under water-stressed conditions.…”

Global Environmental Change in Drylands: Ecohydrological Controls on Plant Communities

“…Moreover, we notice that this model does not account for other factors, including rainfall seasonality (Vico et al, 2015) and plant life histories (i.e., annuals or perennials; evergreen or deciduous) (Kos et al, 2012), which play an important role in determining plant community composition in savannas. In fact, an increase in winter rainfall increases deep soil water and thus favors trees (deep rooted plants) over grasses (shallow rooted plants) (Brown et al, 1997;Germino and Reinhardt, 2014).…”

“…In fact, an increase in winter rainfall increases deep soil water and thus favors trees (deep rooted plants) over grasses (shallow rooted plants) (Brown et al, 1997;Germino and Reinhardt, 2014). The high inter-annual variability of rainy season duration favors deciduous trees over evergreen trees, which may affect the competition with grasses (Vico et al, 2015). The legacy effect of trees and grasses attributed to water and/or carbohydrate storage, available seeds/meristems, and/or nutrient availability from litter decomposition in response to rainfall fluctuations are also expected to be affected by plant life histories (Sherry et al, 2008;Sala et al, 2012;Anderegg et al, 2015).…”