Disentangling elevation, annual flooding regime and salinity as hydrochemical determinants of halophyte distribution in non-tidal saltmarsh

Vélez-Martín, Alberto, Davy, Anthony J., Luque, Carlos J. and Castellanos, Eloy Manuel (2020) Disentangling elevation, annual flooding regime and salinity as hydrochemical determinants of halophyte distribution in non-tidal saltmarsh. Annals of Botany. ISSN 0305-7364

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Abstract

Background and Aims Hydrological disconnection, especially in a Mediterranean climate, creates coastal saltmarshes with an annual cycle of flooding that are unlike tidally inundated systems. Winter rainfall produces long, continuous hydroperiods, alternating with continuous exposure caused by evaporation in warm, rain-free summers. We aimed to distinguish the effects of elevation, hydroperiod and salinity on annual and perennial halophytes in such a system. Methods We recorded vegetation and sediment salinity in permanent quadrats on a marsh in the Doñana National Park, Spain, over 7 consecutive years with widely differing rainfall. Elevation was determined from LIDAR data and the duration of the annual hydroperiod from satellite imagery. The independent effects of collaterally varying elevation, hydroperiod and salinity on species distribution were examined using GLMs and hierarchical partitioning. Key Results Hydroperiod and salinity were both inversely related to elevation but interannual fluctuations in rainfall facilitated discrimination of independent effects of the three collaterally varying factors on halophyte distribution. Perennial distribution was strongly structured by elevation, whereas many annual species were more sensitive to hydroperiod. The independent effects of salinity varied according to individual species’ salt tolerance from positive to negative. Thus life-history and, in the case of annuals, phenology were important in determining the relative impact of elevation and hydroperiod. Conclusions The consequences of elevation for halophyte distribution in seasonally flooded saltmarshes are fundamentally different from those in tidal marshes, because protracted and frequent flooding regimes require different adaptations, and because of the unpredictability of flooding from year-to-year. These differences could explain greater species diversity in non-tidal marshes and the absence of key saltmarsh species prominent in tidal marshes. The vegetation of non-tidal marshes will be particularly susceptible to the more extreme annual cycles of temperature and rainfall predicted for Mediterranean climates.

Item Type: Article
Uncontrolled Keywords: coastal marsh,hydroperiod,flooding regime,life-history,marsh embankment,mediterranean climate,remote sensing,salt tolerance
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: LivePure Connector
Date Deposited: 16 Apr 2020 00:46
Last Modified: 13 Jul 2020 23:58
URI: https://ueaeprints.uea.ac.uk/id/eprint/74761
DOI: 10.1093/aob/mcaa078

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