Linking the patterns in soil moisture to leaf water potential, stomatal conductance, growth, and mortality of dominant shrubs in the Florida scrub ecosystem

Abstract

Patterns in soil moisture availability affect plant survival, growth and fecundity. Here we link patterns in soil moisture to physiological and demographic consequences in Florida scrub plants. We use data on different temporal scales to (1) determine critical soil moisture content that leads to loss of turgor in leaves during predawn measurements of leaf water status (< crit ), (2) describe the temporal patterns in the distribution of < crit , (3) analyze the strength of relationship between rainfall and soil moisture content based on 8 years of data, (4) predict soil moisture content for 75 years of rainfall data, and (5) evaluate morphological, physiological and demographic consequences of spring 2006 drought on dominant shrubs in Florida scrub ecosystem in the light of wateruptake depth as determined by stable isotope analysis (δ 18 O). Based on 1998-2006 data, the soil moisture content at 50 cm depth explained significant variation in predawn leaf water potential of two dominant shrubs, Quercus chapmanii and Ceratiola ericoides (r 2 =0.69). During 8 years of data collection, leaves attained < crit only during the peak drought of 2000 when the soil moisture fell below 1% by volume at 50 and 90 cm depth. Precipitation explained a significant variation in soil moisture content (r 2 =0.62). The patterns in predicted soil moisture for 75 year period, suggested that the frequency of drought occurrence has not increased in time. In spring 2006, the soil reached critical soil moisture levels, with consequences for plant growth and physiological responses. Overall, 24% of plants showed no drought-induced damage, 51% showed damage up to 50%, 21% had intense leaf shedding and 2% of all plants died. Over the drought and recovery period (May-October 2006), relative height growth was significantly lower in plants with greater die-back. All species showed a significant depression in stomatal conductance, while all but deep-rooted palms Sabal etonia and Serenoa repens showed significantly lower predawn (< pd ) and mid-day (< md ) leaf water potential in dry compared to wet season. Plants experiencing less severe die-back exhibited greater stomatal conductance, suggesting a strong relationship between physiology and morphology. Based on results we suggest that the restoration efforts in Florida scrub should consider the soil moisture requirements of key species.

Variation in tolerance to drought among Scandinavian populations of Arabidopsis lyrata

“…It is possible that traits, favoured in alpine habitats for reasons other than their effect on tolerance to drought, also carry benefits in dry environments. Leaf damage and senescence may reflect an inability to maintain internal water balance during drought (Saha et al 2008), but leaf senescence can also be a mechanism that increases the ability to survive dry periods, by reducing leaf surface area and evapotranspiration (Sinclair 2000). In the present study, high leaf damage was associated with low survival and biomass of survivors in the drought treatment.…”

Seasonal water use by deciduous and evergreen woody species in a scrub community is based on water availability and root distribution

“…According to Markesteijn and Poorter () and consistent with our first hypothesis, the evergreen species should be considered ‘drought delayers’ because they delayed the effects of the drought by accessing deep water when shallow water was depleted. Deciduous species lost their leaves in the early dry season, but leafed out in the late dry season when the drought conditions can be most severe due to low water moisture and high vapor pressure deficit (Weekley et al ., ; Saha et al ., ). Contrary to our second hypothesis, deciduous species only avoided the first half of the dry season and used a ‘drought delayer’ strategy for the last half of the dry season.…”

“…Dry seasonal ecosystems are defined by a pronounced and consistent dry season that results in water limitation, especially in shallow and/or sandy soils with low water retention (Murphy and Lugo, 1986;Menges and Gallo, 1991;Weekley et al, 2007;Saha et al, 2008). Woody plant species in the Florida sandhill plant community may function with high water availability during the wet season and low water availability and decreasing soil water potentials during the dry season by different strategies.…”

Quantifying ecological memory in plant and ecosystem processes

“…; Saha et al . ). Conversely, a ‘fast’ time scale is assumed for computing antecedent vapour pressure deficit ( D ant ) because stomata are directly exposed to atmospheric conditions, which vary at minute to hourly scales, and they likely respond quickly to changes in vapour pressure deficit (Damour et al .…”