Functional Responses of WoodyProsopis caldeniaSeedlings to Drought and Livestock Grazing in Semiarid Rangelands of Argentina

Abstract

In the semiarid rangelands of Central Argentina overgrazing and drought alter the competitive balance between woody and herbaceous vegetation, favoring an increase in Prosopis caldenia. The objective of this study was to evaluate the effect of competition in perennial grasses and water stress on the relative growth rate (RGR) and related functional attributes of P. caldenia seedlings in sites with different grazing histories: a site exposed to long term (40 or more years) continuous grazing by cattle (grazed experimental site), and a long-term (around 30 years) exclosure (ungrazed experimental site). The total average RGR of the seedlings that grew in the grazed site was significantly higher, whereas the additional water supply favored those seedlings that grew in the ungrazed site. Significant relationships existed between the RGR and all the attributes measured, except in the ungrazed site where only those attributes related to leaf traits were correlated with the RGR. The above-and below-ground biomass of perennial grasses negatively affected the RGR of the P. caldenia seedlings in both experimental sites and soil moisture favored the RGR of the seedlings in the ungrazed site. Our work reveals the ability of seedlings of P. caldenia to take advantage of changes in environmental conditions, such as the release of resources due to overgrazing and to increase its RGR, which ensures its establishment.

Inter- and intrapopulation variation in the response of tree seedlings to drought: physiological adjustments based on geographical origin, water supply and species

“…Conversely, other species tolerate drought stress based on a ‘water conservative strategy’ by avoiding water loss during dry and wet periods adjusting cuticular transpiration (E c ) and stomatal closure ( Villar-Salvador et al 2004 ). However, several authors agree that the main physiological drought adaptation strategy of arid climate plants seems to be the need to maintain a high water content and cell turgor, which might have a direct effect on their subsequent growth and seed production processes ( López et al 2013 ; Villalobos and Peláez 2015 ). Nevertheless, not all plants have the same strategies to respond to periods of water stress.…”

Differentiation in seed mass and seedling biomass allocation in Prosopis laevigata throughout its distribution range in Mexico is associated to water availability

“…Previous studies conducted on adult trees or seedlings of other Prosopis species inhabiting hyper arid deserts, such as P. caldenia, P. glandulosa, P. flexuosa and P. pallida (Ansley et al 2007, Guevara et al 2010, de Villalobos & Peláez 2015, Salazar et al 2019) have revealed a significant capacity for phenotypic adjustment through plastic responses of biomass allocation in response to water availability in mesquites. The results here presented suggest that besides phenotypic plasticity, potentially genetically determined functional differences among populations may be very important for survival during the very crucial stages of germination and seedling emergence, perhaps before plastic responses can come into play.…”

Seed germination and early seedling survival of the invasive speciesProsopis juliflora(Fabaceae) depend on habitat and seed dispersal mode in the Caatinga dry forest

“…across semiarid regions of Argentina and Sudan ( Campos et al, 2011 ; Morandini, Giamminola & Viana, 2013 ; Yoda et al, 2015 ). High Prosopis caldenia Burkart seed mortality has also been related to soil water availability reduction across semiarid rangelands of Central Argentina ( De Villalobos, Peláez & Elia, 2005 ; De Villalobos & Peláez, 2015 ; Risio et al, 2016 ).…”