Olive yield as a function of soil moisture dynamics

Abstract

This study introduces a water-driven crop model aiming to quantitatively link olive yield to climate and soil moisture dynamics using an ecohydrological approach. A mathematical model describing soil moisture, evapotranspiration and assimilation dynamics of olive orchards is developed here. The model is able to explicitly reproduce two different hydroclimatic phases in Mediterranean areas: the well-watered conditions in which evapotranspiration and assimilation assume their maximum values and the real conditions where the limitations induced by soil moisture availability are taken into account. Annual olive yield is obtained by integrating the carbon assimilation during the growing season, including the effects of vegetation water stress on biomass allocation. This numerical model has been tested on an olive orchard located in Sicily (Italy) obtaining a satisfactory reproduction of historical olive yield data. This model is useful for simulating the influence of soil moisture dynamic on biomass growth, fruit productivity, also in a context of climatic change

Future Climate Forcings and Olive Yield in a Mediterranean Orchard

“…With increasing water stress, when θ decreases from zero to one, vegetation progressively shifts from a condition of growth not limited by water availability, to stressed conditions, which limit evapotranspiration and assimilation, inducing a reorganization of the available resources allocation. Consequently, the harvesting index, HI, defined as the ratio between the biomass allocated in fruits and the total assimilated biomass, has been assumed as linearly proportional to the dynamic water stress according to the following relationship [20]:…”

“…The knowledge of the soil moisture dynamics through the growing season allows vegetation water stress evaluation, which, in turn, affects the amount of biomass allocated in fruits, namely olive yield, using the harvesting index. Full details about model components and parameter values are reported in Viola et al [20], while the basic concepts are summarized in Section 2.1.…”

“…Evapotranspiration and carbon assimilation are a strong nonlinear function of soil moisture [26,27]. Using a daily stepwise function relating soil moisture condition to actual evapotranspiration and assuming that this relation is also valid for the assimilation, the actual evapotranspiration and the assimilation can then be evaluated as a function of climate and soil moisture conditions [20]. Assimilation is then integrated over the entire growing season, obtaining the total biomass.…”

“…Given these premises, this work aims to investigate how climate changes could affect olive yield in a Mediterranean orchard using a crop model that has been recently proposed for simulating the olive biomass and yield in response to the available soil water dynamics in both rainfed and irrigated conditions [20]. Differently from common pollen-based models [21,22], which are used to forecast short-term yields, the model is structured to deal with external climatic forcings and provides as a result soil moisture and biomass dynamics, making them suitable for simulating the behavior of olive orchards in future climatic scenarios when the following variables could be altered from the current mean values: CO 2 concentration, rainfall amount, temperature, wind speed and solar radiation.…”

Response of maize and olive to climate change under the semi-arid conditions of southern Spain

“…There are some models that calculate different processes of the olive productivity, as the photosynthesis, transpiration or water use efficiency (Diaz-Espejo et al, 2002Connor and Fereres, 2005). Other models calculate the biomass production based on annual radiation (Villalobos et al 2006), the functional approach based on the relation between yield and potential evapotranspiration (Viola et al, 2012) or calculates the potential olive oil production based on a three-dimensional model of canopy photosynthesis and respiration and the dynamic distribution of assimilates among organs (Morales et al, 2016). However, there is a need to improve the olive crop models under elevated both temperatures and CO 2 concentrations (Moriondo et al, 2015).…”