Plant water relations and edaphoclimatic conditions affecting acorn production in a holm oak (Quercus ilex L. ssp. ballota) open woodland

Abstract

Acorn production patterns and the annual evolution of water relations parameters of Quercus ilex ssp. ballota (Desf.) Samp. in a dehesa (an open woodland forest) subject to various soil treatments (ploughing, ploughing ? sowing, control) were studied in southwest Spain from June 2006 to December 2008. The effects of soil water holding capacity and effective soil depth on soil and plant water status and acorn production were also investigated. Water parameters showed significant differences between the ploughing treatment and the control, and there were also significant temporal differences. Xylem water potential ranged from -3.4 ± 0.1 to -0.7 ± 0.2 MPa, and cuticular transpiration was 62.4-192.9 mmol H 2 O kg -1 s -1 . Acorn production did not differ significantly according to soil treatment, and showed large intra-specific variability. Individual values ranged from 0 to 1,220 g m -2 (fresh weight). Positive relationships were found between xylem water potential, cuticular transpiration and relative water content measured at midsummer, and acorn production during the three studied years. These results suggest that climatic conditions and soil water availability have a strong influence on plant water status, and therefore on acorn development during summer. The results also reflect the ability of this species to adapt to the Mediterranean climate by preserving water during dry periods, which to a large extent can be attributed to stomatal closure at high relative water content levels, and low cuticular transpiration during these periods.

Shrub encroachment of Iberian dehesas: implications on total forage productivity

“…Soil water depletion in mid summer may have a negative effect on early acorn ripening and, ultimately, on acorn yield (Carevic et al 2010). At the sites in this study, Rolo and Moreno (2011) reported a worsening of hydric status of trees growing among Retama by the end of summer, explained by the high spatial overlap of Q. ilex and deep Retama roots .…”

“…It is hypothesised that the contrasting rooting profiles of Cistus and Retama determined these differences. Carevic et al (2010) observed a close relationship between acorn productivity and the physiological state of oak trees. At the sites in the present study, the physiological status of scattered Q. ilex trees was monitored over three consecutive summers (Rolo and Moreno 2011).…”

Is selective thinning an adequate practice for adapting Quercus ilex coppices to climate change?

“…Summer water shortage is already a primary limiting factor for tree growth, seed production, and seedling recruitment in these regions (Carevic et al 2010;Castro et al 2005;Espelta et al 2008). Therefore, future increases in aridity will likely cause profound changes in the structure and composition of Mediterranean-type forests, especially where the water demand of the dominant species is already marginally met (Bréda et al 2006;Breshears et al 2009).…”

Towards an integration of plant ecophysiological traits for the conservation of endangered species in ecosystems under water stress

“…In addition, it appears that physiological traits in plants can be used as predictors of other traits. For example, previous research in Mediterranean ecosystems found that low xylem water potential and a decrease in cuticular transpiration during summer months limited acorn production in Quercus ilex stands during autumn (Alejano et al, 2008;Carevic et al, 2010). Similarly, Moriana et al (2007) concluded that water relations in drought-induced olive trees in a semiarid habitat had an effect on the concentration of phenolic compounds in the oil they produced.…”