Can we use shelterwoods in Mediterranean pine forests to promote oak seedling development?

Abstract

International audienceThe use of shelterwoods to favour the development of natural or underplanted seedlings is common in temperate forests but rare in the pine forests of the Mediterranean area. Our aim was to assess the use of shelterwoods in Aleppo pine (Pinus halepensis) woodlands in southern France to promote the survival and growth of two co-occurring oak species: the deciduous Quercus pubescens and the evergreen Quercus ilex. Twelve Aleppo pine stands were selected and differentially thinned to create a light shelterwood (G = 32 m2/ha, irradiance 13%), a medium shelterwood (G = 19 m2/ha, irradiance 33%) and a dense shelterwood (G = 10 m2/ha, irradiance 52%). A total of 1248 sowing points, half composed of Q. pubescens and half of Q. ilex, were then set up in these three conditions. Seedling survival and growth were monitored for three years and plant stress was assessed by measuring predawn leaf potential and photosynthetic performance through the Fv ∕Fm ratio. Soil moisture was also recorded at two depths during two growing seasons. Survival was high for both species in all three conditions due to three consecutive wet years. The lowest survival was recorded for Q. pubescens in the dense shelterwoods. Growth in diameter and height increased from the dense to the light shelterwoods. Shrubs developed more strongly in the light shelterwood, and increasing shrub cover enhanced height growth. Photosynthetic performance was lowest for Q. pubescens in dense shelterwoods and highest in light shelterwoods, whereas the reverse was true for Q. ilex. The lowest predawn potentials were recorded in the dense shelterwoods even though higher soil water content values were measured in this treatment during the summer drought. We show that light shelterwoods were more beneficial to growth than denser ones, indicating control by light availability during the three years of the study. However, as lower soil moisture and faster understorey development were also recorded in this condition, more extended observation is needed to determine whether this benefit persists in subsequent years

Short-term dynamics of Quercus ilex advance regeneration in a Pinus nigra plantation after the creation of small canopy gaps

“…In a Pinus halepensis Mill. shelterwood in southern France, Prévosto et al (2011a) found that the growth of sown Q. ilex was higher in the stands with lower BA (10 m 2 ha -1 ). We observed an important increase in the height of Q. ilex regeneration in the years immediately after the canopy opening, whereas in the pine plantation no evidences of a clear height increase were found during the same period of time.…”

Multiyear impacts of partial throughfall exclusion on Buxus sempervirens in a Mediterranean forest

“…However, it does not support the hypothesis, derived from f ield studies with seedlings in Mediterranean-type 210 J. Rodriguez-Calcerrada et al / Forest Systems (2013) 22(2), 202-213 habitats (Valladares and Pearcy, 2002;Rodríguez-Calcerrada et al, 2010b;Prévosto et al, 2011), that increasing shade would exacerbate sensitivity to increased drought. One explanation for this result is that we studied large, mature saplings well established in the understory.…”

Designing acorn protection for direct seeding of quercus species in high predation areas

“…The results confirm the viability of Quercus ilex direct seeding in forest restoration and document predation as a major current limitation in Mediterranean environments in the absence of protection. Partial shading/ shelter appears to have a major influence on acorn early survival and growth (Pausas et al, 2004;Rodríguez-Calcerrada et al, 2008;Prévosto et al, 2011b). Micromammal and rabbit activity was evident and dramatic all over the study site.…”