Germination and regeneration mechanisms in Mediterranean degenerate forests

Abstract

Abstract. Germination and developmental behaviour during juvenile stages are of importance in relation to succession mechanisms acting on plant communities. This is particularly so in the Mediterranean region, where the climatic summer drought causes stress. We investigated and compared germination and development of four tree species in two parts of the French Mediterranean region where the original dominant tree species (Quercus pubescens) has been largely replaced by Quercus ilex in the southern part, and Castanea sativa in the northern part. Observed differences in germination rates and developmental behaviour, especially shootroot ratio and the role of water supply, suggest that other species may eventually replace the current dominant species.

Late Holocene vegetation changes in relation with climate fluctuations and human activity in Languedoc (southern France)

“…During the last 1000 years, the enhanced dryness could have favored Pinus and evergreen Quercus. However, ecological studies in southern France demonstrate that in the near future Quercus pubescens, the present deciduous species in this area, could replace Quercus ilex and Pinus halepensis in many places (Bacilieri et al, 1993). Indeed, Pinus halepensis is a pioneer species of Mediterranean ecological successions that will typically be replaced by Q. ilex.…”

“…Indeed, Pinus halepensis is a pioneer species of Mediterranean ecological successions that will typically be replaced by Q. ilex. Furthermore, it is known that Q. ilex inhibits the germination of its own seeds and not those of Q. pubescens (Barbero et al, 1990;Bran et al, 1990;Bacilieri et al, 1993;Li and Romane, 1997). Such processes of auto-allelopathy enable the replacement of Q. ilex by Q. pubescens.…”

Seedling bank dynamics in managed holm oak (Quercus ilex) forests

“…The dynamics of the seedling bank has been used to hypothesise about the past and the future of holm oak forests. Thus, different authors (Bacilieri et al [1], Li and Romane [19]) suggest that the low seedling regeneration in holm oak stands in southern France may lead to the replacement of holm oak by downy oak (Quercus humilis = Q. pubescens), while Espelta et al [12] consider that the present seedling dynamics in holm oak forests in NE Spain prevents vigorous regeneration and, consequently, population renewal. Nevertheless, most of these studies on holm oak forests are based on data obtained from chronosequences, but not from monitoring the seedling bank over time.…”

“…It would be expected that holm oak seedlings remain in the understory of holm oak stands until the canopy is opened by thinning and they can resume growth. Specific objectives are: (1) to determine the spatial (within and between plots) and temporal (between years) variability in the size and composition of the seedling bank; (2) to investigate the patterns of seedling recruitment, mortality growth and biomass allocation determining these dynamics.…”

Linking restoration outcomes with mechanism: the role of site preparation, fertilisation and revegetation timing relative to soil density and water content

“…Although there is clearly some uncertainty regarding the long term survival and growth of seedlings, the first year in particular seems the most critical in seedling establishment in MCEs (Gomez-Aparicio et al 2004; as the timing of opening rains and water availability during summer drought determines the growing season length, root production and hence survival and persistence (Martinez et al 1998). The importance of the first year following revegetation will become ever more important in an increasingly unpredictable Mediterranean climate as the effects of climate change become more apparent (Bacilieri et al 1993;Klausmeyer and Shaw 2009). 4 Several practical site preparation techniques have shown to increase the establishment success of planted seedlings in MCEs, including ripping (mechanically disturbing the top 5-100cm of the soil to increase roughness and negate compaction and soil erosion) (Turner et al 2006;Koch and Samsa 2007), and ashbed creation (combustion of coarse woody debris piles) which increases water infiltration and nutrient availability (Hatch 1960;Loneragan and Loneragan 1964). Plant treatments that have been shown to increase seedling establishment include the addition of nutrients (Martinez et al 1998;Ruthrof et al 2010), though treatment effects may vary across species, site and other treatments such as watering (Standish et al 2012).…”