Natural regeneration of Spanish black pine [Pinus nigra Arn. ssp. salzmannii (Dunal) Franco] at contrasting altitudes in a Mediterranean mountain area

Abstract

Information on plant seed dispersal, natural loss dynamics of seeds and germination are critical for understanding natural regeneration mechanisms. The aim of this study was to assess the effect of different forest stand densities on seedfall, seed predation, and seedling germination of two populations of the endangered Spanish black Pine forests located at lower (Central population) and higher elevation near the limit of the species’ range (peripheral population) in the Cuenca Mountains of Central Spain. The seed predation and germination experiment also included a nested site preparation treatment. Seed fall varied significantly between 2006 and 2005 or 2007 in both populations. During the only mast year of 2006, higher seedfall was observed at lower elevation and in higher density stands. Predation rates were influenced by the seed crop since predators consumed more than 75 % of seeds in years with lower production and less than 15 % in a mast year. Seed germination is influenced by forest habitat, stand density and soil scalping. For common habitat types, and in a high seed production year, better seed germination rates were observed in medium and dense stands (25–30 and 35–40 m2 ha−1, respectively, in terms of basal area). No statistical difference in seed germination rate was found for Spanish black pine forest at its ecological distribution limit between lower and higher densities (15–20 and 35–40 m2 ha−1, in terms of basal area). In both sites, closed stands with soil scalping exhibited higher germination rates.

Natural regeneration in Iberian pines: A review of dynamic processes and proposals for management

“…Similarly, the predator satiation hypothesis states that large seed crops are likely to satiate seed predators, which thus would destroy a lower percentage of crop (Kelly, 1994). Moreover, seed production is significantly lower at the altitudinal limit of the species distribution than in the most favourable habitat (Lucas-Borja et al, 2012), confirming that pines under stressed conditions tend to produce solely male cones or even stop reproducing (Shmida et al, 2000). Seed production in mast years can be up to 10-fold greater than that of a non-mast year, with average values over 70 seeds/m2 on mast years and favourable locations, and less than 10 seeds/m2 on non-masting years and/ or altitudinal limits .…”

“…In this sense, and according to their low shade tolerance, P. halepensis seedlings require earlier liberation (Scarascia-Mugnozza & Schirone, 1984), followed by P. pinea and P. pinaster (Ruano et al, 2009;Manso et al, 2014a). On the opposite side, P. sylvestris and P. nigra are the species whose seedlings can survive longer periods under the shade of parent trees (Calama et al, 2015b;Lucas-Borja et al, 2016).…”

Large-Scale Regeneration Patterns of Pinus nigra Subsp. salzmannii: Poor Evidence of Increasing Facilitation Across a Drought Gradient

“…This prediction has been validated for a broad range of environments and species, including species of the Pinus genus [14][15][16]. However, the stress-gradient hypothesis has been challenged by empirical evidence coming from arid and semi-arid areas.…”

Seed Origin and Protection Are Important Factors Affecting Post-Fire Initial Recruitment in Pine Forest Areas

“…In this regard, it is noteworthy that the study occurred under two relatively wetter spring seasons (see precipitation in April 2011 and 2012 from Figure 2). Higher water availability during spring 2011 meant that the seedlings were able to survive without shrub or canopy cover protection as is normally needed in warmer and drier circumstances that characterize the Mediterranean climate [25]. It is possible that with sufficient soil moisture and seed hydration, sunlight favoured a longer taproot and longer shoots in seedlings, enabling them to penetrate the soil and survive better [45].…”