Population dynamics of Podocarpus lambertii in southern Brazilian forest–grassland mosaics

Abstract

The grasslands conversion to forests is occurring globally and modifying the population dynamics of species. Here, we characterized the population dynamics of Podocarpus lambertii Klotzsch ex Endl. over four years in southern Brazilian forest–grassland mosaics. We asked (i) if the studied P. lambertii population would decrease or increase over time and (ii) what the role of forest patches is in the growth and recruitment of a P. lambertii population. Thus, we studied forest–grassland mosaics, stratified the population into four demographic classes, evaluated the population dynamics, and estimated the correlation between canopy cover and average number of individuals. All individuals of P. Lambertii occurred in forest patches. Density was high but decreased from seedlings to the reproductive stage. The population growth rate was λ = 1.025, and the recruitment of individuals was high and variable among years. The transition and mortality rates showed a pattern of reduction from seedlings to the reproductive stage. Mortality rate for seedlings and juveniles was low and concentrated at the smaller heights. The correlations between canopy cover and the average number of individuals were positive and significant. The ecological characteristics of this species and specific conditions provided by forest patches allow population growth and species conservation in the southern Brazilian forest–grassland mosaics.

Genetic diversity and fine-scale genetic structure of the conifer Podocarpus lambertii in a forest-grassland mosaic from Southern Brazil

“…This inverse relation was already registered for several species (Vekemans & Hardy, 2004;Gonzales et al, 2010). Thus, the high density registered for the species in the study site (Bernardi et al, 2019) may help to explain the mainly absence of FGSG depicted.…”

“…Furthermore, our data revealed a highly aggregated spatial pattern for all the categories, (Figure 3). Podocarpus lambertii abundance is positive related to the canopy cover (Bernardi et al, 2019), which helps to explain the aggregated spatial pattern. Thus, the occurrence of FSGS only for Juvenile and to a short extent (7.1 m), as well as the nonoccurrence of FSGS in the other categories remains intriguing.…”

“…This situation is similarly observed in 12 additional P. lambertii populations from southern Brazil (Bittencourt et al, 2019), emphasizing the imperative for comprehensive measures that extend beyond local efforts. Another factor that can amplify genetic drift is the small population sizes, which does not appear to be a significant concern for P. lambertii, as they are known to occur at high densities (Bernardi et al, 2019).…”

“…Podocarpus lambertii naturally occur in forest-grasslands and continuous forest, in two disjoint areas, one in the northern Bahia (11°32.82'S,41°9.16'W) and another between Minas Gerais and southern Rio Grande do Sul (29°27.32'S, 54°26.26'W) (Bernardi et al, 2020). This is a native and dioecious species, endemic to Brazil, pollinated by bees (Carvalho 2004) and by wind (Bernardi et al, 2019). Seed dispersal mainly conducted by birds that feed on the pseudofruits -mature seed cones with seeds sitting above the fleshy red, fused bracts (Kuniyoshi 1983).…”

“…Moreover, FSGS studies make it possible to establish optimal distances between individuals for seed collection, in order to maximize the capture of genetic diversity for species conservation (Montagna et al, 2019). Additionally, forest patches in grasslands mosaic, in a mutual association, are extremely important to P. lambertii for promoting specific conditions, in particular, those related to light, that favor the population dynamics of the own species (Bernardi et al, 2019).…”