Spatial distribution analysis of Dicksonia sellowiana Hook. in Araucaria forest fragments with different sizes

Abstract

Dicksonia sellowiana Hook. (Dicksoniaceae) is target of extractive exploitation and is threatened with extinction. We analyzed the population structure, the spatial distribution pattern of D. sellowiana and its relationship with environmental parameters within three fragments of Araucaria Forest in Rio Grande do Sul, Brazil. The fragments are of different sizes, namely, large (H1LF) with 246 ha, medium (H2MF) with 57 ha and small (H3SF) with 5.2 ha. Within each site, 1 ha was delimited, divided into 100 subplots (100 m2), of which 20 were selected with a draw. In each subplot, counting of the individuals, the registration of the caudice height and the coverage of leaves (SC) (m2), measurements of photosynthetically active radiation (PAR), canopy opening degree (CO), soil moisture (SM) and litter thickness (LT). The temperature (T) was measured inside each site. A total of 792 plants were sampled, of which 551 were concentrated in H1LF, 108 in H2MF and 133 in H3SF. An average of 1320 ha-1 individuals were estimated. Of the total including the three fragments, 96.9% of the individuals are in the first class of height (up to 0.8 m), indicating a great potential of population development. The spatial distribution pattern (AI) was aggregated in the three populations and the plants presented a heterogeneous total coverage, between 4.73 m2 (H2MF) and 2,223.47 m2 (H1LF). The highest values ​​of SC and SM were more related to the distribution of individuals in H1LF whereas the opposite was recorded in H2MF. The highest values ​​of PAR, LT and CO correlated with the distribution of D. sellowiana in H3SF. In addition to revealing that the H1LF population is among the most dense in southern Brazil, the results demonstrated a significant structural distinction between the interior populations of the fragments, in spite of them being located near to one another and being part of the same natural field matrix.

Diversity and Genetic Structure of Dicksonia navarrensis (Dicksoniaceae) Populations in the Mexican Sierra Madre Oriental

“…Even though the dispersal capacity of the spores of this species is very high, the probability that they will find suitable conditions for germination, gametophyte production and sporophyte formation is low, but studies are required to confirm that argument. In contrast, populations of D. sellowiana are distributed over a larger geographic area in the Atlantic Forest of South America (Mallman et al, 2019), have a high density of individuals, and have a continuous influx of gametophytes into populations (Schmitz et al, 2006;Fagundes et al, 2020); these three characteristics could be related to the corresponding values of H E , higher than those estimated for D. navarrensis in the present study.…”

“…In contrast, populations of D . sellowiana are distributed over a larger geographic area in the Atlantic Forest of South America (Mallman et al, 2019), have a high density of individuals, and have a continuous influx of gametophytes into populations (Schmitz et al, 2006; Fagundes et al, 2020); these three characteristics could be related to the corresponding values of H E , higher than those estimated for D . navarrensis in the present study.…”

Environmental factors affect population structure of tree ferns in the Brazilian subtropical Atlantic Forest

“…The influence of temperature and precipitation variables on Cyatheaceae species was reported by other authors (Tryon & Tryon 1982;Fernandes 1997). The positive correlation of Dicksonia sellowiana with precipitation (Bio18) indicates that it prefers humid sites, as observed by Mantovani (2004) and Mallmann et al (2018). Moreover, the positive correlation with the mean temperature of the driest quarter (Bio8) indicates that sites with higher temperatures do not completely inhibit the occurrence of Dicksonia sellowiana.…”

Natural regeneration in a mixed ombrophilous forest remnant in southern Brazil

“…Also noteworthy is the absence of Dicksonia sellowiana, a characteristic species of MOF, in the natural regeneration of PEAR. According to Mallmann et al (2019), canopy cover and soil moisture are environmental factors that influence the establishment and growth of D. sellowiana. Specific studies should be conducted to explain the absence of these species in the regenerating component of PEAR.…”