Can We Predict Male Strobili Production in Araucaria angustifolia Trees with Dendrometric and Morphometric Attributes?

Abstract

Knowledge of the formation and correlation of reproductive structures with dendro/morphometric variables of the Araucaria angustifolia tree species is a tool for its conservation and viability for sustainable forest management. We counted visually in araucaria trees the number of male strobili in RGB images acquired by Remotely Piloted Aircraft System (RPAs) over forest remnants. The diameter at the breast height (d), total height (h), crown radii (cr), crown base height (cbh), periodic annual increment in d based on increment rolls were measured, and the morphometric indices and crown efficiency were calculated with these variables. The relationships of these variables with male strobili production were analyzed by Pearson’s correlation and multivariate analysis techniques (cluster, factorial analysis, and main components). The morphometric variables correlated with the production of male strobili were d (r = 0.58, p-0.0002), crown diameter (r = 0.62, p < 0.0001), crown area (r = 0.62, p < 0.0001), coverage index (r = 0.51, p-0.001) and slenderness (r = −0.39, p-0.01). We argue that the production of male strobili is related to the vitality, dimension, density, growth space, and position in the stratum of the tree inside the forest, inferring a relationship between reproductive structures with the shape, size, growth space, and tree density. Such aspects shall be considered in future forest management initiatives in Southern Brazil.

Sustainability Assessment of Araucaria Forest Remnants in Southern Brazil: Insights from Traditional Forest Inventory Surveys

“…This reduction, in turn, leads to a decrease in the production of cones and seeds. As highlighted in a study by Demétrio et al [42], production has been progressively diminishing since 2017, and there is no legislative provision supporting the allocation of part of the production as a seed reserve. Consequently, all production is utilized and sold, posing a threat to the sustainability of the forest structure.…”

“…As detailed in Demetrio et al [42], the quantification of male reproductive structures (strobili) was measured for different diameters and obtained from drone images. The count was carried out through visual inspection and labeling of RGB images.…”

Simulating Sustainable Forest Management Practices Using Crown Attributes: Insights for Araucaria angustifolia Trees in Southern Brazil

“…For example, larger crowns have a higher number of needles and a higher leaf area index than smaller crowns. Therefore, they are more efficient, as they have a greater photosynthetic area per m 2 of soil cover, providing a more significant production [65], and can be used as a competition descriptor [4,23]. Furthermore, it is important to avoid maintaining poor-quality trees in the forest.…”

“…As a result, this tree species is restricted to forest remnants and usually confined to legally protected reserves as a requirement of the Brazilian Forest Act [3]. However, as noticed in several rural properties, legal reserves do not assure integral protection, being still susceptible to illegal logging and overexploiting of edible seeds [4,5], which is one of the important causes of the reduced natural regeneration capacity of these forest remnants.…”