The location of trees and the individualization of their canopies are important parameters to estimate diameter, height, and biomass, among other variables. The very high spatial resolution of UAV imagery supports these processes. A dense 3D point cloud is generated from RGB UAV images, which is used to obtain a digital elevation model (DEM). From this DEM, a canopy height model (CHM) is derived for individual tree identification. Although the results are satisfactory, the quality of this detection is reduced if the working area has a high density of vegetation. The objective of this study was to evaluate the use of color vegetation indices (CVI) in canopy individualization processes of Pinus radiata. UAV flights were carried out, and a 3D dense point cloud and an orthomosaic were obtained. Then, a CVI was applied to 3D point cloud to differentiate between vegetation and nonvegetation classes to obtain a DEM and a CHM. Subsequently, an automatic crown identification procedure was applied to the CHM. The results were evaluated by contrasting them with results of manual individual tree identification on the UAV orthomosaic and those obtained by applying a progressive triangulated irregular network to the 3D point cloud. The results obtained indicate that the color information of 3D point clouds is an alternative to support individualizing trees under conditions of high-density vegetation.

Temperature is one of the most important abiotic factors affecting seed germination, and it is strongly influenced by local site conditions. Seeds of Nothofagus glauca, an endemic and vulnerable species of the Mediterranean region of Chile and the most representative of the Mediterranean forests of South America, were collected. In this study, we evaluated the effect of temperature on different germinative attributes of five N. glauca provenances representative of their natural distribution. The seeds were treated at a constant temperature (i.e., 18 °C, 22 °C, 26 °C, or 30 °C) in the absence of light for 40 days. The results show that in all the provenances, the germination ratio and energy increase linearly with temperature until reaching an optimum temperature (i.e., 22 °C), above which they decrease severely. At 22 °C, the response of average germination speed and germination vigor was significantly higher than with the other temperatures (performance of germination start day was not clear). The base temperature was around 18 °C and the maximum, above 30 °C, which may be close to thermo-inhibition. Given the threat of climate change, it is necessary to increase research in terms of the possible adaptation of this species to increased temperatures and prolonged periods of drought

Background: Araucaria araucana is a mast species that presents a high variability in annual cone production. Researchers have recorded synchronization events in cone production in different populations, which allows the seed production to be concentrated, reducing the percentage of seeds consumed by different animal species. Methods: We sampled three populations located in the Andes Mountains, Araucanía Region, Chile. In 2004 we began the collection of data on cone production, for which we installed permanent plots (1200 m² each) at each location. We identified and labeled each female tree in each plot to monitor its cone production. In 2012 we selected a total of 30 trees near the plots to evaluate the number of seeds per cone. In each February from 2012 to 2014 we selected two mature cones and covered them with a porous mesh for subsequent collection and storage in March. At the beginning of June, we counted and weighed the seeds, determining the average weight, the number of seeds per cone, the germination capacity (GC), and the germination speed (GS). Results: Cone production was synchronous across the three locations. We observed significant differences among the locations and years evaluated. The cones had fewer seeds in 2013 (high production) compared to those in 2012 (low production), but their weights were similar. In 2014 the cones produced smaller seeds in fewer quantities. The difference between the years 2013 and 2014 resulted from the high-energy expenditure in 2013. Regarding GC and GS, there were significant differences among the three locations (GC: F = 45.41, p < 0.01; GS: F = 96.08, p < 0.01), where the highest values were observed in 2013. Conclusions: Both GC and GS are related to seed weight but not to the number of cones produced in a given year. These annual fluctuations in seed production are determining factors in the population dynamics of forest species. Our results allow a better understanding of the reproductive phenology of A. araucana and could help define sustainable use and conservation actions for this species.

Nothofagus alessandrii Espinosa is an endemic species of the coastal Maulino forest of central Chile that has historically been severely threatened by the reduction of its habitat and the isolation of its fragments. In addition, a gradual reduction in precipitation has been observed in recent years across its entire natural distribution area. Although the genus Nothofagus has been extensively analyzed in dendrochronological studies in the Southern Hemisphere, the dendrochronological potential of this species is unknown. In this study, we developed a novel tree-ring chronology of N. alessandrii in order to examine the climate sensitivity of the radial growth and to thus understand its response to climate change in central Chile. Our ring-width chronology showed a series intercorrelation value of 0.48 for the period of 1942–2016 (EPS < 0.85, with 10 trees), showing a strong common growth signal among the trees. N. alessandrii growth was strongly influenced by precipitation from May to November (the austral winter and spring seasons), while the temperature signal was weak. We observed that the radial growth patterns of N. alessandrii chronology showed upward growth trends, with a marked positive slope until the mid-1980s. However, a negative trend was observed for the period of 1985–2016, which was related to the increased drought conditions (rainfall and soil moisture reductions) in past decades and affected the entire natural distribution of the species. We suggest that drier winters and springs would slow the growth of this species. This information is of vital importance to understanding the growth dynamics of N. alessandrii, a critically endangered species, and to take on urgent adaptation and mitigation measures in the face of climate change.