Browsing by Author "Soto, Daniel P."

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    Growth Equations in Forest Research: Mathematical Basis and Model Similarities
    (2021) Salas-Eljatib, Christian; Mehtatalo, Lauri; Gregoire, Timothy G.; Soto, Daniel P.; Vargas-Gaete, Rodrigo
    Purpose of Review Growth equations have been widely used in forest research, commonly to assess ecosystem-level behavior and forest management. Nevertheless, the large number of growth equations has obscured the growth-rate behavior of each of these equations and several different terms for referring to common phenomena. This review presents a unified mathematical treatment of growth-rates besides several well-known growth equations by giving their mathematical basis and representing their behavior using tree growth data as an example. Recent Findings We highlight the mathematical differences among several growth equations that can be better understood by using their differential equations forms rather than their integrated forms. Moreover, the assumed-and-claimed biological basis of these growth-rate models has been taken too seriously in forest research. The focus should be on using a plausible equation for the organism being modelled. We point out that more attention should be drawn to parameter estimation strategies and behavior analysis of the proposed models. Thus, it is difficult for a single model to capture all possible shapes and rates that such a complex biological process as tree growth can depict in nature. We pointed out misleading concepts attributed to some growth equations; however, the differences come from their mathematical properties rather than pure biological reasoning. Using the tree growth data, we depict those differences. Thus, comparisons of some functional forms (at least simple ones) must be carried out before selecting a function for drawing scientific findings.
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    Increase in forest structural complexity along a precipitation gradient is mediated by partial harvests in temperate Patagonian forests
    (2024) Soto, Daniel P.; Seidel, Dominik; Hernandez-Moreno, Angela; Puettmann, Klaus J.; Donoso, Pablo J.
    Increasing forest structural complexity is becoming a common goal in forestry worldwide. However, the lack of empirical quantification clouds its implementation. Here we quantified the long-term effects (> 30 y) of partial harvest on stand structural complexity and net primary productivity using the east-west precipitation gradient (318-2508 mm, mean annual precipitation-MAP) of western Patagonian as a study system. In this gradient, pairs of 1-ha plots on 20 sites (20 plots harvested and 20 plots unharvested) were installed. In each plot terrestrial laser scanning was used to quantify the stand structural complexity index (SSCI), and Sentinel satellite images to obtain the Enhanced Vegetation Index (EVI: proxy of net primary productivity). Generalized linear mixed-effect models were used to relate SSCI to MAP and EVI to SSCI, with harvesting as indicator variable, and site as random variable (two plots nested to same precipitation). Results showed that harvested plots on mesic-to-humid sites (but not on dry sites) had higher SSCI and EVI values compared to unharvested plots, likely due to a greater vertical canopy packing. These results show the influence of precipitation on SSCI, which resulted in a more diversified stand structure and higher EVI. Such insights support site-specific management aimed to increase forest structural complexity.
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    Silvicultural systems and estimated profitability of Nothofagus dombeyi plantations: an option for forestry diversification in Chile
    (2025) Navarro, Celso; Donoso, Pablo J.; Soto, Daniel P.; Vasquez-Grandon, Angelica; Esse, Carlos
    Nothofagus dombeyi plantations have silvicultural and economic potential due to their ecological plasticity, rapid growth rate, and high wood quality. However, there is little research on timber yields, their quality, and the profitability of plantations with this species subjected to different silvicultural regimes. In this study, we evaluated one plantation without and three with intermediate cuttings (pruning and thinning). Growth and yield of timber products were estimated with volume and taper functions. The physical and mechanical properties of the wood from a plantation with intermediate cuttings were determined using national and international standards. The profitability of silvicultural regimes was evaluated using the internal rate of return, the net present value, and land expectation values. In plantations with intermediate cuttings, we estimated yields of 20 m3/ha/year, and the distribution of products was 19, 27, and 54% of veneer logs, timber, and firewood, while the log yield was over 60%. In the unmanaged plantation, these proportions were 3% timber and 97% firewood. Sawn and dried wood meet the requirements associated with moisture content, dimensions, strength, performance and durability, and structural grade, aspects that are considered in different technical standards and current Chilean legal regulations. In managed plantations, the scenario of marketing dry sawn timber presents the highest profitability indicators for discount rates of 6% and 8% (NPV of 7,380 and 2,447 US$/ha). To start an industry based on wood from N. dombeyi plantations, it is necessary to invest in intermediate cuttings, as well as to promote the drying of the wood.