A exploração de impacto reduzido (EIR) é um método florestal conhecido por ter suas atividades fundamentadas em maior planejamento e colheitas controladas de madeira para garantir maior potencial de recuperação em florestas exploradas, sendo um critério essencial para o desenvolvimento sustentável. No entanto, a extração ilegal de madeira e outras práticas insustentáveis de manejo na Amazônia brasileira continuam aumentando em regiões tropicais e são responsáveis pela diminuição da disponibilidade de madeira, criando uma luta cada vez maior para garantir um rendimento sucessivo de espécies exploradas em ciclos de corte consecutivos. Para superar esse problema, investigamos o padrão de crescimento e o valor das espécies florestais manejadas, a fim de dar subsídio à futuras adequações na legislação aplicada ao manejo e garantir a sustentabilidade florestal. Além disso, buscamos conhecer quais fatores bióticos e abióticos podem influenciar o crescimento, mortalidade e recrutamento da floresta após a exploração, a fim de propor tratamentos silviculturais que acelerem a recuperação dessa floresta para o próximo ciclo de corte. Determinamos também as curvas de crescimento das espécies madeireiras e sua valorização econômica com o passar dos anos, bem como analisamos se a gestão adotada atualmente garante a sustentabilidade florestal no futuro. Essa pesquisa ocorreu na Amazônia Oriental, no Brasil, em uma floresta que foi explorada por EIR e EC. A tese consiste em cinco capítulos: a introdução geral, três capítulos de pesquisa e uma síntese com considerações finais dos estudos. No segundo capítulo, os resultados afirmaram que o crescimento da floresta é maior após o uso da EIR, porém fatores de condição das árvores e vizinhança também podem influenciar o crescimento da floresta e de grupos funcionais. Dessa forma, o aumento da quantidade de lianas, danos na copa e competição unilateral por área basal teve efeito negativo no crescimento florestal. Além disso, o aumento do nível de luz e competição multilateral por densidade pode aumentar as taxas de crescimento das árvores. Os fatores de condição das árvores e vizinhança afetam de maneira diferente os grupos funcionais. Descobrimos também que houve aumento significativo das taxas de crescimento após a colheita florestal, mostrando que as espécies aproveitam o ambiente com muita luz para crescer. No terceiro capítulo, os resultados afirmam que as técnicas de exploração florestal influenciam a mortalidade das árvores, sendo a exploração convencional responsável por maior probabilidade de mortalidade após a colheita florestal; as árvores com nível alto de lianas têm maior probabilidade de mortalidade; as árvores com danos na copa têm maior chance de mortalidade; as maiores árvores (DAP maior) são mais suscetíveis à mortalidade. No quarto capítulo, foi observado que o incremento em diâmetro e área basal, para a maioria das espécies, aumenta com o uso de técnicas de baixo impacto na exploração. As espécies têm diminuição do incremento em diâmetro devido a influência de El Niño. O crescimento de espécies como Dipteryx odorata (Aubl.) Willd., Manilkara bidentata (A.DC.) A.Chev., Manilkara elata (Allemão ex Miq.) Monach. e Handroanthus serratifilius (Vahl) S.Grose é muito lento e a alta intensidade de corte na exploração pode diminuir ainda mais a velocidade de crescimento e recuperação dessas espécies. As menores árvores apresentaram menor crescimento e as maiores árvores apresentaram oscilação das taxas de crescimento logo após a exploração. As espécies madeireiras mais valorizadas são as madeiras nobres de alta densidade, porém como elas não têm a sustentabilidade garantida pelas atividades de exploração, com o passar do tempo são substituídas por espécies de baixa densidade. Esse estudo apresenta a interface entre a ciência do manejo, silvicultura de espécies tropicais e sua prática. Dessa forma, auxilia no aperfeiçoamento das leis e normas que regem o manejo e no desenvolvimento de tratamentos silviculturais específicos em florestas tropicais. Nossos resultados mostram como é possível melhorar as técnicas de exploração de madeira, diminuir a competição, os danos florestais e otimizar a recuperação florestal visando alcançar, num futuro próximo, o manejo florestal sustentável. Esse estudo pode ser utilizado como subsídio à silvicultura de espécies e ações de manejo em diferentes ecossistemas florestais por profissionais do manejo, tomadores de decisão e cientistas, para que a ciência e o setor produtivo possam avançar. / Reduced impact logging (RIL) is a well known forestry method that requires extensive planning and controlled timber harvesting to ensure a greater recovery potential for exploited forests, an essential criteria for sustainable development. However, in the Brazilian Amazon, illegal logging and other unsustainable forest management practices continue to increase in tropical regions and are responsible for decreasing the availability of timber, creating an ever-increasing struggle to guarantee successive yields of timber species in consecutive cutting cycles. To overcome this problem, we investigated the growth pattern and value of managed forest timber species to support future legislation amendments applied to the management and guarantee of forest sustainability in Amazonian Brazil. We examined biotic and abiotic factors that may influence forest growth, mortality, and recruitment after exploration, which gave indication to potential silvicultural treatments that can accelerate forest recovery in succeeding cutting cycles. We also determined timber species growth curves and estimated their financial increase potential overtime as well as analyze whether the management practices currently adopted guarantees forest sustainability in the future. This research took place in Eastern Amazonia, Brazil in a forest that had been harvested using RIL and CL (Conventional logging) techniques. This thesis consists of five chapters: the general introduction, three research chapters and a concluding chapter synthsizing the major findings from the study. In the second chapter, results confirm forest growth to be higher after implementing RIL, but factors related to tree and neighborhood condition can influence forest growth and functional groups. Thus, an increased amount of vines, crown damage and unilateral competition by basal area had a negative effect on forest growth. In addition, increasing light levels and multilateral competition may increase rates of tree growth. Furthermore, factors of tree condition and neighborhood seemed to affect the functional groups differently. We also found there was a significant increase in growth rates after harvesting, indicating that species take advantage of the greater availability of light within their environment. In the third chapter, the results affirm that the techniques of forest logging influence the mortality of the trees, being the conventional exploitation responsible for a greater probability of mortality after the forest harvest; trees with high lianas have greater likelihood of mortality; trees with crown damage have higher chance of mortality; the largest trees (DBH larger) are more susceptible to mortality. In the fourth chapter, it was observed that most species diameter and basal areas increased with the use of low impact logging techniques. Decreased in species diameter was mainly attributed to the influence of El Niño events. The growth of species such as Dipteryx odorata (Aubl.) Willd., Manilkara bidentata (A.DC.) A.Chev., Manilkara elata (Allemão ex Miq.) Monach. and Handroanthus serratifilius (Vahl) S.Grose are generally very slow growing and high intensity logging may the rate of growth and recovery of these species even more. The smallest trees recorded presented lower rates of growth compared to larger trees which presented an growth rates that oscillated soon after exploitation. The most valued timber species are those of high density, but as they do not have the sustainability guaranteed by exploration activities, over time they are replaced by low density species. This study presents an interface between the science of forest management, forestry of tropical species and its practice. Therefore, it helps to improve the laws and regulations governing the management and development of specific silvicultural treatments in tropical forests. Our findings show how it is possible to improve logging techniques, reduce competition and forest damage and optimize forest recovery in order to achieve sustainable forest management in the near future. This study can be used as a subsidy to the forestry of species and management actions in different forest ecosystems by management professionals, decision makers and scientists, so that science and the productive sector can move forward.

Human activities are increasing the occurrence of megafires that have the potential to alter the ecology of forest ecosystems. The objective of this study was to understand the impact of a 610 km2 megafire on patterns of forest regeneration and herbivory of three forest types (aspen/fir, oak/maple, and pinyon/juniper) within the burn scar. Sapling density, meristem removal, and height were measured across a transect network spanning the area of the burn scar over three years from 2019-2021. The network consisted of 17 burned/unburned transect pairs in adjacent burned/unburned forest stands (6 aspen/fir, 5 oak/maple, and 6 pinyon/juniper). Species that regenerated through sprouting generally responded positively to fire while regeneration from seed showed very little post-fire response. Browse pressure was concentrated on deciduous tree species and tended to be greater in burned areas but the effect diminished over time. Meristem removal of sprouting species was below the critical threshold resulting in positive vertical growth across years. Our results indicate that forest regeneration within the megafire scar was generally positive and experienced sustainable levels of ungulate browsing that are likely to result in forest recruitment success. Novel fire regimes are becoming increasingly common and megafires have burned across ecotonal boundaries across multiple forest types. Plant community structure and composition may be critically affected by changing fire regimes. Our objective was to investigate how a megafire that burned across multiple forest types impacted understory plant community assembly and biodiversity. Paired vegetation transects were installed in burned and unburned areas across aspen/fir, oak/maple, and pinyon/juniper forests within the 2018 Pole Creek Megafire burn scar. Percent cover of understory plants was measured in the summer of 2022 and plants were identified to the species level. Richness and diversity indices were then calculated and analyzed using mixed effects models. Fire decreased species richness of the aspen/fir forest understory and increased plant cover in pinyon/juniper forests, while not significantly impacting oak/maple understories. The significant effects of fire were largely driven by changes in forb species. Fire decreased the richness of native plants in aspen/fir forests but increased the richness of non-native plants in oak/maple and pinyon/juniper forests. Non-native plant abundance also increased in post-fire pinyon/juniper forests. Our results suggest that forest understory communities show variable responses to megafires that burn across multiple forest types with important implications for post-fire plant community structure, diversity, and invasibility. Large mammal herbivores (ungulates) are increasing in number and spreading into novel habitats throughout the world. Their impact on forest understory plant communities is strong and varies by herbivore, plant growth form, and season. The objective of this study was to determine the individual and collective herbivory impacts of native versus domestic ungulates on the understory plant community composition of post-fire aspen forests. Four-way fencing treatments were installed in 2012 to separate ungulate species, and Daubenmire frames were used to collect percent cover estimates for each understory plant species. Vegetation data were later used to calculate richness and diversity indices. Total understory plant cover, richness, and diversity were not significantly impacted by the herbivory fencing treatment. However, woody plant species' percent cover was 90% greater in full ungulate exclusion plots than in the fenceless controls. Herbivores likely targeted woody plant species due to their high nutrient levels that last longer into the winter than those of forb or graminoid species. Herbivory treatment did not affect non-native species. Our results indicate that herbivore fencing can protect forest understory plant communities, particularly the woody species. Successful regeneration of woody species can benefit the diversity of the entire understory plant community and preserve forest structure.