Raízes finas em plantações de eucalipto: efeitos genéticos e edafoclimáticos
Carregando...
Data
2021-04-29
Autores
Basílio, Josiana Jussara Nazaré
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
Compreender como as variações climáticas irão impactar a produtividade dos ecossistemas florestais se tornou um grande desafio para os fisiologistas de plantas, os quais tem destinado grandes esforços para entender sua capacidade de adaptação e sobrevivência. Neste contexto, o comportamento das raízes finas ao longo do perfil de solo até a profundidade máxima de enraizamento se torna necessário para melhorar a compreensão das interações solo-planta-atmosfera, assim como as estratégias usadas para sobrevivência aos longos períodos de seca. Este estudo teve como objetivo principal avaliar a distribuição de raízes finas em profundidade para genótipos de Eucalytpus cultivados em condições edafoclimáticas contrastantes, com manipulação da disponibilidade hídrica em cada sítio (100% e 70% da disponibilidade hídrica local). Os objetivos específicos foram distribuídos em três capítulos: (i) comparar a distribuição de raízes finas para quatro genótipos de Eucalyptus cultivados em clima tropical e subtropical aos três anos após o plantio; (ii) investigar a distribuição de raízes em profundidade para o clone Eucalyptus mais plantado no Brasil em quatro condições edafoclimáticas distintas três anos após o plantio e (iii) caracterizar as mudanças ocorridas na distribuição de raízes finas dos três para os seis anos de idade em dois genótipos de Eucalyptus. Raízes finas, ou seja, raízes com diâmetro inferior a 2 mm, foram amostradas até a profundidade máxima com auxílio de um trado semi-mecanizado que coletou amostras em três pontos por parcela. Já aos três anos, as raízes finas exploraram grande volume de solo, com massa de raízes finas situando-se entre 3,2 a 9,7 Mg.ha-1. Para esta idade, profundidades de enraizamento situaram-se entre 3 e 11 metros, com cerca de 50% das raízes finas no primeiro 1 metro do solo. Maiores profundidades de enraizamento foram identificadas no sítio subtropical quando comparado ao tropical e os genótipos A1 (E. urophylla) e C3 (E. grandis x E. camaldulensis) apresentaram maiores biomassas de raízes finas quando cultivados em ambientes com presença elevada de déficit hídrico (~580 mm). Aos seis anos o genótipo E. urophylla apresentou amplitude de massa de raízes finas de 1,69 a 10,27 Mg.ha-1, no qual metade da massa de raízes finas prevaleceu no primeiro metro de solo e menos de 10% abaixo de cinco metros de profundidade. Raízes finas atingiram profundidade de enraizamento entre 6,9 a 17,7 metros aos seis anos, sendo que a máxima profundidade foi encontrada no sitio com elevados teores de areia no solo. Verificou-se aumento em cerca de 38% na profundidade máxima de enraizamento para os genótipos A1 e C3 dos três para os seis anos. Já em relação a massa de raízes finas, em ambiente tropical a massa de raízes finas aumentou em 55 % dos três para os seis anos para ambos os genótipos. Comportamento distinto foi observado para o sítio úmido. De maneira geral, os genótipos de Eucalyptus apresentaram elevada plasticidade na distribuição de raízes finas em função da disponibilidade hídrica ao longo do gradiente edafoclimáticos dos sítios, através de uma mudança relativa na alocação de carbono abaixo do solo em função da redução da disponibilidade hídrica.
Understanding how climatic variations will impact the productivity of forest ecosystems has become a major challenge for plant physiologists, who have made great efforts to understand their adaptability and survival. In this context, the behavior of fine roots along the soil profile up to the maximum rooting depth is necessary to improve the understanding of soil-plant-atmosphere interactions, as well as the strategies used to survive long periods of drought. This study aimed to evaluate the distribution of fine roots in depth for Eucalytpus genotypes grown under contrasting edaphoclimatic conditions, with manipulation of water availability at each site (100% and 70% of local water availability). The specific objectives were distributed in three chapters: (i) to compare the distribution of fine roots for four genotypes of Eucalyptus cultivated in tropical and subtropical climate at three years after planting; (ii) investigate the root distribution in depth for the most planted Eucalyptus clone in Brazil in four distinct edaphoclimatic conditions three years after planting and (iii) characterize the changes that occurred in the distribution of fine roots from three to six years of age in two Eucalyptus genotypes. Fine roots, that is, roots with a diameter of less than 2 mm, were sampled to maximum depth with the aid of a semi-mechanized auger that collected samples at three points per plot. At the age of three, thin roots explored a large volume of soil, with a mass of fine roots ranging from 3.2 to 9.7 Mg.ha-1. For this age, rooting depths were between 3 and 11 meters, with about 50% of the fine roots in the first 1 meter of the soil. Greater rooting depths were identified in the subtropical site when compared to the tropical one, and genotypes A1 (E. urophylla) and C3 (E. grandis x E. camaldulensis) showed higher biomass of thin roots when grown in environments with high water deficit (~ 580 mm). At six years old, the E. urophylla genotype showed a range of fine root masses from 1.69 to 10.27 Mg.ha-1, in which half of the mass of fine roots prevailed in the first meter of soil and less than 10% below five meters deep. Thin roots reached rooting depths between 6.9 to 17.7 meters at the age of six, and the maximum depth was found in the site with high levels of sand in the soil. There was an increase of about 38% in the maximum rooting depth for genotypes A1 and C3 from three to six years. Regarding the weight of fine roots, in a tropical environment the weight of fine roots increased by 55% from three to six years for both genotypes. Different behavior was observed for the wet site. In general, Eucalyptus genotypes showed high plasticity in the distribution of fine roots due to water availability along the edaphoclimatic gradient of the sites, through a relative change in the allocation of carbon below the ground due to the reduction in water availability.
Understanding how climatic variations will impact the productivity of forest ecosystems has become a major challenge for plant physiologists, who have made great efforts to understand their adaptability and survival. In this context, the behavior of fine roots along the soil profile up to the maximum rooting depth is necessary to improve the understanding of soil-plant-atmosphere interactions, as well as the strategies used to survive long periods of drought. This study aimed to evaluate the distribution of fine roots in depth for Eucalytpus genotypes grown under contrasting edaphoclimatic conditions, with manipulation of water availability at each site (100% and 70% of local water availability). The specific objectives were distributed in three chapters: (i) to compare the distribution of fine roots for four genotypes of Eucalyptus cultivated in tropical and subtropical climate at three years after planting; (ii) investigate the root distribution in depth for the most planted Eucalyptus clone in Brazil in four distinct edaphoclimatic conditions three years after planting and (iii) characterize the changes that occurred in the distribution of fine roots from three to six years of age in two Eucalyptus genotypes. Fine roots, that is, roots with a diameter of less than 2 mm, were sampled to maximum depth with the aid of a semi-mechanized auger that collected samples at three points per plot. At the age of three, thin roots explored a large volume of soil, with a mass of fine roots ranging from 3.2 to 9.7 Mg.ha-1. For this age, rooting depths were between 3 and 11 meters, with about 50% of the fine roots in the first 1 meter of the soil. Greater rooting depths were identified in the subtropical site when compared to the tropical one, and genotypes A1 (E. urophylla) and C3 (E. grandis x E. camaldulensis) showed higher biomass of thin roots when grown in environments with high water deficit (~ 580 mm). At six years old, the E. urophylla genotype showed a range of fine root masses from 1.69 to 10.27 Mg.ha-1, in which half of the mass of fine roots prevailed in the first meter of soil and less than 10% below five meters deep. Thin roots reached rooting depths between 6.9 to 17.7 meters at the age of six, and the maximum depth was found in the site with high levels of sand in the soil. There was an increase of about 38% in the maximum rooting depth for genotypes A1 and C3 from three to six years. Regarding the weight of fine roots, in a tropical environment the weight of fine roots increased by 55% from three to six years for both genotypes. Different behavior was observed for the wet site. In general, Eucalyptus genotypes showed high plasticity in the distribution of fine roots due to water availability along the edaphoclimatic gradient of the sites, through a relative change in the allocation of carbon below the ground due to the reduction in water availability.
Descrição
Palavras-chave
Déficit hídrico, Idade de cultivo, Profundidade de enraizamento, Raízes finas, Textura do solo, Water deficit, Cultivation age, Rooting depth, Fine Roots, Soil texture