Evaluation of different silvicultural management techniques and water seasonality on yield of eucalyptus stands

Appropriate management of factors that influence forest development is essential to increase yield of forest plantations. The objective of this study was to evaluate the influence of water seasonality, nutritional management, and uniformity on yield of eucalyptus plantations and estimate the potential, attainable, and observed yield of adult eucalyptus stands. We evaluated Eucalyptus clonal stands in six regions of Minas Gerais State, Brazil, in a system of first and second rotation across four age classes using the twin-plots method (TP). In the study, 142 TPs were allocated alongside 142 plots in a continuous forest inventory (CFI) network of a private enterprise. The CFI received operational fertilization and additional fertilization was carried out in the TP. The trees were measured at the beginning of the experiment and at every six months to quantify the production in the wet (PW) and dry (PD) periods of the year. Uniformity of plantations was evaluated using Pvar 50 % and the optimal uniformity index. Potential, attainable, and observed yields were estimated using the average annual increase at seven years of age. The PW showed higher plant yield. There was an effect due to water availability and nutrient level on the yield of the stands. The driest semester of the year produces approximately 30 % of the current annual increase. The stands under the second rotation tend to have less uniformity than the in the first rotation. Potential yield varied depending on rainfall intensity where wetter regions had the highest yield.

Evaluation of different silvicultural management techniques and water seasonality on yield of eucalyptus stands

Appropriate management of factors that influence forest development is essential to increase yield of forest plantations. The objective of this study was to evaluate the influence of water seasonality, nutritional management, and uniformity on yield of eucalyptus plantations and estimate the potential, attainable, and observed yield of adult eucalyptus stands. We evaluated Eucalyptus clonal stands in six regions of Minas Gerais State, Brazil, in a system of first and second rotation across four age classes using the twin-plots method (TP). In the study, 142 TPs were allocated alongside 142 plots in a continuous forest inventory (CFI) network of a private enterprise. The CFI received operational fertilization and additional fertilization was carried out in the TP. The trees were measured at the beginning of the experiment and at every six months to quantify the production in the wet (PW) and dry (PD) periods of the year. Uniformity of plantations was evaluated using Pvar 50 % and the optimal uniformity index. Potential, attainable, and observed yields were estimated using the average annual increase at seven years of age. The PW showed higher plant yield. There was an effect due to water availability and nutrient level on the yield of the stands. The driest semester of the year produces approximately 30 % of the current annual increase. The stands under the second rotation tend to have less uniformity than the in the first rotation. Potential yield varied depending on rainfall intensity where wetter regions had the highest yield.

Evaluation of different silvicultural management techniques and water seasonality on yield of eucalyptus stands

ABSTRACT: Appropriate management of factors that influence forest development is essential to increase yield of forest plantations. The objective of this study was to evaluate the influence of water seasonality, nutritional management, and uniformity on yield of eucalyptus plantations and estimate the potential, attainable, and observed yield of adult eucalyptus stands. We evaluated Eucalyptus clonal stands in six regions of Minas Gerais State, Brazil, in a system of first and second rotation across four age classes using the twin-plots method (TP). In the study, 142 TPs were allocated alongside 142 plots in a continuous forest inventory (CFI) network of a private enterprise. The CFI received operational fertilization and additional fertilization was carried out in the TP. The trees were measured at the beginning of the experiment and at every six months to quantify the production in the wet (PW) and dry (PD) periods of the year. Uniformity of plantations was evaluated using Pvar 50 % and the optimal uniformity index. Potential, attainable, and observed yields were estimated using the average annual increase at seven years of age. The PW showed higher plant yield. There was an effect due to water availability and nutrient level on the yield of the stands. The driest semester of the year produces approximately 30 % of the current annual increase. The stands under the second rotation tend to have less uniformity than the in the first rotation. Potential yield varied depending on rainfall intensity where wetter regions had the highest yield.

Estimation of leaf nutrient concentration from hyperspectral reflectance in Eucalyptus using partial least squares regression

Leaf hyperspectral reflectance has been used to estimate nutrient concentrations in plants in narrow bands of the electromagnetic spectrum. The aim of this study was to estimate leaf nutrient concentrations using leaf hyperspectral reflectance and verify the variable selection methods using the partial least squares regression (PLSR). Two studies were carried out using stands with Eucalyptus clones. Study I was established in Eucalyptus stands with three clones, classifying leaves into five colour patterns using the Munsell chart for plant tissues. Immediately after leaf collection, leaf reflectance was read and the chemical analysis was performed. Study II was carried out in commercial clonal stands of Eucalyptus performing the same leaf sampling and chemical analysis as used in Study I. All leaf reflectance spectra were smoothed and three more pre-processing procedures were applied. In addition, three methods of PLSR were tested. The first derivative was more accurate for predicting nitrogen ( Rcv2=0.95 ), phosphorous ( Rcv2=0.93 ), and sulphur concentration ( Rcv2=0.85 ). The estimates for concentrations of calcium ( Rcv2=0.81 ), magnesium ( Rcv2=0.22 ), and potassium ( Rcv2=0.76 ) were more accurate using the logarithm transformation. Only the estimates for iron concentrations were performed with higher accuracy ( Rcv2=0.35 ) using the smoothed reflectance. The copper concentrations were more accurate ( Rcv2=0.78 ) using the logarithm transformation. Concentrations of boron ( Rcv2=0.68 ) and manganese ( Rcv2=0.79 ) were more accurate using the first derivative, while zinc ( Rcv2=0.31 ) concentration was most accurate using the second derivative.

Estimation of leaf nutrient concentration from hyperspectral reflectance in Eucalyptus using partial least squares regression

Leaf hyperspectral reflectance has been used to estimate nutrient concentrations in plants in narrow bands of the electromagnetic spectrum. The aim of this study was to estimate leaf nutrient concentrations using leaf hyperspectral reflectance and verify the variable selection methods using the partial least squares regression (PLSR). Two studies were carried out using stands with Eucalyptus clones. Study I was established in Eucalyptus stands with three clones, classifying leaves into five colour patterns using the Munsell chart for plant tissues. Immediately after leaf collection, leaf reflectance was read and the chemical analysis was performed. Study II was carried out in commercial clonal stands of Eucalyptus performing the same leaf sampling and chemical analysis as used in Study I. All leaf reflectance spectra were smoothed and three more pre-processing procedures were applied. In addition, three methods of PLSR were tested. The first derivative was more accurate for predicting nitrogen ( Rcv2=0.95 ), phosphorous ( Rcv2=0.93 ), and sulphur concentration ( Rcv2=0.85 ). The estimates for concentrations of calcium ( Rcv2=0.81 ), magnesium ( Rcv2=0.22 ), and potassium ( Rcv2=0.76 ) were more accurate using the logarithm transformation. Only the estimates for iron concentrations were performed with higher accuracy ( Rcv2=0.35 ) using the smoothed reflectance. The copper concentrations were more accurate ( Rcv2=0.78 ) using the logarithm transformation. Concentrations of boron ( Rcv2=0.68 ) and manganese ( Rcv2=0.79 ) were more accurate using the first derivative, while zinc ( Rcv2=0.31 ) concentration was most accurate using the second derivative.(AU)

Padrões de reflectância foliar de eucalipto em diferentes dias e períodos do dia / Eucalyptus leaf reflectance patterns on different days and periods of the day

Diante da complexa relação entre reflectância foliar e aspectos fisiológicos da planta em dias e diferentes horários do dia, a pesquisa foi desenvolvida para averiguar e mensurar o grau da influência do dia e o período do dia em espectros de reflectância foliar de árvores de eucalipto. O experimento foi conduzido em um plantio de eucalipto clonal, híbrido espontâneo de Eucalyptus grandis com centroide nas coordenadas 18º 12' 12",19"S e 43º 34' 20,28"O. Em cada uma das cinco árvores-amostra escolhidas aleatoriamente, amostraram-se quatro folhas distribuídas em cada ponto cardeal. Todas as folhas selecionadas foram avaliadas nos dias 7, 8, 9 e 10 de dezembro de 2013, em dois períodos do dia: entre 8 e 9 horas e entre 15 e 16 horas. A leitura da reflectância foliar foi realizada utilizando um mini-espectrometro com posterior suavização e dessa forma realizou-se a análise de componentes principais e com posterior análise de agrupamento por dendrograma. No geral, a média das reflectâncias foliares no segundo dia foram as menores e as médias do terceiro dia maiores. Em média a reflectância foliar foi menor no período da manhã do que no período da tarde. O dia e o período do dia em que foi realizada a leitura influenciaram de forma aleatória na reflectância foliar de eucalipto. A reflectância foliar do eucalipto pode se alterar em um curto período de tempo, inclusive em um mesmo dia, o que indica a importância da padronização no horário de coleta para futuros estudos.

Faced with the complex relationship between leaf reflectance and physiological aspects of the plant on days and at different times of the day, the research was developed to ascertain and measure the influence of day and period of the day on leaf reflectance of eucalyptus trees. The experiment was carried out in a clonal eucalyptus stand, spontaneous Eucalyptus grandis hybrid with centroid at 18º 12 '12,19"S and 43º 34' 20,28"W. In each of the five sample trees randomly selected, four leaves were sampled at each cardinal point. All selected leaves were evaluated on days 7, 8, 9 and 10 of December 2013, in two periods of the day: between 8 and 9 hours and between 15 and 16 hours. The leaf reflectance was measured using a mini-spectrometer with subsequent smoothing and the analysis of principal components and subsequent analysis of dendrogram cluster were performed. In general, the average leaf reflectance on the second day was the lowest and the third day average was higher. Leaf reflectance was lower in the morning than in the afternoon. The day and period of the day of reading were randomly influenced by eucalypt leaf reflectance. The leaf reflectance of eucalyptus can change in a short time, even in the same day, which indicates the importance of the standardization in the collection schedule for future studies.

Padrões de reflectância foliar de eucalipto em diferentes dias e períodos do dia / Eucalyptus leaf reflectance patterns on different days and periods of the day

Diante da complexa relação entre reflectância foliar e aspectos fisiológicos da planta em dias e diferentes horários do dia, a pesquisa foi desenvolvida para averiguar e mensurar o grau da influência do dia e o período do dia em espectros de reflectância foliar de árvores de eucalipto. O experimento foi conduzido em um plantio de eucalipto clonal, híbrido espontâneo de Eucalyptus grandis com centroide nas coordenadas 18º 12' 12",19"S e 43º 34' 20,28"O. Em cada uma das cinco árvores-amostra escolhidas aleatoriamente, amostraram-se quatro folhas distribuídas em cada ponto cardeal. Todas as folhas selecionadas foram avaliadas nos dias 7, 8, 9 e 10 de dezembro de 2013, em dois períodos do dia: entre 8 e 9 horas e entre 15 e 16 horas. A leitura da reflectância foliar foi realizada utilizando um mini-espectrometro com posterior suavização e dessa forma realizou-se a análise de componentes principais e com posterior análise de agrupamento por dendrograma. No geral, a média das reflectâncias foliares no segundo dia foram as menores e as médias do terceiro dia maiores. Em média a reflectância foliar foi menor no período da manhã do que no período da tarde. O dia e o período do dia em que foi realizada a leitura influenciaram de forma aleatória na reflectância foliar de eucalipto. A reflectância foliar do eucalipto pode se alterar em um curto período de tempo, inclusive em um mesmo dia, o que indica a importância da padronização no horário de coleta para futuros estudos.(AU)

Faced with the complex relationship between leaf reflectance and physiological aspects of the plant on days and at different times of the day, the research was developed to ascertain and measure the influence of day and period of the day on leaf reflectance of eucalyptus trees. The experiment was carried out in a clonal eucalyptus stand, spontaneous Eucalyptus grandis hybrid with centroid at 18º 12 '12,19"S and 43º 34' 20,28"W. In each of the five sample trees randomly selected, four leaves were sampled at each cardinal point. All selected leaves were evaluated on days 7, 8, 9 and 10 of December 2013, in two periods of the day: between 8 and 9 hours and between 15 and 16 hours. The leaf reflectance was measured using a mini-spectrometer with subsequent smoothing and the analysis of principal components and subsequent analysis of dendrogram cluster were performed. In general, the average leaf reflectance on the second day was the lowest and the third day average was higher. Leaf reflectance was lower in the morning than in the afternoon. The day and period of the day of reading were randomly influenced by eucalypt leaf reflectance. The leaf reflectance of eucalyptus can change in a short time, even in the same day, which indicates the importance of the standardization in the collection schedule for future studies.(AU)

Estimating foliar nitrogen in Eucalyptus using vegetation indexes

Nitrogen (N) has commonly been applied in Eucalyptus stands in Brazil and it has a direct relation with biomass production and chlorophyll content. Foliar N concentrations are used to diagnose soil and plant fertility levels and to develop N fertilizer application rates. Normally, foliar N is obtained using destructive methods, but indirect analyses using Vegetation Indexes (VIs) may be possible. The aim of this work was to evaluate VIs to estimate foliar N concentration in three Eucalyptus clones. Lower crown leaves of three clonal Eucalyptus plantations (25 months old) were classified into five color patterns using the Munsell Plant Tissue Color Chart. For each color, N concentration was determined by the Kjeldahl method and foliar reflectance was measured using a CI-710 Miniature Leaf Spectrometer. Foliar reflectance data were used to obtain the VIs and the VIs were used to estimate N concentrations. In the visible region, the relationship between N concentration and reflectance percentage was negative. The highest correlations between VIs and N concentrations were obtained by the Inflection Point Position (IPP, r = 0.97), Normalized Difference Red-Edge (reNDVI, r = 0.97) and Modified Red-Edge Normalized Difference Vegetation Index (mNDI, r = 0.97). Vegetation indexes on the red edge region provided the most accurate estimates of foliar N concentration. The reNDVI index provided the best N concentration estimates in leaves of different colors of Eucalyptus urophylla × grandis and Eucalyptus urophylla × urophylla (R2 = 0.97 and RMSE = 0.91 g kg1).

Estimating foliar nitrogen in Eucalyptus using vegetation indexes

Nitrogen (N) has commonly been applied in Eucalyptus stands in Brazil and it has a direct relation with biomass production and chlorophyll content. Foliar N concentrations are used to diagnose soil and plant fertility levels and to develop N fertilizer application rates. Normally, foliar N is obtained using destructive methods, but indirect analyses using Vegetation Indexes (VIs) may be possible. The aim of this work was to evaluate VIs to estimate foliar N concentration in three Eucalyptus clones. Lower crown leaves of three clonal Eucalyptus plantations (25 months old) were classified into five color patterns using the Munsell Plant Tissue Color Chart. For each color, N concentration was determined by the Kjeldahl method and foliar reflectance was measured using a CI-710 Miniature Leaf Spectrometer. Foliar reflectance data were used to obtain the VIs and the VIs were used to estimate N concentrations. In the visible region, the relationship between N concentration and reflectance percentage was negative. The highest correlations between VIs and N concentrations were obtained by the Inflection Point Position (IPP, r = 0.97), Normalized Difference Red-Edge (reNDVI, r = 0.97) and Modified Red-Edge Normalized Difference Vegetation Index (mNDI, r = 0.97). Vegetation indexes on the red edge region provided the most accurate estimates of foliar N concentration. The reNDVI index provided the best N concentration estimates in leaves of different colors of Eucalyptus urophylla × grandis and Eucalyptus urophylla × urophylla (R2 = 0.97 and RMSE = 0.91 g kg1).(AU)