We used RapidEye and Moderate Resolution Imaging Spectroradiometer (MODIS)/Terra data to study terrain illumination effects on 3 vegetation indices (VIs) and 11 phenological metrics over seasonal deciduous forests in southern Brazil. We applied TIMESAT for the analysis of the Enhanced Vegetation Index (EVI) and the Normalized Difference Vegetation Index (NDVI) derived from the MOD13Q1 product to calculate phenological metrics. We related the VIs with the cosine of the incidence angle i (Cos i) and inspected percentage changes in VIs before and after topographic C-correction. The results showed that the EVI was more sensitive to seasonal changes in canopy biophysical attributes than the NDVI and Red-Edge NDVI, as indicated by analysis of non-topographically corrected RapidEye images from the summer and winter. On the other hand, the EVI was more sensitive to terrain illumination, presenting higher correlation coefficients with Cos i that decreased with reduction in the canopy background L factor. After C-correction, the RapidEye Red-Edge NDVI, NDVI, and EVI decreased 2%, 1%, and 13% over sunlit surfaces and increased up to 5%, 14%, and 89% over shaded surfaces, respectively. The EVI-related phenological metrics were also much more affected by topographic effects than the NDVI-derived metrics. From the set of 11 metrics, the 2 that described the period of lower photosynthetic activity and seasonal VI amplitude presented the largest correlation coefficients with Cos i. The results showed that terrain illumination is a factor of spectral variability in the seasonal analysis of phenological metrics, especially for VIs that are not spectrally normalized.

We investigated the relationships between 11 phenological metrics, topographic shade, and anomalous temperature patterns detected using wavelet analysis in seasonal deciduous forests of south Brazil. To obtain the metrics, we applied the TIMESAT algorithm to the enhanced vegetation index (EVI) from Moderate Resolution Imaging Spectroradiometer (MODIS)/Terra. MODIS acquires data from the study area under a large seasonal amplitude in the solar zenith angle (SZA). We evaluated the effect of topography on phenological metrics by correlating the metrics with shaded relief values. To analyse the inter-annual phenological metric variations with anomalous and regular temperature patterns, we calculated standard anomalies for each metric. Finally, we established relationships between the metrics and the minimum, maximum, and mean temperatures from growing seasons that spanned over 10 seasonal cycles between 2002 and 2012. The correlation results with shaded relief showed that the left (LD) and right derivative (RD), small integral (SInt), seasonal amplitude (SA), base level (BL), and maximum VI value (MV) were sensitive to topographic effects. The seasonal cycles with the highest temperatures in the growing season (2006/2007 and 2009/2010) exhibited a delay at the end of the cycle and a higher interval of duration and productivity, which was indicated by the positive standard anomalies for end of season (EOS), length of season (LOS), large integral (LInt), and SInt. We observed a different result for the lowest temperature cycle (2003/2004). The means for these metrics in anomalous seasons differed significantly from the metrics of other regular cycles at the 0.05 significance level using paired t-tests. Statistically significant correlations were observed between the metrics and minimum and mean temperature values of the 10 seasonal cycles.

The efficiency of solar radiation conversion is a variable often used in crop growth simulation models in which the production of biomass and, consequently, carbon accumulation are related to the conversion of radiant energy into chemical compounds by plants through the process of photosynthesis. The goal of this study was to determine the efficiency of conversion of intercepted photosynthetically active radiation (PARi) into carbon accumulation in shoots of Ilex paraguariensis in intercropping (Ilex paraguariensis A. St. Hil. and Pinus elliottii Engelm) and monoculture. The conversion efficiency of PAR in accumulated carbon was calculated based on the ratio between the accumulated carbon and the PARi involved in the process. Our results demonstrate that the higher conversion efficiency (eb) of photosynthetically active solar radiation intercepted in carbon in yerba mate sprouts was obtained in the intercropping scenario.

This study aimed to estimate biomass and organic carbon in stands of Pinus taeda L. at different ages (14, 16, 19, 21, 22, 23 and 32 years) and located in the municipality of General Carneiro (PR). In order to estimate biomass and organic carbon in different tree components (needles, live branches, dead branches, bark and stem wood), the destructive quantification method was used in which seven trees from each age category were randomly sampled across the stand. Stocks of biomass and organic carbon were found to vary between the different age categories, mainly as a result of existing dissimilarities between ages in association with forest management practices such as thinning, pruning and tree density per hectare.

O presente trabalho foi realizado no município de Boa Ventura do São Roque, PR, com o objetivo de avaliar os teores de carbono nos compartimentos das árvores de 12 espécies arbóreas da Floresta Ombrófila Mista Montana; testar a eficácia do fator de conversão de 0,5 na estimativa do carbono nas espécies, e avaliar a influência do grupo ecológico das espécies quanto aos teores de carbono. Teores de carbono médio foram obtidos, a partir dos compartimentos das árvores e comparados entre si, entre as espécies e com o fator de conversão, visando a avaliar as diferenças interespecíficas e de eficácia do fator. Para analisar a influência dos grupos ecológicos sobre os teores de carbono, procedeu-se com a análise de agrupamentos. Não foi observada diferença significativa entre os teores de carbono encontrados para os diferentes compartimentos das árvores. Entretanto, considerando os teores das 12 espécies avaliadas, Luehea divaricata, Albizia polycephala e Cestrum sp. foram, estatisticamente, diferentes das demais, apresentando concentrações menores. Constatou-se que o fator de conversão de 0,5 superestima os teores de carbono nas árvores a uma média de 14,27%. Não houve correlação entre o grupo ecológico das espécies e seus teores de carbono, considerando que houve a formação de agrupamentos por semelhança nos teores, representados por espécies de diversas fases sucessionais.

Distribuição vertical da biomassa acima do solo em floresta estacional decidual - DOI:10.5039/agraria.v12i3a5448