Wood volume is overestimated in the Brazilian Amazon: Why not use generic volume prediction methods in tropical forest management?

The Amazon has a range of species with high potential for sustainable timber harvesting, but for them to be utilized globally, the merchantable wood volume must be accurately quantified. However, since the 1950s, inadequate methods for estimating merchantable timber volumes have been employed in the Amazon, and Brazilian Government agencies still require some of them. The natural variability of the Amazon Forest provides an abundance of species of different sizes and shapes, conferring several peculiarities, which makes it necessary to use up-to-date and precise methods for timber quantification in Amazon Forest management. Given the employment of insufficient estimation methods for wood volume, this study scrutinizes the disparities between the actual harvested merchantable wood volume and the volume estimated by the forest inventory during the harvesting phase across five distinct public forest areas operating under sustainable forest management concessions. We used mixed-effect models to evaluate the relationships between inventory and harvested volume for genera and forest regions. We performed an equivalence test to assess the similarity between the volumes obtained during the pre-and post-harvest phases. We calculated root mean square error and percentage bias for merchantable volume as accuracy metrics. There was a strong tendency for the 100% forest inventory to overestimate merchantable wood volume, regardless of genus and managed area. There was a significant discrepancy between the volumes inventoried and harvested in different regions intended for sustainable forest management, in which only 22% of the groups evaluated were equivalent. The methods currently practiced by forest companies for determining pre-harvest merchantable volume are inaccurate enough to support sustainable forest management in the Amazon. They may even facilitate the region's illegal timber extraction and organized crime.

Long-term forest degradation surpasses deforestation in the Brazilian Amazon.

Although deforestation rates in the Brazilian Amazon are well known, the extent of the area affected by forest degradation is a notable data gap, with implications for conservation biology, carbon cycle science, and international policy. We generated a long-term spatially quantified assessment of forest degradation for the entire Brazilian Amazon from 1992 to 2014. We measured and mapped the full range of activities that degrade forests and evaluated the relationship with deforestation. From 1992 to 2014, the total area of degraded forest was 337,427 square kilometers (km2), compared with 308,311 km2 that were deforested. Forest degradation is a separate and increasing form of forest disturbance, and the area affected is now greater than that due to deforestation.

Correction to: The impact of long dry periods on the aboveground biomass in a tropical forest: 20 years of monitoring.

An amendment to this paper has been published and can be accessed via the original article.

The impact of long dry periods on the aboveground biomass in a tropical forests: 20 years of monitoring.

BACKGROUND: Long-term studies of community and population dynamics indicate that abrupt disturbances often catalyse changes in vegetation and carbon stocks. These disturbances include the opening of clearings, rainfall seasonality, and drought, as well as fire and direct human disturbance. Such events may be super-imposed on longer-term trends in disturbance, such as those associated with climate change (heating, drying), as well as resources. Intact neotropical forests have recently experienced increased drought frequency and fire occurrence, on top of pervasive increases in atmospheric CO2 concentrations, but we lack long-term records of responses to such changes especially in the critical transitional areas at the interface of forest and savanna biomes. Here, we present results from 20 years monitoring a valley forest (moist tropical forest outlier) in central Brazil. The forest has experienced multiple drought events and includes plots which have and which have not experienced fire. We focus on how forest structure (stem density and aboveground biomass carbon) and dynamics (stem and biomass mortality and recruitment) have responded to these disturbance regimes. RESULTS: Overall, the biomass carbon stock increased due to the growth of the trees already present in the forest, without any increase in the overall number of tree stems. Over time, both recruitment and especially mortality of trees tended to increase, and periods of prolonged drought in particular resulted in increased mortality rates of larger trees. This increased mortality was in turn responsible for a decline in aboveground carbon toward the end of the monitoring period. CONCLUSION: Prolonged droughts influence the mortality of large trees, leading to a decline in aboveground carbon stocks. Here, and in other neotropical forests, recent droughts are capable of shutting down and reversing biomass carbon sinks. These new results add to evidence that anthropogenic climate changes are already adversely impacting tropical forests.

Influence of climate variables in the initial growth of Corymbia citriodora and different species of eucalyptus / Influência das variáveis climáticas no crescimento inicial de Corymbia citriodora e diferentes espécies de eucalipto

This work aimed to analyze possible differences in growth patterns on Eucalyptus species and to identify the determinants climatic variables on the growth. We evaluated six Eucalyptus species (Eucalyptus camaldulensis, Eucalyptus grandis, Eucalyptus urophylla, Eucalyptus saligna, Corymbia citriodora and Eucalyptus globulus) and a Clone (GG100) implanted in an experimental arrangement of randomized blocks. We collected the collar diameter and height of all plants monthly in the course of a year, in addition to climate data (minimum temperature, maximum and rainfall). Sequentially, we obtained the correlations between the current monthly increments (collar diameter and height) and climatic variables (minimum temperature, maximum and rainfall). The Current Monthly Increment of the Collar diameter (CMI D) was not correlated to the climatic variables evaluated and the Current Monthly Increment of the Height (CMI H) was strongly correlated to the minimum temperature for the species E. camaldulensis, C. citriodora, E. saligna, E. urophylla, E. grandis and the GG100 Clone. The Rainfall showed positive correlations regarding the CMI H only for the Clone (GG100) and E. urophylla. Finally, the species E. camaldulensis, E. urophylla, E. grandis, E. saligna presented a mortality rate under 10% which is recommended according to the silvicultural criteria.

Objetivou neste trabalho analisar possíveis diferenças nos padrões de crescimento em espécies de eucalipto e identificar as variáveis climáticas determinantes no crescimento. Foram avaliadas seis espécies de eucalipto (Eucalyptus camaldulensis, Eucalyptus grandis, Eucalyptus urophylla, Eucalyptus saligna, Corymbia citriodora e Eucalyptus globulus) e um Clone (GG100) implantados em arranjo experimental de blocos casualizados. Foram coletados o diâmetro do colo e altura de todas as plantas mensalmente no decorrer de um ano, além dos dados climáticos (temperatura mínima, máxima e precipitação). Sequencialmente foram obtidas correlações entre os incrementos correntes mensais (diâmetro do colo e altura) e as variáveis climáticas (temperatura mínima, máxima e precipitações). O Incremento Corrente Mensal do Diâmetro do Colo não apresentou correlação com as variáveis climáticas avaliadas e o Incremento Corrente Mensal em Altura (ICM H) é fortemente correlacionado com a temperatura mínima para as espécies E. camaldulensis, C. citriodora, E. saligna, E. urophylla, E. grandis e o Clone GG100. A precipitação apresentou correlações positiva com o ICM H somente para o Clone (GG100) e para E. urophylla. Por fim, as espécies E. camaldulensis, E. urophylla, E. grandis, E. saligna apresentaram taxa de mortalidade inferior a 10%, valor este recomendável de acordo com critérios silviculturais.

Funções de distribuição diamétrica em um fragmento de Floresta Ombrófila Mista / Diametric distribution functions in a fragment of Mixed Ombrophylous Forest

Os objetivos deste estudo foram ajustar e selecionar funções de densidade probabilística que caracterizem a estrutura diamétrica desse fragmento e das espécies: Cedrela fissilis (Cedro), Luehea divaricata (Açoita Cavalo), Gochnatia polymorpha (Cambará), Sebastiania commersoniana (Branquilho) e Casearia sylvestris (Cafezeiro) de um fragmento de Floresta Ombrófila Mista com 15,24ha, localizado em Curitiba, Paraná. Para avaliar a distribuição diamétrica dessa floresta e das cinco espécies selecionadas, foram ajustadas sete funções probabilísticas para intervalos de classe de 5cm. Segundo os critérios de seleção adotados, o modelo que melhor representou a distribuição diamétrica para toda a floresta, o cedro, o cambará e o branquilho foi o de Weber; para o cafezeiro, a função Gamma (Adaptada) foi a mais eficiente e para o açoita cavalo nenhuma dessas funções foi aderente. O branquilho, o açoita cavalo, o cafezeiro e a floresta como um todo apresentaram distribuição em "J" invertido ou decrescente. Entretanto, o cedro e o cambará apresentaram distribuição tendendo à unimodalidade com forte assimetria à direita.

The objective of this study was to adjust and select probability density functions that characterize the diametric structure of this forest fragment and for the species: Cedrela fissilis, Luehea divaricata, Gochnatia polymorpha, Sebastiania commersoniana and Casearia sylvestris for a 15.24 hectare fragment of Mixed Ombrophylous Forest, located in Curitiba, State of Paraná. In order to evaluate the diametric distributions of this forest and the five selected species, seven probability functions were adjusted for 5cm class intervals. According to the criteria of selection adopted, the model that best represented the diametric distributions for the whole forest, Cedrela fissilis, Gochnatia polymorpha and Sebastiania commersoniana was the Weber model; for Casearia sylvestris, the Gamma function (adapted) was the most efficient, and for Luehea divaricata, none of these functions showed adherence. The Sebastiania commersoniana, Luehea divaricata, Casearia sylvestris and the forest as a whole showed inverted "J" or decreasing distribution, while, Cedrela fissilis and Gochnatia polymorpha showed an almost unimodal distribution with a strong asymmetry to the right.