Joaquim dos Santos

Tree damage, allometric relationships, and above-ground net primary production in central Amazon forest

The loss of tree mass over time from damage can lead to underestimates in above-ground net primary productivity (ANPP) if not accounted for properly. Bias in the allometric relationship between trunk base diameter (Db, at 1.3 m height or above the buttresses) and mass can also lead to systematic errors in ANPP estimates. We developed an unbiased model of the relationship between Db and tree mass using data from 315 trees ( 5c mDb) harvested in the central Amazon. This model was compared with other theoretical (na 1) and empirical models (na 4). The theoretical model, and one empirical model, made predictions that differed substantially form our central Amazon model. The other three empirical models made predictions that were consistent with our model despite being developed in different tropical forests. Models differed mostly in predicting large tree mass. Using permanent forest inventory plot data, our Db versus tree mass model, and a bole volume model, we estimated that tree damage amounts to 0.9 Mg ha ˇ1 per year (dry mass) of litter production. This damage should be included as a mass loss term when calculating ANPP. Incorporating fine litter data from published studies, we estimated that average ANPP for central Amazon plateau forests is at least 12.9 Mg ha ˇ1 per year (or 6.5 Mg C ha ˇ1 per year). Additional sources of error as described in the text can raise this estimate by as much as 4 Mg ha ˇ1 per year. We hypothesize that tree damage in oldgrowth forests accounts for a significant portion of age related decline in productivity. # 2000 Elsevier Science B.V. All rights reserved.

Respiration from a tropical forest ecosystem: partitioning of sources and low carbon use efficiency

Understanding how tropical forest carbon balance will respond to global change requires knowledge of individual heterotrophic and autotrophic respiratory sources, together with factors that control respiratory variability. We measured leaf, live wood, and soil respiration, along with additional environmental factors over a 1-yr period in a Central Amazon terra firme forest. Scaling these fluxes to the ecosystem, and combining our data with results from other studies, we estimated an average total ecosystem respiration (Reco) of 7.8 μmol·m−2·s−1. Average estimates (per unit ground area) for leaf, wood, soil, total heterotrophic, and total autotrophic respiration were 2.6, 1.1, 3.2, 5.6, and 2.2 μmol·m−2·s−1, respectively. Comparing autotrophic respiration with net primary production (NPP) estimates indicated that only ∼30% of carbon assimilated in photosynthesis was used to construct new tissues, with the remaining 70% being respired back to the atmosphere as autotrophic respiration. This low ecosystem carbon use efficiency (CUE) differs considerably from the relatively constant CUE of ∼0.5 found for temperate forests. Our Reco estimate was comparable to the above-canopy flux (Fac) from eddy covariance during defined sustained high turbulence conditions (when presumably Fac = Reco) of 8.4 (95% ci = 7.5– 9.4). Multiple regression analysis demonstrated that ∼50% of the nighttime variability in Fac was accounted for by friction velocity (u*, a measure of turbulence) variables. After accounting for u* variability, mean Fac varied significantly with seasonal and daily changes in precipitation. A seasonal increase in precipitation resulted in a decrease in Fac, similar to our soil respiration response to moisture. The effect of daily changes in precipitation was complex: precipitation after a dry period resulted in a large increase in Fac, whereas additional precipitation after a rainy period had little effect. This response was similar to that of surface litter (coarse and fine), where respiration is greatly reduced when moisture is limiting, but increases markedly and quickly saturates with an increase in moisture.

Large-scale wind disturbances promote tree diversity in a Central Amazon Forest

Canopy gaps created by wind-throw events, or blowdowns, create a complex mosaic of forest patches varying in disturbance intensity and recovery in the Central Amazon. Using field and remote sensing data, we investigated the short-term (four-year) effects of large (>2000 m2) blowdown gaps created during a single storm event in January 2005 near Manaus, Brazil, to study (i) how forest structure and composition vary with disturbance gradients and (ii) whether tree diversity is promoted by niche differentiation related to wind-throw events at the landscape scale. In the forest area affected by the blowdown, tree mortality ranged from 0 to 70%, and was highest on plateaus and slopes. Less impacted areas in the region affected by the blowdown had overlapping characteristics with a nearby unaffected forest in tree density (583±46 trees ha−1) (mean±99% Confidence Interval) and basal area (26.7±2.4 m2 ha−1). Highly impacted areas had tree density and basal area as low as 120 trees ha−1 and 14.9 m2 ha−1, respectively. In general, these structural measures correlated negatively with an index of tree mortality intensity derived from satellite imagery. Four years after the blowdown event, differences in size-distribution, fraction of resprouters, floristic composition and species diversity still correlated with disturbance measures such as tree mortality and gap size. Our results suggest that the gradients of wind disturbance intensity encompassed in large blowdown gaps (>2000 m2) promote tree diversity. Specialists for particular disturbance intensities existed along the entire gradient. The existence of species or genera taking an intermediate position between undisturbed and gap specialists led to a peak of rarefied richness and diversity at intermediate disturbance levels. A diverse set of species differing widely in requirements and recruitment strategies forms the initial post-disturbance cohort, thus lending a high resilience towards wind disturbances at the community level.

Projeção da dinâmica da floresta natural de Terra-firme, região de Manaus-AM, com o uso da cadeia de transição probabilística de Markov

Os fatores que envolvem os processos da dinâmica da floresta influenciam a sua biodiversidade e, portanto, a qualidade da floresta. A definicao de estrategias que envolve a protecao e o uso adequado da floresta manejada e a recuperacao de areas ja degradadas tornam-se possivel com o estudo da estrutura e dinâmica da floresta primaria por meio de informacoes como a mortalidade, o recrutamento e a permanencia das arvores no sistema florestal. Este trabalho teve como objetivo avaliar a dinâmica de uma floresta nao perturbada e fazer projecoes da dinâmica florestal usando a matriz de transicao probabilistica (Cadeia de Markov). As taxas de recrutamento, mortalidade e incremento foram determinadas a partir de inventarios florestais realizados em dois transectos, nos sentidos Norte-Sul e Leste-Oeste (20 x 2500 m cada, totalizando 10 ha), localizados no km 50 da BR 174, na estrada vicinal ZF-2, Manaus/AM, nos anos de 2000 e 2004. A floresta acumulou 8,34 t.ha-1.ano-1 de biomassa fresca acima do solo. De acordo com projecao para 2008, o numero total de arvores diminuira em 2,67% (de 5987 individuos (2004) para 5827 (2008)) e a mortalidade sera 15% maior (de 264 (2004) para 311 (2008)). O teste Qui-quadrado mostrou que nao ha diferenca significativa (1% de probabilidade) entre as informacoes coletadas e projetadas. Esses resultados permitem concluir que a Cadeia de Markov e um eficiente instrumento para projetar a dinâmica da floresta natural, contribuindo para o planejamento em curto prazo das atividades que utilizam os recursos florestais.

Estudo fitossociológico nas regiões de Carajás e Marabá - Pará, Brasil

O estudo fitossociologico levou em consideracao duas areas localizadas em Carajas e Maraba, na regiao sul do Para. A amostragem abordou dois niveis: 1) Individuos com DAP ≥ 20cm em parcelas de 20m x 200m e, II) Individuos com 5cm ≤ DAP ≤ 20cm em duas sub-parcelas de 10m x 10m no inicio c final das parcelas. Todos os individuos do segundo nivel foram considerados como regeneracao natural do povoamento adulto. Em Carajas utilizou-se 35 (trinta e cinco) unidades amostrais (parcelas) e em Maraba 22 (vinte c duas). Do ponto de vista de composicao floristica, as areas estudadas apresentaram-se heterogeneas, com indices de Shanon-Weaver estimados em 3,66 e 3,71, respectivamente, para Carajas e Maraba. A equacao hipsometrica comum que melhor ajustou os dados observados foi: h = [ d 2.38 + 0.1387 h ] 2 As abundâncias medias foram 131,92 e 127,85 individuos/ha, respectivamente, para Carajas e Maraba. As estimativas de area basal foram 15,41 e 17,35 m2/ha nas regioes de Carajas e Maraba, respectivamente. A funcao de densidade I (Meyer) que melhor ajustou os dados de frequencia por classe de diâmetro (Fi) em funcao do centro de classe (DAP), para Carajas, foi Fi= e(9,56330614 - 0,07139847d) e Fi =e(8,96125691 - 0,06937877d) para Maraba. Tambem estimou-se que cerca de 36% das especies existentes nas regioes estudadas possuem valor economico no mercado madeireiro.

INFLUÊNCIA DO SOMBREAMENTO NA PRODUÇÃO DE MUDAS DE ANGELIM PEDRA (DINIZIA EXCELSA DUCKE)

This experiment was carnea out at Ducke reserve, Amazonas, Brazil in order to detect the influence of shading on the production of D. excelsa seedlings. The shading intensities (30%, 50% and 70%) were obtained by using black plastic screening. The evaluation of height, coll r diameter, shoot and rood dry weight of D. excelsa seedlings was performed after 30, 60 e 90 days in the nursery. The following results were obtained: a) with regard to period, seedlings with higher height were removed with 90 days; for the other paramenters abalyzed, no significant differences were found; b) seedlings with higher height were produced to 30% and 50% shading; collar diameter and seeding height decreased significantly with 70% shading, c) higher above ground dry weight biomass of seedlings were obtained when lower shading levels were used (30% and 50%).

Tamanho de parcela amostral para inventários florestais .

Resultado da investigacao sobre o tamanho ideal de parcela amostral para Inventarios Florestais, feita com base em 32 diferentes tamanhos, simulados, um a um, sobre o Inventario Florestal a 100% de uma area de 80 hectares de floresta tropical umida de terra firme, com arvores de DAP maior ou igual a 25 cm. A parcela que apresentou os melhores resultados foi a de dimensoes de 37,5 x 150 metros.

Madeiras tropicais: análise econômica das principais espécies florestais exportadas

This work analyses Brazilian tropical wood exports for principal forest species, over the period of 1980-98. Tendency models were built to estimate the growth rate and to explain the export performance for each species. The results pointed out that the principal tropical species exported were, in decreasing order, mahogany, jatoba, virola, cedar, angelim, ipe, andiroba, sucupira, tatajuba, cedrorana, assacu, cerejeira, pau-marfim, freijo and jacaranda. Only six species represented 40% of volume and total exported revenue. The species said less known increased their exports from 1991. The exported volume of mahogany, virola, andiroba, sucupira and freijo decreased, on the other hand jatoba, cedar, ipe and cerejeira have increased their share in the international market. About price, all studied species showed a positive tendency along studied period and value relatively low in comparison to the mahogany price..

Situação das indústrias madeireiras do Estado do Amazonas em 2000

Apesar da baixa atividade de usos do solo no Estado, a producao de madeira nao e sustentavel. Isso e causado, principalmente, pela falta de infra-estrutura dos orgaos responsaveis para monitorar os planos de manejo florestal e de corte raso para agricultura e pecuaria. Este estudo apresenta analise de alguns fatores de producao, industrializacao e comercializacao da industria madeireira do Estado do Amazonas, visando viabilizar diagnostico do setor florestal. Essas informacoes possibilitam o estabelecimento de politicas florestais para a regiao. Fez-se a definicao das zonas de producao, onde os principais municipios produtores de serrados foram Manaus, Itacoatiara, Manacapuru e Parintins; e de compensados e laminados foram Manaus e Itacoatiara. Apos essa definicao os dados foram coletados diretamente nas industrias, atraves de questionarios e entrevistas para coletar as seguintes informacoes: principais especies consumidas, produtividade das industrias, origem da materia-prima, transporte, qualificacao de pessoal e treinamento, principais problemas tecnologicos e exportacao. Em 2000, a producao estadual foi de 323.400m3 de madeira em toras. Mais de 50 especies diferentes sao usadas nas serrarias, das quais 16 representaram 80% do volume total, sendo as 5 especies (louro inhamui,angelim pedra,amapa,assacu e macaranduba) contribuiram com 49,34% do consumo total; quanto as industrias de compensado e laminado estas usaram, 17 especies onde as 5 principais (muiratinga, sumauma, copaiba, assacu e amapa) representaram 62,71% do consumo total.Tambem foram coletados dados complementares junto ao IBAMA, SUFRAMA, SEFAZ e IBGE.

Uso de banda dendrométrica na definição de padrões de crescimento individual em diâmetro de árvores da bacia do rio Cuieiras

Este trabalho tem como objetivo analisar padroes de crescimento individual de diversas arvores que ocorrem em duas topossequencias (direcoes Norte-Sul e Leste-Oeste), de uma amostra representativa da floresta de terra-firme na Amazonia Central. Foram selecionados de forma aleatoria, aproximadamente, 300 individuos, sendo 150 em cada topossequencia, distribuidos em mesmas proporcoes nas tres classes topograficas (plato, encosta e baixio) e nas tres classes de diâmetro (10 ≤ DAP < 30 cm; 30 ≤ DAP< 50 cm e DAP≥ 50 cm). Em cada uma dessas arvores foi instalada uma fita metalica, com extremidades parcialmente sobrepostas e ligadas por uma mola; o avanco de uma das pontas, dentro de uma abertura, representa o crescimento em circunferencia, que foi medido com um paquimetro digital. As medicoes foram realizadas mensalmente ao longo de 19 meses, de junho/1999 a dezembro/2000; neste estudo foram considerados apenas os 12 meses do ano 2000. O padrao individual de crescimento em diâmetro varia muito com o passar dos meses (p = 0,00) e apenas razoavelmente quando os meses sao interagidos com as classes de diâmetro (p 0,08); por outro lado, ha fraca uma evidencia (p = 0,25) quando as classes topograficas sao acrescentadas na interacao anterior e praticamente nenhuma evidencia (p = 0,89) quando e analisada a interacao meses e classes topograficas. Dentre todas as arvores selecionadas (300 individuos), foram mantidas na analise 272 individuos. A media do incremento anual em diâmetro, considerando as 272 arvores monitoradas, foi de 1,64 ± 0,21 mm (p = 0,05), ficando dentro do intervalo dos incrementos obtidos no BIONTE e FLONA Tapajos, que e de 1,5 a 2 mm por ano.