Adelmar G. Bandeira

Polycyclic aromatic hydrocarbon (PAH) patterns in climatically different ecological zones of Brazil

Abstract Understanding the global distribution of PAHs requires knowledge of their sources. The objective of our work was to test the hypothesis that termites and woody plants are sources of naphthalene (NAPH), phenanthrene (PHEN), and perylene (PERY) for soils of different tropical climates. We determined the concentrations of 20 PAHs in soil, wood, and different compartments of termite nests (central part, inner wall, outer wall) in the Amazon (Terra firme, Varzea, and Igapo), Pantanal, Cerrado, Mata Atlântica, and Caatinga regions. The sum of 20 PAH concentrations was low in all soils (4.8–347 μg kg −1 , n =47) and much higher in many of the wood (47–3894, n =31) and termite nest samples (29–4208, n =121). In general, NAPH, PHEN, or PERY were most abundant. In the Amazon region, wood samples contained up to 3785 and termite nest samples up to 3645 μg kg −1 of NAPH. In all regions, most termite nests contained higher PERY concentrations (up to 1109 μg kg −1 ) than wood or soil, indicating that PERY was produced or accumulated in these nests. In many termite nests, the central part had larger NAPH and PERY concentrations than the wall, indicating that these compounds may have been produced within the nests. With few exceptions, NAPH dominated the PAH pattern in the Amazon and west Cerrado regions, PHEN in the Mata Atlântica and Caatinga regions, and PERY in the Pantanal and central Cerrado regions. Our results suggest that there are large unknown sources of NAPH, PHEN, and PERY in the tropical environment. It is likely that part of these sources is biological. The release of NAPH and PHEN from these sources seems to depend on climatic factors.

Methane emission from wood-feeding termites in Amazonia

The contribution of termites to the global methane budget has been controversely discussed in the last decade. We measured methane emissions from nests of wood-feeding termite species (Nasutitermes spp.) of primary and secondary forests of Amazonia. The methane emission rates from single termite nests varied in a broad range between 0.01 and 9.4 mg CH4 hour−1 nest−1 (average = 2.0 ± 2.4 mg CH4 hour−1 nest−1), as termite colonies vary considerably in size (biomass). Consequently, data given as methane emission per nest are unsuitable for interspecific comparison. In seek for an appropriate unit the methane flux was related to the biomass of the termites dwelling in the nest. On this basis, the variation between the methane emissions of the nests was far lower (0.4 – 4.9 μg hour−1 g termites−1). Biomass-related methane emission rates averaged 3.0 ± 1.3 μg hour−1 g termites−1, which means that Amazonian termites release significantly (at p = 0.01%) more methane than species from other regions. By extrapolating these emission rates to the estimated global biomass of termites we calculated a total emission of 26 Tg CH4 year−1, which represents about 5 % of the annual methane flux from all sources to the world atmosphere. Termites are unlikely to contribute essentially to the global budget of the “greenhouse gas” methane.

Deforestation and methane release from termites in Amazonia

Abstract To assess the role of termite populations in the change of global atmospheric methane concentrations, we reevaluate the hypothesis that deforestation leads to higher populations of wood-feeding termites and to a significant increase of termite-emitted methane in areas of cleared and burned former primary rain forest. Calculations are based on a model that uses literature information on termite population size in primary forest and pasture 1 to 10 years after forest conversion, wood consumption and methane emission rates of termites. We use two scenarios based on low- and high-end parameters based on data from rain forests in Brazilian Amazonia. In the low-end scenario, termite population biomass is 25 kg-ha−1 in primary forest; 4 kg·ha−1 in year 1 after forest clearing, 51 kg·ha−1 in a six-year-old pasture, and 4 kg·ha−1 in a ten-year-old pasture. In the high-end scenario, all values are doubled and the initial breakdown in year 1 is omitted. Wood consumption rates are 49 and 270 mg wood·g termite day−1 and methane emission rates are 0.0023 and 0.0079 t of carbon released as methane per ton of carbon consumed, in the low- and the high-end scenario, respectively. In the low-end scenario no significant difference exists between the average termite population size in primary forest and pasture modeled over a ten-year period. In the high-end scenario the average population size of years l-10 after clearing is only 31 % over that of primary forest. The population model data combined with the wood consumption rates allow for only 2.3–32.3% of the wood biomass left from forest burn to be consumed by termites within 10 years. The changes in methane emissions from termite population change after deforestation were calculated using two approaches: “Cumulative net emissions” for the region, which measure the 10-year impact of a years forest clearing (e.g. 1.38·106 ha in 1990), increase by 0.0001 to 0.11 Tg CH4 in the 10 year-period in both scenarios, a negligible contribution to the increase of atmospheric methane concentrations of 45 Tg·yr−1. The “annual balance of net methane emissions” from termites in all the different landscapes existing in the whole region in a single year (1990) increases by only 0.004 to 0.33 Tg CH4 (low- and high-end scenario) because of the large proportion of old clearings (>10 years old) with low methane emission rates: Termite populations do not tend to increase as a function of the available wood mass only and therefore methane emissions from termites in cleared areas of former rain forest do not make a significant contribution to the increase of the global methane concentrations in the atmosphere.

Biomass and population structure of Constrictotermes cyphergaster (Silvestri) (Isoptera: termitidae) in the dry forest of caatinga, northeastern Brazil

Biomass and population structure of Constrictotermes cyphergaster (Silvestri) were studied in an area of dry forest of caatinga in the State of Paraiba, northeastern Brazil. Twelve nests of different sizes were randomly collected, being six during the dry season (November 2004 and 2005) and six during the wet season (March 2004). Soldier and worker populations varied between 4880 and 118800 individuals per nest. The ratio between soldiers and workers did not significantly vary between seasons. Biomass (measured as fresh weight) of individuals varied between 13.9 and 408.8 g per nest, and soldiers and workers had significantly greater biomass during the wet season. The estimated density of nests of C. cyphergaster was 59.0 +/- 22.53 active nests/ha. Quantitative data of the study colonies and data on the nest abundance showed that C. cyphergaster encompassed some 278.2 individuals/m(2), with approximately 0.9 g (fresh weight)/m(2). These data suggest that C. cyphergaster is an important consumer of vegetal matter and, therefore, an important species affecting the nutrient cycling and energy flow in the caatinga vegetation.

Ecologia de cupins (Insecta: Isoptera) da Amazônia Central: efeitos do desmatamento sobre as populações

Foram estudadas a distribuicao e diversidade de cupins em areas de floresta primaria, capoeira e pastagem na Amazonia Central, Estado do Amazonas. Foram feitas medidas de umidade do solo, compactacao do solo (taxa de infiltracao de agua no solo) e temperaturas do solo e do ar, para estabelecer relacoes com a distribuicao dos cupins. Com um esforco de coletas aproximadamente equivalente nos tres ambientes, ficou demonstrado que a maioria dos generos se distribui nos tres habitats. Nasutitermes foi o genero mais comum e com maior diversidade, sendo mais frequente em pastagem. O numero total de ninhos de cupins foi tambem maior na pastagem que na floresta primaria. Os cupins do solo podem atingir quase um metro de profundidade e seu numero foi maior na capoeira, seguido da pastagem e por ultimo a floresta. A capacidade de infiltracao de agua no solo e umidade do solo diminuiram com o desmatamento. As flutuacoes diarias de temperaturas do solo e do ar foram maiores na pastagem que na floresta. A retirada da vegetacao primaria e as consequentes modificacoes microclimaticas poderiam ter sido responsaveis pela distribuicao de certos grupos de Isoptera.

Cupins de duas florestas de restinga do nordeste brasileiro

The structure of termite communities was evaluated at two restinga forests (a characteristic type of vegetation occurring on nutrient-poor sandy soils along the Brazilian coastline), located in the municipalities of Mataraca and Cabedelo, State of Paraiba. A standardised sampling protocol was used in both sites. Twenty-five species were found, 19 of them at Mataraca and 15 at Cabedelo, with just 9 species in common to both sites. Species of Nasutitermitinae and wood-feeding groups were dominant at both study sites. The low species richness and frequency of humus-feeders species, and species of the subfamily Apicotermitinae as well, seem to be related to the restinga soil properties. The conspicuous nest (all arboreal) builders were Armitermes holmgreni Snyder, 1926, Microcerotermes exiguus (Hagen, 1858), M. strunckii (Sorensen, 1884), Nasutitermes corniger (Motschulsky, 1855), N. ephratae (Holmgren, 1910), and N. macrocephalus (Silvestri, 1903). The termite fauna of the studied restinga was composed by typical species of other Brazilian ecosystems, such as Atlantic forest and Cerrado, being in agreement with the general pattern of distribution set up by the plant communities and the fauna of vertebrates described elsewhere for other Brazilian restingas.

Densidade e distribuição vertical de Macroinvertebrados em solos argilosos e arenosos na Amazônia Central

A densidade e a distribuicao vertical da macrofauna do solo foram estudadas nas estacoes chuvosa e seca na regiao de Manaus, Estado do Amazonas, Brasil, sob tres tipos de cobertura vegetal, em areas de solo arenoso e de solo argiloso, durante dois anos. Os animais foram coletados manualmente de amostras de solo de 20 x 20 x 30 cm (= 12 litros), divididas em subamostras de 5 cm de espessura. O metodo mostrou-se pouco eficiente, principalmente para coleta de animais menores que 2 mm, por serem pouco visiveis a olho nu. Encontrou-se maior numero de animais no solo arenoso que no solo argiloso. Os grupos mais bem representados foram cupins, formigas e minhocas. Fez-se comparacao entre o numero de individuos coletados na estacao chuvosa e na estacao seca, tendo sido encontrado mais macroinvertebrados nos estratos superiores (0-15 cm) na estacao chuvosa que na estacao seca, e em profundidades maiores (15-30 cm), eles foram mais abundantes na estacao seca, principalmente cupins. Isto foi interpretado como evidencia de migracao vertical da macrofauna para os estratos superiores do solo na estacao chuvosa e para o solo mineral na estacao seca.

Termites in sugar cane in Northeast Brazil: ecological aspects and pest status

The spatial distribution, abundance, and feeding habits of termites in a sugar cane plantation in Northeast Brazil were studied, and based on these ecological parameters, the pest status of the species was evaluated. Four species were found: Amitermes nordestinus Melo & Fontes, Cylindrotermes nordenskioeldi Holmgren, Nasutitermes coxipoensis (Holmgren) and Syntermes nanus Constantino, which we reported by the first time in association to sugar cane. The abundance and spatial distribution (vertical and horizontal) of the termites were influenced mainly by the plant root biomass and soil organic matter. C. nordenskioeldi is harmful to sugar cane, A. nordestinus is a potential pest, while N. coxipoensis and S. nanus are not potential pests. The importance of termites for maintaining the fertility, aeration and porosity of tropical soils is an evidence that basic investigations on reproduction biology and population dynamics of C. nordenskioeldi and A. nordestinus must be encouraged aiming to develop pest control agents and species-specific management techniques.

Térmitas construtores de ninhos conspícuos em duas áreas de Mata Atlântica com diferentes níveis de perturbação antrópica

The effects of selective logging on termite assemblages that build conspicuous nests were studied in two areas of semideciduous Atlantic Forest, located in the Reserva Biológica Guaribas, Northeastern Brazil. The two study areas went through selective logging until 1985 (A17) and 1972 (A30). In 2002, termite nests were studied in two plots of 1 ha (100 x 100 m), being one plot in each area. The nests were placed in each plot and the species were categorized in feeding groups. The structure of the study assemblages was different between the two areas. Diversity and richness of builder species were greater in the A30 area. Species that consume humus were more sensitive to selective logging. Nest abundance of humus feeding species was significantly higher in the A30 area, whereas nests of wood feeding species were significantly more abundant in the area A17. Nest ratio between humus and wood feeding species was 1:3 in the A30 area and 1:12 in the A17 area. Nests with greater volume were observed in the area A30, whereas abundance of inactive nests was significantly higher in A17. The time for habitat resilience after the selective logging influenced patterns of assemblage structure of termites in similar ways as described in other studies in tropical forests.

Caste development systems of the Neotropical termite Constrictotermes cyphergaster (Isoptera, Termitidae)

The caste developmental system of the Neotropical termite Constrictotermes cyphergaster was investigated in 12 natural colonies from the semi-arid Caatinga region of northeastern Brazil. Twelve measurements were taken of different body parts of the larvae, workers, presoldiers, soldiers, nymphs, and alates for morphometric analyses, and principal component analyses (PCA) were performed based on these parameters. The nymphal line comprised one larval instar, followed by five nymphal instars, and alates, in agreement with the developmental pattern described for Termitidae species. The apterous line included two larval instars, followed by workers, presoldiers, and soldiers. Both workers and soldiers were found to be monomorphic and composed only of male specimens, with only one instar phase each. C. cyphergaster, like most of the Nasutitermitinae, has only male soldiers. The presence of male workers, with only one instar, suggests a simplified system of differentiation in the apterous line of C. cyphergaster. These patterns, which had not previously been described for ‘full nasute’ Nasutitermitinae, are similar to the differentiation patterns of the ‘mandibulate nasute’ Cornitermes walkeri.