Tropical Fire Research Articles

HOST SPECIFICITY OF FOUR PSEUDACTEON SPP. (DIPTERA: PHORIDAE), PARASITOIDS OF FIRE ANTS IN ARGENTINA (HYMENOPTERA: FORMICIDAE)

Abstract Several South American species of Pseudacteon have been released for biocontrol of red imported fire ants Solenopsis invicta in the U.S. Here we provide additional data from host specificity tests on 4 additional candidate species, P. nocens, P. nudicornis, P. cultellatus, and P. obtusus, all of which are components of multi-species complexes that occur within Argentinean Solenopsis populations. All 4 species were tested with sequential, no choice exposures to the red imported fire ant S. invicta, and the tropical fire ant, S. geminata. Levels of intra-generic specificity ranged from moderate to high and all 4 species showed greater specificity than some Pseudacteon species already approved for release.

First space‐based observations of formic acid (HCOOH): Atmospheric Chemistry Experiment austral spring 2004 and 2005 Southern Hemisphere tropical‐mid‐latitude upper tropospheric measurements

The first space‐based measurements of upper tropospheric (110–300 hPa) formic acid (HCOOH) are reported from 0.02 cm−1 resolution Atmospheric Chemistry Experiment (ACE) Fourier transform spectrometer solar occultation measurements at 16°S–43°S latitude during late September to early October in 2004 and 2005. A maximum upper tropospheric HCOOH mixing ratio of 3.13 ± 0.02 ppbv (1 ppbv = 10−9 per unit volume), 1 sigma, at 10.5 km altitude was measured during 2004 at 29.97°S latitude and a lower maximum HCOOH mixing ratio of 2.03 ± 0.28 ppbv, at 9.5 km altitude was measured during 2005. Fire counts, back trajectories, and correlations of HCOOH mixing ratios with ACE simultaneous measurements of other fire products confirm the elevated HCOOH mixing ratios originated primarily from tropical fire emissions. A HCOOH emission factor relative to CO of 1.99 ± 1.34 g kg−1 during 2004 in upper tropospheric plumes is inferred from a comparison with lower mixing ratios measured during the same time period assuming HITRAN 2004 spectroscopic parameters.

The role of smoldering combustion on smoke emission in tropical forest fires

The role of smoldering combustion on smoke emission in tropical forest fires

Atmospheric Chemistry Experiment (ACE) measurements of elevated Southern Hemisphere upper tropospheric CO, C2H6, HCN, and C2H2 mixing ratios from biomass burning emissions and long‐range transport

Infrared Fourier transform spectra recorded at 0.02 cm−1 resolution by the Atmospheric Chemistry Experiment (ACE) show elevated levels of the relatively long‐lived biomass burning products CO, C2H6, HCN, and C2H2 in the upper troposphere and lower stratosphere at 15°S–45°S latitude from 30 September to 3 November 2004. Mixing ratios up to 260 ppbv (10−9 per unit volume) for CO, 1470 pptv (10−12 per unit volume) for HCN, and 1.67 ppbv for C2H6 are observed in the upper troposphere and their variations are highly correlated reflecting their similar lifetimes and emission origin. Back trajectory calculations and maps of fire distributions for the time period indicate the elevated levels likely originated from regions of tropical fire emissions in South America or Africa with cases identified with elevated emissions reaching close to the lower stratosphere.

Streamwater quality as affected by wild fires in natural and manmade vegetation in Malaysian Borneo

AbstractIn 1998 a wild fire struck a paired catchment research area under long‐term monitoring of hydrological and nutrient budgets. Streamwater quality as concentrations of dissolved and suspended particulate matter was monitored during 1·5–2·5 years after the fire in streams from seven different catchments. As the catchments, due to earlier experimental treatments, had different vegetations, varying effects related to different fire intensities were observed.The highest, mean stormflow, suspended sediment concentrations resulted from intensive fire in secondary vegetation that had experienced severe soil disturbance in previous treatments (crawler tractor timber extraction 10 years earlier). Stormflow concentrations were typically still about 400 mg l−1 in 1999 (10–21 months after the fire), which was about the maximum recorded concentration in streams during initial soil disturbance in 1988. Forest fire in natural forest resulted in less than half as high stormflow concentrations.For dissolved elements in streamwater there was a positive relation between fuel load (and fire intensity) and concentration and longevity of effects. Stream baseflow dissolved nutrient concentrations were high in the months following the fire. Mean baseflow K concentrations were 8–15 mg l−1 in streams draining catchments with intensive fire in secondary vegetation with large amounts of fuel. After controlled fire for forest plantation establishment in 1988 corresponding concentrations were 3–5 mg l−1, and after forest fire in natural forest in this study about 2 mg l−1.This study shows differences in response from controlled fire for land management, forest fire in natural forests and wild fires in manmade vegetations. These differences relate to resistance and resilience to fire for the involved ecosystems. There is reason to believe that wild fires and repeated wild fires during or after droughts, in successions caused by human influence, may lead to larger losses of ecosystem nutrient capital from sites compared with forest fires in natural forests. As fire in the humid tropics becomes more common, in an increasingly spatially fragmented landscape, it will be important to be aware of these differences. Copyright © 2004 John Wiley & Sons, Ltd.

Carbon emissions from fires in tropical and subtropical ecosystems

AbstractGlobal carbon emissions from fires are difficult to quantify and have the potential to influence interannual variability and long‐term trends in atmospheric CO2 concentrations. We used 4 years of Tropical Rainfall Measuring Mission (TRMM) Visible and Infrared Scanner (VIRS) satellite data and a biogeochemical model to assess spatial and temporal variability of carbon emissions from tropical fires. The TRMM satellite data extended between 38°N and 38°S and covered the period from 1998 to 2001. A relationship between TRMM fire counts and burned area was derived using estimates of burned area from other satellite fire products in Africa and Australia and reported burned areas from the United States. We modified the Carnegie‐Ames‐Stanford‐Approach (CASA) biogeochemical model to account for both direct combustion losses and the decomposition from fire‐induced mortality, using both TRMM and Sea‐viewing Wide Field of view Sensor (SeaWiFS) satellite data as model drivers. Over the 1998–2001 period, we estimated that the sum of carbon emissions from tropical fires and fuel wood use was 2.6 Pg C yr−1. An additional flux of 1.2 Pg C yr−1 was released indirectly, as a result of decomposition of vegetation killed by fire but not combusted. The sum of direct and indirect carbon losses from fires represented 9% of tropical and subtropical net primary production (NPP). We found that including fire processes in the tropics substantially alters the seasonal cycle of net biome production by shifting carbon losses to months with low soil moisture and low rates of soil microbial respiration. Consequently, accounting for fires increases growing season net flux by ∼12% between 38°N and 38°S, with the greatest effect occurring in highly productive savanna regions.

Circadian and Circannual Patterns of Activity and Territory Shifts: Comparing a Native Ant (<I>Solenopsis geminata</I>, Hymenoptera: Formicidae) with Its Exotic, Invasive Congener (<I>S. invicta</I>) and Its Parasitoids (<I>Pseudacteon</I> spp., Diptera: Phoridae) at a Central Texas Site

Abstract We studied the phenologies of phorid flies from the genus Pseudacteon; their host, the native tropical fire ant (TFA), Solenopsis geminata (F.); a second native ant, Monomorium minimum (Buckley); and the non-native red imported fire ant (RIFA), Solenopsis invicta Buren, at a site in Austin, TX. We took a census on an hourly basis from dawn until dusk once a month for a year (July 1998–June 1999). Previous studies have focused largely on the RIFA’s escape from natural enemies (e.g., phorid parasitoids) as an explanation for the ant’s competitive success. Here, we show that the RIFA has additional advantages over its native congener. We found the RIFA had a significantly greater association than the TFA with extremes in ambient temperature, relative humidity, and light levels. However, M. minimum was found at temperatures that were significantly higher than for the RIFA. Native TFA-specific phorids had activity patterns that were similar to their host’s. In addition, we documented the expansion of ...

Using SPOT-4 HRVIR and VEGETATION sensors to assess impact of tropical forest fires in Roraima, Brazil

Due to the El Niño phenomenon, the 1997-1998 dry season in Roraima (Brazil, Amazonia) was particularly pronounced. Consequently, vegetation fires spread widely and were monitored by many satellites in real time. Satellite images are currently being used to monitor vegetation fires either globally for climate studies or more regionally for impact assessment. After reviewing different satellite data used for impact assessment, this paper focuses on the contribution of SPOT-4's imagery provided by high resolution HRVIR and coarse resolution VEGETATION sensors. These sensors are described with emphasis on those characteristics of potential benefit for forest mapping and fire detection. Early images of Roraima from SPOT-4 are analysed and interpreted to delineate the areas already damaged by fire. VEGETATION images provide a first estimate of damaged areas on a regional scale and an indication of the main ecosystems affected. SPOT HRVIR is used to establish a much more precise classification of various ecosystems. Each vegetation class is associated with a biomass density. From the known burned areas, an estimate of burned biomass during the 1998 dry season is computed, as well as total carbon release. On an intensive study site of 20 400 km 2, 3060 km 2 of savannahs and crops and 6980 km 2 of forest have been burned; the corresponding carbon release is estimated as 210 000 t for croplands and savannahs and 23 M t for the evergreen seasonal forest. The estimated burnt surface areas derived from VEGETATION are then cross-validated with HRVIR and thus an attempt is made to extrapolate the burned biomass with the help of VEGETATION on a regional scale.

Combustion in tropical biomass fires: a critical review

Combustion in tropical biomass fires: a critical review

Host Specificity in Two Additional Pseudacteon spp. (Diptera: Phoridae), Parasitoids of Solenopsis Fire Ants (Hymenoptera: Formicidae)

We tested the host specificity of two South American Pseudacteon phorid flies, P. obtusus Borgmeier and P. borgmeieri Schmitz, on North American colonies of the red imported fire ant, Solenopsis invicta Buren, and the tropical fire ant, S. geminata (F.). Sequential host specificity tests conducted in the laboratory indicated that P. obtusus was highly specific to S. invicta. In individual trials, 20 females attacked S. invicta but none attacked S. geminata. Pseudacteon borgmeieri females, in contrast, attacked both Solenopsis species. Six of the eighteen known South American Pseudacteon species have now been tested for host specificity, and 4 of the 6 reveal a high degree of specificity to S. invicta, thus representing good biocontrol candidates.

Infrared solar spectroscopic measurements of free tropospheric CO, C2H6, and HCN above Mauna Loa, Hawaii: Seasonal variations and evidence for enhanced emissions from the Southeast Asian tropical fires of 1997–1998

High spectral resolution (0.003 cm−1) infrared solar absorption measurements of CO, C2H6, and HCN have been recorded at the Network for the Detection of Stratospheric Change station on Mauna Loa, Hawaii, (19.5°N, 155.6°W, altitude 3.4 km). The observations were obtained on over 250 days between August 1995 and February 1998. Column measurements are reported for the 3.4–16 km altitude region, which corresponds approximately to the free troposphere above the station. Average CO mixing ratios computed for this layer have been compared with flask sampling CO measurements obtained in situ at the station during the same time period. Both show asymmetrical seasonal cycles superimposed on significant variability. The first 2 years of observations exhibit a broad January‐April maximum and a sharper CO minimum during late summer. The C2H6 and CO 3.4–16 km columns were highly correlated throughout the observing period with the C2H6/CO slope intermediate between higher and lower values derived from similar infrared spectroscopic measurements at 32°N and 45°S latitude, respectively. Variable enhancements in CO, C2H6, and particularly HCN were observed beginning in about September 1997. The maximum HCN free tropospheric monthly mean column observed in November 1997 corresponds to an average 3.4–16 km mixing ratio of 0.7 ppbv (1 ppbv = 10−9 per unit volume), more than a factor of 3 above the background level. The HCN enhancements continued through the end of the observational series. Back‐trajectory calculations suggest that the emissions originated at low northern latitudes in southeast Asia. Surface CO mixing ratios and the C2H6 tropospheric columns measured during the same time also showed anomalous autumn 1997 maxima. The intense and widespread tropical wild fires that burned during the strong El Niño warm phase of 1997–1998 are the likely source of the elevated emission products.

Abandoned Orange-footed Scrubfowl (Megapodius reinwardt) nests and coastal rainforest boundary dynamics during the late Holocene in monsoonal Australia

Abstract The late Holocene history of monsoon rainforest retreat in northern Australia was explored by radiocarbon dating abandoned Orange-footed Scrubfowl ( Megapodius reinwardt ) nests. Scrubfowl can only build ‘nests’ (large heaps of soil and leaf litter) in coastal rainforests in northern Australia. A detailed study from a site with a known history of rainforest contraction demonstrated that it is impossible to accurately determine the date of rainforest boundary retreat by radiocarbon dating abandoned Scrubfowl nests. Nonetheless radiocarbon dates from abandoned nests at three sites on the coast of the Northern Territory suggested that the rainforests contracted sometime within the late Holocene. It is argued that the cause of such localised rainforest contraction is the combined effect of tropical cyclone damage and subsequent severe fires occurring in the storm debris, and not regional climatic change, a cause shown to be inconsistent with existing ecological and geomorphological data. The observed maintenance of rainforest boundaries under a regime of Aboriginal burning and the geographically patchy occurrence of abandoned Scrubfowl nests does not support the idea that Aborigines have been the primary cause of widespread rainforest retreat in the late Holocene.

Modeling the spectral optical properties of ammonium sulfate and biomass burning aerosols: parameterization of relative humidity effects and model results

The importance of including the global and regional radiative effects of aerosols in climate models has increasingly been realized. Accurate modeling of solar radiative forcing due to aerosols from anthropogenic sulfate and biomass burning emissions requires adequate spectral resolution and treatment of spatial and temporal variability. The variation of aerosol spectral optical properties with local relative humidity and dry aerosol composition must be considered. Because the cost of directly including Mie calculations within a climate model is prohibitive, parameterizations from off-line calculations must be used. Starting from a log-normal size distribution of dry ammonium sulfate, we developed optical properties for tropospheric sulfate aerosol at 15 relative humidities up to 99%. The resulting aerosol size distributions were then used to calculate bulk optical properties at wavelengths between 0.175 and 4 μm. Finally, functional fits of optical properties were made for each of 12 wavelength bands as a function of relative humidity. Significant variations in optical properties occurred across the total solar spectrum. Relative increases in specific extinction and asymmetry factor with increasing relative humidity became larger at longer wavelengths. Significant variation in single-scattering albedo was found only in the longest near-IR band. This is also the band with the lowest single scattering albedo. A similar treatment was done for aerosols from biomass burning. In this case, two size distributions were considered. One was based on a distribution measured for Northern Hemisphere temperate forest fires while the second was based on a measured size distribution for tropical fires. Equilibrium size distributions and compositions were calculated for 15 relative humidities and five black carbon fractions. Mie calculations and band averages of optical properties were done for each of the resulting 75 cases. Finally, fits were made for each of 12 spectral bands as functions of relative humidity and black carbon fraction. These optical properties result in global average forcing from anthropogenic sulfate aerosols of −0.81 Wm -2. The global average forcing for biomass aerosols ranged from −0.23 to −0.25 Wm -2 depending on the assumed size distribution, while fossil fuel organic and black carbon are estimated to heat the atmosphere by about 0.16 Wm -2.

Aborigines and Fire in the Wet Tropics of Queensland, Australia: Ecosystem Management Across Cultures

Australian indigenous people may retain common law native title rights in lands that have been reserved for nature conservation purposes . They are seeking greater equity in management of these places , and recognition of their cultural practices , such as "fire-stick farming." This article examines the approach to fire management of one group of Australian Aborigines , the Kuku-Yalanji , and that of the government managers of the Wet Tropics of Queensland World Heritage Area . The comparative ecosystem management framework used to analyze the cultural interface highlights potential conflicts over the control of management and information, while identifying common interests in maintaining species and communities . Kuku-Yalanji use fire to protect fire-sensitive rainforests as well as to promote fire-prone open forests. The study suggests a Fire Protocol to mediate the different goals of the two groups, and supports the view that implementation of ecosystem management requires a social decision process.

Host Specificity of Fire Ant Decapitating Flies (Diptera: Phoridae) in Laboratory Oviposition Tests

Host specificities of 3 species of Pseudacteon decapitating flies (P. litoralis Borgmeier, P. tricuspis Borgmeier, P. wasmanni Schmitz) were tested in quarantine facilities in Gainesville, FL. Female flies from Brazil were placed into test trays containing either red imported fire ants, Solenopsis invicta Buren; tropical fire ants, Solenopsis geminata Forel; or native ants from 6 other genera (Crematogaster, Pheidole, Aphaenogaster, Neivamyrmex, Forelius, Camponotus). Tests lasted 60–90 min. The 3 species of flies tested were all at least 15 times more likely to attack their natural host, S. invicta, than they were to attack the native fire ant, S. geminata. More than 200 larvae resulted from numerous attacks on S. invicta workers. No larvae resulted from the few possible attacks on S. geminata or the other species of ants that were tested. We induced several P. tricuspis to attack a few S. geminata workers by mixing these workers in with freeze-killed S. invicta workers. One adult fly emerged from these attacks, demonstrating that P. tricuspis can develop in S. geminata workers. This indicates that the field release of P. tricuspis poses some risk to native fire ants; however, the extremely low rates of attack on S. geminata in the laboratory and in the field indicate that this risk would be minimal. The argument is made that this small risk is acceptable because, among other things, native fire ants are under much more risk from expanding populations of imported fire ants than they would be from imported Pseudacteon flies.

Perspectives on Wildfire in the Humid Tropics

Over the last 30 years our understanding of the effects of wildfire on tropical forest environments has expanded enormously. To introduce readers to this topic, we asked Christopher Uhl to recount some of his experiences studying fire in the humid tropics. His account sets the stage for four short contributions that compose this installment of Issues in International Conservation.

Reactions to less common species of fire ants

Background: There are four species of fire ants found in the United States in addition to the most common, Solenopsis invicta. Reactions have been reported from stings of each of these species, but large numbers of insects and adequate amounts of venom for study are very difficult to obtain. Methods: Venom was obtained, the purified allergens were isolated, and the complete amino acid sequences were determined for two of the three allergens from S. richteri. Skin testing and RAST studies were performed on patients with reactions to native fire ant stings and analyzed in comparison with clinical history. Results: The structures of S. richteri allergens have a high degree of similarity to S. invicta allergens. The Sol 2 allergens are less related to each other than either the Sol 1 (phospholipase AB) or Sol 3 (antigen 5) allergens. Patients sensitized to native species of fire ants react primarily to the Sol 1 and Sol 3 allergens, whereas those originally sensitized to S. invicta also react significantly to the Sol 2 and Sol 4 allergens. Some patients are initially sensitized to S. invicta and have life-threatening reactions to stings of native species. The tropical fire ant, S. geminata, has become a serious problem in some areas of the Pacific and South Asia, especially Okinawa and Guam. Conclusions: The venoms from all of the species of fire ants examined appear to be highly cross-reactive. S. invicta imported fire ant venom extracts are probably sufficient for diagnosis and may warrant a clinical trial for immunotherapy of allergic reactions to venoms of any of the other four species. (J Allergy Clin Immunol 1997;100:679-83.)

Sex–ratio regulation: the economics of fratricide in ants

In many insect societies, workers can manipulate the reproductive output of their colony by killing kin of lesser value to them. For instance, workers of the mound-building Formica exsecta eliminate male brood in colonies headed by a single-mated queen. By combining an inclusive fitness model and empirical data, we investigated the selective causes underlying these fratricides. Our model examines until which threshold stage in male brood development do the workers benefit from eliminating males to rear extra females instead. We then determined the minimal developmental stage reached by male larvae before elimination in F. exsecta field colonies. Surprisingly, many male larvae were kept until they were close to pupation, and only then eliminated. According to our model, part of the eliminated males were so large that workers would not benefit from replacing them with new females. Moreover, males were eliminated late in the season, so that new females could no longer be initiated, because matings take place synchronously during a short period. Together, these results indicate that workers did not replace male brood with new females, but rather reduced total brood size during late larval development. Male destruction was probably triggered by resource limitation, and the timing of brood elimination suggests that males may have been fed to females when these start to grow exponentially during the final larval stage. Hence, the evolution of fratricides in ants is best explained by a combination of ecological, demographic and genetic parameters.

Studies on the Life History of a Neogregarine Parasite Found in Leptothorax Ants from North America

Pupal stages of Leptothorax ants collected near West Yellowstone, MT, USA, displayed striking signs and symptoms of disease, i.e., grey to black coloration, irregular pigmentation of compound eyes and toothless mandibles. Light microscope studies revealed heavy infections by a neogregarine, the life history of which is described. The life cycle of the pathogen includes micronuclear and macronuclear schizogonies, gametogony and sporogony. Schizonts of both types vary in size depending on the number of nuclei which is usually defined by doubling, thus giving rise to 8, 16, 32, 64 or even 128 uninucleate merozoites. In smears and sections, micronuclear merozoites are typically arranged in rosettes. In the early transformation of zygotes, sickle-shaped developmental stages have been encountered, so far undescribed from neogregarines. Two spores (oocysts), each developing eight sporozoites, evolve from each gametocyst, as is typical of the genus Mattesia. Mature lemon-shaped spores measure 13.8 9.3 μm in fresh preparations. Infections can be readily transmitted to healthy colonies and to other Leptothorax species by feeding crushed infected pupae. Vegetative life cycle stages grow and multiply in the haemocoel, only to some extent they infect fat body cells. Macronuclear merozoites invade the hypodermis and the fat body but also settle extracellularly in the haemocoel. The disease process terminates with the death of the pupae that harbour abundant spores. Infections of adults have not been observed. Despite some minor differences that may result from development of the pathogen in this host, from the type, sequence and morphology of life cycle stages and from the signs and symptoms of disease, this Mattesia species is identified with M. geminata, first discovered in the tropical fire ant, Solenopsis geminata (Fabricius).

Microclimatic changes and the indirect loss of ant diversity in a tropical agroecosystem.

Recent changes in the coffee agroecosystem of Costa Rica were used to study the mechanism of biodiversity loss in transforming agroecosystems, focusing on the ground-foraging ant community. Coffee farms are being transformed from vegetationally diverse shaded agroforestry systems to unshaded coffee monocultures. We tested the hypothesis that the high-light environment and lack of leaf litter cover in the unshaded system are the determinants of the differences in ground-foraging ant diversity. Four treatments were established within the light gaps of a shaded plantation: shade, leaf litter, shade plus leaf litter, and a control (no shade or leaf litter added). Ants were sampled using tuna fish baits and light and temperature were measured. Shade and leaf litter had a significant effect on the ant fauna but probably for indirect reasons having to do with species interactions. In both shade treatments, Solenopsis geminata, the tropical fire ant, decreased significantly while the other species increased. The possibility that the physical factor changes the nature of competitive interactions between the most abundant species is discussed.