Journal articles: 'Wet-dry tropics'

1

Proctor, John, M. G. Ridpath, and L. K. Corbett. "Ecology of the Wet-Dry Tropics." Journal of Applied Ecology 24, no. 1 (April 1987): 322. http://dx.doi.org/10.2307/2403809.

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King, A. J., C. Doidge, D. Buckle, and K. J. Tyler. "Preliminary evidence of spawning phenologies of freshwater fish in a wet–dry tropical river: the importance of both wet and dry seasons." Marine and Freshwater Research 71, no. 2 (2020): 202. http://dx.doi.org/10.1071/mf18458.

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Wet–dry tropical rivers are characterised by highly predictable, yet highly variable, seasonal flow regimes. The wet season is often regarded as an important period of ecosystem productivity, dispersal and connectivity, and also for freshwater-fish spawning and recruitment. However, few studies have examined fish spawning across hydrological seasons in these rivers. We conducted a pilot study to determine (1) the temporal occurrence (and hence spawning period), and (2) the suitability of standard sampling methods of young fish in the Daly River, Northern Territory, Australia. Fish spawned throughout the year, with spawning phenologies varying substantially among species. The highest diversity and abundance of young fish occurred during the wet season, although early life stages of a high number of species were also present in the dry-season and transition periods. A high number of species spawned all year round, whereas other species had very discrete spawning periods. Three of the four sampling methods tested were successful in catching early life stages and should be employed in future studies. The present study highlighted that all hydrological seasons in the wet–dry tropics are important for fish spawning, and has important implications for future research on the drivers of spawning patterns, and for predicting the effects of flow modifications on freshwater fishes of the wet–dry tropics.

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Hong, Wenjun, Jindian Yang, Jinhuan Luo, Kai Jiang, Junze Xu, and Hui Zhang. "Reforestation Based on Mono-Plantation of Fast-Growing Tree Species Make It Difficult to Maintain (High) Soil Water Content in Tropics, a Case Study in Hainan Island, China." Water 12, no. 11 (November 3, 2020): 3077. http://dx.doi.org/10.3390/w12113077.

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Reforestation has been assumed as a natural solution to recover soil water content, thereby increasing freshwater supply. Mono-plantation of fast-growing species is the first step for performing reforestation to prevent frequent and heavy rain-induced landslide in tropics. However, fast-growing species may have negative hydraulic response to seasonal drought to maintain high growth rate and, thus, may make it difficult for reforestation in tropics to recover soil water content. We tested this hypothesis in a setting involving (a) a reforestation project, which mono-planted eight fast-growing tree species to successfully restore a 0.2-km2 extremely degraded tropical rainforest, and (b) its adjacent undisturbed tropical rainforest in Sanya City, Hainan, China. We found that, for maintaining invariably high growth rates across wet to dry seasons, the eight mono-planted fast-growing tree species had comparable transpiration rates and very high soil water uptake, which in turn led to a large (3 times) reduction in soil water content from the wet to dry seasons in this reforested area. Moreover, soil water content for the adjacent undisturbed tropical rainforest was much higher (1.5 to 5 times) than that for the reforested area in both wet and dry seasons. Thus, the invariably very high water demand from the wet to dry seasons for the mono-planted fast-growing species possesses difficulty in the recovery of soil water content. We suggest, in the next step, to mix many native-species along with the currently planted fast-growing nonnative species in this reforestation project to recover soil water content.

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WARFE, D. M., N. E. PETTIT, P. M. DAVIES, B. J. PUSEY, S. K. HAMILTON, M. J. KENNARD, S. A. TOWNSEND, et al. "The ‘wet-dry’ in the wet-dry tropics drives river ecosystem structure and processes in northern Australia." Freshwater Biology 56, no. 11 (August 11, 2011): 2169–95. http://dx.doi.org/10.1111/j.1365-2427.2011.02660.x.

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Vernes, Karl, and Lisa Claire Pope. "Reproduction in the northern brown bandicoot (Isoodon macrourus) in the Australian Wet Tropics." Australian Journal of Zoology 57, no. 2 (2009): 105. http://dx.doi.org/10.1071/zo09019.

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We investigated timing of reproduction in a wild population of northern brown bandicoots (Isoodon macrourus) in the Australian Wet Tropics. Almost all births occurred during the late dry season and early wet season, and most adult females (78–96%) were carrying pouch young during those times. Litter sizes ranged from 1 to 6 pouch young (mean = 3.1) and was not influenced by season. Adult males had significantly larger testes in the late dry and early wet seasons, corresponding with the peak in births. Daylength was the only environmental factor that predicted the presence of a litter; when daylength exceeded 12 h, more than 70% of captured females were carrying pouch young, and most (94%) births were estimated to have occurred on days with >12 h of daylight. Various environmental factors have been proposed as a cue for breeding in I. macrourus, with daylength though to be the primary cue initiating breeding in temperate Australia, but temperature and rainfall thought to be more important in the tropics. Our data suggest that in the Australian Wet Tropics, increasing daylength in the late dry season acts as the primary cue for breeding.

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Watter, Kurt, Greg S. Baxter, Anthony Pople, and Peter J. Murray. "Dietary overlap between cattle and chital in the Queensland dry tropics." Rangeland Journal 42, no. 3 (2020): 221. http://dx.doi.org/10.1071/rj20075.

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Chital deer (Axis axis) are an ungulate species introduced to northern Queensland, Australia, in an environment where land is managed for large scale cattle production. Rainfall and pasture growth are markedly seasonal and cattle experience a nutritional shortfall each year before monsoon rain. The presence of chital is perceived by land managers to reduce dry-season grass availability and this study sought to estimate the potential effect of free-living chital on regional cattle production. Diet overlap was greatest during the wet season when both ungulates principally consumed grass, and least during the dry season when chital diet comprised only ~50% grass. Using local estimates for energy values of wet and dry season grass, and the maintenance energy requirements of chital and cattle, we estimated the relative dry-matter seasonal grass intakes of both ungulates. The grass consumed annually by 100 chital could support an additional 25 cattle during the wet season and an additional 14 cattle during the dry season.

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KEMP, DARRELL J. "Reproductive seasonality in the tropical butterfly Hypolimnas bolina (Lepidoptera: Nymphalidae) in northern Australia." Journal of Tropical Ecology 17, no. 4 (July 2001): 483–94. http://dx.doi.org/10.1017/s0266467401001365.

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Because seasonality in tropical environments is driven by variation in rainfall, phytophagous tropical organisms are expected to exhibit mechanisms of escape in space and time that allow them to synchronize their breeding efforts with suitably wet periods of the year. This hypothesis was addressed by studying the breeding phenology of the nymphalid butterfly Hypolimnas bolina (L.) in the Australian wet-dry tropics. This species favours small, herbaceous larval foodplants that either die off annually or exhibit marked declines in leaf quality during the dry season. As expected, reproductive activity in H. bolina was broadly correlated with both rainfall and humidity, with individuals spending part of the dry season (early April to late August) sheltering in overwintering sites in a state of reproductive diapause. The timing of the overwintering period was similar between the 2 years, which suggests that individuals respond to seasonally predictable cues such as photoperiod. At least in 1998, the exit of butterflies from overwintering sites was relatively sudden and coincided with the first spring rainfall event. These findings suggest that H. bolina copes with seasonal adversity in the tropics by means of a regularly timed diapause.

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Pomposi, Catherine, Yochanan Kushnir, Alessandra Giannini, and Michela Biasutti. "Toward Understanding the Occurrence of Both Wet and Dry Sahel Seasons during El Niño: The Modulating Role of the Global Ocean." Journal of Climate 33, no. 4 (February 15, 2020): 1193–207. http://dx.doi.org/10.1175/jcli-d-19-0219.1.

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AbstractPrior research has shown that dry conditions tend to persist in the Sahel when El Niño develops. Yet, during the historic 2015 El Niño, Sahel summer precipitation was anomalously high, particularly in the second half of the season. This seeming inconsistency motivates a reexamination of the variability of precipitation during recent El Niño years. We identify and composite around two different outcomes for Sahel summer season: an anomalously wet season or an anomalously dry season as El Niño develops to its peak conditions over the observational record spanning 1950–2015. We find consistently cool temperatures across the global tropics outside the Niño-3.4 region when the Sahel is anomalously wet during El Niño years and a lack of cooling throughout the tropics when the Sahel is anomalously dry. The striking differences in oceanic surface temperatures between wet years and dry years are consistent with a rearrangement of the entire global circulation in favor of increased rainfall in West Africa despite the presence of El Niño.

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Singh, G., S. C. Chapman, P. A. Jackson, and R. J. Lawn. "Lodging reduces sucrose accumulation of sugarcane in the wet and dry tropics." Australian Journal of Agricultural Research 53, no. 11 (2002): 1183. http://dx.doi.org/10.1071/ar02044.

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Previous experiments in the Australian tropics have observed a 'slowdown' in biomass accumulation in mature sugarcane crops. By installing scaffolding to prevent lodging, we eliminated the growth 'slowdown' in 3 experiments to confirm that lodging and stalk death are part of the explanation. In both the wet and dry (irrigated) tropics, lodging of sugarcane significantly decreased both fresh cane yield and commercial cane sugar content (CCS). Prevention of lodging increased cane yield by 11–15%, CCS by 3–12%, and sugar yield by 15–35% at the final harvest in August–September. The rate of increase in CCS in lodged cane was reduced following lodging, although CCS had partially recovered by harvest.A possible component of the lodging effect is a slowdown in the growth due to the ageing of the crop. However, a younger crop (late crop treatment) grew no faster than the scaffolded treatment and so discounted this. In the dry tropics, where cane is irrigated and grows under high radiation, sugar yield was 40 t/ha with scaffolding installed. The increased yield (compared with 35 t/ha in lodged cane) was due to both the survival of an extra 0.8 stalks/m2 and increased accumulation of sugar in live stalks. In 2 years in the wet tropics where sugar yield with scaffolding was 16 t/ha, the same factors, with the addition of increased biomass accumulation in live stalks, were responsible for the increase.

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10

Olawuwo, O. S. "Seasonal Fluctuations In Luteinizing Hormones (lh), Follicle Stimulating Hormones (FSH) And Testosterone Levels In Male African Giant Rats." Journal of Veterinary and Biomedical Sciences 2, no. 2 (December 1, 2020): 161–70. http://dx.doi.org/10.36108/jvbs/9102.20.0281.

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As part of the several efforts to understand the biology of the African Giant rats (AGR) (Cricetomys gambianus), seasonal changes in the gonadotropin and testosterone levels of the adult male African giant rats of about 1 – 1½ years of age in captivity were investigated during wet and dry seasons in the tropics. Male giant rats (n = 10) were kept for 12 months and blood samples were collected monthly (on 15th of each month), during the dry (November – February) and wet (March – June) seasons for Luteinizing hormone (LH), follicle stimulating hormone (FSH) and testosterone assays. The hormones’ levels were evaluated to suggest the best breeding season for giant rat in South-West Nigeria. The result showed that there were significant variation (p<0.001) in LH and FSH levels in the giant rat in the wet season when compared with the dry season. However, testosterone level was significantly lower (p<0.001) in the wet season than in the dry season. The study showed that sexual activities in the male AGR might be higher in the dry season with peak activities in December in the tropics while the gonadotropins prepare the animals for sexual activities in the dry season. Further studies on the seasonal activities of gonadotropins in the female will give more insight into the sexual receptivity and performance in these animals.

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11

Vernes, Karl, Lisa C. Pope, Christopher J. Hill, and Felix Bärlocher. "Seasonality, dung specificity and competition in dung beetle assemblages in the Australian Wet Tropics, north-eastern Australia." Journal of Tropical Ecology 21, no. 1 (January 2005): 1–8. http://dx.doi.org/10.1017/s026646740400224x.

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A trapping study of five mammal species in wet sclerophyll forest adjacent to rain forest in the Australian Wet Tropics was used to examine the seasonal diversity, abundance and dung-specificity of dung beetles associated with mammal dung. A total of 542 dung beetles from 11 species within three genera was recovered from beneath the traps of 1104 mammal captures. The diversity of beetles associated with the dung of the northern bettong (Bettongia tropica), a mycophagous marsupial, differed significantly from the diversity predicted by a null model. Numbers of beetles varied significantly with type of dung, indicating preference by beetles. Beetle numbers were related positively to a 1-mo lag in monthly mean minimum temperature and less strongly to maximum temperature and rainfall. Significantly more beetles per mammal capture were detected in the wet season than in the dry season. Dung beetles showed a strong preference for either the Eucalyptus woodland (six species) or the adjacent Allocasuarina forest (four species), with only one species occurring in both habitat types. Beetle species from the Eucalyptus woodland were typically only detected in the late wet and early dry seasons, while species in the wetter Allocasuarina forest were generally collected during the late dry and early wet seasons. A significant ‘checkerboard’ species effect was detected in both time and space in both habitat types, suggesting that competition for dung was strong.

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12

Watter, Kurt, Greg Baxter, Michael Brennan, Tony Pople, and Peter Murray. "Seasonal diet preferences of chital deer in the northern Queensland dry tropics, Australia." Rangeland Journal 42, no. 3 (2020): 211. http://dx.doi.org/10.1071/rj20015.

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Chital deer (Axis axis) were introduced to the Burdekin dry tropics of north Queensland, Australia, in the late 1800s. Here rainfall and plant growth are highly seasonal and a nutritional bottleneck for grazing animals occurs annually before the wet season. This study describes the seasonal changes in diet and diet preference of chital in this seasonally-variable environment. Rumen samples were taken from 162 deer from two sites over the wet and dry seasons of two consecutive years and sorted macroscopically for identification. Relative seasonal availability of plant groups was estimated using step point sampling of areas grazed by chital. Chital alter their diet seasonally according to availability and plant phenology. Chital utilised 42 plant genera including grasses, forbs, subshrubs, shrubs, trees and litter. Grass consumption ranged from 53% of biomass intake during the dry season to 95% during the wet season. The predominance of grass in the wet season diet exceeded relative availability, indicating a strong preference. Although grass contributed more than half of the dry season diet it was the least preferred plant group, given availability, and the least actively growing. Shrubs were the preferred plant type in the dry season, and least subject to seasonal senescence. Composition and quantity of seasonal pastures vary markedly in north Queensland, and chital alter their diet by consuming those plants most actively growing. The increased dry season intake of non-grass forage appears to be a strategy to limit the detriment resulting from the progressive deterioration in the quality of grass.

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Davis, Aaron M., Richard G. Pearson, Jon E. Brodie, and Barry Butler. "Review and conceptual models of agricultural impacts and water quality in waterways of the Great Barrier Reef catchment area." Marine and Freshwater Research 68, no. 1 (2017): 1. http://dx.doi.org/10.1071/mf15301.

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Adequate conceptual frameworks that link land use to water quality and ecosystem health are lacking for tropical and subtropical freshwater systems, so we review here extensive water-quality research undertaken in the Great Barrier Reef catchment area (GBRCA) and present conceptual models synthesising the dynamics of agricultural pollutants and their ecological effects. The seasonal flow regime defines the following key periods of water-quality risk over the annual hydrological cycle for diverse GBRCA ecosystems: initial ‘pre-flush’ flows during the transition from the dry to the wet season; early wet-season ‘first flush’ flows; peak wet-season flood flows; and sustained base flow or periods of disconnection during the dry season. The level of seasonal contrast varies from the perennial systems of the wet tropics to the intermittent systems of the dry tropics. Major water-quality stressors may be catchment scale (e.g. in streams draining broad-scale agriculture) or more localised (e.g. cattle access, irrigation tail water). Water-quality stressors such as ammonia toxicity and hypoxia (due to organic or nutrient run-off and enhanced plant productivity) are of low relevance to downstream GBR ecosystems but are major threats to fresh waters. Similarly, whereas high contaminant loads in wet-season floods present the highest water-quality risk to marine ecosystems, the greatest risk in fresh waters is often from acute contamination during early wet-season ‘pre-flush’ flows into lentic waters, or continuous input of contaminants over long periods of base flow. Because of differences in the nature of risk periods, water-quality threats and pollutant-delivery mechanisms, the benefits of different management options to improve water quality can also differ among freshwater habitats and between freshwater and marine environments.

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Fritz, Sherilyn C., Paul A. Baker, Tim K. Lowenstein, Geoffrey O. Seltzer, Catherine A. Rigsby, Gary S. Dwyer, Pedro M. Tapia, Kimberly K. Arnold, Teh-Lung Ku, and Shangde Luo. "Hydrologic variation during the last 170,000 years in the southern hemisphere tropics of South America." Quaternary Research 61, no. 1 (January 2004): 95–104. http://dx.doi.org/10.1016/j.yqres.2003.08.007.

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Despite the hypothesized importance of the tropics in the global climate system, few tropical paleoclimatic records extend to periods earlier than the last glacial maximum (LGM), about 20,000 years before present. We present a well-dated 170,000-year time series of hydrologic variation from the southern hemisphere tropics of South America that extends from modern times through most of the penultimate glacial period. Alternating mud and salt units in a core from Salar de Uyuni, Bolivia reflect alternations between wet and dry periods. The most striking feature of the sequence is that the duration of paleolakes increased in the late Quaternary. This change may reflect increased precipitation, geomorphic or tectonic processes that affected basin hydrology, or some combination of both. The dominance of salt between 170,000 and 140,000 yr ago indicates that much of the penultimate glacial period was dry, in contrast to wet conditions in the LGM. Our analyses also suggest that the relative influence of insolation forcing on regional moisture budgets may have been stronger during the past 50,000 years than in earlier times.

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Samaniego-Herrera, Araceli, Alfonso Aguirre-Muñoz, Yuliana Bedolla-Guzmán, Ana Cárdenas-Tapia, María Félix-Lizárraga, Federico Méndez-Sánchez, Orlando Reina-Ponce, Evaristo Rojas-Mayoral, and Flor Torres-García. "Eradicating invasive rodents from wet and dry tropical islands in Mexico." Oryx 52, no. 3 (February 9, 2017): 559–70. http://dx.doi.org/10.1017/s0030605316001150.

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AbstractEradications of invasive rodents from tropical islands have a lower success rate compared to temperate islands. In the tropics the wide range of physical and biological conditions results in a wide variety of island biomes, with unique challenges and windows of opportunity for rodent eradications. We describe and compare research and operational details of six successful eradications of invasive mice Mus musculus and ship rats Rattus rattus carried out during 2011–2015. The work was conducted on six islands in two distinct tropical archipelagos in Mexico (one dry in the Gulf of Mexico; one wet in the Caribbean), and included the first eradication of rats from a mangrove-dominated island > 500 ha. Invasive rodent populations varied among species and islands, even neighbouring islands; overall density was higher on wet islands. Physical and biological features, including the presence of land crabs, determined eradication timing and rates of bait broadcast (higher on wet islands). An interval of 6–10 days between the two bait applications per island was sufficient to eradicate actively breeding mouse and rat populations. Impacts on non-target species were negligible, including those on wild and captive iguanas. Eradication success was rapidly confirmed based on ground monitoring and statistical modelling. Rodent eradications on larger tropical islands should be achievable with directed research to inform planning and implementation.

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Schmeißner, T., R. Krejci, J. Ström, W. Birmili, A. Wiedensohler, G. Hochschild, J. Gross, P. Hoffmann, and S. Calderon. "Aerosol particle properties in the tropical free troposphere observed at Pico Espejo (4765 m a.s.l.), Venezuela." Atmospheric Chemistry and Physics Discussions 10, no. 11 (November 30, 2010): 29153–89. http://dx.doi.org/10.5194/acpd-10-29153-2010.

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Abstract. The first long-term measurements of aerosol number and size distributions in South-American tropical free troposphere were performed from March 2007 until Mai 2009. The measurements took place at the high altitude Atmospheric Research Station Alexander von Humboldt. The station is located on top of the Sierra Nevada mountain ridge at 4765 m a.s.l. nearby the city of Mérida, Venezuela. Aerosol size distribution and number concentration data was obtained with a custom-built Differential Mobility Particle Sizer (DMPS system) and a Condensational Particle Counter (CPC). The analysis of the annual and diurnal variability of the tropical free troposphere (FT) aerosol focused mainly on possible links to the atmospheric general circulation in the tropics. Considerable annual and diurnal cycles of the particle number concentration were observed. Highest total particle number concentrations were measured during the dry season (519±613 cm−3), lowest during the wet season (318±194 cm−3). The more humid FT contained generally higher aerosol particle number concentrations (573±768 cm−3 during dry season, 320±195 cm−3 during wet season) than the dry FT (454±332 cm−3 during dry season, 275±172 cm−3 during wet season), indicating the importance of convection for aerosol distributions in the tropical FT. The diurnal cycle in the variability of the particle number concentration was mainly driven by local orography.

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17

Watt, Annemarie. "Population Ecology and Reproductive Seasonality in Three Species of Antechinus (Marsupialia : Dasyuridae) in the Wet Tropics of Queensland." Wildlife Research 24, no. 5 (1997): 531. http://dx.doi.org/10.1071/wr96033.

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The population and reproductive ecologies of three sympatric species of antechinus were examined in upland rainforests in the wet tropics of Queensland. The three species, Antechinus stuartii adustus, A. flavipes rubeculus and A. godmani, exhibited unusually low trapping success compared with that of sites in temperate regions of Australia. Spatial distributions were extremely patchy both between and within study sites. Comparison with trapping data for temperate populations of A. stuartii and A. flavipes suggests that densities in the wet tropics are among the lowest in Australia. The reproductive season was similar for the three species, commencing during the mid-dry season with juveniles weaned by the early to mid-wet season. The phenomenon of male die-off was observed in the three species. However, the highly synchronous two- week breeding season observed in temperate populations of A. stuartii and A. flavipes was not observed in the tropical populations. The breeding season of the tropical species extended over a six- week period. Timing of reproduction in A. s. adustus and A. f. rubeculus was more similar to temperate than to subtropical populations of A. s. stuartii and A. f. flavipes.

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AW0JOBI, H. A., and O. O. MESHIOYE. "A COMPARISON OF WET MASH AND DRY MASH FEEDING FOR BROILER FINISHER DURING WET SEASON IN TIIE TROPICS." Nigerian Journal of Animal Production 28, no. 2 (January 4, 2021): 143–46. http://dx.doi.org/10.51791/njap.v28i2.1862.

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An experiment was conducted to compare wet mash and conventional dry mash feeding for finisher broilers. Feed intake, live-weight gain, feed efficiency and weights of heart, crop, and abdominal fat deposit were significantly (P<0.05) higher in broilers receiving the wet mash. Water intake and gizzard weight were significantly (P<0.05) higher in birds fed dry mash. No significant (P<0.05) differences were observed in dressing percentage, weights of liver, intestine and the proventriculus. The results of this experiment demonstrated that wet feeding is not deleterious to the performance of broilers in the tropics. It also concluded that wet feeding is desirable not under hot weather conditions alone, but also during the rainy season.

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PRICE-REES, SAMANTHA J., GREGORY P. BROWN, and RICHARD SHINE. "Spatial ecology of bluetongue lizards (Tiliquaspp.) in the Australian wet-dry tropics." Austral Ecology 38, no. 5 (August 20, 2012): 493–503. http://dx.doi.org/10.1111/j.1442-9993.2012.02439.x.

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Townsend, Simon A., Kevin T. Boland, and Tim J. Wrigley. "Factors contributing to a fish kill in the Australian wet/dry tropics." Water Research 26, no. 8 (August 1992): 1039–44. http://dx.doi.org/10.1016/0043-1354(92)90139-u.

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Safarova, Shokhida, Edward Halawa, Andrew Campbell, Lisa Law, and Joost van Hoof. "Pathways for optimal provision of thermal comfort and sustainability of residential housing in hot and humid tropics of Australia – A critical review." Indoor and Built Environment 27, no. 8 (March 27, 2017): 1022–40. http://dx.doi.org/10.1177/1420326x17701805.

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The optimal provision of thermal comfort and energy efficiency for residential housing in the hot and humid tropics presents challenges and opportunities for housing and subdivision designs. Climatic challenges come in the form of high ambient temperature and humidity, especially during the wet season and transition periods. On the other hand, climatic advantages come in the form of breezes coupled with relatively dry air during the dry season, enabling thermal comfort attainment through natural ventilation that employs prevailing breezes. This paper discusses existing design practices for housing and subdivisions in the hot and humid tropics with particular reference to the city of Darwin in Australia’s Northern Territory. This includes several research issues and gaps that have been identified and need to be addressed. The paper also critically assesses how air speed, air temperature and humidity – three of the thermal comfort parameters – play a key role in housing and subdivision design consideration in the hot and humid tropics. In doing so, the paper sheds light on the inadequacy of the current residential energy rating methodology as a tool for assessing tropical housing performance and proposes a new direction for future research to ameliorate these issues for the tropics.

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Mahindawansha, Amani, Christoph Külls, Philipp Kraft, and Lutz Breuer. "Investigating unproductive water losses from irrigated agricultural crops in the humid tropics through analyses of stable isotopes of water." Hydrology and Earth System Sciences 24, no. 7 (July 22, 2020): 3627–42. http://dx.doi.org/10.5194/hess-24-3627-2020.

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Abstract. Reliable information on water flow dynamics and water losses via irrigation on irrigated agricultural fields is important to improve water management strategies. We investigated the effect of season (wet season and dry season), irrigation management (flooded and non-flooded), and crop diversification (wet rice, dry rice, and maize) on soil water flow dynamics and water losses via evaporation during plant growth. Soil water was extracted and analysed for the stable isotopes of water (δ2H and δ18O). The fraction of evaporation losses were determined using the Craig–Gordon equation. For dry rice and maize, water in shallow soil layers (0 to 0.2 m) was more isotopically enriched than in deeper soil layers (below 0.2 m). This effect was less pronounced for wet rice but still evident for the average values at both soil depths and seasons. Soil water losses due to evaporation decreased from 40 % at the beginning to 25 % towards the end of the dry season. The soil in maize fields showed stronger evaporation enrichment than in rice during that time. A greater water loss was encountered during the wet season, with 80 % at the beginning of the season and 60 % at its end. The isotopic enrichment of ponding surface water due to evaporation was reflected in the shallow soils of wet rice. It decreased towards the end of both growing seasons during the wet and the dry season. We finally discuss the most relevant soil water flow mechanisms, which we identified in our study to be those of matrix flow, preferential flow through desiccation cracks, and evaporation. Isotope data supported the fact that unproductive water losses via evaporation can be reduced by introducing dry seasonal crops to the crop rotation system.

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Stirrat, Simon C. "Body condition and blood chemistry of agile wallabies (Macropus agilis) in the wet - dry tropics." Wildlife Research 30, no. 1 (2003): 59. http://dx.doi.org/10.1071/wr01041.

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Seasonal differences in body condition, haematology and serum chemistry of agile wallabies (Macropus agilis) in the wet–dry tropics are described. The mass of wallabies caught in the dry season was lower than predicted for their body size (on the basis of leg length), indicating that they were in poorer condition in the dry season than in the wet season. Several haematology and serum chemistry values indicated that wallabies captured in the late dry season were in an early stage of undernutrition. Plasma and serum protein, serum albumin and serum urea concentrations, all indicators of recent protein intake, and packed cell volume and mean corpuscular volume were lower in the late dry season. However, the results for energy balance were inconclusive. Serum glucose concentration did not vary between seasons, while cholesterol concentration was lower and non-esterified fatty acid concentration was higher in the dry season. The wallabies foraged for a range of alternative food resources in the dry season, when preferred foods were scarce and of poorer quality. The results presented here indicate that although wallabies broadened their diet in the dry season, they were unable to maintain adequate nutritional intake to prevent loss of body condition.

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Schmeissner, T., R. Krejci, J. Ström, W. Birmili, A. Wiedensohler, G. Hochschild, J. Gross, P. Hoffmann, and S. Calderon. "Analysis of number size distributions of tropical free tropospheric aerosol particles observed at Pico Espejo (4765 m a.s.l.), Venezuela." Atmospheric Chemistry and Physics 11, no. 7 (April 7, 2011): 3319–32. http://dx.doi.org/10.5194/acp-11-3319-2011.

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Abstract. The first long-term measurements of aerosol number and size distributions in South-American tropical free troposphere (FT) were performed from March 2007 until March 2009. The measurements took place at the high altitude Atmospheric Research Station Alexander von Humboldt. The station is located on top of the Sierra Nevada mountain ridge at 4765 m a.s.l. nearby the city of Mérida, Venezuela. Aerosol size distribution and number concentration data was obtained with a custom-built Differential Mobility Particle Sizer (DMPS) system and a Condensational Particle Counter (CPC). The analysis of the annual and diurnal variability of the tropical FT aerosol focused mainly on possible links to the atmospheric general circulation in the tropics. Considerable annual and diurnal cycles of the particle number concentration were observed. Highest total particle number concentrations were measured during the dry season (January–March, 519 ± 613 cm−3), lowest during the wet season (July–September, 318 ± 194 cm−3). The more humid FT (relative humidity (RH) range 50–95 %) contained generally higher aerosol particle number concentrations (573 ± 768 cm−3 during dry season, 320 ± 195 cm−3 during wet season) than the dry FT (RH < 50 %, 454 ± 332 cm−3 during dry season, 275 ± 172 cm−3 during wet season), indicating the importance of convection for aerosol distributions in the tropical FT. The diurnal cycle in the variability of the particle number concentration was mainly driven by local orography.

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OLADIMEJI, B. S., O. A. OSINOWO,, J. P. ALAWA, and J. O. HAMBOLU. "SEASONAL EFFECTS ON OESTRUS PATTERNS AND PROGESTERONE PROFILES OF YANKASA EWES OF DIFFERENT AGE-GROUPS IN THE SUB-HUMID TROPICS." Nigerian Journal of Animal Production 28, no. 2 (January 4, 2021): 211–16. http://dx.doi.org/10.51791/njap.v28i2.1938.

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Oestrus patterns and serum progesterone profiles of 10 adult and 10 yearling Yankasa ewes were investigated in the late hot-dry and late-wet seasons in the subhumid tropical climate of Zaria, Nigeria. The proportions of ewes which came on heat once, twice or thrice within the experimental periods in the late hot-dry and late-wet seasons were 25, 15 and 0%, and 5, 10 and 85% respectively, while mean oestrous cycle length was significantly longer (P<0.001) in the hot-dry season than in the late-wet season (30.9 vs 18.4 days) due to the higher incidence of anoestrus in the former. However, the mean duration of oestrus was not affected by season. Mean serum progesterone levels were significantly (P<0.05) higher in the late-wet season than in the late hot-dry season (1.57 vs 0.52 ng/ml). However, there was a highly significant (P<0.001) interaction between season and age group in mean serum progesterone levels due to a relatively greater depression in progesterone levels in yearling ewes during the hot-dry season compared with adult ewes. The observed disruptions in the oestrus cycle and serum progesterone levels of the ewes in the hot-dry season confirm the adverse effect of heat stress on the reproductive behaviour of ewes.

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Anders, Alison M., and Stephen W. Nesbitt. "Altitudinal Precipitation Gradients in the Tropics from Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar." Journal of Hydrometeorology 16, no. 1 (February 1, 2015): 441–48. http://dx.doi.org/10.1175/jhm-d-14-0178.1.

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Abstract A Tropical Rainfall Measuring Mission (TRMM) climatology shows variability in surface precipitation rate–elevation relationships across the tropics. Vertical profiles of radar reflectivity and profiles of specific humidity and cross-barrier moisture fluxes during precipitation events from the Interim European Centre for Medium-Range Weather Forecasts Re-Analysis reveal four precipitation regimes with distinct precipitation mechanisms: 1) a tropical regime with a broad precipitation maximum at ~1500 m where convection is triggered by orographic lifting; 2) a trade winds regime with a near–sea level precipitation maximum dominated by forced ascent due to prevailing winds and the presence of dry air aloft; 3) a wet monsoon regime with a low-elevation precipitation maximum driven by efficient precipitation generation, large low-level cross-barrier moisture fluxes, and multiple convective modes; and 4) a dry monsoon regime with a high-elevation precipitation maximum reflecting intense convection and stratiform rain with a strong evaporation signature. In general, surface precipitation–elevation relationships across the tropics feature lower-elevation precipitation maxima relative to typical midlatitude regimes.

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Pettit, N. E., T. D. Jardine, S. K. Hamilton, V. Sinnamon, D. Valdez, P. M. Davies, M. M. Douglas, and S. E. Bunn. "Seasonal changes in water quality and macrophytes and the impact of cattle on tropical floodplain waterholes." Marine and Freshwater Research 63, no. 9 (2012): 788. http://dx.doi.org/10.1071/mf12114.

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The present study indicates the critical role of hydrologic connectivity in floodplain waterholes in the wet–dry tropics of northern Australia. These waterbodies provide dry-season refugia for plants and animals, are a hotspot of productivity, and are a critical part in the subsistence economy of many remote Aboriginal communities. We examined seasonal changes in water quality and aquatic plant cover of floodplain waterholes, and related changes to variation of waterhole depth and visitation by livestock. The waterholes showed declining water quality through the dry season, which was exacerbated by more frequent cattle usage as conditions became progressively drier, which also increased turbidity and nutrient concentrations. Aquatic macrophyte biomass was highest in the early dry season, and declined as the dry season progressed. Remaining macrophytes were flushed out by the first wet-season flows, although they quickly re-establish later during the wet season. Waterholes of greater depth were more resistant to the effects of cattle disturbance, and seasonal flushing of the waterholes with wet-season flooding homogenised the water quality and increased plant cover of previously disparate waterholes. Therefore, maintaining high levels of connectivity between the river and its floodplain is vital for the persistence of these waterholes.

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Stirrat, Simon C. "Foraging ecology of the agile wallaby (Macropus agilis) in the wet - dry tropics." Wildlife Research 29, no. 4 (2002): 347. http://dx.doi.org/10.1071/wr01028.

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Seasonal changes in diet composition and diet preferences of the agile wallaby (Macropus agilis) were investigated in East Point Reserve, Darwin. The wallabies were almost exclusively grazers in the wet season when the nitrogen content and in vitro digestibility of herbage were high. Evidence suggests that wallabies rarely browsed in the wet season. The diet consisted mainly of non-leguminous forbs, reflecting the abundance of these plants in the study site, but the wallabies showed higher preference for grasses and legumes. In the dry season herbage quality was poor and the wallabies grazed on available green grasses and forbs but also broadened their diet considerably to include a range of alternative foods, including browse, leaf litter, fruits, flowers and roots. A flexible foraging strategy allows agile wallabies to exploit a range of resources in this highly seasonal environment where periods of food shortage may be long and their duration unpredictable.

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Duong, Thi Thuy, Hai Yen Nguyen, Thi Phuong Quynh Le, Trung Kien Nguyen, Thi Thu Huong Tran, Nhu Da Le, Dinh Kim Dang, Thi Nguyet Vu, Virginia Panizzo, and Suzanne McGowan. "Transitions in diatom assemblages and pigments through dry and wet season conditions in the Red River, Hanoi (Vietnam)." Plant Ecology and Evolution 152, no. 2 (July 9, 2019): 163–77. http://dx.doi.org/10.5091/plecevo.2019.1627.

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Background and aims – Biomonitoring is an important tool for assessing river water quality, but is not routinely applied in tropical rivers. Marked hydrological changes can occur between wet and dry season conditions in the tropics. Thus, a prerequisite for ecological assessment is that the influence of ‘natural’ hydrological change on biota can be distinguished from variability driven by water quality parameters of interest. Here we aimed to (a) assess seasonal changes in water quality, diatoms and algal assemblages from river phytoplankton and artificial substrates through the dry-wet season transition (February–July 2018) in the Red River close to Hanoi and (b) evaluate the potential for microscopic counts and high-performance liquid chromatography (HPLC) analysis of chlorophyll and carotenoid pigments for biomonitoring in large tropical rivers. Methods – River water (phytoplankton) and biofilms grown on artificial glass substrates were sampled monthly through the dry (February–April) to wet (May–August) season transition and analysed via microscopic and HPLC techniques. Key results – All phototrophic communities shifted markedly between the dry and wet seasons. Phytoplankton concentrations were low (c. thousands of cells/mL) and declined as the wet season progressed. The dominant phytoplankton taxa were centric diatoms (Aulacoseira granulata and Aulacoseira distans) and chlorophytes (Scenedesmus and Pediastrum spp.), with chlorophytes becoming more dominant in the wet season. Biofilm diatoms were dominated by Melosira varians, and areal densities declined in the wet season when fast-growing pioneer diatom taxa (e.g. Achnanthidium minutissimum, Planothidium lanceolatum) and non-degraded Chlorophyll a concentrations increased, suggesting active phytobenthos growth in response to scour damage. Otherwise, a-phorbins were very abundant in river seston and biofilms indicating in situ Chlorophyll a degradation which may be typical of tropical river environments. The very large range of total suspended solids (reaching > 120 mg/L) and turbidity appears to be a key driver of photoautotrophs through control of light availability. Conclusions – Hydrological change and associated turbidity conditions exceed nutrient influences on photoautotrophs at inter-seasonal scales in this part of the Red River. Inter-seasonal differences might be a useful measure for biomonitoring to help track how changes in suspended solids, a major water quality issue in tropical rivers, interact with other variables of interest.

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Agnew, Danelle, Kirstie A. Fryirs, Timothy J. Ralph, and Tsuyoshi Kobayashi. "Soil carbon dynamics and aquatic metabolism of a wet–dry tropics wetland system." Wetlands Ecology and Management 29, no. 1 (January 8, 2021): 1–25. http://dx.doi.org/10.1007/s11273-020-09745-w.

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Saunders, N. J., and W. L. Peirson. "Climate change adaptation of urban water management systems in the wet/dry tropics." Australasian Journal of Water Resources 17, no. 2 (January 2013): 180–92. http://dx.doi.org/10.7158/w13-016.2013.17.2.

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32

Kirkpatrick, J. B., R. J. Fensham, M. Nunez, and D. M. J. S. Bowman. "Vegetation-radiation relationships in the wet-dry tropics: granite hills in northern Australia." Vegetatio 76, no. 3 (September 1988): 103–12. http://dx.doi.org/10.1007/bf00045472.

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Woinarski, John. "Range extension of the Inland Thornbill Acanthiza apicalis into the wet-dry tropics." Northern Territory Naturalist 16 (July 2000): 28–31. http://dx.doi.org/10.5962/p.295556.

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Davis, Aaron M., Bradley J. Pusey, and Richard G. Pearson. "Contrasting intraspecific dietary shifts in two terapontid assemblages from Australia’s wet-dry tropics." Ecology of Freshwater Fish 21, no. 1 (July 28, 2011): 42–56. http://dx.doi.org/10.1111/j.1600-0633.2011.00521.x.

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35

Braithwaite, Richard W. "Effects of fire regimes on lizards in the wet-dry tropics of Australia." Journal of Tropical Ecology 3, no. 3 (August 1987): 265–75. http://dx.doi.org/10.1017/s0266467400002145.

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ABSTRACTA quantitative analysis of the effect of fire regime on the abundance of common lizard species and genera and the species richness of two lizard groups in Kakadu National Park (12° S) is presented. A surprising range of relationships between species abundance and components of fire regimes was revealed. Carlia amax, Heteronotia binoei and Carlia gracilis appear to be fire-sensitive, Diporiphora bilineata and Carlia triacantha are favoured by early hot fires, Cryptoblepharus plagiocephalus seems relatively unaffected, Carlia foliorum seems very tolerant of fires, while Ctenotus and Sphenomorphus spp. are favoured by low intensity, patchy fires with high intensity spots.Lizard species experiencing the high-frequency fire regimes of the savannas and dry forests of the Australian wet-dry tropics are not able to select habitat at different stages of regeneration after fire but select habitat produced by fires of different types. The implication for management is that no one fire regime is optimal for the fauna as a whole. A range of fire regimes within a park should be maintained in order to retain the whole fauna.

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O'Grady, Anthony P., Derek Eamus, Peter G. Cook, and Sebastien Lamontagne. "Groundwater use by riparian vegetation in the wet - dry tropics of northern Australia." Australian Journal of Botany 54, no. 2 (2006): 145. http://dx.doi.org/10.1071/bt04164.

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Within Australia and globally there is considerable concern about the potential impacts of groundwater extraction on ecosystems dependent on groundwater. In this study we have combined heat pulse and isotopic techniques to assess groundwater use by riparian vegetation along the Daly River in the Northern Territory. The riparian forests of the Daly River exhibited considerable structural and floristic complexity. More than 40 tree species were recorded during vegetation surveys and these exhibited a range of leaf phonologies, implying complex patterns of water resource partitioning within the riparian forests. Water use was a function of species and season, and stand water use varied between 1.8 and 4.1 mm day–1. In general, however, water use tended to be higher in the wet season than during the dry season, reflecting the contribution to stand water use by dry-season deciduous tree species. There was a strong relationship between stand basal area and stand water use in the wet season, but the strength of this relationship was lower in the dry season. The amount of groundwater use, as determined by analysis of deuterium concentrations in xylem sap, was principally a function of position in the landscape. Trees at lower elevations, closer to the river, used more groundwater than trees higher on the levees. By using a combination of techniques we showed that riparian vegetation along the Daly River was highly groundwater dependent and that these water-use requirements need to be considered in regional management plans for groundwater.

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BRABY, M. F. "Phenotypic Variation in AdultMycalesisHübner (Lepidoptera: Nymphalidae: Satyrinae) from the Australian Wet-dry Tropics." Australian Journal of Entomology 33, no. 4 (November 1994): 327–36. http://dx.doi.org/10.1111/j.1440-6055.1994.tb01240.x.

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38

Brusch, George A., Keith Christian, Gregory P. Brown, Richard Shine, and Dale F. DeNardo. "Dehydration enhances innate immunity in a semiaquatic snake from the wet-dry tropics." Journal of Experimental Zoology Part A: Ecological and Integrative Physiology 331, no. 4 (March 14, 2019): 245–52. http://dx.doi.org/10.1002/jez.2260.

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Brown, Gregory P., Richard Shine, and Thomas Madsen. "Responses of three sympatric snake species to tropical seasonality in northern Australia." Journal of Tropical Ecology 18, no. 4 (July 2002): 549–68. http://dx.doi.org/10.1017/s0266467402002365.

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In the Australian wet–dry tropics, temperatures are high year-round but rainfall is concentrated in a 4-mo wet season. Regular nightly surveys in the Fogg Dam Nature Reserve provided data on temporal (monthly, seasonal) variation in biological attributes of three snake species: water pythons (Liasis fuscus, Pythonidae), keelbacks (Tropidonophis mairii, Colubridae) and slatey-grey snakes (Stegonotus cucullatus, Colubridae). Adults of all three taxa were encountered more frequently during the dry season than the wet season, whereas juveniles were more commonly encountered in the wet season. The sex ratio among adult snakes also shifted seasonally, but in different ways in different species. These sex-ratio shifts probably reflect reproductive activity (mate-searching by males, oviposition migrations by females) and were accompanied by increased encounter rates. Feeding rates and body condition of keelbacks (a frog specialist) were highest during the wet season when frogs were most abundant. Rats migrated away from Fogg Dam during the wet season, and most pythons (rat specialists) left this area to follow their prey. The pythons that remained at Fogg Dam exhibited low feeding rates and poor body condition. Slatey-grey snakes (a generalist predator) showed less seasonal variation in feeding rates or body condition. Our data show that tropical seasonality induces strong fluctuations in many attributes of snake populations, and that patterns of response differ both among and within species.

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Muza, Michel N., Leila M. V. Carvalho, Charles Jones, and Brant Liebmann. "Intraseasonal and Interannual Variability of Extreme Dry and Wet Events over Southeastern South America and the Subtropical Atlantic during Austral Summer." Journal of Climate 22, no. 7 (April 1, 2009): 1682–99. http://dx.doi.org/10.1175/2008jcli2257.1.

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Abstract Intraseasonal and interannual variability of extreme wet and dry anomalies over southeastern Brazil and the western subtropical South Atlantic Ocean are investigated. Precipitation data are obtained from the Global Precipitation Climatology Project (GPCP) in pentads during 23 austral summers (December–February 1979/80–2001/02). Extreme wet (dry) events are defined according to 75th (25th) percentiles of precipitation anomaly distributions observed in two time scales: intraseasonal and interannual. The agreement between the 25th and 75th percentiles of the GPCP precipitation and gridded precipitation obtained from stations in Brazil is also examined. Variations of extreme wet and dry anomalies on interannual time scales are investigated along with variations of sea surface temperature (SST) and circulation anomalies. The South Atlantic SST dipole seems related to interannual variations of extreme precipitation events over southeastern Brazil. It is shown that extreme wet and dry events in the continental portion of the South Atlantic convergence zone (SACZ) are decoupled from extremes over the oceanic portion of the SACZ and there is no coherent dipole of extreme precipitation regimes between tropics and subtropics on interannual time scales. On intraseasonal time scales, the occurrence of extreme dry and wet events depends on the propagation phase of extratropical wave trains and consequent intensification (weakening) of 200-hPa zonal winds. Extreme wet and dry events over southeastern Brazil and subtropical Atlantic are in phase on intraseasonal time scales. Extreme wet events over southeastern Brazil and subtropical Atlantic are observed in association with low-level northerly winds above the 75th percentile of the seasonal climatology over central-eastern South America. Extreme wet events on intraseasonal time scales over southeastern Brazil are more frequent during seasons not classified as extreme wet or dry on interannual time scales.

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Chan, Eric K. W., Yixin Zhang, and David Dudgeon. "Arthropod 'rain' into tropical streams: the importance of intact riparian forest and influences on fish diets." Marine and Freshwater Research 59, no. 8 (2008): 653. http://dx.doi.org/10.1071/mf07191.

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Terrestrial arthropods might represent an important energy source for stream predators, but these trophic linkages have seldom been studied in the tropics. Terrestrial arthropod inputs (essentially, arthropod ‘rain’) into four streams with different riparian vegetation (two draining shrublands and two draining forests) were measured over three consecutive seasons (dry, wet, dry) from 2005 to 2007 in monsoonal Hong Kong. Predatory minnows, Parazacco spilurus (Cyprinidae), were collected and their consumption of terrestrial arthropods was estimated. Inputs of arthropods were dominated by Diptera, Collembola, Formicidae and aerial Hymenoptera, accounting for ≥73% of the arthropod abundance. Seasonal variation was marked: numbers in the dry seasons were approximately half (47–57%) those in the wet season, and biomass fell to one-third (33–37%) of the wet-season value. Shrubland streams received 19–43% fewer individuals and 6–34% less biomass than shaded forest streams. An analysis of fish diets in three of the four streams showed that terrestrial insects and spiders were more important prey in the two forest streams, accounting for 35–43% of prey abundance (39–43% by volume) v. 28% (27%) in the shrubland stream. Because riparian vegetation is the source of terrestrial arthropod inputs to streams, degradation of streamside forests that reduce these inputs will have consequences for the diets of stream fishes.

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Haberle, Simon G. "A 23,000-yr Pollen Record from Lake Euramoo, Wet Tropics of NE Queensland, Australia." Quaternary Research 64, no. 3 (November 2005): 343–56. http://dx.doi.org/10.1016/j.yqres.2005.08.013.

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AbstractA new extended pollen and charcoal record is presented from Lake Euramoo, Wet Tropics World Heritage rainforest of northeast Queensland, Australia. The 8.4-m sediment core taken from the center of Lake Euramoo incorporates a complete record of vegetation change and fire history spanning the period from 23,000 cal yr B.P. to present. The pollen record is divided into five significant zones; 23,000–16,800 cal yr B.P., dry sclerophyll woodland; 16,800–8600 cal yr B.P., wet sclerophyll woodland with marginal rainforest in protected pockets; 8600–5000 cal yr B.P., warm temperate rainforest; 5000–70 cal yr B.P., dry subtropical rainforest; 70 cal yr B.P.–AD 1999, degraded dry subtropical rainforest with increasing influence of invasive species and fire.The process of rainforest development appears to be at least partly controlled by orbital forcing (precession), though more local environmental variables and human activity are also significant factors. This new record provides the opportunity to explore the relationship between fire, drought and rainforest dynamics in a significant World Heritage rainforest region.

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Goodchild, A. V. "Gut fill in cattle: effect of pasture quality on fasting losses." Animal Science 40, no. 3 (June 1985): 455–63. http://dx.doi.org/10.1017/s0003356100040149.

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ABSTRACTAn abrupt fall in live weight of grazing cattle occurs at the beginning of the growing season in the seasonally dry tropics. In an experiment with grazing crossbred bulls in central Tanzania designed to monitor changes in gut fill, 16 were slaughtered in the dry season and 14 in the early wet season. Bulls were measured and weighed before, and weighed after, a 20-h fast and then slaughtered. Gut fill was measured and empty body weight (EBW) calculated.During fasting, the ratio gut fill/EBW fell from 0·291 to 0·217 in the dry season and from 0·207 to 0·119 in the wet season. Heart girth/EBW1/3 was 0·2577 and 0·2567 m/kg1/3 in the dry and wet seasons respectively.It was concluded that live weight before or after fasting is seriously affected by season and can give biased predictions of EBW change. On the other hand, heart girth is little affected by season and can be used to monitor relative increases or decreases of EBW within animals.

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44

Stirrat, Simon C. "Activity budgets of the agile wallaby, Macropus agilis." Australian Journal of Zoology 52, no. 1 (2004): 49. http://dx.doi.org/10.1071/zo04005.

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The activity budgets of agile wallabies were investigated in the wet season and dry season in the wet–dry tropics. In the dry season and in clear weather in the wet season the wallabies were essentially nocturnal, foraging throughout the night in open areas and resting during the day in monsoon rainforest patches. The day was clearly partitioned into active and inactive periods, with activity coordination (behaviour synchrony) being high during the night and day and low in the transition between these foraging and resting periods. In overcast weather activity coordination was lower throughout the day. The day was not partitioned into active and inactive periods and the wallabies were observed foraging in the open at all times of day. However, they foraged for no longer over 24 hours than in clear weather when foraging was mainly a nocturnal activity. The wallabies spent more time foraging, moved greater distances while foraging, were less vigilant, and rested and groomed less in the dry season when forage quality was poor.

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45

Braithwaite, R. W. "Shelter selection by a small mammal community in the wet-dry tropics of Australia." Australian Mammalogy 12, no. 2 (1989): 55. http://dx.doi.org/10.1071/am89009.

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The location of shelter used by nine species of small mammals released after capture during a mark-recapture study in tropical woodland and open forest was recorded whenever possible. A quantitative profile of such post-release behaviour by different species permits its incorporation into analyses of habitat selection. Characteristics of post-release behaviour also provide clues about the nature of predation pressure on various species. Arboreal species tended to select tree species with boles having camouflage potential. Small species used small holes. Scansorial species used the greatest range of sheltering sites. Average distance moved to shelter was inversely related to the mean density of a species.

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46

Lynch, Romeny J., Stuart E. Bunn, and Carla P. Catterall. "Adult aquatic insects: Potential contributors to riparian food webs in Australia's wet-dry tropics." Austral Ecology 27, no. 5 (September 18, 2002): 515–26. http://dx.doi.org/10.1046/j.1442-9993.2002.01208.x.

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47

Shine, Richard, and Gregory P. Brown. "Adapting to the unpredictable: reproductive biology of vertebrates in the Australian wet–dry tropics." Philosophical Transactions of the Royal Society B: Biological Sciences 363, no. 1490 (July 18, 2007): 363–73. http://dx.doi.org/10.1098/rstb.2007.2144.

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In the wet–dry tropics of northern Australia, temperatures are high and stable year-round but monsoonal rainfall is highly seasonal and variable both annually and spatially. Many features of reproduction in vertebrates of this region may be adaptations to dealing with this unpredictable variation in precipitation, notably by (i) using direct proximate (rainfall-affected) cues to synchronize the timing and extent of breeding with rainfall events, (ii) placing the eggs or offspring in conditions where they will be buffered from rainfall extremes, and (iii) evolving developmental plasticity, such that the timing and trajectory of embryonic differentiation flexibly respond to local conditions. For example, organisms as diverse as snakes ( Liasis fuscus , Acrochordus arafurae ), crocodiles ( Crocodylus porosus ), birds ( Anseranas semipalmata ) and wallabies ( Macropus agilis ) show extreme annual variation in reproductive rates, linked to stochastic variation in wet season rainfall. The seasonal timing of initiation and cessation of breeding in snakes ( Tropidonophis mairii ) and rats ( Rattus colletti ) also varies among years, depending upon precipitation. An alternative adaptive route is to buffer the effects of rainfall variability on offspring by parental care (including viviparity) or by judicious selection of nest sites in oviparous taxa without parental care. A third type of adaptive response involves flexible embryonic responses (including embryonic diapause, facultative hatching and temperature-dependent sex determination) to incubation conditions, as seen in squamates, crocodilians and turtles. Such flexibility fine-tunes developmental rates and trajectories to conditions–-especially, rainfall patterns–-that are not predictable at the time of oviposition.

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Garcia, Erica A., Neil E. Pettit, Danielle M. Warfe, Peter M. Davies, Peter M. Kyne, Peter Novak, and Michael M. Douglas. "Temporal variation in benthic primary production in streams of the Australian wet–dry tropics." Hydrobiologia 760, no. 1 (May 8, 2015): 43–55. http://dx.doi.org/10.1007/s10750-015-2301-6.

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Pusey, Bradley J., Mark J. Kennard, Michael Douglas, and Quentin Allsop. "Fish assemblage dynamics in an intermittent river of the northern Australian wet-dry tropics." Ecology of Freshwater Fish 27, no. 1 (November 24, 2016): 78–88. http://dx.doi.org/10.1111/eff.12325.

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Horsup, A., and H. Marsh. "The diet of the allied rock-wallaby, Petrogale assimilis, in the wet-dry tropics." Wildlife Research 19, no. 1 (1992): 17. http://dx.doi.org/10.1071/wr9920017.

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The diet of the allied rock-wallaby, Petrogale assimilis, an inhabitant of the wet-dry tropics of North Queensland, was studied over three years by microscopic faecal analysis, feeding observations, and an analysis of the ratios of the natural isotopes of 12*C and 13*C in the faeces. Forbs were the major food item, accounting for 22-65% of the identified epidermis in the faeces, and tended to be actively selected by the wallabies. Browse (20-41%) and plants with stellate trichomes (6-32%) were the next most-important dietary items, the latter being eaten in significantly higher proportions in the dry seasons of 1987 and 1988. Grass comprised only 5-16% of recognisable epidermis in the faeces, but was eaten in significantly higher proportions when fresh new growth was available. Forbs were difficult to identify at night, and most plants that rock-wallabies were recorded eating were those with stellate trichomes rather than forbs. The low incidence of grass in the diet was confirmed by the carbon-ratio analysis.

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Journal articles on the topic 'Wet-dry tropics'

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