Dry Tropical Environments Research Articles

Eucalyptus pellita harvest residue management in sandy tropical soils – nutrient content, decomposition and potential emissions from burning

Plantation forestry on sandy, nutrient poor soils has been developed over the last few decades in seasonally dry tropical monsoon environments. Despite the known benefits of harvest residue conservation between rotations in temperate climes, there are very few studies around the world on Eucalyptus harvest residue management in tropical areas. In Northern Australia on Melville Island 30,000-hectares of Acacia mangium is planned to be converted to Eucalyptus pellita. E. pellita harvest residues comprise high loads of stringy bark, leaves and twigs, posing a fire risk throughout the annual 6-to-8-month dry season in Australia's monsoonal tropics. In this environment, quantifying and demonstrating the anticipated benefits of residue retention is important for determining appropriate responses to fire risk.A 4-hectare experimental trial of 12-year-old E. pellita was cut with trees moved intact to the coupe edge and processed for woodchips. The tree residues from the roadside chipper were pushed back over the site. A total of 35 Mg ha−1 of harvest residue was left on the site, mainly comprised of bark (24.5 Mg ha−1 or 60 % of the total residue mass). Although the leaf and branch residues contained higher concentrations of N, Ca, Cu, K, Mg, Mn, P, and Zn than bark, stem and woodchips, bark N (51.5 kg ha−1) was twice foliage N (26.9 kg ha−1), and contributed to more than 50 % of residue N.Harvest residue bark, leaves and twigs were sampled for a litterbag decomposition study of mass loss on the harvested site. After 10 months about 80 % of bark original weight remained on site (20 % mass loss), compared to about 55 % of the leaves/twigs remaining (45 % mass loss).The potential non-CO2 emissions from the burning of E. pellita harvest residues were estimated at 12.3 Mg CO2-eq ha−1 or 3.35 Mg C ha−1, with the majority of emission arising from the smoldering of bark residues. This study discusses the implications of either retaining or burning harvest residues – for plantation long-term sustainability on sandy tropical sites, and for greenhouse gas emissions.

The effect of rest duration on the physical and chemical quality of Brahman-Cross beef

Brahman Cross (BX) cattle are cattle produced by crossing Brahman cattle with European cattle. Brahman Cross is one of the beef cattle that has high productivity, resistance to high temperatures, resistance to relatively dry tropical environments, and good meat quality. This study was carried out to determine the effect of rest duration on the physical and chemical quality of Brahman Cross cattle on pH, water holding capacity, as well as fat and protein content of meat. The research was conducted at Mabar RPH Medan City. Meat physical and chemical tests were carried out at the Food Chemistry Analysis Laboratory, University of North Sumatera. Furthermore, this study used 48 Brahman Cross cattle and was designed with a statistical T-test consisting of 2 variables and 24 replications. The research treatment consisted of 24 Brahman Cross cattle without rest (0 hours), and 24 Brahman Cross cattle rested for 24 hours. The results showed that the duration of 0 hour rest and 24 hours rest before slaughter had no significant effect (P>0.05) on the pH and protein content, but had a significant effect (P>0.05) on water holding capacity and fat content.

Soil health and dragon fruit cultivation: Assessing the impact on soil organic carbon

Soil organic carbon (SOC) plays a crucial role in soil quality and nutrient availability. Agricultural practices, such as tillage and crop rotations, can affect SOC levels. Pitahaya cultivation, a growing crop in dry tropical environments regions may affect soil quality due to weed management. This study aims to assess the relationship between alternative crop management and pitahaya species on SOC sequestration. Two plots, each for yellow (Selenicereus megalanthus) and red (Hylocereus Undatus) pitahaya, were established. Rice husks were used as a natural mulch to prevent weed growth as a new control alternative. Soil sampling was conducted at different depths (0-5, 5-10, 10-20, and 20-30 cm) and locations (below plant vs row) within the pitahaya plots. The study found at the 0-5 cm section presents the highest concentration of organic carbon at 2.01%, 1.77%, and 1.97% below plant in red, yellow, and row in yellow plantation respectively. In comparison with 1.26% in row red plantation, they are significant differences. The analysis of carbon accumulation showed variability in each of the locations from 0-30 cm. Without significant differences with 50.34, 49.40, and 47.95 (t ha-1) below the yellow plant, row, and below red plant respectively. In the whole soil profile with 38,10 t ha-1 the row of the red plant is significantly different. Likewise, the age of the plantation or crop plays another important role in soil organic carbon sequestration. Despite having the same management, soil type, climate, and irrigation, the significant effect in this study shows that the different age of the plantations (2 years) marks a significant difference between the two plantations. The roots of the older plantation extend their roots more horizontally and achieve more organic carbon sequestration in the rows compared to the younger plantation.

Wood anatomical spectrum of co-occurring species in early and late-successional tropical dry forest communities

Key messageAnalysis of wood anatomical traits revealed that drought tolerance predominates in early-successional communities, and vessel variability is relevant for species’ ecological success in seasonally dry tropical environments.Successional tropical dry forests harbor a diverse array of species subjected to a strong seasonal precipitation regime. Considering that wood encompasses diverse functional properties related to stem hydraulics and mechanical support, in this study, we asked which quantitative anatomical traits are exhibited by co-occurring species in early (EC)- and late (LC)-successional communities. We used generalized linear mixed-effects models to estimate and compare means and standard deviations of wood traits (vessel area, vessel density, vessel grouping, and fiber dimensions) between eight EC and between 13 LC co-occurring species. Wood traits were highly heterogeneous. High vessel redundancy, a property associated with water safety involved in the prevention of hydraulic failure, prevails among species coexisting in EC but is maintained through succession by the same species in LC. Highly variable fiber dimensions indicate that species coexisting in LC possess different characteristics associated with mechanical resistance. Low wood density species typical of LC, which are absent from EC, displayed wood anatomical features associated with drought-evasion mechanisms. This result implies that deforestation not only reduces taxonomic but also functional diversity. Future research should adopt a standard deviation analysis approach, as this will allow confirming the high variability in vessel diameter, even in diffuse porous species, as a key feature for the ecological success of plants facing succession-driven changes in seasonally dry environments.

Stylosanthes scabra: genetic variability of forage quality traits

Stylosanthes scabra Vogel is a tropical legume grown in dry tropical and subtropical environments. The objective of this research was to evaluate the genetic diversity of forage quality traits for 80 accessions of S. scabra. Seven plants from each accession were planted in a single-line plot with no replicates at Embrapa Cerrados, Brazil. All plants were harvested 90 days after planting. Crude protein (CP), in vitro dry matter digestibility (IVDMD), neutral detergent fibre (NDF), acid detergent fibre (ADF), lignin (LIG), hemicellulose (HEMIC) and cellulose (CELLU) were estimated. Data were submitted to principal component analysis (PCA) and a cluster analysis was performed to identify groups of similarity. Simpson and Shannon–Weaver diversity indices estimated the genetic diversity. The average values of CP, IVDMD, NDF, ADF, LIG, HEMIC and CELLU were 220g/kg, 560g/kg, 516.8g/kg, 368g/kg, 69.4g/kg, 148.8g/kg and 298.6g/kg, respectively. There was a significant difference among collection sites for IVDMD, ADF and CELLU. The first two principal components accounted for 73% of the total variation. The 80 accessions resulted in four clusters, among which significant differences were observed for CP, IVDMD and ADF. Group IV, with 24 accessions, had the highest CP and IVDMD concentrations and the lowest ADF concentration, being the highest-quality forage group. Diversity indices were 0.78 and 0.81 for Simpson’s and Shannon–Weaver’s, respectively. In conclusion, there is genetic diversity for forage quality traits among S. scabra.

Desiccation and temperature resistance of the larger grain borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae): pedestals for invasion success?

AbstractThe larger grain borer, Prostephanus truncatus (Horn) is an invasive insect pest species of global economic concern. It however remains unknown how P. truncatus succeeds under increasing temperatures and desiccation effects associated with projected climate change. Here, we investigated the effects of desiccation and high‐temperature stress on physiological fitness of P. truncatus larvae and adults. Specifically, we measured critical thermal maxima, heat knockdown time and water loss rates following heat and desiccation acclimation. Results showed beneficial heat acclimation effects on heat tolerance (critical thermal maxima and heat knockdown time). Similarly, desiccation acclimation significantly improved both heat tolerance traits, indicating cross‐tolerance effects, not for heat knockdown time in larvae. In all cases, adults exhibited more improved heat tolerance than larvae. Conversely, heat acclimation increased water loss rates, and more so in larvae than adults. Improved heat tolerance plus abiotic stress cross‐tolerance of P. truncatus may explain its enhanced physiological and ecological fitness in dry tropical and changing climate environments. These results are important in explaining the role of physiology in insect invasions and may inform pest management and forecasting.

Stoichiometric ratios in the soil of native and forage areas in a seasonally dry tropical forest

The availability of potassium (K), calcium (Ca) and magnesium (Mg) in the soil affects the nutrition and productivity of the plant cover. The Ca:Mg, Ca:K and Mg:K stoichiometric ratios indicate the nutrient load balance in the soil. However, limited attention has been paid to providing a scientific basis for how changes in land use, especially the cultivation of forage, impacts the availability and reserves of base cations in semi-arid regions, since, in these environments, fertiliser is not used. Therefore, the aim of this study was to quantify the concentrations of soil K, Ca and Mg in areas of preserved Caatinga (PC), and areas where buffel grass (BG) has been cultivated for 40 years and Leucaena grass (LE) for 11 years. Four 100 x 100 cm trenches were opened in each type of plant cover and collections were made in the 0-5, 5-10, 10-15 and 15-20 cm layers. The concentrations of K, Ca and Mg and their ratios were determined and compared using the Mann-Whitney test. The soil under buffel grass showed higher concentrations of K and Mg, and a lower concentration of Ca. Compared to PC, LE presented a lower Ca content in the 0-5 cm layer only. BG had the lowest values for the Ca:Mg and Ca:K stoichiometric ratios due to depletion of the Ca. Despite being soluble and easily leached, K remained in the soil under each type of cover, favoured by the semi-arid climate. Soil Ca, which is exported due to grazing of the produced biomass, should be replaced so as not to compromise the support capacity of seasonally dry tropical environments through the cultivation of forages.

Accuracy and limitations for spectroscopic prediction of leaf traits in seasonally dry tropical environments

Generalized assessments of the accuracy of spectroscopic estimates of ecologically important leaf traits such as leaf mass per area (LMA) and leaf dry matter content (LDMC) are still lacking for most ecosystems, and particularly for non-forested and/or seasonally dry tropical vegetation. Here, we tested the ability of using leaf reflectance spectra to estimate LMA and LDMC and classify plant growth forms within the cerrado and campo rupestre seasonally dry non-forest vegetation types of Southeastern Brazil, filling an existing gap in published assessments of leaf optical properties and plant traits in such environments. We measured leaf reflectance spectra from 1648 individual plants comprising grasses, herbs, shrubs, and trees, developed partial least squares regression (PLSR) models linking LMA and LDMC to leaf spectra (400–2500 nm), and identified the spectral regions with the greatest discriminatory power among growth forms using Bhattacharyya distances. We accurately predicted leaf functional traits and identified different growth forms. LMA was overall more accurately predicted (RMSE = 8.58%) than LDMC (RMSE = 9.75%). Our model including all sampled plants was not biased towards any particular growth form, but growth-form specific models yielded higher accuracies and showed that leaf traits from woody plants can be more accurately estimated than for grasses and forbs, independently of the trait measured. We observed a large range of LMA values (31.80–620.81 g/m2) rarely observed in tropical or temperate forests, and demonstrated that values above 300 g/m2 could not be accurately estimated. Our results suggest that spectroscopy may have an intrinsic saturation point, and/or that PLSR, the current approach of choice for estimating traits from plant spectra, is not able to model the entire range of LMA values. This finding has very important implications to our ability to use field, airborne, and orbital spectroscopic methods to derive generalizable functional information. We thus highlight the need for increasing spectroscopic sampling and research efforts in drier non-forested environments, where environmental pressures lead to leaf adaptations and allocation strategies that are very different from forested ecosystems. Our findings also confirm that leaf reflectance spectra can provide important information regarding differences in leaf metabolism, structure, and chemical composition. Such information enabled us to accurately discriminate plant growth forms in these environments regardless of lack of variation in leaf economic traits, encouraging further adoption of remote sensing methods by ecologists and allowing a more comprehensive assessment of plant functional diversity.

Management of phosphorus nutrition of beef cattle grazing seasonally dry rangelands: a review

This review examines the effects of phosphorus (P) deficiency as a major constraint to productivity of cattle grazing rangelands with low-P soils. Nutritional deficiency of P may severely reduce liveweight (LW) gain of growing cattle (e.g. by 20–60 kg/annum) and the productivity of breeder cow herds as weaning rate, mortality and calf growth. In seasonally dry tropical environments, the production responses to supplementary P occur primarily during the rainy season when the nutritional quality of pasture as metabolisable energy (ME) and protein is high and pasture P concentration is limiting, even though the P concentrations are higher than during dry season. When ME and nitrogen of rainy-season pasture are adequate, then P-deficient cattle typically continue to gain LW slowly, but with reduced bone mineralisation (i.e. osteomalacia). In beef breeder herds when diet P is insufficient, cows with high bone P reserves can mobilise bone P reserves during late pregnancy and early lactation. Mobilisation may contribute up to the equivalent of ~7 g diet P/day (one-third of the P requirements) in early lactation, and, thus, allow acutely P-deficient breeders to maintain calf growth for at least several months until depletion of cow body P reserves. However, severe P deficiency in cattle is usually associated with reduced voluntary intake (e.g. by 20–30% per kg LW), severe LW loss and poor reconception rates. When P intake is greater than immediate requirements, breeders can replenish bone P. Replenishment in mature cows occurs slowly when ME intake is sufficient only for slow LW gain, but rapidly at ME intakes sufficient for rapid LW gain. Bone P replenishment also occurs in late-pregnant heifers even when losing maternal LW. Intervals of mobilisation and replenishment of body P reserves will often be important for P nutrition of beef breeder cows through annual cycles. Diagnosis of P deficiency in grazing cattle is difficult and must encompass estimation of both diet P intake and availability of P from body reserves. Cattle behaviour (e.g. pica, osteophagea), low soil P concentrations and low herd productivity provide valuable indicators. Some constituents of blood (plasma inorganic P, calcium, plasma inorganic P:calcium ratios and endocrine markers) are valuable indicators, but the threshold values indicative of P deficiency at various ME intakes are not well established. It is evident that knowledge of both the nutritional physiology and requirements for P provide opportunities to better manage P nutrition to alleviate production losses in low-input systems with beef cattle grazing rangelands.

Orchid Bees (Hymenoptera: Apidae: Euglossini) in Seasonally Dry Tropical Forest (Caatinga) in Brazil

Euglossini bees are important Neotropical pollinators, but there is a lack in the knowledge about this fauna in dry tropical environments. The aims of this study were to evaluate the richness and abundance of euglossine bees in two fragments of seasonally dry tropical forest (Caatinga), as well as to assess the distribution of euglossine species richness in the Caatinga environment. Males were collected along 12 consecutive months, using traps with aromatic baits. The species richness (S=5) was lower than in rainforests and savannas. Euglossa cordata (L.) was the dominant species in the assemblage, representing 70% of the individuals. The highest abundance occurred in the rainy season. Euglossini fauna presents low local species richness in Caatinga areas, however the beta diversity is higher, since assemblages in different habitats have differences in species composition.

Contrasting carbon cycle responses of the tropical continents to the 2015-2016 El Niño.

The 2015-2016 El Niño led to historically high temperatures and low precipitation over the tropics, while the growth rate of atmospheric carbon dioxide (CO2) was the largest on record. Here we quantify the response of tropical net biosphere exchange, gross primary production, biomass burning, and respiration to these climate anomalies by assimilating column CO2, solar-induced chlorophyll fluorescence, and carbon monoxide observations from multiple satellites. Relative to the 2011 La Niña, the pantropical biosphere released 2.5 ± 0.34 gigatons more carbon into the atmosphere in 2015, consisting of approximately even contributions from three tropical continents but dominated by diverse carbon exchange processes. The heterogeneity of the carbon-exchange processes indicated here challenges previous studies that suggested that a single dominant process determines carbon cycle interannual variability.

Spirituality in Place: Capturing the Essence of North Queensland through Painting

For centuries, artists have been inspired by place. This perception and awareness of place can also involve a spiritual connection. Artists from both Aboriginal culture and white settlement in Australia have painted works which reveal a deep spiritual connection to place. One of the geographical areas that has inspired several artists is North Queensland, which offers a rich tapestry of dry and wet tropical environments. This article considers an historical overview and deconstructs the work of four contemporary painters (Firth-Smith, Silver, Watson, and Cheshire) who have been inspired by the place that is North Queensland, in order to consider the ways in which their work reveals a spiritual connection to place.

Variations in N mineralization and herbaceous species diversity due to sites, seasons, and N treatments in a seasonally dry tropical environment of India

Nitrogen (N) is an essential element for plant growth, however enriched N deposition may have seriously impacts on air, water, soil and vegetations. In this reference, we assessed the impacts of N applications on the rates of N-mineralization and their counter effects on the composition and diversity of herbaceous vegetation in a seasonally dry tropical environment of India. For this; 135, 1×1m plots distributed in 15 locations were established at the Banaras Hindu University, India. Since 1st January 2007, within each location, equal numbers of 1×1m plots were treated with three doses of N (0kgNha−1yr−1/control, 60kgNha−1yr−1 and 120kgNha−1yr−1). Soil and vegetation samples were collected in year 2010. The data on soil N mineralization, rainfall and species numbers were collected monthly and the data on Shannon diversity index were collected seasonally. The data were subjected to appropriate statistical analyses. The NMS ordination suggested that the sites, N levels and seasons caused substantial differences in the rate of soil N-mineralization, species composition and diversity of herbaceous species. Results showed that moderate levels of rainfall and N applications (60kgNha−1yr−1) facilitated the accumulation of herbaceous species diversity by accelerating the process of soil N-mineralization due to increased availability of soil–N and decreased C:N ratio of the soil. The study did not support the N-saturation theory for the N-mineralization rates as well as species diversity possibly due to loss of added N through the process of volatization, denitrification and consumed by the nitrophilic species, which warrants in-depth study of microbial dynamics to explore the mechanisms associated with N mineralization in N perturbed ecosystems, particularly from dry tropical environments of India which are nutrient and moisture limited.

Upper thermal limits of Drosophila are linked to species distributions and strongly constrained phylogenetically

Upper thermal limits vary less than lower limits among related species of terrestrial ectotherms. This pattern may reflect weak or uniform selection on upper limits, or alternatively tight evolutionary constraints. We investigated this issue in 94 Drosophila species from diverse climates and reared in a common environment to control for plastic effects that may confound species comparisons. We found substantial variation in upper thermal limits among species, negatively correlated with annual precipitation at the central point of their distribution and also with the interaction between precipitation and maximum temperature, showing that heat resistance is an important determinant of Drosophila species distributions. Species from hot and relatively dry regions had higher resistance, whereas resistance was uncorrelated with temperature in wetter regions. Using a suite of analyses we showed that phylogenetic signal in heat resistance reflects phylogenetic inertia rather than common selection pressures. Current species distributions are therefore more likely to reflect environmental sorting of lineages rather than local adaptation. Similar to previous studies, thermal safety margins were small at low latitudes, with safety margins smallest for species occupying both humid and dry tropical environments. Thus, species from a range of environments are likely to be at risk owing to climate change. Together these findings suggest that this group of insects is unlikely to buffer global change effects through marked evolutionary changes, highlighting the importance of facilitating range shifts for maintaining biodiversity.

OzFACE: the Australian savanna free air CO2 enrichment facility and its relevance to carbon-cycling issues in a tropical savanna

A free air CO2 enrichment (FACE) facility has recently been constructed in a tropical savanna in north-eastern Queensland, Australia. The system has a novel and cost-effective design and uses an industrial source of pure CO2 piped directly to the site. We describe the design details of this facility and assess the likely contribution it will make towards advancing our understanding of the direct impacts of rising atmospheric CO2 on savannas. These include addressing uncertainties about future shifts in the tree–grass balance and associated changes in carbon stocks, responses of C4 grasses in dry tropical environments, potential sequestration of soil carbon, and the modifications of CO2 responses by moisture and nutrient interactions. Tropical regions have been poorly represented in climate change research, and the work at the OzFACE facility will complement existing and ongoing FACE studies at temperate latitudes.

Effect of leaf habit and soil type on nutrient resorption and conservation in woody species of a dry tropical environment

We examined 90 dry tropical tree species growing on contrasting soil types (relatively infertile Ultisol and more fertile Inceptisol) for leaf traits such as leaf habit, specific leaf mass (SLM, leaf dry mass per leaf area), leaf chemistry (nutrient concentrations and C/N ratios), and nutrient resorption. Across the species, SLM ranged from 4.06 to 15.74 mg·cm–2 in mature leaves and from 2.60 to 15.12 mg·cm–2 in senesced leaves. Mature leaf N and P concentrations varied from 0.86% to 4.11% and 0.13% to 0.21%, respectively. Senesced leaf N concentrations varied from 0.49% to 1.90% and P from 0.04% to 0.47%. Resorption efficiencies varied from 26% to 83% (mean = 58.32% ± 1.20%) for N and from 16% to 80% (mean = 49.57% ± 1.48%) for P indicating that the woody species of dry tropical environments resorbed different nutrients in substantial amounts to support new growth. Deciduous species had greater resorbed nutrient pools and resorption efficiencies than evergreen species. Compared with the nutrient-rich environment, species from the nutrient-poor environment had a lower resorbed P pool and lower resorption efficiencies for N and P, but had similar N and P concentrations in mature leaves. Resorption efficiencies for C, N, and P were generally correlated, suggesting that the resorbed C pool acted as a vehicle for mobilizing nutrients, especially N. Species with a low or high C/N ratio in senesced leaf and a low or high N resorption efficiency occurred in both nutrient-poor and nutrient-rich environments, as well as among deciduous and evergreen leaf habits, indicating individualistic adaptations to optimize the efficiency of nutrient resource use and conservation of the dry tropical woody vegetation.Key words: leaf chemistry, leaf traits, resorption efficiency, resorbed nutrient pools, substrate-quality stability.

Changes in Soil Nutrients Following Burning Burning of Dry Tropical Savanna

The effects of fire in dry tropical savanna ecosystems on plant available nutrients (nitrate-N, ammonium-N and phosphate - P); N - mineralization rate; soil microbial biomass C, N and P; canopy biomass and root biomass were studied during selected months. Parameters studied were the vegetative, reproductive, flowering and fruiting, fruitfall, early senescence and late senescence. The values of nitrate-N, ammonium-N and phosphate - P, N- mineralization and nitrification rate; microbial C, N and P, canopy biomass and root biomass indicated significant difference due to month and treatment, but were not significant due to year. Following fire, the increase in the build up of microbial biomass in the dry season and canopy growth and N-mineralization rate in the wet season are nutrient conserving mechanisms that prevent nutrient loss. Therefore fire can be a management tool for better productivity and nutritive quality in dry tropical environments.

THE EARLIEST REMAINS OF GRASSES IN THE FOSSIL RECORD

New fossils provide the earliest unequivocal evidence of grasses. Spikelets and inflorescence fragments with included pollen from the Paleocene/Eocene Wilcox Formation in western Tennessee have a suite of diagnostic characters that limits their affinities to Poaceae. Associated vegetative remains are also suggestive of grasses, but are not well enough preserved for an unequivocal identification. These fossils indicate a minimal time of origin for the family, are consistent with an Upper Cretaceous origin of Poaceae, and suggest that as in wind‐pollinated Hamamelididae, wind pollination evolved in grasses or persisted in the grass lineage (if a wind‐pollinated grass sister group is presumed) in dry tropical environments.

The Earliest Remains of Grasses in the Fossil Record

New fossils provide the earliest unequivocal evidence of grasses. Spikelets and inflorescence fragments with included pollen from the Paleocene/Eocene Wilcox Formation in western Tennessee have a suite of diagnostic characters that limits their affinities to Poaceae. Associated vegetative remains are also suggestive of grasses, but are not well enough preserved for an unequivocal identification. These fossils indicate a minimal time of origin for the family, are consistent with an Upper Cretaceous origin of Poaceae, and suggest that as in wind-pollinated Hamamelididae, wind pollination evolved in grasses or persisted in the grass lineage (if a wind-pollinated grass sister group is presumed) in dry tropical environments.

The Causes and Consequences of Synchronous Flushing in a Dry Tropical Forest

The seasonal pattern of leaf production and fate of leaf cohorts were assessed in 59 species of woody plants over a period of 28 months in a West African dry forest (mean annual rainfall 1100 mm). In all species, leaves were produced in synchronous flushes. Flushing patterns varied somewhat between species and between individuals within species, although all flushing activity was restricted to wet periods. Damage to leaves by folivorous insects was largely confined to newly flushed leaves. Insects inflicted severe damage to 13 percent of new leaf cohorts. Species having potential deterrents to folivore attack (hairy leaves or secondary compounds) were attacked less frequently than species without apparent protection. Prolonged flushing activity brought about an added risk of insect attack in species lacking such protection. Drought is considered to be the most important single factor affecting the growth, distribution, and phenology of woody species in this dry forest. The restriction of leaf production to short, synchronous flushing periods is adequately explained in terms of physiological constraints relating to the avoidance of moisture stress. A consequence of this rapid flushing, however, may be escape from folivory. FLUSHING, OR THE SYNCHRONOUS PRODUCTION OF A NEW LEAF CROP, is characteristic of both temperate and tropical woody species (Richards 1952, Kramer and Kozlowski 1979). The pattern of leaf production in individual shoots, plants, and populations is generally periodic in the tropics (Alvim 1964, Longman and Jenik 1974, Leigh and Smythe 1978, Reich and Borchert 1982), but it is only in seasonally dry tropical environments that large numbers of shoots, individuals, and species flush in synchrony (Njoku 1963, Hopkins 1970, Daubenmire 1972, Frankie et al. 1974, Borchert 1980, Lieberman 1982, Reich and Borchert 1982, 1984). Rapid, synchronous flushing may be viewed as an adaptation to exploit scarce and intermittent water supplies and to avoid producing young, uncutinized foliage when the danger of desiccation is great. Young leaves are particularly vulnerable to folivore attack due to their lack of mechanical protection and their high nutrient and water content (Feeny 1970, Rockwood 1974, Scriber and Slansky 1981). McKey (1974) and Feeny (1976) suggest that the production of leaves in rapid, synchronous flushes may contribute to escape from folivory. They hypothesize that flushing occurs when folivores are at low density or are inactive, and that the majority of new leaves may therefore have the opportunity to mature and harden prior to an increase in the folivore population. Water conservation and escape from folivory are suggested explanations for the phenomenon of rapid synchronous flushing, but no study has been reported in which both possibilities are considered. In this paper we describe patterns of flushing phenology and folivory in a dry tropical forest in Ghana. In the context of flushing, we examine the incidence of folivory in relation to plant chemical and morphological traits, and ask whether rapid, synchronous production of leaves provides a significant means of folivore escape. We also evaluate the relative importance of folivory and drought in the evolution of leaf flushing patterns in species of this dry tropical forest.