Seasonal variation in in vitro immune activity of milk leukocytes in elite and non-elite crossbred cows of Indian sub-tropical semi-arid climate

Immunity of mammary gland in terms of in vitro activity of milk leukocytes has been evaluated during hot-humid, summer, and winter season in elite (n = 10) and non-elite (n = 10) crossbred cows. Milk samples were collected from all the cows throughout the year at 15-day interval. Milk somatic cell counts (SCC) and differential leukocyte counts (DLC) were evaluated microscopically. Milk neutrophils, macrophages, and lymphocytes were isolated and cultured in vitro. In vitro PI of milk neutrophils and macrophages was evaluated by colorimetric NBT (nitro-blue tetrazolium) reductive assay. Mitogen-induced milk lymphocyte blastogenic response was measured by colorimetric MTT (thiazolyl blue tetrazolium bromide) assay. Milk SCC was found to be significantly (p < 0.01) higher in elite cows compared to non-elite cows irrespective of season. There was significant (p < 0.05) increase in milk SCC during hot-humid season compared to winter season in both the group of the cows. There was no significant difference between group and season in terms of DLC. In vitro phagocytic index of elite cows was significantly (p < 0.01) higher than non-elite cows. The phagocytic index was significantly (p < 0.01) decreased in summer and hot-humid season compared to winter season in both the group of animals. Macrophages isolated from elite cows having significantly (p < 0.01) lower phagocytic index than non-elite cows which significantly (p < 0.01) decreased during summer and hot-humid season compared to winter. In vitro milk lymphocyte proliferative response was significantly (p < 0.01) lower in elite cows. Activity of B-lymphocytes decreased significantly (p < 0.01) during summer and hot-humid season than winter, but activity of T-lymphocytes remains unaltered during different seasons. In conclusion, the mammary immunity in terms of in vitro activity of milk leukocytes is compromised during summer and hot-humid season in elite crossbred cows; therefore, better care and management should be taken in high-yielding cows during summer and hot-humid season to minimize intramammary infections.     

Seasonal changes in blood biochemical and endocrine responses of different indigenous goat breeds of tropical island agro-ecological environment

The objective of the current study was to observe the impact of two seasons viz. summer (February–May) and monsoon (June–August) on the blood biochemical and hormonal responses in different indigenous goats of tropical island agro-ecological environment maintained under extensive management system. Sixty animals of three different indigenous goat breeds were included in the study: Andaman local goat (AL, n = 20), Andaman local?×?Malabari (AL?×?M, n = 20), and Teressa goat (n = 20). Sixty serum samples (n = 10/season/breed) from the three groups of animals were analyzed. Study revealed that there was a significant increase (p ≤ 0.05) in serum total protein in Teressa goats during summer than monsoon. Serum albumin showed significant variation (p ≤ 0.05) between AL and AL?×?M during summer whereas significant variation of albumin (p ≤ 0.05) was observed between AL and Teressa, AL?×?M and Teressa during monsoon season. Significant differences in serum albumin (p ≤ 0.05) were also observed in AL and AL?×?M during summer and monsoon seasons, respectively. The serum cortisol levels were significantly higher (p ≤ 0.05) in AL goats during summer than in monsoon season. Thus, the study could able to establish the seasonal variation in biochemical and hormonal values of indigenous goat breeds in hot and humid tropical island environment.     

Comparative assessment of native,crossbred and exotic pigs during different seasons (winter,spring and summer) based on rhythmic changes in the levels of serum cortisol,lactate dehydrogenase levels and PBMC HSP70 mRNA expression pattern

The present study was conducted to ascertain the adaptive capability of pigs to different seasons based on changes in serum cortisol and lactate dehydrogenase (LDH) levels, and peripheral blood mononuclear cell (PBMC) heat shock protein 70 (HSP70) mRNA expression. Based on average THI, the seasons were classified as winter (November–February), spring (March–June), and summer (July–October). Hormone cortisol was found to be influenced by season (p < 0.01), age (p < 0.05), and genetics of the animal (p < 0.05). However, level of LDH was not influenced by either of these factors. HSP70 mRNA expression was higher in almost all age groups in crossbred and exotic pigs during summer in comparison to other seasons. Lower HSP70 gene expression was observed in almost all age groups of native pigs in comparison to crossbred and exotic during summer. In conclusion, native pigs were acclimatized for thermal stress in comparison to crossbred and exotic breeds of pigs. Also, the expression pattern of HSP70 gene is breed-specific, most likely due to variations in thermal tolerance and adaptation to different environmental conditions. Both serum cortisol and HSP70 gene may act as reliable biological markers for assessing the adaptive capabilities of pigs to different seasons.     

Impact of season on antioxidants,nutritional metabolic status,cortisol and heat shock proteins in Hariana and Sahiwal cattle

The aim of this study was to evaluate the effects of summer and winter seasons on antioxidant status, body reserve mobilization and biomarkers of stress in Hariana and Sahiwal cows. Twelve lactating cows (six of each Hariana and Sahiwal cows) were included in summer (May to July) and winter season (November to January) study. Microclimatic observations were recorded on daily basis during the experimental period. In both seasons, blood samples were collected at fortnightly intervals for analysis of total antioxidant activity, non-esterified fatty acids (NEFA), β-Hydroxybutyric acid (BHBA), heat shock protein 70 and 90 (HSP70 and HSP90). Antioxidant activity reduced significantly (p < 0.05) in Hariana cattle during summers as compared to winters; whereas, seasonal variation exerts no effect on antioxidant activity in Sahiwal. Blood NEFA concentration was similar among both the breeds over both the seasons but reduced significantly (p < 0.05) during summer season as compared to winters in both the breeds. BHBA concentration was significantly higher (p < 0.05) in Hariana cows than Sahiwal cows during winters, however, no effect on BHBA level was observed during summer season in both the breeds. Significantly, lower plasma cortisol level (p < 0.05) was found during winter season in Sahiwal as well as Hariana cows. Further, Sahiwal exhibited lower plasma cortisol as compared to Hariana in both the seasons. HSP 70 and 90 showed non-significant differences between breeds within both the seasons. However, significantly, lower plasma HSP 70 levels (p < 0.05) were reported during winter season in Sahiwal as well as in Hariana cows. Results of present study revealed that indigenous Sahiwal is more heat tolerant as compared to Hariana breed.     

Seasonal variation in nutritional composition and anti-proliferative activity of brown seaweed, <Emphasis Type="Italic">Sargassum oligocystum</Emphasis>

This study investigated the nutritional components and anti-proliferative activity of Sargassum oligocystum against an adriamycin-resistant human small cell lung carcinoma cell line (GLC4/Adr). The seaweed samples were collected from Nang Rong Beach, Chonburi Province, Thailand in February (the hot/dry season), May (the early monsoon season), August (the monsoon season) and December (the cool/dry season) of 2012. In general, the nutritional composition of S. oligocystum was high during the hot dry and early monsoon season. Additionally, four different types of extract were obtained: ethanolic extract (E1), lipophilic extract (E2), acidic extract (E3) and alkali extract (E4). The highest anti-proliferative activity was found in samples collected during the monsoon season. It is noteworthy that the E2 extract collected during the monsoon season was the most effective, with an IC₅₀ (half maximal inhibitory concentration) value of 2.52 ± 0.54 μg mL^?1. The anti-proliferative activity showed a positive correlation with vitamin E (α-tocopherol) in the extracts. However, there were no clear correlations between the total phenolic or fucoxanthin contents and anti-proliferative activity. These results indicate that S. oligocystum has potential as an alternative source for functional food or cancer treatments in the future.     

Coral community responses to declining water quality: Whitsunday Islands,Great Barrier Reef,Australia

A five-year period (2002–2006) of below-median rainfall followed by a six-year period (2007–2012) of above-median rainfall and seasonal flooding allowed a natural experiment into the effects of runoff on the water quality and subsequent coral community responses in the Whitsunday Islands, Great Barrier Reef (Australia). Satellite-derived water quality estimates of total suspended solids (TSS) and chlorophyll-a (Chl) concentration showed marked seasonal variability that was exaggerated during years with high river discharge. During above-median rainfall years, Chl was aseasonally high for a period of 3 months during the wet season (February–April), while TSS was elevated for four months, extending into the dry season (March–June). Coinciding with these extremes in water quality was a reduction in the abundance and shift in the community composition, of juvenile corals. The incidence of coral disease was at a maximum during the transition from years of below-median to years of above-median river discharge. In contrast to juvenile corals, the cover of larger corals remained stable, although the composition of communities varied along environmental gradients. In combination, these results suggest opportunistic recruitment of corals during periods of relatively low environmental stress with selection for more tolerant species occurring during periods of environmental extremes.     

Age-related and seasonal variations in plasma uncarboxylated osteocalcin in male Murrah buffaloes

The present study aims to investigate the age-related and seasonal variations in plasma uncarboxylated osteocalcin (UcOCN) in male Murrah buffaloes. In experiment 1, body weight, body dimensions and plasma UcOCN levels were estimated in 120 male Murrah buffaloes aged between 18 days and 8 years. We observed a significant (p < 0.0001) decrease in plasma UcOCN with age and their levels ranged between 0.25 and 9.25 ng/ml. In experiment 2, the plasma UcOCN, cortisol, triiodothyronine (T₃), thyroxine (T₄) and prolactin levels were determined during spring and summer in 6–34 months (n = 24) old male Murrah buffaloes. Significant (p < 0.0001) higher plasma UcOCN levels were observed in spring than in summer. The plasma T₃ and T₄ levels were positively correlated with plasma UcOCN, whereas the plasma cortisol and prolactin were negatively correlated. Further, to observe the effect of season on temporal variations of UcOCN, Murrah buffaloes aged between 4–6 (n = 5), 14–16 (n = 5) and 28–30 (n = 5) months were bled at an interval of 30 min, between 0700 and 01030 h, during both the seasons. We observed significant effects of season (p < 0.0001), age (p < 0.0001) and season-by-age interaction (p < 0.01) on plasma UcOCN. The reasons for variations in plasma UcOCN with age and season will be discussed.     

Cloacal temperature responses of broiler chickens administered with betaine and ascorbic acid during the hot-dry season

The experiment was performed to evaluate cloacal temperature (CT) responses in broiler chickens, administered with betaine and ascorbic acid (AA) during the hot–dry season. Broilers were divided into four groups: Group I (control) was given sterile water; Group II, betaine at 250 mg/kg; Group III, AA at 50 mg/kg and Group IV, betaine (250 mg/kg) + AA (50 mg/kg). The different solutions were given orally for 42 days. Dry-bulb temperature (DBT), relative humidity (RH) and temperature-humidity index (THI) in the pen, and CT of each broiler chicken were measured bihourly (06:00–18:00 h) on days 28, 35 and 42. DBT, RH and THI values were outside the thermo-neutral zone for broiler chickens. Results showed that AA lowered (p < 0.001) CT, while betaine + AA increased (p < 0.001) CT, compared with controls. In conclusion, betaine + AA or AA alone modulated CT responses of broiler chickens subjected to the thermal stress in the hot–dry season.     

Evaluation of adaptability to different seasons in goat breeds of semi-arid region in India through differential expression pattern of heat shock protein genes

The present study was conducted to examine differential expression pattern of HSP genes and adaptability in Indian goat breeds of semi-arid region. The study was conducted in five animals from each breed viz. Barbari, Sirohi, and Jhakrana during winter, thermo-neutral and summer seasons. The respiratory rate (RR) and rectal temperature (RT) of the goats were recorded at 09:00 h during the study period. The blood samples were collected for RNA isolation, cDNA synthesis, and quantitative analysis of HSP genes expression by quantitative RT-PCR. The RR increased significantly (p < 0.01) during summer as compared to winter and thermo-neutral season however, RT did not change (p > 0.05) during different seasons. The expression of HSP genes was significantly (p < 0.01) increased during summer (high THI) as compared to thermo-neutral season in all the goat breeds. Among HSPs, only HSP90 was upregulated (p < 0.01) in Jhakrana goats during winter as compared to thermo-neutral season. The deviation in expression of HSP genes during summer and winter with respect to thermo-neutral season was minimum in Barbari goats. Therefore, it can be concluded that Barbari goats possessed better adaptability during summer and winter as compared to Sirohi and Jhakrana goats in semi-arid climatic conditions of India.     

Pollen in aeolian dust with relation to allergy and asthma in Kuwait

The studying of spatial and temporal distribution of pollen is essential, but rarely tackled in the region including Kuwait. Pollen grains and aeolian dust in the state of Kuwait were seasonally monitored from August 2009 to August 2011 to identify and correlate spatially and temporally pollen data with human health asthma and allergy data. The year 2010–2011 yielded a high in deposited dust and pollen compared to 2009–2010 by 33.2 and 9.9%, respectively. The spring (April–May) and the autumn (October–November) seasons marked the most top pollen distribution for Chenopodiaceae, Gramineae (Poaceae), Cyperaceae, Fabaceae, and Plantaginaceae. The pollen graphs for summer (July–August) and winter (January–February) seasons showed low pollen distribution due to the severe drought, dust storms, winter wind and rainfall. There are no correlations found between pollen deposition and the number of asthma patients. The annual dust deposited rate in Kuwait during 2010/2011 was 373 t km^?2 which represented a 33.2% increase compared with 2009/2010. The study has concluded that pollen of Malvaceae, Compositae and Chenopodiaceae is the most common triggers of allergy in Kuwait. Additionally, a positive correlation between the number of allergy patients and deposited dust was observed during March 2010 and 2011.     

Water Use Efficiency by Switchgrass Compared to a Native Grass or a Native Grass Alfalfa Mixture

Perennial grass systems are being evaluated as a bioenergy feedstock in the northern Great Plains. Inter-annual and inter-seasonal precipitation variation in this region will require efficient water use to maintain sufficient yield production to support a mature bioenergy industry. Objectives were to evaluate the impact of a May–June (early season) and a July–August (late season) drought on the water use efficiency (WUE), amount of water used, and biomass production in monocultures of switchgrass (Panicum virgatum L.), western wheatgrass (Pascopyrum smithii (Rydb.) Á. Löve), and a western wheatgrass–alfalfa (Medicago sativa L.) mixture using an automated rainout shelter. WUE was strongly driven by biomass accumulation and ranged from 5.6 to 7.4 g biomass mm^?1 water for switchgrass to 1.06 to 2.07 g biomass mm^?1 water used with western wheatgrass. Timing of water stress affected WUE more in western wheatgrass and the western wheatgrass–alfalfa mixture than switchgrass. Water deficit for the western wheatgrass–alfalfa mixture was 23 % lower than western wheatgrass (P?=?0.0045) and 31 % lower than switchgrass (P?<?0.0001) under the May–June stress water treatment, while switchgrass had a 37 and 38 % greater water deficit than did western wheatgrass or western wheatgrass–alfalfa mixture, respectively (P?<?0.001) under the July–August water stress treatment. Water depletion was always greatest in the upper 30 cm. Switchgrass had greater WUE but resulted in greater soil water depletion at the end of the growing season compared to western wheatgrass and a western wheatgrass–alfalfa mixture which may be a concern under multi-year drought conditions.     

Impacts of weather on northern bobwhite sex ratios,body mass,and annual production in South Texas

A landscape-scale assessment of how bobwhite productivity varies in relation to weather does not exist for northern bobwhite (Colinus virginianus). We collected age and sex ratio and body mass data from hunter-harvested bobwhites in 16 counties of South Texas (n = 72,797 bobwhites) during 2001–2009 hunting seasons. We evaluated annual bobwhite production (juvenile:adult age ratios) as a function of cumulative April–August rainfall using National Oceanic and Atmospheric Administration (NOAA) weather station data from Falfurrias and Hebbronville, Texas. We observed minimal among-year change in percent males harvested (51.0–54.5% male) and mean mass (156–160 g) of bobwhites across South Texas. We found no relationship between percent male or body mass and weather. We documented a positive, linear relationship between cumulative April–August rainfall and bobwhite age ratios (r² = 0.94); we also documented a negative, linear relationship between summer (Jun–Aug) mean maximum daily temperature and bobwhite age ratios (r² = 0.38). Our results suggest that rainfall is a landscape-scale indicator of annual bobwhite production in South Texas and can thus be used to manage annual expectations of quail hunters prior to the hunting season. © The Wildlife Society, 2012     

Offspring sex ratio in sheep,cattle, goats and pigs: influence of season and lunar phase at conception

This study assessed the relationship between season and lunar phase at conception on offspring sex ratio of four livestock species (sheep, cattle, goats and pigs). The sex of 66,830 lambs (1995–2015); 25,546 calves (2011–2015); 5671 kids (2002–2007) and 1916 piglets was recorded. Moon phases were categorized as either new moon, crescent moon, full moon or decrescent moon. Sex ratio, expressed as proportion of males (males/males + females), was tested against the expected value of 1:1. In sheep, offspring sex ratio and lunar phase were not correlated; season had a significant (p = 0.002) effect on offspring sex ratio. The proportion of males born of spring and winter matings was significantly higher than it was among offspring born of summer (p < 0.05) or autumn (p < 0.01) conceptions. Offspring sex ratios in spring (p < 0.05), autumn (p < 0.01) and winter (p < 0.05) differed significantly from the expected. In cattle, moon phase and season did not affect the offspring sex ratio; however, the interaction effect was highly significant (p = 0.001). The overall piglet sex ratio (0.522), and the sex ratios among piglets conceived during a crescent moon and those conceived in summer differed significantly (p < 0.05) from 1:1. Research including additional factors such as hormonal treatments prior to insemination, food availability, weather and maternal and paternal factors might provide the underlying reasons for the effects of season and moon phase on offspring sex ratio in some livestock species.     

Seasonal distribution of airborne pollen in Manila,Philippines, and the effect of meteorological factors to its daily concentrations

Pollen-related allergic diseases are a growing health problem. Thus, information on prevalence of airborne pollen may serve as guide for clinicians to accurately manage allergic diseases. In this study, an aeropalynological survey was conducted from November 2013 to October 2014 in Manila, Philippines, to determine the seasonal distribution of the most prevalent airborne pollen and correlate the influence of meteorological factors on their daily concentrations. A volumetric pollen trap was placed on a rooftop, 21 m above ground level. A total of 5677 pollen grains from 18 pollen types were identified, of which Urticaceae, Cannabaceae, Poaceae and Moraceae were the most prevalent. Other pollen types observed that represented 1 % of the total pollen concentration, in descending order, were Terminalia catappa, Myrtaceae, Muntingia calabura, Verbenaceae, Amaranthaceae, Cyperaceae, Caricaceae and Mimosa sp. Of the total airborne pollen, 87 % were obtained during the dry season (November–May). Pollen concentrations peaked (55 %) during the summer months (March–May), indicating a positive correlation (p < 0.01) between pollen concentration and temperature (maximum and mean). Alternatively, only 13 % of the pollen concentrations were obtained during the wet season (June–October). It was observed that pollen concentrations were negatively correlated (p < 0.01) with rainfall and humidity. As the pollen collection was done for one sampling year, only an approximation of the daily concentration of the pollen types was identified and correlated with meteorological factors. Further data collection is required to generate an accurate pollen calendar for use in allergy studies.     

Effects of rotational and continuous grazing on herbage quality,feed intake and performance of sheep on a semi-arid grassland steppe

Compared to continuous grazing (CG), rotational grazing (RG) increases herbage production and thereby the resilience of grasslands to intensive grazing. Results on feed intake and animal performance, however, are contradictory. Hence, the objective of the study was to determine the effects of RG and CG on herbage mass, digestibility of ingested organic matter (dOM), organic matter intake (OMI) and live weight gain (LWG) of sheep in the Inner Mongolian steppe, China. During June–September 2005–2008, two 2-ha plots were used for each grazing system. In RG, plots were divided into four 0.5-ha paddocks that were grazed for 10 days each at a moderate stocking rate. Instead, CG sheep grazed the whole plots throughout the entire grazing season. At the beginning of every month, dOM was estimated from faecal crude protein concentration. Faeces excretion was determined using titanium dioxide in six sheep per plot. The animals were weighed every month to determine their LWG. Across the years, herbage mass did not differ between systems (p = 0.820). However, dOM, OMI and LWG were lower in RG than in CG (p ≤ 0.005). Thus, our study showed that RG does not improve herbage growth, feed intake and performance of sheep and suggests that stocking rates rather than management system determine the ecological sustainability of pastoral livestock systems in semi-arid environments.     

Breeding seasonality and population dynamics of three rodent species in the Magamba Forest Reserve, Western Usambara Mountains, north-east Tanzania

We investigated breeding seasonality and population dynamics of three rodent species, Lophuromys flavopuncatus, Grammomys dolichurus and Praomys delectorum, in the Magamba Forest, Western Usambara Mountains, north‐east Tanzania. Capture–mark–recapture studies were conducted in 2002–2004. Reproductive conditions of males and females showed temporal variations, an indication of breeding seasonality. Animals were reproductively active between February and May. Rainfall in November–January was instrumental for the onset of breeding and continued throughout the wet season. The recruitment of new individuals born during the season led to highest population densities between end of May and August. Populations declined progressively towards the end of the dry season (September–October). Only P. delectorum showed a marked density increase during January–February, indicating greater survival and/or recruitment during the November–January rains. The study shows that despite a relatively stable environment of the forest reserve, rainfall has strong influence on reproduction and population dynamics, probably because of its effect on primary food resources.     

Phenology of Tree Species in Bolivian Dry Forests

Phenological characteristics of 453 individuals representing 39 tree species were investigated in two dry forests of the Lomerío region, Department of Santa Cruz, Bolivia. The leaf, flower, and fruit production of canopy and sub–canopy forest tree species were recorded monthly over a two–year period. Most canopy species lost their leaves during the dry season, whereas nearly all sub–canopy species retained their leaves. Peak leaf fall for canopy trees coincided with the peak of the dry season in July and August. Flushing of new leaves was complete by November in the early rainy season. Flowering and fruiting were bimodal, with a major peak occurring at the end of the dry season (August–October) and a minor peak during the rainy season (January). Fruit development was sufficiently long in this forest that fruiting peaks actually tended to precede flowering peaks by one month. A scarcity of fruit was observed in May, corresponding to the end of the rainy season. With the exception of figs (Ficus), most species had fairly synchronous fruit production. Most canopy trees had small, wind dispersed seeds or fruits that matured during the latter part of the dry season, whereas many sub–canopy tree species produced larger animal– or gravity–dispersed fruits that matured during the peak of the rainy season. Most species produced fruit annually. Lomerio received less rainfall than other tropical dry forests in which phenological studies have been conducted, but rainfall can be plentiful during the dry season in association with the passage of Antarctic cold fronts. Still, phenological patterns in Bolivian dry forests appear to be similar to those of other Neotropical dry forests.     

Variation in evergreen and deciduous species leaf phenology in Assam, India

In the present study phenological activities such as leaf and shoot growth, leaf pool size and leaf fall were observed for 3 years (March 2007–March 2010) in 19 tree species (13 evergreen and 6 deciduous species) in a wet tropical forest in Assam, India. The study area receives total annual average rainfall of 2,318 mm of which most rain fall (>70 %) occurs during June–September. Both the plant groups varied significantly on most of the shoot and leaf phenology parameters. In general, growth in deciduous species initiated before the evergreen species and showed a rapid shoot growth, leaf recruitment and leaf expansion compared to evergreen species. Leaf recruitment period was significantly different between evergreen (4.2 months) and deciduous species (6.8 months). Shoot elongation rate was also significantly different for evergreen and deciduous species (0.09 vs. 0.14 cm day^?1 shoot^?1). Leaf number per shoot was greater for deciduous species than for evergreen species (34 vs. 16 leaves). The average leaf life span of evergreen species (328 ± 32 days) was significantly greater than that of deciduous species (205 ± 16 days). The leaf fall in deciduous species was concentrated during the winter season (Nov–Feb), whereas evergreens retained their leaves until the next growing season. Although the climate of the study area supports evergreen forests, the strategies of the deciduous species such as faster leaf recruitment rate, longer leaf recruitment time, faster shoot elongation rate during favorable growing season and short leaf life span perhaps allows them to coexist with evergreen species that have the liberty to photosynthesize round the year. Variations in phenological strategies perhaps help to reduce the competition among evergreen and deciduous species for resources in these forests and enable the coexistence of both the groups.     

Cross-correlation analysis of invasive mango mealybug and its associated natural enemies in relation to meteorological factors: implications for biological control

Damage caused by invasive downey snow line mealybug, Rastrococcus iceryoides Green (Hemiptera: Pseudococcidae) has been reported to vary between 30% to complete crop loss where no control measure is applied. The current studies seek to determine factors influencing R. iceryoides population outbreaks, parasitoid – host and predator–prey relationships as well as predict optimal management strategies through weather modelling over a period of 28 months from 2008 to 2010 in Tanzania. The highest incidence of R. iceryoides was recorded during the dry season coinciding with the major mango fruiting season. The relationship between R. iceryoides and the parasitoid was positive but not significant, which implies the influence on outbreaks was negligible probably due to low percent parasitism (<12%). However, the predator abundance was directly and significantly related to that of R. iceryoides. Average temperature, average relative humidity, rainfall, and R. iceryoides abundance were autocorrelated to each other. Cross-correlation coef?cients vary significantly from ?0.286 to 0.589 for the pair-variable between R. iceryoides, temperature, relative humidity, rainfall, parasitism and predators. Our findings showed that temperature was the key climatic variable that significantly influenced R. iceryoides outbreaks while rainfall was significantly negatively associated with the pest. Time series analyses show R. iceryoides population increased 4 months after an increase in average temperature in all the sites, 11 months after rainfall and 11 months after relative humidity in Kibaha and Dar es Salaam, respectively. Our findings revealed that R. iceryoides is an excellent target for classical biological control. Thus, the importation of promising co-evolved parasitoid specific to R. iceryoides from the aboriginal home is crucial in formulating an efficient and sustainable management approaches against the invasive mealybug pest in mango agro-ecosystems.     

Cool-dry season depression in gas exchange of canopy leaves and water flux of tropical trees at the northern limit of Asian tropics

Trees on the northern boundary of Asian tropics experience hot-humid and cool-dry seasons, but little is known about their seasonal dynamics in canopy physiology. We used a canopy crane to reach the canopy of nine tropical tree species and measured canopy leaf gas exchange, water status, and trunk sap flux during the hot-humid and cool-dry seasons in Xishuangbanna, China. We found that most tree species exhibited significant reductions in maximum photosynthetic rate (A_max), stomatal conductance (g_smax), predawn and midday leaf water potentials, and maximum sap flux density in the cool-dry season. Compared to the hot-humid season, A_max declined by 19–60%, and maximum water flux declined by ?14% (an increase) to 42%. The cool-dry season decline in A_max of four species can be partly explained by an increased stomatal limitation (decreased g_smax and intercellular CO₂ concentrations). Therefore, a predicted increase in drought in this region may decrease the carbon sequestration and productivity of these forests. We did not find a tradeoff between performance (A_max in the hot-humid season) and persistence through the cool-dry season; species with higher A_max in the hot-humid season did not show higher percent seasonal declines in the cool-dry season. A_max was significantly and positively associated with the trunk sap flux for both seasons, but the association was weaker in the cool-dry season. Thus, our results suggest that some tradeoffs and trait associations are environment dependent. Our results are important for understanding carbon and water fluxes of seasonal tropical forests and their responses to environmental changes.