Seasonal Decline Research Articles

Water Stress Patterns of Xerophytic Plants in an Urban Landscape

Efficient water use in urban landscapes is a common objective throughout the western United States. Vegetative species promoted for their drought tolerance characteristics are often included in landscapes designed for resource conservation. However, water requirements of most common landscape species have not been quantified. This is especially true for xerophytic species. This lack of landscape plant water requirement data is a significant constraint on the design of efficient irrigation systems and management practices affecting urban landscape water use. Current irrigation practices often fail to consider the unique physiology of xerophytic species, and irrigation scheduling models may not be appropriate for xeric landscapes using xerophytic vegetation as the primary method of reducing water use. This work describes the seasonal patterns of growth and xylem water status for four regionally native xeric shrub species planted in an unirrigated urban landscape in the semi-arid environment of central Oregon. The four species (Artemisia tridentata, Holodiscus microphyllus, Ericameria nauseosa, and Ribes cereum) exhibited substantial growth over the course of 18 months without irrigation in a heavily modified urban soil profile. Water potential of the four species was strongly correlated with surface (10 cm) soil moisture (r ≥ 0.90), less so with reference monthly evapotranspiration (r ≤ 0.55), and only weakly with water vapor deficit (r ≤ 0.22). In A. tridentata and H. microphyllus, xylem water potential became more negative during the growing season and tracked the seasonal decline in soil moisture. In contrast, the xylem water potential of E. nauseosa and R. cereum tracked soil moisture early in the season but became less responsive to soil moisture in the driest months, suggesting different drought adaptation strategies in these species. Three of the four species showed no visual signs of drought stress and maintained acceptable aesthetics even as soil moisture decreased to less than 10%. However, R. cereum exhibited a drought dormancy strategy that made it less aesthetically desirable. These results suggest that extreme xerophytic shrubs provide an opportunity for significant reductions in water use in urban landscapes.

Evaluation of fecal hormones for noninvasive research on reproduction and stress in humpback whales (Megaptera novaeangliae)

Fecal hormone analysis shows high potential for noninvasive assessment of population-level patterns in stress and reproduction of marine mammals. However, the marine environment presents unique challenges for fecal sample collection. Data are still lacking on collection methodology and assay validations for most species, particularly for those mysticete whales that have variable diets. In this study we tested collection techniques for fecal samples of free-swimming humpback whales (Megaptera novaeangliae), and validated immunoassays for five steroid and thyroid hormones. Resulting data were used for preliminary physiological validations, i.e., comparisons to independently confirmed sex and reproductive state. Pregnant females had significantly higher fecal progestins and glucocorticoids than did other demographic categories of whales. Two possible cases of previously undetected pregnancies were noted. Males had significantly higher fecal testosterone metabolites than nonpregnant females. Fecal glucocorticoids were significantly elevated in pregnant females and mature males compared to nonpregnant females. Calf fecal samples had elevated concentrations of all fecal hormones. Fecal thyroid hormones showed a significant seasonal decline from spring to summer. Though sample sizes were small, and sampling was necessarily opportunistic, these patterns indicate that noninvasive fecal hormone analysis may facilitate studies of reproduction, stress and potentially energetics in humpback whales.

The Water Hyacinth Microbiome: Link Between Carbon Turnover and Nutrient Cycling.

Water hyacinth (WH), a large floating plant, plays an important role in the biogeochemistry and ecology of many freshwaters globally. Its biogeochemical impact on wetland functioning is strongly mediated by the microbiome associated with its roots. However, little is known about the structure and function of this WH rhizobiome and its relation to wetland ecosystem functioning. Here, we unveil the core and transient rhizobiomes of WH and their key biogeochemical functions in two of the world's largest wetlands: the Amazon and the Pantanal. WH hosts a highly diverse microbial community shaped by spatiotemporal changes. Proteobacteria lineages were most common, followed by Actinobacteria and Planctomycetes. Deltaproteobacteria and Sphingobacteriia predominated in the core microbiome, potentially associated with polysaccharide degradation and fermentation of plant-derived carbon. Conversely, a plethora of lineages were transient, including highly abundant Acinetobacter, Acidobacteria subgroup 6, and methanotrophs, thus assuring diverse taxonomic signatures in the two different wetlands. Our findings point out that methanogenesis is a key driver of, and proxy for, community structure, especially during seasonal plant decline. We provide ecologically relevant insights into the WH microbiome, which is a key element linking plant-associated carbon turnover with other biogeochemical fluxes in tropical wetlands.

Composition and settling properties of suspended particulate matter in estuaries of the Chesapeake Bay and Baltic Sea regions

Our goal was to understand how differences in source material (allochthonous vs. autochthonous) and phytoplankton communities (diatoms vs. cyanobacteria) influence composition and settling properties of suspended particulate matter. We characterized the composition and settling properties of suspended particulate matter in two systems—one which has a high hydrologic loading factor (watershed to surface area ratio), and a diatom-dominated phytoplankton community (James River Estuary, USA), and a second, where hydrologic inputs are proportionally smaller, and the summer phytoplankton community is dominated by cyanobacteria (Curonian Lagoon, Lithuania). In the James, we found that TSS concentrations were positively related to discharge, whereas POC concentrations were negatively correlated with discharge and positively correlated with Chl-a. We infer that suspended particulate matter in this system was largely derived from allochthonous inputs, but that the organic matter fraction was derived from autochthonous production. In the Curonian Lagoon, TSS concentrations were correlated with Chl-a, but not discharge, indicating that suspended particulate matter was largely of autochthonous origin. In the James, the proportion of settleable materials was greater during high TSS concentrations, indicating that high discharge events delivered heavier particulates. In the Curonian Lagoon, we observed a seasonal decline in settling rates associated with the shift from mixed (diatoms and chlorophytes) to cyanobacteria-dominated phytoplankton, which we attribute to the presence of positively buoyant cyanobacteria. We found that a comparative approach yielded useful insights regarding sources, composition, and settling properties of suspended particulate matter in two estuaries that differ in hydrologic loading and phytoplankton community composition. Our findings suggest that the presence of positively buoyant cyanobacteria favors export losses of particulate C, N, and P to marine waters over retention through sedimentation in transitional zones.

Investigation of subglacial weathering under the Greenland Ice Sheet using silicon isotopes

Subglacial chemical weathering plays a key role in global silicate weathering budgets, contributing to the cycling of silicon (Si) in terrestrial and marine systems and the potential drawdown of carbon dioxide from the atmosphere. Here, we use data from two Greenland Ice Sheet (GrIS) catchments to demonstrate how Si isotopes from dissolved and amorphous particulate fractions (δ30DSi and δ30ASi respectively) can be used together with major ion data to assess the degree of secondary silicate weathering product formation and redissolution in subglacial environments. We compare a time-series of summer melt seasons from the two study sites, which differ in catchment size (∼600 km2 for Leverett Glacier (LG) and ∼36 km2 for Kiattuut Sermiat (KS)). Subglacial waters from LG have elevated Na+ and K+ ions in relation to Ca2+ and Mg2+ ions, indicating a predominance of silicate weathering, whilst meltwaters from KS are characterised by carbonate weathering (hydrolysis and carbonation) throughout the melt season. Both catchments have mean δ30DSi values substantially lower than average riverine values (KS 0.41‰, LG −0.25‰, versus a global riverine mean of 1.25‰) and display a seasonal decline, which is more pronounced at LG. The δ30ASi values (discharge weighted mean values KS −0.44‰, LG −0.22‰) are lighter than the bedrock (mean values KS −0.18 ± 0.12‰, LG 0.00 ± 0.07‰) in both catchments, indicating a secondary weathering product origin or leaching of lighter isotopes during initial weathering of crushed rock. When used in combination, the major ion and silicon isotope data reveal that the extent of silicate weathering and secondary phase redissolution are more pronounced at LG compared to KS. Contrasting weathering regimes and subglacial hydrology between catchments need to be considered when estimating the δ30Si composition of silica exported into polar oceans from the GrIS, with larger catchments likely to produce fluxes of lighter δ30Si. As larger catchments dominate freshwater export to the ocean, GrIS meltwater is likely to be very light in isotopic composition, and the flux is likely to increase with ice melt as the climate warms.

Interspecific aggression declines seasonally in breeding great tits Parus major

AbstractDuring the breeding season, great tits show aggression to protect their nest from intra‐ and interspecific intruders. Aggression is a labile trait that can be plastically expressed as a result of individual differences (e.g., personality), seasonal gradients in the costs and benefits of aggression, or other environmental components (e.g., number of competitors). Competitors may try to take over great tit nests, because the number of suitable nesting sites is limited, and great tits may guard high quality territories. Taking over a great tit nest may be especially fruitful in early phenological stages (egg laying) when great tits frequent their nests less often. However, great tits may compensate for this vulnerability by being more aggressive toward intruders during early nesting stages, a pattern that has already been established in an intraspecific context. Previous studies have shown that interspecific intruders were most likely to die from great tit aggression during great tit egg laying, suggesting great tits may also be more aggressive during this phase in an interspecific context. Here, I tested this hypothesis with simulated territorial intrusions in great tit territories using taxidermized blue tits Cyanistes caeruleus (hereafter called blue tit models). Great tit aggression (number of calls and approach distance toward blue tit model) was assayed during egg laying, incubation, and chick rearing in the breeding season of 2014. Although sample size was low due to a high fraction of non‐responders (n = 44 out of 89 assays across 26 out of 35 individuals), I found that great tits showed a seasonal decline in aggressiveness, which is congruent with intraspecific results on this study species. I discuss my findings in the context of differential adjustment to climate change between interspecific competitors.

Temperature induced shifts in leaf water relations and growth efficiency indicate climate change may limit aspen growth in the Colorado Rockies

Higher temperatures and evaporative demand forecasted for Colorado forests by the end of the century suggest that soil water limitation increasingly will negatively impact whole plant performance. At the same time, upslope or poleward migration of plant ranges in response to warming may result in species experiencing cooler overnight temperatures, particularly if extremes in climate increase. In 2014 we established three experimental gardens along a temperature/elevation gradient to test the implications of shifting temperatures on tree function. Quaking aspen (Populus tremuloides) seedlings from a mid-elevation population were established in all three gardens and leaves were sampled monthly during the 2017 growing season. From these, we quantified the magnitude and timing of osmotic regulation, the relationships between leaf osmotic potential (Ψosm), midday leaf water potential (Ψmid), and soil moisture conditions under different temperature regimes, and growth efficiency (change in basal area/growing day). We observed a strong relationship between Ψosm and soil moisture, and a strong seasonal decline in Ψosm at the warmest and intermediate sites while the coldest site experienced a later increase in osmolytes associated with the highest degree of freeze tolerance. Growth efficiency was highest at the intermediate-temperature site – closest in elevation to the seed source location – but declined asymmetrically with warming or cooling. The novel abiotic conditions at both non-local sites resulted in declines in growth efficiency, suggesting that aspen will experience suboptimal conditions whether it stays in areas experiencing warming temperatures or if it migrates upslope to areas with colder overnight temperatures.

The role of fruit exposure in the late season decline of grape berry mesocarp cell vitality

Loss of cell vitality in the mesocarp of grape (Vitis vinifera L.) berries during late ripening is programmed and under genetic control. Environmental factors such as temperature and vine water status, however, have a strong influence on the onset and extent of cell death. Following preliminary observations made on field experiment fruit, the hypothesis that exposure (increased light interception and wind velocity) at the berry level is important to the progression of cell death was tested. Transpiration, mesocarp cell vitality and total soluble solids concentration were compared in exposed and sheltered berries within single Shiraz vines. At oenological maturity (24 °Brix), exposed berries exhibited the same extent of cell death as sheltered berries, and it was not until four weeks later that cell death was more extensive in the exposed treatment. Therefore, under the conditions of this study, increased exposure over the ripening period was not a strong predictor of the extent of cell vitality at maturity. However, the results are consistent with an increase in the importance of environmental effects (including rain and exposure) on mesocarp cell death over the course of berry development, particularly in overripe fruit.

Causes of seasonal decline in reproduction of the cooperatively‐breeding acorn woodpecker

Clutch size and reproductive success decline seasonally in a wide range of temperate avian taxa. Two competing hypotheses have been proposed to explain such declines: the ‘timing’ hypothesis, which states that conditions affecting reproduction decline intrinsically with date, and the ‘quality’ hypothesis, which proposes that high‐quality individuals or individuals in high‐quality situations breed earlier. We contrasted the relative importance of these two hypotheses using a long‐term dataset of the cooperatively‐breeding acorn woodpecker Melanerpes formicivorus in central coastal California (USA). This population exhibits an 11% seasonal decline in clutch size, a 60% seasonal decline in fledging success, and a 77% seasonal decline in fledgling overwinter survival. Clutch size tracks seasonal availability of flying insects, which are a likely ecological driver of the seasonal decline in reproduction and, because of the nonlinear relationship of flying insects with date, constitute a likely factor constraining even earlier nesting. By parsing lay date data into within‐female and between‐female components, we found that only the within‐female component had a statistically significant direct effect on clutch size, supporting the timing hypothesis. For both fledging success and overwinter survival, however, both within‐ and between‐female effects were highly significant, with between‐female effects (differences in female quality) being stronger than within‐female effects. These results suggest that timing per se is a key factor affecting the seasonal decline in clutch size, but that both differences in female quality and an intrinsic seasonal decline in conditions drive the even more dramatic seasonal declines in fledging success and overwinter survivorship of fledglings.

Context‐dependent conservation of the cavity‐nesting European Roller

To maximize the effectiveness of conservation interventions, it is crucial to have an understanding of how intraspecific variation determines the relative importance of potential limiting factors. For bird populations, limiting factors include nest‐site availability and foraging resources, with the former often addressed through the provision of artificial nestboxes. However, the effectiveness of artificial nestboxes depends on the relative importance of nest‐site vs. foraging resource limitations. Here, we investigate factors driving variation in breeding density, nestbox occupation and productivity in two contrasting study populations of the European Roller Coracias garrulus, an obligate cavity‐nesting insectivorous bird. Breeding density was more than four times higher at the French study site than at the Latvian site, and there was a positive correlation between breeding density (at the 1‐km2 scale) and nest‐site availability in France, whereas there was a positive correlation between breeding density and foraging resource availability in Latvia. Similarly, the probability of a nestbox being occupied increased with predicted foraging resource availability in Latvia but not in France. We detected no positive effect of foraging resource availability on productivity at either site, with most variation in breeding success driven by temporal effects: a seasonal decline in France and strong interannual fluctuations in Latvia. Our results indicate that the factors limiting local breeding density can vary across a species' range, resulting in different conservation priorities. Nestbox provisioning is a sufficient short‐term conservation solution at our French study site, where foraging resources are typically abundant, but in Latvia the restoration of foraging habitat may be more important.

Seasonal decline of the tomato leafminer, Tuta absoluta, in the shifting landscape of a vegetable‐growing area

AbstractInsect pest populations exhibit seasonal dynamics in response to changes in resource availability or other environmental factors such as climatic conditions, natural enemies, and intra‐ or interspecific competition. Understanding such dynamics is critical for developing effective integrated pest management strategies. The objective of the present study was to identify factors driving the seasonal decline of the tomato leafminer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), in the shifting landscape of a vegetable‐growing area in Senegal. A set of 42 tomato fields was monitored for the number of T. absoluta adults caught in pheromone traps and for the incidence of larvae, during 5 months from June to November 2016 in the Niayes area (Senegal). The surface of solanaceous host crops, climatic conditions, and abundance of natural enemies were also monitored. A drastic decline in T. absoluta abundance was observed during the rainy season. The decrease in resource availability, especially tomato crops, in the surrounding landscape of monitored fields was the main factor affecting the population dynamics during the rainy season. However, alternative host crops such as eggplant and Ethiopian eggplant, can provide ‘reservoirs’ for residual populations of the pest. For applied purpose, it would be interesting to focus the management efforts on residual populations during the rainy season, to make more difficult the reconstitution of populations during the dry season.

Variation in body condition of songbirds during breeding season in relation to sex, migration strategy and weather

Animal body reserves are often linked with demographic parameters such as breeding success and survival. During breeding season individuals face a trade-off between maintaining body reserves and investing in reproduction. Factors influencing the body reserves of species during breeding season are poorly understood. In this study, we used long-term trapping data from Finnish Constant Effort Sites program to evaluate the impact of sex, migration behaviour, and weather on body reserve index (BRI) of old and young birds during breeding season in 20 species. Our main interest was to study how variation in weather conditions influences the BRI of breeding passerine birds. Weather variables did not explain BRI of adults. However, we found that BRI of young birds was weakly negatively connected with mean temperature, but this may have low biological importance. BRI of adult males increased towards the end of August, but female BRI showed a seasonal decline throughout June and July.

Gestational Age and Maternal Serum 25-hydroxyvitamin D Concentration Interact to Affect the 24,25-dihydroxyvitamin D Concentration in Pregnant Adolescents

Interpretation of serum vitamin D biomarkers across pregnancy is complex due to limited understanding of pregnancy adaptations in vitamin D metabolism. During pregnancy, both gestational age and serum 25-hydroxyvitamin D [25(OH)D] concentrations may influence the concentrations of 1,25-dihydroxyvitamin D [1,25(OH)2D], 24,25-dihydroxyvitamin D [24,25(OH)2D], and parathyroid hormone (PTH). We aimed to identify predictors of change in serum 25(OH)D across gestation in pregnant adolescents and to assess the contribution made by cholecalciferol (vitamin D3) supplementation. We sought to determine whether gestational age and 25(OH)D concentration interacted to affect serum 1,25(OH)2D, 24,25(OH)2D, or PTH. Pregnant adolescents (n=78, 59% African American, mean ± SD age: 17±1 y) living in Rochester, NY (latitude 43°N) were supplemented with 200 IU or 2000 IU vitamin D3/d and allowed to continue their daily prenatal supplement that contained 400 IU vitamin D3. Serum was collected at study entry (18±5 wk of gestation), halfway through study participation, and at delivery (40±2 wk). Serum concentrations of the biochemical markers were modeled with linear mixed-effects regression models. Vitamin D3 supplement intake and season of delivery determined change in 25(OH)D across pregnancy. Fall-winter delivery was associated with a decline in 25(OH)D unless vitamin D3 supplement intake was >872 IU/d. The interaction of gestational age and 25(OH)D affected 24,25(OH)2D concentrations. For a given 25(OH)D concentration, model-predicted serum 24,25(OH)2D increased across gestation except when 25(OH)D was <13 ng/mL. Below this threshold, 24,25(OH)2D was predicted to decline over time. Mean serum 1,25(OH)2D was elevated (>100 pg/mL) throughout the study. Our results suggest that when maternal serum 25(OH)D was low, its catabolism into 24,25(OH)2D decreased or remained stable as pregnancy progressed in order to maintain persistently elevated serum 1,25(OH)2D. Furthermore, in adolescents living at latitude 43°N, standard prenatal supplementation did not prevent a seasonal decline in 25(OH)D during pregnancy. This study was registered at clinicaltrials.gov as NCT01815047.

Dynamics and evolution of Turgay‐type vegetation in Western Siberia throughout the early Oligocene to earliest Miocene—a study based on diversity of plant functional types in the carpological record

AbstractBased on ecospectra of 66 published carpofloras we study dynamics and evolution of Turgay vegetation in Western Siberia during the early Oligocene to earliest Miocene. The ecospectra are obtained using a Plant Functional Type (PFT) classification system comprising 26 herbaceous to arboreal PFTs. The carpofloras originate from seven floristic levels covering the time‐span from the Rupelian to early Aquitanian. Key elements of these levels are documented based on original collection materials. Although impacted by local edaphic conditions, the ecospectra can be interpreted in terms of changing vegetation. Our data show that warm temperate mesophytic, mixed conifer‐broad‐leaved deciduous forest assemblages persisted throughout the Oligocene and earliest Miocene in this core area of Turgai type vegetation. This is in line with comparatively stable climate conditions persisting in the studied time‐span, showing a minor temperature decline and coeval moderate increase in seasonality and precipitation. Concurrently, the reconstructed ecospectra contradict significant continental drying throughout the Oligocene and earliest Miocene. Spatial variability of the proportions of PFTs within the single floristic horizons primarily reflects local edaphic conditions. High diversities of PFTs characteristic for swamp vegetation are mainly confined to the early Oligocene and have a regional focus. Our results indicate that taxonomical diversity, particularly concerning mesic herbs and deciduous shrubs and trees, increased towards the end of the Oligocene. This increase in biodiversity probably can be attributed to an increase in rainfall and extension of terrestrial habitats after the final retreat of the Paratethys.

Higher rates of prebreeding condition gain positively impacts clutch size: A mechanistic test of the condition‐dependent individual optimization model

Abstract A combination of timing of and body condition (i.e., mass) at arrival on the breeding grounds interact to influence the optimal combination of the timing of reproduction and clutch size in migratory species. This relationship has been formalized by Rowe et al. in a condition‐dependent individual optimization model (American Naturalist, 1994, 143, 689‐722), which has been empirically tested and validated in avian species with a capital‐based breeding strategy. This model makes a key, but currently untested prediction; that variation in the rate of body condition gain will shift the optimal combination of laying date and clutch size. This prediction is essential because it implies that individuals can compensate for the challenges associated with late timing of arrival or poor body condition at arrival on the breeding grounds through adjustment of their life history investment decisions, in an attempt to maximize fitness. Using an 11‐year data set in arctic‐nesting common eiders (Somateria mollissima), quantification of fattening rates using plasma triglycerides (an energetic metabolite), and a path analysis approach, we test this prediction of this optimization model; controlling for arrival date and body condition, females that fatten more quickly will adjust the optimal combination of lay date and clutch size, in favour of a larger clutch size. As predicted, females fattening at higher rates initiated clutches earlier and produced larger clutch sizes, indicating that fattening rate is an important factor in addition to arrival date and body condition in predicting individual variation in reproductive investment. However, there was no direct effect of fattening rate on clutch size (i.e., birds laying on the same date had similar clutch sizes, independent of their fattening rate). Instead, fattening rate indirectly affected clutch size via earlier lay dates, thus not supporting the original predictions of the optimization model. Our results demonstrate that variation in the rate of condition gain allows individuals to shift flexibly along the seasonal decline in clutch size to presumably optimize the combination of laying date and clutch size. A plain language summary is available for this article.

Summer dry-down modulates the isotopic composition of soil CO2 production in snow-dominated landscapes.

In mountainous landscapes, soil moisture is highly dynamic due to the effects of topography and the temporal variability imposed by seasonal precipitation, including rainfall and snow. Soil moisture is known to affect ecosystem carbon exchange both aboveground and belowground, as well as the stable isotopic composition of exchanged CO2. In this study we used an extensive suite of measurements to examine the effects of seasonal changes in soil moisture on the isotopic composition of soil CO2 production at the landscape level. We show that the seasonal decline in soil moisture (i.e., summer dry-down) appeared to impose a trend in the δ13C of soil CO2 production (δP) with more negative δP early in the growing season when soils were wet, and more positive δP as the growing season progressed and soils dried out. This seemingly generalizable pattern for a snow-dominated watershed is likely to represent the variability of recently assimilated C, tracked through the plant-soil system and imprinted in the respired CO2. Thus, our observations suggest that, at least for mountainous environments, seasonal changes in δP are largely mediated by soil moisture and their spatial variability is partially organized by topography.

Benefits of 8-wk Mindfulness-based Stress Reduction or Aerobic Training on Seasonal Declines in Physical Activity.

ABSTRACTMindfulness-based stress reduction (MBSR) and aerobic exercise training (AET) programs improve health and well-being. Exercise participation has been related to mindfulness and may be altered by MBSR training.PurposeThis study aimed to compare 8 wk of MBSR, AET, and no-treatment control during the fall season on objectively measured physical activity in healthy adults.MethodsParticipants (n = 66) wore an ActiGraph GT3X+ accelerometer for 7 d prerandomization and after 8 wk MBSR or AET interventions, or neither (control). Mean daily minutes (min) of moderate-to-vigorous physical activities (MVPA) were calculated along with weekly time spent in bouts of MVPA ≥10 min (MVPABouts) to assess physical activity sufficient to meet national guidelines. Groups were compared on pairwise changes in outcomes across time. Effect sizes were calculated using Cohen’s d.ResultsSufficient data (≥3 weekdays, ≥1 weekend day, and ≥10 h·d−1) were obtained from 49 participants (18 MBSR, 14 AET, and 17 control). Daily MVPA decreased in all groups from prerandomization to postintervention (August to November); control decreased 17.9 ± 25.7 min·d−1, MBSR decreased 5.7 ± 7.5 min·d−1, and AET decreased 7.4 ± 14.3 min·d−1 (mean ± SD), without significant differences among the groups (all P > 0.05). MVPABouts decreased 77.3 ± 106.6 min·wk−1 in control and 15.5 ± 37.0 min·wk−1 in MBSR (between-group difference: P = 0.08; d = 0.86), whereas it increased by 5.7 ± 64.1 min·wk−1 in AET (compared with control: P = 0.029; d = 0.97; compared with MBSR; P = 0.564; d = 0.29).ConclusionData from participants in a randomized controlled trial showed that although AET increases MVPA bouts compared with no treatment, MBSR training may also mitigate the influence of shorter day length and cooler weather on participation in physical activities. Future research is needed to determine how MBSR affects exercise to inform interventions. Interventions combining MBSR and exercise may be particularly successful at increasing physical activity participation.

Thermal Tolerance and Survival of Nile Tilapia and Blue Tilapia under Rapid and Natural Temperature Declination Rates

AbstractBlue Tilapia Oreochromis aureus and Nile Tilapia O. niloticus are indigenous to Africa and the Middle East but now are globally popular in aquaculture and for private and public stocking as forage fish for sport species and biological control for nuisance vegetation. The invasive nature of these species at a global scale and the lack of recent and applicably tested thermal tolerance methodology require research to assess the current potential for invasion risk in North Carolina and elsewhere. In this thermal tolerance experiment we focused on a moderate declination rate (1°C per 3 d) and a slow declination rate (1°C per week) in water temperature to assess the thermal minima of Blue Tilapia, common Nile Tilapia, and a “white” strain of Nile Tilapia. The moderate rate was used to compare results to previous literature, and the slow rate was used to mimic natural seasonal water temperature decline in North Carolina. As lineage and breeding history may vary by supplier, fish from multiple suppliers within each species group were tested. Our results indicate that in general, these tilapias cannot survive below 8°C. We did not observe differences in temperature at death or survival curves between species in the moderate rate treatment. Under the slow declination rate, we found significant differences in the mean temperatures at death of Blue Tilapia (9.5°C) and white Nile Tilapia (9.3°C) relative to the less‐cold‐tolerant common Nile Tilapia (10.8°C); this result was reflected in statistically different survival curves. In addition, although there was some variation in temperature at death among different supplier groups (0.0–0.6°C) within a species, all fish died at 8°C or above. Our results suggest that selective breeding of white Nile Tilapia may have resulted in increased thermal tolerance during the process of developing this color variant. Furthermore, the minimum lethal temperature of 8°C may explain why these tilapia species have been restricted to reservoirs with heated effluent in North Carolina.

Smallholder dairy cattle feeding technologies and practices in Tanzania: failures, successes, challenges and prospects for sustainability

ABSTRACTIn Tanzania, milk production under smallholder farming systems is season sensitive, fluctuations of feeds in both quantity and quality being the major driver. A dry season decline in milk production of over 40% due to feed scarcity is a common phenomenon. Adoption of improved feed production, conservation and utilization technologies and practices in dairy farming communities is poor. This review work was based on a key question which states “Why is adoption of improved dairy nutrition technologies and practices in Tanzania still poor despite being promoted for decades?”. We have shown that major opportunities for curbing dry season animal feed shortage include on-farm optimization of production and use of high yielding pasture varieties including napier grass (Pennisetum purperium Schumach.) and leguminous fodder species. Crop residues in particular maize stover needs to be optimized for effective dry season feeding. The major reasons for low adoption of proven technologies include limited technical knowhow among smallholder dairy farmers augmented by limited extension services and technological costs. For enhancing sustainable uptake; we suggest promotion of on-farm research, public-private partnerships and dairy farmers’ cooperative associations. These are vital for facilitating smooth access to information, investment capital, reliable inputs and markets among the smallholder dairy farmers.

'Stick with your own kind, or hang with the locals?' Implications of shoaling strategy for tropical reef fish on a range-expansion frontline.

Range shifts of tropical marine species to temperate latitudes are predicted to increase as a consequence of climate change. To date, the research focus on climate-mediated range shifts has been predominately dealt with the physiological capacity of tropical species to cope with the thermal challenges imposed by temperate latitudes. Behavioural traits of individuals in the novel temperate environment have not previously been investigated, however, they are also likely to play a key role in determining the establishment success of individual species at the range-expansion forefront. The aim of this study was to investigate the effect of shoaling strategy on the performance of juvenile tropical reef fishes that recruit annually to temperate waters off the south east coast of Australia. Specifically, we compared body-size distributions and the seasonal decline in abundance through time of juvenile tropical fishes that shoaled with native temperate species ('mixed' shoals) to those that shoaled only with conspecifics (as would be the case in their tropical range). We found that shoaling with temperate native species benefitted juvenile tropical reef fishes, with individuals in 'mixed' shoals attaining larger body-sizes over the season than those in 'tropical-only' shoals. This benefit in terms of population body-size distributions was accompanied by greater social cohesion of 'mixed' shoals across the season. Our results highlight the impact that sociality and behavioural plasticity are likely to play in determining the impact on native fish communities of climate-induced range expansion of coral reef fishes.