Analyses of landuse change impacts on catchment runoff using different time indicators based on SWAT model

Previous researches mainly focused on the runoff responses to landuse change based on annual, seasonal or monthly time scales, there are few studies based on daily scale. We conducted a comprehensive investigation into runoff responses on the daily scale as well as annual and monthly time scales using SWAT, and compared the impacts of time scales with different time indicators quantitatively. Jinjiang, a coastal catchment of southeast China with a humid sub-tropical climate, was used for simulations. A calibrated SWAT model produced satisfactory reproduction of annual, monthly and daily runoff processes over a nine-year (2002–2010) period at three gauging stations. Runoff was then simulated and compared using the same meteorological input but two different landuse scenarios (1985 and 2006, with reduced forest and increased cropland and urbanized area). The results showed varying change in runoff among three time scales and three catchments. The annual runoff had the smallest increase between two scenarios, monthly runoffs had medium rates (increasing in all months except October–November), and daily runoff had the largest rates with the increase in flood peaks but decrease in drought flows, because of the variable influence on interception/evapotranspiration loss, percolation and antecedent soil water storage. Indicators of different time scales (annual runoff, monthly runoff, maximum 1-day and 5-day flood runoff, minimum 1-day and 7-day runoff) proved appropriate for analysing landuse change impacts.     

The reproductive behavior of six species of Namib desert tenebrionid beetles (Coleoptera: Tenebrionidae)

The reproductive behavior of six species of tenebrionid beetles (Coleoptera: Tenebrionidae) was studied in the Namib Desert of southern Africa. In three species, males follow closely behind females (following behavior), while in the other three species, males mount females and remain clasped to them for extended periods (riding behavior). Following behavior occurs before and sometimes after copulation, while riding behavior occurs primarily after copulation. Males of all six species guard females from contesting males, although the effectiveness of guarding is greater in riding species. The evolution of the two male mating strategies does not appear to be related to operational sex ratio differences but, rather, to differential tendencies of females to remate. Variation in total pair duration within following and riding species may be attributed partly to species differences in operational sex ratio. However, pair durations are not affected by experimental manipulations of sex ratio in each species.     

Effects of ambient temperature on avian incubation behavior

Ambient temperature is commonly thought to influence avian incubation behavior. However, results of empirical studies examining correlationsbetween ambient temperature and bout duration are equivocal.We propose that these equivocal results can be partly explainedby developing a conceptual understanding of how we should expecttemperature to influence incubation. We demonstrate why linearcorrelation analyses across a wide range of temperatures canbe inappropriate based on development of an incubation model for small birds that incorporates how ambient temperature influencesboth embryonic development and adult metabolism. We found supportfor predictions of the model using incubation data from orange-crownedwarblers (Vermivora celata) in Arizona. Both off- and on-boutduration were positively correlated with ambient temperaturebetween 9° and 26°C, but unrelated to ambient temperature<9° and 26-40°C. Bout durations declined as ambienttemperature approached or exceeded 40°C. Incubating orange-crowned warblers appeared to avoid bouts off the nest <7 min andbouts on the nest <20 min. Time of day, duration of theprevious bout, and variation among nests all explained variationin both on- and off-bout duration. Although we found supportfor the general shape of the incubation model, temperature still explained only a small portion of the overall variation in on-and off-bout duration. Results of previous studies were generallyconsistent with the model for off-bout duration; most studiesin colder environments reported positive correlations withtemperature, and the one negative correlation reported was from a hot environment. However, the relationships between on-boutduration and temperature reported in previous studies wereless consistent with our model and our data. Although somediscrepancies could be explained by considering our model,some studies reported negative correlations in cold environments.The effect of ambient temperature on duration of on-bouts probablydiffers among species based on the amount of fat reserves females typically carry during incubation and the extent of male incubationfeeding. Additional studies of the effects of temperature onavian incubation will help improve the general model and ultimatelyaid our understanding of energetic and ecological constraintson avian incubation.     

Rates of small-scale species mobility in alvar limestone grassland

Abstract. Small-scale species frequency and cumulative species frequency were studied in four plots in limestone grassland of the Veronica spicata-Avenula pratensis association on Stora Alvaret on the Baltic island of Öland, Sweden. Species mobility was expressed as increase in cumulative species frequency in 20 subplots of 100 cm². Observed cumulative frequencies from 1985–1989 in all four plots, and from 1985–1995 in one plot were compared with values following from two null models, a ‘minimal mobility’ model and a random mobility model. In ca. 50 % of the cases the observed cumulative frequency was not significantly different from the random expectation. However, in many such cases the mean annual frequency was either very high or very low. Three ways of calculating the mobility rate are presented though only one is used: (observed cumulative frequency -lowest annual frequency) / expected cumulative frequency. Values × 100 range from 0 to 100. There were slight differences between the four plots which were interpreted in terms of differences in grazing intensity and soil depth. It is stressed that the idea of the Carousel model has never been meant to suggest that all species would show random mobility, which we now quantify, but that species differ in their mobility rate and that the mean rate is much higher than generally realized.     

Tree vigour influences secondary growth but not responsiveness to climatic variability in Holm oak

Many tree species from Mediterranean regions have started to show increased rates of crown defoliation, reduced growth, and dieback associated with the increase in temperatures and changes in the frequency and intensity of drought events experienced during the last decades. In this regard, Quercus ilex L. subsp. ballota [Desf.] (Holm oak), despite being a drought-tolerant species widely distributed in the Mediterranean basin, it has recently started to show acute signs of decline, extended areas from Spain being affected. However, few studies have assessed the role of climatic variability (i.e., temperature, precipitation, and drought) on the decline and resilience of Holm oak. Here, we measured secondary growth of seventy Holm oaks from a coppice stand located in central Spain. Sampled trees had different stages of decline, so they were classified into four vigour groups considering their crown foliar lost: healthy (0%), low defoliated (<25%), highly defoliated (25–70%), and dying (70–100%). Our results showed that during the study period (1980–2009) the highly defoliated and dying Holm oaks grew significantly less than their healthy and low defoliated neighbours, suggesting permanent growth reduction in the less vigorous individuals. Despite these differences, all four vigour groups showed similar responses to climatic variations, especially during winter and late spring – early summer seasons, and similar resilience after severe drought events, managing to significantly recover to pre-drought growth rates after only two years. Our findings, hence, illustrate that tree vigour influences secondary growth but not responsiveness to climatic variability in Holm oak. Still, as reduced growth rates are frequently associated with the process of tree mortality, we conclude that the less vigorous Holm oaks might not be able to cope with future water stress conditions, leading to increased mortality rates among this emblematic Mediterranean species.     

Strategies in Mediterranean grassland annuals in relation to stress and disturbance

Abstract. Morphological (size and shape) and functional (growth, reproduction and phenology) attributes are used to characterize 42 annual species of Mediterranean grasslands according to their strategy. Principal component analysis of the matrix of 42 species x 9 attributes shows that the main trend of variation is related to plant size. Larger species have larger seeds, lower relative growth rates and lower reproductive output. The second and third trends of variation are related to plant shape. Ordination of species shows differences in shape between taxa and growth forms (grasses, legumes, forbs). The relative abundance of species with different attributes vary with the level of stress (water and nutrient availability) and disturbance (grazing and ploughing). Size is related to stress, with larger plants dominating in productive habitats and smaller ones in the most unproductive. Disturbance is related to shape and phenology, since grazing favours species with low canopies and ploughing favours species with shorter life cycles, that are usually small in size. Relations between plant attributes and habitat characteristics are examined within the more general framework of plant strategy theory.     

The role of climate change in the widespread mortality of holm oak in open woodlands of Southwestern Spain

Forest decline and increasing tree mortality are of global concern and the identification of the causes is necessary to develop preventive measures. Global warming is an emerging factor responsible for the increasing tree mortality in drought-prone ecosystems. In the southwestern Iberian Peninsula, Mediterranean holm oak open woodlands currently undergo large-scale population-level tree die-off. In this region, temperature and aridity have increased during recent decades, but the possible role of climate change in the current oak mortality has not been investigated.To assess the role of climate change in oak die-off in managed open woodlands in southwestern Spain, we analyzed climate change-related signals in century-long tree ring chronologies of dead holm oaks. We examined the high/low-frequency variability in growth and the relationship between growth and climate.Similar to other Mediterranean forests, growth was favored by precipitation from autumn of the year prior to ring formation to spring of the year of ring formation, whereas high temperatures during spring limited growth. Since the 1970s, the intensity of the high-frequency response to water availability increased simultaneously with temperature and aridity. The growth trends matched those of climatic changes. Growth suppressions occurred during droughts in the 1970s, 1980s and 1990s. Widespread stand-level, age-independent mortality occurred since 2005 and affected trees that cannot be considered old for the species standards.The close relationship between growth and climate indicate that climate change strongly controlled the growth patterns. This suggests that harsher climatic conditions, especially increased aridity, affected the tree performance and could have played a significant role in the mortality process. Climate change may have exacerbated or predisposed trees to the impact of other factors (e.g. intense management and pathogens). These observations could suggest a similar future increase in oak mortality which may occur in more northern oak open woodlands if aridity further increases.     

Dendrochronological analysis of Sequoia sempervirens in an interior old-growth forest

Dendrochronological studies of large and old Sequoia sempervirens are limited by access and complex crossdating, but core sampling at regular height intervals along the main trunks of five standing trees allowed for reconstruction of growth, height, and age while providing within-tree replication for crossdating. We developed a crossdated ring-width chronology (1453–2015) for redwoods growing in an easternmost old-growth forest in the Napa Range of California, determined aboveground tree attributes, investigated the inter-annual climate-growth relationships since the late 19th century, and documented long-term growth trends. Age, height, f-DBH (functional diameter at breast height), and aboveground biomass of these co-dominant trees ranged from 241 to 783 years, 45.7 to 61.5 m, 117.0 to 226.9 cm, and 9.34 to 33.62 Mg, respectively. Bootstrapped correlation and response function analysis showed radial growth positively related to May through August Palmer Drought Severity Index (PDSI) and negatively related to maximum June temperature (r ≥ │0.47│, P < 0.0001), explaining 33.3% of ring-width variation. Bootstrapped correlations over a moving 40-year window indicated strengthening relationships with PDSI and minimum temperature. The long-term growth trend, reflected by the size-detrended metric of residual wood volume increment (RWVI), varied over time and showed an average one-year decrease of 13.3% for 20th and 21st century droughts. A fire detected in August 1931 corresponded with a one-year decrease in RWVI of 43.1% followed by >100% increase within five years. Growth dynamics for redwoods in this interior forest provide a point of comparison for redwoods previously studied in old-growth forests along the latitudinal gradient, highlighting range-wide trends and site-specific differences in responses to climate and fire.     

Association between misalignment of circadian rhythm and obesity in Korean men: Sixth Korea National Health and Nutrition Examination Survey

ABSTRACT

Background: The disruption of circadian rhythm has been found to associate with obesity in vivo and in vitro. Sleep duration, eating habits, total feeding time, and nightshift work can also affect circadian rhythms. This study investigated the association between misalignment of circadian rhythm and obesity in Korean men, using a cross-sectional database.

Methods: This study used data from the Korean National Health and Nutrition Examination Survey (KNHANES), whose study population was 3,658 men aged 18 to 60 years. General and abdominal obesity was defined as a body mass index (BMI) ≥ 25 kg/m² and waist circumference ≥ 90 cm, respectively. Circadian rhythm factors were determined with a self-report questionnaire and included breakfast frequency, sleep duration, and work time. Frequency of breakfast was divided into regular breakfast (five to seven times a week) and irregular breakfast (less than five times a week). Sleep duration was divided into less than 7 hours, 7–9 hours, and over 9 hours. Working time was defined as day/evening, night shift, and other type. The adjusted odds ratios (aORs) and 95% confidence intervals (CIs) for general and abdominal obesity were calculated using multivariable logistic regression according to the number of factors that disturb the circadian rhythm.

Results: Participants with 1 (aOR 1.34, 95% Cl 1.10–1.61) and ≥2 (aOR 1.62, 95% Cl 1.29–2.05) factors disturbing circadian rhythms were associated with elevated risk for general obesity. Similarly, those with 1 (aOR 1.33, 95% Cl 1.09–1.63) and ≥2 (aOR 1.70, 95% Cl 1.32–2.20) factors had elevated risk for abdominal obesity.

Conclusions: Factors disturbing the circadian rhythm were associated with general and abdominal obesity. Additional studies are needed, and associations with metabolic diseases should be investigated.     

Multi-species response to rapid environmental change in a large estuary system: A biochronological approach

The sensitivity of species to environmental change is dependent on their ecological requirements (i.e. specialist v. generalist), and hence likely to be species-specific. Identifying species level variation in environmental sensitivity informs assessments of community vulnerability and assists in developing adaptive management strategies. We investigated species-specific sensitivity in fish to understand the vulnerability of differing life histories and ecological requirements to rapid environmental alteration (i.e. drought). Biochronologies of fish growth, based on increment widths in otoliths, were analysed using a mixed modelling approach. We assessed multi-decadal responses in fish growth to environmental variation in the terminal system of Australia’s largest river, for three long-lived fish species with differing life histories and ecological requirements: a freshwater specialist and two estuarine generalists. Biochronologies were between 20 and 38 years long, spanned a decade of severe drought and showed considerable inter-annual variation in growth. Precipitation influenced the growth of the obligate freshwater specialist, Macquaria ambigua ambigua. Temperature and salinity influenced the growth of the two estuarine generalists: Argyrosomus japonicus (estuarine opportunist) and Acanthopagrus butcheri (estuarine dependent), respectively. These results suggest that generalisations about how species respond to environmental change may mask species-specific responses to dependent on the constraints of their ecological requirements (i.e. specialist v. generalist). These findings also highlight the importance of considering the diversity of life history strategies that inhabit an ecosystem when developing conservation and management strategies.