Overnight formation of a bouldery alluvial fan by a torrential rain in a granitic mountain (Mt. Seoraksan, Republic of Korea)

Mt. Seoraksan, Korea, is a rugged granitic mountain where extremely steep slopes and strongly seasonal rainfall have facilitated bedrock exposure and geomorphic changes mainly by rockfalls and streamflows. Although the environment was not suitable for alluvial fan formation, a bouldery alluvial fan, 170 m long and 330 m wide, formed overnight by a heavy summer rain in 2006. The fan consists of several meter-high boulder mounds and gently undulating cobble bars/sheets that are arranged in a fluvial longitudinal bar-like pattern. They are interpreted to have formed by highly competent and turbulent sheetfloods, which temporarily had the properties of hyperconcentrated flood flows. Formation of the whole alluvial fan by a single, casual hydro-meteorological event is inferred to have been possible because a threshold condition was reached in the source area. A rainfall event, which would have had no extreme effects before reaching the threshold, could probably trigger massive remobilization of bouldery sediments on the valley floors. The Seoraksan alluvial fan thus demonstrates the role of a geomorphic threshold in causing drastic changes in the hydrologic performance of the watershed. The morphology and sedimentology of the Seoraksan alluvial fan suggest that the fan is a modern example of a sheetflood-dominated alluvial fan, which has largely been ignored in spite of their potential diversity and abundance in glacial to periglacial, tropical, and temperate environments.

Bisphenol A Acts As Developmental Agonist in Culex Quinquefasciatus Say

Plastic – derived Bisphenol A (BPA) contaminated sewages in Trivandrum, Kerala, India are mosquito breeding sites. After summer rain, BPA in the stagnant water samples ranged between 0.86 and 1.14ppm. 1.0 ppm BPA is considered as environmentally relevant concentration. Present study revealed that BPA is a developmental agonist of Culex quinquefasciatus. Embryonic and larval development are shortened by BPA but pupal development is unaffected. Under the atmospheric temperature of 26 to 310C lifecycle was completed within 312 hours but during summer it was completed within 278 hours, meanwhile atmospheric temperature ranged between 30 and 370C. Reduction in the duration of development due to BPA was 50 to 70 hours during summer and 60 to 80 hours in other seasons. Larval – pupal stadium of the mosquito has three surges of 20-hydroxy ecdysone(20-HE), at 24,32 and 48th hour of the 4th instar. BPA resulted dose-dependent advancement of 20-HE peaks, Phospholipase A2 induction and expression of Ecdysone receptor EcRA and Ecdysone inducible gene E75A, which culminated in early pupation. Adults emerging from 1.0 ppm BPA treatment did not show significant difference in sanguivory and fecundity compared to control but pupae developed in 2 and 4 ppm BPA were significantly small.

Effects of Longer Droughts on Holm Oak Quercus ilex L. Acorn Pests: Consequences for Infestation Rates, Seed Biomass and Embryo Survival

The effects of climate change on oaks Quercus spp. constitute a main environmental concern for the conservation of temperate forests. In this context, we assessed the consequences of longer droughts on the interactions between the holm oak Quercus ilex L. and its main acorn pests. Infested acorns were prematurely abscised before reaching their potential size. The volume of the acorns attacked by Cydia fagiglandana (Lepidoptera) was smaller than those attacked by Curculio elephas (Coleoptera); however, their weight did not differ because Curculio larvae consumed more cotyledon. For the same reason, embryo survival likelihood was not lower in Cydia acorns despite their smaller size. Delays of late summer rain reduced infestation by Curculio, as soil hardness hampers adult emergence from their underground cells. By contrast, late and scarce precipitations benefited Cydia; rainfall might hamper adult flight and eggs/L1 larvae survival. There was not a “zero-sum” effect, because the decrease of Curculio infestation rates was not fully compensated by an increase of Cydia. Under the longer droughts projected for the Mediterranean Basin, our results predict lower infestation rates and higher acorn survival likelihood. However, further studies including other environmental factors are needed to better forecast the net consequences for holm oak fitness.

Using a dew point temperature scaling framework to interpret changes in hourly extremes from convection-permitting model simulations

<p>While summer rain storms are very intermittent, chaotic and influenced by multiple atmospheric drivers, some statistics of observed short duration precipitation actually display surprisingly simple, regular behaviour. As an example, 10-min rainfall extremes derived from Dutch climate data show a dependency of 13% per degree over an almost 20-degree dew point temperature range. Similar behaviour has also been found in hourly precipitation observations. Each degree of warming reflects 6-7% more moisture in the air,  following from the well-known Clausius-Clapeyron (CC) relation which is the cornerstone to understand and quantify the influence of climate change on precipitation extremes.  According to the above finding, however, precipitation intensities may be increasing with temperature at a rate twice the commonly expected CC rate. In this presentation we will use output from a number of 10-year simulations for present-day and future climate with the convection permitting model HCLIM-AROME to investigate how hourly extremes respond to warming in both a pseudo global warming (PGW) and a GCM driven setup. In particular, we use the scaling diagram -- different percentiles of the rainfall distribution, usually the 90, and 99th conditioned on the occurrence of rain, as a function of dew  point temperature -- as a analysis environment. Focus will be on how the scaling diagram is affected by climate change, and what information can be derived from these changes in scaling. While changes in the scaling diagram between present-day and future climate are in general consistent with a CC prediction, evidence of super CC behaviour, between 10 and 14 % per degree dew point, is also present. The same applies to changes in the most extreme events from the simulations, which show super CC behaviour in both PGW and GCM driven setups when scaled with the appropriate dew point temperature change. </p>

Seasonal origins of soil water used by trees

Rain recharges soil water storages and either percolates downward into aquifers and streams or is returned to the atmosphere through evapotranspiration. Although it is commonly assumed that summer rainfall recharges plant-available water during the growing season, the seasonal origins of water used by plants have not been systematically explored. We characterize the seasonal origins of waters in soils and trees by comparing their midsummer isotopic signatures (δ2H) to seasonal isotopic cycles in precipitation, using a new seasonal origin index. Across 182 Swiss forest sites, xylem water isotopic signatures show that summer rain was not the predominant water source for midsummer transpiration in any of the three sampled tree species. Beech and oak mostly used winter precipitation, whereas spruce used water of more diverse seasonal origins. Even in the same plots, beech consistently used more winter precipitation than spruce, demonstrating consistent niche partitioning in the rhizosphere. All three species' xylem water isotopes indicate that trees used more winter precipitation in drier regions, potentially mitigating their vulnerability to summer droughts. The widespread occurrence of winter isotopic signatures in midsummer xylem implies that growing-season rainfall may have minimally recharged the soil water storages that supply tree growth, even across diverse humid climates (690–2068 mm annual precipitation). These results challenge common assumptions concerning how water flows through soils and is accessed by trees. Beyond these ecological and hydrological implications, our findings also imply that stable isotopes of δ18O and δ2H in plant tissues, which are often used in climate reconstructions, may not reflect water from growing-season climates.

Seed yield and subsequent emergence pattern of subterranean clover cultivars in response to summer rain

At Lincoln University, Canterbury, seven subterranean cultivars rated in Australia as having different levels of ‘hardseedeness’ were established. Monocultures were sown in autumn and allowed to grow and set seed. Seed yields ranged from 340 to 1050 kg/ha. Heavy rain in early January 2016 resulted in a “false strike” of ≤ 4.0% of seeds during the subsequent dry February. A second emergence event in March also resulted in a “false strike” with a further 7 to 15% of total seeds lost. However, cultivars established >1000 seedlings/m2 after early winter rain, which is considered adequate for future persistence. Emergence was consistent with Australian hardseededness rankings. Cultivars with hardseed ranks <4 may be more suitable for dryland systems in New Zealand due to their early emergence and the ability to exploit the late summer and autumn rains.