Wet Summer Months Research Articles

A muted El Niño-like condition during late MIS 3

The evolutionary dynamics of El Niño Southern Oscillation (ENSO) over the last glacial period remains understudied, despite its potential in providing a “cold case” for climate sensitivity studies. Here, we investigate SE Asian-Pacific paleoclimate records to decipher the dominant underlying mechanism that governed tropical Asian-Pacific hydrology during MIS 3. Our results suggest that the glacial emergence of the Sunda Shelf likely altered the atmospheric circulation pattern in Southeast (SE) Asia and led to the realignment of rainfall patterns between Thailand and Indonesia during the last glacial period. We also propose that the long-term hydrological regime change in the tropical Asian-Pacific region during MIS 3 was mainly influenced by an El Niño-like mechanism. An intense El Niño-like condition led to strong aridity in SE Asia during mid MIS 3. By late MIS 3, an enhanced seasonality dampened the intensity of the El Niño-like conditions, thus, leading to muted aridity in SE Asia. The alternating warm and wet summer months and droughts during winter favoured the proliferation of C4 plant types in Northern Thailand from mid MIS 3 to late MIS 3.

Seasonal and Diurnal Cycles of Surface Boundary Layer and Energy Balance in the Central Andes of Perú, Mantaro Valley

The present study presents a detailed analysis of the diurnal and monthly cycles the surface boundary layer and of surface energy balance in a sparse natural vegetation canopy on Huancayo observatory (12.04 ∘ S, 75.32 ∘ W, 3313 m ASL), which is located in the central Andes of Perú (Mantaro Valley) during an entire year (May 2018–April 2019). We used a set of meteorological sensors (temperature, relative humidity, wind) installed in a gradient tower 30 m high, a set of radiative sensors to measure all irradiance components, and a set of tensiometers and heat flux plate to measure soil moisture, soil temperatures and soil heat flux. To estimate turbulent energy fluxes (sensible and latent), two flux–gradient methods: the aerodynamic method and the Bowen-ratio energy-balance method were used. The ground heat flux at surface was estimated using a molecular heat transfer equation. The results show minimum mean monthly temperatures and more stable conditions were observed in June and July before sunrise, while maximum mean monthly temperatures in October and November and more unstable conditions in February and March. From May to August inverted water vapor profiles near the surface were observed (more intense in July) at night hours, which indicate a transfer of water vapor as dewfall on the surface. The patterns of wind direction indicate well-defined mountain–valley circulation from south-east to south-west especially in fall–winter months (April–August). The maximum mean monthly sensible heat fluxes were found in June and September while minimum in February and March. Maximum mean monthly latent heat fluxes were found in February and March while minimum in June and July. The surface albedo and the Bowen ratio indicate semi-arid conditions in wet summer months and extreme arid conditions in dry winter months. The comparisons between sensible heat flux ( Q H ) and latent heat flux ( Q E ), estimated by the two methods show a good agreement (R 2 above 0.8). The comparison between available energy and the sum of Q E and Q H fluxes shows a good level of agreement (R 2 = 0.86) with important imbalance contributions after sunrise and around noon, probably by advection processes generated by heterogeneities on the surface around the Huancayo observatory and intensified by the mountain–valley circulation.

Measurement of water-use by <i>Jatropha curcas</i> L. using the heat-pulse velocity technique

In response to the proposed introduction of the potential bio-diesel species Jatropha curcas (Linnaeus) to South Africa, field experiments were conducted to investigate its likely water-use impacts relative to other forms of vegetative land use. As no existing water-use data could be found for this species worldwide, sap flow in Jatropha curcas trees was measured continuously for a 17-month period at two sites in eastern South Africa. These consisted of young (4-year-old) trees at a relatively wet site and mature (12-year-old) trees at a dry site. The heat-ratio method of the heat-pulse technique was utilised, together with measurements of meteorological variables and soil water. Sap- flow rates varied according to tree age, season, prevailing meteorological conditions, and soil moisture levels. Peak sap-flow rates occurred during the warm wet summer months, but due to the deciduous nature of the species, water use was negligible during winter. Scaled-up sap-flow measurements resulted in estimates of total annual transpiration of 1 983 l (147 mm) for a 4-year-old J. curcas tree, and 4 884 l (362 mm) for a 12-year-old J. curcas tree. The study concluded that the J. curcas trees studied were conservative in their water use, and were unlikely to transpire more water than indigenous vegetation types of the area.

Snowmelt runoff and groundwater discharge in Himalayan rivers: a case study of the Satluj River, NW India

The Himalayas are one of the largest cryospheric systems outside the Polar Regions, and include more than 12,000 glaciers spread over an area of about 33,000 km2. The Himalayan glaciers and snow packs retreating at an accelerating rate, thereby creating an alarming situation for the huge population that resides in northwestern India and southeastern Pakistan, as they depend on surface water resources in the region and rivers emanating from the Himalayas. This work attempts to quantify the contribution of different sources such as glacial/ice/snow melt and groundwater discharge to the Satluj River using the stable isotopes based hydrograph separation method at Ropar (foot hill) and Yusufpur in plain of Punjab, India. A mass balance model of three-component mixing has been engaged using the values of δ18O and electrical conductivity of the river water, and its discharge fraction, to estimate the time-varying relative proportion of each component from July 2013 to January 2014. The proportion of glacier melt was found to peak up to ~ 64% at Ropar and ~ 15% at Yusufpur during the wet summer months. The fraction of groundwater discharge was found to vary between 10–20% at Ropar and 25–35% at Yusufpur (Punjab plain) over time. The observed trend of d-excess (deuterium excess) values of river water also suggests that the glaciers and snow packs at higher altitudes contain a significant fraction of snow derived from vapor originating in the Mediterranean region, driven by the mid-latitude westerlies known as western disturbances.

Effects of environmental parameters on the chestnut gall wasp and its complex of indigenous parasitoids.

The chestnut gall wasp (CGW), Dryocosmus kuriphilus, an invasive pest native to China, has caused severe yield and economic losses to chestnut production in Europe since its arrival in 2002. In Southern Italy, the complex of indigenous parasitoids colonizing CGW was monitored between 2013 and 2015, with the aim of estimating the composition of the indigenous parasitoid complex, its ability to control CGW populations, and the interactions of both factors with several measured environmental parameters. We compared results among three differently managed field types. Results showed an increase in the rate of parasitism both when the host population density was lower and in unmanaged chestnut stands with more natural conditions. The percentage of parasitism in galls was related to morphological traits of the galls and to higher seasonal temperatures, which reduced the parasitism intensity because CGW develops earlier under such conditions. The host-parasitoid mortality inside galls varied among sites and was associated mostly with rot fungi during wet spring and summer months. Parasitoid species richness was similar among the study sites, but the proportion of parasitoid species differed between orchards and unmanaged coppice stands. The timing of attack by parasitoids followed a species-specific successional sequence throughout the larva-to-adult life cycle of the CGW. These interactions should be considered in future research on trophic relationships and when modeling invasive scenarios for new pest species.

Seasonal variations of nitrous oxide fluxes and soil denitrification rates in subtropical freshwater and brackish tidal marshes of the Min River estuary

Estuarine tidal marshes provide favorable conditions for nitrous oxide (N2O) production. Saltwater intrusion caused by sea-level rise would exert complex effects on the production and emission of N2O in estuarine tidal marshes; however, few studies have been conducted on its effects on N2O emissions. Salinity gradients are a common occurrence in estuarine tidal marshes. Studies on production and emission of N2O in tidal marshes with different salinities may elucidate the impact of saltwater intrusion on the emission of greenhouse gases. This study explores the seasonal variations of N2O fluxes and soil denitrification rates in freshwater (Daoqingzhou wetland) and brackish (Shanyutan wetland) tidal marshes dominated by Cyperus malaccensis var. brevifolius (shichito matgrass) in the Min River estuary, southeastern China. N2O fluxes in both marshes showed strong temporal variability. The highest N2O fluxes were observed in the hot and wet summer months, whereas the lowest fluxes were observed in the cold winter and autumn months. N2O fluxes from the freshwater marsh (48.81±9.01μgm−2h−1) were significantly higher (p<0.05) than those from the brackish-water marsh (27.69±4.01μgm−2h−1). Soil denitrification rates showed a similar temporal pattern, with the highest rates observed in summer and the lowest in winter. Similarly, soil denitrification rates were significantly higher (p<0.05) in the freshwater marsh (32.72±19.15μmolNm−2h−1) than in the brackish-water marsh (4.97±2.64μmolNm−2h−1). Temperature and the salinity, sulfate (SO42−), and ammonia nitrogen (NH4+-N) concentrations of the overlying water were key factors affecting soil denitrification rates. N2O fluxes and soil denitrification rates demonstrated negative correlations with salinity and SO42− concentrations in both marshes. The results indicate that increased seawater intrusion would reduce N2O emissions from estuarine tidal wetlands and exert a negative feedback on the climate system.

Coupled hydraulic-mechanical simulation of seasonally induced processes in the Mont Terri rock laboratory (Switzerland)

This paper focuses on hydraulic-mechanical effects in the Mont Terri rock laboratory (Switzerland) and investigates their impact on pore pressure, the convergence of a niche and the evolution of pre-existing cracks in the wallrock of the niche. A comparison of measurements with numerical simulation results is conducted. The presented in situ measurements include long-term data on temperature, relative humidity, and niche convergence, as well as crackmeter and jointmeter measurements determining the aperture of a bedding-parallel crack. Furthermore, time-domain-reflectometry measurements were carried out in a borehole located in the niche wall close to the crack. They provide information on the water content of the claystone. The numerical simulation is carried out with OpenGeoSys. It contains a 2-dimensional coupled hydraulic-mechanical model considering orthotropy, swelling and shrinkage effects, linear elastic material behaviour and an excavation damaged zone characterized by a zone of lower rock strength. An additional focus is laid on the evolution of cracks in the wallrock of the niche. The presented model approach allows a prediction of the temporal evolution of a desaturated zone incorporating a seasonally influenced part. The comparison with measured water contents yields good agreement. Simulation results and measurements consistently predict a convergence of the niche. The evolution of the crack aperture is influenced by long-term as well as seasonallyinfluenced effects. Due to the convergence of the niche, the long-term trend is characterized by closure of the crack. Furthermore, the seasonally influenced desaturation in winter results in opening of the crack, while the resaturation in the warm and wet summer months leads to closure of the crack. Finally, the comparison of simulation results with measurements indicates qualitative agreement. As a matter of fact, the numerical model seems to represent significant effects concerning the evolution of the crack aperture of a single crack.

Relationship between magnitude of phytoplankton blooms and rainfall in a hyper-eutrophic lagoon: A continuous monitoring approach

To evaluate the effect of rainfall intensity on phytoplankton blooms, a continuous monitoring system was deployed during 2015 in a hyper-eutrophic lagoon in Taiwan. Intensive rainfall occurs during the wet summer months, from May to September. Salinity in the lagoon was found to decrease with increasing intensity of rainfall. The magnitude of phytoplankton blooms also increased linearly with increasing rainfall intensity. The chlorophyll a concentration rose by an order of magnitude during the heaviest rainfall. Blooms may be fueled by nutrient enrichment caused by drainage or run-off water from surrounding areas that is channeled into the lagoon during rainfall events. During bloom periods, the rates of net primary production and ecosystem respiration were high. However, this ecosystem was autotrophic for most of the year. As extreme rainfall is predicted to increase, the results of this study imply that the frequency and magnitude of phytoplankton blooms may increase in the future.

A stable isotopic study of the diet of &lt;i&gt;Potamonautes sidneyi&lt;/i&gt; (Brachyura: Potamonautidae) in two coastal lakes of the iSimangaliso Wetland Park, South Africa

Potamonautes sidneyi Rathbun 1904, is a dominant freshwater crab in KwaZulu-Natal, South Africa. Recent flood events in the iSimangaliso Wetland Park have allowed a substantial range expansion of this species, including previously hypersaline and desiccated areas. A stable isotope study was conducted to examine the feeding habits of the populations from Lake Sibaya and Mpophomeni Stream, two contrasting sites in the iSimangaliso Wetland Park. Juveniles from Mpophomeni Stream were more depleted in δ 13 C and more enriched in δ 15 N compared to adults, indicating a more carnivorous diet and higher trophic position. A general shift in diet was observed at both sites, with consumption of aquatic invertebrates and sedimentary organic matter more prevalent in the wet summer months, while greater proportions of detritus and microphytobenthos were consumed in autumn/winter. No significant difference was observed between adults from the two sites despite the abiotic variations. The species appears to play a complex role in the trophic web, by acting as an intermediate consumer facilitating the flow of nutrients across levels and by breaking down decomposing organic matter, allowing for rapid recycling of nutrients within its ecosystem. Keywords : diet, trophic role, stable isotopes, freshwater, brachyurans, opportunistic feeders

Energy saving potential and life cycle environmental impacts of a vertical greenery system in Hong Kong: A case study

Although there is increasing demand for vertical greening in urban areas, few studies have examined its environmental impacts. The aim of this study was to quantify the environmental benefits and burdens of a commercially available vertical greenery system (VGS). The electricity consumption for cooling in flats with and without a VGS (8.22 m2) in a public housing estate in Hong Kong was compared. A life cycle assessment (LCA) was conducted to analyze the environmental burdens of the VGS in its material, transportation, use and end-of-life stages. The daily electricity saving by the VGS in sunny, cloudy and rainy day in summer were 1.30, 0.84 and 0.71 kW h, respectively. The VGS saved as much as 16% of the electricity consumed for air-conditioning in August and September which are typical hot and wet summer months. The material stage contributed to 43–97% of all the environmental impact categories. A comparison of the environmental burdens and benefits gained from cooling showed that the environmental burden of the VGS in regard to abiotic depletion of fossil fuels could be paid back in 20 years. Overall, vertical greeneries installed on building walls can conserve energy for cooling in summer and are an environmentally sustainable option in cities where there is little land available for urban landscaping and gardening.

Hydrological extremes in the Aksu-Tarim River Basin: Mid-latitude dynamics

Analyses of precipitation (1961–2010) from 39 meteorological stations in the Tarim River Basin revealed a trend from dryer towards wetter conditions induced by an increase of the number of wet extremes. A first (1961–1986) and second (1987–2010) period are the basis for a dynamical analysis of changing drought and wetness extremes which are closely related to cyclonic activity over the European continent and circulation anomalies in the Northern Hemisphere mid-latitudes. Wave train, cyclone tracks, water flux and potential vorticity (PV) front analysis of the wet and dry months show the following result: (1) The extreme wet and dry cases in winter and summer are characterized by distinguished wave train patterns upstream of the Tarim River Basin. All wave trains originate in the Atlantic–European sector pointing towards wave train dynamics as one possible mechanism underlying the connection patterns observed. (2) The selected extreme cases show that exceptional precipitation events can be connected to characteristic cyclone tracks and a PV front in the upper troposphere even if cyclone tracks never cross the Tarim Basin. Extremely wet winters are characterized by cyclone tracks close to the western and northern boundary of the Tarim Basin whereas, during extremely dry winters, such cyclone tracks are absent. Wet summers are characterized by long-lived cyclonic anomalies at the north western corner of the Tarim River Basin [see also (3)]. During dry summers such anomalies are absent. (3) On a more local level the hydrological extreme events are linked to special dynamical structures of the upper tropospheric PV front. In winter strong (extreme) precipitation is connected to a strong non-linear wave development or a wave-breaking event over the Tarim River Basin. Together with non-linear wave development moisture and precipitation areas are advected towards the Tarim River Basin. In dry winters the upper tropospheric PV front is much more zonally oriented and wave-breaking is less frequent. Strong precipitation events are connected to strong breaking events and to the formation of long-lived nearly stationary cyclones over or north of the Tarim River Basin during extremely wet summer months.

Field investigation of the quality of fresh and aged leachates from selected landfills receiving e-waste in an arid climate

The management of electronic waste (e-waste) is a serious problem worldwide and much of it is landfilled. A survey of four selected landfills in an arid region of South Australia was conducted to determine the proportion of e-waste in municipal waste and the properties of each landfill site. Leachate and groundwater samples were collected upgradient and downgradient of the landfills for analysis of polybrominated diphenyl ethers (PBDEs) and 14 metals and metalloids, including Al, As, Ba, Be, Cd, Co, Cr, Cu, Fe, Ni, Pb, Sb, V and Zn. Our data demonstrate that the selected landfills in South Australia continue to receive municipal waste containing in excess of 6%, or 25,000tonnes per year, of e-waste. The leachates and groundwater collected from the landfills contained significantly elevated concentrations of Pb with the highest concentration in groundwater of 38μg/l, almost four times higher than the Australian drinking water guideline of 10μg/l. The presence of PBDEs was detected in both leachate and groundwater samples. Total PBDEs values of 2.13–59.75ng/l in leachate samples were 10 times higher than in groundwater samples, which recorded a range of 0.41–6.53ng/l at all sites. Moreover, the concentrations of metals and metalloids in sampled groundwater contained elevated levels of Al, As, Fe, Ni and Pb that exceeded Australian drinking water guideline values. For these reasons potential leaching of these contaminants is of concern and while difficult to attribute elevated contaminant levels to e-waste, we do not recommend continued disposal of e-waste in old landfills that were not originally designed to contain leachates. The survey also revealed temporal variation in the electrical conductivity and concentrations of As, Cd and Pb present in leachates of landfills in arid Mediterranean climates. These results are consistent with the marked variations in rainfall patterns observed for such climates. The solute concentration (EC and other ions including As, Cd and Pb) declines in the leachates during wet winter months (June to September), in contrast to tropical countries where such changes are observed during wet summer months.

Metabolic acceleration quantifies biological systems' ability to up-regulate metabolism in response to episodic resource availability

Precipitation often arrives discretely in semi-arid ecosystems. Under these conditions, natural selection might favor rapid metabolic responses to the sudden availability of otherwise limiting resources. We introduce and define metabolic acceleration (α) as the first derivative of the metabolic rate of a living system with respect to time. As such, α describes the capacity of a biological system to up- and down-regulate metabolism and may be applied across scales and processes. To better understand the responses of roots and soil microbes to seasonal patterns of rainfall and plant activity, we compared soil respiratory acceleration (αsoil) derived from soil respiration time-series among three microhabitats (under mesquite, under bunchgrasses, and in intercanopy soils) in a semi-arid shrubland near Tucson, Arizona. Across microhabitats, αsoil was greatest during the warm, wet summer months and lowest during cool winter months. Throughout the year, αsoil beneath mesquite was greater than beneath bunchgrasses or in intercanopy soils. Finally, microhabitat-specific responses of αsoil to spring and monsoonal rainfall events were consistent with seasonal contrasts in the photosynthetic activity of deeply-rooted mesquite shrubs and warm-season bunchgrasses. By quantifying the capacity of living systems to respond to episodic resource availability, metabolic acceleration provides a new perspective and potentially unifying metric for biological responses to environmental heterogeneity.

Influence of Arctic sea ice on European summer precipitation

The six summers from 2007 to 2012 were all wetter than average over northern Europe. Although none of these individual events are unprecedented in historical records, the sequence of six consecutive wet summers is extraordinary. Composite analysis reveals that observed wet summer months in northern Europe tend to occur when the jet stream is displaced to the south of its climatological position, whereas dry summer months tend to occur when the jet stream is located further north. Highly similar mechanisms are shown to drive simulated precipitation anomalies in an atmospheric model. The model is used to explore the influence of Arctic sea ice on European summer climate, by prescribing different sea ice conditions, but holding other forcings constant. In the simulations, Arctic sea ice loss induces a southward shift of the summer jet stream over Europe and increased northern European precipitation. The simulated precipitation response is relatively small compared to year-to-year variability, but is statistically significant and closely resembles the spatial pattern of precipitation anomalies in recent summers. The results suggest a causal link between observed sea ice anomalies, large-scale atmospheric circulation and increased summer rainfall over northern Europe. Thus, diminished Arctic sea ice may have been a contributing driver of recent wet summers.

Seasonal reproduction in the eastern rock elephant‐shrew: influenced by rainfall and ambient temperature?

AbstractBecause environmental conditions vary seasonally in most regions, many small mammals reproduce at a specific time of the year to maximize their reproductive success. In the tropics and subtropics, the breeding season is usually determined by the extent of the dry and rainy seasons. We investigated the seasonality of reproduction in the eastern rock elephant‐shrew (Elephantulus myurus), over a 12‐month period and attempted to elucidate the factors that may influence seasonal reproduction in this endemic African mammal. E. myurus breeds seasonally during the warm and wet spring and summer months and cessation of breeding occurs during the cold and dry winter months of the southern hemisphere. Pregnant females were only collected from August through to January. Ovarian size and plasma progesterone started to increase a few months prior to the first rains, were highest in October and decreased thereafter. Follicular growth and corpora body numbers corresponded to this seasonal reproductive pattern. Testes and seminiferous tubule size and plasma testosterone concentration has already started to increase during the coldest months, 2 months prior to reproductive onset in females. We propose that seasonal reproduction evolved in E. myurus because of seasonally changing food availability brought about by severe seasonal changes in rainfall and ambient temperature. The direct effects of rainfall and ambient temperature on reproduction of E. myurus are ambiguous, and we discuss other environmental factors that may trigger reproductive onset in this species.

Seasonal changes in reproductive development in male spiny mice (Acomys spinosissimus) from South Africa

Seasonal reproduction is a common characteristic of many small mammals which inhabit seasonal environments in temperate regions, the sub-tropics as well as the tropics. It is important for an animal to reproduce during the most favourable time of the year to ensure the survival of the young and maximize reproductive success. In southern Africa, female spiny mice (Acomys spinosissimus) breed during the warm and wet spring and summer months, whereas the reproductive pattern of males is unknown although an opportunistic breeding pattern has been implicated. We investigated testes mass and volume, seminiferous tubule diameter, spermatogenesis and plasma testosterone concentrations in a South African population of male spiny mice on a 2-monthly basis over one year. Testes mass and volume started to increase in July/August and was high from September until December. Seminiferous tubule diameter and spermatogenesis increased during the same months. Plasma testosterone concentration was elevated from July/August to November/December. Development of the reproductive characteristics of male spiny mice was correlated with high rainfall and high ambient temperatures, but reproductive development had already started during the dry season and the coldest months. This shows that reproductive development in males may not be dependent on climatic conditions, and other factors, such as photoperiod, may trigger the onset of reproduction. The data, however, suggest that A. spinosissimus is a true seasonal breeder with reproduction confined to the spring and summer months in southern Africa.

Large‐scale circulations and Tibetan Plateau summer drought and wetness in a high‐resolution climate model

AbstractExtratropical and tropical influences on Tibetan Plateau severe and extreme dry and wet summer months are investigated focussing on the large‐scale circulation and using results of the coupled climate model ECHAM5/MPI‐OM. A pre‐industrial control run and scenario runs for the 4th Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) are considered. Tibetan Plateau precipitation in months of wetness and drought is related to atmospheric circulation anomalies in the North‐Atlantic/European sector and to sea surface temperature anomalies in the Tropics. Drought on the Tibetan Plateau is associated with a pronounced wave train bridging Eurasia from the North Atlantic to Asia. Increased transient eddy activity in the North Atlantic storm track has a more south‐west to north‐east orientation. This supports a high pressure anomaly over the eastern North Atlantic and Scandinavia which excites a cross Eurasian wave train reducing the moisture inflow to the Tibetan Plateau from the Arabian Sea. A concurrent warming in the tropical Indian Ocean increases the low level monsoonal westerlies deviating the moisture transport from the Bay of Bengal towards the Indochinese Peninsula and the Philippines. Wetness on the Tibetan Plateau is dominated by a cooling in the tropical oceans, whereas atmospheric flow is predominantly zonal in the extratropics of North America and Europe. Thus, moisture inflow can reach the Tibetan Plateau via the Arabian Sea, the Bay of Bengal and the mid‐latitude westerlies. Future scenarios show little change of atmospheric flow composites for wetness and dryness; the Tibetan Plateau droughts increase by 10% for an A1B‐scenario, while extreme wet summer months are reduced by approximately 1%. Copyright © 2010 Royal Meteorological Society

A comparison of conventional cloning options for annatto (Bixa orellana L.)

SummaryAnnatto (Bixa orellana L.) is a tree indigenous to tropical America that has been naturalised throughout the Indian sub-continent. The plant is chiefly valued for its carotenoid pigments, annatto. Methods for the clonal propagation of hardwood and softwood cuttings, air-layering, budding, and grafting of annatto were investigated. Hardwood cuttings collected during the wet Summer months (June-July) were treated with indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), or naphthaleneacetic acid (NAA) at varying concentrations. The highest percentage rooting (63.4%), along with highest number of roots (8.33 per cutting) were achieved by hardwood cuttings after 12 h of 2.5 mM IAA treatment. Among the various auxin treatments of softwood cuttings, 5.0 mM IBA in combination with 5.0 mM NAA for 5 min resulted in a significant (P < 0.05) rooting percentage (56.7%). The responses of softwood cuttings to an auxin analogue (boric acid) and/or to thiamine hydrochloride (vitamin B) were inferior to synthetic auxins. When subjected to air-layering, hardwood branches gave 100% rooting without any application of hormone. Among the different types of budding methods attempted (patch, T, or I), patch budding produced the highest efficiency (78%) of propagation. Splice-grafting could also be used for conventional propagation of annatto, with a 50% survival rate. Annatto can therefore be cloned by adopting these methods. Propagation based on softwood cuttings facilitated moderate-scale cloning of this valuable, elite germplasm.

Characteristics of wet and dry weather heavy metal discharges in the Yeongsan Watershed, Korea

A comprehensive water quality monitoring program was conducted in the Yeongsan (YS) River, Korea from 2005 to present to investigate wet and dry weather pollutant discharge in an attempt to establish point and non-point pollution management strategies. As part of this monitoring program, 11 heavy metal species were measured during dry and wet weather conditions in the YS River, where Gwangju City (GJ), a subcatchment of the YS River, was further monitored to clarify the responsibility of different metal species discharged into the mainstream. Monthly grab water samples showed that greater amounts of metals along the YS River were discharged during the wet summer months due largely to storm runoff. In addition, further monitoring results revealed that GJ, a highly urbanized area, was a significant contributor of the heavy metals being discharged into the YS River during both wet and dry weather. The most abundant metal species discharged from GJ were manganese, aluminum and iron with different contributions of wet and dry weather flows to the total discharge load. Wet weather flow was a significant contributor to the annual dissolved metal loads, accounting for 44–93% of the annual load depending on the metal species, with the exception of chromium and cadmium (9% and 27%, respectively). Mostly, metal loads during wet weather were shown to be proportional to the rainfall depth and antecedent dry period. A substantial fraction of metals were also associated with solids, suggesting that sedimentation might be an appropriate management practice for reducing the metal load generated in GJ. Overall, although dissolved metal concentrations in YS River were at an acceptable level for aquatic community protection, continual metal discharge throughout the year was considered to be a potential problem in the long-term due to gradual water quality degradation as well as continuous metal accumulation in the system.

The genus Pythium in Taiwan, China (1) — a synoptic review

The genus Pythium, with slightly over 280 described species, has been classified traditionally with other filamentous, coenocytic, sporangia-producing fungi as “Phycomyetes”. However, with recent advances in chemical, ultrastructural and molecular studies, Pythium spp. are now considered as “fungus-like organisms” or “pseudo-fungi” and are placed in the Kingdom Chromista or Kingdom Straminopila, distinct from the true fungi of the Kingdom Fungi or Kingdom Mycota. They are widely distributed throughout the world as soil saprophytes or plant pathogens. Because of the warm moist maritime climate, Taiwan, China, is especially rich in Pythium species. To date, 48 species of Pythium have been reported from Taiwan, China, with the dominant species being Py. vexans, Py. spinosum, Py. splendens, Py. aphanidermatum, Py. dissotocum and Py. acanthicum. There is no definite geographical distribution of Pythium spp. in Taiwan, China. Twenty nine species of Pythium have proven to be plant pathogens attacking a wide variety of woody and herbaceous plants primarily causing pre- and post-emergence seedling damping-off, root rot, stem rot and rotting of fruits, tubers and ginger rhizomes, resulting in serious economic losses. The most important plant pathogenic species include Py. aphanidermatum and Py. Myriotylum, which are most active during the hot and wet summer months; whereas Py. splendens, Py. spinosum, Py. ultimum and Py. irregulare cause the greatest damage in the cool winter. Most Pythium spp. are non-specific pathogens, infecting mainly juvenile or succulent tissues. This review attempts to assess the taxonomic position of the genus Pythium and provide details of the historical development of the study of Pythium as pathogens in Taiwan, China, causing diseases of sugarcane, trees, vegetables, fruits, specialty crops and flowering plants, as well as measures to control these diseases. Of special note is the introduction of the S-H mixture which, when used as soil amendment, effectively controls many soil-borne Pythium diseases during the early stages of plant growth. The diversity of Pythium species in Taiwan, China, is discussed in comparison with the situation in the mainland of China and suggestions are made to fully utilize Pythium spp. as agents for biological control, in industry and medicine.