Winter Dry Season Research Articles

Processes controlling dripwater hydrochemistry variations in Xueyu Cave, SW China: implications for speleothem palaeoclimate signal interpretations

Cave dripwater hydrochemistry responds to environmental changes, both within and outside of the cave, and thereby conveys this information to any stalagmite fed by the drips. As stalagmites are important archives of climate proxy information, understanding how dripwater hydrochemistry responds to environmental forcing is critical. However, despite the large number of speleothems in SW China, the response of dripwater to regional climate variability is not yet adequately understood. A 3‐year study of three drip sites in Xueyu Cave, Chongqing Municipality, SW China, revealed the most important mechanisms controlling dripwater chemical variability. The principal chemical indices (pH, specific conductivity, Ca2+, Mg2+, Sr2+ and ) in collected dripwaters and the local climate data were analysed in this study. The principal controls on the hydrochemistry were found to be the external climate and its changes, groundwater residence time, cave ventilation and prior calcite precipitation (PCP) processes. Dripwater hydrochemistry showed strongly coherent seasonal patterns despite the fact that all sites are Ca–HCO3 type waters and supersaturated with calcite. Seasonal changes in dripwater hydrochemistry were influenced by the soil and vadose zone CO2 content as well as groundwater residence time in the upper karst zone. Cave‐air CO2 seasonal variations were consistent with changes in dripwater PCO2 and cave ventilation. Trace element ratios (Mg/Ca and Sr/Ca) of dripwater were controlled by PCP processes. Seasonal variations in dripwater Mg/Ca and Sr/Ca ratios in Xueyu Cave showed inverse changes with the Asia Monsoon Index during the monitoring period, reflecting the seasonal climate changes that may have been recorded in the speleothems. Based on a linear regression of PCO2 and the Ca2+ data in the cold–dry winter season, a 130‐ppm shift in cave‐air PCO2 results in a 1‐ppm shift in dripwater Ca2+ concentration in Xueyu Cave. This study illustrates the importance of understanding factors controlling the changes in the composition of dripwater before it reaches the speleothem.

Comparative economic analysis of inter-crop based conservation bench terrace and conventional systems in a sub-humid climate of India

Economic performance of two land configuration systems, namely conservation bench terrace (CBT) and conventional (sloping borders), were evaluated through an experimental study conducted during 1997–2005 in a sub-humid climate of India. Energy use efficiencies of the two systems were also evaluated. The two systems were cultivated with maize+cowpea in rainy season followed by wheat+mustard in dry winter season. For CBT, an additional intervention of rice cultivation was done during rainy season in its recipient area. Mathematical relationships were established between seasonal and effective rainfalls as well as between effective rainfall and crop equivalent yields. These relationships were then utilized for evaluating economic efficiency of various combinations of the two inter-crop based land configuration systems. Excess runoff from the combinations was considered as rainwater harvested into a common tank for recycling as supplemental irrigation during intervening dry spells in the rainy season and the remaining during dry winter season. In this way, the best combination for inter-crop based systems adoptable to a region experiencing rainfall uncertainty i.e. regular intervening dry spells was identified. Sensitivity analysis was carried out to analyze response of the combinations to changes in economic parameters. Based on the analysis of experimental data, net present value of CBT system was observed to be 56% higher than the conventional system due to higher average crop equivalent yields. Net energy return, energy ratio and energy profitability of CBT system were higher by more than 100% as compared to conventional system, thus indicating better energy use efficiency. Benefit–cost analysis of the system combinations under different rainfall probabilities suggested that a combination with higher proportion of CBT will be more remunerative. However, the 75:25 (CBT:conventional) combination was observed to be the best for minimizing risks associated with erratic rainfall at all probability levels. Sensitivity analysis of various combinations indicated that CBT predominant combinations will be least affected by changes in considered economic parameters. From the study, it was concluded that adoption of 75:25 (CBT:conventional) combination can be recommended for sustaining crop productivity by generating sufficient runoff for harvesting and its subsequent recycling as supplemental irrigation during both seasons on mildly sloping lands in sub-humid climates.

Summertime Moisture Transport to the Southern South American Altiplano: Constraints from In Situ Measurements of Water Vapor Isotopic Composition

Abstract Austral summer transport of water vapor to the southern South American Altiplano is investigated using in situ measurements of water vapor isotopic composition collected from 1 November 2012 to 10 February 2013 on the Chajnantor Plateau in the Chilean Andes. Onset of the wet season in December was associated with an increase in mixing ratios from an average of 1500 ppmv during the winter dry season to 5400 ppmv in early December. Water vapor isotopes δD and δ18O increased from dry season averages of −235‰ and −31‰, respectively, to wet season averages of −142‰ and −17‰, reaching as high as −70‰ and −17‰, respectively. The highest water vapor δ values were close to those measured in coastal settings, suggesting little condensation during transport to the site. About 5% of the wet season data have δ values that are lower than expected for Rayleigh distillation and are associated with high relative humidity (>75%), easterly winds, and periods of low outgoing longwave radiation over the Altiplano, consistent with moistening by deep convection. The remainder of the data have δ values that are greater than expected for Rayleigh distillation, up to 250‰ above the Rayleigh curve. These data are consistent with mixing between very dry air and moist air from the boundary layer. The data show intraseasonal variability coherently linked to the position of the Bolivian high, with moist air associated with a southward displacement in the Bolivian high. The humidity over the southern Altiplano during the wet season reflects a balance among advective drying, advective moistening with little condensation, and convective moistening.

Ripple marks indicate Mid-Devonian paleo-wind directions in the Orcadian Basin (Orkney Isles, Scotland)

Abstract Few climate proxies provide information on paleo-wind directions. However, fossilized bedform elements can provide insight into the direction of flow that formed them. Wave-formed ripple marks, for example, which developed in shallow waters, extend transversely to the wind direction. In this study, Middle Devonian paleo-wind directions are reconstructed by measuring the orientation of 511 fossilized wave ripple marks in the Rousay Flagstone Formation on the island of Westray, Orkney, Scotland. The orientation of ripple marks was measured in four different localities on the island. A chi-squared test demonstrates that these four ripple-mark subsets show the same distribution of ripple mark orientation and thus indicates that the studied ripple marks display the same distribution of paleo-winds. Two dominant ripple mark orientations were observed at all studied localities. The most abundant ripple mark orientation suggests paleo-winds from the present-day North or South. Second most abundant are ripple marks that suggest paleo-winds from the present-day ENE or WSW (70° or 250°). When a 40° clockwise rotation of Orkney since the Middle Devonian is taken into account, the ripple marks suggest that the dominant wind directions were south-southeast (SSE) and north-northeast (NNE) in the tropical setting of the Orcadian basin. The SSE wind-direction is represented by the abundant ripple marks, with a present-day near N–S orientation of the line perpendicular to the crests. These ripple marks are also characterized by the largest wavelengths. The abundance of the latter ripple marks with long wavelengths is the result of a lower water level and thus a larger wave-exposed surface during the dry winter season, from April to July, which was mainly characterized by SSE paleo-trade winds.

A Spatial and Seasonal Pattern of Water Quality in the Sundarbans River Systems of Bangladesh

ABSTRACT Rahaman, S.M.B.; Rahaman, M.S.; Ghosh, A.K.; Gain, D.; Biswas, S.K.; Sarder, L.; Islam, S.S., and Sayeed, A.B., 2015. A spatial and seasonal pattern of water quality in the Sundarbans river systems of Bangladesh. Comprehensive field measurements were made in three major river systems (RSs) of the Sundarbans during October 2010 to August 2011 under post-monsoon, dry winter, and monsoon seasons to assess the pollution status. Fifteen experimental sites were set for collection of water samples from discrete layers under different tidal conditions. Salinity, temperature, pH, and dissolved oxygen (DO) were determined in situ and chemical oxygen demand (COD), biological oxygen demand (BOD), total nitrogen (TN), total phosphorus (TP), nitrate, phosphate, and ammonium were measured through laboratory analysis. Mean DO was recorded between 3.93 and 7.37 mg/L with an average 5.44 mg/L. Highest average DO was noticed at Rupsha-Passur RS during post-monsoon, whereas the lowest was in Kholpetua-Arpangashia RS...

Climate change and water resources management in the Upper Santa Cruz River, Arizona

Episodic streamflow events in the Upper Santa Cruz River recharge a shallow alluvial aquifer that is an essential water resource for the surrounding communities. The complex natural variability of the rainfall-driven streamflow events introduces a water resources management challenge for the region. In this study, we assessed the impact of projected climate change on regional water resources management. We analyzed climate change projections of precipitation for the Upper Santa Cruz River from eight dynamically downscaled Global Circulation Models (GCMs). Our analysis indicates an increase (decrease) in the frequency of occurrence of dry (wet) summers. The winter rainfall projections indicate an increased frequency of both dry and wet winter seasons, which implies lower chance for medium-precipitation winters. The climate analysis results were also compared with resampled coarse GCMs and bias adjusted and statistically downscaled CMIP3 and CMIP5 projections readily available for the contiguous U.S. The impact of the projected climatic change was assessed through a water resources management case study. The hydrologic framework utilized includes a rainfall generator of likely scenarios and a series of hydrologic models that estimate the groundwater recharge and the change in groundwater storage. We conclude that climatic change projections increase the uncertainty and further exacerbate the already complicated water resources management task. The ability to attain an annual water supply goal, the accrued annual water deficit and the potential for replenishment of the aquifer depend considerably on the selected management regime.

Effect of the vacuolar Na+/H+ antiporter transgene in a rice landrace and a commercial rice cultivar after its insertion by crossing

The vacuolar Na+/H+ antiporter is known to alleviate saline stress by sequestering Na+ in both wild-type Arabidopsis and rice and when over-expressed in many transgenic plants. Here we report on the effect of the NHX1 transgene on the salt tolerance properties it confers to a rice landrace and a commercial cultivar suitable for the dry winter season, but which suffers loss due to seasonal stresses, particularly in the coastal areas. The Nipponbare Na+/H+ antiporter 1.9 kb cDNA was cloned into pCAMBIA1305.1 under the control of the CaMV35S promoter and transformed into tissue-culture-responsive rice landrace Binnatoa (BA). The best-expressing transgenic line at T2 was found to be significantly tolerant at the seedling stage and was advanced to T3. The transgene was then transferred to the tissue-culture recalcitrant farmer-popular commercial rice genotype, BRRIdhan 28 (BR28) by crossing. The data generated both from semi-quantitative RT-PCR and western blot hybridization revealed that the transgene showed similar expression in the crossbred BR28 plants and BA transgenic line. Comparative stress tolerance tests, however, revealed that the BR28 crossbred lines were significantly less tolerant than its transgenic parent BA at both seedling and reproductive stages. A single successful transgenic event may therefore not show the same performance in the recipient genetic background, if introgressed by crossing.

Densidades de semeadura e safras de cultivo no desempenho produtivo de cultivares de feijoeiro-comum

Seeding rates and seasons of cultivation on growth performance of cultivars of common bean While there are others aspects associated, such as climate, soil and crop management, the growth habit of the cultivar is one of the main factors involved in answer in gof common bean to sowing density. Thus, the use of appropriate seeding rate is critical to obtaining the best technological solutions that result inhigher grain yields in the common bean. With goal of estudy the effects of seeding density and seasons about yield of grains and primary components of yield of common bean cultivars, was conduced a experiment in the experimental farm of the UNIMONTES, in Janaúba, MG, in the dry seanson and winter season in the year of 2011. The treatments were arranged in factorial scheme 4x5, involving four cultivars of bean (Ouro Vermelho, Ouro Negro, Madrepérola e Manteigão Vermelho) and five seeding density (100, 200, 300, 400 e 500 thousand plants ha-1). In both seasons, the experimental design utilized was randomized complete block, with four replications. At harvest was evaluated the final stand, yield of grains e primary components (number of pods by plant, number of grain by pod and mass of hundred grains). It was realized joint analysis of data for seasons of growth, and the effects of sowing density were subjected to regression analysis, however the effects of cultivars were studied by Tukey test and seasons by F test at 1and 5%. With the exception of Ouro Negro, grown in the winter season, which the highest grain yield is obtained with sowing density around 300 thousand plants by hectare, the increase in density of seeding does not affect the yield of common bean under the conditions considered in this study. Irrespective of sowing density, the common bean cultivated in the dry season show a greater number of seeds by pod, greater average weight of hundred grains, than common bean grown in the winter season.

Examination of the rumen bacteria and methanogenic archaea of wild impalas (Aepyceros melampus melampus) from Pongola, South Africa.

Although the rumen microbiome of domesticated ruminants has been evaluated, few studies have explored the rumen microbiome of wild ruminants, and no studies have identified the rumen microbiome in the impala (Aepyceros melampus melampus). In the present study, next-generation sequencing and real-time polymerase chain reaction were used to investigate the diversity and density of the bacteria and methanogenic archaea residing in the rumen of five adult male impalas, culled during the winter dry season in Pongola, South Africa. A total of 15,323 bacterial 16S rRNA gene sequences (from five impala), representing 3,892 different phylotypes, were assigned to 1,902 operational taxonomic units (OTUs). A total of 20,124 methanogen 16S rRNA gene sequence reads (from four impala), of which 5,028 were unique, were assigned to 344 OTUs. From the total sequence reads, Bacteroidetes, Proteobacteria, and Firmicutes were the most abundant bacterial phyla. While the majority of the bacterial genera found were unclassified, Prevotella and Cupriavidus were the most abundant classified genera. For methanogens, the genera Methanobrevibacter and Methanosphaera represented 94.3% and 4.0% of the classified sequences, respectively. Most notable was the identification of Methanobrevibacter thaueri-like 16S rRNA gene sequence reads in all four impala samples, representing greater than 30% of each individual's total sequences. Both data sets are accessible through NCBI's Sequence Read Archive (SRA), under study accession number SRP [048619]. The densities of bacteria (1.26 × 10(10)-3.82 × 10(10) cells/ml whole rumen contents) and methanogens (4.48 × 10(8)-7.2 × 10(9) cells/ml of whole rumen contents) from five individual impala were similar to those typically observed in domesticated ruminants.

Environmental significance and hydrochemical processes at a cold alpine basin in the Qilian Mountains

Isotope geochemistry of precipitation, river water, well water and spring water in the Babao River basin, China, during different seasons showed that regional runoff was dominated by precipitation in summer and autumn and by underground water in winter and spring. The δ18O and δD values of precipitation and spring water displayed a clear altitude effect. Water from the main stream and tributaries displayed a converse altitude effect in the summer-wet season. The isotopic composition of the various water sources was not well correlated with elevation during the winter-dry season. The spatial distribution of the stable isotope signals of river water demonstrated the influence of rainfall inputs, evaporation and variable flow. An end-member mixing model used for hydrograph separation indicated that in the summer-wet season, the Babao River water was recharged by precipitation (71.9 %), spring water (11.7 %) and well water (16.4 %), whereas the winter-dry season recharge was sourced from spring water (28.2 %) and well water (71.8 %).

Sources of Atmospheric Moisture for the La Plata River Basin*

Abstract The La Plata River basin (LPRB) is the second largest basin of South America and extends over a highly populated and socioeconomically active region. In this study, the spatiotemporal variability of sources of moisture for the LPRB are quantified using an extended version of the Dynamic Recycling Model. Approximately 63% of mean annual precipitation over the LPRB comes from South America, including 23% from local LPRB sources and 20% from the southern Amazon. The remaining 37% comes mostly from the southern Pacific and tropical Atlantic Oceans. The LPRB depends largely on external sources during the dry winter season, when local evaporation reaches a minimum and moisture outflow increases. Variations in the transport of moisture from the Amazon to the LPRB depend more on variations of the atmospheric circulation than on evaporation, at both the monthly and daily time scale. In particular, weak atmospheric flow allows the accumulation of moisture over the Amazon basin, followed by an above-normal release of moisture downwind when the atmospheric flow strengthens again. Water vapor transport with these characteristics was observed for 20% of the days of the summer season during the 1980–2012 period, leading to higher-than-average convergence of moisture of terrestrial origin over the LPRB. During the positive (negative) phase of the El Niño–Southern Oscillation (ENSO), more (less) moisture from Amazonian evaporation reaches the LPRB. The Amazonian contribution to the LPRB is reduced (increased) during the positive (negative) phase of the Antarctic Oscillation (AAO), when surface pressure over southern South America is above (below) normal.

Soil Co 2 Flux in the Different Ecosystems of North East India

We examined monthly and seasonal changes in soil CO 2 flux in the grassland, bamboo and Dipterocarpus forest ecosystems of Manipur, North East India. Soil CO 2 flux was recorded to be highest during rainy season and lowest during cool and dry winter season. Soil CO 2 flux rate was recorded to be highest in forest followed by grassland and bamboo forest. Multiple regression revealed that up to 92% of variation in soil CO 2 flux could be explained by soil moisture, soil temperature and soil organic carbon in three different ecosystems. Annual amount of CO 2 flux from soil was estimated at 694.86, 671.16 and 1029.25 g C m -1 y -1 in grassland, bamboo and Dipterocarpus forest ecosystems respectively. Thus the results indicate that soil CO 2 flux rate is highly influenced by seasons, environmental factors and types of vegetation in the different ecosystems of NE India.

Characterisation of stable isotopes to identify residence times and runoff components in two meso-scale catchments in the Abay/Upper Blue Nile basin, Ethiopia

Abstract. Measurements of the stable isotopes oxygen-18 (18O) and deuterium (2H) were carried out in two meso-scale catchments, Chemoga (358 km2) and Jedeb (296 km2) south of Lake Tana, Abay/Upper Blue Nile basin, Ethiopia. The region is of paramount importance for the water resources in the Nile basin, as more than 70% of total Nile water flow originates from the Ethiopian highlands. Stable isotope compositions in precipitation, spring water and streamflow were analysed (i) to characterise the spatial and temporal variations of water fluxes; (ii) to estimate the mean residence time of water using a sine wave regression approach; and (iii) to identify runoff components using classical two-component hydrograph separations on a seasonal timescale. The results show that the isotopic composition of precipitation exhibits marked seasonal variations, which suggests different sources of moisture generation for the rainfall in the study area. The Atlantic–Indian Ocean, Congo basin, Upper White Nile and the Sudd swamps are the potential moisture source areas during the main rainy (summer) season, while the Indian–Arabian and Mediterranean Sea moisture source areas during little rain (spring) and dry (winter) seasons. The spatial variation in the isotopic composition is influenced by the amount effect as depicted by moderate coefficients of determination on a monthly timescale (R2 varies from 0.38 to 0.68) and weak regression coefficients (R2 varies from 0.18 to 0.58) for the altitude and temperature effects. A mean altitude effect accounting for −0.12‰/100 m for 18O and −0.58‰/100 m for 2H was discernible in precipitation isotope composition. Results from the hydrograph separation on a seasonal timescale indicate the dominance of event water, with an average of 71 and 64% of the total runoff during the wet season in the Chemoga and Jedeb catchments, respectively. Moreover, the stable isotope compositions of streamflow samples were damped compared to the input function of precipitation for both catchments. This damping was used to estimate mean residence times of stream water of 4.1 and 6.0 months at the Chemoga and Jedeb catchment outlets, respectively. Short mean residence times and high fractions of event water components recommend catchment management measures aiming at reduction of overland flow/soil erosion and increasing of soil water retention and recharge to enable sustainable development in these agriculturally dominated catchments.

The effects of Typhoon Morakot on concentration of airborne particulates derived from unvegetated riverbanks

Landslides frequently occur during large earthquakes and storms in Taiwan, supplying large volumes of sediment to downslope areas. When coupled with the intense northeast monsoon over Taiwan in the dry winter season, this can lead to high concentrations of airborne particulates that are hazardous to human health. Air quality monitoring stations near unvegetated riverbanks recorded high concentrations of particulate matter less than 10 μm (PM10) after Typhoon Morakot in 2009. The objective of this study was, therefore, to analyze the effects on air quality of sediment caused by the typhoon. A deflation module was simulated, and the resulting estimates were compared with observed data from the Taitung monitoring station for 2004 and 2005. The relationship of dust flux to average atmospheric dust concentration was analyzed for October to December 2001–2010. Analysis showed that the 2001–2008 data are highly correlated (0.78) with the average concentration. The intercept of 28.07 represented the background concentration with no dust emission, from October to December of 2001–2008. Based on the dust flux potential in 2009, the average yearly PM10 concentration would be 37.98 µg/m3; however, the measured concentration was 61.67 µg/m3 from October to December. This suggests the strong influence of dust re-suspended from unvegetated riverbanks by Typhoon Morakot.

Water-soluble organic carbon aerosols during a full New Delhi winter: Isotope-based source apportionment and optical properties

Water-soluble organic carbon (WSOC) is a major constituent (~ 20–80%) of the total organic carbon aerosol over the Indian subcontinent during the dry winter season. Due to its multiple primary and secondary formation pathways, the sources of WSOC are poorly characterized. In this study, we present radiocarbon constraints on the biomass versus fossil sources of WSOC in PM2.5 for the 2010/2011 winter period for the megacity Delhi, situated in the northern part of the heavily polluted Indo-Gangetic Plain. The fossil fuel contribution to Delhi WSOC (21 ± 4%) is similar to that recently found at two South Asian background sites. In contrast, the stable carbon isotopic composition of Delhi WSOC is less enriched in 13C relative to that at the two receptor sites. Although potentially influenced also by source variability, this indicates that near-source WSOC is less affected by atmospheric aging. In addition, the light absorptive properties of Delhi WSOC were studied. The mass absorption cross section at 365 nm (MAC365) was 1.1–2.7 m2/g with an Absorption Angstrom Exponent ranging between 3.1 and 9.3. Using a simplistic model the relative absorptive forcing of the WSOC compared to elemental carbon in 2010/2011 wintertime Delhi was estimated to range between 3 and 11%. Taken together, this near-source study shows that WSOC in urban Delhi comes mainly (79%) from biomass burning/biogenic sources. Furthermore, it is less influenced by photochemical aging compared to WSOC at South Asian regional receptor sites and contributes with a relatively small direct absorptive forcing effect.

Ventilation and Relative Humidity in Swedish Buildings

An important factor for comfort ratio in the indoor environment and affecting human health and well-being is the relative humidity. Studies have shown that about 70% of the staff at Swedish offices, schools and kindergartens experiences that the air is too dry during the winter season. Studies show that the relative humidity in indoor environments influences the incidence of respiratory infections and allergies. Important factors for the air environment indoors is to limit the number of airborne particles, since these are conveyors of both bacteria and viruses, and to keep the humidity at a level above 40% and below 70%, making the survival of viruses and bacteria minimized. Measurement results show that there is significant difference in the relative humidity during the winter season between the mechanically ventilated buildings with relative humidity levels below 10% than in buildings with natural ventilation. An important issue is how human health is affected by during longer periods and during much of the day live in environments with low relative humidity. Several researchers have noted that the incidence of respiratory infections increase during the winter when people are exposed to long periods of low humidity indoors. This means that the consequences of low humidity in the indoor environment should be considered and evaluated in a completely different way than is done today.

Effect of Summer Supplementary Feeding on Cattle Performance in Low Rainfall Grassland Savanna, South Darfur, Sudan

In a tropical ranch of animal production, which was divided by fire lines into 20 equal grazing paddocks of one mile square each, a grazing experiment was conducted as controlled rotational grazing with forty-five (45) cross-bred Sudanese improved Baggara cattle which were divided into four feeding systems (groups). A drop in condition scores of the farm cattle stock herd was treated during dry summer by supplementary feeding with four types of supplements to investigate the changes in average body weight changes, heart girth and condition scores, through dry summer, wet summer and winter seasons. The results showed that, animals of group three (G3) which supplemented with groundnut cake performed better in all body parameters under study when compared with group one (G1) and group two (G2) being supplemented with groundnut haulm, Stover respectively and group four (G4) which was kept under natural grazing as control group (Natural grazing alone) which reveals the worse body measurement traits performance under study. The effect of seasonal changes showed a significant difference (P < 0.05) between the seasons in average body weight in groundnut cake supplements both in dry and wet summer obtained better average body weight (162.53 Kg and 174.56 Kg respectively) than in groundnut haulm (in dry and wet summer -143.60 Kg and 163.50 Kg respectively), Stover supplements and natural grazing (controlled) groups. The results also showed that, the heart girth and condition score were significantly different (P < 0.05) between the treatments in wet summer and winter. While showing no significant difference between the treatments in dry summer, group supplemented with groundnut cake during the dry summer reported better performance in condition scores than other groups.

Stream water carbon controls in seasonally snow-covered mountain catchments: impact of inter-annual variability of water fluxes, catchment aspect and seasonal processes

Stream water carbon (C) export is one important pathway for C loss from seasonally snow-covered mountain ecosystems and an assessment of overarching controls is necessary. However, such assessment is challenging because changes in water fluxes or flow paths, seasonal processes, as well as catchment specific characteristics play a role. For this study we elucidate the impact of: (i) changes in water flux (by comparing years of variable wetness), (ii) catchment aspect [north-facing (NF) vs. south-facing (SF)] and (iii) season (snowmelt vs. summer) on all forms of dissolved stream water C [dissolved organic C (DOC), chromophoric dissolved organic matter (CDOM) and dissolved inorganic C (DIC)] in forested catchments within the Valles Caldera National Preserve, New Mexico. The significant correlation between annual water and C fluxes (e.g. DOC r2 = 0.83, p < 0.02) confirms annual stream water discharge as the overarching control on C efflux, likely from a well-mixed ground water reservoir as indicated by previous research. However, CDOM exhibited a dominantly terrestrial fluorescence signature (59–71 %) year round, signaling a strong riparian and near stream soil control on CDOM composition. During snowmelt, the role of water as C transporter was superimposed on its control as C reservoir, when the NF stream transported significantly more soil C (40 % DOC, 56 % DIC) than the SF stream as a result of hillslope flushing. Inter-annual variations in winter precipitation were paramount in regulating annual stream C effluxes, e.g., reducing C effluxes three-fold after a dry (relative to wet) winter season. During the warmer summer months % dissolved oxygen saturation decreased, δ13CDIC increased and CDOM assumed a more microbial signature, consistent with heterotrophic respiration in the stream and riparian soils. As a result of stream C incubation and soil respiration, \( P_{{{\text{CO}}_{2} }} \) increased up to 12 times atmospheric values leading to substantial degassing.

Remedial strategy of algal proliferation in a regulated river system by integrated hydrological control: an evolutionary modelling framework

We simulated water-quality measures in a regulated river system (the lower Nakdong River) under simultaneous discharge control at upriver dams and an estuarine barrage with the goal of reducing phytoplankton biomass (chlorophyll a concentration). We used genetic programming (GP) to create a rule-set-based predictive model for the chlorophyll a concentration based on 16 years (1994–2009) of meteorological, hydrological, and limnological data. The rule-set model used eight variables, including water temperature, dam and estuarine barrage discharge, phosphate and silica concentrations, and accurately predicted the phytoplankton biomass (determination coefficients, r2, for training and test data were 0.52 and 0.45, respectively). According to sensitivity and scenario analyses, a larger water volume resulting from increased discharge from upriver dams and decreased discharge from an estuarine barrage would reduce chlorophyll a concentrations at the study site. This result provided ample evidence that simultaneous manipulation of dam and estuarine discharge rates could effectively increase river flow and flush aggregated algal populations downstream. Additionally, we considered that even small increases in river flow could play a role in diluting phytoplankton biomass during the dry winter season when estuarine discharge remains low. These two hydrological mechanisms could be used as selective strategies for water-resource management.

A new gall-inducing genus and species of Eriococcidae (Hemiptera: Sternorrhyncha: Coccoidea) on Sapindaceae from Brazil.

A new gall-inducing genus and species of felt scales (Hemiptera: Coccoidea: Eriococcidae) found on the leaves and twigs of Matayba guianensis (Sapindaceae) in Brazil is described: Bystracoccus Hodgson gen n. and B. mataybae Hodgson, Isaias & Oliveira sp. n. This is the first record of an eriococcid inducing leaf and stem galls on Sapindaceae and is only the second example of a member of the Eriococcidae to induce stem galls in which the insects diapause during the dry (winter) season. Only the adult female, second-instar female and crawler are known. The species overwinters as the first-instar nymph in pit galls on the twigs but spends the rest of the year associated with two-chambered galls on the leaves. It has recently become clear that South America has a rich felt-scale insect fauna many of which induce galls. It has proved very difficult to place this new genus in a family as it appears to fall between the Eriococcidae and Beesoniidae but is here placed in the eriococcids based on the similarity of the first-instar nymphs and the abundance of this family in the Neotropics. However, the dorsum of the abdomen of the mature adult female becomes heavily sclerotised, forming a round plug-like structure that completely fills the gall orifice. This structure shows remarkable morphological similarities to that of the beesoniid Danumococcus parashoreae Takagi & Hodgson found on Parashorea tomentella (Dipterocarpaceae) in Sabah, Malaysia, with which it is compared along with other eriococcid genera known from South America.