The solute budget of a forest catchment and solute fluxes within a Pinus radiata and a secondary native forest site,southern Chile

Solute concentrations and fluxes in rainfall, throughfall and stemflow in two forest types, and stream flow in a 90 ha catchment in southern Chile (39°44′S, 73°10′W) were measured. Bulk precipitation pH was 6·1 and conductivity was low. Cation concentrations in rainfall were low (0·58 mg Ca²⁺ l^?1, 0·13 mg K⁺ l^?1, 0·11 mg Mg²⁺ l^?1 and <0·08 mg NH₄–N l^?1), except for sodium (1·10 mg l^?1). Unexpected high levels of nitrate deposition in rainfall (mean concentration 0·38 mg NO₃–N l^?1, total flux 6·3 kg NO₃–N ha^?1) were measured. Concentrations of soluble phosphorous in bulk precipitation and stream flow were below detection limits (<0·09 mg l^?1) for all events. Stream‐flow pH was 6·3 and conductivity was 28·3 μs. Stream‐water chemistry was also dominated by sodium (2·70 mg l^?1) followed by Ca, Mg and K (1·31, 0·70 and 0·36 mg l^?1). The solute budget indicated a net loss of 3·8 kg Na⁺ ha^?1 year^?1, 5·4 kg Mg²⁺ ha^?1 year^?1, 1·5 kg Ca²⁺ ha^?1 year^?1 and 0·9 kg K⁺ ha^?1 year^?1, while 4·9 kg NO₃–N ha^?1 year^?1 was retained by the ecosystem. Stream water is not suitable for domestic use owing to high manganese and, especially, iron concentrations. Throughfall and stemflow chemistry at a pine stand (Pinus radiata D. Don) and a native forest site (Siempreverde type), both located within the catchment, were compared. Nitrate fluxes within both forest sites were similar (1·3 kg NO₃–N ha^?1 year^?1 as throughfall). Cation fluxes in net rainfall (throughfall plus stemflow) at the pine stand generally were higher (34·8 kg Na⁺ ha^?1 year^?1, 21·5 kg K⁺ ha^?1 year^?1, 5·1 kg Mg²⁺ ha^?1 year^?1) compared with the secondary native forest site (24·7 kg Na⁺ ha^?1 year^?1, 18·9 kg K⁺ ha^?1 year^?1 and 4·4 kg Mg²⁺ ha^?1 year^?1). However, calcium deposition beneath the native forest stand was higher (15·9 kg Ca²⁺ ha^?1 year^?1) compared with the pine stand (12·6 kg Ca²⁺ ha^?1 year^?1). Copyright © 2002 John Wiley & Sons, Ltd.     

High-frequency monitoring of hydrological and biogeochemical fluxes in forested catchments of southern Chile

The variability of rainfall-dependent streamflow at catchment scale modulates many ecosystem processes in wet temperate forests. Runoff in small mountain catchments is characterized by a quick response to rainfall pulses which affects biogeochemical fluxes to all downstream systems. In wet-temperate climates, water erosion is the most important natural factor driving downstream soil and nutrient losses from upland ecosystems. Most hydrochemical studies have focused on water flux measurements at hourly scales, along with weekly or monthly samples for water chemistry. Here, we assessed how water and element flows from broad-leaved, evergreen forested catchments in southwestern South America, are influenced by different successional stages, quantifying runoff, sediment transport and nutrient fluxes during hourly rainfall events of different intensities. Hydrograph comparisons among different successional stages indicated that forested catchments differed in their responses to high intensity rainfall, with greater runoff in areas covered by secondary forests (SF), compared to old-growth forest cover (OG) and dense scrub vegetation (CH). Further, throughfall water was greatly nutrient enriched for all forest types. Suspended sediment loads varied between successional stages. SF catchments exported 455 kg of sediments per ha, followed by OG with 91 kg/ha and CH with 14 kg/ha, corresponding to 11 rainfall events measured from December 2013 to April 2014. Total nitrogen (TN) and phosphorus (TP) concentrations in stream water also varied with rainfall intensity. In seven rainfall events sampled during the study period, CH catchments exported less nutrients (46 kg/ha TN and 7 kg/ha TP) than SF catchments (718 kg/ha TN and 107 kg/ha TP), while OG catchments exported intermediate sediment loads (201 kg/ha TN and 23 kg/ha TP). Further, we found significant effects of successional stage attributes (vegetation structure and soil physical properties) and catchment morphometry on runoff and sediment concentrations, and greater nutrients retention in OG and CH catchments. We conclude that in these southern hemisphere, broad-leaved evergreen temperate forests, hydrological processes are driven by multiple interacting phenomena, including climate, vegetation, soils, topography, and disturbance history.     

Organic carbon and nutrient fluxes to the coastal zone from the Sepik River outflow

The Sepik River is a major contributor of water, sediment and associated organic loads to the coastal waters of northern New Guinea and the Bismarck Sea. We compare dissolved and particulate organic carbon data from September 1997 during an extremely dry El Nino year with those from 1996, 1999 and 2000 during La Nina wet season discharges. Estimated Sepik River flux of DOC is 3.2×10¹⁰ mol yr⁻¹ and POC is 1.1×10¹¹ mol yr⁻¹. The estimates for total river nutrient fluxes to the sea are 1.1×10¹⁰ mol yr⁻¹ for nitrogen and 4.6×10⁸ mol yr⁻¹ for phosphorus. The Sepik DOC flux is about equal to that combined from all four major rivers that enter the Gulf of Papua on the south coast of PNG. The Sepik inorganic PIC flux is low (1.4×10⁸ mol yr⁻¹) as the river does not drain carbonate soils. With a narrow continental shelf, and strong coastal currents, much of this exported material is available for long distance transport into the coastal Bismarck Sea and beyond.     

Water and heat fluxes above a lowland dipterocarp forest in Peninsular Malaysia

We measured the fluxes of sensible and latent heat between a low‐land dipterocarp forest in Peninsular Malaysia and the atmosphere. No clear seasonal or interannual changes in latent heat flux were found from 2003 to 2005, while sensible heat flux sometimes fluctuated depending on the fluctuation of incoming radiation between wet and dry seasons. The evapotranspiration rates averaged for the period between 2003 and 2005 were 2·77 and 3·61 mm day^?1 using eddy covariance data without and with an energy balance correction, respectively. Average precipitation was 4·74 mm day^?1. Midday surface conductance decreased with an increasing atmospheric water vapour pressure deficit and thus restricted the excess water loss on sunny days in the dry season. However, the relationship between the surface conductance and vapour pressure deficit did not significantly decline with an increase in volumetric soil water content even during a period of extremely low rainfall. Copyright © 2009 John Wiley & Sons, Ltd.     

Oxygen and hydrogen isotopic characterization of rainfall and throughfall in four South Korean cool temperate forests

Understanding the isotopic composition of precipitation in a forested catchment is critical for ecohydrological studies. Changes in the water isotopes of rainfall were assessed during its passage through the canopy in throughfall, and the effect of different forest stands on the isotope composition of throughfall. In a cool temperate forest in Korea, rainfall and throughfall samples collected under Pinus densiflora (red pine), Castanea crenata (chestnut), Robinia pseudoacacia (black locust) and mixed stands (mix of these three species) were analysed for oxygen and hydrogen isotopes. Throughfall δ¹⁸O and δD were enriched compared to rainfall. A difference of δ¹⁸O and δD among throughfall may be related to the difference in interception–storage capacity of different species due to dissimilar canopy characteristics. Since isotopic composition of throughfall and rainfall are different due to canopy isotopic effects, use of rainfall isotopic signatures for ecohydrological studies in forested ecosystem can lead to biases.     

Changes in carbon and nutrient fluxes from headwaters to ocean in a mountainous temperate to subtropical basin

Water erosion provides major links in global cycles of carbon (C), nitrogen (N) and phosphorus (P). Although significant research on erosion mechanisms has been done, there is still little knowledge on C, N and P fluxes across landscapes to the ocean and their controlling factors in subtropical climates. A four‐year study quantifying and comparing particulate and dissolved C, N and P from multiple scales (microplot, plot, microcatchment, subcatchment, catchment, sub‐basin and basin) was performed in Thukela basin (≈30 000 km²), South Africa. The basin climate was largely subtropical‐humid [mean annual precipitation (MAP) > 980 mm yr^‐1], but temperate (MAP >2000 mm yr^‐1) on the highlands. Open grassland, cropland and bushland were the major land uses. On average, 65, 24 and 4 g m^‐2 yr^‐1 C, N and P were displaced from original topsoil positions, but only 0.33, 0.005 and 0.002 mg m^‐2 yr^‐1 were, respectively, exported to the ocean. The fluxes decreased by 95, 97 and 84%, respectively, from plot to microcatchment outlet; and decreased further in downstream direction by >99% from microcatchment to basin outlet. The hillslope (microplot to microcatchment) fluxes correlated strongly with rainfall parameters. Particulate contributions dominated hillslope fluxes at 73, 81 and 76% of total annual C, N and P, respectively. Although particulate C dominated in the microcatchment‐catchment reach (55%), N (54%) and P (69%) were dominated by dissolved forms. The lower basin zone was dominated by dissolved flux contributions at 93, 81 and 78% for C, N and P for the sub‐basin outlet. These results suggested spatially varying drivers of C, N and P losses from the landscape to the ocean, via the river network. Deposition was envisaged the dominant hillslope level loss process, which gradually gave way to mineralization and biotic uptake in the river network as flux contributions shifted from being predominantly particulate to dissolved forms. Copyright © 2017 John Wiley & Sons, Ltd.     

Impacts of milkfish (Chanos chanos) aquaculture on carbon and nutrient fluxes in the Bolinao area,Philippines

Sediment oxygen consumption, TCO2 production and nutrient fluxes across the sediment-water interface were measured in sediments within and along a transect from four fish pens with production of milkfish (Chanos chanos) in the Bolinao area, The Philippines. The four fish pens were each representing a specific period in the production cycling. There was a positive linear relationship between the rates of sedimentation inside the fish pens and the sediment oxygen consumption indicating that the benthic processes were controlled by the input of organic matter from fish production. The nutrient fluxes were generally higher inside the fish pens, and nitrate was taken up (1.7-5.8 mmol m(-2) d(-1)) whereas ammonium (1-22 mmol m(-2) d(-1)) and phosphate (0.2-4.7 mmol m(-2) d(-1)) were released from the sediments. The sediments were enriched in organic matter with up to a factor 4 compared to outside. A mass balance for one crop of milkfish was constructed based on production data and on measured fluxes of nutrients in the fish pens to assess the loss of carbon and nutrients to the environment. There was a loss to the surroundings of carbon and nitrogen of 51-68% of the total input, whereas phosphorus was buried in the sediments inside the fish pens which acted as net sinks of phosphorus. The results obtained suggest that fish pen culture as practiced in the Bolinao area, leads to even greater impacts on benthic carbon and nutrient cycling than those found in suspended cage cultures.     

Throughfall enrichment and stream nutrient chemistry in small headwater catchments with different land cover in southern Chile

Land cover changes have a great impact on nitrogen (N) and phosphorous (P) fluxes catchments. In this study, we wanted to compare different land covers: deciduous (D), evergreen (E) (both native forests), and exotic Eucalyptus globulus plantation (EP), affected precipitation, and stream discharge on N and P species concentrations and fluxes, under a low deposition climate in south‐central Chile. For this, we collected bulk precipitation, throughfall, and stream water samples after 41 rainfall events in E and EP, during the period June 2009–March 2011, and 31 rainfall events in D, during the period October 2009–March 2011. The highest canopy enrichment of N and P species for throughfall was observed in deciduous forest, while E. globulus showed the minimum enrichment. Total nitrogen (total‐N) discharge in EP was about 8.6 times higher than that of E and D catchments. Total‐N annual retention was positive only in E and D catchments. However, EP catchment showed a net loss (?4.79 kg N ha/year). The biggest difference was observed in nitrate stream concentrations, which showed low values for E (3.4 ± 1.3 μg/L), while EP and D showed higher nitrate concentrations (84.9 ± 16.7 and 134.7 ± 36.7 μg/L, for EP and D, respectively). Total phosphorous (total‐P) discharge flux was low in EP (0.4 kg P ha/year), and negligible in E and D forests (<0.1 kg P ha/year). Total‐P annual retention was near to 1.0 kg N ha/year (on E and D), while a net loss (?1.5 kg N ha/year) was observed for EP. We attribute the observed differences in nutrient throughfall enrichment due to high multi‐stratified canopies in the native forests. Both deciduous and evergreen native forest‐covered catchments showed the highest retention of total‐N and total‐P, in contrast to Eucalyptus‐covered plantation.     

Tectono-metamorphic history of the Tacagua ophiolitic unit (Cordillera de la Costa, northern Venezuela): Insights in the evolution of the southern margin of the Caribbean Plate

Abstract   The southern margin of the Caribbean Plate is well exposed in the Cordillera de la Costa of northern Venezuela, where amalgamated terranes consisting of continental and oceanic units occur. In the Cordillera de la Costa, metamorphosed oceanic units crop out along the coast near Caracas. Among them, the Tacagua unit is characterized by metaserpentinites and metabasites showing mid-oceanic ridge basalt geochemical affinity. These lithologies, representative of a disrupted ophiolite sequence, are associated with metasediments consisting of calcschists alternating with pelitic and psammitic schists, whose protoliths were probably represented by deep-sea hemipelagic and turbiditic deposits. In the Tacagua unit, a polyphase deformation history has been reconstructed, consisting of four folding phases from D1 to D4 . Geological setting suggests an involvement of the Tacagua unit in the processes connected with a subduction zone. The following deformations (from D2 to D4 ) observed in the field might be related to the exhumation history of the Tacagua unit. The late deformation history consists of an alternation of deformation phases characterized by displacement parallel ( D2 and D4 phases) and normal ( D3 phase) to plate boundary between the Caribbean and South America Plates. All lines of geological evidence suggest that the whole evolution of the Tacagua unit was acquired in a setting dominated by oblique convergence, in which alternation of strike-slip and pure compressional or pure extensional tectonics occurred through time.     

Seasonal snowpack dynamics and runoff in a cool temperate forest: lysimeter experiment in Niigata,Japan

Seasonal snowpack dynamics are described through field measurements under contrasting canopy conditions for a mountainous catchment in the Japan Sea region. Microclimatic data, snow accumulation, albedo and lysimeter runoff are given through the complete winter season 2002–03 in (1) a mature cedar stand, (2) a larch stand, and (3) a regenerating cedar stand or opening. The accumulation and melt of seasonal snowpack strongly influences streamflow runoff during December to May, including winter baseflow, mid‐winter melt, rain on snow, and diurnal peaks driven by radiation melt in spring. Lysimeter runoff at all sites is characterized by constant ground melt of 0·8–1·0 mm day⁻¹. Rapid response to mid‐winter melt or rainfall shows that the snowpack remains in a ripe or near‐ripe condition throughout the snow‐cover season. Hourly and daily lysimeter discharge was greatest during rain on snow (e.g. 7 mm h⁻¹ and 53 mm day⁻¹ on 17 December) with the majority of runoff due to rainfall passing through the snowpack as opposed to snowmelt. For both rain‐on‐snow and radiation melt events lysimeter discharge was generally greatest at the open site, although there were exceptions such as during interception melt events. During radiation melt instantaneous discharge was up to 4·0 times greater in the opening compared with the mature cedar, and 48 h discharge was up to 2·5 times greater. Perhaps characteristic of maritime climates, forest interception melt is shown to be important in addition to sublimation in reducing snow accumulation beneath dense canopies. While sublimation represents a loss from the catchment water balance, interception melt percolates through the snowpack and contributes to soil moisture during the winter season. Strong differences in microclimate and snowpack albedo persisted between cedar, larch and open sites, and it is suggested further work is needed to account for this in hydrological simulation models. Copyright © 2005 John Wiley & Sons, Ltd.     

Stormflow generation in a small rainforest catchment in the Luquillo Experimental Forest,Puerto Rico

Various complementary techniques were used to investigate the stormflow generating processes in a small headwater catchment in northeastern Puerto Rico. Over 100 samples were taken of soil matrix water, macropore flow, streamflow and precipitation, mainly during two storms of contrasting magnitude, for the analysis of calcium, magnesium, silicon, potassium, sodium and chloride. These were combined with hydrometric information on streamflow, return flow, precipitation, throughfall and soil moisture to distinguish water following different flow paths. Geo‐electric sounding was used to survey the subsurface structure of the catchment, revealing a weathering front that coincided with the elevation of the stream channel instead of running parallel to surface topography. The hydrometric data were used in combination with soil physical data, a one‐dimensional soil water model (VAMPS ) and a three‐component chemical mass‐balance mixing model to describe the stormflow response of the catchment. It is inferred that most stormflow travelled through macropores in the top 20 cm of the soil profile. During a large event, saturation overland flow also accounted for a considerable portion of the stormflow, although it was not possible to quantify the associated volume fully. Although the mass‐balance mixing model approach gave valuable information about the various flow paths within the catchment, it was not possible to distill the full picture from the model alone; additional hydrometric and soil physical evidence was needed to aid in the interpretation of the model results. Copyright © 2004 John Wiley & Sons, Ltd.     

Carbon and water cycling in a Bornean tropical rainforest under current and future climate scenarios

We examined how the projected increase in atmospheric CO₂ and concomitant shifts in air temperature and precipitation affect water and carbon fluxes in an Asian tropical rainforest, using a combination of field measurements, simplified hydrological and carbon models, and Global Climate Model (GCM) projections. The model links the canopy photosynthetic flux with transpiration via a bulk canopy conductance and semi-empirical models of intercellular CO₂ concentration, with the transpiration rate determined from a hydrologic balance model. The primary forcing to the hydrologic model are current and projected rainfall statistics. A main novelty in this analysis is that the effect of increased air temperature on vapor pressure deficit (D) and the effects of shifts in precipitation statistics on net radiation are explicitly considered. The model is validated against field measurements conducted in a tropical rainforest in Sarawak, Malaysia under current climate conditions. On the basis of this model and projected shifts in climatic statistics by GCM, we compute the probability distribution of soil moisture and other hydrologic fluxes. Regardless of projected and computed shifts in soil moisture, radiation and mean air temperature, transpiration was not appreciably altered. Despite increases in atmospheric CO₂ concentration (C_a) and unchanged transpiration, canopy photosynthesis does not significantly increase if C_i/C_a is assumed constant independent of D (where C_i is the bulk canopy intercellular CO₂ concentration). However, photosynthesis increased by a factor of 1.5 if C_i/C_a decreased linearly with D as derived from Leuning stomatal conductance formulation [R. Leuning. Plant Cell Environ 1995;18:339–55]. How elevated atmospheric CO₂ alters the relationship between C_i/C_a and D needs to be further investigated under elevated atmospheric CO₂ given its consequence on photosynthesis (and concomitant carbon sink) projections.     

Spatial characterization of land surface energy fluxes and uncertainty estimation at the Salar de Atacama,Northern Chile

We use Advanced Spaceborne Thermal Emission and Reflection radiometer (ASTER) data to estimate spatial energy flux and evaporation distributions at the Salar de Atacama, a playa in Northern Chile. Our approach incorporates ASTER surface kinetic temperature, emissivity, and reflectance data, ground-based meteorological measurements, and empirical parameters. Energy flux distributions are estimated using either spatially constant or spatially distributed values of model parameters, with spatially distributed parameters assigned separately to each land cover category in an image classification. We test the sensitivity of energy budget calculations to state variable and parameter values by conducting Monte Carlo simulations for regions with ground energy budget measurements. Results show that assigning spatially distributed model parameters via land cover classifications yields significant improvements to ground and sensible heat flux predictions. Latent heat fluxes cannot, however, be predicted with sufficient accuracy to allow estimation of area-integrated evaporative moisture loss at this low-evaporation playa.     

Modélisation du bilan hydrologique de la partie sud de la Mer d'Aral entre 1993 et 2001 / Hydrological balance modelling of the southern Aral Sea between 1993 and 2001

Abstract

Since the beginning of the 1990s, the Aral Sea is made of two separate entities: the Small Aral in the north and the Great Aral in the south. In this study, the water and salt balance of the Great Aral is analysed using newly available data: on the one hand, altimetric data of the sea level provided by the TOPEX/Poseidon satellite; and on the other, climate data provided by the ECMWF and NOAA within the framework of global climate re-analysis. These data indicate that the Great Aral received a mean groundwater inflow of about 4 km³ year^-1 between 1993 and 2001. Without this contribution, the Aral Sea would disappear even faster than is being observed today. Moreover, the temporal resolution of the data shows a systematic phase difference between the model prediction and satellite measurements. This phase shift is considered to be due to the formation of temporary lakes between the last station measuring the Amu-Darya discharge and its mouth in the Great Aral.     

Water balance,nutrient and carbon export from a heath forest catchment in central Amazonia,Brazil

Carbon storage values in the Amazon basin have been studied through different approaches in the last decades in order to clarify whether the rainforest ecosystem is likely to act as a sink or source for carbon in the near future. This water balance, dissolved organic carbon (DOC) and nutrient export study were carried out in a micro‐scale heath forest (Campina) catchment in central Amazonia, Brazil. For a 1‐year study period (18 March 2007 until 19 March 2008), rainfall amounted to 3054 mm; of which, 1532 mm was evaporated by the forest (4.1 mm day^?1). Rainfall interception loss amounted to 15.6% of gross rainfall. Surface runoff amounted to 485 mm, whereas another 1071 mm was discharged as regional groundwater outflow. Accumulated DOC exports in surface runoff amounted to 15.3 g m^?2 year^?1, whereas the total carbon exported was 55.9 g m^?2. This is much higher than that observed for a nearby tall rainforest catchment in central Amazonia (DOC export < 20 g m^?2). As Campina heath forest areas cover a significant proportion of the Amazon Basin, these differences in ecosystem hydrological carbon exports should be taken into account in future studies assessing the carbon budget for the Amazon Basin. Macro‐nutrient exports were low, but those of calcium and potassium were higher than those observed for tall rainforest in the Amazon, which may be caused by a lower retention capacity of the heath forest ecosystem. Copyright © 2015 John Wiley & Sons, Ltd.     

Gully erosion reduces carbon and nitrogen storage and mineralization fluxes in a headwater catchment of south‐eastern Queensland,Australia

Increased erosion associated with land use change often alters the flux of sediments and nutrients, but few studies have looked at the interaction between these disrupted cycles. We studied the effects of gully erosion on carbon and nitrogen storage in surface soil/sediment and herbaceous vegetation and on C and N mineralization in a headwater catchment used for cattle grazing. We found significantly lower C and N stored in an incising gully compared with an intact valley. This storage was significantly higher in an adjacent stabilizing gully, although not to the levels found in the intact valley. The intact valley had two to four times higher soil/sediment concentrations of total organic C, total N and Colwell extractable P than the incising gully. Lower storage was not explained by differences in vegetation biomass density or silt and clay content. Vegetation accounted for only 8% of C and 2% of N storage. Although not a significant store in itself, vegetation has an important indirect role in restoring and maintaining soil/sediment C and N stocks in eroding areas. We found significant linear relationships between C and N mineralization rates and soil/sediment C and N content, with lower rates occurring in the eroded sediment. These findings support our initial hypothesis that gully erosion reduces C and N storage and mineralization rates in eroding catchments. The implications of this study include a change to the quality of eroded sediments in headwater catchments, causing C‐poorer and N‐poorer sediments to be exported but overall loads to increase. Copyright © 2013 John Wiley & Sons, Ltd.     

Seasonal evolution of meltwater generation,storage and discharge at a non‐temperate glacier in Svalbard

In glacierized catchments, meteorological inputs driving surface melting are translated into runoff outputs mediated by the glacier hydrological system: analysis of the relationship between meteorology and diurnal and seasonal patterns of runoff should reflect the functioning of that system, with the role of meltwater storage likely to be of particular importance. Daily meltwater storage is determined for a glacier at 78 °N in the Svalbard archipelago, by comparing inputs calculated from a surface energy balance model with measured outputs (proglacial discharge). Solar radiation, air temperature, wind speed and proglacial discharge are then analysed by regression and time‐series methods, in order to assess the meteorology–discharge relationship and its variation at diurnal and seasonal time‐scales. The recorded discharge time‐series can be divided into two contrasting intervals: up to early August, proglacial discharge was high and variable, mean hydrographs showed little indication of diurnal cycling, ARIMA models of discharge indicated a non‐seasonal, moving‐average generating process, and there was a net loss of meltwater from storage; from early August, proglacial discharge was low and relatively invariable, but with clearer diurnal cycles, regression models of discharge showed substantially improved correlations with air temperature and solar radiation, ARIMA models indicated a non‐seasonal, autoregressive generating process, and eventually a seasonal component, and there was a net gain in meltwater storage. The transition between the two periods is brief compared with the duration of the melt season. The runoff response to meteorology therefore lacks the strongly progressive element previously identified in mid‐latitude glacierized catchments. In particular, the glacier hydrological system only appears responsive to diurnal forcing following the depletion of the seasonal snowpack meltwater store. Copyright © 2001 John Wiley & Sons, Ltd.     

Streamwater quality as affected by wild fires in natural and manmade vegetation in Malaysian Borneo

In 1998 a wild fire struck a paired catchment research area under long‐term monitoring of hydrological and nutrient budgets. Streamwater quality as concentrations of dissolved and suspended particulate matter was monitored during 1·5–2·5 years after the fire in streams from seven different catchments. As the catchments, due to earlier experimental treatments, had different vegetations, varying effects related to different fire intensities were observed. The highest, mean stormflow, suspended sediment concentrations resulted from intensive fire in secondary vegetation that had experienced severe soil disturbance in previous treatments (crawler tractor timber extraction 10 years earlier). Stormflow concentrations were typically still about 400 mg l^?1 in 1999 (10–21 months after the fire), which was about the maximum recorded concentration in streams during initial soil disturbance in 1988. Forest fire in natural forest resulted in less than half as high stormflow concentrations. For dissolved elements in streamwater there was a positive relation between fuel load (and fire intensity) and concentration and longevity of effects. Stream baseflow dissolved nutrient concentrations were high in the months following the fire. Mean baseflow K concentrations were 8–15 mg l^?1 in streams draining catchments with intensive fire in secondary vegetation with large amounts of fuel. After controlled fire for forest plantation establishment in 1988 corresponding concentrations were 3–5 mg l^?1, and after forest fire in natural forest in this study about 2 mg l^?1. This study shows differences in response from controlled fire for land management, forest fire in natural forests and wild fires in manmade vegetations. These differences relate to resistance and resilience to fire for the involved ecosystems. There is reason to believe that wild fires and repeated wild fires during or after droughts, in successions caused by human influence, may lead to larger losses of ecosystem nutrient capital from sites compared with forest fires in natural forests. As fire in the humid tropics becomes more common, in an increasingly spatially fragmented landscape, it will be important to be aware of these differences. Copyright © 2004 John Wiley & Sons, Ltd.     

Water fluxes at a fluctuating water table and groundwater contributions to wheat water use in the lower Yellow River flood plain,China

Capillary upflow from and deep percolation to a water table may be important in crop water supply in irrigated areas of the lower Yellow River flood plain, north China. These fluxes at the water table and the variations of the capillary upflow in relation to crop evapotranspiration need to be investigated to quantify the effect of a water table on soil water balance and to improve agricultural water management. A large weighing lysimeter was used to determine daily crop evapotranspiration, daily capillary upflow from and daily percolation to a fluctuating water table during a rotation period with wheat growing in a dry season and maize in a rainy season. The water table depth varied in the range 0·7–2·3 m during the maize growth period and 1·6–2·4 m during the wheat growth period. Experimental results showed that the capillary upflow and the percolation were significant components of the soil water balance. Three distinctly different phases for the water fluxes at the water table were observed through the rotation period: water downward period, the period of no or small water fluxes, and water upward period. It implied that the temporal pattern of these water fluxes at the water table was intimately associated with the temporal distribution of rainfall through the rotation period. An empirical equation was determined to estimate the capillary upflow in relation to wheat evapotranspiration and root zone soil water content for local irrigation scheduling. Coupled with the FAO‐Penman–Monteith equation, the equation offers a fast and low cost solution to assess the effect of capillary upflow from a water table on wheat water use. Copyright © 2007 John Wiley & Sons, Ltd.