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Forest Catchment (forest + catchment)
Selected AbstractsClimatic influence on the inter-annual variability of late-Holocene minerogenic sediment supply in a boreal forest catchmentEARTH SURFACE PROCESSES AND LANDFORMS, Issue 4 2010Gunilla Petterson Abstract Processes controlling sediment yield vary over a range of timescales, although most process-based observations are extremely short. Lake sediments, however, can be used to extend the observational timescale and are particularly useful when annually laminated (varved) sediment is present. The sediment record at Kassjön (N. Sweden) consists of ,6400 varves, each 0·5,1 mm thick. Image analysis was used to determine grey-scale variation and varve thickness from which annual minerogenic accumulation rate (MinAR) (mg cm,2 year,1) was inferred for the period 4486 BC , AD 1900. MinAR varies on annual to centennial scales and mainly reflects channel bank erosion by the inflow streams. The mineral input reflects the intensity of the spring run-off, which is dependent on the amount of snow accumulated during the winter, and hence MinAR is a long-term record of variability in past winter climate; other factors will be a variable response to catchment uplift, vegetation succession and pedogenesis. A major shift from low to high MinAR occurred ,250 BC, and peaks occurred around AD 250, 600, 1000, 1350 and 1650. Wavelet power spectrum analysis (confirmed by Fourier analyses) indicated significantly different periodicities throughout the period 4000 BC , AD 1700, including 275 years for the period 4000 BC , 2900 BC, 567 years for the period 2901 BC , 1201 BC, and 350 and 725 years for the period 1200 BC , AD 1700. The long-term, centennial scale variability (,350 years) may reflect solar forcing (cf the 385-year peak in tree-ring calibrated 14C activity) but interestingly, there is no obvious link to high frequency forcing, such as the North Atlantic Oscillation. The high resolution component of the record highlights the relevance of varved lake sediment records for understanding erosion dynamics in undisturbed forested catchments and their link to long-term climate dynamics and future climate change. Copyright © 2010 John Wiley & Sons, Ltd. [source] The solute budget of a forest catchment and solute fluxes within a Pinus radiata and a secondary native forest site, southern ChileHYDROLOGICAL PROCESSES, Issue 13 2002Geertrui Y. P. Uyttendaele Abstract 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 ,s. 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. [source] Effects of hydrogeomorphic region, catchment storage and mature forest on baseflow and snowmelt stream water quality in second-order Lake Superior Basin tributariesFRESHWATER BIOLOGY, Issue 5 2003Naomi E. Detenbeck SUMMARY 1. In this study we predict stream sensitivity to non-point source pollution based on the non-linear responses of hydrological regimes and associated loadings of non-point source pollutants to catchment properties. We assessed two hydrologically based thresholds of impairment, one for catchment storage (5,10%) and one for mature forest (<50% versus >60% of catchment in mature forest cover) across two different hydrogeomorphic regions within the Northern Lakes and Forest (NLF) ecoregion: the North Shore [predominantly within the North Shore Highlands Ecological Unit] and the South Shore (predominantly within the Lake Superior Clay Plain Ecological Unit). Water quality samples were collected and analysed during peak snowmelt and baseflow conditions from 24 second-order streams grouped as follows: three in each region × catchment storage × mature forest class. 2. Water quality was affected by a combination of regional influences, catchment storage and mature forest. Regional differences were significant for suspended solids, phosphorus, nitrogen: phosphorus ratios, dissolved organic carbon (DOC) and alkalinity. Catchment storage was significantly correlated with dissolved silica during the early to mid-growing season, and with DOC, specific conductance and alkalinity during all seasons. Total nitrogen and dissolved nitrogen were consistently less in low mature forest than in high mature forest catchments. Catchment storage interacted with the influence of mature forest for only two metrics: colour and the soluble inorganic nitrogen : phosphorus ratio. 3. Significant interaction terms (region by mature forest or region by storage) suggest differences in regional sensitivity for conductance, alkalinity, total organic carbon, and colour, as well as possible shifts in thresholds of impact across region or mature forest class. 4. Use of the NLF Ecoregion alone as a basis for setting regional water quality criteria would lead to the misinterpretation of reference condition and assessment of condition. There were pronounced differences in background water quality between the North and South Shore streams, particularly for parameters related to differences in soil parent material and glacial history. A stratified random sampling design for baseflow and snowmelt stream water quality based on both hydrogeomorphic region and catchment attributes improves assessments of both reference condition and differences in regional sensitivity. [source] Rainfall distribution is the main driver of runoff under future CO2 -concentration in a temperate deciduous forestGLOBAL CHANGE BIOLOGY, Issue 1 2010SEBASTIAN LEUZINGER Abstract Reduced stomatal conductance under elevated CO2 results in increased soil moisture, provided all other factors remain constant. Whether this results in increased runoff critically depends on the interaction of rainfall patterns, soil water storage capacity and plant responses. To test the sensitivity of runoff to these parameters under elevated CO2, we combine transpiration and soil moisture data from the Swiss Canopy Crane FACE experiment (SCC, 14 30,35 m tall deciduous broad-leaved trees under elevated CO2) with 104 years of daily precipitation data from an adjacent weather station to drive a three-layer bucket model (mean yearly precipitation 794 mm). The model adequately predicts the water budget of a temperate deciduous forest and runoff from a nearby gauging station. A simulation run over all 104 years based on measured sap flow responses resulted in only 5.5 mm (2.9%) increased ecosystem runoff under elevated CO2. Out of the 37 986 days (1 January 1901,31 December 2004), only 576 days produce higher runoff in the elevated CO2 scenario. Only 1 out of 17 years produces a CO2 -signal >20 mm a,1, which mostly depends on a few single days when runoff under elevated CO2 exceeds runoff under ambient conditions. The maximum signal for a double preindustrial CO2 -concentration under the past century daily rainfall regime is an additional runoff of 46 mm. More than half of all years produce a signal of <5 mm a,1, because trees consume the ,extra' moisture during prolonged dry weather. Increased runoff under elevated CO2 is nine times more sensitive to variations in rain pattern than to the applied reduction in transpiration under elevated CO2. Thus the key driver of increased runoff under future CO2 -concentration is the day by day rainfall pattern. We argue that increased runoff due to a first-order plant physiological CO2 -effect will be very small (<3%) in a landscape dominated by temperate deciduous forests, and will hardly increase flooding risk in forest catchments. Monthly rainfall sums are unsuitable to realistically model such CO2 effects. These findings may apply to other ecosystems with comparable soil water storage capacity. [source] | ||||||||||