The long-term water balance (1972–2004) of upland forestry and grassland at Plynlimon, mid-Wales

Marc, Vincent; Robinson, Mark

doi:10.5194/hess-11-44-2007

Cited by 78 publications

(86 citation statements)

References 38 publications

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“…And forests are aerodynamically rougher than grasslands, so they are able to exchange sensible heat more effectively across a smaller temperature gradient, than grasslands. Consequently, forests may recharge less groundwater than other vegetation classes (Kim and Jackson, 2012) and provide less run-off for stream flow (Marc and Robinson, 2007) compared to grasslands.…”

Section: Discussionmentioning

confidence: 99%

How will land use affect air temperature in the surface boundary layer? Lessons learned from a comparative study on the energy balance of an oak savanna and annual grassland in California, USA

Baldocchi¹,

Ma²

2013

Tellus B: Chemical and Physical Meteorology

104

117

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A B S T R A C TWe investigated the effect of land use on differences in air temperature. We based our analysis on a decade of weather and energy flux measurements, collected over two contrasting landscapes, an oak savanna and an annual grassland, growing under the same climate conditions. Over the decade, the daily-averaged, potential air temperature above the aerodynamically rougher and optically darker oak savanna was 0.58C warmer than that above the aerodynamically smoother and optically brighter annual grassland. However, air temperature differences were seasonal. Smallest differences in potential air temperature occurred towards the end of spring, when much of the soil moisture reservoir was depleted. Largest differences in potential air temperature occurred during the winter rain season when the grass was green and transpiring and when the trees were senescent or deciduous. To understand the effect of land use on the local climate, we examined the concomitant changes in net radiation, sensible and latent heat exchange, the aerodynamic roughness (R a ), the surface resistance to water transfer (R s ), aerodynamic surface temperature and the growth of the planetary boundary layer, with measurements and model computations. Overall, these biophysical variables provide us with mechanistic information to diagnose and predict how changes in air temperature will follow changes in land use or management. In conclusion, land use change is responsible for having a marked impact on the local climate of a region. At the local level, the change in the surface energy balance, towards a darker and rougher surface, will produce an additive increment to climate warming induced by a greater greenhouse gas burden in the atmosphere.

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Section: Discussionmentioning

confidence: 99%

How will land use affect air temperature in the surface boundary layer? Lessons learned from a comparative study on the energy balance of an oak savanna and annual grassland in California, USA

Baldocchi¹,

Ma²

2013

Tellus B: Chemical and Physical Meteorology

104

117

View full text Add to dashboard Cite

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“…[20] The proposed parameter regionalization method is demonstrated using data from the Plynlimon experimental catchments [Beven and Binley, 1992;Kirby et al, 1991;Marc and Robinson, 2006;Robinson and Dupeyrat, 2005]. The Plynlimon catchments are located in Wales and comprise the Wye and Severn river headwaters (Figure 2) (Table 2), although this coverage declined after the mid-1980s when tree felling started.…”

Section: Catchment Descriptionmentioning

confidence: 99%

Bayesian conditioning of a rainfall-runoff model for predicting flows in ungauged catchments and under land use changes

Bulygina¹,

McIntyre²,

Ballard³

et al. 2010

Role of Hydrology in Managing Consequences of a Changing Global Environment

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[1] A novel method is presented for conditioning rainfall-runoff models for ungauged catchment and land use impact applications. The method conditions the model on information from multiple regionalized response indices using a formal Bayesian approach. Two indices that hold information about soil type and land use effects are the base flow index from the Hydrology of Soil Type (HOST) classification and curve number from the U.S. Department of Agriculture's Soil Conservation Service soil and land use classification. These indices are used to constrain a five-parameter probability distributed moisture model for subcatchments of the Wye (grazed grassland) and Severn (mainly afforested) catchments in the United Kingdom. The base flow index and curve number constrain only two of the five model parameters, indicating that ideally, other sources of information would be sought. Nevertheless, the procedure significantly reduces the prior uncertainty in runoff prediction and gives predictions close to those of the calibrated models. For the case study, the introduction of the curve number in addition to the base flow index has only a small effect on model performance and uncertainty; however, it allows a distinction between the effects of soil type and land management for the purpose of scenario analysis. The principal assumptions used in the method are the applicability of the curve number classification system and its mapping to UK soil types and the likelihood function used for Bayesian conditioning.

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“…The paper discusses what can be concluded about the principal mechanisms controlling the observed streamwater NO 3 dynamics along the River Hafren using both low-and high-frequency data, with particular focus on the controls on long-term changes in the streamwater nitrate concentrations and the relative importance of soil and instream processes in controlling the observed water chemistry. (Green and Marsh, 1997;Marc and Robinson 2007;Neal, 1997Neal, , 2004. This study focuses on a small stream, the Hafren, which drains one of the main subcatchments of the Plynlimon catchment and forms the headwaters of the River Severn Shand et al, 2007Shand et al, , 2005.…”

Section: Introductionmentioning

confidence: 99%

Upland streamwater nitrate dynamics across decadal to sub-daily timescales: a case study of Plynlimon, Wales

et al. 2013

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Abstract. Streamwater nitrate dynamics in the River Hafren, Plynlimon, mid-Wales were investigated over decadal to sub-daily timescales using a range of statistical techniques. Long-term data were derived from weekly grab samples and high-frequency data from 7-hourly samples (2007)(2008)(2009)) both measured at two sites: a headwater stream draining moorland and a downstream site below plantation forest. This study is one of the first to analyse upland streamwater nitrate dynamics across such a wide range of timescales and report on the principal mechanisms identified. The data analysis provided no clear evidence that the long-term decline in streamwater nitrate concentrations was related to a decline in atmospheric deposition alone, because nitrogen deposition first increased and then decreased during the study period. Increased streamwater temperature and denitrification may also have contributed to the decline in stream nitrate concentrations, the former through increased N uptake rates and the latter resultant from increased dissolved organic carbon concentrations. Strong seasonal cycles, with concentration minimums in the summer, were driven by seasonal flow minimums and seasonal biological activity enhancing nitrate uptake. Complex diurnal dynamics were observed, with seasonal changes in phase and amplitude of the cycling, and the diurnal dynamics were variable along the river. At the moorland site, a regular daily cycle, with minimum concentrations in the early afternoon, corresponding with peak air temperatures, indicated the importance of instream biological processing. At the downstream site, the diurnal dynamics were a composite signal, resultant from advection, dispersion and nitrate processing in the soils of the lower catchment. The diurnal streamwater nitrate dynamics were also affected by drought conditions. Enhanced diurnal cycling in Spring 2007 was attributed to increased nitrate availability in the post-drought period as well as low flow rates and high temperatures over this period. The combination of high-frequency short-term measurements and long-term monitoring provides a powerful tool for increasing understanding of the controls of element fluxes and concentrations in surface waters.

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The long-term water balance (1972–2004) of upland forestry and grassland at Plynlimon, mid-Wales

Cited by 78 publications

References 38 publications

How will land use affect air temperature in the surface boundary layer? Lessons learned from a comparative study on the energy balance of an oak savanna and annual grassland in California, USA

How will land use affect air temperature in the surface boundary layer? Lessons learned from a comparative study on the energy balance of an oak savanna and annual grassland in California, USA

Bayesian conditioning of a rainfall-runoff model for predicting flows in ungauged catchments and under land use changes

Upland streamwater nitrate dynamics across decadal to sub-daily timescales: a case study of Plynlimon, Wales

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