Overland Flow on Small Plots at the Jonkershoek Forestry Research Station

Versfeld, D. B.

doi:10.1080/00382167.1981.9630222

Cited by 16 publications

(7 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The high overland flow measured in this study, even off the control plot, are in sharp contrast to the almost neg1igible runoff response (0.05% of rainfall) recorded from gentler sloping (25%) plots elsewhere in the Jonkershoek Valley (Versfeld, 1981) where none of the treatments of hoe, slash and burn, or thinning of pine plantation had a significant effect.…”

Section: Factors Controlling Overland Flow and Soil Losscontrasting

confidence: 83%

See 1 more Smart Citation

The hydrological effects of fire in South African mountain catchments

Scott

1993

Journal of Hydrology

169

124

View full text Add to dashboard Cite

Stream-flow and storm-flow in four small catchments were analysed by the paired catchment method for a response to fire. Two of the catchments were vegetated with over-mature fynbos (the indigenous scrub vegetation of the southwestern Cape Province, South Africa) , one was afforested to Pinus radiata and the fourth to Eucalyptus fastigata. One of the fynbos catchments was burned in a prescribed fire in the late dry season. The other catchments burned in wildfires. Neither of the fynbos catchments showed a change in storm-flows. Annual total flow increases of around 16% were in line with predictions, being related to the reductions in transpiration and interception. The manner of stream-flow and storm-flow generation appeared to have remained unaltered despite the fire. The two timber plantation catchments experienced large and significant increases in stormflow and sediment yields , while total flow increased by 12% in the pine catchment and decreased marginally in the eucalypt catchment. After fire , storm hydrographs were higher and steeper though their duration was little changed. These fire effects are considered to be due to changes in storm-flow generation consistent with an increased delivery of overland flow to the stream channel. This was caused , in part, by reduced infiltration resulting from water repellency in the soils of the burned catchments. The inherent wettability of a wide range of soil types and textures from beneath timber plantations and other vegetation types over a broad geographic distribution in South Africa was measured by fou r methods. Soils with high repellency ratings , unrelated to fire , are common and are most likely to occur beneath plantations of Eucalyptus and Acacia spp. and indigenous forest. Water repellent soils played a ro le, at two of the three locations, in the generation of overland flow from small plots exposed to simulated rainfall. However, the inherent repellency of the dry soils was extreme , such that fire-induced water repellency was not a factor in the response of the plots. The important role of fire in this experiment was in burning-off of repellency in the surface layer of the soil and in removing ground cover. III PREFACE The experimental work for this thesis was carried out in the experimental catchments of the Jonkershoek Forestry Research Centre near Stellenbosch and the Ntabamhlope research catchments near Estcourt, at field sites near Richmond and Mid-Illovo, Natal, and in the laboratories of the Jonkershoek Forestry Research Centre and the Departments of Agricultural Engineering and Agronomy of the University of Natal , Pietermaritzburg , under the supervision of Professor Roland E. Schulze. These studies represent my own original research and have not previously been submitted in any form for any degree or diploma to any University. Where use has been made of the work of others this is specifically acknowledged in the text.

show abstract

Section: Factors Controlling Overland Flow and Soil Losscontrasting

confidence: 83%

“…The soils are friable and deep, with the texture class being mainly sandy loams. Their high gravel and rock content, low bulk density and high pore volume result in a high infiltrability and percolation rate (Versfeld, 1981).…”

mentioning

confidence: 99%

The hydrological effects of fire in South African mountain catchments

Scott

1993

Journal of Hydrology

169

124

View full text Add to dashboard Cite

show abstract

“…In the present study, the rapid response of discharge to rainfall during both winter events, when soil-moisture levels were high, indicates that percolation time was short, and direct runoff -the sum of channel precipitation, surface runoff and rapid interhow (Ward, 1975) -the major component of streamflow. Surface runoff (overland flow) appears to be of minor importance in vegetated mountain catchments in the fynbos biome (Versfeld, 1981), and is probably confined to dynamic, expanding and contracting seep zones -which include saturated areas surrounding stream channels and areas of low hydraulic conductivity.…”

Section: Discussionmentioning

confidence: 99%

Hydrochemical response during storm events in a South African mountain catchment: the influence of antecedent conditions

1993

View full text Add to dashboard Cite

The influence of different antecedent conditions on hydrochemical response during storm events was investigated in a small, south-western Cape mountain catchment. Winter and summer storms (four in total) were sampled both before and after the catchment was deliberately burnt. During winter storms, discharge responded rapidly to rainfall, and direct runoff represented the major component of streamflow. Marked lags were observed between rainfall and discharge peaks during the summer storms, and streamflow was dominated by delayed interflow. Chloride, PO: --P and NO, -N exhibited variable response to discharge according to seasonal variations in soil-moisture levels, whereas the response of HCOq , H' and NH2 -N was not influenced by season. The movement of ions appears to be affected more by geochemical processes operating within the soil than by plant-uptake dynamics, as the prescribed burn appeared to have little effect on relationships between ionic concentration and discharge. The findings of the study highlight the complexity of relationships between solute concentration and discharge.

show abstract

“…The geology consists of sandstone and quartzite with intermittent thin shale bands of Table Mountain Group, underlain by Cape Granite. The soils are acid, loam to sandy loam with a low bulk density (Versfeld 1981). In Jonkershoek two main soil types are distinguished.…”

Section: Site Descriptionmentioning

confidence: 99%

Carbon sequestration and environmental effects of afforestation with Pinus radiata D. Don in the Western Cape, South Africa

et al. 2007

View full text Add to dashboard Cite

A three-step methodology to assess the carbon sequestration and the environmental impact of afforestation projects in the framework of the Flexible Mechanisms of the Kyoto Protocol (Joint Implementation and Clean Development Mechanism) was developed and tested using a dataset collected from the Jonkershoek forest plantation, Western Cape, South Africa, which was established with Pinus radiata in former native fynbos vegetation and indigenous forest. The impact of a change in land use was evaluated for a multifunctional, a production and a non- conversion scenario. First, the carbon balance was modelled with GORCAM and was expressed as (1) C sequestration in tC ha(-1) year(-1) in soil, litter, and living biomass according to the rules of the first commitment period of the Kyoto Protocol, and (2) CO2 emission reductions in tC ha(-1) year(-1), which includes carbon sequestered in the above-mentioned pools and additionally in wood products, as well as emission reductions due to fossil fuel substitution. To estimate forest growth, three data sources were used: (1) inventory data, (2) growth simulation with a process-based model, and (3) yield tables. Second, the effects of land use change were assessed for different project scenarios using a method related to Life Cycle Assessment (LCA). The method uses 17 quantitative indicators to describe the impact of project activities on water, soil, vegetation cover and biodiversity. Indicator scores were calculated by comparing indicator values with reference values, estimated for the climax vegetation. The climax vegetation is the site-specific ecosystem phase with the highest exergy content and the highest exergy flow dissipation capacity. Third, the land use impact per functional unit of 1 tC sequestered was calculated by combining the results of step 1 and step 2. The average baselines to obtain carbon additionality are 476 tC ha(-1) for indigenous forest and 32 tC ha(-1) for fynbos. Results show that the influence of the growth assessment method on the magnitude of C sequestration and hence on the environmental impact per functional unit is large. When growth rate is assessed with the mechanistic model and with the yield table, it is overestimated in the early years and underestimated in the long term. The main conclusion of the scenario analysis is that the production forest scenario causes higher impacts per functional unit than the multifunctional scenario, but with the latter being less efficient in avoiding CO2 emissions. The proposed method to assess impacts on diverse components of the ecosystem is able to estimate the general tendency of the adverse and positive effects of each scenario. However, some indicators, more specifically about biodiversity and water balance, could be improved or reinterpreted in light of specific local data about threat to biodiversity and water status

show abstract

Overland Flow on Small Plots at the Jonkershoek Forestry Research Station

Cited by 16 publications

References 2 publications

The hydrological effects of fire in South African mountain catchments

The hydrological effects of fire in South African mountain catchments

Hydrochemical response during storm events in a South African mountain catchment: the influence of antecedent conditions

Carbon sequestration and environmental effects of afforestation with Pinus radiata D. Don in the Western Cape, South Africa

Contact Info

Product

Resources

About