Stream Discharge in Tropical Headwater Catchments as a Result of Forest Clearing and Soil Degradation
نویسندگان
چکیده
Tropical Africa is affected by intense land-use change, particularly forest conversion to agricultural land. In this study, the stream discharge of four small headwater catchments located within an area of 6 km in western Kenya was examined for 2 years (2007 and 2008). The four catchments cover a degradation gradient ranging from intact forest to agricultural land under maize cultivation for 5, 10, and 50 years. The runoff ratio (e.g., annual catchment discharge expressed as a percentage of rainfall) increased with increasing duration of cultivation from an average of 16.0% in the forest to 32.4% in the 50-yr-old agricultural catchment. Similarly, the average runoff ratio due to the stormflow component was 0.033 in the forest and increased gradually to 0.095 with increasing duration of cultivation. The conversion from forest to agricultural land in the first 5 years caused about half of the total observed increases in runoff ratio (46.3%) and discharge in relation to rainfall (50.6%). The other half of the changes in discharge occurred later during soil degradation after forest clearing. With increasing duration of cultivation, soil bulk density rb at a depth of 0–0.1 m increased by 46%, while soil organic carbon (SOC) concentrations and total porosity decreased by 75% and 20%, respectively. The changes in hydrological responses that occurred in the initial years after forest clearing may suggest a significant potential for improved land management in alleviating runoff and enhanced storm flow and moisture retention in agricultural watersheds.
منابع مشابه
The effect of land use and discharge changes on the coefficients of suspended sediment rating curve in Zagros forest areas
Extended abstract 1- Introduction The forests of the Zagros vegetation area cover about six million hectares (40%) of Iran's forest area, which is dominated by oak species. These forests are exposed to a number of threats, including land use change, deforestation, over grazing, deliberate and unintentional fires, pest and disease attacks, and climate change. Although accurate and timely...
متن کاملRiparian zones in southern Appalachian headwater catchments: Carbon and nitrogen responses to forest cutting
There is little understanding about the role eastern US forested headwater riparian areas play in protecting aquatic habitats and water quality from impacts of side slope forest harvest. To better understand this important riparian area function, we selected three sites frommanagement units with a 2-age regeneration silvicultural prescription located on the Nantahala National Forest, North Caro...
متن کاملDetermining Hydraulic Conductivity from Soil Characteristics with Applications for Modelling Stream Discharge in Forest Catchments
متن کامل
Water chemistry in 179 randomly selected Swedish headwater streams related to forest production, clear-felling and climate
From a policy perspective, it is important to understand forestry effects on surface waters from a landscape perspective. The EU Water Framework Directive demands remedial actions if not achieving good ecological status. In Sweden, 44 % of the surface water bodies have moderate ecological status or worse. Many of these drain catchments with a mosaic of managed forests. It is important for the f...
متن کاملLarge Carbon Dioxide Fluxes from Headwater Boreal and Sub-Boreal Streams
Half of the world's forest is in boreal and sub-boreal ecozones, containing large carbon stores and fluxes. Carbon lost from headwater streams in these forests is underestimated. We apply a simple stable carbon isotope idea for quantifying the CO2 loss from these small streams; it is based only on in-stream samples and integrates over a significant distance upstream. We demonstrate that convent...
متن کامل