The influence of watershed run‐off on the hydrology, forest floor litter and soil carbon of headwater wetlands

Abstract

ABSTRACTThe effects of land use and land cover (LULC) on aquatic systems have been extensively studied however less research has focused on headwater wetlands. This study was conducted to evaluate the effects of watershed land conversion and associated run‐off on the hydrology and carbon cycling of headwater wetlands in coastal Alabama, USA. A total of 15 headwater wetlands were selected to reflect a range of surrounding LULC across coastal Alabama. Land use and soil data were utilized to estimate watershed run‐off curve numbers (CN) that were used with precipitation data to calculate surface run‐off (Q). Within each wetland, water level recorders were installed to monitor ground water levels for 1 year and data were used to generate hydrological metrics related to stage and flashiness. Data varied among sites, but wetlands with higher watershed CN tended to have a greater tendency for water level measurements to exceed the normal fluctuation range (outliers). Carbon dynamics associated with leaf litter and soil storage were also measured during this time period. Leaf litter traps were installed to determine litter fall carbon input (CLF). Bimonthly monitoring of forest floor carbon (CFF) was conducted to evaluate its relationship to watershed run‐off. Soil carbon content was quantified in each wetland by collecting 40‐cm cores analysed at 10 cm sections. Watershed run‐off characteristics (CN and Q) were significantly related to mean CFF and CFF : CLF (CFF adjusted for the amount of CLF) suggesting that hydrologic export and possibly decomposition increased with run‐off. Surface soil (0–10 cm) carbon content was related to median groundwater level; however, no relationship was detected between soil carbon and CN or Q. Copyright © 2013 John Wiley & Sons, Ltd.