A study into the impacts of water table and nitrogen pulse on cellulose decomposition rates and carbon release in active peatland

Abstract

Since the 1980s overstocking of sheep has become an increasing problem on UK uplands. This study examined the effect of livestock urination, and also water table depth, on active peatland on cellulose decomposition and fluvial carbon release. Urination was simulated using synthetic sheep urine (SSU) and applied to quadrats of active peatland at Redlake Mire on South Dartmoor and compared to quadrats without SSU treatment. Cellulose decomposition was measured using the cotton strip assay (CSA) method as a measure of microbial activity by examining a loss in tensile strength of cotton strips buried for 45 days from September 20th to November 3rd 2012. Carbon release was measured via dissolved and particulate organic carbon (DOC and POC) concentration analyses. Application of SSU caused a biologically significant (P < 0.1) reduction in cotton tensile strength (CTSL) of approximately 8% compared to cotton strips buried with SSU, which is less than previous studies. Despite this, no statistically significant effects of SSU were found, which was most likely due to wet weather conditions during the fieldwork causing a high water table, meaning an anaerobic environment was maintained, making oxygen the limiting factor. This study suggests livestock urination does have some detrimental impact on peat so stocking patterns should be carefully considered; however peatland restoration and preservation projects will be most beneficial if they focus on hydrology making rewetting and maintenance of a high water table a priority.