Carbon pools and fluxes in a tupelo (Nyssa aquatica)-baldcypress (Taxodium distichum) swamp 24-years after harvest disturbances

摘要

Bottomland forests are often productive ecosystems with large quantities of above- and belowground carbon, yet few long-term research projects relating to harvest effects in bottomland hardwood forests exist. This project evaluated the long-term (24-years after harvest) effects of three disturbance treatments on the carbon budget of a tupelo-baldcypress swamp in southwestern Alabama. The site was clearcut in 1986 and timber removed by helicopter. Disturbance treatments were: 1. helicopter (HELI), 2. skidder transportation simulation (SKID), and 3. glyphosate herbicide removal of vegetation following harvesting during years one and two (GLYPH). An adjacent portion of the original stand provides a non-harvested reference (REF) condition. Measurements included aboveground biomass, belowground biomass, soil carbon, soil CO_2 efflux and estimates of buried coarse woody debris on the site. SKID treatments had the highest aboveground biomass (73.9 Mg ha ~1) and total carbon storage (206.1 Mg ha ~1) of the three treatments. GLYPH treatments had the lowest carbon storage (144.2 Mg ha ~1) and lower aboveground woody biomass (26.4 Mg ha ~1). HELI and SKID treatments were similar, but have slightly less in total forest carbon (168.7 Mg ha ~1) than the REF condition. Belowground coarse woody debris storage increased carbon storage on these sites with an additional 8-13 Mg ha ~1 being stored. GLYPH treatments had the highest total soil CO_2 efflux followed by HELI and SKID treatments, respectively. Higher biomass and carbon storage of SKID treatments is explained by the flood tolerance of tupelo, diverse micro-topography created by skidder traffic, and decreased soil aeration of skidder-rutted areas immediately after harvest which favored tupelo coppice.