Article

Carbon exchange of a mature, naturally regenerated pine forest in north Florida

Global Change Biology (Impact Factor: 8.22). 08/2008; 14(11). DOI: 10.1111/j.1365-2486.2008.01675.x
Source: OAI

ABSTRACT We used eddy covariance and biomass measurements to quantify the carbon (C) dynamics of a naturally regenerated longleaf pine/slash pine flatwoods ecosystem in north Florida for 4 years, July 2000 to June 2002 and 2004 to 2005, to quantify how forest type, silvicultural intensity and environment influence stand-level C balance. Precipitation over the study periods ranged from extreme drought (July 2000-June 2002) to above-average precipitation (2004 and 2005). After photosynthetic photon flux density (PPFD), vapor pressure deficit (VPD) >1.5 kPa and air temperature <10 °C were important constraints on daytime half-hourly net CO₂ exchange (NEEday) and reduced the magnitude of midday CO₂ exchange by >5 μmol CO₂ m⁻² s⁻¹. Analysis of water use efficiency indicated that stomatal closure at VPD>1.5 kPa moderated transpiration similarly in both drought and wet years. Night-time exchange (NEEnight) was an exponential function of air temperature, with rates further modulated by soil moisture. Estimated annual net ecosystem production (NEP) was remarkably consistent among the four measurement years (range: 158-192 g C m⁻² yr⁻¹). In comparison, annual ecosystem C assimilation estimates from biomass measurements between 2000 and 2002 ranged from 77 to 136 g C m⁻² yr⁻¹. Understory fluxes accounted for approximately 25-35% of above-canopy NEE over 24-h periods, and 85% and 27% of whole-ecosystem fluxes during night and midday (11:00-15:00 hours) periods, respectively. Concurrent measurements of a nearby intensively managed slash pine plantation showed that annual NEP was three to four times greater than that of the Austin Cary Memorial Forest, highlighting the importance of silviculture and management in regulating stand-level C budgets.

Download full-text

Full-text

Available from: Gregory Starr, Jul 01, 2015
5 Followers
 · 
323 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We investigated the effect of understory vegetation on soil C and N dynamics in two Pinus ponderosa plantations under contrasting edaphic and climatic conditions, where understory is often removed to reduce fire risk and competition for water and nutrients. A dual-isotope (C-13 and N-15) experiment was used to trace C and N from various litter mixtures (i.e., pine and understory litter, as well as their mixture, with and without isotope label replicated in a completely randomized design at each site) and into multiple soil depths and physical fractions following 10 years of decomposition. The presence of understory shrubs increased decomposition and accumulation of C and N from P. ponderosa litter in forest soils. Patterns of C and N accumulation varied with both treatment (litter composition) and environmental conditions (site), but the general response was similar in both plantations. Understory removal favored accumulation of undecomposed residues (light fraction), while addition of understory litter induced aggregate formation and accumulation of litter-derived C and N in occluded and mineral fractions. After 10 years of decomposition, most of litter biomass was lost (70-89%) and litter-derived C and N represented less than 1% of the original soil pool, but the presence of understory vegetation increased accumulation of litter C and N into occluded soil fractions. Despite large C and N losses the presence of understory vegetation increased the long-term productivity of forest soils, enhancing turnover, stabilizing organic matter and conserving N.
    Forest Ecology and Management 05/2014; 329. DOI:10.1016/j.foreco.2014.04.025 · 2.67 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Old growth forests have traditionally been viewed as an insignificant sink or source in the global carbon cycle and therefore, flux tower studies of net ecosystem exchange (NEE) and evapotranspiration (LE) using flux measurements in these ecosystems are limited. Here we report eddy covariance (EC) fluxes of carbon dioxide and water above and below the canopy of an old growth Mountain Ash (Eucalyptus regnans) forest over an 18 month period. Mountain Ash species are the world’s tallest angiosperm and recognized as the most carbon-dense forests, which potentially makes them an important component of the terrestrial carbon and water budgets in Australia. Results showed that for 2006, the ecosystem was a large net sink of carbon of 377 ± 49 g C m−2 year−1. Throughout the study period, daytime Gross Primary Productivity (GPP) was limited mainly by radiation, but there were important secondary drivers regulating carbon uptake, especially in summer, when atmospheric and soil water deficits were high. The highest rates of NEE occurred during spring, when the ecosystem was not limited by radiation or moisture, and the lowest rates were observed during autumn and winter. In 2006, GPP for the ecosystem was 2615 g C m−2 year−1, and ecosystem respiration (Re) was 2238 g C m−2 year−1. During the summer and autumn of 2006, the understorey fluxes accounted for 29% of ecosystem GPP, 33% of evapotranspiration, and 53% of night time Re, a significant proportion of carbon dioxide and water exchange given that the understorey biomass is only one tenth of the ecosystem biomass. Results from this study highlighted the importance of the understorey vegetation in regulating old growth forest carbon and water balances, which has important implications for forest management practices.
    Agricultural and Forest Meteorology 12/2013; 182:215-224. DOI:10.1016/j.agrformet.2013.07.003 · 3.89 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Information on the effect of direct drivers such as hurricanes on ecosystem services is relevant to landowners and policy makers due to predicted effects from climate change. We identified forest damage risk zones due to hurricanes and estimated the potential loss of 2 key ecosystem services: aboveground carbon storage and timber volume. Using land cover, plot-level forest inventory data, the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model, and a decision tree-based framework; we determined potential damage to subtropical forests from hurricanes in the Lower Suwannee River (LS) and Pensacola Bay (PB) watersheds in Florida, US. We used biophysical factors identified in previous studies as being influential in forest damage in our decision tree and hurricane wind risk maps. Results show that 31% and 0.5% of the total aboveground carbon storage in the LS and PB, respectively was located in high forest damage risk (HR) zones. Overall 15% and 0.7% of the total timber net volume in the LS and PB, respectively, was in HR zones. This model can also be used for identifying timber salvage areas, developing ecosystem service provision and management scenarios, and assessing the effect of other drivers on ecosystem services and goods.
    Journal of Environmental Management 09/2013; 129:599-607. DOI:10.1016/j.jenvman.2013.08.029 · 3.19 Impact Factor