Bio-micrometeorology of a Sierra Nevada montane meadow

Abstract

This study examines the role of restoration on the ecologic characteristics and functioning of meadow ecosystems, particularly vegetation and soil characteristics and atmospheric exchanges of carbon, water, and energy. The rate and sign of the exchanges were measured using eddy covariance in a restored montane meadow during the growing season. During the total study period the large daily gross primary production (GPP) and respiration (Re) values (-30 and +27 g C m^-2d^-1 respectively) produced an atmospheric sink of CO₂ of 2.32 g C m^-2d^-1.  The available energy (QN) is predominantly utilized by evapotranspiration, with most of the available energy going into water phase change. A large reduction in soil moisture content over the study period correlates to a shift in NEE from a sink to a source of atmospheric CO₂, a decline in the latent heat flux (QE) (17.6 to 11.7 MJ m^-2d^-1) and increase in the sensible heat flux (QH) (-0.7 MJ m^-2d^-1 to 1.8 MJ m^-2d^-1.) Sampling and analysis of vegetation and soil was conducted both within the measurement footprint and in a degraded meadow for comparison.  The restored meadow had greater live vegetation cover, litter, species richness, and biomass both above and below the ground in comparison to the degraded meadow.  There were also fewer invasive species and xeric plants such as shrubs and the soils contained more moisture and organic material.  The improved ecosystem characteristics at the restored site in addition to QE and NEE sensitivity to soil moisture, illustrate the important impact of restoring water table levels for ecosystem functioning.