Examining the short-term impacts of diverse management practices on plant phenology and carbon fluxes of Old World bluestems pasture

Abstract

Burning, grazing, and baling (hay harvesting) are common management practices for tallgrass pasture. To develop and adopt sustainable management practices, it is essential to better understand and quantify the impacts of management practices on plant phenology and carbon fluxes. In this study, we combined multiple data sources, including in-situ PhenoCam digital images, eddy covariance data, and satellite data (Landsat and Moderate Resolution Imaging Spectroradiometer (MODIS)) to examine the impacts of burning, baling, and grazing on canopy dynamics, plant phenology, and carbon fluxes in a tallgrass pasture in El Reno, Oklahoma in 2014. Landsat images were used to assess the baling area and the trajectory of vegetation recovery. MODIS vegetation indices (VIs) were used in the Vegetation Photosynthesis Model (VPM) to estimate gross primary production (GPP VPM) at a MODIS pixel for the flux tower (baled) site. For comparison between baled and unbaled conditions, we used MODIS VIs for a neighbor MODIS pixel (unbaled) and ran VPM. Daily PhenoCam images and green chromatic coordinate (GCC) tracked canopy dynamics and plant phenology well. The grassland greened up immediately after burning in April. GCC values showed two peaks with the similar magnitude because of quick recovery of grassland after baling. Satellite-derived VIs and GPP VPM showed that the pasture recovered in one month after baling. The GPP VPM matched well (R 2 = 0.89) with the eddy covariance-derived GPP (GPP EC). Grazing in the late growing season did not influence plant phenology (VIs and GCC) and carbon uptake (GPP) as plants were in the late growing stage. Neither did it affect GPP differently in those two conditions because of even grazing intensity. The reduction in GPP after baling was compensated by higher GPP after large rain events in late July and early September, causing little seasonal differences in GPP (-0.002 g C m-2 day-1) between the baled and unbaled conditions. Interactions of different management 3 practices with climate make it complicated to understand the impacts of different management practices on carbon dynamics and plant phenology. Thus, it is necessary to further investigate the responses of tallgrass pastures to different management practices under different climate regimes at multiple temporal and spatial scales.

Enhanced gross primary production and evapotranspiration in juniper‐encroached grasslands

“…A global accuracy assessment showed the R 2 and root-mean-square error (RMSE) of GPPvpm for GRA, WSA, and SAV were 0.79, 0.80, 0.70, and 1.2, 0.76, 0.7 gC m −2 day −1 , respectively. In Oklahoma, the R 2 and RMSE for GRA from the previous publications were 0.89 and 1.3 gC m −2 day −1 on average Wagle et al, 2014;Zhang et al, 2016;Zhou et al, 2017). The assessment of GPPvpm on the mesquite juniper woody savanna (US-FR2) in Texas, USA, showed a R 2 and RMSE of 0.73 and 1.13 gC m −2 day −1 using 3-year (2004-2006) 8-day data (Zhang et al, 2016).…”

“…The GPP estimates from the VPM simulations have been validated for grasslands (GRA;Doughty et al, 2018;Wagle et al, 2014;Zhang et al, 2016Zhang et al, , 2017, woody savannas (WSA; Wang et al, 2016;Zhang et al, 2016Zhang et al, , 2017, and savannas (SAV; Jin et al, 2013;Zhang et al, 2017) using eddy flux tower GPP (GPP EC ) data from around the globe (Supporting Information Table S1). In Oklahoma, the R 2 and RMSE for GRA from the previous publications were 0.89 and 1.3 gC m −2 day −1 on average Wagle et al, 2014;Zhang et al, 2016;Zhou et al, 2017). In Oklahoma, the R 2 and RMSE for GRA from the previous publications were 0.89 and 1.3 gC m −2 day −1 on average Wagle et al, 2014;Zhang et al, 2016;Zhou et al, 2017).…”

Climate Effects on Tallgrass Prairie Responses to Continuous and Rotational Grazing

“…The VPM can be driven by either site level data [45][46][47] or remote sensing data [48]. The GPP data for the two pairs of MODIS pixels in two replicates ( Figure 1) were collected from the global VPM-GPP (8-day and 500 m resolution) product [48] and the annual sums of GPP were calculated for each year.…”

Seasonal and interannual variability of land–atmosphere coupling across the Southern Great Plains of North America using the North American regional reanalysis

“…However, as noted for the SGP region, the results from Wei and Dirmeyer (2012) compare favourably with the results of this study even though the data sets (NARR vs MERRA) and scales of analysis were different along with different approaches in methodologies. The greater question is whether the results of such studies compare favourably with the growing length of record soil and atmospheric observations collected at surface observing stations such as the Oklahoma Mesonet Illston et al, 2008), surface flux sites in the domain (e.g., Ameriflux; Baldocchi et al, 2001;Zhou et al, 2017), and satellite observations. Future work should seek to complete a holistic analysis across varying in situ, satellite, and reanalysis data sets.…”