Influence of management and precipitation on carbon fluxes in great plains grasslands

Abstract

a b s t r a c tSuitable management and sufficient precipitation on grasslands can provide carbon sinks. The net carbon accumulation of a site from the atmosphere, modeled as the Net Ecosystem Productivity (NEP), is a useful means to gauge carbon balance. Previous research has developed methods to integrate flux tower data with satellite biophysical datasets to estimate NEP across large regions. A related method uses the Ecosystem Performance Anomaly (EPA) as a satellite-derived indicator of disturbance intensity (e.g., livestock stocking rate, fire, and insect damage). To better understand the interactions among management, climate, and carbon dynamics, we evaluated the relationship between EPA and NEP data at the 250 m scale for grasslands in the Central Great Plains, USA (ranging from semi-arid to mesic). We also used weekly estimates of NEP to evaluate the phenology of carbon dynamics, classified by EPA (i.e., by level of disturbance impact). Results show that the cumulative carbon balance over these grasslands from 2000 to 2008 was a weak net sink of 13.7 g C m −2 yr −1 . Overall, NEP increased with precipitation (R 2 = 0.39, P < 0.05) from west to east. Disturbance influenced NEP phenology; however, climate and biophysical conditions were usually more important. The NEP response to disturbance varies by ecoregion, and more generally by grassland type, where the shortgrass prairie NEP is most sensitive to disturbance, the mixed-grass prairie displays a moderate response, and tallgrass prairie is the least impacted by disturbance (as measured by EPA). Sustainable management practices in the tallgrass and mixed-grass prairie may potentially induce a period of average net carbon sink until a new equilibrium soil organic carbon is achieved. In the shortgrass prairie, management should be considered sustainable if carbon stocks are simply maintained. The consideration of site carbon balance adds to the already difficult task of managing grasslands appropriately to site conditions. Results clarify the seasonal and interannual dynamics of NEP, specifically the influence of disturbance and moisture availability.

Atmospheric observations inform CO2 flux responses to enviroclimatic drivers

“…The response of NEE here is consistent with this earlier work. However, we find that all four examined TBMs consistently show the opposite relationship, more consistent with the expected relationship at longer timescales, where increased precipitation leads to increased carbon uptake [Chimner and Welker, 2011;Piao et al, 2013;Rigge et al, 2013].…”

FENOLOGÍA Y PRODUCTIVIDAD PRIMARIA NETA AÉREA DE SISTEMAS PASTORILES DE Panicum maximun EN EL DPTO. MORENO, SANTIAGO DEL ESTERO, ARGENTINA, DERIVADA DEL NDVI MODIS

“…La falta de precipitaciones o sequía reduce el crecimiento de la vegetación e induce a un decrecimiento en la capacidad fotosintética que es detectado y cuantificado mediante el NDVI y anomalías del NDVI (Tucker & Choudhury, 1987). De acuerdo a Rigge et al (2013) el déficit de precipitaciones y la elevada variabilidad interanual limitan la Productividad Neta del Ecosistema, por cuanto las pasturas se vuelven una fuente neta de carbono durante años con sequía. La PPNA de las ECSP afectadas con anomalías negativas de precipitación (08-09 y 12-13) fue un 78,7 % menor que la PPNA de las ECSP con anomalías positivas de precipitación media.…”

“…Similares resultados obtuvieron Chiossone & Vicini (2012) al comunicar que la sequía redujo la productividad del Panicum maximun en un 70% en la Provincia del Chaco. Por el contrario, las ECSP con anomalías positivas de precipitaciones tuvieron similar PPNA, de acuerdo a Rigge et al (2013) las pasturas son sumideros de carbono cuando presentan disponibilidad de precipitaciones y manejo adecuado.…”

“…Moreno, Santiago del Estero, son importantes desde el punto de vista ganadero debido a que sustentan ~268.000 cabezas de bovinos (Argentina, 2013) y desde un punto de vista ecológico como fuente de biodiversidad y diversificación del paisaje rural (Di Bella et al, 2004) y como sumidero de carbono (Rigge et al, 2013).…”

Monitoring Protocols: Options, Approaches, Implementation, Benefits

“…This can be accomplished by constructing indicator ranges from different climate years and analyzing for departure (e.g., Wylie et al 2012;Rigge et al 2013). Alternatively, remote-sensing-derived indicators can be analyzed directly for trends over time or used as a covariate to analyze or interpret field observations (e.g., White et al 2005;Dardel et al 2014;Brandt et al 2014).…”