Net Primary Production and Ecosystem Carbon Flux of Brazilian Tropical Savanna Ecosystems From Eddy Covariance and Inventory Methods

• Published in: Journal of geophysical research. Biogeosciences 2022-08, Vol.127 (8), p.n/a
• Main Authors: Vourlitis, George L., Pinto, Osvaldo Borges, Dalmagro, Higo J., Enrique Zanella de Arruda, Paulo, Almeida Lobo, Francisco, Souza Nogueira, José
• Format: Article
• Language: English
• Subjects: Amazon Basin; Availability; biometric measurements; Carbon; Carbon dioxide; cerrado; climate change; Covariance; Ecosystems; ecosystems ecology; Estimates; Forests; Grasslands; Methods; micrometeorology; Moisture effects; Net Primary Productivity; Pantanal; Primary production; Productivity; Rainforests; Savannahs; Soil moisture; Storage; Tropical forests; Vortices; Water availability; Wood
• ISSN: 2169-8953; 2169-8961
• DOI: 10.1029/2021JG006780

Estimates of net primary (NPP) and ecosystem production (NEP) are needed for tropical savanna, which is structurally diverse but understudied compared to tropical rainforest. We used eddy covariance and inventory methods to estimate carbon (C) fluxes for an upland mixed grassland and a seasonally flooded forest to determine the correspondence between these methods and assess the contribution of C cycling components to the total NPP. Both techniques provided similar estimates of net ecosystem CO2 exchange (−3.0 ‒ 2.3 MgC ha−1 y−1 for eddy covariance vs. −2.0 ‒ 4.3 MgC ha−1 y−1 for inventory), gross primary production (7.5–16.3 MgC ha−1 y−1 for eddy covariance vs. 8.7–18.4 MgC ha−1 y−1 for inventory), and total NPP (0.9–7.5 MgC ha−1 y−1 for eddy covariance vs. 2.0–9.5 MgC ha−1 y−1 for inventory). Belowground NPP accounted for 49%–53% of the total NPP for both ecosystems, followed by aboveground litter (26%–27%) and wood (16%–17%) production. Increases in water availability increased the potential for C storage, but the mechanism was different in the savanna types. Compared to other savanna ecosystems, the mixed grassland had a lower productivity and C use efficiency (CUE = NPP/GPP = 0.28), while the Cerrado forest had a high CUE (0.58) and similar C flux rates to other tropical savanna forests. The agreement in the C cycle estimates derived from the eddy covariance and inventory methods increases our confidence in the productivity estimates for these tropical savanna ecosystems. Plain Language Summary Estimates of net primary and ecosystem production are needed for tropical savannas, which are highly diverse but understudied compared to tropical forests. Several methods have been used to measure primary and ecosystem production; however, these approaches have errors and uncertainties. We used available methods to estimate the productivity of a grass‐dominated savanna in the southern Amazon Basin and a seasonally flooded forest in the northern Pantanal to assess the correspondence in the productivity estimated from these methods and evaluate the contribution of above and belowground processes to the overall ecosystem productivity. Productivity estimates derived from the different techniques were similar. Belowground processes accounted for 49%–53% of the productivity followed by leaf (26%–27%) and wood (16%–17%) production. Increases in water availability increased the productivity for both savanna types, but for different reasons. An increase in soil moistur