Hurricanes cause severe impacts on the ecosystem, which substantially affects the carbon cycle at the local or regional scale. During the hurricanes, the loss of many vegetation/trees in the forest and agricultural lands causes more carbon to be released into the atmosphere. Studying the effects of hurricanes on the terrestrial carbon cycle, which includes gross primary product (GPP), net ecosystem exchange (NEE), heterotrophic respiration (Rh), and their interactions with land-use change, flood, and others are critical to understand the effect on the terrestrial ecosystem. The main objective of this research was to evaluate the impact of three hurricanes (Harvey, Irma, and Maria in 2017) on the carbon cycle and study the interactions among the flood events, land uses, and terrestrial carbon cycling in the state of Texas, Florida, Puerto Rico using satellite measurements. This study analyzed the GPP, NEE, and Rh distributions in the coastal climate zones in Texas, Florida, and Puerto Rico during hurricane season using Soil Moisture Active Passive (SMAP) carbon products. SMAP Carbon products (Res=9 km) were evaluated using CO2 flux data measured at EC flux site on the Prairie View A&M University Research Farm, Texas. Results showed Florida (Irma) had higher carbon emissions and lower GPP during the hurricane compared to Texas (Harvey), and Puerto Rico (Maria). For example, hurricanes Harvey (08/26/2017), Irma (09/10/2017), and Maria (09/20/2017) caused 2.6, 4.1, and 3.03 gC/m2, of carbon emissions when the recorded daily precipitations were 162, 135, and 241 mm, respectively. However, mostly carbon uptakes or low (<1 gC/m2) carbon emissions were observed on the same day in 2016 and 2018. The analysis showed that the amount of precipitation is not the only driving factor causing increased carbon emission; the characteristics of the drainage area also affect the carbon cycle and emission. Overall, the results showed that hurricanes increase carbon emissions. This study helps to understand the impact of hurricanes on the carbon cycle through analyses of spatial and temporal variations of carbon emission and uptake during the hurricane season.

Most climate change impacts are linked to terrestrial vegetation productivity, carbon stocks and land use change. Changes in land use and climate drive the dynamics of terrestrial carbon cycle. These carbon cycle dynamics operate at different spatial and temporal scales. Quantification of the spatial and temporal variability of carbon flux has been challenging because land-atmosphere-carbon exchange is influenced by many factors, including but not limited to, land use change and climate change and variability. The study of terrestrial carbon cycle, mainly gross primary product (GPP), net ecosystem exchange (NEE), soil organic carbon (SOC) and ecosystem respiration (Re) and their interactions with land use and climate change, are critical to understanding the terrestrial ecosystem. The main objective of this study was to examine the interactions among land use, climate change and terrestrial carbon cycling in the state of Texas using satellite measurements. We studied GPP, NEE, Re and SOC distributions for five selected major land covers and all ten climate zones in Texas using Soil Moisture Active Passive (SMAP) carbon products. SMAP Carbon products (Res=9 km) were compared with observed CO2 flux data measured at EC flux site on Prairie View A&M University Research Farm. Results showed the same land cover in different climate zones has significantly different carbon sequestration potentials. For example, cropland of the humid climate zone has higher (-228 g C/m2) carbon sequestration potentials than the semiarid climate zone (-36 g C/m2). Also, shrub land in the humid zone and in the semiarid zone showed high (-120 g C/m2) and low (-36 g C/m2) potentials of carbon sequestration, respectively, in the state. Overall, the analyses indicate CO2 storage and exchange respond differently to various land covers, and environments due to differences in water availability, root distribution and soil properties.