Anthropogenic and climate controls on satellite-observed fires in managed ecosystems

Humans interact with climate to influence global fire regimes with regional and global consequences. One of the important challenges today is to understand the roles of human and climate in controlling contemporary trends in fire regimes, which would also enable more sustainable patterns of fire use in managed ecosystem. In this dissertation, I first examined efficacy of agricultural burning reporting within the United Nations Framework Convention on Climate Change (UNFCCC) by Moderate Resolution Imaging Spectroradiometer (MODIS) observation of active fires. I then developed a new way to partition MODIS observed total fires in the contiguous U.S. to different forms of management using Monitoring Trends in Burn Severity (MTBS) dataset and MODIS land cover products. I separately assessed the contribution of different fire types to long-term trends in fires in the contiguous U.S. and their sensitivity to climate. In addition, I examined the value of terrestrial water storage (TWS) observations from the Gravity Recovery and Climate Experiment (GRACE) as a long-term predictor of climatic and hydrologic controls on fires in the contiguous U.S., with implications for fire forecast and fire risk assessment. Current fourteen crops targeted by the UNFCCC reporting requirements covered 71% of global harvest area and 66% of active fires in croplands globally. Inter-country comparisons showed that current reporting countries made an internally consistent country-level report (r2 = 0.79), but fire emissions that were regularly reported by these countries accounted for only 6% of active fires in global croplands. I recommended an optimization set of crops would raise the coverage by crop to 75% at a global scale, and an extension for emission reporting to important agricultural burning countries that would raise the coverage to 55% of active fires worldwide. Cropland and prescribed fires represented 77% of active fire detections in the contiguous United States. In the west, cropland fires had a large decreasing trend (6% per year), likely in response to the implementation of intensive air quality management policies. This trend was compensated at the national scale by increases in the south and southeast regions. Potential evapotranspiration (PE) had a weaker influence on year-to-year variations of cropland and prescribed fires during the fire season that was ten-fold smaller than on wildland fires. My analysis suggested a potential exists to significantly modify or reduce landscape fire emissions in the U.S. by changing the way fires are used in heavily managed ecosystems. I found a significant long-term decline at -0.87 to -1.32 cm/yr in TWS in the southeast that was matched by a long-term increase in annual fires during 2003-2012 (r2 = 0.45 and 0.50). Across the south and southeast, decreases in TWS preceded more severe fire seasons, with optimal lead times between 0 and 5 months. In the north central part of the U.S., a positive relationship was found between TWS and fires at long lead times of 9 months prior to the spring fire season, indicating the importance of fuel availability as a key driver of the number of fires in this region. My result suggested that GRACE terrestrial water storage may reveal a different set of information during the cold season, for ground water deficits, and among different ecosystems.