loading page

AGU Poster
  • Andrew Barton
Andrew Barton

Corresponding Author:[email protected]

Author Profile


www.PosterPresentations.co m The American Southwest is experiencing increased aridity and wildfire incidence, triggering conversion of some frequent-fire forests to non-forest. These dynamics are well-established in ponderosa pine forests, but we know far less about Madrean pine-oak forests in the Sky Islands of Mexico and USA. We have documented scarce pine regeneration and vigorous post-fire oak resprouting in these forests over 27 yrs. We investigated pine regeneration patterns in long-term plots during severe drought, 10 yrs after the Horseshoe 2 Megafire in the Chiricahua Mountains, AZ-a follow-up to a 5-yr assessment. Our goals were to (1) document changes in pine regeneration and (2) develop remote-sensing tools to identify pine refugia across landscapes. For (2), we tested whether two remotely-sensed predictors-Landsat NDVI & ECOSTRESS evapotranspiration-provided predictive power beyond indices of fire severity and topographic moisture. INTRODUCTION The reliability of projections and restoration under intensifying drought and wildfire depends on a fine-grained understanding of refugia for at-risk tree populations. Fire Severity: Landsat differenced Normalized Burn Ratio (dNBR; 30-m resolution): • NBR = (NIR-SWIR) / (NIR + SWIR), dNBR = Pre-fire NBR-Post-fire NBR Topography: • elevation • topo relative moisture index (TRMI) = aspect + position + % slope + surface shape Landsat Normalized Difference Vegetation Index (NDVI; 30-m resolution): • vegetation greenness: NDVI = (NIR-R) / (NIR+ R) ECOSTRESS evapotranspiration (70-m resolution): • land surface temperature + other inputs à Priestly-Taylor algorithm à ET • Conversion of pine-oak forest to oak shrublands continued 6-10 yrs post-fire. Few pine recruits were found in a matrix of dense, oak sprouts, especially after severe fire (FIG 1) • Fewer large pine seedlings in 2021 (a dry season of record aridity) than 2016 • P. leiophylla post-fire resprouts continue to survive and, unlike seedlings, are beginning to overtop the oak resprout canopy (FIG 2) CONCLUSIONS • Nearly three decades of conversion of pine-oak forest to oak shrublands after high-severity wildfire. • Post-fire resprouting, unusual in pines, may be a lifeline for P. leiophylla. • Remotely-sensed Landsat NDVI, combined with topography and fire severity, do a good job of predicting the locations of pine refugia. • ECOSTRESS ET does not help, likely due to larger, less stationary pixels than NDVI • Field data and models suggest P. engelmannii is more drought sensitive and at risk to climate change and wildfires than P. leiophylla. REFERENCES ACKNOWLEDGEMENTS
16 Dec 2023Submitted to ESS Open Archive
18 Dec 2023Published in ESS Open Archive