Regional aboveground live carbon losses due to drought-induced tree dieback in piñon-juniper ecosystems.

Abstract Recent large-scale dieback of pinon–juniper (P–J) woodlands and forests across the western US occurred as a result of multi-year drought and subsequent insect and disease outbreaks. P–J vegetation is spatially extensive, thus large-scale mortality events such as the one that has occurred over the past several years could significantly alter regional carbon (C) budgets. Our objective was to use a remote sensing technique coupled with field-based data to estimate changes in aboveground live C stocks across a 4100 km 2 region of Colorado caused by P–J tree mortality. We hypothesized that dieback would amplify the phenological dynamics of P–J vegetation, and these variations would be related to drought-induced losses of live P–J aboveground biomass (AGB) that are discernible using time-series remote sensing vegetation data. Here, we assess live P–J AGB loss using dry season fractional photosynthetic vegetation cover (PV) derived from multi-year Landsat images. Our results showed a strong linear positive relationship between the maximum decline in PV and field-measured losses of live P–J AGB during the period 2000–05 ( r 2  = 0.64, p  = 0.002). These results were then used to map AGB losses throughout the study region. Mean live aboveground C loss (± sd) was 10.0 (± 3.4) Mg C ha − 1 . Total aboveground live P–J C loss was 4.6 Tg C, which was approximately 39 times higher than the concurrent C loss attributed to wildfire and management treatments within or near to the national forests of the study region. Our results suggest that spatially extensive mortality events such as the one observed in P–J woodlands across the western US in the past decade may significantly alter the ecosystem C balance for decades to come. Remote sensing techniques to monitor changes in aboveground C stocks, such as the one developed in our study, may support regional and global C monitoring in the future.

[1]  P. Rich,et al.  Phenology of mixed woody-herbaceous ecosystems following extreme events: net and differential responses. , 2008, Ecology.

[2]  G. R E G O R,et al.  Net Changes in Regional Woody Vegetation Cover and Carbon Storage in Texas Drylands, 1937±1999 , 2022 .

[3]  T. Kitzberger,et al.  Factors predisposing episodic drought‐induced tree mortality in Nothofagus– site, climatic sensitivity and growth trends , 2004 .

[4]  J. Palutikof,et al.  Climate change 2007 : impacts, adaptation and vulnerability , 2001 .

[5]  G. Asner,et al.  Spectral unmixing of vegetation, soil and dry carbon cover in arid regions: Comparing multispectral and hyperspectral observations , 2002 .

[6]  Thomas R. Crow,et al.  Estimating aboveground biomass using Landsat 7 ETM+ data across a managed landscape in northern Wisconsin, USA , 2004 .

[7]  P. Weisberg,et al.  Density-dependent tree mortality in pinyon-juniper woodlands , 2008 .

[8]  Didier Tanré,et al.  Second Simulation of the Satellite Signal in the Solar Spectrum, 6S: an overview , 1997, IEEE Trans. Geosci. Remote. Sens..

[9]  M. Keller,et al.  From the Cover : Condition and fate of logged forests in the Brazilian Amazon , 2006 .

[10]  Joanna Isobel House,et al.  Conundrums in mixed woody–herbaceous plant systems , 2003 .

[11]  R. D. Ramsey,et al.  Mapping moderate-scale land-cover over very large geographic areas within a collaborative framework : A case study of the Southwest Regional Gap Analysis Project (SWReGAP) , 2007 .

[12]  L. Dutra,et al.  Tropical Forest Measurement by Interferometric Height Modeling and P-Band Radar Backscatter , 2005, Forest Science.

[13]  Todd M. Scanlon,et al.  Determining land surface fractional cover from NDVI and rainfall time series for a savanna ecosystem , 2002 .

[14]  T. Wilbanks,et al.  Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change , 2007 .

[15]  A. Pitman,et al.  Impact of land cover change on the climate of southwest Western Australia , 2004 .

[16]  T. Tsujimori,et al.  Balancing the Global Carbon Budget , 2007 .

[17]  A. Taylor,et al.  Widespread Increase of Tree Mortality Rates in the Western United States , 2009, Science.

[18]  S. Goetz,et al.  Mapping and monitoring carbon stocks with satellite observations: a comparison of methods , 2009, Carbon balance and management.

[19]  Roberta E. Martin,et al.  Multiscale analysis of tree cover and aboveground carbon stocks in pinyon-juniper woodlands. , 2009, Ecological applications : a publication of the Ecological Society of America.

[20]  B. Bradley,et al.  Relationships between expanding pinyon–juniper cover and topography in the central Great Basin, Nevada , 2008 .

[21]  Peter J. Weisberg,et al.  Spatial Patterns of Pinyon–Juniper Woodland Expansion in Central Nevada , 2007 .

[22]  Guy R. McPherson,et al.  Ecology and Management of North American Savannas , 1998 .

[23]  P. Hanson,et al.  Drought disturbance from climate change: response of United States forests. , 2000, The Science of the total environment.

[24]  J. McPhee,et al.  Drought and Climate in Arizona: Top Ten Questions & Answers , 2004 .

[25]  R. Zamora,et al.  Pine processionary caterpillar Thaumetopoea pityocampa as a new threat for relict Mediterranean Scots pine forests under climatic warming , 2003 .

[26]  E. Pennisi.  Western U.S. Forests Suffer Death by Degrees , 2009, Science.

[27]  W. Schlesinger.  Biogeochemistry: An Analysis of Global Change , 1991 .

[28]  B. Law,et al.  Forest Attributes from Radar Interferometric Structure and Its Fusion with Optical Remote Sensing , 2004 .

[29]  C. Daly,et al.  A Statistical-Topographic Model for Mapping Climatological Precipitation over Mountainous Terrain , 1994 .

[30]  A. J. Belsky.  Tree/grass ratios in East African savannas: a comparison of existing models. , 1990 .

[31]  R. Scholes,et al.  Tree-grass interactions in Savannas , 1997 .

[32]  Niall P. Hanan,et al.  Tree–grass coexistence in savannas revisited – insights from an examination of assumptions and mechanisms invoked in existing models , 2004 .

[33]  E. Vivoni,et al.  Ecohydrology of water‐limited environments: A scientific vision , 2006 .

[34]  C. Pieters,et al.  Remote geochemical analysis : elemental and mineralogical composition , 1993 .

[35]  Cho‐ying Huang,et al.  Postfire stand structure in a semiarid savanna: cross-scale challenges estimating biomass. , 2007, Ecological applications : a publication of the Ecological Society of America.

[36]  Debra P. C. Peters,et al.  High-resolution images reveal rate and pattern of shrub encroachment over six decades in New Mexico, U.S.A. , 2003 .

[37]  W. Cohen,et al.  Lidar Remote Sensing for Ecosystem Studies , 2002 .

[38]  N. West.  Juniper-Pinon Savanna and Woodlands of Western North America , 1999 .

[39]  C. Allen.  Interactions Across Spatial Scales among Forest Dieback, Fire, and Erosion in Northern New Mexico Landscapes , 2007, Ecosystems.

[40]  J. Shaw,et al.  Forest Inventory and Analysis (FIA) Annual Inventory Answers the Question: What Is Happening to Pinyon-Juniper Woodlands? , 2005, Journal of Forestry.

[41]  B. Walker,et al.  Aspects of the Stability and Resilience of Savanna Ecosystems , 1982 .

[42]  Kelly K. Caylor,et al.  Determinants of woody cover in African savannas , 2005, Nature.

[43]  B. Huntley,et al.  Ecology of Tropical Savannas , 1987, Ecological Studies.

[44]  P. Gessler,et al.  Wavelet estimation of plant spatial patterns in multitemporal aerial photography , 2005 .

[45]  K. Price,et al.  Regional vegetation die-off in response to global-change-type drought. , 2005, Proceedings of the National Academy of Sciences of the United States of America.

[46]  Gregory P. Asner,et al.  Changes in Vegetation Structure after Long-term Grazing in Pinyon-Juniper Ecosystems: Integrating Imaging Spectroscopy and Field Studies , 2003, Ecosystems.

[47]  A. Huete,et al.  Overview of the radiometric and biophysical performance of the MODIS vegetation indices , 2002 .

[48]  K. Elliott,et al.  Biomass distribution and productivity of Pinus edulis-Juniperus monosperma woodlands of north-central Arizona , 1992 .

[49]  Michael A. Wulder,et al.  Surveying mountain pine beetle damage of forests: A review of remote sensing opportunities , 2006 .

[50]  R. Fensham,et al.  Temporal and spatial patterns in drought-related tree dieback in Australian savanna , 1999 .

[51]  Roberta E. Martin,et al.  Carnegie Airborne Observatory: in-flight fusion of hyperspectral imaging and waveform light detection and ranging for three-dimensional studies of ecosystems , 2007 .

[52]  N. Cobb,et al.  Relationship of stand characteristics to drought-induced mortality in three southwestern piñion-juniper woodlands. , 2009, Ecological applications : a publication of the Ecological Society of America.

[53]  M. Keller,et al.  Selective Logging in the Brazilian Amazon , 2005, Science.

[54]  A. Knapp,et al.  Variation among biomes in temporal dynamics of aboveground primary production. , 2001, Science.

[55]  Nicholas C. Coops,et al.  Assessment of QuickBird high spatial resolution imagery to detect red attack damage due to mountain pine beetle infestation , 2006 .

[56]  M. Floyd,et al.  Historical and recent fire regimes in Piñon-Juniper woodlands on Mesa Verde, Colorado, USA , 2004 .

[57]  W. Kurz,et al.  Mountain pine beetle and forest carbon feedback to climate change , 2008, Nature.

[58]  R. Birdsey,et al.  National-Scale Biomass Estimators for United States Tree Species , 2003, Forest Science.