Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder

Carol A. Wessman

Research Interests

Ecosystem ecology, landscape ecology, regional and global biogeochemical cycling, ecological applications of remote sensing and geographic information systems. Current research includes studies of ecosystem controls over biophysical fluxes (CO2, water and energy) within global grasslands and semiarid lands utilizing remotely sensed spectral data in conjunction with simulation models; scaling site-level ecology to landscape and regional scales in the alpine; quantitative methods that link spatial patterns and ecological processes at broad spatial and temporal scales.

Current Research

Multiple forest disturbances, their interactions, and cumulative effects on carbon dynamics in forest ecosystems

Disturbances have a strong role in the carbon balance of many ecosystems, and the cycle of vegetation growth, disturbance, and recovery is very important in determining the net carbon balance of terrestrial biomes. Despite potentially large losses of carbon in disturbance events (due to combustion, decomposition, or other mechanisms), resilient systems can recover that balance to remain neutral over the disturbance return interval. Conversely, lack of recovery may initiate alternate regimes with a different carbon balance. Compound disturbances are phenomena of growing concern and can further impact ecosystems in novel ways, altering disturbance intensity, severity, and recovery trajectories.

This research focuses on carbon stocks in a compound disturbance environment, with special attention on black carbon (charcoal). Black carbon is a potential source of long-term carbon sequestration, as it is very resistant to decomposition, formed in fires, and has numerous other benefits such as increasing soil fertility. We extensively surveyed a compound disturbance event (wind, logging, and fire) in a Colorado subalpine forest for impacts on carbon stocks, black carbon, and regeneration. We considered all major pools, including organic and mineral soil, and contrasted them with neighboring undisturbed forests as a reference.

The disturbances had an additive effect on carbon loss, with increasing numbers of disturbances resulting in progressively decreasing carbon/black carbon stocks. We interpret this as resulting from substrate availability and fire intensity, and there was no significant difference between unburned and burned plots in terms of total black carbon. Given literature-derived decay rates, it appears that high-intensity fires may actually reduce net black carbon in these forests over the entire fire return interval, with additional disturbances compounding the loss.

Overall, high-intensity disturbances remove a large amount of carbon, and multiple disturbances compound this effect. Differences in regeneration have a small but significant difference on current carbon stocks, a difference that likely will get larger as time progresses due to differential species characteristics. Disturbances, and their interactions, will have long-lasting legacies for carbon, black carbon, and ecosystem structure and function.



View Publications

  • Cattau ME; Wessman C; Mahood A; Balch JK. (Jan 2020). Anthropogenic and lightning-started fires are becoming larger and more frequent over a longer season length in the USA. Global Ecology and Biogeography , 29(4), 668-681. 10.1111/geb.13058
  • Cattau, M. E., Mahood, A., Wessman, C., and Balch, J. (2019). Anthropogenic and lightning-started fires are becoming larger, more intense, and more frequent over a longer season length in the U.S. 10.1111/geb.13058
  • Adams, MS, RB Adams, CA Wessman and B Demmig-Adams. (12-Aug 2016). Nutritional Cues Tie Living Organisms to Their Environment and Its Sustainability. FRONTIERS IN NUTRITION, 3. 10.3389/fnut.2016.00028
  • Gartner, MH, TT Veblen, S Leyk and CA Wessman. (10-Nov 2015). Detection of mountain pine beetle-killed ponderosa pine in a heterogeneous landscape using high-resolution aerial imagery. INTERNATIONAL JOURNAL OF REMOTE SENSING, 36(21), 5353-5372. 10.1080/01431161.2015.1095369
  • Beals, SC, DL Preston, CA Wessman and TR Seastedt. (SEP 2015). Resilience of a novel ecosystem after the loss of a keystone species: plague epizootics and urban prairie dog management. ECOSPHERE, 6(9). 10.1890/ES15-00244.1
  • Buma, B, RE Poore and CA Wessman. (SEP 2014). Disturbances, Their Interactions, and Cumulative Effects on Carbon and Charcoal Stocks in a Forested Ecosystem. ECOSYSTEMS, 17(6), 947-959. 10.1007/s10021-014-9770-8
  • Buma, B, ET Pugh and CA Wessman. (20-Oct 2013). Effect of the current major insect outbreaks on decadal phenological and LAI trends in southern Rocky Mountain forests. INTERNATIONAL JOURNAL OF REMOTE SENSING, 34(20), 7249-7274. 10.1080/01431161.2013.817717
  • Buma, B and CA Wessman. (15-Oct 2013). Forest resilience, climate change, and opportunities for adaptation: A specific case of a general problem. FOREST ECOLOGY AND MANAGEMENT, 306, 216-225. 10.1016/j.foreco.2013.06.044
  • Hinners, SJ, CA Kearns and CA Wessman. (OCT 2012). Roles of scale, matrix, and native habitat in supporting a diverse suburban pollinator assemblage. ECOLOGICAL APPLICATIONS, 22(7), 1923-1935. 10.1890/11-1590.1
  • Madronich, MB, JP Greenberg, CA Wessman and AB Guenther. (JUL 2012). Monoterpene emissions from an understory species, Pteridium aquilinum. ATMOSPHERIC ENVIRONMENT, 54, 308-312. 10.1016/j.atmosenv.2012.02.047
  • Buma, B and CA Wessman. (15-Feb 2012). Differential species responses to compounded perturbations and implications for landscape heterogeneity and resilience. FOREST ECOLOGY AND MANAGEMENT, 266, 25-33. 10.1016/j.foreco.2011.10.040
  • Buma, B and CA Wessman. (MAY 2011). Disturbance interactions can impact resilience mechanisms of forests. ECOSPHERE, 2(5). 10.1890/ES11-00038.1
  • Golubiewski, NE and CA Wessman. (JUN 2010). Discriminating urban vegetation from a metropolitan matrix through partial unmixing with hyperspectral AVIRIS data. CANADIAN JOURNAL OF REMOTE SENSING, 36(3), 261-275. 10.5589/m10-041
  • Kokaly, RF, GP Asner, SV Ollinger, ME Martin and CA Wessman. (SEP 2009). Characterizing canopy biochemistry from imaging spectroscopy and its application to ecosystem studies. REMOTE SENSING OF ENVIRONMENT, 113, S78-S91. 10.1016/j.rse.2008.10.018
  • Browning, DM, SR Archer, GP Asner, MP McClaran and CA Wessman. (JUN 2008). Woody plants in grasslands: Post-encroachment stand dynamics. ECOLOGICAL APPLICATIONS, 18(4), 928-944. 10.1890/07-1559.1
  • Hughes, RF, SR Archer, GP Asner, CA Wessman, C McMurtry, J Nelson and RJ Ansley. (SEP 2006). Changes in aboveground primary production and carbon and nitrogen pools accompanying woody plant encroachment in a temperate savanna. GLOBAL CHANGE BIOLOGY, 12(9), 1733-1747. 10.1111/J.1365-2486.2006.01210.x
  • Mangan, JM, JT Overpeck, RS Webb, C Wessman and AFH Goetz. (MAR 2004). Response of Nebraska Sand Hills natural vegetation to drought, fire, grazing, and plant functional type shifts as simulated by the century model. CLIMATIC CHANGE, 63(2-Jan), 49-90. 10.1023/B:CLIM.0000018516.53419.90
  • Asner, GP, S Archer, RF Hughes, RJ Ansley and CA Wessman. (MAR 2003). Net changes in regional woody vegetation cover and carbon storage in Texas Drylands, 1937-1999. GLOBAL CHANGE BIOLOGY, 9(3), 316-335. 10.1046/j.1365-2486.2003.00594.x
  • Hudak, AT, CA Wessman and TR Seastedt. (APR 2003). Woody overstorey effects on soil carbon and nitrogen pools in South African savanna. AUSTRAL ECOLOGY, 28(2), 173-181. 10.1046/j.1442-9993.2003.01265.x
  • Hudak, AT and CA Wessman. (20-Sep 2001). Textural analysis of high resolution imagery to quantify bush encroachment in Madikwe Game Reserve, South Africa, 1955-1996. INTERNATIONAL JOURNAL OF REMOTE SENSING, 22(14), 2731-2740. 10.1080/01431160119030
  • Bateson, CA, GP Asner and CA Wessman. (MAR 2000). Endmember bundles: A new approach to incorporating endmember variability into spectral mixture analysis. IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING, 38(2), 1083-1094. 10.1109/36.841987
  • Vierling, LA and CA Wessman. (8-Jun 2000). Photosynthetically active radiation heterogeneity within a monodominant Congolese rain forest canopy. AGRICULTURAL AND FOREST METEOROLOGY, 103(3), 265-278. 10.1016/S0168-1923(00)00129-5
  • Asner, GP, CA Wessman, CA Bateson and JL Privette. (OCT 2000). Impact of tissue, canopy, and landscape factors on the hyperspectral reflectance variability of arid ecosystems. REMOTE SENSING OF ENVIRONMENT, 74(1), 69-84. 10.1016/S0034-4257(00)00124-3
  • Asner, GP, BH Braswell, DS Schimel and CA Wessman. (FEB 1998). Ecological research needs from multiangle remote sensing data. REMOTE SENSING OF ENVIRONMENT, 63(2), 155-165. 10.1016/S0034-4257(97)00139-9
  • Asner, GP, CA Wessman, DS Schimel and S Archer. (MAR 1998). Variability in leaf and litter optical properties: Implications for BRDF model inversions using AVHRR, MODIS, and MISR. REMOTE SENSING OF ENVIRONMENT, 63(3), 243-257. 10.1016/S0034-4257(97)00138-7
  • Asner, GP, CA Wessman and DS Schimel. (NOV 1998). Heterogeneity of savanna canopy structure and function from imaging spectrometry and inverse modeling. ECOLOGICAL APPLICATIONS, 8(4), 1022-1036.
  • Asner, GP, CA Wessman and S Archer. (NOV 1998). Scale dependence of absorption of photosynthetically active radiation in terrestrial ecosystems. ECOLOGICAL APPLICATIONS, 8(4), 1003-1021. 10.1890/1051-0761(1998)008[1003:SDOAOP]2.0.CO;2
  • Asner, GP, CA Bateson, JL Privette, N El Saleous and CA Wessman. (27-Nov 1998). Estimating vegetation structural effects on carbon uptake using satellite data fusion and inverse modeling. JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 103(D22), 28839-28853. 10.1029/98JD02459
  • Hudak, AT and CA Wessman. (DEC 1998). Textural analysis of historical aerial photography to characterize woody plant encroachment in South African savanna. REMOTE SENSING OF ENVIRONMENT, 66(3), 317-330. 10.1016/S0034-4257(98)00078-9
  • Wessman, CA, CA Bateson and TL Benning. (MAY 1997). Detecting fire and grazing patterns in tallgrass prairie using spectral mixture analysis. ECOLOGICAL APPLICATIONS, 7(2), 493-511. 10.2307/2269515
  • Asner, GP, CA Wessman and JL Privette. (JUL 1997). Unmixing the directional reflectances of AVHRR sub-pixel landcovers. IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING, 35(4), 868-878. 10.1109/36.602529
  • Asner, GP and CA Wessman. (1-Nov 1997). Scaling PAR absorption from the leaf to landscape level in spatially heterogeneous ecosystems. ECOLOGICAL MODELLING, 103(1), 81-97. 10.1016/S0304-3800(97)00080-X
  • NEL, EM, CA WESSMAN and TT VEBLEN. (JUN 1994). DIGITAL AND VISUAL ANALYSIS OF THEMATIC MAPPER IMAGERY FOR DIFFERENTIATING OLD-GROWTH FROM YOUNGER SPRUCE-FIR STANDS. REMOTE SENSING OF ENVIRONMENT, 48(3), 291-301. 10.1016/0034-4257(94)90003-5
  • WALKER, DA, JC HALFPENNY, MD WALKER and CA WESSMAN. (MAY 1993). LONG-TERM STUDIES OF SNOW-VEGETATION INTERACTIONS. BIOSCIENCE, 43(5), 287-301. 10.2307/1312061
  • NEL, EM and CA WESSMAN. (DEC 1993). CANOPY TRANSMITTANCE MODELS FOR ESTIMATING FOREST LEAF-AREA INDEX. CANADIAN JOURNAL OF FOREST RESEARCH-REVUE CANADIENNE DE RECHERCHE FORESTIERE, 23(12), 2579-2586. 10.1139/x93-319
  • WESSMAN, CA. (1992 1992). IMAGING SPECTROMETRY FOR REMOTE-SENSING OF ECOSYSTEM PROCESSES. REMOTE SENSING OF THE EARTHS SURFACE AND ATMOSPHERE, 12, 361-368. 10.1016/0273-1177(92)90241-O
  • WESSMAN, CA. (1992). SPATIAL SCALES AND GLOBAL CHANGE - BRIDGING THE GAP FROM PLOTS TO GCM GRID CELLS. ANNUAL REVIEW OF ECOLOGY AND SYSTEMATICS, 23, 175-200. 10.1146/annurev.es.23.110192.001135
  • WESSMAN, CA. (FEB 1991). REMOTE-SENSING OF SOIL PROCESSES. AGRICULTURE ECOSYSTEMS & ENVIRONMENT, 34(4-Jan), 479-493. 10.1016/0167-8809(91)90131-G
  • USTIN, SL, CA WESSMAN, B CURTISS, E KASISCHKE, J WAY and VC VANDERBILT. (DEC 1991). OPPORTUNITIES FOR USING THE EOS IMAGING SPECTROMETERS AND SYNTHETIC APERTURE RADAR IN ECOLOGICAL MODELS. ECOLOGY, 72(6), 1934-1945.
  • WESSMAN, CA, JD ABER and DL PETERSON. (AUG 1989). AN EVALUATION OF IMAGING SPECTROMETRY FOR ESTIMATING FOREST CANOPY CHEMISTRY. INTERNATIONAL JOURNAL OF REMOTE SENSING, 10(8), 1293-1316.
  • PETERSON, DL, JD ABER, PA MATSON, DH CARD, N SWANBERG, C WESSMAN and M SPANNER. (FEB 1988). REMOTE-SENSING OF FOREST CANOPY AND LEAF BIOCHEMICAL CONTENTS. REMOTE SENSING OF ENVIRONMENT, 24(1), 85-&. 10.1016/0034-4257(88)90007-7
  • WESSMAN, CA, JD ABER, DL PETERSON and JM MELILLO. (JAN 1988). FOLIAR ANALYSIS USING NEAR-INFRARED REFLECTANCE SPECTROSCOPY. CANADIAN JOURNAL OF FOREST RESEARCH-REVUE CANADIENNE DE RECHERCHE FORESTIERE, 18(1), 6-11.
  • WESSMAN, CA, JD ABER, DL PETERSON and JM MELILLO. (8-Sep 1988). REMOTE-SENSING OF CANOPY CHEMISTRY AND NITROGEN CYCLING IN TEMPERATE FOREST ECOSYSTEMS. NATURE, 335(6186), 154-156. 10.1038/335154a0