Ken Krauss

Research Ecologist

Short Biography

Dr. Krauss completed an M.S. in Forestry at Louisiana State University in 1997, and a Ph.D. in Environmental and Evolutionary Biology from the University of Louisiana at Lafayette in 2004.  He has been a scientist with the federal government since 1997, first with the USDA Forest Service in Stoneville, Mississippi and, then, in Honolulu, Hawaii, where he studied sedimentation, systematics, regeneration, growth, invasion biology, and ecophysiology of Pacific island forested wetlands in the Federated States of Micronesia and Hawaii.  Dr. Krauss began working at the USGS National Wetlands Research Center (NWRC) in 2001, where he maintains an expertise in forest ecology and ecophysiology, and serves as one of NWRC’s climate change scientists focusing on mangroves and tidal freshwater forested wetlands.

Krauss, K.W., & M.C. Ball. 2012. On the halophytic nature of mangroves. Trees – Structure and Function (in press)

Cormier, N., K. W. Krauss, & W. H. Conner. 2012. Periodicity in stem growth and litterfall in tidal freshwater forested wetlands: influence of salinity and drought on nitrogen recycling. Estuaries and Coasts (in press)

Krauss, K.W., J.L. Whitbeck, & R.J. Howard. 2012. On the relative roles of hydrology, salinity, temperature, and root productivity in controlling soil respiration from coastal swamps (freshwater).  Plant and Soil 358: 265-274.

Osland, M.J., A.C. Spivak, J.A. Nestlerode, J.M. Lessmann, A.E. Almario, P.T. Heitmuller, M.J. Russell, K.W. Krauss, F. Alverez, D.D. Dantin, J.E. Harvey, A.S. From, N. Cormier, & C.L. Stagg. 2012. Ecosystem development after mangrove creation: plant-soil change across a 20-year chronosequence. Ecosystems 15: 848-866

Friess, D.A., K.W. Krauss, E.M. Horstman, T. Balke, T.J. Bouma, D. Galli, & E.L. Webb. 2012. Are all intertidal wetlands naturally created equal? Bottlenecks, thresholds and knowledge gaps to mangrove and saltmarsh ecosystems. Biological Reviews 87: 346-366.

Cretini, K.F., J.M. Visser, K.W. Krauss, & G.D. Steyer. 2012. Development and use of a floristic quality index for coastal Louisiana marshes. Environmental Monitoring and Assessment (in press)

Krauss, K.W., & J.L. Whitbeck. 2012. Soil greenhouse gas fluxes during wetland forest retreat along the lower Savannah River, Georgia (USA). Wetlands 32: 73-81.

Krauss, K.W., A.S. From, T.W. Doyle, T.J. Doyle, & M.J. Barry. 2011. Sea-level rise and landscape change influence mangrove encroachment onto marsh in the Ten Thousand Islands Region of Florida, USA. Journal of Coastal Conservation 15: 629-638.

Krauss, K.W. & D.A. Friess. 2011. World Atlas of Mangroves. Wetlands 31: 1003-1005. [book review]

Zhou, L., D. L. Creech, K.W. Krauss, D. L. Kulhavy, & Y. Yunlong. 2010. Can we improve the salinity tolerance of Taxodium genotypes by using varietal and hybrid crosses? HortScience 45: 1773-1778.

Kumara, M.P.,  L.P. Jayatissa, K.W. Krauss, D.H. Phillips, & M. Huxham. 2010. High density enhances sediment accretion, surface elevation and tree survival in mangrove stands. Oecologia 164: 545-553.

Huxham, M., M. Kumara, L. Jayatissa, K.W. Krauss, J. Kairo, J. Langat, M. Mencuccini, M. Skov & B. Kirui. 2010. Intra and inter-specific facilitation in mangroves may increase resilience to climate change threats. Philosophical Transactions of the Royal Society of London B 365: 2127-2135.

Krauss, K.W. & J.A. Duberstein. 2010. Sap flow and water use of freshwater wetland trees exposed to saltwater incursion in a tidally influenced South Carolina watershed. Canadian Journal of Forest Research 40: 525-535.

Krauss, K.W., D.R. Cahoon, J.A. Allen, K.C. Ewel, J.C. Lynch, & N.C. Cormier. 2010. Surface elevation change and susceptibility of different mangrove zones to sea-level rise on Pacific high islands of Micronesia. Ecosystems 13: 129-143.

Doyle, T.W., K.W. Krauss, W.H. Conner & A.S. From. 2010. Predicting the retreat and migration of tidal forests of the northern Gulf Coast, USA, under sea-level rise. Forest Ecology and Management 259: 770-777.

Krauss, K.W. 2009. Mangrove energetics. Ecology 90: 3588-3589. [book review]

Krauss, K.W., T.W. Doyle, & R.J. Howard. 2009. Is there evidence of adaptation to tidal flooding in saplings of baldcypress subjected to different salinity regimes? Environmental and Experimental Botany 67: 118-126.

Krauss, K.W., J.A. Duberstein, T.W. Doyle, W.H. Conner, R.H. Day, L.W. Inabinette, & J.L. Whitbeck. 2009. Site condition, structure, and growth of baldcypress along tidal/non-tidal salinity gradients. Wetlands 29: 505-519.

Lindquist, E.S., K.W. Krauss, P.T. Green, D.J. O'Dowd, P.M. Sherman, & T.J. Smith III. 2009.  The role of land crabs: key factors in tropical coastal forest recruitment. Biological Reviews 84: 203-223

Doyle, T.W., K.W. Krauss, & C.J Wells. 2009. Landscape analysis and pattern of hurricane impact and circulation on mangrove forests of the Everglades. Wetlands 29: 44-53.

Krauss, K.W., T.W. Doyle, T.J. Doyle, C.M. Swarzenski, A.S. From, R.H. Day, & W.H. Conner. 2009. Water level observations in mangrove swamps during two hurricanes in Florida. Wetlands 29: 142-149.

Krauss, K.W., C.E. Lovelock, K.L. McKee, L. López-Hoffman, S.M.L. Ewe & W.P. Sousa.  2008. Environmental drivers in mangrove establishment and early development: a review. Aquatic Botany 89: 105-127.

Doyle, T.W., W.H. Conner, R.H. Day, K.W. Krauss & C.M. Swarzenski. 2007. Wind damage and salinity effects of Hurricanes Katrina and Rita on coastal baldcypress forests of Louisiana. Pages 161-168 in G.S. Farris, G.J. Smith, M.P. Crane, L.L. Robbins, D.L. Lavoie (eds.), Science and the Storms: the USGS Response to the Hurricanes of 2005. U.S. Geological Survey Circular 1306. 283 p.

Krauss, K.W., P.J. Young, J.L. Chambers, T.W. Doyle & R.R. Twilley. 2007. Sap flow characteristics of neotropical mangroves in flooded and drained soils. Tree Physiology 27: 775-783.

Krauss, K.W., B.D. Keeland, J.A. Allen, K.C. Ewel & D.J. Johnson. 2007. Effects of season, rainfall, and hydrogeomorphic setting on mangrove tree growth in Micronesia. Biotropica 39: 161-170.

Krauss, K.W. 2007. Physiological ecology and ecohydrology of coastal forested wetlands. USGS Fact Sheet 2007-3018. 4 p.

Conner, W.H., T.W. Doyle & K.W. Krauss, Eds., 2007. Ecology of Tidal Freshwater Forested Wetlands of the Southeastern United States. Springer. 505 p.

Krauss, K.W., J.L. Chambers & D. Creech. 2007. Selection for salt tolerance in tidal freshwater swamp species: advances using baldcypress as a model for restoration. Pages 385-410 in  W.H. Conner, T.W. Doyle, K.W. Krauss (eds.), Ecology of Tidal Freshwater Forested Wetlands of the Southeastern United States.  Springer. 505 p.

Conner W.H., K.W. Krauss & T.W. Doyle. 2007. Ecology of tidal freshwater forests in coastal deltaic Louisiana and northeastern South Carolina. Pages 223-253 in  W.H. Conner, T.W. Doyle, K.W. Krauss (eds.), Ecology of Tidal Freshwater Forested Wetlands of the Southeastern United States. Springer. 505 p.

Conner, W.H., C.T. Hackney, K.W. Krauss & J.W. Day, Jr. 2007. Tidal freshwater forested wetlands: future research needs and an overview of restoration. Pages 461-485 in  W.H. Conner, T.W. Doyle, K.W. Krauss (eds.), Ecology of Tidal Freshwater Forested Wetlands of the Southeastern United States. Springer. 505 p.

Krauss, K.W., T.W. Doyle, R.R. Twilley, V.H. Rivera-Monroy & J.K. Sullivan. 2006. Evaluating the relative effects of hydroperiod and soil fertility as growth constraints in south Florida mangroves. Hydrobiologia 569: 311-324.

Cardona-Olarte, P., R.R. Twilley, K.W. Krauss, & V.H. Rivera-Monroy. 2006. Responses of neotropical mangrove seedlings grown in mono and mixed cultures under treatments of hydroperiod and salinity. Hydrobiologia 569: 325-341.

Krauss, K.W., R.R. Twilley, T.W. Doyle & E.S. Gardiner. 2006. Leaf gas exchange characteristics of three neotropical mangrove species in response to varying hydroperiod. Tree Physiology 26: 959-968.

Allen, J.A. & K.W. Krauss. 2006. The influence of propagule flotation longevity and light availability on the establishment of introduced mangrove species in Hawai¢i. Pacific Science 60: 367-376.

Allen, J.A., K.W. Krauss, K.C. Ewel, B.D. Keeland & E.E. Waguk. 2005. A tropical freshwater wetland: I. Structure, growth, and regeneration. Wetlands Ecology and Management 13: 657-669.

Krauss, K.W., T.W. Doyle, R.R. Twilley, T.J. Smith III, K.R.T. Whelan & J.K. Sullivan. 2005. Woody debris in mangrove forests of south Florida. Biotropica 37: 9-15.

Krauss, K.W. & J.A. Allen. 2003. Influences of salinity and shade on seedling photosynthesis and growth of two mangrove species, Rhizophora mangle and Bruguiera sexangula, introduced to Hawaii. Aquatic Botany 77: 311-324.

Krauss, K.W., J.A Allen & D.R. Cahoon. 2003. Differential rates of surface elevation change and vertical accretion among aerial root types in Micronesian mangrove forests. Estuarine, Coastal and Shelf Science 56: 251-259.

Allen, J.A., K.W. Krauss & R.D. Hauff. 2003. Factors limiting the intertidal distribution of the mangrove species Xylocarpus granatum. Oecologia 135: 110-121.

Krauss, K.W. & J.A. Allen. 2003. Factors influencing the regeneration of the mangrove, Bruguiera gymnorrhiza (L.) Lamk., on a tropical Pacific island. Forest Ecology and Management 176: 49-60.

Gardiner, E.S. & K.W. Krauss. 2001. Photosynthetic light response of flooded cherrybark oak (Quercus pagoda) seedlings grown in two light regimes. Tree Physiology 21: 1103-1111.

Krauss, K.W., R.A. Goyer, J.A. Allen & J.L. Chambers. 2000. Tree shelters effective in coastal swamp restoration (Louisiana). Ecological Restoration 18: 200-201.

Allen, J.A., K.W. Krauss, N.C. Duke, O. Björkman, D.R. Herbst & C. Shih. 2000. Bruguiera species in Hawai’i: systematic considerations and ecological implications. Pacific Science 54: 331-343.

Krauss, K.W., J.L. Chambers, J.A. Allen, D.M. Soileau, Jr. & A.S. DeBosier. 2000. Growth and nutrition of baldcypress families planted under varying salinity regimes in Louisiana, USA. Journal of Coastal Research 16: 153-163.

Krauss, K.W., J.L. Chambers, J.A. Allen, B. Luse & A.S. DeBosier. 1999. Root and shoot responses of Taxodium distichum seedlings subjected to saline flooding. Environmental and Experimental Botany 41: 15-23.

Doyle, T.W. & K.W. Krauss. 1999. The sands and sambars of St. Vincent Island. Florida Wildlife 53: 22-25.

Krauss, K.W., J.L. Chambers & J.A. Allen. 1998. Salinity effects and differential germination of several half-sib families of baldcypress from different seed sources. New Forests 15: 53-68.

Allen, J.A., W.H. Conner, R.A. Goyer, J.L. Chambers & K.W. Krauss. 1998. Chapter 4: Freshwater forested wetlands and global climate change. Pages 33-44 in G.R. Guntenspergen and B.A Vairin (eds.), Vulnerability of coastal wetlands in the Southeastern United States: climate change research results, 1992-97. U.S. Geological Survey, Biological Resources Division Biological Science Report USGS/BRD/BSR-1998-0002. 101 p.

My Science Topics

My USGS Science Strategy Areas

My research group conducts ecological, hydrological, and eco-physiological research on coastal forests and on transitions between forested wetlands and marsh.  Our primary goal is fostering a better understanding of the impacts and consequences of climate and land use change on coastal wetlands and watersheds. 

Mangrove Research focuses on either general ecological topics or on water, and involves rating seedling, sapling, stand, and landscape-level ecological and physiological responses of coastal mangrove vegetation to environmental stressors.  We are also interested in learning about the specific role of mangrove vegetation in moderating those same stressors at the landscape scale.  We often include studies on regeneration, tree growth, sedimentation, or early seedling development that attempt to answer basic questions about mangrove ecosystem biology, and assist land managers with data collection to support important decisions associated with climate change uncertainty.

Tidal Freshwater Forested Wetland Research focuses on the consequences of habitat change from forested states to marsh with sea-level rise, salt water intrusion, microtopographic loss, and biogeochemical alteration.  Much of this research is funded by the USGS Climate and Land Use Change R&D Program, and includes a number of collaborators to develop carbon budgets, understand shifts in nitrogen cycling with greater delivery of saltwater or more persistent flooding, quantify water use at the individual tree and stand levels, and describe elevation dynamics and the role that microtopography plays in natural tidal swamps.

Sapflow and water use of freshwater wetland trees exposed to saltwater incursion in a tidally influenced South Carolina watershed (Georgetown, South Carolina, USA)

Sea-level rise and human modification of the landscape have vectored salinity into many historically freshwater forested wetlands in the southeastern United States.  While salinity changes approaching 2 ppt eventually lead to the conversion of freshwater forested wetlands to oligohaline marshes, baldcypress (Taxodium distichum) trees often survive for decades before eventually succumbing to salinity. We wanted to know why.  We found that trees undergoing perennial exposure to salinity used very little water in deeper sapwood regions, forcing trees on saline sites to use approximately 76% less water than trees on freshwater sites.  As the capacity for water use is reduced, less foliage is maintained and less saline water is taken up, facilitating longer survival times on unfavorable sites. [Can. J. For. Res. 40, 525-535]

Modeling hydrologic flow and vegetation response across the Tamiami Trail and coastal watershed of Ten Thousand Islands NWR (Naples, Florida, USA)

Major restoration projects have been proposed to restore freshwater flow across the Tamiami Trail (U.S. Hwy. 41) into coastal marshes and estuaries of the northern Everglades with little or no understanding of the hydrologic coupling in the region.  We just completed a project designed to monitor hydrologic activities and develop numerical models of water flow and salinity mixing across the marsh-mangrove ecotone of Ten Thousands National Wildlife Refuge (NWR).  Model applications will be extended to predict vegetation migration and succession under changing freshwater delivery regimes in Ten Thousand Islands NWR. 

Sedimentation patterns and surface elevation change in Pacific island mangroves (Kosrae and Pohnpei, Federated States of Micronesia)

We used a combination of surface-elevation tables and marker horizons to determine how sedimentation patterns for mangroves in fringe, riverine, and interior hydrogeomorphic settings differ in four river basins on two high islands in the Federated States of Micronesia.  All sites maintained a strong capacity to offset elevation losses by way of vertical accretion over 6.5 years of study.  Sites closest to the ocean lost elevation relative to sea-level rise, while riverine and interior sites maintained a more sustainable balance.  This research suggested differential, and not uniformly bleak, susceptibilities for Pacific high island mangroves to sea-level rise, and indicated that protection of mangrove zones closest to the ocean may slow the rate of conversion to open water. [Ecosystems 13, 129-143]

Identifying controls over soil greenhouse gas fluxes as coastal wetland forests retreat with sea-level rise (Savannah, Georgia, USA)

Forest retreat is a consequence of sea-level rise along many Atlantic and Gulf Coastal estuaries.  We studied the monthly balance of efflux among three prominent greenhouse gases – carbon dioxide, methane, nitrous oxide – from tidal freshwater forested wetlands as they converted to oligohaline marsh across a salinity range of 0.1 to 4.7 ppt (i.e., 0 to 13% seawater) over a two-year period.  We found that carbon dioxide dominated greenhouse gas fluxes on all sites, and that hydrology, not salinity, dictated the volume of greenhouse gas emissions from these oligohaline tidal wetlands.  Modeling greenhouse gas losses from these ecosystems across similar salinity regimes as measured here may be accomplished most efficiently by using projected, or actual, site hydrology. [Wetlands 32, 73-81]  

Whole-tree Transpiration, Stand Water Use, and Growth of Pisonia grandis Trees in Competition with Coconut Palm (Cocos nucifera) (Palmyra Atoll, Line Islands)

A concerted, multi-institutional research effort has been directed at understanding the basic ecological underpinnings of Palmyra Atoll National Wildlife Refuge, ranging from research on coral reefs to the terrestrial flora, forests, and fauna.  On the terrestrial side, Palmyra Atoll hosts a number of migrant sea birds for foraging and breeding activity, but has been under the pressures of development (esp. during U.S. Military occupation, 1938-1961), sea-level rise, and biotic invasions necessitating the need for a comprehensive, but adapting, management plan.  Through sap flow studies initiated in 2011, we are understanding how introduced coconut palm (Cocos nucifera) forests are affecting root-zone hydrology and water uptake of native forests on the atoll.