At the UNH Ecohydrology lab, we bring a wide variety of methodological approaches to bear on a variety of questions ranging from species-specific ecophysiology to ecosystem-scale evaluations of the impacts of forest management, climate variability, on water cycling and water stress. Our signature methodologies which we have applied in a wide range of systems include:
Precipitation manipulation experiments
Experiments in forested ecosystems that allow the controlled and direct study of plant- and ecosystem-scale responses to water stress. Examples include the Northern Forest DroughtNet projects in New Hampshire and the Wayqecha cloud forest drought experiment in Peru.
SELECTED PUBLICATIONS:
Brum M, Vadeboncoeur MA, Asbjornsen H, Puma Vilca BL, Galiano D, Horwath AB, Metcalfe DB. 2023. Ecophysiological controls on water use of tropical cloud forest trees in response to experimental drought. Tree Physiology, 43:1514-1532. doi: 10.1093/treephys/tpad070
Asbjornsen H, McIntire CD, Vadeboncoeur MA, Jennings KA, Coble AP, Berry ZC. 2021. Sensitivity and threshold dynamics of Pinus strobus and Quercus spp. in response to experimental and naturally-occurring severe droughts. Tree Physiology, 41:1819-1835. doi: 10.1093/treephys/tpab056
Asbjornsen H, Campbell JL, Jennings KA, McIntire CD, Vadeboncoeur MA, Templer PH, Phillips R, Bauerle TL, Bowles F, Dietze M, Frey S, Groffman P, Guerrieri R, Hanson PJ, Kelsey E, Knapp AK, McDowell NG, Meir PW, Novick KA, Ollinger SV, Pockman W, Schaberg PG, Wullschleger SD, Smith MD, Rustad LE. 2018. Guidelines and considerations for designing field experiments simulating precipitation extremes in forest ecosystems. Methods in Ecology and Evolution, 9: 3210-2325. doi:10.1111/2041-210X.13094 [PDF available from USFS]
Sap flow sensors
We employ both the heat-ratio and Granier approaches to measure vertical fluxes of water through trees. We have deployed these types of sensors in a wide range of environments, and various species, sizes of trees.
SELECTED PUBLICATIONS:
Coble AP, Contosta AR, Smith RG, Siegert NW, Vadeboncoeur MA, Jennings KA, Stewart AJ, Asbjornsen H. 2020. Influence of forest-to-silvopasture conversion and drought on components of evapotranspiration. Agriculture, Ecosystems and Environment, 295: 106916. doi:10.1016/j.agee.2020.106916 [PDF available from USFS]
McIntire CD, Huggett BA, Dunn E, Munck IA, Vadeboncoeur MA, Asbjornsen H. Pathogen-induced defoliation impacts on transpiration, leaf gas exchange, and non-structural carbohydrate allocation in eastern white pine (Pinus strobus). Trees – Structure and Function, in press. doi: 10.1007/s00468-020-02037-z
Gutiérrez López JA, Licata J, Pypker T, Asbjornsen H. 2019. Effects of heater wattage on sap flux density estimates using an improved tree-cut experiment. Tree Physiology. 39: 679–693. doi:10.1093/treephys/tpy137
Sinacore K, Asbjornsen H, Hernandez Santana V, Hall JS. 2019. Drought differentially affects growth, transpiration, and water use efficiency of mixed and monospecific planted forests. Forests 10: 153. doi:10.3390/f10020153v (open access)
Brum M, Gutiérrez López JA, Asbjornsen H, Licata J, Pypker T, Sanchez G, Oiveira RS. 2018. ENSO effects on the transpiration of eastern Amazon trees. Philosophical Transactions of the Royal Society B - Biological Sciences 373: 20180085. doi:10.1098/rstb.2018.0085
Isotopic dendrochronology
This approach enables analyses of interannual variability and long-term trends in the carbon and water relations of trees based on the width and stable isotope ratios of tree rings.
SELECTED PUBLICATIONS:
Vadeboncoeur MA, Jennings KA, Ouimette AP, Asbjornsen H. 2020. Correcting tree-ring ẟ13C time series for tree-size effects in eight temperate tree species. Tree Physiology, 40: 333- 349. doi: 10.1093/treephys/tpz138
Guerrieri R, Jennings K, Belmecheri S, Asbjornsen H, Ollinger S. 2017. Evaluating climate signal recorded in tree-ring δ13C and δ18O values from bulk wood and α-cellulose for six species across four sites in the northeastern US. Rapid Commununications in Mass Spectrometry. 31: 2081–2091. doi:10.1002/rcm.7995
Jennings KA, Guerrieri R, Vadeboncoeur MA, Asbjornsen H. 2016. Response of Quercus velutina growth and water use efficiency to climate variability and nitrogen fertilization in a temperate deciduous forest in the northeastern U.S. Tree Physiology, 36:428-443. doi:10.1093/treephys/tpw003
We are always interested in collaborative opportunities to apply these approaches to interesting ecological, physiological, and global-change questions in a variety of ecosystem types.