TY - JOUR
T1 - Small gradients in salinity have large effects on stand water use in freshwater wetland forests
AU - Duberstein, Jamie A.
AU - Krauss, Ken W.
AU - Baldwin, Michael J.
AU - Allen, Scott T.
AU - Conner, William H.
AU - Salter, John S.
AU - Miloshis, Michael
PY - 2020/10/1
Y1 - 2020/10/1
N2 - Salinity intrusion is responsible for changes to freshwater wetland watersheds globally, but little is known about how wetland water budgets might be influenced by small increments in salinity. We studied a forested wetland in South Carolina, USA, and installed sap flow probes on 72 trees/shrubs along a salinity gradient. Species investigated included the trees baldcypress (Taxodium distichum [L.] Rich.), water tupelo (Nyssa aquatica L.), swamp tupelo (Nyssa biflora Walt.), and the shrub waxmyrtle (Morella cerifera (L.) Small). This study improves upon past reliance on greenhouse seedling studies by adding measurements of trees/shrubs along a salinity gradient, and better describes the role of low salinity on water use in freshwater wetland forests. We measured patterns of water use related to salinity, atmospheric conditions and season, and hypothesized that salinity would influence wetland forest water use through two mechanisms: salinity disturbances would yield stands with species and size classes that transpire less and individual trees with less conductive xylem tissue (i.e., sapwood). Both hypotheses held. At salinity concentrations ranging from fresh to 3 psu, forest structural changes alone resulted in stand water use reductions from 494 mm year-1 in freshwater stands to 316 mm year-1 in stands of slightly higher salinity. Tree sapwood function (inferred from radial sap flux profiles) also changed along this gradient and reduced sap flow rates by an additional 13.3% per unit increase in salinity (psu). Thus, stand water use was further reduced to 190 mm year-1 on saline sites. We found that forest structure is not the only change that affects water use in salinized watersheds; individual tree eco-physiological responses to salinity, manifesting in different radial sap flow profiles, are important as well.
AB - Salinity intrusion is responsible for changes to freshwater wetland watersheds globally, but little is known about how wetland water budgets might be influenced by small increments in salinity. We studied a forested wetland in South Carolina, USA, and installed sap flow probes on 72 trees/shrubs along a salinity gradient. Species investigated included the trees baldcypress (Taxodium distichum [L.] Rich.), water tupelo (Nyssa aquatica L.), swamp tupelo (Nyssa biflora Walt.), and the shrub waxmyrtle (Morella cerifera (L.) Small). This study improves upon past reliance on greenhouse seedling studies by adding measurements of trees/shrubs along a salinity gradient, and better describes the role of low salinity on water use in freshwater wetland forests. We measured patterns of water use related to salinity, atmospheric conditions and season, and hypothesized that salinity would influence wetland forest water use through two mechanisms: salinity disturbances would yield stands with species and size classes that transpire less and individual trees with less conductive xylem tissue (i.e., sapwood). Both hypotheses held. At salinity concentrations ranging from fresh to 3 psu, forest structural changes alone resulted in stand water use reductions from 494 mm year-1 in freshwater stands to 316 mm year-1 in stands of slightly higher salinity. Tree sapwood function (inferred from radial sap flux profiles) also changed along this gradient and reduced sap flow rates by an additional 13.3% per unit increase in salinity (psu). Thus, stand water use was further reduced to 190 mm year-1 on saline sites. We found that forest structure is not the only change that affects water use in salinized watersheds; individual tree eco-physiological responses to salinity, manifesting in different radial sap flow profiles, are important as well.
KW - Baldcypress
KW - Ecohydrology
KW - Salinity
KW - Sap flow
KW - Water tupelo
KW - Wetlands
UR - http://www.scopus.com/inward/record.url?scp=85086829620&partnerID=8YFLogxK
U2 - 10.1016/j.foreco.2020.118308
DO - 10.1016/j.foreco.2020.118308
M3 - Article
AN - SCOPUS:85086829620
VL - 473
SP - 1
EP - 13
JO - Forest Ecology and Management
JF - Forest Ecology and Management
SN - 0378-1127
M1 - 118308
ER -