title: Edge type affects leaf-level water relations and estimated transpiration of Eucalyptus arenacea.
abstract: While edge effects on tree water relations are well described for closed forests, they remain under-examined in more open forest types. Similarly, there has been minimal evaluation of the effects of contrasting land uses on the water relations of open forest types in highly fragmented landscapes. We examined edge effects on the water relations and gas exchange of a dominant tree (Eucalyptus arenacea Marginson & Ladiges) in an open forest type (temperate woodland) of south-eastern Australia. Edge effects in replicate woodlands adjoined by cleared agricultural land (pasture edges) were compared with those adjoined by 7- to 9-year-old eucalypt plantation with a 25m fire break (plantation edges). Consistent with studies in closed forest types, edge effects were pronounced at pasture edges where photosynthesis, transpiration and stomatal conductance were greater for edge trees than interior trees (75m into woodlands), and were related to greater light availability and significantly higher branch water potentials at woodland edges than interiors. Nonetheless, gas exchange values were only ∼50% greater for edge than interior trees, compared with ∼200% previously found in closed forest types. In contrast to woodlands adjoined by pasture, gas exchange in winter was significantly lower for edge than interior trees in woodlands adjoined by plantations, consistent with shading and buffering effects of plantations on edge microclimate. Plantation edge effects were less pronounced in summer, although higher water use efficiency of edge than interior woodland trees indicated possible competition for water between plantation trees and woodland edge trees in the drier months (an effect that might have been more pronounced were there no firebreak between the two land uses). Scaling up of leaf-level water relations to stand transpiration using a Jarvis-type phenomenological model indicated similar differences between edge types. That is, transpiration was greater at pasture than plantation edges in summer months (most likely due to greater water availability at pasture edges), resulting in significantly greater estimates of annual transpiration at pasture than plantation edges (430 vs. 343lm(-2)year(-1), respectively). Our study highlights the need for landscape-level water flux models to account for edge effects on stand transpiration, particularly in highly fragmented landscapes.
authors.affiliation: Department of Forest and Ecosystem Science, Melbourne School of Land and Environment, The University of Melbourne, Water Street, Creswick, Victoria 3363, Australia.
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Wright
authors.forename: Michael
authors.initials: M
authors.lastname: Tausz
authors.forename: Sabine
authors.initials: S
authors.lastname: Kasel
authors.forename: Liubov
authors.initials: L
authors.lastname: Volkova
authors.forename: Andrew
authors.initials: A
authors.lastname: Merchant
authors.forename: Lauren T
authors.initials: LT
authors.lastname: Bennett
mesh_terms: D005052:Eucalyptus / Q000502:physiology*; D008027:Light; D008834:Microclimate; D008954:Models, Biological; D010788:Photosynthesis / Q000502:physiology; D018515:Plant Leaves / Q000502:physiology; D054046:Plant Stomata / Q000502:physiology*; D018526:Plant Transpiration / Q000502:physiology*; D012621:Seasons; D014197:Trees / Q000502:physiology; D014739:Victoria; D014867:Water / Q000502:physiology*
chemical_list: D014867:Water