© 2001 Heron Publishing—Victoria, Canada
Effects of nutrition and soil water availability on water use in a Norway spruce stand
Nathan Phillips (1), Johan Bergh (2), Ram Oren (3) and Sune Linder (2)
1. Geography Department, Boston University, Boston, MA 02215, USA / 2. Department for Production Ecology, Swedish University of Agricultural Sciences, Uppsala, Sweden / 3. School of the Environment, Duke University, Durham, NC, USA / Received August 18, 2000
Summary
We investigated effects of nutrition and soil water availability on sap flux density, transpiration per unit leaf area (EL), and canopy stomatal conductance (GS) of Norway spruce (Picea abies L. (Karst.)) in northern Sweden during the 1996 growing season. Our objectives were to determine (1) if artificially imposed
drought (65% rain diversion) reduces soil water sufficiently to cause physiological limitations to whole-tree and plot-scale
water transport, and (2) whether increased capacity for water transport resulting from fertilization-induced increases in
leaf (> 3-fold) and sapwood areas (> 2.3-fold) deplete soil water sufficiently to cause a negative feedback on GS and EL. We monitored soil water content (θ) and soil water potential (ΨS) in control (C), drought (D), fertilized (F) and irrigated + fertilized (IL) treatment plots, along with site meteorological
conditions. Ten trees per plot were monitored for sap flow. Although there were significant treatment differences in mean
daily EL (C > D > F; P < 0.01) and GS (C > D > F; P < 0.05), variation in absolute magnitudes was small. Therefore, transpiration differences on a unit ground
area basis (EC) were nearly proportional to leaf area differences. Precipitation was well distributed throughout the study period and so
ΨS remained high, except during short dry periods in Plot F when it declined rapidly. Thus, although soil water was not limiting
to GS, EL or EC when precipitation was uniformly distributed throughout the growing season, we cannot conclude that water availability would
not limit GS in fertilized stands if the seasonal distribution of precipitation were altered.
Keywords:
canopy conductance, fertilization, Picea abies, sapflux, transpiration.
