Leaf water relations of competitive Fagus sylvatica and Quercus petraea trees during 4 years differing in soil drought

Abstract

Leaf water relations of competitive mature Fagus and Quercus trees were compared during four seasons with low, moderate, or high soil drought intensities in humid northwestern Germany. Leaf conductances (gl) typically were higher by about 30% in Quercus than in Fagus sun leaves. Predawn leaf water potentials (Ψpd) and osmotic potentials (Πo, Πp) were remarkably similar for the two species. Fagus had significantly lower leaf tissue elasticities (εmax) than Quercus in dry but not in wet summers. Interannual variabilities in water status parameters were large for gl and seasonal bulk leaf turgor (P) minima; moderate for εmax and daily water potential (Ψ) minima; and small for Πo, Πp, and the relative leaf water content at zero turgor. Fagus regulated water loss conservatively with only limited reductions in P and Ψ in wet or moderately dry seasons but large decreases in Ψpd,gl, photosynthesis, and growth during occasional severe droughts. Quercus displayed patterns of a stress-tolerating species (lower εmax, a less drought-sensitive stomatal regulation, and apparently significant drought-induced osmotic adjustment). In temperate humid environments, tree water relations should be studied for at least three or four seasons to account for large interannual variabilities in water status parameters.

Competition for water between beech seedlings and surrounding vegetation in different light and vegetation composition conditions

“…Despite its acclimatation to contrasting sunlight conditions [5], beech stomatal regulation may not be sufficient to fully maintain xylem integrity, and partial cavitation may develop. Similar conclusions were recently drawn by Backes and Leuschner (2000) during occasional severe droughts in a mixed beech -sessile oak (Quercus petraea Matt.) forest.…”

Leaf water status and stem xylem flux in relation to soil drought in five temperate broad-leaved tree species with contrasting water use strategies

“…In the dry period, air temperature and saturation deficit were generally higher than in the wet period, resulting partly in higher fluxes (* means n = 1). trees (up to 250-290 mmol m −2 s −1 ) have been reported by Backes (1996); Backes and Leuschner (2000); Roberts and Rosier (1994); Tognetti et al (1995). Our g L for C. betulus are in the middle range of the values reported by Keel et al (2007).…”

“…High Ψ L with low daily and seasonal amplitudes and a high apparent L c in the root-toleaf path characterize sycamore as a drought avoiding species (Tognetti et al, 1995). Beech can not avoid daily fluctuations in Ψ L and often large and severe drops in Ψ pd and Ψ noon during extended drought (Backes and Leuschner, 2000). We propose that high J sd and therefore a strongly decreasing Ψ noon 101p9 Ann.…”

Variation in fine root biomass of three European tree species: Beech (Fagus sylvaticaL.), Norway spruce (Picea abiesL. Karst.), and Scots pine (Pinus sylvestrisL.)

“…Leuschner & Hertel (2003) found significant correlations between fine root biomass and precipitation for spruce and beech also in the temperate forests. According to Leuschner et al (2004) beech can grow in regions with both high and low rainfall (500 to 2000 mm year 71 ), even if it is a drought-sensitive species (Backes & Leuschner, 2000). However, not only the total annual rainfall but its seasonal distribution is important for soil water availability and its effects on fine roots.…”