Canopy throughfall of Picea abies (L.) Karst. as depending on trace gas concentrations

Abstract

A b s t r a c tAt six sites in central Germany consequences of SO2, NOx and 03 deposition and of acid precipitation on canopy throughfall of sulphate, nitrate, ammonium, organic acids and of metal cations from Norway spruce crowns were investigated in the field. Measured canopy throughfall rates (mmol ion kg-l needle dw a-1 are separated in (i) "background" ion throughfall rates in clean air and (ii) trace gas-(or acid interception)-dependent throughfall rates at ambient trace gas concentrations. Based on synchronously measured pollution, precipitation and canopy throughfall data, statistical response functions are given, which allow the separate estimation of annual rates of sulphur and nitrogen deposition into spruce canopies if only annual means of SO2 or NO2 concentrations in air are known. The specific SO2 deposition rate of (0.841+0.214) mmol S kg -1 needle dw a -1 (nPa SO2 Pa-l) -1 is 2.3 times higher than the specific stomatal SO2 uptake. The NO2-dependent nitrogen deposition of (2.464 4-0.707) mmol N kg-1 needle dw a-l (nPa NO2 Pa-1)-1 is 2.2 times higher than the specific stomatal NOx (NO2 + NO) uptake. These ratios (2.3~2.2) are explained by the percentage of annual hours with open needle stomata. The shape of observed "epicuticular" SO2 and NOx deposition curves and of stomatal SO2 and NOx uptake curves are congruent. As for stomatal NOx uptake, there is an apparent compensation point at (5 to 8) nPa NO2 Pa-1 There is significant SO2-dependent canopy throughfall of Ca>K>AI>Mg> Fe in this order of relative importance. NOx deposition in spruce canopies reduces K + throughfall and it weakly promotes throughfall of Mn z+ and Zn 2+. There was no significant codeposition of sulphate and ammonium and no ion exchange of intercepted H30 + with nutrient cations at the measured ambient pH values of the precipitation water. In the presence of 03, throughfall of Mn 2+ is reduced and throughfall of K +, Ca 2+ and A13+ is enhanced. In the cooperative presence of SO2, NO2 and 03 pollution in the field there is a 1.3-fold increase of the annual K + demand and a 1.5-fold Mg 2+ demand of spruce canopies relative to the situation in clean air. This trace gas-dependent additional cation demand of spruce canopies corresponds to a needle loss percentage of (23 to 33)% if the additional K + and Mg 2+ throughfall could not be recycled in spruce ecosystems. Observed canopy thinning ranges from (13 to 26)% at the investigated six spruce stands.Abbreviations: Aspee -Specific needle surface area per kg needle dry matter (m2kg -1 needledw);Atot-Totalneedle surface of spruce stands (ha ha-l); [gas]a-Ambient trace gas concentration (gas = SO2; NO2 or 03) in air (nPa Pa-1 = ppb); GP -Number of days per annual growth period d a-1 );iC+30_ Acid interception rate (Eq H3 O + kg-1 * Fax no: +499310886158 296 needle dw a-t); ko-Trace gas-independent ion throughfall rate constant (mmol kg -l needle dw a -1); kgas-SO2-,NO2-or O3-dependent ion throughfall rate per unit of trace gas pollution (mmol kg-1 needle dw a-1 (nPa Pa-1 )-1); KH30 -Spec...

Plant and Soil System Responses to Ozone After 3 Years in a Lysimeter Study with Juvenile Beech (Fagus sylvatica L.)

“…Enhanced K + leaching from needles of ozone treated Sitka spruce especially those with visible damage was also observed by Lucas et al (1993) and is supported by analyses of canopy throughfall in a spruce stand showing significant increase of K in leachates under elevated ozone (Slovik et al, 1996). The extent of K leaching may be influenced by the integrity of plant membranes and thus by the oxidative stress caused by ozone (Lucas et al 1993;Slovik et al 1996;Schraudner et al 1997).…”

NH3 and NO2 fluxes between beech trees and the atmosphere – correlation with climatic and physiological parameters

“…In the field, lower (0n6 nmol mol −" , Rondo! n & Granat, 1994) as well as higher (3n2 nmol mol −" , Slovik et al, 1996) NO # compensation points have been published for spruce. (Stewart et al, 1990 ;Schneider et al, 1996 ;Geßler et al, 1998a,c).…”

“…In the field, lower (0n6 nmol mol −" , Rondo! n & Granat, 1994) as well as higher (3n2 nmol mol −" , Slovik et al, 1996) NO # compensation points have been published for spruce. calculated NO # compensation points of 1n2 nmol mol −" for leaves of wheat (Triticum aestivum).…”

Stomatal uptake of SO2, NOx and O3 by spruce crowns (Picea abies) and canopy damage in Central Europe

“…These sites were chosen, since (i) detailed radiation data, which are necessary for modelling stomatal conductances (cf. below), are not available at most other sites, (ii) modelled trace gas uptake can be compared with 'epicuticular' trace gas absorption (Slovik et al, 1996a), (iii) modelled stomatal SO^ uptake can be compared with SO^^" accumulation in ageing needles (cf. Slovik et al, 1995) and (iv) modelled stomatal transpiration can be compared with water balance data obtained by methods used in forest hydrology (cf.…”