Prediction of leaf area index in eucalypt plantations: effects of water stress and temperature

Abstract

A calibration curve was established to convert plant area index of Eucalyptus nitens (Deane and Maiden) Maiden, assessed with a Li-Cor LAI-2000, to leaf area index, LAI. Based on a comparison of this calibration curve with existing calibration curves for other species, we concluded that a generic calibration curve may be applicable for the assessment of LAI in eucalypt plantations. The Li-Cor LAI-2000 measurements were used to correlate the equilibrium LAI of E. nitens plantations with mean annual temperature. These and other data were then combined to develop relationships between LAI in both E. nitens and E. globulus Labill. plantations and mean annual temperature and water stress. In plantations of both species, LAI declined linearly with water stress. However, marked differences in the effect of suboptimal growth temperatures on LAI were observed between species: on cold sites, LAI of E. nitens was markedly higher than LAI of E. globulus. A simple analytic model of net primary production (NPP) was developed. In this model, increasing LAI increased light interception and hence dry matter production, but simultaneously increased canopy respiration. Consequently, for a given light utilization coefficient (epsilon), there was a value of LAI that maximized NPP. The model was parameterized for E. globulus and used to investigate the influences of water stress and mean annual temperature on LAI through their effects on epsilon. The model indicated that the value of LAI that was predicted to maximize NPP under various water and temperature stress regimes was similar to the value of LAI observed in the field under similar conditions only if leaf longevity was linked to water and temperature stress.

Productivity, carbon isotope discrimination and leaf traits of trees of Eucalyptus globulus Labill. in relation to water availability

“…L varied in response to fertilizer application in the study of Smethurst et al (2003) whereas in the current study it was assumed that L was most heavily influenced by water availability owing to similar land-use history and establishment practices among sites, including fertilizer application. The lack of relation between L and water availability found here is similar to that found by Battaglia et al (1998) who, although concluding that L was related to an index of water stress and to temperature, found a great deal of scatter in both relations. Despite similar land-use history and establishment practices, inherent differences in site fertility may partially explain the lack of relation between L and water availability in our results and in those of Battaglia et al (1998).…”

“…The lack of relation between L and water availability found here is similar to that found by Battaglia et al (1998) who, although concluding that L was related to an index of water stress and to temperature, found a great deal of scatter in both relations. Despite similar land-use history and establishment practices, inherent differences in site fertility may partially explain the lack of relation between L and water availability in our results and in those of Battaglia et al (1998). The weak negative correlation observed between evaporative demand and L is consistent with the relation between L and temperature proposed by Battaglia et al (1998).…”

“…Despite similar land-use history and establishment practices, inherent differences in site fertility may partially explain the lack of relation between L and water availability in our results and in those of Battaglia et al (1998). The weak negative correlation observed between evaporative demand and L is consistent with the relation between L and temperature proposed by Battaglia et al (1998). Overall, our results suggest that L was a less important influence on productivity than stomatal and canopy conductance.…”

Temperate forest trees and stands under severe drought: a review of ecophysiological responses, adaptation processes and long-term consequences

“…Any additional demand on already limited reserves may delay, if not inhibit, recovery of the growth potential. As a consequence, tree ring width or leaf area is frequently smaller during several years following a severe drought [12,83]. Moreover, physiological disorders increase tree vulnerability to secondary stresses like insect damage [120], frost or another drought.…”

“…The main response of shrubs to contrasted precipitation regimes in a chaparral range is to modulate accordingly leaf area index, not to adjust physiological functions [110]. In temperate forests, repeated episodes of drought cause a decrease in leaf area index on an inter-annual time pace [12,83] and hence promote a decline of gross primary productivity [82]. Mediterranean and dry-tropical vegetations adapt to severe and frequent drought episodes by adjusting species composition, leaf area duration, leaf area index, root-to-shoot ratio, leaf thickness and through physiological acclimation processes.…”