No abstract

In five California evergreen trees and shrubs cooccurring in this study but most common in habitats of different moisture availability, leaf nitrogen was a major determinant of photosynthetic capacity. Within each species, stomatal conductance was highly correlated with photosynthetic capacity, resulting in little variation in the concentration of CO in the intercellular spaces. Among species, intercellular CO concentrations varied significantly. Under controlled conditions, the leaves that realized the highest photosynthesis per unit of leaf nitrogen tended to realize the lowest photosynthesis per unit of water transpired. The ratio of photosynthesis to transpiration, an instantaneous measure of intrinsic water-use efficiency, was highest in the species commonly found in the direst habitats and lowest in the species most common in the wettes habitats.

We studied the influence of litter quality on the decomposition rate of leaves from nine Mediterranean shrubs and trees using litter bag methods for a 2—yr period at two ecosystems in southwest Spain. Linear and nonlinear regressions were calculated between mass loss and the concentrations of the major organic and inorganic constituents of leaves (lignin, cutin, cellulose, tannins, crude fat, soluble carbohydrates, nitrogen, and phosphorus) and between mass loss and leaf toughness in order to determine the best predictor of leaf litter decomposition in these ecosystems. In addition, ratios between some of the litter quality parameters were examined as mass loss predictors. Loss of soluble components from leaves was used to define two phases of decomposition: a leaching phase that lasted 2—4 mo and a postleaching phase. Leaf toughness and the ratio of toughness: phosphorus concentration were the best indicators of mass loss during the leaching phase in both ecosystems, and cutin: nitrogen or cutin: phosphorus ratios were the best predictors of mass loss in the postleaching phase, but only in the drier and more nutrient—poor ecosystem. When the two phases were combined, leaf toughness, toughness: nitrogen, and/or cutin: nitrogen significantly explained the mass loss in both ecosystems.

Summary• The construction costs ( CC ) are reported of leaves from 162 wild woody species from 14 contrasting environments (desert to rain forest) and with different leaf life-spans.• Calorimetric methods were used to estimate the CC of deciduous, semideciduous and evergreen leaves.• Leaf CC showed a wide range (78%) between species, and deciduous species showed a slightly lower CC (6%) than both semideciduous and evergreen species. Mean leaf CC differed between ecosystems, with the highest and lowest CC in the tundra and rain forest, respectively. Leaf CC was positively correlated with lipid concentration. Leaf size (log) and specific leaf area (SLA, leaf area per leaf dry mass) were negatively correlated with leaf CC . Leaf CC did not show differences between different leaf life-spans or ecosystems when leaf size (log) or SLA were included as covariates.• The small differences in leaf CC among leaf life-span types and ecosystems (6% and 23%, respectively) suggest that SLA is more important in determining differences in the carbon balance between species than leaf CC . Leaf size is shown to be an important trait associated with other leaf characteristics.