Seasonal changes in energy allocation by white oak (Quercusalba)

Abstract

Seasonal patterns of change in lipids, sugars, starch, labile (ethanol soluble) constituents, holocellulose, and lignin were studied in six forest-grown white oak (Quercusalba L.) trees. Contents of metabolically active constituents in leaves, twigs, branches, boles (upper and lower), and roots (support and small lateral) were used to construct whole-tree budgets of energy allocation. [14C]Sucrose was also concurrently supplied to the study trees to follow the fate and efficiency of utilization of food reserves. Results showed that white oak rapidly mobilized and replaced food reserves during the critical period of canopy generation in the spring. Starch was more important as a reserve food than lipids or sugar. Large fluctuations in starch in roots in spring and fall suggested a bimodal belowground growth pattern. Labile constituents showed the most pronounced seasonal changes and dominated the calculated whole-tree energy flux patterns. Rapid decline in labile compounds in early spring and a parallel increase in holocellulose suggested a possible pattern of mobilization and resupply of stored reserves associated with in cell wells. This possibility was supported by a concurrent shift of labile 14C to nonlabile 14C in tissues. Canopy generation was calculated to have cost ≤17.7 kg of glucose (1.6 g glucose/g of canopy) of which 13 kg appeared to have come from within the canopy.

Using longitudinal survival probabilities to test field vigour estimates in sugar maple (Acer saccharum Marsh.)

“…1a). Average growth rates during these defoliations were (although not significantly) higher in vigorous than in moribund trees, possibly indicating that their greater carbon reserves allowed for quick foliage replacement and growth recovery (McLaughlin et al, 1980). Survival probabilities corroborate, at least partially, the visual tree vigour classification used for tree marking.…”

Carbohydrate Allocation to Storage as a Basis of Interspecific Variation in Sapling Survivorship and Growth

“…This reflects the large seasonal increase in carbohydrate storage in deciduous species (Wargo 1971, McLaughlin et al 1980, Kozlowki 1992. To avoid confounding these differences between evergreen and deciduous species, I have compared TNC within the two groups separately.…”

Fine‐root mortality rates in a temperate forest: estimates using radiocarbon data and numerical modeling

“…L 2 receives stored and new photosynthate and loses C via respiration ( R 23 ), transfer of carbon to L 3 (characterized by the turnover time τ ts ), and mortality (τ L 23 ). We chose a value of τ ts (0.5 yr) that produced average annual L 2 values that were within the range of published values for nonstructural carbohydrate concentrations for white oak roots (< 10 mm in diameter) growing in the Walker Branch Watershed (McLaughlin et al ., 1980). L 3 receives C from L 2 , loses C via root mortality (τ L 23 ), and C associated with L 3 respiration is removed from L 2 .…”