Non‐structural carbon compounds in temperate forest trees

Abstract

The current carbon supply status of temperate forest trees was assessed by analysing the seasonal variation of nonstructural carbohydrate (NSC) concentrations in leaves, branch wood and stem sapwood of 10 tree species (six deciduous broad-leafed, one deciduous conifer and three evergreen conifer trees) in a temperate forest that is approximately 100 years old. In addition, all woody tissue was analysed for lipids (acylglycerols). The major NSC fractions were starch, sucrose, glucose and fructose, with other carbohydrates (e.g. raffinose and stachyose) and sugar alcohols (cyclitols and sorbitol) playing only a minor quantitative role. The radial distribution of NSC within entire stem cores, assessed here for the first time in a direct interspecific comparison, revealed large differences in the size of the active sapwood fraction among the species, reflecting the specific wood anatomy (ring-porous versus diffuse-porous xylem). The mean minimum NSC concentrations in branch wood during the growing season was 55% of maximum, and even high NSC concentrations were maintained during times of extensive fruit production in masting Fagus sylvestris . The NSC in stem sapwood varied very little throughout the season (cross species mean never below 67% of maximum), and the small reductions observed were not significant for any of the investigated species. Although some species contained substantial quantities of lipids in woody tissues ('fat trees'; Tilia , Pinus , Picea , Larix ), the lipid pools did not vary significantly across the growing season in any species. On average, the carbon stores of deciduous trees would permit to replace the whole leave canopy four times. These data imply that there is not a lot of leeway for a further stimulation of growth by ongoing atmospheric CO 2 enrichment. The classical view that deciduous trees rely more on C-reserves than evergreen trees, seems unwarranted or has lost its justification due to the greater than 30% increase in atmospheric CO 2 concentrations over the last 150 years.

Spectroscopic Remote Sensing of Non-Structural Carbohydrates in Forest Canopies

“…Chemical analyses of the 6136 leaf samples indicated extremely wide-ranging concentrations of NSC, from 16.5% to 84.5% of total leaf mass (Table 3). Parallel to the spectra, this NSC range approximately meets the range reported for live, fresh foliar material worldwide [1,5,9]. Based on this range of chemical values, the PLSR analyses indicated that NSC can be estimated at the leaf level from reflectance with high precision (mean R 2 = 0.73 ± 0.06) and accuracy (average %RMSE = 12.9%) ( Table 3).…”

Biomass productivity and water use relation in short rotation poplar coppice (Populus nigra x P. maximowiczii) in the conditions of Czech Moravian Highlands

“…The higher gross WUE P as a consequence of precipitation could be explained by a few reasons. Firstly, by using the long-term water use effi ciency based on AB increment and not on CO 2 uptake and transpiration ratio, the relative carbon allocation to roots or AB can play important role (Höll, 1985;Lindroth et al, 1994;Dickmann et al, 2001;Hoch et al, 2003). During the period with reduced soil water availability, the assimilated carbohydrates are directed away from shoots and towards root growth.…”

Evaluating the Community Land Model in a pine stand with shading manipulations and <sup>13</sup>CO<sub>2</sub> labeling

“…Plant storage pools in the form of non-structural carbohydrates are known to play an important role in regulating allocation to structural pools, and they may make up a significant portion of total biomass (e.g., Hoch et al, 2003). Simple models that account for non-structural carbohydrates better compare with observed 14 C and stem growth, indicating the importance of the pools over seasonal to decadal timescales .…”