关键词: 非结构性碳水化合物, 树种, 树皮, 边材, 心材, 误差分析

Abstract: [Objective] Estimating nonstructural carbohydrates (NSC) storage in trunk is important because the NSC is the major buffer of carbon for survival and growth of trees, and also reflects dynamics in carbon balance between uptake and investment and the responsive capacity of trees to various stresses. The NSC concentration in trunk may vary among different species and different tissues, but their effects on estimation of NSC storage in trunk are rarely examined. The objective of this study was to assess the effects of inter-specific and inter-tissue variations in NSC concentrations on NSC storage in trunks of larch (Larix gmelinii, non-porous species), walnut (Juglans mandshurica, semi-ring-porous species), and elm (Ulmus japonica, ring-porous species).[Method] Three dominant trees of each species were randomly selected and harvested in late growing season. Once a sampled tree was fell, a 5 cm-thick disc was cut from each 1-m interval trunk (18 to 21 discs in total for each tree).The discs were then partitioned into bark, sapwood, and heartwood tissues for NSC concentration determination. The biomass of all tissues was measured with the standard methods. The concentrations of soluble sugar and starch were measured with a modified phenol-sulfuric acid method. The relative errors in the estimates of NSC storage in trunk induced by inter-specific, inter-tissue and vertical variations in NSC concentrations were quantified based on the measurements of NSC concentration and biomass.[Result] Species, stem tissue and trunk height significantly influenced the concentration of soluble sugar, starch and TNC (the sum of sugar and starch; P<0.01, except for the height effect on starch). The mean TNC concentration in bark of the three species (8.3%) was 3- and 5-times as much as that in sapwood and heartwood, respectively. The larch had the highest TNC concentration in bark (12.0%), but lowest TNC concentration in sapwood (1.9%). There was no significant difference in the TNC concentration in heartwood among the species. The relative vertical variations in TNC concentration of the tissues for the three species averaged at about 50%. The NSC concentration in bark and whole trunk increased with the increase of trunk length, while the NSC concentration in sapwood and heartwood of branchless trunk declined slightly with the increase of trunk length. Partitioning the variability in the trunk TNC storage estimation, we found that tree species contributed 32% of the variability, tissue contributed >25%, and trunk length variation alone contributed to 9%.[Conclusion] Species, tissue and trunk length significantly influenced the estimation of NSC storage in trunk, and the strength of the impact ranked as species> tissue> trunk length.

Key words: nonstructural carbohydrates, tree species, bark, sapwood, heartwood, error analysis