Exploring the factors affecting carbon and nutrient concentrations in tree biomass components in natural forests, forest plantations and short rotation forestry

Abstract

Background: Coupling biomass models with nutrient concentrations can provide sound estimations of carbon and nutrient contents, enabling the improvement of carbon and nutrient balance in forest ecosystems. Although nutrient concentrations are often assumed to be constant for some species and specific tree components, at least in mature stands, the concentrations usually vary with age, site index and even with tree density. The main objective of this study was to evaluate the sources of variation in nutrient concentrations in biomass compartments usually removed during harvesting operations, covering a range of species and management conditions: semi-natural forest, conventional forest plantations and short rotation forestry (SRF). Five species (Betula pubescens, Quercus robur, Eucalyptus globulus, Eucalyptus nitens and Populus spp.) and 14 genotypes were considered. A total of 430 trees were sampled in 61 plots to obtain 6 biomass components: leaves, twigs, thin branches, thick branches, bark and wood. Aboveground leafless biomass was pooled together for poplar. The concentrations of C, N, K, P, Ca, Mg, S, Fe, Mn, Cu, Zn and B were measured and the total biomass of each sampled tree and plot were determined. The data were analysed using boosted regression trees and conventional techniques. Results:The main sources of variation in nutrient concentrations were biomass component > > genotype (species) ≈ age > tree diameter. The concentrations of Ca, Mg and K were most strongly affected by genotype and age. The concentrations of P, K, Ca, Mg, S and Cu in the wood component decreased with age, whereas C concentrations increased, with a trend to reach 50% in the older trees. In the SRF, interamerican poplar and P. trichocarpa genotypes were comparatively more efficient in terms of Ca and K nutrient assimilation index (NAI) (+ 65-85%) than eucalypts, mainly because leafless biomass can be removed. In the conventional eucalypt plantations (rotation 15 years), debarking the wood at logging (savings of 225% of Ca and 254% of Mg for E. globulus) or the use of selected genotypes (savings of 45% of P and 35% of Ca) will provide wood at a relatively lower nutrient cost. Considering all the E. globulus genotypes together, the management for pulp with removal of debarked wood shows NAI values well above (× 1.7-× 3.9) the ones found for poplar or eucalypt SRF and also higher (× 1.6-× 4.0) than the ones found for oak and birch managed in medium or long rotations. The annual rates of nutrient removal were low in the native broadleaved species but the rates of available soil nutrients removed were high as compared to poplar or eucalypts. Management of native broadleaved species should consider nutrient stability through selection of the biomass compartments removed.

Aggregated Biomass Model Systems and Carbon Concentration Variations for Tree Carbon Quantification of Natural Mongolian Oak in Northeast China

“…This finding is in accordance with those that have been reported elsewhere in the literature, which show significant differences in carbon concentration in components of the balsam fir in Canada [43], 10 Chinese temperate tree species in northeast China [37], and eight subtropical tree species in southern China [44]. Moreover, Rodríguez-Soalleiro et al [34] confirmed the importance of biomass components and tree species as the source of variation in carbon concentration of several broadleaved species, which were found to explain about 52% and 17% of the variance, respectively. Overall, carbon concentration was found highest in foliage (0.4670), lowest in root (0.4406), and slightly lower in branches (0.4491) than stem (0.4568).…”

“…Thus, approximately 10% bias would be generated if one is relying on 0.50 as a generic carbon conversion factor to estimate carbon stock [31][32][33]. Clearly, species-, component-, and even region-specific carbon concentration measurements are absolutely needed in order to decrease the inaccuracy of carbon stock quantification [34].…”

A Complete Assessment of Carbon Stocks in Above and Belowground Biomass Components of a Hybrid Eucalyptus Plantation in Southern Brazil

“…Thus, the general application of 50% C to all components would lead to a slight over-prediction of 3.4 Mg C ha −1 (relative error of 2.3%). Weighted averages of 47.7% for the aboveground biomass of E. globulus and E. nitens in Spain [12] and 49.77% for the above and belowground components of the same species in Tasmania [35] have previously been reported.…”

“…Increasing the carbon stock depends on the biomass allocation of each species and the C concentrations in each component [12]. Biomass allocation depends on the resources available at the site as well as the type of management [13], stand age [3,9], and rotation length [14].…”

Biomass and dominance of conservative species drive above-ground biomass productivity in a mediterranean-type forest of Chile

“…In line with the hypothesis of vegetation quantity, AGBP in the matorral migth increase with higher tree density, as it reduces environmental stresses, such as high radiation, high soil evaporation and soil erosion (Mooney and Dunn 1970). Besides, according to the hypothesis of soil resources availability, AGBP in the matorral might increase with increasing soil nitrogen (Kummerow et al 1982) and soil water contents (Rodríguez-Soalleiro et al 2018;Meza et al 2018), since soil nutrients and water deficiencies are common factors limiting the growth of mediterranean-type forests (Mooney and Dunn 1970).…”