Estimation of biomass allocation and carbon density of Rhododendron simsii shrubland in the subtropical mountainous areas of China
Aims As an important potential carbon sink, shrubland ecosystem plays a vital role in global carbon balance and climate regulation. Our objectives were to derive appropriate regression models for shrub biomass estimation, and to reveal the biomass allocation pattern and carbon density in Rhododendron simsii shrubland. <br> Methods We conducted investigations in 27 plots, and developed biomass regression models for shrub species to estimate shrub biomass. The biomass of herb and litterfall were obtained through harvesting. Plant samples were collected from each plot to measure carbon content in different organs. <br> Important findings The results showed that the power and linear models were the most appropriate equation forms. The D and D2H (where D was the basal diameter (cm) and H was the shrub height (m)) were good predic-tors for organ biomass and total biomass of shrubs. All of the biomass models reached extremely significant level, and could be used to estimate shrub biomass with high accuracy. It was more difficult to predict leaf and annual branch biomass than stem biomass, because leaf and annual branch were susceptible to herbivores and inter-plant competition. The mean biomass of the shrub layer was 20.78 Mg·hm–2, in which Rhododendron simsii and Sym-plocos paniculata biomass accounted for 93.63%. Influenced by both environment and species characteristics, the biomass of the shrub layer organs was in the order of stem>root>leaf>annual branch. The root:shoot ratio of the shrub layer was 0.32, which was less than other shrubs in subtropical regions. The relative higher aboveground biomass allocation reflected the adaptation of plants to the warm and humid environment for more photosynthesis. The mean total community biomass was 26.26 Mg·hm–2, in which shrub layer, herb layer and litter layer ac-counted for 79.14%, 7.62% and 13.25%, respectively. Litter biomass was relatively high, which suggested that this community had high nutrient return. There were significant correlations among aboveground biomass, belowground biomass and total biomass of shrub layer and herb layer. The mean biomass carbon density of the community was 11.70 Mg·hm–2 and the carbon content ratio was 44.55%. The carbon density was usually ob-tained using the conversion coefficient of 0.5 in previous studies, which could overestimate carbon density by 12.22%.
regression modelroot/shoot rationutrient returnaboveground biomassbelowground biomasscarbon content ratio
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