Abstract
Forests are a large carbon sink with an additional substitution effect in the merchantable timber compartment of harvested trees, where carbon stored within the same volume of wood varies depending on wood density. Here, we investigated mean annual air-dry wood density variations depending on cambial age, annual radial increment, and two different stem heights of Larix gmelinii (Rupr.), Quercus mongolica Fisch. ex. Ledeb., and Pinus tabulaeformis Carr. from a first climatic region (Mulan Forest) and exclusively of P. tabulaeformis from a second climatic region (Zhongtiaoshan Forest) in the temperate zone of China. We applied linear mixed-effects models with partly transformed variables and estimated marginal means for pairwise comparisons. Results showed that mean wood density was not significantly different between L. gmelinii (0.626 g cm−3) and Q. mongolica (0.596 g cm−3), but significantly different between P. tabulaeformis from the two different climatic regions (0.445 g cm−3 in Mulan Forest and 0.521 g cm−3 in Zhongtiaoshan Forest). Mean annual wood density within trees except for P. tabulaeformis from Mulan Forest was initially increasing until an intermediate cambial age, after which it decreased again to lower values. These findings showed that tree age had to be considered in assessing carbon sequestration in wood. It also could play an important role in decision making for forest management in Mulan Forest and show the benefit of the wood properties and carbon storage potential of the faster growing L. gmelinii compared to Q. mongolica. Furthermore, these findings gave an indication that intermediate old forest stands for some tree species accumulated more carbon per year within their woody biomass than young stands or old growth forests. Our results may have an impact on the planning of rotation lengths and of tree species composition for forest stands in Mulan Forest and Zhongtiaoshan Forest.
Highlights
Forest ecosystems are some of the largest sinks of terrestrial carbon on the globe [1]; they absorb billions of tons of atmospheric CO2 yearly and contribute to climate change mitigation [2]
Our results may have an impact on the planning of rotation lengths and of tree species composition for forest stands in Mulan Forest and Zhongtiaoshan Forest
Our study showed that mean wood density was not significantly different between L. gmelinii and
Summary
Forest ecosystems are some of the largest sinks of terrestrial carbon on the globe [1]; they absorb billions of tons of atmospheric CO2 yearly and contribute to climate change mitigation [2]. Within a forest, carbon is stored mainly in the living aboveground biomass and in the organic matter of the mineral soil [3]. The amount of carbon stored within the same volume of wood varies between tree species depending on wood density. To its importance for biomass production and the carbon storage potential, wood density has an effect on the quality of the manufactured end-product as it is linked to several physical and material characteristics such as stiffness and strength [7]. Density varies between trees of the same species as it depends on multiple factors such as local climate [9], genetic provenance [10], and age [11]. Wood density varies within an individual tree both horizontally between tree rings and vertically between different stem heights [12]
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