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Optimizing stand structure for tradeoffs between overstory and understory vegetation biomass in a larch plantation of Liupan Mountains, Northwest China

Ahmad, Bilal, Wang, Yanhui, Hao, Jia, Liu, Yanhui, Bohnett, Eve, Zhang, Kebin
Forest ecology and management 2019 v.443 pp. 43-50
Larix, biomass, canopy, ecosystem services, forest ecosystems, forest management, forests, models, mountains, overstory, plantations, quantitative analysis, stand structure, trees, understory, China
Understory vegetation biomass (UVB) is necessary for forest stability and supply of numerous forest ecosystem services (FES). However, UVB is often ignored in traditionally managed overly dense plantations. A tradeoff approach between the overstory biomass (OB) and UVB, based on the quantitative evaluation of overstory stand structure effects on UVB, was examined using 82 sample plots of larch (Larix Principis-rupprechetii) plantation in the Liupan Mountains (LPM), northwest China. Results showed that with rising tree density at given age, the single tree biomass decreased, but the OB increased. The UVB decreased significantly with rising OB. The optimal canopy density of 0.7 was suggested to balance OB and UVB. The corresponding proper tree densities calculated using fitted model were about 2600, 2000, 1600, 1250, 1000 trees/ha for the ages of 15, 20, 25, 30, 35 years, respectively. These proper tree densities lead to an increase of single tree biomass by 0.8%, 4.1%, 3.9%, 4.1%, 5.5%, an increase of UVB by 0.9%, 10.1%, 16.1%, 32.2%, 88.5%, but a decrease of OB by 2.9%, 13.26%, 12.5%, 13.3%, 18.5%, compared with the stands having the maximum tree densities of 2700, 2400, 1900, 1500 and 1300 trees/ha. The study can help to guide the multifunctional forest management and to uplift FES of degraded plantation.