Responses of energy partitioning and surface resistance to drought in a poplar plantation in northern China

Abstract

Abstract. Poplar (Populus sp.) plantations have been used broadly for combating desertification, urban greening, and paper and wood production in northern China. However, given the high water use by the species and the regional dry environment, the long-term sustainability of these plantations needs to be evaluated. Currently, the understanding of energy partitioning and canopy resistance to water vapor and CO2 in poplar plantations is limited, impeding an accurate assessment of their true ecosystem functions. This study examined the variability of canopy bulk resistance parameters and energy partitioning over a four-year period encompassing both dry and wet conditions in a poplar (Populus euramericana CV. "74 / 76") plantation ecosystem located in northern China. Available energy (Net radiation Rn minus Soil Heat Flux, G) partitioning to latent (LE) and sensible (H) heat was responsive to climatological drought, with LE/(Rn-G) ranging from 62% in wet years (e.g. 2007 and 2008) to 53% in dry years (e.g. 2006 and 2009), and H/(Rn-G) from 25 to 33% between wet and dry years. Correspondingly, the Bowen ratio (β=H/LE) were 0.83 and 1.57. Surface resistance (Rs) had the greatest response to drought (+43%), but the aerodynamic and climatological resistances did not change significantly (p > 0.05). Partial correlation analysis indicated that Rs was the dominant factor in controlling the Bowen ratio. Furthermore, Rs was the major factor controlling LE during the growing season, even in wet years, as indicated by the decoupling coefficient (Ω = 0.45 and 0.39 in wet and dry years, respectively), and the LE / LEeq ratio ranged from 0.81 and 0.68 in wet and dry years, respectively. In general, the dry surface conditions dominated in this poplar plantation ecosystem regardless of soil water availability suggesting that fast-growing and water use-intensive species like poplar plantations are poorly adapted for the water limited region.

Spatiotemporal dynamic of subtropical forest carbon storage and its resistance and resilience to drought in China

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Phenolic acids inhibit the photosynthetic productivity of poplar

“…Poplar is an important industrial timber species (Griu and Lunguleasa 2016), and owing to its fast growth rate and broad adaptability, it is widely cultivated in many countries, such as those in Europe, America, and China, and plays a large role in meeting the demand for wood (Heilman 1999, Kang et al 2015. However, owing to the shortage of land resources, continuous cropping is widely applied in poplar plantations in many countries, which brings about a series of problems, such as reduced soil nutrient contents, severe pests, and diseases, and significantly lowered forest productivity (Afas et al 2008, Wang andXin 2016).…”