Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Volume 12, issue 14
Biogeosciences, 12, 4245–4259, 2015
https://doi.org/10.5194/bg-12-4245-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 12, 4245–4259, 2015
https://doi.org/10.5194/bg-12-4245-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 21 Jul 2015

Research article | 21 Jul 2015

Energy partitioning and surface resistance of a poplar plantation in northern China

M. Kang1, Z. Zhang1, A. Noormets2, X. Fang1, T. Zha1, J. Zhou3, G. Sun4, S. G. McNulty4, and J. Chen5 M. Kang et al.
  • 1Key Laboratory of Soil and Water Conservation and Desertification Combating, Ministry of Education, College of Soil and Water Conservation, Beijing Forestry University, Beijing 100083, PR China
  • 2Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, NC, USA
  • 3Beijing Municipal Station of Agro-environmental Monitoring, Beijing 100029, PR China
  • 4Eastern Forest Environmental Threat Assessment Center, Southern Research Station, USDA Forest Service, Raleigh, NC, USA
  • 5Landscape Ecology & Ecosystem Science (LEES) Lab, Center for Global Change and Earth Observations (CGCEO), and Department of Geography, Michigan State University, East Lansing, MI 48823, USA

Abstract. Poplar (Populus sp.) plantations have been, on the one hand, broadly used in northern China for urban greening, combating desertification, as well as for paper and wood production. On the other hand, such plantations have been questioned occasionally for their possible negative impacts on water availability due to the higher water-use nature of poplar trees compared with other tree species in water-limited dryland regions. To further understand the acclimation of poplar species to semiarid environments and to evaluate the potential impacts of these plantations on the broader context of the region's water supply, we examine the variability of bulk resistance parameters and energy partitioning in a poplar (Populus euramericana cv. "74/76") plantation located in northern China over a 4-year period, encompassing both dry and wet conditions. The partitioning of available energy to latent heat flux (LE) decreased from 0.62 to 0.53 under mediated meteorological drought by irrigation applications. A concomitant increase in sensible heat flux (H) resulted in the increase of a Bowen ratio from 0.83 to 1.57. Partial correlation analysis indicated that surface resistance (Rs) normalized by leaf area index (LAI; Rs:LAI) increased by 50 % under drought conditions and was the dominant factor controlling the Bowen ratio. Furthermore, Rs was the main 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). Rs was also a major regulator of the LE / LEeq ratio, which decreased from 0.81 in wet years to 0.68 in dry years. All physiological and bioclimatological metrics indicated that the water demands of the poplar plantation were greater than the amount available through precipitation, highlighting the poor match of a water-intensive species like poplar for this water-limited region.

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We found that energy partitioning to latent and sensible heat and surface resistance was dramatically responsive to climatological drought. All physiological and bioclimatological metrics (Bowen ratio, surface resistance, and Priestley-Taylor coefficient) indicated that the water demands of the poplar plantation were greater than the amount available through precipitation, highlighting the poor match of a water-intensive species like poplar to a water-limited region in northern China.
We found that energy partitioning to latent and sensible heat and surface resistance was...
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