EGU2020-21654, updated on 12 Jun 2020
https://doi.org/10.5194/egusphere-egu2020-21654
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Variation in canopy energy exchange characteristics across an ecosystem mosaic in the dry Mediterranean region

Madi Amer, Rafael Stern, Eyal Rotenberg, and Dan Yakir
Madi Amer et al.
  • Weizmann Institute of Science, Earth and Planetary sciences Department, Rehovot, Israel

Assessment of the plant-climatic interactions in the land biosphere requires a combined perspective of both the biogeochemical effects (BGC; such as the carbon sink), and the biogeophysical effects (BGP; such as the vegetation albedo and radiative balance), which can often have contrasting consequences for ecosystem functioning and climate. Aiming to increase our knowledge on semi-arid ecosystems that are insufficiently represented in global studies, we examine the variations in key BGP features among different vegetation types in a dry Mediterranean region in southern Israel.

The study included planted pine forest (pinus halepensis), natural broad-leaf oak maquis (Quercus calliprinos), wheat field and a managed grassland, located in close proximity (within 2 km) under the same climatic conditions (mean annual temperature = 20.8C, annual mean precipitation, P= 403 mm, aridity index = 0.4). Using a state-of-the-art mobile laboratory, we carried out measurement campaigns of eddy covariance fluxes of CO2, sensible, H, and latent, LE, heat fluxes, and the radiation balance (incoming and outgoing short- and long-wave radiations) between the ecosystems and the atmosphere in different seasons during 2016-2018.

The results showed significant differences in net radiation and in albedo among the ecosystem, with net radiation values of ~666, ~582, ~443 and 456 W m-2 and albedo values of ~0.13, ~0.16, ~0.19 and ~0.20 for pines, maquis, wheat and grassland, respectively. The lowest albedo of the pine stand was associated with the largest H (a ‘convector effect’) of ~583 W m-2 compared to ~313, ~198 and ~176 W m-2 in the maquis, wheat and grassland ecosystems (midday means of peak activity season). The pine stand was also more adjusted to stress conditions than the oak maquis ecosystem through ‘avoidance’ of high activities during extreme conditions of heat and drought (reducing canopy conductance and associated fluxes). It is likely that the observed differences between the pine and oak maquis stand help explain the greater expansion of pine stands into the semi-arid regions, even to areas with mean annual P of 290 mm (aridity index = 0.2) where oak maquis cannot be found.

How to cite: Amer, M., Stern, R., Rotenberg, E., and Yakir, D.: Variation in canopy energy exchange characteristics across an ecosystem mosaic in the dry Mediterranean region, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21654, https://doi.org/10.5194/egusphere-egu2020-21654, 2020

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Presentation version 1 – uploaded on 07 May 2020
  • CC1: Energy balance closure, Quentin Lejeune, 07 May 2020

    Hello, do you think the higher energy balance closure mismatch over pines affect your comparison across ecosystems? You mentioned in the chat that you apply a sort of correction factor, but I am not very fmiliar with that. Could you maybe detail a bit? Thanks!

    • AC1: Reply to CC1, Madi Amer, 07 May 2020

      Dear Quentin,

      Thank you for your question.
      Sorry if I was not clear enough, everything was too fast. But in the case of the fluxes and the energy closure, we do not apply any special correction factor. We did the same processing and post-processing analysis for all ecosystems.
      Soil and other types of storage seem to influence the short term energy balance, which must be balanced eventually. The issue is that the storage can be influenced by ecosystem structure, and the pine ecosystem is the one with the indeed most complex, tallest and denser understory vegetation, for example