18 December, 2019 (Fisher, NPH, JULES-ED)

Fisher, R., McDowell, N., Purves, D., Moorcroft, P., Sitch, S., Cox, P., Huntingford, C., Meir, P. and Ian Woodward, F. (2010), Assessing uncertainties in a second‐generation dynamic vegetation model caused by ecological scale limitations. New Phytologist, 187: 666-681. doi:10.1111/j.1469-8137.2010.03340.x

• Question:

  1. How demographic processes of two-dimensional spatial scales influence simulations of community structure, and responses of ecosystems to climate change?

• Context:

  • Recently second-generation DGVMs have become advanced in their capability to simulate short-term surface gas and energy exchanges and atmospheric CO₂.
  • However, the 2^nd gen. DGVMs are still lack in representation of demographic processes because of insufficient observations.
  • This poor representations of competition and coexistence may bring uncertainties in simulation of the community structure and responses of ecosystem to climate change.

• Answer

  1. Varying the five unconstrained parameters (seed advection, seed mixing, sapling survival, competitive exclusion, and plant mortality) introduced diverse predictions of community structure ranging from monocultures to equal co-dominance of the seven PFTs.
  2. When exposed to a climate change scenario, the competing impacts of CO₂ fertilization and increasing plant mortality caused ecosystem biomass to diverge substantially between simulations.

• Implication:

  • Demographic processes represent a large source of uncertainty in DGVM predictions.

• Unanswered:

  • Examining the uncertainties caused poor representations of demographic processes by top-down approach

• Comment:

  • The uncertainties from demographic processes may show an interaction effect with other uncertainties (e.g. NSC, hydraulics, phenology, nutrient …).
  • Attaching another module explicitly seems like a great way of preliminary test.