iLand News

iLand status report

Saturday 09 of April, 2011

Hello world, hard to believe that two years have passed already since we started on this modeling endeavor. This also means that I (Rupert) am on my way back to Europe after two years in the Pacific Northwest – two truly great years, full of amazing people, forests, and ideas. I thus wanted to take this opportunity to share a bit more information about the current status of iLand.

The model currently

  • simulates individual tree regeneration, growth and mortality in a process-based manner
  • scales seamlessly from the level of individual trees to landscapes (currently tested up to 10^4 ha)
  • simulates carbon, nitrogen and water cycles (currently implemented at a resolution of 100m)
  • includes management and disturbance via a flexible java script interface (currently, those are modeled deterministically in the system, i.e. disturbance regime and landscape scale management allocation and patterns are not yet an emerging property of the simulation)

For model testing, the hierarchical multi-scale approach taken in iLand proved to be highly useful, overcoming the frequent limitations of landscape models with regard to evaluation against empirical data. In a multi-criteria evaluation of iLand, we successfully tested the model against

  • tree growth and mortality in old-growth forest ecosystems of the Western Cascades in Oregon, using long-term vegetation data (at the individual tree level)
  • carbon compartments and stocks of the same long-term vegetation plots (stand level)
  • forest inventory and analysis data for stand productivity over a wide ecological gradient in Oregon and Austria (stand level)
  • gradient nearest neighbor maps of species distribution for a 6400 ha Western Cascades landscape (landscape level)
  • gradient nearest neighbor estimates of (wall-to-wall) stand structure for the same landscape (stand to landscape level)
  • indices of canopy complexity derived from Lidar (stand to landscape level)
  • aboveground carbon maps derived from Lidar (stand to landscape level)

Based on these promising evaluation results, we are currently in the process of applying iLand to questions of landscape complexity and disturbance history at the HJ Andrews experimental forest (for the bigger picture and some hypotheses, see here). More specifically, we’re aiming to use the model to

  • disentangle the functional importance and role of landscape heterogeneity (e.g. on ecosystem C exchange and storage)
  • address the effects of disturbances, and particularly long-term disturbance legacies, on structure and functioning of forest landscapes

Here are some screenshots of the 6400ha HJ Andrews landscape simulated with iLand:

<img src='tiki-view_blog_post_image.php?imgId=11' border='0' alt='image' width=700/>
<img src='tiki-view_blog_post_image.php?imgId=12' border='0' alt='image' width=700/>
<img src='tiki-view_blog_post_image.php?imgId=13' border='0' alt='image' width=700/>
Figure: Three screenshots of a 500 year iLand simulation for the 6400ha HJ Andrews watershed. Top panel: after a landscape scale high severity fire event around year 1500. Middle panel: before the fire period of the mid 19th century. Lower panel: in the year 2000, after a period of patch clear-cutting.

Model development in the last year of the project will focus in particular of implementing process-oriented disturbance modules in order to simulate disturbance dynamics, and particularly the interaction between disturbances, as emerging property of the model. To that end we will

  • adopt an existing fire model tested and established for the Pacific Northwest
  • adopt a previously developed bark beetle model for the European spruce bark beetle (see here for more details)
  • look into process-based wind disturbance models for incorporation into iLand, such as WINDA

So quite a lot going on, on the ‘iLand’, as you can see… stay tuned to read about our results, and hear more news from the landscape modeling frontier!