New version of PnET-Succession

[Brian Miranda]

A new version (v2.0) of the PnET-Succession extension is now available (https://sites.google.com/site/landismodel/extensions/pnet-succession).  This is a substantial update to the extension, and is not backwards compatible with previous versions.  You will need to modify parameter files to run the new version.  See the list below for enhancements and bug fixes.

 What’s new in version 2.0

• New generic parameter: PrecipEvents.  Divides incoming monthly precipitation into discrete events within the month (n=PrecipEvents) and applies each portion randomly during the sequence of processing canopy sublayers.  This prevents large cohorts from consuming a disproportionate share of the available water in a given month. 
  
• New generic parameter: Wythers.  Option to apply the foliar respiration correction as proposed by Wythers et al (2013).
  
• New generic parameter: DTEMP.  Option to apply the temperature reduction factor (DTEMP) of PnET-II rather than the original PnET-Succession v1.2 temperature reduction factor.  The v1.2 temperature reduction factor does not explicitly penalize photosynthesis at temperatures above PsnTOpt. 
  
• New ecoregion parameter: SnowSublimFrac.  Snowpack is reduced by this amount prior to snowmelt, representing sublimation.
  
• New output options for woody senescence and foliage senescence by species.

Bug fixes:

·         A bug in the calculation of transpiration was fixed. 

·         A bug that caused the decomposition of dead pools to not be simulated during spin-up in prior versions was fixed.

·         A bug in the calculation of runoff was fixed.

·         Biomass values provided to disturbance extensions in prior versions were the sum of above- and below-ground woody biomass, but no foliar biomass.  Version 2.0 includes aboveground and foliar biomass to be consistent with other Biomass Succession extensions and is therefore more compatible with biomass disturbance extensions.  Specific biomass pools can be now output as maps and total pool sizes using the Output-PnET extension (Section 10).

·         Defoliation (by an external disturbance extension) is now applied during June (previously it was January when deciduous species had no foliage).

·         A bug in the processing of cohorts killed by disturbance was fixed.  The bug prevented disturbances from recording the cohorts being removed.

·         A bug in the calculation of snow melt was fixed.  The bug caused all snow pack to melt at the same time.  The rate of snowmelt was changed to 2.74 mm/°C/day (see 2.4.2.1).

·         When snowpack is present, surface PAR is set to 0 which eliminates soil water evaporation under snow (though sublimation of snow occurs instead)

[DW]

Thanks for the update for everyone involved - I think this extension has great potential. 

I have a question though - I wonder whether runoff (adjusted by PrecLossFrac) and transpiration is reported correctly in site.csv (generated by pnetoutputsites)? 

Runoff is always 0 regardless of PrecLossFrac, and transpiration is also 0 even when my trees are growing. But then perhaps I'm making a foolish mistake. 

Thanks!

DW Ko 

I 

[Brian Miranda]

Thanks for the feedback.  I have a couple thoughts on what you are seeing.  First, the water lost due to PrecLossFrac is not considered Runoff.  Runoff is specifically water that does not enter the soil due to the saturation of the soil.  So the fact that you are not seeing any Runoff (the way it is defined) is not alarming, and I suspect most applications will not have Runoff of this kind.  But your comment made me realize that the water lost due to PrecLossFrac is not reported anywhere, and it probably should.  I'll work on adding this for the next update we do.

Your second observation that transpiration is 0 despite growing cohorts would appear to be an issue.  But, I suspect it is actually a problem with the PnET Output extension.  The output extension needs to be updated to be consistent with the updates to the succession extension.  I have completed those updates and a new version of the PnET Output extension will be available soon (maybe as early as today).  Please try your simulations with this new version of the output extension, and if this issue still exists let me know.

Cheers,

-Brian Miranda