Improving longleaf pine mortality predictions in the Southern Variant of the Forest Vegetation SimulatorR. Justin DeRose 1John D. Shaw 2Giorgio Vacchiano 3James N. Long 1

1 Utah State University, 2 Rocky Mountain Research Station, 3 Universit di Torino

OutlineSize-density relationshipsFVS-predicted mortalityLongleaf pineMortality in longleafSimulate natural mortality using FVSConclusions / Recommendations

Size-Density RelationshipsDensity management diagramTrajectory through time

Mortality in SN variant3 types = f(Dqx)

Background mortalityDensity-dependent mortality, SDI > 55% & Dq < 10.0, x =1.6 Density-dependent mortality, SDI > 55% Dq > 10.0, x = 2

Longleaf pine DMDMature Stand Boundary (MSB)LL range-wide datasetEven-agedPure = f(Dqx) then, Perhaps x > 2 Stand # 10001

Mechanisms?Increasing chance of density-independent mortality?Less occupied growing space?Zeide (1985), self-intolerance?Assmann (1970) crown disengagement?

ImportanceIncreasingly managing for large D treesRCW (Shaw and Long, 2007, SJAF)(F & W Guidelines)

Simulate MSBTHIN keyword every cycle?Iteratively adjust BAMax / SDIMax?Use MSB to constrain size-density relationship?

Results Event Monitor, FixMort keywordIF Dq approaches MSB THEN 10% mortality / cycle

Results

ConclusionsFVS models background mortality fine at small diametersSelf-thinning mortality appears fineBAMax mortality is unrealistic

ConclusionsWe need a better approximation of natural mortality We have a fix, albeit roughIterative FixMort simulates well butMust know MSB for your species

RecommendationsReplace BAMax mortality Species-specific fitted relationships (like MSB)

AcknowledgementsForestry Branch of the Fort Bragg Natural Resource Division U.S. Army Environmental Center P. Wefel and J. Stancar for their continuing supportD. Donnelly for early project support

Mention Ft. Bragg data for longleaf pineDensity mediated mortality is a function of D^xWe explored various mortality ratesFor large diameter stands