Possum damage to forests

Pen Holland

IntroductionNew

Zealand

Region

Site

Tree

Leaf

inte

rest

proc

esse

s

observationsbrow

se

Description and predictionLooks bad…

Description and prediction...but not that bad?

The field assessment

Browse damage Proportion of leaves chewed

Foliage cover index Fraction of sky blanked out

F = 0.45?D > 0.25 &

D ≤ 0.5F = 0.35?

Still alive

Browse on kamahi

Trees have leaves

Leaf life span

Consumption rate

Foliage biomass

which grow and fall offand sometimes get eaten

Whole/browsed foliage biomass

Predicting tree mortality

Leaf life span

Consumption rate

Canopy healthFoliage Cover Index

Browse damage

Whole/browsed foliage biomass

Foliage biomass

as a result of possums eating leaves

Predicting site mortality

(kamahi)

as a result of possums feeding on kamahi

Predicting site mortalityHow many

kamahi trees of what size at

this site?

How do I like to

distribute my

feeding among kamahi trees?

How many possums are

there?

Predicting site mortalityCoombs Rotorangi

Number of kamahi per hectare 200 100

Sample of dbh sizes (mean) 26 cm 32 cm

Kamahi showing no browse 65% 27%

Possum trap catch index 32.8% 44.7%

Coombs Rotorangi

Predicting site mortality

DataModel prediction

Calculating mortality

DataModel prediction

Mortality Risk

Summary

Model of leaf turnover and possum consumption parameterized for kamahi using field data and literature

Prediction of tree mortality at a new site only required a single site visit for data collection

Looking forwardHow many

kamahi trees of what size at

this site?

How do I like to

distribute my

feeding among kamahi trees?

How many possums are

there?

Looking forward

How many trees of what size and species at this

site?

How do possum populations

change through time?

Why do I like to

distribute my feeding among any

trees? When will I stop and

feed elsewhere?

Acknowledgements

Landcare Research

Roger Pech

Wendy Ruscoe

Mandy Barron

Lincoln University

Richard Duncan

Possum clipart from http://www.wettropics.gov.au