Lecture 11 - Selective logging Flashcards
describe the prevalence of logging
- between 2000-2005, 20% of tropical forests were logged
- over 400 million hectares of tropical forest in permanent timber estate
- logged forests now dominate remaining tropical forest cover
- 22% of animals in tropical forests live in protected areas and 42% live in active or former logging concessions
describe the difference between temperate and tropical logging
- in temperate zones = clear cutting
- in the tropics = selective logging = only large marketable trees removed - smaller or less desirable species left
- damaged forest remains
- damage depends on how much wood cut
what are the impacts of selective logging
- reduced tree size
- creating more logging roads
- further damaged forest and reduced future timber yields
what are concessions management plans?
- only cut trees above set DBH (50-60cm)
- harvest in rotations, typically 40-70yrs apart
(re entry logging is starting in some areas)
what is ecosystem functioning?
‘the biological, geochemical and physical processes that operate within an ecosystem, sustaining it and enabling it to supply ecosystem services’
examples of ecosystem functions
structural components: nutrient cycling, seed dispersal, pollination
interactions within and between the structural components of ecosystems: biodiversity, soil, water etc
3 effects of logging on biodiverstiy
1) species composition
2) ICUN red-listed bird species
3) % of unlogged species persisting
how would you study birds, dung beetles and lead-litter ants
birds - point counts and understorey birds with mist nets
dung beetles - baited pitfall traps
leaf-litter ants - winkler traps
when studying taxa what would you observe
study their key functional roles e.g. seed dispersal, nutrient recycling and predation
what have studies shown to be the effects of logging on biodiversity
- species composition differs
- red-listed birds have significantly decline in once logged and twice logged forests
- most primary forest species persist
what are the negatives of logging
- changes species composition
- some species apparently extinct in landscape
- logging is harmful, re-logging magnifies ham
positives of logging
- substantial amount of biodiversity persists
- includes red listed species e.g. orang-utans (primary forest species)
what is the biggest threat to logged forests
conversion to agriculture which causes a massive loss of biodiversity
what is functional diversity?
- incorporates array of functional traits
e. g. feeding guilds, behavioural forging strategies, morphological adaptations - yields a single continuous measure
- directly relates to ecosystem functioning
what is functional richness?
the maximum amount of function trait spread - so the greater the number of functional trait combinations the greater the volume fo functional space
- experiment showed this to be dramatically different between primary forest and oil palm for both birds and dung beetles
describe functional diversity after agricultural conversion
- FD is similar in logged forest to primary but declines after conversion
what can be a positive of twice logged forests
disturbance tolerant species in twice logged forest introduces additional functional traits
describe how the balance of functional traits can alter as the community composition changes
- in some cases there is a direct replacement of one species for another
- in other cases there is a complete absence or addition of a particular trait
- some traits become more or less common
give an example of shifts of functional traits
- in oil palm granivorous bird species increased in abundance
- addition of water related species which don’t occur in forest
- loss of bark gleaning species (e.g. woodpeckers)
- dung beetles were also absent in oil palm when they are highly abundant in forest
- the most abundant species were also smaller
- decline in number of diet generalist species
how can they look at the impact of logging on trophic (feeding) ecology?
- experiment looking at the Nitrogen isotopes of bird claws - assimilate bird diet over 2-3 months - determine how high individuals feed up the food chain
- results show birds in degraded forest feed higher up the food chain
what are the impacts of logging on functioning?
- logged forest retains high diversity of functional traits whereas oil palm results in a loss
- functional overlap in logged forest- resilience to further disturbance
- same species eat more insects than fruit in logged forest
- food web plasticity endows communities with resiliance to disturbance
what are ecosystem services?
provides human society with many ‘services’
e. g. primary forests store billions tons of carbon - carbon sinks for 3+ decades, absorbing more carbon than they emit
- mitigates climate change
what are the impacts of logging on ecosystem services?
- carbon storage declines after logging but an average of 76% of carbon is retained one year post logging
- 47%-97% range, reflecting variation in logging intensity
3 points summarising effects of selective logging
1) logging is harmful to biodiversity but they do retain much biodiversity value
2) there are hidden impacts on functional ecology
3) logged forests store and absorb much carbon
