Climate change - Demongraphic mechanisms

Question 1

Mechanisms matter

Answer 1

Helps understand bioclimatic models
•Different models of plants using co-occurance as a demographic factor (spp interactions)
-improved predictions of models

Question 2

Mechanistic models include…

Answer 2

• Bio-physical threshold - how temp influences ectotherm foraging duration
• Life history - winter survival and summer recruitment
• Recruitment and foraging - combines two above

Question 3

3 types of mechanisms…

Answer 3

1. Direct impacts - physiology
2. Indirect impacts - altered species interactions
3. Indirect impacts - habitat change and human responses

Question 4

Heat and drought stress

Answer 4

Arid areas becoming worse

Under CC small birds peak water requirements increase by 150-200% - increase risks of massive die off

Question 5

Drought analysis in trees

Answer 5

Forest die back in Pinon and ponderosa pine and Douglas fir
•tree ring analysis - look back in time and see droughts impacts
•forest drought stress index increases then the greenness of forests declines too
•tree death - bark beetle outbreak (annoying pest)
•risk of forests fires increases - more flammable material

Question 6

Suitability maps

Answer 6

Based on max productivity
Shows areas of suitability for two tree spp in UK which are drastically going to change
-more places becoming less suitable

Question 7

Heat and drought stress vs resilience

Answer 7

•Rook pop declines with higher temp anomalies (heat waves)
-responses predicted based on thermal ranges
-spp in warmer regions = more resilient
•Implies those at poles at risk?
-wild fruit fly showed those in tropics has a smaller range than those at greater latitudes

Question 8

Heat stress and interspecific interactions

Answer 8

Lizard - outside temp impacts body temp, a +3°C rise in body temp no longer at optimum
•adding a closely related lizard spp
•original lizard moves into cooler, more forested/shaded areas where new spp already occurs
•introducing interspecific competition driving potential pop decline due to shifts in habitat use

Question 9

Some spp benefit

Answer 9

•2 spp of birds are limited by colder winters as limits access to food and foraging
-evidence of colder winters limiting survival and pop growth - CC good for them
•Some spp are resilient
-certain vegetation e.g.
-drought impacted plants move into deeper soils for water, but community may reach its limit eventually as soil depth won’t buffer impacts