phenology, productivity, and climate (terrestrial lecture 5)

Question 1

What is phenology?

What does it affect?

Answer 1

Phenology is the study of timing of recurring natural phenomena, especially in relation to climate

Affects nearly all aspects of environment, including:

• abundance, distribution and diversity of organisms
• ecosystem functioning or services
• trophic interactions and food webs
• global cycles of water, nutrients and carbon

Question 2

How does phenology constrain growing season length?

GSL of tropical forest, boreal forest and arctic tundra?

Answer 2

• the time spent growing is roughly the same as the time spent sequestering C
• GSL linked to ecosystem C uptake
• GSL influences feedback to climate
• GSL influenced by climate

GSL:
Tropical forest - 365 days
Boreal forest - 150 days
Arctic Tundra - 100 days

Question 3

How have growing season lengths changed?

Answer 3

-GSL has been increasing by 0.22–0.34 days yr-1
(global average) since 1982
- increase of 30 days between 1982 and 2012

30% trends in boreal/alpine biome in the northern hemisphere

Question 4

How are non native trees influencing phenology?

Answer 4

understorey species in eastern USA deciduous forests:
- no consistent effect on spring phenology, extended autumn phenology by 4 weeks compared to natives (Fridley, 2012)

leaf chlorophyll ~ photosynethesis capacity
- leaf chlorophyll same in spring, but retained longer in autumn by non-natives

• most species do most of photosynthesis in spring before canopies close, natives a bit better at this
• when tree canopy lost in autumn, non-natives gain C from photosynthesis, natives gain almost none. important growth period for non natives

Question 5

Phenology across trophic levels:

Thackery et al., 2016:

Answer 5

Differences in phenological responses can desynchronise interactions - e.g. pollinator & flowering phenology getting out of sync

Climate Sensitivity Profile approach applied (includes temp and precip) to >10,000 species:

• sensitivity = shift in phenology
  (days) per degree Celsius or mm precipitation change
• primary producers most responsive, then primary consumers, then secondary consumers

Question 6

How will UK phenology change by 2050?

Answer 6

• uk to get warmer and drier
• all shifts predicted to be an
  earlier phenology
• different phenologies cause problems for trophic interactions e.g. mismatch between food availability and breeding seasons

Question 7

Phenology in high latitude ecosystems:

GSL?
Bud bursts?

Answer 7

GSL is short, as little as 6 weeks in high arctic, but increasing according to normalised difference vegetation index (NVDI) w season starting earlier & ending delayed. This is a good proxy for greater productivity.

Buds burst soon after (or during) snow melt to maximise GSL

• five days at 5oC can stimulate bud burst downy birch (sub Arctic Finland)
• springs earlier and autumns later