L. 4: Seasonality changes, geography, populations, C. 3-Allen Flashcards
Global hydrological fluxes
Move one thing, everything changes. There will be more RFWR (renewable freshwater resources) available, but uneven distribution in time and space (changes in seasonality and extreme events) (snowmelt dominated regions).
projected changes
Global average temperature up.
Global average sea level up.
Northern hemisphere snow cover down.
Precipitation up in Arctic high latitude areas, moist tropics.
anthropogenic change to land surface
Lower surface albedo.
Forest mortality will release carbon–vegetation feedback.
Role of forests
Provide ecological, economic and social services to natural systems and populations (e.g., biodiversity refuge, food, medicine, regulate hydrological cycle, forest products).
Exchange energy, water, CO2 with atmosphere. Store 45% terrestrial carbon, but low albedo, so positive feedback to warming. But hydrological cycle, ET cooling enhances clouds and precipitation, negative feedback to warming.
Source or sink of carbon?
role of tropical forest
Evaporative cooling, mitigates warming.
role of boreal forest
Low albedo, enhanced warming in Arctic.
role of temperate forest
unknown
increment borer
Used in dendrochronological field work
divergence problem
TRWs (tree ring width chronology) match/ correlate with climate and summer temperature for first half of 20th century, but not from 1950 on. Density is better with correlation (tree rings wider).
Arctic response
Tundra is greening, boreal areas are browning. Area is becoming source of carbon rather than sink because of changes in albedo, melting permafrost (more water).
Effect of climate change on ecotones (Allen)
Response of vegetation is expected to be the most extreme and rapid in ecotones, especially semi arid ones, with higher tree mortality and slower growth from drought, which also made them more vulnerable to competition for water from shrubs and bark beetle infestation.
