Lecture 4 - Forest Ecophysiology Flashcards
What is ecophysiology?
It is the study of functions and activities of organisms in their environment
What is included in forest ecophysiology?
- genetics, pathology, entomology, ecology
- silviculture and the impact of management
- how forests will respond to climate change
First step in understanding forests is to understand how trees “make a living”
How do tree leaves help trees make a living?
The tree leaves are basically solar panels of trees and are responsible for photosynthesis - they take in CO2 from atmosphere, release O2 and H2O by transpiration (which is moderated by stomata)
What does photosynthetic efficiency depend on?
It depends on leaf morphology and leaf orientation in trees (sun vs. shade leaves). Measured by Leaf Area Index (LAI), the leaf surface area per ground unit, and the larger the LAI the greater the rate of photosynthetic activity and greater capacity to sequester carbon.
How do woody structures help trees make a living?
Wood of trees is unique to trees (distinguishes them from other plants) and acts as structural support. It is also a medium between leaves and roots for transportation of H2O and nutrients (xylem - H2O and phloem - nutrients)
What is lignification?
For a plant to become woody due to the deposition of lignin in cell walls.
What is the difference between softwoods and hardwoods?
- Softwoods: are woods of conifers and have honeycomb structures, which allow them to grow faster, but they are less dense, less strong and tend to be lighter in colour
- Hardwoods: are woods of deciduous trees and have a structure that consists of thick-walled fibres, so they tend to be strong, dense and darker in colour
How do roots help trees make a living?
They provide anchorage and nutrients from soil for trees, in which more than half of trees’ biomass is in the roots.
- coarse roots (≥2mm) are structural
- fine roots (<2mm) exchange nutrients with the soil and uptake water, can do so for so long before fine root turnover & are mostly confined to upper 20cm of soil
What is fine root turnover?
It is when the fine roots of a tree fulfill their purpose for so long before dying off and growing new roots while the old ones turn in organic matter and add nutrients to soil.
How does root symbiosis help trees make a living?
A symbiotic relationship b/w:
- tree roots and fungi (mycorrhiza) allows for increased scavenging by roots for nutrients
- roots and N-fixing bacteria gives bacteria resources & home in nodules while it provides NH4+ for trees (N fixing tree species found on nutrient poor sites - ex. alders, black locusts, etc.)
How do flowers, fruits and seeds help trees make a living?
They play an important role in reproduction (sexual is fruit and seeds). The timing of flower/seed production, seed ripening and dispersal influence reproduction & long-term survival. Some trees will rely on pollinators, others will rely on wind pollination, and others will rely on the scattering of seeds through animal defecation, all of which also influences tree reproduction.
Why have trees developed specific strategies to cope with environmental stressors?
B/c they are sessile (can’t move as an individual) so they must cope with stressors
ex. deciduous trees shed leaves
- in north, leaf shedding prevents large buildup of snow on branches
- in south, leaf shedding protects trees in the dry season (lack of water)
How are changing leaf colours a coping mechanism for trees?
- leaves are nutrient-rich and nutrients are retranslocated to roots for winter (initiated by shortening photoperiod)
- the retranslocation breaks down chlorophyll (creates red, yellow and orange) and anthocyanins (creates purple and pink)
How do evergreens deal with cold weather?
Their needles are cold tolerant, which is an adaptation strategy through tissue (needle) dehydration
- ex. red pine can withstand temps of -190°C
What triggers winter dormancy and spring emergence in trees?
- winter dormancy occurs through shortening photoperiod and cold temperatures
- spring emergence occurs through longer photoperiod and warm temperatures (trees require a specific duration of freeze before they respond to spring warming, usually 30-120 days)
