Tropical plants reach peak rates of at higher

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Tropical plants reach peak rates of at higher temperatures than plants from cooler regions - Low temperatures cause slow metabolic activity due to kinetics of enzymes Xerophytes: plants that can survive in dry conditions Mesophytes: moderately moist conditions Hydrophytes: in water or very wet soils Evaporation + transpiration = evapotranspiration - Effective precipitation – the amount of precipitation that is actually stored in the soil - Sunlight radiation and temperature drive transpiration process as well as evaporation of intercepted rainfall - More light at top of canopy = more transpiration than lower canopy Tree water demand: the amount of water a tree needs in order to maintain its metabolism at optimum levels in order to meet its physiological needs Eclrophyllous leaves - Hard evergreen, leathery leaves – designed to reduce moisture loss – thick cuticles - Mediterranean plants Environmental Impacts - Environmental conditions can also influence plant development and ‘enhance’ or ‘decrease’ gene expression in plants - A plant species that has grown near a stream or water body may be less tolerant of drought than a plant of the same species that developed elsewhere Water demand takeaways - Water use by plant species is not straightforward – there are many complex influences to consider - Plant species (genetic predispositions) - Plant maturity - Size relative to other surrounding plants (relation to canopy)
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- Relative humidity - Temperature - Soil type / geology - Soil moisture Acclimation: the physiological “adjustment” within the organisms lifetime in response to eg. Environmental stress/ change - Time scale difference between adaptation and acclimation \ Sun versus shade leaves - More edges on sun leaves - More surface area on shade leaves Forests can be classified based on common biological and ecological characteristics - Deciduous: broad-leaf and flowering forests (angiosperms) - Coniferous: needle-leaf and cone-bearing forests (gymnosperms) Deciduous Forests - Leaves die off seasonally – dormancy during cold seasons is an adaptation Broad- leaves - Better at light interception - Better at exchanging gases - Lots of water needed for transpiration - Better adapted for humid and wet climates - Annual cycles of leaves need lots of nutrients - Harder to be successful in poorer soils Coniferous Forests - Bear cones and evergreen leaves Needle-Leaves - Narrow shape reduces surface area - Waterproof cuticle - Important for groups that are frozen - Fewer stomata that are sunken - Important for drying winds - Can photosynthesize all year long - More resistant to damage and herbivory Generalized Characteristics - Better adaptations for colder climates - Better able to establish in poorer soil quality (moisture and nutrients) - Better adapted for windier environments - More continuous and gradual growth Dominant Tree Species - Severe winter temperatures, short growing seasons, cold soils, permafrost more prevalent as you go north - Best suited to harsh climate, thin and acidic soils - Common Species - Spruce (picea) – black ,white - Tamarack (larix)
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