describe how trees impact on climate condition and rainfall over the region?
Answers
1. Carbon
Carbon dioxide (CO2) in the atmosphere is a greenhouse gas. All plants take in CO2 when they photosynthesize, fixing it into sugar and ultimately into the plant tissue itself. At the same time, soils release CO2 through decomposition and plants respire it in order to maintain tissues. The two numbers – CO2 leaving the atmosphere through photosynthesis and CO2 entering it through respiration – are both large and close in magnitude, with slightly more leaving the air than entering. Changes in this delicate balance are one way that the land surface influences global temperature. Planting new trees tips the balance further toward carbon going into the land, at least for a while. When the forest matures, growth and decomposition come back into balance.
CO2 gets mixed quickly by the atmosphere. So after 1-2 years, a release or uptake of CO2 anywhere affects CO2 everywhere. Right now, plants on average take C02 out of the air (helping keep Earth cool), and it doesn’t really matter where those plants live.
2. Energy
Energy is received by the Earth’s surface directly from the sun and also via long-wave radiation from the atmosphere. The land surface has to balance this incoming energy by radiating energy away and through evaporation and conduction of heat. The hotter the surface, the more it radiates and conducts. So if there is a change in evaporation or in the incoming energy, the only way for the surface to balance the budget is to change temperature. There are three main ways that plants influence the amount and type of energy exchanged between the land and the atmosphere:
Albedo, or plant color:
Plants have different colors, which cause them to absorb different amounts of energy from the sun (the term “albedo” refers to the fraction of light reflected, i.e. how “shiny” something is). In general, trees are darker than grasses, which are darker than bare soil. If we start growing trees where there was once grass or bare ground, the surface will absorb more incoming energy from the sun. **All else being equal**, the surface would have a higher temperature.
Water fluxes:
Plants also release water through their leaves (called transpiration) while photosynthesizing. Just as your skin cools when your sweat evaporates, transpiration cools leaves. The amount a plant transpires is directly related to how much it photosynthesizes. Plants that photosynthesize a lot also pump out a lot of water, and with it a lot of energy. If we replace less productive plants or bare soil with highly productive plants, **all else being equal**, the surface will have a cooler temperature.
Surface roughness:
Trees and plants affect how ‘rough’ the surface feels to the winds. The rougher the surface, the more it slows the winds down, and so trees in particular can affect near surface winds, and this affect leads to a small differences in local stability which can have varying (but small) impacts on fluxes of water and energy from the land surface