How Do Latitude & Altitude Affect the Plants That Grow in an Area?

Latitude is the distance on a planet from the equator, north or south. The latitude system is based on 90 degrees with the equator being 0 degrees and the north and south poles being 90 degrees. Further, cartographer's also divide the earth's surface into three areas: the tropics around the equator, the frigid zones near the north and south poles, and the temperate zones between the tropics and the frigid zones. Altitude is the distance from the surface of the Earth. The altitude of a mountain is not measured from the terrestrial surface but instead from the surface of the oceans known as sea level. Plants have adapted to the conditions found at different latitudes and altitudes.

Generally speaking, the greater your latitude the cooler it is. The equator has the hottest areas on Earth because the equator receives the most direct sunlight all year long. Because the Earth is roughly circular, the higher latitudes are further away from the sun and thus don't receive as much sunlight as the equator. In addition, the Earth has an atmosphere that buffers the heat of the sun's rays. Sunlight has to travel further through the atmosphere at the poles than it does at the equator because of the angle of incidence of the curved surface of the earth. Sunlight loses energy bouncing off the molecules in the atmosphere, so it heats the surface of the planet less at the poles than at the equator. With higher temperatures, plants have adapted to using less water during the day or they would wilt in the higher heats. In northern climates, plants have developed strategies to maximize daylight hours for photosynthesis and using nighttime to respire. Photosynthesis, like most chemical processes, advances faster in warmer temperatures so plants have to adapt to reduced growth in colder climates.

Because of the Earth's angle of rotation in respect to the sun, the Earth has seasons. When the northern hemisphere is leaning toward the sun, it's summer here. When the rotation of the Earth moves it so that the southern hemisphere is leaning toward the sun, it's summer in the southern hemisphere. The change of season causes the temperatures further from the equator to change greatly. In some areas, the temperature can reach 100 degrees Fahrenheit in the summer and minus 20 degrees Fahrenheit in the winter. The temperature at the equator also changes during the year because of rainy seasons that cool the land temperatures but not as much as at higher latitudes. Plants have to adapt to these temperature variations. Some plants sleep through the winter, such as deciduous trees that lose their leaves and herbaceous perennials that die back to ground level, while others, such as conifers, reduce their activities but continue to photosynthesize. Some plants have learned to create a bit of antifreeze in their cells to allow them to survive the seasonal temperatures without freezing.

Plants are well adapted for where they live. Plants that live at higher altitudes have to adapt to colder temperatures. Because the summer season at higher altitudes is so short, annuals have a big advantage, growing, flowering and setting seed in a few weeks. Deciduous trees can't survive at high altitudes because the summer is too short to allow them to grow leaves and store enough energy to survive the longer winters.

For plants that live at higher altitudes, preventing water loss is a big challenge. Higher altitudes have lower humidity levels, meaning that water loss is naturally greater and there is less rainfall meaning there is less water available for replacement. In addition, the wind at higher altitudes is a factor. Successful high-altitude plants have developed strategies to help them reduce water loss, such as having a waxy coating on the surface of their leaves, called suberin, and having their stomata in small divots of the leaf's surface to reduce wind damage. Stomata are the pores in the plant's surface that allows it to breathe and transport minerals from the roots to the leaves. Another way to reduce water loss is to stay small. Smaller plants that hug the ground don't suffer from the wind as much. Even the evergreen trees at high altitudes are smaller. Deciduous tree leaves would lose too much water to allow them to survive at the highest altitudes.