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In physical geography, tundra (/ ˈ t ʌ n d r ə, ˈ t ʊ n-/) is a type of biome where tree growth is hindered by frigid temperatures and short growing seasons. There are three regions and associated types of tundra: Arctic tundra, [ 2 ] alpine tundra , [ 2 ] and Antarctic tundra.
Many desert ecosystems are limited by available water levels, rather than rates of radiation or temperature. Water flow in these ecosystems can be thought of as similar to energy flow; in fact, it is often useful to look at water and energy flow together when studying desert ecosystems and ecology. [3]
Terrestrial ecosystems occupy 55,660,000 mi 2 (144,150,000 km 2), or 28.26% of Earth's surface. [5] Major plant taxa in terrestrial ecosystems are members of the division Magnoliophyta (flowering plants), of which there are about 275,000 species, and the division Pinophyta (conifers), of which there are about 500 species.
Fungi are also very common in rainforest areas as they can feed on the decomposing remains of plants and animals. The great diversity in rainforest species is in large part the result of diverse and numerous physical refuges , [ 25 ] i.e. places in which plants are inaccessible to many herbivores, or in which animals can hide from predators.
Deserts and xeric (Ancient Greek ξηρός xērós 'dry') shrublands form the largest terrestrial biome, covering 19% of Earth's land surface area. [2] Ecoregions in this habitat type vary greatly in the amount of annual rainfall they receive, usually less than 250 millimetres (10 in) annually except in the margins.
Rainforests are home to half of all the living animal and plant species on the planet. [7] Two-thirds of all flowering plants can be found in rainforests. [5] A single hectare of rainforest may contain 42,000 different species of insect, up to 807 trees of 313 species and 1,500 species of higher plants. [5]
Ecological pyramids begin with producers on the bottom (such as plants) and proceed through the various trophic levels (such as herbivores that eat plants, then carnivores that eat flesh, then omnivores that eat both plants and flesh, and so on). The highest level is the top of the food chain. Biomass can be measured by a bomb calorimeter.
The adversity of soil and climatic conditions proves to low production levels, as well as little biomass accumulation due to slow rates of nutrient release in cold and wet soils, specifically as a result of limited nitrogen and phosphorus (Nadelhoffer et al. 1996) Additionally, there are low temperatures and strong winds in the tundra causing most vegetation to be dominated by woody plants ...