According to the Food and Agriculture Organization, forests are land of more than 0.5 hectares with trees taller than 5 meters and a canopy cover of 10% and more. Agricultural or urban land with these characteristics are not considered forests (Food and Agriculture Organisation, n.d.). There are different types of forest in this world, characterised by its location at the latitudes. 

The major types of forests include: tropical, temperate, and boreal forests. These major forest types may be further divided into more specific subgroups (UC Berkeley, 1996). 

Tropical 

Tropical forests are found between latitudes 23.5° N and 23.5° S (UC Berkeley, 1996). Temperatures range between 25 to 28 degrees Celsius all year round, with varying amounts of rainfall from one area to another (National Geographic, 2011).  The varying precipitation but stable climatic condition allows different ecosystems to form and hence are able to support a great diversity of living organisms. Optimal humidity, temperature, and rainfall also allow the steady decomposition of organic matter and weathering of soil (Madaan, n.d.). As a result, soils in the Tropics are nutrient-poor as they are prone to leaching (Taylor, 2020). 

Table 1. Subcategories of tropical forest.

Temperate
Temperate forests are usually found in eastern North America, North-Eastern Asia, West and Central Europe. These forests experience winter where there are months without plant growth. There are two subcategories of temperate forests:

Temperate deciduous: This type of forest is mainly found in China, Japan and Canada. They experience four distinct seasons with an annual rainfall of 30 to 60 inches all year round. Precipitation falls as rain in spring, summer and autumn, and snow falls during winter. The climate hence results in extremely fertile soil, supporting biodiversity that are adapted to cold winters (Madaan, n.d.; UC Berkeley, 1996).

Temperate coniferous: Normally found in coastal regions, these forests are characterised by mild winters and high rainfall. They are found mainly in mountainous regions, in countries such as New Zealand, South Japan, South Western and South America. Due to a high annual precipitation rate of about 50 to 200 inches, growing seasons are long and soil has thick layers of decaying matter. The most abundant type of vegetation are the evergreen coniferous trees (Madaan, n.d.; Yale University, n.d.).

Boreal or Taiga 
These forests are located between 50 degrees North and 60 degrees South, situated in places like Siberia, Northern Asia and Scandinavia (65% found here). Characterised by long winters and short summers, they receive 15 to 40 inches or snow annually. The cold temperatures undermine rates of decomposition, hence resulting in thin soil.

The geographical distribution of forests could mean varying effects of pollution, due to the global atmospheric circulation and global ocean circulation – pollution may take different routes to be transported, resulting in differing impacts. This will be further elaborated in future blog posts.

Stay tuned and see you!

References:

Choong, M. F. A. (2020). Primary vegetation [PowerPoint slides]. Unpublished manuscript, GES1021 Natural Heritage of Singapore, National University of Singapore, Singapore

Food and Agriculture Organisation. (n.d.). Comparative framework and Options for harmonization of definitions. Retrieved September 02, 2020, from http://www.fao.org/3/y4171e/y4171e10.htm

Madaan, S. (n. d.). Earth Eclipse: What is a Forest?. https://www.eartheclipse.com/environment/types-of-forests.html

National Geographic Society. (2019, June 21). Distribution of Forests. Retrieved September 02, 2020, from https://www.nationalgeographic.org/encyclopedia/distribution-forests/

National Geographic Society. (2020, February 05). Forest Biome. Retrieved September 02, 2020, from https://www.nationalgeographic.org/encyclopedia/forest-biome/

Taylor, D. (2020). Basic pollution chemistry, and some important pollutant groups [Powerpoint slides]. Unpublished manuscript, GE3246 Environmental Pollution, National University of Singapore, Singapore

UC Berkeley. (1996). University of California Museum of Paleontology. Retrieved September 02, 2020, from https://ucmp.berkeley.edu/exhibits/biomes/forests.php

Yale University. (n.d.). Temperate Zone. Retrieved September 02, 2020, from https://globalforestatlas.yale.edu/temperate-zone