Geophysical factors of the upper forest line on the equatorial and tropical islands of the Pacific and Indian oceans
Abstract
Joint effect of altitude, island area and atmospheric circulation for the altitudinal position of the forest belt is described basing on publications and materials of six voyages to the tropical islands of the Pacific and Indian oceans. Two landscape types prevail above the foggy forest zone, i.e. fern-wet-meadow on the slopes facing the trade winds and dry shrublands, analogues of subtropical maquis, above the upper limit of trade winds or on the leeward slopes. In the former case the upper forest line depends on the permanently high relative humidity, up to 95–100%. A logarithmic dependence of the upper forest line altitude on the island area has been revealed. The island area determines the degree of transformation of marine air masses entering the islands. Specific heat capacity of the island surface is 4–5 times lower than that of water; in the daytime a greater share of energy is consumed for turbulent heat exchange with the atmosphere as compared to water. Therefore, the level of moisture condensation on small islands is lower than on larger ones, and the process of photosynthesis in trees is either inhibited or absent.
About the Author
K. N. Dyakonov
Lomonosov Moscow State University
Russian Federation
Russian Federation
Faculty of Geography, Department of Physical Geography and Landscape Science, Head of the Department, Professor, Corresponding member of the RAS
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Review
For citations:
Dyakonov K.N. Geophysical factors of the upper forest line on the equatorial and tropical islands of the Pacific and Indian oceans. Vestnik Moskovskogo universiteta. Seriya 5, Geografiya. 2020;(6):3-9. (In Russ.)
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