Biomes Of The World

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             VEGETATION. Vegetation patterns are responsive to the interaction of temperature (latitudinal and altitudinal gradients) and precipitation (more complex, often longitudinal gradients because of the east-west tendency of the winds, as well as well-defined latitudinal ones) patterns. The degree of seasonality also has a major effect. The earth's surface is forested with trees except where too cold, too dry, or too wet. Herbaceous vegetation is dominant nearer extremes, with no vegetation at all at the coldest and driest extremes. .
             Vegetation is the sum of its parts, the parts being individual plants of individual species, and the species present and their relative proportions are important descriptive components of it. Descriptions of vegetation take into account plant species and their abundance and size distribution, life forms (trees, shrubs, herbs, bryoids, epiphytes, lianas), seasonal functions (evergreen vs. deciduous), and leaf shapes, sizes, and textures. .
             DIVERSITY. There are two major components of diversity: within-habitat (diversity may vary greatly between two forest types, for example) and between-habitat (this covers diversity for an entire area, thus also dependent on the diversity of habitats present). Within-habitat diversity is highest in forests of the equatorial lowlands, and lower with increased latitude, altitude, seasonal variation in climate, simplicity of vegetation, and any environmental extreme, to very low near poles and on high mountains. There are similar latitudinal gradients in fresh and salt water, also decreased aquatic diversity with depth and chemical extremes. There is also lowered diversity on peninsulas and islands because of problems of historical access. .
             PLANT ADAPTATIONS. The basic needs of plants are homeostasis, space, food, predator avoidance, and reproduction. There is no locomotion, thus plants are subject to vicissitudes of the environment, so they are often narrowly restricted to particular combinations of temperature, humidity, salinity, soil water, and chemistry (where homeostasis is thus assured).