As we have parceled, subdivided, and cleared the land, we have interrupted or destroyed the horizontal connectivity of plant communities. When we do this, we cut off vital links used by wildlife and plants to move freely across the landscape. In effect, we create islands, isolated fragments of vegetation surrounded by cities, suburbs, and farm fields. The health of the plant community, both locally and globally, depends on the connections we have severed. In isolated pockets, plants and animals interbreed, reducing genetic diversity and endangering their survival over the long haul.
Isolated patches are also more vulnerable to destruction by pests and diseases.
Once plants are eliminated, the island cannot be re-colonized by many species, and the diversity of plant life is reduced forever. As gardeners, we have the ability to repair these broken connections. Our gardens, one by one, can re-establish links to parks, nature preserves and other green spaces, and restore the health of the environment. Horizontal Structure Light, moisture, slope, and soil have a direct effect on where a plant or group of plants grow in a forest, grassland, desert, or other plant community. Plants form horizontal patterns of distribution in response to these environmental and edaphic, or soil-related, factors, better known to gardeners as microclimates .