What Is a Plant Community?
Even a brief examination of the overall landscape of Point Lobos will show that the plant species occur in aggregations which are called plant communities. Standing at one bend on the Cypress Grove trail, one can look to the left and see the cypress forest; straight ahead, a small meadow area; and to the right, an area of dense shrub growth growing right up to the edge of the pine forest. Each of these groups of plants is a relatively distinct grouping of plant species. Each community exists where it does as a result of complex interactions among a number of factors: climate, soils, topography, biota, fire, man
A plant community can be defined as an assemblage of plant species which interact among themselves and with their environment within a time-space boundary. The spatial boundaries of plant communities, called ecotones, can be gradual or abrupt. These are biologically the most productive areas: animals may find shelter in one area and more abundant food in another. Plant communities are often named for the dominant species of the community. A species may be dominant either by its physical size, such as the Monterey Cypress forest, or by its numerical dominance. Not all communities have one species which is dominant; these are named for physical or generic characteristics, such as grasslands or scrub, or by habitat, such as coastal bluff communities.
A classic plant community structure can be best seen here in the Monterey Pine forest: a tree species dominating the community by its sheer size, the quantity of nutrients its roots absorb and by the needle or leaf litter dropped; a shrub layer of Ceanothus, Coffeeberry and Poison Oak, and an understory of low-growing plants such as the Wood-mint and Douglas Iris.
Poison Oak in Green and Red Stages
Not all plant communities follow this structure. The Northern Coastal Scrub community consists mainly of shrub species growing tightly together with a weakly developed understory. Grassland communities generally consist only of grasses and very low-growing herbaceous plants. A careful look at the soils, fog patterns, exposure to salt spray or slope characteristics can give a clue to the differences in the growing conditions in each location.
In addition to the mechanical action of the waves, variations in salinity, and substrate (rock or sand), tidal action strongly affects the distribution of the intertidal marine vegetation. Two high and two low tides of unequal height occur along this coast every 25 hours. During extreme tides, minus tides may occur to -2 feet, plus tides to +7 feet, creating a 9 foot intertidal zone. Being covered and uncovered by salt water, then being exposed to the air for extended periods of time has a profound effect on the marine vegetation and the animals which live in it. The durations of inundation and exposure define the plant species which can survive in a given location.
The greatest diversity of marine life occurs on rocky substrate. Kelp, a Brown Alga, grows from a hold-fast on the rocks. This is not a root system, merely a support. The Giant Kelp and Bull Kelp break off during winter storms and regrow from the hold-fast each year. Giant Kelp can grow as rapidly as one foot per day during the summer months.
Plants found in Zone 1: Spray zone to wet at high tide:
Blue-green Algae (Cyanoactria), Green Film Alga (Enteromorpha)
Plants found in Zone 11: Wet twice each day:
Nail-brush Alga (Endociadia muricta), Rock Weed (Fucus gardneri), Turkish Towel (Mastocarpus papillatus), Rock Weed (Pelvetiopsis and Pelvetia silvetia), Ruffled Purple Rockweed (Porphyra perforata).