• Pacific Grove’s Forests: Undergoing natural plant succession from Monterey Pines to Coast Live Oaks

    By Bruce Cowan

    The Monterey pine forest is a changing entity. In the Huckleberry Hill area of the Del Monte forest and at Jacks Peak, Monterey pines dominate, with various understories including native grasses and chaparral. While Monterey pine is somewhat a fire dependent species, in areas of the comparatively sparse native grasses the pines are reproducing well even without fire—in fact in some places they are becoming very overcrowded. Where shrubby understory is naturally dense, fewer pine seedlings can grow until a fire clears the understory, whereas in native grass cover pine seedlings can come up whenever there is adequate rainfall.

    In some areas of Pacific Grove, especially Washington Park and Rip Van Winkle Open Space, there is another factor: coast live oaks which replace pines in a process called natural plant succession.

    Most of the Pacific Grove forest burned in the early 20th century, and pines quickly sprang up all over PG’s forest. Most of these pines are old and declining now, as their normal life span is 80 to 100 years.

    Where soil is fairly good, coast live oaks thrive. As oaks grow they become what is called the “climax species”, dominating the forest until, say, another major fire occurs. This is because pines cannot grow well in the shade of oaks, while oaks can do fine under pines. Oaks live 200 to 30 years. Most of Pacific Grove’s natural forested areas are on the way to becoming a native oak forest. More young oaks would be visible, except the presently high population of deer in PG keeps them suppressed.

    Overall the Monterey pines in Pacific Grove are declining from overage, windthrow and pitch canker. Eventually we will have mainly an oak forest.

    How does one define
    a healthy forest?

    One way to tell if a forest is healthy and capable of self-regeneration is to look at the understory. Washington Park is an example of a forest that is largely unhealthy because, aside from native poison oak, blackberry and wood mint, the understory is mostly invasive non native weeds including rattlesnake grass, ryegrass, ripgut grass, foxtail grass, yellow oxalis and newcomer called panic veldt grass. Pine and oak seedlings cannot compete with these weeds, so reforestation must include planting, or spreading of wood chips to suppress the weeds. This is also true within Monarch Sanctuary, which has very little native understory.

    By contrast, while Rip Van Winkle Open Space (Dog Park) has some problems with invasive plants, including French broom and pampas grass which are undergoing eradication efforts, and weedy non-native grasses mostly around the edges, on the whole the understory in Rip Van Winkle is fairly healthy and consists mostly of native plants. In addition to poison oak and blackberry, these include creeping snowberry, wood mint, wild iris, a few huckleberry, several kinds of native grasses, bracken fern, yerba buena and sticky monkey flower. Most of these, aside from poison oak and blackberry, survive only in relatively undisturbed areas of a forest. In some parts of Rip Van Winkle forest no weeds can be seen at all—only native plants. On the downside, some areas near the main entrance have been trampled so almost no vegetation exists.

    Rattlesnake grass and other weedy annual grasses and weeds are not good in a forest because they increase fire hazard as they dry, and often must be mowed. They also out-compete most native groundcovers and tree seedlings. Mowing scatters the rattlesnake and other weedy grass seeds further, so eventually the result is a stand of mature trees and a mowed weedy understory—not a real forest in the ecological sense.

    This story is a portion of an article written for a committee working on the problem of parking at Rip Van Winkle Open Space

    posted to Cedar Street Times on February 27, 2009

    Topics: Current Edition, Green


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