PLANT COMMUNITIES
The vegetation of San Diego is categorized into plant communities. Each community contains specific plants adapted to the physical, chemical and biological parameters of their microenvironments. Specific parameters include temperature, solar radiation, wind exposure, soil composition, salinity, moisture and types of interacting organisms present. The boundaries between plant communities are not distinct but overlap into neighboring communities. An example is the intermingling of plants from the coastal sage scrub and chaparral communities.
COASTAL SAGE SCRUB
The coastal sage scrub plant community is scattered on coastal hills and slopes and extends inland to those regions subjected to maritime moisture. This vegetation is frequently found growing in shallow sandy to rocky soils and on South facing slopes exposed to solar desiccation. These microenvironments tend to contain less seasonal moisture available then that of the neighboring chaparral community. However, these two communities frequently intermingle in the same locality and coastal sage scrub plants may be pre-climatic to chaparral plants.
Coastal sage scrub plants are typically low growing, non-sclerophyllous shrubs with many brittle branches and are sometimes referred to as soft chaparral. The roots of these plants exploit the upper soil layers for moisture allowing for rapid growth after winter rainfall. Their growing season is usually longer than typical chaparral plants. Some species survive the dry summers and autumns by utilizing water from their succulent vegetation or by dropping their water demanding leaves. At this time these deciduous plants may appear as dried dead bundles only to spring back to life with their green foliage during the rainy season.
The dominant shrubs in this community are California Sagebrush (Artemisia californica), California Buckwheat (Eriogonum fasciculatum), Black Sage (Salvia mellifera), Deerweed (Acmispon glaber), Bush Sunflower (Encelia californica), Lemmonadeberry (Rhus integrifolia), Live Forevers (Dudleya spp.), Coastal Prickly Pear (Opuntia littoralis), Coast Barrel Cactus (Ferocactus viridescens), and Bladderpod (Peritoma arborea).
CHAPARRAL
The chaparral plant community normally inhabits the mesas and mountain slopes of the interior but also intermingles with the coastal sage scrub community along the coast particularly on mesas and north facing slopes where moisture is more plentiful. This community is composed of mainly sclerophyllous shrubs with distinctive small, thick, evergreen leaves which persist on the shrub for two to three years. Chaparral sometimes forms an impenetrable thicket of vegetation with a large canopy five to fifteen feet high. This elfin forest lacks herbaceous understudy and is a haven for fauna and adventurous children who love to explore.
Chaparral is both drought and fire adapted. The shrubs survive the hot summer droughts by utilizing extensive root systems for gathering water and having small leaves which reduces overheating. Some chaparral species have a waxy coating on their leaves which reduces water loss through evaporation. The chaparral community is also interwoven with fire for a natural and healthy burn cycle between ten and forty years. Old unburned strands of chaparral are unhealthy and senile with low species diversity, low annual growth and the accumulation of deadwood. Senility in part is achieved by plant toxin accumulation, poor soil structure and low amounts of solar radiation. This latter aspect is due to the large canopies which prevent light from reaching the lower portions of this community. Old strands of chaparral also contain a higher potential of fuel in the deadwood which contributes to extremely hot and uncontrollable fires which dot Southern California. These fires are more abundant during the Santa Ana winds.
Fires though hazardous to human lifestyles and structures are beneficial for the chaparral. These fires modify the plant community by increasing light exposure and by recycling nutrients to the soil. The post burn environment lends itself to the quick replacement of this important watershed through the germination of herbaceous plants and by the gradual recovery of the shrubs. Shrubs are adapted to fire and recover because some species have subsurface crowns which resprout or have seeds whose germination is enhanced by the heat of the fire. The floristic pattern of species changes in the years after a fire with the young stages being dominated by herbaceous plants and in some instances pioneer coastal sage scrub plants. These early stages are soon out competed by the climax chaparral shrubs.
The major shrubs of the chaparral are Chamise (Adenostoma fasciculatum), Zaca's Manzanita (Arctostaphylos glandulosa), Shrub Oaks (Quercus dumosa and Quercus berberidifolia), Ceanothus (Ceanothus tomentosus), Toyon (Heteromeles arbutifolia), and Mountain Mahogany (Cercocarpus minutifolus).
TORREY PINE WOODLAND
The Torrey Pine, Pinus torreyana, is the most restricted and rarest pine in North America and it grows in the Torrey Pine woodland or Pacific coniferous forest. This pine is probably the remnant of an ancient coastal forest which has been reduced during the drying period of the last ten thousand years to the sandy soils of the sandstone bluffs and ravines of Torrey Pines State Reserve and Santa Rosa Island. Extensive root systems and blankets of summer fog aid in the tree's survival and propagation. The trees along the bluff are twisted and gnarled into spectacular shapes by the omnipresent winds while those sheltered are more robust and erect.
The vegetation associated with the Torrey Pine woodland are a mixture of plants from the coastal sage scrub and chaparral plant communities. Further studies need to be undertaken to examine the woodland microclimate for plants normally absent from the previous two plant communities.
COASTAL STRAND
The sandy beaches and sand dunes of the coastal strand plant community encounter the edge of the sea. This arrangement creates a harsh environment for plant growth and survival because of persistent winds laden with salt and sand. The forever shifting sands with their poor water-holding ability and low fertility also stress plants. The few species adapted to this region are usually prostrate and have creeping stems which can root at their nodes. These features aid in anchoring the plant with its continuous lateral growth into large colonies. Some plant species contain deep tap roots, which serve the dual purpose of anchoring the plant to the soil and in acquiring water. The presence of pubescent or fuzzy leaves on some species serves as a surface for water condensation, which nourishes the plant and reduces water loss by lowering the effects of evaporation. Water is also stored in the succulent leaves and stems of some plants. The major species in this plant community are Sand Verbena (Abronia umbellata); Beach Primrose (Camissoniopsis cheiranthifolia subsp. suffruticosa); and Sea Rocket (Cakile maritima).
GRASSLANDS
The grasslands of Mission Trails contain a few native grasses, but most have been replaced by non-native species. Non grass species growing in the grasslands include Blue Dicks (Dichelostemma capitatum), Onions (Allium spp.), Mariposa Lilies (Calochortus splendens), and Blue-Eyed Grass (Sisyrinchium bellum).
SALT MARSH
This community covers a relatively small area of the coast and is centered around sloughs, lagoons, estuaries and bays. These areas are generally rich in nutrients but are subjected to fluctuations in acidity, exposure, oxygen concentrations and salinity. Salt marsh plants succeed in this environment, where most others cannot compete, because they have adapted to these extreme and variable conditions. Salinity fluctuations occur due to the degree of tidal flushing, if any, the rate of evaporation and the amount of fresh water obtained from rain or runoff from the neighboring hills and mesas. Salt marsh plants are adapted to this saline environment by excreting their excess salt of by storing large amount of water for dilution. Some salt marsh plants tolerate water saturated soils, which are frequently poor of oxygen, by having an oxygen transport system between their leaves and roots or by storing oxygen in large chambers in their roots.
These environmental conditions vary as the marsh transforms into the upland plant communities. Thus, a vertical pattern of plant distribution occurs with different species being abundant in the different zones.
The salt marsh is a highly productive ecosystem making it an extremely important wildlife habitat. It serves as a nursery for fish and shellfish and a feeding and nesting ground for resident and migratory birds.
The common species include Salt Grass (Distichlis spicata), Pacific Pickleweed (Salicornia pacifica), Glasswort (Arthrocnemum subterminale), Alkali Heath (Frankenia grandifolia), and various Saltbushes (Atriplex spp.).
RIPARIAN WOODLAND
The riparian plant community is the wetlands associated with river basins and lake shorelines that include the perennial San Diego River, and the intermittant Oak and Spring Canyon creeks. The deciduous trees of Willows and Cottonwoods grow in this moist environment along with Mule Fat (Baccharis salicifolia). This community plays an important habitat for other plant and animal species.
FRESHWATER MARSH
Torrey Pines contains an area of the freshwater marsh community that is fed by Penasquitos and Carmel creeks.. The plant species often include Rushes (Juncus spp.), Cattails (Typha domingensis and Typha latifolia), Sedges (Carex spp.), and California Tules (Schoenoplectus californicus).
The vegetation of San Diego is categorized into plant communities. Each community contains specific plants adapted to the physical, chemical and biological parameters of their microenvironments. Specific parameters include temperature, solar radiation, wind exposure, soil composition, salinity, moisture and types of interacting organisms present. The boundaries between plant communities are not distinct but overlap into neighboring communities. An example is the intermingling of plants from the coastal sage scrub and chaparral communities.
COASTAL SAGE SCRUB
The coastal sage scrub plant community is scattered on coastal hills and slopes and extends inland to those regions subjected to maritime moisture. This vegetation is frequently found growing in shallow sandy to rocky soils and on South facing slopes exposed to solar desiccation. These microenvironments tend to contain less seasonal moisture available then that of the neighboring chaparral community. However, these two communities frequently intermingle in the same locality and coastal sage scrub plants may be pre-climatic to chaparral plants.
Coastal sage scrub plants are typically low growing, non-sclerophyllous shrubs with many brittle branches and are sometimes referred to as soft chaparral. The roots of these plants exploit the upper soil layers for moisture allowing for rapid growth after winter rainfall. Their growing season is usually longer than typical chaparral plants. Some species survive the dry summers and autumns by utilizing water from their succulent vegetation or by dropping their water demanding leaves. At this time these deciduous plants may appear as dried dead bundles only to spring back to life with their green foliage during the rainy season.
The dominant shrubs in this community are California Sagebrush (Artemisia californica), California Buckwheat (Eriogonum fasciculatum), Black Sage (Salvia mellifera), Deerweed (Acmispon glaber), Bush Sunflower (Encelia californica), Lemmonadeberry (Rhus integrifolia), Live Forevers (Dudleya spp.), Coastal Prickly Pear (Opuntia littoralis), Coast Barrel Cactus (Ferocactus viridescens), and Bladderpod (Peritoma arborea).
CHAPARRAL
The chaparral plant community normally inhabits the mesas and mountain slopes of the interior but also intermingles with the coastal sage scrub community along the coast particularly on mesas and north facing slopes where moisture is more plentiful. This community is composed of mainly sclerophyllous shrubs with distinctive small, thick, evergreen leaves which persist on the shrub for two to three years. Chaparral sometimes forms an impenetrable thicket of vegetation with a large canopy five to fifteen feet high. This elfin forest lacks herbaceous understudy and is a haven for fauna and adventurous children who love to explore.
Chaparral is both drought and fire adapted. The shrubs survive the hot summer droughts by utilizing extensive root systems for gathering water and having small leaves which reduces overheating. Some chaparral species have a waxy coating on their leaves which reduces water loss through evaporation. The chaparral community is also interwoven with fire for a natural and healthy burn cycle between ten and forty years. Old unburned strands of chaparral are unhealthy and senile with low species diversity, low annual growth and the accumulation of deadwood. Senility in part is achieved by plant toxin accumulation, poor soil structure and low amounts of solar radiation. This latter aspect is due to the large canopies which prevent light from reaching the lower portions of this community. Old strands of chaparral also contain a higher potential of fuel in the deadwood which contributes to extremely hot and uncontrollable fires which dot Southern California. These fires are more abundant during the Santa Ana winds.
Fires though hazardous to human lifestyles and structures are beneficial for the chaparral. These fires modify the plant community by increasing light exposure and by recycling nutrients to the soil. The post burn environment lends itself to the quick replacement of this important watershed through the germination of herbaceous plants and by the gradual recovery of the shrubs. Shrubs are adapted to fire and recover because some species have subsurface crowns which resprout or have seeds whose germination is enhanced by the heat of the fire. The floristic pattern of species changes in the years after a fire with the young stages being dominated by herbaceous plants and in some instances pioneer coastal sage scrub plants. These early stages are soon out competed by the climax chaparral shrubs.
The major shrubs of the chaparral are Chamise (Adenostoma fasciculatum), Zaca's Manzanita (Arctostaphylos glandulosa), Shrub Oaks (Quercus dumosa and Quercus berberidifolia), Ceanothus (Ceanothus tomentosus), Toyon (Heteromeles arbutifolia), and Mountain Mahogany (Cercocarpus minutifolus).
TORREY PINE WOODLAND
The Torrey Pine, Pinus torreyana, is the most restricted and rarest pine in North America and it grows in the Torrey Pine woodland or Pacific coniferous forest. This pine is probably the remnant of an ancient coastal forest which has been reduced during the drying period of the last ten thousand years to the sandy soils of the sandstone bluffs and ravines of Torrey Pines State Reserve and Santa Rosa Island. Extensive root systems and blankets of summer fog aid in the tree's survival and propagation. The trees along the bluff are twisted and gnarled into spectacular shapes by the omnipresent winds while those sheltered are more robust and erect.
The vegetation associated with the Torrey Pine woodland are a mixture of plants from the coastal sage scrub and chaparral plant communities. Further studies need to be undertaken to examine the woodland microclimate for plants normally absent from the previous two plant communities.
COASTAL STRAND
The sandy beaches and sand dunes of the coastal strand plant community encounter the edge of the sea. This arrangement creates a harsh environment for plant growth and survival because of persistent winds laden with salt and sand. The forever shifting sands with their poor water-holding ability and low fertility also stress plants. The few species adapted to this region are usually prostrate and have creeping stems which can root at their nodes. These features aid in anchoring the plant with its continuous lateral growth into large colonies. Some plant species contain deep tap roots, which serve the dual purpose of anchoring the plant to the soil and in acquiring water. The presence of pubescent or fuzzy leaves on some species serves as a surface for water condensation, which nourishes the plant and reduces water loss by lowering the effects of evaporation. Water is also stored in the succulent leaves and stems of some plants. The major species in this plant community are Sand Verbena (Abronia umbellata); Beach Primrose (Camissoniopsis cheiranthifolia subsp. suffruticosa); and Sea Rocket (Cakile maritima).
GRASSLANDS
The grasslands of Mission Trails contain a few native grasses, but most have been replaced by non-native species. Non grass species growing in the grasslands include Blue Dicks (Dichelostemma capitatum), Onions (Allium spp.), Mariposa Lilies (Calochortus splendens), and Blue-Eyed Grass (Sisyrinchium bellum).
SALT MARSH
This community covers a relatively small area of the coast and is centered around sloughs, lagoons, estuaries and bays. These areas are generally rich in nutrients but are subjected to fluctuations in acidity, exposure, oxygen concentrations and salinity. Salt marsh plants succeed in this environment, where most others cannot compete, because they have adapted to these extreme and variable conditions. Salinity fluctuations occur due to the degree of tidal flushing, if any, the rate of evaporation and the amount of fresh water obtained from rain or runoff from the neighboring hills and mesas. Salt marsh plants are adapted to this saline environment by excreting their excess salt of by storing large amount of water for dilution. Some salt marsh plants tolerate water saturated soils, which are frequently poor of oxygen, by having an oxygen transport system between their leaves and roots or by storing oxygen in large chambers in their roots.
These environmental conditions vary as the marsh transforms into the upland plant communities. Thus, a vertical pattern of plant distribution occurs with different species being abundant in the different zones.
The salt marsh is a highly productive ecosystem making it an extremely important wildlife habitat. It serves as a nursery for fish and shellfish and a feeding and nesting ground for resident and migratory birds.
The common species include Salt Grass (Distichlis spicata), Pacific Pickleweed (Salicornia pacifica), Glasswort (Arthrocnemum subterminale), Alkali Heath (Frankenia grandifolia), and various Saltbushes (Atriplex spp.).
RIPARIAN WOODLAND
The riparian plant community is the wetlands associated with river basins and lake shorelines that include the perennial San Diego River, and the intermittant Oak and Spring Canyon creeks. The deciduous trees of Willows and Cottonwoods grow in this moist environment along with Mule Fat (Baccharis salicifolia). This community plays an important habitat for other plant and animal species.
FRESHWATER MARSH
Torrey Pines contains an area of the freshwater marsh community that is fed by Penasquitos and Carmel creeks.. The plant species often include Rushes (Juncus spp.), Cattails (Typha domingensis and Typha latifolia), Sedges (Carex spp.), and California Tules (Schoenoplectus californicus).