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).
GRASSLANDS
The grasslands of Mission Trails contain a few native grasses such as Purple Needle Grass (Stipa pulchra) and Deer Grass (Muhlenbergia rigens), but most have been replaced by non-native species such as Wild Oats (Avena fatua) and Madrid Brome (Bromus madritensis). Non grass species growing in the grasslands include Blue Dicks (Dichelostemma capitatum), Onions (Allium spp.), Mariposa Lilies (Calochortus splendens), and Blue-Eyed Grasses (Sisyrinchium bellum).
OAK WOODLAND
The oak woodland is dominated by evergreen Coast Live Oak (Quercus agrifolia) and mixes with the coastal sage shrub and chaparral communities. This woodland is found in drier environments including intermittent creeks.
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, Cottonwoods, and Sycamores 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
Mission Trails contains a small area of the freshwater marsh community associated with Kumeyaay (Hollis) lake. The plant species often include
Rushes (Juncus spp.), Cattails (Typha domingensis and Typha latifolia), Sedges (Carex spp.), and California Tule (Schoenoplectus californicus).
VERNAL POOLS
Vernal pools are seasonal wetlands that usually fill with rain water in the winter and spring, hence their name.These pools form when the downward movement of water is hindered by an impervious sub-layer of material. These pools dry out in the summer and early fall months, thus creating a unique community of plants such as San Diego Mesa Mint (Pogogyne abramsii) and aquatic animals that stay dormant in the absence of water. There are very few remaining pools in Mission Trails.
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).
GRASSLANDS
The grasslands of Mission Trails contain a few native grasses such as Purple Needle Grass (Stipa pulchra) and Deer Grass (Muhlenbergia rigens), but most have been replaced by non-native species such as Wild Oats (Avena fatua) and Madrid Brome (Bromus madritensis). Non grass species growing in the grasslands include Blue Dicks (Dichelostemma capitatum), Onions (Allium spp.), Mariposa Lilies (Calochortus splendens), and Blue-Eyed Grasses (Sisyrinchium bellum).
OAK WOODLAND
The oak woodland is dominated by evergreen Coast Live Oak (Quercus agrifolia) and mixes with the coastal sage shrub and chaparral communities. This woodland is found in drier environments including intermittent creeks.
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, Cottonwoods, and Sycamores 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
Mission Trails contains a small area of the freshwater marsh community associated with Kumeyaay (Hollis) lake. The plant species often include
Rushes (Juncus spp.), Cattails (Typha domingensis and Typha latifolia), Sedges (Carex spp.), and California Tule (Schoenoplectus californicus).
VERNAL POOLS
Vernal pools are seasonal wetlands that usually fill with rain water in the winter and spring, hence their name.These pools form when the downward movement of water is hindered by an impervious sub-layer of material. These pools dry out in the summer and early fall months, thus creating a unique community of plants such as San Diego Mesa Mint (Pogogyne abramsii) and aquatic animals that stay dormant in the absence of water. There are very few remaining pools in Mission Trails.