Biogeography, Landforms, & Water

Plant Adaptations:

Los Angeles has a Mediterranean climate, which can be characterized as having mild, wet winters and hot, dry summers. The plants in this region possess the following adaptations: an increased resistances to periods of droughts with deep root systems to access underground water, and seasonal growth patterns which take advantage of the winter period for more growth and the summer period for conserving resources (1).

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Animal Adaptations:

Some of the animal adaptations include: having a nocturnal behavior especially during the hotter months which allows them to find food when the temperatures are cooler, and seasonal migration for certain birds and animals to find more suitable habitats when the temperatures change. (2)

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Biomes and Ecoregions:

The primary biome in Los Angeles is the Mediterranean biome. Some of the ecoregions found include:

The California Coastal Sage and Chaparral which has coastal sage scrub and chaparral vegetation
The Southern California Mountains and Valleys which has diverse habitats from the oak woodlands to coniferous forests at the higher elevations
The Southern California Coastal which includes sandy beaches, estuaries and tide pools (3)

Influence of Topography:

The presence of mountains creates elevation gradients which results in changes to temperature, precipitation and vegetation. This influences the distribution of various species to their specific altitudes. (4) The coastal areas also influence the climate and they often experience cooler temperatures which impact specific types of plants and animals who thrive in these environments. The presence of valleys and plains also provide habitats for species who have adapted to warmer and drier conditions. The Riparian zones, created by rivers and streams, support species who are adapted to more wet conditions.

Factors Influencing Vegetation and Wildlife:

Some of the factors which influence vegetation and wildlife in Los Angeles include:

The topography: including mountains, valleys and coastal regions which create different climates and habitats.
The availability of water and Riparian zones which provide habitats for several species of plants and animals.
Fire regimes which influence the certain types of vegetation that can survive and contribute to processes such as nutrient cycling and seed germination.
Urbanization which has the power to change landscapes, reduce natural habitats, and introduce non-native and invasive species. (5)

Environmental Threats:

Los Angeles faces many environmental threates which affect the ecosystems and biodiversity. Some of the main threats include: air pollution, climate change, urbanization and habitat loss, wildfires, invasive species, drought, water quality and scarcity, and the sea level rise. (6)

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Rock Types:

Some of the common rock types include:

Sedimentary Rocks include Sandstone and Shale.
Metamorphic Rocks include Schist and Gneiss
Igneous Rocks include Granite and Basalt
Alluvial Deposits include Gravels and Sands

The geologic history involves the tectonic processes and interactions between the Pacific Plate and the North American Plate. This interaction led to the formation of the fault systems, the mountain ranges, and the rock types listed above. The San Andreas Fault is a major feature in Los Angeles and has also played a huge role in shaping this ecosystem. (8)

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Plate Tectonics:

As mentioned in the Rock Types blurb, the landforms have been significantly influenced by the tectonic processes between the Pacific Plate and the North Amercian Plate.

The key tectonic processes include:

San Andreas Fault: The past seismic activity along this fault has resulted in the creation of the mountain ranges, valleys and other landforms . This Fault remains an active tectonic feature and continues to shape the landscape (8)
The Erosion and Uplift: The tectonic activity with these plate interactions have resulted in an uplift in certain areas and this has produced various mountain ranges such as the San Gabriel Mountains. The current processes continue to shape the landscape and rivers/streams help transport sediments and carve out the valleys.
The Coastal Features: these have been formed through tectonic processes and the sea-level changes. The sea-level and the erosion continues to change the landforms.

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Plate Boundaries:

The major plate boundary is between the Pacific Plate and the North American Plate. These plates interact along the San Andreas Fault mostly. The strike-slip motion along this fault results in displacements as well as seismic activity throughout the region. The proximity to this fault also makes Los Angeles more susceptible to earthquakes. (8)

Weathering and Erosion:

Key weathering and erosion processes include:

Water Erosion: Precipitation and runoff play a significant role in this erosion. Over time, the water erosion has shaped valleys, canyons and other landscapes.
Wind Erosion: This happens especially in the arid areas. The sediments blown from wind can lead to the formation of sand dunes.
Coastal Erosion: This occurs with wave action and tidal forces which shapes coastlines. (9)
Chemical Weathering: This includes dissolution and oxidation and affects rocks and minerals.
Biological Weathering: The plant roots, burrowing animals and the microbial organisms play a role in this. The past events impacted the soil development and contributed to the evolution of the landscape. (10)

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Liquid Water:

Liquid water plays an important role in Los Angeles and impacts the area through lakes, rivers and other bodies of water. There are several watersheds which contribute to the city's water resources as well. Some key watersheds are the Los Angeles River Watershed and the San Gabriel River Watershed. The Santa Ana River is also a crucial source of water and is mostly used for irrigation and the urban supply. (11)

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Glaciers:

Glaciers are typically found in colder climates with higher latitudes and elevations. In Los Angeles, the temperature is warmer and the climate is more arid. The Mediterranean climate is also not conducive to the glacial formation or preservation. (12)

Other Processes:

Some other processes include:

Marine and Coastal Processes: The wave action and coastal erosion helped to shape Southern California's coastline. This resulted in sea cliffs, coastal bluffs and marine terraces. (13)
Volcanic Processes: The history of the region's geology includes these processes. Basalt can be located in certain areas and the past volcanic activity has played a role in the composition of the landscape. (14)
Human-Induced Landforms: The urbanization and human activities resulted in man-made landforms such as roads, reservoirs and embankments. (15)

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Works Cited: