Ecology – Notes

Owens Valley*

Owens Valley happens to be one of the most singular and interesting places in the United States. It is located in the western part of the continent – between the Sierra Nevada and the Inyo Mountains. This valley forms part of the geomorphic province of Basin and Range, characterized by mountains and valleys as unique features resulting from the process of Earth crust movement.

Geomorphology: The Shape of the Land

The Owens Valley lies within crust of the Basin and Range province, which is famous for its “horst and graben” structure. Consider the crust of the earth to be rifting apart: the surface breaks, and some blocks go down while others rise up. This process forms a pattern of highs and lows. Owens Valley is one of these low areas, known as a “graben,” while surrounding mountains are the high areas known as “horsts.” The elevation of the valley varies from about 3000 to 6000 feet and includes flat and gently sloping areas.

Erosion, the wearing away of rocks and soil by water and wind, and deposition combine in the process whereby these materials are laid down in new places. Through such continuous action, an alluvial fan—the fan-shaped deposit of soil and rocks at the base of the mountains—and a basin fill, or a layering of sediments on the floor of the valley, form over time.

Soil and Vegetation: Life on the Land

Soils in Owens Valley vary considerably. On the alluvial fans, Torrifluvents and Torriorthents soils are well drained and support a wide variety of plant life. Elsewhere in the basin-fill areas, the soils may be poorly drained and these areas may support different kinds of plants. There is even dune sand in places!

The vegetation of Owens Valley differs according to soil and location. You might find plants such as saltbush and greasewood that are tolerated on salty soils in the areas of basin fill. On the alluvial fans, there were plants like shadscale and hop-sage that could stand the drier conditions. Higher up on the fans, there is black bush with sagebrush. South of Owens Lake, creosote bush is the predominant plant.

Climate: Hot and Dry

Long-term temperatures and rainfall—Owens Valley has a hot and dry climate. Average annual precipitation, or the amount of rain that falls in an average year, is only about 4 to 8 inches. Most of this rain falls during the winter months. The mean annual temperature varies from 55° to 65° F. Because it is so dry, plants and animals must be tough in order to survive with little water.

Water: The Lifeline

Water plays a major role in the Owens Valley way of life. Along the middle of this long valley runs the Owens River, which furnishes water to many plants, animals, and people. Centuries ago, Owens Lake used to overflow periodically and send water to the neighboring valleys. Nowadays, so much of the Owens River water is exported to Los Angeles that Owens Lake is virtually dry.

Conclusion

Owens Valley is a place both fascinating in geology and ecology. Distinct landform, variety of soils, and flora hardiness testify to the ability of life to adapt to the rigors of heat and dryness. Understanding Owens Valley would help us recognize the sensitive links between land, water, plants, and animals that give this part of the world its special identity.

*AI

Yucca Moths and Joshua Trees: A Mutualistic Relationship

https://mojavedesert.net/trees/yucca-brevifolia

Introduction The relationship between Joshua trees (Yucca brevifolia) and yucca moths (Tegeticula synthetica) is a classic example of mutualism, where both species benefit from their interaction. This symbiotic relationship is essential for the reproduction of Joshua trees and the lifecycle of yucca moths.

Yucca Moth Pollination Process

Flowering: Joshua trees typically bloom from February to late April, producing clusters of creamy white to green flowers. The blooming process depends on sufficient rainfall and a winter freeze.
Moth Activity: Female yucca moths visit Joshua tree flowers during their active period. Unlike most insects that visit flowers for nectar, yucca moths have a unique role. The female moth collects pollen from the anthers of one flower and forms it into a ball using specialized tentacles near her mouth.
Pollination: The moth deliberately transfers the pollen ball to the stigma of another Joshua tree flower. This deliberate act ensures cross-pollination, which is crucial for the genetic diversity and reproductive success of the Joshua tree.
Egg Laying: After pollinating the flower, the female moth lays her eggs inside the flower’s ovary. This ensures that her larvae will have a food source when they hatch.
Larval Feeding: As the seeds develop within the flower’s ovary, the moth eggs hatch into larvae. These larvae feed on a portion of the developing seeds. Despite this seed predation, enough seeds typically remain viable to ensure successful reproduction of the Joshua tree.

Selective Abortion Joshua trees have developed a mechanism to ensure seed survival despite the larvae feeding. They can selectively abort ovaries that contain too many moth eggs. This limits the number of larvae that can develop and ensures that sufficient seeds remain viable for the tree’s reproduction.

Mutual Benefits

For the Joshua Tree: The deliberate pollination by the yucca moth increases the likelihood of successful seed set and promotes genetic diversity due to cross-pollination.
For the Yucca Moth: The Joshua tree provides a secure environment for the moth to lay its eggs and a reliable food source for the larvae.

Unique Adaptations

Yucca Moth: Specialized tentacles for collecting and transferring pollen. This adaptation is unique among insects and has specifically evolved to pollinate Joshua trees.
Joshua Tree: Flower structure that accommodates the yucca moth’s pollination behavior. The tree’s ability to selectively abort seed pods with too many larvae is also a crucial adaptation for managing seed predation.

Ecological Importance The relationship between Joshua trees and yucca moths is a cornerstone of the Mojave Desert ecosystem. This mutualism ensures the reproduction and survival of Joshua trees and supports a complex web of life, providing food and habitat for various species of birds, mammals, reptiles, and insects.

Conclusion The intricate pollination mechanism between Joshua trees and yucca moths highlights these species’ deep co-evolution and interdependence. This mutualistic relationship is essential for their survival and plays a vital role in maintaining the ecological balance of the Mojave Desert.

Allelopathic Properties of the Creosote Bush

Introduction

The desert creosote bush (Larrea tridentata) is a remarkable plant native to the arid regions of North America and is known for its resilience and adaptability. One of the most intriguing aspects of this plant is its allelopathic properties. Allelopathy refers to the biochemical interactions between plants, where one plant releases chemicals that can inhibit neighboring plants’ growth, survival, and reproduction. This essay explores the allelopathic properties of the creosote bush, examining its chemical mechanisms, ecological impacts, and potential applications.

Overview of the Creosote Bush

The creosote bush dominates in the southwestern United States and northern Mexico deserts. It thrives in extreme conditions characterized by high temperatures, low rainfall, and poor soil quality. The plant is well-adapted to these harsh environments, with small, waxy leaves to minimize water loss and an extensive root system to maximize water uptake. Beyond its physical adaptations, the creosote bush employs chemical strategies to maintain its dominance in the desert ecosystem.

Chemical Mechanisms of Allelopathy

The allelopathic properties of the creosote bush are primarily attributed to the secondary metabolites it produces. These compounds include phenolic acids, flavonoids, and lignins, which are released into the soil and air through various plant parts such as leaves, roots, and stems. Among these, phenolic compounds like nordihydroguaiaretic acid (NDGA) play a crucial role.

NDGA is a potent antioxidant and a significant allelopathic agent. It inhibits competing plants’ seed germination and root growth by disrupting cellular respiration and photosynthesis. Studies have shown that soils beneath creosote bushes have higher concentrations of NDGA, leading to reduced germination rates and stunted growth of other plant species. This chemical warfare allows the creosote bush to secure essential resources such as water and nutrients by minimizing competition.

Ecological Impacts

The allelopathic properties of the creosote bush have significant ecological implications. By suppressing the growth of other plants, the creosote bush creates a unique microhabitat that influences plant diversity and distribution in desert ecosystems. This phenomenon leads to a mosaic of vegetation patterns, where patches dominated by creosote bushes are interspersed with bare soil or sparse vegetation.

The reduced plant diversity around creosote bushes can impact other trophic levels, including herbivores and predators. For instance, herbivorous insects and small mammals that rely on various plant species for food may find fewer resources in areas dominated by creosote bushes. Consequently, the allelopathic effects of the creosote bush can influence the distribution and abundance of these animals.

Additionally, the altered plant community structure can affect soil properties. The reduced litter input from other plant species may lead to lower organic matter content and changes in soil microbial communities. These changes can further reinforce the creosote bush’s dominance, creating a feedback loop that maintains its competitive edge.

Potential Applications

Understanding the allelopathic properties of the creosote bush has practical applications in agriculture and weed management. The compounds responsible for allelopathy, such as NDGA, could be explored as natural herbicides. These bioherbicides offer an environmentally friendly alternative to synthetic chemicals, potentially reducing the ecological footprint of agricultural practices.

Furthermore, studying allelopathy in the creosote bush can inform sustainable land management strategies in arid regions. By recognizing the impacts of allelopathic plants on ecosystem dynamics, land managers can make informed decisions to promote biodiversity and maintain ecological balance. For example, controlling the spread of creosote bushes in areas where they threaten native plant communities could help preserve biodiversity.

Challenges and Future Research

While the creosote bush’s allelopathic properties offer exciting possibilities, there are challenges to consider. The complexity of natural ecosystems means that the effects of allelopathy are not always straightforward. Factors such as soil type, climate, and interactions with other organisms can influence the outcome of allelopathic interactions. Therefore, comprehensive field studies are essential to fully understanding the ecological impacts of allelopathy in diverse settings.

Future research should also explore allelopathy’s genetic and molecular basis in the creosote bush. Identifying the genes and regulatory pathways involved in the production of allelopathic compounds could provide insights into the evolutionary origins of this trait and its potential for manipulation. Additionally, investigating the interactions between allelopathic compounds and soil microorganisms could reveal new aspects of plant-microbe interactions and their role in shaping plant communities.

Conclusion

The allelopathic properties of the desert creosote bush highlight the intricate and dynamic nature of plant interactions in arid ecosystems. The creosote bush significantly influences plant community structure, soil properties, and overall ecosystem dynamics by producing secondary metabolites. While challenges remain in fully understanding and harnessing these properties, the potential applications in agriculture and land management are promising. Continued research into the allelopathic mechanisms of the creosote bush will advance our ecological knowledge and contribute to the development of sustainable practices in managing natural and agricultural systems.

Western Fence lizards are out at Tin Can Point

This turquoise colored fence lizard (Sceloporus occidentalis) was seen out in the warmth of early Spring at Tin Can Point. Tin Can Point is just up from Fern Lodge Junction on the Gabrielino Trail. It’s the first switchback you’d encounter after the trail passes through the canyon live oak forest and then enters the chaparral, just a few minutes up from the trail junction.

A beautiful fence lizard basks in the gentle warmth of early Spring at Tin Can Point. See inset of the Chantry Flat – Mt. Wilson Trails map, below, to see where this point is. As of this writing, a cold wet pacific storm is dropping nearly six days of chilly rain and snow in much of the San Gabriel mountains. Big Santa Anita Canyon dam has received over 5 1/2″ of rain in the last week. Something I just learned recently about these Western Fence lizards is that their populations have the effect of reducing the incidence of Lyme’s disease in the ticks that live in the chaparral, such as found covering much of the slopes of the Big Santa Anita Canyon! Apparently, a protein in the lizard’s blood kills the bacterium in the tick’s gut, which is good news for hikers and even their dogs during the spring and autumn months.

Like most reptiles, Western Fence lizards hibernate, at least for a little while each winter throughout their habitats which are wide-spread throughout California. As for food, these lizards eat spiders and various insects such as mosquitos, beetles and grasshoppers. The females lay several small clutches of eggs (3-17) in the spring, the young emerging in the summer.

Detail of Gabrielino Trail section, Chantry Flat – Mt. Wilson Trails map.

On your next hike out from Chantry Flats, watch for for lizards flitting about on the trails and sunning themselves on the myriad stretches of rock. As for the various types of reptiles to be found in the Big Santa Anita, Western Fence lizards are abundant and deserve a place in the sun!

source: Wikipedia, Western Fence lizards

A Natural History of the Mojave Desert

The Mojave Desert, located in the southwestern United States, is a vast, arid region known for its unique and resilient ecosystems. Its natural history can be divided into several key aspects:

Geology and Geography: The Mojave Desert has varied topography, including valleys, dunes, and mountains. It is home to the famous Death Valley, the lowest and one of the hottest places in North America. The Mojave’s geological history includes volcanic activity, the formation of mountain ranges, and the erosion that created its present landscapes.
Climate: This desert is known for its extreme temperatures and aridity. Its high temperatures vary day and night due to the lack of humidity and sparse cloud cover. Rainfall is scarce and unpredictable, often leading to drought conditions.
Flora and Fauna: The Mojave Desert supports a range of life adapted to its harsh conditions. Notable plants include the Joshua tree (Yucca brevifolia), symbolic of the Mojave, and various cacti and shrubs adapted to survive with minimal water. Animal life includes reptiles like the desert tortoise, mammals such as the bighorn sheep, and numerous bird species that navigate the challenging environment.
Ecological Dynamics: The ecosystems of the Mojave are shaped by limited water resources and extreme temperatures, leading to unique interactions among species. Plants and animals have evolved various adaptations for survival, including water conservation mechanisms and nocturnal activity patterns.
Human Impact and Conservation: Human activity has significantly impacted the Mojave Desert. Issues include water resource extraction, urban expansion, and the development of renewable energy installations. Conservation efforts are ongoing to protect its biodiversity and landscape, with areas like the Mojave National Preserve established to safeguard habitats and natural features.
Cultural History: The desert has been inhabited by Native American tribes for thousands of years, each with rich cultural histories and connections to the land. More recently, it has played a role in American history through mining, military use, and as a site for artistic and literary inspiration.

The Mojave Desert’s natural history is a complex tapestry of geological, climatic, biological, and human factors, making it a fascinating subject for study and exploration.

Littering, Dumping, Vandalism & Theft in the Mojave.

How do we prevent it?

Addressing littering, illegal dumping, vandalism, and theft in natural areas like the Mojave Desert requires a multifaceted approach, considering prevention and remediation. Here are some strategies that can be employed:

Education and Awareness

Public Education Campaigns: Educating the public about the ecological, cultural, and historical significance of the Mojave Desert can foster a sense of stewardship. Campaigns can highlight the negative impacts of littering, dumping, vandalism, and theft.
School Programs: Integrating environmental education into school curriculums can instill values of conservation and respect for nature in young people.

Enforcement and Regulation

Increased Surveillance: Deploying more rangers or utilizing surveillance technology in high-risk areas can deter potential offenders.
Stricter Penalties: Implementing harsher penalties for violations can serve as a deterrent. This could include higher fines, community service in environmental cleanup, and legal action for more serious offenses.
Quick Response to Incidents: Rapid response to reports of dumping, vandalism, or theft can help catch perpetrators and serve as a deterrent to others.

Community Engagement and Participation

Volunteer Cleanup Events: Organizing community cleanups can address existing litter and dumping and foster a sense of community ownership and responsibility.
Adopt-a-Spot Programs: Encouraging individuals, families, or groups to “adopt” areas of the desert for regular monitoring and maintenance can help maintain cleanliness and report issues quickly.

Infrastructure and Accessibility

Better Waste Management Facilities: Providing accessible and convenient disposal options near the Mojave area can reduce the likelihood of illegal dumping.
Improved Signage: Clear, informative signage about rules, regulations, and the importance of preservation can serve as both an educational tool and a deterrent.

Technology and Innovation

Mobile Apps: Developing and promoting mobile apps that allow visitors to report litter, dumping, vandalism, or theft in real-time can aid in quick responses and create a database of problem areas.
Social Media: Utilizing social media platforms to share information, organize cleanup events, and foster a digital community of stewards can enhance engagement and awareness.

Partnerships

Collaboration with Local Businesses: Engaging local businesses in sponsorship opportunities for cleanup events or educational programs can enhance resources and community involvement.
Partnerships with Environmental Organizations: Working with NGOs and environmental groups can bring expertise, volunteers, and additional resources for conservation efforts.

Solving these issues in the Mojave Desert requires persistent efforts across multiple fronts. It’s about creating and nurturing a culture of respect and care for the environment, backed by effective enforcement and community involvement.

Mojave Desert Ecological Transitions

The Mojave Desert, located in the southwestern United States, is a unique and ecologically diverse ecosystem known for its extreme temperatures, arid conditions, and distinct plant and animal life. Various factors, including topography, climate, and human activities, influence the transitions within the Mojave Desert ecosystem.

Here are some key ecological transitions within the Mojave Desert:

Elevation Gradients:
- The Mojave Desert exhibits significant elevation gradients, ranging from below sea level in Death Valley to higher elevations in mountainous regions such as the Spring Mountains and the Mojave National Preserve. These elevation changes lead to variations in temperature, precipitation, and vegetation types.
Flora and Fauna Shifts:
- Plant and animal species are adapted to specific elevation ranges within the Mojave Desert. As you move from lower to higher elevations, you may encounter shifts in vegetation types, with desert shrubs giving way to pinyon-juniper woodlands and eventually to coniferous forests.
Water Availability:
- Water availability is a critical factor influencing ecological transitions in the Mojave Desert. Oasis ecosystems, supported by underground aquifers or natural springs, provide unique habitats in contrast to the surrounding arid landscapes. These oases can support a higher diversity of plant and animal life.
Playa Ecosystems:
- Playas, or dry lake beds, are common features in the Mojave Desert. During rainfall, playas can fill with water, creating temporary wetland habitats that support a burst of life, including migratory birds and amphibians. However, these ecosystems are highly dependent on unpredictable precipitation patterns.
Human Impact:
- Human activities, such as urban development, agriculture, and infrastructure projects, have significantly altered the Mojave Desert landscape. Urban areas like Las Vegas and Los Angeles have expanded into the desert, leading to habitat fragmentation and loss. Human activities can disrupt natural ecological processes and contribute to invasive species encroachment.
Climate Change Effects:
- The Mojave Desert is not immune to the impacts of climate change. Changes in temperature and precipitation patterns can affect the distribution of plant and animal species, alter vegetation composition, and influence the timing of biological events, such as flowering and migration.
Fire Ecology:
- Fire is a natural ecological process in many ecosystems, including the Mojave Desert. Some plant species in the desert have adapted to fire, and periodic wildfires can shape vegetation patterns. However, altered fire regimes due to human activities or climate change can have complex effects on the ecosystem.

Understanding these ecological transitions is crucial for effective conservation and management of the Mojave Desert. Conservation efforts need to consider the interconnectedness of various factors and address the challenges posed by human activities and climate change to maintain the health and biodiversity of this unique desert ecosystem.

Mojave Desert Ecotones

Ecotones are transitional zones between different ecosystems, characterized by a mix of species from adjacent ecosystems and often exhibiting unique ecological dynamics. In the case of the Mojave Desert, there are several ecotones where the desert transitions into other ecosystems. Here are some notable ecotones in the Mojave Desert:

Mojave Desert Scrub to Pinyon-Juniper Woodland:
- At higher elevations in the Mojave Desert, the vegetation transitions from typical desert scrub, dominated by creosote bush (Larrea tridentata), Joshua trees (Yucca brevifolia), and other drought-tolerant plants, to pinyon-juniper woodlands. Pinyon pine (Pinus monophylla) and juniper (Juniperus spp.) become more prevalent in these transitional areas.
Pinyon-Juniper Woodland to Coniferous Forest:
- In the mountainous regions surrounding the Mojave Desert, pinyon-juniper woodlands transition further into coniferous forests. Species such as ponderosa pine (Pinus ponderosa) and white fir (Abies concolor) become more dominant. This transition is often associated with increasing elevation and cooler temperatures.
Desert Washes and Riparian Zones:
- Where desert washes, or arroyos, intersect with the Mojave Desert, there are ecotones characterized by riparian vegetation. These transitional zones may include cottonwood (Populus fremontii) and willow (Salix spp.) trees, providing habitat for different plant and animal species compared to the surrounding arid landscape.
Desert to Playa Ecosystems:
- The transition from the desert to playa ecosystems, such as dry lake beds, represents another ecotone. Playas can support unique vegetation adapted to periodic flooding and provide a habitat for migratory birds during wet periods.
Urban-Wildland Interface:
- There is an ecotone known as the urban-wildland interface, where urban areas encroach upon the Mojave Desert. The interaction between human-dominated landscapes and the natural desert environment characterizes this transition zone. Human activities in these areas can have significant impacts on the desert ecosystem.
Mojave Desert to Great Basin Transition:
- In the northern reaches of the Mojave Desert, there is a transition zone where the desert ecosystem merges with the Great Basin. This transition is marked by changes in vegetation and species composition influenced by elevation and precipitation.

Understanding and protecting these ecotones is crucial for preserving biodiversity and maintaining ecosystem resilience in the Mojave Desert. These transitional zones often support unique assemblages of plants and animals that are adapted to the specific conditions found at the boundaries between different ecosystems. Human activities, including urban development and climate change, can impact these ecotones, emphasizing the importance of conservation and sustainable management practices in the region.

Mojave Desert Ecozones

https://mojavedesert.net/ecology/

Ecozones, also known as ecological zones or ecoregions, are geographic areas with distinct ecological characteristics, including climate, vegetation, and animal life. In the case of the Mojave Desert, several ecozones can be identified, each with its unique set of features. These ecozones help to categorize and understand the diverse environments within the broader Mojave Desert region.

Here are some key Mojave Desert ecozones:

Lower Colorado River Valley:
- This ecozone includes the area along the lower course of the Colorado River, extending into southeastern California. Riparian habitats, including marshes and wetlands, along the riverbanks characterize it. The presence of water allows for a higher diversity of plant and animal life compared to the more arid parts of the Mojave Desert.
Mojave Desert Basin and Range:
- The Mojave Desert Basin and Range ecozone cover the central and southern parts of the Mojave Desert. It includes vast expanses of arid lands with characteristic desert scrub vegetation, dominated by creosote bush, Joshua trees, and various cacti. Basins and mountain ranges mark the terrain.
Mojave High Desert:
- This ecozone encompasses higher elevations within the Mojave Desert, including areas with pinyon-juniper woodlands and coniferous forests. It is found in mountainous regions such as the Spring Mountains and the Mojave National Preserve. The Mojave High Desert exhibits cooler temperatures and a different plant and animal community compared to lower elevations.
Sonoran Desert Transition:
- Along the Mojave Desert’s southern boundary is a transition zone into the Sonoran Desert. This ecozone exhibits characteristics of both deserts and supports a mix of plant species from both regions. A warmer and subtropical climate influences the Sonoran Desert Transition ecozone compared to the central Mojave.
Mojave Desert Playas:
- Playas, or dry lake beds, are characteristic features of the Mojave Desert landscape. These flat, unvegetated areas are part of the Mojave Desert Playas ecozone. They are important for unique plant and animal communities adapted to the periodic flooding during rain events.
Mojave-Upland Desert Scrub:
- This ecozone includes upland areas within the Mojave Desert, characterized by desert scrub vegetation. It represents the transitional zone between lower elevations and the Mojave High Desert, showcasing variations in plant composition and adaptations to different environmental conditions.

Understanding these ecozones is essential for the Mojave Desert’s conservation efforts and management strategies. Each ecozone has its ecological processes, biodiversity, and environmental challenges. Conservation initiatives should consider each ecozone’s specific characteristics to ensure the long-term health and sustainability of the Mojave Desert ecosystem.