Structure and Functions of Desert Ecosystems:
In ecology, desert ecology is the sum of the interactions between both biotic and abiotic processes in arid regions, and it includes the interactions of plant, animal, and bacterial populations in a desert habitat, ecosystem, and community. Some of the abiotic factors also include latitude and longitude, soil, and climate. Each of these factors have caused adaptations to the particular environment of the region. The biotic processes include animals and plants and the way they interact. Although deserts have severe climates, some plants still manage to grow. In hot deserts plants are called xerophytic meaning they are able to survive long dry periods. They may close their pores in daytime; they store water in their stems and leaves. Some of these plants include popcorn flower, barrel cactus and Saguaro cactus.
Deserts are most notable for their dry climates resulting from rain-blocking mountain ranges and remoteness from oceanic moisture. Deserts occupy one-fifth of the Earth's land surface and occur in two belts: between 15° and 35° latitude in both the southern and northern hemispheres. These bands are associated with the high solar intensities that all areas in the tropics receive, and being too far from the equator to receive rain from the Intertropical Convergence Zone.
Deserts support diverse communities of plant and animals that have evolved resistance to and methods of circumventing the extreme temperatures and arid conditions. Desert ecology is characterized by dry, alkaline soils, low net production and opportunistic feeding patterns by herbivores and carnivores. Lichens and blue-green algae are significant primary producers in the desert. The detrital food chain is less important in desert ecology than in the ecology of other regions.
- In a desert, producers are mainly shrubs/bushes; some grasses & a few trees.
- Dominant plant species include: Succulents (water - retaining plants adapted to arid climate or soil conditions) & hardy grasses.
- Besides some lower plants such as lichens & xerophytic mosses are also present.
- These include animals such as insects, reptiles which are capable of living in xeric conditions
- Besides some nocturnal rodents, birds & some mammalians like camel etc. are also found.
- Due to poor vegetation with very low amount of dead organic matter, decomposers are poor in desert ecosystem.
- The common decomposers are some bacteria & fungi, most of which are hemophilic.
2.Abiotic components: Due to high temperature & very low rainfall, the organic substances are poorly present in the soil.
Effects of Vehicular Routes on Soils in the Mojave Desert: Vehicular routes can directly affect soils by removing them, adding to them, changing their physical and chemical composition, or covering them with gravel or asphalt. Many of these changeshave effects that extend beyond the route corridor, and contribute to indirect and dispersed landscape effects on plants and animals.
Vehicular routes that run parallel to elevation contours can also alter runoff patterns by redirecting water along roadside ditches to low points along the road, after which water continues on downslope in a more concentrated stream than otherwise would have occurred. This process concentrates channels at higher slope positions (Montgomery 1994), resulting in more elongated first-order drainage basins, and accelerated rates of soil erosion (Forman and Alexander 1998). These effects become more pronounced as the route corridor becomes more impervious to surface flow, such as along raised roadbeds or where diversion berms or "chevrons" have been constructed upslope of paved highways.
Effects of Vehicular Routes on Vegetation in the Mojave Desert: Vegetation cover and productivity can significantly increase along vehicular routes with paved (Johnson et al 1975, Vasek et al. 1975, Lightfoot and Whitford 1991) and dirt (Johnson et al. 1975, Vasek et al. 1975, Hessing and Johnson 1982, Starr and Mefford 2002) surfaces. This effect has been attributed to either release from competition from nearby plants removed along the road corridor, enhancement of soil moisture from rainfall flowing off the road surface to the base of the berm facing the roadside, or enhancement of rainfall flowing off of the upslope landscape to thebase of the berm facing the surrounding desert (Johnson et al. 1975, Vasek et al. 1975).
Effects of Vehicular Routes on Animals in the Mojave Desert: Animals are directly affected by habitat loss associated with the development of vehicularroutes, and by mortalities caused by collisions with vehicles traveling on these routes. Studies of the federally listed desert tortoise indicate that population densities are lower near vehicular routes (Nicholson 1978, Berry and Turner 1984, Boarman et al. 1997). Fenced exclusion of ground-dwelling vertebrates from a limited-access highway in the western Mojave Desert reduced road kills of desert tortoises by 93%, and of vertebrates in general by 88% (Boarman and Sazaki 1996). However, another study from a limited-access highway in thenorthern Mojave Desert suggests that rodents rarely crossed the highway (Garland and Bradley1984). Thus, generalizations about the direct effects of vehicular routes on rates of animal mortality are difficult to make, because responses may vary among route types, and among taxa withdiffering behavioral characteristics and habitat preferences.
Management Implications: The current decision process of route designation in the Mojave Desert is site specific,and relies to various degrees on biological, cultural,and recreational information. For example, if aroute passes through high priority habitat for sensitive species, or provides access to sensitive cultural sites, then the route may be considered undesirable and targeted for closure. However, if the route provides access to recreation areas, then it may be deemed desirable and targeted for possible designation as an open route. Effects of routes on
physical processes (e.g. dust production or soil erosion) are rarely considered. Final decisions must balance different aspects of resource protection with other land uses, and the decision process needs to be supported by as much objective science as possible for decisions withstand intense scrutiny.