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Staff posing with an enormous invasive thistle (NPS Photo by Shari Cappo-Fisher) |
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Alien plants are non native plants that have been introduced purposely or accidentally to an area. Exotic species are spread into areas in many ways. Seeds are carried by wildlife on fur and feathers. Seeds are transported by humans to different areas via clothing, shoe soles, and tread of tires. Fill dirt, brought into areas for maintainance purposes, often contains exotic seeds in their dormant stage ready to take hold in a new area. Wind and water are also involved in alien plant spread by creating transport routes for seeds to travel.
Alien plant species threaten the natural environment at Lava Beds National Monument. The aggressive spread of these species is of great concern to the delicate ecological balance found within the monument's natural environments. Large numbers of alien plant species have invaded our boundaries and have taken hold in the delicate soils found within the monument. Non-native plants pose serious effects on the environments in which they invade. Native plants and animals suffer these effects most severely. The native plants and animals of Lava Beds are in competition for survival with several alien plant species and are often suppressed due to the presence of these exotics in the area. Few if any native species utilize these plants as a food source. As these exotic plants invade the areas in which the native plants grow, the native species decrease thus decreasing food and shelter for the areas wildlife. Wildlife populations decline as they are forced to forage elsewhere. The ecological balance between the native plants and animals of the area crumbles leaving extensive damage as the natural resources of the area deplete.
CHEATGRASS (Bromus Tectorum) The most widespread exotic of the area, Cheatgrass, covers over 15,000 acres of the park. This low nutrition exotic grass is unpalatable for most of its lifecycle. Cheatgrass is an annual grass which germinates and grows in the spring. The grass becomes unpalatable in early summer as it changes from a green to a reddish purple. It then seeds and dies as it begins to grow and die. Its seeds are sharp and barb-like thus enabling them to burrow easily into fur and clothing. Cheatgrass is very competitive and it flourishes in dry grasslands. When Cheatgrass invasion occurs native species such as Sagebrush, Bitterbrush and Bunchgrass tend to die off due to various reasons. These native plants have widley spaced growth patterns unlike cheatgrass. Cheatgrass grows among these species over crowding as well as creating a steady fuel bed for fires during the annual fire season. Increased fire frequencies and higher intensity fires are characteristic of areas invaded by Cheatgrass. Landscapes dominated by cheatgrass burn hotter and greater thus lessening the diversity and richness of the fire sensitive native plant species. This in turn disturbs the wildlife habitats of the area as increased fire alters the landscape and vegetation.
JIM HILL MUSTARD (Sisymbrium Altissimum): Jim Hill Mustard, also refered to as Tumbleweed, covers approximently 3,000 acres of the park. Like Cheatgrass, this species is extensivly spread throughout the park making it infeasible to control directly. This exotic is native to Europe but has taken hold in American soils due to its unfortunate introduction. It thrives in disturbed areas such as fields and roadsides. This weed is an annual plant that grows into erect stalks free of hair or leaves. It then produces yellowish flowers and seeds. It is often refered to as tumbleweed due to its tendency to tumble across the open land spreading its seeds along the way. There are few if any predators in the park which threaten this exotic species therefore allowing it to thrive.
COMMON MULLEIN (Verbascum thapsus): Common Mullein is widespread throughout Lava Beds, covering approximately 200 acres. Mullein is a branched biennial taking two years to complete its life cycle. In the first year a rosette of basal leaves is produced. An erect flowering stem reaching up to six feet is produced the second year. The leaves are paddle shaped, upward becoming lance shaped. The spike-like stalk becomes covered with yellow flowers blooming from June to August. Mullein seeds can remain viable for over 100 years. Mullein is an invasive species introduced from Eurasia. Mullein is invasive along roadsides, disturbed or burned sites, waste places, open areas, dry sandy soils, but can establish in undisturbed backcountry.
WOOLY MULLEIN (Vernascum Thapsus) Wooly Mullein is an exotic well established within Lava Beds. It is thought to cover over 500 acres of the monument. It is a biennial, taking two years to complete its life cycle. The first year after germinating, Mullein grows vegetatively up to six feet in height producing large green hairy leaves. Year two the plant produces yellow flowers and many seeds. After dropping its seeds, the Mullein seeds may lay dormant for more than 15 years. Mullein is a common weed in Northern California. It establishes itself in disturbed areas such as along roadsides. Mullein colonies cover vast expanses of land, smuthering out most or all native vegetation from among them. It was introduced from Eurasia and has few predators in the area. Mullein is commonly attacked by mechanical methods using herbicides and by uprooting established plants.
RUSSIAN THISTLE (Salsola kali) Russian thistle is said to cover approxamently 500 acresof the monument. It is an exotic which originated from Eurasia and has flourished in the condition available in the park. Russian Thistle is an annual which becomes a tumbleweed style plant at the end of its life cycle. It is a dense plant consisting of an intricate branch arrangement. It grows into a round bushy clump and is covered in thorns. The thorns serve as a deterent from predators allowing the exotic to grow uninhibited across the park. Thistle produces tiny black seeds which disperse as the dead plant blows across the desert floor. Hikers may experience the sting of thistle as they brush against its painful thorns.
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