Saturday, August 14, 2010

Tamarix chinensis

Salt Cedar - Tamarix chinensis

Not all of the plants out in the Mojave are desirable. There are any number of noxious weeds and invasive species infecting the landscape. One of the most reviled is the salt cedar, or tamarisk. Brought in from Asia as a landscape and riparian stabilizing plant, this vegetative menace quickly spread out of control, clogging waterways and consuming vast quantities of water. This species is able to form monocultures, forcing out native species by out competing them for water, salinating the soil, and rapidly shading them out. A tamarisk plant grows at a prodigious rate, and will overtop most of its neighbors in short order. These plants are also hideously fecund, producing a storm of seedlings that can blanket an area. The one saving grace is that the seeds are very short lived, but given the number produced, their wind dispersal mechanism and the speed at which they are produced, means that with only a few surviving, they can quickly re-infest an area.

Removal of tamarisk is a high priority for the BLM in our area. We spend a good number of resources on removal and control. In some areas, we have managed to completely remove the plant, and the native vegetation is recovering nicely. Most of the actual removal requires the use of herbicides. However, the application method is so precise that there is virtually no outward contamination of the surrounding area. The plants are cut down, and a thin film of herbicide is painted onto the stump. Those that are small enough to be removed manually are pulled with the use of weed wrenches and good old elbow grease. The reason that simply mechanically removing all of the tamarisk is not practical is thus: they are root sprouting, so leaving one large chunk of the root in the ground will allow the plant to re-grow. This is why seedlings can be removed, since they haven't developed a strong enough system to come back, but larger trees need be poisoned, since they also produce prodigiously large roots. There have been some recent breakthroughs with biological control using a parasitic beetle, but until the technique is fully tested, herbicide is the only practical and viable option to get rid of this pest.

There are those that say we should not remove the tamarisk for various reasons. However, most of their arguments do not truly hold water when scrutinized with even basic logic or analysis. One of the most often sited is that tamarisk do not use more water than a tree of equivalent size. Yes, it is technically true that a salt cedar the same size as a willow is using the same amount of water. However, there are typically many many more tamarisk occupying an area than native vegetation would, and form monocultural stands where there is nothing but tamarisk. Not only that, but they will also recruit to areas that are too dry for the native species to hold, and still use the same volume of water. There are streams in parts of the desert where after tamarisk has been removed and native vegetation has returned, the creek will actually begin flowing again, where as when the tamarisk was present, it was completely dry.

Another of these arguments is that the salt cedar provides habitat for wildlife. Yes, it does, to a degree. When you look at the species diversity and health between salt cedar stands and equivalent stands of native vegetation, the health and diversity of the native stands are always greater. Many native species will use salt cedar because in many cases, they have no other choice. Either all of the good habitat has been taken up by other occupants, or there is nothing but salt cedar available.

Ultimately, the complete eradication of this species from our region is the best for our desert vegetative communities.

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