Activity 1: Fire
Warmer climate is increasing the severity, duration, and area of seasonal wildfires. Since 1986, longer and warmer summers have have produced more intense fire seasons. Fire frequency has increased by 4 and the area burned has increased by 6 in comparison to the 16 years prior to 1986. Westerling et al. used a comprehensive set of data throughout the western United States to analyze these patterns. The length of the fire season has increased and the burning times also increased from 7.5-37.1 days. He attributed this to a warmer spring season and a 1-4 week early melting of snowpack. The decrease in lasting snowpack is causing the forests in higher elevations in become susceptible to fires earlier in the year, and therefore run the risk of longer burn periods as well. The increase in stand density is also a valid argument for the cause in fire intensity. Past fire suppression increases the fuel load a particular forest has [1].
For the Teanaway in particular, dendrochronological techniques were used to recreate the areas fire history. Fire scar information and data provided by the General Land Office revealed that fire frequency was variable throughout the Teanaway River area. Most fires were small, but there were larger fires every 27 years or so, which coincided with seasonal drought. Annual rates of wildfire have actually decreased circa 1900 due to timber harvesting in the area [2].
Many dominant trees in the Cascades are fire sensitive, increasing the risk of low fire intensities becoming higher in intensity. Higher elevations in the Cascades may take much longer to recover because of this. The eastern side of the Cascades is drier than the western side, which also decreases the ease in which a forest can reestablish [3].
There are past accounts and evidence showing that Indoamericans used fire burning to intentionally change a landscape for their own benefit. They would choose times where conditions favors low intensity burning and promoted the regeneration of understory vegetation and open landscapes for easier travel and hunting. Former grasslands and woodlands are being recognized by conifers that were traditionally suppressed by intentional fire. Historically, there was a much greater expanse of shrubland. There was a more diverse structure, lass fuel loading, lower crown restoration, especially in the drier regions. An experimental approach to fire/ecosystem management is needed that will incorporate learning, or adaptive management techniques. These management options will be difficult to figure out ecologically as well as economically and socially, as existing paradigms about fire and fire management are difficult to alter [4].
There were four regimes that were traditionally used by Native Americans. One was Nonlethal, wish was a frequent use of low intensity fire to create park-like forests with little understory vegetation. It is difficult to prescribe this method of management because the forests have changed so much in composition. The abundance of understory vegetation makes it more dangerous than it was in the past. Another fire that occurred was Lethal. It kills most, if not all, the trees that occurred in a stand as well as the understory vegetation. These stands are often dense and filled with varying levels of fuel to facilitate intense burning at all levels of the forest. Historically, these were uncommon, though they occur more often today due to current forest structures. There are also two other regimes that result in mixed legality at mid and high elevations. Because of climate change, advanced fuel loads, disease and pest threats, it is becoming clear that the forest health needs to be maintained. Current management plans are attempting to mimic traditional strategies (prescribed burns) for reducing the intensity of wildfires [5].
[1] http://www.cskt.org/fire_history.swf
[2] http://www.cfr.washington.edu/classes.esc.401/FireEcologyPNW.htm
[3] Wright&Agee.pdf
[4] InlandPNWForestHistory.pdf
[5] ScienceFiresRunning06.pdf
Activity 2: Mountain Pine Beetle
The mountain pine beetle is native to the pine forests of North America. The beetles bury into the bark of pine trees and lay their eggs. When the larvae emerge, they eat away at the trees from the inside out. Once mature, the beetles move on to the next tree. The denser the stand, the easier it is for the beetles to move between trees. They also carry the blue stain fungi from tree to tree, which is incredibly damaging to the trees they inhabit. They eventually kill the trees, which increases the fuel load of the stand and decreases the overall health of the forest. Their populations experience outbreaks periodically which also reduces the carbon uptake of the forests, assisting in overall climate change which therefore increases beetle productivity. The current outbreaks in British Colombia, Canada are worse than they ever have before. The impact converted the forest from being a carbon sink into a carbon source, and is in huge risk for extremely severe wildfires [1].
[1] MtnPineBeetleClimChangeNature08.pdf
Activity 3: Spruce Budworm
The spruce budworm makes its living on the grand fir, subalpine fir, engelmann spruce, douglas fir, and western larch. The adults lay their eggs on the underside of needles in midsummer. The larvae hibernate in the bark surfaces. In the spring, the larvae re-emerge and tunnel into older foliage or they float away on silk threads. They then land on surround trees where they feed and then eventually pupate. Once they pupate, they fly away to find a mate. It is a defoliating insect, meaning it does directly kill trees, but a lack of foliage on a conifer can eventually kill the tree. If the tree doesn't die, then it is weakened, and annual infection can increase susceptibility to mountain pine beetle attacks [1].
It is distributed throughout northwestern and western north america. Young stands are incredibly vulnerable to the spruce budworm because they are located in the understory. When the larvae float down from taller trees, the young saplings are perfect landing spots and hosts for the worms. Chemicals, siviculture and insecticides can be used to manage their populations [2].
[1] http://ext.nrs.wsu.edu/forestryext/foresthealth/notes/westernbudworm.htm
[2] http://www.na.fs.fed.us/spfo/pubs/fidls/westbw/fidl-wbw.htm
Activity 4: Serpentine Soils
Serpentine is a mineral that is derived from the mafic rock minerals. Serpentinite is a rock made up of serpentine minerals. The minerals contain large amounts of iron, magnesium, and very little silicon, potassium, calcium, molybdenum. There are also high amounts of heavy metals like mickel, cobalt, and chormium. The serpentine soils are usually green, blue, black, or red. It is often soapy and shiny and breaks easily. The formation of serpentine require low pressure, temperatures between 100-300 degrees Celsius and a pH greater than 10. Soil profile is generally poor from a high pH and a low capacity for holding water. They also lack nitrogen, phosphorus, and molybdenum. Therefore productivity is usually very poor. The only plants that can grow here are specialized for the serpentine soils. The general landscape is generally open and bare, with few shrubs on the ground and stunted conifers [1].
[1] http://www.cfr.washington.edu/classes.esc.401/SerpentineMMcK.pdf
No comments:
Post a Comment