USA Forests are changing in ways theyve never experienced before because todays growing conditions are different from anything in the past. The climate is changing at an unprecedented rate, exotic diseases and pests are present, and landscapes are fragmented by human activity often occurring at the same time and place.
The current drought in California serves as a reminder and example that forests of the 21st century may not resemble those from the 20th century. When replanting a forest after disturbances, does it make sense to try to reestablish what was there before? Or, should we find re-plant material that might be more appropriate to current and future conditions of a changing environment?
Restoration efforts on U.S. Forest Service managed lands call for the use of locally adapted and appropriate native seed sources. The science-based process for selecting these seeds varies, but in the past, managers based decisions on the assumption that present site conditions are similar to those of the past.
This may no longer be the case.
Forest managers are already altering the species they use when replanting since species like chestnut, elm, butternut and the ashes have been, and are being, decimated by exotic diseases and pests. We dont yet know what a changing climate will bring.
Forest Service scientists and geneticists are spearheading efforts to provide tools to adapt reforestation practices for changing conditions. These practices include selecting seed of proper species and location, choosing trees resistant to disease and pests, using the appropriate seedling type, controlling vegetation, and identifying proper spacing to plant tree seedlings.
Making an accurate prediction of which plants will succeed in a new environment is difficult, so geneticists employ a strategy that is not unlike your retirement portfolio: we diversify. By increasing the genetic diversity on a site, either by adding novel species or seed sources within species, we increase the chance that suitable genetic material will exist in the new environment. But we dont want to add any ole diversity, we try to add species and seed sources that would have the best chance of thriving in a new environment.
Our forests are confronting challenges from a changing climate, diseases, insects, and human disturbance. While we cant be sure of what the future will hold, we use science to better understand the future and then try to consider that future when we plant and manage our forests.
Winters have started approaching the northern region of India that also includes Delhi-NCR along with Punjab and Haryana. Due to this, minimums have also started dropping in many parts of North India including Delhi and NCR. In fact, as per the temperatures recorded on October 15 and October 17, the minimums ofDelhi and NCR went down to 17°C.
As per experts, an increase in the pollution level normally occurs during the winter months. However, there are a few reasons that could enhance the pollution level in Delhi and the adjoining areas. The very first reason that can be attributed to an increase in pollution level in the national capital is crop fires in the neighboring state ofHaryana andPunjab.
These two states lie in northwest proximity of Delhi and normal pattern of winds during this season is northwesterly. These winds drag the smoke and fine particles of the burnt crop and mix them with Delhis atmosphere. Moreover, the temperatures also start dipping, therefore, the air near the earths surface tends to condense leading to formation of haze.
Whenever the winds are light or calm, these air pollutants get mixed with the haze or mist and forms a blanket of smoke haze which remains suspended for few hours in the mornings. Thereafter, the haze disappears as the sun rises and temperatures increases during the day.
But as the winter progresses in the month of December and January, the duration of haze, mist or fog gets extended and these pollutants remain suspended in the atmosphere for longer duration of time. Other factors including the smoke emitting from vehicles and factories and dust from construction sites also add to the rising pollution levels.
Sometimes this situation can continue for days altogether. However, relief is expected only when a strong Western Disturbance gives rain over the region. It is then that these pollutants settle down for a few days.
Another criterion which reduces the pollution levels is the strong and moderate dry winds from northwest or west which carry away these pollution particles. In a nutshell, it can be said that in October, intensity and duration of pollution remain less though increases in November as winters sets in.
– See more at: http://www.skymetweather.com/content/weather-news-and-analysis/delhis-pollution-level-increases-as-winter-approaches/#sthash.FRlJsEib.dpuf