The pictures in this post are from those two excursions, starting with the drive through the countryside to the grower's location, in a chronological order of progression. I had been waiting for a pleasant day to make the trip to this nursery, because I think it's important to verify that whatever is killing trees around the world - an increase in the mortality rate that is now well documented by scientific surveys - is not due to localized outbreaks of insects, disease or fungus; nor is it long-term drought from climate change, nor is it even necessarily the depletion of calcium and magnesium in the soils from acid rain although certainly all those things are occurring, and bad. But, the shrubs and young trees being grown in nurseries are watered, and the soil is enriched or supplemented with nutrients, and yet they are demonstrably dying off and exhibiting the identical symptoms of damage from air pollution as older trees situated in a wide range of habitats. My intention all along for the nursery was to wander around inconspicuously, if not surreptitiously, taking pictures - so it was a bit of a shock when the proprietor greeted me as soon as I parked and insisted on giving me a tour of the facility in his pickup truck.
Cause of soil erosion The rate of erosion depends on many factors. Climatic factors include the amount and intensity ofprecipitation, the average temperature, as well as the typical temperature range, and seasonality, the wind speed, storm frequency. The geologic factors include the sediment or rock type, its porosity and permeability, the slope gradient of the land, and whether the rocks are tilted, faulted, folded, or weathered.
The biological factors include ground cover from vegetation or lack thereof, the type of organisms inhabiting the area, and the land use. In general, given similar vegetation and ecosystems, areas with high-intensity precipitation, more frequent rainfall, more wind, or more storms are expected to have more erosion.
Sediment with high sand or silt contents and areas with steep slopes erode more easily, as do areas with highly fractured or weathered rock. Porosity and permeability of the sediment or rock affect the speed with which the water can percolate into the ground.
If the water moves underground, less runoff is generated, reducing the amount of surface erosion. Sediments containing more clay tend to erode less than those with sand or silt.
Here, however, the impact of atmospheric sodium on erodibility of clay should be considered. The factor that is most subject to change is the amount and type of ground cover. In an undisturbed forest, the mineral soil is protected by a litter layer and an organic layer.
These two layers protect the soil by absorbing the impact of rain drops. These layers and the underlying soil in a forest are porous and highly permeable to rainfall.
Typically, only the most severe rainfall and large hailstorm events will lead to overland flow in a forest. If the trees are removed by fire or logging, infiltration rates become high and erosion low to the degree the forest floor remains intact.
Severe fires can lead to significantly increased erosion if followed by heavy rainfall. In the case of construction or road building, when the litter layer is removed or compacted, the susceptibility of the soil to erosion is greatly increased.
Roads are especially likely to cause increased rates of erosion because, in addition to removing ground cover, they can significantly change drainage patterns, especially if an embankment has been made to support the road.
A road that has a lot of rock and one that is "hydrologically invisible" that gets the water off the road as quickly as possible, mimicking natural drainage patterns has the best chance of not causing increased erosion.
Many human activities remove vegetation from an area, making the soil easily eroded. Logging can cause increased erosion rates due to soil compaction, exposure of mineral soil, for example roads and landings.
However it is the removal of or compromise to the forest floor not the removal of the canopy that can lead to erosion. This is because rain drops striking tree leaves coalesce with other rain drops creating larger drops.
When these larger drops fall called throughfall they again may reach terminal velocity and strike the ground with more energy then had they fallen in the open.
Terminal velocity of rain drops is reached in about 8 meters. Because forest canopies are usually higher than this, leaf drop can regain terminal velocity.A conservative projection suggests that by the middle of the next century, developing countries will be using about 50 percent of the world's energy, while the U.S.
proportion of world energy use would fall to about 18 percent. Expected Future Changes in Ozone Two-dimensional (2-D) models and three-dimensional (3-D) coupled Chemistry-Climate Models (CCMs), both of which have achieved significant successes in simulating many or nearly all of the factors that affect ozone and their feed-backs, have been used to project the evolution of ozone throughout the 21st century.
Jun 22, · Under full compliance with the Montreal Protocol, the ozone layer is expected to recover to benchmark levels- the time before significant ozone layer depletion- before the middle of the century in mid-latitudes and the Arctic, and somewhat later in the Antarctic.
What influence will future solar activity changes over the 21st century have on projected global near-surface temperature changes? Gareth S.
Jones, Mike Lockwood, and Peter A. Stott During the 20th century, solar activity increased in magnitude to a so-called grand maximum. Continued declines in ODS emissions are expected to result in a near complete recovery of the ozone layer near the middle of the 21st century.
The long time scale for this recovery is due to the slow rate at which ODS are removed from the atmosphere by natural processes.
Continued declines in ODS emissions are expected to result in a near complete recovery of the ozone layer near the middle of the 21st century. The long time scale for this recovery is due to the slow rate at which ODS are removed from the atmosphere by natural processes.