Hydrologic cycle and water resources

Trees, and plants in general, affect the hydrological cycle in a number of significant ways: their canopies intercept precipitation, some of which evaporates back to the atmosphere (canopy interception); their litter, stems and trunks slow down surface runoff; their roots create macropores - large conduits - in the soil that increase infiltration of water; they reduce soil moisture via transpiration; their litter and other, organic residue change soil properties that affect the capacity of soil to store water.

As a result, the presence or absence of trees can change the quantity of water on the surface, in the soil or groundwater, or in the atmosphere. This in turn changes erosion rates and the availability of water for either ecosystem functions or human services.

The forest may have little impact on flooding in the case of large rainfall events, which overwhelm the storage capacity of forest soil if the soils are at or close to saturation.

Soil erosion

Deforestation generally increases rates of soil erosion, by increasing the amount of runoff and reducing the protection of the soil from tree litter. This can be an advantage in excessively leached tropical rain forest soils. Forestry operations themselves also increase erosion through the development of roads and the use of mechanized equipment.

China's Loess Plateau was cleared of forest millennia ago. Since then it has been eroding, creating dramatic incised valleys, and providing the sediment that gives the Yellow River its yellow color and that causes the flooding of the river in the lower reaches (hence the river's nick-name 'China's sorrow'). Removal of trees does not always increase erosion rates. In certain regions of southwest US, shrubs and trees have been encroaching on grassland. The trees themselves enhance the loss of grass between tree canopies. The bare intercanopy areas become highly erodible. The US Forest Service, in Bandelier National Monument for example, is studying how to restore the former ecosystem, and reduce erosion, by removing the trees.

Landslides

Tree roots bind soil together, and if the soil is sufficiently shallow they act to keep the soil in place by also binding with underlying bedrock. Tree removal on steep slopes with shallow soil thus  increases the risk of  landslides,

which can threaten people living nearby.

Controlling deforestation

Farming

New methods are being developed to farm more food crops on less farm land, such as high-yield hybrid crops, greenhouse, autonomous building gardens, and hydroponics. The reduced farm land is then dependent on massive chemical inputs to maintain necessary yields. In cyclic agriculture, cattle are grazed on farm land that is resting and rejuvenating. Cyclic agriculture actually increases the fertility of the soil. Selective over farming can also increase the nutrients by releasing such nutrients from the previously inert subsoil. The constant release of nutrients from the constant exposure of subsoil by slow and gentle erosion is a process that has been ongoing for billions of years.

Forest management

Efforts to stop or slow deforestation have been attempted for many centuries because it has long been known that deforestation can cause environmental damage sufficient in some cases to cause societies to collapse. In Tonga, paramount rulers developed policies designed to prevent conflicts between short-term gains from converting forest to farmland and long-term problems forest loss would cause, whilst during the seventeenth and eighteenth centuries in Tokugawa Japan the shoguns developed a highly sophisticated system of long-term planning to stop and even reverse deforestation of the preceding centuries through substituting timber by other products and more efficient use of land that had been farmed for many centuries. In sixteenth century Germany landowners also developed silviculture to deal with the problem of deforestation. However, these policies tend to be limited to environments with good rainfall, no dry season and very young soils (through volcanism or glaciation). This is because on older and less fertile soils trees grow too slowly for silviculture to be economic, whilst in areas with a strong dry season there is always a risk of forest fires destroying a tree crop before it matures.

Afforestation

Today, in China, where large scale destruction of forests has occurred, the government has required that every able-bodied citizen between the ages of 11 and 60 plant three to five trees per year or do the equivalent amount of work in other forest services. The government claims that at least 1 billion trees have been planted in China every year since 1982. In western countries, increasing consumer demand for wood products that have been produced and harvested in a sustainable manner are causing forest landowners and forest industries to become increasingly accountable for their forest management and timber harvesting practices.

The Arbor Day Foundation's Rain Forest Rescue program is a charity that helps to prevent deforestation. The charity uses donated money to buy up and preserve rainforest land before the lumber companies can buy it. The Arbor Day Foundation then protects the land from deforestation. This also locks in the way of life of the primitive tribes living on the forest land.

7.Переведите письменно (рекомендуется для зрительно-письменного перевода):

1. Государственный лесной фонд России – совокупность всех лесов естественного происхождения и искусственно-выращенных.

2. В составе государственного лесного фонда России различают лесные площади (сельскохозяйственные угодья, просеки, дороги и т.п.).

3. Лесные культуры – это искусственно созданные лесные насаждения на месте вырубoк в безлесных районах, под пологом леса, который предназначен для рубки.

4. Лесные полосы – это искусственно созданные лесные насаждения

в виде лент из рядов деревьев, полезащитные, садозащитные, приовражные.

5. Лесные полосы задерживают снег, предотвращают эрозию почвы, защищают объекты от снежных и песчаных заносов.

6. Лесоустройство – это система мероприятий по организации и ведению лесного хозяйства.

7. Лесоустройство включает изучение и таксацию леса, инвентаризацию лесных насаждений, установление размеров и методов пользования лесом, способов рубок и их объемов, разработку рекомендаций для повышения продуктивности лесов.

8. Переведите устно (рекомендуется для перевода с «листа»):