| Associated soil orders with major forest ecosystem of the world |
Associated soil orders with major forest ecosystem of the world………………………..
Coniferous forests:
| Major ecosystems | Soil order |
| Boreal forest | Spodsols, histosols, entisols |
| Sub-alpine forest | Spodsols, inceptisols, alfisols, mollisols.(SIMA) |
| Low land coniferous forest | Ultisols, spodsols. |
Temperate forest:
| Major ecosystems | Soil order |
| Temperate zone mixed forest | ultisols, alfisols |
| Temperate zone deciduous forest | Spodsols, ultisols, alfisols, mollisols (SUMA) |
| Temperate zone broad leaved forest | Vertisols. |
| Temperate zone rain forest | Oxisols, Ultisols, inceptisols. |
Shrub & woodland formation:
| Major ecosystems | Soil order |
| Mediterranean sclerophyllous | alfisols, mollisols, aridisols, Vertisols |
| Semi desert woodlands | alfisols, mollisols, aridisols, inceptisols |
Tropical forest:
| Major ecosystems | Soil order |
| Rain forest | Oxisols, spodsols. |
| Monsoon forest | Oxisols, Ultisols, Vertisols |
| Other tropical forests – Thorn forest -Semi desert shrub savanna woodlands | Aridisols Argids |
Tropical forest ecosystem………………………………
1) Rain forest:
Location—
· Found in undisturbed areas where year round rain falls & temperatures are favorable for a biological activity.
· 3 distinct formations -- American, African & Indi-Malaysian.
Characteristics—
· Remarkably similar in structure & good appearance.
· Almost thousands of species of woody plants, forests are evergreen & growth rate continuous all the year.
· Many trees have leathery, dark green, laurel type leaves.
· Trees support a variety of plants that can survive without soil contact, such as orchids, ferns, mosses etc.
· A dense climax rain forest has a compact, multistoried canopy that allows little light to penetrate to the ground.
· The high temperature & humidity ensures continuous supply of litter leaching the forest floor, is rapidly decomposed.
· The improved acidic soils support luxuriant vegetation.
· Weathering & leaching of nutrients elements are rapid in rain forest.
· Organic matters, content of mineral soils is generally higher than might be expected.
· The decomposition rate of soil organic matter is reduced by the presence of aluminum components of the low level of phosphorus, which slow the decomposing organisms.
· Associated soils—Oxisols with rain forest, spodsoils with less well drained sandy soil.
2) Monsoon forest:
Location—
· In tropical areas where significant seasonal droughts are experienced, the rain forest gives monsoon deciduous forests.
· Found in central & south America, Indo Malaysia & Africa.
Characteristics—
· The formation of forests is not distinct as the evergreen rain forests & consists of transitional zone semi-evergreen as well as deciduous forests.
· The transitional forest is similar in structure & appearance to the rain forest except that the trees are not so tall.
· Monsoon forest is found with relatively mild drought periods, usually no more than 5 months& less than 9cm of rain each.
· With more distinctive drought periods, the forest becomes seasonal deciduous. Ex –Teak .
· Epiphytes are less abundant in areas with distinctive dry periods.
· Associated soils—soils are highly weathered than those of rain forest & include various soil orders such as ultisols, oxisols & vertisols.
3) Other tropical forests:
a) Thorn forests—
Location:
· Found in Northern Venezuela, Colombia, Northeast Brazil, West indies, Mexico, Thailand & a vast areas of Africa & Australia.
Characteristics:
· In drier areas, many dominant disappear & persists have a lower, separating canopy.
· Many low growing bushing trees & shrubs posses thorns & woody plants form closed canopy.
· Both deciduous & evergreen species are found in this formation & leaves are generally small & posses other xenomorphic adaptations.
b) Semi desert shrub & savanna woodlands:
Location:
· Situated in true desert areas adjacent to the tropical thorn forest.
Characteristics:
· Trees occupy only a small percentage of the soil area, yet they often have a effect on that area.
· The soil beneath the scattered trees & dark colored than adjoining soil.
· The demarking is likely due not only to the organic matter produced by the trees also to the entrapment of windblown debris of the tree.
Boreal forest…………………………………..…(short note)
Location:
· These vast northern forests composed largely of coniferous extend to south & tundra “timberless” across much of Canada & across northern Europe.
Characteristics:
1) Conifers are well developed to those areas of cold & short growing seasons.
2) Although Boreal forest may appear to be homogenous its physiognomy & species composition are not uniform.
3) The mean annual rainfall of nearly all the boreal forest is less than 90cm & in most places less than 45cm.
4) The evapotranspiration rate is relatively low, even in summer & the surface soil beneath the dense tree canopy is moist.
5) The summers are warm enough so that permafrost is eliminated & the soils tend to be highly leached.
6) The debris returned to the surface under conifers is usually low in nitrogen & the essential bases.
7) The positive water balance of the boreal results in a high water table. Where water table remains with 50cm of the soil surface for a large part of the year.
8) Trees grow with great difficulty & forest replace with mires. Consequently extensive ----of the boreal zone are covered by organic soils that do not support the zonal coniferous vegetation.
9) Various mosses, a few flowering plants & dwarf shrubs types of vegetations are usually found.
10) Windthrow mounds are numerous in boreal forest. They are formed by the uprooting of trees in storms & this disturbance not only creates mound surface morphology but also complicates of characterization of boreal soils.
11) Human beings have little impact of the boreal forest.
12) The soils & climates are not well suited for agriculture.
13) Many migratory birds & animals abound in summer such as moose, caribou, grouse, etc due winter food security.
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| Prepared by Rasel 23 |
