| Afforestation effect on soils |
Physio-chemical changes in soil occur through afforestation………………………..
· Afforestation causes accumulation of litter on forest floor which encourages soil faunal activity & influences soil aeration, moisture status, drainage & permeability.
· Afforestation enhances atmospheric decomposition & permeability.
· Afforestation causes translocation of nutrients from deeper soil layers by root activity.
· Afforestation changes the rate of chemical weathering of parent materials.
Factors on which the rate of change of soil…………………………………..
· Type of forest.
· Forest management & harvesting.
· Differences in planted species.
· Soil & site condition.
Physical changes in soil properties that caused by roots……………………………………..
· Aggregation of soil particles.
· Increase soil aeration & drainage.
· Allow downward mixing of soil particles.
· Retards soil erosion.
Good soil structure………………………………………………..
· When different soil particles are sufficiently aggregates together, it is called good soil structure.
· This agent responsible for soil aggregation is root effect, microbial activities, cementing agent etc.
Bad soil structure…………………………………………………
· When different soil particle are not aggregate together, it is called bed soil structure.
Afforestation effect on physical properties of soil ……………………………………………………..
a) Organic matter:
· The most obvious effect of afforestation is accumulation of litter or organic matter on the surface of the soil. The accumulation rate of organic matter is the balance between the total litter falls minus decomposition.
· The litter fall depends upon forest type & decomposition rate depends on climatic factors, edaphic factors, & microbial population.
· Accumulation rate is rapid at an early stage in the life time of the population with decomposition eventually becoming equal to input.
b) Porosity & bulk density:
· Both coniferous & broadleaved species usually improves soil porosity.
· Afforestation improves soil bulk density too. Plantations decrease the bulk density of a wet soil & increase the bulk density of coarse textured soil.
c) Soil moisture:
· Afforestation tends to reduce soil moisture content in wet soils such as in moorlands & peats.
· The capacity of forest soil to hold more water related to litter production. In coarse textured soils this is considered as a improvement in soil physical properties.
· Soils under plantation are usually seen to increase water holding capacity compared to similar soils under cultivation.
d) Soil aggregation:
· Soil aggregates are generally more stable under forest than agricultural land.
· The stability of soil aggregates improves with increasing age under both broadleaved & coniferous forest.
e) Soil temperature:
· Forest cover reduces extreme seasonal & daily temperature in soil.
· Both forest canopy & floor intercept solar radiation in summer & reduce loss of heat from in winter.
· In cold climates, afforestation delays freezing to occur & keeps deeper layer of soil warmer.
f) Soil depth:
· Although tree growth tends to increase soil depth & the rates vary depending upon original site condition.
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| Prepared by Rasel 23 |
