Influence of Forest Canopy on Soil Fertility

Forest trees generally influence the soil fertility underneath the tree canopies especially if situated on nutrient poor environment. Researchers have found enhanced soil fertility in the forms of island of fertility in the immediate surroundings of plants. Under most circumstances, canopy serves as nutrient trap whereby nutrients present in the fine dust particles slowly get deposited onto the leave surfaces which eventually get into soil by throughfall or by stemflow.  Additionally, more litter fall will likely accumulate underneath the tree canopy which during decomposition will likely liberate organically tied up nutrients in the forms that might be utilized by tree on soil limited by nutrients.

Since, atmospheric dust is intercepted by forest canopy; therefore we might see its signature underneath a tree canopy on top few millimeter of the forest soil.  Because, dust deposited onto the canopy might have two routes to enter into the soil.  Firstly, washed with rain water and fall onto the soil surface and is known as throughfall and secondly, with water that runs along the shoots and stems and enter the soil at the base of stem.  This is referred to as stemflow. Stem flow and throughfall are responsible for the transport of precipitation and nutrients from the canopy to the soil and serve as important path ways of P inputs to the forest soils.  Both influence not only the composition and structure of tropical forests, but also the internal nutrient recycling, which play an important role in the plant nutrition, particularly in forests growing on nutrient poor soils.

Generally, the normal inputs of nutrients in stemflow are lower than those of incident rainfall, indicating that epiphytic organisms and lichens growing on the bark could absorb them. Stem flow inputs tend to increase from tall forest to medium and low forest, which is more related with the decrease in stem flow amount from tall forest to medium and low forests then with changes in the elemental concentration of stem flow between the forests. Internal recycling includes the nutrients transferred from aboveground biomass to the forest soils in the form of litter fall and also those nutrients leached from the various plant parts to the soil when rainfall passes through the forest canopy as throughfall and stemflow. In contrast to litter fall, throughfall and stemflow add nutrients directly to the available nutrients pool without the intervention of any process of decomposition on the forest floor.

The fluxes of nutrients as throughfall and stem flow are much more rapid than those in litter fall because the nutrients in the water flows are largely in dissolved inorganic forms. Therefore, these fluxes are considered important pathways in the internal nutrient dynamics of the forests. Forest trees generally influence the soil fertility underneath the tree canopies especially if situated on nutrient poor environment. Researchers have found enhanced soil fertility in the forms of island of fertility in the immediate surroundings of plants. Under most circumstances, canopy serves as nutrient trap whereby nutrients present in the fine dust particles slowly get deposited onto the leave surfaces which eventually get into soil by throughfall or by stemflow.  Additionally, more litter fall will likely accumulate underneath the tree canopy which during decomposition will likely liberate organically tied up nutrients in the forms that might be utilized by tree on soil limited by nutrients.