Planting trees and glasses 植树种草
Ganzhou, a typical red soil hilly area in Jiangxi province, is a pilot area for high-quality development of soil and water conservation in China. Through a series of following innovative initiatives, soil erosion in Ganzhou has been effectively prevented and controlled. One of these measures is planting trees and grasses. Here are its working pricipal and impacts on soil erosion.
How planting trees and glasses works?
01 Canopy and understory vegetation layer 树冠层和林下植被层
The canopy and understory act as an umbrella, cutting the raindrop potential and blocking some of the precipitation. Plant interception can be regarded as two parts: first, the amount of water evaporating from the surface of branches and leaves during precipitation; Second, the amount of water that remains on the trees and leaves when the precipitation stops, which is also eventually consumed by evaporation. After interception, it prevents raindrops from splashing the topsoil and prevents soil particles from being crushed; On the other hand, the amount of rainfall falling to the ground is greatly reduced, thus reducing the surface runoff and thus reducing the amount of soil erosion. The lower the canopy, the greater the canopy, and the thicker the understory, the stronger this effect is. In mid-latitude conditions, a basically closed forest ecosystem can trap about 15%-30% of the annual precipitation. The tree canopy has a strong ability to intercept precipitation. At the same time, canopy can reduce the solar long-wave radiation, reduce wind speed and temperature, and reduce the pressure difference of saturated water in forest air, so as to reduce the evaporation of soil water.
02 Litter layer枯枝落叶层
When the rainfall-bearing capacity of forest canopy and understory reaches saturation, water droplets falling from tree canopy and plant canopy have greater impact on ground soil. The second barrier is a layer of litter formed by forest litter. The forest produces a lot of litter every year, of which the largest number and the largest role is the leaves of tree species, accounting for about 60%-80%. Compared with a forest canopy, a layer of litter covers the ground and prevents raindrops from splashing the soil more effectively. These litter have great porosity, can absorb and permeate precipitation, and have strong water conservation performance. The maximum water retention rate is more than 136.56%, and the maximum water retention is more than 9.32t/hm².
When the precipitation intensity exceeds the critical water-holding capacity of forest canopy interception and forest litter and soil, slope runoff will be produced. Because of the presence of litter, the flow of runoff through it is slowed down by obstruction.
When the soil surface of the forest is covered with litter, the evaporation of water on the soil surface is hindered, and the evaporation of soil is reduced.
03 Root soil layer根系土壤层
When the soil layer thickness is constant, the water conservation performance of the forest land mainly depends on the pore characteristics of the soil, especially the porosity of the soil with large non-capillary pores, and the infiltration performance is strong, thus reducing surface runoff.
Its impacts on soil erosion
To intercept precipitation； to improve soil properties； to delay runoff, flood control and disaster reduction ；to inhibit soil evaporation ；to consolidate soil and protect slope ；to conserve precipitation.
Plant measures can play a positive role in the prevention and control of soil and water loss caused by wind erosion, water erosion and gravity erosion. The mechanism is mainly that the above-ground part of vegetation can reduce wind speed, weaken raindrop energy and delay the formation of runoff, etc., while the underground part can enhance soil permeability, slow down the formation of surface runoff and enhance soil stability. Based on these mechanisms, the surface with vegetation preserves soil and water well.