Reduced soil infiltration rate and water-holding capacity
Explanation
Forests function as a critical component of the hydrological cycle, primarily by facilitating groundwater recharge. The vegetation cover, leaf litter, and root systems create a porous soil structure that allows precipitation to permeate the ground rather than flowing away as surface runoff.
Detailed Analysis:
- Mechanism of Infiltration: In a healthy forest ecosystem, the canopy breaks the velocity of falling raindrops, preventing soil compaction. The forest floor, rich in humus and organic matter, acts as a sponge, absorbing water. Tree roots create macropores (channels) that allow water to percolate deep into the soil, recharging the water table.
- Impact of Deforestation: When vegetation is removed, the soil is exposed to the direct impact of rain, leading to surface sealing and compaction. This significantly reduces the infiltration rate. Consequently, most rainwater becomes surface runoff, causing soil erosion and flash floods instead of seeping down to replenish groundwater reserves.
- Analysis of Incorrect Options:
- Cessation of transpiration by trees: Transpiration is the loss of water from plants to the atmosphere. While deforestation stops this process, the cessation of transpiration would theoretically conserve soil water. The lowering of the water table is caused by the failure of recharge (infiltration), not the lack of transpiration.
- Excessive rainfall washing away the groundwater: Rainfall is the source of groundwater recharge. It does not "wash away" groundwater. Surface runoff washes away topsoil, but this is a consequence of poor infiltration, not the direct removal of groundwater.
- Increased root absorption by remaining vegetation: Deforestation results in the removal of roots, leading to decreased absorption, which is not the cause of a lowering water table.
Key Takeaway:
Deforestation lowers the groundwater table primarily because it destroys the soil's ability to absorb and filter rainwater (infiltration), converting potential groundwater recharge into immediate surface runoff.