How afforestation affects the water cycle in drylands: A process-based comparative analysis.

Area of Science:

• Ecohydrology
• Forestry science
• Environmental science

Background:

• Large-scale afforestation programs, like China's, contribute to global greening and UN Sustainable Development Goals.
• However, poorly implemented afforestation can lead to ecological and water security issues.
• Existing research highlights reduced water yield at the watershed scale due to afforestation, but plot-scale data on water partitioning is scarce.

Purpose of the Study:

• To investigate the ecohydrological impacts of afforestation on the Loess Plateau using a paired plot approach.
• To analyze how forest structure and environmental factors influence the water balance in a black locust plantation.
• To compare the water balance components of a black locust plantation with adjacent natural grassland.

Main Methods:

• Implementation of a "Paired Plot" study design comparing a black locust plantation with adjacent natural grassland.
• Measurement of ecohydrological components, including water balance elements, at the plot scale.
• Investigation of forest structure and environmental factors affecting the water cycle.

Main Results:

• The understory vegetation, not the overstory trees, was identified as the primary water consumer in the black locust plantation.
• Forest transpiration demonstrated strict physiological regulation.
• Annual seepage was minimal under the forest during years with average rainfall, unlike in grassland.

Conclusions:

• Large-scale afforestation in drylands necessitates thorough ecohydrological evaluation to balance green and blue water resources.
• Reforestation efforts for climate change mitigation (carbon sequestration) must consider regional water security implications.
• Effective watershed management requires understanding the complex water dynamics influenced by afforestation practices.