Multifunctional Forestry and Forest Management: Eco-hydrological Considerations

Increasing forest cover mainly for controlling severe soil erosion in dryland regions, such as the Loess Plateau in northwest China, can cause a drastic water yield reduction and threaten the water supply for regional development. Thus, multifunctional forestry is required, which pays special attention to balancing the hydrological impacts and other services of forests, through integrated forests–water–land management. In this way, certain water yield and stand stability against environmental stressors can be maintained, without reducing the dominant service of erosion control and other services provided by forests. This should be realised at different spatial scales, including consideration of rational forest cover and optimal spatial distribution of forests within basins, the site-matching species composition, and the optimal stand structure. The concrete approaches for meeting these requirements are summarised. For the multifunctional management of water-retention forests at stand scale, the indexes of ideal stand structure are set up, including a ground coverage of above 0.7 to control soil erosion, a canopy density of around 0.7 to maintain natural regeneration, and a ratio of tree height (m) to diameter at breast height (DBH, cm) of below 0.7 to minimise disasters by snow/storm. Then, five decision-making steps for multifunctional management of water-retention forests are suggested: (1) site quality investigation and classification; (2) site-specific determination of main functions and their priorities; (3) investigation of current stand structure characteristics; (4) diagnosis of structure/functions of current stand; and (5) arrangement of structure/function-oriented management measures. Finally, some examples of multifunctional forest management are illustrated.