China’s Conversion of Cropland to Forest Program (CCFP), otherwise known as ‘Grain for Green’, is the world’s largest afforestation-based Payments for Ecosystem Services (PES) program. Its success is renowned worldwide. And as with any success story, the lessons that CCFP offers are aplenty. One such lesson is on the importance of species and site conditions. A recent paper in Agricultural and Forest Meteorology contributes to underlining this importance.
Led by collaborators in China (Ying Zhao and Li Wang), University of Connecticut, and Utrecht University, the study used ‘environmental fingerprinting’ (aka stable isotope) techniques to understand the water use strategies of two exotic shrub species, Salix psammophila and Caragana korshinskii. Both shrubs have been widely used for revegetating the Loess Plateau. Our study has identified the water use strategies of these two exotic species.
The knowledge that this study has generated could inform ecological restoration. For example, it could be used to understand how these species might contribute to an optimal coexistence with native species.
On the one hand, promoting S. psammophila may prove beneficial with respect to deep soil water resources conservation given its shallow soil water use strategy. The same strategy, however, could result in a competitive relationship with shallow-rooted grasses. On the other hand, limiting the planting density of S. psammophila may come at a cost, particularly decreasing soil stability. This could result in suboptimal habitat conditions for other herbaceous species.
In contrast to S. psammophila, C. korshinskii’s deep water use strategy may provide favorable water conditions for shallow-rooted herbaceous species. This suggests that C. korshinskii is more suitable than S. psammophila for kickstarting revegetation in water-limited regions. Relative suitability notwithstanding, it may be necessary to identify an optimal level of C. korshinskii planting density to mitigate against the risks of deep soil water resources depletion.
Overall, our study contributes to the body of knowledge that may serve as a guide for evaluating the suitability of these species in the present and future management of the Loess Plateau.
As Louis Putzel, Senior Scientist at The Center for International Forestry Research (CIFOR) so succinctly put it a few years back: From an ecological perspective, restoration of degraded areas is a science that requires very specific knowledge of local ecology, good matching of species and practices to sites.
Poster image credit: The University of British Columbia