A framework for identifying plant species to be used as 'ecological engineers' for fixing soil on unstable slopes.
Bottom Line: Significant differences between all factors were found, depending on species.We then combined these results with those concerning root physiological traits, which were used as a proxy for root metabolic activity.We also propose a conceptual model describing how to position plants on an unstable site, based on root system traits.
Affiliation: AgroParis Tech, UMR AMAP, Montpellier, France.
Major reforestation programs have been initiated on hillsides prone to erosion and landslides in China, but no framework exists to guide managers in the choice of plant species. We developed such a framework based on the suitability of given plant traits for fixing soil on steep slopes in western Yunnan, China. We examined the utility of 55 native and exotic species with regard to the services they provided. We then chose nine species differing in life form. Plant root system architecture, root mechanical and physiological traits were then measured at two adjacent field sites. One site was highly unstable, with severe soil slippage and erosion. The second site had been replanted 8 years previously and appeared to be physically stable. How root traits differed between sites, season, depth in soil and distance from the plant stem were determined. Root system morphology was analysed by considering architectural traits (root angle, depth, diameter and volume) both up- and downslope. Significant differences between all factors were found, depending on species. We estimated the most useful architectural and mechanical traits for physically fixing soil in place. We then combined these results with those concerning root physiological traits, which were used as a proxy for root metabolic activity. Scores were assigned to each species based on traits. No one species possessed a suite of highly desirable traits, therefore mixtures of species should be used on vulnerable slopes. We also propose a conceptual model describing how to position plants on an unstable site, based on root system traits.
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Mentions: The quantity of N present in roots depended on species (F8,231 = 33.48; P<0.001, Figure 10a) and the interaction between species and root diameter (F15,224 = 26.32; P<0.001, Fig; 10a). A. codonocephala had the highest quantity of N present in roots, regardless of root diameter (Figure 10a). The leguminous P. stricta also possessed high levels of N in fine roots (Figure 10a), as did the fine roots of the leguminous B. championii, but to a lesser exent (Figure 10a).