SummaryAlthough fine roots are important components of the global carbon cycle, there is limited understanding of root structure-function relationships among species. We determined whether root respiration rate and decomposability, two key processes driving carbon cycling but always studied separately, varied with root morphological and chemical traits, in a coordinated way that would demonstrate the existence of a root economics spectrum (RES).Twelve traits were measured on fine roots (diameter ≤ 2 mm) of 74 species (31 graminoids and 43 herbaceous and dwarf shrub eudicots) collected in three biomes.The findings of this study support the existence of a RES representing an axis of trait variation in which root respiration was positively correlated to nitrogen concentration and specific root length and negatively correlated to the root dry matter content, lignin : nitrogen ratio and the remaining mass after decomposition. This pattern of traits was highly consistent within graminoids but less consistent within eudicots, as a result of an uncoupling between decomposability and morphology, and of heterogeneity of individual roots of eudicots within the fine-root pool.The positive relationship found between root respiration and decomposability is essential for a better understanding of vegetation-soil feedbacks and for improving terrestrial biosphere models predicting the consequences of plant community changes for carbon cycling.

Background Plants alter their environment in a number of ways. With correct management, plant communities can positively impact soil degradation processes such as surface erosion and shallow landslides. However, there are major gaps in our understanding of physical and ecological processes on hillslopes, and the application of research to restoration and engineering projects.Scope To identify the key issues of concern to researchers and practitioners involved in designing and implementing projects to mitigate hillslope instability, we organized a discussion during the From this discussion, ten key issues were identified, considered as the kernel of future studies concerning the impact of vegetation on slope stability and erosion processes. Each issue is described and a discussion at the end of this paper addresses how we can augment the use of ecological engineering techniques for mitigating slope instability. Conclusions We show that through fundamental and applied research in related fields (e.g., soil formation and biogeochemistry, hydrology and microbial ecology), reliable data can be obtained for use by practitioners seeking adapted solutions for a given site. Through fieldwork, accessible databases, modelling and collaborative projects, awareness and acceptance of the use of plant material in slope restoration projects should increase significantly, particularly in the civil and geotechnical communities.

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Vegetation can signiˆcantly contribute to stabilise sloping terrain by reinforcing the soil: this reinforcement depends on the morphological characteristics of the root systems and the tensile strength of single roots. This paper describes an investigation on the reinforcing eŠect of soil-root matrix in the laboratory using a modiˆed large shear box apparatus (300 mm×300 mm). Four diŠerent species of plant namely Vertiveria zizanoides, Leucaena leucocephala, Bixa orellana and Bauhinia purpurea were planted in special boxes containing residual soil compacted to a known density. The results show that roots signiˆcantly contribute to the increase in soil shear strength. The presence of the roots only aŠects the apparent cohesion of the soil and no signiˆcant change in angle of friction is observed. L. leucocephala shows the outstanding increase in its root strength in which the strength varies with depth and time e.g., under soil suction-free condition (matric suction＝0), the roots have increased the cohesion by 116.6z (0.1 m), 225.0z (0.3 m) and 413.4z (0.5 m) after six months of growth. In twelve months, it is observed that the increase in cohesion is more than three-fold of the six months growth period at 0.1 m depth. The results also indicate that shear strength is in‰uenced by root proˆle and to some extent, the physiological parameters of the plants.