Factors Controlling Vegetation Establishment and Water Erosion on Motorway Slopes in Valencia, Spain

Abstract

In semiarid Mediterranean areas, the widespread environmental impact caused by the construction of motorways, railways, and pipelines has created an increasing need for effective restoration. We examined the influence of slope characteristics on vegetation and water erosion on 71 motorway slopes in a semiarid Mediterranean region. Specifically, we studied the effect of slope angle, type (roadfill vs. roadcut) and aspect (north vs. south) on soil properties, vegetation cover, species richness, floristic composition, and water-caused erosion. Temporal dynamics of soil water content was monitored and related to the soil water potential in order to explain possible differences in vegetation cover between slope types. The main factors influencing vegetation on motorway slopes were the angle, type, and aspect of the slope. Vegetation was almost completely lacking on roadcuts with slopes greater than 45 . On gentler slopes, vegetation cover was 4478% on roadfills but did not reach 10% on roadcuts, regardless of aspect. The main soil properties affected by the slope type and aspect were the organic matter content, soil available P, and water content. Rill erosion, gully erosion, and mass movement were all significantly higher on roadcuts than roadfills. A total of 308 spontaneous colonizers and seeded species were recorded. The type and aspect of the slope also controlled species composition. The short duration of available water in the soil with respect to soil water potential proved to be a limiting factor to plant colonization on roadcuts and southfacing slopes as well as the low soil fertility in the case of roadcuts. Our results underscore the difficulty of revegetating slopes with angles greater than 45 , where the probability of seeds moving downhill is high. Future efforts should focus on increasing the surface roughness or building terraces at regular intervals in order to reduce slope angle to less than 45 and favor seed trapping and germination. On gentler slopes, adjusting of seed mixes according to dominant species associated with each slope type and aspect should improve considerably the success of roadside revegetation.

Effects of wood chip amendments on the revegetation performance of plant species on eroded marly terrains in a Mediterranean mountainous climate (Southern Alps, France)

“…The novelty value of our results concerns the positive effect of wood chips for revegetation in a steep slope context. Bochet and García-Fayos (2004) underscored "the difficulty of revegetating slopes with angles greater than 45 • (100 %), where the probability of seeds moving downhill is high." Other applications have to be examined in larger contexts of restoration and bioengineering works.…”

Comparing Potential Unstable Sites and Stable Sites on Revegetated Cut-Slopes of Mountainous Terrain in Korea

“…• Quadrat method (5 m × 5 m), measured three times at each site Bochet and Garcia-Fayos (2004) [13], MOLIT (2009) [36] Number of tree species (no. )…”

“…• Number of tree species by plant nomenclature Bochet and Garcia-Fayos (2004) [13], MOLIT (2009) [36] …”

“…Slope revegetation works have been widely implemented on large and steep slopes in temperate zones [6,11,12]. However, revegetated slopes frequently fail due to heavy rain and drought [13]. The reasons for failure include the elimination of seeds by water running over uncovered and crusted soils and withered plants due to the inappropriate use of commercial species without the consideration of neighboring environments and due to extreme changes in local climate, such as intermittent dry seasons and heavy rainfall [14,15].…”

Research on Species Ecological Adaptability of Shrub Vegetation of Highway Slope

“…The chosen grass seeds should be determined by the purpose of protection, climate, soil property and construction season, etc [5] . So far, achievements in terms of recovery technology for slope vegetation have been made in areas with good growing environment which have normal temperature and rainfall [6][7][8] . However, there has been relatively little scientific study on restoration research of highway vegetation in subtropical areas which have the issues of sever water and soil loss, large amount of rainfall, unequal distribution of rainfall.…”