The ecohydrological potential of Vetiver Grass (Chrysopogon zizanioides) for Forest Rehabilitation in abandoned quarries

Quarrying causes extensive degradation of soils, vegetation, and ecosystems, and these effects are further exacerbated by severe weather events and climate change. Consequently, abandoned quarries are some of the most difficult environments to rehabilitate due to the loss of critical ecological functions. Soft engineering solutions, such as vetiver grass (Chrysopogon zizanioides), have been widely used to control erosion, however its potential for water uptake, and application for companion planting in a rehabilitation setting is yet to be explored. Existing literature suggests that vetiver will not only be highly resilient to the harsh environment in abandoned quarries, but it may also improve the hydraulic and microclimatological conditions to aid tree survival and reestablishment. Furthermore, rehabilitation of degraded lands through the extensive root networks of grasses also offers opportunities for enhanced carbon sequestration. 

This study aims to determine the ecohydrological potential of vetiver grass to improve the growth rate and survival of forest saplings in abandoned quarries at two study locations. Soil moisture probes were installed at depths of 10, 20, and 40 cm throughout hedgerows with and without vetiver of varying ages. Soil temperature, air temperature, relative humidity, and rainfall were recorded, and plant, soil, stream, and rainfall samples were collected for stable isotope analysis. Results show that show that vetiver significantly influenced soil moisture, and vapor pressure deficit (VPD) with effects varying by season and site (p <0.05; a = 0.05). While there was some improvement in soil chemical and physical properties within the shallow rooting zone (p <0.05; a = 0.05), there was no improvement to sapling survival at either site. Stable water isotope analyses show that saplings and Vetiver relied on the same shallow 0–20 cm water sources, indicating competition likely driven by limited rooting depth. Nonetheless, if integrated thoughtfully, vetiver can support biodiversity and increase rooting complexity, improving water and nutrient cycling.

These findings highlight vetiver’s capacity to modify microclimatic and shallow soil conditions but also reveal some constraints for its use as a companion species in early forest restoration. Future work should examine soil amendments or pre-rehabilitation treatments to enhance rooting depth and reduce competition before implementing vetiver-based interventions.