Effects of plant growth and spacing on soil hydrological changes: a field study

Abstract

Effects of plant growth on soil hydrological changes need to be considered for long-term vegetation management of geotechnical infrastructure. Most existing studies focused on one particular plant age. This study quantifies the effects of plant growth on the evolution of soil hydraulic properties and matric suction over time, through field monitoring and numerical soil–plant–atmosphere interaction modelling. A full-scale flat landfill cover in China was monitored for more than a year. Four 6 m × 6 m grass plots made of compacted silty sand were formed, three of which were vegetated with shrubs having different plant spacing (0·5, 0·8 and 1·1 m), while the fourth one was left grassed. In addition to monitoring matric suction changes, multiple soil cores were sampled to determine the root length density (RLD) and saturated hydraulic conductivity (ks) after 2, 4, 7 and 13 months of transplantation. Regardless of plant spacing, ks always reduced during the first 2–3 months of growth. When a threshold RLD of 2 cm/cm3 was reached, ks increased substantially. This was especially the case for closely spaced shrubs, whose roots were decayed. Suction preserved upon rainfall depended on the plant growth-induced changes in ks. Although closely spaced (0·5 m) shrubs preserved the most suction during the first 6 months of growth, the beneficial hydrological effects vanished after growing for 9 months because of the shrub growth-induced increase in ks. Instead, the widely spaced (1·1 m) shrubs, which showed the least increase in ks, preserved the most suction in later stages. Nonetheless, the spacing of shrubs did not affect the annual cumulative percolation of the landfill cover very significantly, which narrowly ranged between 3·1 and 4·7% of the annual precipitation during the monitoring period.

Hydro-mechanical modeling of a vegetated slope subjected to rainfall

“…The plant species in this study is Schefflera heptophylla, which is compatible with the mentioned region and widely used due to its ability of drought tolerant and control of soil erosion. Various parameters of this plant for modeling were retrieved from the experimental literature for the planting density of 180 mm [12]. Due to the consideration of plant growth and actual conditions during analyzing, Table 2 shows a summary of the properties of the plant during four months.…”

“…Table 2. Properties of the Schefflera heptophylla [12] The maximum possible transpiration rate is depended on the soil moisture. The presence of wet conditions causes oxygen deficiency, and the presence of dry conditions limits water availability.…”

“…The presence of vegetation due to its hydrological and mechanical effects causes slope stabilization [5,[8][9][10]. From a hydrological point of view, plant transpiration due to root water uptake reduces the volumetric water content in the soil and increases the matric suction [5,[11][12][13]. The increase in matric suction and hence the enhancement of shear strength causes the stability of slopes [14,15].…”

Slope Orientation and Vegetation Effects on Soil Thermo-Hydraulic Behavior. An Experimental Study

“…A seed mix 80% Cynodon dactylon and 20% Festuca arundinacea was hand sowed with a seeding density of 34 g/m 2 and an average plant spacing of 30 ± 5 mm. Seed sowing density and distance are factors affecting the hydraulic behavior of soils [50,56]. These perennial species were chosen because they have a high drought tolerance, increase soil strength due to their roots and are commonly used in bioengineering for slope revegetation in warm climates [45,[57][58][59][60][61].…”

Exploring implication of variation in biochar production on geotechnical properties of soil

“…Biochar addition in soil was found to alter the physical properties such as porosity, saturated hydraulic conductivity, surface area, crack potential and soil water retention characteristics (SWRC) [15][16][17]. Those changes in soil physical properties may promote the growth of vegetation, which affects the soil hydrological responses and stability of earthen infrastructures [18][19][20][21]. The soil mechanical properties such as shear strength, erosion potential and liquefaction potential were also reported to be altered by biochar [22,23].…”