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A simplified probabilistic analysis of water content and wilting in soil vegetated with non-crop species

Garg, Ankit, Hazra, Budhaditya, Zhu, Hong, Wen, Yangping
Catena 2019 v.175 pp. 123-131
Cynodon dactylon, Schefflera, agricultural land, evapotranspiration, grasses, green roofs, irrigation, monitoring, normal distribution, planning, probability, soil water, subtropics, topographic slope, transpiration, trees, vegetation, volumetric water content, water analysis, water content, wilting
The long-term performance of green infrastructures (e.g., vegetated slopes, green roof, bio-retention systems, etc.) can be affected by the wilting of vegetation (i.e., tendency of evapotranspiration (ET) to be nil) attributed to the decrease in volumetric soil water content. Therefore, it is important to explore an approach to investigate the wilting time of vegetation so that mitigation measures can be taken to ensure the serviceability of green infrastructure. The technical note aims to 1) conduct probabilistic analysis of volumetric soil water content in slopes vegetated with non-crop tree and grass species; and 2) further explore this analysis method for estimating probability of wilting (tendency of transpiration becoming nil) of the selected vegetation species under natural climate conditions. For this investigation, two non-crop species namely, Ivy tree (Schefflera heptaphylla) and Bermuda grass (Cynodon dactylon), commonly grown in subtropical regions in world were selected. A normal distribution was found as the best fit to the measured volumetric water content under the impact of both species. The estimated mean value was found significantly higher in Cynodon dactylon slope compared with that of Schefflera heptaphylla slope, while the coefficient of variation among the species is similar. The probability of wilting of C. dactylon is found lower than that of Schefflera heptaphylla. In the present study, the significance of using probabilistic approach for characterizing the distribution of volumetric soil water content to assess the reliability of vegetated infrastructure was highlighted. The study is useful for estimating the behaviour of vegetation for better planning of restoration and rehabilitation measures. This differs from those in agricultural fields with the usually shorter period for monitoring of vegetation growth (mostly within 3 months), and they are usually subjected to controlled manual irrigation.