Evaluation on soil bioengineering measures in agricultural areas: Poorer durability of wooden structures and better aboveground habitat improvements

Abstract

Although soil bioengineering is increasingly used worldwide, the measures being used today are still based on an empirical approach. Most of the existing literature has primarily focused on mechanical soil reinforcement provided by plant roots and the search for available indigenous plant species, whereas wooden structures and aboveground habitat improvements have been poorly addressed in the literature. Nevertheless, it is of great importance to identify and replicate the most durable structural forms and parameters of bioengineering measures, especially during the initial phase of plant colonization. This paper mainly presents an evaluation of the effect of time (restoration ages), structural forms and structural parameters (materials and construction standards) on wooden structural durability and aboveground habitat improvements using soil bioengineering measures in agricultural areas. The results indicate that the wooden structural durability declines over time, and can be impacted by restoration ages, structural forms and structural parameters, whereas, aboveground habitat improvements measures show a positive response to restoration ages and structural parameters. The wooden structural form with multi-row timber piles (e.g., TTP) and structural parameter (e.g., Project A) was significantly more durable than were others. A temporary warning value (restoration age 7, seven years after the completion of the project) for the reconstruction of tilted timber piles is proposed, and two approaches are proposed regarding higher survival rate at restoration age one. The structural parameters of Project A showed a significantly better affect only for plant height from restoration age 6 to restoration age 9, and significantly higher amphibian abundance within the same restoration age, which means the measure of A may provide a better habitat than that of B. These results confirm the efficacy of this type of streambank soil bioengineering measure in agricultural areas and indicate its future application, and raise practical and scientific issues regarding structural durability and aboveground ecological restoration for management as well as for studies related to design improvement.