Revegetation of the riparian zone of the Three Gorges Dam Reservoir leads to increased soil bacterial diversity

Abstract

As one of the most active components in soil, bacteria can affect soil physicochemical properties, its biological characteristics, and even its quality and health. We characterized dynamics of the soil bacterial diversity in planted (with Taxodium distichum) and unplanted soil in the riparian zone of the Three Gorges Dam Reservoir (TGDR), in southwestern China, in order to accurately quantify the changes in long-term soil bacterial community structure after revegetation. Measurements were taken annually in situ in the TGDR over the course of 5 years, from 2012 to 2016. Soil chemical properties and bacterial diversity were analyzed in both the planted and unplanted soil. After revegetation, the soil chemical properties in planted soil were significantly different than in unplanted soil. The effects of treatment, time, and the interaction of both time and treatment had significant impacts on most diversity indices. Specifically, the bacterial community diversity indices in planted soil were significantly higher and more stable than that in unplanted soil. The correlation analyses indicated that the diversity indices correlated with the pH value, organic matter, and soil available nutrients. After revegetation in the riparian zone of the TGDR, the soil quality and health is closely related to the observed bacterial diversity, and a higher bacterial diversity avails the maintenance of soil functionality. Thus, more reforestation should be carried out in the riparian zone of the TGDR, so as to effectively mitigate the negative ecological impacts of the dam. Vegetating the reservoir banks with Taxodium distichum proved successful, but planting mixed stands of native tree species could promote even higher riparian soil biodiversity and improved levels of ecosystem functioning within the TGDR.

Evaluating the Effects of Pressure Indicators on Riparian Zone Health Conditions in the Three Gorges Dam Reservoir, China

“…Our research results are consistent with earlier findings, indicating that the diversity of riparian zone condition is subject to the unique geographical location and different pressure indicators of a particular basin [17,46]. The research sites are located in the riparian zones of the TGDR region, falling in Southwest China [4,27,29,44,45,52]. The natural environment of the riparian zone has changed due to pressure indicators within the mountainous region, and this variation continues and has been highlighted in previous studies [4,21].…”

“…The research sites are located in the riparian zones of the TGDR region, falling in Southwest China [4,27,29,44,45,52]. The natural environment of the riparian zone has changed due to pressure indicators within the mountainous region, and this variation continues and has been highlighted in previous studies [4,21]. Due to its unique geographical circumstances and heterogeneous vegetation characteristics, the riparian zones of the TGDR has a diverse condition and pressure pattern [27,52].…”

“…The study found that stress exerted by different indicators on riparian conditions of the TGDR was mainly caused by high-pressure activities related to the operation of the dam. Old parts of the riparian zone have been replaced by the inundated area, and with this process, most of the native vegetation has disappeared [4,21,55,57].…”

“…The study sites are situated within the riparian zones of the TGDR region (31°2′34.0″ N 109°33′41.0″ E), comprising of 15 counties, having a gross area of 0.0451 million km 2 , and beginning from Jiang Jin county of Chongqing Municipality and ending at Zi Gui county of Hubei province, China (Figure 1). These areas fall within the humid subtropical monsoon climate, and receive the mean annual rainfall of approximately 1160.9 ± 118.7 mm, with mean yearly air temperature range over 17.5 ± 1.2 • C [4,21,44]. The soil in the areas is purple soil (Table 1), formed from the calcareous purplish sand shale (Regosols in FAO Taxonomy).…”

“…Due to shallow weathering of rocks, soil maturity is low. Erosion of water and soil is serious in less-developed areas along the banks of riversides [4]. At the moment, dominant available woody species in the riparian zone of the TGDR are Salix matsudana, Taxodium ascendens, and Taxodium distichum [21,27,45].…”