Abstract
Hydrological conditions determine the distribution of plant species in wetlands, where conditions such as water depth and hydrological fluctuations are expected to affect the interspecific interactions among emergent wetland species. To test such effects, we conducted a greenhouse experiment with three treatment categories, interspecific interaction (mixed culture or monoculture), water depth (10 or 30 cm depth), and hydrological fluctuation (static or fluctuating water level), and two common emergent wetland plant species, Scirpus planiculumis Fr. (Cyperaceae) and Phragmites australis var. baiyangdiansis (Gramineae). An increase in the water depth significantly restrained the growth of both S. planiculumis and P. australis, while hydrological fluctuations did not obviously alter the growth of either species. In addition, both water depth and hydrological fluctuations significantly affected the interspecific interaction between these two wetland species. P. australis benefited from interspecific interaction under increasing water depth and hydrological fluctuations, and the RII values were clearly positive for plants grown at a water depth that fluctuated around 30 cm. The results may have some implications for understanding how S. planiculumis and P. australis, as well as wetland communities, respond to the natural variation or human modification of hydrological conditions.
Highlights
Plants in natural wetland ecosystems often experience hydrological disturbances (McGowan et al, 2011), and water level regulation is considered to be a useful tool in vegetation restoration (Leira and Cantonati, 2008; Yuan et al, 2017)
To better understand the importance of water depth and its fluctuations in the interactions among emergent plants in wetlands, we addressed the following questions: (1) Do water depth and hydrological fluctuations affect the growth of wetland plants? (2) Are the interspecific interactions among emergent species affected by hydrological fluctuations and water depth? To answer these questions, we conducted a greenhouse experiment testing the effects of three treatment categories on two common emergent wetland plants collected from the banks of the Chaobai River in Beijing
Disturbances caused by hydrological fluctuations changed the effect of interspecific interactions for S. planiculumis (Table 2; significant interaction effect of I × F on the total biomass and aboveground biomass): aboveground biomass (P = 0.044) of plants significantly increased in mixed culture compared with these biomass values in the monoculture treatment under static hydrological conditions, while these differences were not obvious under the fluctuating conditions (Figure 2)
Summary
Plants in natural wetland ecosystems often experience hydrological disturbances (McGowan et al, 2011), and water level regulation is considered to be a useful tool in vegetation restoration (Leira and Cantonati, 2008; Yuan et al, 2017). Hydrological Conditions and Interspecific Interaction numerous studies have focused on plant-plant interactions along gradients of environmental disturbance (Bertness, 1991; Weigelt et al, 2002; Wang and Li, 2016) and have put forward the stressgradient hypothesis (SGH), which predicts that facilitation and competition simultaneously affect neighboring plants and that the net outcome of these interactions shifts from negative to positive with increases in environmental stress (Bertness and Callaway, 1994; Maestre et al, 2009; Smit et al, 2009; He et al, 2013) This is a well-supported hypothesis (Liancourt et al, 2005; Maestre et al, 2005; Lortie and Callaway, 2006), but few studies have focused on the effects of hydrological disturbances, such as changes in water depth and hydrological fluctuations, on interspecific interactions among emergent wetland species (Luo et al, 2015)
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