Abstract
Flooding is an important factor influencing the biomass production of vegetation in natural wetland ecosystems. However, how biomass production is linked to flooding patterns in wetland areas remains unclear. We utilized gauging station data, a digital elevation model, vegetation survey data, and a Landsat 8 image to study the effects of average inundation depth (AID) and inundation duration (IDU) of flooding on end-of-season biomass of vegetation in Poyang Lake wetland, in particular, after operation of Three Gorges Dam. The end-of-season biomass of wetland vegetation showed Gaussian distributions along both the AID and IDU gradients. The most favorable flooding conditions for biomass production of vegetation in the wetland had an AID ranging from 3.9 to 4.0 m and an IDU ranging from 39% to 41%. For sites with a lower AID (<3.9 m; IDU < 39%), the end-of-season biomass values were positively related, whereas for sites with a higher AID (4.0 m; IDU > 41%), the end-of-season biomass values were negatively related. After the operation of the Three Gorges Dam, flooding patterns characterized by AID and IDU of the Poyang Lake wetland were significantly alleviated, resulting in a mixed changing trend of vegetation biomass across the wetland. Compared with 1980–2002, the increase of end-of-season biomass in lower surfaces caused by the alleviated flooding pattern far exceeded the decrease of end-of-season biomass in higher surfaces, resulting in an end-of-season biomass increase of 1.0%–6.7% since 2003. These results improved our understanding of the production trends of vegetation in the wetland and provided additional scientific guidance for vegetation restoration and wetland management in similar wetlands.
Highlights
Plants are the primary producers in wetland ecosystems, providing food and habitat for many species of fish, amphibians, water birds, and other forms of life (Fisher and Willis, 2000; Kingsford and Thomas, 2004; Xie et al, 2015)
Low end-of-season biomass values occurred in the depressions and regions near to the main lake water surfaces; high end-of-season biomass values occurred in the moderate elevation part of the wetland; and moderate end-of-season biomass values occurred in the ridges of the wetland
We discussed the response of vegetation biomass to land surface exposure time after flooding in the Poyang Lake wetland to reveal the influence of Three Gorges Dam on biomass production (Dai, 2018)
Summary
Plants are the primary producers in wetland ecosystems, providing food and habitat for many species of fish, amphibians, water birds, and other forms of life (Fisher and Willis, 2000; Kingsford and Thomas, 2004; Xie et al, 2015). In seasonally inundated herbaceous wetlands, which are affected by non-stationary flooding patterns, biomass production of vegetation usually changes rapidly and shows strong spatial heterogeneity (Poff et al, 1997; Dornova, 2012; Byrd et al, 2014; Watson and Corona, 2018). Trade-offs in site specific impacts from flooding are difficult to quantify at the landscape scale, yet the net balance of consequences is important for continued management of these diverse ecosystems. This is true in large, heterogeneous ecosystems, such as the Poyang Lake wetland, China (Sang et al, 2014)
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