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Poyang Lake wetland plays an important ecological service function. Frequent drought events have caused significant changes in the distribution pattern of wetland plants. This study analyzed the changes in the distribution elevation of wetland plants in Poyang Lake from 2000 to 2020, including the optimal elevation, and upper and lower limit elevations, and revealed the impacts of drought on the ecological niches of typical wetland plants. The results showed that the wetland plants were distributed in a regular strip pattern according to the elevation gradient. The Polygonum hydropiper–Phalaris arundinacea (PP), Carex cinerascens (Cc), Phragmites australis–Triarrhena lutarioriparia (PT), and Artemisia selengensis (As) communities were mainly distributed at elevations of 8.70–13.62 m, 10.35–14.99 m, 12.00–16.28 m, and 11.82–18.46 m, with optimal elevations of 11.16, 12.67, 14.14, and 15.14 m, respectively. Although the optimal elevations and upper limit elevations of four typical wetland plants exhibited different changing trends, their lower limit elevations showed the significant downward trends, especially for Cc and PP communities. Moreover, drought caused a varying degree of decrease (0.16–0.34 m) in the optimal elevations of four typical wetland plants, the upper and lower limit elevations of most wetland plants had also decreased in dry years.

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  • The wetland plants were distributed in a regular strip pattern according to the elevation gradient.

  • The lower limit elevations of four typical wetland plants showed significant downward trends.

  • Drought caused a varying degree of decrease in the optimal elevations.

  • The upper and lower limit elevations of most wetland plants decreased in dry years.

distribution elevation, drought, ecological niches, Poyang Lake, wetland plant
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Poyang Lake is the largest freshwater lake in China, with a complex water exchange relationship with surrounding water systems. The water level and area of the lake vary greatly, with seasonal lake level fluctuations of over 10 m throughout the year. During the flood season, the lake level rises and the maximum lake area reaches nearly 4,000 km2. However, after entering the dry season, the lake surface shrinks to less than 1,000 km2 and the floodplain is exposed (Hu et al. 2010). Due to the significant changes in the water level and area of Poyang Lake, over 2,000 km2 of floodplain wetlands have been formed in the lake area (Dai et al. 2019; Hu & Lin 2019; Li et al. 2023a, 2023b). The Poyang Lake floodplain wetland has abundant wetland vegetation resources and species diversity (Huang & Guo 2007; Li et al. 2023a). According to the latest survey, the Poyang Lake wetland has 154 species of phytoplankton in 54 families, 74 species of meadow and swamp plants in 25 families, and 102 species of aquatic vascular plants in 38 families (Department of Water Resources of Jiangxi Province 2009). The Poyang Lake wetland has become one of the areas with the richest biological resources in China's wetland ecosystem.

However, due to the dual impacts of climate change and human activities, the water level of Poyang Lake has fluctuated abnormally in recent years, resulting in frequent extreme hydrological events, especially the advance and extension of the dry season, the decline of lake water level, and the shrinkage of lake surface (Li et al. 2023a, 2023b). The hydrological drought trend of Poyang Lake is increasingly serious (Guo et al. 2012; Tian et al. 2023; Ye et al. 2023), which poses a serious threat to the ecological security of Poyang Lake wetlands. Especially, Poyang Lake entered the dry season 100 days earlier than the historical average in 2022, and the water level in the dry season also broke the record of the lowest lake water level in history (https://www.whb.cn/zhuzhan/cs/20220815/481081.html). On July 20, 2023, the water level at Xingzi station in Poyang Lake dropped to 11.99 m, which became the lowest level in the same period since records began in 1951. 2023 has become the earliest year for Poyang Lake to enter the dry season, which is 17 days earlier than that in 2022, and 103 days earlier than the historical average. The severe droughts have affected the ecological environment and agricultural production, and even affected the lives and health of local people (Zhang et al. 2014; Wang et al. 2023; Zhang et al. 2023; Li et al. 2023a, 2024).

At present, many studies have been carried out on the dynamic changes of wetland vegetation in Poyang Lake and its response to the lake water regime. For example, You et al. (2015) investigated the vegetation distribution of two typical wetlands in the main branch and south branch of Ganjiang River (one of the tributaries of Poyang Lake) from 1973 to 2012 and found that the wetland vegetation distribution moved down and expanded to the center of the lake. Dai et al. (2019) and You et al. (2016) revealed the spatiotemporal dynamic change process of the Carex cinerascens–Phalaris arundinacea community and Phragmites australis–Triarrhena lutarioriparia community in Poyang Lake wetland based on the Landsat images from 1989 to 2009. Chen et al. (2014) analyzed the distribution pattern of emergent and submerged vegetation in Poyang Lake from 2000 to 2012 based on MODIS time series images. Zheng et al. (2021) compared the vegetation coverage of the Poyang Lake wetland before and after the operation of the Three Gorges Project and found that the vegetation growth rate accelerated after 2003. Han et al. (2018) found that the total area of Poyang Lake wetland vegetation and the area of C. cinerascens community, Polygonum hydropiper–P. arundinacea community and P. australis–T. lutarioriparia community had an obvious increasing trend from 2000 to 2014. Wu et al. (2010) investigated the biomass of Bang Lake (a typical saucer sub-lake in Poyang Lake) and found that the vegetation biomass decreased significantly from 1994 to 2009. Specifically, the biomass of P. australis–T. lutarioriparia community decreased by 1,025 g/m2, and the biomass of C. cinerascens community decreased from 1,717 to 566 g/m2 (Wu et al. 2010). In addition, the field survey showed that the plants above the elevation of 15.0 m in Poyang Lake wetland, such as C. cinerascens and T. lutarioriparia, showed dwarfing in 2013 compared to that in 1983, and the richness and diversity of wetland species significantly decreased (Hu & Lin 2019).

Droughts are one of the significant stress factors in wetland ecosystems. Frequent droughts and their lagging effects have serious impacts on the growth, distribution pattern and succession of wetland plants, as well as the structure and function of ecosystems (Vicca et al. 2016; Berdugo et al. 2020; Zhu et al. 2023), and even lead to a decline in various ecosystem functions (Griffin-Nolan et al. 2018; Kong et al. 2023). However, previous studies have mainly focused on the distribution, vegetation landscape pattern, and biodiversity of wetland vegetation communities in Poyang Lake. Less attention has been paid to the distribution elevation and ecological niche changes of typical wetland plants, especially the impacts of hydrological droughts on ecological niches of different wetland plants are still unclear, which is crucial to measuring the growth status of plants in Poyang Lake wetland. Our initial study obtained the spatial distribution patterns of wetland vegetation in Poyang Lake from 2000 to 2020 through the spatiotemporal fusion of Landsat and MODIS images (Lin et al. 2023). Therefore, this study further analyzes the change characteristics of distribution elevation for different wetland plants in Poyang Lake (including the most suitable elevation, upper and lower elevation limits) and reveals the impacts of droughts on the ecological niche of typical wetland plants. The results provide important support for evaluating the ecological health status of wetland vegetation in Poyang Lake under the influence of drought and maintaining the ecological service function of wetlands.

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Study area

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Poyang Lake is located in the middle reaches of the Yangtze River, with a drainage area of 16.22 × 104 km2 (Figure 1). The lake receives water primarily from five major tributaries in its basin (Li et al. 2017). The average annual inflows of Gan River, Fu River, Xin River, Rao River, and Xiu River into the lake were 683 × 108 m3, 123 × 108 m3, 179 × 108 m3, 135 × 108 m3, and 84 × 108 m3, accounting for 47.1, 8.5, 12.3, 9.4, and 5.8% of the total water inflow into Poyang Lake, respectively. The water level of Poyang Lake exhibits great seasonal fluctuations throughout the year. Specifically, as the floods of the five tributaries entered the lake from April to May, the lake water level began to rise rapidly. From June to August, the lake water level remained high due to the Yangtze River flood, and in September, it began to recede as the Yangtze River flood weakened. In November, the Poyang Lake entered a dry season and continued until March of the following year. Seasonal water level fluctuations caused periodic inundation and exposure of the Poyang Lake floodplain, forming over 2,000 km2 of wetlands (Liu et al. 2012). The unique hydrological rhythm and wetland habitat of Poyang Lake have created rich wetland vegetation resources and species diversity (Huang & Guo 2007).
Figure 1
Location of the Poyang Lake wetland and distribution of wetland vegetation.
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Location of the Poyang Lake wetland and distribution of wetland vegetation.

Figure 1
Location of the Poyang Lake wetland and distribution of wetland vegetation.
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Location of the Poyang Lake wetland and distribution of wetland vegetation.

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The distribution of vegetation in the Poyang Lake wetland shows a clear strip pattern, with different vegetation communities occupying specific ecological niche spaces (Zhou 2011; Xu et al. 2015). Overall, it shows four typical strip-shaped vegetation landscapes from the high-level floodplain in the far lake area to the lowland in the center of the lake, including the mesophytic grassland, emergent vegetation, hygrophilous vegetation, and submerged vegetation. At an elevation of over 17 m, it is mainly distributed as mesophytic plants, such as Artemisia capillaris and Cynodon dactylon; the emergent plants are mainly distributed in the coastal areas at an elevation of 15–17 m, including P. australis and T. lutarioriparia, accompanied by Artemisia selengensis and P. hydropiper; the hygrophilous plants are mainly distributed in the beach between 12 and 15 m, mainly consisting of Carex and P. arundinacea, accompanied by A. selengensis; the submerged plants are mainly distributed on the coastal beaches at an elevation of 9–12 m, mainly including Potamogeton wrightii morong, Vallisneria natans, etc. (Liu & Ye 2000; Zhou 2011). Moreover, to accurately reveal the changing trends of wetland plants in different lake areas, the Poyang Lake wetland was divided into three regions according to elevation as shown in Figure 1(b).

Data

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The MODIS data used in the study are vegetation index composite product MOD13Q1 from NASA (National Aeronautics and Space Administration) (http://ladsweb.modaps.eosdis.nasa.gov), which combines Terra and Aqua satellite data. Its time span is from February 2000 to December 2020, with a spatial resolution of 250 m × 250 m and a temporal resolution of 8 d. Meanwhile, all available Landsat TM/ETM + /OLI data for the same period were obtained from USGS (United States Geological Survey) (http://glovis.usgs.gov), with a spatial resolution of 30 m × 30 m. After cloud removal, band restoration, and atmospheric correction, 153 Landsat NDVI data were obtained by selecting the red and near-infrared bands for calculation. In addition, the terrain of the lake area was derived from the digital elevation model with a spatial resolution of 4.8 m provided by the Jiangxi Provincial Hydrological Bureau in 2010. After reprojection and resampling, elevation data with a spatial resolution of 30 m was generated, and elevation gradients were set in steps of 0.5 m in the study to analyze the changes in the distribution elevation of wetland plants. The observed daily lake water level at Xingzi station, a representative hydrological station in Poyang Lake, was collected from the Hydrological Bureau of the Yangtze River Water Resources Commission from 2000 to 2020, to determine different types of hydrological years. Specifically, 2000, 2001, 2003, 2005, 2014, and 2015 were considered as normal years; 2002, 2010, 2012, 2016, and 2020 were typical wet years; and 2004, 2006, 2007, 2008, 2009, 2011, 2013, and 2018 were typical dry years.

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This study fused the MODIS data and Landsat data based on a spatiotemporal adaptive fusion model for NDVI products (STAFFN) developed by Chen et al. (2018) to obtain an NDVI dataset with high temporal and spatial resolutions.
(1)
(2)
(3)
(4)
where ω is the size of the moving window; Wij is a weight determined by spectral similarity (Sij) and spatial distance difference (dij); Pij is a set of similar pixels represented by a binary matrix.

Based on the fused high spatiotemporal resolution NDVI dataset of Poyang Lake wetland, this study adopted the classification algorithm of wetland plant community proposed by Han et al. (2018) to classify the study area into eight landscapes: water, mudflat, floating aquatic macrophytes community (Fam), P. hydropiper–P. arundinacea community (PP), C. cinerascens community (Cc), P. australis–T. lutarioriparia community (PT), A. selengensis community (As), and forest (Lin et al. 2023). For details of the STAFFN model and wetland vegetation classification method, please refer to Chen et al. (2018), Han et al. (2018) and Lin et al. (2023).

In addition, previous studies have confirmed that Gaussian regression can effectively describe the relationship between plant species distribution and environmental factors. Therefore, a Gaussian regression model was used in the study to analyze the distribution characteristics of different wetland plant communities along the elevation gradient. The Gaussian regression model equation is:
(5)
where y represents the area of wetland plant communities; x refers to elevation gradient; μ is the optimal distribution elevation corresponding to the maximum distribution area of plant communities; t is the tolerance of the species, used to describe the ecological breadth of plant species. Generally, [μ − 2t, μ + 2t] is considered the normal ecological interval of the species, and [μ − t, μ + t] is the suitable ecological interval.
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Spatial patterns of wetland landscape types

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The changes in the landscape patterns of the Poyang Lake wetland from 2000 to 2020 are shown in Figure 2. It is seen that the spatial distribution of different landscape types varied in different years. Overall, the landscape types along the elevation gradients from the lake center to the outside were water bodies, Fam, mudflats, PP community, Cc community, PT community, As community and forests, respectively. Water and mudflats accounted for 20 and 24% of the lake area, respectively. Wetland vegetation was widely distributed in the lake area, with different plants exhibiting a regular strip distribution according to elevation gradients. Among them, the Cc community had the widest area, accounting for nearly 30% of the total wetland area, followed by the PT and PP communities, with an area of over 10%. The distribution of Fam and As communities was relatively small, accounting for only 1–2%.
Figure 2
The changes in the landscape patterns of the Poyang Lake wetland from 2000 to 2020.
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The changes in the landscape patterns of the Poyang Lake wetland from 2000 to 2020.

Figure 2
The changes in the landscape patterns of the Poyang Lake wetland from 2000 to 2020.
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The changes in the landscape patterns of the Poyang Lake wetland from 2000 to 2020.

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The area-elevation distribution curves of the four most typical plant communities, including PP, Cc, PT and As communities, in different regions of the Poyang Lake wetland, are shown in Figure 3 and their corresponding ecological thresholds are presented in Table 1. The optimal elevations for the PP, Cc, PT and As communities in the whole wetland were 11.16, 12.67, 14.14 and 15.14, respectively. Among them, the As community was mainly distributed between elevation of 11.82–18.46 m, with the largest ecological width of 6.64 m, followed by the PP community, which was distributed between elevation of 8.70–13.62 m, with an ecological width of 4.92 m. The Cc community was distributed between 10.35 and 14.99 m, while the PT community was between 12.00 and 16.28 m. However, there were certain differences in the ecological intervals of the four typical wetland plants in different regions. The PP community was mainly distributed at elevations of 10.04–13.92 m, 10.43–12.55 m, and 10.49–13.69 m in Regions I, Ⅱ, and Ⅲ, with the optimal elevations increasing to 11.98, 11.49, and 12.09 m, respectively. The distribution elevation of the Cc community varied less among different regions. The distribution of PT and As communities were more concentrated in Region I, with a decrease in ecological width, and their optimal elevations were decreased to 13.75 and 14.93 m in Region Ⅱ, respectively (Table 1).
Table 1

Ecological thresholds of typical wetland plant communities in Poyang Lake

Wetland plantsElevationWhole (m)Region I (m)Region Ⅱ (m)Region Ⅲ (m)
PP optimal 11.16 11.98 11.49 12.09 
suitable interval 9.93–12.39 11.01–12.95 10.96–12.02 11.29–12.89 
ecological interval 8.70–13.62 10.04–13.92 10.43–12.55 10.49–13.69 
Cc optimal 12.67 12.69 12.62 12.89 
suitable interval 11.51–13.83 11.53–13.85 11.59–13.65 11.90–13.88 
ecological interval 10.35–14.99 10.37–15.01 10.56–14.68 10.91–14.87 
PT optimal 14.14 14.33 13.75 14.15 
suitable interval 13.07–15.21 13.51–15.15 12.52–14.98 13.09–15.21 
ecological interval 12.00–16.28 12.69–15.97 11.29–16.21 12.03–16.27 
As optimal 15.14 15.06 14.93 15.01 
suitable interval 13.48–16.80 14.07–16.05 13.45–16.41 13.27–16.75 
ecological interval 11.82–18.46 13.08–17.04 11.97–17.89 11.53–18.49 
Wetland plantsElevationWhole (m)Region I (m)Region Ⅱ (m)Region Ⅲ (m)
PP optimal 11.16 11.98 11.49 12.09 
suitable interval 9.93–12.39 11.01–12.95 10.96–12.02 11.29–12.89 
ecological interval 8.70–13.62 10.04–13.92 10.43–12.55 10.49–13.69 
Cc optimal 12.67 12.69 12.62 12.89 
suitable interval 11.51–13.83 11.53–13.85 11.59–13.65 11.90–13.88 
ecological interval 10.35–14.99 10.37–15.01 10.56–14.68 10.91–14.87 
PT optimal 14.14 14.33 13.75 14.15 
suitable interval 13.07–15.21 13.51–15.15 12.52–14.98 13.09–15.21 
ecological interval 12.00–16.28 12.69–15.97 11.29–16.21 12.03–16.27 
As optimal 15.14 15.06 14.93 15.01 
suitable interval 13.48–16.80 14.07–16.05 13.45–16.41 13.27–16.75 
ecological interval 11.82–18.46 13.08–17.04 11.97–17.89 11.53–18.49 

Note: PP, Polygonum hydropiper–Phalaris arundinacea; Cc, Carex cinerascens; PT, Phragmites australis–Triarrhena lutarioriparia; As, Artemisia selengensis.

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Figure 3
Area-elevation distribution curves of typical wetland plants in the Poyang Lake.
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Area-elevation distribution curves of typical wetland plants in the Poyang Lake.

Figure 3
Area-elevation distribution curves of typical wetland plants in the Poyang Lake.
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Area-elevation distribution curves of typical wetland plants in the Poyang Lake.

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Trends of ecological thresholds of typical wetland plants

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The change trends of the optimal elevation, upper and lower distribution limits of the four typical plants in the Poyang Lake wetland from 2000 to 2020 are shown in Figure 4. The optimal elevations of Cc, PT, and PP communities generally showed downward trends. Specifically, the optimal elevation of the Cc community decreased from 13.25 to 12.69 m, with a decrease of 0.56 m, the PT community decreased from 14.66 to 14.26 m, with a decrease of 0.40 m, and the PP community decreased from 12.09 to 10.94 m, with a decrease of 1.15 m (Figures 4(a), 4(d), 4(j)). However, the optimal elevation of the As community showed an upward trend, increasing from 15.23 to 18.71 m and moving up by 3.48 m (Figure 4(g)). The upper limit elevations of the four typical wetland plants also showed different trends. Among them, the upper limit elevations of both PT and As communities showed upward trends (Figures 4(e), 4(h)), especially the most significant changes in As community, with the upper limit elevation moving up by about 4.0 m in the past 20 years, while the upper limit elevations of Cc and PP communities showed no significant trends, fluctuating around 14.9 and 13.5 m, respectively (Figures 4(b), 4(k)). However, the lower limit elevations of the four wetland plants showed significant downward trends, especially for Cc and PP communities. The Cc community decreased from 11.33 to 10.06 m, with a decrease of 1.27 m, and the PP community moved down from 10.19 m in 2000 to 8.44 m in 2020, with a decrease of 1.75 m (Figures 4(c), 4(l)). The decreases in the lower limit elevations of PT and As communities were generally within 1.0 m (Figures 4(f), 4(i)).
Figure 4
The change trends of ecological thresholds of four typical plants in the Poyang Lake wetland from 2000 to 2020.
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The change trends of ecological thresholds of four typical plants in the Poyang Lake wetland from 2000 to 2020.

Figure 4
The change trends of ecological thresholds of four typical plants in the Poyang Lake wetland from 2000 to 2020.
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The change trends of ecological thresholds of four typical plants in the Poyang Lake wetland from 2000 to 2020.

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Figures 5–7 show the change trends of the optimal elevation, upper and lower distribution limits of four typical wetland plants in Regions I, Ⅱ, and Ⅲ of Poyang Lake wetland, respectively. The optimal elevations and upper limit elevations of different wetland plants had different trends in different regions. Such as the optimal elevation of the PP community in Region I decreased from 12.46 m in 2000 to 11.70 m in 2020, with a decrease of 0.76 m, while in Region Ⅱ, it moved up a total of 0.59 m at a speed of 0.02 m/a. In Region Ⅲ, the optimal elevation did not change significantly and fluctuated around 12.2 m. Similarly, for the upper limit elevation, the Cc community decreased by 0.71 m in Region I, and moved up from 14.98 to 15.22 m in Region Ⅲ, with an increase of 0.24 m, while the change was not significant in Region Ⅱ, fluctuating around 14.6 m. However, the lower limit elevations of all wetland plants showed downward trends in each region. Especially, the Cc and PP communities showed significant downward movement in Regions I and Ⅲ, with a decrease of about 1.0 m, and the decrease in the As community in Regions I and Ⅱ even exceeded 2.0 m.
Figure 5
The change trends of ecological thresholds of four typical wetland plants in Region I from 2000 to 2020.
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The change trends of ecological thresholds of four typical wetland plants in Region I from 2000 to 2020.

Figure 5
The change trends of ecological thresholds of four typical wetland plants in Region I from 2000 to 2020.
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The change trends of ecological thresholds of four typical wetland plants in Region I from 2000 to 2020.

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Figure 6
The change trends of ecological thresholds of four typical wetland plants in Region II from 2000 to 2020.
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The change trends of ecological thresholds of four typical wetland plants in Region II from 2000 to 2020.

Figure 6
The change trends of ecological thresholds of four typical wetland plants in Region II from 2000 to 2020.
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The change trends of ecological thresholds of four typical wetland plants in Region II from 2000 to 2020.

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Figure 7
The change trends of ecological thresholds of four typical wetland plants in Region III from 2000 to 2020.
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The change trends of ecological thresholds of four typical wetland plants in Region III from 2000 to 2020.

Figure 7
The change trends of ecological thresholds of four typical wetland plants in Region III from 2000 to 2020.
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The change trends of ecological thresholds of four typical wetland plants in Region III from 2000 to 2020.

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Impacts of drought on ecological thresholds

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Figure 8 shows the optimal elevation changes of four typical wetland plants in different hydrological years. It is seen that the optimal elevations of the Cc, PT, As and PP communities in the Poyang Lake wetland had decreased in dry years to varying degrees compared to that in normal years, with decreases of 0.34, 0.23, 0.15, and 0.16 m, respectively. Especially for the PT community in Region Ⅱ, drought caused its optimal elevation to decrease by more than 0.45 m. The impacts of drought on the optimal elevations of the PT and PP communities in Region I and the As community in Region Ⅲ were relatively mild.
Figure 8
Changes in the optimal elevations of four typical wetland plants in different hydrological years.
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Changes in the optimal elevations of four typical wetland plants in different hydrological years.

Figure 8
Changes in the optimal elevations of four typical wetland plants in different hydrological years.
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Changes in the optimal elevations of four typical wetland plants in different hydrological years.

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Figures 9 and 10 show the changes of the upper and lower distribution limits of four typical wetland plants in different hydrological years, respectively. It is seen tshat drought had a significant impact on the upper limit elevation of the As community in the Poyang Lake wetland, but its impacts on the other three wetland plants were relatively small. Especially in Regions I and Ⅱ, the upper limit elevation of the As community decreased by 0.56 and 1.07 m, respectively, while in Region Ⅲ, it moved up by 0.2 m (Figure 9). However, drought had a significant impact on the lower limit elevations of the four wetland plants. Among them, the lower limit elevations of the Cc, PT and PP communities decreased by 0.62, 0.55, and 0.41 m, respectively, while the As community increased by 0.33 m in the dry years. It should be pointed out that the lower limit elevations of all four wetland plants in Region Ⅲ showed a decrease of 0.17–0.48 m in dry years (Figure 10).
Figure 9
Changes in the upper limit elevations of four typical wetland plants in different hydrological years.
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Changes in the upper limit elevations of four typical wetland plants in different hydrological years.

Figure 9
Changes in the upper limit elevations of four typical wetland plants in different hydrological years.
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Changes in the upper limit elevations of four typical wetland plants in different hydrological years.

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Figure 10
Changes in the lower limit elevations of four typical wetland plants in different hydrological years.
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Changes in the lower limit elevations of four typical wetland plants in different hydrological years.

Figure 10
Changes in the lower limit elevations of four typical wetland plants in different hydrological years.
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Changes in the lower limit elevations of four typical wetland plants in different hydrological years.

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The vegetation in the Poyang Lake wetland was distributed in a strip pattern along the water level gradient, with different plants occupying different ecological niches (Zhou 2011; Xu et al. 2015). This study found that the distribution elevations of wetland plants in the Poyang Lake showed downward trends, especially with a significant decrease in the lower limit elevation. This was consistent with the results of Han et al. (2015) and Lin et al. (2023), who found that the vegetation in the Poyang Lake wetland has been expanding towards the center of the lake since 2000. You et al. (2015) studied the vegetation distribution of two typical wetlands at the main tributary estuary of Gan River in Poyang Lake from 1973 to 2012 and found that the distribution elevation of wetland plants shifted downwards and expanded into the lake. These changes were closely related to the hydrological conditions of Poyang Lake (Feng et al. 2012; Han et al. 2015; Li et al. 2023a). Since 2000, the dry water situation in Poyang Lake has been continuously worsening, with the average lake water level continuously low (Li et al. 2023a, 2023c); in particular the duration of the lake level below 8.0 m has been extended by 13 days and the dry water period has been advanced by 20–75 days (Zhang et al. 2013; Ye et al. 2022). The low water in Poyang Lake has led to the rapid occupation of ecological niches in low-elevation areas by the PP and Carex communities.

In addition, the current study revealed that the optimal elevation, upper and lower limit elevations of most wetland plants in Poyang Lake decreased in dry years to varying degrees. The beaches of the lake were exposed earlier and the area expanded in dry years, providing favorable conditions for the growth of wetland plants. Han et al. (2018) found that when the water depth decreased from 1.8–2.1 m to 1.5–1.8 m, the probability of the occurrence of Carex community increased from 24.5% to 41.8%, and when the water depth decreased from 0.9–1.2 m to 0.6–0.9 m, the probability of the occurrence of the PT community increased to 64.8%. On the other hand, changes in hydrological conditions also affect the competitive relationships between different wetland plant communities. Carex is adjacent to the habitats of P. australis and T. lutarioriparia communities, and competes for survival space and water due to interspecific competition (Qin et al. 2010; Lin et al. 2023). In dry years, after the lake water recedes, P. australis, T. lutarioriparia and Carex communities showed different relative competitive advantages and seized ecological niches with lower elevation. In a word, hydrological conditions are the main controlling factors for the distribution and succession of wetland plant communities in Poyang Lake. The changes in the distribution elevation of wetland plants are essentially a further extension of the impact of hydrological changes (Lin et al. 2023).

Therefore, in order to mitigate the impacts of drought on wetland plants in Poyang Lake and avoid ecological disasters, it is necessary to strengthen the joint operation of reservoir groups in the local basin to replenish water for the downstream lake and improve the level of water resource optimization and management in the lake area. Moreover, the numerous shallow sub-lakes in the Poyang Lake wetland should be fully utilized to regulate floods and alleviate drought, build resilient wetlands, increase horizontal hydrological connectivity, and thereby increase the ecological space and vegetation ecosystem stability of the Poyang Lake wetland.

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This study analyzed the changes in the most suitable elevation, upper and lower limit elevations of different wetland plants in Poyang Lake from 2000 to 2020 and revealed the impacts of hydrological drought on the ecological niches of typical wetland plants. The results showed that different plants in the Poyang Lake wetland were distributed in a regular strip pattern according to the elevation gradient. The PP, Cc, PT and As communities were mainly distributed at elevations of 8.70–13.62 , 10.35–14.99 , 12.00–16.28 and 11.82–18.46 m, with corresponding optimal elevations of 11.16, 12.67, 14.14, and 15.14 m, respectively. The optimal elevations of Cc, PT and PP communities showed decreasing trends from 2000 to 2020, but an upward trend for the As community. The upper limit elevations of both PT and As communities showed upward trends, while the upper limit elevations of Cc and PP communities fluctuated around 14.9 and 13.5 m, respectively, with no significant trends. However, the lower limit elevations of the four wetland plants showed significant downward trends, especially for Cc and PP communities. Moreover, the optimal elevations of the four typical wetland plants had decreased in dry years, with decreases of 0.16–0.34 m. Especially for the PT community in Region Ⅱ, drought caused its optimal elevation to decrease by more than 0.45 m. In addition, drought had also caused a varying degree of decrease in the upper and lower limit elevations of most wetland plants in Poyang Lake.

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This work was supported by the National Key Research and Development Program of China (Grant No. 2022YFC3204102); the Ganpo Excellent Talent Support Program of Jiangxi–Training Program for Academic and Technical Leaders in Major Disciplines (Grant No. 20232BCJ22011); and the National Natural Science Foundation of China (Grant No. 42071028 and 42171104).

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Data cannot be made publicly available; readers should contact the corresponding author for details.

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The authors declare there is no conflict.

Berdugo
M.
,
Delgado-Baquerizo
M.
,
Soliveres
S.
,
Hernandez-Clemente
R.
,
Zhao
Y.
,
Gaitan
J. J.
,
Gross
N.
,
Saiz
H.
,
Maire
V.
,
Lehman
A.
,
Rillig
M. C.
,
Sole
R. V.
 &
Maestre
F. T.
2020
Global ecosystem thresholds driven by aridity
.
Science
367
,
787
–
790
.
Google Scholar
Crossref
Search ADS
PubMed
 
Chen
L. F.
,
Jin
Z. Y.
,
Michishita
R.
,
Cai
J.
,
Yue
T. X.
,
Chen
B.
 &
Xu
B.
2014
Dynamic monitoring of wetland cover changes using timeseries remote sensing imagery
.
Ecological Informatics
24
,
17
–
26
.
Google Scholar
Crossref
Search ADS
 
Chen
B.
,
Chen
L.
,
Huang
B.
,
Michishita
R.
 &
Bing
X.
2018
Dynamic monitoring of the Poyang Lake wetland by integrating landsat and MODIS observations
.
ISPRS Journal of Photogrammetry and Remote Sensing
139
,
75
–
87
.
Google Scholar
Crossref
Search ADS
 
Dai
X.
,
Wan
R.
,
Yang
G.
,
Wang
X.
,
Xu
L.
,
Li
Y.
 &
Li
B.
2019
Impact of seasonal water-level fluctuations on autumn vegetation in Poyang Lake wetland, China
.
Frontiers of Earth Science
13
,
398
–
409
.
Google Scholar
Crossref
Search ADS
 
Department of Water Resources of Jiangxi Province
2009
Encyclopedia of Rivers and Lakes in Jiangxi
.
Changjiang Press
,
Wuhan
(In Chinese)
.
Feng
L.
,
Hu
C. M.
,
Chen
X. L.
,
Cai
X. B.
,
Tian
L. Q.
 &
Gan
W. X.
2012
Assessment of inundation changes of Poyang Lake using MODIS observations between 2000 and 2010
.
Remote Sensing of Environment
121
,
80
–
92
.
Google Scholar
Crossref
Search ADS
 
Griffin-Nolan
R. J.
,
Carroll
C. J. W.
,
Denton
E. M.
,
Johnston
M. K.
,
Collins
S. L.
,
Smith
M. D.
 &
Knapp
A. K.
2018
Legacy effects of a regional drought on aboveground net primary production in six central US grasslands
.
Plant Ecology
219
(
5
),
505
–
515
.
Google Scholar
Crossref
Search ADS
 
Han
X. X.
,
Feng
L.
,
Hu
C. M.
 &
Chen
X. L.
2018
Wetland changes of China's largest freshwater lake and their linkage with the Three Gorges Dam
.
Remote Sensing of Environment
204
,
799
–
811
.
Google Scholar
Crossref
Search ADS
 
Hu
Z.
 &
Lin
Y.
2019
Analysis of evolution process and driving factors for aquatic vegetations of Poyang Lake in 30 years
.
Resources and Environment in the Yangtze Basin
28
,
1947
–
1955
.
(In Chinese)
.
Google Scholar
 
Hu
Z. P.
,
Ge
G.
,
Liu
C. L.
,
Chen
F. S.
 &
Li
S.
2010
Structure of Poyang Lake wetland plants ecosystem and influence of lake water level for the structure
.
Resources and Environment in the Yangtze Basin
19
(
6
),
597
–
605
.
(In Chinese)
.
Google Scholar
 
Huang
J. G.
 &
Guo
Z. Y.
2007
The wetland biodiversity and its conservation countermeasures in the Poyang Lake
.
Research of Soil and Water Conservation
14
(
1
),
305
–
307
.
(In Chinese)
.
Google Scholar
 
Kong
R.
,
Zhang
Z. X.
,
Zhang
Y.
,
Wang
Y. M.
,
Peng
Z. H.
,
Chen
X.
 &
Xu
C. Y.
2023
Detection and attribution of changes in terrestrial water storage across China: Climate Change versus vegetation greening
.
Remote Sensing
15
,
3104
.
Google Scholar
Crossref
Search ADS
 
Li
X. H.
,
Ye
X. C.
,
Yao
J.
,
Lin
Y. L.
,
Xu
C. Y.
 &
Yuan
C. Y.
2023a
Influences of increasing water release of the three Gorges reservoir during dry season on water regimes of downstream lake
.
Hydrological Processes
37
(
5
),
e14895
.
Google Scholar
Crossref
Search ADS
 
Li
X. H.
,
Yuan
C. Y.
,
Sun
T.
 &
Fan
H. X.
2024
Identifying the spatiotemporal patterns of drought-flood alternation based on IMERG product in the humid subtropical Poyang Lake basin, China
.
Journal of Hydrology: Regional Studies
54
,
101912
.
Google Scholar
 
Lin
Y. L.
,
Li
X. H.
,
Tan
Z. Q.
,
Song
Y. Y.
 &
Xu
C. Y.
2023
Dynamic characteristics of vegetation communities in the floodplain wetland of Poyang Lake based on spatiotemporal fusion of remote sensing data
.
Journal of Lake Sciences
35
(
4
),
1408
–
1422
.
(In Chinese)
.
Google Scholar
 
Liu
X. Z.
 &
Ye
J. X.
2000
Jiangxi Wetlands
.
China Forestry Publishing House
,
Beijing
.
Google Scholar
 
Liu
Q.
,
Yan
B. Y.
 &
Ge
G.
2012
Theory and Practice of Ecological Restoration of Poyang Lake Wetland
.
Science Press
,
Beijing
.
Google Scholar
 
Qin
X. Y.
,
Xie
Y. H.
 &
Chen
X. S.
2010
Competition and facilitation among wetland plants: A review
.
Chinese Journal of Ecology
29
(
1
),
117
–
123
.
(In Chinese)
.
Google Scholar
 
Tian
J. X.
,
Zhang
Z. X.
,
Fu
Y. H.
,
Tao
H.
,
Zhu
B.
 &
Yang
L.
2023
Does CMIP6 inspire more confidence in projecting precipitation over China?
International Journal of Climatology
43
,
4965
–
4986
.
Google Scholar
Crossref
Search ADS
 
Vicca
S.
,
Balzarolo
M.
,
Filella
I.
,
Granier
A.
,
Herbst
M.
,
Knohl
A.
,
Longdoz
B.
,
Mund
M.
,
Nagy
Z.
,
Pintér
K.
,
Rambal
S.
,
Verbesselt
J.
,
Verger
A.
,
Zeileis
A.
,
Zhang
C.
 &
Peñuelas
J.
2016
Remotely-sensed detection of effects of extreme droughts on gross primary production
.
Scientific Reports
6
,
28269
.
Google Scholar
Crossref
Search ADS
PubMed
 
Wang
R.
,
Li
X. H.
,
Zhang
Q.
,
Cheng
J. X.
,
Li
J. F.
,
Zhang
D.
 &
Liu
Y. B.
2023
Projection of drought-flood abrupt alternation in a humid subtropical region under changing climate
.
Journal of Hydrology
624
,
129875
.
Google Scholar
Crossref
Search ADS
 
Wu
J. D.
,
Liu
G. H.
 &
Jin
J. F.
2010
Analysis of plant species structure in autumn in Poyang Lake Wetland
.
Jiangxi Science
28
(
4
),
549
–
554
.
(In Chinese)
.
Google Scholar
 
Ye
X. C.
,
Wu
J.
 &
Li
X. H.
2022
Compound driving mechanism of water level change in the Poyang Lake
.
Scientia Geographica Sinica
42
(
2
),
352
–
361
.
(In Chinese)
.
Google Scholar
 
Ye
X. C.
,
Wu
J.
,
Li
X. H.
,
Li
Y. L.
,
Zhang
Q.
 &
Xu
C. Y.
2023
Multi-source remote sensing data and image fusion technology reveal significant spatiotemporal heterogeneity of inundation dynamics in a typical large floodplain lake system
.
Journal of Hydrology: Regional Studies
50
,
101541
.
Google Scholar
 
You
H. L.
,
Xu
L. G.
,
Liu
G. L.
,
Wu
Y. M.
,
Liu
L. Z.
 &
Jiang
J. H.
2016
Change of wetland landscape at Poyang Lake and its response to water level fluctuation
.
Chinese Journal of Ecology
35
(
9
),
2487
–
2493
.
(In Chinese)
.
Google Scholar
 
Zhang
M.
,
Ni
L. Y.
,
Xu
J.
,
He
L.
,
Fu
H.
 &
Liu
Z. G.
2013
Annual dynamics of the wetland plants community in Poyang Lake in response to water-level variations
.
Research of Environmental Science
26
(
10
),
1057
–
1063
.
(In Chinese)
.
Google Scholar
 
Zhang
Q.
,
Ye
X. C.
,
Werner
A. D.
,
Li
Y. L.
,
Yao
J.
,
Li
X. H.
 &
Xu
C. Y.
2014
An investigation of enhanced recessions in Poyang Lake: Comparison of Yangtze River and local catchment impacts
.
Journal of Hydrology
517
,
425
–
434
.
Google Scholar
Crossref
Search ADS
 
Zheng
L. L.
,
Xu
J. Y.
,
Wang
D. D.
,
Xu
G. Y.
,
Tan
Z. Q.
,
Xu
L. G.
 &
Wang
X. L.
2021
Acceleration of vegetation dynamics in hydrologically connected wetlands caused by dam operation
.
Hydrological Processes
35
,
e14026
.
Google Scholar
Crossref
Search ADS
 
Zhou
W. B.
2011
The Impact of Water Level Changes in Poyang Lake on Its Ecosystem
.
Science Press
,
Beijing
.
Google Scholar
 
© 2024 The Authors
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