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BackgroundThe Three Gorges project has caused many ecosystem problems. Ecological restoration using readily-available plants is an effective way of mitigating environmental impacts. Two perennial submergence-tolerant ecotypes of Calamagrostis arundinacea were planted in an experimental field in the drawdown zone. Responses of the two plant ecotypes to flooding stress in the drawdown zone were unknown.Methodology/Principal FindingsCarbohydrate content and membrane stability, two key factors for survival of plants under flooding stress, of two ecotypes (designated “dwarf” and “green”) of C. arundinacea growing at different elevations of the drawdown zone were investigated. Live stems (LS) and dead stems (DS) of the two plant ecotypes at eight elevations (175, 170, 162, 160, 158, 155, 152 m and 149 m) were sampled. Contents of soluble sugar, starch and malondialdehyde (MDA), as well as plasma membrane permeability of live stems were measured. The lowest elevations for survival of dwarf and green C. arundinacea were 160 m and 158 m, respectively. Soluble sugar content of live stems of both ecotypes decreased with elevation, with amounts from an elevation of 170 m being lower than from an elevation of 175 m. MDA content and plasma membrane permeability in live stems of green C. arundinacea did not increase with the decrease in elevation, while these measures in dwarf C. arundinacea from an elevation of 162 m were significantly higher than from an elevation of 175 m.ConclusionsCarbohydrate content, especially soluble sugar content, in both ecotypes was more sensitive to flooding stress than membrane stability. Green C. arundinacea had a higher tolerance to submergence than dwarf C. arundinacea, and thus green C. arundinacea can be planted at lower elevations than dwarf C. arundinacea.

Potassium and fulvic acid (FA) fertilizer applications are two important measures for improving cotton growth. However, there are few studies on the application interactive effects of controlled-release potassium chloride (CRK) in combination with FA on cotton production. To explore the effects of CRK combined with FA on cotton, field experiments were conducted in 2018 and 2019 using a split-plot design. The main plots were assigned to two types of potassium fertilizer – controlled-release potassium chloride (CRK) and potassium sulfate (KS) – while low, moderate, and high FA application rates (90, 180, and 270 kg ha −1 ) were assigned to the subplots. The cotton yield, fiber quality, net profit, soil available potassium concentration, potassium use efficiency, and leaf photosynthesis were markedly affected by potassium fertilizer and FA. The cotton boll number and boll weight in the 2 years and the yield in 2019 were all affected by the interaction between potassium fertilizer and FA. Compared to the other potassium treatments, the CRK × FA180 treatment increased the seed yield and net profit by 4.29–14.92% and 13.72–62.30%, respectively, over the 2 years. The potassium agronomy efficiency and potassium recovery efficiency (KRE) of the CRK × FA180 treatment were also improved by 6.25–30.77% and 3.82–12.78% compared to those of the other potassium treatments. Overall, the FA180 treatment resulted in better cotton growth than that in the FA90 and FA270 treatments. The release period of CRK in the field during the growth period of cotton was longer than that detected by 25°C static water extraction, which increased the soil available potassium content and met the potassium demands over the whole cotton growth period. Therefore, the application of CRK in combination with 180 kg ha −1 FA is the best choice for cotton fertilization.