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In the initial growth stage from April to June, the actual evapotranspiration of the A. capillaris and P. australis communities totaled 157–163 and 328–338 mm, respectively, and were equal to the potential level (Table 4). This period is also the wet season in Poyang Lake, and the rainfall infiltration amounted to 752–1,110 mm, accounting for approximately 55% of the annual amount. It is obvious that in this stage, rainfall can satisfy the evapotranspiration water demand and water was not a limiting factor for vegetation growth. With large amounts of rainfall infiltrating, the root zone bottom was mainly experiencing downward soil water movement (Figure 7). The cumulative amount of percolation in the A. capillaris and P. australis communities comprised about 74%–90% of the rainfall infiltration.

Table 4

Water balance of the A. capillaris and P. australis communities in initial (April–June) and main (July–October) growth stages in high (2012) and low (2013) water table years

CommunityHydrological yearStageTpTaEaETaRinGDΔWAETa/Tp
A. capillaris High initial 96 96 61 157 752 74 557 107 −5 1.00 
main 349 334 96 430 209 439 375 −161 −4 0.96 
Low initial 90 90 73 163 1,110 877 66 −4 1.00 
main 367 203 54 257 143 13 51 −154 −2 0.55 
P. australis High initial 125 125 17 142 510 96 457 10 1.00 
173a 173a 13a 186a – – – – – 
main 458b 458b 43b 501b – – – – – 0.92 
277 219 39 258 136 161 92 −50 
Low initial 307 307 31 338 937 182 762 15 −4 1.00 
main 943 510 89 599 137 401 39 −95 0.54 
CommunityHydrological yearStageTpTaEaETaRinGDΔWAETa/Tp
A. capillaris High initial 96 96 61 157 752 74 557 107 −5 1.00 
main 349 334 96 430 209 439 375 −161 −4 0.96 
Low initial 90 90 73 163 1,110 877 66 −4 1.00 
main 367 203 54 257 143 13 51 −154 −2 0.55 
P. australis High initial 125 125 17 142 510 96 457 10 1.00 
173a 173a 13a 186a – – – – – 
main 458b 458b 43b 501b – – – – – 0.92 
277 219 39 258 136 161 92 −50 
Low initial 307 307 31 338 937 182 762 15 −4 1.00 
main 943 510 89 599 137 401 39 −95 0.54 

Note:Tp, Ta, Ea, Rin, G, and D, in mm; ΔW, changes of root zone soil water storage, in mm; AE, absolute error, in mm. Data marked with superscripts ‘a’ and ‘b’ represent water flux calculated in the flood period from May 16 to June 30, 2012 and from July 1 to August 31, 2012, respectively. Ea represents soil/water evaporation when the land was exposed/flooded, respectively.

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