Dinámicade crecimiento de hymenachne Amplexicaulis en un humedalherbáceo en el Estado miranda(venezuela)

hymenachne amplexicaulis (poaceae) is a robust, rhizomatous perennial grass; it forms dense monospecific colonies in seasonally flooded environments and along riverbanks in tropical and subtropical wetlands of america. the objective of this study was to determine the effects of seasonal variations of water depth on the growth, above ground biomass and production of h. amplexicaulis in a freshwater marsh situated in miranda state (venezuela) between february and december 2001. h. amplexicaulis showed variations in the biometric characteristics, such as height, length of internode, density of culms related to changes of water depth. the mean height of culms varied between 1.4 and 1.8 m, with the highest value in deep water. mean density of culms was 35 culm/m2 and ranged between 24 y 49 culms/m2, with the highest values during the first rain period (august). mean total biomass was 1015±351 dry g/m2 and varied between 310 and 1465 dry g/m2, with the lowest value during the second rain period (december) and the highest value during the the first rain period. flowering and fructification began in october and finished in february; inflorescence biomass, including flowers and fruits, ranged between 1.4 and 14.9 dry g/m2, and it represented less than 1% of total biomass. the annual net primary production was of 822 dry g/m2/year. h. amplexicaulis tolerate continual flood conditions, but in deep water there was a significative decreasing in the total biomass and their components (leaf, culms, standing dead material and inflorescences), which may indicate limitations of gaseous interchange and nutrient uptake