Differences in flooding tolerance between species from two wetland habitats with contrasting hydrology: implications for vegetation development in future floodwater retention areas

Contains fulltext : 75490.pdf (publisher's version ) (Closed access)* Background and Aims - Plants need different survival strategies in habitats differing in hydrological regimes. This probably has consequences for vegetation development when former floodplain areas that are currently confronted with soil flooding only, will be reconnected to the highly dynamical river bed. Such changes in river management are increasingly important, especially at locations where increased water retention can prevent flooding events in developed areas. It is therefore crucial to determine the responses of plant species from relatively lowdynamic wetlands to complete submergence, and to compare these with those of species from river forelands, in order to find out what the effects of such landscape-scale changes on vegetation would be. * Methods - To compare the species’ tolerance to complete submergence and their acclimation patterns, a greenhouse experiment was designed with a selection of 19 species from two contrasting sites: permanently wet meadows in a former river foreland, and frequently submerged grasslands in a current river foreland. The plants were treated with short (3 weeks) and long (6 weeks) periods of complete submergence, to evaluate if survival, morphological responses, and changes in biomass differed between species of the two habitat. * Key Results - All tested species inhabiting river forelands were classified as tolerant to complete submergence, whereas species from wet meadows showed either relatively intolerant, intermediate or tolerant responses. Species from floodplains showed in all treatments stronger shoot elongation, as well as higher production of biomass of leaves, stems, fine roots and taproots, compared with meadow species. * Conclusions - There is a strong need for the creation of temporary water retention basins during high levels of river discharge. However, based on the data presented, it is concluded that such reconnection of former wetlands (currently serving as meadows) to the main river bed will strongly influence plant species composition and abundance.11 p

Effects of soil water table regime on tree community species richness and structure of alluvial forest fragments in Southeast Brazil

In order to determine the influence of soil water table fluctuation on tree species richness and structure of alluvial forest fragments, 24 plots were allocated in a point bar forest and 30 plots in five forest fragments located in a floodplain, in the municipality of São Sebastião da Bela Vista, Southeast Brazil, totalizing 54, 10 X 20 m, plots. The information recorded in each plot were the soil water table level, diameter at breast height (dbh), total height and botanical identity off all trees with dbh > 5 cm. The water table fluctuation was assessed through 1 m deep observation wells in each plot. Correlations analysis indicated that sites with shallower water table in the flooding plains had a low number of tree species and high tree density. Although the water table in the point bar remained below the wells during the study period, low tree species richness was observed. There are other events taking place within the point bar forest that assume a high ecological importance, such as the intensive water velocity during flooding and sedimentation processes

Respostas morfofisiológicas de plantas de açacu (Hura crepitans L.) provenientes de várzeas do rio Amazonas: efeito da anoxia do solo

Neste trabalho foram avaliadas as respostas morfofisiológicas de plantas de açacu (Hura crepitans) sob a anoxia do solo com diferentes idades (90 e 120 dias) e períodos de inundação (0, 10, 20 e 30 dias). O estudo identificou que as plantas desenvolveram mecanismos adaptativos (estruturas morfológicas como lenticelas hipertróficas e raízes adventícias) e apresentaram comportamento fisiológico que lhes propiciaram tolerância à anoxia. As respostas das plantas ao excesso de água no solo incluíram inibição do crescimento vegetativo, clorose e senescência foliar. O estresse hídrico por anoxia comprometeu a viabilidade das plantas de 90 dias de idade, enquanto as plantas de açacu de 120 dias de idade mostraram-se tolerantes ao alagamento