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Macrophyte Species Richness (macrophyte + species_richness)
Selected AbstractsDoes flooding of rice fields after cultivation contribute to wetland plant conservation in southern Brazil?APPLIED VEGETATION SCIENCE, Issue 1 2010Ana S. Rolon Abstract Question: Does flooding of rice fields after cultivation contribute to wetland plant conservation in southern Brazil? Location: Rice fields in the coastal plain of southern Brazil. Methods: Six rice fields with different management practices were randomly selected (three dry rice fields and three flooded rice fields). Six collections were carried out over the rice cultivation cycle. Richness and biomass were measured using the quadrat method. Results: A total of 88 macrophyte species was recorded. There was no statistical interaction between management practices and rice cultivation phases for macrophyte richness and biomass. Macrophyte species richness and biomass changed over time, but were similar between flooded and dry rice fields. The first three axes generated by detrended correspondence analysis explained 29% of the variation in species composition and the multivariate analysis of variance showed that there was a statistical interaction between management practices and agricultural periods. Conclusions: Rice fields may help to conserve an important fraction of the aquatic macrophyte diversity of wetlands of southern Brazil by providing the setting up of a greater number of species within the agricultural landscape. However, rice fields must not be viewed as surrogate systems for natural wetlands. The difference in species composition between flooded and dry rice fields is interesting in terms of biodiversity conservation. If rice producers could keep part of their agricultural land flooded during the fallow phase, this management practice could be an important strategy for the conservation of biodiversity in areas where natural wetlands have been converted to rice fields. [source] Effects of an exotic invasive macrophyte (tropical signalgrass) on native plant community composition, species richness and functional diversityFRESHWATER BIOLOGY, Issue 6 2010THAÍSA SALA MICHELAN Summary 1.,The issue of freshwater species being threatened by invasion has become central in conservation biology because inland waters exhibit the highest species richness per unit area, but apparently have the highest extinctions rates on the planet. 2.,In this article, we evaluated the effects of an exotic, invasive aquatic grass (Urochloa subquadripara, tropical signalgrass) on the diversity and assemblage composition of native macrophytes in four Neotropical water bodies (two reservoirs and two lakes). Species cover was assessed in quadrats, and plant biomass was measured in further quadrats, located in sites where tropical signalgrass dominated (D quadrats) and sites where it was not dominant or entirely absent (ND quadrats). The effects of tropical signalgrass on macrophyte species richness, Shannon diversity and number of macrophyte life forms (a surrogate of functional richness) were assessed through regressions, and composition was assessed with a DCA. The effects of tropical signalgrass biomass on the likelihood of occurrence of specific macrophyte life forms were assessed through logistic regression. 3.,Tropical signalgrass had a negative effect on macrophyte richness and Shannon and functional diversity, and also influenced assemblage composition. Emergent, rooted with floating stems and rooted submersed species were negatively affected by tropical signalgrass, while the occurrence of free-floating species was positively affected. 4.,Our results suggest that competition with emergent species and reduction of underwater radiation, which reduces the number of submersed species, counteract facilitation of free-floating species, contributing to a decrease in plant diversity. In addition, homogenisation of plant assemblages shows that tropical signalgrass reduces the beta diversity in the macrophyte community. 5.,Although our results were obtained at fine spatial scales, they are cause for concern because macrophytes are an important part of freshwater diversity. [source] The responses of floodplain primary production to flood frequency and timingJOURNAL OF APPLIED ECOLOGY, Issue 1 2001A.I. Robertson Summary 1,River regulation and abstraction have dramatically altered the natural flow regime of many rivers world-wide, but experimental investigations of the biological effects are infrequent. In the mid-region of the Murray River, Australia, river regulation has reduced the frequency and duration of spring floods and increased the frequency of summer floods. We used controlled floods (treatments: no floods, spring floods, summer floods and spring + summer floods) to determine how the growth of river red gum Eucalyptus camaldulensis trees, aquatic macrophytes and biofilms varied with the seasonal timing and frequency of flooding. 2,After 6 years of controlled flooding, above-ground net production of wood by river red gum trees was equal and greatest in plots receiving spring + summer floods and summer floods (mean 496 g m,2 year,1). Production was significantly lower in plots receiving spring floods or no controlled floods, which had similar rates of production (mean 330 g m,2 year,1). 3,During 2 years of measurement in wetlands created by flooding, production and species richness of aquatic macrophyte were both greater in spring than in summer floods. The history of flood frequency at any experimental site did not affect macrophyte production or species richness. The aquatic macrophyte community in shallow regions of wetlands differed significantly with the seasonal timing of floods, but not flood frequency. 4,The accumulation of chlorophyll a and total mass of biofilm on wood surfaces in wetlands created by flooding were greater in spring (mean chlorophyll a, 0·88 µg cm,2; mean mass, 0·066 mg cm,2) than in summer floods (mean chlorophyll a, 0·09 µg cm,2; mean mass, 0·034 mg cm,2). The history of flood frequency at any experimental site did not affect accumulation of either the autotrophic or heterotrophic components of biofilms. 5,Spring flooding, while not as beneficial for tree growth, is critical for the growth of wetland macrophytes, the maintenance of macrophyte species richness, and favours better development of autotrophic biofilms. Maintenance of both the timber harvest and wetland conservation values of these floodplains will require the return of more natural flood flows in the spring period. Restoration of floodplain rivers requires a thorough understanding of the relationships between ecological functions and the natural flow regime. [source] Macrophyte species diversity in formerly cultivated wetlands in UgandaAFRICAN JOURNAL OF ECOLOGY, Issue 4 2008Josephine Esaete Abstract The diversity of major macrophytes was assessed in cultivated areas in Bukasa and Kinawataka wetlands in Central Uganda. One thousand and seventy-two plots of 1 × 1 m were established in 69 cultivated areas. Data were collected on species richness and abundance. Two-way analysis of covariance (ANCOVA) showed how cropping regimes affected macrophyte species richness and abundance. There were 127 plant species belonging to 37 families in cultivated areas. Of the 127 species, 42 were macrophytes and of the 37 families, fourteen contained macrophyte species. Plant species diversity was higher in the short-term cropping regime areas (11.3 species per 1 m2) than in the long-term cropping regime areas (9.3 species per 1 m2). However, macrophyte species richness was similar in the short-term (3.2 species per 1 m2) and the long-term (3.3 species per 1 m2) cropping regimes. The dominant families were Poaceae, Asteraceae and Cyperaceae with more than ten species each. The higher plant species diversity in cultivated areas than in uncultivated was because of nonmacrophyte species, thus cropping regime does not influence macrophyte species diversity. Increase in diversity of nonmacrophyte species in short-term cropping regime implies that the use of wetlands for agricultural crop growing may alter plant species composition and diversity during secondary succession. Résumé La diversité des principaux macrophytes a étéévaluée dans les régions cultivées des zones humides de Bukasa et de Kinawataka, au centre de l'Ouganda. On a établi 1072 plots d'1x1m, dans 69 zones cultivées. On a récolté des données sur la richesse et l'abondance des espèces. Une analyse de la covariance à deux voies (ANCOVA) a montré comment les régimes agricoles affectaient la richesse et l'abondance des espèces de macrophytes. Il y avait 127 espèces végétales appartenant à 37 familles dans les zones cultivées. De ces 127 espèces, 42 étaient des macrophytes, et des 37 familles, 14 comprenaient des espèces de macrophytes. La diversité des espèces végétales était plus élevée dans les surfaces subissant un régime cultural court (11,3 espèces/m2) que dans les surfaces soumises à un régime de culture plus long (9,3 espèces/m2). Cependant, la richesse en espèces de macrophytes était comparable pour le régime court (3,2 espèces/m2) et pour le plus long (3,3 espèces/m2). Les familles dominantes étaient les Poaceae, les Asteraceae et les Cyperaceae, qui comptaient chacune plus de 10 espèces. La diversité spécifique plus grande observée dans les aires cultivées était due aux espèces non macrophytes, et on peut donc dire que le régime de culture n'influence pas la diversité des espèces de macrophytes. L'augmentation de la diversité des espèces non macrophytes dans les cultures à régime court implique que l'utilisation des zones humides pour l'agriculture peut altérer par la suite la composition et la diversité des espèces végétales. [source] | ||||||||||