Effects of flooding and artificial burning disturbances on plant species composition in a downstream riverside floodplain

Abstract

Our objective was to detect environmental and disturbance factors that determine plant species composition in a downstream riverside floodplain of the Shinano River, where both natural flooding and artificial fire disturbances predominate. We classified the natural vegetation into five types by physiognomy, i.e., burnt field, intact (unburnt) field, early-successional forest, later-successional forest, and margin of channel. We deployed 14 transect belts containing 713 plots of 1 m · 1 m at these sites. In the plots, we determined plant occurrences and values of five environmental (soil moisture, soil texture, relative elevation above the river, horizontal distance from the river, and light conditions) and two disturbance factors (scouring of plants by flooding and fire). Plant species compositions and environmental and disturbance factors were different among the sites. Logistic regression analysis showed that burning stimulated the occurrences of herbaceous annuals and conversely constrained those of woody and fern species, suggesting that fire disturbance resets the succession. Scouring of plants by flooding also affected the occurrences of many species, and had a positive influence on that of herbaceous winter annuals in particular. Canonical correspondence analysis indicated that the distributional characteristics of the plant species in the riverside floodplain were influenced primarily by distance from the river, reflecting the magnitude of flood disturbance. We conclude that (1) magnitude of flood disturbance is the primary factor determining plant species composition, and (2) burning maintains early successional vegetation and simultaneously creates a unique plant species composition by stimulating the germination of buried viable seeds transported by flood.

Aquatic ecosystem responses to fire and flood size in the Okavango Delta: observations from the seasonal floodplains

“…This view is consistent with other studies that demonstrate, through artificial fire experiments on floodplains, that flooding is the primary factor which determines plant species composition (Ishida et al 2008).…”

Off‐channel temporary pools contribute to native riparian plant species diversity in a regulated river floodplain

“…This richness is likely related to variation in natural stream flow, which is an important component of river ecosystem maintenance (Poff et al 1997). Flooding is a disturbance that regulates riparian plant species richness in accordance with the intermediate disturbance hypothesis (Pollock et al 1998); flooding destroys existing vegetation and creates open habitat for colonization (Naiman and De´camps 1997;Ishida et al 2008) and simultaneously transports numerous plant propagules (Boedeltje et al 2003;Jansson et al 2005). Flooding also dictates vegetation zoning according to variations in plant flood tolerance or life form (Blom and Vosenek 1996;Hupp and Osterkamp 1996).…”

Lista atualizada e aspectos sobre a conservação da flora vascular do Parque Estadual do Turvo, Rio Grande do Sul, Brasil

“…Devido à alta seletividade ambiental (Steenis 1978, Klein 1979, essas plantas são as primeiras a serem ameaçadas pela instalação de empreendimentos hidrelétricos. A construção de hidrelétricas causa drásticas alterações na dinâmica dos cursos d'água, diminuindo a velocidade do fluxo, aumentando a profundidade do rio nos locais de instalação dos reservatórios e alterando os ciclos históricos de cheias e secas, o que impacta diretamente a manutenção dessas plantas nesses ambientes (Lytle & Poff 2004, Ishida et al 2008. A criação de lagos artificiais para geração energética é responsável pela inundação de milhares de hectares, tornando áreas permanentemente submersas, o que acarreta a destruição da vegetação e promove a expulsão de populações ribeirinhas (Rocha & Pase 2015).…”