Year‐to‐year changes in water level drive the invasion of Vochysia divergens in Pantanal grasslands

Abstract

Abstract. In recent decades, cattle ranchers of the Pantanal of Mato Grosso, Brazil, have pointed to the accelerated spread of several herbaceous and woody plant species that invade natural and artificial pastures (campos). It has been speculated that overgrazing by an increasing number of cattle, lack of grazing in abandoned areas, or large‐scale changes in environmental conditions may be the reason for this invasion. This study focuses on ecological and ecophysiological aspects of Vochysia divergens (cambará), a flood‐tolerant tree that began spreading in the Pantanal during the last 30 years and is considered a very aggressive invasive plant. The study shows that the spread of cambará can be related to natural multi‐years wet periods. During multi‐years dry periods the species is reduced by the increasing impact of fires in the Pantanal. This points to the great importance of multi‐years climatic events on the vegetation cover of the Pantanal and indicates a very dynamic development in plant communities.

Physiological responses to extreme hydrological events in the Pantanal wetland: heterogeneity of a plant community containing super‐dominant species

“…In particular, C. americana , L. parvifolia and V. divergens produce copious amounts of seed that ripen between Oct and Jan (Lorenzi ), which is before seasonal flooding but after the beginning of the rainy season when soil moisture is adequate for germination. This hydrological window of opportunity is critical for the germination, recruitment and expansion of super‐dominant species like V. divergens in the Pantanal (Nunes da Cunha & Junk ), and the physiological tolerance to large fluctuations in hydrology presumably allows these species to persist once established.…”

“…). Some of these species have the capacity to invade grass‐dominated savanna, forming monospecific stands (Nunes da Cunha & Junk , ; Santos et al. ) and alter ecosystem properties (Vourlitis et al.…”

“…Such super‐dominant species represent an important threat to the current status of wetlands in South America (Nunes da Cunha & Junk , ; Santos et al. ; Dalmagro et al.…”

“…In fact, none of the over 500 tree species occurring within the Pantanal are endemic to the biome (Junk et al 2006). Some of these species have the capacity to invade grass-dominated savanna, forming monospecific stands (Nunes da Cunha & Junk 2001& Junk , 2004Santos et al 2006) and alter ecosystem properties ). These species, while native, have invaded so aggressively that they have been referred as 'super-dominant', or native species that have the properties of invasive species that can alter environmental characteristics (Matos & Pivello 2009 (Junk et al 2006;Santos et al 2006).…”

Effects of shrub encroachment on the anuran community in periodically flooded grasslands of the largest Neotropical wetland

“…Present legal restrictions on pasture clearing (Campos‐Filho ; Cezar et al . ), together with year‐to‐year changes in water level (Nunes da Cunha & Junk ; Santos et al . ), can provide conditions that favour plant encroachment by species originally found in forested habitats but which are able to colonize open areas (e.g.…”