Download Download

Seasonal dynamics of the shoreline vegetation in the Zapatosa floodplain lake complex, Colombia Udo Schmidt-Mumm* & Georg Janauer Department of Limnology and Oceanography, University of Vienna, Althanstraße 14, A-1090 Vienna, Austria; [email protected], [email protected] * Correspondence Received 29-IX-2013. Corrected 20-I-2014. Accepted 18-II-2014. Abstract: Floodplain lakes and associated wetlands in tropical dry climates are controlled by pronounced and severe seasonal hydrologic fluctuations. We examined the plant community response to a bimodal flooding pattern in the Zapatosa Floodplain Lake Complex (ZFLC), Northern Colombia. We measured floristic and quantitative change in four sampling periods emphasizing seasonal differences in plant abundance and life-form structure. Of 79 species identified in the lake complex, 52 were used to characterize eight community types via classification and ordination procedures. Results showed that community structure does not change significantly during the flooding/receding stages. But maximum drawdown phase significantly disrupts the aquatic community structure and the exposed shorelines become colonized by ruderal terrestrial plants. Early rainfalls at the beginning of the wet season are emphasized as an important feature of plant regeneration and community development. The general strategy of the ZFLC vegetation can be framed into the flood pulse concept of river-floodplain systems. Thus, plant communities are mainly responding to disturbances and destruction events imposed by extreme water level fluctuations. Rev. Biol. Trop. 62 (3): 1073-1097. Epub 2014 September 01. Key words: Cesar River, flood pulse, littoral, macrophytes, Magdalena River, shallow lakes, bimodal seasonality. Floodplains play an important role regard- Yule, Mathooko, & Pringle, 2008; Warfe et al., ing the biogeochemistry and ecology of tropi- 2011). The interactions between rivers and their cal river systems. Plant and animal life of this surrounding floodplain motivated Junk, Bayley, particular system are adapted to the seasonal and Sparks (1989) to propose the ‘flood pulse variations in space and time caused by extreme concept’ as a main force controlling the biota of water level fluctuations. This seasonality also tropical floodplains. They considered the flood- represents an important factor in the speciation plain as the area periodically inundated by the of several aquatic and wetland plants (Haynes waters of rivers, lakes, lagoons, and/or under- & Holm-Nielsen, 1989). The dynamic char- ground water, or by direct precipitation. The acter of these systems gives rise to complex concept aims to explain the physical and chemi- primary and secondary production processes cal conditions that obligate the biota to respond that are difficult to predict in detail, but nutri- through different phenological, morphological, ent input from rivers and streams are important anatomical and/or physiological adaptations to in general, as a significant contribution can predictable hydrological cycles. Given its alter- be expected following rainfall from the sur- nation between aquatic and terrestrial phases, rounding watershed. Nutrient cycling proceeds the flooded area of the shoreline is defined as mainly through heterotrophic processes via bac- ‘aquatic-terrestrial transitional zone’ (ATTZ). teria, fungi, micro-zooplankton and shredding- Recently the pulse concept was reviewed by invertebrates (Melack & Fisher, 1990; Wantzen, Junk and Wantzen (2004), as likewise expanded Rev. Biol. Trop. (Int. J. Trop. Biol. ISSN-0034-7744) Vol. 62 (3): 1073-1097, September 2014 1073 to temperate rivers (Tockner, Malard, & Ward, 2008; Padial et al., 2009; Thomaz, Carvalho, 2000) and lakes (Wantzen, Junk, & Rothhaupt, Padial, & Kobayashi, 2009; Sousa, Thomaz, & 2008). Another emerging concept related to the Murphy, 2011). flood pulse is the homogenization effect of the Additionally, aquatic and wetland vegeta- inundation process mediated through increas- tion of tropical floodplains are considered of ing lateral and longitudinal connectivity. In this prime importance for a variety of biota. For case hydrological connectivity, referring here to instance, macroinvertebrates living on macro- water mediated transfer of matter, energy, and/ phytes and in the root zones of floating mats are or organisms within or between elements of using this habitat for shelter and food resource, the hydrologic cycle (Pringle, 2001), homog- serving also as primary food supply for fish enizes the limnological (physical, chemical) and and other vertebrates (primarily amphibians, biological characteristics of contiguous water reptilians and birds; Junk, 1973; Poi de Neiff bodies along river floodplain systems (Thomaz, & Carignan, 1997; Poi de Neiff, 2003; Takeda, Bini, & Bozelli, 2007). Souza-Franco, Melo, & Monkolski, 2003). Fur- The herbaceous vegetation of tropical thermore, aquatic vegetation represents a key floodplain systems is very heterogeneous, factor in the selection of habitats by fish (Chick highly productive and plays an important role & McIvor, 1997; Gomes, Bulla, Agostinho, in nutrient cycling. For example, in the middle Vasconcelos, & Miranda, 2012), serving as ref- Amazon it occupies approximately 0.5% of the uge to avoid predators (Chick & McIvor, 1997; basin but contributes 5% of the total organic Warfe & Barmuta, 2004), as spawning habi- matter to the downstream transport (Hedges et tat, and as nurseries for initial life stages and al., 1986). Plant communities in tropical sea- juveniles (Grenouillet & Pond, 2001; Bulla, sonally flooded wetlands and floodplain lakes Gomes, Miranda, & Agostinho, 2011). have been thoroughly studied for Northern The ‘Zapatosa Floodplain Lake Complex’ Australia (Casanova & Brock, 2000; Finlayson, (ZFLC) and its associated wetlands, part of an 2005; Warfe et al., 2011), India (Unni, 1971; even larger floodplain system called the Mom- Middleton, 1999; van der Valk, Middleton, pox Depression, is considered one of the most Williams, Mason, & Davis, 1993), and Africa (Rees, 1978; Müller & Deil, 2005). In tropical important freshwater ecosystems of the Magda- and subtropical South America studies on the lena River basin in Northern Colombia. In spite different aspects of the flooding cycles and of its importance, hydrobiological information their effect on aquatic vegetation were carried on the river basin is practically inexistent, out in the Orinoco floodplains of Venezu- dealing mostly with the local inventory and elan (Castroviejo & López, 1985; Rial, 2000; ecology of fish assemblages (Ríos-Pulgarín, 2006), the Amazon (Junk, 1970; 1986; Junk & Jiménez-Segura, Palacio, & Ramírez Restrepo, Piedade, 1993; 1997; Ferreira, Piedade, Wit- 2008), aquatic and wetland plants (Schmidt- tmann, & Franco, 2010; Piedade et al., 2010), Mumm, 1987), and a generalized overview on the Pantanal (Do Prado, Heckman, & Martins, macrophyte vegetation (Rangel-Ch., 2010). In 1994; Frey, 1995; Fortney et al., 2004; Pott & the Magdalena River fish stocks have collapsed Pott, 2004; Kufner, Scremin-Dias, & Guglieri- due to overexploitation and basin mismanage- Caporal, 2011; Pott, Pott, Lima, Moreira, & ment, and the relationship between fish migra- Oliveira, 2011), coastal Brazil (Rolon, Lac- tion and the bimodal flood pattern of the river erda, Maltchik, & Guadagnin, 2008), and par- is very poorly understood, following Galvis ticularly the Paraná due to increasing river and Mojica (2007) who also highlighted the impoundments (e.g., Franceschi, Torres, Prado, urgent need to study the floristic composi- & Lewis, 2000; Murphy et al., 2003; Thomaz, tion and ecology of the floating mats and Souza, & Bini, 2003; Santos & Thomaz, 2007; inundated forests for better understanding fish Sabattini & Lallana, 2008; Santos & Thomaz, migration dynamics. 1074 Rev. Biol. Trop. (Int. J. Trop. Biol. ISSN-0034-7744) Vol. 62 (3): 1073-1097, September 2014 In this study, we aimed on identifying Caribbean and Atlantic coasts of South America. the influence of the distinct bimodal seasonal It is noteworthy to mention that the dissolved flooding and drought cycle spanning over one load is of the same magnitude as the Orinoco year. Using transects, we examined the shore- River, similar to the Paraná River, and ten times line of the ZFLC with emphasis on seasonal lower than that of the Amazonas River (Restrepo differences in macrophyte abundances and life- & Kjerfve, 2000; 2004). form structure. The specific objectives of this The rain pattern and water level fluctuation study were to: (1) compare and characterize in the ZFLC follows a bimodal tetra-seasonal the composition and community structure of regime, although water level rises with a lag of the littoral herbaceous vegetation between four around one month after initiation of the wet sea- ecologically distinct dry/wet flooding phases son. The first and smaller flood (ca. 2.6m over within the ZFLC; (2) determine the existence average water level) occurs between May and of a zonation pattern in the plant commu- July, the second between October and Decem- nity composition along the spatial inundation ber (ca. 5m over average water level). A lesser gradient; and (3) provide baseline data for drought, the Caribbean mid-summer drought management that can be used to evaluate long- (‘veranillo’) caused by the intensification and term floristic and structural changes in the expansion of the North Atlantic subtropical high aquatic vegetation. Related to objective (2), we pressure cell (Poveda,

Load more