INVESTIGADORES
MARCHETTI Zuleica Yael
artículos
Título:
Vegetation and its relationship with geomorphologic units in the Parana River floodplain, Argentina
Autor/es:
MARCHETTI, ZULEICA Y.; LATRUBESSE, EDGARDO M.; PEREIRA MA. SOLEDAD; RAMONELL, CARLOS G.
Revista:
JOURNAL OF SOUTH AMERICAN EARTH SCIENCES
Editorial:
PERGAMON-ELSEVIER SCIENCE LTD
Referencias:
Lugar: Amsterdam; Año: 2013
ISSN:
0895-9811
Resumen:
The
Parana River is one of the most important fluvial systems of South America and
its floodplain includes the most diverse subtropical ecosystem on the continent.
However, the relationship between basic aspects, such as the vegetation and
geomorphology of the river floodplain, has scarcely been investigated. In this paper, the annual dynamics of
vegetation in relation to the geomorphologic and hydrological characteristics of
a river floodplain around 31º 30 S, are analyzed. The annual dynamics of
vegetation was investigated using values of the Normalized Difference Vegetation
Index (NDVI) obtained from satellite images at two scales of spatial analysis:
the first, at the geomorphologic unit level, through several transects crossing
the total width of each unit and, the second, through some transects selected
from each unit. Our analysis considered variables of different temporal
stability (such as geomorphology, hydrology, vegetation, precipitation, and
ground temperature), using scenes corresponding to two hydrological cycles of
the system (2009 and 2010), which represented relatively dry and humid
years. Five main geomorphologic units were identified in the floodplain of this
anabranching system, which were named considering the predominant landforms and
the most important (or typical) water course of each area: Bars and Islands of
the Main Channel of the Parana River (BI-MCH), Scroll Bars of the Colastine
Branch (SB-C), Scroll Bars of the San Javier River Channel (SB-SJ), Crevasse
Splays and Levees of the Malo - Mendieta minor channels (CSL-MM), and Crevasse
Splays and Levees of the Santa Fe - Coronda river channels (CSL-SFC). These
major units are assembled at different general levels and with variable slopes,
which partially control the permanence and other characteristics of the flood flow.
The crevasse splays and river levees units were predominantly characterized by
herbaceous-bushy marshy vegetation, with low mean NDVI values, while SB-C and
BI-MCH units showed two types of forests. The latter showed the highest NDVI
values. Unit SB-SJ showed mixed characteristics between the two above-mentioned
groups. Mean NDVI values were different among the varying geomorphologic units
and during the studied years, showing extreme values of 0.25 and 0.80 after
both hydrological cycles. According to our results, the main variations in the
seasonal dynamics of vegetation show a higher dependence on the dynamics of the
hydrological cycle than on surface temperature or precipitation. The
hydrological dynamics of the Parana River floodplain are in turn regulated by
its geomorphological architecture, so the annual dynamics of vegetation
activity in this system are finally influenced by the geomorphologic unit´s level,
rather than by the short duration modeling processes (i.e., hydrological cycles
or drought-flood pulses).