Grasslands of the World.pdf - Disasters and Conflicts - UNEP

V.A. DEREGIBUS & M.F. GARBULSKY
Grasslands of Patagonia 133
Plate 4.2
A typical Patagonian shrub steppe.
rather than the potential expected vegetation types typical of most structural
classification maps. This section follows the grouping of biomes proposed by
Paruelo et al. (1998), but endeavours to produce a synthesis of both structural
and functional aspects of the vegetation of each biome .
Patagonian shrub steppes
This vegetation type (Unit Jg 11 in Figure 4.5) accounts for close to 20 percent
of the semi -arid area (Paruelo, Jobbágy and Sala, 1998b) (Plate 4.2). Overall,
the MAP of this area is below 200 mm; vegetation cover varies between 30
and 50 percent and annual above ground net primary productivity (ANPP )
estimated from NDVI -I values (the annual integral of the Normalized
Difference Vegetation Index ) is 490 kg/ha/yr (León et al., 1998; Paruelo,
Jobbágy and Sala, 1998b). The physiognomy of this unit is that of a bi-layered
shrubland: an upper layer of shrubs circa 100 cm high, and a lower layer made
up of shrubs with crown heights that rarely exceed 15–20 cm (León et al., 1998).
The most conspicuous shrubs are Chuquiraga avellanedae , Lycium ameghinoi ,
L. chilense , Verbena ligustrina , Prosopis denudans and Colliguaya integerrima
(León et al., 1998; Roig, 1998). Grasses of the genera Stipa , Festuca and Poa , such
as Stipa neaei , S. speciosa , Festuca argentina and Poa ligularis , occur as a sparse
understorey (León et al., 1998). Shrub steppes occur in transition areas between
the grass steppes and the semi-deserts (Paruelo, Jobbágy and Sala, 1998b).