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

Grasslands of Patagonia 135
end of the moisture gradient. Dominant species of the grass-shrub steppes
are the same as those mentioned above, except for the shrubs Junellia tridens ,
Nardophyllum obtusifolium , Berberis buxifolia and Chiliotrichum diffusum,
and the grasses Stipa ibarii , Poa dusenii , Festuca pallescens, F. gracillima and
F. pyrogea (León et al., 1998; Roig, 1998).
Grass steppes
Grass steppes (Unit Id 12 in Figure 4.5) also span the latitudinal extent of
mainland Patagonia as a belt along the Andean foothills, that widens in the
south, reaching the Atlantic Ocean, and giving way to the Magellanic steppes
that occupy all of the area surrounding the Straits of Magellan, on the mainland
and the northern tip of Tierra del Fuego (Figure 4.5) (Paruelo, Jobbágy and
Sala, 1998; Cibils and Coughenour, 2001). This vegetation unit occurs in areas
where MAP exceeds 250 mm. Average ANPP is about 900 kg/ha/yr according
to NDVI -I-derived estimates reported by Paruelo, Jobbágy and Sala (1998).
There are about 34 and 40 plant species in the sub-Andean and Magellanic
steppes, respectively (Golluscio, León and Perelman, 1982; Boelcke, Moore
and Roig, 1985). Vegetation cover is about 65 percent on sub-Andean grass
steppes, where Festuca pallescens accounts for up to 70 percent of plant cover
and occurs along with F. magellanica , F. pyrogea , Deschampsia elegantula ,
D. flexuosa , Phleum commutatum , Elymus patagonicus and Rytidosperma
virescens (León et al., 1998). Magellanic steppes exhibit two main variants:
dry steppes on the eastern portion of the mainland, and mesic grasslands in
the west and southeast of the mainland and the northern region of Tierra del
Fuego, where MAP exceeds 350 mm. Vegetation cover ranges from 60 to over
80 percent; the dominant plant on both variants of the Magellanic steppe is
Festuca gracillima , a 25-cm-tall tussock-forming bunchgrass that is the most
conspicuous life form of this ecosystem (Boelcke, Moore and Roig., 1985;
Collantes, Anchorena and Cingolani, 1999). Other grass and grass-like species
are associated with the tussocks, such as Poa dusenii , P. poecila , Rytidosperma
virescens, Bromus setifolius , Deschampsia flexuosa, Agropyron magellanicum ,
Festuca magellanica, Agrostis tenuis , Carex andina , C. argentina , among
others (Boelcke, Moore and Roig, 1985). Empetrum rubrum -dominated
communities occur as heathland blended in the grass steppes on south-facing
slopes of moraine hills on moister Magellanic steppes (Collantes, Anchorena
and Cingolani, 1999).
Monte shrubland s and Monte ecotone
A third of semi -arid Patagonia is taken up by Monte vegetation units (Units
Jh 11, Ig 4 and Hg 11 in Figure 4.5) (Plate 4.3), exhibiting ANPP levels
ranging from 650 to 730 kg/ha/yr (Paruelo, Jobbágy and Sala, 1998b). Hg 11
scrubland is the most productive and is an ecotone between the Monte and
Espinal phytogeographic provinces (Cabrera, 1971; Paruelo, Jobbágy and Sala,