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

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Grasslands of the world
(Cavagnaro et al., 2001; Wassner and Ravetta, 2001); within-genus shrub
genetic diversity (Bottini et al., 2001); the effects of pruning or cloning treatments
(Arena, Peri and Vater, 2001; Peri, Arena and Vater, 2001); segregation
of shrub species in relation to rainfall gradients (Marcolin and Bustos, 2001);
allocation patterns or morphological attributes in sympatric shrub species
(Stronatti et al., 2001; Vilela, Agüero and Ravetta, 2001); and factors influencing
insect herbivory in shrubs (D’Ambrogio and Fernández, 2001; Villacide
and Farina, 2001).
A few researchers are studying seed biology or germination dynamics in
relation to presence of microphytic crusts (Villasuso et al., 2001), litter accumulation
(Rotundo and Aguiar, 2001), plant life-form (Vargas and Bertiller,
2001), or grazing (Oliva, Collantes and Humano, 2001). Finally, there are a
small number of studies addressing miscellaneous issues ranging from secondary
succession patterns on cultivated rangelands to endophyte fungi in a series
of grasses from Patagonia (Cibils, Peinetti and Oliva, 2001; Vila Aiub et al.,
2001).
Management activities
The need for management tools to regulate grazing and slow down rates
of vegetation deterioration has led to the development of a number of
vegetation-based pasture assessment routines over the past decade. Most of
these (developed primarily by INTA) are being used in almost all provinces of
Argentinian Patagonia , either by government agencies or private consultants
(Borrelli and Oliva, 1999; Nakamatsu, Escobar and Elissalde, 2001; Bonvissuto,
2001; Siffredi et al., 2002).
The rangeland assessment methods used in the provinces of Río Negro
and Chubut (generally areas of shrub-steppe vegetation ) basically involve: the
measurement of vegetation cover (forage species cover, in particular); and estimation
of ANPP using annual precipitation data (see appendix in Golluscio,
Deregibus and Paruelo, 1998). The routine used in Santa Cruz (generally
applied to grass -steppes and semi -deserts ) involves: the measurement of forage
biomass (short-grasses, sedges and forbs); and grass key species stubble
heights (Borrelli and Oliva, 1999). The output of all methods is an estimate of
sheep carrying capacity . Whereas the biomass-based method involves yearly
monitoring , the vegetation-cover-based methods do not. In all cases, however,
assessment routines are fairly labour-intensive and therefore, in some instances,
their use becomes economically unviable. A number of efforts aim at reducing
labour costs by using up-to-date technological tools to facilitate a more widespread
adoption of range assessment routines.
Scientists at the Universidad de Buenos Aires (IFEVA-UBA) are using
Landsat TM image analysis to derive primary productivity estimates from
NDVI values to calculate carrying capacity at individual pasture scales (Paruelo
et al., 2001). Another approach that is currently being investigated by INTA