Arid and Semi-Arid Ecosystems

Abstract

Arid and semi-arid ecosystems in South America are best illustrated by two desert regions, the Peruvian and Atacama Deserts of the Pacific coast and the Monte Desert of central Argentina. The caatinga of northeast Brazil is often described as semi-arid, but mostly receives 500–750 mm of annual rainfall and is better regarded as dry savanna. Small areas of Venezuela and Colombia near the Caribbean coast, and nearby offshore islands, support desert-like vegetation with arborescent cacti, Prosopis, and Capparis, but generally receive up to 500 mm annual rainfall. Substrate conditions, as much or more than climate, determine the desert-like structure and composition of these communities, and thus they are not discussed further here. Extensive areas of Patagonian steppe also have semi-arid conditions, as discussed in chapter 14. The Peruvian and Atacama Deserts form a continuous belt along the west coast of South America, extending 3,500 km from near the northern border of Perú (5°S) to north-central Chile near La Serena (29°55’S), where the Mediterranean- type climate regime becomes dominant. The eastward extent of the Peruvian and Atacama Deserts is strongly truncated where either the coastal ranges or Andean Cordillera rise steeply from the Pacific coast and, as a biogeographic unit, the desert zone may extend from 20 to 100 km or more inland. A calculation of the area covered by these deserts depends in part on how this eastern margin is defined. Thus the Peruvian Desert covers between 80,000 and 144,000 km2, while the Atacama Desert of Chile extends over about 128,000 km2 if the barren lower slopes of the Andes are included. Actual vegetated landscapes are far smaller and for the lomas of Perú change dramatically between years depending on rainfall. Only about 12,000 km2 of the Atacama contain perennial plant communities, largely in the southern portion known as the Norte Chico but also including a narrow coastal belt of lomas extending northward almost to Antofagasta and the Prosopis woodlands of the Pampa del Tamarugal. The vegetated areas of the coastal lomas of Perú and Chile together probably do not exceed 4,000 km2 as a maximum following El Niño rains.

The South American Dung Beetle GenusEnnearabdusLansberge (Coleoptera: Scarabaeidae: Scarabaeinae: Eucraniini)

“…Potential distribution of E. lobocephalus . The potential distribution area of E. lobocephalus predicted by the model coincides with the area defined as Central Monte and Northern Monte and the Monte-Chaco transition zone as defined by Rundel et al ( 2007 ) and delimitated by Morello ( 1958 ) through chorological and ecological criteria. The area in the predicted distribution includes six Argentinean provinces (political): Catamarca, La Rioja, Santiago del Estero, Córdoba (western), San Juan, Mendoza, and a small disjunct area in the Salta province ( Figure 15 ).…”

“…Some Patagonian elements are also present in the Central and southern part of the Monte ( Roig et al 1980 ; Roig-Juñent et al 2001 ). Within the Monte, E. lobocephalus is distributed in the Northern Monte and Central Monte (as defined by Roig Juñent and Flores 2001 ; Rundel et al 2007 ). Northern Monte and Central Monte have an annual mean temperature of 13–15° C and annual precipitation of 80–400 mm.…”

Actualistic taphonomy of barn owl pellet‐derived small mammal bone accumulations in arid environments of South America

“…is a mosaic of shrubby steppes of Larrea spp., Acantholippia spp. and Junellia spp., open mesquite forests of Prosopis , and large proportions of bare sandy soils (Rundel et al ., 2007). Rainfall, mainly in summer, ranges from 30 to 350 mm per year in this region with a permanent water deficit, and with the Andean cordillera as its western boundary.…”

“…The present taphonomic study analyses the relative abundance of skeletal elements, breakage patterns and digestion in modern barn owl pellet‐derived small mammal bone and tooth accumulations. Three pellet samples were recovered in the central Monte Desert (northeastern Mendoza, Argentina), one of the most arid regions of South America (Rundel et al ., 2007). Taphonomic results were compared with those reported both for South American predators, particularly owls, and for similar predators from different parts of the world.…”

A Revision of the Argentinean Endemic GenusEucraniumBrullé (Coleoptera: Scarabaeidae: Scarabaeinae) with Description of one New Species and New Synonymies

“…Morphological divergence of Eucranium and known geographic distribution suggest that the genus constitutes an endemic taxon in Chaco and Monte biogeographic provinces. Biogeographically, the Monte and Chaco are interesting regions forming an extensive transitional zone between Neotropical and Andean biotas ( Rundel et al 2007 ; Morrone 2006 ). South American deserts constitute very old habitats as elucidates from the presence of many endemic suprageneric and generic taxa well adapted to arid conditions ( Roig Juññent et al 2001 ; Ocampo and Hawks 2006 , Ocampo et al 2010 ).…”