Seedling recruitment and survival of two desert grasses in the monte of Argentina

In the Monte Austral Neuquino, Argentina, vegetation is arranged in patches. Understanding the mechanisms involved in their distribution is critical for preventing desertification. The working hypothesis was that vegetation patches reduce environmental stress on the plants. Plant patches were classified into four microenvironments: windward; below the dominant shrubs (subcanopy); vegetation at the patch periphery (canopy edge) and bare patch interspaces (open). We determined seedling survival of the dominant species in each microenvironment, using a marking method of seedlings established from sown seeds. In addition, we measured the environmental characteristics in the four microenvironments, and associated them with seedling survival. Study species were the perennial grasses Leymus erianthus (Phil.) Dubcovsky, Stipa neaei Nees ex Steudel and Poa ligularis Nees ex Steudel, and the shrubs Larrea divaricata Cav. and Atriplex lampa Gill ex Moquin. Results supported the hyphothesis only for L. erianthus and S. neaei (but not for the other three species that showed higher seedling survival in the subcanopy than in the patch interspaces after 1 year from sowing). This study determined that (1) reduced environmental stress does not guarantee seed germination and seedling survival of a given species in the plant community and (2) seedling establishment will not be possible for any species of the plant community in the patch interspaces under the study conditions in the region. This is mostly because soil temperatures can reach up to 50°C in the patch interspaces in years of scanty precipitation during late spring and summer. Copyright © 2010 John Wiley & Sons, Ltd.     

Assessment of a fisheries legal framework for potential development of an ecosystem approach to fisheries management in large rivers

Most small‐scale fisheries of large floodplain rivers are still managed under conventional top‐down regulations that limit the application of an ecosystem approach to fisheries (EAF) due to inappropriate legal frameworks. Using the Parana–Paraguay River fisheries (Argentina) as an example, this study examines the extent to which existing provincial legislations can be prepared for the adoption of an EAF. An Ecosystem Fishing Legal Approach (EFLA) framework is proposed based on different criteria across an environmental–ecological, fishing, social, economic and institutional template. Policy Component Scores (PCS) and an Integrated Policy Legal Index (IPLI) were applied to assess the degree of compliance by current provincial legislations to EAF implementation. Cluster analysis was used to recognise the potential for articulating a legal framework at a basin scale. The EFLA framework, which provided an accurate picture of how provinces were poorly prepared to adopt an EAF for the Paraguay–Parana fisheries, and represents a suitable tool that can be adapted and extended to other basins around the world.     

Spatial and temporal responses of forest birds to human approaches in a protected area and implications for two management strategies

Little is known about the responses of forest birds, other than raptors, to human disturbance despite their being highly sensitive to habitat disruption. We tested five hypotheses about the spatial and temporal interactions between recreationists and wildlife by using five South American birds as model species. We measured two components of flight distance, horizontal (distance between a visitor and the base of a perching tree) and vertical (distance between the base of a tree and the perch), and estimated the third diagonal component (distance between a visitor and the perch). We found that (a) the relationships between horizontal and vertical components of flight distance were negative (rufus-collared sparrow, golden-billed saltator, chiguanco thrush), positive (spot-winged pigeon), and neutral (bay-winged cowbird), suggesting that different components are used as clues to the proximity of people when birds vacated the perching tree; (b) the distance to the nearest pathway correlated positively with flight distance components of two species (bay-winged cowbird and spot-winged pigeon); and (c) physical structure of the vegetation affected differently flight distances of all species. Interspecific comparisons showed that (d) all flight distance components increased linearly with body size, and (e) species differed in landing distances but not in response duration: large-bodied species tended to land farther than smaller-bodied ones. By implementing buffer zones (areas without access to visitors), spatial restrictions would conflict with recreational activities. We recommend re-distributing (but not restricting) human visitation by varying the number of visitors and area of visitation according to the spatial requirements of differently sized species.     

The legal and administrative setting for the use of water resources in Mendoza, Argentina

The legal-administrative setting for the use of waterresources in Mendoza Province is founded on differentlegal rules. This includes the National Constitution,the Argentine Civil Code, National Laws, theConstitution of the Provincial State, the GeneralWater Law, (legal) administrative regulations of theGeneral Department of Irrigation.The current water law is based on the roman law, onthe Arab irrigation water rights which were brought toArgentina by the Spaniards and on the practices of theoriginal American pre-Colombian intermediate law.The latter is marked by a strong regional sense. Assuch, the water law is strongly influenced by theregions elements of nature and attempts to offersolutions to problems.The legal rules are discussed from a behavioral andorganizational perspective. Examples from the LowerTunuyan System are given to illustrate the day-to-dayeffects on irrigation water management.     

阿根廷2006—2010年拖拉机生产与市场发展浅析

介绍了阿根廷拖拉机生产和市场销售情况,分析了阿根廷拖拉机市场特点及发展趋势。     

Herd demographics correlated with the spatial distribution of a foot-and-mouth disease epidemic in Buenos Aires province, Argentina

During a recent foot-and-mouth disease epidemic in Argentina, cattle herds affected in 2001 were located mainly (69%) in Buenos Aires province. The densities of outbreaks (no. of outbreaks per km²) and cattle-demographic variables in the province were estimated using a geographical information system and kernel function. Before the epidemic officially was recognized, the density of outbreaks was correlated (r_sp = 0.28–0.47) with the geographic distribution of small (≤100 cattle), dairy and fattening herds. During the mass-vaccination campaign to control the epidemic (April–July), the density of outbreaks was most strongly correlated (r_sp = 0.20–0.25) with the distribution of large (>500 cattle) and breeding herds. After the end of the mass-vaccination campaign, large herds and number of cows were most strongly correlated (r_sp = 0.16–0.26) with outbreak density. These relationships might indicate that: (1) the disease spread more rapidly or was more easily detected in intensive production systems at the beginning of the epidemic; (2) vaccination and other control methods applied were less effective in large, semi-intensive production systems; (3) incomplete vaccine protection was responsible for herd outbreaks that occurred after the end of the mass-vaccination campaign.     

Sedimentological study of aeolian soil parent materials in the Río Sauce Grande basin, Buenos Aires province, Argentina

Sedimentological characteristics of aeolian soil parent materials in the Río Sauce Grande basin, southern Buenos Aires province, were analysed using grain-size distributions, transport mechanisms, dynamics of the sedimentary process and the nature of calcareous layers. Samples were collected from C horizon of 13 profiles distributed over all the piedmont areas and plains. Calcium carbonate in these materials is either inherited from the parent material or was redistributed by pedogenic processes. Their amounts in Ck horizons increase from the upper to the lower basin, and are inversely related to the thickness of soil parent material, to mean annual rainfall and to the calcrete depth.The cumulative grain-size plots show that the sediments were transported by both aeolian saltation and aeolian suspension. Most of them have coarser and more heterogeneous grain size distributions than typical loess of the northern hemisphere, indicating a larger and more fluctuating wind energy than is required for the formation of typical loess. Deposits in the upper and middle basins were deposited in two main aeolian episodes which can be related to the dry periods of the Late Pleistocene and the Late Holocene recorded in southern Buenos Aires province. In some thin profiles of the middle and lower basins, the large clay content of the calcic C horizon was probably inherited from one or more previous pedogenic events. There is a systematic increase of particle size towards the lower basin, which may be related to an increase of energy towards the lower basin or to the influence of littoral dune fields along much of the Atlantic coastal zone.     

Erosion predictions with the Wind Erosion Equation (WEQ) using different climatic factors

Little information is available on the performance of the Wind Erosion Equation (WEQ) for estimating wind erosion under differing climatic conditions. The objective of this study was to assess the fitting of measured and WEQ‐estimated wind erosion with different climatic C factors. Results showed that WEQ underestimated the annual wind erosion by 45 per cent when loaded with the historic C, obtained with climatic data records between 1981 and 1990. The monthly averaged C factor (monthly C, n = 12) underestimated the erosion by 29 per cent, the C factors of each one of the six studied years (annual C, n = 6) underestimated the erosion by 19 per cent, and the C factors of each one of the evaluated months (monthly C, n = 72) overestimated the erosion by 31 per cent. Precipitation explained most of C factors variability. C factors corresponding to high precipitation periods predicted low erosion amounts in no‐till (NT) and conventional tillage (CT). C factors corresponding to low precipitation periods calculated high erosion rates in CT (143 t ha⁻¹ y⁻¹) and low in NT (2·4 t ha⁻¹ y⁻¹). The historical C factor predicted no erosion in NT and 7·1 t ha⁻¹ y⁻¹ in CT. These results indicated that the WEQ should be used with variable C factors in order to assess different climatic scenarios of the semiarid Argentina. Copyright © 2007 John Wiley & Sons, Ltd.