Effects of patch attributes, barriers, and distance between patches on the distribution of a rock-dwelling rodent (Lagidium viscacia)

We tested whether size of habitat patches and distance between patches are sufficient to predict the distribution of the mountain vizcacha Lagidium viscacia a large, rock-dwelling rodent of the Patagonian steppe Argentina, or whether information on other patch and landscape characteristics also is required. A logistic regression model including the distance between rock crevices and depth of crevices, distance between a patch and the nearest occupied patch, and whether or not there was a river separating it from the nearest occupied patch was a better predictor of patch occupancy by mountain vizcachas than was a model based only on patch size and distance between patches. Our results indicate that a simple metapopulation analysis based on size of habitat patches and distance between patches may not provide an accurate representation of regional population dynamics if patches vary in habitat quality independently of patch size and features in the matrix alter connectivity. This revised version was published online in August 2006 with corrections to the Cover Date.     

Growth and elemental composition (C,N, H) in larvae and early juveniles of a South American salt marsh crab,Chasmagnathus granulata (Decapoda: Grapsidae)

The semiterrestrial grapsid crab Chasmagnathus granulata Dana is one of the most predominant inhabitants of brackish salt marsh ecosystems in South America. Its early postembryonic stages were reared in the laboratory from hatching of the first larval stage through the first juvenile crab instar, and changes in the quantity and elemental composition of biomass (measured as dry weight, W; carbon, C; nitrogen, N; hydrogen, H) were investigated in short intervals of time (every 1 or 2 d). In a series of successive developmental stages, the accumulation of biomass per individual can be described as an exponential function of the number of moults. In contrast, the pattern of growth within individual moulting cycles is described with best fit of observed and predicted data as a quadratic function of development time elapsed since last ecdysis. Weight-specific instantaneous growth rates show decreasing trends within the moulting cycle. Cumulative biomass increments during larval development of C. granulata are among the highest on record for brachyuran crabs. The quantities and patterns of larval growth are in this species similar as in most marine brachyuran crabs, for which data are available, but different from those in some other semiterrestrial grapsid crab species, which live in similar brackish water habitats as C. granulata. Hence, the early postembryonic stages of C. granulata do not show special bioenergetic adaptations to the non-marine conditions, which prevail in the adult habitat of this species. This reflects a strategy of larval export to the sea, i.e. a reproductive dependence of this species on the marine environment.     

Four hundred years in the history of pinniped colonies around Mar del Plata,Argentina

1. Historical records show the area of Mar del Plata (38°05′ S/57°32′ W, Argentina) as inhabited by extensive seal colonies; the present study describes the evolution of their size and location from the 16th century to the present. 2. Southern sea lion (Otaria flavescens Shaw 1800), South American fur seal (Arctocephalus australis Zimmerman 1783) and southern elephant seal (Mirounga leonina Linnaeus 1758) colonies, which consisted of between 80 000 and 165 000 animals, were subject to no commercial harvest, and only small local catches were performed by transient aboriginal groups. 3. During the second half of the 19th century coastal zones were rapidly colonized by man and by the turn of the century, the pinniped rookeries finally disappeared. Such a dramatic decline was not only due to spatial competition with man, but also to the indirect effect of pinniped over-exploitation in other areas of the south-western Atlantic. 4. No seal colonies were recorded in Mar del Plata during the 20th century until the mid sixties, when small non-breeding groups of sea lions and fur seals established themselves in the area. 5. The seal rookeries' decline in Mar del Plata provides an interesting example of how human activity may severely affect the conservation of pinniped colonies, even with no direct action through massive catches. © 1998 John Wiley & Sons, Ltd.     

Essential oil and by-products of distillation of bay leaves (Laurus nobilis L.) from Argentina

Preliminary chemical studies were undertaken during one year on plant materials collected in a 40 ha field located in Henderson, Province of Buenos Aires, in order to determine the technical viability of the industrial production of essential oil from bay leaves (Laurus nobilis L., Lauraceae) growing in Argentina. The oils were extracted at a pilot scale plant and analyzed by GC–FID-MS. The apparent density of the plant material used for the distillation ranged from 90 g L⁻¹ to 170 g L⁻¹, depending on the type of material. The quality of the volatile oils obtained complied with market requirements and were in agreement with values reported from other countries. No considerable variations were observed in the chemical composition of the oils throughout the year. Taking in account the composition of the sub-fractions obtained during the distillation process, the quality of the final essential oil can be adjusted by fractional distillation. The occurrence of alcohol terpenes and phenols in the condensed waters (hydrolate) makes them a possible alternative to be used in industry. Moreover, and due to the good energetic and digestibility values obtained, our results showed that the exhausted plant material obtained after distillation could be a putative fibrous feed for ruminants. Both, hydrolate and exhausted plant materials are resources that can enhance added values in new endeavours. This is the first report on bay leaves essential oil production at industrial scale in Argentina.     

Native plants on experimental urban green roofs support higher community-level insect abundance than exotics

Urbanization is one of the multiple factors leading to global insect declines. As urbanization grows, green roofs represent a nature-based solution that could provide habitat for plants and animals within cities. Several characteristics of green roofs could enhance insect biodiversity. Nevertheless, little is known about the effects of plant origin on insect abundance from a multi-taxa perspective. Thus, our main goal was to evaluate the effects of plant origin, local resources, and urbanization level on green roofs’ overall insect abundance, the abundance of different taxonomic orders, and community composition. Using experimental green roofs, we compared insect communities between native and exotic plants across an urbanization gradient, in Córdoba city, central Argentina. On the roofs of 30 houses, we installed two blocks of a modular extensive green roof system, with either native or exotic plant species (6 species each). In March 2019, we used yellow pan traps and pitfall traps (N = 360) to sample insects and measured flower abundance and plant cover at each plant treatment. The urbanization level of each house was estimated by the Normalized Difference Vegetation Index (NDVI), the Normalized Difference Built-up Index (NDBI), and the Land Surface Temperature (LST). A total of 35,257 insects from 12 orders were registered, with Diptera, Hymenoptera, and Hemiptera as the dominant groups. Native plants supported significantly higher total insect abundance on both types of traps, independently from the urbanization level, flower abundance, or plant cover of each roof. The abundance of most of the taxonomic orders was higher in natives as well, but particular effects of the covariables were detected for certain groups. In addition, plant origin was an important factor for insect composition. Our results highlight that green roof design should prioritize native plants to enhance insect conservation while achieving more sustainable cities.     

First report of alien Drosera rotundifolia in a high conservation value Patagonian peat bog

Drosera L. (Droseraceae) is a genus of insectivorous plants distributed worldwide with 240 species, 40 of which are found in South America. In the temperate forests of Chile and Argentina the only species present is D. uniflora. In a peat bog in Nahuel Huapi National Park, Argentina, a new species of Drosera was found in February 2018. To identify the species, we used morphological characters, and in addition, we sequenced two individuals for the nuclear region ITS and the chloroplast gene rbcL. Other Drosera sequences for these molecular regions were downloaded from GenBank, and a phylogenetic analysis was done to confirm the morphological identification of the Patagonian individuals. Morphologically and genetically, the species found in Nahuel Huapi is D. rotundifolia, a mostly Northern Hemisphere species. This is an alien species to the region and is thought to have been transported to the bog by tourists that visit the area. The presence of an exotic species represents a threat to this particular ecosystem with high conservation value. Currently, the National Park is taking control actions order to remove all individuals of the recently detected species. This study represents the first report of an alien species of Drosera in southern South America growing in the wild. This potentially invasive species may not only have negative impacts on the natural peat bog habitats in southern Argentina and Chile, but may also reach bogs in other temperate parts of the world.     

Determining the optimal size of water users' associations

In 1985 the General Irrigation Department (DGI) of the Province of Mendoza, Argentina, launched a water users' associations reorganization program to attain administratively more effective associations. At that time there were 760 water users' associations (WUAs) managing a total irrigated area of 360,000 ha. Under the reorganization program all water users' associations of less than 1000 ha were merged into larger organizations. The main obstacle to the viability of small WUAs was the lack of adequate funding to perform their irrigation water management responsibilities. At that time it was thought that the ideal administrative area should range from 10,000 to 15,000 ha. Eight years after the reorganization, the total number of WUAs was reduced to 360. This paper reviews the experience with the reorganization program. It concludes that the optimal size should be between 3000 and 10,000 ha to minimize management costs. This conclusion is based on the detailed budgets of nine new WUAs administering from 500 to 14,000 ha.     

Pampas deer conservation with respect to habitat loss and protected area considerations in San Luis, Argentina

Ozotoceros bezoarticus celer is the most endangered subspecies of pampas deer. Although common in the Argentine Pampas 100 years ago, it persists in only two small populations. The largest population has survived due to the rarity of roads, internal farm subdivisions, and the low cattle density. However, habitat condition for this population has changed dramatically in the last 16 years. Five Landsat images (1985, 1992, 1997, 1999, 2001), covering 4608 km², were used to quantify pampas deer habitat loss due to the replacement of natural grassland by exotic pastures and crops. Image classification showed that natural grassland cover was reduced from 84.5 to 37.8% between 1985 and 2001. The annual transformation rate increased significantly from 1.4 to 10.9%. Average paddock size was significantly reduced from 1470 to 873 ha, and the number of paddocks increased from 129 to 227. The land within this area proposed for a national park has not escaped these habitat changes. In the last 6 years the amount of replaced area within the proposed park has increased from 9.1 to 51.1% due to actions by ranchers to avoid inclusion within park boundaries. Three patches of natural grassland still remain within the pampas deer distribution, one of which is the proposed national park. The implementation of a national park is a decisive challenge for the survival of pampas deer and its habitat in Argentina.     

Soil organic matter dynamics along a rice chronosequence in north-eastern Argentina: Evidence from natural C abundance and particle size fractionation

We studied the consequences of rice cultivation and its subsequent abandonment for soil organic matter (SOM) dynamics in north-eastern Argentina. Two chronosequences, which included a pristine grassland with C4 vegetation as a control, and several stages of rice (C3) fields abandoned for 1, 2, 4, 6 and 15 years were selected, and soil samples from the first 10 cm were gathered from each plot. Natural ¹³C abundance coupled with particle-size fractionation were employed to characterize SOM changes through time discriminated by SOM origin. Soil samples up to 50 cm were also collected throughout one chronosequence. Most changes in SOM occurred on the first 20 cm layer and, bulk density, carbon and nitrogen content, as well as δ¹³C remained similar at greater depths. After the rice cropping, the bulk density was slightly greater than in the natural grassland, and remained stable after the abandonment. Carbon and nitrogen contents remained almost stable in the surface layer during the cultivation. δ¹³C varied accordingly with the changes in vegetation cover with a C4 signature in the natural grassland and mainly a C3 signature in the rice fields. The abandonment of the rice cropping induced a decrease of the soil organic matter content, mainly of natural grassland origin, during the first 4 years. When the abandonment extended, the SOM content (from C4 origin) increased slowly and after 15 years, was almost the same as that of the natural grassland. The carbon turnover was greater in the coarser fractions than in the finer ones, confirming that soil organic carbon in the sand fraction was relatively labile. However, all the fractions were affected by inputs and outputs of C derived from rice and natural grassland. This fact could indicate that the former protected carbon could become less stable due to cultivation.     

Evaluation of Introduced and Naturalised Populations of Red Clover(<Emphasis Type="Italic">Trifolium pratense</Emphasis> L.) at Pergamino EEA-INTA,Argentina

Red clover (Trifolium pratense L.) is a temperate forage species that is extensively used in Argentina, but little effort in breeding has been made so far. Meanwhile, red clover breeding is strong in Europe and North America. In order to contribute to the utilisation of red clover genetic resources, 39 accessions of different origins were evaluated at Pergamino Inta Experimental Station. A broad phenotypic variation was detected for many of the 14 attributes considered. Variables that discriminate populations are related to seed production and winter yield. Two different groups clustered according to morphologic and productive mean attributes, and these groups were related to geographic origin of accessions.