Los bosques nativos son los ecosistemas naturales que más atención reciben de la sociedad en relación con su conservación y manejo. El alcance de la definición de bosque nativo ha cambiado con el tiempo, lo cual afecta la implementación de diversos instrumentos que usan las instituciones (e.g., cuando se identifican las coberturas de bosques alcanzados por los inventarios forestales en las diferentes jurisdicciones). Esto conduce a diferentes resultados e interpretaciones, incluso hasta erróneas (e.g., con el monitoreo de las coberturas de bosque nativo). El objetivo de este trabajo es analizar la definición actual de bosque nativo implementada por el Gobierno de la Nación Argentina en el marco de la Ley 26331/07 para la gestión de las políticas institucionales, y realizar una nueva propuesta de definición que contemple los vacíos que en ella aparecen, fundamentándolos según el conocimiento científico disponible. La definición propuesta difiere de la original en que incluye un tamaño de parche mínimo con una determinada conectividad y composición del paisaje circundante. Asimismo, se discuten otros aspectos necesarios para su implementación, además de los impactos que podrían producirse a diferentes escalas espaciales en la gestión del bosque nativo.

La Reserva de Biosfera Parque Costero del Sur (MAB-UNESCO) incluye una porcion de los bosques dominados por tala (Celtis tala) coronillo (Scutia buxifolia) conocidos como Talares. Los mismos constituyen la comunidad boscosa mas extensa de la Provincia de Buenos Aires. Esta Reserva posee una superficie de 26.581 ha, formadas por un 73 % de distintos tipos de pastizales, 9 % deTalares, 9 % de Pajonales 1% de Bosques Riberenos. El resto lo constituyen areas cultivadas. El relevamiento estructural se llevo a cabo en tres tipos de bosque: los dominados por el tala, coronillo los de codominancia de ambas especies. Los valores totales de densidad area basal para cada tipo de bosque fueron de 953 ind. ha'' 29,92 m2.ha''; 795 ind. ha'' 30,17 m2.ha''; 1.004 ind. ha ' y 32,71 m2.ha', respectivamente. Se calculo tambien la distribucion de dichos parametros por clase diametrica por especie.

La caida y masa de hojarasca fue estudiada en un bosque seco dominado por Celtis tala, (tala), y Scutia buxifolia (coronillo) ubicado a 20 km al SE de Magdalena (35° 11' S, 57° 17' W provincia de Buenos Aires). El promedio de calda de hojarasca fina fue 6,1 Mg.ha'.ano-' co rrespondiendo 59 % a hojas, 20% a ramas 1 cm de diametro fueron de 2,5 Mg.ha-'.ano-' y 6,3 Mg.ha-'. Los valores de k, (cafda/masa) para la hojarasca fina y ramas > 1 cm fueron de 0,81 ano-' y 0,39 ano respectivamente. La caida de hojas presento maximos otonales y primaverales respondiendo a los maximos de caida de C. tala y S. buxifolia respectivamente. Las ramas no presentaron patrones estacionales de caida, mientras que la maxima estacionalidad se presento en la caida de flores y frutos. Se utilizaron dos modelos teoricos que predicen valores de caida de hojarasca fina a partir de la temperatura y precipitacion. El valor hallado para el area de estudio fue menor que lo predicho por los modelos. Los modelos utilizan un indice de disponibilidad de agua para predecir los valores de caida. Las diferencias halladas podrian atribuirse a la alta permeabilidad de los suelos de la zona y su incidencia en la disponibilidad de agua.

Fil: Albanesi, Sebastian Alejandro. Consejo Nacional de Investigaciones Cientificas y Tecnicas; Argentina. Fundacion ProYungas; Argentina

Fil: Albanesi, Sebastian Alejandro. Consejo Nacional de Investigaciones Cientificas y Tecnicas; Argentina. Fundacion ProYungas; Argentina

Floristic composition and tree size distribution of different forest patches were studied between 1600 and 1800 m altitude in fue Subtropical Montane Forests of Parque Biologico Sierra de San Javier, Argentina. Quadrats (20 x 20 m) wete sampled in 12 sites. Sites were ordered using correspondence analysis. Ttie first ordinatioh axis was clearly associated to a gradient in complexity IIIId diversity. The less complex forests were d6minated by Alnusacuminata,' . Podocarpus pdrlatorei, and Crinodendron tucUmanum. Richest and most com.plex fotests were domiDat'ed.by Myrtaceae species such aS Bleplu;irocalyx salicifolius, Myrcianthes mato and Myrcianthes pseudomato, acct>mpanied bY ' Cedrela, lillpi, Ilex argentiTUl, P1'fPIus tucumanensis, and pthers. Intermediate values of diversity and cOplplelPty were found in mature forests of ', acuminata and P. parlatorei; and in forests dominated by the treetets I),unalia lorentzii, Sambucus peruviana and Solanum grossum. Sites were grouped using the Twinspan software package. Within eachcluster, diameter distribution of the most important species was used to describe tegeneration trends. Myrtaceae species showed an inverted-f' distribution of diarneter, suggesting a continous regeneration mode. On the other hand,species which dominate simple forests such as A. acuminata, P. parlatorei, and C. tucumanum showed bell-shaped diameter distribution, suggesting lack of regeneration under the canopy. These conclusions were also supported by seedling and sapling densities. The results suggest tlu;it A. acuminata, P. parlatorei, and C. tucumanum are pioneer species, and that the forests dominated by such species were originated in grasslands or shrublands. These species seems to be gradually replaced by shade tolerant taxa originating patchy heterogeneity and landcape diversity as a result of discrete eveIlts of recruitment followed by forest succession.

We conducted a 55-day long camera-trap survey in the Yungas subtropical forest in NW Argentina, to assess the effect of human accessibility, conservation status of the area, domestic animals and elevation on the diversity and composition of the large and medium-sized native terrestrial mammal assemblage. We deployed 24 camera-trap stations at distances of ∼2 km from each other. The study area is covered by continuous forest and has its center in the small community of Acambuco, in the Acambuco Provincial Reserve. The main economic activity in the area is oil/gas exploitation. Local residents raise cattle, hunt and use timber and non-timber forest products. The human impact was indirectly measured with an accessibility cost model. We used a multiple regression ANCOVA to assess the effect of elevation (range: 628–1170 masl), accessibility, protection status (reserve vs not) and frequency of records of domestic animals on the native mammal species richness and on a nonmetric multidimensional scaling (NMDS) ordination based on the frequency of records of the native mammals recorded at >3 camera-trap stations. We recorded 15 species of native mammals. Native mammal species richness decreased with elevation. Elevation was correlated with NMDS axes. Other predictive variables had no effect on species richness or the NMDS ordination, probably as a result of the relatively narrow range of conditions assessed in this study. The effect of elevation on mammal assemblages should be considered in landscape planning processes aimed at promoting biodiversity conservation.

Las Yungas subtropicales se extienden por el noroeste de Argentina y sur de Bolivia, ocupando aproximadamente 56 000 km2. Se caracterizan por su amplia distribución altitudinal (400-2300 msnm), donde el recambio de especies de árboles determina la ocurrencia de tres pisos altitudinales (selva pedemontana, selva montana y bosque montano) con cambios consistentes en la fenología foliar y los síndromes de dispersión de las especies arbóreas. Dominan las especies caducifolias en los extremos del gradiente, y las especies semicaducifolias y siempreverdes en las elevaciones intermedias. Por su parte, las especies dispersadas por el viento o la gravedad caracterizan la parte baja del gradiente, mientras que las dispersadas por animales caracterizan los pisos superiores de vegetación. Los cambios físicos y biológicos en el gradiente altitudinal condicionan los usos y las estrategias de conservación de las Yungas subtropicales. La desforestación alcanzaba 18% de la superficie original de este ambiente en Argentina en la década de los 70 y 31% en el año 2010, principalmente (>90%) en las zonas bajas y planas. Las Yungas de Argentina presentan protección formal estatal (nacional, provincial y municipal) en 22% de su extensión actual, sin considerar las categorías internacionales, que pueden ser instrumentos valiosos, si se logra una implementación efectiva de los criterios de uso sustentable de los recursos naturales. Adicionalmente, los planes de ordenamiento territorial en marcha vinculados a compensaciones económicas podrían jugar un papel importante en el marco de estrategias regionales de uso y conservación.

The Andean bear (Tremarctos ornatus): Myth and truth of its presence in Argentina. Among the many faunal inventories conducted in Northwestern Argentina, only one senior author claims to have found reliable evidence on the current presence of Tremarctos ornatus. We assessed the 34 published records of this species against more than 800 points of similar surveys which recorded the occurrence of jaguar, tapir, monkeys and carnivore attacks on cattle in Salta and Jujuy, but turned negative for the Andean bear. Based on our studies there and in Bolivia, we think it is most unlikely that a bear popula- tion exists in Argentina, and recommend more caution in the use of anecdotic reports and animal sign before proclaiming such a significant finding. Palabras clave. Evidencia anecdotica. Indicios. Noroeste argentino. Oso andino. Yungas.

Abstract:We identified and quantified regional and local environmental factors and spatial variation associated with tree-species composition across a 2000-m altitudinal gradient of Andean forest in north-western Argentina. A network of 47 1-ha plots was established along the altitudinal gradient within an area of about 25 000 km2; all trees ≥ 10 cm dbh were identified and measured. Constrained ordinations and variance-partitioning analyses were performed to investigate the determinants of tree-species distribution at the regional scale, across and within forest types (i.e. dry and cloud forests). We marked and measured a total of 22 240 trees belonging to 160 species. Significant environmental factors and spatial location combined accounted for 35% of total variation explained. A high proportion of variation was explained by climatic factors that were spatially structured; after removing the spatial effect, climate explained more variation in species composition across the complete gradient than did local factors. Relative importance of regional and local factors varied with geographic extent. Local factors explained more variation in tree-species composition at the within-forest scale than at the scale of the complete gradient. Our findings support the conceptual model of multi-scale controls on vegetation distribution, where local community composition and abundance result from processes at both regional and local scales.

M. González-Espinosa, M.R. Parra-Vázquez, M.H. Huerta-Silva, N. Ramírez-Marcial, J.J. Armesto, A.D. Brown, C. Echeverría, B.G. Ferguson, D. Geneletti, J.D. Golicher, J. Gowda, S.C. Holz, E. Ianni, T. Kitzberger, A. Lara, F. López-Barrera, L. Malizia, R.H. Manson, J.A. Montero-Solano, G. Montoya-Gómez, F. Orsi, A.C. Premoli, J.M. ReyBenayas, I. Schiappacasse, C. Smith-Ramírez, G. Williams-Linera, A.C. Newton

After one growing season of recovery, vegetation cover and height, species richness, and life forms composition were surveyed in 15 sites located along a gas-pipeline track running through an altitudinal range from 400-2000 m in the subtropical mountains of north-western Argentina (23°S). Vegetation cover was negatively correlated with altitude but was generally high at all sites (> 60%) after one year. Total species richness and maximum vegetation height did not vary significantly with altitude. Cover of grasses, and cover and species richness of trees, small shrubs and climbers were negatively correlated with altitude. Herb species richness correlated positively with altitude. Large shrub richness and cover showed no statistical relationship with altitude. The relative cover of herbs and grass species richness did not vary along the altitudinal gradient. Overall, these results indicate that in the altitudinal range studied, vegetation recovery is relatively high after this type of disturbance, probably due to low dispersal limitations and to the availability of species well adapted to intense disturbances. Vegetation recovery after gas-pipeline construction or similar perturbations may lead to relatively fast ecological restoration in subtropical montane forest ecosystems.

Abstract The Upper Bermejo River Basin (UBRB) is the most bio-diverse region in Argentina. A rugged territory and a long history of human settlement, combined with social and political isolation, have resulted in large areas with well-preserved forests, a large number of wild plant and animal species, and indigenous crops. Several factors, including agriculture expansion, intense logging activities, and oil and gas prospecting, are posing a threat to biodiversity. Current national parks and reserves are not enough to secure the survival of functional populations, especially of the large mammals. Conservation of biodiversity in the UBRB requires a broader approach: e.g. protection of the most sensitive areas outside present reserves; maintaining the remaining forest matrix under sustainable management regimes, involving the local communities in the process; and encouraging uses synergetic with conservation. Recent purchases by private enterprises of new protected areas, the willingness of local administrations to establish a new legal conservation framework, and local communities considering sustainable management of their lands, represent encouraging opportunities for the region.

Leaf area loss for two dominant tree species in a Celtis tala Gill ex Planch (Ulmaceae) and Scutia buxifolia Reiss (Rhamnaceae) forest was studied at eastern Buenos Aires, Argentina. Leaf consumption in these species was compared with that of the other two tree species also present in that forest. These comparisons were made through estimation of consumed leaves/total leaves ratio on twigs formed during the last growing season. Consumption was related to leaf characteristics and exposition (sun and shade leaves). Annual leaf area loss was 8.7 % of total fall for two dominant species as a whole. For two dominant species, the most of consumption occured on that foliar size which accounted greater foliar area. Sun leaves showed lower consumption higher toughness and lower water content than shaded ones. Consumption was negatively correlated with toughness and positively with water content. These correlations were observed either when sun and shade leaves were analyzed together or separate.