Francisco A. Squeo

Extreme climatic events shape arid and semiarid ecosystems

6 Climatic changes associated with the El Nino Southern Oscillation (ENSO) can have a dramatic impact on ter- restrial ecosystems worldwide, but especially on arid and semiarid systems, where productivity is strongly lim- ited by precipitation. Nearly two decades of research, including both short-term experiments and long-term studies conducted on three continents, reveal that the initial, extraordinary increases in primary productivity percolate up through entire food webs, attenuating the relative importance of top-down control by predators, providing key resources that are stored to fuel future production, and altering disturbance regimes for months or years after ENSO conditions have passed. Moreover, the ecological changes associated with ENSO events have important implications for agroecosystems, ecosystem restoration, wildlife conservation, and the spread of disease. Here we present the main ideas and results of a recent symposium on the effects of ENSO in dry ecosystems, which was convened as part of the First Alexander von Humboldt International Conference on the El Nino Phenomenon and its Global Impact (Guayaquil, Ecuador, 16-20 May 2005).

Bofedales: high altitude peatlands of the central Andes

Existe un grupo excepcional de turberas (bofedales) de alta montana en el mundo situados en la estepa arida de los Andes centrales. Los bofedales en el norte de Chile estan presentes en la parte mas arida de su rango. Las principales especies de plantas responsables de la formacion de turba corresponden a miembros de Juncaceae. El agua fresca y medianamente salina de los bofedales proviene de agua subterranea asociada a riachuelos proveniente de glaciares, derretimiento de nieve y lluvia. Investigaciones paleoecologicas sugieren que algunos bofedales son integrantes recientes del paisaje, habiendose desarrollado durante los ultimos tres mil anos o menos. Estos bofedales son entidades unicas, extremadamente fragiles por su dependencia del agua, sensibles a los cambios climaticos y vulnerables a la alteracion humana tal como la actividad minera en la region. Se requiere mucho mas trabajo para desarrollar programas de manejo y conservacion, con solidas bases cientificas, de las plantas y animales que viven en ellos, y para asegurar la capacidad futura de pastoreo de la cual dependen los pueblos indigenas

Freezing tolerance and avoidance in high tropical Andean plants: Is it equally represented in species with different plant height?

SummaryFreezing tolerance and avoidance were studied in several different sized species of the tropical high Andes (4200 m) to determine whether there was a relationship between plant height and cold resistance mechanisms. Freezing injury and supercooling capacity were determined in ground level plants (i.e. cushions, small rosettes and a perennial herb), intermediate height plants (shrubs and perennial herbs) and arborescent forms (i.e. giant rosettes and small trees). All ground-level plants showed tolerance as the main mechanism of resistance to cold temperatures. Arborescent forms showed avoidance mechanisms mainly through supercooling, while intermediate plants exhibited both. Insulation mechanisms to avoid low temperatures were present in the two extreme life-forms. We suggest that a combination of freezing tolerance and avoidance by insulation is least expensive and is a more secure mechanism for high tropical mountain plants than supercooling alone.

Identification of priority areas for conservation in an arid zone: application of parsimony analysis of endemicity in the vascular flora of the Antofagasta region, northern Chile

Endemic taxa are those restricted to a specific area, and could bedefined as the exclusive biodiversity of a region. An area of endemismcontains taxa found nowhere else and could be catalogued as irreplaceable and of highpriority for conservation. proposed the parsimony analysis of endemicity (PAE) as a tool to detect areas ofendemism. PAE, a method of historical biogeography, is analogous to cladisticmethods used in phylogenetics analysis, and unites areas (taxa in cladistics)based on their shared species (characters in cladistics) according to the mostparsimonious solution. In this paper we determined with PAE, prioritary areasfor conservation on the basis of concentrations of endemic species in the aridregion of Antofagasta, northern Chile, and compared the results with theirrepresentation in the current Chilean National Parks and Reserves System. Wefound two areas suggested as priorities, one located in the north Andean zone ofthe region, and another at the coast. The area with the higher biodiversity andconcentration of endemics was that located at the coast. However, coastalecosystems are currently under-represented in the Chilean National Parks andReserves System. The establishment of a new protected area in the coastal zoneof the region of Antofagasta is currently under consideration, coinciding withthe area suggested with PAE as priority. This new area would not only allowconserving species with evident problems of conservation, but also preserving anarea where higher levels of endemism exist.

Cold resistance mechanisms in high desert Andean plants

Freezing tolerance and freezing avoidance were studied, during the growing season, in plant species from two different elevations (3200 m and 3700 m) in a desert region of the high Andes (29° 45′S, 69° 59′W) in order to determine whether there was a relationship between plant height and cold resistance mechanisms. Freezing injury and supercooling capacity were determined in plants of different height, from ground-level (<20 cm tall) to tall shrubs (27–90 cm). All ground-level plants showed freezing tolerance as the main mechanism for resistance to freezing temperatures. Tall shrubs avoided freezing temperatures, mainly through supercooling. Supercooling was only present in plants occupying the lower elevation (i.e., 3200 m). Both avoidance and tolerance mechanisms are present in a single genus (i.e., Adesmia).

Towards the creation of an integrated system of protected areas in Chile: achievements and challenges

Background: Chile is committed to extending its National System of Protected Areas (NSPA), focusing on eco-regions whose ecosystems are currently under-represented in the NSPA. A newly proposed law aims to create a Service of Biodiversity and Protected Areas that would unify the terrestrial and marine systems. The proposed law would allow the inclusion of private protected areas. Aims: We evaluate the current status of the conservation areas and propose an eco-regional plan that would allow reaching the overall target to bring 10% of all natural ecosystems under protection. Methods: A GAP analysis for all Chilean terrestrial and marine environments considered two protection scenarios: (1) public protected areas only, and (2) a combination of public and private protected areas. Afterwards, a multi-scale MARXAN assessment including 1367 conservation objects was carried out to identify suitable protected areas. Results: Chile does not meet its conservation target in four out of its 11 terrestrial eco-regions and in none of its eight marine eco-regions. To achieve the target of having 10% of all natural ecosystems (and conservation objects identified within them) under protection, an expansion of terrestrial public and private protected areas that currently cover 21.4% of Chile is required to reach 37.5%; marine protected areas need to cover 11.8% of Chiles exclusive economic zone. Conclusions: The under-represented conservation objects in protected areas in the highly biodiverse Mediterranean region require a proactive strategy towards establishing private protected areas. The proposed conservation law represents a first step in the right direction to extend the NSPA.

SPATIAL HETEROGENEITY OF HIGH MOUNTAIN VEGETATION IN THE ANDEAN DESERT ZONE OF CHILE

In the Andean desert zone of Chile, three vegetational belts can be distinguished: the subalpine belt ( 1 m) are found exclusively on north-facing slopes in rocky sites with shallow soils, and this may be related to thermal refuges. In contrast, many subshrubs and perennial herbs grow mainly on south-facing slopes or on hillsides with deep sediments. Most leguminous species grow on soils rich in calcium, and this may be due to their greater ability to fix atmospheric nitrogen. Large areas with hypothermal anomalies have no vegetation, except when covered by sediments of other origins (such as volcanic or intrusive). At the same altitudinal level, the chemical characteristics, drainage of the substrate, and winter snow accumulation determine which species are present.

Phenotypic response of Lycopersicon chilense to water deficit

La variacion fenotipica que induce el ambiente en las plantas ha sido considerada como una respuesta que maximiza la adaptacion a ambientes heterogeneos. Lycopersicon chilense, una especie de tomate endemica del Desierto de Atacama, presenta variaciones fenotipicas altitudinales en sus ambientes naturales, las que podrian deberse a diferentes grados de disponibilidad de agua en el suelo. Se hipotetiza que (a) semillas de poblaciones provenientes de distintos ambientes, crecidas en un ambiente comun, presentaran fenotipos semejantes, si las poblaciones no estan diferenciadas geneticamente y que (b) las diferentes poblaciones al ser sometidas a dos niveles de sequia deberian variar su constitucion fenotipica con respecto al grupo control. Se estudio la respuesta de 20 rasgos fenotipicos en nueve poblaciones de Lycopersicon chilense sometidas a distintos niveles de riego. Las semillas fueron colectadas en un gradiente altitudinal (desde los 20 a los 3.075 m de altitud), germinadas, puestas a crecer a las mismas condiciones climaticas y sometidas a tres niveles de riego: bajo (80 % CC), moderado (40 % CC) y severo (20 % CC). A pesar de las diferencias climaticas en sus ambientes naturales, la respuesta fenotipica de las plantas fue semejante en las nueve poblaciones cuando crecieron en un ambiente comun. Diferencias significativas entre las poblaciones se encontraron en tres de los 20 rasgos investigados (el numero de semillas por fruto, el peso fresco de los frutos y el volumen de los frutos). El deficit hidrico indujo una respuesta fenotipica en 12 caracteres. Los mas significantivos fueron: peso seco de las raices, cobertura, numero de frutos cuajados y el numero de semillas por fruto. Interaccion entre las poblaciones y el tratamiento de deficit hidrico se encontro solo en el numero de semillas por fruto, el peso fresco de los frutos y el volumen de los frutos. Nuestros datos indican que la respuesta fenotipica parece no diferir entre las poblaciones cuando estas crecen bajo condiciones ambientales similares. Probablemente la respuesta fenotipica de Lycopersicon chilense en sus ambientes naturales esta mas relacionada con ajustes fisiologicos y metabolicos que con una diferenciacion genetica.

Crónica de un conflicto anunciado: Tres centrales termoeléctricas a carbón en un hotspot de biodiversidad de importancia mundial

El aumento de la demanda energetica chilena en los ultimos anos ha promovido la creacion de una gran cantidad de proyectos de generacion electrica. La posible instalacion de tres centrales termoelectricas a carbon al norte de la Region de Coquimbo y en las inmediaciones de areas definidas como claves para la conservacion y manejo de la biodiversidad marina (e.g., reservas marinas, areas de manejo y explotacion de recursos bentonicos) y terrestre (e.g., reserva nacional, sitios prioritarios), ha generado conflictos sociales y controversias sobre su ubicacion y compatibilidad con los usos propuestos para el area. El presente comentario plantea el conflicto que se origina entre la necesidad de cubrir los requerimientos energeticos de Chile y la implementacion de iniciativas de conservacion y manejo de recursos naturales. Se describe la importancia y relevancia ecologica y economica del area de posible instalacion de las termoelectricas y se revisan los principales impactos reportados para este tipo de tecnologia sobre la salud humana y ecosistemica. Finalmente, se proponen enfoques y herramientas que pueden asistir en la toma de decisiones y en la resolucion de conflictos.

Enhanced facilitation at the extreme end of the aridity gradient in the Atacama Desert: a community‐level approach

Plant facilitation is now recognized as an important process in severe environments. However, there is still no agreement on how facilitation changes as conditions become increasingly severe. The classic stress gradient hypothesis (SGH) predicts a monotonic increase in facilitation, which rises in frequency as conditions approach the extreme end of the environmental gradient. However, few studies have evaluated the validity of the SGH at the community level, the level at which it was formulated. Moreover, few studies have tested the SGH at either extreme of the gradient, and very few have excluded the effect of livestock on community response to stress. In line with the SGH, we hypothesized that several spatial pattern summary statistics would change monotonically from the least to the most arid sites, indicating increasingly aggregated patterns. In this study, we performed an evaluation of the SGH both within communities of shrub species and across a large portion of the Atacama Desert, and we isolated the abiotic component of the SGH. Our environmental gradient covered an extreme aridity gradient (< 20-130 mm annual precipitation). To perform point pattern analysis, we established 13 sites with environmental conditions representing four distinct levels of this gradient. Further, we conducted species co-occurrence analyses at 19 sites along the gradient. Both sets of analyses showed stronger positive spatial associations among plants at the most extreme end of the gradient. This was true regardless of whether we included all individuals, only small individuals located around large ones, or individuals in species pairs. Moreover, species tended to show greater co-occurrence as environmental severity increased. This increase in aggregation in the plant community seems to correlate with an increase in the strength of positive interspecific interactions, rather than greater clustering within each species. These monotonic increases in species co-occurrence and spatial association in more severe environments are consistent with some of the predictions of SGH, and collectively these results suggest that as the climate becomes more arid, positive species pairs interactions tend to be prevalent in the community.