Alejandro Peñaloza

Nurse effect of Bolax gummifera cushion plants in the alpine vegetation of the Chilean Patagonian Andes

Abstract It has been proposed that in the harsh arctic and alpine climate zones, small microtopographic variations that can generate more benign conditions than in the surrounding environment could be perceived as safe sites for seedling recruitment. Cushion plants can modify wind pattern, temperature and water availability. Such modifications imply that cushion plants could act as ‘nurse plants’ facilitating the recruitment of other species in the community. This effect should be more evident under stressful conditions. We tested these hypotheses comparing the number of species that grow inside and outside Bolax gummifera cushions at two elevations (700 and 900 m a.s.l.) in the Patagonian Andes of Chile (50 °S). At both elevations, and in equivalent areas, the number of species was registered within and outside cushions. A total of 36 and 27 plant species were recorded either within or outside B. gummifera cushions at 700 and 900 m a.s.l., respectively. At 700 m a.s.l., 33 species were recorded growing within cushions and 29 outside them, while at 900 m a.s.l. these numbers were 24 and 13 respectively. At both elevations there were significantly more species growing within than outside cushions, and the proportion of species growing within cushions increased with elevation. Thus there is a nurse effect of cushion plants and it is more evident at higher elevations. Shelter from wind and increased soil water availability seem to be the factors that increase plant recruitment within cushions. Nomenclature: Marticorena & Quezada (1985).

Positive associations between the cushion plant Azorella monantha (Apiaceae) and alpine plant species in the Chilean Patagonian Andes

Low growing, compact cushion plants are a common and often dominant life form in temperate and subpolar alpine habitats. The cushion life-form can modify wind patterns, temperature and water availability and thus cushion species could be expected to act as nurse-plants facilitating the establishment of other alpine plant species on their surfaces. It has been suggested that the nurse effect should be most pronounced under more stressful environmental conditions, as found with increasing elevation in the alpine. One of the approaches used to detect the nurses has been the study of spatial associations among species, in which extreme clumping within or beneath one species has been interpreted as evidence of nursing. We characterized microclimatic conditions (soil and air temperature) within and outside cushions of Azorella monantha at two elevations (700 m a.s.l., corresponding to an elevation just above treeline, and 900 m a.s.l., corresponding to the upper limit of the cushion belt zone) on Cerro Diente in the Patagonian alpine of southern South America (50° S) and recorded all plant species growing upon cushions of various sizes and for paired sampling areas of equivalent sizes outside cushions. At 5 cm depth, soil temperature was slightly higher under cushions than under bare ground, but only significantly so at 900 m. Air temperature at ground level was significantly higher in the cushion microhabitat at both 700 m and 900 m, with the difference being more exaggerated at the highest elevation. At 700 m, a total of 27 species were recorded growing within cushions as compared to 29 outside cushions. At 900 m the corresponding numbers were 34 and 18. At the highest elevation, significantly more species grow within cushions than for equal areas outside cushions. Here moreover, 17 (48.6%) species grew preferentially within cushions, with eight of the latter being limited to the cushion microhabitat at this elevation. However, at 700 m there was no significant difference in species richness in the two microhabitats, and only one species (3.1%) grew preferentially on cushions. Considering individual species, nine occurring at both elevations showed non-preferential recruitment on cushions at 700 m, but significantly higher frequencies on cushions at 900 m. Results suggest striking altitudinal variation in the association with Azorella monantha on Cerro Diente, ranging from a very strong at 900 m to near absence at 700 m. Milder air and soil temperatures, shelter from wind, and greater water availability within cushions as opposed to outside cushions are discussed as possible factors favoring strong plant recruitment on cushions at higher elevations in the harsh Patagonian alpine environment.

Altitudinal vegetation belts in the high-Andes of central Chile (33°S)

La delimitacion de los pisos altitudinales de vegetacion andina se ha basado principalmente en criterios fisionomicos. Sin embargo, un criterio mas objetivo para la delimitacion es usar metodos basados en la composicion y abundancia relativa de las especies presentes. Mientras estos metodos requieren de un mayor esfuerzo de muestreo, son mas detallados y permiten detectar factores fisicos involucrados en la delimitacion altitudinal de la vegetacion. Los objetivos de este articulo son: 1) describir los cambios altitudinales de la de vegetacion por sobre el limite arboreo, 2) comparar la delimitacion de los pisos de vegetacion usando fisionomia y metodos floristicos (uno cualitativo basado en cambios en la composicion de especies, y otro cuantitativo basado en cambios en la abundancia relativa de las especies); y 3) detectar algunos factores medioambientales responsables de los patrones de distribucion altitudinal de la vegetacion entre los 2.100 y 3.700 msnm en los Andes de Santiago, Chile central (33°S). Se encontro una completa concordancia entre los diferentes metodos en delimitar el piso subandino. Sin embargo, en el piso andino inferior (el piso de los cojines) los metodos floristicos lo subdividieron en 2-3 sub-pisos. Las altitudes 3.500-3.700 m que forman el piso andino superior segregaron en forma separada en los metodos floristicos ya que no tienen especies en comun. En consecuencia, la descripcion fisonomica pierde informacion relevante sobre la distribucion de las especies, especialmente a mayores altitudes. La temperatura media anual y el contenido de nitrogeno del suelo fueron los principales factores medioambientales involucrados en la delimitacion altitudinal de la vegetacion de los Andes de Chile central

Leaf litter of Kageneckia angustifolia D. Don (Rosaceae) inhibits seed germination in sclerophyllous montane woodlands of central Chile

Leaf litter accumulation can have either positive, negative or neutral effects on seed germination and seedling recruitment. In montane woodlands of the Mediterranean zone of central Chile, large amounts of leaf litter accumulate beneath the crowns of the summer semi-deciduous tree Kageneckia angustifolia and no regeneration of this or other plant species has been observed beneath this tree throughout the year. In a sample plot of 5000 m2 we selected ten K. angustifolia trees and measured (1) leaf litter accumulation beneath and outside canopy; (2) the effects of time elapsed since burial on viability of K. angustifolia seeds with and without a leaf litter cover; (3) field seed germination with presence or absence of leaf litter and (4) the possible chemical effects of K. angustifolia leaf litter leachates on seed germination of its own seeds and of other two co-occurring native shrubs species (Guindilia trinervis and Solanum ligustrinum). Our results show that a considerable accumulation of leaf litter occurred beneath K. angustifolia, and litter negatively affected seed viability and germination of this species in the field. Under laboratory conditions, K. angustifolia leaf litter leachates inhibited seed germination of its own seeds and of the two native shrub species. Chemical effects are likely involved in the negative effects of leaf litter on the recruitment of K. angustifolia in the montane sclerophyllous woodland of central Chile.

Genetic self-compatibility in a South American species of Ourisia (Scrophulariaceae)

Abstract Controlled hand self- and cross-pollination and emasculations were performed on Ourisia poeppigii Benth. (Scrophulariaceae) from the Chilean Patagonia. Ourisia poeppigii is highly self-compatible and strongly autogamous. No evidence of obligate agamospermy was seen. This first breeding system record for a South American species of the genus Ourisia accords with a report of self-compatibility provided by Schlessman (1986) for Ourisia macrocarpa Hook. f. ssp. calycina (Col.) Arroyo from New Zealand. However, O. poeppigii is potentially more strongly autogamous than the New Zealand species.

Efecto nodriza intra-específico de Kageneckia angustifolia D. Don (Rosaceae) sobre la germinación de semillas y sobrevivencia de plántulas en el bosque esclerófilo montano de Chile central

El bosque esclerofilo montano de Chile central (32-33° S, 1.500-2.100 m de altitud) esta dominado por poblaciones de Kageneckia angustifolia (Rosaceae), especie semidecidua de verano que forma un dosel muy abierto. Esto sugiere que, a diferencia de lo que ocurre en el matorral esclerofilo de menor altitud donde el cerrado dosel de arboles y arbustos generan condiciones microclimaticas diferentes a los espacios abiertos, en el bosque montano no existiria una marcada diferencia microclimatica entre bajo el dosel y los espacios abiertos. Por otro lado, en el bosque montano, las precipitaciones ocurren principalmente en forma de nieve, la que se acumula preferentemente en los espacios entre los arboles, pudiendo facilitar el reclutamiento de nuevos individuos en este microhabitat, fenomeno que se conoce como efecto nodriza. Se estudio el probable efecto nodriza a nivel intra-especifico de K. angustifolia comparando el microclima de los ambientes bajo dosel y los espacios abiertos, y el efecto de la acumulacion de nieve en la germinacion de semillas y sobrevivencia de plantulas de en un bosque esclerofilo montano ubicado en el Santuario de la Naturaleza Yerba Loca, 50 km al este de Santiago (33° S, 1.600 m de altitud). De acuerdo a las variables microclimaticas estudiadas (PAR, humedad del aire y suelo, y temperatura del aire y suelo), en el bosque montano no existen diferencias microclimaticas entre los espacios abiertos y bajo el dosel. Solo la acumulacion de nieve fue significativamente mayor en los espacios abiertos. La germinacion fue menor y mas tardia en los espacios abiertos, lo que estaria relacionado con la mayor acumulacion de nieve. Las plantulas originadas mas tempranamente tienen mas tiempo para desarrollarse y pasar en forma exitosa la sequia estival en comparacion con las plantulas que emergen mas tardiamente. Esto explicaria la menor sobrevivencia de las plantulas en los espacios abiertos

ADICIONES Y NOTAS A LA FLORA DEL PARQUE NACIONAL LLULLAILLACO, II REGION, CHILE

Se presentan nuevos registros de 16 especies, 10 generos y 1 familia para la flora del Parque Nacional Llullaillaco (Region de Antofagasta). Con esto la flora total del parque se eleva a 126 especies, contenidas en 74 generos y 31 familias. El numero de especies endemicas en el PN Llullaillaco se eleva a 21 (16,6%). Este porcentaje de endemismo es uno de los mas altos documentados para un parque nacional ubicado en los Andes de Chile. Ademas, se senalan algunos comentarios nomenclaturales para algunas especies previamente documentadas en otros estudios