Mariela Núñez-Ávila

Old-Growth Temperate Rainforests of South America: Conservation, Plant-Animal Interactions, and Baseline Biogeochemical Processes

A structural and compositional definition of old-growth forest is presented, which places emphasis on the lack of recurrent human impact, the presence of a shade-tolerant canopy with emergent pioneers, and a patch area that minimises edge effects. Using this definition, we provide an overview of the current conservation status, relevance of plant–animal interactions, and unique features of nutrient fluxes in old-growth forests of southern South America. Chile hosts the largest area and latitudinal extent of old-growth temperate forest remaining in the southern hemisphere, reaching 56° S in the Cape Horn Archipelago. Despite recent public and private efforts to protect remaining old-growth forests and their endemic biodiversity, they continue to decline steeply as a result of new routes of access to commercial stands, lack of protection of coastal areas, anthropogenic fire, and expansion of monoculture-based forestry toward higher latitudes and altitudes. Pollinators (insects and birds) and vertebrate frugivores (birds and an arboreal marsupial) are important mutualists of many Chilean rain forest trees, vines and epiphytes. There is evidence to suggest that some native pollinators and animal seed vectors may be highly susceptible to changes in forest structure due to loss of old-growth forest cover. Forest fragmentation and loss of keystone, animal-pollinated emergent trees due to logging and fires, have radically changed pollinator assemblages in rural landscapes, leading to reproductive dependence on European honey bees and other exotic species. Regarding other ecosystem functions, nutrient cycles in unpolluted old-growth forests of southern Chile are characterised by strong inorganic nitrogen (N) retention and large organic N leakage to forest streams. Non-symbiotic N fixation in litter and soil tends to increase in older stands. Knowledge of these “unpolluted nutrient cycles”, particularly N and P, is still meager despite its relevance to understanding the consequences of increased global disruption of element cycles by humans. Development of baseline measurements and experiments in southern Chilean old-growth temperate forests can enhance our understanding of unpolluted ecosystem functioning.

Relict islands of the temperate rainforest tree Aextoxicon punctatum (Aextoxicaceae) in semi-arid Chile: genetic diversity and biogeographic history

Aextoxicon punctatum, the only representative of the family Aextoxicaceae, is a tree species endemic to temperate forests of western South America. This species exhibits a disjunct distribution pattern, with few isolated populations occurring on coastal hilltops of the Chilean semi-arid zone (SAZ), 30-32 ◦ S; small populations mixed with sclerophyllous forest in some gorges of the central Chilean Mediterranean coastal range (MCR), 32-39 ◦ S; more continuous forests extended along the southern temperate coastal range (TCR), 39-43 ◦ S; and fragmented populations eastward in the south temperate central depression and Andean foothills (TAF), 39-41 ◦ S. This geographic disjunction is the result of climatic and tectonic changes that took place in southern South America since the late Tertiary, leading to the isolation of forest fragments in the SAZ from the rest of the distribution. According to palynological evidence, populations of TCR and TAF originated from postglacial population expansions from refuges located on the coastal range, north of 40 ◦ S. We examined how the present genetic structure and diversity of Aextoxicon populations in Chile reflects this biogeographic history. Random amplified polymorphic DNA (RAPD) markers were used to characterise genetic differences within and among 16 populations of this species throughout its natural range. AMOVA and UPGMA analysis showed high genetic differentiation between the geographically closer SAZ and MCR populations, suggesting a long history of restricted genetic exchange between populations in these two zones. Estimates of Shannons genetic diversity and percentage polymorphism were relatively low compared with other southern temperate forest trees (mainly conifers) that were less affected by the glaciations. Positive correlations between genetic and geographic distances were found for TCR but not for TAF populations, suggesting earlier postglacial population expansion southwards along the TCR and more recent eastward migration from coastal locations to TAF during the Holocene.

Estación Biológica Senda Darwin: Investigación ecológica de largo plazo en la interfase ciencia-sociedad

This article discusses Senda Darwin Biological Station and the work of the scientists who study the anthropological role in ecological processes there.

Decomposing recruitment limitation for an avian‐dispersed rain forest tree in an anciently fragmented landscape

Summary 1. Forest fragmentation may intensify recruitment limitation through impacts on seed production, dissemination and seedling establishment processes. In an ancient mosaic of fog-dependent rain forest patches on coastal hilltops of semi-arid Chile (30 °S), we investigated how aridity-driven habitat fragmentation affected the recruitment of the fleshy-fruited, dioecious tree Aextoxicon punctatum (Aextoxicaceae) and the role of birds in seed dispersal across patches. 2. We hypothesized that reduced fragment size enhanced recruitment limitation due to constraints on tree fecundity, avian disperser activity and seedling recruitment, caused primarily by strong edge effects in small fragments. 3. We mapped adult Aextoxicon trees and placed 686 seed traps distributed in 3 small ( 0.9 ha) in the forest patch mosaic. To identify seed sources, endocarps of 282 dispersed seeds from seed traps were genotyped and compared with 155 genotyped females using nine microsatellite markers. Seed dispersal curves for different forest patches were constructed using maximum likelihood methods. Further, seed addition experiments were conducted in the six fragments to assess recruitment probabilities. 4. Lower density and basal areas of reproductive female trees, in addition to shorter fruiting periods and lower seed yields, led to strong source limitation in small patches. Three bird species accounted for the bulk of visits to fruiting trees, but were less active in smaller patches. Dispersal curves were strongly leptokurtic with maximum dispersal distances related to the shape of patches. Important proportions (5–40%) of genotyped seeds in all patches were immigrants. However, seeds arrived mainly at patch edges or below reproductive trees where germination and survival are reduced. Fewer seedlings originated from experimentally added seeds in small patches subjected to greater edge effects. 5. Synthesis. In summary, we provide evidence for source, dispersal and establishment limitation of this dioecious tree in an aridity-driven fragmented landscape. Small fragment size and edge effects had negative impacts on fecundity and seedling establishment. Although bird-mediated seed dispersal favoured immigration between patches, recruitment from such seeds will be unlikely because of low quality of deposition sites.

A framework for the classification Chilean terrestrial ecosystems as a tool for achieving global conservation targets

Countries that are signatories of the Convention of Biological Diversity are committed to the goal of protecting 17% of their natural ecosystems by 2020. The lack of an up-to-date, operational classification and cartography of regional ecosystems seriously limits the assessment of progress towards this goal. Here, we present a broad ecosystem framework, which combines land use, functional traits of dominant plant species, and climatic factors for the classification of terrestrial ecosystems and apply this framework to classify Chilean terrestrial ecosystems. This new classification is consistent with the recently proposed IUCN framework to assess ecosystem conservation status. Using this framework, we identified and described 30 Chilean terrestrial ecosystems, including land units of natural and anthropogenic origin. We also provide a cartographic representation of ecosystems for land planning purposes and an overall assessment of their conservation status. We evaluated the representation of the 30 ecosystems in the Chilean National System of Protected Areas (NSPA) and in Private Protected Areas (PPA), identifying 15 ecosystems underrepresented (below the 17% target) in the NSPA, in contrast to only 11 when the area of NSPA+PPA was considered. The proposed classification can be broadly applicable to assess the conservation status of ecosystems elsewhere, using similar conceptual and methodological tools. The development of functional ecosystem classifications for different countries must be encouraged to facilitate monitoring of global conservation targets.

Introducción a la Sección Especial de Revista Bosque: Avances de una red de sitios de estudios ecológicos a largo plazo en el suroeste de Sudamérica

En este prefacio a la seccion especial, dedicada a la investigacion ecologica de largo plazo en Chile, se comentan brevemente los temas tratados en cada uno de los articulos y se destaca su relevancia en el contexto del monitoreo y la investigacion sobre los ecosistemas de Chile y en el ambito del analisis del cambio global.

Propuesta para la consolidación de una Red Chilena de Estudios Socio-Ecológicos de Largo Plazo

El ser humano ha desencadenado profundas y rapidas transformaciones de los ecosistemas afectando su capacidad de mantener los procesos y funciones que sustentan la biosfera. El desarrollo de investigacion socio-ecologica de largo plazo, incluyendo monitoreo y experimentacion, es esencial para detectar, prevenir y mitigar la degradacion de los ecosistemas a escala local, regional y global. El fortalecimiento y expansion de una Red de sitios de Estudios Socio-Ecologicos de Largo Plazo (LTSER) en Chile requiere integrar los esfuerzos de una diversidad de instituciones academicas, publicas y privadas. La investigacion socio-ecologica en esta red de sitios requiere ademas un marco conceptual de preguntas relevantes y comparativas que sean abordadas desde diversas disciplinas. En este trabajo se identificaron las preguntas relevantes para el desarrollo de la Red LTSER en Chile, se presenta un marco conceptual, una propuesta de organizacion, y se discuten las necesidades de infraestructura y financiamiento para la operacion de esta red nacional de observatorios naturales.