Agustina Malizia

Liana-host tree associations in a subtropical montane forest of north-western Argentina

In a subtropical montane forest of north-western Argentina (27 ◦ S, 1000 m elevation), we analysed the effect of crown illumination, trunk diameter, foliar phenology and tree species identity as determinants of liana-host tree associations, as well as the spatial pattern of liana abundance in a 6-ha permanent plot. We recorded 2346 liana individuals ≥ 2 cm and 2320 trees ≥ 10 cm dbh. Sixty-five per cent of the trees hosted at least one liana stem. Large and well-lit trees were more likely to support lianas and supported more liana abundance than small and shaded trees. Yet, when trees were standardized by their size (liana basal area/tree basal area ratio), lianas were more abundant in smaller and less-exposed trees. Foliar phenology and tree species identity showed no association with the frequency of liana colonization and their abundance. Overall, tree features played a minor or even neutral role in structuring the liana community within this forest. Instead, lianas showed a positive autocorrelation at spatial scales up to 40 m. This suggests that lianas might be mostly structured by light- and dispersal-related factors such as those involving canopy access or canopy disturbances, with a negligible effect of host species identity and foliar phenology.

Landscape context and microenvironment influences on liana communities within treefall gaps

Abstract Questions: How do gap aspect, openness, age and gap density in the surroundings affect diversity and composition of lianas within treefall gaps? Are the variation patterns in liana communities within treefall gaps associated with their climbing mechanisms? Location: Subtropical montane forests in northwestern Argentina. Methods: We used ordination analyses (NMDS) and multiple regressions to describe liana communities (species and climbing groups, stems ≥ 1 cm) in 35 gaps located in a 6-ha plot and to assess relationships with aspect, canopy and subcanopy openness, age and density of recent (three to eight years old) and old (> 8 years old) gaps. Results: Treefall gaps segregated in the ordination diagrams based on their liana species and climbing mechanisms composition: gaps surrounded by a higher density of recent gaps showed higher densities of lianas species using tendrils, spines / hooks and voluble stems. Liana density and richness (independent of stem density) were also positively associated with the density of recent gaps in the surroundings, and negatively associated to gap age. The number of liana species corrected per area was negatively associated to gap aspect and subcanopy openness, and absolute number of liana species was positively associated to gap canopy openness. Conclusions: This study integrates the analysis of different factors influencing liana communities within treefall gaps, and shows that spatial context of gap density (a variable largely neglected in previous studies) is particularly important on lianas composition and diversity, probably by increasing propagule input and the availability of small trellises for support. Nomenclature: Zuloaga & Morrone (1999).

Large-scale patterns of turnover and Basal area change in Andean forests.

General patterns of forest dynamics and productivity in the Andes Mountains are poorly characterized. Here we present the first large-scale study of Andean forest dynamics using a set of 63 permanent forest plots assembled over the past two decades. In the North-Central Andes tree turnover (mortality and recruitment) and tree growth declined with increasing elevation and decreasing temperature. In addition, basal area increased in Lower Montane Moist Forests but did not change in Higher Montane Humid Forests. However, at higher elevations the lack of net basal area change and excess of mortality over recruitment suggests negative environmental impacts. In North-Western Argentina, forest dynamics appear to be influenced by land use history in addition to environmental variation. Taken together, our results indicate that combinations of abiotic and biotic factors that vary across elevation gradients are important determinants of tree turnover and productivity in the Andes. More extensive and longer-term monitoring and analyses of forest dynamics in permanent plots will be necessary to understand how demographic processes and woody biomass are responding to changing environmental conditions along elevation gradients through this century.

Rapid Structural and Compositional Change in an Old-Growth Subtropical Forest: Using Plant Traits to Identify Probable Drivers

Recent studies have shown directional changes in old-growth tropical forests, but changes are complex and diverse, and their drivers unclear. Here, we report rapid net structural and compositional changes in an old-growth subtropical forest and we assess the functional nature of these changes to test hypothetical drivers including recovery from past disturbances, reduction in ungulate browsing, CO2 fertilization, and increases in rainfall and temperature. The study relies on 15 years of demographic monitoring within 8 ha of subtropical montane forest in Argentina. Between 1992 and 2007, stem density markedly increased by 50% (12 stems ha−1 y−1) and basal area by 6% (0.13 m2 ha−1 y−1). Increased stem density resulted from enhanced recruitment of understory treelets (Piper tucumanum, Eugenia uniflora, Allophylus edulis) into small size classes. Among 27 common tree species, net population growth was negatively correlated with maximum tree size and longevity, and positively correlated with leaf size and leaf nutrient content, especially so when initial population size was controlled for. Changes were inconsistent with predictions derived from past disturbances (no increase in shade-tolerant or long-lived late-succesional species), rainfall or temperature increase (no increase in evergreen or deciduous species, respectively). However, the increase in nutrient-rich soft-leaved species was consistent with exclusion of large herbivores two decades before monitoring started; and CO2 fertilization could help explain the disproportionate increase in small stems. Reductions in populations of large vertebrates have been observed in many otherwise undisturbed tropical forests, and our results suggest they can have important structural and functional repercussions in these forests.

Invasion of Ligustrum lucidum (Oleaceae) in subtropical secondary forests of NW Argentina: declining growth rates of abundant native tree species

Aims Ligustrum lucidum, native of China, is one of the dominant exotic and invasive tree species in secondary forests in Argentina. 1) We assessed its invasion during 20 years in post-agricultural secondary forests dominated by native tree species, and 2) evaluated tree demographic rates of native individuals under and away from L. lucidum trees that invaded these forests. Locations Four 1-ha permanent plots of secondary forests in the subtropical Andes of Tucuman, Argentina. Methods We quantified the invasion of L. lucidum individuals (≥ 10 cm diameter) from 1991 to 2011 within four 1-ha plots of secondary forests and analyzed annual growth and mortality rates of native tree individuals (≥ 10 cm diameter) under and away from L. lucidum trees. For this, we compared tree demographic rates of all native individuals together (community level) under and away from individuals of L. lucidum, referred to as exotic and native neighbourhoods, respectively. Then, we described the relative growth rate of native tree species in exotic / native neighbourhoods (species level) and related them with their demographic life histories and morpho- physiological traits. Results Both density and basal area of L. lucidum increased from 0.1 to 4% between 1991 and 2011. Native tree individuals grew 65% less in exotic neighborhoods compared to native neighborhoods. Relative growth rate showed negative values under L .lucidum individuals for the abundant species Ocotea porphyria, Parapitadenia excelsa, Juglans austalis and Allophylus edulis, indicating competition; while less abundant species Terminalia triflora, Cupania vernalis and Blepharocalix saliscifolius showed positive growth values under L. lucidum suggesting a facilitation process. Thus, L. lucidum competes efficiently with some native tree species particularly with those abundant species that dominate the canopy. Conclusions Ligustrum lucidum is invading post-agricultural secondary forests dominated by native tree species. While invading, L. lucidum competes with native abundant tree species that dominate the main structure of the forest canopy. As this invasive trend will likely increase in the near future, L. lucidum may alter forest structure, composition and dynamics as well ecosystem functioning. This article is protected by copyright. All rights reserved.

Research Priorities for the Conservation and Sustainable Governance of Andean Forest Landscapes

The long-term survival of Andean forest landscapes (AFL) and of their capacity to contribute to sustainable development in a context of global change requires integrated adaptation and mitigation responses informed by a thorough understanding of the dynamic and complex interactions between their ecological and social components. This article proposes a research agenda that can help guide AFL research efforts for the next 15 years. The agenda was developed between July 2015 and June 2016 through a series of workshops in Ecuador, Peru, and Switzerland and involved 48 researchers and development experts working on AFL from different disciplinary perspectives. Based on our review of current research and identification of pressing challenges for the conservation and sustainable governance of AFL, we propose a conceptual framework that draws on sustainability sciences and social–ecological systems research, and we identify a set of high-priority research goals and objectives organized into 3 broad categories: systems knowledge, target knowledge, and transformation knowledge. This paper is intended to be a reference for a broad array of actors engaged in policy, research, and implementation in the Andean region. We hope it will trigger collaborative research initiatives for the continued conservation and sustainable governance of AFL.

Gleditsia triacanthos (Fabaceae) in Argentina: a review of its invasion

Gleditsia triacanthos L. is a woody species native to North America that has invaded Uruguay, Spain, Australia, South Africa and several countries of Central and Eastern Europe. In Argentina, it has become one of the most important invasive woody species and has a high potential to continue spreading. In this study, we review different aspects of G. triacanthos invasion in Argentina that include descriptions of invaded ecoregions and environments, intrinsic characteristics of the species, invasion dynamics and impacts. In addition, we discuss mechanisms that potentially explain its success, control strategies and natural barriers to its invasion. We reviewed a total of 91 articles and book chapters, of which 62 were developed in Argentina. Studies reported that the invasion of G. triacanthos in different ecoregions was favoured by intrinsic characteristics of the species, together with the interaction with cattle and disturbances, which cause negative impacts on flora, fauna and ecosystem processes. Disturbances were proposed as the main mechanism to explain this species’ invasion, but other hypotheses such as the release of natural enemies and/or propagule pressure might also be important. Further studies are required, mainly on the impacts on ecosystem processes and on the control, production of organic compounds and mutualistic interactions (with nitrogen-fixing bacteria and mycorrhizal fungi).

First report of the lesser wax moth Achroia grisella F. (Lepidoptera: Pyralidae) consuming polyethylene (silo-bag) in northwestern Argentina

In this note, we report the lesser wax moth Achroia grisella F. (Lepidoptera: Pyralidae) (LWM), a beehive pest, for the first time in Argentina. In addition, we report observations of the larvae of this pest species consuming “silo-bags,” a material commonly used in the country for hive management. Silo-bags are composed of three layers of polyethylene and one anti-UV layer and no records of insects consuming this material are found in the literature. Our report represents a warning for apiculture in Argentina, especially when honey production has been observed to decrease recently. This decrease may be a result of a combination of factors, which may include the poor monitoring of hive health, and inappropriate management of pests such as A. grisella. In addition, our observations on silo-bag consumption represent a call for attention to beekeepers that use this material to conserve heat in the hives and open questions about the mechanisms involved in silo-bag consumption by the larvae.

Geographical, Taxonomical and Ecological Aspects of Lianas in Subtropical Forests of Argentina

Lianas are more diverse and typically more abundant in tropical than temperate forests, with subtropical forests being intermediate. In this chapter, we analyze geographical, taxonomical and ecological patterns of lianas in subtropical forests of Northern Argentina, including Mountain Forests (MF), Atlantic Forests (AF); and Dry and Humid Chaco Forests (DCh and HCh, respectively). A total of 184 woody species of climbing plants were recognized in all four subtropical forests, with 35 species exclusive to MF, 38 exclusive to AF, while DCh and HCh had 2 and 8 exclusive species, respectively. In MF most liana species belonged to Sapindaceae and Bignoniaceae (16 % each), followed by Malpighiaceae (11 %) and Apocynaceae (10 %). In AF most liana species belonged to Bignoniaceae (21 %) followed by Apocynaceae (12 %), Fabaceae (11 %), Malpighiaceae (11 %) and Sapindaceae (10 %). Considering all liana species together, the most common climbing mechanisms included tendrils and twiners. The highest liana density was observed in the semideciduous Atlantic Forest, followed by the deciduous Humid Chaco Forest and the semideciduous Montane Forest. The semideciduous Atlantic Forest has also relatively high liana species richness as compared to other subtropical forests, followed by semideciduous MF. Besides geographical location and forest disturbances, little is known about how lianas respond to other environmental factors that drive patterns of liana density and diversity in these subtropical forests.