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Copyright of Ecologia Austral is the property of Asociacion Argentina de Ecologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revista de la Asociación Geológica Argentina is the property of Asociacion Geologica Argentina and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Arthropods are key nodes for the provision of ecosystem services such as pest control, but their response to land-use change is highly variable depending on the scale of analysis and the natural enemies' life histories. We evaluate the effects of landscape- and local-scale variables of natural enemies' communities on small-scale agriculture. We consider functional response traits to attain a mechanistic understanding of the effect of land-use changes on the biodiversity and resilience of natural enemies' communities. Predator and parasitoid arthropods were collected from thirteen raspberry farms to estimate functional diversity, complementarity, and redundancy indices. We found no effects of landscape heterogeneity, local habitat, or management practices on natural enemies' functional diversity. Regarding resilience, complementarity was high at most of the sites and was not affected by the landscape or local variables. However, redundancy was affected by two management practices. Weed control decreased natural enemies' abundance as well as the abundance of walker generalist predators and flying specialist parasitoids, while habitat richness decreased flying generalist predators. These results highlight the importance of management when the landscape matrix is heterogeneous. We conclude that small-scale agriculture in a heterogeneous landscape supports a functionally diverse enemy community, potentially promoting the resilience of pest control to land-use change. [ABSTRACT FROM AUTHOR]

Native forests are the natural ecosystems with the greatest social concern in terms of conservation and management. The scope of the definition of native forest has changed over time, which has influenced the adoption of different forest management instruments carried out by different institutions (e.g., the forest cover obtained from forest inventories in jurisdictions of Argentina). This leads to different results and misunderstandings, which often leads to incomparable outputs (e.g., native forest cover). The objective of this work was to analyse the current definition of the native forest implemented by the Argentine Government within the framework of Law 26331/07, which regulates the implementation of institutional policies. We propose a new definition based on the available scientific knowledge, and try to correct the conceptual gaps identified in the aforementioned law. The proposed definition differs from the original one in the inclusion of the minimum patch size, as well in the assessment of the connectivity and composition of the surrounding landscape. Other main aspects for its implementation are discussed, as well as the impacts at different spatial scales. [ABSTRACT FROM AUTHOR]

Copyright of Bosque (03048799) is the property of Facultad de Ciencias Forestales, Universidad Austral de Chile and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Ecologia Austral is the property of Asociacion Argentina de Ecologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Living trees in declining Austrocedrus chilensis (D.Don) Pic. Sern. et Bizarri forests exhibit cambial mortality or death of part of the cambium causing incomplete formation of rings around the circumference, which represents a potential source of error when determining tree ages and years of death. We sampled 12 stands to quantify the incidence of cambial mortality and tested whether its occurrence is independent of the health condition and canopy position of living trees. Trees were cored and statistically cross-dated. Cambial mortality was identified when the outer-ring date differed from the year of sampling. Of the 811 trees sampled, 307 exhibited cambial mortality with duration ranging from 1 to 39 years. Cambial mortality was most common in subcanopy trees independent of their health condition. Symptomatic canopy trees also exhibited a greater than expected incidence of cambial mortality. The presence of cambial mortality represented a source of error when ages were estimated from ring counts, reiterating the importance of cross-dating for determining accurate tree ages. Cambial mortality also poses complex challenges for estimating the years of tree death. Using the cumulative frequency of cambial mortality duration, we present a novel method for estimating error in tree ages from ring counts and selecting class widths to more accurately depict age structures and mortality rates. Resume: Dans les forets deperissantes d'Austrocedrus chilensis (D.Don) Pic. Sern. et Bizarri, la mortalite cambiale ou la mort d'une partie du cambium chez les arbres vivants provoquent la formation de cernes annuels incomplets autour de la circonference, ce qui constitue une source potentielle d'erreur lorsqu'on veut determiner l'age ou l'annee de la mort des arbres. Nous avons echantillonne 12 peuplements pour quantifier l'incidence de la mortalite cambiale et determine si ce phenomene est independant de l'etat de sante et de la position des arbres vivants dans le couvert forestier. Des carottes de bois ont ete prelevees et les arbres ont ete dates statistiquement par recoupement dendrochronologique. La mortalite cambiale a ete identifiee lorsque la date du cerne annuel externe ne correspondait pas a l'annee de l'echantillonnage. La mortalite cambiale a ete detectee chez 307 des 811 arbres echantillonnes et elle etait presente depuis un a 39 ans. La mortalite cambiale etait plus frequente chez les arbres qui occupaient la partie inferieure du couvert forestier, peu importe leur etat de sante. La mortalite cambiale etait plus frequente que prevu chez les arbres symptomatiques dans le couvert forestier. La presence de mortalite cambiale constituait une source d'erreur lorsque l'age etait determine en comptant les cernes annuels, ce qui reitere l'importance de la datation croisee pour determiner l'age exact des arbres. La mortalite cambiale pose egalement des defis complexes lorsqu'il s'agit de determiner l'annee de la mort des arbres. En utilisant la frequence cumulative de la duree de la mortalite cambiale, nous presentons une nouvelle methode pour estimer l'erreur lorsque l'age des arbres est mesure en comptant les cernes annuels et pour choisir la classe de largeur afin de representer de facon plus juste la structure d'age et le taux de mortalite. [Traduit par la Redaction], Introduction Reconstruction of tree establishment and forest disturbances require accurate estimates of tree age and mortality dates. Age-class distributions have been used to describe tree establishment and invasion patterns at [...]

Summary: The distribution of regeneration makes it possible to assess whether populations of tree species will maintain or change their distributions. For Neotropical dry forests there is little information on the potential changes in the distribution of tree species. Here, we evaluate the potential distributions of adults and seedlings of eight timber tree species of the Piedmont Forest of north-western Argentina by recording the presence of seedlings and adults in plots and modelling with MaxEnt software using three bioclimatic variables. The potential distribution areas of seedlings and adults and the percentage of overlap of seedlings with respect to adults were calculated. The potential distribution for adults was 694 457 ± 62 535 ha, and this figure was 656 564 ± 194 769 ha for seedlings. The potential distribution of seedlings of Calycophyllum multiflorum covered the smallest area (184 496 ha) and had the least overlap with the adults (18%). The difference in the overlap of the potential distribution areas between adults and seedlings suggests that there could be changes in the future distribution of this tree species and C. multiflorum should therefore be the focus of conservation strategies so that the species can follow its bioclimatic niche as the climate changes. [ABSTRACT FROM AUTHOR]

The transformative claim of agroecology research draws on transdisciplinarity and participatory action research to operationalize horizontal learning and experimentation for knowledge co-creation and change in action. Drawbacks to recent research strategies in this field are lack of action orientation, and limited roles and low level of control attributed to farmers, particularly in defining scope and methods for collaboration and joint experimentation. In response, in this article we conceptualize a co-inquiry approach for agroecology research adopted from participatory action research and explore its operationalization and outcomes with a group of organic horticultural farmers in Argentina. We assess how co-inquiry considers farmers' experience in the knowledge co-creation process to achieve contextualized research questions and actionable results, and reflect on potentials and constraints of extended roles attributed to farmers and their increased control over inquiry process and contents. We found that co-inquiry facilitates extended roles of farmers as co-researchers and thereby encourages horizontal learning based on systems thinking, through a joint explorative assessment of the systems operators' purposes, context, and experience, and through joint choice of methodology, experimentation and reflection. [ABSTRACT FROM AUTHOR]

We present the first network of tree-ring chronologies for co-occurring Nothofagus nervosa and Nothofagus obliqua in Argentina. Using standard dendrochronological techniques, we developed seven tree-ring width chronologies for each species, encompassing their E-W distribution along a precipitation gradient. Chronology statistics indicated thatN. nervosa andN. obliqua are strong candidates for research in dendrochronology. The chronologies were used to study and compare the temporal and spatial growth patterns of each species. Correlation and principal components analysis of the tree-ring chronologies serve as evidence of a strong common signal, indicating shared regional growth patterns across the gradient with some exceptions between sites and species. These results indicate the high potential of N. nervosa and N. obliqua for their use in dendroclimatology. [ABSTRACT FROM AUTHOR]

Copyright of Ecologia Austral is the property of Asociacion Argentina de Ecologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Tree mortality is a key driver of forest dynamics and its occurrence is projected to increase in the future due to climate change. Despite recent advances in our understanding of the physiological mechanisms leading to death, we still lack robust indicators of mortality risk that could be applied at the individual tree scale. Here, we build on a previous contribution exploring the differences in growth level between trees that died and survived a given mortality event to assess whether changes in temporal autocorrelation, variance, and synchrony in time-series of annual radial growth data can be used as early warning signals of mortality risk. Taking advantage of a unique global ring-width database of 3065 dead trees and 4389 living trees growing together at 198 sites (belonging to 36 gymnosperm and angiosperm species), we analyzed temporal changes in autocorrelation, variance, and synchrony before tree death (diachronic analysis), and also compared these metrics between trees that died and trees that survived a given mortality event (synchronic analysis). Changes in autocorrelation were a poor indicator of mortality risk. However, we found a gradual increase in inter-annual growth variability and a decrease in growth synchrony in the last ∼20 years before mortality of gymnosperms, irrespective of the cause of mortality. These changes could be associated with drought-induced alterations in carbon economy and allocation patterns. In angiosperms, we did not find any consistent changes in any metric. Such lack of any signal might be explained by the relatively high capacity of angiosperms to recover after a stress-induced growth decline. Our analysis provides a robust method for estimating early-warning signals of tree mortality based on annual growth data. In addition to the frequently reported decrease in growth rates, an increase in inter-annual growth variability and a decrease in growth synchrony may be powerful predictors of gymnosperm mortality risk, but not necessarily so for angiosperms. [ABSTRACT FROM AUTHOR]

The Austrocedrus chilensis forests in Argentina experience a process of decline and mortality with important impacts on the structure and population dynamics. Although its study has received significant attention over time, knowledge related to the growth of the regeneration and its response to the gradual changes in the canopy over time driven by mortality is incipient. The objective of this study was to investigate, through dendrochronological methods, the population dynamics and the radial growth of the regeneration of individuals of Nothofagus dombeyi and A. chilensis in declining forests in the northwest of Río Negro Province, Argentina. Overstory mortality and canopy changes significantly impacted the understory structure through the establishment and growth patterns of regeneration. The average radial growth, the average age and the average diameter of the individuals of A. chilensis and N. dombeyi differed significantly. There is a positive response in the average growth of both species when the basal area loss by mortality exceeds 20 %, probably due to the higher number of changes in the instantaneous rates of growth of individuals. Based on our results, we can predict a transition from the current pure and single-cohort forests of A. chilensis towards irregular forests of mixed composition. [ABSTRACT FROM AUTHOR]

Highlights: [•] We reconstructed species-specific growth responses and natural regeneration ingress. [•] Most surviving canopy and understory tree species released after the epidemic. [•] There was a strong pulse of natural regeneration ingress 10–20years post attack. [•] The epidemic resulted in more structurally and compositionally diverse stands. [•] The recovery and self-organization of unsalvaged stands was a complex process. [Copyright &y& Elsevier]

Abstract: Using dendrochronology, combined with tree- and stand-level information, we reconstructed the temporal dynamics of ‘mal del ciprés’, a widespread decline of Austrocedrus chilensis forests in Argentina. We developed 12 new site-specific ring-width chronologies representing the growth of trees with no external (crown) or internal (radial growth) symptoms of decline. By comparing the ring-width series of individual trees with these reference chronologies, we detected reduced radial growth, likely due to ‘mal del ciprés’, in 301 symptomatic and dead overstory trees out of 1082 sampled trees. Radial growth decline also occurred in 67 living trees with asymptomatic crowns providing evidence that radial growth decline can be an early indicator of ‘mal del ciprés’. The length of the radial growth decline averaged 27years for all trees and was 29 and 22years for living symptomatic and dead overstory trees, respectively; the maximum decline length was 80years. At the site level, the onset of radial growth decline ranged from the early 1920s to the 1960s, preceding dates reported in historical records. By 1979, ⩾75% of trees per site exhibited radial growth decline. We conclude that decline in radial growth precedes crown symptoms in at least some A. chilensis trees in forests with ‘mal del ciprés’. Reduced radial growth prior to external crown symptoms implies that water uptake had been reduced, possibly because of root damage from Phyophthora or drought or their interactions. It also suggests salvage harvests that aim to eradicate trees with crown symptoms and facilitate growth of residual trees may not be the most effective management response to ‘mal del ciprés’. [Copyright &y& Elsevier]

Abstract: This study presents new evidence of historic low-to-moderate-severity fires, intermixed with high-severity fires, in the foothills of the Rocky Mountains of west-central Alberta, Canada. High-severity fires that burned 120–300years ago initiated even-aged cohorts of fast-growing lodgepole pine at each of the six study sites. Evidence of subsequent, low-to-moderate-severity fires included single and double fire scars on thin-barked lodgepole pine that were as small as 3.6cm in diameter at the time of the fire, but survived. These low-to-moderate-severity fires resulted in structurally complex stands with a broad range of tree diameters and multiple cohorts of lodgepole pine, white and black spruce, and subalpine fir. At the site level, fire return intervals were variable, ranging from 29 to 167years, but most were <80years. Of the 9years in which we documented low-to-moderate-severity fires, only the fires in 1889 and 1915 scarred trees at more than one site, indicating that these fires were small and had local effects. The new knowledge of historical, low-to-moderate-severity fires provided by this study has important implications for ecologically sustainable forest management. Although we recognize that further research needs to determine the extent of low-to-moderate-severity fires at the landscape scale, our results clearly indicate that a mixed-severity fires occurred at least locally. A broader range of silvicultural systems than is currently practiced would be consistent with historic forest dynamics. [Copyright &y& Elsevier]

Abstract: The forests of Austrocedrus chilensis (D. Don) Pic. Sern. et Bizarri in Argentina suffer decline and mortality throughout their natural distribution known as ‘mal del ciprés’. While several aspects of this, to date, temporally unpredictable process of overstory tree mortality have been the focus of detailed studies, there has been little research on tree growth and stand dynamics in symptomatic forests nor stand development patterns and prediction of future stand structure. We studied 12 stands in northern Patagonia (Province of Río Negro) using stand reconstruction studies to examine the changes in stand structure over time as a consequence of overstory mortality and the implications of these structural changes on the establishment and growth of the residual overstory. Dendrochronological analyses were used to reconstruct stand establishment and structure over time, and to study past diameter growth patterns. Mortality in A. chilensis forests was variable in time among stands. As expected, overstory mortality led to the successful establishment of trees in the understory in all stands; however, the response of residual overstory trees was variable. Understory establishment was low in some stands and high in others depending on the density of the overstory. While overstory trees in almost all stands released after the onset of the mortality, the pattern was not distinctive, varying in time, number and magnitude. In some stands, growth releases occurred after single or multiple tree deaths suggesting a relationship between processes, while in others this was not the case. Even when the patterns of recruitment in the understory and the overstory response varied greatly among stands, when examined together, some general patterns emerged. This study is the first to intensively explore the dynamics of A. chilensis forests affected by ‘mal del ciprés’. Additionally, this study showed that arbitrarily categorizing disturbances as discrete or chronic masks the true process of release of growing space and the resulting stand dynamics. [Copyright &y& Elsevier]

• Tree-ring variations allow a retrospective quantification of drought effects. • Droughts influence the growth of A. chilensis all along the precipitation gradient. • The negative effect of drought on A. chilensis growth is more important in the year of the event. • A. chilensis shows a high growth recovery post-drought along the precipitation gradient. • Mixed forests have the strongest capacity to reduce the impact of drought. Extreme weather events are increasing in frequency and magnitude due to climate change. In this context, the impacts of droughts on forest mortality will increase making it more relevant to determine the resilience of native forests to drought. Austrocedrus chilensis is an endemic conifer adapted to dry-mesic environmental conditions in the Patagonian Andes. We sampled 9 sites along a 60 km transect encompassing the West-East precipitation gradient (2000–500 mm yr−1) located at Nahuel Huapi National Park (Argentina). We measured tree-ring widths of living and dead trees growing in three forest types (mixed, closed, and open) along the precipitation gradient. We characterized extreme droughts using six stations precipitation series and CRUTS v4 temperature records. The extreme summer drought of 1943–44 appears to have influenced the growth patterns of A. chilensis over the next 30 years in all trees along the precipitation gradient. Based on basal area increments before, during, and after ten extreme droughts, we calculated the growth resilience components: resistance (Rt), recovery (Rc), and relative resilience (rRs) for living and dead trees. The Rt and rRs show low values (index < 1) whereas Rc was higher (index > 1) for all trees and forest types. Differences among forest types were only significant for Rt. In turn, living and dead trees showed significant differences for Rt in closed forests. Our results also indicate that A. chilensis trees with a high capacity to maintain growth rates during droughts (resistance) in wetter environments (mixed and closed forests) have a larger chance of survival than in drier forests. Consequently, an increase in the intensity and frequency of drought events suggested by future climate change scenarios could affect the carbon reservoirs related to Patagonian forests and their ecosystem services to people. [ABSTRACT FROM AUTHOR]

• Simulation of individual tree growth requires advanced, stand dynamics-based models that can capture the relationship between climate, competition, and tree growth. • Machine learning algorithms provide flexibility in modelling complex relationships between climate, competition, and tree growth. • This App allows easy and user-friendly application of Recurrent Neural Network algorithms for modelling individual tree growth. • This App is one methodological contribution to current generation of advanced models that could be used to help researchers understand individual tree growth in response to climate change. PredictingTreeGrowth is free and open-source application software written in Python 3.7 that allows easy and fast development of predictive models using the Recurrent Neural Network (RNN)/Long Short-Term Memory (LSTM) framework. RNNs have an upgraded architecture able to capture tree growth mechanisms related to time ordering and size dependence. The motivation for this App is to demystify the use of Machine Learning algorithms and allow accessibility of Machine Learning algorithms by the scientific community. Its simple graphical user interface (GUI) provides straightforward tools for building predictive models with the RNN algorithm. [ABSTRACT FROM AUTHOR]