Aurora Gaxiola’s research while affiliated with Pontifical Catholic University of Chile and other places

Leaf litter decomposition is a key process for nutrient cycling with broad ecosystem‐level consequences. However, we still cannot explain an important amount of the observed variability in decomposition rates. Therefore, a mechanistic model of how litter quality impacts the metabolic capacity of microbial decomposers to degrade litter at a given rate could improve our understanding of litter decomposition. Elemental imbalances between leaf litter and microbial decomposers can lead to nutrient‐limited decomposition. Microbial decomposers can deal with elemental imbalances via three main physiological mechanisms; by adjusting their carbon use efficiency (i.e. the proportion of assimilated carbon that is not respired), accumulating nitrogen or adjusting extracellular enzyme allocation between carbon (C) and nitrogen (N). Therefore, decomposer communities that adjust to elemental imbalances using these strategies should decompose litter faster than those unable to adjust. In this study, in a reciprocal transplant microcosm, we experimentally evaluated whether differences in the capacity of decomposers to reduce elemental imbalances help explain variability in decomposition rates. We used litter and soils from three coexisting woody species with contrasting litter C:N. Throughout the decomposition experiment, we quantified litter biomass loss, the allocation to β‐1,4‐glucosidase and β‐N‐acetylglucosaminidase (i.e. C and N degrading enzymes), and N accumulation. These data allowed us to identify the main strategies through which decomposers deal with elemental imbalances and their concomitant effects on litter decomposition rates. Our results confirm that litter decomposition rates are strongly controlled by litter quality, but differences in decay rates are a function of C and N demands of decomposers. Here, decomposers dealt with elemental imbalances mainly through N accumulation and, to a lesser extent, through extracellular enzyme allocation and lower carbon use efficiency. However, when enzymatic allocation and N accumulation were insufficient to reduce elemental imbalances, decomposition rates were slower irrespective of litter quality. Finally, we show that the effectiveness of physiological strategies used by decomposers to reduce elemental imbalances will affect decomposition rates, a key ecosystem process. Read the free Plain Language Summary for this article on the Journal blog.

Ecosystems provide a variety of benefits to human society and humanity’s utilization of ecosystems affects their composition, structure, and functions. Global change drivers demand us to study the interactions between ecological and social systems, and advise strategies to protect the large fraction of Chilean unique ecosystems. Long-term research and monitoring are vital for meaningful understanding of human impacts and socio-ecological feedback, which occur over multiple spatial and time-scales and can be invisible to traditional grant-sponsored short-term studies. Despite the large fraction of unique ecosystems, Chilean government agencies have not established long-term monitoring programs to inform and guide management decisions for use, conservation, and adaptation to climate change. Responding to this void, the Chilean Long-Term Socio-Ecological Research Network (LTSER-Chile) was created, comprising nine study sites funded by a variety of private and public institutions, that broadly seeks to understand how global change is altering biodiversity and ecosystem functions. The LTSER-Chile is currently in a phase of institutional consolidation to achieve its objectives of alignment with international efforts, fill the need for high-quality, long-term data on social, biological and physical components of Chilean ecosystems, and develop itself as an open research platform for the world. Despite the wide diversity of ecosystems ecncompased by LTSER-Chile sites, several common variables are monitored, especially climatic and hydrographic variables and many ecological indicator variables that consider temporal fluctuations, population and community dynamics. The main challenges currently facing the LTSER-Chile are to secure funding to maintain existing long-term monitoring programs, to persuade public and private decision-makers about its central role in informing and anticipating socio-ecological problems, and to achieve greater ecosystem representation by integrating new long-term study sites. This will require a more decisive political commitment of the State, to improve the stewardship of our unique terrestrial and marine ecosystems, and the realization that sound ecologically-sustainable policies will never be possible without a national monitoring network. We argue that the State should build on LTSER and several other private and university initiatives to provide the country with a monitoring network. In the absence of this commitment, the LTSER system is subject to discontinuity and frequent interruptions, which jeopardizes the long-term effort to understand the functioning of nature and its biodiversity.

This paper contributes to a critical re-reading of the notion of climate services. It does so by problematizing the discontinuity between young people’s commitment to climate change, and the lack of a common vision regarding climate policy among governments. In this essay, youth commitment is characterized in terms of participation in the Global Youth Climate Pact (GYCP, 2015–2022). Here, young people share projects from their own high schools and communities and participate in a citizen consultation. Most projects have achieved a good success score, increasing over the years, especially for those carried out in emerging and developing countries. Some of them were presented at the COPs. In contrast, a textual analysis of intended nationally determined contributions (INDC) illustrates divergent understandings of the Paris Agreement and exemplifies the poor results of governmental climate diplomacy. This study establishes the need to closely monitor early warning signs of climate change in conjunction with high schools and school communities. The initiatives of young people are building a civic and planetary awareness for climate change in contrast with governmental division and inertia. In this sense, climate services, directed to young people, could contribute to design a sustainable future. We approach the practices, attitudes, and commitments of young people from the angle of cooperation rather than a moral vision of responsibility. Particularly, we propose a dialogical link between the treatment of climate issues and its effects on the constitution of networks, notably as they relate to practices of action, that is, the way in which distinct groups of young people develop relationships with their environments, organize themselves, and act and transform reality.

El presente estudio implementa la hoja de ruta denominada “gran impulso para la sostenibilidad” propuesta por la CEPAL utilizando a Chile como caso de estudio. La ruta se genera adoptando una perspectiva de límites planetarios para calcular las brechas ambientales de Chile y con miras a la identificación de políticas públicas que fomenten el desarrollo de estrategias de crecimiento económico que sean ambientalmente sostenibles.

Cushion plants are specialized keystone species of alpine environments that can have a positive effect on ecosystem structure and function. However, we know relatively little about how cushion plants regulate the diversity and composition of soil microbial communities, major drivers of soil processes and ecosystem functioning. Identifying what factors drive the diversity and composition of soil microbial communities in high-elevation ecosystems is also fundamental to predict how global changes will affect their conservation and the services and functions they provide. Thus, we sampled four sites along the southern Andes following the vegetation belt of Azorella cushion species. The field sites spread along a latitudinal gradient and had contrasting levels of aridity, UV-B radiation, mean temperature and soil properties. Overall, Azorella, as well as aridity and UV-B radiation, were the major drivers of the distribution, composition and diversity of soil microbial communities in the studied ecosystems of the Chilean Andes. UV-B radiation affected particularly soil fungi, while soil properties such as pH, total C and N content, essential predictors of microbial diversity globally, had a much lower effect on the composition of soil microbial communities. Understanding the factors driving the structure and composition of microbial communities, particularly the role of cushion plants and the feedbacks between plant, climate and soil is of uttermost importance for the preservation of the functionality of high-elevation ecosystems threatened by climate change.

Litter decomposition is a key process for carbon and nutrient cycling in terrestrial ecosystems and is mainly controlled by environmental conditions, substrate quantity, and quality as well as microbial community abundance and composition. In particular, the effects of climate and atmospheric nitrogen (N) deposition on litter decomposition and its temporal dynamics are of significant importance, since their effects might change over the course of the decomposition process. Within the TeaComposition initiative, we incubated Green tea and Rooibos tea at 530 sites across nine biomes. We assessed how macroclimate and atmospheric inorganic N deposition under current and predicted scenarios (RCP 2.6, RCP 8.5) might affect the litter decomposition rates measured after 3 and 12 months. Our study shows that the early to mid-term litter decomposition rates at the global scale were affected predominantly by litter quality (explaining 73% and 62% of the total variance in decomposition after 3 and 12 months, respectively) followed by climate and N deposition. The effects of climate was not litter-specific, and became increasingly significant as decomposition progressed, with MAP explaining 2% and MAT 4% of the variation after 12 months incubation. The effect of N deposition was litter-specific, and significant only for 12-month decomposition of Roibos tea at the global scale. However, in the temperate biome where atmospheric N deposition rates are relatively high, the 12-month loss of Green and Rooibos teas decreased significantly with increasing N deposition, explaining 9.6% and 1.1% of the variance, respectively. The expected changes in macroclimate at the global scale by the end of this century are estimated to increase the 12-month easily decomposable litter by 1.1 –3.5% and of the more stable substrates by 3.8 – 10.6%, relative to current mass loss. In contrast, expected changes in atmospheric N deposition will decrease the mid-term decomposition rate of high quality litter by 1.4 -2.2% and that of low-quality litter by 0.9 - 1.5% in the temperate biome. Our results suggest that projected increases in N deposition may have the capacity to dampen the climate-driven increases in litter decomposition depending on the biome and decomposition stage of substrate. Keywords: Tea bag, Green tea, Rooibos tea, Litter decomposition, Carbon turnover, Nitrogen deposition, TeaComposition initiative