Biology subjects

Astigarraga, J.

Publications and source records attributed to Astigarraga, J..

5 recordsLinked to original sources

bioRxiv2026

Contrasting trends in forest growth and mortality of major European tree species under increasing climatic stress

Forests play a crucial role in mitigating climate change as primary terrestrial carbon sinks. While some studies suggest that global warming enhances forest productivity, a growing body of evidence highlights detrimental impact primarily driven by increased water stress. Yet the extent to which positive effects of climate change offset its negative impacts on tree species productivity remains unclear at large spatial extents. We assessed forest growth and mortality for the 21 most abundant tree species in Europe using National Forest Inventory data from more than 50,000 plots and 700,000 trees to disentangle the relative importance of climate and forest structure. Specifically, we examined how vapor pressure deficit (VPD) anomalies across species climatic edges and stand developmental stages affect forest growth and mortality occurrence and intensity (i.e. whether mortality occurred and the amount of basal area lost). Then, we aggregated the responses across species and separately for broad-leaved and needle-leaved species to assess whether forest growth and mortality differed between major functional groups. Although the importance of forest growth and mortality drivers varied markedly among species, climate had a stronger influence on mortality than on growth, particularly in needle-leaved species. Forest growth declined and mortality increased along VPD anomaly in most species and forests studied. Responses were most pronounced at arid species edges in early-stage broad-leaved forests and at wet edges in late-stage needle-leaved forests, where differences between functional groups were also highest. We evidence the need to parametrise species-specific models of forest growth and mortality across large spatial extents to better understand and predict effects of climate change on forest productivity. In addition, our results emphasize the importance of improving the understanding of forest mortality processes given the strong influence of climate on mortality, while also further studying vulnerable populations to climate change in arid edges of species distributions.

ecology↗

bioRxiv2025

Harvesting effects on forest condition indicators across Iberian forests: Implications for the EU Nature Restoration Regulation

O_LIForest degradation is posing a growing threat to biodiversity conservation, climate regulation and nature contributions to people worldwide. The EU Nature Restoration Regulation (NRR) recognise the need of healthy forests and has established indicators to assess the condition of forest ecosystems. Forest management practices, especially harvesting may contribute to improve these indicators by, for example, reducing tree density and promoting tree species diversification. C_LIO_LIHere, we assessed temporal trends in forest condition indicators (hereafter, indicators) across Iberian forests since the 80s and evaluated how harvesting occurrence and intensity modulated these trends. Using 46,354 plots from the Spanish Forest Inventory (1986-2022), we analysed trends in indicators depending on stand diversity (monospecific or mixed), protection status (protected or unprotected), origin of the stand (natural or planted), and biogeographical region (Mediterranean or temperate). C_LIO_LIOverall, indicators increased over time. Harvesting occurrence reduced the increases in aboveground carbon stocks, structural diversity, tree species diversity, and standing deadwood; however, it contributed to increase the proportion of native species in specific forest types. Medium to high harvesting intensity negatively impacted aboveground carbon stocks, while medium intensities increased tree species diversity but reduced the structural diversity. C_LIO_LISynthesis and applications. Our results suggest that indicators are increasing as stand develops in absence of disturbances such as harvesting. Tree harvesting cannot be considered as a silver bullet to achieve the objectives of the NRR, but it can contribute under certain conditions - specifically at low intensities for carbon stocks and at medium intensities for species diversity. The naturally positive trend of indicators underlines the need to establish thresholds values and minimum rates of changes that distinguish restoration outcomes from natural dynamics. Finally, our study also highlights the key role of forest inventories in monitoring forest condition over time and across diverse landscapes. C_LI

ecology↗

bioRxiv2024

TOP-DOWN CLIMATIC PROCESSES MODULATE BIODIVERSITY-FUNCTIONING RELATIONSHIPS ACROSS NORTH AMERICAN FORESTS

Experimental evidence indicates that more diverse communities sustain higher levels of ecosystem functioning. Generally, bottom-up processes accounting for community selection and complementarity effects on biodiversity are used to explain biodiversity effects on ecosystem functioning. However, top-down macroecological processes can also influence the distribution of ecosystem functions across large environmental gradients and, importantly, biodiversity patterns. Here, we tested whether past climate instability, current climate, and climate-driven species abundance explain tree richness gradients, and therefore, determine the relationship between species richness and ecosystem functioning using 137,808 forest inventory plots across continental extents including forests of Canada, the US, and Mexico. Consistent with previous research, we found a positive monotonic relationship between species richness and biomass (measured as level stand basal area) across North American forests. However, structural equation models revealed that the indirect effect of past climate instability, current climate conditions, and climate-driven individuals abundance underlie species richness patterns and the positive covariation between species richness and biomass. The importance of top-down climatic processes varied from boreal to tropical regions, yet their significant effects were pervasive across all forest types, indicating that climate strongly modulates the strength of the relationships between species richness and basal area. Our results help to understand the assembly processes driving the ubiquitous positive monotonic relationship between species richness and basal area across continental extents. This knowledge, obtained from adopting a macroecological perspective, helps understanding biodiversity-functioning relationships, which are usually explained by mechanisms at the community level. Significance statementMore biodiverse communities sustain higher levels of ecosystem functions (BEF hypothesis). The role of biotic interactions among trees within ecological communities determining BEF has been widely studied, but it is not well known how past climatic variability, current climate, and species abundance determine BEF. Using 137,808 forest inventory plots across North American forests located in Canada, the US, and Mexico, we document a positive relationship between tree species richness and stand basal area. Detailed analysis revealed that the positive BEF relationship is underlined by a strong and indirect effect of past and current climate. Our results highlight the importance of top-down climate processes operating at macroecological scales to understand biodiversity-functioning relationships.

ecology↗

bioRxiv2023

Abundance of Northern Hemisphere tree species declines in the warm and arid regions of their climatic niches

Climate change is expected to drive species towards colder and wetter regions of their distribution with alternative processes such as forest management having the potential to alter species displacements. Here, using data from more than two million monitored trees from 73 widely-distributed species, we quantify changes in tree species abundance across Northern Hemisphere forests and find a widespread decline in abundance across the whole of species climatic niches. Yet, our analysis revealed that this decline is heavily influenced by alterations at the stand-level and consequent stand development. Remarkably, when accounting for stand development, our findings show a consistent trend of species abundance optimum shifting towards cold and wet regions within their climatic niches. We provide species-specific information on the direction and magnitude of climate-driven changes in abundance that should be taken into account when designing conservation, management and restoration plans in an era of unprecedented human-caused environmental change.

ecology↗

bioRxiv2023

Forest structural diversity determines tree growth synchrony in response to climate change

After centuries of deforestation, many industrialised countries are experiencing an increase in forest area and biomass due to changes in land- and forest-use since the mid-20th century. At the same time, the impacts of climate change on forests are aggravating, but the interplay between past land- and forest-use (i.e. land- and forest-use legacies) and climate change in forest functioning remains elusive. Here using network theory and linear mixed models, we quantified how land- and forest-use legacies modulate tree growth synchrony in response to climate change. We analysed tree growth data from European beech (Fagus sylvatica L.) stands with different histories of forest management at the species rear edge. We found that tree growth synchrony increased following heatwaves, late spring frosts, and reduced precipitation. Interestingly, the greatest tree growth synchrony occurred in recently-established forests, while stands containing large trees and heterogeneous tree sizes showed much lower growth synchrony. Our results highlight the importance of maintaining large trees and structurally heterogeneous forests to mitigate the negative effects of climate change on forest productivity, and thereby, increase forest resilience to future forest climate risks.

ecology↗