Predicting effects of climate change on productivity and persistence of forest trees

The return of tall forests: Reconstructing the canopy resilience of an extensively harvested primary forest in Mediterranean mountains

Understanding recovery times and mechanisms of ecosystem dynamics towards the old-growth stage is crucial for forest restoration, but still poorly delineated in Mediterranean. Through tree-ring methods, we reconstructed the return of a tall canopy after severe human disturbance in a mixed beech (Fagus sylvatica) and silver fir (Abies alba) forest, located at a mountain site in the southern edge of both species' range (Gariglione, south Italy). The primary forest was extensively harvested between 1930 and 1950, removing up to 91 % of the biomass. Growth histories, climate-growth relationships and time-series of growth dominance in Gariglione were compared with a network of protected mature and old-growth beech forests distributed along a wide elevational gradient in the same region. We found that the renewed tall canopy of Gariglione is mainly composed of remnant trees, which include uncut trees and saplings, and the post-harvesting regeneration mostly represented by fir. Canopy beech trees reached maximum basal area increment (BAI) in the 1970s, 40-50 years after cutting. Then, beech BAI shifted towards negative trends in phase with drying climate (PDSI), while fir maintained a sustained growth until 2000. This growth asynchrony between the two species conferred community stability over the last decades. The network comparison highlighted the common negative impact of summer drought on high-frequency growth signals of beech in south Italy. However, analysis of long-term mean growth trends indicates decreasing BAI limited to Gariglione beech, revealing relevant differences due to site ecology and its interactions with legacy effects of past management in driving growth responses to climate change. Indeed, lowland mature beech forests showed increasing BAI in the last decades, while primary high-mountain forests displayed a remarkably stable low oscillating growth. In all the Mediterranean forests we studied, large and old trees showed a marked growth acclimation despite ongoing climate warming, demonstrating the effectiveness of landscape rewilding.

Identification of SNPs Associated with Drought Resistance in Hybrid Populations of Picea abies (L.) H. Karst.-P. obovata (Ledeb.)

BACKGROUND/OBJECTIVES

The spruces of the Picea abies-P. obovata complex have a total range that is the most extensive in the world flora of woody conifers. Hybridization between the nominative species has led to the formation of a wide introgression zone, which probably increases the adaptive potential of the entire species complex. This study aimed to search the genes associated with drought resistance, develop primers for the informative loci of these genes, identify and analyze SNPs, and establish the parameters of nucleotide diversity in the studied populations.

METHODS

The objects of this study were eight natural populations of the spruce complex in the Urals. Nucleotide sequences related to drought resistance spruce genes with pronounced single-nucleotide substitutions were selected, based on which 16 pairs of primers to their loci were developed and tested.

RESULTS

Based on the developed primers, six pairs of primers were chosen to identify SNPs and assess the nucleotide diversity of the studied populations. All selected loci were highly polymorphic (6 to 27 SNPs per locus). It was found that the Pic01 locus is the most variable (Hd = 0.947; π = 0.011) and selectively neutral, and the Pic06 locus is the most conservative (Hd = 0.516; π = 0.002) and has the most significant adaptive value.

CONCLUSIONS

The nucleotide diversity data for the studied populations reveal similar values among the populations and are consistent with the literature data. The discovered SNPs can be used to identify adaptive genetic changes in spruce populations, which is essential for predicting the effects of climate change.

Uncovering the Research Gaps to Alleviate the Negative Impacts of Climate Change on Food Security: A Review

Climatic variability has been acquiring an extensive consideration due to its widespread ability to impact food production and livelihoods. Climate change has the potential to intersperse global approaches in alleviating hunger and undernutrition. It is hypothesized that climate shifts bring substantial negative impacts on food production systems, thereby intimidating food security. Vast developments have been made addressing the global climate change, undernourishment, and hunger for the last few decades, partly due to the increase in food productivity through augmented agricultural managements. However, the growing population has increased the demand for food, putting pressure on food systems. Moreover, the potential climate change impacts are still unclear more obviously at the regional scales. Climate change is expected to boost food insecurity challenges in areas already vulnerable to climate change. Human-induced climate change is expected to impact food quality, quantity, and potentiality to dispense it equitably. Global capabilities to ascertain the food security and nutritional reasonableness facing expeditious shifts in biophysical conditions are likely to be the main factors determining the level of global disease incidence. It can be apprehended that all food security components (mainly food access and utilization) likely be under indirect effect via pledged impacts on ménage, incomes, and damages to health. The corroboration supports the dire need for huge focused investments in mitigation and adaptation measures to have sustainable, climate-smart, eco-friendly, and climate stress resilient food production systems. In this paper, we discussed the foremost pathways of how climate change impacts our food production systems as well as the social, and economic factors that in the mastery of unbiased food distribution. Likewise, we analyze the research gaps and biases about climate change and food security. Climate change is often responsible for food insecurity issues, not focusing on the fact that food production systems have magnified the climate change process. Provided the critical threats to food security, the focus needs to be shifted to an implementation oriented-agenda to potentially cope with current challenges. Therefore, this review seeks to have a more unprejudiced view and thus interpret the fusion association between climate change and food security by imperatively scrutinizing all factors.

Assessment of the Morphological Pattern of the Lebanon Cedar under Changing Climate: The Mediterranean Case

The effects of climate change on species can influence the delicate balance in ecosystems. For this reason, conservation planning needs to take account of connectivity and the related ecological processes within the framework of climate change. In this study, we focus on the change in the ecological connectivity of the Lebanon cedar (Cedrus libani A. Rich.), which is widely distributed in the Mediterranean, particularly in the Amanus and Taurus Mountains. To this end, we evaluated the changes in spatial units providing connectivity in the potential and future distributions of the species through ecological niche modelling, morphological spatial pattern analysis, and landscape metrics. The results suggest that the species is moving to the northeast. According to the future projections, we predict that the potential habitat suitability of the species will shrink significantly and that, in the case of pessimistic scenarios, the extent of the suitable habitats will decrease, particularly in the western and central Taurus Mountain chains. A comparison of potential and future cores indicates that there will be a slight increase under the RCP 4.5 2050 scenario, whereas core areas will decrease in the RCP 4.5 2070, RCP 8.5 2050, and RCP 8.5 2070 scenarios. In addition, it is predicted that bridges would increase in the RCP 4.5 2070 and RCP 8.5 2050 scenarios but decrease in other scenarios.

Experimental warming across a tropical forest canopy height gradient reveals minimal photosynthetic and respiratory acclimation

Tropical forest canopies cycle vast amounts of carbon, yet we still have a limited understanding of how these critical ecosystems will respond to climate warming. We implemented in situ leaf-level + 3°C experimental warming from the understory to the upper canopy of two Puerto Rican tropical tree species, Guarea guidonia and Ocotea sintenisii. After approximately 1 month of continuous warming, we assessed adjustments in photosynthesis, chlorophyll fluorescence, stomatal conductance, leaf traits and foliar respiration. Warming did not alter net photosynthetic temperature response for either species; however, the optimum temperature of Ocotea understory leaf photosynthetic electron transport shifted upward. There was no Ocotea respiratory treatment effect, while Guarea respiratory temperature sensitivity (Q₁₀ ) was down-regulated in heated leaves. The optimum temperatures for photosynthesis (T_opt ) decreased 3-5°C from understory to the highest canopy position, perhaps due to upper canopy stomatal conductance limitations. Guarea upper canopy T_opt was similar to the mean daytime temperatures, while Ocotea canopy leaves often operated above T_opt . With minimal acclimation to warmer temperatures in the upper canopy, further warming could put these forests at risk of reduced CO₂ uptake, which could weaken the overall carbon sink strength of this tropical forest.