Weather–Growth Responses Show Differing Adaptability of Scots Pine Provenances in the South-Eastern Parts of Baltic Sea Region

Local adaptation and plasticity of growth play important roles in the adaptability of trees to changing conditions. Under accelerating climatic changes, the adaptive capacity of metapopulations can be exceeded, implying a necessity for assisted gene flow to sustain the productivity of forests. Such management is knowledge intensive, and information on the responsiveness of metapopulations (provenances) across the climatic gradient can aid more comprehensive projections of their performance. The plasticity of growth responses to weather conditions of five provenances of Scots pine with differing field performance across the climatic gradient of the south-eastern Baltic Sea region was assessed using dendrochronological methods and generalized additive models. Weather conditions related to water availability in summer, as well as during dormancy, were the main regional drivers of an increment in the provenances. The provenances differed by the plasticity of responses according to field performance, indicating adaptation in terms of growth sensitivity and uneven adaptability. The weather–growth responses of the top-performing provenances to summer weather were more plastic, providing advantages under a changing climate. Accordingly, regional sensitivity and plasticity of growth responses could be used for the screening of genotypes best suited for the projected climates. In addition, the estimated growth responses encourage supplementation of the local breeding populations with the top-performing provenances originating from sites with the projected climates.

Soil Phosphorus Exchange as Affected by Drying-Rewetting of Three Soils From a Hawaiian Climatic Gradient

Current understanding of phosphorus (P) dynamics is mostly based on experiments carried out under steady-state conditions. However, drying-rewetting is an inherent feature of soil behavior, and as such also impacts P cycling. While several studies have looked at net changes in P pool sizes with drying-rewetting, few studies have dynamically tracked P exchange using isotopes, which would give insights on P mean residence times in a given pool, and thus P availability. Here, we subjected three soils from a climatic gradient on the Kohala peninsula from Hawaii to 5-month drying-rewetting treatments. The hypotheses were that physico-chemical and biotic processes would be differently affected by repeated drying-rewetting cycles, and that response would depend on climatic history of the soils. Soils were labeled with 33P and 18O enriched water. At select time intervals, we carried out a sequential extraction and measured P concentration, 33P recovery (only first 3 months), and incorporation of 18O from water into phosphate. This allowed tracing P dynamics in sequentially extracted pools as well as O dynamics in phosphate, which are driven by biological processes. Results showed that P concentration and 33P recovery were predominantly driven by soil type. However, across all soils we observed faster dilution of 33P from resin-P into less mobile inorganic pools under drying-rewetting. On the other hand, O dynamics in phosphate were mostly governed by drying-rewetting treatment. Under drying-rewetting, considerably less O was incorporated from water into phosphate of resin-P, microbial-P and HCl-P, suggesting that drying-rewetting reduced biological P cycling. Hence, our results suggest that repeated drying-rewetting increases inorganic P exchange while reducing biological P cycling due to reduced microbial activity, independent of climatic history of the soils. This needs to be considered in P management in ecosystems as well as model representations of the terrestrial P cycle.

Effect of Climatic Gradient on Species Diversity and Structure of Faidherbia Albida Parkland in Burkina Faso (West Africa)

Background: Faidherbia albida parkland provide many ecosystem goods and services to people, ranging from provisioning to regulating services. Despite this importance, these parks are degraded due to overexploitation, which is accentuated by the adverse effects of climate change. In this context of climate change, little information exists on the state of these F. albida parkland, particularly their diversity and structure along the North-South climatic gradient. This study aims to determine the effect of climatic gradient of F. albida parklands in order to provide updated data for sustainable management. Floristic diversity and population structure were assessed through forest inventories in the three climatic zones of Burkina Faso. Thus, 99 circular plots of 1 ha were sampled in three zones, including 33 per climatic zone. The data processing concerned the calculation of diversity indices (Shannon, Piélou equitability, and species richness), importance value indices, and the calculation of the means of the dendrometric parameters. The analyses were based on the comparison of medians using the Kruskal-wallis test, and the effect of the climatic gradient on the different variables was tested using generalized linear models. All of these analyses were carried out using the R.4.0.5 software. Results: The dendrometric parameters and floristic diversity vary significantly (Pv˂0.05) according of climatic zone. Furthermore, based on ecological importance value indices and diameter class structure, the majority of dominant species (11) show a regressive dynamic in all three climatic zones characterized by abundance of old individuals at expense of young ones. This reflects an ageing and continuous destruction of these parklands. However, species such as V. tortilis (Sahelian zone) and A. indica (Sudano-Sahelian and Sudanian zones) show good dynamics. As for F. albida, its structure is regressive in all climatic zones.Conclusion: Although the climatic gradient has a significant effect on the diversity and species structure of F. albida parkland, their current dynamics are thought to be due to unsustainable management of local populations.