This is a repository copy of Tropical tree growth driven by dry-season climate variability.

Photosynthetic activity is a fundamental process in the physiology of plants, and its regulation plays an important role in determining the effect of abiotic factors. Quinoa is a plant species of agronomic and nutritional interest that has been recognized for its adaptability to extreme environmental conditions, however, climate change may result in unfavorable conditions capable of affecting the natural development of this species, which is of great interest culture and research in South America. To evaluate the response of quinoa to stress, techniques could be used that quantify the loss of light energy through its dissipation in the form of heat. However, the measurement of chlorophyll fluorescence is the most widely used and accessible technique for field research, which allows to recognize the relationships between the plant and agroclimatic factors. This review summarizes the physiological effects of heat, radiation, salinity, and nutrient and water availability, as well as their possible interactions on quinoa.

Aim: How tree taxonomic and phylogenetic diversity vary with elevation at multiple spatial scales may provide new insights into the ecological and evolutionary processes influencing biogeographical patterns. The effect of water-and energy-related climatic variables on forests diversity across elevations, as well as how clades have evolved on and established across mountain regions lack consensus. Here, we tested whether changes in biodiversity with elevation are consistent with one of, or multiple, competing hypotheses: the water-energy dynamics (WED), species-energy relationship (SER), Tropical Niche Conservatism (TNC) and Out of The Tropics hypothesis (OTT). Location: Patia watershed, ColombiaTaxon: Seed plants (trees) Methods: We used a large dataset of 490 0.1 ha forest plots in nine elevational belts (545-3410 m a.s.l) that correspond to three different life zones, and quantified alpha and gamma scales using taxonomic and phylogenetic diversity indices. We fitted linear mixed-effects models to evaluate how taxonomic and phylogenetic alpha diversity changed with elevation, precipitation and aboveground biomass. We assessed taxonomic and phylogenetic beta diversity using the Sørensen index and its spatial turnover and nestedness components.Results: Taxonomic and phylogenetic alpha diversity decrease with elevation. Yet, at the gamma scale, taxonomic and phylogenetic diversity predominantly increased with elevation. Taxonomic and phylogenetic beta diversity were strongly influenced by species turnover, and followed a hump-shaped pattern with elevation.Main conclusions: Overall, diversity shows a decreasing trend at the local scale, while coarse-scale gamma diversity followed a pattern of nonlinear increases for both taxonomic and phylogenetic diversity. Evidence supports the influence of SER and WED on diversity patterns across elevations, yet neither evolutionary hypotheses had sufficient empirical support to be conclusive.

Forest harvesting and fire are major disturbances in boreal forests. Forest harvesting has modified stand successional pathways, which has led to compositional changes from the original conifer-dominated forests to predominantly mixed and hardwood forests. Boreal fire regimes are expected to change with future climate change. Using the LANDIS-II spatially explicit landscape model, we evaluated the effects of forest management scenarios and projected fire regimes under climate change in northeastern Canadian boreal forests, and we determined the subsequent alteration in stand- and landscape-level composition, succession, and spatial configuration of boreal forests. We observed that, in contrast to successional pathways that followed fire, successional pathways that followed forest harvesting favored mixed forests with a prevalence of shade-intolerant hardwoods for up to 300 y after harvesting. This trend was exacerbated under climate change scenarios where forests became dominated by hardwood species, particularly in ecoregions where these species were found currently in low abundance. Our results highlight the failure of existing forest management regimes to emulate the effects of natural disturbance regimes on boreal forest composition and configuration. This illustrates the risks to maintaining ecosystem goods and services over the long term and the exacerbation of this trend in the context of future climate change.

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