The global abundance of tree palms

Aim Palms are an iconic, diverse and often abundant component of tropical ecosystems that provide many ecosystem services. Being monocots, tree palms are evolutionarily, morphologically and physiologically distinct from other trees, and these differences have important consequences for ecosystem services (e.g., carbon sequestration and storage) and in terms of responses to climate change. We quantified global patterns of tree palm relative abundance to help improve understanding of tropical forests and reduce uncertainty about these ecosystems under climate change. Location Tropical and subtropical moist forests. Time period Current. Major taxa studied Palms (Arecaceae). Methods We assembled a pantropical dataset of 2,548 forest plots (covering 1,191 ha) and quantified tree palm (i.e., ≥10 cm diameter at breast height) abundance relative to co‐occurring non‐palm trees. We compared the relative abundance of tree palms across biogeographical realms and tested for associations with palaeoclimate stability, current climate, edaphic conditions and metrics of forest structure. Results On average, the relative abundance of tree palms was more than five times larger between Neotropical locations and other biogeographical realms. Tree palms were absent in most locations outside the Neotropics but present in >80% of Neotropical locations. The relative abundance of tree palms was more strongly associated with local conditions (e.g., higher mean annual precipitation, lower soil fertility, shallower water table and lower plot mean wood density) than metrics of long‐term climate stability. Life‐form diversity also influenced the patterns; palm assemblages outside the Neotropics comprise many non‐tree (e.g., climbing) palms. Finally, we show that tree palms can influence estimates of above‐ground biomass, but the magnitude and direction of the effect require additional work. Conclusions Tree palms are not only quintessentially tropical, but they are also overwhelmingly Neotropical. Future work to understand the contributions of tree palms to biomass estimates and carbon cycling will be particularly crucial in Neotropical forests

Assessing dendrochronological potential of escallonia myrtilloides in the high Andes of Peru

There is a significant dendrochronological gap in the Puna of the central Andes of Peru, which motivates research on new species. In this study, we present the first tree-ring chronologies of Escallonia myrtilloides. We collected samples at San Pedro Saño and Sapallanga in Peru, analyzed the anatomical characteristics that delimit the annual growth rings, and developed two tree-ring chronologies through conventional dendrochronological techniques. The tree-ring chronologies cover the period 1940–2015 (76 years) for San Pedro Saño and 1960–2015 (56 years) for Sapallanga. The E. myrtilloides chronologies presented similar values of mean sensitivity, Rbar and EPS to those recorded for Polylepis tarapacana, Polylepis pepei, and Polylepis rugulosa in the Puna region. The analysis of the climate-growth relationships indicated positive correlations with precipitation and negative correlations with temperature in particular months of the current growing season (October–April). This precipitation/temperature-sensitive record highlights the high value of E. myrtilloides for future studies on the influence of climate on tree growth in the central Andes

Assessing the Hydric Deficit on Two <i>Polylepis</i> Species from the Peruvian Andean Mountains: Xylem Vessel Anatomic Adjusting

The impact of drought on vessel architecture and function has been broadly assessed for a variety of tree species in the last decades, but the hydraulic plasticity under temperature increase has scarcely been studied. The effect of drought on tree-ring width and specific hydraulic conductivity depends on relict-tree species resilience to climatic adaptability and its wood anatomical responses to climatic oscillations. We assessed the vessel architecture adaptation of two threatened Peruvian Andean Polylepis species (P. rodolfo-vasquezii and P. tarapacana). We found that historical Peruvian drought years differentially affected Polylepis species, where P. rodolfo-vasquezii showed vessel anatomical features significantly sensitive to drought events when contrasted with P. tarapacana. The drought effect influenced the capacity of Polylepis species to adjust the tree-ring width and vessel anatomical traits of their hydraulic system. Our results suggest that drought events influence Polylepis species’ adaptability and resilience to dry periods and could also restrict them from remaining as a part of the Peruvian Andean puna and mountain ecosystems

Assessing the Hydric Deficit on Two Polylepis Species from the Peruvian Andean Mountains: Xylem Vessel Anatomic Adjusting

The impact of drought on vessel architecture and function has been broadly assessed for a variety of tree species in the last decades, but the hydraulic plasticity under temperature increase has scarcely been studied. The effect of drought on tree-ring width and specific hydraulic conductivity depends on relict-tree species resilience to climatic adaptability and its wood anatomical responses to climatic oscillations. We assessed the vessel architecture adaptation of two threatened Peruvian Andean Polylepis species (P. rodolfo-vasquezii and P. tarapacana). We found that historical Peruvian drought years differentially affected Polylepis species, where P. rodolfo-vasquezii showed vessel anatomical features significantly sensitive to drought events when contrasted with P. tarapacana. The drought effect influenced the capacity of Polylepis species to adjust the tree-ring width and vessel anatomical traits of their hydraulic system. Our results suggest that drought events influence Polylepis species&rsquo; adaptability and resilience to dry periods and could also restrict them from remaining as a part of the Peruvian Andean puna and mountain ecosystems

Tropical tree growth driven by dry-season climate variability

Interannual variability in the global land carbon sink is strongly related to variations in tropical temperature and rainfall. This association suggests an important role for moisture-driven fluctuations in tropical vegetation productivity, but empirical evidence to quantify the responsible ecological processes is missing. Such evidence can be obtained from tree-ring data that quantify variability in a major vegetation productivity component: woody biomass growth. Here we compile a pantropical tree-ring network to show that annual woody biomass growth increases primarily with dry-season precipitation and decreases with dry-season maximum temperature. The strength of these dry-season climate responses varies among sites, as reflected in four robust and distinct climate response groups of tropical tree growth derived from clustering. Using cluster and regression analyses, we find that dry-season climate responses are amplified in regions that are drier, hotter and more climatically variable. These amplification patterns suggest that projected global warming will probably aggravate drought-induced declines in annual tropical vegetation productivity. Our study reveals a previously underappreciated role of dry-season climate variability in driving the dynamics of tropical vegetation productivity and consequently in influencing the land carbon sink

Tropical tree growth driven by dry-season climate variability

Interannual variability in the global land carbon sink is strongly related to variations in tropical temperature and rainfall. This association suggests an important role for moisture-driven fluctuations in tropical vegetation productivity, but empirical evidence to quantify the responsible ecological processes is missing. Such evidence can be obtained from tree-ring data that quantify variability in a major vegetation productivity component: woody biomass growth. Here we compile a pantropical tree-ring network to show that annual woody biomass growth increases primarily with dry-season precipitation and decreases with dry-season maximum temperature. The strength of these dry-season climate responses varies among sites, as reflected in four robust and distinct climate response groups of tropical tree growth derived from clustering. Using cluster and regression analyses, we find that dry-season climate responses are amplified in regions that are drier, hotter and more climatically variable. These amplification patterns suggest that projected global warming will probably aggravate drought-induced declines in annual tropical vegetation productivity. Our study reveals a previously underappreciated role of dry-season climate variability in driving the dynamics of tropical vegetation productivity and consequently in influencing the land carbon sink