• Energy Research

Aim Climate change causes shifts in species distributions, or ‘migrations’. Despite the centrality of species distributions to biodiversity conservation, the demonstrated large migration of tropical plant species in response to climate change in the past, and the expected sensitivity of species distributions to modern climate change, no study has tested for modern species migrations in tropical plants. Here we conduct a first test of the hypothesis that increasing temperatures are causing tropical trees to migrate to cooler areas. Location Tropical Andes biodiversity hotspot, south-eastern Peru, South America. Methods We use data from repeated (2003/04–2007/08) censuses of 14 1-ha forest inventory plots spanning an elevational gradient from 950 to 3400 m in Manu National Park in south-eastern Peru, to characterize changes in the elevational distributions of 38 Andean tree genera. We also analyse changes in the genus-level composition of the inventory plots through time. Results We show that most tropical Andean tree genera shifted their mean distributions upslope over the study period and that the mean rate of migration is approximately 2.5–3.5 vertical metres upslope per year. Consistent with upward migrations we also find increasing abundances of tree genera previously distributed at lower elevations in the majority of study plots. Main conclusions These findings are in accord with the a priori hypothesis of upward shifts in species ranges due to elevated temperatures, and are potentially the first documented evidence of present-day climate-driven migrations in a tropical plant community. The observed mean rate of change is less than predicted from the temperature increases for the region, possibly due to the influence of changes in moisture or non-climatic factors such as substrate, species interactions, lags in tree community response and/or dispersal limitations. Whatever the cause(s), continued slower-than-expected migration of tropical Andean trees would indicate a limited ability to respond to increased temperatures, which may lead to increased extinction risks with further climate change.

AbstractAlpine grassland vegetation supports globally important biodiversity and ecosystems that are increasingly threatened by climate warming and other environmental changes. Trait-based approaches can support understanding of vegetation responses to global change drivers and consequences for ecosystem functioning. In six sites along a 1314 m elevational gradient in Puna grasslands in the Peruvian Andes, we collected datasets on vascular plant composition, plant functional traits, biomass, ecosystem fluxes, and climate data over three years. The data were collected in the wet and dry season and from plots with different fire histories. We selected traits associated with plant resource use, growth, and life history strategies (leaf area, leaf dry/wet mass, leaf thickness, specific leaf area, leaf dry matter content, leaf C, N, P content, C and N isotopes). The trait dataset contains 3,665 plant records from 145 taxa, 54,036 trait measurements (increasing the trait data coverage of the regional flora by 420%) covering 14 traits and 121 plant taxa (ca. 40% of which have no previous publicly available trait data) across 33 families.

Societal Impact StatementThe approach that we take to our science is as important as the questions that we address if we would like our research to inform management. Here, we discuss our experience of using networks of permanent forest inventory plots to support sustainable management and conservation of intact tropical forests. A key conclusion is that to maximize the use of data from such large international networks within policymaking, it is crucial that leadership is widely shared among participants. Such an approach helps to address ethical concerns surrounding international collaborations and also achieves greater policy impact.SummaryLong‐term data from permanent forest inventory plots have much to offer the management and conservation of intact tropical forest landscapes. Knowledge of the growth and mortality rates of economically important species, forest carbon balance, and the impact of climate change on forest composition are all central to effective management. However, this information is rarely integrated within the policymaking process. The problem reflects broader issues in using evidence to influence environmental management, and in particular, the need to engage with potential users beyond the collection and publication of high‐quality data. To ensure permanent plot data are used, (a) key “policy windows”—opportunities to integrate data within policy making—need to be identified; (b) long‐term relationships need to be developed between scientists and policy makers and policymaking organizations; and (c) leadership of plot networks needs to be shared among all participants, and particularly between institutions in the global north and those in tropical countries. Addressing these issues will allow permanent plot networks to make tangible contributions to ensuring that intact tropical forest persists over coming decades.

Liverworts and mosses are a major component of the epiphyte flora of tropical montane forest ecosystems. Canopy access was used to analyse the distribution and vertical stratification of bryophyte epiphytes within tree crowns at nine forest sites across a 3400 m elevational gradient in Peru, from the Amazonian basin to the high Andes. The stable isotope compositions of bryophyte organic material (13C/12C and18O/16O) are associated with surface water diffusive limitations and, along with C/N content, provide a generic index for the extent of cloud immersion. From lowland to cloud forest δ13C increased from −33‰ to −27‰, while δ18O increased from 16.3‰ to 18.0‰. Epiphytic bryophyte and associated canopy soil biomass in the cloud immersion zone was estimated at up to 45 t dry mass ha−1, and overall water holding capacity was equivalent to a 20 mm precipitation event. The study emphasizes the importance of diverse bryophyte communities in sequestering carbon in threatened habitats, with stable isotope analysis allowing future elevational shifts in the cloud base associated with changes in climate to be tracked.

Les modèles généraux de dynamique forestière et de productivité dans les Andes sont mal caractérisés. Nous présentons ici la première étude à grande échelle de la dynamique des forêts andines à l'aide d'un ensemble de 63 parcelles forestières permanentes assemblées au cours des deux dernières décennies. Dans le centre-nord des Andes, le renouvellement des arbres (mortalité et recrutement) et la croissance des arbres ont diminué avec l'augmentation de l'altitude et la diminution de la température. De plus, la surface terrière a augmenté dans les forêts humides montagnardes inférieures, mais n'a pas changé dans les forêts humides montagnardes supérieures. Cependant, à des altitudes plus élevées, l'absence de changement net de la surface terrière et l'excès de mortalité par rapport au recrutement suggèrent des impacts environnementaux négatifs. Dans le nord-ouest de l'Argentine, la dynamique des forêts semble être influencée par l'histoire de l'utilisation des terres en plus des variations environnementales. Pris ensemble, nos résultats indiquent que les combinaisons de facteurs abiotiques et biotiques qui varient selon les gradients d'élévation sont des déterminants importants du renouvellement et de la productivité des arbres dans les Andes. Un suivi et des analyses plus approfondis et à plus long terme de la dynamique des forêts dans les parcelles permanentes seront nécessaires pour comprendre comment les processus démographiques et la biomasse ligneuse répondent aux conditions environnementales changeantes le long des gradients d'altitude tout au long de ce siècle. Los patrones generales de dinámica forestal y productividad en la Cordillera de los Andes están mal caracterizados. Aquí presentamos el primer estudio a gran escala de la dinámica forestal andina utilizando un conjunto de 63 parcelas forestales permanentes ensambladas en las últimas dos décadas. En los Andes centro-norte, la rotación de árboles (mortalidad y reclutamiento) y el crecimiento de los árboles disminuyeron con el aumento de la elevación y la disminución de la temperatura. Además, el área basal aumentó en los bosques húmedos montanos inferiores, pero no cambió en los bosques húmedos montanos superiores. Sin embargo, en altitudes más altas, la falta de cambio neto en el área basal y el exceso de mortalidad sobre el reclutamiento sugieren impactos ambientales negativos. En el noroeste de Argentina, la dinámica forestal parece estar influenciada por la historia del uso de la tierra, además de la variación ambiental. En conjunto, nuestros resultados indican que las combinaciones de factores abióticos y bióticos que varían según los gradientes de elevación son determinantes importantes de la rotación y la productividad de los árboles en los Andes. Será necesario un monitoreo y análisis más extenso y a más largo plazo de la dinámica forestal en parcelas permanentes para comprender cómo los procesos demográficos y la biomasa leñosa están respondiendo a las condiciones ambientales cambiantes a lo largo de los gradientes de elevación a lo largo de este siglo. General patterns of forest dynamics and productivity in the Andes Mountains are poorly characterized. Here we present the first large-scale study of Andean forest dynamics using a set of 63 permanent forest plots assembled over the past two decades. In the North-Central Andes tree turnover (mortality and recruitment) and tree growth declined with increasing elevation and decreasing temperature. In addition, basal area increased in Lower Montane Moist Forests but did not change in Higher Montane Humid Forests. However, at higher elevations the lack of net basal area change and excess of mortality over recruitment suggests negative environmental impacts. In North-Western Argentina, forest dynamics appear to be influenced by land use history in addition to environmental variation. Taken together, our results indicate that combinations of abiotic and biotic factors that vary across elevation gradients are important determinants of tree turnover and productivity in the Andes. More extensive and longer-term monitoring and analyses of forest dynamics in permanent plots will be necessary to understand how demographic processes and woody biomass are responding to changing environmental conditions along elevation gradients through this century. تتسم الأنماط العامة لديناميكيات الغابات والإنتاجية في جبال الأنديز بالضعف. نقدم هنا أول دراسة واسعة النطاق لديناميكيات غابات الأنديز باستخدام مجموعة من 63 قطعة أرض حرجية دائمة تم تجميعها على مدى العقدين الماضيين. في شمال وسط جبال الأنديز، انخفض معدل دوران الأشجار (الوفيات والتجنيد) ونمو الأشجار مع زيادة الارتفاع وانخفاض درجة الحرارة. بالإضافة إلى ذلك، زادت المساحة القاعدية في الغابات الرطبة الجبلية السفلى ولكنها لم تتغير في الغابات الرطبة الجبلية العليا. ومع ذلك، في المرتفعات المرتفعة، يشير الافتقار إلى صافي التغير في المنطقة القاعدية وزيادة الوفيات على التجنيد إلى آثار بيئية سلبية. في شمال غرب الأرجنتين، يبدو أن ديناميكيات الغابات تتأثر بتاريخ استخدام الأراضي بالإضافة إلى التباين البيئي. تشير نتائجنا مجتمعة إلى أن مجموعات العوامل اللاأحيائية والأحيائية التي تختلف عبر تدرجات الارتفاع هي محددات مهمة لدوران الأشجار والإنتاجية في جبال الأنديز. سيكون من الضروري إجراء عمليات رصد وتحليل أكثر شمولاً وأطول أجلاً لديناميكيات الغابات في قطع الأراضي الدائمة لفهم كيفية استجابة العمليات الديموغرافية والكتلة الحيوية الخشبية للظروف البيئية المتغيرة على طول تدرجات الارتفاع خلال هذا القرن.