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The article discusses the 1st International Workshop on Liana Forest Ecology, which focused on the impact of lianas on carbon and water cycling in tropical forests. Lianas, woody vines that climb trees, are increasing in abundance due to forest disturbance and climate change. The workshop brought together scientists from 14 countries to discuss topics such as liana distribution, hydraulics, life histories, reproductive phenology, and the role of lianas in carbon and nutrient cycling. The workshop highlighted the need for further research to understand the ecological consequences of increasing liana density in tropical forests. [Extracted from the article]

Climate change and other anthropogenic disturbances are increasing liana abundance and biomass in many tropical and subtropical forests. While the effects of living lianas on species diversity, ecosystem carbon, and nutrient dynamics are receiving increasing attention, the role of dead lianas in forest ecosystems has been little studied and is poorly understood. Trees and lianas coexist as the major woody components of forests worldwide, but they have very different ecological strategies, with lianas relying on trees for mechanical support. Consequently, trees and lianas have evolved highly divergent stem, leaf, and root traits. Here we show that this trait divergence is likely to persist after death, into the afterlives of these organs, leading to divergent effects on forest biogeochemistry. We introduce a conceptual framework combining horizontal, vertical, and time dimensions for the effects of liana proliferation and liana tissue decomposition on ecosystem carbon and nutrient cycling. We propose a series of empirical studies comparing traits between lianas and trees to answer questions concerning the influence of trait afterlives on the decomposability of liana and tree organs. Such studies will increase our understanding of the contribution of lianas to terrestrial biogeochemical cycling, and help predict the effects of their increasing abundance. [ABSTRACT FROM AUTHOR]

Summary: Understanding how intra‐annual stem growth responds to atmospheric and soil conditions is essential for assessing the effects of climate extremes on forest productivity. In species‐poor forests, such understanding can be obtained by studying stem growth of the dominant species. Yet, in species‐rich (sub‐)tropical forests, it is unclear whether these responses are consistent among species.We monitored intra‐annual stem growth with high‐resolution dendrometers for 27 trees belonging to 14 species over 5 yr in a montane subtropical forest. We quantified diel and seasonal stem growth patterns, verified to what extent observed growth patterns coincide across species and analysed their main climatic drivers.We found very consistent intra‐annual growth patterns across species. Species varied in the rate but little in the timing of growth. Diel growth patterns revealed that – across species – trees mainly grew before dawn when vapour pressure deficit (VPD) was low. Within the year, trees mainly grew between May and August driven by temperature and VPD, but not by soil moisture.Our study reveals highly consistent stem growth patterns and climatic drivers at community level. Further studies are needed to verify whether these results hold across climates and forests, and whether they can be scaled up to estimate forest productivity. [ABSTRACT FROM AUTHOR]

Tropical forests are experiencing increases in vapour pressure deficit (D), with possible negative impacts on tree growth. Tree‐growth reduction due to rising D is commonly attributed to carbon limitation, thus overlooking the potentially important mechanism of D‐induced impairment of wood formation due to an increase in turgor limitation. Here we calibrate a mechanistic tree‐growth model to simulate turgor limitation of radial stem growth in mature Toona cilitata trees in an Asian tropical forest. Hourly sap flow and dendrometer measurements were collected to simulate turgor‐driven growth during the growing season. Simulated seasonal patterns of radial stem growth matched well with growth observations. Growth mainly occurred at night and its pre‐dawn build‐up appeared to be limited under higher D. Across seasons, the night‐time turgor pressure required for growth was negatively related to previous midday D, possibly due to a relatively high canopy conductance at high D, relative to stem rehydration. These findings provide the first evidence that tropical trees grow at night and that turgor pressure limits tree growth. We suggest including turgor limitation of tree stem growth in models also for tropical forest carbon dynamics, in particular, if these models simulate effects of warming and increased frequency of droughts. [ABSTRACT FROM AUTHOR]

To develop a high‐resolution paleoclimate proxy record facilitating adaptation measures on drought impacts, we constructed a regional composite tree‐ring chronology of teak (Tectona grandis) by combining three local site chronologies from southern Myanmar. Our regional tree‐ring record is strongly correlated with the November–April self‐calibrated Palmer drought severity index and enabled us to reconstruct drought variability for the period 1802–2016. The reconstruction explained 46.5% of the actual self‐calibrated Palmer drought severity index variance. Over the past two centuries, we detected one extreme (1812) and six severe drought years (1810, 1811, 1816, 1852, 1887, and 1980). Dry periods coincided with six major famines that occurred in India. Spatial correlation analyses revealed that drought occurrence is linked to broader‐scale atmospheric circulations of the Pacific and Indian Oceans, especially during the positive phase of the El Niño–Southern Oscillation. Our reconstruction provides a useful historical perspective for assessing adaptation measures intent on mitigating future drought impacts in Myanmar. Plain Language Summary: We developed a 226‐year‐long ring‐width regional chronology of teak by combining three site chronologies from southern Myanmar. Teak growth is mainly controlled by moisture availability during the dry season, making teak a suitable species for assessing drought variation in southern Myanmar. We reconstructed a 215‐year drought history and find prolonged droughts occurred in 1808–1823, 1837–1843, 1863–1876, 1883–1891, 1895–1901, 1908–1912, 1922–1930, 1941–1945, 1952–1963, 1976–1994, and 2010–2015. We also found a strong association between drought variability in southern Myanmar and sea surface temperatures in the Pacific and Indian Oceans, as well as the El Niño–Southern Oscillation phenomenon. The results are useful to devise necessary policies and strategies for coping with the adverse impacts of drought and protecting the livelihoods of regional populations. Key Points: The radial growth of teak in southern Myanmar is mainly limited by moisture availability during the dry seasonDry episodes in the past 200 years in southern Myanmar coincided with six major famines in India and other regional drought reconstructionsDrought variations in southern Myanmar may be linked to large‐scale climate drivers, mainly tropical SST variations and El Niño events [ABSTRACT FROM AUTHOR]

High‐elevation forests are experiencing high rates of warming, in combination with CO2 rise and (sometimes) drying trends. In these montane systems, the effects of environmental changes on tree growth are also modified by elevation itself, thus complicating our ability to predict effects of future climate change. Tree‐ring analysis along an elevation gradient allows quantifying effects of gradual and annual environmental changes. Here, we study long‐term physiological (ratio of internal to ambient CO2, i.e., Ci/Ca and intrinsic water‐use efficiency, iWUE) and growth responses (tree‐ring width) of Himalayan fir (Abies spectabilis) trees in response to warming, drying, and CO2 rise. Our study was conducted along elevational gradients in a dry and a wet region in the central Himalaya. We combined dendrochronology and stable carbon isotopes (δ13C) to quantify long‐term trends in Ci/Ca ratio and iWUE (δ13C‐derived), growth (mixed‐effects models), and evaluate climate sensitivity (correlations). We found that iWUE increased over time at all elevations, with stronger increase in the dry region. Climate–growth relations showed growth‐limiting effects of spring moisture (dry region) and summer temperature (wet region), and negative effects of temperature (dry region). We found negative growth trends at lower elevations (dry and wet regions), suggesting that continental‐scale warming and regional drying reduced tree growth. This interpretation is supported by δ13C‐derived long‐term physiological responses, which are consistent with responses to reduced moisture and increased vapor pressure deficit. At high elevations (wet region), we found positive growth trends, suggesting that warming has favored tree growth in regions where temperature most strongly limits growth. At lower elevations (dry and wet regions), the positive effects of CO2 rise did not mitigate the negative effects of warming and drying on tree growth. Our results raise concerns on the productivity of Himalayan fir forests at low and middle (<3,300 m) elevations as climate change progresses. [ABSTRACT FROM AUTHOR]

Tropical lianas deploy most of their leaves towards the top of the forest canopy, whereas trees exhibit a more stratified crown. Forest canopies are often exposed to hot and windy conditions, and how lianas cope with the extremely high transpirational demands under these environments remains unknown., We investigated stem hydraulic properties, leaf drought tolerance, diurnal changes in leaf and stem water potentials (Ψleaf and Ψstem), stomatal conductance ( gs), photosynthetic rate, sap flow and stem native percentage loss of conductivity ( PLC) for four liana species in a tropical forest in southwest China. Five co-occurring tree species were also selected for comparison., Lianas reached maximal transpiration at a relatively lower vapour pressure deficit (<1 kPa) than did co-occurring trees, suggesting vigorous photosynthesis during the morning. However, liana gs declined markedly over the day, with low gs at midday and afternoon. Lianas generally had higher stem sapwood-specific conductivity and maximum sap flux density but were less tolerant to drought-induced cavitation than were evergreen trees. Both lianas and trees lost leaf turgor in the top canopy at midday, but lianas lost leaf turgor earlier (∼2 h) than trees., Seven of eight species exhibited midday increases in PLC when xylem tensions were released to −0·3 to −0·5 MPa for PLC measurements. On average, lianas experienced high PLC (35·9%), along with a greater degree of disequilibrium between leaf and stem water potentials than trees (ΔΨstem-leaf: 1·37 MPa vs. 0·75 MPa) during the day. Earlier stomatal closure and efficient water transport may help lianas maintain higher Ψstem than trees despite having similar Ψleaf., Our results provide evidence that physiological regulation and efficient water transport mediate daily water relations in tropical lianas and may explain how lianas operate efficiently in tropical seasonal forests. Further studies involving a broader range of species are needed to confirm our findings. [ABSTRACT FROM AUTHOR]

Fog is an important supplemental source of water in regions with heavy fog and little rainfall. In the present study, we used the stable isotope content of xylem water to investigate the dry season water source partition between soil and fog water of two evergreen tree species ( Cleistanthus sumatranus and Lasiococca comberi), two deciduous tree species ( Mayodendron igneum and Lagerstroemia tomentosa), two liana species ( Acacia pennata and Combretum latifolium) and understory seedlings of three tree species ( C. sumatranus, L. comberi and Celtis philippensis) in a tropical karst forest in southern Yunnan, China. The soil gravimetric water content (GWC) and volumetric water content (VWC), pre-dawn leaf water potential (Ψpre-dawn) and leaf water absorbance were also measured. There were no significant differences in both GWC and VWC among 10 to 100 cm depths in the dry season. In the dry season 2009, Ψpre-dawn of the two evergreen tree species and the understory seedlings down to −4.5 to −6.3 MPa, and which were significantly lower than those of a normal dry season. The proportion that fog contributed to xylem water ranged from 15.8% (understory seedling of C. sumatranus) to 41.3% (liana species C. latifolium). After immersing in water for 3 h, leaves of all the studied species absorbed a significant volume of water. Our results reveal that the woody plants in the tropical karst forest of Xishuangbanna use fog water as an important supplement in the dry season, with more fog water being used by lianas than by trees. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

• The evolution of lignified xylem allowed for the efficient transport of water under tension, but also exposed the vascular network to the risk of gas emboli and the spread of gas between xylem conduits, thus impeding sap transport to the leaves. A well-known hypothesis proposes that the safety of xylem (its ability to resist embolism formation and spread) should trade off against xylem efficiency (its capacity to transport water). • We tested this safety-efficiency hypothesis in branch xylem across 335 angiosperm and 89 gymnosperm species. Safety was considered at three levels: the xylem water potentials where 12%, 50% and 88% of maximal conductivity are lost. • Although correlations between safety and efficiency were weak (r² < 0.086), no species had high efficiency and high safety, supporting the idea for a safety-efficiency tradeoff. However, many species had low efficiency and low safety. Species with low efficiency and low safety were weakly associated (r² < 0.02 in most cases) with higher wood density, lower leaf- to sapwood- area and shorter stature. • There appears to be no persuasive explanation for the considerable number of species with both low efficiency and low safety. These species represent a real challenge for understanding the evolution of xylem. [ABSTRACT FROM AUTHOR]

Lianas exhibit peak abundance in tropical forests with strong seasonal droughts, the eco-physiological mechanisms associated with lianas coping with water deficits are poorly understood., We examined soil water partitioning, sap flow, and canopy eco-physiological properties for 99 individuals of 15 liana and 34 co-occurring tree species in three tropical forests that differed in soil water availability., In the dry season, lianas used a higher proportion of deep soil water in the karst forest ( KF; an area with severe seasonal soil water deficit ( SSWD)) and in the tropical seasonal forest ( TSF, moderate SSWD), permitting them to maintain a comparable leaf water status than trees in the TSF or a better status than trees in the KF. Lianas exhibited strong stomatal control to maximize carbon fixation while minimizing dry season water loss. During the dry period, lianas significantly decreased water consumption in the TSF and the KF. Additionally, lianas had a much higher maximum photosynthetic rates and sap flux density in the wet season and a lower proportional decline in photosynthesis in the dry season compared with those of trees. , Our results indicated that access to deep soil water and strong physiological adjustments in the dry season together with active wet-season photosynthesis may explain the high abundance of lianas in seasonally dry forests. [ABSTRACT FROM AUTHOR]

Aim Xylem structures are closely related to a tree's hydraulic efficiency and mechanical stability, both of which affect the life history and ecological strategy of a species. Although mechanical strength and hydraulic capacity can be shaped by the environment, no such associations between hydraulic efficiency and climatic variables have been reported across a wide range of tree species. Location Yunnan, south-west China. Methods We compiled a data set for vessel density, vessel diameter ( D), potential hydraulic conductivity ( Kp), wood density ( WD), modulus of rupture ( MOR) and modulus of elasticity ( MOE) from 316 angiosperm tree species. Our objective was to examine the correlations among xylem traits and climatic variables. We hypothesized that both hydraulic efficiency and mechanical strength would vary along climatic gradients, but that a trade-off would occur between them. Results All xylem traits varied significantly across species, but the magnitudes of variation were greater for vessel traits than for mechanical properties. Values for Kp and D increased with mean annual temperature ( MAT) in both evergreen and deciduous trees, but they were significantly correlated with aridity index ( AI) in evergreen species only. Both WD and MOR were significantly correlated with MAT only in evergreen trees. MOR decreased with increasing AI in the evergreens, but not in deciduous trees. These findings indicated that xylem development in evergreens is more sensitive to environmental changes than in deciduous trees. However, stem hydraulic traits are independent of mechanical properties. Main conclusions Consistent with our hypothesis, both hydraulic efficiency and mechanical strength of angiosperm trees are influenced by the environment, with temperature having a more important effect on hydraulic efficiency than precipitation. However, no trade-off exists between efficiency and strength. This absence of a link is explained because angiosperms have xylem tissue that specifically functions in either mechanical strength or water transport. [ABSTRACT FROM AUTHOR]

1. Stem xylem characteristics have a great impact on growth and adult stature of trees because of their role in mechanical support, long-distance water transport and whole-plant carbon allocation. Yet, despite the potential causal link between xylem traits and plant growth/adult stature, most studies have tried to link wood density, an indirect but easy to measure proxy for wood properties, to tree growth and size. 2. To determine whether xylem traits outperform wood density as predictors of tree growth and stature, we evaluated the covariation among wood density, xylem anatomical traits, tree diameter growth rate and adult stature in 40 Asian tropical tree species through principal component analyses and through bivariate correlation, both across species and across phylogenetically independent contrasts. 3. Vessel diameter exhibited a tight negative relationship with vessel frequency. Wood density showed a significant correlation with vessel diameter and density, but not with vessel fraction. Most correlations between functional traits indicate adaptive coordination, demonstrated by significant correlations between phylogenetically independent contrasts. 4. Across species, diameter growth rate and adult stature were positively correlated with vessel lumen diameter and potential hydraulic conductivity, but not with wood density. Thus, our results suggest that xylem anatomical traits that are linked to hydraulic conductivity are better predictors of tree growth rate and adult stature than wood density. 5. Synthesis. We found that xylem anatomical traits have a more significant influence on whole-plant performance due to their direct association with stem hydraulic conductivity, whereas wood density is decoupled from hydraulic function due to complex variations in xylem components. [ABSTRACT FROM AUTHOR]

Monthly mean (TEM), maximum ( Tmax) and minimum ( Tmin) surface air temperatures at 119 meteorological stations on the Yunnan Plateau (YP, Southwest China) were analysed for temporal trends and spatial variation patterns during the period 1961-2004. Linear trend analyses revealed that annual temperature over the YP increased at a rate of 0.3 °C/decade during the period 1961-2004, while warming trend of 0.33 °C/decade and 0.26 °C/decade was observed for winter and summer temperatures, respectively. Warming trends of nighttime minimum temperature are more pronounced than those of daytime maximum temperature, especially during winter season. Consequently, a decreasing trend of diurnal temperature ranges (DTR = Tmax − Tmin) was observed. Five spatial patterns of temperature variability were objectively defined by rotated empirical orthogonal function (EOF) analysis, which are associated with distinct temporal temperature variations and geographical area over the YP. Annual temperature increases were found to be most pronounced in the southern and northwestern (high-elevation) parts of the YP, whereas the hot-dry valleys along the Yangtze and Red River basins experienced cooling during the past four decades. Copyright © 2010 Royal Meteorological Society [ABSTRACT FROM AUTHOR]