Search

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]

Lianas are an important component of subtropical forests, but the mechanisms underlying their spatial distribution patterns have received relatively little attention. Here, we selected 12 most abundant liana species, constituting up to 96.9% of the total liana stems, in a 20‐ha plot in a subtropical evergreen broadleaved forest at 2472–2628 m elevation in SW China. Combining data on topography (convexity, slope, aspect, and elevation) and host trees (density and size) of the plot, we addressed how liana distribution is shaped by host tree properties, topography and spatial autocorrelation by using principal coordinates of neighbor matrices (PCNM) analysis. We found that lianas had an aggregated distribution based on the Ripley's K function. At the community level, PCNM analysis showed that spatial autocorrelation explained 43% variance in liana spatial distribution. Host trees and topography explained 4% and 18% of the variance, but less than 1% variance after taking spatial autocorrelation into consideration. A similar trend was found at the species level. These results indicate that spatial autocorrelation might be the most important factor shaping liana spatial distribution in subtropical forest at high elevation. [ABSTRACT FROM AUTHOR]

The scandent shrub plant form is a variant of liana that has upright and self-supporting stems when young but later becomes a climber. We aimed to explore the associations of stem and leaf traits among sympatric lianas, scandent shrubs and trees, and the effects of growth form and leaf habit on variation in stem or leaf traits. We measured 16 functional traits related to stem xylem anatomy, leaf morphology and nutrient stoichiometry in eight liana, eight scandent shrub and 21 tree species co-occurring in a subalpine cold temperate forest at an elevation of 2600–3200 m in Southwest China. Overall, lianas, scandent shrubs and trees were ordered along a fast–slow continuum of stem and leaf functional traits, with some traits overlapping. We found a consistent pattern of lianas > scandent shrubs > trees for hydraulically weighted vessel diameter, maximum vessel diameter and theoretical hydraulic conductivity. Vessel density and sapwood density showed a pattern of lianas = scandent shrubs < trees, and lianas < scandent shrubs = trees, respectively. Lianas had significantly higher specific leaf area and lower carbon concentration than co-occurring trees, with scandent shrubs showing intermediate values that overlapped with lianas and trees. The differentiation among lianas, scandent shrubs and trees was mainly explained by variation in stem traits. Additionally, deciduous lianas were positioned at the fast end of the trait spectrum, and evergreen trees at the slow end of the spectrum. Our results showed for the first time clear differentiation in stem and leaf traits among sympatric liana, scandent shrub and tree species in a subalpine cold temperate forest. This work will contribute to understanding the mechanisms responsible for variation in ecological strategies of different growth forms of woody plants. [ABSTRACT FROM AUTHOR]

Large‐diameter hail is unusual in the lowland tropics; consequently, its impact on water flux responses of trees and lianas due to foliage loss is unknown. In December 2012, Xishuangbanna Tropical Botanical Garden (21°55′N) in southern Yunnan, China, experienced the most severe hailstorm in approximately 30 years, with hailstones of 8‐ to 17‐mm diameter falling for 10–30 min. We assessed the effect of this hailstorm on sap flux density (SFD) in response to foliage loss in six tree and three liana species. Among the trees, for a given atmospheric vapour pressure deficit (VPD), Tectona grandis and Dipterocarpus tuberculatus showed a significant reduction in sap flux density and water use during the post‐hailstorm week in comparison to pre‐hailstorm week. In contrast, a liana Ventilago calyculata showed a significant increase in SFD during the first post‐hailstorm week, whereas the other tree and liana species showed no significant change in their SFD and water use. T. grandis also showed visible wilting during the first 5 days post‐hailstorm. However, this tree species showed recovery from wilting and also no more reduction in SFD after ~7–9 days. D. tuberculatus also showed SFD recovery a week post‐hailstorm. We conclude that the impact of a heavy hailstorm on the water flux of tropical trees and lianas was mild or neglectable. Our study documented a rare severe hailstorm occurrence and its impact on ecosystem processes of tropical forest and enhances our understanding about water flux of tropical woody species exposed to hailstorm. [ABSTRACT FROM AUTHOR]

Summary: Vulnerability curves (VCs) describe the loss of hydraulic conductance against increasing xylem tension, providing valuable insights about the response of plant water transport to water stress. Techniques to construct VCs have been developed and modified continuously, but controversies continue.We compared VCs constructed using the bench‐top dehydration (BD), air‐injection‐flow (AI), pneumatic‐air‐discharge (PAD), optical (OP) and X‐ray‐computed microtomography (MicroCT) methods for tropical trees and lianas with contrasting vessel lengths.The PAD method generated highly vulnerable VCs, the AI method intermediate VCs, whereas the BD, OP and MicroCT methods produced comparable and more resistant VCs. Vessel‐length and diameter accounted for the overestimation ratio of vulnerability estimated using the AI but not the PAD method. Compared with directly measured midday embolism levels, the PAD and AI methods substantially overestimated embolism, whereas the BD, MicroCT and OP methods provided more reasonable estimations.Cut‐open vessels, uncertainties in maximum air volume estimations, sample‐length effects, tissue cracks and shrinkage together may impede the reliability of the PAD method. In conclusion, we validate the BD, OP and MicroCT methods for tropical plants, whereas the PAD and AI need further mechanistic testing. Therefore, applications of VCs in estimating plant responses to drought need to be cautious. [ABSTRACT FROM AUTHOR]

Xylem vessels are used by most angiosperm plants for long-distance water and nutrient transport. Vessel length is one of the key functional traits determining plant water-transport efficiency. Additionally, determination of maximum vessel length is necessary for correct sample collection and measurements in hydraulic studies to avoid open-vessel and cutting-under-tension artifacts. Air injection and silicone injection (BLUESIL RTV141A and B mixtures) are two widely used methods for maximum vessel length determination. However, the validity of both methods needs to be carefully tested for species with different vessel lengths. In this study, we tested the air-injection and silicone-injection methods using eight species with different vessel lengths: short (<0.5 m), medium (0.5–1 m) and long (>1 m). We employed a novel approach using RTV141A injection without the RTV141B hardener as a reference method because RTV141A cannot penetrate inter-vessel pit membranes and is not prone to hardening/solidification effects during the injection process. The results revealed that the silicone-injection method substantially underestimated the maximum vessel length of all eight species. However, the air-injection method tended to overestimate the maximum vessel length in five out of eight species. The ratio of underestimation of the silicone-injection method was higher for species with longer vessels, but the overestimation of the air-injection method was independent of the vessel length. Moreover, air injection with different pressures—ranging from 40 to 300 kPa—resulted in comparable results. We conclude that the conventional silicone-injection method can underestimate the vessel length, whereas the air-injection method can overestimate the maximum vessel length, particularly for long-vessel led species. We recommend RTV141A-only injection for determining the maximum vessel length, and it can also be used to validate the use of the air-injection and conventional silicone-injection methods for a given species. [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]