Lianas Significantly Reduce Aboveground and Belowground Carbon Storage: A Virtual Removal Experiment

Lianas are structural parasites of trees that cause a reduction in tree growth and an increase in tree mortality. Thereby, lianas negatively impact forest carbon storage as evidenced by liana removal experiments. In this proof-of-concept study, we calibrated the Ecosystem Demography model (ED2) using 3 years of observations of net aboveground biomass (AGB) changes in control and removal plots of a liana removal experiment on Gigante Peninsula, Panama. After calibration, the model could accurately reproduce the observations of net biomass changes, the discrepancies between treatments, as well as the observed components of those changes (mortality, productivity, and growth). Simulations revealed that the long-term total (i.e., above- and belowground) carbon storage was enhanced in liana removal plots (+1.2 kgC m–2 after 3 years, +1.8 kgC m–2 after 10 years, as compared to the control plots). This difference was driven by a sharp increase in biomass of early successional trees and the slow decomposition of liana woody tissues in the removal plots. Moreover, liana removal significantly reduced the simulated heterotrophic respiration (−24%), which resulted in an average increase in net ecosystem productivity (NEP) from 0.009 to 0.075 kgC m–2 yr–1 for 10 years after liana removal. Based on the ED2 model outputs, lianas reduced gross and net primary productivity of trees by 40% and 53%, respectively, mainly through competition for light. Finally, model simulations suggested a profound impact of the liana removal on the soil carbon dynamics: the simulated metabolic litter carbon pool was systematically larger in control plots (+51% on average) as a result of higher mortality rates and faster leaf and root turnover rates. By overcoming the challenge of including lianas and depicting their effect on forest ecosystems, the calibrated version of the liana plant functional type (PFT) as incorporated in ED2 can predict the impact of liana removal at large-scale and its potential effect on long-term ecosystem carbon storage

Within-site variability of liana wood anatomical traits : a case study in Laussat, French Guiana

Research Highlights: We investigated the variability of vessel diameter distributions within the liana growth form among liana individuals originating from a single site in Laussat, French Guiana. Background and Objectives: Lianas (woody vines) are key components of tropical forests. Lianas are believed to be strong competitors for water, thanks to their presumed efficient vascular systems. However, unlike tropical trees, lianas are overlooked in field data collection. As a result, lianas are often referred to as a homogeneous growth form while little is known about the hydraulic architecture variation among liana individuals. Materials and Methods: We measured several wood hydraulic and structural traits (e.g., basic specific gravity, vessel area, and vessel diameter distribution) of 22 liana individuals in a single sandy site in Laussat, French Guiana. We compared the liana variability of these wood traits and the correlations among them with an existing liana pantropical dataset and two published datasets of trees originating from different, but species-rich, tropical sites. Results: Liana vessel diameter distribution and density were heterogeneous among individuals: there were two orders of magnitude difference between the smallest (4 µm) and the largest (494 µm) vessel diameters, a 50-fold difference existed between extreme vessel densities ranging from 1.8 to 89.3 vessels mm−2, the mean vessel diameter varied between 26 µm and 271 µm, and the individual theoretical stem hydraulic conductivity estimates ranged between 28 and 1041 kg m−1 s−1 MPa−1. Basic specific gravity varied between 0.26 and 0.61. Consequently, liana wood trait variability, even within a small sample, was comparable in magnitude with tree surveys from other tropical sites and the pantropical liana dataset. Conclusions: This study illustrates that even controlling for site and soil type, liana traits are heterogeneous and cannot be considered as a homogeneous growth form. Our results show that the liana hydraulic architecture heterogeneity across and within sites warrants further investigation in order to categorize lianas into functional groups in the same way as trees

Root system markup language: toward an unified root architecture description language

The number of image analysis tools supporting the extraction of architectural features of root systems has increased over the last years. These tools offer a handy set of complementary facilities, yet it is widely accepted that none of these software tool is able to extract in an efficient way growing array of static and dynamic features for different types of images and species. We describe the Root System Markup Language (RSML) that has been designed to overcome two major challenges: (i) to enable portability of root architecture data between different software tools in an easy and interoperable manner allowing seamless collaborative work, and (ii) to provide a standard format upon which to base central repositories which will soon arise following the expanding worldwide root phenotyping effort. RSML follows the XML standard to store 2D or 3D image metadata, plant and root properties and geometries, continuous functions along individual root paths and a suite of annotations at the image, plant or root scales, at one or several time points. Plant ontologies are used to describe botanical entities that are relevant at the scale of root system architecture. An xml-schema describes the features and constraints of RSML and open-source packages have been developed in several languages (R, Excel, Java, Python, C#) to enable researchers to integrate RSML files into popular research workflow

Modeling the Impact of Liana Infestation on The Demography and Carbon Cycle of Tropical Forests

There is mounting empirical evidence that lianas affect the carbon cycle of tropical forests. However, no single vegetation model takes into account this growth form, although such efforts could greatly improve the predictions of carbon dynamics in tropical forests. In this study, we incorporated a novel mechanistic representation of lianas in a dynamic global vegetation model (the Ecosystem Demography Model). We developed a liana‐specific plant functional type and mechanisms representing liana–tree interactions (such as light competition, liana‐specific allometries, and attachment to host trees) and parameterized them according to a comprehensive literature meta‐analysis. We tested the model for an old‐growth forest (Paracou, French Guiana) and a secondary forest (Gigante Peninsula, Panama). The resulting model simulations captured many features of the two forests characterized by different levels of liana infestation as revealed by a systematic comparison of the model outputs with empirical data, including local census data from forest inventories, eddy flux tower data, and terrestrial laser scanner‐derived forest vertical structure. The inclusion of lianas in the simulations reduced the secondary forest net productivity by up to 0.46 tC ha−1 year−1, which corresponds to a limited relative reduction of 2.6% in comparison with a reference simulation without lianas. However, this resulted in significantly reduced accumulated above‐ground biomass after 70 years of regrowth by up to 20 tC/ha (19% of the reference simulation). Ultimately, the simulated negative impact of lianas on the total biomass was almost completely cancelled out when the forest reached an old‐growth successional stage. Our findings suggest that lianas negatively influence the forest potential carbon sink strength, especially for young, disturbed, liana‐rich sites. In light of the critical role that lianas play in the profound changes currently experienced by tropical forests, this new model provides a robust numerical tool to forecast the impact of lianas on tropical forest carbon sinks

Lianas Significantly Reduce Aboveground and Belowground Carbon Storage: A Virtual Removal Experiment

Lianas are structural parasites of trees that cause a reduction in tree growth and an increase in tree mortality. Thereby, lianas negatively impact forest carbon storage as evidenced by liana removal experiments. In this proof-of-concept study, we calibrated the Ecosystem Demography model (ED2) using 3 years of observations of net aboveground biomass (AGB) changes in control and removal plots of a liana removal experiment on Gigante Peninsula, Panama. After calibration, the model could accurately reproduce the observations of net biomass changes, the discrepancies between treatments, as well as the observed components of those changes (mortality, productivity, and growth). Simulations revealed that the long-term total (i.e., above- and belowground) carbon storage was enhanced in liana removal plots (+1.2 kgC m–2 after 3 years, +1.8 kgC m–2 after 10 years, as compared to the control plots). This difference was driven by a sharp increase in biomass of early successional trees and the slow decomposition of liana woody tissues in the removal plots. Moreover, liana removal significantly reduced the simulated heterotrophic respiration (−24%), which resulted in an average increase in net ecosystem productivity (NEP) from 0.009 to 0.075 kgC m–2 yr–1 for 10 years after liana removal. Based on the ED2 model outputs, lianas reduced gross and net primary productivity of trees by 40% and 53%, respectively, mainly through competition for light. Finally, model simulations suggested a profound impact of the liana removal on the soil carbon dynamics: the simulated metabolic litter carbon pool was systematically larger in control plots (+51% on average) as a result of higher mortality rates and faster leaf and root turnover rates. By overcoming the challenge of including lianas and depicting their effect on forest ecosystems, the calibrated version of the liana plant functional type (PFT) as incorporated in ED2 can predict the impact of liana removal at large-scale and its potential effect on long-term ecosystem carbon storage

Liana optical traits increase tropical forest albedo and reduce ecosystem productivity

Environmental Biolog

Nära till naturen : en diskussion om riktlinjer för grundtillgång på friluftsmarker nära tätorter /

This study tested a method to quantify and locate hydraulic lift (HL, defined as the passive upward water flow from wetter to dryer soil zones through the plant root system) by combining an experiment using the stable water isotope 1H218O as a tracer with a soil–plant water flow model. Our methodology consisted in (i) establishing the initial conditions for HL in a large rhizobox planted with Italian ryegrass (Lolium multiflorum Lam.), (ii) labeling water in the deepest soil layer with an 18O-enriched solution, (iii) monitoring the water O isotopic composition in soil layers to find out changes in the upper layers that would reflect redistribution of 18O-enriched water from the bottom layers by the roots, and (iv) comparing the observed soil water O isotopic composition to simulation results of a three-dimensional model of water flow and isotope transport in the soil–root system. Our main findings were that (i) the depth and strength of the observed changes in soil water O isotopic composition could be well reproduced with a modeling approach (RMSE = 0.2‰, i.e., equivalent to the precision of the isotopic measurements), (ii) the corresponding water volume involved in HL was estimated to account for 19% of the plant transpiration of the following day, i.e., 0.45 mm of water, and was in agreement with the observed soil water content changes, and (iii) the magnitude of the simulated HL was sensitive to both plant and soil hydraulic properties

Development and analysis of the Soil Water Infiltration Global database

In this paper, we present and analyze a novel global database of soil infiltration measurements, the Soil Water Infiltration Global (SWIG) database. In total, 5023 infiltration curves were collected across all continents in the SWIG database. These data were either provided and quality checked by the scientists who performed the experiments or they were digitized from published articles. Data from 54 different countries were included in the database with major contributions from Iran, China, and the USA. In addition to its extensive geographical coverage, the collected infiltration curves cover research from 1976 to late 2017. Basic information on measurement location and method, soil properties, and land use was gathered along with the infiltration data, making the database valuable for the development of pedotransfer functions (PTFs) for estimating soil hydraulic properties, for the evaluation of infiltration measurement methods, and for developing and validating infiltration models. Soil textural information (clay, silt, and sand content) is available for 3842 out of 5023 infiltration measurements ( ∼ 76%) covering nearly all soil USDA textural classes except for the sandy clay and silt classes. Information on land use is available for 76% of the experimental sites with agricultural land use as the dominant type ( ∼ 40%). We are convinced that the SWIG database will allow for a better parameterization of the infiltration process in land surface models and for testing infiltration models. All collected data and related soil characteristics are provided online in *.xlsx and *.csv formats for reference, and we add a disclaimer that the database is for public domain use only and can be copied freely by referencing it. Supplementary data are available at https://doi.org/10.1594/PANGAEA.885492 (Rahmati et al., 2018). Data quality assessment is strongly advised prior to any use of this database. Finally, we would like to encourage scientists to extend and update the SWIG database by uploading new data to it

Revisiting crop root systems ideotypes for water uptake : new tools and models

Root water uptake is critical for yield determination in agriculture. Water stress is indeed the most significant environmental stress in crops worldwide. It is even expected to become more and more severe in many regions of the globe while nowadays already millions of people remain chronically undernourished. In such context, understanding the plant mechanisms to efficiently take up water in a heterogeneous changing environment would be of great benefit in the quest for more resilient food production systems. Several authors proposed plant root system ideotypes for water uptake defined as ideal plant models, which are expected to yield a greater quantity or quality of grain when developed as cultivars. Such plant models are characterized by an ensemble of properties (alternatively called phene states) that are responsible for their improved performance in terms of transpiration, such as root structural (e.g. root length, elongation rates) and functional (e.g. radial or axial hydraulic conductivity) properties. However current definitions of crop root system ideotypes are of limited in terms of interest for several reasons. They usually do not contain quantitative characteristics and do not include the time dimension. They are not associated to specific pedo-climatic conditions while it has been demonstrated that no root system can perform ideally in any situation. Furthermore root water uptake strategy is not uniquely defined by an ensemble of phene states: other combinations of phene states could lead to similar water uptake behaviors. The main objective of this thesis is to advance the current understanding of plant optimal water uptake and growth strategies for maximising crop yield. Such plants would minimize the water stress over their crop cycle and particularly at critical development stages. New definitions of crop quantitative eco-ideotypes for root water uptake, i.e. ideal root systems that avoid water stress over their crop cycle or, at least, at flowering were proposed. Such plant models display optimal water uptake and growth strategies that are determined by macroscopic parameter trajectories in time. In turn, these trajectories and their changes are entirely explained by an ensemble of phene states. As no plant can perform ideally in any situation, the ideotypes are systematically associated to specific pedo-climatic situations. To reach these eco-ideotypes, focus was first put on water flow in root system hydraulic architecture.The current numerical resolution method of the water flow equation was improved by integrating the analytical solution valid at the segment scale in a root system hydraulic tree model. Plant macroscopic parameters were also shown to be analytically calculable based on functional and structural parameters at root and root system scales. An online flexible software, MARSHAL, was also elaborated designed to easily generate contrasted root system hydraulic architecture of maize crop. This unique software is compatible with current functional-structural models to bridge the gap between local root phenes, macroscopic parameters and plant performance in contrasted pedo-climatic situations The second research section of the thesis was dedicated to the hydraulic property quantification of maize, ryegrass and lupine roots using a combination of local or global measurements of proxies of water uptake and inverse modelling. In all cases, good correspondence between measurements and simulations were obtained, as well as uncertainty of the fitted parameters. Finally the novel analytical relationships between root local phene states and macroscopic parameters were used to explore the parametric space given in the literature and to generate corresponding macroscopic parameters. The sensitivity of hydraulic and architectural plant-scale parameters (root system volume, convex hull, root system conductance and depth of standard uptake) to local phene states were then analyzed. These macroscopic parameters, together with their changes with time, define the plant strategy for water uptake that can be adapted to certain pedo-climatic conditions as shown through simulations of the water flow in the soil-plant-atmosphere continuum using R-SWMS. The model predicted cumulative transpiration were successfully correlated with observed plant yields. The coupled soil-plant model was further used to assess the impact of individual local phene change, which leads to contrasted effects depending on the pedo-climatic situation. Finally macroscopic parameter trajectories were shown to explain plant performances and strategies.(AGRO - Sciences agronomiques et ingénierie biologique) -- UCL, 201