The role of tree height and wood density for the water use, productivity and hydraulic architecture of tropical trees

Tropical forests are the world’s most productive terrestrial ecosystems and of central importance for global carbon and water cycles. Global climate projections predict increases in average temperature and an elevated frequency of extreme drought events throughout large parts of the tropics. In response to these changes, increases in mortality rates particularly among large trees have already been reported for many tropical forest ecosystems. Hence, there is a need for better predictions of the performance of tropical forest trees under more frequent drought conditions, which the present work seeks to address a) by more accurately quantifying how much water plants use and b) by advancing the knowledge about plant traits and mechanisms that control plant water use, growth performance and drought responses. To achieve this, this study is separated in two parts, the first of which aims at methodological improvements of water use and transpiration estimates, while the second part focuses on disentangling the relationship between tree height, wood density and wood anatomical properties, and quantifying their common effect on the productivity and water relations. The backbone of this thesis is formed by data from a field study on five research sites situated on a rainfall gradient along the Pacific coastline of Costa Rica, which are complemented by additional results from a laboratory-based study of sap flux sensor performance and a large observational dataset from tropical forests in Indonesia. In Part I, I first present accessory results from a laboratory-based calibration experiment based on 66 stems from five temperate diffuse-porous tree species. Three commonly applied sensor systems, thermal dissipation probes (TDP), heat field deformation (HFD) sensors, and heat ratio method (HRM) sensors, were validated against gravimetrically determined flow rates to compare them in terms of bias, precision and accuracy. Our results indicate a systematic underestimation of true sap flux density by on average 23-45% with the TDP method, and a relatively low precision (but lower bias) with HFD sensors. The best performance was observed for HRM sensors if restricted to low flow ranges. Based on the methods comparison, we conclude that the TDP and HFD methods require species-specific empirical calibration for optimal performance, and that for all methods there is a within-species variability in calibration relationships that puts a limit on accuracy. In the light of these findings, I then discuss the outcome of a field study of sap flux measurements using the HFD method. In this work, we analyzed a dataset of sap flow measurements from 38 trees belonging to eight tropical dry forest tree species from Costa Rica. Based on a Bayesian hierarchical modelling approach, we developed a model for radial sap flux profiles that allowed to propagate model uncertainty when predicting the shape of HFD-based radial profiles onto new trees and new tree species, and describe how to integrate these model predictions with single-point sensor readings from other sensor systems in order to improve their accuracy. We found that tree height had a credible effect on both the shape of radial profiles and whole-tree water use, with larger trees having the bulk of flow closer to the bark and reaching higher transpiration rates. Compared to water use estimates based on radial profiles, estimates that assumed constant flow over the entire sapwood overestimated water use by 26% on average. In Part II, I first show results from a dataset comprising trait averages from 99 tropical forest tree species from Sumatra and Sulawesi (Indonesia). In this study, we used structural equation models (SEM) to analyze the relationships between tree size, wood density, wood anatomical traits related to hydraulic efficiency, empirically determined sap flux density, biomass productivity and tree water use, and compared the results to simple bivariate associations. We found a strong correlation between water use and growth, which was completely explained by their common dependence on tree size and sap flux density. While wood hydraulic traits were closely associated with growth and water use, our model suggested that this relationship was mainly driven by a confounding size effect. After accounting for tree size, only a relatively small effect of wood properties remained that was mediated by sap flux density. I then present a second SEM-based study that builds upon data from 201 tropical rainforest trees belonging to 40 species distributed along the rainfall gradient in Costa Rica. In this study, we found a strong dependence of biomass increment from canopy position and tree diameter, while the effects of wood density and wood hydraulic traits diminished after controlling for size effects. Notably, differences in growth along the rainfall gradient were completely explained by the effect of annual precipitation on canopy height. We further found trees belonging to species that are more affiliated to drier habitats to have smaller sapwood nonstructural carbohydrate concentrations and to be more common in the upper canopy. Supplementary, unpublished results from an analysis of vulnerability curves measured from Costa Rican tropical rainforest trees indicate that the strong size effect in growth, water use and wood hydraulic trees surprisingly was mirrored by a size dependence in embolism resistance, with the highest embolism resistance in the largest and most fast-growing species. In addition, we found embolism resistance to be strongly associated with stem sapwood properties, with a significantly higher embolism resistance for species with harder wood and lower vessel diameters. In summary, the present work provides a set of methodological refinements to sap flow measurement methodology that has the potential to significantly improve the accuracy of tree level transpiration estimates. In addition, it adds to the growing body of evidence indicating that tree size and/or canopy position are important covariates that have to be controlled for when studying relationships between plant traits. In particular, we show that observed positive correlations of biomass increment and water use with wood properties can largely be attributed to a confounding size effect, which suggests that the functional importance of wood anatomical traits may often be overstated

Providing assistance to incarcerated fathers who have child support obligations can help their post-release community reintegration

Among the growing discussions about race, justice, inequality and incarceration there has been a greater concern over the financial obligations placed on those who are convicted of crimes. In new research, Caterina G. Roman and Nathan W. Link examine the effects of ongoing child support payments on incarcerated fathers after their release, finding that less than a third had their payments changed whilst in prison, and that over 90 percent had payments in arrears after release. They argue that the multiple social services involved with incarcerated fathers both pre and post imprisonment need to provide more coordinated support so that child support orders do not become unwieldy, burdensome arrears

Viruses in Cancers of the Digestive System: Active Contributors or Idle Bystanders?

the human virome, which is a collection of all the viruses that are present in the human body, is increasingly being recognized as an essential part of the human microbiota. the human gastrointestinal tract and related organs (e.g., liver, pancreas, and gallbladder)-composing the gastrointestinal (or digestive) system-contain a huge number of viral particles which contribute to maintaining tissue homeostasis and keeping our body healthy. however, perturbations of the virome steady-state may, both directly and indirectly, ignite/sustain oncogenic mechanisms contributing to the initiation of a dysplastic process and/or cancer progression. In this review, we summarize and discuss the available evidence on the association and role of viruses in the development of cancers of the digestive system

Above‐ and belowground strategies of tropical montane tree species are coordinated and driven by small‐scale nitrogen availability

The question whether the strategies of above- and belowground plant organs are coordinated as predicted by the plant economics spectrum theory is still under debate. We aim to determine the leading dimensions of tree trait variation for above- and belowground functional traits, and test whether they represent spectra of adaptation along a soil fertility gradient in tropical Andean forests.We measured leaf, stem and fine root functional traits, and individual-level soil nutrient availability for 433 trees from 52 species at three elevations between 1000 and 3000 m a.s.l.We found close coordination between above– and belowground functional traits related to the trade-off between resource acquisition and conservation, whereas root diameter and specific root length formed an independent axis of covarying traits. The position of a tree species along the acquisition–conservation axis of the trait space was closely associated with local soil nitrogen, but not phosphorus, availability.Our results imply that above- and belowground plant functional traits determine at which edaphic microhabitats coexisting tree species can grow, which is potentially crucial for understanding community assembly in species-rich tropical montane forests

Addressing controversies in the xylem embolism resistance–vessel diameter relationship

Although xylem embolism is a key process during drought-induced tree mortality, its relationship to wood anatomy remains debated. While the functional link between bordered pits and embolism resistance is known, there is no direct, mechanistic explanation for the traditional assumption that wider vessels are more vulnerable than narrow ones. We used data from 20 temperate broad-leaved tree species to study the inter- and intraspecific relationship of water potential at 50% loss of conductivity (P50) with hydraulically-weighted vessel diameter (Dh) and tested its link to pit membrane thickness (TPM) and specific conductivity (Ks) on species level. Embolism-resistant species had thick pit membranes and narrow vessels. While Dh was weakly associated with TPM, the P50 – Dh relationship remained highly significant after accounting for TPM. The interspecific pattern between P50 and Dh was mirrored by a link between P50 and Ks, but there was no evidence for an intraspecific relationship. Our results provide robust evidence for an interspecific P50 – Dh relationship across our species. As a potential cause for the inconsistencies in published P50 – Dh relationships, our analysis suggests differences in the range of traits values covered, and the level of data aggregation (species, tree, or sample level) studied.The data file is provided in a .csv format and can be opened with spreadsheet software such as LibreOffice or Microsoft Excel. Funding provided by: Deutsche ForschungsgemeinschaftCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100001659Award Number: 218894163Funding provided by: Deutsche ForschungsgemeinschaftCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100001659Award Number: 410768178This dataset is a supplement to Isasa et al. (2023) Addressing controversies in the xylem embolism resistance – vessel diameter relationship (DOI: 10.1111/nph.18731) with the raw data for the 20 temperate angiosperm tree species discussed in this manuscript. The dataset contains vulnerability curve parameters measured with the flow-centrifuge method, measurements of maximum specific conductivity obtained with a XylEm Plus device, as well as wood anatomical parameters from light microscopy (vessel diameter) and transmission electron microscopy (pit membrane characteristics). A detailed description of the measurement methods can be found in the original manuscript. For a description of the variable names of the provided variables including context about their measurement and the corresponding units, please see the README document ("README.md")

Anatomical adjustments of the tree hydraulic pathway decrease canopy conductance under long-term elevated CO2_2

The cause of reduced leaf-level transpiration under elevated CO$_2$ remains largely elusive. Here, we assessed stomatal, hydraulic, and morphological adjustments in a long-term experiment on Aleppo pine (Pinus halepensis) seedlings germinated and grown for 22–40 months under elevated (eCO$_2$; c. 860 ppm) or ambient (aCO$_2$; c. 410 ppm) CO$_2$. We assessed if eCO$_2$-triggered reductions in canopy conductance (g$_c$) alter the response to soil or atmospheric drought and are reversible or lasting due to anatomical adjustments by exposing eCO$_2$ seedlings to decreasing [CO$_2$]. To quantify underlying mechanisms, we analyzed leaf abscisic acid (ABA) level, stomatal and leaf morphology, xylem structure, hydraulic efficiency, and hydraulic safety. Effects of eCO$_2$ manifested in a strong reduction in leaf-level g$_c$ (−55%) not caused by ABA and not reversible under low CO$_2$ (c. 200 ppm). Stomatal development and size were unchanged, while stomatal density increased (+18%). An increased vein-to-epidermis distance (+65%) suggested a larger leaf resistance to water flow. This was supported by anatomical adjustments of branch xylem having smaller conduits (−8%) and lower conduit lumen fraction (−11%), which resulted in a lower specific conductivity (−19%) and leaf-specific conductivity (−34%). These adaptations to CO$_2$ did not change stomatal sensitivity to soil or atmospheric drought, consistent with similar xylem safety thresholds. In summary, we found reductions of g$_c$ under elevated CO$_2$ to be reflected in anatomical adjustments and decreases in hydraulic conductivity. As these water savings were largely annulled by increases in leaf biomass, we do not expect alleviation of drought stress in a high CO$_2$ atmosphere

Full genome characterization of porcine circovirus type 3 isolates reveals the existence of two distinct groups of virus strains

Background: The occurrence of the novel porcine circovirus type 3 (PCV3) was reported from the Americas, Asia arid Europe. Although this virus was detected in association with various clinical syndromes in pigs, its role as possible swine pathogen remains unclear. PCV3 was detected with high prevalence in Polish farms, but to date no genome sequences were available from European PCV3 strains. Methods: We collected 1060 serum samples from piglets at the age of 20-24 weeks from 53 farms distributed all over Germany. PCV3 DNA was detected using a real-time PCR and subsequently complete PCV3 genome sequences were obtained after multiply primed rolling circle amplification and sequencing of overlapping PCR products. Phylogenetic analysis was performed by neighbor-joining method and maximum likelihood method. Results: We obtained 15 complete PCV3 genome sequences as well as nine partial sequences including the putative ORFs 1, 2 and 3 from PCV3 viremic animals in German pig farms. Phylogenetic analysis of these German as well as 30 full genome sequences received from GenBank divided the PCV3 strains into two main groups and several subclusters. Furthermore, we were able to define group specific amino acid patterns in open reading frame 1 and 2. Conclusion: PCV3 is distributed with high prevalence in German pig industry. Phylogenetic analysis revealed two clearly separated groups of PCV3 strains, which might be considered as PCV3 genotypes. Specific nucleotide and amino acid marker positions may serve for easy and fast intraspecies classification and genotyping of PCV3 strains. No correlation between PCV3 variants with their geographical origin was evident We found the same diversity of PCV3 strains in Germany as in other countries. We hypothesize that PCV3 is not a newly emerging virus in the German pig population. Future studies will have to show, if PCV3 genotype specific biological properties are evident

Might some gamma ray bursts be an observable signature of natural wormholes?

The extragalactic microlensing scenario for natural wormholes is examined. It is shown that the main features of wormhole lensing events upon the light of distant Active Galactic Nuclei (AGNs) are similar to some types of already observed Gamma Ray Bursts (GRBs). Using recent satellite data on GRBs, an upper limit to the negative mass density -- ${\cal O} (10^{-36})$ g cm$^{-3}$ -- under the form of wormhole-like objects is presented.Comment: extended version, additions on GRB physics, background sources and cosmological consequences. Two ps figures. Accpeted for publication in Phys. Rev.

Electric Vehicles with Range Extenders : Evaluating the Contribution to the Sustainable Development of Metropolitan Regions

Electric vehicles play a key role in strategic development plans of urban regions in Europe because they are seen as a promising technology to promote environmental quality, livability, and sustainability. Studies on electric mobility mostly concentrate on battery electric cars and disregard hybrid technologies which could address the weakness of range limitations. Therefore, this paper studies the impact of extended range electric vehicle (EREV) solutions on travel behavior, energy demand, environment, and overall sustainable development in the greater Stuttgart region in Germany. An integrated large-scale simulation approach merging different models is applied for future scenarios in 2025. The results show that with EREVs (1) most travel patterns can be fulfilled, (2) the impact on electricity generation is marginal, and (3) there is a high potential to reduce local emissions in areas with high traffic density. Overall, electric mobility is evaluated as one component toward sustainable development in the study area. This study demonstrates the complexity of the topic and highlights the importance of addressing this issue with a multidisciplinary approac