Altered dynamics of forest recovery under a changing climate

Forest regeneration following disturbance is a key ecological process, influencing forest structure and function, species assemblages, and ecosystem–climate interactions. Climate change may alter forest recovery dynamics or even prevent recovery, triggering feedbacks to the climate system, altering regional biodiversity, and affecting the ecosystem services provided by forests. Multiple lines of evidence – including global‐scale patterns in forest recovery dynamics; forest responses to experimental manipulation of CO₂, temperature, and precipitation; forest responses to the climate change that has already occurred; ecological theory; and ecosystem and earth system models – all indicate that the dynamics of forest recovery are sensitive to climate. However, synthetic understanding of how atmospheric CO₂ and climate shape trajectories of forest recovery is lacking. Here, we review these separate lines of evidence, which together demonstrate that the dynamics of forest recovery are being impacted by increasing atmospheric CO₂ and changing climate. Rates of forest recovery generally increase with CO₂, temperature, and water availability. Drought reduces growth and live biomass in forests of all ages, having a particularly strong effect on seedling recruitment and survival. Responses of individual trees and whole‐forest ecosystems to CO₂ and climate manipulations often vary by age, implying that forests of different ages will respond differently to climate change. Furthermore, species within a community typically exhibit differential responses to CO₂ and climate, and altered community dynamics can have important consequences for ecosystem function. Age‐ and species‐dependent responses provide a mechanism by which climate change may push some forests past critical thresholds such that they fail to recover to their previous state following disturbance. Altered dynamics of forest recovery will result in positive and negative feedbacks to climate change. Future research on this topic and corresponding improvements to earth system models will be a key to understanding the future of forests and their feedbacks to the climate system.     

The Receptor-Like Protein ReMAX of Arabidopsis Detects the Microbe-Associated Molecular Pattern eMax from Xanthomonas

As part of their immune system, plants have pattern recognition receptors (PRRs) that can detect a broad range of microbe-associated molecular patterns (MAMPs). Here, we identified a PRR of Arabidopsis thaliana with specificity for the bacterial MAMP eMax from xanthomonads. Response to eMax seems to be restricted to the Brassicaceae family and also varied among different accessions of Arabidopsis. In crosses between sensitive accessions and the insensitive accession Shakhdara, eMax perception mapped to RECEPTOR-LIKE PROTEIN1 (RLP1). Functional complementation of rlp1 mutants required gene constructs that code for a longer version of RLP1 that we termed ReMAX (for receptor of eMax). ReMAX/RLP1 is a typical RLP with structural similarity to the tomato (Solanum lycopersicum) RLP Eix2, which detects fungal xylanase as a MAMP. Attempts to demonstrate receptor function by interfamily transfer of ReMAX to Nicotiana benthamiana were successful after using hybrid receptors with the C-terminal part of ReMAX replaced by that of Eix2. These results show that ReMAX determines specificity for eMax. They also demonstrate hybrid receptor technology as a promising tool to overcome problems that impede interfamily transfer of PRRs to enhance pathogen detection in crop plants.     

Modelling dendritic ecological networks in space: an integrated network perspective

Dendritic ecological networks (DENs) are a unique form of ecological networks that exhibit a dendritic network topology (e.g. stream and cave networks or plant architecture). DENs have a dual spatial representation; as points within the network and as points in geographical space. Consequently, some analytical methods used to quantify relationships in other types of ecological networks, or in 2‐D space, may be inadequate for studying the influence of structure and connectivity on ecological processes within DENs. We propose a conceptual taxonomy of network analysis methods that account for DEN characteristics to varying degrees and provide a synthesis of the different approaches within the context of stream ecology. Within this context, we summarise the key innovations of a new family of spatial statistical models that describe spatial relationships in DENs. Finally, we discuss how different network analyses may be combined to address more complex and novel research questions. While our main focus is streams, the taxonomy of network analyses is also relevant anywhere spatial patterns in both network and 2‐D space can be used to explore the influence of multi‐scale processes on biota and their habitat (e.g. plant morphology and pest infestation, or preferential migration along stream or road corridors).     

Morphological and genetic analyses of xeniid soft coral diversity (Octocorallia; Alcyonacea)

Studies on the biodiversity and evolution of octocorals are hindered by the incomplete knowledge of their taxonomy, which is due to few reliable morphological characters. Therefore, assessment of true species diversity within abundant and ecologically important families such as Xeniidae is difficult. Mitochondrial genes provide a reliable solution to this problem for a wide range of taxa. However, low mutation rates of the mitochondrial DNA in octocorals result in insufficient variability for species discrimination. We compared the variation of a fragment of the Signal Recognition Particle 54 gene (SRP54, proposed for octocorals) and the mitochondrial ND6/ND3 marker among members of the xeniid genera Ovabunda, Xenia, Heteroxenia and Bayerxenia. The mean uncorrected pairwise sequence divergence was 39 % for SRP54 compared to 2 % for ND6/ND3. Morphological assignments were not always supported by genetics: Species diversity was underestimated (one case) or overestimated, probably reflecting intraspecific polymorphisms or hinting at recent speciations. ND6/ND3 is informative for some species-level assignments, whereas SRP54 shows the variability needed for species delimitations within this understudied taxon. Our results on both genes show their potential for evolutionary and biodiversity studies in Xeniidae.     

Diversion of phagosome trafficking by pathogenic Rhodococcus equi depends on mycolic acid chain length

Rhodococcus equi is a close relative of Mycobacterium spp. and a facultative intracellular pathogen which arrests phagosome maturation in macrophages before the late endocytic stage. We have screened a transposon mutant library of R. equi for mutants with decreased capability to prevent phagolysosome formation. This screen yielded a mutant in the gene for β‐ketoacyl‐(acyl carrier protein)‐synthase A (KasA), a key enzyme of the long‐chain mycolic acid synthesizing FAS‐II system. The longest kasA mutant mycolic acid chains were 10 carbon units shorter than those of wild‐type bacteria. Coating of non‐pathogenic E. coli with purified wild‐type trehalose dimycolate reduced phagolysosome formation substantially which was not the case with shorter kasA mutant‐derived trehalose dimycolate. The mutant was moderately attenuated in macrophages and in a mouse infection model, but was fully cytotoxic.Whereas loss of KasA is lethal in mycobacteria, R. equi kasA mutant multiplication in broth was normal proving that long‐chain mycolic acid compounds are not necessarily required for cellular integrity and viability of the bacteria that typically produce them. This study demonstrates a central role of mycolic acid chain length in diversion of trafficking by R. equi.     

Evaluating hormonal mechanisms of vitamin D receptor agonist therapy in diabetic kidney disease: the VALIDATE-D study

Studies have shown that group Therapeutic Patient Education (TPE) may empower patients with type 2 diabetes to better manage their disease. The mechanism of these interventions is not fully understood. A reduction in resistance to treatment may explain the mechanism by which TPE empowers participants to improve self-management. The Objective of this study was to examine the effectiveness of diabetes groups in reducing resistance to treatment and the association between reduced resistance and better management of the disease. In a program evaluation study, we administered validated questionnaires to measure resistance to treatment (RTQ) in 3 time periods: before the intervention (T1), immediately after the intervention (T2) and six months later (T3). Clinical measures (HbA1C, blood pressure, HDL, LDL and total cholesterol, Triglycerides and BMI) were retrieved from Maccabi Healthcare Services computerized systems, for T1;T2 and a year post intervention (T3). Linear mixed models were used adjusting for age, gender, social support and family status. 157; 156 and 106 TPE participants completed the RTQ in T1; T2 and T3 respectively. HbA1C and systolic and diastolic blood pressure were significantly reduced in the group which achieved a reduction in three out of the five RTQ components. For the other clinical measurements no significant changes were observed. Our findings suggest that reducing resistance to treatment, through an educational program for patients with diabetes, is associated with a better disease control. Identifying patients with higher resistance to treatment, and including components that reduce resistance in patient education programs, have the potential to increase the effectiveness of these programs.     

Wave exposure shapes reef community composition and recovery trajectories at a remote coral atoll

In a time of unprecedented ecological change, understanding natural biophysical relationships between reef resilience and physical drivers is of increasing importance. This study evaluates how wave forcing structures coral reef benthic community composition and recovery trajectories after the major 2015/2016 bleaching event in the remote Chagos Archipelago, Indian Ocean. Benthic cover and substrate rugosity were quantified from digital imagery at 23 fore reef sites around a small coral atoll (Salomon) in 2020 and compared to data from a similar survey in 2006 and opportunistic surveys in intermediate years. Cluster analysis and principal component analysis show strong separation of community composition between exposed (modelled wave exposure > 1000 J m⁻³) and sheltered sites (< 1000 J m⁻³) in 2020. This difference is driven by relatively high cover of Porites sp., other massive corals, encrusting corals, soft corals, rubble and dead table corals at sheltered sites versus high cover of pavement and sponges at exposed sites. Total coral cover and rugosity were also higher at sheltered sites. Adding data from previous years shows benthic community shifts from distinct exposure-driven assemblages and high live coral cover in 2006 towards bare pavement, dead Acropora tables and rubble after the 2015/2016 bleaching event. The subsequent recovery trajectories at sheltered and exposed sites are surprisingly parallel and lead communities towards their respective pre-bleaching communities. These results demonstrate that in the absence of human stressors, community patterns on fore reefs are strongly controlled by wave exposure, even during and after widespread coral loss from bleaching events.

     

Electron and proton transport in wheat exposed to salt stress: is the increase of the thylakoid membrane proton conductivity responsible for decreasing the photosynthetic activity in sensitive genotypes?

Photosynthesis Research - Effects of salinity caused by 150&nbsp;mM NaCl on primary photochemical reactions and some physiological and biochemical parameters (K+/Na+ ratio, soluble sugars,...