Relative density of United States forests has shifted to higher levels over last two decades with important implications for future dynamics

Tree size-density dynamics can inform key trends in forest productivity along with opportunities to increase ecosystem resiliency. Here, we employ a novel approach to estimate the relative density (RD, range 0–1) of any given forest based on its current size-density relationship compared to a hypothetical maximum using the coterminous US national forest inventory between 1999 and 2020. The analysis suggests a static forest land area in the US with less tree abundance but greatly increased timber volume and tree biomass. Coupled with these resource trends, an increase in RD was identified with 90% of US forest land now reaching a biologically-relevant threshold of canopy closure and/or self-thinning induced mortality (RD > 0.3), particularly in areas prone to future drought conditions (e.g., West Coast). Notably, the area of high RD stands (RD > 0.6) has quintupled over the past 20 years while the least stocked stands (RD < 0.3) have decreased 3%. The evidence from the coterminous US forest RD distribution suggest opportunities to increase live tree stocking in understocked stands, while using density management to address tree mortality and resilience to disturbances in increasingly dense forests.

Improving the understanding of cytoneme-mediated morphogen gradients by in silico modeling

Morphogen gradients are crucial for the development of organisms. The biochemical properties of many morphogens prevent their extracellular free diffusion, indicating the need of an active mechanism for transport. The involvement of filopodial structures (cytonemes) has been proposed for morphogen signaling. Here, we describe an in silico model based on the main general features of cytoneme-meditated gradient formation and its implementation into Cytomorph, an open software tool. We have tested the spatial and temporal adaptability of our model quantifying Hedgehog (Hh) gradient formation in two Drosophila tissues. Cytomorph is able to reproduce the gradient and explain the different scaling between the two epithelia. After experimental validation, we studied the predicted impact of a range of features such as length, size, density, dynamics and contact behavior of cytonemes on Hh morphogen distribution. Our results illustrate Cytomorph as an adaptive tool to test different morphogens gradients and to generate hypotheses that are difficult to study experimentally.

Male age and Wolbachia dynamics: Determining how fast and why bacterial densities and cytoplasmic incompatibility strengths vary

Endosymbiotic Wolbachia bacteria infect divergent arthropod and nematode hosts. Many strains cause cytoplasmic incompatibility (CI) that kills uninfected embryos fertilized by Wolbachia-modified sperm. Infected embryos are protected from CI, promoting Wolbachia spread to high equilibrium frequencies balanced by imperfect maternal transmission. CI strength varies widely in nature and tends to decrease as males age. Understanding the causes of CI-strength variation is crucial to explain Wolbachia prevalence in host populations. Here, we investigate how fast and why CI strength decreases with male age in two model systems: wMel in Drosophila melanogaster and wRi in D. simulans. Average wMel CI strength decreases rapidly (19%/ day), and wRi CI strength decreases slowly (6%/ day) as males age; thus, within three days, wMel-infected males do not cause CI, whereas twelve-day-old wRi-infected males still cause minor, yet significant, CI. We tested if reductions in Wolbachia densities or CI gene expression as males age could explain this pattern. Indeed, wRi densities and CI gene expression decrease in testes as males age, but wMel densities and CI gene expression surprisingly increase with male age as CI strength decreases. Phage WO lytic activity and wMel Octomom copy number-an ampliconic gene region that influences wMel proliferation-do not explain age-dependent Wolbachia densities. However, the expression of Relish, an essential gene in the Drosophila immune deficiency pathway, strongly correlates with wMel densities. Together, these results suggest that testes-wide Wolbachia density and CI gene expression are insufficient to explain age-dependent CI strength across strains and that Wolbachia density is variably impacted by male age across Wolbachia-host associations. We hypothesize that host immunity may underlie variation in age-dependent density dynamics. More broadly, the rapid decline of wMel CI strength during the first week of D. melanogaster life likely contributes to wMel frequency variation observed on several continents.

Improving the understanding of cytoneme-mediated morphogen gradients by in silico modeling

Morphogen gradients are crucial for the development of organisms, but there is still no agreement on the mechanisms involved in their establishment. The biochemical properties of many morphogens prevent their extracellular free diffusion, indicating the need for an active mechanism for transport. The involvement of filopodial structures (cytonemes) has been proposed for morphogen signaling, although a detailed description of the mechanism is pending. Here, we describe the development of an in silico model based on the main general features of cytoneme-meditated gradient formation and its implementation into an open software tool we named Cytomorph. We have tested the spatial and temporal adaptability of our model experimentally quantifying Hedgehog (Hh) gradient formation in Drosophila and found that Cytomorph is able to reproduce the gradient and explain its scaling between different epithelia. After experimental validation, we studied the predicted impact of a range of features such as length, size, density, dynamics and contact behavior of cytonemes on morphogen distribution. Our results illustrate Cytomorph as an adaptive tool to test and generate hypotheses that are difficult to study experimentally.

The diamondback moth Plutella xylostella: ecological and biological aspects, harmfulness, population control

Data on prevalence, biological and physiological characteristics of the diamondback moth Plutella xylostella (Lepidoptera: Plutellidae) are presented. Pest damage is described. Reasons causing increase in harmfulness and economic importance of the insect are noted. An increase in the number of generations able to develop during growing season and earlier pest emergence are recorded under conditions of Siberian region. Factors contributing to the insect density dynamics, including plant species and variety, entomophagous arthropods and entomopathogenic microorganisms, have been considered. Range of chemical insecticides recommended for diamondback moth management in Russian Federation has been indicated. An increase in resistance to chemicals and certain entomopathogens in P. xylostella populations in different regions of the world has been recorded. Possibility of pheromone traps exploitation for efficient pest detection and monitoring has been established. Perspectives of novel efficient and safe means of pest density regulation have been defined.

Modelling quenching mechanisms of disordered molecular systems in presence of molecular aggregates

The exciton density dynamics recorded in time-resolved spectroscopic measurements is a useful tool to recover information on energy transfer (ET) processes that can occur at different timescales, up to the...

Density Dynamics and Plankton Diversity in Pond with Different Bases at Faculty of Fisheries and Marine Education Pond

The availability of plankton in the waters is influenced by nutrient content, and the waters physics-chemical conditions. The higher the nutrient content in a waters, the higher phytoplankton abundance in the waters will be.This research is conducted at faculty of fisheries and marine education pond Airlangga University. It is aimed to density dynamics and plankton diversity in pond with different bases. This research method uses survey method.The reseach results shows that the highest density in tarpaulin pond is located at point four on the first day that reaches 1,822,000 ind/l, The highest total density on the ground pools is got on first day on the first point of 245,000 ind/l.