High Potential Growth Rates Research Articles (Page 1)

Understanding the relationships between species' demography and functional traits is crucial for gaining a mechanistic understanding of community dynamics. While leaf morphology represents a key functional dimension for plants worldwide (i.e., the leaf economics spectrum), its ability to explain variation in trees' life history strategies remains limited. Plant growth is influenced by both leaf morphology and allocation; hence, incorporating both dimensions is essential but rarely done. Additionally, trait–performance relationships have mainly been studied in tropical communities, leaving gaps in our understanding of temperate forests where different seasonality patterns may alter these relationships. We examined whether species' leaf area index (leaf area per crown size, LAI), a measure of leaf allocation, explains the variation of juvenile tree species' potential growth rates in a winter‐deciduous broadleaf forest. LAI has not been characterized as a species‐level trait, but its ability to predict plant productivity at the ecosystem scale highlights its potential for explaining plant growth. We evaluated species' maximum LAI both individually and in conjunction with wood density (WD) and leaf mass per area (LMA). We expected that models would improve when both leaf morphology (LMA) and leaf allocation (LAI) were included and that species with denser crowns would have higher potential growth rates. LAI and LMA were significant predictors of growth but only when both were incorporated, and together explained a high proportion of species' growth variations (R2adj = 0.59). We found evidence of a trade‐off between LAI and LMA, with a negative relationship between them and each having a positive influence on species' growth, suggesting that there are multiple allocation strategies to achieve fast growth. A surprisingly positive LMA–growth relationship contrasts with observations from tropical forests. We did not find significant relationships with WD in this forest. Our results highlight that incorporating leaf allocation improves models of trait–performance relationships. They also suggest, in agreement with the limited literature, that temperate forests may exhibit different trait–performance relationships from those of tropical forests, where LMA is negatively related to growth and WD is often important. Clarifying the details and contexts of trait–performance relationships is crucial for applying the functional trait framework to understanding community structure and dynamics of forests globally.

Organic polar small molecules exhibit spontaneous orientation polarization (SOP) in vacuum-deposited amorphous films. This phenomenon arises because of the asymmetric molecular interactions at the interface between the film surface and vacuum during the deposition process. Here, we investigate the impact of functional groups on the SOP of bent-shaped polar molecules. The results demonstrate that the differences in polarizability between the head and tail functional groups in polar molecules drive the orientation polarization in the films. Enhancing the SOP involves the introduction of two functional groups with distinct polarizabilities in the head and tail groups to promote asymmetric interactions. The developed polar molecule, incorporating bulky alkyl and sulfonyl groups, exhibits a high surface potential growth rate of +321 mV nm−1 in the SOP film. These findings enable the precise control of the molecular orientation in amorphous films and the development of highly polarized electret materials without charging processes.

This study aims to determine the effect of Return on Asset (ROA), Sales Growth, Liquidity and Company Size on the capital structure of the banking industry listed on the Indonesia Stock Exchange in 2019-2023. This study uses secunter data with panel data regression as an analysis tool and data processing assistance with Eviews. The results of hypothesis testing show that ROA has no significant effect on capital structure, that companies that use relatively small debt have a high rate of return on investment. Sales growth does not have a significant effect on the mode structure, where companies that have a high potential sales growth rate will tend to generate greater cash flow so that the company will ultimately rely more on internal funding. Liquidity has a significant effect on the capital structure, where if the greater the liquidity, the greater the capital structure and if the smaller the liquidity, the smaller the capital structure. The size of the company does not have a significant effect on the capital structure, this can be interpreted that the size of a company does not affect the capital structure of the Company. The results of this study are also expected to be a reference for future research to increase the number of research variables and increase the number of research populations in various sectors and increase the research period.

Abstract Recent increases in wildlife cause negative impacts on humans through both economic and ecological damage, as well as the spread of pathogens. Understanding the population dynamics of wildlife is crucial to develop effective management strategies. However, it is difficult to estimate accurate and precise population size over large spatial and temporal scales because of the limited data availability. We addressed these issues by first fitting a random encounter and staying time (REST) model based on camera trap data to construct an informative prior distribution for a capture rate parameter in a harvest‐based Bayesian state‐space model. We constructed a Bayesian state‐space model that integrated administration data on the number of captured wild boar with the prior distribution of capture efficiency estimated by camera trap data. The model with informative prior distribution from the REST model successfully estimated population dynamics, whereas the model using only the administration data did not, owing to a lack of parameter convergence. We identified areas where (1) wild boars exhibit a high potential population growth rate and a high carrying capacity, (2) current trapping efforts are effectively suppressing local populations, and (3) trapping reinforcement is required to control populations in the whole region. The model could be used to predict future trends in populations under the assumptions of ongoing trapping pressure. This will help identify spatially explicit trapping efforts to achieve target population levels.

Abstract QuestionsTwo central pathways have been proposed to dictate the relationship between community structure and ecosystem function: the “diversity effect” — trait variation allowing complementary resource use, and the “mass ratio effect” — ecosystem function determined overwhelmingly by the functional traits of the dominant species which shape the “functional identity”, i.e., community‐weighted mean trait values. However, the distinct effect of each pathway on ecosystem function is difficult to determine as they are complementary and shaped by environmental heterogeneity. We examined the distinct effects of functional diversity (FD) and identity (FI) on water consumption and use efficiency (WUE), vegetative and reproductive biomass production and reorganization capacity under variable water availability.MethodsEight semiarid annual plant species, varying in natural size range, were grown in different assemblages representing various levels of FD and FI. Assemblages were based on species potential growth rate (PGR) and grown under two water availability levels. We measured total biomass, seed biomass, root to shoot ratio and water consumption.ResultsFD had a distinct positive effect on water consumption, total biomass and seed production but not on WUE. Mean PGR (FI) had a distinct positive effect on water consumption and total biomass production, but a negative effect on WUE and seed production. FD and FI had no clear effects on reorganization capacity or stability in total biomass production in response to decreased water availability.ConclusionsWe present the discrete contributions of FD and FI to ecosystem function. The positive effect of FD on biomass production reflects better exploitation of the growing space and reduced competition through greater size diversity, emphasizing the importance of interplant interactions and differentiation for enhancing ecosystem function. The positive effect of FI on biomass production reflects the higher performance of high PGR species, albeit at the expense of WUE and seed production resulting from higher competition.

Loblolly pine plantations in the western portion of the species’ range are sometimes planted with genotypes from the eastern portion of its range to improve plantation productivity. Advances in loblolly pine breeding have led to the development of clonally propagated genotypes with higher potential growth rates and better form than more commonly planted half-sib genotypes. At a site in the western portion of the loblolly pine range, four genotypes from the eastern portion of the loblolly pine range were established. Two genotypes (HS756 and HS8103) were half-sib, and two genotypes (V9 and V93) were varieties. The V93 genotype was propagated from the HS756 genotype. The objective of this study was to determine the effects of genotype on seasonal trends in gas exchange parameters at the leaf and crown levels, growth, and biomass allocation patterns. During the two-year study, one year had precipitation and temperature trends similar to the long-term average and one year had extreme drought, with record heat. The HS756, V9, and V93 genotypes had the highest height growth throughout the study. The V93 genotype was sensitive to the drought; its leaf- and crown-levelAsatandgs, declined during the drought more markedly than those of the other genotypes. Although itsAsatandgswere affected by drought, height growth productivity of V93 may have been sustained during the drought by its biomass partitioning pattern of allocating higher proportions of its root biomass to small and fine roots and its aboveground biomass to foliage. These results suggest that a variety such as V93 could be more susceptible to changes in C fixation and water uptake with recurrent drought.

Desert annuals are a critically important component of desert communities and may be particularly responsive to increasing atmospheric (CO2 ) because of their high potential growth rates and flexible phenology. During the 10-year life of the Nevada Desert FACE (free-air CO2 enrichment) Facility, we evaluated the productivity, reproductive allocation, and community structure of annuals in response to long-term elevated (CO2 ) exposure. The dominant forb and grass species exhibited accelerated phenology, increased size, and higher reproduction at elevated (CO2 ) in a wet El Niño year near the beginning of the experiment. However, a multiyear dry cycle resulted in no increases in productivity or reproductive allocation for the remainder of the experiment. At the community level, early indications of increased dominance of the invasive Bromus rubens at elevated (CO2 ) gave way to an absence of Bromus in the community during a drought cycle, with a resurgence late in the experiment in response to higher rainfall and a corresponding high density of Bromus in a final soil seed bank analysis, particularly at elevated (CO2 ). This long-term experiment resulted in two primary conclusions: (i) elevated (CO2 ) does not increase productivity of annuals in most years; and (ii) relative stimulation of invasive grasses will likely depend on future precipitation, with a wetter climate favoring invasive grasses but currently predicted greater aridity favoring native dicots.

During the 2010–2011 ‘Impacts of Climate Change on the EcoSystems and Chemistry of the Arctic Pacific Environment’ project, we measured photosynthetic parameters in natural Arctic phytoplankton assemblages from the Chukchi and Beaufort seas. Water‐column samples were taken from the near surface (3.1 ± 0.9 m) and subsurface (28 ± 10.3 m) at ∼ 85 stations each year representing a wide range of ecological conditions, including under sea ice (UI) and in open water (OW). The physiological response of phytoplankton to light was used to assess photo‐acclimation, photosynthetic efficiency, and maximum chlorophyll a (Chl a) normalized rates of carbon fixation. Phytoplankton from the subsurface were acclimated to lower irradiance, as evidenced by higher photosynthetic efficiencies (α*), reduced mean absorption spectra (ā*) associated with heavy pigment packaging, higher maximum quantum yields of photosynthesis (Φm), increased Chl a content (Chl a : POC), and higher potential growth rates (μm) than surface samples. In addition, phytoplankton growing in the UI subsurface had higher μm, increased Φm, and higher Chl a content, as well as reduced ā* compared with those found in OW. P*m did not vary between habitats despite vastly different nutrient and light conditions (averaging ∼ 1 mg C mg−1 Chl a h−1), except where nitrate exceeded > 10 mg m−3, in which case P*m averaged 5–6 mg C mg−1 Chl a h−1. Results from a stepwise regression analysis of photosynthetic parameters vs. environmental factors indicate that the concentration of inorganic nitrogen (significant relationships with P*m, α*, Φm, μm, and Chl a : POC) and temperature at sample depth (a strong indicator of habitat type; significant relationship with β*, ā*, Φm, μm, and Chl a : POC) are the best predictors of photosynthetic variables. In addition, the amount of light available at sample depth significantly predicted both Ek and Chl a : POC. Our results suggest that it is the balance between light and nutrient availability in the various environments encountered in the seasonal sea ice zone that result in the pattern of photo‐physiological data presented here. A significant proportion of primary production has now been observed to occur under the sea ice; therefore, our results may be a change from prior conditions in the region.

SummaryPast studies have shown that the strength of top‐down herbivore control on plant physiological performance, abundance and distribution patterns can shift with abiotic stress, but it is still unclear whether herbivores generally exert stronger effects on plants in stressful or in nonstressful environments.One hypothesis suggests that herbivores' effects on plant biomass and fitness should be strongest in stressful areas, because stressed plants are less able to compensate for herbivore damage. Alternatively, herbivores may reduce plant biomass and fitness more substantially in nonstressful areas, either because plant growth rates in the absence of herbivory are higher and/or because herbivores are more abundant and diverse in nonstressful areas.We test these predictions of where herbivores should exert stronger effects by measuring individual performance, population size structure and densities of a common subshrub,Hibiscus meyeri, in a large‐scale herbivore exclosure experiment arrayed across an aridity gradient in East Africa.We find support for both predictions, with herbivores exerting stronger effects on individual‐level performance in arid (stressful) areas, but exerting stronger effects on population size structure and abundance in mesic (nonstressful) areas. We suggest that this discrepancy arises from higher potential growth rates in mesic areas, where alleviation of herbivory leads to substantially more growth and thus large changes in population size structure. Differences in herbivore abundance do not appear to contribute to our results.Synthesis. Our work suggests that understanding the multiple facets of plant response to herbivores (e.g. both individual performance and abundance) may be necessary to predict how plant species' abundance and distribution patterns will shift in response to changing climate and herbivore numbers.

A 4-year fertilization experiment with nitrogen (N) and phosphorus (P) was carried out in natural gaps of a subtropical forest in northeastern Argentina. Saplings of six dominant canopy species differing in shade tolerance were grown in five control and five N + P fertilized gaps. Hydraulic architectural traits such as wood density, the leaf area to sapwood area ratio (LA : SA), vulnerability to cavitation (P50) and specific and leaf-specific hydraulic conductivity were measured, as well as the relative growth rate, specific leaf area (SLA) and percentage of leaf damage by insect herbivores. Plant growth rates and resistance to drought-induced embolisms increased when nutrient limitations were removed. On average, the P50 of control plants was -1.1 MPa, while the P50 of fertilized plants was -1.6 MPa. Wood density and LA : SA decreased with N + P additions. A trade-off between vulnerability to cavitation and efficiency of water transport was not observed. The relative growth rate was positively related to the total leaf surface area per plant and negatively related to LA : SA, while P50 was positively related to SLA across species and treatments. Plants with higher growth rates and higher total leaf area in fertilized plots were able to avoid hydraulic dysfunction by becoming less vulnerable to cavitation (more negative P50). Two high-light-requiring species exhibited relatively low growth rates due to heavy herbivore damage. Contrary to expectations, shade-tolerant plants with relatively high resistance to hydraulic dysfunction and reduced herbivory damage were able to grow faster. These results suggest that during the initial phase of sapling establishment in gaps, species that were less vulnerable to cavitation and exhibited reduced herbivory damage had faster realized growth rates than less shade-tolerant species with higher potential growth rates. Finally, functional relationships between hydraulic traits and growth rate across species and treatments were maintained regardless of soil nutrient status.

Dynamic relationships among equity flows, equity returns and dividends: Behavior of U.S. investors in China and India

Pizzatto & Shine (2012) noted the serious impacts that the introduced cane toad Rhinella marina has caused to its predators in Australia. The toad’s range is expanding at an increasing rate and additional negative consequences are predicted. Control measures have been ineffective or in some cases have not been tried. Female toads have a very high fecundity, and the species has a high potential growth rate. High removal rates of the toad population are needed to eliminate the species, suggesting that physical removal is not practical (Shine & Doody, 2010). One approach to controlling the toad species is biological control, which has been effective in some cases in Australia and elsewhere (Saunders et al., 2010). Biological control usually involves introduction of a species that in its native range controls the population of the pest species. However, introducing an exotic species as a biocontrol agent can have negative effects on nontarget species and potentially on ecosystem function (Simberloff & Stiling, 1996). Use of a native species as a biological control agent eases these concerns, but may involve a protocol to increase the abundance and distribution of a native control agent. In the case of the cane toad, one goal of biocontrol can be slowing the rate of expansion. Individuals at the leading edge of expansion have greater locomotor endurance, and the authors suggest that this may be due to escape from a lungworm parasite that infects toads behind the leading edge. Therefore, the authors test aspects of a general hypothesis that posits that lungworm parasites can be used as a biocontrol agent to slow the toads’ advance. This may not be an entirely satisfactory solution, but slowing the toads’ advance might buy time to develop other ways to control the species’ numbers. As the lungworm is already present in the toads and likely was present in the toads when they were introduced to Australia in 1935, it is not considered an exotic species. The authors suggest that one way to increase the prevalence of lungworm infection is to infect a native tree frog species, Litoria caerulea, which does not seem to be negatively affected by the parasite. They also propose three primary assumptions necessary for biocontrol to work in this case: the parasite does not harm the tree frogs, the tree frogs can maintain an infection over the long term, and infective larvae of the parasite can be transmitted to cane toads and reduce viability of the toads. They test aspects of these assumptions in their paper. Pizzatto and Shine showed that the tree frogs were infected at a 50% rate at the end of the experiment, and this was after placing the lungworm in the mouths of the frogs. All parasite-exposed frogs survived, and their growth rate was not different from that of uninfected controls. It would be important to compare the growth of infected frogs and uninfected frogs as the ‘parasite-exposed’ treatment apparently contained frogs that were not infected or had cleared the infection. Of those frogs that were infected, they had on average a low intensity (1.67 parasites per frog). It is unclear that this intensity would have the desired effect of transmission of larvae to toads. To test for transmission to the toads, lungworm larvae were put in boxes housing five toads. About half of the toads were infected under these laboratory conditions. In terms of fitness effects on the toads, there was no survival difference between infected and uninfected, no difference in body mass and no difference in sprint speeds. The authors did find that toads exposed to lungworms had lower stamina than did controls. Laboratory conditions are likely to maximize transmission of parasites as toads were under high density conditions, and their movements were constrained. However, under these conditions, parasite prevalence in frogs and toads averaged 50%. Importantly, only minor fitness effects were seen in the toads. Based on these results, it seems doubtful that control would be effective in nature. There are other reasons to be skeptical that biocontrol would be effective in this case. Is the lungworm a factor in population control in other parts of the toads’ range where prevalence is high? If not, why would it be expected to work bs_bs_banner

The influence of competition between lichen colonization and erosion on the evolution of soil surfaces in the Tabernas badlands (SE Spain) and its landscape effects

Abstract The invasive grass Bromus tectorum (cheatgrass, downy brome) has extensive ecological breadth in its introduced range, and is increasing in abundance at high elevations. As a predominantly selfing species with high potential population growth rates, it is a likely candidate for having general-purpose genotypes that facilitate its invasion into high elevations. We evaluated evidence for general-purpose genotypes by examining phenotypic and molecular variation in B. tectorum from low- and high-elevation sites in the Rocky Mountains. Common garden experiments revealed that plants from high elevations germinated faster, but no other phenological, morphological, or physiological differences were found between elevations. Leaf length was longer for low-elevation sites in a common garden using field-collected seeds, but this was not found in a common garden using greenhouse-grown seeds, suggesting maternal effects. For most traits, there was significant phenotypic variation among sites and individuals. ...

Metabolic rates and thermal tolerances of chemoautotrophic symbioses from Lau Basin hydrothermal vents and their implications for species distributions

Abstract Ample evidence exists that an increase in the inbreeding level of a population reduces the value of fitness components such as fecundity and survival. It does not follow, however, that these decreases in the components of fitness impact population dynamics in a way that increases extinction risk, because virtually all species produce far more offspring than can actually survive. We analyzed the effects of the genetic quality (mean fitness) of individuals on the population growth rate of seven natural populations in each of two species of wolf spider in the genus Rabidosa, statistically controlling for environmental factors. We show that populations of different sizes, and different inbreeding levels, differ in population dynamics for both species. Differences in population growth rates are especially pronounced during stressful environmental conditions (low food availability) and the stressful environment affects smaller populations (<500 individuals) disproportionately. Thus, even in an invertebrate with an extremely high potential growth rate and strong density‐dependent mortality rates, genetic factors contribute directly to population dynamics and, therefore, to extinction risk. This is only the second study to demonstrate an impact of the genetic quality of individual genotypes on population dynamics in a wild population and the first to document strong inbreeding–environment interactions for fitness among populations. Endangered species typically exist at sizes of a few hundred individuals and human activities degrade habitats making them innately more stressful (e.g. global climate change). Therefore, the interaction between genetic factors and environmental stress has important implications for efforts aimed at conserving the Earth's biodiversity.

The purpose of this paper is to analyze Egypt's experience in deploying e-signature with Public Key Infrastructure (PKI) support. The paper identifies the supply and demand drivers and the size and potential growth of the market in Egypt. It is shown that the supply of the e-signature in Egypt is a cost-plus based. The market is relatively competitive and the market size is currently small, thus has high potential growth rate. Fully utilized deployed e-signature systems in major public utilities and services could lead to savings that amount to USD 100 million, an amount equal to Egypt's total IT exports per year. Outsourcing managed PKI services for financial and large-sized enterprises and e-government initiatives will drive large demand. Further developments in major information security-related areas are necessary and suggested.

Ariake Sound is a shallow, eutrophic estuarine system, located in the western part of Japan. We conducted field surveys and experiments in late autumn in 2002, 2003 and 2004 to clarify plankton community structure and trophic interactions in this system. A large photosynthetic dinofla- gellate (Akashiwo sanguinea) was persistent and the dominant phytoplankton species in all years. Diatoms and other photosynthetic flagellates were relatively minor components of the assemblage. The growth of photosynthetic flagellates such as Prorocentrum micans and cryptophycean flagellates under nutrient-enriched conditions was almost balanced with the grazing losses caused by a micro- zooplankton population dominated by protozoans, rotifers and cyclopoid copepods. Thus, P. micans and cryptophycean flagellates could not propagate their populations in the field. Diatoms had high potential growth rates and were subjected to low grazing pressure by the micro- and mesozooplank- ton. However, diatom growth was severely limited by light in this highly turbid estuarine system, and light limitation probably prevented diatoms from becoming dominant. A. sanguinea was grazed on by the ciliate Tiarina fusus, but the growth rates of A. sanguinea exceeded grazing losses by T. fusus; other zooplankton species did not graze on this dinoflagellate effectively. A. sanguinea accumulated at the surface layer in the turbid water during daytime, and thus could utilize light effectively. Low grazing pressure by zooplankton and avoidance of light limitation seem to have led to the persistent dominance of A. sanguinea, even though the potential growth rate of this species is moderate to low.

Biological control of harmful algal blooms: A modelling study

Abstract Sprouting vigour is determined by the plant amount of reserves and intrinsic growth rate of plants. While the first factor has been well studied, the second is far less understood. Although a higher growth rate would imply a higher sprouting vigour, fast‐growing species may have less below‐ground reserves, and thus, a lower sprouting potential. The relative importance of both opposite effects was little explored in the literature. To analyse the influence of growth rate on sprouting vigour, one growth season after a fire we measured plant height of the old (pre‐fire) and new (post‐fire) tissue in 194 individuals of 14 woody species from a woodland in central Argentina. We calculated a mean value of pre‐ and post‐fire height for each species, and obtained from a database potential height at maturity, wood density (WD) and specific leaf area (SLA), as surrogates of intrinsic growth rate. We performed a forward stepwise multiple regression using WD and SLA, together with mean pre‐fire height or potential height as independent variables, and mean post‐fire height (as an indicator of resprout vigour) as the dependent variable. Interactions were also tested. Pre‐fire height, WD and their interaction term were the variables that best explained post‐fire height. We also analysed the relationship between pre‐ and post‐fire size for each species independently by fitting hyperbolic functions. Then we correlated both parameters of the functions to species characteristics (WD, SLA, potential height and mean pre‐fire height). Both parameters of the hyperbolic functions were significantly correlated only with WD, but not with the other species characteristics. All results together indicate that species with low WD (i.e. high potential growth rate) regrow more vigorously than species with high WD when pre‐fire individuals were tall. In contrast, when pre‐fire individuals were small, WD had no influence on sprout vigour. A trade‐off between allocation of biomass to underground reserves and shoot growth seems to be responsible for the patterns obtained. For small individuals, below‐ground reserves seem to play a more important role than inherent growth rate (here measured through WD) in determining the sprouting vigour, while for large individuals, growth rate seems more important than reserves.