Forest response to natural disturbance: changes in structure and diversity on a North Carolina Piedmont forest in response to catastrophic wind events

Large hurricanes have profound impacts on temperate forests, but owing to their infrequent nature these effects rarely have been examined in detail. In 1996 Hurricane Fran significantly damaged many long-term census plots in Duke Forest in Piedmont North Carolina, thereby providing a unique research opportunity. I combined over 20 years of pre-hurricane and five years of post-hurricane data on individual trees, seedlings and saplings to determine how hurricanes affect forest structure, diversity, and succession. Several plots severely damaged in 1954 by Hurricane Hazel allowed comparison of recovery patterns and evaluation of long-term effects. I first assessed hurricane-induced structural and compositional changes and evaluated mortality risk factors. Fran caused widespread uprooting of large canopy trees. Stand-level damage severity varied substantially across the distributed network of permanent plots. Hurricane-induced mortality of large-size hardwoods was often delayed. Although tree damage was primarily caused by winds and rainfall, damage was also found to be correlated with site exposure, topographical position, tree size, and species susceptibility to wind. Next, to test the hypothesis that hurricanes maintain local tree diversity through increased heterogeneity and resource availability I examined changes in understory survivorship, recruitment, and growth. The understory experienced highly variable population impacts as well as subtle changes in tree diversity. Following Fran both seedlings and saplings exhibited an immediate drop in stem density followed by a rebound. In addition, the hurricane resulted in release of established, shade-intolerant or mid-tolerant seedlings and saplings, thereby potentially increasing future canopy tree diversity. Finally, I assessed whether hurricanes have long-term effects on tree diversity and succession. Past hurricanes appear to have accelerating succession in even-aged pine stands toward a later, hardwood-dominated successional stage, and to have shifted the hardwood forests toward more diverse composition, although with increasing dominance of red maple. I concluded that large, infrequent hurricanes play an important role in shaping forest structure and maintaining tree diversity in the Piedmont region. However, the effects on tree composition and diversity vary greatly and depend on local damage severity, pre-hurricane stand characteristics, and the temporal and spatial scales at which the changes are observed

Distributions of Exotic Plants in Eastern Asia and North America

Although some plant traits have been linked to invasion success, the possible effects of regional factors, such as diversity, habitat suitability, and human activity are not well understood. Each of these mechanisms predicts a different pattern of distribution at the regional scale. Thus, where climate and soils are similar, predictions based on regional hypotheses for invasion success can be tested by comparisons of distributions in the source and receiving regions. Here, we analyse the native and alien geographic ranges of all 1567 plant species that have been introduced between eastern Asia and North America or have been introduced to both regions from elsewhere. The results reveal correlations between the spread of exotics and both the native species richness and transportation networks of recipient regions. This suggests that both species interactions and human-aided dispersal influence exotic distributions, although further work on the relative importance of these processes is needed

Interactive DNA Sequence and Structure Design for DNA Nanotechnology and DNA Computation

DNA sequence and structure design are very important for DNA nanotechnology and DNA computation. A computer aided design tool is needed for exploring DNA sequence and structure of interests before experimental synthesis, which is a very time and labor consuming process. In this paper, an interactive DNA sequence and structure design software tool called DNA shop is proposed and implemented

Integrating LANDIS model and a multi-criteria decision-making approach to evaluate cumulative effects of forest management in the Missouri Ozarks, USA

Public forest management requires consideration of numerous objectives including protecting ecosystem health, sustaining habitats for native communities, providing sustainable forest products, and providing noncommodity ecosystem services. It is difficult to evaluate the long-term, cumulative effects and tradeoffs these and other associated management objectives. To demonstrate the capabilities of techniques suitable to support such evaluations we combined a spatially explicit landscape-scale, succession and disturbance model (LANDIS) with wildlife habitat suitability models and a multi-criteria decisionmaking framework to compare four management alternatives across a 700 km2 area of the Mark Twain National Forest in Missouri, USA. We estimated the combined, cumulative effects of tree species succession, fire disturbance, fuel accumulation, fire hazard, wind disturbance and timber harvest on future species composition, age class distribution, timber products, and wildlife habitat suitability for eastern wild turkey and eastern gray squirrel. We applied a structured, multi-criteria, decision-making framework (PROMETHEE) to analyse forest conditions and to derive weighted composite scores for seven criteria applied to each alternative management scenario. The approach provides a systematic, repeatable, transparent, spatially explicit framework for evaluating the long-term, landscape-scale cumulative effects of management alternatives. The methodology does not encompass all the factors that influence decisions about public land management, but it captures many important ones. The underlying models provide a way to test and accumulate knowledge about forest response to succession and disturbance and to use those relationships to support decision making with the best available science

Interactive DNA Sequence and Structure Design for DNA Nanoapplications

DNA sequence and structure design is very important for DNA nanoapplications. A computer-aided design tool is needed for exploring DNA sequence and structure of interests before experimental synthesis, which is a time- and labor-consuming process. In this paper, an interactive DNA sequence and structure design software tool called DNA shop is proposed and implemented. The visualization tool can generate DNA structures by specifying, selecting, and moving DNA sequences around and display corresponding structures. Using the tool, DNA sequence and structure can be visually inspected in three-dimensional space before experimental studies

Integrating LANDIS model and a multi-criteria decision-making approach to evaluate cumulative effects of forest management in the Missouri Ozarks, USA

Public forest management requires consideration of numerous objectives including protecting ecosystem health, sustaining habitats for native communities, providing sustainable forest products, and providing noncommodity ecosystem services. It is difficult to evaluate the long-term, cumulative effects and tradeoffs these and other associated management objectives. To demonstrate the capabilities of techniques suitable to support such evaluations we combined a spatially explicit landscape-scale, succession and disturbance model (LANDIS) with wildlife habitat suitability models and a multi-criteria decisionmaking framework to compare four management alternatives across a 700 km2 area of the Mark Twain National Forest in Missouri, USA. We estimated the combined, cumulative effects of tree species succession, fire disturbance, fuel accumulation, fire hazard, wind disturbance and timber harvest on future species composition, age class distribution, timber products, and wildlife habitat suitability for eastern wild turkey and eastern gray squirrel. We applied a structured, multi-criteria, decision-making framework (PROMETHEE) to analyse forest conditions and to derive weighted composite scores for seven criteria applied to each alternative management scenario. The approach provides a systematic, repeatable, transparent, spatially explicit framework for evaluating the long-term, landscape-scale cumulative effects of management alternatives. The methodology does not encompass all the factors that influence decisions about public land management, but it captures many important ones. The underlying models provide a way to test and accumulate knowledge about forest response to succession and disturbance and to use those relationships to support decision making with the best available science

Identifying determinants of spatial agglomeration of healthcare resources by using spatial econometric methods: a longitudinal study in China

BackgroundHealthcare resources are necessary for individuals to maintain their health. The Chinese government has implemented policies to optimize the allocation of healthcare resources and achieve the goal of equality in healthcare for the Chinese people since the implementation of the new medical reform in 2009. Given that no study has investigated regional differences from the perspective of healthcare resource agglomeration, this study aimed to investigate China’s healthcare agglomeration from 2009 to 2017 in China and identify its determinants to provide theoretical evidence for the government to develop and implement scientific and rational healthcare policies.MethodsThe study was conducted using 2009–2017 data to analyze health-resource agglomeration on institutions, beds, and workforce in China. An agglomeration index was applied to evaluate the degree of regional differences in healthcare resource allocation, and spatial econometric models were constructed to identify determinants of the spatial agglomeration of healthcare resources.ResultsFrom 2009 to 2017, all the agglomeration indexes of healthcare exhibited a downward trend except for the number of institutions in China. Population density (PD), government health expenditures (GHE), urban resident’s disposable income (URDI), geographical location (GL), and urbanization level (UL) all had positive significant effects on the agglomeration of beds, whereas both per capita health expenditures (PCHE), number of college students (NCS), and maternal mortality rate (MMR) had significant negative effects on the agglomeration of institutions, beds, and the workforce. In addition, population density (PD) and per capita gross domestic product (PCGDP) in one province had negative spatial spillover effects on the agglomeration of beds and the workforce in neighboring provinces. However, MMR had a positive spatial spillover effect on the agglomeration of beds and the workforce in those regions.ConclusionThe agglomeration of healthcare resources was observed to remain at an ideal level in China from 2009 to 2017. According to the significant determinants, some corresponding targeted measures for the Chinese government and other developing countries should be fully developed to balance regional disparities in the agglomeration of healthcare resources across administrative regions

Improvement of Flame Retardancy of Polyurethane Foam Using DOPO-Immobilized Silica Aerogel

In this work, silica aerogel was modified by 9,10-dihydro-9-oxa-10-phosphaphenanthrene-1-oxide (DOPO). Then DOPO-immobilized silica aerogel nanoparticles were used as a flame retardant to prepare flame-retardant polyurethane foams. Microscale combustion calorimeter and cone calorimeter tests were employed to evaluate the flame retardancy of polyurethane foams. It was found that both the heat release rate and the total heat release of the composites were reduced with the incorporation of DOPO immobilized silica aerogel. It is speculated that the DOPO-immobilized silica aerogel nanoparticles can inhibit the degradation of polyurethane and catalyze the formation of carbonaceous carbon on the surface

Reduction of structural impacts and distinction of photosynthetic pathways in a global estimation of GPP from space-borne solar-induced chlorophyll fluorescence

Quantifying global photosynthesis remains a challenge due to a lack of accurate remote sensing proxies. Solar-induced chlorophyll fluorescence (SIF) has been shown to be a good indicator of photosynthetic activity across various spatial scales. However, a global and spatially challenging estimate of terrestrial gross primary production (GPP) based on satellite SIF remains unresolved due to the confounding effects of species-specific physical and physiological traits and external factors, such as canopy structure or photosynthetic pathway (C-3 or C-4). Here we analyze an ensemble of far-red SIF data from OCO-2 satellite and ground observations at multiple sites, using the spectral invariant theory to reduce the effects of canopy structure and to retrieve a structure-corrected total canopy SIF emission (SIFtotal). We find that the relationships between observed canopy-leaving SIF and ecosystem GPP vary significantly among biomes. In contrast, the relationships between SIFtotal and GPP converge around two unique models, one for C-3 and one for C-4 plants. We show that the two single empirical models can be used to globally scale satellite SIF observations to terrestrial GPP. We obtain an independent estimate of global terrestrial GPP of 129.56 +/- 6.54 PgC/year for the 2015-2017 period, which is consistent with the state-of-the-art data- and process-oriented models. The new GPP product shows improved sensitivity to previously undetected 'hotspots' of productivity, being able to resolve the double-peak in GPP due to rotational cropping systems. We suggest that the direct scheme to estimate GPP presented here, which is based on satellite SIF, may open up new possibilities to resolve the dynamics of global terrestrial GPP across space and time.Peer reviewe