We present a study of the effect of gold nanoparticles (Au NPs) on TiO 2 on charge generation and... more We present a study of the effect of gold nanoparticles (Au NPs) on TiO 2 on charge generation and trapping during illumination with photons of energy larger than the substrate band gap. We used a novel characterization technique, photoassisted Kelvin probe force microscopy, to study the process at the single Au NP level. We found that the photoinduced electron transfer from TiO 2 to the Au NP increases logarithmically with light intensity due to the combined contribution of electron−hole pair generation in the space charge region in the TiO 2 −air interface and in the metal−semiconductor junction. Our measurements on single particles provide direct evidence for electron trapping that hinders electron−hole recombination, a key factor in the enhancement of photo(electro)catalytic activity.
Rainfall is an indispensable link in the atmospheric water cycle, which plays a critical role in ... more Rainfall is an indispensable link in the atmospheric water cycle, which plays a critical role in forest hydrology. Quercus acutissima and Cunninghamia lanceolata are two fast-growing and economically important tree species in the middle and lower reaches of the Yangtze River. They are extensively applied in the restoration of vegetation, hydraulic engineering, and the development of artificial forests. The primary aims of this study were to describe and compare the changes in soil water content following rainfall events, while elucidating their relationships to environmental factors. From September 2012 to August 2013, we monitored the soil moisture at different depths every 30 min using commercially available soil moisture measuring devices. Hourly meteorological data were monitored over an open area at 200 m from the sample site, including photosynthetically active radiation (Par), air temperature (Ta), relative air humidity (RH), vapor pressure deficits (Vpd), rainfall, and wind ...
Transpiration is an important component of the water balance in forest ecosystems. Quercus acutis... more Transpiration is an important component of the water balance in forest ecosystems. Quercus acutissima and Cunninghamia lanceolata are two important, fast-growing and commercial tree species that have been extensively used for vegetation restoration, water conservation and building artificial forests in the Yangtze River Delta Region of China. The primary objective of this study was to characterize sap flow densities of the two species by comparing diurnal, nocturnal and seasonal sap flow patterns and their relationships with environmental factors. Sap flow densities (Sd) were measured between September 2012 and August 2013 using the commercially-available thermal dissipation probes. Hourly meteorological data were measured in an open field, located 200 m away from the study site. Standard meteorological data were logged hourly at this site, including photosynthetically active radiation (Par), air temperature (Ta), relative air humidity (Rh), vapor pressure deficit (Vpd) and precipitatio...
A predicted impact of a warming climate is an upslope shift of montane plant species. These 24 up... more A predicted impact of a warming climate is an upslope shift of montane plant species. These 24 upslope shifts may be amplified by land-use changes or attenuated by forest recoveries at low 25 elevations where historical disturbances were ceased allowing for plant regrowth. Consequently, 26 species may shift downslope back to low elevations where they had been previously harvested. 27 The cessation-driven downslope shifts are hypothesized to dampen or even reverse climate-28 driven upslope shifts. We tested this hypothesis by a 20-year (1989-2009) forest inventory 29 dataset from five mountainous areas in eastern China. In our study region, intense deforestation 30 occurred mostly at low elevations until 1970, but was then ceased to facilitate natural forest 31 recovery. Based on the analyses of 30,216 woody plants in 609 plots, we found that: (1) forest 32 recovery occurred over the 20-year survey period, and increment rates of both recruitment and 33 basal area increased up to 2004. However, in the last period (2004-2009), increment rates of 34 basal area leveled off and recruitment was close to zero; (2) forest recovery was faster at lower 35 elevations, as indicated by the higher increment rates there; (3) despite rising regional 36 temperatures, the mean elevations of study species showed a downslope shift over the 20 years; 37 and (4) the contribution of forest recovery to elevational shifts was supported by the fact that the 38 species shifts were positively related to elevational changes in the recruitment increment, e.g., 39 the negative (or downslope) shifts occurred in association with higher increments at lower 40 elevations. These results suggest that, the cessation of disturbances and consequent lowland 41 forest recovery had greater effects on the species distributions than did warming climate. In 42 mountain systems that are being allowed to recover from historical disturbances, the effects of 43 forest recovery on species distributions should be explicitly accounted for when assessing and 44 predicting climate change impacts. 45
Foundation species provide habitat to other organisms and enhance ecosystem functions, such as nu... more Foundation species provide habitat to other organisms and enhance ecosystem functions, such as nutrient cycling, carbon storage and sequestration, and erosion control. We focus on freshwater wetlands because these ecosystems are often characterized by foundation species; eutrophication and other environmental changes may cause the loss of some of these species, thus severely damaging wetland ecosystems. To better understand how wetland primary producer foundation species support other species and ecosystem functions across environmental gradients, we reviewed ~150 studies in subtropical, boreal, and temperate freshwater wetlands. We look at how the relative dominance of conspicuous and well-documented species (i.e., sawgrass, benthic diatoms and cyanobacteria, Sphagnum mosses, and bald cypress) and the foundational roles they play interact with hydrology, nutrient availability, and exposure to fire and salinity in representative wetlands. Based on the evidence analyzed, we argue tha...
Ecotoxicology and environmental safety, Jan 30, 2018
The influence of acid rain on plant growth includes direct effects on foliage as well as indirect... more The influence of acid rain on plant growth includes direct effects on foliage as well as indirect soil-mediated effects that cause a reduction in root growth. In addition, the concentration of NO in acid rain increases along with the rapid growth of nitrogen deposition. In this study, we investigated the impact of simulated acid rain with different SO/NO (S/N) ratios, which were 1:0, 5:1, 1:1, 1:5 and 0:1, on Chinese fir sapling growth from March 2015 to April 2016. Results showed that Chinese fir sapling height growth rate (HGR) and basal diameter growth rate (DGR) decreased as acid rain pH decreased, and also decreased as the percentage of NO increased in acid rain. Acid rain pH significantly decreased the Chlorophyll a (Chla) and Chlorophyll b (Chlb) content, and Chla and Chlb contents with acid rain S/N 1:5 were significantly lower than those with S/N 1:0 at pH 2.5. The chlorophyll fluorescence parameters, maximal efficiency of Photosystem II photochemistry (Fv/Fm) and non-photo...
A large body of theory predicts that populations diffusing in heterogeneous environments reach hi... more A large body of theory predicts that populations diffusing in heterogeneous environments reach higher total size than if non-diffusing, and, paradoxically, higher size than in a corresponding homogeneous environment. However, this theory and its assumptions have not been rigorously tested. Here, we extended previous theory to include exploitable resources, proving qualitatively novel results, which we tested experimentally using spatially diffusing laboratory populations of yeast. Consistent with previous theory, we predicted and experimentally observed that spatial diffusion increased total equilibrium population abundance in heterogeneous environments, with the effect size depending on the relationship between r and K. Refuting previous theory, however, we discovered that homogeneously distributed resources support higher total carrying capacity than heterogeneously distributed resources, even with species diffusion. Our results provide rigorous experimental tests of new and old t...
The Journal of comparative neurology, Jan 20, 2016
To generate rhythmic motor behaviors, both single neurons and neural circuits require a balance b... more To generate rhythmic motor behaviors, both single neurons and neural circuits require a balance between excitatory inputs that trigger action potentials and inhibitory inputs that promote a stable resting potential (E/I balance). Previous studies have focused on individual neurons and have shown that, over a short spatial scale, excitatory and inhibitory (E/I) synapses tend to form structured territories with inhibitory inputs enriched on cell bodies and proximal dendrites and excitatory inputs on distal dendrites. However, systems-level E/I patterns, at spatial scales larger than single neurons, are largely uncharted. We used immunostaining for PSD-95 and gephyrin post-synaptic scaffolding proteins as proxies for excitatory and inhibitory synapses respectively to quantify the numbers and map the distributions of E/I synapses in zebrafish spinal cord at both an embryonic stage and a larval stage. At the embryonic stage, we found that PSD-95 puncta outnumber gephyrin puncta, with the...
ABSTRACT Few studies have quantified the combined effects of environmental conditions, the planti... more ABSTRACT Few studies have quantified the combined effects of environmental conditions, the planting of elite full-sib pine families, intra-specific competition, and intensive silvicultural treatment on unit area production of loblolly pine and slash pine. This study examined these factors at age 2 and 10 years for factorial experiments in the Western Gulf (WG) area of the southeastern United States. The experiments consisted of seven pine families (five elite and one poor full-sib loblolly pine families, one elite full-sib slash pine family), two silvicultural intensities (high and low intensity), and three sites. Two deployment methods (mixed and pure-family plots) were used to examine crop and competition ideotypes from among the loblolly families deployed. Family and site were significant main effects at both ages for both individual tree (diameter, height) and stand growth (basal area, volume), and culture was only significant at age 2 years. Significant interactions of culture × site and family × site for different growth metrics indicated varying cultural treatment and family performance effects at the different sites, but family response was consistent across cultural treatments. At age 2 and 10 years, the deployment main effect was significant for tree height, and for stand basal area and volume. A deployment × site × family interaction for DBH identified a competition ideotype (fast grower) and crop ideotype (slow grower) at the better overall site. The competition ideotype that performed best was not from the WG region, while the slash pine families performed poorly and suffered high levels of storm damage. For loblolly pine, wind damage was the most severe for the plots with low silvicultural intensity. Overall, these results suggested that high performing loblolly pine families do well under a variety of conditions in the WG region and that the competition ideotype and stand uniformity may result in less mortality and greater resistance to wind damage.
Halophytic communities such as mangrove forests and buttonwood hammocks tend to border freshwater... more Halophytic communities such as mangrove forests and buttonwood hammocks tend to border freshwater plant communities as sharp ecotones. Most studies attribute this purely to underlying physical templates, such as groundwater salinity gradients caused by tidal flux and topography. However, a few recent studies hypothesize that self-reinforcing feedback between vegetation and vadose zone salinity are also involved and create a bistable situation in which either halophytic dominated habitat or freshwater plant communities may dominate as alternative stable states. Here, we revisit the bistability hypothesis and demonstrate the mechanisms that result in bistability. We demonstrate with remote sensing imagery the sharp boundaries between freshwater hardwood hammock communities in southern Florida and halophytic communities such as buttonwood hammocks and mangroves. We further document from the literature how transpiration of mangroves and freshwater plants respond differently to vadose zone salinity, thus altering the salinity through feedback. Using mathematical models, we show how the self-reinforcing feedback, together with physical template, controls the ecotones between halophytic and freshwater communities. Regions of bistability along environmental gradients of salinity have the potential for large-scale vegetation shifts following pulse disturbances such as hurricane tidal surges in Florida, or tsunamis in other regions. The size of the region of bistability can be large for low-lying coastal habitat due to the saline water table, which extends inland due to salinity intrusion. We suggest coupling ecological and hydrologic processes as a framework for future studies.
We present a study of the effect of gold nanoparticles (Au NPs) on TiO 2 on charge generation and... more We present a study of the effect of gold nanoparticles (Au NPs) on TiO 2 on charge generation and trapping during illumination with photons of energy larger than the substrate band gap. We used a novel characterization technique, photoassisted Kelvin probe force microscopy, to study the process at the single Au NP level. We found that the photoinduced electron transfer from TiO 2 to the Au NP increases logarithmically with light intensity due to the combined contribution of electron−hole pair generation in the space charge region in the TiO 2 −air interface and in the metal−semiconductor junction. Our measurements on single particles provide direct evidence for electron trapping that hinders electron−hole recombination, a key factor in the enhancement of photo(electro)catalytic activity.
Rainfall is an indispensable link in the atmospheric water cycle, which plays a critical role in ... more Rainfall is an indispensable link in the atmospheric water cycle, which plays a critical role in forest hydrology. Quercus acutissima and Cunninghamia lanceolata are two fast-growing and economically important tree species in the middle and lower reaches of the Yangtze River. They are extensively applied in the restoration of vegetation, hydraulic engineering, and the development of artificial forests. The primary aims of this study were to describe and compare the changes in soil water content following rainfall events, while elucidating their relationships to environmental factors. From September 2012 to August 2013, we monitored the soil moisture at different depths every 30 min using commercially available soil moisture measuring devices. Hourly meteorological data were monitored over an open area at 200 m from the sample site, including photosynthetically active radiation (Par), air temperature (Ta), relative air humidity (RH), vapor pressure deficits (Vpd), rainfall, and wind ...
Transpiration is an important component of the water balance in forest ecosystems. Quercus acutis... more Transpiration is an important component of the water balance in forest ecosystems. Quercus acutissima and Cunninghamia lanceolata are two important, fast-growing and commercial tree species that have been extensively used for vegetation restoration, water conservation and building artificial forests in the Yangtze River Delta Region of China. The primary objective of this study was to characterize sap flow densities of the two species by comparing diurnal, nocturnal and seasonal sap flow patterns and their relationships with environmental factors. Sap flow densities (Sd) were measured between September 2012 and August 2013 using the commercially-available thermal dissipation probes. Hourly meteorological data were measured in an open field, located 200 m away from the study site. Standard meteorological data were logged hourly at this site, including photosynthetically active radiation (Par), air temperature (Ta), relative air humidity (Rh), vapor pressure deficit (Vpd) and precipitatio...
A predicted impact of a warming climate is an upslope shift of montane plant species. These 24 up... more A predicted impact of a warming climate is an upslope shift of montane plant species. These 24 upslope shifts may be amplified by land-use changes or attenuated by forest recoveries at low 25 elevations where historical disturbances were ceased allowing for plant regrowth. Consequently, 26 species may shift downslope back to low elevations where they had been previously harvested. 27 The cessation-driven downslope shifts are hypothesized to dampen or even reverse climate-28 driven upslope shifts. We tested this hypothesis by a 20-year (1989-2009) forest inventory 29 dataset from five mountainous areas in eastern China. In our study region, intense deforestation 30 occurred mostly at low elevations until 1970, but was then ceased to facilitate natural forest 31 recovery. Based on the analyses of 30,216 woody plants in 609 plots, we found that: (1) forest 32 recovery occurred over the 20-year survey period, and increment rates of both recruitment and 33 basal area increased up to 2004. However, in the last period (2004-2009), increment rates of 34 basal area leveled off and recruitment was close to zero; (2) forest recovery was faster at lower 35 elevations, as indicated by the higher increment rates there; (3) despite rising regional 36 temperatures, the mean elevations of study species showed a downslope shift over the 20 years; 37 and (4) the contribution of forest recovery to elevational shifts was supported by the fact that the 38 species shifts were positively related to elevational changes in the recruitment increment, e.g., 39 the negative (or downslope) shifts occurred in association with higher increments at lower 40 elevations. These results suggest that, the cessation of disturbances and consequent lowland 41 forest recovery had greater effects on the species distributions than did warming climate. In 42 mountain systems that are being allowed to recover from historical disturbances, the effects of 43 forest recovery on species distributions should be explicitly accounted for when assessing and 44 predicting climate change impacts. 45
Foundation species provide habitat to other organisms and enhance ecosystem functions, such as nu... more Foundation species provide habitat to other organisms and enhance ecosystem functions, such as nutrient cycling, carbon storage and sequestration, and erosion control. We focus on freshwater wetlands because these ecosystems are often characterized by foundation species; eutrophication and other environmental changes may cause the loss of some of these species, thus severely damaging wetland ecosystems. To better understand how wetland primary producer foundation species support other species and ecosystem functions across environmental gradients, we reviewed ~150 studies in subtropical, boreal, and temperate freshwater wetlands. We look at how the relative dominance of conspicuous and well-documented species (i.e., sawgrass, benthic diatoms and cyanobacteria, Sphagnum mosses, and bald cypress) and the foundational roles they play interact with hydrology, nutrient availability, and exposure to fire and salinity in representative wetlands. Based on the evidence analyzed, we argue tha...
Ecotoxicology and environmental safety, Jan 30, 2018
The influence of acid rain on plant growth includes direct effects on foliage as well as indirect... more The influence of acid rain on plant growth includes direct effects on foliage as well as indirect soil-mediated effects that cause a reduction in root growth. In addition, the concentration of NO in acid rain increases along with the rapid growth of nitrogen deposition. In this study, we investigated the impact of simulated acid rain with different SO/NO (S/N) ratios, which were 1:0, 5:1, 1:1, 1:5 and 0:1, on Chinese fir sapling growth from March 2015 to April 2016. Results showed that Chinese fir sapling height growth rate (HGR) and basal diameter growth rate (DGR) decreased as acid rain pH decreased, and also decreased as the percentage of NO increased in acid rain. Acid rain pH significantly decreased the Chlorophyll a (Chla) and Chlorophyll b (Chlb) content, and Chla and Chlb contents with acid rain S/N 1:5 were significantly lower than those with S/N 1:0 at pH 2.5. The chlorophyll fluorescence parameters, maximal efficiency of Photosystem II photochemistry (Fv/Fm) and non-photo...
A large body of theory predicts that populations diffusing in heterogeneous environments reach hi... more A large body of theory predicts that populations diffusing in heterogeneous environments reach higher total size than if non-diffusing, and, paradoxically, higher size than in a corresponding homogeneous environment. However, this theory and its assumptions have not been rigorously tested. Here, we extended previous theory to include exploitable resources, proving qualitatively novel results, which we tested experimentally using spatially diffusing laboratory populations of yeast. Consistent with previous theory, we predicted and experimentally observed that spatial diffusion increased total equilibrium population abundance in heterogeneous environments, with the effect size depending on the relationship between r and K. Refuting previous theory, however, we discovered that homogeneously distributed resources support higher total carrying capacity than heterogeneously distributed resources, even with species diffusion. Our results provide rigorous experimental tests of new and old t...
The Journal of comparative neurology, Jan 20, 2016
To generate rhythmic motor behaviors, both single neurons and neural circuits require a balance b... more To generate rhythmic motor behaviors, both single neurons and neural circuits require a balance between excitatory inputs that trigger action potentials and inhibitory inputs that promote a stable resting potential (E/I balance). Previous studies have focused on individual neurons and have shown that, over a short spatial scale, excitatory and inhibitory (E/I) synapses tend to form structured territories with inhibitory inputs enriched on cell bodies and proximal dendrites and excitatory inputs on distal dendrites. However, systems-level E/I patterns, at spatial scales larger than single neurons, are largely uncharted. We used immunostaining for PSD-95 and gephyrin post-synaptic scaffolding proteins as proxies for excitatory and inhibitory synapses respectively to quantify the numbers and map the distributions of E/I synapses in zebrafish spinal cord at both an embryonic stage and a larval stage. At the embryonic stage, we found that PSD-95 puncta outnumber gephyrin puncta, with the...
ABSTRACT Few studies have quantified the combined effects of environmental conditions, the planti... more ABSTRACT Few studies have quantified the combined effects of environmental conditions, the planting of elite full-sib pine families, intra-specific competition, and intensive silvicultural treatment on unit area production of loblolly pine and slash pine. This study examined these factors at age 2 and 10 years for factorial experiments in the Western Gulf (WG) area of the southeastern United States. The experiments consisted of seven pine families (five elite and one poor full-sib loblolly pine families, one elite full-sib slash pine family), two silvicultural intensities (high and low intensity), and three sites. Two deployment methods (mixed and pure-family plots) were used to examine crop and competition ideotypes from among the loblolly families deployed. Family and site were significant main effects at both ages for both individual tree (diameter, height) and stand growth (basal area, volume), and culture was only significant at age 2 years. Significant interactions of culture × site and family × site for different growth metrics indicated varying cultural treatment and family performance effects at the different sites, but family response was consistent across cultural treatments. At age 2 and 10 years, the deployment main effect was significant for tree height, and for stand basal area and volume. A deployment × site × family interaction for DBH identified a competition ideotype (fast grower) and crop ideotype (slow grower) at the better overall site. The competition ideotype that performed best was not from the WG region, while the slash pine families performed poorly and suffered high levels of storm damage. For loblolly pine, wind damage was the most severe for the plots with low silvicultural intensity. Overall, these results suggested that high performing loblolly pine families do well under a variety of conditions in the WG region and that the competition ideotype and stand uniformity may result in less mortality and greater resistance to wind damage.
Halophytic communities such as mangrove forests and buttonwood hammocks tend to border freshwater... more Halophytic communities such as mangrove forests and buttonwood hammocks tend to border freshwater plant communities as sharp ecotones. Most studies attribute this purely to underlying physical templates, such as groundwater salinity gradients caused by tidal flux and topography. However, a few recent studies hypothesize that self-reinforcing feedback between vegetation and vadose zone salinity are also involved and create a bistable situation in which either halophytic dominated habitat or freshwater plant communities may dominate as alternative stable states. Here, we revisit the bistability hypothesis and demonstrate the mechanisms that result in bistability. We demonstrate with remote sensing imagery the sharp boundaries between freshwater hardwood hammock communities in southern Florida and halophytic communities such as buttonwood hammocks and mangroves. We further document from the literature how transpiration of mangroves and freshwater plants respond differently to vadose zone salinity, thus altering the salinity through feedback. Using mathematical models, we show how the self-reinforcing feedback, together with physical template, controls the ecotones between halophytic and freshwater communities. Regions of bistability along environmental gradients of salinity have the potential for large-scale vegetation shifts following pulse disturbances such as hurricane tidal surges in Florida, or tsunamis in other regions. The size of the region of bistability can be large for low-lying coastal habitat due to the saline water table, which extends inland due to salinity intrusion. We suggest coupling ecological and hydrologic processes as a framework for future studies.
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