The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
Max A Moritz - One of the best experts on this subject based on the ideXlab platform.
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effect of tree to shrub Type Conversion in lower montane forests of the sierra nevada usa on streamflow
PLOS ONE, 2016Co-Authors: Ryan R Bart, Christina Tague, Max A MoritzAbstract:Higher global temperatures and increased levels of disturbance are contributing to greater tree mortality in many forest ecosystems. These same drivers can also limit forest regeneration, leading to vegetation Type Conversion. For the Sierra Nevada of California, little is known about how Type Conversion may affect streamflow, a critical source of water supply for urban, agriculture and environmental purposes. In this paper, we examined the effects of tree-to-shrub Type Conversion, in combination with climate change, on streamflow in two lower montane forest watersheds in the Sierra Nevada. A spatially distributed ecohydrologic model was used to simulate changes in streamflow, evaporation, and transpiration following Type Conversion, with an explicit focus on the role of vegetation size and aspect. Model results indicated that streamflow may show negligible change or small decreases following Type Conversion when the difference between tree and shrub leaf areas is small, partly due to the higher stomatal conductivity and the deep rooting depth of shrubs. In contrast, streamflow may increase when post-Conversion shrubs have a small leaf area relative to trees. Model estimates also suggested that vegetation change could have a greater impact on streamflow magnitude than the direct hydrologic impacts of increased temperatures. Temperature increases, however, may have a greater impact on streamflow timing. Tree-to-shrub Type Conversion increased streamflow only marginally during dry years (annual precipitation < 800 mm), with most streamflow change observed during wetter years. These modeling results underscore the importance of accounting for changes in vegetation communities to accurately characterize future hydrologic regimes for the Sierra Nevada.
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remote sensing analysis of vegetation recovery following short interval fires in southern california shrublands
PLOS ONE, 2014Co-Authors: Ran Meng, Philip E Dennison, Carla M Dantonio, Max A MoritzAbstract:Increased fire frequency has been shown to promote alien plant invasions in the western United States, resulting in persistent vegetation Type change. Short interval fires are widely considered to be detrimental to reestablishment of shrub species in southern California chaparral, facilitating the invasion of exotic annuals and producing “Type Conversion”. However, supporting evidence for Type Conversion has largely been at local, site scales and over short post-fire time scales. Type Conversion has not been shown to be persistent or widespread in chaparral, and past range improvement studies present evidence that chaparral Type Conversion may be difficult and a relatively rare phenomenon across the landscape. With the aid of remote sensing data covering coastal southern California and a historical wildfire dataset, the effects of short interval fires (<8 years) on chaparral recovery were evaluated by comparing areas that burned twice to adjacent areas burned only once. Twelve pairs of once- and twice-burned areas were compared using normalized burn ratio (NBR) distributions. Correlations between measures of recovery and explanatory factors (fire history, climate and elevation) were analyzed by linear regression. Reduced vegetation cover was found in some lower elevation areas that were burned twice in short interval fires, where non-sprouting species are more common. However, extensive Type Conversion of chaparral to grassland was not evident in this study. Most variables, with the exception of elevation, were moderately or poorly correlated with differences in vegetation recovery.
John Kouvetakis - One of the best experts on this subject based on the ideXlab platform.
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degenerate parallel conducting layer and conductivity Type Conversion observed from p ge1 ysny y 0 06 grown on n si substrate
Applied Physics Letters, 2012Co-Authors: Mee-yi Ryu, Yung Kee Yeo, M. Ahoujja, Tom R. Harris, Richard T. Beeler, John KouvetakisAbstract:Electrical properties of p-Ge1−ySny (y = 0.06%) grown on n-Si substrate were investigated through temperature-dependent Hall-effect measurements. It was found that there exists a degenerate parallel conducting layer in Ge1−ySny/Si and a second, deeper acceptor in addition to a shallow acceptor. This parallel conducting layer dominates the electrical properties of the Ge1−ySny layer below 50 K and also significantly affects those properties at higher temperatures. Additionally, a conductivity Type Conversion from p to n was observed around 370 K for this sample. A two-layer conducting model was used to extract the carrier concentration and mobility of the Ge1−ySny layer alone.
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Degenerate parallel conducting layer and conductivity Type Conversion observed from p-Ge1−ySny (y = 0.06%) grown on n-Si substrate
Applied Physics Letters, 2012Co-Authors: Mee-yi Ryu, Yung Kee Yeo, M. Ahoujja, Tom R. Harris, Richard T. Beeler, John KouvetakisAbstract:Electrical properties of p-Ge1−ySny (y = 0.06%) grown on n-Si substrate were investigated through temperature-dependent Hall-effect measurements. It was found that there exists a degenerate parallel conducting layer in Ge1−ySny/Si and a second, deeper acceptor in addition to a shallow acceptor. This parallel conducting layer dominates the electrical properties of the Ge1−ySny layer below 50 K and also significantly affects those properties at higher temperatures. Additionally, a conductivity Type Conversion from p to n was observed around 370 K for this sample. A two-layer conducting model was used to extract the carrier concentration and mobility of the Ge1−ySny layer alone.
Keun Huh - One of the best experts on this subject based on the ideXlab platform.
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The effect of rebamipide on gastric xanthine oxidase activity and Type Conversion in ethanol-treated rats
Free radical biology & medicine, 1996Co-Authors: Keun Huh, Seob Shin, Sang H. LeeAbstract:Rebamipide, a novel antipeptic ulcer drug, 2-(4-chlorobenzoylamino)-3-[2(1H)-quinolinone-4-yl]-propionic acid, was studied for its inhibitory effect on gastric xanthine oxidase activity and Type Conversion of the enzyme that has a profound role in free radical generation. Intraperitoneal administration of rebamipide at 60 mg/kg body weight reduced gastric mucosal hemorrhagic lesions and lipid peroxidation, which was proportional to the inhibitory effect of rebamipide on alcohol-induced xanthine oxidase-Type Conversion and enzyme activity. It was also observed that the activity of xanthine oxidase was significantly inhibited by administration of rebamipide at 60 mg/kg body weight, leading to a significant reduction of lipid peroxide content in alcohol-treated rats. The results suggest that alcohol-induced gastric mucosal lesions might be, in part, due to the increased activity of xanthine oxidase and Type Conversion rate of the enzyme and the protective effect of rebamipide on gastric mucosal lesions would result from its ability to protect against oxidative stress on gastric mucosal lesions of alcohol-treated rats.
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Effect of heat-treated ceruloplasmin on the hepatic xanthine oxidase activity and Type Conversion
Archives of Pharmacal Research, 1995Co-Authors: Keun Huh, Seob Shin, Sang-il LeeAbstract:The effect of ceruloplasmin or copper ion on hepatic xanthine oxidase activity and Type Conversion was investigated using rat liverin vitro. It was observed that ceruloplasmin increased xanthine oxidase Type Conversion depending on duration of its storage. Xanthine oxidase (Type O) activity and Type Conversion in incubation mixture was increased by the addition of heated celuroplasmin in a temperature dependent manner. The Type Conversion of xanthine oxidase induced by heated ceruloplasmin was retumed to normal by the treatment with DTT or penicillamine. The effect of copper ion on Type Conversion of xanthine oxidase was similar to that of heated ceruloplasmin.
Hyun-seok Kim - One of the best experts on this subject based on the ideXlab platform.
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Annealing induced p-Type Conversion and substrate dependent effect of n-ZnO/p-Si heterostructure
Materials Letters, 2017Co-Authors: A. Kathalingam, Hyun-seok KimAbstract:Abstract This paper reports the conductivity Type Conversion of ZnO nanorod thin film by annealing. The n-Type conductivity of hydrothermally prepared ZnO nanorods was changed to p-Type ZnO through thermal treatment in air ambient without doping process. The ZnO nanorod films were grown on p-Si (1 1 1) and p+-Si (1 0 0) substrates by hydrothermal method. SEM and XRD measurements showed the excellent crystalline quality and uniform morphology of the grown ZnO nanorod films. Furthermore, substrate and annealing temperature-dependent I-V responses of the films were also studied. A Schottky diode Type behavior was shown by ZnO NRs grown on low resistive p-Type silicon with a reasonable photoConversion efficiency.
Jon E. Keeley - One of the best experts on this subject based on the ideXlab platform.
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Extent and drivers of vegetation Type Conversion in Southern California chaparral
Ecosphere, 2019Co-Authors: Alexandra D. Syphard, Teresa J. Brennan, Jon E. KeeleyAbstract:The native chaparral shrublands of Southern California support exceptional biodiversity and provide critical ecological services, but increased fire frequency threatens to extirpate much of the chaparral due to long regeneration times needed between fires for many species. When short fire intervals inhibit shrub recovery, this favors invasion of exotic herbaceous species, and vegetation Type Conversion from woody shrubs to grassland is therefore a serious ecological concern in this biodiversity hotspot. Despite a history of field studies documenting the detrimental effect of short‐interval fire, the extent of vegetation Type Conversion and the conditions under which it occurs have not been documented at a landscape scale. Our objective was thus to provide an unbiased assessment of how and how much vegetation Type Conversion is occurring in Southern California chaparral. We used a chronosequence of aerial photographs to quantify percentage woody and herbaceous cover change from 1953 to 2016 across randomly sampled plots in San Diego County, then related Conversion and decline to a range of explanatory variables including fire, proximity to human disturbance, and biophysical landscape characteristics. Within the 63‐yr study period, there was substantial net woody cover loss, and in the plots that were initially more than 75% woody cover in 1953, 59% experienced a decline, with a mean woody cover loss of 22.5%. Of these, 28% heavily Type‐converted to the point that herbaceous vegetation covered more than 50% of the plot. The top drivers for woody Conversion and decline included a fire interval shorter than 15 yr and total number of fires, actual evapotranspiration, and elevation. Although human land use variables were not strong independent contributors to either chaparral Conversion or decline, 26% of the initial vegetated plots were directly converted to development or other human disturbance Types. The combination of direct habitat loss and unintentional vegetation Type Conversion represents a substantial ecological impact in Southern California that can have far‐reaching impacts via loss of ecological services and by increasing the flammability of the landscape in general. Efforts to reduce fire frequency will be key to preventing further losses.