Detecting Channel Riparian Vegetation Response to Best-Management-Practices Implementation in Ephemeral Streams With the Use of Spot High-Resolution Visible Imagery     

Kendall Vande Kamp  Matthew Rigge  Nels H. Troelstrup  Alexander J. Smart  Bruce Wylie 《Strength and Conditioning Journal》2013,66(1):63-70

Heavily grazed riparian areas are commonly subject to channel incision, a lower water table, and reduced vegetation, resulting in sediment delivery above normal regimes. Riparian and in-channel vegetation functions as a roughness element and dissipates flow energy, maintaining stable channel geometry. Ash Creek, a tributary of the Bad River in western South Dakota contains a high proportion of incised channels, remnants of historically high grazing pressure. Best management practices (BMP), including off-stream watering sources and cross fencing, were implemented throughout the Bad River watershed during an Environmental Protection Agency (EPA) 319 effort to address high sediment loads. We monitored prairie cordgrass (Spartina pectinata Link) establishment within stream channels for 16 yr following BMP implementation. Photos were used to group stream reaches (n=103) subjectively into three classes; absent (estimated <5% cover; n=64), present (estimated 5–40% cover; n=23), and dense (estimated >40% cover; n=16) based on the relative amount of prairie cordgrass during 2010 assessments of ephemeral channels. Reaches containing drainage areas of 0.54 to 692 ha were delineated with the use of 2010 National Agriculture Imagery Program (NAIP) imagery. Normalized difference vegetation index (NDVI) values were extracted from 5 to 39 sample points proportional to reach length using a series of Satellite Pour l’Observation de la Terre (SPOT) satellite imagery. Normalized NDVI (nNDVI) of 2152 sample points were determined from pre- and post-BMP images. Mean nNDVI values for each reach ranged from 0.33 to 1.77. ANOVA revealed significant increase in nNDVI in locations classified as present prairie cordgrass cover following BMP implementation. Establishment of prairie cordgrass following BMP implementation was successfully detected remotely. Riparian vegetation such as prairie cordgrass adds channel roughness that reduces the flow energy responsible for channel degradation.  相似文献   

Spring Clipping,Fire, and Simulated Increased Atmospheric Nitrogen Deposition Effects on Tallgrass Prairie Vegetation     

Alexander J. Smart  Tabithia K. Scott  Sharon A. Clay  David E. Clay  Michelle Ohrtman  Eric M. Mousel 《Strength and Conditioning Journal》2013,66(6):680-687

Defoliation aimed at introduced cool-season grasses, which uses similar resources of native grasses, could substantially reduce their competitiveness and improve the quality of the northern tallgrass prairie. The objective was to evaluate the use of early season clipping and fire in conjunction with simulated increased levels of atmospheric nitrogen deposition on foliar canopy cover of tallgrass prairie vegetation. This study was conducted from 2009 to 2012 at two locations in eastern South Dakota. Small plots arranged in a split-plot treatment design were randomized in four complete blocks on a warm-season grass interseeded and a native prairie site in east-central South Dakota. The whole plot consisted of seven treatments: annual clip, biennial clip, triennial clip, annual fire, biennial fire, triennial fire, and undefoliated control. The clip plots consisted of weekly clipping in May to simulate heavy grazing. Fire was applied in late April or early May. The subplot consisted of nitrogen applied at 0 or 15 kg N · ha^?1 in early June. All treatments were initially applied in 2009. Biennial and triennial treatments were reapplied in 2011 and 2012, respectively. Canopy cover of species/major plant functional groups was estimated in late August/early September. Annual clipping was just as effective as annual fire in increasing native warm-season grass and decreasing introduced cool-season grass cover. Annual defoliation resulted in greater native warm-season grass cover, less introduced cool-season grass cover, and less native cool-season grass cover than biennial or triennial defoliation applications. Low levels of nitrogen did not affect native warm-season grass or introduced cool-season cover for any of the defoliation treatments, but it increased introduced cool-season grass cover in the undefoliated control at the native prairie site. This study supports the hypothesis that appropriately applied management results in consistent desired outcomes regardless of increased simulated atmospheric nitrogen depositions.  相似文献   

Research Notes     

D. McE. Alexander 《The Journal of Horticultural Science and Biotechnology》2013,88(1):85-86

By selecting suitable cuttings and rooting under mist in a heated bed, small plants were obtained which gave ripe fruit bunches two months earlier than was possible from vines in the field. Under Australian conditions cuttings taken towards the end of December gave the best results.  相似文献   

Microstructure of viscoelastic thermal compressed (VTC) wood using computed microtomography     

Gernot Standfest  Andreja Kutnar  Bernhard Plank  Alexander Petutschnigg  Frederick A. Kamke  Manfred Dunky 《Wood Science and Technology》2013,47(1):121-139

The paper describes for the first time the analysis of the structure of compressed wood using computed tomography. The anatomical structures of Douglas-fir and hybrid poplar before and after densification with the viscoelastic thermal compression (VTC) process were described by pore size distributions and mean pore sizes and compared. The compression of Douglas-fir mainly affected earlywood, while the compression of hybrid poplar mainly occurred in the vessels. In both wood species, the densification resulted in a significant decrease in the pore volumes. The porosity decreased to less than half of the original value for Douglas-fir earlywood and to approximately one-quarter for the vessels in hybrid poplar. The relevant mean pore sizes also decreased dramatically to about one-quarter compared to the original values. In contrast, latewood in Douglas-fir and libriform fibers in hybrid poplar are quite stable under compression. Douglas-fir latewood retained its original structure after compression and did not show any reduction in pore size. The results confirmed that the anatomical structure of VTC densified wood can be described by pore size distributions and mean pore sizes. However, in the case of broad or bimodal distributions, the mean pore sizes are of less significance.  相似文献   

Boreal forest sensitivity to increased temperatures at multiple successional stages     

David A. Lutz  Herman H. Shugart  Dmitry V. Ershov  Jacquelyn K. Shuman  Alexander S. Isaev 《Annals of Forest Science》2013,70(3):299-308

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Interaction of spittlebug and forage grass under different carbon dioxide concentrations     

Roberta B. Ferreira  Jair C. Moraes  Alexander M. Auad  Marcy G. Fonseca 《Journal of pest science》2013,86(2):161-166

This study evaluated the impact of different CO₂ levels on the biological characteristics of Mahanarva spectabilis (Distant) and on the performance of forage grasses. The signal grasses Brachiaria decumbens Stapf (susceptible) and Brachiaria brizantha (A. Rich.) (resistant), the elephant grass Pennisetum purpureum (Schum.), including the Roxo de Botucatu cultivar (susceptible) and the Pioneiro cultivar (resistant) and the insects were kept in climate-controlled chambers with constant low (250 ppm) CO₂ levels, constant high (500 ppm) CO₂ levels, or fluctuating CO₂ levels (mean, 368 ppm). Among these three CO₂ treatments, no significant differences were found in the nymphal survival of M. spectabilis when the nymphs were fed on two signal grass species. On the other hand, under a constant low CO₂ level (250 ppm), nymphal survival rates were significantly lower when the insects were kept in Roxo de Botucatu and Pioneiro cultivars. The mean adult longevity values for M. spectabilis were not significantly different among the three levels of CO₂ evaluated. We observed that increased CO₂ levels improved the performance of M. spectabilis and elephant grass cultivars in accumulating dry mass, which was not evident in signal grass. We further conclude that the levels of susceptibility and resistance of the forages tested will be maintained in future scenarios under which atmospheric CO₂ levels are expected to increase.  相似文献   

Reduced incidence of tick paralysis cases in dogs and cats at two emergency clinics in South-East Queensland since 2015: new generation prophylactics as possible explanatory variables     

EM Ireland  J Heller  EM Leister  AM Padula 《Australian veterinary journal》2023,101(9):356-365

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Diel movement of bullhead (Cottus perifretum) in a lowland stream     

Alexander Kobler  Yves Humblet  Guy Knaepkens  Brecht Engelen  Marcel Eens 《Ecology of Freshwater Fish》2012,21(3):453-460

Abstract – Passive integrated transponder tags have been successfully applied in Cottus spp. and have enabled researchers to gather more information about the movement patterns of individual fish in the wild. In two succeeding years during springtime, a portable antenna was used to determine diel movements of bullhead (Cottus perifretum). In 2007, bullhead (N = 26) moved significantly farther distances at night (mean, 0.42 m·h^?1) and dawn (mean, 0.35 m·h^?1) than during daytime (mean, 0.11 m·h^?1; mixed model, P < 0.001, respectively; P = 0.001), which may be due to foraging activities for Gammarus spp. Irrespective of diel period, smaller fish covered significantly longer distances (P = 0.001). In 2008, similar diel movement patterns were observed, but the differentiation between daytime (mean, 0.12 m·h^?1) and night periods (mean, 0.18 m·h^?1) was not significant (mixed model, P = 0.087; N = 49 bullhead). It is discussed that longer tracking intervals used in 2008 (three times per 24‐h instead of every two hours) were not suitable to detect the sheer magnitude of distances covered during a diel period. It is shown that this may be due to ‘site fidelity’ of some individuals: after swimming several metres at night, they returned to the exact location they previously occupied during daytime. In 2008, sex and body size were not related to diel movement. The present study is the first to present a quantitative differentiation between diel distances covered in a Cottus spp.  相似文献   

Water stress and warming impact nutrient use efficiency of Mombasa grass (Megathyrsus maximus) in tropical conditions     

Dilier Olivera Viciedo  Renato de Mello Prado  Carlos A. Martinez  Eduardo Habermann  Roberto Botelho Ferraz Branco  Marisa de Cssia Piccolo  Alexander Calero Hurtado  Kolima Pea Calzada  Luis F. Lata Tenesaca 《Journal of Agronomy and Crop Science》2021,207(1):128-138

Temperature and other abiotic factors, such water and nutrient availability, play an important role for plants in response to the changing environments. At this regard, both warming and drought might affect the nutrient use efficiency (NUE) and growth of Megathyrsus maximus a C4 forage grass of high interest for cattle feeding. However, the nutrient requirements of this species under climate change are unknown. Therefore, we aimed to evaluate the individual and combined effects of two levels of temperature: ambient and elevated temperature (2°C above ambient temperature), and two levels of soil water availability: irrigated plants and non‐irrigated plants on accumulation of leaf nutrients, NUE and biomass production of M. maximus. Temperature control was performed by a temperature free‐air‐controlled enhancement (T‐FACE) system under field conditions. In general, we observed that warming under well‐irrigated conditions increased the leaf accumulation of most nutrients, improving the NUE of N, P, K, Ca, Mg, Cu, Mn and Zn. Plant growth was also enhanced under warming effects, with higher leaf dry mass accumulation and root development. Meanwhile, drought decreased NUE of K, Ca, B and leaf dry biomass, while root growth was stimulated. The combined effects of warming and drought on nutrient accumulation, NUE and plant growth tended to be greater than the individual effects expected from a single factor; thus, warming mitigated the negative impacts of individual drought. In summary, our findings suggest that warming and drought, both as individual and combined factors, will change the nutrient requirements of M. maximus in tropical ecosystems.  相似文献   

Prevalence of feline leukaemia provirus DNA in feline lymphomas     

Weiss AT  Klopfleisch R  Gruber AD 《Journal of Feline Medicine and Surgery》2010,12(12):929-935

A significant drop in the prevalence of feline leukaemia virus (FeLV) antigenaemic cats and antigen-associated lymphomas has been observed after the introduction of FeLV vaccination and antigen-testing with removal of persistently antigenaemic cats. However, recent reports have indicated that regressively infected cats may contain FeLV provirus DNA and that lymphoma development may be associated with the presence of provirus alone. In the present study, we investigated the presence of FeLV antigen and provirus DNA in 50 lymphomas by immunohistochemistry and semi-nested polymerase chain reaction, respectively. Interestingly, almost 80% of T-cell lymphomas and 60% of B-cell lymphomas contained provirus DNA while only 21% of T-cell lymphomas and 11% of B-cell lymphomas expressed FeLV antigen. In conclusion, our results support previous hypotheses that vaccination and removal of persistently antigenaemic cats have led to a drop in FeLV antigen-expressing lymphomas. However, FeLV provirus DNA is still present in a high percentage of feline lymphomas.  相似文献