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141.
Paul C. Stoy Mathew Williams Mathias Disney Ana Prieto-Blanco Brian Huntley Robert Baxter Philip Lewis 《Landscape Ecology》2009,24(7):971-986
Transferring ecological information across scale often involves spatial aggregation, which alters information content and
may bias estimates if the scaling process is nonlinear. Here, a potential solution, the preservation of the information content
of fine-scale measurements, is highlighted using modeled net ecosystem exchange (NEE) of an Arctic tundra landscape as an
example. The variance of aggregated normalized difference vegetation index (NDVI), measured from an airborne platform, decreased
linearly with log(scale), resulting in a linear relationship between log(scale) and the scale-wise modeled NEE estimate. Preserving
three units of information, the mean, variance and skewness of fine-scale NDVI observations, resulted in upscaled NEE estimates
that deviated less than 4% from the fine-scale estimate. Preserving only the mean and variance resulted in nearly 23% NEE
bias, and preserving only the mean resulted in larger error and a change in sign from CO2 sink to source. Compressing NDVI maps by 70–75% using wavelet thresholding with the Haar and Coiflet basis functions resulted
in 13% NEE bias across the study domain. Applying unique scale-dependent transfer functions between NDVI and leaf area index
(LAI) decreased, but did not remove, bias in modeled flux in a smaller expanse using handheld NDVI observations. Quantifying
the parameters of statistical distributions to preserve ecological information reduces bias when upscaling and makes possible
spatial data assimilation to further reduce errors in estimates of ecological processes across scale. 相似文献
142.
143.
Robert A. Mccleery 《Landscape Ecology》2009,24(4):483-493
Predator stimuli created by humans in the urban environment may alter animals’ anti-predator behaviors. I hypothesized that
habituation would cause anti-predator behaviors to decrease in urban settings in response to humans. Additionally, I hypothesized
that populations habituated to humans would show reduced responses to other predator stimuli. I observed three populations
of squirrels (urban, suburban and rural) responses to human approaches, red-tailed hawk vocalizations (Buteo jamaicensis) and coyote (Canis latrans) vocalizations. Mahalanobis distances of anti-predator behaviors in response to human approaches were consistent with the
urban–rural gradient. Flight initiation distances (X
2 = 26.33, df = 2, P < 0.001) and amount of time dedicated to anti-predator behavior (X
2 = 10.94, df = 2, P = 0.004) in response to human approaches were also consistent with the urban–rural gradient. Supporting the habituation hypothesis,
naive juvenile squirrels increased flight initiation distances (X
2 = 35.89, df = 1, P < 0.001) and time dedicated to anti-predator behaviors (X
2 = 9.46, df = 1, P = 0.002) relative to adult squirrels in the same urban environment. Time dedicated to anti-predator behaviors differed among
all three sites in response to both coyote (X
2 = 9.83, df = 2, P = 0.007) and hawk (X
2 = 6.50, df = 2, P = 0.035) vocalizations. Responses to both vocalizations on rural sites (coyote = 45%, hawk = 55%) greater than twice that
found on the urban sites (coyote = 11%, hawk = 20%). This is possibly the first case of a transfer of habituation demonstrated
under field conditions. 相似文献
144.
145.
Combining top-down and bottom-up dynamics in land use modeling: exploring the future of abandoned farmlands in Europe with the Dyna-CLUE model 总被引:9,自引:0,他引:9
Land use change is the result of interactions between processes operating at different scales. Simulation models at regional
to global scales are often incapable of including locally determined processes of land use change. This paper introduces a
modeling approach that integrates demand-driven changes in land area with locally determined conversion processes. The model
is illustrated with an application for European land use. Interactions between changing demands for agricultural land and
vegetation processes leading to the re-growth of (semi-) natural vegetation on abandoned farmland are explicitly addressed.
Succession of natural vegetation is simulated based on the spatial variation in biophysical and management related conditions,
while the dynamics of the agricultural area are determined by a global multi-sector model. The results allow an exploration
of the future dynamics of European land use and landscapes. The model approach is similarly suitable for other regions and
processes where large scale processes interact with local dynamics. 相似文献
146.
L.H. Wang X.H. Gu M.Y. Hua S.L. Mao Z.H. Zhang D.L. Peng X.F. Yun B.X. Zhang 《Scientia Horticulturae》2009
The root-knot nematodes (Meloidogyne spp.) are important nematode pests and cause serious diseases in pepper in the world. No molecular markers linked to the nematodes resistance N gene have been reported. In this paper, ‘Carolina Wonder’ (Capsicum annuum L.), a sweet pepper line resistant to root-knot nematode with N gene, ‘20080-5-29’ (C. annuum L.), an inbred line susceptible to root-knot nematode with good horticultural characteristics, and their F2 progeny with 320 individuals were used as materials. Evaluation of resistance and susceptibility of parental lines, F1 and F2 progeny inoculated with root-knot nematodes (Meloidogyne incognita) were carried out. ‘Bulked segregant analysis’ method was used to search for polymorphic markers from 512 pairs of AFLP primers. Based on the assessment of resistance and susceptibility and polymorphism of the AFLP marker in F2 population, the genetic linkage distance between the AFLP marker and the N gene was estimated. One AFLP marker E39/M41-339 was obtained and transferred to a SCAR marker amplifying a 315 bp DNA fragment linked to the N resistant allele and a 331 bp fragment linked to the N+ susceptible allele. The distance between the molecular marker and the nematodes resistance N gene is 6.3 cM. This research delivered a valuable tool for the marker assisted selection of nematodes resistance in pepper. 相似文献
147.
Bahiagrass (Paspalum notatum) is a warm-season grass used primarily in pastures and along highways and other low maintenance public areas in Florida.
It is also used in landscapes to some extent because of its drought tolerance. Bahiagrass can survive under a range of moisture
conditions from no irrigation to very wet conditions. Its well-watered consumptive use has not been reported previously. In
this study, bahiagrass crop coefficients (K
c) for an irrigated pasture were determined for July 2003 through December 2006 in central Florida. The eddy correlation method
was used to estimate crop evapotranspiration (ETc) rates. The standardized reference evapotranspiration (ETo) equation (ASCE-EWRI standardization of reference evapotranspiration task committee report, 2005) was applied to calculate
ETo values using on site weather data. Daily K
c values were estimated from the ratio of the measured ETc and the calculated ETo. The recommended K
c values for bahiagrass are 0.35 for January–February, 0.55 for March, 0.80 for April, 0.90 for May, 0.75 for June, 0.70 for
July–August, 0.75 for September, 0.70 for October, 0.60 for November, and 0.45 for December in central Florida. The highest
K
c value of 0.9 in May corresponded with maximum vapor pressure deficit conditions as well as cloud free conditions and the
highest incoming solar radiation as compared to the rest of the year. During the summer (June to August), frequent precipitation
events increased the cloud cover and reduced grass water use. The K
c annual trend was similar to estimated K
c values from another well-watered warm-season grass study in Florida. 相似文献
148.
Estimation of actual evapotranspiration for a drip-irrigated Merlot vineyard using a three-source model 总被引:3,自引:3,他引:0
A study was performed in order to evaluate the three-source model (Clumped model) for direct estimation of actual evapotranspiration
(ETa) and latent heat flux (LE) over a drip-irrigated Merlot vineyard trained on a vertical shoot positioned system (VSP) under
semi-arid conditions. The vineyard, with an average fractional cover of 30%, is located in the Talca Valley, Region del Maule,
Chile. The performance of the Clumped model was evaluated using an eddy covariance system during the 2006/2007 and 2007/2008
growing seasons. Results indicate that the Clumped model was able to predict ETa with a root mean square error (RMSE), mean bias error (MBE), and model efficiency (EF) of 0.33, −0.15 mm day−1 and 74%, respectively. Also, the Clumped model simulated the daytime variation of LE with a RMSE of 36 W m−2, MBE of −8 W m−2, and EF of 83%. Major disagreement (underestimated values) between observed and estimated values of ETa was found for clear days after rainfall or foggy days, but underestimated values were less than 10% of the data analysis.
The results obtained in this study indicate that the Clumped model could be used to directly estimate vine water requirements
for a drip-irrigated vineyard trained on a VSP. However, application of the Clumped model requires a good characterization
of the drip-irrigated vineyard architecture. 相似文献
149.
Surface velocity coefficients for application of the float method in rectangular and compound open channels 总被引:1,自引:1,他引:0
A three-dimensional mathematical hydraulic model was applied to calculate velocity profiles and discharge under steady, uniform
flow conditions in rectangular and compound open-channel cross sections. The velocity profiles were used to calculate surface
velocity coefficients for use with the float method for discharge estimation in the field. Surface velocity coefficients were
calculated at increments of one-eighth of the base width from the vertical walls to the center of the cross section, and submergence
of the float object from 0 to 30 cm, with a 5-cm depth increment. Model results were summarized to show the relationship between
surface velocity coefficient and channel characteristics compared to values published by the US Bureau of Reclamation (USBR).
For rectangular cross sections, the coefficients from the model are generally higher than the published USBR values. But the
coefficients from the model and USBR are in very close agreement for the tested compound cross sections. The published coefficients
by the USBR are a function of only average water depth. However, the model results show that the coefficient is also related
to channel size, cross-sectional aspect ratio, surface roughness height, float submergence and lateral location of the float
object. These factors should be included in the determination of the surface velocity coefficient to improve the discharge
estimations from the application of the float method. 相似文献
150.
When using saline waters, sprinkling irrigation at night is a recommended practice to reduce evaporation, salt absorption
by the wetted leaves and its negative effects on crops. We measured shoot ion concentrations (Cl−, Na+ and K+) and total dry matter (TDM) in alfalfa subject to diurnal and nocturnal saline sprinkler irrigations and established potential
relationships among them. The work was carried out along the 2004–2006 growing seasons using EC waters from 0.5 to 5.6 dS m−1. Saline sprinkling irrigations linearly increased shoot Cl− and Na+ and decreased shoot K+. Even though daytime evaporation was much higher than nigh-time, shoot ion accumulation and TDM were similar in the diurnal
and nocturnal irrigations. The salinity tolerance of alfalfa decreased in year 2006 due to increases in shoot Cl− and, particularly, shoot Na+. The lower threshold for shoot Na+ (276 meq kg−1) than for shoot Cl− (726 meq kg−1) shows that alfalfa is more sensitive to Na+ than to Cl−, and that Na+ accumulation is the preponderant cause of alfalfa yield decline after 3 years of sprinkling with saline waters. 相似文献