Carbonate determination in soils by mid-IR spectroscopy with regional and continental scale models.

A Partial Least Squares (PLS) carbonate (CO3) prediction model was developed for soils throughout the contiguous United States using mid-infrared (MIR) spectroscopy. Excellent performance was achieved over an extensive geographic and chemical diversity of soils. A single model for all soil types performed very well with a root mean square error of prediction (RMSEP) of 12.6 g kg-1 and was further improved if Histosols were excluded (RMSEP 11.1 g kg-1). Exclusion of Histosols was particularly beneficial for accurate prediction of CO3 values when the national model was applied to an independent regional dataset. Little advantage was found in further narrowing the taxonomic breadth of the calibration dataset, but higher precision was obtained by running models for a restricted range of CO3. A model calibrated using only on the independent regional dataset, was unable to accurately predict CO3 content for the more chemically diverse national dataset. Ten absorbance peaks enabling CO3 prediction by mid-infrared (MIR) spectroscopy were identified and evaluated for individual and combined predictive power. A single-band model derived from an absorbance peak centered at 1796 cm-yielded the lowest RMSEP of 13.5 g kg-1 for carbonate prediction compared to other single-band models. This predictive power is attributed to the strength and sharpness of the peak, and an apparent minimal overlap with confounding co-occurring spectral features of other soil components. Drawing from the 10 identified bands, multiple combinations of 3 or 4 peaks were able to predict CO3 content as well as the full-spectrum national models. Soil CO3 is an excellent example of a soil parameter that can be predicted with great effectiveness and generality, and MIR models could replace direct laboratory measurement as a lower cost, high quality alternative.

Gas Exchange and Co-regulation of Photochemical and Nonphotochemical Quenching in Bean during Chilling at Ambient and Elevated Carbon Dioxide.

The effects of elevated (700 micromol mol(-1)) and ambient (350 micromol mol(-1)) CO(2) on gas exchange parameters and chlorophyll fluorescence were measured on bean (Phaseolus vulgaris) during 24 h chilling treatments at 6.5 degrees C. Consistent with previous research on this cultivar, photosynthetic decline during chilling was not significantly affected by CO(2) while post-chilling recovery was more rapid at elevated compared to ambient CO(2). Our primary focus was whether there were also CO(2)-mediated differences in demand on nonphotochemical quenching (NPQ) processes during the chilling treatments. We found that photosystem II quantum yield and total NPQ were similar between the CO(2) treatments during chilling. In both CO(2) treatments, chilling caused a shift from total NPQ largely composed of q(E), the protective, rapidly responding component of NPQ, to total NPQ dominated by the more slowly relaxing q(I), related to both protective and damage processes. The switch from q(E) to q(I) during chilling was more pronounced in the elevated CO(2) plants. Using complementary plots of the quantum yields of photochemistry and NPQ we demonstrate that, despite CO(2) effects on the partitioning of NPQ into q(E) and q(I) during chilling, total NPQ was regulated at both CO(2) levels to maximize photochemical utilization of absorbed light energy and dissipate only that fraction of light energy that was in excess of the capacity of photosynthesis. Photodamage did occur during chilling but was repaired within 3 h recovery from chilling in both CO(2) treatments.

Effects of elevated carbon dioxide on gas exchange and photochemical and nonphotochemical quenching at low temperature in tobacco plants varying in Rubisco activity.

Elevated (700 micromol mol-1) and ambient (350 micromol mol-1) CO2 effects on total ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activity, photosynthesis (A), and photoinhibition during 6 d at low temperature were measured on wild type (WT), and rbcS antisense DNA mutants (T3) of tobacco (Nicotiana tabacum L.) with 60% of WT total Rubisco activity. Prior to the low temperature treatment, A and quantum yield of PSII photochemistry in the light adapted state (phiPSII) were significantly lower in T3 compared to WT at each CO2 level. At this time, total nonphotochemical quenching (NPQTotal) levels were near maximal (0.75-0.85) in T3 compared to WT (0.39-0.50). A was stimulated by 107% in T3 and 25% in WT at elevated compared to ambient CO2. Pre-treatment acclimation to elevated CO2 occurred in WT resulting in lower Rubisco activity per unit leaf area and reduced stimulation of A. At low temperature, A of WT was similar at elevated and ambient CO2 while stimulation of A by elevated CO2 in T3 was reduced. In addition, at low temperature we measured significantly lower photochemical quenching at elevated CO2 compared to ambient CO2 in both genotypes. NPQTotal was similar (0.80-0.85) among all treatments. However, a larger proportion of NPQTotal was composed of qI,d, the damage subcomponent of the more slowly relaxing NPQ component, qI, in both genotypes at elevated compared to ambient CO2. Greater qI,d, at elevated CO2 during and after the low temperature treatment was not related to pre-treatment differences in total Rubisco activity.

Climate change and shifts in spring phenology of three horticultural woody perennials in northeastern USA.

We evaluated spring phenology changes from 1965 to 2001 in northeastern USA utilizing a unique data set from 72 locations with genetically identical lilac plants (Syringa chinensis, clone "Red Rothomagensis"). We also utilized a previously validated lilac-honeysuckle "spring index" model to reconstruct a more complete record of first leaf date (FLD) and first flower date (FFD) for the region from historical weather data. In addition, we examined mid-bloom dates for apple (Malus domestica) and grape (Vitis vinifera) collected at several sites in the region during approximately the same time period. Almost all lilac sites with significant linear trends for FLD or FFD versus year had negative slopes (advanced development). Regression analysis of pooled data for the 72 sites indicated an advance of -0.092 day/year for FFD (P=0.003). The slope for FLD was also negative (-0.048 day/year), but not significant (P=0.234). The simulated data from the "spring index" model, which relies on local daily temperature records, indicated highly significant (P<0.001) negative slopes of -0.210 and -0.123 day/year for FLD and FFD, respectively. Data collected for apple and grape also indicated advance spring development, with slopes for mid-bloom date versus year of -0.20 day/year (P=0.01) and -0.146 (P=0.14), respectively. Collectively, these results indicate an advance in spring phenology ranging from 2 to 8 days for these woody perennials in northeastern USA for the period 1965 to 2001, qualitatively consistent with a warming trend, and consistent with phenology shifts reported for other mid- and high-latitude regions.