The study comparatively analyzed the variability of some agrochemical indices related to agricultural and forest land, in the area of the “Cenad Forest Protected Area”, Timis County, Romania. Within the agrochemical indices, the soil reaction (pH), total nitrogen content (TN %), phosphorus content (P, ppm), potassium content (K, ppm), calcium content (Ca, ppm) and magnesium content (Mg, ppm) were determined. The ANOVA test confirmed the presence of the variance and the statistical safety of the data (F> Fcrit, p <0.001; Alpha = 0.001). The correlation analysis showed some correlations and their statistical significance between TN and pH (r = -0.993**), between K and pH (r = -0.963*), between Ca and pH (r = 0.963*), and between K and TN (r = 0.974*). The variation of the mineral elements was described by polynomial equations, in different conditions of statistical safety: TN variation in relation to the soil reaction (pH) in conditions of R2 = 0.986, p = 0.117; variation of potassium (K) in relation to the soil reaction (pH) under conditions of R2 = 0.993, p = 0.080; variation of calcium (Ca) in relation to soil reaction (pH) under conditions of R2 = 0.978, p = 0.147; variation K in relation to TN under conditions of R2 = 0.997, p = 0.0531. Based on the coefficient of variation, the agrochemical indices presented differentiated values, CVTN = 50.4183, CVCa = 40.0339, CVK = 22.9719, CVP = 21.9803, CVMg = 12.0496, CVpH = 3.1064. In the PCA, correlation matrix, PC1 explained 71.422% of variance, and PC2 applied 26.357% of variance. The regression analysis evaluated the variation of P in relation to the soil pH and the Ca content, respectively the Mg content and found models in the form of equations, as well as 3D graphic and in the form of isoquants models. From the analysis of the 3D models of variation of P in relation to the considered indices, it was found differentiated situations, respectively the decrease of the P availability in relation to Ca and the increase of the P availability in relation to Mg, at the same pH range.
The study analyzed leaves of ivy, Hedera helix L., in order to characterize the geometry of the leaves. The leaf samples were taken from the Protected Area "Padurea Cenad", Timis County, Romania. The dimensions of the leaves (L, w) were determined by measurement, with a precision of 0.5 mm. The leaves were scanned, 1:1 ratio. From the analysis of the leaf images, the perimeter (Per) and scanned leaf area (SLA) were determined. The correction factor (CF), specific to ivy leaves, was found (CF=0.69) for the purpose of use in non-destructive methods of measuring the leaf area (MLA) based on a general formula of the type MLA=L·w·CF. The fitting relationship between MLA and SLA was described by a linear equation, under statistical safety conditions (p<0.001). Different ratios between leaf parameters were calculated in order to characterize the leaf geometry (L/w, Per/L, Per/w, SLA/L, SLA/w, SLA/Per, MLA/L, MLA/w). Different levels of correlation between basic leaf parameters, leaf surface and the calculated ratios were identified, with statistical certainty for most cases (p<0.001). Both from the correlation analysis and from the regression analysis, a tighter relationship of MLA with foliar parameters (L, w) was found than in the case of SLA (based on r, R2, F test, and RMSEP values). From the analysis of the values obtained for the coefficient of variation (CV), the highest variability was found in the case of SLA (CVSLA=38.6726), followed by MLA (CVMLA=36.8300), and the lowest variability in the case of the ratio Per/w (CVPer/w=10.1515). The regression analysis facilitated the finding of some equations that described the variation of SLA and MLA with leaf parameters (L, w, Per) in conditions of statistical safety (p<0.001). 3D graphic models and in the form of isoquants were also generated, which represented the MLA variation in relation to the dimensional parameters of the ivy leaves studied.
The study analyzed and evaluated the content of some microelements and heavy metals in the conditions of two categories of agricultural and forest land. The study location was in the "Padurea Cenad" Protected Area and the bordering agricultural area, Timis County, Romania. Among microelements, the content of iron (Fe, ppm), manganese (Mn, ppm), copper (Cu, ppm) and zinc (Zn, ppm) was analyzed, and among heavy metals, the content of chromium (Cr, ppm), nickel (Ni, ppm) and lead (Pb, ppm) was analysed. The ANOVA test was used to quantify the statistical reliability of the data, and to evaluate the presence of variance in the data set (Alpha=0.001). The correlation level of the determined microelements and heavy metals was evaluated by correlation analysis (Pearson), and the statistical safety was evaluated based on p parameters (p <0.05; p <0.01; p <0.001). Correlations of different intensity levels were recorded between the analyzed elements (eg r=0.914 between Fe and Cu; r=0.916 between Fe and Ni; r=0.935 between Mn and Zn; r=0.933 between Mn and Cr; r= 0.920 between Zn and Cr; r=0.990 between Ni and Pb; r=0.851 between Fe and Pb; r=-0.732 between Mn and Ni; r=-0.731 between Mn and Pb). A high level of variability was recorded in the case of Pb content (CVPb=43.8455), and a low level of variability in the case of Mn content (CVMn=8.1807). Intermediate values was recorded in the other cases, CVCr=25.4583, CVNi=23.9941, CVCu=23.0055, and CVFe=21.0282 respectively. According to PCA, PC1 explained 70.240% of variance, and PC2 explained 22.469% of variance. Separate positioning in relation to the content of microelements and heavy metals (as biplot) was found at CP1-A and CP2-F. Associated with the content of Mn, Zn and Cr (as biplot) CP2-A was positioned, and associated with Fe, Cu, Ni and Pb (as biplot) CP1-F was associated.
The present study evaluated the relationship between dimensional parameters of annual growth of shoots in woody species. The biological material was represented by the species Tilia cordata L., from the area of the Cenad Forest Protected Area, Timis County, Romania. The length of the internodes (IL) and the diameter of the internodes (ID) were determined in relation to the position of the internodes on the shoot (IP). The length of the internodes (IL), in relation to their position on the shoot, was described by a polynomial equation of degree 3, in statistical safety conditions, according to R2 = 0.832, p = 0.00014. The diameter of the internodes (ID), in relation to their position on the shoot (IP), was described by a polynomial equation of degree 2, in statistical safety conditions, according to R2 = 0.982, p <0.001. Within PCA, PC1 explained 63.002% of variance, and PC2 explained 36.998% of variance. Cluster Analysis led to the grouping of internodes based on Euclidean distances, in relation to the values of IL and ID parameters, in statistical safety conditions (Coph. Corr = 0.913). The highest degree of similarity was found in the case of internodes I7 and I8, in which case SDI = 0.2786. The regression analysis facilitated the obtaining of an equation that described the variation of the internode diameter (ID) in relation to the internode position (IP) and internode length (IL) analyzed simultaneously, in statistical safety conditions according to R2 = 0.995, p <0.001. 3D and isoquant models were obtained to represent the ID variation in relation to IP and IL. From the comparative analysis of the real data and the graphical representation of the models from the obtained equations, deviations of the ID values were found in the case of internodes I6, I7, I8 and I9 from the theoretical model. This can be associated with certain stress conditions generated by vegetation factors during the formation of the respective internodes. The approach can be extended to other arboreal or fruit species of economic interest.
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