Abstract:To assess the relationship between plant population distribution and soil nutrition in Songnen alkaline grassland, soil nutrition field (SNF) was applied to calculate in process of principal component analysis (PCA). However, PCA require calculating again when new data input datasheet, this disadvantage limited it in field application. Consequently, it was necessary to produce a new approach in calculating SNF, which was able to reveal position of new data in axes of soil nutrition.
Soil quality degradation index (SQDI) was widely used to evaluate soil quality, which estimated the differences of soil properties between standard soil type and test-soil type. From this way, soil quality, i.e., degradation or improvement, was examined. In this paper, soil nutrition data of 1999 was applied to calculate both SQDI and SNF, to analyze the relationship between plant population distribution and soil nutrition in Songnen alkaline grassland, finally discuss it applicability and adaptability.
The standard soil type was sampled in soil where aboveground biomass of Aneurolepidium chinense was the highest in Songnen alkaline grassland, thirteen soil factors, such as organic materials, total N, total P, total K, total Na, total Ca, total Mg, total alkalinity (CO2-3+HCO-3), soluble salt, K+ and Na+ contents, pH and as well as moisture, were used to calculate SQDI. The curve shapes of SQDI were similar to those of PCA, but the range of SNF calculated by SQDI was more extensively than that of PCA. In the result of PCA, the amount of soil factors reduced from thirteen to nine (organic materials, total N, total P, total Na, total Ca, total alkalinity, soluble salt, K+ and Na+ contents) and continued reduced to five (organic materials, total N, total alkalinity, soluble salt and Na+ contents), each curve shape calculated by SQDI and PCA was also similar, yet the results of SNF (e.g., range of values) calculated by five factors were different from the results of nine and/or thirteen soil factors. The results also suggested that we may use nine soil factors to calculate SNF by SQDI rather than thirteen soil factors.
To test application of SQDI for calculating SNF, six new plots were established in the same field in 2007 where we had done in 1999, SQDI was individually calculated by thirteen and nine soil factors respectively, and the value of which were correspondingly located on the soil nutrition axes. The results showed that used SQDI to calculate SNF was feasibility and veracity in assessment soil quality degradation in Songnen alkaline grassland.