| The arid valley of the upper Minjiang River, located in the transition zone between Western Sichuan plain and Qinghai Tibet Plateau, was one of the most important ecological control area in China, and the valley had a strong foehn effect. The annual average evaporation in this area was nearly 3 times higher than the average annual rainfall. At Valley and the lower slope, sparse shrub was the main vegetation.In this paper,we take vegetation and soil of different slopes as research object of the arid valley of the upper Minjiang River core.By the methods of Geostatistics, We employed content characteristics> semi variance structure features, spatial distribution of soil total phosphorus, available phosphorus, total nitrogen, available nitrogen, total potassium, available potassium and organic matter.We analysis the relationship between the nutrient and vegetation in upper reaches of Minjiang River Valley area of soil drought.In order to provide basic data and technical support andecosystem protection and restoration of vegetation in the region. The results showed that:(1) There were significant differences in soil nutrient content in three plots. The content of total phosphorus, total nitrogen, alkali hydrolysable nitrogen, available potassium and organic matter were highest in half sunny and half shaded slope, while available phosphorus and total potassium content were highest in shaded slope. The content of total phosphorus, available phosphorus, total nitrogen and available potassium were significantly different between different slope directions. Alkaline hydrolysis nitrogen> organic matter and total potassium content in half sunny and half shaded slope were significantly different from those in shaded slope and sunny slope.(2) In all three plots, available phosphorus content was low and available phosphorus content in sunny slope was severely lacking, available phosphorus content of nearly 65% sample was less than 5mg/kg; Although total nitrogen content was still in low leve in sunny slope and nearly 65% sample was less than 5mg/kg.The content in half sunny and half shaded slope and sunny slope could satisfy the basic need. The content of available potassium were severely lacking in sunny slope, and were potentially lacking in shaded slope. The content of available potassium in half sunny and half shaded slope could basically satisfy the plant growth.(3) The coefficients of variation of soil nutrient indices were in the range of 10%-100% which has all reached moderate variability. The coefficient of variation of available phosphorus was largest in all three plots and were all above 50%, indicating a higher variability. The coefficient of variation of other soil nutrients indexes in the three plots were less than 35%, indicating that they were more stable in soil. The coefficient of variation of total nitrogen in sunny slope was smallest which was only 11% and had a small variation.(4) The fitting degree of the semi-variance theory model of total potassium, available potassium and available phosphorus were very high, especially the fitting degree of potassium model was higher than 70%, while the fitting degree of total nitrogen, available nitrogen and organic matter in sunny slope were around 15%.The ratios of nugget of the total phosphorus, total nitrogen and organic matter in sunny slope, the total phosphorus and available phosphorus in shaded slope and the total phosphorus, available phosphorus, total potassium and available potassium in half sunny and half shaded slope were all less than 25% indicating a fairly strong spatial correlation. Meanwhile, the ratio of nugget of alkali hydrolyzable nitrogen in sunny slope were 100%,indicating a low correlation. The ratios of nugget of other soil nutrient indices were all between 25% and 75%,indicating a moderate spatial correlation.(5) Spatial interpolation analysis was carried out using Arcgis software, and the results showed that:the distribution of total phosphorus in shaded slope and half sunny and half shaded slope were gradually decreasing from south to north, while in sunny slope the total phosphorus decreased gradually from center to north and south direction; Available phosphorus content in sunny slope decreased gradually from southwest to northeast and decreased gradually from center to the east and west directions in shaded slope, while in half sunny and half shaded slope available phosphorus content increased gradually from south to north; Total nitrogen in the sunny slope increased gradually from the middle to the East and west sides, and in shaded slope it decreased gradually from west to east. Total nitrogen content had the same change trend with available phosphorus content in half sunny and half shaded slope; The distribution of alkali hydrolyzable nitrogen content in the sunny showed patch effect; Total potassium in all three slopes showed higher in north and lower in south; Organic matter in shaded slope showed a regular change trend which was decreased gradually from west to east. Organic matter in sunny slope decreased from the south to north and in half sunny and half shaded slope decreased gradually from the middle to surroundings.(6) On the whole, soil phosphorus, nitrogen, potassium and organic matter content under vegetation were higher than those of forest gap in the arid valley of the upper Minjiang River. The enrichment ratio of soil nutrient indexes were all higher than 1 except soil phosphorus and potassium in half sunny and half shaded slope. Our results showed that the shrub had "fertile island" effect, and the shrub in sunny slope and shaded slope had a stronger effect in enriching nutrient.(7) The enrichment ratios of Artemisia sacrorum on available phosphorus, total nitrogen, available nitrogen and organic matter were higher than those of Kawaka Akiku, especially that in available phosphorus and nitrogen. Artemisia sacrorum showed a stronger aggregation effect on soil nutrients. |
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