Analysis Of Declination Of Pinus Tabulaeformis And It’s Rejuvenation Technologies In Baotou City

Baotou city is an important industrial city in China. Pinus tabulaeformis Carr. is the dominant planted trees in the city. In recent years, the phenomena of needle reddening took place in a large area of the city. The needle reddening postpones the pheno logical phase of the trees. To understand the cause of needle reddening, the environmental factors, such as soil moisture, nutrients, phenomena environment and atmospheric pollution have been studied through a series of laboratory test, field survey and statistics. The main conclusions are as follows:(1) Higher density of reddening needles appears at the southern side of the crown than at the northern side; higher density appears at the middle and upper crown than at the bottom crown; the reddening peak appears in September for that-year needles; the reddening peak appears from July to August for the first-year needles and in May for the multi-year needles.(2) Needle reddening is irrelevant with needle insects and diseases, and the seedling origin and planting time.(3) Needle reddening is positively correlated with soil pH.(4) From soil assays, the contents of soil organic matter, alkaline hydrolysis N, and available K are negatively correlated with needle reddening; the contents of effective Fe, Mn, and Cu are positively correlated with needle reddening; the content of available P is in some extent effective to needle reddening, but not significantly.(5) From needle assays, it is found that with the increase of reddening needles, the contents of N, Mg, Fe, Mn, Cu and Zn decrease; contents of K and Ca increase; and the content of P decreases in the first-year leaves and increases in the second-year leaves.(6) In the normal pine forests, the contents of N, K and Fe in needles are positively correlated with the contents in soil. In severe needle-reddening pine forests, the contents of nitrogen and potassium are irrelevant with their contents in soil; but iron is negatively correlated. This shows that the soil environment could impact the absorption of N, K and Fe from the soil by the trees, which leads to the lack of these elements in needles and finally induces needle reddening.(7) Nitrogen fertilization is effective to re-green first-year reddening needles (2.0-2.5 kg/tree works the best), but the effect is not obvious to the second-year reddening needles; K fertilization is effective to re-green mild needle reddening trees (1.5-2.0 kg/tree works the best), but not effective to severe reddening trees; application of humic acid can effectively inhibit the occurrence of needle reddening in health trees, and can re-green the trees with reddening needles (140-180g/tree works the best); Foliar fertilization of iron is significantly effective to re-green reddening needles:trees with mild reddening is more effective than trees with severe reddening needles, and the first-year needles is more effective than the second-year needles within the same tree; irrigation with recycled water will not result in reddening needles.