| Nitrogen, phosphorus and potassium are essential obbligato direct nutritive element which have a limit role for forest growth and development, the growth of individual plants, productivity growth and the whole ecosystem of communities have a limited role. Almost all the nitrogen, phosphorus and potassium absorbed from the soil by trees, forest productivity is often influenced by soil fertility status, while growth and development of trees will have an impact on the soil. In this study, 22-year-old Larch Forests was chosen for the study, which conducted by nitrogen and phosphorus fertilization experiment for three consecutive years, determined the content of N, P, K of needles, stems, fine roots and soil samples and available N, available P, available K of soil in different growth stages, analyse soil and plant N: P stoichiometry characteristics, clear the effect of fertilization on biomass and potassium content and distribution, select the fertilizer treatment which has higher fertilizer utilization, discuss the correlation between nitrogen, phosphorus and potassium in soil and nitrogen, phosphorus and potassium in root, stem, leaf. The main results were as follows:The fertilization treatment of Nitrogen and phosphorus can significantly improve the needles in nitrogen, phosphorus, potassium content in leaves, Single nitrogen can improve nitrogen content; Single phosphorus can increase the phosphorus content, potassium content. The most productive period in the growing season, N content in leaves is higher. In the mid and late growing season, the stem and fine root phosphorus potassium content is higher.Fertilization can increase the soil nutrient content in a certain extent, the content of nitrogen, phosphate fertilizer on soil of north China larch N, P, K all have important influence. The fertilization treatment of nitrogen can improve nitrogen and potassium content in soil, and phosphorus content is slightly lower. The fertilization treatment of P can improve N, P, K content in soil. The fertilization treatment of nitrogen and phosphorus can significantly improve N, P, K content in the soil. Soil total nitrogen increased after the seasons to reduce, total nitrogen in July and August of soil is low. Soil total phosphorus reduced with seasons, soil total phosphorus in July and August is higher. Soil potassium is lower before the rising, is lower total potassium in soil in July and August, soil available N, P, K rise before reduced. Soil available nutrient content changes with full effect nutrients, nitrogen can improve the soil available nitrogen and phosphorus, potassium application can improve the soil available nitrogen, available phosphorus and available potassium, the effect of nitrogen and phosphorus is more significant.The fertilization treatment of nitrogen and phosphorus has the important influence in N/P of soil and plantation. The fertilization treatment of single phosphorus and single nitrogen will increase N/P in the soil. The fertilization treatment of single nitrogen will increase N/P of needles, fine root and stem. The fertilization treatment of single phosphorus can decrease N/P of needles, fine root and stem; The fertilization treatment of nitrogen and phosphorus can increase N/P of needles, fine root and stem, but the effect is not significant. After fertilization, the soil N/P is higher, as the change of seasons, different fertilizer treatments in the soil N/P has fallen. The results showed that phosphorus fertilizer have an impact on soil N/P, as the change of time, gradually restore balance of soil ecosystem. N/P of needles, fine root and stem as time changes, presents a trend of reducing the rise, the most productive period in the growing season(July and August) to achieve maximum value. In the growing season, soil N/P value in the range of 0.21 to 0.98; N/P of needles range of 1.03-6.05; the N/P in fine roots range of 2.66-11.65; N/P of Stems range of 1.42-1.42. In this study, under different fertilizer treatments, the north China larch needles in the N/P values are lower than other scholar’s research results shows that experimental area of north China larch restricted by N. North China larch plantations biomass of different organs of size distribution is stem > fine root> needle. Single nitrogen and nitrogen and phosphorus can obviously increase biomass of the needles, fine root and stem, single phosphorus increased biomass of needles, fine root and stem, effect is relatively small. The fertilization treatment can increase total potassium content of the needles, stem, fine root and plant, and among them, the effect of nitrogen and phosphorus is significant. At the beginning of the growing season, the fertilization of larix pricipis-rupprechtii potassium content distribution has an important influence. The fertilization treatment of single nitrogen, single phosphorus and nitrogen phosphorus will reduce the ratio of potassium in the fine root and needles, increasing the ratio of potassium in the stem, The fertilization treatment of nitrogen and phosphorus is remarkable. At the beginning of the growing season, the north China larch potassium keep weight distribution of fine root > stem > needles, which are the largest proportion of fine roots, potassium is about 50%. In the most productive period, the fertilization treatment of nitrogen and phosphorus can significantly reduce potassium the proportion of the needles in the fine root, increasing the ratio of potassium in the stem, the effect of the fertilization treatment of nitrogen and phosphorus is more significant, single nitrogen increased potassium proportion of fine roots, the effect is not significant. In mid and late growing season, nitrogen and phosphorus fertilizer can reduce the ratio of potassium in fine roots with needles, increase the proportion of the stem. The fertilization treatment of nitrogen and phosphorus significantly increase the ratio of potassium in the stem, single nitrogen and phorous processing will also increase the ratio of potassium in stems, but the effect is not significant. Fertilizer use efficiency will change along with the increase in fertilizer rate, low nitrogen treatment is higher than high levels of nitrogen fertilizer utilization rate, the fertilization treatment of nitrogen and phosphorus can improve the utilization efficiency of nitrogen and phosphate fertilizer. High utilization rate of fertilizer is low nitrogen and phosphate fertilizer treatment. The correlation of total nitrogen and total phosphorus content is significantly in needles, stem, fine root(p ≤0.01). The total phosphorus, available nitrogen content in the soil and north China larch needles, fine roots and stems of N, P, K content is a significant correlation. |
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