| Pinus bungeana, the endemic plant species of China, has high economic and ornamental value. The natural forest of Pinus bungeana has a widely distribution in China but the distribution areas are very small and scrappy in small quantities. In addition, the quantities of Pinus bungeana gradually decrease due to the variations of environmental conditions and man-made sabotage. It has important practical significance for understanding the nutrient regulation mechanism of Pinus bungeana by using ecological stoichiometry methods to find nutrient concentration relationships among of Pinus bungeana needle, litter fall and soil. To determine the driving force of patterns of needle stoichiometry for Pinus bungeana, we also studied the relationships between needle stoichiometry and environmental factors.Pearson Analysis of SPSS software was used in nutrient concentration of needle, litter fall and soil, to clarify the nutrient cycling in Pinus bungeana and find the limiting nutrient element. We also evaluated the relationship between needle stoichiometry and environmental factors and explored how the environmental factors influence the needle stoichiometry of Pinus bungeana. A RBF artificial neural network model was developed by chemical properties of soil, geographical factors, climatic factors as input factors, needle C, N and P concentration of Pinus bungeana as output factors. The results showed that:(1) the study area of Pinus bungeana needle C concentration was 422.36~451.24 mg g-1,mean 432.01 mg g-1, range of needle N concentration was 17.01~26.08 mg g-1, mean 19.09 mg g-1, range of needle P concentration was 1.14~2.89 mg g-1, the average is 1.56 mg g-1. The average needle N concentration is less than the leaf N concentration of global and China’s plants, while the average needle P concentration is much higher than the leaf P concentration of global and China’s plants; spatial variability of Pinus bungeana needle C concentration less than N, the concentration of P in needles; the average value of needle N:P is 14, indicating a nationwide Pinus bungeana on the whole is not limited by N, not limited by P, but the different regions of Pinus bungeana N, P elements limit is different, in the distribution of Pinus bungeana in southwest region of N:P average of 7.30, its limited by N; northern in addition to five deer mountain was limited by N, other regions is not affected by the N and P limitation; central and western areas and is not affected by the N and P limitation; south of Lingchuan County n limitation, Shennong mountain was limited by P.(2) Among the components of Pinus bungeana forest, needle litter N and N have strong correlation, coefficient of 0.62; needles P and soil P significantly two times, with the increasing of soil P needle P increased first and then decreased; the litter and soil nutrient elements correlation is weak; needle litter soil between the three the nutrient of little relevance,is related to microbial distribution in soil and climatic conditions, with the passage of time,the litter decomposition is continuously, and different elements content in needles gradually become larger and the relationship is weak.(3) Pinus bungeana needle C concentration changes with the latitude and longitude showed no obvious regularity, this may be because the needle C elements were mainly derived from CO2 in the air rather than in soil, which is caused by the change of geographical factors for changing environmental conditions has little effect on needle C elements; needle N concentration with the increase of longitude first decreased and then increased, change the trend in latitude direction is not obvious, which may be related to the concentration of N is more affected by the change of precipitation is related to the longitude gradient; needle P concentration in the longitude and latitude gradient showed strong trend, as longitude increased decreased first and then decreased, and the influence in the latitudinal direction than the longitude and the concentration of P, which may be more affected by temperature changes on the latitudinal gradient.(4) The ecological stoichiometry of Pinus bungeana needle values by regression analysis,geography, climate and soil factors, no significant changes in C, N, trend of needle P concentration and altitude, that altitude changes in needle nutrient concentration had little effect; there are two type of relationship of needle C, N, P and other 9 influence factors, these9 factors can be divided into two categories, one is based on the change of precipitation on the latitudinal gradient temperature and longitude gradient, the other is the nutrient content in soil,needle C, N, shows the influence of the concentration of P is mainly hydrothermal conditions and the distribution of soil nutrient content.(5) The influence of 9 variables of Pinus bungeana needle ecological stoichiometry value as a factor in the input layer, the C, N, P in needles of Pinus bungeana were as RBF artificial network output layer neurons to establish Pinus bungeana needle ecological stoichiometry prediction model, and analyze the error with the measured values, the error range is less than 20%, indicating the structure prediction the model of artificial neural network is more reasonable, predicted value has higher precision and reliability, and can be used in prediction of ecological stoichiometry in a large range of values of the needles of Pinus bungeana. |
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