The N, P And Si Distribution And Control Mechanisms Across Bamboo Forest And Grassland Ecosystem

Ecology stoichiometry and phylogeny have been the important tools for investigating plant growth,development and biomes succession. The plant ecological stoichiometry trait can reflect the relationship between plant and environment, and the plant phylogenic variation can be used to analyze the relationship between the element content variation and plant classification.In this study, we selected the typical bamboo forest ecosystem in southern China and Inner Mongolia typical grassland ecosystem in northern China for collecting the bamboo leaves and the grass plants. The Kjeldahl and molybdenum blue colorimetric method were used to analyze the traits of N, P and Si content of plant, and to research the distribution trait of N, P and Si among bamboo forest and grassland ecosystem from the perspective of ecological stoichiometry and phylogenetics.With analyzing the leaf N, P and N: P ratio in different kinds of bamboo across the bamboo forest ecological system, the result revealed that the mean leaf N content was 19.10 ± 3.87 mg g-1; the mean leaf P content was 1.45 ± 0.34 mg g-1; the mean N:P ratio was 13.46 ± 2.73. From the perspective of ecotype classification, the variation of leaf N content and N: P ratio was: Clustered bamboo > Scattered bamboo > Mixed Bamboo; the variation of leaf P content was: Clustered bamboo > Mixed Bamboo >Scattered bamboo. Phylogenetically, in bambusatae, bambuseae and subtribe, the mean leaf N content among Bambusatae, Bambuseae and Bambuseae were all the highest. It main because that there were the stronger ability of nitrogen fixation of bamboo species(e.g. B. alphonsekarri). Soil nutrient restriction on the N, P element of bamboo forest ecosystem was very significant. So in the bamboo forest management, on the one hand, improving the soil N, P content to promote the growth of bamboo;on the other hand, we can cultivate some bamboo species with strong nitrogen fixation ability. All these measures could improve the bamboo forest ecosystem productivity.We analyzed the data about the leaf N and P content and N:P ratios of 127 plant species from North China, and the data showed that the average value of N, P content and N:P ratios for all species was7.05 ± 6.50 mg g–1, 1.99 ± 0.97 mg g–1 and 9.73 ± 4.83, respectively. Phylogenetically, in order-level, N and P content in most common orders of meadow steppe were higher than that of typical steppe while the N:P ratios in meadow steppe were lower than in typical steppe; and in family-level, the highest N content was found in Leguminosae and the highest N:P ratios were found in Gramineae. The climate and Si factor were closely correlated with N:P stoichiometry(p < 0.05). The phylogenetics play an essential role on shaping grassland N:P stoichiometry. The Graminales plants with high N:P ratios would become the dominant species in North China grassland.The leaf Si content varied largely among bamboo species, between 2.52% ± 0.21% and 8.87% ±0.14%, the mean value was 5.24% ± 1.39%. In bambusatae level, the leaf Si content of Arundinariatae(5.98%) was higher than that of Bambusatae(5.01%); in bambuseae level, the leaf Si content of Arundinariina(5.98%) was higher than that of Bambuseae(5.04%) and Shibataeeae(5.01%); among subtribe level, the leaf Si content of Shibataeinae was the lowest, while the mean leaf Si content of Sasinae was the highest(p < 0.05); among 12 genuses, the mean leaf Si cotent varied from 2.52%(Chimonobambusa) to 7.52%(Sasa). There has large number of phytoliths in bamboo, and plant Si element can participate in atmospheric carbon cycle within phytoliths. The plant Si phylogeny control of bamboo forest ecosystem would play a very important role in improving the atmospheric environment.The Si content of grassland plant species ranged from 0.02% ± 0.00% to 5.77 ± 0.02%, the mean Si content of species was 0.52% ± 0.23%. The Si content among three classes ranged in the following order: Equisetopsida(ferns) > Monocotyledoneae > Dicotyledoneae, it main because that ferns lack stable mechanical tissues for support and make use of a meshwork of Si O2 fibres in the cell walls and lumina of certain plant cells to reinforce mechanical tissues in order to support the weight of the fronds.Among 21 orders, the highest Si content was found in the Equisetales species; Graminales(1.05 ±0.40%) was the second highest after Equisetales; the highest Si content was found in Myrtales(0.04%).The mean Si content of typical steppe(0.65 ± 0.56%) was slightly higher than that of meadow steppe(0.41 ± 0.35%). In general, the phylogenetic control plays an essential role in the Si content variation across grassland ecosystem.