Carbon,Nitrogen And Phosphorus Stoichiometry In Different Tissues Of Vitex Rotundifolia In A Sandy Hill Of Poyang Lake

Plants, as the producers, constitute a notably crucial component of biosphere for their significant role in the structure and function of Eco-system.The nutritive element contents in plants and their distribution in various organs are not only influenced by soil acidity but also the their structural characteristics and laws of growth, which can be attributed to both environment and phylogeny. The research to the the chemistry measure configuration and driving factor of C, N, P, as the fundamental life elements,contribute positively to understanding the adaptation tactics to the particular environment of plants, as well as their influence to the changes of environment in the future.Poyang lake sandy hills, as the typical distribution area of desertification in the south, are ridges and mounds composed of loose sand, which essentially reflect degradation of Eco-system.In July, 2014, dominant species—Vitex rotundifolia in sandy hills were collected from eight sampling sites along desertification intensity gradient by the author and her classmates in Duobao village, Duchang county. By analyzing the measuring content of C, N, P in different organs of plants(Flower, leaves, branches, stolons and fine roots), this thesis attempts to discuss the distribution and stoichiometric relationship of nutrient elements in Vitex rotundifolia of various organs as well as its influence by the degrees of desertification. Also, it reveals the relationship between the content of C,N,P and stoichiometric ratio, which lays a solid scientific foundation for a further study on sand adaptation mechanism of Vitex rotundifolia.This paper figures out the Vitex rotundifolia sand adaptation mechanism as well. The main results are as follows:(1) The content of carbon, nitrogen and phosphorus in Vitex rotundifolia ranges from 306.60 to 508.54mg·g-1, 3.29 to 38.00mg·g-1and 0.62 to 1.74mg·g-1separately.The means(±standard deviation) are 410.24±13.14mg·g-1, 16.95±3.45mg·g-1 and1.20±0.26mg·g-1. The ratio of C:N in Vitex rotundifolia fluctuates between10.57~121.90 and C:P ratio varies in the range of 168.91~1802.82, N:P ratio in3.86~73.26. There is little significance in the correlation(P>0.05) between the content of C, N, P in various organs of Vitex rotundifolia and the stoichiometric ratio. And it shows a negative correlation.(2) Vitex rotundifolia flowers has the largest P content, and the largest N:P ratio of all organs. However it has the minimum C:P and C:N value and differentdesertification gradient. nitrogen and phosphorus of different organs content were in the order of flower > leaf > fine roots > stolons > branches. The C:N are showed:stolons > shoots > fine roots > leaves > flowers. The C: P are showed: branches>stolons> leaf> fine root> flower. N: P ratio was not significantly different.(3) The leaf area could not indicate the effects of desertification intensity on Vitex rotundifolia. SLA varied from 81.6 to 206.3cm2·g-1. SLA showed significant intraspecific difference(P<0.05). Leaf N ranged from 16.0 to 23.2 mg·g-1, whereas leaf P varied from 0.82 to 2.20 mg·g-1. Both leaf N and P showed no significant intraspecific difference. SLA was significantly positively correlated with leaf N, but not with leaf P. SLA was very sensitive to desertification intensity variation, and decreased with the increase of desertification. However, leaf N and P, as well as N:P stoichiometry were not sensitive to the desertification variation, and maintained relatively stable. According to the ratio of leaf N:P, Vitex rotundifolia was more limited by phosphorus, rather than nitrogen.(4) Among the correlations between the content of carbon in different organs of Poyang single leaf vitex and the stoichiometric ratio. The correlation between branches and creeping stem are the closest, followed by the correlation between branches and flowers, stolons, which mainly appears in the N and C: N ratio.(5) The content of carbon in different organs of Poyang single leaf vitex changes little with the intensity of desertification. Instead, the content of carbon in different organs of Poyang single leaf vitexchanges remarkable with the desertification degree. And differences in organs are dominant factors which affect the stoichiometric ratio of Vitex rotundifolia. The desertification degree and the interaction of different organs significantly affects the Vitex rotundifolia C, N, P content and the stoichiometry.