Characteristics Of Elements Contents In Trees From Nonggang Karst Forest And Their Associations With Habitats

The research on the characteristic of elements contents in forest plants helps to kown the interactions between plants and the ecological processes involved of forest ecosystem, and provides a theoretical basis for conservation, utilization and management of forest resources. In this paper, the contents of elements in leafs, branches and flowers of some trees which showed good associations with their habitats in Nonggang karst forest were made analysis, and the allocation of elements nutrients in different organs was discussed. Besides, the adaptative significances of elements concentrations and distributions were elucidated. The main results were as follows:(1) The rank of the average amount for elements in leafs is C>Ca>N>K>Mg>S>P >Na>Mn>Fe>Cu>Zn>A1. The concentrations of Mg and Ca in leaf were in high level, characterizing the soil in karst was magnesium and calcium-rich. Principal component analysis showed that characteristics of elements contents among tree species had a certain law which could reveal a differentiation of tree species habitat.(2) The rank of the average amount for elements in branches is C>Ca>N>K>P≈S >Mg>Fe>Mn>Zn>Cu. Cu tended to be low in branch, and was not detected in some species. The mean and variance coefficient of P content in branch of trees in this area both were high relatively, compared with branch of trees in other areas. Trees grown in this area might have the unique and diverse patterns of phosphorus uptake and utilization.(3) The rank of the average amount for elements in flowers is C>Ca>N>K>P>S >Mg>Fe>Mn>Cu>Zn. Carbon content of flowers was 55.47±1.18%, which was relatively higher. It reflected that tree species in Nonggang karst forest invested more material and energy in flower.(4) In the comparision among leaf, branch and flower, leaf was higher of N, Ca, Mg, S, Cu, Zn, Fe and Mn contents; branch was relatively rich in C content, whereas poorer of other elements; flower was higher of C, P and K contents, especially P. Phosphorus might be the most important nutrient element in floral development. Other elements in flower were also comparatively high except Mg. The leaf elements contents had good relationship with branch and flower elements contents. And the three major nutrient elements (N, P and K) in flower were closely related to the contents of some elements in leaf and branch.(5) There were some significantly correlated elements pairs in leaf, branch and flower, respectively with 19%,9% and 16% of their all elements pairs. It was found that leaf had the most. This partly reflected the synergistic or antagonistic actions between elements in leaf were more obvious. And there was a strict requirements regarding proportion between elements in leaf.(6) Among different slope positions (peak, slope and valley), trees species grown in slope were hihger than valley and peak were lowest of leaf and flower mineral element contents, this order was identical to the soil natural fertilities. The chartcters of elements contents in leaf and flower could reflect the soil fertility conditions. There was variability among trees species from different habitats in the elements distribution:In peak where drought and nutrient deficiency was obvious, trees were high in carbon content and low in other elements contents. In valley where light resource was relatively insufficient, trees had laid more emphasis on elements contents of leaf and branch, especially branch. Trees grown in slope had a relatively good and stable survival conditions, they would tend toward K-selection or competitive life history, and giving special attention to flower nutrition.The charateristics of elements contents in plants were mainly decided by the soil nutrient contents and plants biological characteristics. Under the influence of soil and other envirionmental factors, for adaptation, plants selectively absorbed elements through synergistic and antagonistic action, controlled and adjusted the elements contents and distributions in different organs. The contents of elements in leaf, branch and flower of different trees grown in Nonggang karst forest presented the elements distribution and the trophic status of plants in this forest, and reflected the variations of habitat conditions in different topography positions and the ecological adaptations of plants species.