| Ancient and famous trees, as an important component of city greening and beautifying, are living specimens and historical relics to research society and nature and many other fields, owing to reflect and record objectively the social development history and the species vicissitudes of nature. However, ancient and famous trees aging are increasing seriously, so the comprehensive evaluation of ancient and famous trees aging is particularly important. In view of the above situation, this paper chose the ancient camphor trees as the test materials for which have a larger number in ancient and famous trees. In the test, a evaluation standard was established for assessing ancient tree aging in terms of the general conditions of tree, crown, trunk and root. Then four aspects of the ancient camphor trees having different growth potential were analysised and researched, includeding the camphor aging appearance evaluation, the dynamic change of fine roots growth, the basic physiology metabolism indexes of leaves, the content variation of mineral elements, in order to providing the theory basis for ancient and famous trees aging evaluation and the regeneration and fertilization of aging ancient trees. Main results obtained were as follows:(1) In the evaluation standard of ancient tree aging,13 integrated visual indicators were chosen. The weight sorting of each index from high to low was tree vigour, butt rot and damage, crown dieback, leaf color and spot, corruption branch, tree hole, the quantity of germination of new treetop, the leaf quantity, trunk pests, leaf and branches pests, phylliform and leaf size, parasitism, and root permeability. Three indexes that vigour(0.194), butt rot and damage(0.165), crown dieback(0.164), whose weight were relatively higher then others, were the important indexes to reflect trees aging degree in the evaluation standard. According to the evaluation criteria established, tested camphor trees were evaluated. And the evaluation results were studyed by Grey Relational Cluster Analysis, determineing the classification indexes of aging trees. According to the correlation degree of ancient camphor trees with the ideal camphor trees, the camphor trees in tests could be divided intoⅠ,ⅡandⅢ3 grades. Namely, the ancient camphor trees wasⅠgrade when the correlation degree was more then 0.750; the ancient camphor trees wasⅡgrade when the correlation degree was between 0.500 and 0.750; the ancient camphor trees wasⅢgrade when the correlation degree was less then 0.500. According to the principal component analysis of morphological indicators, three main components were extracted, whose accumulative total variance contribution rate was 81.978%, and the three main components could reflect the original information better. The first principal component's variance contribution was 64.317%, including tree vigour, the quantity of germination of new treetop, corruption branch, crown dieback, the leaf quantity, leaf color and spot and phylliform and leaf size, So renamed the first principal component crown, branches and leaves; the second principal component's variance contribution was 8.894%, including leaf and branches pests, butt rot and damage, trunk pests, and root permeability, So renamed the second principal component diseases and insect pests; the third principal component's variance contribution was 8.766%, including tree hole.(2) With the method of minirhizotron, the paper regularly monitored the fine roots growth stuation of tested ancient camphor trees, and analysed the physical and chemical properties of rhizosphere soil around the trees. The diameter range of fine roots in ancient camphor mainly distributed in 0.3cm～0.5cm. There were two peak periods for fine root diameter growth, two peak periods for fine root, espectively in early winter(November), late spring and early summer(April and May). Meanwhile, fine root length growth, fine root surface area extending increased and fine root volume increased mainly concentrated between March and June. The number of fine root had rapidly declined with whose turnover and replacement in late autumn. By clustering analysis, choose the Euclidean distance dij=2.5, the tested camphor trees could be divided into 4 grades:Ⅰ,Ⅱ,ⅢandⅣ. There were differences in mean diameter of fine roots, monthly extending growth of fine root length, monthly extending increment of fine root surface area, monthly extending increment of fine root volume between tested ancient camphor trees. Camphor treesⅠgrade: <Dmean>0.5cm, Dmax=0.75cm; Lmax>4000mm; Amax>1000mm2; Vmax>400mm3. Camphor treesⅡgrade:0.4cm<Dmean<0.5cm; Lmax≈2000mm; Amax≈250mm2; Vmax≈100mm3. Camphor treesⅢgrade:0.3cm<Dmean<0.4cm; Lmax≈750mm; Amax≈60mm2; Vmax≈30mm3. Camphor treesⅣgrade:Dmea<O.3cm, Dmin=0.15cm; Lmax<100mm; Amax<20mm2; Vmax<10mm3. Meanwhile in the testbed soil, low soil water content, low soil porosity, high soil bulk density, slightly alkaline pH value, low N and P content; high K content; all these soil condition deteriorationes made impacts on the normal growth and physiological function of the ancient trees roots, which in turn cause the premature senility of ancient trees.(3) In the test, physiological parameters of camphor trees having different growth potential were analyzed, including chlorophyll content, soluble sugar content, soluble protein content, malondialdehyde (MDA) content and superoxide dismutase (SOD) activity. The aging camphor trees had significant differences with the vigorous and healthy camphor trees. By clustering analysis, choose the Euclidean distance dij=10, the camphor trees in tests could be divided into 3 grades:Ⅰ,Ⅱ,Ⅲ. Along with the aging of camphor, chlorophyll content, the soluble protein content, the soluble sugar content and the SOD activeness reduced; while the MDA content obviously rise.(4) The paper determined and analysised the content changes of 12 kinds of mineral elements (N, P, K, Ca, Mg, Mn, Zn, Fe, Cu, B, Na, Al) in leaves of tested camphor trees. Between different season, there were difference in the contents of Mg and Fe, that the contents of Mg and Fe first increased and then decreased in four seasons, but no significant difference in the others. Between different camphor trees, there were significant difference in each element above. By clustering analysis, choose the Euclidean distance dij=5, the tested camphor trees could be divided into 3 grades:Ⅰ,Ⅱ,Ⅲ. With the aggravate of aging degree, the content of Na and A1 in camphor leaves showed a upward trend, while the others showed a downward trend; N, P, K's ratio imbalance was more serious, the proportion of N increased, while the proportion of P reduced. Camphor treesⅠgrade, N:P: K was 12:1:7; Camphor treesⅡgrade, N:P:K was 15:1:7; Camphor treesⅢgrade, N:P:K was 25:1:9. According to the principal component analysis, three main components were extracted, whose accumulative total variance contribution rate was 94.908%. The first principal component's variance contribution was 69.245%, including P, K, Cu, Fe, Mg, B; the second principal component's variance contribution was 13.452%, including N; the third principal component's variance contribution was 12.211%, including Ca, Al, Zn, Mn.(5) By the correlation analysis between morphological appearance, fine root indicators and main mineral elements, it was found that the main mineral elements N, P, K, Ca, Mg contents of ancient camphor tree leaves had significant positive correlations with morphological appearance such as indexes crown, branches, leaves, plant diseases and insect pests, and had moderate positive correlation with fine root length, fine root surface area and fine root volume; while had no correlation with the diameter of fine roots. Crown, branches, leaves, and plant diseases and insect pests had medium to low positive correlation with fine root length, fine root surface area and fine root volume; but had no correlation with the diameter of fine roots. So the contact between mineral nutrition elements and morphological appearance was relatively close, the contact between mineral nutrition elements and fine roots indexes was smaller. |
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