| Based on the theories and methodologies of phytocoenology and ecology. Theresearch was directed at four Phoebe bournei communities (numbered A, B, C and D)located at Fengtou village, Dongping town, Zhenghe county in Fujian province.1200m2 plot was designed in each community to conduct detailed field investigationand to measure ecological indexes. According to the coverage of the main layers, thedisturbance traces (paths in plots, the number and the size of stumps, the number ofthe cutting branches), the distance from forest stand to residential area and the firstand second grade roads, the disturbing intensities grade were defined as. communityA—undisturbed, community B—slightly disturbed, community C—intermediatedisturbed and community D—heavily disturbed. The ecological characteristics(suchas floristic composition, life form, species diversity, species abundance distribution,population spatial pattern, population niche, interspecific association, forest litter anddynamics of nutrient return from litter fall, water holding capacity of litter layer)were analyzed thereby. The responses of Phoebe bournei community to the differentdisturbing intensities were presented.1 The disturbance had minor effect on the properties of the Phoebe bourneicommunity floras. The floras were dominated by pantropic dietribution type. But thedisturbances of different intensities had affected the composition. 42 families,66genera,102 species of vascular were found in community A, 38 families, 54 genera, 92species in community B, 41 families, 63 genera, 99 species in community C, 34families, 50 genera, 78 species in community D.2 The four communities had similar life form spectrum.. Phaneroplyta occupied adominant position in each community. But in each community had a differentproportions of different life form groups. Microphyll, coriaceous leaf, integrifolious,simple leaf, evergreen leaf each made up the dominant percentage in fourcommunities. Macrophyll in community A surpassed that in community B, C and D inproportion. Leptophyll appeared in community B, C and D. Community Band C had aproportion of papery plants. Thin leaf plants were only found in community A and B. The percentage of the tolerant-shade plants decreased with the increasing ofdisturbing intensities. The percentage of the tolerant-shade plants in community A was53.92%, and that in community B and C dropped to 48.37% and 47.61%, respectively.The percentage of the light-demanding plant in community C and D stepped up to29.03% and 31.75%, respectively, which showed that the light-demanding plant had themuch probabilities to intrude into the disturbed community.3 The species richness in community decreased in order A＞C＞B＞D, and thechange of community generalαdiversity was as similar as to. But the change of theecological dominance had a contrary trend, that was D＞B＞C＞A. There a negativeassociation between ecological dominance and species diversity. The result ofdiversity showed that the similar degree among communities decreased, difference among habitantincreased with the disturbing intensities increasing.4 The species abundance grade of tree layer was 5 in community A, B, C, and thatwas 4 in community D. The species abundance grade of shrub layer was 7 incommunity A, B, C, and that was 6 in community D. The species abundancedistribution and simulation results were best in community A.5 Phoebe bournei population all performed pattern of clustering distribution. Thedisturbances did not lead to quality change of spatial pattern of Phoebe bourneipopulation on the whole. But disturbance had affected the congregating intensity insome degree. With the disturbing intensities increasing, the congregating intensityincreased. The distribution pattern of Phoebe bournei population varied with age.With the population age increased, the distribution pattern had a trend from clusteringto random, the cluttering intensity decreased some what.6 The niches of the main populations of tree layer in four communities were examined.The niche breadth of Phoebe bournei population was biggest in each community, BSWwas 0.83,0.75,0.70,0.70, and BL was 0.75,0.73, 0.61, 0.60 in community A, B, C, andD. With the disturbing intensities increasing, niche breadth of Phoebe bournei becamenarrow. There existed niche overlap among 79.1% of the pairs of the population incommunity A, 80% in community B, 82.5% in community C and 85% in communityD, the percentage increased with the disturbing intensities increasing. The height niche breadth of Phoebe bournei population is not biggest in each community, BSWwas 0.47, 0.48, 0.43, 0.30, BL was 0.26, 0.38, 0.35, 0.30. The height niche overlapexisted among the all the pairs of the populations in community A, There existedheight niche overlap among 93.33% of the pairs of the population in community B,92.5% in community C, 90.83% in community D. The pairs of the population whichheight niche overlap lager than 0.6 had a percentage 42.5% in community A, 34.1% incommunity B, 30.84% in community C, 30.80% in community, which decreasedwith the disturbing intensities increasing.7 The interspecific associations of dominant tree populations which important valuecame out before 15 were analyzed. The result showed that overall association was notsignificant and tended to no correlation among all species, and it meant that species ofthe community were mostly independently distributed. The stronger of the disturbingintensities, the higher of the percentage of negative association pairs, lower of thepercentage of positive association pairs. It suggested that disturbance influenced onthe interspecific correlation in some degrees.8 The annual litter accumulation in the community A, B, C, and D were 7010.75kg/hm2, 6904.54 kg/hm2, 6237.45 kg/hm2 and 5509.64 kg/hm2, respectively, whichdecreased with the disturbing intensities increasing. Difference existed amongcommunities in their litter compositions, with the change fallen leaves＞branches＞fallen flowers and fruits＞others. The fallen leaves accumulation decreased withdisturbing intensities increasing, the branches and others accumulation changed to thecontrary. There were similar percentage of fallen flowers and fruits in eachcommunity. The dynamics of litter showed significant seasonal patterns, with the firstpeak occurring in April, and the second in August. Nutrient concentrations in the littervaries with forest types, litter components and shedding times, with N rangingfrom5.30 to8.94 g/kg, P from 0.33 to 0.76 g/kg, K from 0.60 to 2.280 g/kg, Ca from14.07 to 19.40g/kg, Mg from 1.46 to 3.8 g/kg. Annual fluxes of the five nutrientelements via litter in the four communities consistently decreased in the order: Ca＞N＞Mg＞K＞P, and each decreased with the disturbing intensities increasing.9 The cumulated mass of litters in community decreased with the disturbing intensities increasing.The cumulated mass of litters in community A was 1.15 timesthe weight of that in community B, 1.52 times the weight of that in community C,2.41 times the weight of that in community D. |
