关键词: 散生竹, 冰雪灾害, 环境解释, 尖削度, 毛竹

Abstract: The stand condition and growth analysis characteristics of P.edulis were measured and the management type was quantified.Nonmetric multidimensional scaling(NMS)was used to analyze the orientation of total sample plots and canonical correspondence analysis(CCA)was applied to analyze the multifactor environmental variances;meanwhile,Monte Carlo test was applied to check up the results of above methods.Community separation was clearly shown by NMS ordination with a final stress of 7.734 5>5 and a final instability of 0.000 09<0.000 1.A three-dimensional solution was found after 143 iterations and total sample plots were divided into two parts,I.e.,Shuangshi group(SI)and Shimen(SII),which were depended on lowest height of living branch,stand density and gradient.Monte Carlo test proved that all three axes had a smaller stress than a random solution.CCA showed that 48.1% variance was explained by the first axes and 68.4% explained cumulatively in SI,60.5% variance was explained by the first axes and 95.6% explained cumulatively in SII respectively.So snow disaster was more complex than ice disaster.Furthermore,the correlations between sample plots and axis responded to the percentage of variance explained by each axe.Monte Carlo test showed that there was difference between eigenvalue of real data and simulated data(P<0.01)as same as species-environmental correlation(P=0.0350<0.05)of SI and SII respectively,what indicated that events were not at random,but did represent the relationship between environment variables and biological information.CCA implied that obtruncation influenced the quantity of uprooting,breakage and split,but it was not shown in the analysis of ordination.And stand density affected the morphological structure and sensitivity responding to snow/ice of P.heterocycla.Data did not show that the difference of slope direction,maybe,for the havoc in the investigation area both on south and north slope,but indicated that correlation between damage degree of snow/ice disaster and diameter at breast height existed,and there was one critical value between density and taper.So selective cutting should be appended on the list of management to achieve reasonable stand density and better taper of bamboo which was much less than arbor(average value=0.007 8<0.01)implying that it was easy to fall under snow/ice pressure.Properties of taper played an important role in bamboo forest management.Different phenomena like bending,breakage,uprooting and split were reflected by different series of variances showed by 3-dimension illustration,so it should be treated variously on forest management.As a whole,the nonlinear nature of energy and water exchanges between the land surface and the atmosphere makes the aggregation of parameters a challenge for analysis,so CCA and NMS indicated that effects of all kinds of disturbance on bamboo ecosystem were a kind of multifactor integration function same to respond of plastical behavior of bamboo forest ecosystem.

Key words: Monopodium, snow/ice disaster, environmental interpretation, taper, P.edulis