Fire-adapted Traits And Ecological Adaptation Significance Of Four Pines In Southwest China

In this study,Pinus yunnanensis,P.kesiya var.langbianesis,P.densata and P.massoniana,four major pines in southwest China were investigated in 18 sample sites in Yunnan Province,Guizhou Province,Guangxi Zhuang Autonomous Region,Hunan Province and Anhui Province.Fire-adapted traits of four pines were collected and measured,the differences of the traits among four pines were analyzed and compared.According to differences of the fire-adapted traits,which were formed by different fire regime in the their distribution areas,and the Principal Component Analysis of fire-adapted traits,we proposed their fire-adapted life history strategies.Finally,based on the results of Principal Component Analysis and Cluster Analysis,wild fire could be supposed to an evolutionary driving factor and affected,the evolution and distribution of four pines in southwest China.The main results of this study were as follows:（1）The relative bark thickness of four pines was 1.50±0.62mm·cm^-1,1.04±0.53mm·cm^-1,1.15±0.43mm·cm^-1and0.97±0.39mm·cm^-1respectively.The relative bark thickness of P.yunnanensis was the largest,followed by P.densata,P.kesiya var.Langbianensis and P.massoniana.The degree of serotiny of P.yunnanensis was 29.03±25.05%.Only a few serotinous individuals were found in P.densata,P.kesiya var.Langbianensis and P.massoniana,serotiny was not a common phenomenon for them.The percentage of under branches height was 13.53±8.61%,16.90±11.33%,11.68±10.84%,25.57±15.77%,respectively.There was a significantly difference in the ratio of needle length to diameter among the four pines（P.kesiya var.langbianensis>P.yunnanensis>P.massoniana>P.densata）.The seed wind loading of four pines was 178.35±39.33g·m^-2,198.94±49.45g·m^-2,201.35±57.11g·m^-2and165.03±49.58g·m^-22 respectively.The seeds of P.Yunnanensis,P.massoniana,P.densata have obvious thermal shock effect,but no in P.kesiya var.Langbianensis.After treated at 150℃for 1 min,the germination rate of seeds of four pines was72±7.58%,54.50±11.89%,80.74±5.00%and 82.79±9.89%respectively.The height growth of seedlings of P.yunnanensis was significantly lower than that of the other pines after growing two years.（2）The fire-adapted life history strategy of P.yunnanensis was the intermediate of fire-tolerators and fire-embracers;P.kesiya var.Langbianensis and P.massoniana were fire-tolerators;P.densata was not a typical fire-tolerators with a little fire-embracers.（3）There was a significant correlation between some fire adaptation traits and fire risk grade.Relative bark thickness,degree of serotiny,wood density and fire risk grade had a extremely significantly positive correlation;seed wing loading and fire risk grade had a significantly positive correlation;there was a significant negative correlation between fire risk grade and plant height growth in two year.（4）The results of Cluster Analysis showed that the four kinds of pines were obviously divided into two groups at first.One was P.yunnanensis and P.densata,their characteristics of fire-adapted traits were thick bark,cone retained in long time and large proportion of outer bark.Another was P.kesiya var.Langbianensis and P.massoniana,their characteristics of fire-adapted traits were thin bark,cone retained in short time,self-pruning and small proportion of outer bark.Four species had obvious ecological divergences of fire-adapted traits,and the differences of fire-adapted traits between species were adaptive to differences in fire regime in their distribution areas.The results suggested that the fire-adapted traits of the four pines were closely related to fire regime in distribution region of P.yunnanensis,P.kesiya var.langbianesis,P.densata and P.massoniana in southwest China,and fire played an important role in the evolution and distribution of four pines.Fire-adapted life history strategy of four pines were interpreted as character syndromes in response to different fire regime in their distribution regions.The fire-adapted life history strategy ofP.yunnanensis was the intermediate type of fire-tolerators and fire-embracers;P.kesiya var.Langbianensis and P.massoniana were fire-tolerators;P.densata was fire-tolerators and tends to fire-embracers.