A Study On The Effects Of Fire On The Intra-species Divergence Of Pinus Yunnanensis

Three varieties of Pinus yunnanensis:P.yunnanensis var.yunnanensise,P.yunnanensis var.tenuifolia and P.yunnanensis var.pygmaea were set as the research objects.We obtained the fire-related characteristics by the field survey sampling in Yunnan Province,Guizhou province,Guangxi Province and sichuanProvince,total of 27 counties made studies to three species of fire adaptation traits.Then,we combined with their natural distribution of the climate characteristics,analyzed the trade-off of these adaptive traits among the various species for the discussing of its habitat adaptation strategies.The effects of fire on the Intra-species divergence of P.yunnanensis was further discussed.The results indicated that:The role of fire in the ecosystem of the area is further revealed,and the influence of fire on the differentiation of P.yunnanensisis is discussed.The results showed as below:(1)There are obvious differences between the main fire adaptation traits of P.yunnanensis var.yunnanensis,P.yunnanensis var.tenuifolia and P.yunnanensis var.pygmaea.The relative bark thickness of P.yunnanensis var.yunnanensis is l.43 ± 0.50 mm/cm.Coniferous,delayed opening degree of cone,germination ability and seed thermal impact effect are among the middle,in which exists a widespread natural pruning phenomenon.The needles of P.yunnanensis var.Tenuifolia are longest 25.96 ±2.90 cm,the under crown height proportion of branches under the maximum value of 0.51 ± 0.16,while the initiation ability,seed heat impact effect.the extent of the cone and the relative bark thickness in three variants are weakest.The strongest germination capacity is P.yunnanensis var.pygmaea,cone delayed opening up to 43.05%,the highest thermal impact effect,the relative bark thickness in the middle 0.97 ± 0.539 mm/cm,the length of the P.yunnanensis var.pygmaea needles minimum 17.92 ± 3.80 cm.(2)The adaptation strategy of P.yunnanensis var.yunnanensis to fire habitat,tend to the heat-tolerant and fire-dependent intermediate type,because of frequent ground fire,but the fire did not reach the canopy,quickly burned down the forest drops,heat and smoke on the cone open and seed germination has promoted effect.The adaptation strategy of P.yunnanensis var.tenuifolia,to fire habitat bias to the flame tolerant type,frequent ground fires,rapidly burning off the forest under combustible,but rarely formed canopy fires.The adaptation tactics of the P.yunnanensis var.pygmaea to fire,lean to the dependence,that is,encounter canopy fire,retain the lower branch,so that the fire can reach the canopy,but some mechanisms can be recovered quickly after the fire.(3)The Intra-species divergence of P.yunnanensis is inextricably linked to fire,and the P.yunnanensis var.yunnanensis and P.yunnanensis var.pygmaea are the different growth types,and the climatic conditions of habitat are basically consistent,and their differences may be mainly caused by the different risk of forest fires.While the P.yunnanensis var.tenuifolia and P.yunnanensis var.yunnanensis are different climatic types,the difference is mainly due to the different climate,resulting in different risks of fire occurrence,but the effect of P.yunnanensis population,no other two varieties strongly.Forest fires play an important role in the Intra-species divergence of P.yunnanensis,and the formation of P.yunnanensis var.yunnanensis,P.yunnanensis var.tenuifolia and P.yunnanensis var.pygmaea is an ecological adaptation to the difference of fire condition.Three kinds of pine forest fire has different adaptation countermeasures,proposed to three varieties of P.yunnanensis,the development of forest fireproofing measures and fire management should be different strategies,should not be generalized.And the three kinds of P.yunnanensis are adapted to the different measures,and propose different strategies for the three varieties of P.yunnanensis,the development of forest fire prevention measures and the management should be formulated and should not be generalized.