Ecological Differentiation And Adaptation Significance Of Flammability Of Needles In Pinus Yunnanensis

Plant flammability is an important driver of fire in terrestrial ecosystems and thus has a fundamental role in ecosystem dynamics and species evolution.Plants had different flammability strategies in different fire-prone ecosystems: Non-flammable,Fastflammable and Hot-flammable(with low ignitability,high flame spread rate and high heat release,respectively).These strategies allowed plant to survive and reproduce in different fire regime.In my paper,Pinus yunnanensis under different fire regime(P.yunnanensis var.yunnanensis between different fire risk level,the varieties P.yunnanensis var.tenuifolia and P.yunnanensis var.pygmaea)were set as the main research objects.Besides,P.densata,P.massoniana and P.tabuliformis were set as the interspecific reference subjects.The needles of them were collected(a total of 52 sample sites)under different fire regime and the traits and flammability were determined.The indicators of needle traits were length,width and ratio of length to width,and the indexes of flammability were ignition delay time(ignitability),flame residence time(flame spread rate),total heat released(heat release),maximum temperature and smoldering time.By comparing the results of measurement of traits and flammability indexes of needles for the P.yunnanensis var.yunnanensis between different fire risk levels,the three varieties(P.yunnanensis var.yunnanensis,P.yunnanensis var.tenuifolia and P.yunnanensis var.pygmaea),and P.yunnanensis var.yunnanensis,P.densata,P.massoniana and P.tabuliformis).Based on the results of principal component analysis and three main dimensions of spatial analysis of flammability,we proposed their flammability strategies respectively and discussed intraspecific ecological differentiation and interspecific evolution of plant flammability strategy.The main results of this study were as follows:(1)The flammability strategies had ecological differentiation the P.yunnanensis var.yunnanensis between different fire risk level,it was that level 2 and 5 fire risk of plant habitat was fast-flammable relatively,while level 3 and 4 was hot-flammable relatively.The results indicated that plant flammability also had the intraspecific ecological differentiation,and the relationship between plant flammability and fire regime is consistent with the law of the theoretical framework of flammability.(2)The flammability strategy had obvious ecological differentiation the three varieties of P.yunnanensis.The P.yunnanensis var.tenuifolia was fast-flammable,P.yunnanensis var.pygmaea was hot-flammable,and P.yunnanensis var.yunnanensis was an intermediate type of fast-flammable and hot-flammable.The results showed that the differentiation distance of flammability strategy increased with the increased of fire regime,which further supported the hypothesis of the theoretical framework of flammability.(3)The flammability strategy had ecological differences,the P.yunnanensis var.yunnanensis and P.densata,P.massoniana and P.tabuliformis.It was,the P.massoniana was fast-flammable,P.yunnanensis var.yunnanensis,P.densata and P.tabuliformis were hot-flammable.The ecological differentiation of flammability strategy among P.yunnanensis var.yunnanensis,P.densata and P.tabuliformis had a small gap.The results indicated that between these species of flammability differences reflected the fire regime in the distribution area of plants to a certain extent,which conforms to the hypothesis of the theoretical framework of flammability.(4)Based on the correlation analysis between the characteristics of climatic and the indexes of three main dimensions of flammability,that showed the characteristics of climatic such as temperature,precipitation and altitude would affect the flammability strategy.In conclusion,the flammability strategy had an intraspecific and interspecific ecology differences,which is closely related to the fire regime of different habitats in their respective distribution areas.In my study,the variation law of the flammability of needles was consistent with the predicted law of the theoretical framework of flammability,so needle flammability was an adaptive response to habitat fire regime.