The Key Phenophases Of Veratrum Oxysepalum And Relationship With Environmental Factors From Tundra In The Western Slope Of The Changbai Mountains

The alpine tundra of the Changbai Mountains,which is located on a small area of the uppermost section of the volcanic cone,is the fairly typical mountain tundra ecosystem in East Asia.And because its environmental characteristics are similar to those of polar alpine tundra,the Changbai Mountains tundra is highly valuable for scientific research.Vegetation in the alpine tundra of the Changbai Mountains exhibits the strongest response to global warming.Specifically,herbaceous plants have encroached into the tundra zone,and the proportion of herbaceous plants was larger than that of shrubs.Shrub tundra was transforming into shrubgrass tundra.As the only two mountain tundra zones of China,the process and the mechanism of that transform is extremely urgent to explore.Veratrum oxysepalum has many characteristics,as follows: 1).its distribution in many aspects,including western,northern and southern slope;2).expansion speed is obvious;3).its growth period is short.Veratrum oxysepalum takes advantage of its time preponderance to absorb soil nutrient elements and become one of the main encroachment species.Based on digital camera technology,we acquired a series of comparatively accurate methods?steps and data of Veratrum oxysepalum,which is completed in the alpine tundra of the Changbai Mountain.The study revealed the characteristics and differences of Veratrum oxysepalum key phenological phases in different altitudes of the alpine tundra,explored the effect of environmental factors(temperature of air and soil,soil water content and air relative humidity)to that of Veratrum oxysepalum,and analysed the change of leaf and soil nutrient elements.The main results are as follows:1).Veratrum oxysepalum is mainly distributed in low-lying land and valley of alpine tundra,where is rich in soil water and soil nutrients.The growth rate of Veratrum oxysepalum is not uniform,the growth period is short.After snow cover melted,Veratrum oxysepalum turns green at the start of June,then,it grew rapidly and turn mature at the start of July.The length of stay mature is relatively long in its growth period.And the altitude is lower,the length of that is longer.At the end of July,Veratrum oxysepalum showed decay signs and decayed rapidly.In the start or middle of August,overground part of plants turns into dormancy.2).The Greenup period of Veratrum oxysepalum from all altitudes in the alpine tundra in the Changbai Mountains is put off with altitude rising,with a vertical lapse rate of 0.33 d/100 m,0.89 d/100 m,respectively.The Senescence and Dormancy period all advance with altitude rising,with the vertical lapse rate,is 1.00 d/100 m and 2.11d/100 m,respectively.The length of growing season shortens 2.44 d/100 m with altitude rising.3).The contribution of soil temperature,soil water content,air temperature and air relative humidity to the growing condition of Veratrum oxysepalum,especially,air temperature,soil temperature,and soil water directly affect its growing condition.At the start of growing season in the alpine tundra,soil water is abundant,it is the rising of temperature that triggered the Greenup date of Veratrum oxysepalum.Then,with the temperature rising to the highest value and fall down,soil water deeply affects the growing condition of Veratrum oxysepalum.4).In the soil under Veratrum oxysepalum root,the differences of organic carbon,total nitrogen,total phosphorus and total potassium with altitude are significant,but that of different phenophases are steady.The available nutrient elements of soil and that of leaf changed observably with altitude rising.The available nutrient elements of soil and that of the leaf,which both of Greenup date,is larger than both of maturity and senescence date.That is not only related to the special characteristics of winter alpine tundra soil nutrition accumulation,but also connected with the growing rate of Veratrum oxysepalum is not uniform during the whole growing season.5).The value of CCI(Chlorophyll Content Index)in the vegetation growth period presents a greatly effect by tundra environment.The difference of CCI from all altitudes and phenophases are significant.The value of CCI presents a decreasing trend with altitude rising.In each altitudinal stage,the value of CCI reaches a peak in the maturity or senescence date.We compared the foliar nutrient resorption efficiencies of N,P,K and C from Veratrum oxysepalum.We found that nutrient resorption efficiencies of N and P were higher,suggesting that Veratrum oxysepalum having a higher degree of acclimation to the harsh environment.At present,the vegetation of alpine tundra in the Changbai Mountains is having observably transformation.This study can offer some reference value and experiences to the mechanism and process of the transformation from shrub tundra to shrub-herb tundra.