| As pioneer tree species in temperate and boreal forests,Betula spp.Play an important role in the restoration of secondary forests.Under the current climate change,little is known about the anatomical characteristics of the xylem of different birch species in response to climate change and their adaptation strategies.Therefore,we aim to study the relationship between the characteristics of Betula spp.xylem anatomy and climate,to reveal the response and adaptation strategies of Betula spp.to climate change,and to provide theoretical basis for accurately assessing the impact of climate change on different Betula spp.populations.In this paper,three natural birch species(B.platyphylla,B.ermanii and B.costata)from Fenghuangshan National Forest Park in Heilongjiang Province,Gangshan National Forest Park in Liaoning province and Laotoudingzi National Nature Reserve were selected as the research objects.the characteristics of xylem vessels and wood fiber cells of three species of birch were compared by using tree-ring chronology and tree-ring anatomy,the relationship between the characteristics of vessel and wood fiber cells and seasonal climatic factors,time stability,and the resistance and resilience of growth to extreme climate were analyzed.The results:B.platyphylla,B.ermanii and B.costata belong to the same loose wood.The anatomical structure of the xylem is similar,but there are some differences: B.platyphylla has the widest average wheel width,small and many vessels,and large and many wood fiber cells,the cell wall of wood fiber is the thinnest.The smaller average wheel width of B.platyphylla and the significantly larger and less vessels may make B.costata more prone to embolism,with the smallest and thickest wood fiber cells.The annual radial growth of B.costata was the most uniform,with the least number and area of vessel and wood fiber cells.Under different temperature gradients,the responses of 3 species of birch to climatic factors were not significantly different,and the climate of Northeast China was suitable for birch growth.Compared with the same tree species in different locations,the differences of vessel anatomical characteristics of different tree species in the same location were more obvious.Except B.ermanii in Lantau Peak,the vessel number of three birch species was positively correlated with seasonal precipitation,with the strongest positive correlation in B.costata(p < 0.05).The increase of temperature in spring and summer,the variation of B.platyphylla vessel number in different areas,and the increase of non-growing season temperature(November-April)in the last year reduced the number of B.platyphylla vessel.Compared with the vascular anatomy,the climatic factors had less influence on the characteristics of the wood fiber cells.With the increase of precipitation in summer and autumn,more fiber cells were produced,and the increase of mean temperature and mean maximum temperature in summer was unfavorable to the increase of fiber cells in B.platyphylla.Less precipitation will cause the cell wall to thicken.As the climate warms,B.platyphylla tends to have smaller vessels and more wood fiber cells,while B.platyphylla tends to have larger vessels and fewer wood fiber cells.B.ermanii and birch catheter features better time stability.In areas where the climate was warm and dry,birch tended to adjust vessel characteristics to respond to rapid warming.The resistance and resilience to drought and high temperature in the growing season and the non-growing season of the three birch species were similar,and the resistance and resilience to drought in the growing season were lower.In this study,we found that different xylem vessels and wood fiber cells of B.platyphylla had different strategies to cope with climate warming,and B.platyphylla adopted a more conservative strategy(producing more and smaller vessels)to cope with climate change,B.costata uses a strategy of using large conduits to increase the efficiency of water transport,which can lead to its first decline or even death,while B.ermanii has fewer and smaller conduits but is least responsive to climate change. |
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