Variation Of Leaf Stomatal Traits Along Thealtitudinal Gradient In Taibai Mountain,China

Stomata are the main channels for water and gas exchange between plants and their environment,which could adjust the balance between plant carbon assimilation and water loss,and reflect,to some extent,the adaptability of plants to environmental changes.In this study,we investigated stomatal traits in 210 plants(subordinate to 68 families and 155 genera)along an elevation gradient in the northern slope of Taibai Mountain,and explored the patterns of stomatal traits and their influencing factors.Using the scaling-up method,we examined the variation of stomatal traits along the altitude gradient at the species level,growth type level and community level,respectively,and qualified the influences of environmental variables and plant functional type(PFT).We aimed to reveal the adaptive strategies of plant communities to environmental changes from the perspective of stomata.The results obtained were as follows:1.At the species level,the stomatal length(SL),stomatal density(SD)and potential conductance index(PCI)showed increasing along the elevation gradients.The difference in stomatal width(SW)along the elevation was not significant(P>0.05).The relationship between stomatal traits changes with the environment.Significant trait relationships(P<0.05),including negative correlation between SD and SL,positive correlation between SL and SW,stomatal size(SL and SW)and PCI,were all found in three different altitudes.However,the negative correlation between SD and SW only at low and high altitudes(P<0.05)and the positive correlation between SD and PCI was significantly correlated with low and middle altitudes(P<0.05).The total effects of climate,soil and plant functional(PFT)explained the variation of 14.42%-22.23%of the stomatal traits.Of all the factors considered,PFT had the greatest influence on stomatal traits,and explained the spatial variability of 11.50%of traits.Moreover,soil independent factors had greater influence than climate factors on the variation of stomatal traits along the elevation gradient(3.2%vs.0).2.Different growth types of stomatal traits varied with altitude.In the tree layer,The SD_T and PCI_T decreased with the increased elevation,whereas the SL_T and SW_T showed initially increased,reached a maximum at middle altitude,and then decreased.In the shrub layer,only SW_S showed a significant negative correlation with altitude(P<0.05).In the herb layer,four stomata traits increased with the increased altitude.There was a significant negative correlation between SD_T and SL_T in the tree layer(P<0.01),but this correlation was not significant in the shrub layer.Furthermore,SD_H and SL_H showed positive correlation in the herb layer.SW and PCI showed positive correlation in all growth types.In the herb layer,the relationship between traits was significantly correlated except SD_H and SW_H(P<0.01).In the tree layer,climate and soil together explained 79.99%-97.90%variation of stomatal traits,and their interaction was the main factor,explaining 34.41%-89.27%variation.In the shrub layer,climate and soil together explained 30.31%-70.06%variation.The interpretation of the climate was 54.30%;In the herb layer,climate and soil together explained a total of 30.97%-58.33%of trait variation.Similarly,the maximum interpretation was climate,explaining5.94%-41.75%variation.3.At the community scale,stomatal traits showed clear patterns along the altitudinal gradient.SD_C decreased linearly with altitude,whereas SL_C and SW_C showed double-peak pattern,and PCI_C first decreased and then increased with the increasing altitude.A significant negative correlation was observed between SD_C and SL_C,while SL_C and PCI_C,SW_C and PCI_C,SL_C and SW_C showed a significant positive correlation(P<0.01).Climate and soil variables together explained the variability of 44.87%-87.03%of the stomatal traits at the community level.The interaction was the main influencing factors of variation in stomatal traits,explaining 2.36%-59.95%variation.4.Great differences of stomatal traits were found among different levels.Compared with the species level,the community-level stomatal traits showed more clear trends along the altitudinal gradient.Moreover,the relationship between stomatal traits differed at different levels.In addition,the plant functional type was the dominant factor of specie-level trait variation,while climate independent effect and the interaction of climate and soil explained most of trait variation at both of the growth type and community levels.