| Low mountains and hilly region of Shandong Province mainly includes limestone mountain and gneiss mountain area,both of which belong to special difficult site.The carbonate rock with calcite as its main component is the parent material of this kind of mountain.The thin soil layer leads to its poor water storage capacity,which seriously restricts the productivity of these undeveloped mountains.Vevegetation is an important measure of ecological environment restoration in low mountains and hilly region of Shandong Province.The hydraulic structure of woody plants is closely related to the drought adaptation strategy,but the research on afforestation and greening tree species commonly used in low mountains and hilly region of Shandong Province is still insufficient.To observe the differences of anatomical characteristics of different tree species and to explore the relationship between the differences of anatomical characteristics and hydraulic characteristics is of theoretical significance to the drought tolerance mechanism of plants facing drought stress environment,at the same time,it is of great practical significance to the screening of drought-resistant plants and the restoration of vegetation low mountains and hilly region of Shandong Province.Based on this,15 tree species for mountain afforestation and landscaping(Ailanthus altissima,Cotinus coggygria,Quercus acutissima,Ulmus pumila,Juglans regia,Magnolia denudate,Liriodendron chinensis,Cercis chinensis,Bothrocaryum controversum,Platanus acerifolia,Platanus acerifolia,Buxus megistophylla,Ligustrum compactum,Ilex cornuta,Osmanthus fragrans,Eriobotrya japonica)were studied in this study,according to the research of previous scholars and the actual afforestation experience,it can be divided into two categories: drought-resistant tree species and non-drought-resistant tree species,and deciduous tree species and evergreen tree species according to different life types.By measuring the anatomical traits of xylem and leaves and non-structural carbon concentrations,photosynthesis,the differences in hydraulic structural characteristics and the correlations between hydraulic functional traits of different tree species were compared to explore the differences in drought adaptation strategies of these tree species.The results show that:(1)There was a large variability among 24 xylem traits between different tree species.vessel wall thickness,maximum vessel diameter,paratracheal parenchyma fraction,axial parenchyma fraction and NSC concentration of drought-resistant tree species were significantly larger than those of non-drought-resistant tree species,and there was no significant difference between other xylem anatomical characters of drought-resistant tree species and non-drought-resistant tree species.The mean vessel diameter,maximum vessel diameter and Kp of deciduous tree species were significantly larger than that of evergreen tree species,and fiber cell wall thickness,vessel density and fiber cell wall/fiber cell were significantly smaller than that of deciduous tree species,there was no significant difference in NCS concentration between the two species.(2)There was great variability among 8 leaf traits and photosynthetic parameters among different tree species.Both the thickness of SLA,sponge tissue thickness,lower epidermis thickness and PT/ST were significantly smaller than that of that of the non-resistant tree species,and there was no significant difference in photosynthesis parameters.The MLA,SLA,Pn and Tr of deciduous tree species were significantly larger than that of evergreen tree species,the palisade tissue thickness and sponge tissue thickness of evergreen tree species were significantly smaller than that of evergreen tree species,and there was no significant difference between the other leaf anatomical traits.(3)The study of drought-resistant and non-drought-resistant tree species found a significant correlation between vesselt wall thickness and mean vessel diameter,maximum vessel diameter and Kp,and Kp has significant correlation between maximum vessel diameter,this was more pronounced in drought-resistant species than in non-drought-resistant species.there was no significant difference in photosynthesis parameters.a significant positive correlation between the parenchyma fraction and paratracheal parenchyma fraction,and a significant negative vessel between catheter connectivity and Huber values.this relationship only existed in drought-resistant tree species.Study on deciduous and evergreen tree species,a significant negative correlation was found between the Huber value and the maximum vessel diameter and vessel fraction.Kp had a significant positive correlation with the maximum vessel diameter and the mean vessel diameter,there was also such a relationship among deciduous tree species,but there was no such relationship among evergreen tree species.(4)The analysis of hydraulics characteristics of different tree species shows that drought-resistant tree species have high water transport efficiency and high anti-embolism ability,and their hydraulics characteristics show a good synergy between water transport efficiency and safety.Deciduous tree species and evergreen tree species show different hydraulic characteristics: deciduous tree species have high efficiency of water transport but poor anti-embolism ability,adopt more risky water transport mode and drought avoidance strategy;evergreen tree species give priority to ensure anti-embolism ability,adopt more conservative safe water conveyance mode and drought tolerance strategy,and their hydraulic characteristics reflect high efficiency-safety trade-off relationship.Different hydraulic structure characteristics and drought adaptation strategies make the niche differences between deciduous and evergreen tree species,reduce water use competition,and help the two co-exist in low mountains and hilly region of Shandong Province.(5)In this study,anatomical characteristics of xylem(such as vessel characteristics,parenchyma characteristics,etc.)and leaf anatomical features(PT/ST,etc.)can be used as priority traits for drought resistance evaluation of tree species,and it can provide a reference for the selection of tree species in low mountains and hilly region of Shandong Province. |
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