沈阳市区不同环境下银杏水力特征和非结构性碳水化合物含量

银杏为重要的城市绿化树种,但在城市环境中常出现生长不良和受害的现象,作为行道树时该树种衰退死亡现象尤为多发,相关生理机制还有待深入研究。本研究选取生长在沈阳市区行道和公园两个不同生境的银杏,对其受胁迫伤害程度、水力功能性状及非结构性碳水化合物含量(NSC)等进行了对比分析。结果表明: 行道银杏枝条及叶片相比公园中的银杏受害程度更严重,但两种生境下生长的银杏枝条都表现出较低的栓塞程度,且导水率脆弱性曲线无显著差异,平均P₅₀均低于-2.8 MPa。行道银杏表现出比公园银杏显著降低的叶面积比导率、管胞直径、水力学直径、枝条可溶性糖和NSC含量等。水力失败不是行道银杏受害的直接原因,但该环境中生长的银杏枝条具有更小的管胞直径和较低的胡伯尔值,限制了整枝水平上的水分运输和光合碳同化能力。行道条件下银杏树为了应对更严重的干热等胁迫很可能需投入更多的NSC用于修复伤害,从而进一步导致该条件下枝条NSC含量降低,使得该条件下银杏树木碳失衡风险增加。在相同生境(街道或公园)下银杏的水力功能性状和NSC含量等表现出较大的样点间差异,反映出城市环境较大的异质性。

Hydraulics and non-structural carbohydrate contents of Ginkgo biloba under different environmental conditions in Shenyang City,China.

Ginkgo biloba is an important urban ornamental tree species, but poor growth and damages often occur in urban environments. As a street tree species, the decline and death of G. biloba is particularly frequent, with the relevant physiological mechanism being unclear. In this study, we compared hydraulic characteristics, non-structural carbohydrate (NSC) contents and health status between G. biloba trees growing along the streets and those in parks in Shenyang City. The results showed that G. biloba growing along the streets showed higher degrees of branch and leaf mortality than those growing in the parks. Branches of G. biloba growing in both conditions showed lower degrees of xylem embolism. Branch hydraulic vulnerable curves of G. biloba under the two growing conditions also showed no significant difference, with the average P₅₀ being lower than -2.8 MPa. G. biloba growing along the streets had lower leaf area specific conductivity, smaller tracheid diameter, smaller hydraulic diameter, lower soluble sugar content and total NSC than those growing in parks. Hydraulic failure was not the direct reason for the decline and mortality of G. biloba growing along streets. Under the more stressed growth conditions along the streets, G. biloba had smaller tracheid diameters in stems and lower Huber values, which limited the ability of water transport and photosynthetic carbon assimilation at the whole branch level. In addition, in order to deal with more serious stress such as greater heat and drought stresses, G. biloba might need to invest more NSC to repair damage, which further decreaded NSC contents in branches and increased the risk of carbon imbalance. At the same habitat (street or park), xylem hydraulics and NSC contents of G. biloba also showed relatively large difference among sampling sites, which reflected large heterogeneity of urban environment for tree growth.