基于CiteSpace的兰花保鲜研究进展及可视化分析

为更全面系统了解兰花保鲜国内外研究现状和进展情况，以英文数据库Web of Science(WOS)和中文数据库中国知网(CNKI)收录的兰花保鲜研究文献为数据源，采用CiteSpace计量工具，用文献计量分析方法和知识图谱可视化技术对1989—2021年国内外各科研院所发表的研究文献进行梳理统计和数据分析。分析表明，世界范围内兰花保鲜研究论文发文量总体呈现缓慢上升趋势；研究领域中影响力最大的依次是中国、泰国和美国；研究的兰花种类主要集中于石斛兰、蝴蝶兰和文心兰；其中中国学者重点研究蝴蝶兰和文心兰，泰国研究团队主要研究石斛兰；研究方向主要集中于衰老生理方面，其中内源激素乙烯是兰花衰老生理研究的重点，而如何抑制乙烯是兰花保鲜研究中生理实验的热点。根据统计数据综合分析推断，兰花衰老的分子机制、利用分子技术延长花朵寿命将成为兰花保鲜前沿研究重点与新兴趋势。     

Best practices to use the iPad Pro LiDAR for some procedures of data acquisition in the urban forest

The search for means to improve urban forest inventories is challenging for small communities and cities with a limited budget. Mobile applications on iPad or iPhone seem promising equipment to make some inventory practices cheaper and faster, although procedures of use are still limited. So, we tested the LiDAR scanner application on an iPad Pro 2020 for trunk perimeter measures and the position for 10 different groups of species in the Polish Airmen Park, Kraków (Poland). For each group, in 10 trees, we measured the perimeter at breast height (PBH) and relative tree trunk position. The first procedure tested the estimation of PBH according to the distance of an iPad Pro from the trunk, the time of 3D data acquisition and the number of turns around trees. The second procedure tested PBH estimations according to the number of trees scanned in just one try (3, 6 and 10 trees). The third procedure tested the estimation of the relative position of tree trunks from other trees. In each procedure, we compared 3D point clouds generated by an App running on iPad Pro with data from a measuring tape and FARO FOCUS 3D (TLS) point clouds. The results showed that the shorter the distance from the iPad Pro to the trunk surface, the more precise the PBH estimation, not significantly different (p > 0,01) from TLS values. Distances between 1.0 and 2.0 m would be most suitable for the iPad Pro application but performing two turns around the tree trunk would improve results for PBH measurements. Trees scanned as 3-tree groups with the iPad Pro presented the smallest PBH differences compared to TLS point clouds. No significant differences (p > 0,01) were found between the methods for estimating the distance among trees, which shows that the iPad Pro can deliver a precise relative position of tree trunks.     

Feasibility study on the estimation of the living vegetation volume of individual street trees using terrestrial laser scanning

As an important part of urban greening, the canopy of street trees has ecological benefits, such as oxygen production, noise reduction, and dust reduction. The living vegetation volume (LVV) can reflect the spatial structure of the canopy intuitively and enables the estimation of the ecological service value of street trees. Terrestrial laser scanning (TLS) has shown excellent performance for providing three-dimensional data of individual trees with high precision, enabling the accurate quantification of the LVV. In this study, we divided the LVV into the total living vegetation volume (tLVV) and the effective living vegetation volume (eLVV); the latter does not include branches. The eLVV of 40 ginkgo trees separated in two roads in Nanjing was calculated from TLS data. A novel method named LAIM for accurate eLVV calculation based on point cloud data was proposed. The point cloud data of individual tree was segmented along the Z-axis and image processing methods were used. With this, eLVV of each tree was obtained. The results were compared with data obtained from a clustered point cloud generated using convex hulls. The Bland-Altman analysis was used to investigate the consistency of the two methods. Furthermore, we used correlation analysis and all-subsets regression to choose the variables, and the eLVV was fitted using six models. Finally, we evaluated O₂ production, CO₂ and SO₂ absorption by the street trees based on eLVV, the ecological benefits of street trees were quantified. The results showed the following: (1) The number of layers and the dilation size of the point cloud were crucial parameters in the LAIM. (2) For ginkgo trees, the mean difference between the eLVV obtained from the LAIM and the convex hull method was − 0.53–0.19 m³, indicating that the results were highly consistent for the two methods. (3) The eLVV fitting performance was better for the exponential function model (R² =0.8523, RMSE=0.6838 m³) and linear model (R² =0.8361, RMSE=0.7224 m³). The tree height and crown width significantly affected the eLVV estimation. (4) The evaluation about ecological benefits of Zhaoyang Road was better than Cuizhu Road. The quantified ecological benefits were conducive to road ecological evaluation. This study quantified the eLVV of individual trees using TLS, highlighting the importance of live vegetation in urban greening. The results can provide technical support for estimating the ecological service value of urban street trees.