RESUMEN

Brandisia is a shrubby genus of about eight species distributed basically in East Asian evergreen broadleaved forests (EBLFs), with distribution centers in the karst regions of Yunnan, Guizhou, and Guangxi in southwestern China. Based on the hemiparasitic and more or less liana habits of this genus, we hypothesized that its evolution and distribution were shaped by the development of EBLFs there. To test our hypothesis, the most comprehensive phylogenies of Brandisia hitherto were constructed based on plastome and nuclear loci (nrDNA, PHYA and PHYB); then divergence time and ancestral areas were inferred using the combined nuclear loci dataset. Phylogenetic analyses reconfirmed that Brandisia is a member of Orobanchaceae, with unstable placements caused by nuclear-plastid incongruences. Within Brandisia, three major clades were well supported, corresponding to the three subgenera based on morphology. Brandisia was inferred to have originated in the early Oligocene (32.69 Mya) in the Eastern Himalayas-SW China, followed by diversification in the early Miocene (19.45 Mya) in karst EBLFs. The differentiation dates of Brandisia were consistent with the origin of keystone species of EBLFs in this region (e.g., Fagaceae, Lauraceae, Theaceae, and Magnoliaceae) and the colonization of other characteristic groups (e.g., Gesneriaceae and Mahonia). These findings indicate that the distribution and evolution of Brandisia were facilitated by the rise of the karst EBLFs in East Asia. In addition, the woody and parasitic habits, and pollination characteristics of Brandisia may also be the important factors affecting its speciation and dispersal.

RESUMEN

The air purification potential of plants has been widely studied and recognized. However, their specific capacities in retaining water-soluble (WSPM) and water-insoluble (WIPM) atmospheric particulate matter (PM) are still unclear. In order to recommend tree species with high air phytoremediation ability, the retention characteristics for WSPM and WIPM of five tree species under different haze pollution levels and PM retention durations in Beijing were evaluated after introducing ultrasonic cleaning procedure to the conventional leaf cleaning methods. The daily PM amount retained these species in the six central districts in Beijing (SCBD) was roughly estimated based on the field tree survey data in 171 plots randomly distributed within the Fifth Ring Road. The updated leaf cleaning method improved the evaluation accuracy for WSPM and WIPM by 54% and 31%, respectively. The particles retained by the broadleaf and coniferous species were mainly composed of WSPM (71%) and WIPM (64%), respectively. The diameter distribution of PM varied markedly with species, PM retention duration, and pollution level. However, it always showed a unimodal pattern for WSPM and no uniform patterns for WIPM. The average relative capacities of different species in retaining WSPM of TSP (PM ≤ 100 µm) were more stable with time, and the corresponding rank was Sophora japonica > Salix babylonica > Ginkgo biloba > Pinus tabuliformis > Sabina chinensis. Whereas, as to the WIPM of TSP, their order changed to S. japonica > P. tabuliformis > S. babylonica > G. biloba > S. chinensis. During the study period, the TPM (WIPM+WSPM) of TSP retained by these species per day in the SCBD reached 132.6 t (76.1 t WSPM + 56.5 t WIPM), accounting for a considerable proportion of the daily dust-fall amount. These findings can contribute to selecting greening tree species and managing the urban forest to improve urban air quality.

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RESUMEN

Based on the conventional cleaning methods (water cleaning (WC) + brush cleaning (BC)), this study evaluated the influence of ultrasonic cleaning (UC) on collecting various sized particulate matter (PM) retained on leaf surfaces. We further characterized the retention efficiency of leaves to various sized PM, which will help to assess the abilities of urban trees to remove PM from ambient air quantitatively. Taking three broadleaf tree species (Ginkgo biloba, Sophora japonica, and Salix babylonica) and two needleleaf tree species (Pinus tabuliformis and Sabina chinensis) as the research objects, leaf samples were collected 4 days (short PM retention period) and 14 days (long PM retention period) after the latest rainfall. PM retained on the leaf surfaces was collected by means of WC, BC, and UC in sequence. Then, retention efficiencies of leaves (AEleaf) to three types of the various sized PM, including easily removable PM (ERP), difficult-to-remove PM (DRP), and totally removable PM (TRP), were calculated. Only around 23%-45% of the total PM retained on leaves could be cleaned off and collected by WC. When the leaves were cleaned through WC+BC, the underestimation of the PM retention capacity of different tree species was in the range of 29%-46% for various sized PM. Almost all PM retained on leaves could be removed if UC was supplemented to WC+BC. In conclusion, if the UC was complemented after the conventional cleaning methods, more PM on leaf surfaces could be eluted and collected. The procedure developed in this study can be used for assessing the PM removal abilities of different tree species.

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