Leaf reflectance and functional traits as environmental indicators of urban dust deposition.

BACKGROUND: How to quickly predict and evaluate urban dust deposition is the key to the control of urban atmospheric environment. Here, we focus on changes of plant reflectance and plant functional traits due to dust deposition, and develop a prediction model of dust deposition based on these traits. RESULTS: The results showed that (1) The average dust deposition per unit area of Ligustrum quihoui leaves was significantly different among urban environments (street (18.1001 g/m2), community (14.5597 g/m2) and park (9.7661 g/m2)). Among different urban environments, leaf reflectance curves tends to be consistent, but there were significant differences in leaf reflectance values (park (0.052-0.585) > community (0.028-0.477) > street (0.025-0.203)). (2) There were five major reflection peaks and five major absorption valleys. (3) The spectral reflectances before and after dust removal were significantly different (clean leaves > dust-stagnant leaves). 695 ~ 1400 nm was the sensitive range of spectral response. (4) Dust deposition has significant influence on slope and position of red edge. Red edge slope was park > community > street. After dust deposition, the red edge position has obviously "blue shift". The moving distance of the red edge position increases with the increase of dust deposition. The forecast model of dust deposition amount established by simple ratio index (y = 2.517x + 0.381, R2 = 0.787, RMSE (root-mean-square error) = 0.187. In the model, y refers to dust retention, x refers to simple ratio index.) has an average accuracy of 99.98%. (5) With the increase of dust deposition, the specific leaf area and chlorophyll content index decreased gradually. The leaf dry matter content, leaf tissue density and leaf thickness increased gradually. CONCLUSION: In the dust-polluted environment, L. quihoui generally presents a combination of characters with lower specific leaf area, chlorophyll content index, and higher leaf dry matter content, leaf tissue density and leaf thickness. Leaf reflectance spectroscopy and functional traits have been proved to be effective in evaluating the changes of urban dust deposition.

Biogenic volatile organic compounds from 14 landscape woody species: Tree species selection in the construction of urban greenspace with forest healthcare effects.

Biogenic volatile organic compound (BVOC) is an important part of forest healthcare effect, while it has not received enough attention in urban greenspace construction. Consequently, the aim of this study was to analyze BVOC emission rates and compositions released from leaves and flowers of landscape species in urban greenspace and to make suggestions for species selection and planting configuration in urban greenspace construction. BVOC emissions were collected and analyzed using dynamic flow enclosure technique with GC-MS in summer months (for leaf) and spring months (for flower) from 14 woody landscape species in northern China, which are 2 coniferous species (Pinus tabuliformis and Sabina vulgaris) and 12 broad-leaved species (Viburnum opulus, Kolkwitzia amabilis, Philadelphus pekinensis, Lonicera maackii, Cercis chinensis, Deutzia parviflora, Berberis thunbergia, Kerria japonica, Rosa xanthina, Syringa oblata, Syringa reticulata, and Cerasus serrulata). We found leaf emission rates of coniferous species were more than 20 µg∙g-1Dw∙h-1 and mainly consisted of monoterpenes, while that of sampled broad-leaved species were less than 10 µg∙g-1Dw∙h-1 and mainly consisted of fatty acid derivatives. Most broad-leaved species had relatively high emission rates of flowers, ranging from 15 to 115 µg∙g-1Dw∙h-1. Flower emissions of Syringa oblata and Syringa reticulata contained large amounts of aldehydes, and that of other broad-leaved species mainly contained terpenes, alcohols, and esters. We suggest the species with leaves that release large amounts of monoterpenes, and species with flowers that release large amounts of fragrant compounds are classified as healthcare species, while species with a dense crown and low emission rates of pungent compounds are classified as space-creation species. Based on this, planners could design urban greenspace with healthcare effects, and develop multi-functional, innovative, and sustainable urban greenspaces.