In addition to causing significant damage to human health, air pollutionalso keeps the growth of trees, one of the elements they canmitigate this typical urban ecological problem.
Researchers at the University of Sao Paulo (USP) in Brazilshow that atmospheric pollutants limit the growth of trees and the ecosystemtree-supplied services such as filtering of absorption pollutionmetals in the air in the bark, CO2 absorption, heat reductionisland effect by reducing solar radiation, mitigating rainwaterdrainage and humidity control.
The study is supported by the Sao Paulo Research Foundation FAPESP. The results are published in the journalThe Science of the Common Environment,
"We found that in years when the levels of particulate matter in the atmosphere were higher, for example, the trees were less. As a result, they later began to provide ecosystem services that play an important role in reducing urban pollution and mitigating or adapting the city to climate change later in life, "said Giuliano Mazeli Lokoseli, a research associate at the University of Sao Paulo . (IB-USP) with a scholarship from FAPESP and the first author of the study.
Using Tipuana tipu (Tipuana tipu) as a model, also known asrosewood or type, high tree with large sprinkling canopy andubiquitous in the city, researchers measure the impact of airpollution and time on tree growth in Sao Paulo. They analyzed samplesof 41 tipuanas at the age of 36 on average and located at different distancesof the Capuava industrial complex in Mawa,the metropolitan area. Capuawa is one of the most industrialized areasin the region, with oil refineries, cement plants and fertilizersplants, as well as for heavy and road transport.
Samples of the tree growth rings were taken using a toolcalled Pressler's auger auger, who has a hollow screw-up battledesigned to extract a cylindrical part of wood from lifetree across its entire radius with relatively little damage to the plant.All samples were taken at a chest height of approximately 1.3 mthe surface layer of the soil.
By analyzing the chemical composition of the bark and the size of the barkresearchers have been able to measure variations in the airlevels of contamination based on the different chemical elements to which. ttrees have been exposed during their development and to consider how thisfactor affects the growth of trees.
"Tipuana is an excellent marker that clearly represents the levelsair pollution with heavy metals and other chemical elements in"said Lokosely.
Metals and other chemicals suspended in the air are absorbedcrust. The particles are deposited on the leaves, increasing their sizetemperature and reduction of light supply for photosynthesis. Growthrings show how pollution has affected the plant life a year agoyear. The thicker rings show years of stormy growth and lower levelswhile the thinner rings show the opposite.
Analysis of growth rings shows that these types grew faster in 1974the warmer parts of Capuava with higher levels of phosphorus in the air.Phosphorus is a known macroelement for plants and acts as a basis for thistheir energy metabolism through photosynthesis and respiration.
On the other hand, trees close to traffic and exposed to high levelsof aluminum, barium and zinc associated with car wearingparts (such as tires, brake linings and connecting plates) appear lessgrowth over time.
Particles up to 10 micrometers (PM10) in diameterplants and factories reduce the average growth of trees with so many37%.
– Trees exposed directly to high levels of pollution by. Tfactories in the area are growing less in terms of stem diameter developmentthroughout their lives than plants exposed to medium and low levels,"said Lokosely. "Under normal growth conditions, typhoonthe breast diameter can reach up to 1 meter. "
Time series for PM10 in Capuawa for 20 yearsreceived from the Sao Paulo State Environmental Corporation (CETESB)and compared with the results of the bark and leaf analysis.
Researchers have found that PM10 levels represent 41% of the year-over-yeartree growth variability, with higher levels of contamination during. tThe driest months (April-September) slow down growth rates.
– The diameter increases very quickly when the tree grows normallybut little change when the growth rate is slow, "says Lokosely. "Thethe amount of ecosystem services provided by a high tree can be 70times bigger than for a small tree. "
Effects on Trees
According to the authors of the study heavy metals and particlesaffects tree growth by altering the optical properties of the leavessurfaces. As mentioned, these pollutants increase the temperature and decreasethe presence of light for photosynthesis. They can also reduce gasthe metabolism due to the accumulation of foliar droplets (pores that open and closeto allow the intake of carbon dioxide and the release of oxygen).
"We plan to try to find out whether pollution also affectslongevity of these trees. Given that pollution is very limitedphysiological systems that impede plant growth, probably alsothey are more vulnerable to effects that lead to aging, "says MarkosBuckeridge, Professor at IB-USP and Chief Investigator at IB-USPresearch project.
Urban pollution is likely to also harm other species in the same waya family such as tipuana found in São Paulo, as partridgewood (Caesalpiniapluviosa) and the iron tree (C. leiostachya).
"Measures to reduce air pollution, such as promoting the use of biofuels,electrification of transport and development of materials forreducing heavy metal emissions, may improve the maintenance of. tthese trees and the ecosystem services they provide, "Buckering said.