Researchers from Coimbra recorded the highest density of eucalyptus on land affected by the October 2017 wildfires ever identified outside Australia.
A group of researchers from the Escola Superior Agrária de Coimbra (ESAC) and the Center for Functional Ecology of the University of Coimbra conducted an experiment on five plots in Santa Comba Dão that burned in the fires of October 15, 2017 and, in one of the locations, counted an eucalyptus density of 804 thousand plants per hectare, the highest ever recorded in scientific literature outside Australia in plants from natural regeneration, the researcher, Joaquim Sande Silva, told Lusa.
The highest previous value that the researchers had found in the literature was an estimate of 20,000 eucalyptus per hectare, in Galicia, Spain, with the normal density for an eucalyptus for production being between 1,000 to 1,400 trees per hectare.
Joaquim Sande Silva points out that these results have to take into account the fact that the land was analyzed when the plants were very young, and the mortality rate will considerably reduce the density found in the land.
However, even applying a mortality rate of 30% per year, the density, after seven years, will be much higher than that registered by any other study, with 39 thousand plants per hectare, note the researchers, in a recently published scientific article .
“As in all populations, there is a very high natural density at the beginning, which is decreasing. However, everything indicates that this abnormal density of plants will remain at higher stages of development”, stressed Joaquim Sande Silva.
For this abnormal density of eucalyptus, there is an important combination of factors, one of the most relevant being the time when the fires of October 2017 occurred.
“The fire hit the trees at a time when the soil was already damp. Optimum germination conditions were in place as soon as the capsules released the seeds after the passage of the fire and it will have been decisive for this explosion of plants”, he stressed.
For the researcher, this high recorded density will also have consequences on the size of the eucalyptus, where the destiny of many of those parcels will be abandonment, favoring the occurrence of new fires, he warned.
In addition to the already existing horizontal fuel continuity for a fire, with a dense eucalyptus and with plants with different heights, there is also “vertical fuel continuity”.
“The fire starts at the surface and here easily reaches the canopies, because it has plants of various dimensions. These are the perfect conditions for the spread of the fire”, he noted.
This investigation arose from a partnership between the Câmara de Santa Comba Dão and the team of researchers to study and control the natural regeneration of eucalyptus after the fires.
In this municipality in the district of Viseu, the team worked on five plots, with “in more than half of the plots there was not a single species of herbs or shrubs present”, in addition to eucalyptus, he noted.
The researchers tested two eucalyptus management techniques – one using herbicides and the other when cutting -, recommending the use of cutting due to the environmental impacts of the use of herbicides.
However, said Joaquim Sande Silva, the cut must be made “at very early ages” of the plants, and treatment in the first year of life is recommended.
“From the moment the plants are three or four meters high, the only solution is to carry out highly damaging work for the soil, with heavy machinery to start all over again,” he stressed.
In the case of the territory affected by the great fires in October, “the window of opportunity has passed,” said the investigator.
Source: Renascença – Noticias by rr.sapo.pt.
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