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Current research

I am currently developing my post-doctoral studies at the Dept. of Forest Mycology and Pathology. My area of expertise is forest pathology, and I am interested in understanding the ecology and the epidemiology of forest pathogens in order to encompass a low impact of forest diseases with economically viable forest management activities. I am attracted by the idea of providing scientifically proved facts to the forestry sector. At present I am working with the root and butt rot pathogens Heterobasidion parviporum and H. annosum s.s., although in the past I gained experience with other pathogens such as H. abietinum, Armillaria sp., Melampsorella caryophyllacearum and V. album.

Trees have co-evolved with their pathogens thus under natural conditions it could be expected that damages caused by fungal pathogens would be low. Forest management can disturb the equilibrium between the pathogen and the host favouring the former, increasing its damages, and causing economical losses. A good example of such situation is depicted by the fungal pathogen Heterobasidion annosum on conifer forests. Heterobasidion annosum is almost inexistent in primary forests while it is rather common in managed forests. Under natural conditions it could be expected that bark injuries would be the main entrance point for this pathogen. But, even in such cases, H. annosum is a poor colonizer, revealing the proficiency of the tree defence system. When we manage the forest we create stumps and we therefore open a back-door for the entrance of such pathogen in tree root systems. Airborne spores of the fungus profusely germinate on stumps and colonize the stump. Mycelium spreads towards the stump root system and infects the neighbouring trees via root-to-root contacts. When infected trees are felled, the pathogen remains in the root system, so when the new forest generation is established, trees become infected again via root-to-root contacts.

Currently I am working together with Jan Stenlid  along five lines of research:

i) Modelling of Heterobasidion annosum disease

I am involved in the project Future Forests in which we are currently calibrating and validating a model for simulating the development of the disease caused by H. annosum. We evaluated the accuracy of Rostand model for its use in Sweden by using data from 34 plots, where the decay development has been followed for 15 years. By using an inoculum expansion of 0.20 m∙year-1, Rotstand gave unbiased predictions of decay development 15 years after infection with a relative error of 40.5% e.g. 20±8% of trees with decay.

ii) Epidemiology of Heterobasidion sp.

In Europe butt rot on Norway spruce (Picea abies (L.) Karst.) is caused by two fungal species, H. annosum s.s. and H. parviporum. After analysing a long term experiment, we have shown that both species differ in the way they spread in the stand. In nature, the presence of one species or the other was believed to be determined by the amount of airborne inoculum of each species. Our results showed that even using the same amount of inoculum,  H. parviporum was able to develop faster in the stand, while H. annosum s.s. was able to spread from a smaller amount of stumps. H. annosum s.s. created big genets, mainly in areas in which no competition with the other species was found suggesting that stump-to-tree spread and tree-to-tree spread do not seem to pose a problem for this species. The observed pattern could explain the tendency of observing H. parviporum more often than H. annosum s.s.in stands that become infected via thinning stumps. 

iii) Effects of Heterobasidion annosum on tree growth

As early as the 1990´s it was hypothesised that defence responses of the tree against decay may explain 50% of the growth losses. In a 15 years period (since stump infection until tree decay) no significant changes were observed on tree growth due to decay. But results from a more recent study suggested that longer periods of time are required for detecting periodic increment reductions. Most importantly, this increment reduction seemed to be exclusive for trees having built a reaction zone for compartmentalizing the decay. Further research is being carried out at presence with the using of dendrochronology tools in order to understand this process.     

iv) Practical control methods for H. annosum

We have recently reported data on the outcome of long term experiments showing that protection treatments of stumps have a persistent effect 15 years after application. Our results are noteworthy because on one hand they proved consistent at regional level and on the other hand treatments were applied as normal forest operations. In stands planted in agricultural land, the effect of stump protection was clear and while no rot was observed after 15 years in treated plots, untreated plots showed decay levels of 22% or 33%. In stands planted in forest land decay was caused by carryover of inoculum from the previous generation, however, we detected an effect of the treatment on the genetic structure of the fungus as new genets were established in unprotected plots as opposed to protected plots. These results are in line with simulations suggesting that on forest stands with previous presence of H. annosum the effect of stump protection may be delayed in time. Even when decay in early ages is dominated by carry-over, stump treatment is predicted to be still economically profitable .

v) Device for detecting decay in standing trees

We have assessed the accuracy of the Rotfinder, a device that can be used for detecting decay in Norway spruce trees. The device proved to have an accuracy of 86% (sensitivity of 75.5 % and specificity of 90.9%) when measurements were performed at stump level and when we aim to detect sections with more than 15% of decay in the section. The student Carmen Romeralo did her MSc project on this topic, currently a PhD student at the University of Valladolid (Spain).