Response of Pinus sylvestris and Fagus sylvatica seedlings to mechanical injuries in shade and under competition
In order to evaluate the impact of root injuries and defoliation on seedlings Pinus sylvestris and Fagus sylvatica, including such traits as growth, survival, biometrical parameters of leaves and roots as well as on secondary metabolite level and carbohydrates, I examined various mechnisms which are initiated in injured seedlings. I explored growth and chemical responses of pine and beech to simulated injuries of seedlings during the whole growing season (spanning over six month period) in 2005 and 2006 on one and two-years old seedling respectively.
I investigated how injuries of seedlings affect subsequent plant growth under diverse light conditions: 50 and 5% of full light in 2005 and 100, 50, 15 and 5% in 2006.
For estimating the competition ability of injured seedlings I used an annual grass Bromus strilis in both years.
In 2005 four treatments were applied to beech: removing one cotyledon and/or 20% of the root system and eight treatments to pine: removing one, three and five (of six) cotyledons and/or 20% of the root system. In 2006 four treatments were applied for both species (removing 50% of leaves and/or 20% of the root system). I designed the experiment as completely randomized with replicates plots and blocks for each treatment.
In both species cotyledon damage had a significant effect on seedlings growth and mortality during the establishment phase. Removing 50% of leaves of two-years old seedlings also significantly decreased biomass of leaves and shoots as well as the rate of root extension. Defoliate seedlings produced significantly fewer leaves than control plants. The less severe the defoliation, the smaller was the reduction of plant biomass and the earlier the recovery after the artificial injuries. Competiton with grasses exacerbated the eartly negative effects of cotyledon damage on individual seedling size. In general, root growth as well as aboveground shoot were inhibited by grasses. Seedlings grew bigger under high light conditions as a result of enhanced net assimilation rate. The mortality of seedling was especially pronounced in 5% of full light conditions. I did not observed any changes in secondary metabolite level in leaves and roots in pine and beech in both years.