Forest field work for a new experiment
Updated: Mar 1, 2022
by Kostas Georgopoulos
Human activity in the form of intensive agriculture and deforestation have led to a global deterioration of ecosystem biodiversity over the years. Over time, these activities degrade soils and leave long lasting legacy effects which hamper our attempts at restoring these ecosystems through means of afforestation. In an effort to recover from the legacies that the human footprint leaves on nature, considerable research focus and financial investment is being allocated to restoring degraded ecosystems to a level that resembles their natural state.
Restoring soil biodiversity is crucial as plants constantly interact with a wide range of microbes in the soil (eg; symbiotic bacteria and fungi) which help them acquire nutrients and fend off pathogens. These microbes are often also major drivers of nutrient cycling in the soils. It is thus apparent that a loss of soil biodiversity would also result in the loss of several important ecosystem functions such as C-sequestration.
While afforestation is often utilized to restore degraded lands to a mature forest, restoring these habitats through such means takes considerable time as the degraded land has to first go through all the successional steps to become a mature forest. Thus we look to more effective methods of ecosystem restoration.
Soil inoculation has been continuously suggested as a means of speeding up the process of ecosystem restoration by promoting the establishment of target plant and soil communities. Current restoration programs tend to focus mainly on plants despite the importance of soil microbes and the role they play as it is often assumed that soil microbes will passively colonize the soil after successful plant species establishment. However, due to dispersal restrains this has proven to be quite limited. By inoculating soil from a mature forest to a degraded land, we are effectively introducing new, diverse soil communities to the soil thus enhancing their colonization and survival rates and promoting the establishment of target plant species. It is likely that different inoculation methods, such as varying amounts of inoculum and litter mixing can affect the success of inoculation in varying ways.
In order to understand how different soil inoculation methods affect the establishment and growth of trees, Gaspar Mejias Kromhout is setting up a new experiment for his BSc thesis. Together, we set off to the Meijendel dunes in the Netherlands to collect soils and litter from forests with Maple, Alder and Oak stands. As Maple associates with Arbuscular Mycorrhiza fungi, Oak with Ectomycorrhiza fungi and Alder with both, creating inocula from each donor site allows us to make a distinction between the different possible effects of the microbial communities from each site on tree performance. Arable soil was also collected from the Unifarm in Wageningen. Using these soils we aim to establish mesocosm experiments where we will test the effects of different soil inoculation methods on tree performance and mycorrhizal colonization. We expect that when soil from maple stands is mixed with soil from oak stands to create an inoculum, plant growth and mycorrhizal colonization will be the most optimal.
Despite the intense rain and wind, our trip to Meijendel proved to be a fun one and we look forward to setting up the mesocosms and monitoring the results.