Resumen:
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The restoration of ex-arable fields is a common issue in North-West Europe, having a species rich
heathland as a target ecosystem. This is a long process which can take decades due to the different
successional stages ...[+]
The restoration of ex-arable fields is a common issue in North-West Europe, having a species rich
heathland as a target ecosystem. This is a long process which can take decades due to the different
successional stages the system needs to go through. There are many factors playing a role in this
secondary succession gradient, as for instance seed bank quality and diversity, abiotic factors as
nitrogen or organic matter content and biotic factors as soil biota (which is the living part of the soil
and contributes strongly to create the optimal conditions). Soil biota generates a complex soil food
web based on multi-trophic interactions, and it has a strong influence in the presence/absence of
different species and its abundance, both above and belowground.
In this master thesis we wanted to evaluate the importance of soil biota in driving the succession of
plants along the restoration process in 9 different ex-arable fields. Mainly, we focused on the effect of
different plant pathogenic fungi on early successional wild plant species performance, and whether
the impact on the plants is strongly related to the time since agricultural abandonment. The capacity
of soil biota to reduce impact of pathogenic fungi on plants is known as suppressive capacity and is
mainly expressed in agricultural fields were similar plant species grow generation after generation on
the same field. In this study we want to test whether in a natural situation the biotic soil components
would also develop from an initial conductive stage to a mature suppressive stage over the course of
succession. For this purpose we set up two experiments: the first was a pre-test to find out which plants and fungi
were the most appropriate plants and fungal species to be used for the main experiment. In the main
experiment we measured the effect of three different fungi (Gaeumannomyces graminis,
Botrytiscinerea and Verticillium albo-atrum.) on two plants species (Achillea millefolium and Plantago
lanceolata.), on soils from three different successional stages (recent- , mid- and long-term ago taken
out of agricultural production). Our hypothesis was that soils belonging to the late successional stage
are more suppressive, resulting in lower fungal impact on the plants. We hypothesized that over the
course of succession soil biota becomes more diverse and there is more competition due to the fact
that easily decomposable organic matter decreases, and suppressiveness might be enhanced
undirectly by this fact. The results rejected the hypothesis. Only in the pot where we added Botrytis
cinerea there was suppressive capacity by the soil biota on the fungus, but this effect diminished
towards later successional soils. The soils showed no soil suppression at all towards the other two
soil
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