Effects of Management Practices and Topography on Ectomycorrhizal Fungi of Maritime Pine during Seedling Recruitment

Arthur Guignabert,Florian Delerue,Mark Bakker,Laurent Augusto,Maya Gonzalez

doi:10.3390/f9050245

Abstract

Symbiosis with ectomycorrhizal (ECM) fungi can be important for regeneration success. In a context of increasing regeneration failures in the coastal forest of maritime pine in Southwest France, we tried to identity whether differences in ECM communities could partly explain the variation of regeneration success and how they are influenced by forest practices and stand characteristics. In particular, we focused on the effects of harvesting methods (comparing mature forest with seed-tree regeneration and clear-cuts) and topography (bottom-, mid-, and top positions). Five field trials (two in regeneration failure areas and three in successful areas) were used to sample 450 one-year-old seedlings. Assessments of ECM of seedling nutrient concentrations and of seedling growth based on exploration types were made. ECM root colonisation was similar in all harvesting treatments, suggesting that enough inoculum remained alive after logging. Harvesting-induced effects modifying soil properties and light availability respectively impacted ECM composition and seedling growth. Topography-induced variations in water and nutrient availability led to changes in ECM composition, but had little impact on seedling growth. Contact, short-distance, and long-distance exploration types improved the nutritional status of seedlings (Ca, K, and N), showing that mycorrhization could play an important role in seedling vitality. However, neither ECM root colonisation nor exploration types could be related to regeneration failures.

Highlights

Maritime pine (Pinus pinaster Aït in Soland) is the dominant forestry tree species in south-westernFrance, covering almost one million ha [1]
The four exploration types were observed at all sites, and throughout most of the individual root systems examined; 73% and 25% of the seedlings had respectively four and three exploration types on their root system
Jarvis et al [29], who looked at both species and exploration types in Pinus sylvestris across Scotland, found that soil moisture and precipitation were the main drivers of ECM species composition, while temperature had an influence on exploration types

Summary

Introduction

Maritime pine (Pinus pinaster Aït in Soland) is the dominant forestry tree species in south-westernFrance, covering almost one million ha [1]. Most of the forest range in the interior land plains is renewed by planting, whereas natural regeneration is used in the coastal area, which represents 10% of this forest [1]. In addition to wood production, these coastal forests have a multifunctional role, including soil erosion protection, preservation of biodiversity, and tourism/public usage [2]. To accommodate these multiple objectives, the use of natural regeneration to renew forest stands limits soil disturbance (no soil ploughing, such as before plantations) and improves the conservation of genetic diversity and the capacity of forests to adapt to global change. The regeneration status is Forests 2018, 9, 245; doi:10.3390/f9050245 www.mdpi.com/journal/forests

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Conclusion