Identification and spatial extent of understory plant species requiring vegetation control to ensure tree regeneration in French forests

Abstract

Key message Fifteen species are most susceptible to require vegetation control during tree regeneration in the range of our study. Among these 15 species, Rubus fruticosus, Pteridium aquilinum, and Molinia caerulea cover each more than 300,000 ha of open-canopy forests. Context Vegetation control, i.e., the reduction of competitive species cover, is often required to promote tree seedling establishment during the forest regeneration stage. The necessity to control understory vegetation largely depends on the species to be controlled. In order to plan forest renewal operations, it is critical to identify which species require vegetation control during the regeneration stage and to quantify the forest area affected by these species. Aims We aimed at identifying the main species requiring vegetation control and at estimating the forest area they cover at the national level. Methods Using National Forest Inventory data, we created four indicators based on two levels of plant cover, cross-referenced with two levels of canopy opening, and compared them to the outcome of a survey of forest manager practices. Results The best indicator was the one that represented the proportion of forests with open canopy where the species was present with a large cover in the understory. In non-Mediterranean France, according to the indicator, a total of 15 species were found to frequently require vegetation control during the tree regeneration stage. Pteridium aquilinum, Molinia caerulea, and Rubus fruticosus were the main species, and each covered more than 300,000 ha of forest with open canopies, representing about 13% of the total forest area with open canopies outside of the Mediterranean area. Conclusions Forests covered by species requiring vegetation control according to forest managers represent a large share of the forest area undergoing regeneration. This study provides the first list of species that require vegetation control based on a methodological protocol that makes it possible to calculate the area associated with each species.

Insect-habitat-plant interaction networks provide guidelines to mitigate the risk of transmission of Xylella fastidiosa to grapevine in Southern France

“…Finally, we found several nymphs of A. alni on Pteridium aquilinum (opportunistic extra samplings, Appendix 9, Fig. S9.4), one of the most ubiquitous species in the world, able to develop below forest canopies and in open areas (Dumas et al, 2022). More work is needed to determine if A. alni only occasionally feeds on that fern, or if bracken covers represent a significant reservoir of this xylem feeder.…”

A New Approach for Feeding Multispectral Imagery into Convolutional Neural Networks Improved Classification of Seedlings

“…This information is needed in order to allocate tending and thinning operations in seedling forests, defined as the removal of competing understory vegetation and clustered and unwanted tree species from crop trees, respectively. This information plays a crucial role in assisting forest managers in the allocation of silvicultural operations, aiming at ensuring tree growth of the species of interest and future wood supply [3,[9][10][11][12], as well as other ecological functions of seedling stands [13,14]; for example, it is important to give more growing space for coniferous seedlings than dominating and often unwanted deciduous seedlings [15] and understory [16,17], as deciduous seedlings, especially birches, outgrow coniferous seedlings during the early growth stages [15,18,19]. An RS-based forest inventory could collect the required information in a more spatially explicit and timely manner compared to field visits, which are considered to be time-consuming, costly, laborious, and often subjective.…”