Green treasures: Investigating the biodiversity potential of equine yards through the presence and quality of landscape features in the Netherlands

Data classification To determine whether landscape features from the current survey would qualify as LFs in terms of functional size, and could thus contribute to biodiversity, all landscape features were classified using the geometric specifications of the EU Functional Landscape Feature Classes (FLFC) as set out by Czu´cz, Baruth, Terres, et al. [10] (see Table 2). Whenever LFs did not comply with these specifications in terms of functional size, i.e., because they were either too Table 1. Content of survey questions regarding LFs and biodiversity features (with *denoting the elements that were included in the calculation of overall Percentage Property Coverage (PPC). Type of landscape and biodiversity features Qualifying criteria Number Size Solitary tree Number present Average circumference (cm) measured 1.3 m from the ground Monumental tree Number present Average circumference (cm) measured 1.3 m from the ground Pollard tree Number present Average circumference (cm) measured 1.3 m from the ground Tree lane* Number present Average length and width (m) Tree row* Number present Average length and width (m) Fruit orchard* Number present Average length and width (m) Hedgerow* Number present Average length and width (m) Trimmed hedge* Number present Average length and width (m) Woody strip* Number present Average length and width (m) Forage wall* Number present Average length and width (m) Flowering strip* Number present Average length and width (m) Embankment* Number present Average length and width (m) Buffer strip* Number present Average size in m2

Monocultural grassland n/a Average size in m2 Herbaceous grassland n/a Average size in m2 Pond* Number present Average size in m2 Permanent woodpile* Number present Average size in m2 Cluttered corner* Number present Average size in m2 Birdhouse Number present n/a Bat box Number present n/a Insect hotel Number present n/a Proven nesting site Number present Average size in m2 https://doi.org/10.1371/journal.pone.0301168.t001 PLOS ONE Biodiversity potential of equine yards through landscape features PLOS ONE | https://doi.org/10.1371/journal.pone.0301168 April 11, 2024 4 / 16