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

expected, yards with more LFs also had a greater PPC on their property. Interestingly the size of monocultural grasslands did not explain PPC whilst the size of herbaceous grasslands did (Table 4). The variables explaining the most variation (as indicated through R-square) in PPC included Number of LFs (18.1%), Tree rows (8.4%) and Wild hedges (7.2%; Table 4). All other variables explained less than 5% of variation in PPC (Table 4). Multivariable hierarchical regression results Inspection of the data, using the scatterplot of the standardised residuals, showed that assump- tions of normality, linearity, and homoscedasticity had not been violated. Residuals were approximately rectangular in distribution with most of the scores concentrated along the 0 point. Multicollinearity was assessed by examining Tolerance and Variance Inflation Factor (VIF). Tolerance values ranged from 0.775 to 0.997 and the VIF ranged from 1.003 to 1.290, indicating no issues with multicollinearity. Multivariable hierarchical linear regression analysis revealed that model 1, which included the yard descriptors, explained 21% of the variance (F(3,447) = 39.709; p < 0.001), with Yard size and Number of LFs contributing significantly to the model (Tables 5 and 6). Model 2, which also included the 14 LF variables explained 47.2% of the variation in PPC (F(14,436) = 27.815; p < 0.001; Tables 5 and 6). The following LF variables contributed significantly to the final model: Tree rows, Fruit orchard, Wild hedges, Flowering strips, Buffer strips, Embank- ments, Cluttered corners (Table 6).

Table 3. Descriptives of participating yards, including Mann-Whitney U test of differences. Overall Commercial Private Differences between Commercial and Private yards (U-value; p-value) Participating yards (N) 507 87 (17.2%) 420 (82.8%) Yard size (ha) Mean±SD 3.15±6.98 9.16±12.89*** 1.9±3.97*** U = 6199; Median; range 1.5;63.52 3.36;59.65 1.2; 63.52 <0.001 Number of horses Mean±SD 7.16±12.68 24.99±23.38*** 3.47±1.54*** U = 1770.5; Median; range 4;120 16; 120 3; 8 <0.001 Number of LFs Mean±SD 10.36±3.44 9.95±4.31 10.45±3.23 U = 16523; Median; range 10;19 10;19 10; 18 0.159 Percentage property coverage (PPC) in % with LFs Mean±SD 11.77±14.66 9.08±13.87*** 12.33±14.77*** U = 14163; Median; range 5.85; 94.6 3.35; 62.43 6.57; 94.6 <0.001 Type of soil Clay 23.9% 29.9% 22.6% N/a Loam 3.6% 6.9% 2.9% Peat on sand 0.8% 2.3% 0.5% Peat 5.9% 3.4% 6.4% Sand 61.1% 49.4% 63.6% Silt loam 1.0% 2.3% 0.7% Don’t know 3.7% 5.7% 3.3% *<0.05 **<0.01 ***<0.001 https://doi.org/10.1371/journal.pone.0301168.t003 PLOS ONE Biodiversity potential of equine yards through landscape features PLOS ONE | https://doi.org/10.1371/journal.pone.0301168 April 11, 2024 7 / 16