Relative importances for predictors of butterfly species richness, butterfly composition (principal curve score), and butterfly density as determined by boosted regression tree analysis, using procedure gbm.step [52, 53].

Importances with daggers (†) are associated with predictors that were not included in a simplified model (as determined by gbm.simplify). Ten-fold cross-validated correlation between observed and predicted response are shown at the bottom for full and simplified models as well as squared correlation for full model. Model represents predictions for individual surveys (n = 21 surveys per site) across 25 sites (total n = 525).

带剑号（†）的特征重要性分值，对应未被纳入简化模型的预测变量（该简化模型由gbm.simplify函数确定）。完整模型与简化模型的观测值与预测响应值间的十倍交叉验证相关系数已在文末给出，同时一并提供完整模型的平方相关系数。本模型针对25个站点的独立调查数据生成预测结果，每个站点包含21份调查样本，总样本量共计n=525。