Increase of Tree Species Mingling enhances the resistance of Pinus armandii forests to Dendroctonus armandi infestation.

Abstract

Pinus armandii Franch., a key native conifer in China, faces severe Dendroctonus armandi infestation, threatening forest ecosystems. Reducing infestation probability and enhancing resistance are essential for transforming Pinus armandii forests. This study investigates the correlation between stand structure, topographic factors, and the probability of Pinus armandii infestation by Dendroctonus armandi. Based on these correlations, it selects suitable mixed-species combinations of native tree species with low infestation probabilities that are adapted to regional characteristics. A random survey was conducted in 58 plots (6,021 trees) in Shennongjia. Logistic regression and analysis of variance (ANOVA) revealed: (1) Infestation rate increased with elevation, peaking at 84.38% above 2,000 m; between 1,500-2,100 m, probability rose 4.3% per 100 m elevation gain; (2) Steeper slopes (> 25°) reduced infestation (46.03%), with risk decreasing 1.9% per 1° slope increase (0°-40°); (3) Larger DBH (> 30 cm) trees had higher infestation (82.93%), increasing 4.5% per 1 cm DBH; (4) Higher species mingling (four neighboring non-Pinus trees) lowered infestation to 63.39%, reducing risk by 54.3% per mingling unit; (5) Healthy Pinus armandii were frequently neighbored by Litsea pungens, Carpinus cordata, Phellodendron chinense, and Betula platyphylla. Prioritizing slopes > 25° and elevations < 2,000 m for afforestation, mixed with Litsea pungens, Carpinus cordata, or Betula platyphylla, can mitigate infestation. These findings provide actionable strategies to enhance Pinus armandii forest resilience against Dendroctonus armandi threats.