# Contrasting Conservation Outcomes for Ground-Dwelling and Aerial Insects in Masson Pine Plantations: Reduced Ground-Dwelling Insect Diversity but Comparable Aerial Insect Diversity to Natural Forests

## TL;DR

Masson pine plantations support similar flying insect diversity to natural forests but have fewer ground-dwelling insects, suggesting a need for management changes to improve habitat quality.

## Contribution

The study reveals contrasting conservation outcomes for ground-dwelling versus aerial insects in Masson pine plantations and identifies management strategies to improve ground insect diversity.

## Key findings

- Aerial insect diversity and composition in Masson pine plantations are comparable to those in natural forests.
- Ground-dwelling insect diversity is significantly lower in plantations, with shifts in community composition linked to understory tree density, litter calcium content, and litter cover.
- Mixed planting with broad-leaved trees can enhance ground-dwelling insect diversity by improving litter nutrients and understory vegetation.

## Abstract

Masson pine plantations cover huge areas of southern China and are vital for timber and reforestation. But do they support wildlife as well as natural forests? In our study, we compared insect communities in these pine plantations with those in nearby natural forests. We found that flying insects, such as flies and moths, showed similar levels of family diversity and composition in both plantation and natural forests, probably because they can easily move between habitats. In contrast, ground-dwelling insects, such as beetles and crickets, were less diverse and consisted of different taxa in the pine plantations compared to natural forests. The main reasons were fewer trees in the understory, thicker layers of pine needles, and lower Ca levels in the litter—making the habitat less suitable for many ground-dwelling insects. To help these important ground-dwelling insects thrive, forest managers can plant native broad-leaved trees together with pines. This simple change improves litter nutrition, reduces needle buildup, and allows more plants to grow underneath—creating a healthier home for insects.

Masson pine (Pinus massoniana Lamb.) is the most widely planted tree species in southern China, playing a critical role in forestry production and reforestation. Understanding the contribution of Masson pine plantations to biodiversity conservation is essential for sustainable land-use policies. We conducted comparative studies to examine the family diversity and composition of ground-dwelling and aerial insects in Masson pine plantations and adjacent natural forests at regional (spanning five forest types across Guangxi, China) and local (at Yachang, Guangxi) scales. We investigated the mechanisms driving the differences in insect community assemblages between the two forest types at the local scale. Our results indicated that aerial insect diversity and composition in Masson pine plantations were comparable to those in natural forests. However, ground-dwelling insects in plantations showed a significant decline in diversity and a notable shift in community composition, with a decrease in highly mobile omnivores (e.g., Drosophilidae and Nitidulidae) and an increase in crawling detritivores (e.g., Blattidae and Gryllidae). These patterns were consistent at both regional and local scales. At the local scale, the shift in ground-dwelling insect community composition was linked to decreased understory tree density (explaining 45.9% of the compositional variation), reduced litter Ca content (29.7%), and increased litter cover (13.5%) in plantations. To enhance ground-dwelling insect diversity in Masson pine plantations, mixed planting with broad-leaved species offers an effective management strategy. This approach both enriches litter nutrients and reduces needle litter accumulation, thereby supporting the recovery of understory vegetation.