Introduction

Insects play a critical role in ecosystems and are widely used as indicators of biodiversity (Basset et al., 2012; Samways, 2007; Thomas, 2005). Their distribution and number of individuals are influenced by various factors, including season, forest type, climate, and environmental change, all of which serve as important indicators for evaluating ecosystem health and stability (Kremen et al., 1993). Therefore, accurate assessment and monitoring of insect diversity are essential for establishing policies for conservation and ecosystem management (Andersen, 1999; Didham et al., 2012).

Among various methods for surveying insects, light traps are commonly used to capture nocturnal insects because of their efficiency (Intachat & Woiwod, 1999). Light traps utilize the phototactic behavior of insects and are particularly useful in studies on community structure and seasonal variation of nocturnal species (Frank, 1988). However, survey results may be influenced by trap placement, survey timing and location, and duration of operation (Yela & Holyoak, 1997). Therefore, standardization of trap setup and collection protocols is necessary for clarify the differences in insect diversity by season and forest type (Thomas, 2005).

The bucket light trap is advantageous because of its lightweight design, allowing for easy installation and high sampling efficiency across various environments (Brown et al., 2000). This study was conducted as part of a methodological improvement initiative for the terrestrial insect components of the National Ecosystem Survey. It aimed to compare insect diversity according to season and forest type using bucket light traps and to provide guidelines for optimal trap deployment in terms of timing and location. The results of this study are expected to serve as a valuable foundation for standardizing insect monitoring and evaluating ecosystem changes.

Materials and Methods

Results

Discussion

Seasonal analysis showed that summer had the highest number of species (567 species) and individuals (6,215 individuals), followed by autumn (474 species and 4,298 individuals) and spring (432 species and 3,018 individuals). Compared to spring and autumn, summer showed approximately 31.2% and 19.6% higher number of species and 105.9% and 44.6% higher number of individuals than those in autumn and spring, respectively.

By forest type, the mixed forest had the highest number of species (720 species) and individuals (5,139 individuals), followed by the deciduous forest (645 species and 4,559 individuals) and coniferous forest (580 species and 3,833 individuals). Compared to coniferous and deciduous forests, the mixed forest showed approximately 24.1% and 11.6% more species and 34.1% and 12.7% more individuals respectively.

Statistical analysis by season revealed significant differences in both the number of species and number of individuals. Specifically, significant differences were observed between spring and summer (P<0.001), spring and autumn (P<0.025), and summer and autumn (number of species: P<0.004; number of individuals: P<0.001). These findings suggest that surveys conducted in summer are more effective for identifying insect diversity. Therefore, it is advisable to include summer sampling in biodiversity monitoring programs (Samways, 2007; Yela & Holyoak, 1997). In particular, when conducting multi-season surveys, including summer as a core period can enhance compliance with the National Ecosystem Survey guidelines and improve the monitoring of ecosystem changes (Didham et al., 2012; Kremen et al., 1993).

Regarding forest types, a significant difference in the number of species was observed between coniferous and mixed forests, but no significant differences were found between other forest types. These findings suggests that mixed forests are more favorable for surveying insect communities and securing higher diversity (Andersen, 1999; Brown et al., 2000). Consequently, mixed forests with both coniferous and deciduous components are recommended as priority sites for insect diversity assessments.

Additionally, variations in the number of species and individuals were observed even within the same forest type, depending on the diversity of vegetation and understory development. These results align with previous studies emphasizing the importance of understory vegetation for insect diversity (Thomas, 2005). Therefore, in mixed forests, survey sites with well-developed understory vegetation, including shrubs and herbaceous plants, should be prioritized for more effective biodiversity assessment.

In conclusion, this study clearly demonstrated differences in nocturnal insect diversity by season and forest type. The findings provide a scientific basis for biodiversity monitoring and ecosystem assessment. In particular, the effectiveness of surveys conducted in mixed forests among forest types and during summer among seasons was validated, highlighting the potential for standardizing insect monitoring protocols and improving national survey guidelines.

However, this study has several limitations. First, the results were based on data collected during a single year, which may not capture inter-annual variability in insect diversity. Second, forest types were classified without accounting for fine-scale habitat variables such as understory structure, canopy cover, and vegetation age, which could influence insect assemblages.

Future studies should incorporate multi-year data and include more detailed assessments of microhabitat characteristics. Additionally, identifying indicator species for each forest type would strengthen biodiversity assessment frameworks and contribute to more effective insect-based conservation strategies. These efforts would support ongoing improvements to national biodiversity monitoring guidelines and facilitate evidence-based conservation planning.