Population distribution patterns and ecological niches of two Sirex species damaging Pinus sylvestris var. mongolica
Author of the article:WANG Ming1** BAO Min1 AO Te-Gen2 REN Li-Li1*** LUO You-Qing1***
Author's Workplace：1. Beijing Key Laboratory for Forest Pest Control, Beijing Forestry University, Beijing 100083, China; 2. Tongliao Control and Quarantine Station of Forest Pest, Tongliao 028000, China
Key Words：Pinus sylvestris var. mongolica, Sirex noctilio Fabricius, Sirex nitobei Matsumura, spatial distribution, population niche
Abstract：
[Objectives] Sirex noctilio Fabricius, an invasive species, is a major international forest quarantine pest that mainly damages Pinus sylvestris var. mongolica Litv in some parts of China. S. nitobei Matsumura is an indigenous species that is widely distributed in China. The spatial distribution patterns, and temporal and spatial niches of these species in P. sylvestris var. mongolica forests were investigated according to the population niche theory with the aim of identifying competitive and symbiotic relationships between these species that can guide the prevention and control of S. noctilio. [Methods] Ten sample plots were selected through field investigations in Jinbaotun forest farm, Inner Mongolia, Tongliao City, and population distribution indices were used to analyze the spatial distribution patterns of both species in these plots over two consecutive years. Damaged pines were randomly selected and felled. Adult molting periods and quantity were noted, eclosion holes were marked using sulfuric acid paper to count the preferred eclosion sites of each species, and the coexistence mechanism of the two species was quantitatively described. [Results] Both species had a clustered distribution. The DBH of damaged trees ranged from 16 cm to 18 cm. The adult molting period of S. noctilio was from the end of June to the beginning of September, whereas that of S. nitobei was from the end of August to the end of September. We were able to deduce that the infesting period of S. noctilio occurs earlier than that of S. nitobei in our study area. The sex (female: male) ratio of S. noctilio was 0.604 whereas that of S. nitobei was 0.174. The niches of each species differed. [Conclusion] S. noctilio and S. nitobei had relatively abundant resources and lower than average population densities, causing the spatial niche of each species to diverge. We suspect that competition between these species is relatively low in the early stage of colonization by S. noctilio. Aggregation indices indicate that both species have an aggregated distribution.