The ecological impact of pest-induced tree dieback on insect biodiversity in Yunnan pine plantations, China

Abstract

China has recently announced a reform of forestry policy, with a major goal being to transform from plantation to heterogeneous forests, which have higher resistance to pests and disease and house more biodiversity. One driver of reform is increased intensity and frequency of pest-induced tree-dieback events. To inform management, we ask what effects these events have on insect biodiversity in Pinus yunnanensis monocultures in Yunnan province, the province with one of the highest proportions of forest cover in China. We sampled aerial arthropods (mostly insect) biodiversity along gradients of Pinus yunnanensis dieback severity using Malaise traps and used metabarcoding to characterise the insect community. We used MS-GDM ('multi-site generalized dissimilarity modelling of zeta diversity'), zeta-decline analysis, and iNEXT ('Interpolation and extrapolation for species diversity') to assess community change as functions of forest-structure covariates. Metabarcoding of Malaisetrapped insects reveals that bark-beetle induced forest dieback does not result in detectable differences in species diversity but does result in compositional change, with the biggest turnover occurring between 0% and infested-0%-open-canopy forests and 20%-infested-20%-open-canopy forests. Zeta-decline analysis found that the insect community in low-infestation forests is characterized by a stochastic assembly, while in highinfestation forests, the community structure is consistent with niche assembly. Our results thus suggest that bark-beetle dieback mimics natural forest-gap dynamics, consistent with the interpretation of bark beetles as a keystone species in European conifer forests, where it has been proposed that forest heterogeneity can be created efficiently by allowing natural disturbances, including bark-beetle outbreaks, to proceed naturally, without being mitigated by deadwood removal and dense replanting. In Yunnan's situation, and given predicted increases in bark-beetle dieback severity and frequency, this strategy should probably be supplemented with anthropogenic treatments, such as deadwood enhancement and planting of multiple tree species, to accelerate the succession of plantations into heterogeneous forests.

Climate Change Alters Temperate Forest Canopies and Indirectly Reshapes Arthropod Communities

“…This would also allow to investigate the outcomes of crown diebacks at larger spatial scales, i.e., from tree to the landscape level, which could be more relevant for stakeholders and conservation managers, but also for the study of local biodiversity (Jackson and Fahrig, 2015;Percel et al, 2019). These approaches could be combined with high throughput metabarcoding that allows to characterize arthropod communities over large spatial scales (e.g., Cai et al, 2021;Sire et al, 2021).…”

Zeta diversity differentiates factors driving community assembly of rare and common ectomycorrhizal fungi

“…The value of n (i.e., the number of sites compared) is termed the “zeta order,” and assessing how patterns of zeta diversity change with increasing zeta order can provide insight into the processes acting upon species along the continuum of infrequent rare species (patterns at lower zeta orders) to widespread common species (patterns at higher zeta orders; Hui & McGeoch, 2014; Latombe et al, 2017; McGeoch et al, 2019). The zeta diversity framework has previously been used to investigate environmental drivers and patterns of community assembly in plants (e.g., Hui et al, 2018; Latombe, Richardson, Pyšek, et al, 2018), invertebrates (e.g., Cai et al, 2021; Latombe et al, 2019), parasites (e.g., Krasnov et al, 2020), birds (e.g., Ascensão et al, 2020; Latombe et al, 2017), fish (e.g., Pettersen et al, 2021), amphibians (e.g., da Fonte et al, 2021) and bacteria (e.g., Bay et al, 2020).…”

Non-destructive DNA metabarcoding of arthropods using collection medium from passive traps

“…2012), including their response to environmental disturbances (Barsoum et al . 2019; Wang et al . 2021a; Sire et al .…”

“…Indeed, as this approach identifies species through comparison with DNA barcode reference sequences (Ratnasingham & Hebert, 2007), operators are not required to have taxonomic expertise, providing DNA reference libraries are sufficiently comprehensive and curated by experts (Hebert et al 2003). Despite the incompleteness of DNA reference libraries, metabarcoding has already proven efficient for monitoring arthropod biodiversity (Yu et al 2012), including their response to environmental disturbances (Barsoum et al 2019;Wang et al 2021a;Sire et al 2022).…”