Soil microbial diversity in adjacent forest systems – contrasting native, old growth kauri (Agathis australis) forest with exotic pine (Pinus radiata) plantation forest

Abstract

Globally, the conversion of primary forests to plantations and agricultural landscapes is a common land use change. Kauri (Agathis australis) is one of the most heavily impacted indigenous tree species of New Zealand with <1% of primary forest remaining as fragments adjacent to pastoral farming and exotic forest plantations. By contrasting two forest systems, we investigated if the fragmentation of kauri forests and introduction of pine plantations (Pinus radiata) are significantly impacting the diversity and composition of soil microbial communities across Waipoua kauri forest, New Zealand. Using next generation based 16S rRNA and ITS gene region sequencing, we identified that fungal and bacterial community composition significantly differed between kauri and pine forest soils. However, fungal communities displayed the largest differences in diversity and composition. This research revealed significant shifts in the soil microbial communities surrounding remnant kauri fragments, including the loss of microbial taxa with functions in disease suppression and plant health. Kauri dieback disease, caused by Phytophthora agathidicida, currently threatens the kauri forest ecosystem. Results from this research highlight the need for further investigations into how changes to soil microbial diversity surrounding remnant kauri fragments impact tree health and disease expression.

Erosion reduces soil microbial diversity, network complexity and multifunctionality

“…S8). Similar to these results, previous studies have also reported that Actinobacteria was negatively related to soil moisture [41,109], and has contrasting response patterns in responding to land-use change or exotic trees in forest ecosystem when compared with soil properties (i.e., organic matter, total C and N, available N) [110,111]. Given the significant response to erosion and their relationships to MF (Fig.…”

Increased Soil Bacterial Abundance but Decreased Bacterial Diversity and Shifted Bacterial Community Composition Following Secondary Succession of Old-Field

“…This further confirmed that litter, root biomass, and WSOC were overarching driving factors for variation in soil bacterial community composition [40,59]. Plant-specific traits (e.g., litter and root) contributed significantly to soil nutrient availability by supplying plentiful C-rich compounds to the soil [63,64]. WSOC is a key fraction of the soil labile organic C pool, which is considered to be a direct reservoir of easily assimilable C for microbial growth and metabolism [49].…”

Chromosome-level assembly of the Phytophthora agathidicida genome reveals adaptation in effector gene families

“…In the case of trees such as kauri that can live for over a thousand years, it would be naive to think that a single mechanism will achieve durable resistance. Disease resistance or tolerance needs to encompass a diversity of mechanisms and function within a broader ecological setting that includes the effects of soil, companion plants and, importantly, potential protective effects of the microorganisms that naturally live in, on and around the tree (i.e., the host holobiont) ( Pautasso et al, 2015 ; Padamsee et al, 2016 ; Lewis et al, 2019 ; Terhonen et al, 2019 ; Wang et al, 2019b ; Byers et al, 2020 ; Wang et al, 2020a ). However, by increasing our knowledge of the molecular interactions between Phytophthora pathogens and their hosts, in a broad ecological setting, we stand a better chance of protecting those plant hosts against the devastating effects of disease.…”