Zhao-Jun Bu

Bacterial communities are vital to northern peatlands' carbon and nutrient cycling, one of the Earth's largest terrestrial carbon stores. However, their diversity and ecological roles at broad geographic scales remain partially understood, limiting our ability to predict their response to global change. Here, we combine a trans‐Holarctic survey across 171 Sphagnum ‐dominated peatlands (SDPs) with a continental‐scale reciprocal transplantation experiment to quantify how bacterial diversity shapes carbon and nutrient cycling across bioclimatic gradients. We show that bacterial diversity and composition differ markedly among peatland bioclimatic regions and are primarily structured by the universal abiotic drivers of northern ecosystems: minimum temperature, snow cover, and soil water content. Ecological models further revealed that deterministic processes accounted for approximately 80% of bacterial community assembly, highlighting the strong influence of environmental filtering. Biodiversity‐Ecosystem Function analyses identified bacterial richness as a key driver of carbon and nutrient cycling. Using moving‐window structural equation models, we identified a critical bacterial richness threshold, below which extracellular enzyme activities increased by ~60%. This transition coincided with stronger environmental filtering and shifts towards bacterial communities with a greater predicted potential for extracellular nutrient acquisition and heterotrophic metabolism. Together, these findings demonstrate that bacterial richness underpins peatland biogeochemical functioning and suggest that biodiversity loss may accelerate carbon turnover, weakening the capacity of northern peatlands to retain carbon. As climate change threatens this unique microbiome, safeguarding bacterial diversity will be critical for maintaining ecosystem resilience and the stability of this globally important carbon sink.

Despite the critical role of Sphagnum mosses in carbon (C) sequestration, it remains unclear how climate governs their distribution and C sink function. To address this, a reciprocal transplant experiment was performed over 2 years in two peatlands in the Changbai Mountains, utilizing moss monolith mesocosms from low‐elevation ( S. imbricatum ), high‐elevation ( S. fuscum ), and wide‐elevation‐range ( S. magellanicum ) Sphagnum species. We found that when low‐elevation Sphagnum populations were transplanted upward, both the non‐structural carbohydrates (NSC) content and photosystem II efficiency (Φ _PSII ) increased, with concomitant reduced ecosystem respiration (ER) and enhanced C sequestration at high elevation. In contrast, for high‐elevation populations, downward transplant significantly weakened gross primary productivity (GPP), primarily by reducing Sphagnum photosynthesis and physiological performance, accompanied by slightly enhanced peat decomposition, ultimately suppressing net ecosystem productivity (NEP) by more than 50%. These results indicate that the 4°C temperature difference associated with the elevational gradient does not restrict the upward distribution of warm‐adapted S. imbricatum and S. magellanicum populations, but it severely restricts the downward distribution of cold‐adapted S. fuscum and S. magellanicum populations. Altered vegetation composition and microbial community coincided with NEP changes in ex‐situ transplants. Our study demonstrates that geographical origin, rather than genetic divergence, strongly affects the short‐term performance of Sphagnum under both cooling and warming conditions. Climate thus controls the distribution and C sink capacity of cold‐ but not warm‐adapted Sphagnum , highlighting the vulnerability of cold‐adapted Sphagnum to warming.

Microhabitats play a crucial role in linking macroclimatic conditions with local plant establishment, yet current research often fails to capture the fine-scale processes shaping species’ responses in natural environments. The characteristic repetitive hummock-hollow structures in peatlands provide an ideal model system to test this because the microhabitats differ markedly in hydrologic and nutrient conditions. This study aimed to examine how hummocks and hollows drive species differentiation in geographic distribution, climatic niche, and regeneration niche, and to compare the responses of tracheophytes and bryophytes. We integrated newly collected data with existing global distribution and germination datasets, building a comprehensive database of 41 peatland species of tracheophytes and bryophytes. Based on global occurrence records (GBIF, CVH), we estimated species’ geographic range size and climatic niche. Regeneration niche breadth was further evaluated using dormancy-breaking treatments and germination responses across temperature regimes. At the geographic scale, microhabitat type did not significantly affect species’ geographic range or climatic niche centers (median). Instead, climatic adaptation diverged between taxa: tracheophytes primarily broadened their niche breadth, while bryophytes relied more on niche symmetry (environmental stability). At the regeneration scale, tracheophyte species from variable hummocks exhibited broader regeneration niche through shallow-dormancy strategies, whereas hollow species adopted deep-dormancy “best-bet” strategies. In contrast, bryophytes showed a wider regeneration niche breadth than tracheophytes. Microhabitats do not directly determine species’ macro-distribution but act as environmental filters that shape life-history strategies during regeneration (dormancy and germination), thereby indirectly regulating species niche and distribution. Our results highlight the importance of linking micro-scale processes with geographic scale patterns and demonstrate that tracheophytes and bryophytes adopt fundamentally different adaptive strategies when facing environmental change.

Peatlands store substantial amounts of carbon (C) in the form of peat, but are increasingly threatened by drought and shrub encroachment under climate warming. However, how peat decomposition and its temperature sensitivity (Q₁₀) vary with depth and plant litter input under these stressors remains poorly understood. We incubated peat from two depths with different degrees of decomposition, either alone or incubated with Sphagnum divinum shoots or Betula ovalifolia leaves, under five temperature levels and two moisture conditions in growth chambers. We found that drought and Betula addition increased CO₂ emissions in both peat layers, while Sphagnum affected only shallow peat. Deep peat alone or with Betula exhibited higher Q₁₀ than pure shallow peat. Drought increased the Q₁₀ of both depths’ peat, but this effect disappeared with fresh litter addition. The CO₂ production rate showed a positive but marginal correlation with microbial biomass carbon, and it displayed a rather similar responsive trend to warming as the microbial metabolism quotient. These results indicate that both deep and dry peat are more sensitive to warming, highlighting the importance of keeping deep peat buried and waterlogged to conserve existing carbon storage. Additionally, they further emphasize the necessity of Sphagnum moss recovery following vascular plant encroachment in restoring carbon sink function in peatlands.

Peatlands are the most important global soil carbon reservoirs due to low decomposition rates. However, the influence of peatland plant litter quality and geographic environment on decomposition remains poorly understood. This article aims to explore the interactive effects of geographical origin and plant functional groups on the initial chemical characteristics and decomposition processes of peatland litter, elucidating how climate‐driven biochemical legacies regulate decomposition dynamics. Plant materials were collected from three peatlands in East China spanning distinct bioclimatic regimes along a latitudinal gradient: Dajiuhu (31°29′N), Hani (42°13′N), and Mangui (52°19′N) peatlands. A 3‐year decomposition experiment was conducted in Hani peatland starting in October 2014, using standardized litter bags containing nine species from three functional groups: mosses ( Sphagnum ), graminoids ( Carex ), and shrubs ( Betula ). Fresh plant materials from all sites was translocated to Hani peatland for decomposition experiment. Decomposition rates and key biochemical traits were quantified through sequential destructive sampling at 0‐, 1‐, 2‐, and 3‐year post‐deployment. Results showed decomposition rates of plant litter descending as Carex > Betula > Sphagnum . Latitudinal origin significantly affected decomposition; the northernmost Mangui litter exhibited the lowest mean decomposition (41.1%) compared to Hani (45.4%) and Dajiuhu (44.4%). Total phenolics (β = −0.62) and lignin (including Sphagnum ‐specific lignin‐like substances, β = −0.93) significantly inhibited decomposition. Interactive effects between geographical origin and functional group were significant, with Carex decomposition most sensitive to latitude. These findings demonstrate that geographic environment and plant functional group type jointly regulate peatland litter decomposability through biochemical traits. Climate warming may accelerate decomposability, potentially diminishing the carbon accumulation function of peatlands, underscoring the necessity to integrate latitudinal gradients and functional diversity into peatland carbon models.

Smoke‐mediated spore germination in mosses is a fire‐adaptive evolutionary trait that might control plant composition after fire. How capsule size, either alone or in combination with smoke, affects spore germination in peatland mosses remains unknown. We selected three peatland mosses, Sphagnum fuscum, S. squarrosum, and Polytrichum strictum and measured volumes of 40 capsules per species, categorizing them into large‐ and small‐capsule groups. We then assessed spore diameters within each capsule group and examined how capsule size affects spore germination following smoke‐water treatment. We found a positive correlation between capsule and spore size only in S. squarrosum. Spore viability was consistent across capsules in all species. Large‐capsule spores had higher germination than small‐capsule spores in Sphagnum. However, germination was slower in spores from large than small capsules in Sphagnum species, suggesting a trade off between germination percentage and germination speed. Smoke water enhanced germination speed in large‐capsule but not in small‐capsule spores in all species. Smoke water released dormancy in large‐capsule spores of S. squarrosum and S. fuscum by 100 % and 45 %, respectively, which was significantly higher than that in small‐capsule spores (33 % and 4 %). There was no such capsule size‐dependent difference in P. strictum. The study suggests that the variation inspore germinability among capsules and consistency in smoke‐responsive germination of spores, regardless of capsule size, represent dual expressions of bet‐hedging (spreading germination time) and best‐bet (germinating in best time) strategies in Sphagnum, enabling them to maintain population persistence in peatlands subject to natural and anthropogenic disturbances.

The Changbai Mountains, recognized as one of the global biodiversity hotspots, remain underexplored in terms of chrysophycean stomatocysts, despite their rich biological diversity. This study investigated the diversity of chrysophycean stomatocysts in fifteen surface Sphagnum samples and thirteen peat core samples collected from Hani, Jinchuan, Gushantun and Yuanchi Peatlands of the Changbai Mountains, northeastern China. Sixty-eight morphotypes of stomatocysts were identified and described according to the International Statospore Working Group, with five new morphotypes. This is the first record of chrysophycean stomatocysts in the Changbai Mountains, highlighting rich morphotypes of stomatocysts in these temperate peatlands, and hence the results can improve our knowledge on the diversity of stomatocysts in the temperate monsoon regions and create a taxonomical basis for further stomatocyst-based environmental monitoring and paleoenvironmental studies.