Temperature adaptation of bacterial communities in experimentally warmed forest soils

A detailed understanding of the influence of temperature on soil microbial activity is critical to predict future atmospheric CO₂ concentrations and feedbacks to anthropogenic warming. We investigated soils exposed to 3–4 years of continuous 5 °C‐warming in a field experiment in a temperate forest. We found that an index for the temperature adaptation of the microbial community, T_min for bacterial growth, increased by 0.19 °C per 1 °C rise in temperature, showing a community shift towards one adapted to higher temperature with a higher temperature sensitivity (Q_{10(5–15 °C)} increased by 0.08 units per 1 °C). Using continuously measured temperature data from the field experiment we modelled in situ bacterial growth. Assuming that warming did not affect resource availability, bacterial growth was modelled to become 60% higher in warmed compared to the control plots, with the effect of temperature adaptation of the community only having a small effect on overall bacterial growth (<5%). However, 3 years of warming decreased bacterial growth, most likely due to substrate depletion because of the initially higher growth in warmed plots. When this was factored in, the result was similar rates of modelled in situ bacterial growth in warmed and control plots after 3 years, despite the temperature difference. We conclude that although temperature adaptation for bacterial growth to higher temperatures was detectable, its influence on annual bacterial growth was minor, and overshadowed by the direct temperature effect on growth rates.     

Non-climatic thermal adaptation: implications for species' responses to climate warming

There is considerable interest in understanding how ectothermic animals may physiologically and behaviourally buffer the effects of climate warming. Much less consideration is being given to how organisms might adapt to non-climatic heat sources in ways that could confound predictions for responses of species and communities to climate warming. Although adaptation to non-climatic heat sources (solar and geothermal) seems likely in some marine species, climate warming predictions for marine ectotherms are largely based on adaptation to climatically relevant heat sources (air or surface sea water temperature). Here, we show that non-climatic solar heating underlies thermal resistance adaptation in a rocky–eulittoral-fringe snail. Comparisons of the maximum temperatures of the air, the snail''s body and the rock substratum with solar irradiance and physiological performance show that the highest body temperature is primarily controlled by solar heating and re-radiation, and that the snail''s upper lethal temperature exceeds the highest climatically relevant regional air temperature by approximately 22°C. Non-climatic thermal adaptation probably features widely among marine and terrestrial ectotherms and because it could enable species to tolerate climatic rises in air temperature, it deserves more consideration in general and for inclusion into climate warming models.     

Relationships between temperature responses and bacterial community structure along seasonal and altitudinal gradients

In this study, soil bacterial communities and the temperature responses (Q10) of substrate-induced respiration were compared between an alpine dry meadow and a subalpine forest in the Colorado Rocky Mountains. Bacterial communities in three seasons from each environment were described with 16S rRNA gene clone libraries. The main goal of this comparison was to relate phylogenetic differences among bacterial communities with variation in soil respiratory temperature sensitivities along seasonal and altitudinal gradients. The warmer, lower elevation, subalpine forest soil exhibited large seasonal variations in Q10. Subalpine Q10 values were highest in summer, and were higher than alpine values in all seasons except winter. Q10 in alpine soils were consistently low throughout the year. Alpine and subalpine bacterial communities both varied seasonally, and were markedly distinct from each other. Based on Fst analysis, subalpine communities from colder times of year were more similar to the alpine communities than were subalpine summer communities. Principle component analysis of the pairwise genetic distances (Fst) between communities produced two factors that accounted for 69% and 22% of the total variance in the data set. These factors demonstrated a significant relationship between bacterial community structure and temperature response when regressed on log-transformed Q10 data.     

Adaptation of soil microbial communities to temperature: comparison of fungi and bacteria in a laboratory experiment

Temperature not only has direct effects on microbial activity, but can also affect activity indirectly by changing the temperature dependency of the community. This would result in communities performing better over time in response to increased temperatures. We have for the first time studied the effect of soil temperature (5–50 °C) on the community adaptation of both bacterial (leucine incorporation) and fungal growth (acetate-in-ergosterol incorporation). Growth at different temperatures was estimated after about a month using a short-term assay to avoid confounding the effects of temperature on substrate availability. Before the experiment started, fungal and bacterial growth was optimal around 30 °C. Increasing soil temperature above this resulted in an increase in the optimum for bacterial growth, correlated to soil temperature, with parallel shifts in the total response curve. Below the optimum, soil temperature had only minor effects, although lower temperatures selected for communities growing better at the lowest temperature. Fungi were affected in the same way as bacteria, with large shifts in temperature tolerance at soil temperatures above that of optimum for growth. A simplified technique, only comparing growth at two contrasting temperatures, gave similar results as using a complete temperature curve, allowing for large scale measurements also in field situations with small differences in temperature.     

The future of soil invertebrate communities in polar regions: different climate change responses in the Arctic and Antarctic?

The polar regions are experiencing rapid climate change with implications for terrestrial ecosystems. Here, despite limited knowledge, we make some early predictions on soil invertebrate community responses to predicted twenty‐first century climate change. Geographic and environmental differences suggest that climate change responses will differ between the Arctic and Antarctic. We predict significant, but different, belowground community changes in both regions. This change will be driven mainly by vegetation type changes in the Arctic, while communities in Antarctica will respond to climate amelioration directly and indirectly through changes in microbial community composition and activity, and the development of, and/or changes in, plant communities. Climate amelioration is likely to allow a greater influx of non‐native species into both the Arctic and Antarctic promoting landscape scale biodiversity change. Non‐native competitive species could, however, have negative effects on local biodiversity particularly in the Arctic where the communities are already species rich. Species ranges will shift in both areas as the climate changes potentially posing a problem for endemic species in the Arctic where options for northward migration are limited. Greater soil biotic activity may move the Arctic towards a trajectory of being a substantial carbon source, while Antarctica could become a carbon sink.     

Effect of drying and rewetting on bacterial growth rates in soil

The effect of soil moisture on bacterial growth was investigated, and the effects of rewetting were compared with glucose addition because both treatments increase substrate availability. Bacterial growth was estimated as thymidine and leucine incorporation, and was compared with respiration. Low growth rates were found in air-dried soil, increasing rapidly to high stable values in moist soils. Respiration and bacterial growth at different soil moisture contents were correlated. Rewetting air-dried soil resulted in a linear increase in bacterial growth with time, reaching the levels in moist soil (10 times higher) after about 7 h. Respiration rates increased within 1 h to a level >10 times higher than that in moist soil. After the initial flush, there was a gradual decrease in respiration rate, while bacterial growth increased to levels twice that of moist soil 24 h after rewetting, and decreased to levels similar to those in moist soil after 2 days. Adding glucose resulted in no positive effect on bacterial growth during the first 9 h, despite resulting in more than five times higher respiration. This indicated that the initial increase in bacterial growth after rewetting was not due to increased substrate availability.     

Dissimilar responses of fungal and bacterial communities to soil transplantation simulating abrupt climate changes

Both fungi and bacteria play essential roles in regulating soil carbon cycling. To predict future carbon stability, it is imperative to understand their responses to environmental changes, which is subject to large uncertainty. As current global warming is causing range shifts toward higher latitudes, we conducted three reciprocal soil transplantation experiments over large transects in 2005 to simulate abrupt climate changes. Six years after soil transplantation, fungal biomass of transplanted soils showed a general pattern of changes from donor sites to destination, which were more obvious in bare fallow soils than in maize cropped soils. Strikingly, fungal community compositions were clustered by sites, demonstrating that fungi of transplanted soils acclimatized to the destination environment. Several fungal taxa displayed sharp changes in relative abundance, including Podospora, Chaetomium, Mortierella and Phialemonium. In contrast, bacterial communities remained largely unchanged. Consistent with the important role of fungi in affecting soil carbon cycling, 8.1%–10.0% of fungal genes encoding carbon‐decomposing enzymes were significantly (p < 0.01) increased as compared with those from bacteria (5.7%–8.4%). To explain these observations, we found that fungal occupancy across samples was mainly determined by annual average air temperature and rainfall, whereas bacterial occupancy was more closely related to soil conditions, which remained stable 6 years after soil transplantation. Together, these results demonstrate dissimilar response patterns and resource partitioning between fungi and bacteria, which may have considerable consequences for ecosystem‐scale carbon cycling.     

模拟增温对湿地植物凋落物分解及细菌群落的影响

植物凋落物分解是湿地生态系统物质循环的重要组成部分,随着全球气候变化的逐渐加剧,气候变暖对湿地植物凋落物分解的影响已引起人们的广泛关注。本研究通过凋落物袋法对比研究了山东省南四湖湿地中芦苇和香蒲两种典型湿地植物的凋落物分解过程,利用开顶式生长室(Open-top Chamber, OTC)模拟了大气增温(2.0±0.5)℃—(4.0±0.5)℃对凋落物分解特征和细菌群落的影响。结果显示,增温显著加速了两种植物凋落物的分解速率,而木质素/氮(Lignin/N)、纤维素/氮(Cellulose/N)是影响凋落物分解速率的重要因子,与分解速率呈显著负相关。增温显著增加了细菌群落的丰度和多样性,碳是厚壁菌门(Firmicutes)等细菌丰度变化的驱动因子,而木质素、木质素/氮是拟杆菌门(Bacteroidota)等细菌丰度变化的驱动因子。细菌群落共现网络显示,在增温条件下,凋落物分解的细菌群落网络主要由共生关系组成。气候变暖提高了细菌之间的相互关系和互惠程度,加快了植物凋落物的分解进程,进而影响了湿地生态系统的碳收支平衡。     

Carbon losses due to soil warming: Do autotrophic and heterotrophic soil respiration respond equally?

Global warming has the potential to increase soil respiration (R_S), one of the major fluxes in the global carbon (C) cycle. R_S consists of an autotrophic (R_A) and a heterotrophic (R_H) component. We combined a soil warming experiment with a trenching experiment to assess how R_S, R_A, and R_H are affected. The experiment was conducted in a mature forest dominated by Norway spruce. The site is located in the Austrian Alps on dolomitic bedrock. We warmed the soil of undisturbed and trenched plots by means of heating cables 4 °C above ambient during the snow‐free seasons of 2005 and 2006. Soil warming increased the CO₂ efflux from control plots (R_S) by ∼45% during 2005 and ∼47% during 2006. The CO₂ efflux from trenched plots (R_H) increased by ∼39% during 2005 and ∼45% during 2006. Similar responses of R_S and R_H indicated that the autotrophic and heterotrophic components of R_S responded equally to the temperature increase. Thirty‐five to forty percent or 1 t C ha⁻¹ yr⁻¹ of the overall annual increase in R_S (2.8 t C ha⁻¹ yr⁻¹) was autotrophic. The remaining, heterotrophic part of soil respiration (1.8 t C ha⁻¹ yr⁻¹), represented the warming‐induced C loss from the soil. The autotrophic component showed a distinct seasonal pattern. Contribution of R_A to R_S was highest during summer. Seasonally derived Q₁₀ values reflected this pattern and were correspondingly high (5.3–9.3). The autotrophic CO₂ efflux increase due to the 4 °C warming implied a Q₁₀ of 2.9. Hence, seasonally derived Q₁₀ of R_A did not solely reflect the seasonal soil temperature development.     

Thermal adaptation of soil microbial respiration to elevated temperature

In the short‐term heterotrophic soil respiration is strongly and positively related to temperature. In the long‐term, its response to temperature is uncertain. One reason for this is because in field experiments increases in respiration due to warming are relatively short‐lived. The explanations proposed for this ephemeral response include depletion of fast‐cycling, soil carbon pools and thermal adaptation of microbial respiration. Using a > 15 year soil warming experiment in a mid‐latitude forest, we show that the apparent ‘acclimation’ of soil respiration at the ecosystem scale results from combined effects of reductions in soil carbon pools and microbial biomass, and thermal adaptation of microbial respiration. Mass‐specific respiration rates were lower when seasonal temperatures were higher, suggesting that rate reductions under experimental warming likely occurred through temperature‐induced changes in the microbial community. Our results imply that stimulatory effects of global temperature rise on soil respiration rates may be lower than currently predicted.     

土壤呼吸对温度升高的适应

土壤呼吸是陆地生态系统碳循环的重要环节之一 ,其对温度升高的敏感程度在相当大的程度上决定着全球气候变化与碳循环之间的反馈关系。土壤呼吸对温度升高的适应是个比较普遍的现象 ,其表现形式主要为随着温度的持续升高和升温时间的延长 ,土壤呼吸对温度升高反应的敏感程度下降。产生这一现象的机制包括影响因子主导地位的转移和温度以外其他因子的协同变化。土壤呼吸对温度升高的适应可以视为碳循环对全球变暖的负反馈效应 ,它可能会在一定程度上缓和陆地生态系统对全球气候系统之间的耦合作用 ,并且导致土壤呼吸对全球温度升高响应的时空差异。由于目前生态系统模型多数没有考虑土壤呼吸的对温度升高的适应性 ,而采用统一的 Q1 0 值 ,其对未来土壤呼吸和未来气候变化幅度的预测可能存在偏差     

Adaptation of soil bacterial communities to prevailing pH in different soils

Abstract: The bacterial community response to pH was studied for 16 soils with pH(H₂O) ranging between 4 and 8 by measuring thymidine incorporation into bacteria extracted from the soil into a solution using homogenization-centrifugation. The pH of the bacterial solution was altered to six different values with dilute sulfuric acid or different buffers before measuring incorporation. The resulting pH response curve for thymidine incorporation was used to compare bacterial communities from the different soils. There was a correlation between optimum pH for thymidine incorporation and the soil pH(H₂O). Even bacterial communities from acid soils had optima corresponding to the soil pH, indicating that they were adapted to these conditions. Thymidine incorporation was also compared with leucine incorporation for some soils. The leucine to thymidine incorporation ratio was constant over the tested pH interval when incorporation values were adjusted for isotope dilution. A good correlation was found between the scores along the first component (explaining 80% of the variation) and soil pH ( r ² = 0.85), if principal component analysis of the pH response curves for thymidine incorporation was used. The pH response curves differed most for the extreme pH values used, and a linear relationship was found between the logarithm of the ratio of thymidine incorporation at pH 4.3 to incorporation at pH 8.2 and the soil pH ( r ² = 0.86). Thus, a simplified technique using only two pH values, when measuring the thymidine incorporation, could be used to compare the response to pH of bacterial communities.     

Plant population differentiation and climate change: responses of grassland species along an elevational gradient

Mountain ecosystems are particularly susceptible to climate change. Characterizing intraspecific variation of alpine plants along elevational gradients is crucial for estimating their vulnerability to predicted changes. Environmental conditions vary with elevation, which might influence plastic responses and affect selection pressures that lead to local adaptation. Thus, local adaptation and phenotypic plasticity among low and high elevation plant populations in response to climate, soil and other factors associated with elevational gradients might underlie different responses of these populations to climate warming. Using a transplant experiment along an elevational gradient, we investigated reproductive phenology, growth and reproduction of the nutrient‐poor grassland species Ranunculus bulbosus, Trifolium montanum and Briza media. Seeds were collected from low and high elevation source populations across the Swiss Alps and grown in nine common gardens at three different elevations with two different soil depths. Despite genetic differentiation in some traits, the results revealed no indication of local adaptation to the elevation of population origin. Reproductive phenology was advanced at lower elevation in low and high elevation populations of all three species. Growth and reproduction of T. montanum and B. media were hardly affected by garden elevation and soil depth. In R. bulbosus, however, growth decreased and reproductive investment increased at higher elevation. Furthermore, soil depth influenced growth and reproduction of low elevation R. bulbosus populations. We found no evidence for local adaptation to elevation of origin and hardly any differences in the responses of low and high elevation populations. However, the consistent advanced reproductive phenology observed in all three species shows that they have the potential to plastically respond to environmental variation. We conclude that populations might not be forced to migrate to higher elevations as a consequence of climate warming, as plasticity will buffer the detrimental effects of climate change in the three investigated nutrient‐poor grassland species.     

Size and structure of bacterial, fungal and nematode communities along an Antarctic environmental gradient

The unusually harsh environmental conditions of terrestrial Antarctic habitats result in ecosystems with simplified trophic structures, where microbial processes are especially dominant as drivers of soil-borne nutrient cycling. We examined soil-borne Antarctic communities (bacteria, fungi and nematodes) at five locations along a southern latitudinal gradient from the Falkland Islands (51 degrees S) to the base of the Antarctic Peninsula (72 degrees S), and compared principally vegetated vs. fell-field locations at three of these sites. Results of molecular (denaturing gradient gel electrophoresis, real-time PCR), biochemical (ergosterol, phospholipid fatty acids) and traditional microbiological (temperature- and medium-related CFU) analyses were related to key soil and environmental properties. Microbial abundance generally showed a significant positive relationship with vegetation and vegetation-associated soil factors (e.g. water content, organic C, total N). Microbial community structure was mainly related to latitude or location and latitude-dependent factors (e.g. mean temperature, NO3, pH). Furthermore, strong interactions between vegetation cover and location were observed, with the effects of vegetation cover being most pronounced in more extreme sites. These results provide insight into the main drivers of microbial community size and structure across a range of terrestrial Antarctic and sub-Antarctic habitats, potentially serving as a useful baseline to study the impact of predicted global warming on these unique and pristine ecosystems.     

Nitrogen availability mediates soil carbon cycling response to climate warming: A meta-analysis

Global climate warming may induce a positive feedback through increasing soil carbon (C) release to the atmosphere. Although warming can affect both C input to and output from soil, direct and convincing evidence illustrating that warming induces a net change in soil C is still lacking. We synthesized the results from field warming experiments at 165 sites across the globe and found that climate warming had no significant effect on soil C stock. On average, warming significantly increased root biomass and soil respiration, but warming effects on root biomass and soil respiration strongly depended on soil nitrogen (N) availability. Under high N availability (soil C:N ratio < 15), warming had no significant effect on root biomass, but promoted the coupling between effect sizes of root biomass and soil C stock. Under relative N limitation (soil C:N ratio > 15), warming significantly enhanced root biomass. However, the enhancement of root biomass did not induce a corresponding C accumulation in soil, possibly because warming promoted microbial CO₂ release that offset the increased root C input. Also, reactive N input alleviated warming-induced C loss from soil, but elevated atmospheric CO₂ or precipitation increase/reduction did not. Together, our findings indicate that the relative availability of soil C to N (i.e., soil C:N ratio) critically mediates warming effects on soil C dynamics, suggesting that its incorporation into C-climate models may improve the prediction of soil C cycling under future global warming scenarios.     

Thermal adaptation of heterotrophic soil respiration in laboratory microcosms

Respiration of heterotrophic microorganisms decomposing soil organic carbon releases carbon dioxide from soils to the atmosphere. In the short term, soil microbial respiration is strongly dependent on temperature. In the long term, the response of heterotrophic soil respiration to temperature is uncertain. However, following established evolutionary trade‐offs, mass‐specific respiration (R_mass) rates of heterotrophic soil microbes should decrease in response to sustained increases in temperature (and vice‐versa). Using a laboratory microcosm approach, we tested the potential for the R_mass of the microbial biomass in six different soils to adapt to three, experimentally imposed, thermal regimes (constant 10, 20 or 30 °C). To determine R_mass rates of the heterotrophic soil microbial biomass across the temperature range of the imposed thermal regimes, we periodically assayed soil subsamples using similar approaches to those used in plant, animal and microbial thermal adaptation studies. As would be expected given trade‐offs between maximum catalytic rates and the stability of the binding structure of enzymes, after 77 days of incubation R_mass rates across the range of assay temperatures were greatest for the 10 °C experimentally incubated soils and lowest for the 30 °C soils, with the 20 °C incubated soils intermediate. The relative magnitude of the difference in R_mass rates between the different incubation temperature treatments was unaffected by assay temperature, suggesting that maximum activities and not Q₁₀ were the characteristics involved in thermal adaptation. The time taken for changes in R_mass to manifest (77 days) suggests they likely resulted from population or species shifts during the experimental incubations; we discuss alternate mechanistic explanations for those results we observed. A future research priority is to evaluate the role that thermal adaptation plays in regulating heterotrophic respiration rates from field soils in response to changing temperature, whether seasonally or through climate change.     

Microbial responses to warming enhance soil carbon loss following translocation across a tropical forest elevation gradient

Tropical soils contain huge carbon stocks, which climate warming is projected to reduce by stimulating organic matter decomposition, creating a positive feedback that will promote further warming. Models predict that the loss of carbon from warming soils will be mediated by microbial physiology, but no empirical data are available on the response of soil carbon and microbial physiology to warming in tropical forests, which dominate the terrestrial carbon cycle. Here we show that warming caused a considerable loss of soil carbon that was enhanced by associated changes in microbial physiology. By translocating soils across a 3000 m elevation gradient in tropical forest, equivalent to a temperature change of ± 15 °C, we found that soil carbon declined over 5 years by 4% in response to each 1 °C increase in temperature. The total loss of carbon was related to its original quantity and lability, and was enhanced by changes in microbial physiology including increased microbial carbon‐use‐efficiency, shifts in community composition towards microbial taxa associated with warmer temperatures, and increased activity of hydrolytic enzymes. These findings suggest that microbial feedbacks will cause considerable loss of carbon from tropical forest soils in response to predicted climatic warming this century.     

The responses of microbial temperature relationships to seasonal change and winter warming in a temperate grassland

Microorganisms dominate the decomposition of organic matter and their activities are strongly influenced by temperature. As the carbon (C) flux from soil to the atmosphere due to microbial activity is substantial, understanding temperature relationships of microbial processes is critical. It has been shown that microbial temperature relationships in soil correlate with the climate, and microorganisms in field experiments become more warm‐tolerant in response to chronic warming. It is also known that microbial temperature relationships reflect the seasons in aquatic ecosystems, but to date this has not been investigated in soil. Although climate change predictions suggest that temperatures will be mostly affected during winter in temperate ecosystems, no assessments exist of the responses of microbial temperature relationships to winter warming. We investigated the responses of the temperature relationships of bacterial growth, fungal growth, and respiration in a temperate grassland to seasonal change, and to 2 years’ winter warming. The warming treatments increased winter soil temperatures by 5–6°C, corresponding to 3°C warming of the mean annual temperature. Microbial temperature relationships and temperature sensitivities (Q₁₀) could be accurately established, but did not respond to winter warming or to seasonal temperature change, despite significant shifts in the microbial community structure. The lack of response to winter warming that we demonstrate, and the strong response to chronic warming treatments previously shown, together suggest that it is the peak annual soil temperature that influences the microbial temperature relationships, and that temperatures during colder seasons will have little impact. Thus, mean annual temperatures are poor predictors for microbial temperature relationships. Instead, the intensity of summer heat‐spells in temperate systems is likely to shape the microbial temperature relationships that govern the soil‐atmosphere C exchange.     

水热条件变化对黑土细菌群落结构的影响及其演替特征

全球气候变化导致的水热条件变化,对土壤微生物群落结构及功能产生重要影响。深入理解这些变化如何影响微生物群落的结构及其随时间的演替,对于有效预测和适应未来的气候变化至关重要。【目的】在气候变化背景下,本研究旨在探索黑土细菌群落的多样性、组成和结构,以及群落演替特征的变化情况。【方法】利用中国科学院海伦、封丘、鹰潭农田生态系统国家野外科学观测研究站长期土壤置换实验平台,选择寒温带地区(中国海伦)的黑土作为研究对象,并将其移置于暖温带地区(封丘)和中亚热带地区(鹰潭)以模拟水热条件增加。通过采集2005年至2011年的63个黑土样本(包括原位、移置封丘县和移置鹰潭市),利用16S rRNA基因高通量测序技术,研究了水热条件变化对黑土细菌群落多样性、组成和结构的影响;同时结合土壤理化性质,分析环境因素与微生物群落特征间的关系,并计算物种周转率(w)。【结果】经过6年的移置,将寒温带黑土移至暖温带和中亚热带后,土壤的理化性质发生了显著改变。土壤有机质和全氮含量显著降低,地上部生物量显著减少。土壤细菌群落的多样性下降,群落组成和结构发生了显著变化。主要细菌类群包括疣微菌门(Verrucomicrobia)、变形菌门(Proteobacteria)、酸杆菌门(Acidobacteria)和放线菌门(Actinobacteria)等,其中疣微菌门在移置鹰潭地区后的相对丰度显著增加。此外,气候因子与微生物群落特征高度相关。非度量多维尺度分析显示,群落结构随水热条件和时间的变化而演替,这与微生物时间周转率的增加相关。在不同水热条件下,细菌群落的时间周转率差异显著,依次为0.030 (海伦)<0.033 (封丘)<0.045 (鹰潭)。【结论】6年的水热条件增加显著降低了细菌群落的多样性,显著改变了其组成和结构,并加快了细菌群落时间周转率的响应。     

自然增温对南亚热带森林土壤微生物群落与有机碳代谢功能基因的影响

基于海拔高度下降气温上升的关系,将模拟的生态系统(含植物和土壤)从高海拔整体移位至低海拔地区,实现自然增温的效果。通过对自然增温条件下土壤环境因子及其相关理化性质的动态监测,结合磷脂脂肪酸分析与宏基因组学方法,测定土壤微生物群落结构以及与土壤有机碳分解相关基因丰度,探究自然增温对鼎湖山南亚热带山地常绿阔叶林土壤有机碳代谢的影响及其微生物学机制。结果表明:(1)增温处理显著改变了0—10 cm土壤温度与湿度:2016—2018年间土壤温度显著上升2.48℃,湿度显著下降23.93%。(2)增温处理下,干季土壤有机碳含量与湿季土壤硝态氮含量显著降低,其他土壤理化因子无显著变化。(3)增温处理下,干季和湿季土壤微生物群落结构发生改变,且湿季变化显著。土壤湿度是影响干季和湿季土壤微生物群落结构变化的主要因子,解释了干季50.2%的变异度与湿季79.2%的变异度。(4)宏基因组结果表示:增温抑制了干季山地常绿阔叶林土壤有机碳代谢基因丰度,增强了湿季山地常绿阔叶林土壤有机碳代谢基因丰度。以上结果表明,增温通过改变土壤微生物生物量和群落结构以及有机碳代谢相关功能基因的丰度,最终影响南亚热带山地常绿阔...