Effects Of Soil Warming Research Articles

Soil respiration related to the molecular composition of soil organic matter in subtropical and temperate forests under soil warming

The chemical composition and degradability of soil organic matter (SOM) are among the most important factors influencing the feedback between soil CO2 emissions and climate warming. We hypothesized that the response of soil respiration to long-term warming in various forest ecosystems depends on how soil warming alters the chemical composition of SOM. Therefore, we compared the effects of long-term soil warming on soil respiration, SOM molecular structure, and bacterial and fungal diversity in two forest ecosystems in the southern subtropical and warm temperate zones of China. In the subtropical forest, soil warming did not affect soil respiration in the short term (2–3 years) but decreased it in the longer term (10 years, −10%). The decline in soil respiration was associated with an increased aliphaticity of SOM and lower O-alkyl C content, along with an increased abundance of microbial K-strategists over time. In the warm temperate forest, soil warming significantly stimulated soil respiration by 35% in the short term and 30% in the long term. The sustained positive response to warming was likely related to the increased decomposability of SOM owing to increased root C input. Our results suggest that the molecular composition of SOM is affected by warming and in turn feeds back to longer-term soil respiration responses. The different responses at the two study sites suggest considerable variation in the feedback within different forest ecosystems.

Contrasting effects of nitrogen addition and soil warming on soil respiration in an old-growth subtropical forest

Primary forest occupies 34 % of the global forest area and contributes to the mitigation of atmospheric carbon (C) dioxide through C sequestration in vegetation and soil. Environmental changes, including climate warming and increased nitrogen (N) deposition, have been found to affect soil C dynamics. However, there is a major gap in knowledge regarding the response and potential mechanisms of primary forest C cycling to climate warming and increased N deposition. We conducted a three year (2018–2020) field-based soil warming (+3 °C above ambient soil temperature), N addition (50 kg N ha−1 year−1) and their interaction experiment in an over 300-year-old primary forest in subtropical China, and measured soil respiration monthly. In addition, soil enzyme activities and physico-chemical properties were also analyzed. Three years of W treatment did not significantly increase soil respiration, while N treatment significantly decreased it by 24.29 %. Cumulative soil respiration in N and WN treatments decreased by 2.17 and 2.14 Mg C ha−1 year−1, while W treatment increased annual cumulative soil respiration by 0.95 Mg C ha−1 year−1. W treatment indirectly affected soil respiration through its negative impact on C-degrading enzymatic activities and soil moisture. N treatment directly impacted soil respiration and indirectly by effect on soil organic C. These findings demonstrate that soil respiration in the old-growth subtropical forest would cause a minor soil C-climate feedback to 3 °C warming within the first three years, and N deposition may have not strong interaction with warming.

Indirect effects of soil warming on litter decomposition via changes in litter quality of dominant tree species in three cool-temperate forests

Indirect effects of soil warming on litter decomposition via changes in litter quality of dominant tree species in three cool-temperate forests

Effects of winter soil warming on crop biomass carbon loss from organic matter degradation

Global warming poses an unprecedented threat to agroecosystems. Although temperature increases are more pronounced during winter than in other seasons, the impact of winter warming on crop biomass carbon has not been elucidated. Here we integrate global observational data with a decade-long field experiment to uncover a significant negative correlation between winter soil temperature and crop biomass carbon. For every degree Celsius increase in winter soil temperature, straw and grain biomass carbon decreased by 6.6 ( ± 1.7) g kg-1 and 10.2 ( ± 2.3) g kg-1, respectively. This decline is primarily attributed to the loss of soil organic matter and micronutrients induced by warming. Ignoring the adverse effects of winter warming on crop biomass carbon could result in an overestimation of total food production by 4% to 19% under future warming scenarios. Our research highlights the critical need to incorporate winter warming into agricultural productivity models for more effective climate adaptation strategies.

Differential Responses of Soil Nitrogen Forms to Climate Warming in Castanopsis hystrix and Quercus aliena Forests of China

Climate warming impacts soil nitrogen cycling in forest ecosystems, thus influencing their productivity, but this has not yet been sufficiently studied. Experiments commenced in January 2012 in a subtropical Castanopsis hystrix Hook. f. and Thomson ex A. DC. plantation and in May 2011 in a temperate Quercus aliena Blume forest, China. Four treatments were established comprising trenching, artificial warming (up to 2 °C), artificial warming + trenching, and untreated control plots. The plots were 2 × 3 m in size. In 2021 and 2022, soil nitrogen mineralization, soil nutrient availability, fine root biomass and microbial biomass were measured at 0–20 cm soil depth in 6 replicate plots per treatment. Warming significantly increased soil temperature in both forests. In the C. hystrix plantation, warming significantly increased available phosphorus (AP) and fine root biomass (FRB), but it did not affect soil microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), microbial biomass phosphorus (MBP) and their ratios. Warming depressed the net mineralization rate (NMR) and net ammonification rate (NAR) of the C. hystrix plantation, probably because the competition for nitrogen uptake by fine roots and microorganisms increased, thus decreasing substrates for nitrogen mineralization and ammonification processes. Trenching and warming + trenching increased the net nitrification rate (NNR), which might be related to decreased NH4+-N absorption of trees in the trenched plots and the increased microbial activity involved in soil nitrification. In the Q. aliena forest, warming significantly increased NH4+-N, MBC/MBN, Root C/N, Root N/P, and decreased pH, MBN, MBN/MBP and Root P; and there was no effect of trenching. Notably, the NAR, NNR and NMR were largely unaffected by long-term warming. We attributed this to the negative effect of increasing NH4+-N and decreasing MBN/MBP offsetting the positive effect of soil warming. This study highlights the vulnerability of subtropical forest stands to long-term warming due to decreased soil N mineralization and increased NO3−-N leaching. In contrast, the soil N cycle in the temperate forest was more resilient to a decade of continuous warming.

Soil warming effects on the transpiration of trees and shrubs in a subtropical secondary forest: A manipulative experiment

The climate warming can increase the productivity of some species while decrease that of others, therefore, knowledge of species-specific responses to warming is helpful to understand the possible trajectory of forest ecosystems. Despite the importance of the subtropical secondary broadleaf forests developed from afforestation in South China, our understanding of how the transpiration of trees and shrubs co-growing in these forests responds to soil warming is limited. To explore the effects of soil warming on transpiration and associated ecophysiological traits of trees and shrubs in wet and dry seasons, as well as to clarify respective contributions of trees and shrubs transpiration to the stand total, we conducted a manipulative experiment of soil warming (+2 ℃, WA) and control (CK) in a subtropical secondary broadleaf forest in South China, and continuously monitored the transpiration (based on sap flow) of trees, Schima superba and Acacia auriculiformis, and that (derived from leaf temperature and microclimate) of shrubs, Psychotria asiatica and Castanopsis chinensis, from 2021 to 2022. We also measured leaf water potentials, leaf nutrient status, and δ13C-derived intrinsic water use efficiency (WUEi). Soil warming did not significantly alter the transpiration of trees, with the exception of A. auriculiformis in 2022, whereas it notably increased transpiration of both shrubs. We attributed the stimulation of shrubs’ transpiration mainly to the more favorable leaf water potentials under warming condition. Due to the increased transpiration, the contribution of shrubs to stand transpiration was consequently increased, highlighting the potential role of shrubs in the hydrological dynamics of forest ecosystems. Additionally, the WUEi, soil main macro-nutrients, and leaf nutritional status of all species were not significantly affected by soil warming. These findings indicated that the carbon-water exchange and nutrient status of the studied plants can be maintained even when exposed to moderate increases in soil temperature and relatively drier condition, reflecting the resilience of the subtropical secondary broadleaf forest to possible climate warming. Further research on the interaction and competition of co-existing trees and shrubs under soil warming will improve the prediction of forest dynamics under future climate change, which benefits the efforts to conserve such forests in order to address the environmental pressure in the region.

The effects of elevated CO2 and temperature on soil organic carbon and total nitrogen contents and mineralization in the 0 to 50 cm paddy soil layer were masked by different land use history

Global warming can accelerate soil organic matter (SOM) decomposition resulting in faster carbon (C) loss and positive climate-C feedback. Previous studies on response of SOM decomposition to climate change mainly focus on plow soil layer. However, the effects of elevated CO2 and soil warming on soil organic carbon (SOC) and total nitrogen (TN) contents and mineralization are rarely studied in subsoil layer. In this study, soil samples were collected from the 0–50-cm paddy soil layer of the Tsukuba free-air CO2 enrichment experimental site with elevated CO2 (+200 ppm) and soil warming (+2 °C), Japan, after 5-year rice growth season. The amounts of SOC, TN, δ13C, and δ15N were analyzed. A 4-week anaerobic incubation experiment was conducted to measure C decomposition and N mineralization potentials. Due to the intrinsic variation in SOC and TN contents in soil layers and fields, the effects of elevated CO2 and soil warming on C decomposition and N mineralization potentials could not be determined here. However, the effect of elevated CO2 on δ13C was only found in 0‒10-cm soil layer. In the 0–50-cm soil profiles, significant correlations were observed among SOC and TN, δ13C and δ15N, decomposed C and mineralized N, and δ13C of decomposed C. The variables associated with soil C and N pools, and dynamics showed large spatial heterogeneity within paddy field, due to variation in the original land use history. Therefore, great caution should be exercised when evaluating the effects of elevated CO2 and temperature on SOM decomposition and sequestration in paddy soil profiles.

Above- and belowground phenology responses of subtropical Chinese fir (Cunninghamia lanceolata) to soil warming, precipitation exclusion and their interaction

Plant phenology plays an important role in nutrient cycling and carbon balance in forest ecosystems, but its response to the interaction of global warming and precipitation reduction remains unclear. In this study, an experiment with factorial soil warming (ambient, ambient +5 °C) and precipitation exclusion (ambient, ambient −50 %) was conducted in a subtropical Chinese fir (Cunninghamia lanceolata) plantation. We investigated the effects of soil warming, precipitation exclusion, and their interactions on Chinese fir phenology involving tree height and fine root growth. In the meantime, the impact of tree height growth and related climatic factors on fine root production was also assessed. The results showed that: (1) more variable phenology responses were observed in fine root growth than in tree height growth to the climatic treatments; the duration of fine root growth and tree height growth was significantly reduced by the precipitation exclusion and warming treatment, respectively; phenology differences of fine root and tree height growth caused by the solo warming and precipitation exclusion treatment were further enhanced by the combined treatment; and despite the greater inter-annual phenology stability of tree height growth than that of fine root growth, both of them showed insignificant response to all the climate treatments; (2) asynchrony of phenology between tree height and fine root growth was significantly enlarged by solo warming and precipitation exclusion treatments, and further enlarged by the combined treatment; (3) fine root production was significantly and positively correlated with air, and soil temperature, and tree height growth as well, which was altered by warming and precipitation exclusion treatments. Our results demonstrated that climatic changes significantly and differently alter phenology of, and extend the phenology asynchrony between, above and below ground plant components, and also highlight the climate-sensitive and variable nature of root phenology. Overall, these phenology responses to climatic change may weaken the close link between fine root production and tree height growth, which may result in temporal mismatch between nutrient demand and supply in Chinese fir plantation.

Seasonal dynamics in photosynthetic characteristics and growth of Cunninghamia lanceolata saplings and their response to soil warming

In order to understand the response and adaptation mechanisms of photosynthetic characteristics and growth for Cunninghamia lanceolata saplings in the subtropical region to global warming, we conducted the root-box warming experiment (ambient, ambient+4 ℃) at the Sanming Forest Ecosystem National Observation and Research Station in Fujian Province to investigate the effects of soil warming on the photosynthetic characteristics and growth of C. lanceolata saplings in different seasons. The results showed that the net photosynthetic rate (Pn) and stomatal conductance (gs) of C. lanceolata significantly decreased in summer compared with in spring and autumn. Soil warming had no effect on the Pn and gs of C. lanceolata. However, the interaction between warming and season significantly impacted the leaf water use efficiency (WUE). The tree height and ground diameter growth of C. lanceolata significantly increased in spring compared with in summer and autumn. Warming significantly reduced ground diameter growth, and it diminished the net diameter growth by 48.1% in autumn. However, warming had no impact on the tree height growth of C. lanceolata in each season. The specific leaf area, soluble sugar, and non-structural carbohydrates contents of C. lanceolata significantly improved in summer and autumn compared with in spring. Warming had rarely influence on leaf functional traits in each season. In conclusion, the response of photosynthesis for C. lanceolata to soil warming was insignificant. The photosynthesis of C. lanceolata exhibited significant seasonal dynamics, primarily controlled by gs. C. lanceolata adapted to soil warming by adjusting WUE, and it adjusted to high temperatures and drought stress in summer by increasing soluble sugar content and specific leaf area. The effect of warming on ground diameter growth of C. lanceolata was primarily driven by soil moisture. The seasonal difference in the growth of C. lanceolata was influenced by the photosynthesis of C. lanceolata and the trade-off between the utilization and storage of photosynthetic products.

Individual and interactive effects of warming and nitrogen supply on CO2 fluxes and carbon allocation in subarctic grassland.

Climate warming has been suggested to impact high latitude grasslands severely, potentially causing considerable carbon (C) losses from soil. Warming can also stimulate nitrogen (N) turnover, but it is largely unclear whether and how altered N availability impacts belowground C dynamics. Even less is known about the individual and interactive effects of warming and N availability on the fate of recently photosynthesized C in soil. On a 10-year geothermal warming gradient in Iceland, we studied the effects of soil warming and N addition on CO2 fluxes and the fate of recently photosynthesized C through CO2 flux measurements and a 13 CO2 pulse-labeling experiment. Under warming, ecosystem respiration exceeded maximum gross primary productivity, causing increased net CO2 emissions. N addition treatments revealed that, surprisingly, the plants in the warmed soil were N limited, which constrained primary productivity and decreased recently assimilated C in shoots and roots. In soil, microbes were increasingly C limited under warming and increased microbial uptake of recent C. Soil respiration was increased by warming and was fueled by increased belowground inputs and turnover of recently photosynthesized C. Our findings suggest that a decade of warming seemed to have induced a N limitation in plants and a C limitation by soil microbes. This caused a decrease in net ecosystem CO2 uptake and accelerated the respiratory release of photosynthesized C, which decreased the C sequestration potential of the grassland. Our study highlights the importance of belowground C allocation and C-N interactions in the C dynamics of subarctic ecosystems in a warmer world.

The start of frozen dates over northern permafrost regions with the changing climate.

The soil freeze-thaw cycle in the permafrost regions has a significant impact on regional surface energy and water balance. Although increasing efforts have been made to understand the responses of spring thawing to climate change, the mechanisms controlling the global interannual variability of the start date of permafrost frozen (SOF) remain unclear. Using long-term SOF from the combinations of multiple satellite microwave sensors between 1979 and 2020, and analytical techniques, including partial correlation, ridge regression, path analysis, and machine learning, we explored the responses of SOF to multiple climate change factors, including warming (surface and air temperature), start date of permafrost thawing (SOT), soil properties (soil temperature and volume of water), and the snow depth water equivalent (SDWE). Overall, climate warming exhibited the maximum control on SOF, but SOT in spring was also an important driver of SOF variability; among the 65.9% significant SOT and SOF correlations, 79.3% were positive, indicating an overall earlier thawing would contribute to an earlier frozen in winter. The machine learning analysis also suggested that apart from warming, SOT ranked as the second most important determinant of SOF. Therefore, we identified the mechanism responsible for the SOT-SOF relationship using the SEM analysis, which revealed that soil temperature change exhibited the maximum effect on this relationship, irrespective of the permafrost type. Finally, we analyzed the temporal changes in these responses using the moving window approach and found increased effect of soil warming on SOF. In conclusion, these results provide important insights into understanding and predicting SOF variations with future climate change.

Straw return counteracts the negative effects of warming on microbial community and soil multifunctionality

Climate warming is one of the most serious threats to soil biodiversity and ecosystem stability. Straw return has been extensively recommended as an environmentally friendly management to increase soil health and agricultural productivity. However, little is known about their interactive effects on microbial communities and soil functioning. We investigated the effects of soil warming, straw return, and their interactions on soil microbial communities, functional genes, enzyme activities related to C, N and P cycling, and multifunctionality in a two-factorial experiment in a wheat-maize rotation system. Soil warming decreased fungal diversity (by 20%) and functional genes associated with organic matter decomposition, N fixation, nitrification, denitrification, and organic P mineralization compared with ambient temperature. Soil multifunctionality mediated by enzyme activities were reduced under warming because of lower soil moisture, nutrient availability, and root-derived labile organic matter inputs. The close relationships of microbial diversity and functional genes with soil multifunctionality highlighted the importance of soil biodiversity in maintaining agroecosystem functioning related to nutrient cycling. Under soil warming and ambient temperature, straw return resulted in higher bacterial diversity (by 3.6%) and microbial functional genes abundances of C, N and P cycling compared to straw removal, and consequently raised soil multifunctionality. This was primarily because straw buffered soil temperature amplitude and moisture variation, as well as the additional nutrient supply within the added straw. Overall, straw return created favorable habitats for microorganisms, and thereby mitigated the adverse effects of warming on microbial communities and soil functionality. Our study provided the possibility to increase soil biodiversity and further ecosystem services related to organic matter decomposition and nutrient turnover by straw addition, especially under climate warming.

Soil warming decreased dissolved organic carbon quantity and quality in subtropical forests.

Soil dissolved organic carbon (DOC) is the most active part in forest soil carbon pool, the responses of which to climate warming has profound effects on forest carbon cycling. Based on a manipulative soil warming experiment in subtropical evergreen broad-leaved forests, we collected soil solutions in situ and used ultraviolet-visible, infrared and three-dimensional fluorescence spectroscopy analyses to explore the effects of soil warming (+4 ℃, 1 year) on soil DOC quantity and quality along the soil profile. The results showed that soil DOC flux remained constant along the soil profile. Soil DOC mainly included two humic-like fractions and one microbial metabolite. Warming significantly decreased soil DOC flux and the abundance of aromatic and hydrophobic components, and increased the amount of low molecular weight carbohydrates. Furthermore, soil warming increased the relative proportion of humic-like fractions in the surface soil layer (0-10 cm) and microbial metabolite in the deep soil layer (30-40 cm), indicating that warming might accelerate microbial turnover in the deep layer. Overall, soil warming not only decreased soil DOC content, but also simplified the composition of soil DOC in subtropical evergreen broad-leaved forests.

Effect of soil warming on growth and physiology of aspen seedlings from Alberta, Canada

Boreal tree species are migrating northwards due to rising temperatures, and differences in heat tolerance can impact the range limits of boreal species. Soil warming may benefit tree growth by promoting root development, or harm growth by creating a high-stress environment, increasing root respiration rates. We assessed the impact of soil warming on the growth of 2-year-old trembling aspen seedlings from 10 families. These families originated from Peace River, in central Alberta, and Camrose, near the southern boreal fringe in Alberta, Canada. We correlated growth traits with climatic data from each region and analyzed the effect of soil warming on the gas exchange of seedlings from Camrose. Families from Peace River exhibited greater growth overall, regardless of warming treatment, while families from Camrose showed a positive growth response under soil warming. Camrose families exposed to soil warming showed greater total leaf area and total leaf biomass compared to those without warming. A Principal Component Analysis (PCA) showed that, regardless of region, some families displayed stronger positive responses and appeared better adapted to soil warming than others. The overall positive response of the Camrose families to soil warming suggests that they have the capacity to take advantage of warmer environmental conditions. Our results indicate regional growth differences in aspen families in Alberta and variation in performance between families within a region, indicating there is differential capacity within local populations to acclimate under rapid climate change.

Does long-term soil warming affect microbial element limitation? A test by short-term assays of microbial growth responses to labile C, N and P additions.

Increasing global temperatures have been reported to accelerate soil carbon (C) cycling, but also to promote nitrogen (N) and phosphorus (P) dynamics in terrestrial ecosystems. However, warming can differentially affect ecosystem C, N and P dynamics, potentially intensifying elemental imbalances between soil resources, plants and soil microorganisms. Here, we investigated the effect of long-term soil warming on microbial resource limitation, based on measurements of microbial growth (18 O incorporation into DNA) and respiration after C, N and P amendments. Soil samples were taken from two soil depths (0-10, 10-20 cm) in control and warmed (>14 years warming, +4°C) plots in the Achenkirch soil warming experiment. Soils were amended with combinations of glucose-C, inorganic/organic N and inorganic/organic P in a full factorial design, followed by incubation at their respective mean field temperatures for 24h. Soil microbes were generally C-limited, exhibiting 1.8-fold to 8.8-fold increases in microbial growth upon C addition. Warming consistently caused soil microorganisms to shift from being predominately C limited to become C-P co-limited. This P limitation possibly was due to increased abiotic P immobilization in warmed soils. Microbes further showed stronger growth stimulation under combined glucose and inorganic nutrient amendments compared to organic nutrient additions. This may be related to a prolonged lag phase in organic N (glucosamine) mineralization and utilization compared to glucose. Soil respiration strongly positively responded to all kinds of glucose-C amendments, while responses of microbial growth were less pronounced in many of these treatments. This highlights that respiration-though easy and cheap to measure-is not a good substitute of growth when assessing microbial element limitation. Overall, we demonstrate a significant shift in microbial element limitation in warmed soils, from C to C-P co-limitation, with strong repercussions on the linkage between soil C, N and P cycles under long-term warming.

增温和氮添加对杉木不同序级细根形态和化学性状的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 增温和氮添加对杉木不同序级细根形态和化学性状的影响 DOI: 10.5846/stxb202204291200 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金重点项目（31830014）；国家重点研发计划项目课题项目（2021YFD2200403） Effects of soil warming and nitrogen addition on the morphological and chemical characteristics of fine roots in different order classes of the Chinese fir Author: Affiliation: Fund Project: National Natural Science Foundation of China(31830014);Topics of state key R & D projects（2021YFD2200403） 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:全球气候变暖与氮（N）沉降是两个同时存在的全球变化主要因素，但目前关于二者的研究多以单因子为主。细根形态和化学性状等功能性状在促进植物养分获取和森林生物地球化学循环方面起着关键作用，但目前气候变暖、N沉降以及两者交互对细根形态和化学性状的影响尚不清楚。在福建三明森林生态系统国家野外科学观测研究站陈大观测点开展土壤增温与N添加双因子试验，包括对照（无增温，无氮添加）、低氮（+4gN m-2 a-1）、高氮（+8gN m-2 a-1）、增温（+5℃）、增温+低氮（+5℃，+4gN m-2 a-1）、增温+高氮（+5℃，+8gN m-2 a-1）六个处理，探讨增温与N添加对杉木（Cunninghamia Lanceolata）细根形态和化学性状的影响。结果表明：（1）增温显著增加了细根直径（D）。增温和N添加的交互作用对细根比根长（SRL）、比表面积（SRA）及组织密度（RTD）均存在显著影响，与对照相比，增温处理及增温+高氮处理均降低了细根SRL和SRA；不同处理间细根RTD无显著差异。N添加与序级交互作用对细根SRA存在显著影响，仅低氮添加显著增加了1级根SRA。（2）增温和N添加交互作用对细根碳（C）含量存在显著影响，与对照相比，仅增温+高氮处理显著增加了细根C含量。N添加与序级交互作用对细根C含量存在显著影响，仅在1级细根中，高氮添加的细根C含量要显著高于低氮添加。增温、N添加以及序级三者交互作用对细根N含量及碳氮比（C ： N）存在显著影响，与对照相比，低氮和高氮处理对细根N含量及C ： N影响因序级而异；增温处理、增温+低氮处理以及增温+高氮处理均显著提高了细根N含量，降低了细根C ： N；与高阶根相比，低阶根N含量和C ： N对单独增温处理及增温+低氮处理响应要更为敏感。以上结果表明，不同细根功能性状对增温、N添加及两者交互的响应存在差异，这种差异主要与细根序级和N添加水平有关；增温和N添加抑制了细根SRL和SRA，但促进了细根N含量并降低了细根C ： N，这将有助于理解亚热带地区森林地下养分循环以及C固存对全球环境变化的响应。 Abstract:Global warming and nitrogen deposition are two main global change drivers, often occurring simultaneously. However, most of related studies referred to only single factor. Fine root functional traits such as morphology and chemical properties play a key role in promoting plant nutrient acquisition and forest biogeochemistry cycling. The effects of climate warming, N deposition and their interactions on fine root morphology and chemical properties remain unclear. To explore the effects of warming and N addition on the morphological and chemical characteristics of fine roots of Cunninghamia Lanceolata. We conducted a two-factor experiment of soil warming and nitrogen addition, which consisted control (CT), low nitrogen treatment (LN), high nitrogen treatment (HN), warming treatment (W), warming and low nitrogen treatment (WLN), warming and high nitrogen treatment (WHN), at the Forest Ecosystem and Global Change Research Station of Fujian Normal University, Chenda, Sanming, Fujian Province. The results showed that:(1) the warming significantly increased fine root diameter (D). The interaction of warming and N addition had significant effects on the specific root length (SRL), specific surface area (SRA) and root tissue density (RTD) of fine roots. Compared with CT, the W and WHN reduced fine root SRL and SRA; there was no significant difference in RTD of fine roots among different treatments. The interaction of N addition and order had significant effects on fine root SRA. Low nitrogen addition only increased SRA of first order root significantly. (2) The interaction of warming and N addition had a significant effect on fine root C concentration, and only WHN significantly increased fine root C concentration. The interaction of N addition and order had significant effects on fine root concentration. The fine root C concentration of high N addition was significantly higher than that of low N addition. The interaction of warming, N addition and order had significant effects on fine root N concentration and C:N. Compared with CT, the effects of LN and HN on fine root N content and C:N varied with the order; The W, WLN and WHN significantly increased the fine root N concentration and decreased the fine root C:N. Compared with high-order root, low-order root N concentration and C:N were more sensitive to the effects of W and WLN. The results showed that the responses of fine root morphology and chemical characteristics to warming, N addition and their interaction were different, and the differences were mainly regulated by fine root branch order and N addition level; The warming and N addition promoted fine root N concentration and decreased fine root C:N, which would contribute to understand the subsurface nutrient cycling and the response of C sequestration to global environmental change in subtropical forests. 参考文献 相似文献 引证文献

Effects of field soil warming on the growth and physiology of Juglans mandshurica seedlings.

Global climate change will increase surface soil temperature, with consequences on plant seedling growth and population dynamics. In this study, we carried out a field experiment to investigate the effects of 2 ℃ soil warming on the growth and physiological characteristics of 1- and 2-year-old seedlings of a dominant tree species in broadleaved Korean pine forest, Juglans mandshurica. The results showed that soil warming significantly increased basal diameter, root length, total leaf area, leaf dry weight, root dry weight, total biomass, apparent photosynthetic electron transfer rate (ETR), PSⅡ actual photochemical efficiency (ΦPSⅡ), and apparent photosynthetic electrophotochemical quenching coefficient (qP) of 1-year-old seedlings by 18.3%, 66.7%, 94.4%, 105.9%, 95.8%, 37.8%, 89.5%, 100.0%, and 71.4%, respectively. Soil warming significantly increased basal diameter, total leaf area, leaf dry weight, total biomass, leaf superoxide dismutase activity, peroxidase activity, catalase activity and free proline content, ETR, ΦPSⅡ, and qP of 2-year-old seedlings by 12.5%, 180.5%, 97.3%, 42.5%, 23.9%, 20.4%, 14.9%, 20.7%, 66.7%, 283.3% and 284.6%, respectively. There was an interaction between seedling age and soil warming on the root-shoot ratio and the ΦPSⅡ and qP in chlorophyll fluorescence parameters, in that soil warming significantly reduced the root-shoot ratio of 2-year-old seedlings and that the increase of chlorophyll fluorescence parameters of 2-year-old seedlings (4.1-4.6 times) was much higher than that of 1-year-old seedlings (1.5-1.8 times). Soil warming of 2 ℃ was beneficial to the growth of 1- and 2-year-old J. mandshurica seedlings and increased their regeneration potential. In particular, 2-year-old J. mandshurica seedlings responded to soil warming by increasing leaf area, improving leaf photochemical efficiency, and enhancing protective enzyme activity to increase resistance.

Soil CH4 and N2O response diminishes during decadal soil warming in a temperate mountain forest

Global warming is considered to impact the fluxes of methane (CH4) and nitrous oxide (N2O) between forest soils and the atmosphere, but it is unclear whether the responses change over time. In this study the response of soil CH4 and N2O fluxes to field soil warming (+4 °C) were determined during years 2–5 and 14–16 in a soil warming experiment in a temperate forest. In the second and sixteenth year of soil warming, temperature sensitivities of CH4 and N2O fluxes were assessed in-situ by gradually rising field soil temperatures to ∼10 °C above ambient within a short period of three to four days. Production of dinitrogen (N2) was measured ex-situ in the sixteenth year of warming. Soil warming significantly reduced CH4 uptake (-19.5%) and increased N2O emissions (+41.6%) during the first years of warming, whereas no warming effects on soil CH4 and N2O fluxes were observed during the later years. Dinitrogen production was up to ten times higher than N2O production, though the high spatiotemporal variability masked any significant effects of soil warming on soil N2 fluxes. Temperature sensitivities (Q10) for CH4 uptake and N2O emissions were 2.07 and 4.06, respectively, in the second year of warming and 1.52 and 1.79, respectively, in the sixteenth year of soil warming. The diminishing warming response of the soil N2O fluxes likely were caused by longer-term changes in soil N availability and/or simultaneous acclimation of the soil microbial community to soil warming. Soil moisture was largely unaffected by soil warming, and soil temperature alone was only a weak predictor of soil CH4 fluxes. Methane fluxes therefore can be expected to be generally less affected than N2O fluxes. Overall, our results suggest that soil warming has only limited and transient effects on soil CH4 and N2O fluxes in this type of temperate forest.

Effects of Soil Warming on Soil Microbial Metabolism Limitation in a Quercus acutissima Forest in North Subtropical China

In order to explore the influence of climate warming on soil microbial metabolism in the ecosystem and reveal the relationship between soil microbial metabolism limitation and environmental factors, in this study, the effects of warming on soil enzyme activities and nutrient availability were investigated by setting underground heating cables at 2 °C and 4 °C soil warming in a typical Quercus acutissima forest in the northern subtropics, and enzyme stoichiometric models were used to evaluate the limits of soil microbial metabolism. The results showed that soil warming significantly increased the activities of β-1,4-glucosidase (BG) and L-leucine aminopeptidase (LAP), and significantly increased the contents of nitrate nitrogen (NO3−-N) and available phosphorus (AP) in soil. The soil warming increased soil microbial C limitation and alleviated soil microbial P limitation. Our study showed that the change of soil microbial C and P limitation caused by warming may cause a large amount of SOM decomposition in a short period, leading to a large fluctuation of soil carbon turnover, which is not conducive to the stability of the soil C pool. This study provides important insights linking microbial metabolism to soil warming and improves our understanding of C cycling in forest systems.

Simulating Temperature in a Soil Incubation Experiment

The study of warming impact on soils requires a realistic and accurate representation of temperature. In laboratory incubation studies, a widely adopted method has been to render constant temperatures in multiple chambers, and via comparisons of soil responses between low- and high-temperature chambers, to derive the warming impact on soil changes. However, this commonly used method failed to imitate both the magnitude and amplitude of actual temperatures as observed in field conditions, thus potentially undermining the validity of such studies. With sophisticated environmental chambers becoming increasingly available, it is imperative to examine alternative methods of temperature control for soil incubation research. This protocol will introduce a state-of-the-art environmental chamber and demonstrate both conventional and new methods of temperature control to improve the experimental design of soil incubation. The protocol mainly comprises four steps: temperature monitoring and programming, soil collection, laboratory incubation, and warming effect comparison. One example will be presented to demonstrate different methods of temperature control and the resultant contrasting warming scenarios; that is, a constant temperature design referred to as stepwise warming (SW) and simulated in situ temperature design as gradual warming (GW), as well as their effects on soil respiration, microbial biomass, and extracellular enzyme activities. In addition, we present a strategy to diversify temperature change scenarios to meet specific climate change research needs (e.g., extreme heat). The temperature control protocol and the recommended well-tailored and diversified temperature change scenarios will assist researchers in establishing reliable and realistic soil incubation experiments in the laboratory.