Xiaojuan Feng

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• PhD
• Professor at Institute of Botany, Chinese Academy of Sciences

The tremendous reservoir of soil organic carbon (SOC) in wetlands is being threatened by water-table decline (WTD) globally. However, the SOC response to WTD remains highly uncertain. Here we examine the under-investigated role of iron (Fe) in mediating soil enzyme activity and lignin stabilization in a mesocosm WTD experiment in an alpine wetland....

The means through which microbes and plants contribute to soil organic carbon (SOC) accumulation remain elusive due to challenges in disentangling the complex components of SOC. Here we use amino sugars and lignin phenols as tracers for microbial necromass and plant lignin components, respectively, and investigate their distribution in the surface...

Climate projection requires an accurate understanding for soil organic carbon (SOC) decomposition and its response to warming. An emergent view considers that environmental constraints rather than chemical structure alone control SOC turnover and its temperature sensitivity (i.e., Q10 ), but direct long-term evidence is lacking. Here, using compoun...

Sphagnum wetlands are global hotspots for carbon storage, conventionally attributed to the accumulation of decay-resistant litter. However, the buildup of mineral-associated organic carbon (MAOC) with relatively slow turnover has rarely been examined therein. Here, employing both large-scale comparisons across major terrestrial ecosystems and soil...

The carbon storage of wetlands is related to inhibited enzyme activity (particularly phenol oxidase) under oxygen-deprived conditions. However, phenol oxidase response to field drainage is highly uncertain, constraining our ability to predict wetland carbon–climate feedbacks. Here, using literature data, laboratory simulations and a pair-wise surve...

Peer review is a critical evaluation process, one that is time‐consuming but needed to maintain quality and credibility in science. At JGR Biogeosciences we are honoring the many 2024 reviewers who donated their time and expertise to ensure rigor, novelty, inclusiveness, and open practices for improving and advancing biogeosciences research.

Multiple global change drivers have caused a large carbon (C) debt in our soils. To remedy this debt, understanding the role of microorganisms in soil C cycling is crucial to tackle the C soil loss. Microbial carbon use efficiency (CUE) is a parameter that captures the formation of microbially-derived soil organic matter (SOM). While it is known th...

Plain Language Summary Mineral protection of organic carbon (OC) by reactive metal (mainly iron and aluminum) (hydr) oxides is one of the key mechanisms promoting the long‐term stabilization of soil organic carbon (SOC). However, the sources and turnover of (metal‐) bound OC in natural soils remain poorly constrained, hampering our understanding of...

Microbe-mediated carbon (C) transformation plays a crucial role in the accumulation of soil organic C (SOC). However, microbial conversion efficiency of newly-added labile C and native SOC to necromass remain under-investigated. Here we collected the rhizosphere and non-rhizosphere soils under broadleaved and coniferous trees of varying nutrient av...

Plain Language Summary The roots of most (>80%) grassland plants are colonized by endogenous microbes, in particular arbuscular mycorrhizal fungi (AMF). However, the direct contribution of root‐borne microbial necromass carbon (MNC) to grassland soil organic carbon (SOC) remains unknown. Here we conduct a benchmark quantification of root‐borne MNC...

Plant phosphorus (P) acquisition strategy is considered to be an intrinsic driver behind plant succession. However, variations in plant P acquisition strategies in connection to soil P fraction changes after wetland drainage remain unclear. To address this issue, here we conducted a study in six distinct wetlands that experienced long‐term (>20 yea...

Boreal forests fix substantial amounts of atmospheric carbon (C). However, the timescales at which this C is cycled through the ecosystem are not yet well understood. To elucidate the temporal dynamics between photosynthesis, allocation and respiration, we assessed the radiocarbon (C14 ${}^{14}\mathrm{C}$) disequilibrium (D) between different C poo...

Soil carbon sequestration is listed by the United Nations Framework Convention on Climate Change as one of the key ways to achieve long-term “carbon neutrality” in the context of global warming. Soil carbon sequestration is a complex biogeochemical process that involves plants, microbes, and rock minerals at its core. Yet, its regulation mechanisms...

The established paradigm assumes that drainage may decrease the vast soil organic carbon (SOC) reservoir in global wetlands. Yet drainage can also promote SOC stabilization by fostering the accrual of metal-bound organic carbon (bound OC) upon oxygen exposure. Here, this emergent mechanism is tested for the first time at a regional scale, using lit...

Microbial carbon use efficiency (CUE), a key parameter to characterize microbial carbon conversion efficiency, is assumed to be similar in soil models for different soil functional pools with varied organic matter composition and nutrient availability, that is, particulate organic matter (POM) and mineral‐associated organic matter (MAOM). However,...

Peer review is a crucial but time‐consuming and sometimes frustrating part of science. The Editors of JGR: Biogeosciences are deeply appreciative of, and sincerely thank, the many 2023 reviewers who donated their time and expertise in support of the journal.

Microbial release of CO2 from soils to the atmosphere reflects how environmental conditions affect the stability of soil organic matter (SOM), especially in massive organic-rich ecosystems like the peatlands and grasslands of the Qinghai–Tibetan Plateau (QTP). Radiocarbon (14C) is an important tracer of the global carbon cycle and can be used to un...

Plain Language Summary The accrual of mineral‐associated organic carbon (MAOC) is one of the key mechanisms promoting the long‐term sequestration of atmospheric CO2 into soil organic carbon (SOC). Both microbial residue production and mineral preservation are vital for MAOC accumulation. However, their relative importance and interactive effects re...

No consistent variation was found in soil respiration Q10 under various O2 conditions. Substrate C quality had a strong effect on Q10 in oxic soils. N limitation had a large impact on Q10 in soils under O2 limitation. Current studies on the temperature sensitivity (Q10) of soil organic matter (SOM) decomposition mainly focus on aerobic conditions....

The diversity of intrinsic traits of different organic matter molecules makes it challenging to predict how they, and therefore the global carbon cycle, will respond to climate change. Here we develop an indicator of compositional-level environmental response for dissolved organic matter to quantify the aggregated response of individual molecules t...

Drainage poses a major threat to the tremendous soil organic carbon (SOC) reservoir in wetlands. However, drainage-induced carbon loss may be mitigated by the accumulation of mineral-associated organic carbon (MAOC) via both microbial processes and iron (Fe)-organic matter (especially lignin) interactions, which remains under-investigated in wetlan...

We made a commitment to better include underrepresented members of our community in the publication pipeline of JGR: Biogeosciences. This commitment consists of regular updates on our policies and practices, and concrete actions we intend to implement over the next year. So far, our progress to tackle biases and ensure equitable research in the bio...

Mineral binding of organic carbon (OC) is one of the key mechanisms promoting soil organic carbon (SOC) persistence, which is vital for the long‐term sequestration of atmospheric carbon dioxide into soils. However, the relative importance of two main types of soil minerals ‐ metal oxides and silicate clay—in SOC protection remains unclear, hamperin...

The sustainability of life on Earth is under increasing threat due to human-induced climate change. This perilous change in the Earth's climate is caused by increases in carbon dioxide and other greenhouse gases in the atmosphere, primarily due to emissions associated with burning fossil fuels. Over the next two to three decades, the effects of cli...

Microbial necromass accrual via anabolism is an important process contributing to the formation and accumulation of stable soil organic C (SOC). Both substrates and microbial community traits impact the rate and efficiency of microbial biomass production, yet their effects on necromass accumulation patterns and efficiency remain unclear. Here we se...

Microbe-mediated carbon transformation plays an important role in soil carbon sequestration, which is considered to be one of the key strategies to achieve carbon neutrality in the long term. Assessing the efficiency of microbial necromass accumulation relative to plant carbon input or microbial respiration will help to identify ways to promote soi...

The land‐to‐ocean export of terrestrial dissolved organic matter (tDOM) links the two largest organic carbon (OC) pools on Earth and is changing due to anthropogenic activity and climate change. Lignin phenols are often utilized as diagnostic markers for tDOM in aquatic systems, but information on the global dissolved lignin flux is still uncertain...

Microbial release of CO2 from soils to the atmosphere reflects how environmental conditions affect the stability of soil organic matter (SOM), especially in massive organic-rich ecosystems like the peatlands and grasslands of the Qinghai-Tibetan Plateau (QTP). Radiocarbon (14C) is an important tracer of the global carbon cycle and can be used to un...

Driven by earthquakes and intense rainfall, steep tectonically active mountains are hotspots of terrestrial organic carbon mobilization from soils, rocks, and vegetation by landslides into rivers. Subsequent delivery and fluvial mobilization of organic carbon from different sources can impact atmospheric CO2 concentrations across a range of timesca...

Plants and microbes are the primary drivers in affecting the formation and accrual of soil organic carbon (SOC) for natural ecosystems. However, experimental evidence elucidating their underlying mechanisms for SOC accumulation remains elusive. Here, we quantified plant and microbial contributions to SOC accrual in successional subtropical forests...

Erosion is the most widespread form of soil degradation and an important pathway of carbon transfer from land into aquatic systems, with significant impact on water quality and carbon cycle. However, it remains debatable whether erosion induces a carbon source or sink, and the fate of eroded soil carbon in aquatic systems remains poorly constrained...

Plants play a central role in governing soil organic carbon (SOC) dynamics, as a direct contributor, a mediator and fuel for microbial processing, and a regulator of soil physiochemical processes. The above processes may occur independently or interactively, sometimes inducing counteracting effects on SOC turnover or storage depending on the soil e...

Soil organic carbon (SOC) plays a central role in ecosystem carbon sequestration and climate change mitigation, and its stability and dynamics are related to sourcing from microbial vs. plant residues. However, SOC sourcing and its regulating mechanisms remain poorly understood in soil's most bioactive compartment, the rhizosphere, which may differ...

Background & Aim: Analyzing biodiversity status requires multi-spatial scale, continuous monitoring across different ecosystems due to its heterogenous nature in both space and time. Therefore, monitoring networks are necessary for biodiversity conservation research. Biodiversity monitoring networks at the global, regional, and national scales,

Redox shifts threaten to reduce the massive soil organic carbon (SOC) stocks in wetlands. However, ferrous iron [Fe(II)] oxidation may stabilize wetland SOC by reducing phenol oxidative activity, inhibiting CO2 emissions, and promoting SOC association with ferric Fe [Fe(III)] (oxyhydr)oxides. Yet the prevalence and efficacy of this mechanism are no...

Forest ecosystems are important global soil carbon (C) reservoirs but their capacity to sequester C is susceptible to climate change factors that alter the quantity and quality of C inputs. To better understand forest soil C responses to altered C inputs, we integrated three molecular composition published datasets of SOM and soil microbial communi...

The Qinghai–Tibetan Plateau (QTP) has experienced atmospheric warming, cryosphere thaw and intensified human activities since the 1970s. These changes have had sometimes striking impacts on the hydrology, ecosystems and biogeochemistry of the region. In this Review, we describe carbon and nitrogen cycling on the QTP. Overall, the QTP has been a net...

Soil microbes assemble in highly complex and diverse microbial communities, and microbial diversity patterns and their drivers have been studied extensively. However, diversity correlations and co-occurrence patterns between bacterial, fungal, and archaeal domains and between microbial functional groups in arid regions remain poorly understood. Her...

Plant and microbial residues are two main sources of soil organic carbon (SOC). While recent studies have extensively examined the distribution of microbial necromass in different ecosystems, how plant residues (in particular, non-lignin components) contribute to SOC accumulation is less clear, especially in forests which make up 50% of the global...

As the primary producer in terrestrial ecosystems, plants are the ultimate source of organic carbon supplied into soils and fueling microbial decomposition. Hence, plants play a key role in the formation and accumulation of soil organic matter. However, due to the complexity of plant‐derived organic matter and soil processes, the fate, persistence...

Heterotrophic soil microbes are increasingly recognized as a key mediator transforming labile organic carbon (OC) into relatively stable soil carbon (C) in the form of microbial necromass (dead cells) and extracellular compounds associated with minerals. However, the accumulation of microbial necromass relative to labile OC consumption and its regu...

The microbial groups of nitrogen fixers, ammonia oxidizers, and denitrifiers play vital roles in driving the nitrogen cycle in grassland ecosystems. However, the understanding of the abundance and distribution of these functional microorganisms as well as their driving factors were limited mainly to topsoil. In this study, the abundances of nitroge...

Sphagnum acid, a major phenolic metabolite of Sphagnum mosses, is considered to play a key role in the remarkable accumulation of organic matter in Sphagnum-dominated wetlands. However, while previous studies have mainly focused on the antimicrobial property of Sphagnum metabolites, the effects of sphagnum acid on other soil biogeochemical processe...

Drainage-induced changes in wetland soil organic carbon (SOC) composition and origin are poorly investigated compared to SOC stocks. Here, using soil fractionation and neutral sugars, we find that long-term drainage increased both plant- and microbial-dominated (i.e., light and mineral-associated, respectively) fractions in a fen while microbial re...

Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are membrane lipids of certain soil bacteria, and their relative distributions are used as a proxy for air temperature and soil pH. While temperature is recorded by the degree of methylation, soil pH is reflected by the amount of internal cyclization and the relative abundance of 6-methyl iso...

Changes in species composition across communities, i.e., β-diversity, is a central focus of ecology. Compared to macroorganisms, the β-diversity of soil microbes and its drivers are less studied. Whether the determinants of soil microbial β-diversity are consistent between soil depths and between abundant and rare microorganisms remains controversi...

Plant species richness (PSR) is known to affect soil organic carbon (SOC) storage. However, due to the complex origin and composition of SOC, mechanisms driving the PSR-SOC relationship are not yet fully revealed, hampering an accurate prediction of SOC dynamics under changing plant diversity. Here we investigate the effect of PSR on SOC accumulati...

Carbohydrates are important components of soil organic matter, which can be decomposed to different types of monosaccharides. Neutral monosaccharides in the soil are also called neutral sugars, including xylose, ribose, arabinose, glucose, galactose, mannose, fucose and rhamnose. Among them, plant-derived sugars mainly include pentoses, such as xyl...

Headwater streams drain >70 % of global land areas but are poorly monitored compared with large rivers. The small size and low water buffering capacity of headwater streams may result in a high sensitivity to local hydrological alterations and different carbon transport patterns from large rivers. Furthermore, alpine headwater streams on the “Asian...

Metal-bound organic carbon (OC) is vital for the persistence of soil organic carbon (SOC). However, its relative importance in different land types (e.g., upland vs. wetland) remains unclear. Here by analyzing metal-bound OC by the classic citrate-bicarbonate-dithionite method (OCCBD) from 62 soils from contrasting environments, we find that OCCBD...

Microbial necromass carbon (MNC) is key to soil organic carbon (SOC) storage. However, mechanisms regulating MNC accumulation on large scales are poorly understood. Here we provide the first batch of regional-scale MNC data based on amino sugars for the Qinghai-Tibet Plateau alpine grasslands. We show that Qinghai-Tibet grasslands have similar micr...

Significance Terrestrial organic-carbon reservoirs (vegetation, soils) currently consume more than a third of anthropogenic carbon emitted to the atmosphere, but the response of this “terrestrial sink” to future climate change is widely debated. Rivers export organic carbon sourced over their watersheds, offering an opportunity to assess controls o...

Subsoils contain > 50% of soil organic carbon (SOC) globally yet remain under-investigated in terms of their response to climate changes. Recent evidence suggests that warmer, drier conditions in alpine grasslands induce divergent responses in SOC decomposition and carbon accrual in top-vs. subsoils. However, longer-term effects on microbial activi...

Background Future ecosystem structure and function will largely depend on root responses to climate change. However, few studies have explored the responses of root production and decomposition to simultaneous warming and altered precipitation in high-latitude and high-altitude ecosystems.Methods Using ingrowth core and root bag methods, we investi...

Headwater streams drain > 70 % of global land areas but are poorly monitored compared with large rivers. The small size and low water buffering capacity of headwater streams may result in a high sensitivity to local hydrological alterations and divergent carbon transport dynamics relative to large rivers. To assess these aspects, here we carry out...

The lack of ecosystem-scale CO 2 enrichment experiments in alpine regions considerably restricts our ability to predict the feedback of the global carbon (C) cycle to climate change. Here we investigate soil C response in an experiment with 5-year CO 2 enrichment and nitrogen (N) fertilization in a Tibetan meadow (4585 m above the sea level). We fo...

n -Alkanes and fatty acids are important molecular markers for the source apportionment of organic matter in the atmosphere. Traditional approaches to date have mostly relied upon the source-specific differences in their molecular distributions and carbon preference index. Alternatively, we demonstrate here the use of stable carbon and radiocarbon...

In the late Miocene, grasslands spread across the forested floodplains of the Himalayan foreland, but the causes of the ecological transition are still debated. Recent seafloor drilling by the International Ocean Discovery Program (IODP) provides an opportunity to study the transition across a larger region as archived in the Indus submarine fan. W...

Leaf wax n-alkanes serve as biomarkers that record environmental information with their carbon isotopic composition (δ¹³Calk) recording water availability. Agricultural and paleoclimate applications would benefit from a greater understanding of how water shortages are recorded in δ¹³Calk across the growing season, and controlled experiments can con...

A key challenge in ecology is to understand the relationships between organismal traits and ecosystem processes. Here, with a novel dataset of leaf length and width for 10 480 woody dicots in China and 2374 in North America, we show that the variation in community mean leaf size is highly correlated with the variation in climate and ecosystem prima...

Aims Owing to different soil environments and organic carbon sources, soil organic carbon (SOC) composition and preservation mechanisms may vary substantially in deep versus surface soils. This study examines vertical variation of various SOC components (including lignin phenols, cutin, suberin and microbial lipids) across the Chinese-Mongolian gra...

The Ganges–Brahmaputra (G-B) River system transports over a billion tons of sediment every year from the Himalayan Mountains to the Bay of Bengal and has built the world’s largest active sedimentary deposit, the Bengal Fan. High sedimentation rates drive exceptional organic matter preservation that represents a long-term sink for atmospheric CO 2 ....

Exploring the biogeographic patterns of soil microbial diversity is critical for understanding mechanisms underlying the response of soil processes to climate change. Using top- and subsoils from an ∼1,500-km temperate grassland transect, we find divergent patterns of microbial diversity and its determinants in the topsoil versus the subsoil. Furth...