Carbon Input Research Articles

Complex Study of Settlements Dating from the Paleolithic to Medieval Period in the Ural Mountains on the Border of Europe and Asia

Soil, geochemical, microbiological, and archeological studies were conducted at eight settlements dating from the Paleolithic to Late Medieval and Modern Ages near the southern Trans-Urals Mountains, Russia. The forest-steppe landscapes, rivers, and abundant mineral resources have attracted people to the region since ancient times. Cultural layers (CLs) are marked by finds of ceramics fragments, animal bones, stone, and metal tools. The properties of CLs include close-to-neutral pH, being well structured, the absence of salinity, enrichment with exchangeable calcium, and anthropogenic phosphorus (0.2–0.4%). The majority of CLs start at a depth of 3–25 cm, extend to 40–60 cm, and contain 6–10% organic carbon (Corg) in the 0–20 cm layer, reflecting carbon input from modern-day processes. At the Ishkulovo site (0.6–0.8 ka BP), Corg decreases to 1.3% because the CL is below 80 cm, and in the absence of fresh organic material input, carbon has been mineralized. The proximity of sites to deposits of copper, chromium, zinc, and manganese in the Ural Mountains creates natural high-content anomalies in the region, as indicated by their abundance in soils and parent rocks. In the past, these elements were also released into CLs from metal products, ceramic fragments, and raw materials used in their manufacture. The sites are quite far (18–60 km) from the Magnitogorsk Metallurgical plant, but industrial stockpiles of S (technogenic coefficient—Ct 30–87%), and, less often, Cr, Mn, and Sr (Ct 30–40%) accumulated in surface layers. These three factors have led to the concentration of pollutants of the first (arsenic, chromium, lead, and zinc) and second (cobalt, copper, and nickel) hazard classes at CLs, often in quantities 2–5 times higher than values for parent materials and geosphere average content (“Clarke” value), and, and less often, more than the allowable content for human health. This may have influenced their health and behavioral functions. Due to the above properties, chernozems have a high buffering capacity and a strong bond with heavy metals. Therefore, no inhibition of microbes was observed. The microbial biomass of the 0–10 cm layer is high, 520–680 µg C/g, and microbes cause the emission of 1.0 C-CO2 µg/g of soil per hour. During the ancient settlements’ development, a favorable paleoclimate was noted based on the data cited. This contributed to the spread of productive paleolandscapes, ensuring the development of domestic cattle breeding and agriculture.

Environmental drivers of seasonal and hourly fluxes of methane and carbon dioxide across a lowland stream network with mixed catchment

Streams serve as open windows for carbon emissions to the atmosphere due to the frequent supersaturation of carbon dioxide (CO2) and methane (CH4) that originates from large carbon input during runoff and associated in-stream processes. Due to the high spatial and temporal variability of the underlying environmental drivers (e.g., concentrations of dissolved CO2 and CH4, turbulence, and temperature), it has remained difficult to address the importance and upscale the emissions to annual whole-system and regional values. In this study, we measured concentrations and calculated emissions of CO2 and CH4 at diel and seasonal scales at 15 stations in a 1.4 km2 stream network that drains a mixed lowland catchment consisting of agriculture (210 km2), forest (56 km2), and lakes, ponds, and wetlands (22 km2) in the upper River Odense, Denmark to evaluate environmental drivers behind the spatiotemporal variability. We used automatically venting floating chambers to calculate hourly diffusive fluxes of CO2 and CH4 and CH4 ebullition. We found: 1) highly supersaturated CO2 and CH4 concentrations (median: 175 and 0.33 µmol L−1, respectively) and high diffusive fluxes of CO2 and CH4 (median: 3,608 and 19 µmol m−2 h−1, respectively); 2) lower daytime than nighttime diffusive emissions of CO2 in spring and summer, but no diel variability of CH4; 3) higher concentrations and emissions of CH4 at higher temperatures; and 4) higher emissions of CH4 at stations located in sub-catchments with higher agricultural coverage. Ebullition of CH4 peaked at two stations with soft organic sediment and low summer flow, and their ebullition alone constituted 30% of total annual CH4 emissions from the stream network. Mean annual CO2 emissions from the hydrological network (37.15 mol CO2 m−2 y−1) exceeded CH4 emissions 100-fold (0.43 mol CH4 m−2 y−1), and their combined warming potential was 1.83 kg CO2e m−2 y−1. Overall, agricultural sub-catchments had higher CH4 emissions from streams, while lakes and ponds likely reduced downstream CH4 and CO2 emissions. Our findings demonstrate that CO2 and CH4 emissions data at high spatial and temporal resolution are essential to frame the heterogeneous stream conditions, understand gas emissions regulation, and upscale to annual values for hydrological networks and larger regions.

Adding labile carbon to peatland soils triggers deep carbon breakdown

Peatlands store vast amounts of carbon, with deep peat carbon remaining stable due to limited thermodynamic energy and transport. However, climate change-induced increases in labile carbon inputs could destabilize these stores. Here, we combined DNA stable isotope probing with stable isotope-assisted metabolomics employing a multi-platform approach to investigate microbial dynamics driving deep peat carbon degradation upon labile carbon (e.g., glucose) amendment. Our findings highlight the vulnerability of deep peat carbon, as glucose addition triggers the breakdown of older organic matter. By uniquely integrating these techniques, we identified active glucose metabolizers to specific microbial populations and mapped carbon flow through microbial networks, elucidating their role in priming recalcitrant carbon mineralization. This multi-omics approach offers crucial insights into how changing resources reshape the peatland microbiome, enhancing our understanding of deep carbon processing, and refining model parameterization to predict microbial responses and carbon cycle feedbacks under global change pressures.

Light limitation enhances microbiome competitiveness and reduces microbial network stability in coastal waters

Abstract Light plays a crucial role in microbiomes, maintaining the amount and transfer of primary productivity and directing ecosystem functioning. Coastal microbiomes are frequently exposed to light-limited conditions, but how their community organization is affected remains unclear. This study aimed to investigate the assembly, association and functional activity of coastal microbiomes (both prokaryotes and eukaryotes) in response to low light. Results presented here show that light limitation reduces the diversity, phylogenetic distance and niche breadth of microbiomes and increases dispersal limitation, especially for microeukaryotes. A reduced proportion of photosynthetic microbes under light-limited conditions, suggests that decreased primary production and carbon input would further alter microbial composition and physiology. Reduced microeukaryotic diversity could enhance the influence of deterministic processes on the community assembly of microbiomes under light-limited conditions. Under light-limited conditions, deterministic processes structure the assembly of microeukaryotes, whereas the assembly of prokaryotes is mostly driven by stochastic processes. Light limitation weakens prokaryotic relations and intensifies microeukaryotic relations. Compositional and functional inefficiency and inefficient element cycling across microbial loops ultimately destabilize the light-limited ecosystems. The metatranscriptomic analysis identified that light deprivation reduces the expressions of genes involved in photosynthesis, nutrient utilization, oxidative phosphorylation, and biosynthesis of antibiotics, but enhances the expressions of genes related to the secretion system, purine metabolism and the citrate cycle. These results provide important insights into how microbiomes alter their composition and co-occurrences in light-limited environments.

Root carbon inputs outweigh litter in shaping grassland soil microbiomes and ecosystem multifunctionality

Global change has the potential to alter soil carbon (C) inputs from above- and below-ground sources, with subsequent influences on soil microbial communities and ecological functions. Using data from a 13-year field experiment in a semi-arid grassland, we investigated the effects of litter manipulations and plant removal on soil microbiomes and ecosystem multifunctionality (EMF). Litter addition did not affect soil microbial α-diversity whereas litter removal reduced bacterial and fungal α-diversity due to decreased C substrate supply and soil moisture. By contrast, plant removal led to larger declines in bacterial and fungal α-diversity, lower microbial network stability and complexity. EMF was enhanced by litter addition but largely reduced by plant removal, primarily attributed to the loss of fungal diversity. Our findings underscore the importance of C inputs in shaping soil microbiomes and highlight the dominant role of plant root-derived C inputs in maintaining ecological functions under global change scenarios.

Soil microbiome interventions for carbon sequestration and climate mitigation.

Mitigating climate change in soil ecosystems involves complex plant and microbial processes regulating carbon pools and flows. Here, we advocate for the use of soil microbiome interventions to help increase soil carbon stocks and curb greenhouse gas emissions from managed soils. Direct interventions include the introduction of microbial strains, consortia, phage, and soil transplants, whereas indirect interventions include managing soil conditions or additives to modulate community composition or its activities. Approaches to increase soil carbon stocks using microbially catalyzed processes include increasing carbon inputs from plants, promoting soil organic matter (SOM) formation, and reducing SOM turnover and production of diverse greenhouse gases. Marginal or degraded soils may provide the greatest opportunities for enhancing global soil carbon stocks. Among the many knowledge gaps in this field, crucial gaps include the processes influencing the transformation of plant-derived soil carbon inputs into SOM and the identity of the microbes and microbial activities impacting this transformation. As a critical step forward, we encourage broadening the current widespread screening of potentially beneficial soil microorganisms to encompass functions relevant to stimulating soil carbon stocks. Moreover, in developing these interventions, we must consider the potential ecological ramifications and uncertainties, such as incurred by the widespread introduction of homogenous inoculants and consortia, and the need for site-specificity given the extreme variation among soil habitats. Incentivization and implementation at large spatial scales could effectively harness increases in soil carbon stocks, helping to mitigate the impacts of climate change.

Soil CO2 efflux response to two decades of altered carbon inputs in a temperate coniferous forest

Global soils play a critical role in carbon (C) cycling and storage, and even minor disturbances to soil C flux can cause CO2 release to the atmosphere, exacerbating the greenhouse effect. This study investigates the long-term effects of forest detrital manipulation on soil CO2 efflux at a temperate forest site in Oregon’s western Cascade Mountains. We assessed the variation in seasonal and diurnal autotrophic and heterotrophic contributions to in situ soil CO2 efflux after 25 + years of detritus additions and removals and found slight increases in soil CO2 efflux rates concurrent with slight increases in soil C stocks, relative to C input rates, that may reflect underlying changes to C cycling in this system resulting from sustained detritus manipulation coupled with environmental change. Total CO2 efflux experienced increased contributions from functionally autotrophic root and rhizosphere respiration relative to the heterotrophic component. Seasonal and diurnal differences between soil respiration rates by treatment suggest a soil moisture buffering effect provided by the extra woody detritus that may support vegetative growth at times when seasonal drought would ordinarily slow plant and soil microbial metabolic activity. Overall, this research highlights the long-term effects of sustained litter additions and removals on soil CO2 efflux, which can help illuminate the response of C cycling in forests to current and future global change.

Future Arctic: how will increasing coastal erosion shape nearshore planktonic food webs?

AbstractArctic regimes. Currently, warming accelerates the erosion of permafrost coasts and the associated discharge of sediment, carbon, and nutrients into the Arctic Ocean. However, the impacts of coastal erosion on planktonic food webs remain understudied. We aimed to (1) understand how coastal erosion impacts nearshore carbon, nutrient, and light regimes; (2) investigate the effects on primary production and energy transfer; and (3) predict how increased erosion will impact the productivity of consumers, and the overall food web interactions. We found that sediment discharge increases turbidity (darkening). This darkening is expected to hamper phytoplankton productivity, while additional carbon input will provide bacteria with direct energy sources, and shift the balance between basal autotrophic and heterotrophic production. Since the heterotrophic pathway has a lower efficiency, its dominance might negatively affect mesozooplankton. Increased Arctic coastal erosion might therefore influence planktonic food webs by changing mechanisms of energy mobilization and transfer to higher trophic levels.

Effects of increased allochthonous dissolved organic carbon on the growth of planktonic biota in freshwater ecosystems: A meta‐analysis

AbstractWater browning, induced by allochthonous dissolved organic carbon (DOC) input, has become a widespread phenomenon in boreal lakes over the past decades. Directly quantifying aquatic organisms' responses to increased DOC concentrations is essential for projecting carbon cycle processes in freshwater ecosystems. In this study, we assessed the impacts of DOC addition on the growth of three freshwater planktonic groups: phytoplankton, zooplankton, and bacteria, and explored potential drivers behind variations in effect size. Background DOC concentrations vary between 0.5 and 25 mg L−1, while total phosphorus concentrations span from 0.0003 to 1.55 mg L−1. Based on a meta‐analysis of 804 observations from 47 publications, we found that DOC addition had a significant positive effect on bacteria, while it had a small but negative impact on both phytoplankton and zooplankton. In different climate zones, DOC addition often stimulated bacterial growth, but it exerted either positive or negative effects on phytoplankton and zooplankton. Additionally, the effect sizes of both phytoplankton and zooplankton showed a significant negative relationship with the magnitude of DOC enrichment, while bacteria exhibited positive responses. Furthermore, the effect sizes of these three taxa correlated negatively with background total phosphorus concentrations and positively with the DOC : total phosphorus ratio. A significant negative correlation between effect size and experimental duration was observed for bacteria. In summary, this synthesis indicates that excessive DOC loading can inevitably inhibit phytoplankton and zooplankton growth. Future studies should focus on the interactions between DOC addition and global change factors to improve forecasts of carbon‐climate feedback in aquatic ecosystems.

Combining predictive soil mapping and process models to estimate future carbon sequestration potential under no-till

There is increasing interest in soil organic carbon (SOC) sequestration as a climate change mitigation strategy. There is a need to estimate the quantity of SOC sequestered historically due to no-till, and the remaining sequestration potential in Saskatchewan. To answer this question, predictive soil mapping results were linked with the Century model to predict SOC stock change over time to a depth of 20 cm considering three different future climate change scenarios. Climate scenarios included low, moderate, and high amounts of climate change and included estimated changes to monthly minimum, average, and maximum temperature, total monthly precipitation, and average monthly relative humidity at an 800 m × 800 m resolution. Historically, the modelled average SOC gain for Saskatchewan was 2.8 Mg ha−1. Future potential simulated SOC was lower over the next 30 years, with average SOC gains estimated to range from 1.4 to 1.7 Mg ha−1 by 2054 and 2.3 to 3.1 Mg ha−1 by 2100. There is also unequal spatial distribution of SOC stock gain potential, with the northern grain growing regions showing lower future potential. The predicted future gains will be at a lower rate than in the past with carbon sequestration rates dropping from 0.06 to less than 0.02 Mg ha−1 year−1. Additional management practices such as improved residue management and the introduction of crop varieties with increased below ground carbon inputs and more stable residues should be explored to offset the diminishing SOC returns from no-till.

Three-year elevated carbon dioxide concentration does not enhance soil organic carbon quantity due to simultaneously facilitated carbon input and decomposition in a single rice paddy soil evidenced by natural 13C tracing.

Soil organic carbon (SOC) markedly contributes to maintaining soil nutrient cycling and mitigating climate change. Elevated carbon (C) dioxide concentration ([CO2]) is widely expected to improve crop yield and increase C storage; however, its effects on rice growth and SOC dynamics remain greatly unclear. Therefore, a three-year (2007-2009) chamber experiment with two [CO2] treatments (380 vs. 680ppm) was conducted during rice growing seasons. Ultisol soil, taken from a sugarcane (C4 plant) field on Ishigaki island, Okinawa, was used to grow rice (C3 plant). The natural 13C tracing method was utilized to measure the fraction of SOC derived from rice plant, and δ13C values and concentrations of CO2 and CH4 dissolved in soil solutions were determined. Elevated [CO2] significantly increased rice aboveground biomass (AGB) by 11.8%-28.8% and assimilated C content by 12.2%-28.3%. However, no significant differences were observed in SOC, total nitrogen (N) content, and the C/N ratios between ambient and elevated [CO2]. Elevated [CO2] induced markedly lower δ13C values in both plant and soil samples relative to ambient [CO2]. The annual fractions of plant-derived C input ranged from 5.0% to 21.2% in ambient [CO2] and from 5.6% to 21.9% in elevated [CO2] without significant differences. Elevated [CO2] stimulated marked increases in dissolved CO2 and CH4 concentrations, and δ13C values of CH4, indicating a positive priming effect of elevated [CO2] on native SOC decomposition for methanogenesis. In conclusion, elevated [CO2] did not affect SOC accumulation by simultaneously increasing C input evidenced by increased AGB, and SOC decomposition as CO2 and CH4 emissions, hence resulting in a stable SOC quantity in rice paddy ecosystems. Our study delves in the nexus between C input and soil C decomposition under elevated CO2 condition, highlighting its significance in prediction of the responses of C storage in paddy ecosystems to future climate change.

Identifying drivers of global spatial variability in organic carbon sequestration in tidal marsh sediments

Tidal marshes are among the most efficient ecosystems on Earth for carbon sequestration with a globally averaged rate of sediment organic carbon accumulation of 210 g C m−2 y−1, but with large spatial variations between marsh sites from 20 to 1700 g C m−2 y−1 worldwide. Previous studies identified certain environmental drivers of spatial variability of carbon sequestration in tidal marshes, but have considered so far a rather limited number of environmental variables. In this study, we started from a large dataset that includes 477 tidal marsh sites scattered worldwide and investigated the influence of 12 different environmental variables on sediment organic carbon content, density and accumulation rates using a Random Forest regression algorithm. We find that variability in organic carbon content is mostly explained by variables determining the tidal inundation regime, such as tidal range and tidal pattern, where high tidal range corresponds with low values of organic carbon content, potentially due to increased soil aeration and decomposition. Organic carbon density is found to increase with increasing marsh vegetation productivity and vegetation cover, which may promote plant carbon inputs into the sediment bed and trapping of sediments supplied by the tides. Further, organic carbon accumulation rate is mostly controlled by sea level rise, which has a positive effect on sediment accretion rate and thus on organic carbon accumulation rate. Our findings highlight that it is not one or a few environmental variables, but the interaction between different variables that affects the spatial variability of organic carbon sequestration in tidal marsh sediments.

Integrated impacts of mariculture on nitrogen cycling processes in the coastal groundwater of Beihai, southern China

Groundwater nitrogen (N) contamination in coastal zones is becoming an increasingly serious global issue. Mariculture, as a major anthropogenic activity, has profound impacts on coastal groundwater and constitutes an important source of coastal N contamination. However, a comprehensive understanding of the impact of mariculture on N cycling (especially N removal) is still lacking. Taking the Daguansha mariculture region in southern China as the study area, we aimed to investigate the environmental impact of mariculture on coastal groundwater and identify N cycling processes influenced by mariculture using hydrogeochemistry, multiple isotopes, coupled with 16S rRNA gene sequencing, and the quantitative polymerase chain reaction (qPCR) experiments. The results showed that the combined effects of seawater intrusion and seepage from land-based mariculture ponds have led to localized groundwater salinization in the region. Meanwhile, mariculture promotes nitrification and anammox processes in groundwater. The dominance of ammonia-oxidizing and anammox bacteria in the upper aquifer is attributable to local salinization, N and organic carbon input, as well as anoxic to suboxic conditions induced by seepage from aquaculture ponds. In addition, the gene abundances of ammonia oxidation (dominated by AOA) and denitrification were positively correlated, indicating their cooperative interaction. This study provides deeper insight into N cycling in coastal groundwater systems affected by extensive mariculture.

(Invited) Cleaning Coastal Environments through Electrocatalysis and Electromicrobiology

Coastal environments play an increasingly important role in the world's food supply. However, excessive inputs of carbon and nitrogen compounds to the seafloor are severely damaging the benthic ecosystem, causing eutrophication, algal blooms and red tides. Therefore, the development of new technologies to maintain the health of the benthic ecosystem is essential for sustainable use of marine resources. In this study, we investigated the redox homeostasis of benthic ecosystems using a marine oligochaete as a model benthic organism to assess the ecological resilience of aquafarms to nutrient influx. Real-time monitoring of the redox potential of a model benthic ecosystem allowed assessment of the homeostatic response of the system to nutrient addition. We also found that the movement and metabolic activity of benthic animals can be controlled by artificially manipulating the redox potential of the sediments. Further, we have developed electrocatalysts for nitrification, denitrification, and anaerobic ammonium oxidation to alleviate the nitrogen nutrient imbalance in marine environments. Given the importance of benthic animals in maintaining coastal ecosystems, electrochemical monitoring, and physiological regulation of marine oligochaetes, together with the electrocatalytic control of nitrogen cycling, could provide an intriguing approach towards sustainable use of marine resources.Reference Shono, M. Ito, A. Umezawa, K. Sakata, A. Li, J. Kikuchi, K. Ito, R. Nakamura, Tracing and regulating redox homeostasis of model benthic ecosystems for sustainable aquaculture in coastal environments, Front. Microbiol., 13:907703. DOI: 10.3389/fmicb.2022.907703 He, H. Ooka, Y. Li, Y. Kim, A. Yamaguchi, K. Adachi, D. Hashizume, N. Yoshida, S. Toyoda, S. H. Kim, R. Nakamura, Regulation of the electrocatalytic nitrogen cycle based on sequential proton–electron transfer, Nat. Catal., 2022, 5, 798-806. He, K. Adachi, D. Hashizume, R. Nakamura, Copper sulfide mineral performs nonenzymatic anaerobic ammonium oxidation through a hydrazine intermediate. Nat.Chem (in press)

Effects of anecic Amynthas aspergillum on the proportion and depth of straw-derived carbon input into soil

Straw mulching significantly affects the soil organic carbon (OC) pool, but its positive effect on soil OC is limited by the slow decomposition rate and shallow depth. Increasing the conversion rate of straw-derived carbon (C) to soil OC and the depth affected are important for enhancing soil carbon storage and mitigating global climate change. Anecic earthworms feed on surface organic residues and dwell underground; and thus, they can carry surface straw directly underground. However, previous studies have focused on European earthworms, and it is still unclear how Chinese widely distributed earthworms, such as the anecic Amynthas aspergillum, affect the conversion rate of straw-derived C into soil OC and the depth affected, and whether these effects are related to soil properties. Using 13C tracing technology, we established treatments with and without A. aspergillum in soil with added straw to examine how A. aspergillum regulate the distribution of straw-derived OC in soil profiles during incubation for 31 days. Soil samples from the plow layer (PL) and plow pan layer (PP) of subtropical corn land were used in this study to represent two soils of different properties. Visible earthworm casts were not observed on the surface soil. A. aspergillum significantly increased the loss of surface straw by 86.1 % and 43.1 % in the PL and PP soils, respectively (p < 0.05). The conversion rate of straw-derived C into soil OC was 21.8 ± 0.5 % in the presence of earthworms in the PL soils, which was significantly greater than that without earthworms (7.9 ± 0.5 %, p < 0.05). The conversion rates were 8.0 % and 12.8 % in the absence and presence of earthworms, respectively, in the PP soils. The A. aspergillum increased the soil depth affected by straw-derived C input in the profiles of both the PL (to 10–20 cm) and PP soils (to 5–10 cm) compared with the treatments without earthworms (0–5 cm). Thus, anecic A. aspergillum promoted the decomposition of straw, enhanced the conversion of straw-derived C into soil OC and depth affected, and the effects of A. aspergillum were greater in the fertile soils. The underground casting behavior of A. aspergillum, may enhance the effects of incorporation of surface straw-derived C in deep soils. We suggest that earthworm regulation combined with straw return could be considered in sustainable agriculture.

Highway to health: Microbial pathways of soil organic carbon accrual in conservation farming systems

Increasing pressure on arable land related to climate change mitigation and adaptation within recent policy frameworks has generated widespread interest in the effect of sustainable agricultural management practices on soil organic carbon (SOC) storage. Current frameworks point to soil microorganisms and their functioning as the key drivers of SOC accrual. This study provides a comprehensive on-farm assessment of changes in SOC formation pathways (physico-chemical and microbial) and the underlying drivers comparing three soil use systems: conservation and conventional farming systems as well as permanently vegetated adjacent reference soils (i.e., field margins) without agricultural land-use.Overall, our results indicated substantial increases in extractable organic carbon (+22 %), microbial biomass carbon (+29 %) and necromass carbon stocks (+11 %) in soils of conservation farming systems as compared to conventional farming systems. Differences between all three soil use systems were strongly pronounced in the surface soil (0–5 cm) and declined in deeper soil layers. Structural equation modelling revealed a varying influence of SOC storage pathways among soil use systems, with microbial-mediated (‘in-vivo’) turnover and direct sorption being the most dominant pathways. Moreover, diversity of crop rotation and tillage intensity were identified as the most important factors influencing extractable organic carbon and carbon-liberating enzyme activity within conservation farming management. Our on-farm approach demonstrates that enhanced bioavailable carbon inputs and reduced soil disturbance are the key drivers for microbially-controlled SOC accrual in arable soils and that conservation farming systems with extended plant coverage and increased crop diversity can substantially advance the restoration of soil health.

Changes in plant carbon inputs alter soil phosphorus dynamics in a coniferous forest ecosystem in subtropical mountain area

Plant carbon input aboveground and underground influences soil biological and physicochemical processes in forest ecosystems. However, compared with the well-known interactions between plant carbon and soil carbon or nitrogen, the impact on soil phosphorus (P) dynamics remains unclear. Here we investigated soil P dynamics in aggregates and bulk soil after one-year of plant carbon removal treatments (RL, removing litter; TG, tree girdling; RLTG, combination of removing litter and tree girdling; CK, control) under subtropical Pinus yunnanensis forest in a soil P-enriched degraded mountain area. Compared to CK, tree girdling significantly decreased the macroaggregate proportion and increased the microaggregate proportion by changing soil total carbon (TC) and Fe concentration. With the decrease of soil TC, the increase of HCl-Pi (inorganic P extracted by HCl) in microaggregate and silt and clay was significantly higher than that in macroaggregate. In addition, easily-available P and non-available P at bulk soils significantly declined and increase under RL and TG treatments, respectively. Redundancy analysis revealed that Fe, TC, and acid phosphatase activity were the main factors affecting P fractions in bulk soils. Higher δ18OP (oxygen isotope composition of phosphate) values of HCl-Pi pool and its significantly negative relationship with soil TC across the all carbon removal treatments, suggesting the weakened ability for plant to unlock soil bioavailable inorganic P combined with minerals induced by different plant carbon removal treatments. Overall, our results highlight that the importance of litter and root carbon in regulating soil P fractions and dynamics by altering the proportion of soil aggregates and the physicochemical properties of bulk soil.

The Regional Scale of Landscape Planning: the Possibilities for Measuring the Effectiveness of Nature-Based Solutions

Aim: The aim of this study is to investigate the measurement of landscape integrity based on ecological support processes in the Federal District, with the aim of defining a multi-scalar and multi-functional Regional Green Infrastructure Network (IVR) based on Nature-Based Solutions (NBS). Theoretical Framework: This topic presents the main concepts and theories that underpin the research. Landscape Ecology, Restoration Ecology, Green Infrastructure and Geodesign stand out, providing a solid basis for understanding the research context. Method: The methodology adopted for this research comprises the analysis of ecological support processes in the landscape, using the multispectral “CO2flux” index, related to the photosynthetic efficiency of vegetation and a proxy for energy, carbon and biomass inputs, which, together with the “Topographic Wetness Index”, related to the flow and accumulation of water and sediment in the landscape, provided the basis for the elaboration of a Geodesign process. Data was collected using multispectral satellite scenes - “Landsat 8”, collected during the dry season. Results and Discussion: The results obtained revealed the design of a mosaic of “hotspots”, corridors and patches that consolidates and intensifies carbon flows in the Federal District's landscape, with positive impacts on territorial resilience. In the discussion section, these results are contextualized in the light of the theoretical framework, highlighting the implications and relationships identified. Possible discrepancies and limitations of the study are also considered in this section. Research Implications: The practical and theoretical implications of this research are discussed, providing “insights” into how the results can be applied, or how to influence practices in the field of landscape planning. These implications can cover the design of Nature-Based Solutions at a regional scale, climate mitigation and adaptation actions for territories, and people's access to ecosystem services. Originality/Value: This study contributes to the literature by proposing the design of a regional network of green infrastructures based on the analysis of the flow of ecological support processes in the landscape, considering different demands and goals for environmental recovery. The relevance and value of this research is evidenced by the possibility of planning and designing mosaics in the landscape based on the identification of networks with greater potential for the provision of ecosystem services and, consequently, for the adaptation and mitigation of territories to climate impacts and those resulting from human occupation.

Past, Present, and Future of Forbs in Old-Growth Tropical and Subtropical Grasslands

Forbs are important contributors to species diversity and ecosystem functions in low-latitude grasslands, where they support diverse herbivore communities and millions of people. Native forb assemblages tolerate disturbances and physiological stressors (fire, herbivory, drought, and frost) that together have shaped their exceptional functional diversity. Yet, compared to trees and grasses, forbs have received much less attention in grassland studies until recently. Here, we review forb-centric literature to illustrate that land conversion and responsible management of fire and herbivory are crucial to maintaining forb diversity. Management practices promoting forb diversity offer (a) high-quality food items and medicinal resources that support rural livelihoods and animal diversity (from wild ungulates and livestock to fossorial rodents and insects), including their adaptive foraging patterns, and (b) carbon and nutrient inputs that regulate belowground processes. Improved understanding of the above- and belowground regeneration strategies of forbs is critical for restoration and conservation to secure their services in future old-growth tropical and subtropical grasslands.

Higher temperature accelerates carbon cycling in a temperate montane forest without decreasing soil carbon stocks

Global warming is expected to accelerate the cycling of soil organic carbon (SOC) and the assimilation of new carbon, but the net effect of those counteracting accelerations and their ultimate effects on SOC are still uncertain. This hinders the prediction of long-term changes in biospheric carbon stocks and SOC-climate feedbacks. Here, we studied the long-term effect of temperature on carbon cycling across a 3.2 °C altitudinal temperature gradient in a temperate forest ecosystem in New Zealand. Across the gradient, soil respiration rates increased with increasing temperature from 9.0 to 10.4 tC ha−1 yr−1, but SOC stocks down to 85 cm depth also tended to increase, from 154 to 176 tC ha−1, albeit non-significantly (P = 0.06). This system was able to maintain higher soil respiration rates at higher temperatures without reducing SOC because the higher respiration rates were sustained by higher litterfall rates. Aboveground litterfall increased from 1.8 to 2.4 tC ha−1 yr−1 and estimated belowground C inputs increased from 7.2 to 8.0 tC ha−1 yr−1 along the temperature gradient. These higher fluxes were associated with significantly (P < 0.05) increased biomass at higher temperatures. As a direct measure of the effect of temperature on carbon cycling processes, we also calculated the turnover rate of forest litter which increased about 1.4-fold across the temperature gradient. This study demonstrates that higher temperatures along the thermal gradient increased plant carbon inputs through enhanced gross primary production, which counteracted SOC losses through temperature-enhanced soil respiration. These results suggest that temperature sensitivities of both plant carbon inputs and SOC losses must be considered for predicting SOC-climate feedbacks.