Root Carbon Research Articles

Efficient potassium (K) recycling and root carbon (C) metabolism improve K use efficiency in pear rootstock genotypes

To investigate K absorption and transport mechanisms by which pear rootstock genotypes respond to low-K stress, seedlings of a potassium-efficient pear rootstock, Pyrus ussuriensis, and a potassium-sensitive rootstock, Pyrus betulifolia, were supplied with different K concentrations in solution culture. Significant differences in the absorption rate, Vmax and Km between the genotypes indicate that P. ussuriensis acclimatizes more readily to low-K stress by regulating its absorption and internal cycling. We also found that the K content in the leaves of P. betulifolia was significantly lower than that of P. ussuriensis, and the proportion of K that was returned to root from shoot, relative to K that was transported from root to shoot, was greater in P. ussuriensis, which suggests that P. ussuriensis more efficiently recycles and reuses K. When the transcriptomes of the two genotypes were compared, we found that photosynthetic genes such as CABs (Chlorophyll a/b-binding proteins), Lhcbs (Photosystem II-related proteins), and Psas (Photosystem Ⅰ associated proteins) displayed lower expression in leaves of P. betulifolia under no-K conditions, but not in P. ussuriensis. However, in the root of P. ussuriensis, carbon metabolism-related genes SS (Sucrose Synthase), HK (HexoKinase) and SDH (Sorbitol Dehydrogenase) and components of the TCA cycle (Tricarboxylic Acid cycle) were differentially expressed, indicating that changes in C metabolism may provide energy for increased K+ cycling in these plants, thereby allowing it to better adapt to the low-K environment. In addition, exogenous supply of various sugars to the roots influenced K+ influx, supporting the conclusion that sugar metabolism in roots significantly affects K+ absorption in pear.

马尾松和杉木人工林细根碳氮磷化学计量特征随土层深度的变化

PDF HTML阅读 XML下载 导出引用 引用提醒 马尾松和杉木人工林细根碳氮磷化学计量特征随土层深度的变化 DOI: 10.5846/stxb202203250740 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 福建省杰出青年基金项目滚动资助项目(2014J07005) Variation of carbon, nitrogen and phosphorus stoichiometric characteristics of fine roots in Masson pine and Chinese fir plantations with soil depth Author: Affiliation: Fund Project: Fujian Outstanding Youth Rolling Grant Project (2014J07005) 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:为探究马尾松和杉木人工林细根碳(C)、氮(N)、磷(P)浓度及其化学计量比随土层深度变化的特征,于2011年4月在福建省三明市金丝湾森林公园陈大林业采育场内测定马尾松和杉木人工林五个土层深度(0-10 cm、10-20 cm、20-40 cm、40-60 cm、60-80 cm)细根的C、N、P浓度、比根长(SRL)及其土壤养分浓度,结果表明:林分类型显著影响细根C浓度,但对细根N、P浓度无显著影响,马尾松人工林细根C浓度显著大于杉木人工林。土层深度显著影响马尾松和杉木人工林细根N、P浓度,对C浓度无影响,细根N、P浓度随土壤深度的增加呈指数下降。马尾松和杉木人工林细根N、P浓度与土壤全氮(TN)、全磷(TP)浓度以及SRL均呈正相关。拟合直线表明马尾松人工林和杉木人工林细根N养分获取能力的不同,马尾松对N养分的获取能力更强,而杉木通过SRL获取养分的能力比马尾松更强,可能体现了两种人工林细根N获取策略的差异。马尾松和杉木人工林在不同土层细根N ∶ P比值(33.5±2.81、30.18±2.10)均大于16,表明两者均受P限制,但细根N ∶ P不受土壤N ∶ P和SRL的影响。马尾松和杉木人工林细根N和P浓度受土层深度的影响,与土壤养分和细根形态特征变化有关。 Abstract:In order to examine the characteristics of fine root carbon (C), nitrogen (N), and phosphorus (P) concentrations and their stoichiometric ratios changing with soil depth in Masson pine (Pinus massoniana) and Chinese fir (Cunninghamia lanceolata) plantations, the experiments were conducted in April 2011, in Jinsiwan Forest Park, Sanming City, Fujian Province. The samples of fine roots in five soil depths (0-10 cm, 10-20 cm, 20-40 cm, 40-60 cm, 60-80 cm) of Masson pine and Chinese fir plantations were collected in the big forestry breeding farm to determine C, N and P concentration as well as specific root length (SRL). Soil nutrient contents were also measured. The results showed that forest type significantly influenced fine root C concentration, but not fine root N and P concentration, and that fine root C concentration was significantly greater in the plantation of Masson pine than in the plantation of Chinese fir. Soil depth significantly influenced fine root N and P concentrations, but not C concentrations, and fine root N and P concentrations decreased exponentially with increasing soil depth in both pinus sylvestris and fir plantations. Fine root N and P concentrations were positively correlated with soil Total nitrogen (TN) and Total phosphorus (TP) concentrations as well as SRL in both Horsetail Pine and Fir plantations. The fitted straight lines indicated the difference in the fine root N nutrient acquisition capacity between horsetail pine and fir plantations, with horsetail pine having a greater ability to acquire N nutrients and fir having a greater ability to acquire nutrients through SRL than horsetail pine, possibly reflecting the difference in fine root N acquisition strategies between the two plantations. The fine root N ∶ P ratios (33.5±2.81 and 30.18±2.10) of both horsetail pine and fir plantations were greater than 16 in different soil layers, indicating that both were P-limited, but fine root N ∶ P was not influenced by soil N ∶ P and SRL. Fine root N and P concentrations in plantations of horsetail pine and fir were influenced by soil depth and were related to changes in soil nutrients and fine root morphological characteristics. 参考文献 相似文献 引证文献

Rhizosphere microbe populations but not root traits induced by drought in Populus euphratica males

How sex-related root traits and soil microbes and their interactions respond to drought remains unclear. Here, we investigated how fine root traits and the composition of rhizosphere microbial communities in Populus euphratica females and males respond to drought in concert in 17-year-old plantations. Females increased specific root length (SRL) in response to drought. However, males showed no changes in their roots but significant increases in arbuscular mycorrhizal hyphal biomass and population of Gram-negative bacteria in the rhizosphere. Also, fungal symbiotroph communities associated with root systems in males differed from those in females under drought. We further demonstrated that the Gram-positive to Gram-negative bacteria ratios positively correlated with the SRL, while fungi to bacteria ratios were negatively correlated. Meanwhile, the relative abundance of symbiotrophs was negatively correlated with the SRL, while saprotroph abundance was positively correlated. Nevertheless, the relative abundance of symbiotrophs was positively correlated with the root carbon content (RCC). These findings indicate that microbial responses to drought depend highly upon the sex of the plant and microbial group and are related to root trait adjustments to drought. This discovery also highlights the role of plant-microbial interactions in the ecosystems of P. euphratica forest plantations.

Changes in the Physiological and Morphometric Characteristics and Biomass Distribution of Forage Grasses Growing under Conditions of Drought and Silicon Application.

Research on mitigating the effects of water scarcity by applying silicon to perennial grasses is still insufficient. This study was conducted to investigate the effect of spring and summer droughts and silicon applications on gas exchange parameters; the morphometric characteristics of root systems; and the biomass distribution of Festulolium braunii, Festuca arundinacea, and Lolium perenne cultivars. Plants were treated with a drought during the tillering phase once a year (during spring or summer regrowth) for 21 days. Foliar nutrition with silicon was applied twice under the drought conditions. Grasses in a pot experiment were cut three times during vegetation. The plants that were exposed to the drought had lower values of the gas exchange parameters than those that were well watered. The beneficial effect of silicon was related to the reduction of excessive water loss through transpiration during the spring drought. Under the drought and silicon applications, the water use efficiency, root dry mass, and length increased compared to the control. Moreover, silicon increased the proportion of both the finer and thicker roots in F. braunii and L. perenne, while the distribution of the root diameter changed least in the more resistant F. arundinacea. Silicon also reduced the carbon content in the roots and increased root carbon accumulation. Our results indicated that Si may help perennial forage grasses cope better with drought stress. This was due to the allocation of carbon to the roots to develop the fine root network, increasing the length and root biomass and improving the water use efficiency.

Changes in diversity patterns and assembly processes of soil nematode communities during forest secondary succession on the Loess Plateau

The secondary succession of plant communities involves considerable changes in belowground communities of microbes and animals. Nematodes are the most abundant animals in soil and play a vital role in maintaining soil biodiversity and functions. Exploring the ecological processes that drive soil nematode diversity and community assembly during secondary succession can help to gain a predictive and mechanistic understanding of soil biodiversity maintenance and ecosystem recovery. In this study, based on the investigation of soil nematode community composition and structure, we examined the changes in nematode α- and β-diversity along forest secondary succession and disentangled the contributions of different community assembly processes (deterministic and stochastic processes) in each successional stage on the Loess Plateau, a key region of ecological restoration in China. The results showed that: (1) Abundances of plant-parasitic and bacterial-feeding nematodes were lower in the pioneer and climax forest stages than in the grassland and shrub stages. Meanwhile, nematode community composition considerably changed, with the dominant trophic group changing from plant-parasitic (grassland stage: 35.48%) and bacterial-feeding (shrub stage: 35.63%) to fungal-feeding (pioneer and climax forest stages: 30.65–36.44%). These changes might be associated with higher carbon-to-nitrogen ratios of fine roots and litters, as well as higher litter phosphorus content (LTP), in pioneer and climax forests; (2) Nematode α-diversity and β-diversity peaked in the shrub stage and decreased substantially in the climax forest stage, but β-diversity differed more significantly between successional stages than α-diversity. Fine root biomass, root carbon to nitrogen ratio, and litter phosphorus content were the main predictors of nematode α- and β-diversity, while geographic distance positively affected nematode β-diversity; (3) In the grassland and climax forest stages, deterministic processes dominated nematode community assembly, probably due to the strong influence of environmental factors such as the quantity or quality of plant resources. Especially, in the climax forest stage, the low quality of plant resources might be responsible for the low nematode diversity and network complexity. In the shrub and pioneer forest stages, the contribution of stochastic processes gradually increased, and nematode networks became more complex. Taken together, our results emphasize the importance of litter and root quality in regulating nematode diversity and community assembly, especially in the late successional stage, which provides insights into forest restoration and sustainable management in the Loess Plateau and other similar arid and semiarid regions.

Quantification of carbon-water dynamics in soil-perennial grass (Bothriochloa ischaemum) feedbacks under drought stress following a double isotope-labelled pulse experiment

Current studies have described photosynthetic and hydraulic processes in plants using parameters from the whole plant or particular organs. Quantification of carbon and water resource consumption and coupling between plant organs is poorly understood but important for predicting carbon and water coupled processes in grassland ecosystem drought responses. We determined the correlations between water transport parameters and carbon allocation in leaves, stems, branches, and roots of the grass Bothriochloa ischaemum, sampled 0, 6, 24, 48, 216, and 360 h after 13C-18O pulse-labeling under three drought treatments: control (CK), mild stress (MS) and serious stress (SS). We found that: (1) The sum of 13C in roots, soil, and rhizosphere soil was higher than the amount of 13C respired by roots under all treatments. The ratio of stored to respired 13C in the SS had a significantly lower than CK, indicating that the underground grass-soil system was a carbon sink rather than a carbon source. (2) 216 h after the application of 18O-labeled water, the proportion of 18O-labeled water in the aboveground portion of plants was up to 60% under MS, significantly greater than under SS (36.5%) and under CK (45.9%). Root density was mainly distributed in the 0–15 cm soil layer under mild drought stress. Both results suggest that grasses respond to mild drought by increasing topsoil root density to absorb soil water and improve the water transfer ratio to the aboveground portion of the plants. (3) During the double-labeling experiment, the ratio of 13C accumulated to 18O consumed in roots under mild drought was significantly higher than in other treatments. In contrast, these ratios in old leaves and stems under drought were significantly lower than in the control treatment, indicating that B.ischaemum experiences a trade-off between increasing root carbon and water utilization and reducing old leaf and stem carbon and water utilization under mild drought stress.

Relationships between tree functional traits and leaf nitrogen and phosphorus resorption efficiencies in subtropical young plantations

We examined the relationship between tree functional traits and leaf nitrogen and phosphorus resorption efficiencies across 29 species in 3-year-old pure plantations in subtropical China. The results showed that the average nitrogen (NRE) and phosphorus (PRE) resorption efficiencies in 29 young plantations were 50.5% and 57.3%, respectively. The average NRE of 22 arbuscular mycorrhizal (AM) tree species was 52.7%, significantly higher than that of the seven ectomycorrhizal (EM) tree species (45.1%). NRE was positively correlated with fine root tissue density across the 29 tree species. PRE was positively correlated with root diameter in the seven EM tree species. Functional traits of 22 AM tree species were not associated with NRE and PRE. Among all of the 29 tree species, mycorrhizal type, specific leaf area, fine root tissue density, leaf thickness, and the interaction effects of mycorrhizal type with leaf thickness explained 27% variation in NRE. Specific root length, fine root carbon content, fine root carbon to nitrogen ratio, mycorrhizal type, leaf carbon content, and the interaction effects of mycorrhizal type with leaf carbon content explained 35% variation in PRE. Root functional trait of subtropical species could predict nitrogen and phosphorus resorption efficiencies. The model with multiple functional traits could better reveal the relative importance of different biological factors on nutrient resorption efficiency.

First assessment of root biomass and root carbon and nitrogen stocks in Turkish floodplain forests.

Estimation of whole root biomass including coarse and larger roots and root balls can provide better understanding of carbon and nitrogen stocks in floodplain forests. Whole root systems of nine ash trees (Fraxinus angustifolia Vahl.) and six alder trees (Alnus glutinosa L.) trees ranging in diameter breast height (dbh) from 29.1 to 72.0cm for ash and from 29.1 to 44.3cm for alder were excavated, and their small < 1cm, medium 1-4cm, larger > 4cm and root-ball biomass, and root carbon and nitrogen stocks were determined in Karacabey floodplain forest in Bursa, Turkey. In addition, for the method comparison, small root biomass (< 1cm) was also determined using soil-core method. The whole root biomass of ash trees varied from 167.7 to 186.8Mgha-1. Alder trees had lower whole root biomass than ash trees ranging from 49.0 to 63.6Mgha-1. The determination of small root biomass by soil excavation method was nearly two-fold higher than by soil core method. Both root carbon and nitrogen stocks showed an increase with increasing root diameter. Among the tree characteristics (dbh, age, height, and volume), the dbh showed the highest correlation with whole root biomass and root carbon and nitrogen stocks for both tree species. It is concluded that young trees can have higher small, medium, and large root biomass and store more C and N in those roots, whereas older trees can have higher root-ball biomass and root-ball carbon and nitrogen stocks in Karacabey floodplain forests.

Can seasonal fire management reduce the risk of carbon loss from wildfires in a protected Guinea savanna?

AbstractFire is fundamental to the functioning of tropical savannas and routinely used as a management tool. Shifting prescribed burning from later to earlier in the growing season has the potential to reduce greenhouse gas emissions. However, large uncertainties surround the impact of seasonal burning on longer term plant and soil carbon sequestration. In this study, we quantify ecosystem carbon storage across burn seasons and histories in a wet‐to‐mesic Guinea tropical savanna in Mole National Park, Ghana. Aboveground (plant and litter) and belowground (soil plus roots) carbon storage was quantified across four burning seasons and histories: recent (&lt;3 years) early‐season burns, recent late‐season burns, old (&gt;4 years) late‐season burns, and long‐unburned (&gt;15 years) sites. We found that recent late‐season burns significantly lowered belowground carbon storage to a depth of 17 cm compared with all other burn seasons and histories. Belowground carbon was 1.2 kg C m−2, or 27% lower, for recent late‐season burns compared with prescribed early‐season burns. However, in older late‐season burns sites, belowground carbon “recovered” after 4–13 burn years to comparable storage as long‐unburned and early‐season burn sites. For most aboveground carbon pools, there was no significant difference in carbon storage across burn seasons and histories, except higher aboveground tree carbon in long‐unburned sites. We suggest that observed changes in belowground carbon are likely due to the turnover and production of root carbon. Prescribed early‐season burning is promoted to reduce greenhouse gas emissions and our findings affirm that early‐season burning has limited impact on plant and soil carbon stocks compared with long‐unburned sites. While early‐season burning regimes will have some patches that become late‐season wildfires, our results suggest on balance early‐season burning regimes are a low‐risk land management practice in reducing plant and soil carbon storage losses and sustaining a patch‐mosaicked landscape with multiple other ecosystem service benefits for savannas.

Estimation and Mapping of Actual and Potential Grassland Root Carbon Storage: A Case Study in the Altay Region, China

The actual root carbon storage (ARCS) and potential root carbon storage (PRCS) of grasslands play an important role in the global carbon balance and carbon neutralization. However, estimation of these indicators is difficult. In addition, their spatial patterns and crucial driving factors also require clarification. In this study, an approach for accurate estimation of ARCS and PRCS was developed incorporating a support vector machine model and high-accuracy surface modeling. Based on field data collected from Altay Prefecture in 2015, the estimation accuracy (R2) of root biomass in the 0–10, 10–20, and 20–30 cm soil layers of grassland were 0.73, 0.63, and 0.60, respectively. In addition, the spatial patterns of actual root carbon density (ARCD) and potential root carbon density (PRCD) were analyzed. The ARCD increased with the increase in elevation. High PRCD was located on hillsides with a gentle slope. The dominant interaction factors for the ARCD spatial pattern were temperature and precipitation, whereas the main interaction factors for the PRCD pattern were temperature and slope. The grassland ARCS and PRCS in Altay Prefecture were estimated to be 48.52 and 22.69 Tg C, respectively. We suggest there is considerable capacity to increase grassland ARCS in the study area.

Elevated O3 Exerts Stronger Effects than Elevated CO2 on the Functional Guilds of Fungi, but Collectively Increase the Structural Complexity of Fungi in a Paddy Soil.

Global climate change is characterized by altered global atmospheric composition, including elevated CO2 and O3, with important consequences on soil fungal communities. However, the function and community composition of soil fungi in response to elevated CO2 together with elevated O3 in paddy soils remain largely unknown. Here we used twelve open-top chamber facilities (OTCs) to evaluate the interactive effect of CO2 (+ 200ppm) and O3 (+ 40ppb) on the diversity, gene abundance, community structure, and functional composition of soil fungi during the growing seasons of two rice cultivars (Japonica, Wuyujing 3 vs. Nangeng 5055) in a Chinese paddy soil. Elevated CO2 and O3 showed no individual or combined effect on the gene abundance or relative abundance of soil fungi, but increased structural complexity of soil fungal communities, indicating that elevated CO2 and/or O3 promoted the competition of species-species interactions. When averaged both cultivars, elevated CO2 showed no individual effect on the diversity or abundance of functional guilds of soil fungi. By contrast, elevated O3 significantly reduced the relative abundance and diversity of symbiotrophic fungi by an average of 47.2% and 39.1%, respectively. Notably, elevated O3 exerts stronger effects on the functional processes of fungal communities than elevated CO2. The structural equation model revealed that elevated CO2 and/or O3 indirectly affected the functional composition of soil fungi through community structure and diversity of soil fungi. Root C/N and soil environmental parameters were identified as the top direct predictors for the community structure of soil fungi. Furthermore, significant correlations were identified between saprotrophic fungi and root biomass, symbiotrophic fungi and root carbon, the pathotroph-symbiotroph and soil pH, as well as pathotroph-saprotroph-symbiotroph and soil microbial biomass carbon. These results suggest that climatic factors substantially affected the functional processes of soil fungal, and threatened soil function and food production, highlighting the detrimental impacts of high O3 on the function composition of soil biota.

Stump height after regenerative cutting of sea-buckthorn (Hippophae rhamnoides) affects fine root architecture and rhizosphere soil stoichiometric properties

This study aimed to clarify the effects of stumping on the fine root architecture of decaying Hippophae rhamnoides plantation in feldspathic sandstone areas, and to determine the optimal stump height that is contributive to the recovery and growth of H. rhamnoides. The fine root architecture, and the econometric properties of soil organic carbon (C), total nitrogen (N) and total phosphorus (P) in fine roots and rhizosphere roots as well as the underlying correlations were analyzed after different stump height treatments (0 cm, 10 cm, 15 cm, 20 cm, no stumping). The above treatments all significantly affected fine root architecture, which grew into fishtail branches in all treatments. Especially, at the stump height of 15 cm, the topological index (0.75), total branching rate (1.91), specific root length (69.69), and average diameter (0.62) of fine roots were all better than after other treatments. Stumping did not significantly affect C content of fine roots, P and C: N ratio of rhizosphere soils, but very significantly affected other nutrient contents and the stoichiometric ratios of both fine roots and rhizosphere soils. These results indicate the stump height of 15 cm better promote the growth of H. rhamnoides. Principal component analysis shows the N, P, C:N of fine roots, and the C, C:P of rhizosphere soils maximally affect the fine root architecture. Our findings are critical for vegetation recovery and soil erosion prevention and control in feldspathic sandstone areas.

Salinity reduces site quality and mangrove forest functions. From monitoring to understanding

Mangroves continue to be threatened across their range by a mix of anthropogenic and climate change-related stress. Climate change-induced salinity is likely to alter the structure and functions of highly productive mangrove systems. However, we still lack a comprehensive understanding of how rising salinity affects forest structure and functions because of the limited availability of mangrove field data. Therefore, based on extensive spatiotemporal mangrove data covering a large-scale salinity gradient, collected from the world's largest single tract mangrove ecosystem – the Bangladesh Sundarbans, we, aimed to examine (QI) how rising salinity influences forest structure (e.g., stand density, diversity, leaf area index (LAI), etc.), functions (e.g., carbon stocks, forest growth), nutrients availability, and functional traits (e.g., specific leaf area, wood density). We also wanted to know (QII) how forest functions interact (direct vs. indirect) with biotic (i.e., stand structure, species richness, etc.) and abiotic factors (salinity, nutrients, light availability, etc.). We also asked (QIII) whether the functional variable decreases disproportionately with salinity and applied the power-law (i.e., Y = a Xb) to the salinity and functional variable relationships. In this study, we found that rises in salinity significantly impede forest growth and produce less productive ecosystems dominated by dwarf species while reducing stand structural properties (i.e., tree height, basal area, dominant tree height, LAI), soil carbon (organic and root carbon), and macronutrient availability in the soil (e.g., NH4+, P, and K). Besides, species-specific leaf area (related to resource acquisition) also decreased with salinity, whereas wood density (related to resource conservation) increased. We observed a declining abundance of the salt-intolerant climax species (Heritiera fomes) and dominance of the salt-tolerant species (Excoecaria agallocha, Ceriops decandra) in the high saline areas. In the case of biotic and abiotic factors, salinity and salinity-driven gap fraction (high transmission of light) had a strong negative impact on functional variables, while nutrients and LAI had a positive impact. In addition, the power-law explained the consistent decline of functional variables with salinity. Our study disentangles the negative effects of salinity on site quality in the Sundarbans mangrove ecosystem, and we recognize that nutrient availability and LAI are likely to buffer the less salt-tolerant species to maintain the ability to sequester carbon with sea-level rise. These novel findings advance our understanding of how a single stressor—salinity—can shape mangrove structure, functions, and productivity and offer decision makers a much-needed scientific basis for developing pragmatic ecosystem management and conservation plans in highly stressed coastal ecosystems across the globe.

Root Biomass and Root Carbon and Nitrogen Stocks of Ash, Alder, and Oak Stands in Karacabey Floodplain Forest

Root Biomass and Root Carbon and Nitrogen Stocks of Ash, Alder, and Oak Stands in Karacabey Floodplain Forest

Effects of variable temperature and moisture conditions on respiration and nonstructural carbohydrate dynamics of tree roots

• Low soil moisture lowered the root respiration rate of boreal Scots pines. Root respiration was clearly higher in warm and dry than cool and moist year. • Root respiration peaked after the aboveground growth began to decrease. • The root fructose and glucose contents correlated negatively with soil moisture. The method used to determine root respiration should be selected carefully. In warming climates, soil water content (SWC) may act as an important factor in determining belowground carbon dynamics in boreal forests. Here, we estimated the respiration and nonstructural carbohydrate (NSC) concentrations of tree roots in a mature Scots pine ( Pinus sylvestris L.) stand in southern Finland during two growing seasons with contrasting weather conditions. Root respiration was estimated with four different methods: 1) incubating excised roots, 2) partitioning forest floor respirations with root exclusion, or 3) based on temperature response functions and 4) modelling with the whole-tree carbon model ‘CASSIA’. In addition, we conducted a drought experiment in a greenhouse to determine the effect of reduced soil-water availability on respiration by incubating soil and roots of Scots pine saplings. We observed that the respiration of incubated roots of Scots pine saplings and soil decreased with drying after excluding the effect of temperature on respiration (R RES ), soil being more sensitive to drought than roots. Similarly, R RES of incubated roots in the field was significantly decreased by lowered SWC, whereas respiration of the entire root system estimated with other methods was clearly higher in dryer and warmer than moister and cooler year. Nevertheless, incubated roots excavated from the topsoil are most affected by drying soil, which might not reflect the response of the entire root system. R RES of incubated roots was negatively associated with root fructose and glucose concentrations. At the same time, root fructose, glucose and sucrose concentrations were negatively associated with SWC due to their role in osmoregulation. Thereby it seems that R RES does not directly follow the changes in NSCs despite the apparent correlation. Our study highlights the responsive nature of root carbon dynamics in varying weather events that should be taken into account in estimating and modelling the impacts of warming climate.

Root stoichiometry explains wheat endophytes and their link with crop production after four decades of fertilization

Fertilization can impact root endophytic microbiomes and food production. However, the impacts of decades of continued fertilization on root microbiomes, and their link with ongoing crop production, remain poorly understood. Here, we used a four decade-long fertilization experiment, including contrasting types of organic and inorganic fertilization, to investigate the effects of long-term fertilization on multi-kingdom root endophytic microbiomes, including keystone species (modules within microbial networks), and their indirect associations with the production of wheat, which is one of the most important crops worldwide. We found that long-term inorganic (nitrogen, phosphorus, potassium (NPK)) and organic (NPK with straw (NPKS) and NPK with cow manure (NPKM)) fertilization had significant impacts on the community composition of endophytic arbuscular mycorrhizal fungi (AMF), bacteria, and non-mycorrhizal fungi. In addition, compared with NPK fertilization, NPKS and NPKM amendments significantly decreased the microbial network complexity, which was associated with changes in the root iron content. Finally, we identified an important subset of keystone root endophyte species within the microbial network (Module #2), which was positively correlated with wheat yield, and affected by changes in root carbon to phosphorus ratio. This study provides evidence that long-term fertilization can affect keystone root endophytic species in the root microbiome, with implications for food security in an over-fertilized world.

Fine-root functional trait response to nitrogen deposition across forest ecosystems: A meta-analysis

Nitrogen (N) deposition has complex effects on vegetation dynamics and nutrient cycling in terrestrial ecosystems. However, how N deposition alters fine root traits remains unclear in forest ecosystems. Here, we carried out a synthesis based on 890 paired observations of 14 fine root traits from 79 articles to assess the effects of N deposition on fine root traits. The results showed that N deposition mainly affected root nutrient content and stoichiometry. Specifically, N deposition increased the root N content, root carbon: phosphorus (C:P) and root nitrogen: phosphorus (N:P) ratio, but decreased the root P content and root C:N ratio. Moreover, N deposition increased fine root respiration, but had no significant effect on other root morphological and physiological traits. N deposition effects on fine root biomass, root tissue density and fungal colonization decreased with N deposition duration. Compared to fine root P content, N deposition effects on fine root C content and C:P ratio increased with N deposition level. Moreover, the interaction between N deposition level and duration significantly affected fine root biomass. N deposition effects on fine-root biomass decreased with greater N deposition duration, especially in high N deposition experiments. Moreover, the effect of N deposition on root diameter decreased with mean annual temperature and mean annual precipitation. N form, forest type and soil depth significantly affect the effect of N deposition on fine root C:P. Therefore, the effects of N deposition on fine root traits were not only determined by N deposition level, duration and their interactions, but also regulated by abiotic factors. These findings highlight the diverse responses of fine root traits to N deposition have strong implications for forest ecosystems soil carbon stocks in a world of increasing N deposition associated with decreased root-derived carbon inputs and increases in fine-root respiration.

Reforesting Native America with Drones: Rooting Carbon with Arborescent Governmentality and Decolonial Geoengineering

The Confederated Colville Tribes collaborated with DroneSeed, a forestry drone start-up, to use drones to replant their tribal forest after a devastating fire. Using concepts from Bernard Stiegler to interrogate ethnographic data, this article argues that forestry drones are pharmaka: their biopolitics can be therapeutic, that is, negentropic, capable of reversing ecological simplification. Drone forestry is a type of arborescent governmentality, a tree-based computer-coded attempt to control the growth of a forest. For the Colville, this negentropy is also an act of sovereignty that protects culture and honors multispecies relationships. For DroneSeed, it is an experiment in negentropic geoengineering, an attempt to profitably leverage technologies and biological regeneration to sequester carbon and reduce global existential risk. Ultimately the project was not the success desired; the failure of technoliberal projects that blend ecological and economic liberalism shows that a more radical approach might be necessary to root carbon and slow capitalism.

Stand structure and carbon storage of a young mangrove plantation forest in coastal area of Bangladesh: The promise of a natural solution

Globally, with the growing importance of mangroves for providing ecosystem services and mitigating climate change, it is still uncertain whether planted mangroves can be the counterpart of natural mangroves, and thus the role of planted mangroves is still less understood. Therefore, this study aimed to assess the stand structure and carbon storage of a young mangrove plantation in Satkhira District, Bangladesh and to compare it with the natural mangrove forest (i.e., Sundarbans) to understand the potential of this young mangrove plantation as a nature-based solution to climate change. In addition, to better understand the spatial dynamics of afforested mangrove forests, we investigated and compared both above and below-ground carbon stocks between the landward and riverward sites. We collected both above (height and diameter at breast height, DBH) and belowground (i.e., coarse and fine root) data from 16 plots with a total area of 1600 m2 in two paired transects, eight plots each in landward and riverward sites. Aboveground carbon stocks were estimated using the species-specific allometric models from the biophysical tree parameters (i.e., height and DBH). Besides, belowground root (≥ 20 mm) carbon was measured by direct weighting after collecting soil samples through coring. Stand structural attributes (i.e., density, basal area, and DBH) showed a significant difference between the two sites, whereas Sonneratia apetala was found as the dominant species (IV = 188.7∼207.1) in both forest sites. The mean carbon stock of this plantation was 49.1 Mg C ha−1, while the mean aboveground carbon (AGC) was 37.3 Mg C ha−1. The landward site contributed significantly more AGC (40.1 Mg C ha−1) than the riverward (34.4 Mg C ha−1) site (p<0.05). Besides, the mean belowground roots carbon (BGRC) of this plantation was 11.8 ± 1.4 Mg C ha−1, where the riverward site contributed significantly more root carbon (14.3 Mg C ha−1) than the landward site (9.4 Mg C ha−1) (p<0.05). Tree density and basal area showed a significant positive relationship with BGRC. Although only two species were planted, after 15 years, we observed the total number of species reached nine. The carbon stock, progressive species richness in this plantation reflects the significance of young mangrove plantations in sequestering carbon to mitigate climate change and biodiversity conservation as nature-based solutions which may be useful for future coastal afforestation and restoration programs.

Root Carbon Resources Determine Survival and Growth of Young Trees Under Long Drought in Combination With Fertilization.

Current increases in not only the intensity and frequency but also the duration of drought events could affect the growth, physiology, and mortality of trees. We experimentally studied the effects of drought duration in combination with fertilization on leaf water potential, gas exchange, growth, tissue levels of non-structural carbohydrates (NSCs), tissue NSC consumption over-winter, and recovery after drought release in oak (Quercus petraea) and beech (Fagus sylvatica) saplings. Long drought duration (>1 month) decreased leaf water potential, photosynthesis, and NSC concentrations in both oak and beech saplings. Nitrogen fertilization did not mitigate the negative drought effects on both species. The photosynthesis and relative height increment recovered in the following rewetting year. Height growth in the rewetting year was significantly positively correlated with both pre- and post-winter root NSC levels. Root carbon reserve is critical for tree growth and survival under long-lasting drought. Our results indicate that beech is more sensitive to drought and fertilization than oak. The present study, in a physiological perspective, experimentally confirmed the view that the European beech, compared to oak, may be more strongly affected by future environmental changes.