Fine Root Carbon Research Articles

Adapting to climate change: responses of fine root traits and C exudation in five tree species with different light-use strategy.

Trees that are categorised by their light requirements have similarities in their growth strategies and adaptation mechanisms. We aimed to understand the complex responses of elevated air humidity on whole tree fine root carbon (C) exudation (ExC) and respiration rate, morphology, and functional distribution in species with different light requirements. Three light-demanding (LD) species, Populus × wettsteinii, Betula pendula, and Pinus sylvestris, and two shade-tolerant species, Picea abies and Tilia cordata saplings were grown in growth chambers under moderate and elevated air relative humidity (eRH) at two different inorganic nitrogen sources with constant air temperature and light availability. The proportion of assimilated carbon released by ExC, and respiration decreased at eRH; up to about 3 and 27%, respectively. There was an indication of a trade-off between fine root released C and biomass allocation. The elevated air humidity changed the tree biomass allocation and fine root morphology, and the responses were species-specific. The specific fine root area and absorptive root proportion were positively related to canopy net photosynthesis and leaf nitrogen concentration across tree species. The variation in ExC was explained by the trees' light-use strategy (p < 0.05), showing higher exudation rates in LD species. The LD species had a higher proportion of pioneer root tips, which related to the enhanced ExC. Our findings highlight the significant role of fine root functional distribution and morphological adaptation in determining rhizosphere C fluxes in changing environmental conditions such as the predicted increase of air humidity in higher latitudes.

The Seasonal Impact of Thinning Intensities on Soil Carbon Cycling in the Lesser Xing’an Range, Northeast China

Forest degradation, driven by human and natural factors, diminishes ecological functions and carbon storage. Understanding the complex dynamics of soil carbon pools is crucial for the global carbon cycle, although these dynamics are poorly understood. This study examines how different thinning intensities influence seasonal soil carbon cycling in degraded forests. ANOVA revealed significant differences in soil properties across treatments (p &lt; 0.05). Redundancy analysis and random forest analyses were used to explore relationships among thinning intensities, soil properties, and carbon sequestration. Thinning significantly altered soil attributes, as revealed by field experiments and data analysis. Moderate thinning (20% intensity) significantly enhanced litter retention and soil nutrient levels year-round (p &lt; 0.05). Seasonal variations affected soil carbon dynamics and lower thinning intensities improved carbon sequestration in spring and summer. Conversely, higher thinning intensities led to carbon loss in autumn and winter. Litter carbon, fine root carbon, and correction factor significantly respond to thinning intensities year-round as examined through redundancy analysis and random forest analyses. Findings indicate moderate thinning effectively enhances soil carbon sequestration in degraded forests. Strategically planned thinning could aid climate change mitigation by boosting forest soil carbon storage, influencing forest management and conservation.

SOIL CARBON STOCKS NOT LINKED TO ABOVEGROUND LITTER INPUT AND CHEMISTRY OF OLD-GROWTH FOREST AND ADJACENT PRAIRIE

ABSTRACT The long-standing assumption that aboveground plant litter inputs have a substantial influence on soil organic carbon storage (SOC) and dynamics has been challenged by a new paradigm for SOC formation and persistence. We tested the importance of plant litter chemistry on SOC storage, distribution, composition, and age by comparing two highly contrasting ecosystems: an old-growth coast redwood (Sequoia sempervirens) forest, with highly aromatic litter, and an adjacent coastal prairie, with more easily decomposed litter. We hypothesized that if plant litter chemistry was the primary driver, redwood would store more and older SOC that was less microbially processed than prairie. Total soil carbon stocks to 110 cm depth were higher in prairie (35 kg C m−2) than redwood (28 kg C m−2). Radiocarbon values indicated shorter SOC residence times in redwood than prairie throughout the profile. Higher amounts of pyrogenic carbon and a higher degree of microbial processing of SOC appear to be instrumental for soil carbon storage and persistence in prairie, while differences in fine-root carbon inputs likely contribute to younger SOC in redwood. We conclude that at these sites fire residues, root inputs, and soil properties influence soil carbon dynamics to a greater degree than the properties of aboveground litter.

Forest management practices change topsoil carbon pools and their stability

Forest management may lead to changes in soil carbon and its stability, and the effects are variable owing to the differences in management methods. Our study aimed to determine the impacts of different forest management practices on soil carbon pools and their stability. We chose a natural oak forest, where different forest-management strategies have been practiced. Forest management strategies included cultivating target trees by removing interference trees (CNFM), optimizing the forest spatial structure by the structural parameters (SBFM), reducing the stand density by harvesting timber (SFCS), and using unmanaged forests as controls (NT). Topsoil (depth of 0–10 cm) was collected after eight years of forest management. Soil organic carbon (SOC), labile organic carbon components and the microbial community were determined, and SOC chemical compositions were assessed by nuclear magnetic resonance. The CNFM and SFCS strategies had smaller dissolved organic carbon contents than the NT and SBFM strategies, and the CNFM strategy increased the ratio of alkyl C and o-alkyl C, indicating that the SOC was more stable. Forest management strategies changed the SOC and its labile C pool by adjusting the soil total nitrogen,β-glucosidase, cellobiohydrolase, fine-root carbon and fungal operational taxonomic units, and the SOC chemical compositions were influenced by the number of fungal species. These findings suggest that the soil organic carbon decreased, but its stability increased in the natural forest under the practice of cultivating target trees by removing interference trees. The SOC pools could be regulated by soil nitrogen, enzyme activity, fine roots, and fungi, while soil fungi could affect SOC stability.

Coordinated variation in root and leaf functional traits of Hippophae rhamnoides treated at different stump heights in feldspathic sandstone areas of Inner Mongolia.

This study was aimed to clarify the effects of stumping on root and leaf traits as well as the tradeoffs and synergies of decaying Hippophae rhamnoides in feldspathic sandstone areas, and to select the optimal stump height that contributed to the recovery and growth of H. rhamnoides. variations and coordination between leaf traits and fine root traits of H. rhamnoides were studied at different stump heights (0, 10, 15, 20cm, and no stumping) in feldspathic sandstone areas. All functional traits of the leaves and roots, except the leaf C content (LC) and the fine root C content (FRC), were significantly different among different stump heights. The total variation coefficient was the largest in the specific leaf area (SLA), which is therefore the most sensitive trait. Compared to non-stumping, SLA, leaf N content (LN), specific root length (SRL) and fine root N content (FRN) all improved significantly at stump height of 15cm, but leaf tissue density (LTD), leaf dry matter content (LDMC), leaf carbon to nitrogen ratio (LC : LN), fine root tissue density (FRTD), fine root dry matter content (FRDMC) and fine root carbon to nitrogen ratio (FRC : FRN) all decreased significantly. The leaf traits of H. rhamnoides at different stump heights follow the leaf economic spectrum, and the fine roots show a similar trait syndrome to the leaves. SLA and LN are positively correlated with SRL and FRN and negatively with FRTD and FRC : FRN. LDMC and LC : LN are positively correlated with FRTD and FRC : FRN, and negatively correlated SRL and RN. The stumped H. rhamnoides changes to the 'rapid investment-return type' resource trade-offs strategy, and the growth rate is maximized at the stump height of 15cm. Our findings are critical to the prevention and control of vegetation recovery and soil erosion in feldspathic sandstone areas.

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

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.

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.

Comparison of Leaf and Fine Root Traits Between Annuals and Perennials, Implicating the Mechanism of Species Changes in Desertified Grasslands.

Annual species show traits, such as shortleaf lifetimes, higher specific leaf area, and leaf nutrient concentrations, that provided a more rapid resource acquisition compared to perennials. However, the comparison of root traits between the annuals and perennials is extremely limited, as well as the trade-offs of leaf and fine root traits, and resource allocation between leaf and root, which may provide insight into the mechanism of species changes in arid and semi-arid areas. With lab analysis and field observation, 12 traits of leaf and fine root of 54 dominant species from Horqin Sandy Land, Northeastern China were measured. The organization of leaf and fine root traits, and coordination between leaf and fine root traits of annual and perennial plants were examined. Results showed that there were differences between annuals and perennials in several leaves and fine root traits important in resource acquisition and conservation. Annuals had higher leaf area (LA), specific LA (SLA), and specific root length (SRL) but lower leaf dry-matter content (LDMC), leaf tissue density (LTD), leaf carbon concentration (LC), and fine root dry-matter content (FRDMC) than perennials. Leaf nitrogen (LN) concentration and fine root nitrogen concentration (FRN) were negatively related to LTD and FRDMC in annuals, while FRN was positively related to FRTD and fine root carbon concentration (FRC), and LA was positively related to LN in perennials. These implied that annuals exhibited tough tissue and low palatability, but perennials tend to have smaller leaves to reduce metabolism when N is insufficient. Annuals showed significant positive correlations between FRC/FRDMC and LDMC/LTD/LC, suggesting a proportional allocation of photosynthate between leaf and fine root. In perennials, significant negative correlations were detected between LN, LC, and SRL, fine root tissue density (FRTD), as well as between LA and FRTD/FRC. These indicated that perennials tend to allocate more photosynthate to construct a deeper and rigid roots system to improve resource absorption capacity in resource-limited habitats. Our findings suggested that annuals and perennials differed considerably in terms of adaptation, resource acquisition, and allocation strategies, which might be partly responsible for species changes in desertified grasslands. More broadly, this work might be conducive to understand the mechanism of species changes and could also provide support to the management and restoration of desertified grassland in arid and semi-arid areas.

Degradation-driven changes in fine root carbon stocks, productivity, mortality, and decomposition rates in a palm swamp peat forest of the Peruvian Amazon

BackgroundAmazon palm swamp peatlands are major carbon (C) sinks and reservoirs. In Peru, this ecosystem is widely threatened owing to the recurrent practice of cutting Mauritia flexuosa palms for fruit harvesting. Such degradation could significantly damage peat deposits by altering C fluxes through fine root productivity, mortality, and decomposition rates which contribute to and regulate peat accumulation. Along a same peat formation, we studied an undegraded site (Intact), a moderately degraded site (mDeg) and a heavily degraded site (hDeg) over 11 months. Fine root C stocks and fluxes were monthly sampled by sequential coring. Concomitantly, fine root decomposition was investigated using litter bags. In the experimental design, fine root stocks and dynamics were assessed separately according to vegetation type (M. flexuosa palm and other tree species) and M. flexuosa age class. Furthermore, results obtained from individual palms and trees were site-scaled by using forest composition and structure.ResultsAt the scale of individuals, fine root C biomass in M. flexuosa adults was higher at the mDeg site than at the Intact and hDeg sites, while in trees it was lowest at the hDeg site. Site-scale fine root biomass (Mg C ha−1) was higher at the mDeg site (0.58 ± 0.05) than at the Intact (0.48 ± 0.05) and hDeg sites (0.32 ± 0.03). Site-scale annual fine root mortality rate was not significantly different between sites (3.4 ± 1.3, 2.0 ± 0.8, 1.5 ± 0.7 Mg C ha−1 yr−1 at the Intact, mDeg, and hDeg sites) while productivity (same unit) was lower at the hDeg site (1.5 ± 0.8) than at the Intact site (3.7 ± 1.2), the mDeg site being intermediate (2.3 ± 0.9). Decomposition was slow with 63.5−74.4% of mass remaining after 300 days and it was similar among sites and vegetation types.ConclusionsThe significant lower fine root C stock and annual productivity rate at the hDeg site than at the Intact site suggests a potential for strong degradation to disrupt peat accretion. These results stress the need for a sustainable management of these forests to maintain their C sink function.

Nonstructural carbohydrates, carbon and nitrogen concentrations in fine roots of Quercus variabilis secondary forests after two different periods of regeneration

Aim of study: Quercus variabilis is a sclerophyllous oak with strong resprouting capabilities and whose regeneration is facilitated by the development of stump shoots following disturbance. During secondary forest regeneration, fine roots are important organs relative to changes in stand characteristics. Here, we aimed to provide novel insights into the chemical composition variations in roots with seasonality and root order hierarchy in a Q. variabilis forest at different periods of regeneration.Area of study: The forest is located next to the Baxianshan National Reserve in the southern part of the Yanshan Mountains, Tianjin, China.Materials and methods: Six plots were established in stands with either eight or 40 years of regeneration for the repeated sampling of fine roots during the growing season of 2019. All roots were classified by branch order. The first three root orders were collected to analyse the concentrations of nonstructural carbohydrate, carbon, and nitrogen.Main results: Short-term regeneration stands showed a reduction in soil moisture and an increase in soil temperature because of the lower canopy cover, compared to long-term stands. Soluble sugar and starch were lower in roots of short-term stands than in those of long-term stands, and the decreasing ratio of both parameters was observed in short-term stands. Less carbon and greater nitrogen concentrations of fine roots were found in short-term stands than in long-term stands, which resulted in weaker C/N ratio values. Nonstructural carbohydrate was stored more in higher order roots than terminal roots and presented greater sensitivity to forest regeneration. Redundancy discriminate analysis demonstrated that the nonstructural carbohydrate concentrations in roots were affected positively by canopy cover and negatively by soil temperature.Research highlights: The seasonal dynamics and branch allocation of chemical reserves in fine roots varied in the different periods of forest regeneration because of the discrepancy between the canopy cover and soil traits. Less nonstructural carbohydrate and a lower C/N ratio at the onset of forest regeneration may elevate the risk of root death.Keywords: soluble sugar; starch; forest regeneration; root order; C/N ratio; redundancy discriminate analysis.

Effect of snow removal on the fine root biomass, dynamics, and carbon and nitrogen concentrations of oak and dwarf bamboo, Sasa in eastern Hokkaido, Japan

ABSTRACT Fine root is a significant component in carbon (C) and nitrogen (N) dynamics in temperate forests. Winter processes affect plant growth and nutrient concentration, however, the effect of reduced snowpack on fine root remains unclear. Here, we conducted snow removal manipulation and investigated the fine root biomass and necromass, dynamics (production, mortality and disappearance) and the C and N concentrations of Quercus crispula (oak) and Sasa nipponica (Sasa), in mineral topsoil (0–10 cm) throughout 1 year. The effect of snow removal on the fine root biomass and necromass was insignificant. The effect of snow removal on the production, mortality and disappearance of fine root, and on total C and N concentrations of fine root biomass and necromass were insignificant. The fine root biomass of oak was significantly greater than that of Sasa, although the fine root necromass of Sasa was significantly greater than that of oak. Fine root necromass showed clear seasonal change, although a seasonal change of fine root biomass was unclear. Total C concentration in the fine root biomass and necromass of oak was significantly higher than that of Sasa. Total N concentration in the fine root necromass in May 2015, when after the snow removal, of Sasa was significantly higher than that of oak, in both snow removal and control plots. Our results showed that the fine root necromass of Sasa supplies more N than that of oak in spring, regardless of snowpack depth.

Water availability drives fine root dynamics in a Eucalyptus woodland under elevated atmospheric CO2 concentration

Abstract Fine roots are a key component of carbon and nutrient dynamics in forest ecosystems. Rising atmospheric [CO2] (eCO2) is likely to alter the production and activity of fine roots, with important consequences for forest carbon storage. Yet empirical evidence of the role of eCO2 in driving root dynamics is limited, particularly for grassy woodlands, an ecosystem type of global importance. We sampled fine roots across seasons over a 2‐year period to examine the effects of eCO2 on their biomass, production, turnover and functional traits in a native mature grassy Eucalyptus woodland in eastern Australia (EucFACE). Fine root biomass, production and turnover varied greatly through time, increasing as soil water content declined. Despite a lack of consistent effects of eCO2 on fine root biomass, production or turnover across the 2‐year sampling period, we found enhanced production pulses under eCO2 between 10‐ and 30‐cm soil depth. In addition, eCO2 led to greater carbon and phosphorus concentrations in fine roots and increased root diameter, but no detectable effects on other morphological traits. Synthesis. We found minor quantitative effects of eCO2 on fine root biomass dynamics that were largely driven by temporal variations in soil water availability. Our results suggest that in this mature grassy woodland, and perhaps also in other similar forested ecosystem types, eCO2 effects are small and transient. This also implies a limited ability of these systems to mitigate climate change through below‐ground mechanisms. A free Plain Language Summary can be found within the Supporting Information of this article.

Improving models of fine root carbon stocks and fluxes in European forests.

Fine roots and above‐ground litterfall play a pivotal role in carbon dynamics in forests. Nonetheless, direct estimation of stocks of fine roots remains methodologically challenging. Models are thus widely used to estimate these stocks and help elucidate drivers of fine root growth and turnover, at a range of scales.We updated a database of fine root biomass, necromass and production derived from 454 plots across European forests. We then compared fine root biomass and production to estimates obtained from 19 different models. Typical input variables used for the models included climate, net primary production, foliage and above‐ground biomass, leaf area index (LAI), latitude and/or land cover type. We tested whether performance could be improved by fitting new multiple regression models, and explored effects of species composition and sampling method on estimated fine root biomass.Average fine root biomass was 332 g/m2, and necromass 379 g/m2, for European forests where the average fine root production was 250 g m−2 year−1. Carbon fraction in fine roots averaged 48.4%, and was 1.5% greater in broadleaved species than conifers.Available models were poor predictors of fine root biomass and production. The best performing models assumed proportionality between above‐ and below‐ground compartments, and used remotely sensed LAI or foliage biomass as key inputs. Model performance was improved by use of multiple regressions, which revealed consistently greater biomass and production in stands dominated by broadleaved species as well as in mixed stands even after accounting for climatic differences. Synthesis. We assessed the potential of existing models to estimate fine root biomass and production in European forests. We show that recalibration reduces by about 40% errors in estimates currently produced by the best available models, and increases three‐fold explained variation. Our results underline the quantitative significance of fine roots (live and dead) to the global carbon cycle.

Appearance can be deceptive: shrubby native mangrove species contributes more to soil carbon sequestration than fast-growing exotic species

Increased recognition of mangrove high carbon storage potential has prompted carbon sequestration as one of the main goals in mangrove afforestation. In southern China, the introduced fast-growing Sonneratia apetala and native Kandelia obovata have been widely afforested since the mid-1980s. While S. apetala has spread extensively, the implications and ecosystem services are yet to be ascertained. Soil/root coring was conducted in two 12-year-old S. apetala and K. obovata plantations, respectively. Fine-root mass and soil physicochemical properties were obtained and compared. Fine-root mass and soil organic carbon stock ranged between 129 and 394 g m−2 and 7.9 and 15.8 Mg C ha−1, respectively. Soil organic carbon stock and fine-root mass were both significantly different between the forests. Organic carbon in soil is significantly correlated to fine-root mass and organic carbon in fine roots. The contribution to soil organic carbon by fine-root mass may be different between the two species. Growth and physiological traits not only may influence stand characteristics but also soil properties that drive overall carbon accumulation. Contrary to the original expectation driving the introduction, the shrubby native K. obovata may have higher potential as a carbon sink than the introduced S. apetala.

Evaluating GPP and Respiration Estimates Over Northern Midlatitude Ecosystems Using Solar‐Induced Fluorescence and Atmospheric CO2 Measurements

AbstractOn regional to global scales, few constraints exist on gross primary productivity (GPP) and ecosystem respiration (Re) fluxes. Yet constraints on these fluxes are critical for evaluating and improving terrestrial biosphere models. In this study, we evaluate the seasonal cycle of GPP, Re, and net ecosystem exchange (NEE) produced by four terrestrial biosphere models and FLUXCOM, a data‐driven model, over northern midlatitude ecosystems. We evaluate the seasonal cycle of GPP and NEE using solar‐induced fluorescence retrieved from the Global Ozone Monitoring Experiment‐2 and column‐averaged dry‐air mole fractions of CO2 (XCO2) from the Total Carbon Column Observing Network, respectively. We then infer Re by combining constraints on GPP with constraints on NEE from two flux inversions. An ensemble of optimized Re seasonal cycles is generated using five GPP estimates and two NEE estimates. The optimized Re curves generally show high consistency with each other, with the largest differences due to the magnitude of GPP. We find optimized Re exhibits a systematically broader summer maximum than modeled Re, with values lower during June–July and higher during the fall than Re. Further analysis suggests that the differences could be due to seasonal variations in the carbon use efficiency (possibly due to an ecosystem‐scale Kok effect) and to seasonal variations in the leaf litter and fine root carbon pool. The results suggest that the inclusion of variable carbon use efficiency for autotrophic respiration and carbon pool dependence for heterotrophic respiration is important for accurately simulating Re.

Retention trees slow post-harvest fine-root decomposition in a coastal temperate rainforest

Fine roots are a dominant, but often overlooked source of carbon (C) in forest soils, and decomposition of this material may have important consequences for C storage and turnover in forest ecosystems. Forest harvesting modifies soil physicochemical properties and microbial communities, which may lead to faster decomposition rates, but the effect of harvesting on fine-root decomposition is rarely investigated. Variable-retention harvesting, where some trees are left on site after harvest, often results in lower soil moisture and temperature, and increased ectomycorrhizal diversity relative to clearcut harvesting. As such, this harvesting practice may influence fine-root decomposition rates. In Douglas-fir forests in coastal British Columbia, we measured fine-root (<2 mm diameter) decomposition rates in variable-retention (aggregate and dispersed arrangements), clearcut, and uncut treatments, and determined if any effects persisted as stands aged. Within the variable-retention treatments, we also examined if fine-root decomposition rates varied with distance from retention trees or retention patches. Further, we determined which soil physicochemical variables best explained variation in fine-root carbon loss after two years of decomposition. Increased tree coverage slowed fine-root decomposition; fine roots decomposed as slowly under variable-retention treatments as in uncut stands, and 15–19% more carbon was retained in these treatments relative to the clearcut treatment. Fine roots also decomposed faster with increasing distance from retention patches or retention trees as decomposition was twofold slower in the aggregate centre relative to open areas, with similar patterns observed in the dispersed retention treatment. However, fine roots decomposed at similar rates in forests and stands with more advanced regeneration, suggesting the effects of harvesting on decomposition rates was not persistent. Across all sampling locations, 37% of the variation in fine-root carbon loss was explained by fine-root biomass, and nitrate, potassium and sulphate availability. Nitrate availability was also positively correlated with the proportional mass of carbon lost during the decomposition experiment, suggesting that fine-root decomposition is sensitive to harvesting-induced changes in soil physicochemistry, and that variable-retention harvesting moderates the effects of harvesting on decomposition rates. These findings indicate that shortly after harvest, retention of even single trees can prevent the increase in fine-root decomposition rates associated with clearcut harvesting in these coastal Douglas-fir forests. Accordingly, management practices such as variable-retention harvesting that retain some trees in a cutblock may reduce soil C losses following forest harvesting.

Bayesian integration of flux tower data into a process-based simulator for quantifying uncertainty in simulated output

Abstract. Parameters of a process-based forest growth simulator are difficult or impossible to obtain from field observations. Reliable estimates can be obtained using calibration against observations of output and state variables. In this study, we present a Bayesian framework to calibrate the widely used process-based simulator Biome-BGC against estimates of gross primary production (GPP) data. We used GPP partitioned from flux tower measurements of a net ecosystem exchange over a 55-year-old Douglas fir stand as an example. The uncertainties of both the Biome-BGC parameters and the simulated GPP values were estimated. The calibrated parameters leaf and fine root turnover (LFRT), ratio of fine root carbon to leaf carbon (FRC : LC), ratio of carbon to nitrogen in leaf (C : Nleaf), canopy water interception coefficient (Wint), fraction of leaf nitrogen in RuBisCO (FLNR), and effective soil rooting depth (SD) characterize the photosynthesis and carbon and nitrogen allocation in the forest. The calibration improved the root mean square error and enhanced Nash–Sutcliffe efficiency between simulated and flux tower daily GPP compared to the uncalibrated Biome-BGC. Nevertheless, the seasonal cycle for flux tower GPP was not reproduced exactly and some overestimation in spring and underestimation in summer remained after calibration. We hypothesized that the phenology exhibited a seasonal cycle that was not accurately reproduced by the simulator. We investigated this by calibrating the Biome-BGC to each month's flux tower GPP separately. As expected, the simulated GPP improved, but the calibrated parameter values suggested that the seasonal cycle of state variables in the simulator could be improved. It was concluded that the Bayesian framework for calibration can reveal features of the modelled physical processes and identify aspects of the process simulator that are too rigid.

武夷山不同海拔黄山松细根碳、氮、磷化学计量特征对土壤养分的适应

PDF HTML阅读 XML下载 导出引用 引用提醒 武夷山不同海拔黄山松细根碳、氮、磷化学计量特征对土壤养分的适应 DOI: 10.5846/stxb201701040034 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31722007，31370589）；福建省自然科学基金项目（2015J01123）；福建省青年拔尖人才支持计划；国家重点研发计划课题（2017YFC0505400） Response of fine root carbon, nitrogen, and phosphorus stoichiometry to soil nutrients in Pinus taiwanensis along an elevation gradient in the Wuyi mountains Author: Affiliation: Fund Project: 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:细根的生态化学计量特征承载着植物生存环境的变化信息，从而为探索全球变化对植物内在机制的影响提供理论依据。以江西武夷山国家级自然保护区内五个不同海拔梯度（1200、1400、1600、1800、2000 m）的黄山松为对象，运用挖掘法采样后测定细根C、N、P含量及化学计量比特征，研究不同的海拔下细根对土壤养分变化的适应规律。结果表明：（1）黄山松细根C含量年平均值为（486.27±64.32）mg/g，海拔对其没有显著的影响，与土壤养分之间不存在显著的相关关系。（2）细根N含量年平均值为（9.26±2.09）mg/g，海拔对其没有显著的影响，但与土壤C含量存在显著的正相关关系。（3）细根P含量年平均值为（0.39±0.13）mg/g，与海拔梯度及土壤P含量均存在极显著正相关关系，而与土壤碳氮比呈显著负相关关系。（4）细根氮磷比为26.94±12.51，与海拔梯度、土壤P含量及土壤碳氮比均显著负相关。因此，黄山松细根吸收N是以消耗C为代价；细根P主要受土壤P供应量的限制；武夷山地区N沉降将进一步增加植物的氮磷比，加剧黄山松生长的P限制。 Abstract:The ecological stoichiometric characteristics of fine roots reflect environmental changes. Thus, they provide a theoretical basis to explore the mechanisms of global changes affecting plants. The objective of the present study was to analyze the stoichiometry of Pinus taiwanensis is fine roots inhabiting five different elevation gradients (i.e., 1,200, 1,400, 1,600, 1,800, and 2,000 m) in Wuyishan National Nature Reserve. The fine roots were collected and the carbon (C), nitrogen (N), and phosphorus (P) concentrations and stoichiometric characteristics were analyzed. The results showed that:(1) The annual average C concentration of fine roots was (486.27±64.32) mg/g, and was not significantly affected by elevation. There was no significant correlation between the C concentration of fine roots and soil nutrients; (2) The annual average N concentration of fine roots was (9.26±2.09) mg/g, and was not significantly affected by elevation. But, there was a close correlation between the N concentration of fine roots and C concentration of soils; (3) The annual average P concentration of fine roots was (0.39±0.13) mg/g, which was closely correlated with altitude gradients and soil P contents, but negatively correlated with the soil C:N ratio; (4) The annual average N:P ratio of fine roots was 26.94±12.51, which was negatively correlated with altitude, soil P concentration, and the soil C:N ratio. Therefore, fine roots absorb N at the expense of C, fine root P is primarily limited by soil P supply, which would be further exacerbated by N deposition in the Wuyi Mountains. 参考文献 相似文献 引证文献

天山森林植物功能性状与碳库沿海拔梯度的变化

PDF HTML阅读 XML下载 导出引用 引用提醒 天山森林植物功能性状与碳库沿海拔梯度的变化 DOI: 10.5846/stxb201707111254 作者: 作者单位: 新疆大学资源与环境科学学院绿洲生态教育部重点实验室,新疆大学资源与环境科学学院绿洲生态教育部重点实验室;新疆林科院森林生态研究所,新疆林科院森林生态研究所,新疆林科院森林生态研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（U1503187）；“十二五”农村领域国家科技计划课题（2015BAD07B03-03）；新疆维吾尔自治区教育厅研究生科研创新项目（XJGRI2017021）；2017年新疆林业科技项目 The variations in plant functional traits and forest carbon content with altitudinal gradients in the Tianshan Mountains Author: Affiliation: Key Laboratory of Oasis Ecology,College of Resource and Environment Science,Xinjiang University,Key Laboratory of Oasis Ecology,College of Resource and Environment Science,Xinjiang University;Institute of Forest Ecology,Xinjiang Academy of Forestry,Institute of Forest Ecology,Xinjiang Academy of Forestry,Institute of Forest Ecology,Xinjiang Academy of Forestry Fund Project: 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:植物功能性状是能够将植物个体特征、群落结构和生态系统功能结合起来的良好载体，但关于在环境梯度上如何通过植物功能性状的连续变化来构建群落、以及植物功能性状如何反映生态系统功能等问题尚有较多疑问。为探讨天山森林植物功能性状与其碳库在海拔梯度上的联系，分析了14个群落尺度上的植物功能性状指标和各组分碳密度沿海拔的变化规律及二者之间的关系。结果表明：（1）受海拔梯度上环境因子的影响，群落尺度上植物功能性状和碳密度的垂直分布并不一致：随海拔升高，叶片碳氮比（C/N）逐渐上升，叶片碳含量（Cleaf）、比根长（SRL）和植株高度（H）升高后降低，叶绿素含量（Chl）、细根磷含量（Proot）、叶片氮磷比（N/P）逐渐下降，细根碳含量（Croot）先升高后趋于平缓，细根氮含量（Nroot）先下降后又有所回升，叶片氮含量（Nleaf）、木质素含量（LLC）、叶干物质含量（LDMC）、细根干物质含量（RDMC）在各海拔段间无显著差异；（2）比根长（SRL）和植株高度（H）通过影响资源的获取和利用，C与P通过对养分的限制和在器官中的分配，从而影响植被光合作用，与天山森林碳密度显著相关；高木质素含量（LLC）导致植物残体分解速率变慢而与土壤碳密度（SCD）和群落总碳密度（TCD）呈显著负相关关系。随海拔升高，植被碳密度（VCD）先升后降，土壤碳密度（SCD）和总碳密度（TCD）逐渐升高。植物功能性状与环境因子和森林的结构功能相互作用、相互影响，三者之间的关系还需在大尺度上进一步验证。 Abstract:Plant functional traits are important characteristics for understanding the relationship between individual, community, and ecosystem functions. In the present study, we established 43 sample sets to examine 12 types of plant functional traits and corresponding carbon density information at the community scale. The objective of this work was to determine the internal relationship between the adaptive variation in functional traits and the carbon density of forest communities along an elevation gradient. The results show that at a higher altitude, the carbon to nitrogen ratio (C/N) in leaves increased linearly, whereas carbon content (Cleaf), specific root length (SRL), and height (H) initially increased and then decreased. Chlorophyll content (Chl) and fine root phosphorus content (Proot) decreased with elevation and fine root carbon content (Croot) initially increased and then flattened out with altitude. Fine root nitrogen content (Nroot) initially decreased and then increased, whereas leaf nitrogen content (Nleaf), lignin content (LLC), and fine root dry matter content (RDMC) showed no significant difference with altitude. SRL, H, the content of C, P in leaf and root showed significant correlations with vegetation carbon density (VCD) and soil carbon density (SCD) in the Tianshan forest, as they have influential effects on the photosynthesis of vegetation, in which SRL and H could affect plants resource acquisition and utilization, whereas C and P would limit nutrient availability. There was a negative correlation between LLC and SCD in the Tianshan forest, as LLC would limit the decomposition rate of plant residue. VCD initially increased and then decreased, whereas SCD and total carbon density (TCD) increased gradually with altitude. Plant functional traits interact with environmental factors and forest structure functions at multi-ecological levels, and the relationship between the three components needs to be validated on a large scale. 参考文献 相似文献 引证文献