Fine Root Litter Research Articles

Fine Roots in Hemiboreal Forest Stands and Clearcut Areas with Nutrient-Rich Organic Soils in Latvia: Morphological Traits, Production and Carbon Input

Within this study, we evaluated the fine root (trees and understory vegetation combined) morphological traits, fine root production (FRP), and carbon (C) input with fine root litter in forest stands (dominated by either coniferous or deciduous trees) and clearcut areas (previously dominated by coniferous trees) with nutrient-rich organic soils. The study was conducted in 26 sites in hemiboreal forest land in Latvia and summarizes the results obtained in a two-year study (2020–2022) using the root ingrowth method. Traits and production of fine roots varied significantly depending on forest development stage (stand or clearcut area), dominant tree species type (coniferous or deciduous), and soil drainage status (drained or naturally wet). According to the results of the second study year, mean FRP among groups of study sites varied from 0.58 ± 0.13 to 1.38 ± 0.28 t ha−1 yr−1, while C input with fine root litter ranged from 0.28 ± 0.06 to 0.68 ± 0.14 t C ha−1 yr−1. More than half (59 ± 4%) of the total FRP occurred in the upper 0–20 cm soil layer. FRP tended to correlate positively with soil C/N ratio and negatively with soil pH and soil nutrient concentration. Incubating ingrowth cores for at least two years is strongly recommended to accurately estimate annual FRP and C input. This helps to avoid potential underestimation that may occur when using results of only one incubation year (12 months after ingrowth core installation). This study provided new insights into the dynamics and traits of fine roots and will help to improve the accuracy of C flow estimation in hemiboreal forests with nutrient-rich organic soils in Latvia.

Fine root morphological traits and production in coniferous- and deciduous-tree forests with drained and naturally wet nutrient-rich organic soils in hemiboreal Latvia

Fine root production is one of the key elements of carbon (C) turnover in soil in afforested peatlands and forest lands with organic soils. We estimated variability in fine root morphology traits and annual production in hemiboreal forests dominated by coniferous trees (Norway spruce) and deciduous trees (silver birch and black alder) with nutrient-rich organic soils in Latvia. In total, 23 research sites were established in drained and naturally wet forests of different ages, and ingrowth core techniques were used to sample fine roots and subsequently determine fine root morphology traits and annual production, and calculate C input through fine root litter. Significant differences in several fine root morphological traits between coniferous- and deciduous-trees-dominated stands were found. Fine root production tended to be higher in coniferous-trees-dominated stands and positively correlated with several forest stand characteristics: stand age, average tree diameter at breast height, basal area and average tree height, but negatively correlated with nitrogen and phosphorus content in soil. C input through fine root litter ranged up to 0.46 ± 0.16 t ha-1 yr-1. It is necessary to conduct further research, including multi-annual estimates in a wider set of forest stands with diverse dominant tree species and growing conditions, to improve estimates, patterns and understanding of C flows through fine root litter in drained and naturally wet organic soils.

Fine root litter quality regulates soil carbon storage efficiency in subtropical forest soils

Decomposing root litter is a major contributor to soil carbon (C) storage in forest soils. During decomposition, the quality of root litter could play a critical role in soil C storage. However, it is unclear whether root litter quality influences soil C storage efficiency. We conducted a two-year greenhouse decomposition experiment using 13C-labeled fine root litter of two tree species to investigate how root litter quality, represented by C to nitrogen (C/N) ratios, regulates decomposition and C storage efficiency in subtropical forest soils in China. ‘High-quality’ root litter (C/N ratio = 26) decayed faster during the first year (0–410 days), whereas ‘low-quality’ root litter (C/N ratio = 46) decomposed faster toward the end of the two-year period (598–767 days). However, over the two years of the study, mass loss from high-quality root litter (29.14 ± 1.42%) was lower than ‘low-quality’ root litter (33.01 ± 0.54%). Nonetheless, root litter C storage efficiency (i.e., the ratio of new root litter-derived soil C to total mineralized root litter C) was significantly greater for high-quality root litter, with twice as much litter-derived C stored in soils compared to low-quality root litter at the end of the experiment. Root litter quality likely influenced soil C storage via changes in microbial diversity, as the decomposition of high-quality litter declined with increasing bacterial diversity, whereas the amount of litter-derived soil C from low-quality litter increased with fungal diversity. Our results thus reveal that root litter quality mediates decomposition and C storage in subtropical forest soils in China and future work should consider the links between root litter quality and soil microbial diversity.

Effects of land-use change and disturbance on the fine root biomass, dynamics, morphology, and related C and N fluxes to the soil of forest ecosystems at different elevations at Mt. Kilimanjaro (Tanzania)

Tropical forests are threatened by anthropogenic activities such as conversion into agricultural land, logging and fires. Land-use change and disturbance affect ecosystems not only aboveground, but also belowground including the ecosystems' carbon and nitrogen cycle. We studied the impact of different types of land-use change (intensive and traditional agroforestry, logging) and disturbance by fire on fine root biomass, dynamics, morphology, and related C and N fluxes to the soil via fine root litter across different ecosystems at different elevational zones at Mt. Kilimanjaro (Tanzania). We found a decrease in fine root biomass (80–90%), production (50%), and C and N fluxes to the soil via fine root litter (60–80%) at all elevation zones. The traditional agroforestry 'Chagga homegardens' (lower montane zone) showed enhanced fine root turnover rates, higher values of acquisitive root morphological traits, but similar stand fine root production, C and N fluxes compared to the natural forest. The decrease of C and N fluxes with forest disturbance was particularly strong at the upper montane zone (60 and 80% decrease, respectively), where several patches of Podocarpus forest had been disturbed by fire in the previous years. We conclude that changes on species composition, stand structure and land management practices resulting from land-use change and disturbance have a strong impact on the fine root system, modifying fine root biomass, production and the C and N supply to the soil from fine root litter, which strongly affects the ecosystems' C and N cycle in those East African tropical forest ecosystems.

Fungal community composition and genetic potential regulate fine root decay in northern temperate forests.

Understanding how genetic differences among soil microorganisms regulate spatial patterns in litter decay remains a persistent challenge in ecology. Despite fine root litter accounting for ~50% of total litter production in forest ecosystems, far less is known about the microbial decay of fine roots relative to aboveground litter. Here, we evaluated whether fine root decay occurred more rapidly where fungal communities have a greater genetic potential for litter decay. Additionally, we tested if linkages between decay and fungal genes can be adequately captured by delineating saprotrophic and ectomycorrhizal fungal functional groups based on whether they have genes encoding certain ligninolytic class II peroxidase enzymes, which oxidize lignin and polyphenolic compounds. To address these ideas, we used a litterbag study paired with fungal DNA barcoding to characterize fine root decay rates and fungal community composition at the landscape scale in northern temperate forests, and we estimated the genetic potential of fungal communities for litter decay using publicly available genomes. Fine root decay occurred more rapidly where fungal communities had a greater genetic potential for decay, especially of cellulose and hemicellulose. Fine root decay was positively correlated with ligninolytic saprotrophic fungi and negatively correlated with ECM fungi with ligninolytic peroxidases, likely because these saprotrophic and ectomycorrhizal functional groups had the highest and lowest genetic potentials for plant cell wall degradation, respectively. These fungal variables overwhelmed direct environmental controls, suggesting fungal community composition and genetic variation are primary controls over fine root decay in temperate forests at regional scales.

Response of fungal and bacterial communities in fine root litter with different diameters to nitrogen application

Response of fungal and bacterial communities in fine root litter with different diameters to nitrogen application

Moso bamboo expansion reduced soil N2O emissions while accelerated fine root litter decomposition: contrasting non-additive effects

Moso bamboo expansion reduced soil N2O emissions while accelerated fine root litter decomposition: contrasting non-additive effects

Increase in carbon input by enhanced fine root turnover in a long-term warmed forest soil

Fine root litter represents an important carbon input to soils, but the effect of global warming on fine root turnover (FRT) is hardly explored in forest ecosystems. Understanding tree fine roots' response to warming is crucial for predicting soil carbon dynamics and the functioning of forests as a sink for atmospheric carbon dioxide (CO2). We studied fine root production (FRP) with ingrowth cores and used radiocarbon signatures of first-order, second- to third-order, and bulk fine roots to estimate fine root turnover times after 8 and 14 years of soil warming (+4 °C) in a temperate forest. Fine root turnover times of the individual root fractions were estimated with a one-pool model. Soil warming strongly increased fine root production by up to 128 % within one year, but after two years, the production was less pronounced (+35 %). The first-year production was likely very high due to the rapid exploitation of the root-free ingrowth cores. The radiocarbon signatures of fine roots were overall variable among treatments and plots. Soil warming tended to decrease fine root turnover times of all the measured root fractions after 8 and 14 years of warming, and there was a tendency for trees to use older carbon reserves for fine root production in warmed plots. Furthermore, soil warming increased fine root turnover from 50 to 106 g C m−2 yr−1 (based on two different approaches). Our findings suggest that future climate warming may increase carbon input into soils by enhancing fine root turnover. If this increase may partly offset carbon losses by increased mineralization of soil organic matter in temperate forest soils is still unclear and should guide future research.

Leaf and Root Litter Species Identity Influences Bacterial Community Composition in Short-Term Litter Decomposition

Microorganisms play a crucial role in litter decomposition in terrestrial ecosystems. The leaf and fine root litters of Robinia pseudoacacia Linn., Quercus acutissima Carr., Pinus tabulaeformis Carr. and Pinus densiflora Sieb. were analysed using the nylon litter bag method and Illumina MiSeq high-throughput sequencing for the amplification of bacterial 16S rRNA V4–V5. We assessed the effects of leaf and root litter species on the bacterial community after one year’s decomposition. The results showed that (1) the remaining mass of fine root litter was smaller than that of the leaf litter for R. pseudoacacia and Q. acutissima, while the opposite result was found for P. tabulaeformis and P. densiflora. (2) The bacterial community structure in leaf litter was most highly correlated with the initial N content and N:P, while that in fine roots was most highly correlated with the lignin content. (3) The bacterial phyla Bacteroidetes, Acidobacteria and Gemmatimonadetes were significantly affected by litter and species, whereas the relative abundances of Firmicutes and Chloroflexi were only affected by litter tissues. The relative abundances of Acidobacteria, Firmicutes and Chloroflexi in fine root litter were higher than those in leaf litter, while the opposite result was found for Bacteroidetes. The bacterial genera Burkholderia-Paraburkholderia, Sphingomonas and Mucilaginibacter were affected by litter tissues (p < 0.05). The relative abundance of Burkholderia-Paraburkholderia in fine root litter was higher than that in leaf litter, while the opposite result was found for Bradyrhizobium, Sphingomonas and Mucilaginibacter. Pearson’s correlation analysis showed that the relative abundances of the dominant phyla and genera were affected by the initial litter properties, especially for Bacteroides, Acidobacteria, Burkholderia and Sphingomonas. These findings indicate that litter tissues and their interactions with species are more important than the species in shaping the bacterial diversity and community composition, which was affected by the initial chemical properties of the litter.

Fine root litter traits of Chamaecyparis obtusa

The purpose of this study was to clarify the process of Chamaecyparis obtusa (Sieb. & Zucc.) Endl. fine root shedding and the morphological traits of the resulting root litter. We developed a method for direct monthly sampling of root litter from the fine root system in the field. We proposed a field incubation method using centrifuge tubes with glass beads as the medium and throughfall as the nutrient solution, in which an undamaged sample of the fine root system still connected to the tree is inserted. Using this method, we collected root litter from C. obtusa for 12 months after the installation. The monthly amounts of the root litter of from the incubated fine root systems differed significantly among the sampling months. On the other hand, the morphological traits such as the root litter length and diameter of each branch order did not differ significantly among months. The first-order root litter was shorter than the incubated living first-order roots. The first-order roots were shed both at the branching positions and in the middle of first-order roots. We concluded that fine root litter with similar morphology is shed every month. Assessment of the fine root litter traits by using the new direct sampling method and the new soil ecological indicator “initial tissue C inputs” from fine roots into forest soil will improve our understanding of forest belowground carbon cycling and its indexation.

Root-order-associated variations in fine-root decomposition and their effects on soil in a subtropical evergreen forest

BackgroundDespite the importance of root decomposition in predicting ecosystem responses to future climate change, the effects of branch order on root decomposition and the feedback to soil still remains poorly understood. Here we separated root samples taken from two tree species (Castanopsis fargesii and Schima superba in subtropical forests along the coastal area in eastern China) into four-order classes (1st–2nd order, 3rd order, 4th order, and 5th order) and conducted a 540-day litterbag incubation experiment in laboratory to examine root mass loss, nutrient release, and the influence on soil during decomposition.ResultsC. fargesii roots of 1st–2nd and 3rd order decayed more slowly than those of 4th and 5th order, but this pattern was not significant for S. superba. Of all the measured root traits, the decomposition rates correlated best with root C/N ratio, diameter and specific root length (SRL) based on the structural equation modeling. Both tree species and root order exhibited significantly effects on root initial traits. Overall, C. fargesii roots decay faster than S. superba, and this appears to be associated with root initial C quality and N concentration. In addition, root order positively affected root decomposition rates mainly through root diameter and SRL. However, no significant difference was found in C and N content between soils below the litterbag with different-order roots.ConclusionsOur findings suggest the effects of branch order on root decomposition are dependent on tree species. Moreover, root morphological properties might also be the controlling factor in root decay besides root chemistry fractions. Overall, the integrative effects should be considered to improve our understanding of the fate of fine-root litter and their contribution to soil C and N pool.

Contrasting dynamics and factor controls in leaf compared with different-diameter fine root litter decomposition in secondary forests in the Qinling Mountains after 5 years of whole-tree harvesting

Plant litter decomposition is a crucial pathway for carbon (C) and nutrient cycling, and controls the net primary productivity in ecosystems worldwide. However, little is known about how multi-type litter (leaf and different diameter fine roots) decomposition rates and nutrient release change at the community level following whole-tree harvesting (WTH). In the present study, we followed decomposition of leaf and different diameter fine root (∅ < 0.5 mm, 0.5–1 mm, 1–2 mm) litters at plot level over 2 years in a secondary forest in the Qinling Mountains after 5 years of five different thinning treatments (0%, 15%, 30%, 45%, and 60%). Our results demonstrated that WTH had no effects on leaf and different diameter fine root litter decomposition at the plot level. Leaves had significantly higher decomposition rate than different diameter fine roots. There were significant positive correlations between decomposition rate of different diameter fine roots, but not related to leaf litter decomposition rate. WTH did not affect the nutrient release of leaf and different diameter fine root litters at the plot level. The nitrogen (N), phosphorous (P) and potassium (K) mass remaining in leaf litters were significantly higher than different diameter fine roots after 2 years decomposition, while different diameter fine roots had higher C mass remaining. Leaf and fine root litter decomposition rates were mainly influenced by stand and litter quality attributes. Nutrient release of leaf and fine root N, P and K were mainly predicted by litter quality characteristics, while there were no consistent driving factors for C release. Our results suggested that WTH had no effects on multi-type litter decomposition and nutrient release at plot level after 5 years of recovery. Moreover, leaf litters had excellent N, P and K nutrient preservation mechanisms, and C conservation in fine root litters.

Stronger effect of litter quality than micro‐organisms on leaf and root litter C and N loss at different decomposition stages following a subtropical land use change

Abstract Litter decomposition contributes largely to global carbon (C) and nitrogen (N) cycling, and it is strongly determined by litter quality and microbial community composition in ways that are poorly understood. Here, we conducted a 2‐year field litter decomposition experiment by collecting leaf and root litter of crops (from cropland), shrubs (from shrubland) and wood (from woodland) and placing samples for decomposition in woodland soil in central China to investigate the effects of litter quality and microbial community composition on C and N losses of leaf and root litter of three species under different decomposition stages. Our results showed that the leaf litter C and N losses of shrubs were significantly higher than those of crops and wood, whereas the root litter C and N losses of crops were significantly higher than those of shrubs and wood. Generally, the leaf litter C and N losses of the three species were higher on average than those of fine root litter during the whole decomposition period. For the C loss of the three species, litter lignin and phosphorus as well as initial litter quality were predominant drivers of root litter decomposition, while litter lignin, cellulose and hemicellulose concentrations were dominant for leaf litter decomposition. For N loss, litter stoichiometry and litter quality directly governed leaf and root litter N loss, and the initial litter quality largely regulated N loss at the late decomposition stage. Unexpectedly, the effect of microbial community composition on litter C and N losses was relatively weak and only exhibited an effect on litter C and N losses during the early stage of decomposition. Thus, our results revealed the huge disparity in C and N loss of plant species and litter types at different decomposition stages, which should be considered jointly when evaluating their roles in plant–soil feedbacks under global land use change. A free Plain Language Summary can be found within the Supporting Information of this article.

Tree Diversity, Initial Litter Quality, and Site Conditions Drive Early-Stage Fine-Root Decomposition in European Forests

Decomposition of dead fine roots contributes significantly to nutrient cycling and soil organic matter stabilization. Most knowledge of tree fine-root decomposition stems from studies in monospecific stands or single-species litter, although most forests are mixed. Therefore, we assessed how tree species mixing affects fine-root litter mass loss and which role initial litter quality and environmental factors play. For this purpose, we determined fine-root decomposition of 13 common tree species in four European forest types ranging from boreal to Mediterranean climates. Litter incubations in 315 tree neighborhoods allowed for separating the effects of litter species from environmental influences and litter mixing (direct) from tree diversity (indirect). On average, mass loss of mixed-species litter was higher than those of single-species litter in monospecific neighborhoods. This was mainly attributable to indirect diversity effects, that is, alterations in microenvironmental conditions as a result of tree species mixing, rather than direct diversity effects, that is, litter mixing itself. Tree species mixing effects were relatively weak, and initial litter quality and environmental conditions were more important predictors of fine-root litter mass loss than tree diversity. We showed that tree species mixing can alter fine-root litter mass loss across large environmental gradients, but these effects are context-dependent and of moderate importance compared to environmental influences. Interactions between species identity and site conditions need to be considered to explain diversity effects on fine-root decomposition.

Effects of sulfuric, nitric, and mixed acid rain on the decomposition of fine root litter in Southern China

BackgroundChina has been increasingly subject to significant acid rain, which has negative impacts on forest ecosystems. Recently, the concentrations of NO3− in acid rain have increased in conjunction with the rapid rise of nitrogen deposition, which makes it difficult to precisely quantify the impacts of acid rain on forest ecosystems.MethodsFor this study, mesocosm experiments employed a random block design, comprised of ten treatments involving 120 discrete plots (0.6 m × 2.0 m). The decomposition of fine roots and dynamics of nutrient loss were evaluated under the stress of three acid rain analogues (e.g., sulfuric (SO42−/NO3− 5:1), nitric (1:5), and mixed (1:1)). Furthermore, the influences of soil properties (e.g., soil pH, soil total carbon, nitrogen, C/N ratio, available phosphorus, available potassium, and enzyme activity) on the decomposition of fine roots were analyzed.ResultsThe soil pH and decomposition rate of fine root litter decreased when exposed to simulated acid rain with lower pH levels and higher NO3− concentrations. The activities of soil enzymes were significantly reduced when subjected to acid rain with higher acidity. The activities of soil urease were more sensitive to the effects of the SO42−/NO3− (S/N) ratio of acid rain than other soil enzyme activities over four decomposition time periods. Furthermore, the acid rain pH significantly influenced the total carbon (TC) of fine roots during decomposition. However, the S/N ratio of acid rain had significant impacts on the total nitrogen (TN). In addition, the pH and S/N ratio of the acid rain had greater impacts on the metal elements (K, Ca, and Al) of fine roots than did TC, TN, and total phosphorus. Structural equation modeling results revealed that the acid rain pH had a stronger indirect impact (0.757) on the decomposition rate of fine roots (via altered soil pH and enzyme activities) than direct effects. However, the indirect effects of the acid rain S/N ratio (0.265) on the fine root decomposition rate through changes in soil urease activities and the content of litter elements were lower than the pH of acid rain.ConclusionsOur results suggested that the acid rain S/N ratio exacerbates the inhibitory effects of acid rain pH on the decomposition of fine root litter.

The coordination between leaf and fine root litter decomposition and the difference in their controlling factors

AbstractAimAs the two largest components of plant detritus input, leaf and root litter together determine ecosystem vegetation turnover and nutrient cycling rates. However, the similarities and differences between the factors controlling their decomposition remain unknown. We evaluated the relationship between leaf and fine root litter decomposition across biomes and analysed how litter traits, climate, soil conditions and decomposers shape their relationship.LocationGlobal.Time period1984–2020.Major taxa studiedVascular plants.MethodsWe collected 352 paired leaf and fine root decomposition rates (k values) and ancillary traits, climate, soil condition and decomposer abundance data from 88 sites spanning the major global biomes. Boosted regression trees (BRTs) were applied to partition the factors that control root and leaf decomposition rates.ResultsAveraged across all biomes, leaf litter decomposes significantly faster (kleaf = .72) than fine root litter (kroot = .42). The BRTs indicated that plant traits best explained the variance in both leaf and root litter decomposition. The key chemical traits of leaf litter and fine root litter, including C:N, [P], N:P, [lignin], [cellulose], [non‐structural carbohydrates] and [tannins], were positively correlated. Therefore, leaf and fine root k values were positively correlated within and across biomes, even after removing the influence of climate, soil conditions and decomposers. However, climate and decomposers had different impacts on leaf and fine root decomposition. Climate induced a greater impact on fine root litter decomposition, whereas decomposers had a greater influence on leaf litter decomposition.Main conclusionsOur finding indicates that plants evolve a coordinated nutrient supply‐and‐demand strategy. The plants with high nutrient demand produce labile leaf and fine root litter, which decomposes fast to meet their high nutrient requirements. However, leaf and fine root decomposition are also mediated by different combinations of trait, climate, soil condition and decomposer factors, which weakens the coordination between leaf and fine root decomposition.

Functional traits of poplar leaves and fine roots responses to ozone pollution under soil nitrogen addition

Concurrent ground-level ozone (O3) pollution and anthropogenic nitrogen (N) deposition can markedly influence dynamics and productivity in forests. Most studies evaluating the functional traits responses of rapid-turnover organs to O3 have specifically examined leaves, despite fine roots are another major source of soil carbon and nutrient input in forest ecosystems. How elevated O3 levels impact fine root biomass and biochemistry remains to be resolved. This study was to assess poplar leaf and fine root biomass and biochemistry responses to five different levels of O3 pollution, while additionally examining whether four levels of soil N supplementation were sufficient to alter the impact of O3 on these two organs. Elevated O3 resulted in a more substantial reduction in fine root biomass than leaf biomass; relative to leaves, more biochemically-resistant components were present within fine root litter, which contained high concentrations of lignin, condensed tannins, and elevated C:N and lignin: N ratios that were associated with slower rates of litter decomposition. In contrast, leaves contained more labile components, including nonstructural carbohydrates and N, as well as a higher N:P ratio. Elevated O3 significantly reduced labile components and increased biochemically-resistant components in leaves, whereas they had minimal impact on fine root biochemistry. This suggests that O3 pollution has the potential to delay leaf litter decomposition and associated nutrient cycling. N addition largely failed to affect the impact of elevated O3 levels on leaves or fine root chemistry, suggesting that soil N supplementation is not a suitable approach to combating the impact of O3 pollution on key functional traits of poplars. These results indicate that the significant differences in the responses of leaves and fine roots to O3 pollution will result in marked changes in the relative belowground roles of these two litter sources within forest ecosystems, and such changes will independently of nitrogen load.

Shifts in microbial metabolic pathway for soil carbon accumulation along subtropical forest succession

The dynamic process of forest succession is important for terrestrial ecosystems where soil organic matter (SOM) primarily controls biogeochemical cycles and is driven by soil microorganisms. Carbon (C) incorporation into SOM occurs along two different microbial metabolic pathways: ex vivo mostly extracellular enzymatic modification and in vivo turnover within the cells, highlighting the importance of microbial catabolism and anabolism respectively during soil C transformation and sequestration. However, identifying the dual C pathways and understanding the microbially-mediated SOM transformation during forest succession remains elusive, particularly with respect to interactions in the rhizosphere. Here, we used a series of biomarkers, including amino sugars, phospholipid fatty acids, and neutral sugars, to explore how forest succession and rhizosphere dynamics affect microbial contribution to soil organic carbon (SOC) in three successional stages of a subtropical forest ecosystem. We observed generally consistent increases in amino sugar and SOC with forest age in both bulk and rhizosphere soil, demonstrating that microorganisms facilitate SOC accumulation through the in vivo pathway along the successional gradient. The ratio of amino sugar-C to SOC (AS-C/SOC) exhibited a greater increase in bulk than in rhizosphere soil along the successional gradient, indicating the microbial in vivo pathway was relatively more important for SOC accumulation in bulk than in rhizosphere soil. Given there was a significant decrease in the ratios of hexose-to-pentose sugars [(galactose + mannose)/(arabinose + xylose), indicating the contribution of sugars derived from microbes and plants to labile soil C], we hold the opinion that relatively limited microbial C processing occurred in the rhizosphere along the forest successional gradient. Therefore, the microbial ex vivo pathway where microorganisms decomposed (structurally modified) fine root litter that was incorporated into SOC was relatively more important in rhizosphere than in bulk soil for SOC variation during forest succession. Our findings emphasize the role of microbes transforming organic matter in both bulk and rhizosphere soil in a subtropical forest successional gradient and help to enhance our understanding of the function and ecosystem services of these environments.

Decomposition and temperature sensitivity of fine root and leaf litter of 43 mediterranean species

AimsData on the decomposition of fine roots are scarce for the Mediterranean basin. This work aims to compare chemical traits, decomposition rate, and temperature sensitivity (Q10) for root and leaf litter of 43 Mediterranean species.MethodsWe carried out a two-years litterbag decomposition experiment using 43 fine roots litter and leaf litter types incubated in laboratory conditions at three different temperatures, i.e. 4 °C, 14 °C, and 24 °C. Litter was characterized for carbon (C), nitrogen (N), lignin and cellulose concentration, C/N, and lignin/N ratios.ResultsFine root litter had lower N content but higher lignin concentration, lignin/N, and C/N ratios compared to leaf litter. The decay rate of fine root litter was slower than leaf litter. For both tissues, the decay rate was negatively associated with lignin concentration, lignin/N, and C/N ratios but positively with N concentration. Q10 was higher for fine root than leaf litter, with a positive correlation with lignin while negative with N concentration.ConclusionsOur findings demonstrate a higher Q10 accompanied by a slower decomposition rate of fine root litter compared to leaf litter in Mediterranean ecosystems. These results must be considered in modeling organic C at the ecosystem scale.

Contrasting Dynamics and Factor Controls in Leaf Compared with Different-Diameter Fine Root Litter Decomposition Following Whole-Tree Harvesting in Secondary Forests in the Qinling Mountains, China

Contrasting Dynamics and Factor Controls in Leaf Compared with Different-Diameter Fine Root Litter Decomposition Following Whole-Tree Harvesting in Secondary Forests in the Qinling Mountains, China