Fine Root Turnover Research Articles

Root growth dynamics during recovery of tropical mountain forest in North-east India

Ever increasing pressures on tropical forests worldwide due to anthropogenic disturbances have greatly affected both above- and belowground functioning of these forests. While fine roots play major ecological roles in forests through assisting in nutrient and water uptake and returning elements to the soil environment, coarse roots play an important role in C sequestration. We studied changes in fine and coarse root biomass, production, turnover and carbon and nitrogen return to the soil in two regenerating forest stands (RFs) following stone-mining that were 5 years (RF-5) and 15 years (RF-15) post-disturbance compared with a natural forest stand (NF) in Mizoram, North-east India. Fine (§2 mm) and coarse root (2-10 mm) biomass differed significantly among the forest stands and ranged from 239 (RF-5) to 415 (NF) and 230 (RF-5) to 436 (NF) g m−2, respectively. Total root (fine + coarse) biomass increased during stand development but the proportion of very fine root (<0.5 mm) to total root production decreased. Fine root biomass decreased with increasing soil depth. Fine and total root biomass showed strong seasonal correlations with soil moisture, more so than for rainfall and temperature, whereas these relationships were less clear for the coarse root biomass. The amount of N (25–55 kg ha−1) and C (1.9–3.6 t ha−1) stored in root biomass increased with stand age with a corresponding increase in production and turnover of C and N to the soil. Disturbance to these tropical forests negatively affected root dynamics, influenced their spatio-temporal patterns, and reduced the production, amount and availability of nutrients returned to the soil along with a strong reduction in the root biomass carbon pool and sequestration in carbon residence time. We observed that root growth, especially fine roots, is dependent on abiotic variables, and plays a significant role in early stages of secondary succession by adding organic matter and nutrients through high turnover rates in these forests.

Self-Similarity, Leaf Litter Traits, and Neighborhood Predicting Fine Root Dynamics in a Common-Garden Forest

While individual tree genotypes are known to differ in their impacts on local soil development, the spatial genetic influence of surrounding neighboring trees is largely unknown. We examine the hypothesis that fine root dynamics of a focal tree is based on the genetics of the focal tree as well as the genetics of neighbor trees that together define litter inputs to soils of the focal tree. We used a common garden environment with clonal replicates of individual tree genotypes to analyze fine root production, turnover and allocation with respect to modeled neighborhood: 1) foliar mass, 2) foliar condensed tannins (CT), 3) genetic identity of trees, and 4) genetic dissimilarity of neighbors. In support of our central hypothesis, we found that the presence of genetically dissimilar trees and high leaf CT contributions to the soil predicted increased fine root production. In fact, the modeled effects of neighbors accounted for ~90% of the explanatory weight of all models predicting root production. Nevertheless, the ultimate fate of those roots in soil (turnover) and the balance of fine roots relative to aboveground tree mass were still more predictable based on the genetics of the individual focal trees (explaining 99% of the variation accounted for by models). Our data provide support for a method allowing a comparison of the relative effects of individuals versus spatial neighborhood effects on soils in a genetic context. Such comparisons are important for placing plant-soil feedbacks in a genetic and evolutionary framework since neighbors can decouple feedbacks between an individual and the surrounding environment.

Fine root dynamics responses to nitrogen addition depend on root order, soil layer, and experimental duration in a subtropical forest

Elevated atmospheric N deposition has been well documented to enhance fine root production in N-limited temperate forests, but how fine roots respond to N deposition in N-rich tropical and subtropical forests remains poorly understood. The sequential coring and minirhizotron methods were applied to quantify fine root biomass, production, and turnover of a N-rich but P-limited subtropical forest in southern China and to assess the responses of these root variables to a gradient of N additions (control (0), low-N (35), medium-N (70), and high-N (105 kg N ha−1 year−1)) during the first 3 years of experimentation. The high- and medium-N additions significantly reduced fine root diameter by about 30% but increased the specific root length by 20–105%, i.e., fine roots became thinner and longer under the experimental N addition. Both low- and medium-N additions generally stimulated fine root production (10–88%) and turnover (3–40%), whereas high-N suppressed them by 32–70% and 8–54%, respectively, varying with sampling season and estimation method. The stimulatory effects were presumably ascribed to the increased fine root growth for P acquisition, the suppressive effect, to the deleterious damage to the root health and micronutrient availability. Overall, the N effects were more pronounced in the surface (0–10 cm) than in the deeper (10–40 cm) soil layers and for the first-order than the higher-order fine roots. Our results indicate that lower-order absorptive fine roots are responsive to elevated N deposition, and complex responses could emerge due to the interactive influences of the N deposition rate, seasonality, and soil depth.

Mathematical Functions to Model the Depth Distribution of Soil Organic Carbon in a Range of Soils from New South Wales, Australia under Different Land Uses

The nature of depth distribution of soil organic carbon (SOC) was examined in 85 soils across New South Wales with the working hypothesis that the depth distribution of SOC is controlled by processes that vary with depth in the profile. Mathematical functions were fitted to 85 profiles of SOC with SOC values at depth intervals typically of 0–5, 5–10, 10–20, 20–30, 30–40, 40–50, 50–60, 60–70, 70–80, 80–90 and 90–100 cm. The functions fitted included exponential functions of the form SOC = A exp (Bz); SOC = A + B exp (Cz) as well as two phase exponential functions of the form SOC = A + B exp (Cz) + D exp (Ez). Other functions fitted included functions where the depth was a power exponent or an inverse term in a function. The universally best-fitting function was the exponential function SOC = A + B exp (Cz). When fitted, the most successful function was the two-phase exponential, but in several cases this function could not be fitted because of the large number of terms in the function. Semi-log plots of log values of the SOC against soil depth were also fitted to detect changes in the mathematical relationships between SOC and soil depth. These were hypothesized to represent changes in dominant soil processes at various depths. The success of the exponential function with an added constant, the two-phase exponential functions, and the demonstration of different phases within the semi-log plots confirmed our hypothesis that different processes were operating at different depths to control the depth distributions of SOC, there being a surface component, and deeper soil component. Several SOC profiles demonstrated specific features that are potentially important for the management of SOC profiles in soils. Woodland and to lesser extent pasture soils had a definite near surface zone within the SOC profile, indicating the addition of surface materials and high rates of fine root turnover. This zone was much less evident under cropping.

An investigation of tree growth in permeable paving

Shallow tree roots can lead to footpath (sidewalk) damage. A layer of gravel has been shown to deter root growth in some situations, including beneath footpaths. Used to manage storm water in highly urbanised catchments, permeable paving incorporates a gravel layer in its base for structural and hydrological purposes. Conducted in Adelaide, South Australia, the experiment reported in this paper tested whether a gravel base layer beneath permeable paving deterred shallow growth of Pyrus calleryana ‘Chanticleer’ roots. After nearly five years of tree growth, results revealed that roots of larger diameter were fewer in number and they grew deeper in the subgrade beneath permeable paving than beneath impermeable paving. Fine root turnover in the permeable pavement base layer indicated that the gravel functioned as a buffer between the footpath surface and roots in the subgrade, potentially minimising pavement damage and maintenance requirements. No differences in tree height or trunk diameter were observed between trees grown in permeable paving and those grown in impermeable paving.

Linking soil nutrient availability, fine root production and turnover, and species composition in a seasonally dry plant community

We studied the relationship between seasonal nutrient availability and fine root density with soil depth to determine potential nutrient uptake strategies of evergreen and deciduous woody species in an infertile, seasonally dry plant community. PO43−, NO3−, and NH4+ were measured with soil depth and across seasons, using ion-exchange resins. Fine root density was measured seasonally by counting the first four root terminal orders (root branching from tip to base). Aboveground stem density and species composition were measured. N and P availability were highest in the shallow soil layer and peaked in the late wet season and not during the initial rains as was hypothesized. Substantial N and P were found at deeper soil depths during the early dry season. Fine root density was highest in the shallow soil layer and in the wet season and underwent substantial turnover from dry to wet season. Stem and root area were correlated. Having high fine root densities in the shallow soil layer benefits P uptake more than N or water uptake. Dormancy in deciduous species decreases fine root turnover but continued nutrient uptake in the dry season by the more abundant evergreen species appears to be of greater importance.

Fine root biomass, production and turnover rates in plantations versus natural forests: effects of stand characteristics and soil properties

Fine roots play a significant role in regulating the biogeochemical cycles of forest ecosystems, but how fine root biomass (FRB), production (FRP) and turnover rates (FRT) vary with forest origins remains not well understood. The meta-analysis approach was used to examine the differences in FRB, FRP and FRT between plantations and their adjacent natural forests based on 238 cases reported in 45 published studies. FRB and FRP were 36.5% and 36.0% lower, respectively, in plantations than in natural forests. FRT was 22.4% higher in plantations relative to natural forests. The decrease in FRB in plantations relative to natural forests varied among plantations with different plant genera and root diameter classes. The general patterns for FRP and FRT in relation to various factors (biogeographic zone, leaf form, leaf seasonality, plant genus in plantations, and root diameter class) did not differ among the groups. The difference in FRB between plantations and natural forests was positively correlated with stand age but negatively related with soil total nitrogen concentration, the difference in FRP was positively affected by diameter at breast height (DBH) and soil pH, and the difference in FRT was positively affected by DBH, tree height, soil bulk density and soil pH and negatively affected by soil organic carbon and total nitrogen concentration. FRB, FRP and FRT exhibit significant differences between plantations and natural forests and that these differences are partially caused by shifts in stand characteristics and variations in soil properties.

Productivity and morphological traits of fine roots in forest ecosystems along an elevation gradient of Yakushima Island

ABSTRACTWe measured the productivity and morphological traits of fine roots in seven forests between 170 and 1550 m along an elevation gradient on Yakushima Island, Japan. Yakushima Island is continuously covered by forests ranging from the lowland evergreen broad-leaved forests below 1000 m to the upland evergreen coniferous forests above. Mean annual temperature decreases linearly and soil nutrient availabilities (both N and P) also decrease with increasing elevation. We employed an in-growth core method to determine fine-root productivity. Mean fine-root biomass ranged from 0.123 to 0.297 kg m−2 in the lowland broad-leaved forests and from 0.092 to 0.097 kg m−2 in the upland coniferous forests. Mean fine-root productivity ranged from 0.063 to 0.173 kg m−2 yr−1 in the lowland broad-leaved forests and from 0.033 to 0.044 kg m−2 yr−1 in the upland coniferous forests. Both mean fine-root biomass and mean fine-root productivity were significantly greater in middle-elevation broad-leaved forests than in the lower broad-leaved or the higher coniferous forests. Fine-root turnover rate tended to be lower and mean specific root length (SRL) tended to be higher in the coniferous forests. In the upland coniferous forests, trees may adapt to nutrient limitation and/or cooler climate by increasing the life span and SRL of fine roots instead of increasing carbon allocation to fine roots, thereby decreasing fine-root productivity. Fine-root dynamics along the elevational gradient on Yakushima reflected the species shift from broad-leaved to coniferous trees rather than the monotonous reduction of temperature and nutrient availability.

Carbon stocks and tree diversity in scattered tree silvopastoral systems in Chiapas, Mexico

Carbon sequestration in livestock systems through silvopastoral practices can help reduce the net greenhouse gas emissions. In this study, we evaluated the above and belowground carbon storage potential of a silvopastoral system and compared to a conventional open pasture system in two sites of Chiapas, Mexico. We established a total of 20 carbon monitoring plots, 10 plots for each system. All the trees of ≥ 2.5 cm DBH were measured within the plots of 1000 m2. Allometric equations were used to calculate biomass carbon stocks. Grass biomass, ground litter, and soil samples were collected from four random locations within the plot. We also calculated tree diversity and other ecological indices of the silvopastoral systems. The aboveground biomass carbon stocks in dispersed tree silvopastoral systems varied between 11.53 ± 1.80 to 14.63 ± 5.50 Mg C ha−1. Soil organic carbon concentrations were higher in silvopastoral systems while soil bulk density was higher in open pasture systems, both affecting the soil organic carbon storage. A total of 29 tree species were registered in the dispersed tree silvopastoral systems. The Sorenson’s similarity index showed that the two study sites significantly differed in terms of their tree community compositions. Such differences were also observed in soil properties and carbon storage. We showed that there was a positive correlation between aboveground biomass and soil organic carbon concentrations. Further research is required to better understand the contributions of fine root and litter turnover on soil organic carbon storage in these systems.

Fine Root Dynamics in Three Forest Types with Different Origins in a Subalpine Region of the Eastern Qinghai-Tibetan Plateau

Fine roots play a crucial role in plant survival potential and biogeochemical cycles of forest ecosystems. Subalpine areas of the Eastern Qinghai-Tibetan Plateau have experienced different forest re-establishment methods after clear-cutting primary forest. However, little is known about fine root dynamics of these forests originating from artificial, natural and their combined processes. Here, we determined fine root traits (biomass, production and turnover rate) of three subalpine forest types, i.e., Picea asperata Mast. plantation forest (artificial planting, PF), natural secondary forest (natural without assisted regeneration, NF) and P. asperata broadleaved mixed forest (natural regeneration after artificial planting, MF) composed of planted P. asperata and naturally regenerated native broadleaved species. At the soil depth of 0–30 cm, fine root biomass was the highest in PF and fine root production was the highest in NF, and both were the lowest in MF. Fine root dynamics of the three forest types tended to decrease with soil depth, with larger variations in PF. Fine root biomass and production were the highest in PF in 0–10 cm soil layer but were not significantly different among forest types in the lower soil layers. There were positive correlations between these parameters and aboveground biomass across forest types in soil layer of 0–10 cm, but not in the lower soil layers. Fine root turnover rate was generally higher in mixed forests than in monocultures at all soil depths. In conclusion, the natural regeneration procedure after clear-cutting in the subalpine region of western Sichuan seems to be superior from the perspective of fine root dynamics.

Unravelling the age of fine roots of temperate and boreal forests

Fine roots support the water and nutrient demands of plants and supply carbon to soils. Quantifying turnover times of fine roots is crucial for modeling soil organic matter dynamics and constraining carbon cycle–climate feedbacks. Here we challenge widely used isotope-based estimates suggesting the turnover of fine roots of trees to be as slow as a decade. By recording annual growth rings of roots from woody plant species, we show that mean chronological ages of fine roots vary from <1 to 12 years in temperate, boreal and sub-arctic forests. Radiocarbon dating reveals the same roots to be constructed from 10 ± 1 year (mean ± 1 SE) older carbon. This dramatic difference provides evidence for a time lag between plant carbon assimilation and production of fine roots, most likely due to internal carbon storage. The high root turnover documented here implies greater carbon inputs into soils than previously thought which has wide-ranging implications for quantifying ecosystem carbon allocation.

Interactive effects of warming and nitrogen addition on fine root dynamics of a young subtropical plantation

Forest aboveground production and soil carbon (C) pools are closely linked to fine root dynamics. Uncertainty about the effects of warming and nitrogen (N) deposition on fine root dynamics limits our ability to predict how C will transfer between biological and atmospheric pools in tropical and subtropical forests. In order to examine the effects of warming and N deposition on fine roots in subtropical plantations, we used a randomized complete block design with factorial soil warming (ambient, ambient + 5 °C) and N deposition (ambient, ambient + 80 kg N ha−1 yr−1) manipulation. Minirhizotrons were used to monitor fine root production, mortality and turnover rate of Chinese fir (Cunninghamia lanceolata) seedlings for two years, and seedling growth was measured. We found warming had positive effects on annual fine root production, mortality and turnover rate both under ambient and increased N addition. N addition had positive effects on annual fine root production, mortality and turnover rate in the warmed plots, but had no influence on annual fine root production, mortality and turnover rate in the unwarmed plots. Warming and N addition had an additive (not interactive) effect on fine root production, mortality and turnover rate. There was an interaction between warming and N addition on living fine root biomass in the second year. These changes can be largely attributed to belowground/aboveground C allocation. There was no evidence of root respiration acclimation to warming. In addition, increased fine root turnover rate after warming implies accelerated root C inputs to soils, which may affect soil C and nutrient dynamics. Nitrogen addition may exacerbate this. There was no acclimation of root respiration to warming, which may alter C balance and cause more CO2 release to the atmosphere through autotrophic respiration.

Positive species mixture effects on fine root turnover and mortality in natural boreal forests

The positive species mixture effects on both above- and below-ground productivity have been well documented in diverse ecosystem types. However, whether the results obtained on productivity can be generalized to other ecosystem processes remains unclear. We investigated the effects of tree species mixtures on fine root biomass turnover and biomass loss from mortality by sampling 18 stands dominated by Populus tremuloides and Pinus banksiana, respectively, and their relatively even mixtures in post-fire boreal forests of two stand ages (8 and 34 years following stand-replacing fire). Fine root biomass turnover and mortality were higher in mixtures than expected from those of single species-dominated stands in both stand ages, with a higher magnitude of mixture effects in the 34-year-old than in the 8-year-old stands. Mixture effects on turnover and mortality did not differ with soil depth in 8-year-old stands, but turnover increased while mortality decreased from the forest floor to the mineral layers in 34-year-old stands. Both turnover and mortality significantly increased with tree species evenness in 34-year-old stands, but not in 8-year-old stands. Root turnover and biomass loss from mortality were positively associated with annual fine root production across all stand types and ages. Our results provide the first evidence for positive mixture effects on fine root biomass turnover and biomass loss from mortality in natural forests. Moreover, our results suggest that the positive mixture effects resulted from increased competition induced by the increase of fine root biomass production in tree species mixtures.

Fine root longevity and below- and aboveground litter production in a boreal Betula pendula forest

1. Fine root turnover plays a critical role in carbon and nutrient cycling in forest ecosystems. In this study, we focused on the most abundant deciduous species in Nordic countries, silver birch (Betula pendula Roth) and its fine root dynamics, including the amount of litter produced by fine roots as well as by aboveground vegetation.2. The minirhizotron method was used to quantify fine root longevity of silver birch and understory fine roots and rhizomes in northern Finland. Fine root biomass per basal area and ectomycorrhizal short root numbers per mg were also quantified. The fine root litter production was estimated by fine root biomass and longevity, and then compared with the aboveground litter collected with litter traps.3. Birch fine root biomass was 1.4-fold higher than that of understory fine roots and rhizomes (234 ± 22, 171 ± 19 g m−2 respectively). Fine root longevity of birch (372 days) was significantly (P < 0.05) shorter than that of understory vegetation (643 days). The birch fine root longevity was positively related to root diameter and soil depth. Hazard analysis showed that thicker roots, long roots, roots produced late in the growing season, and roots growing deeper in the soil had relatively lower mortality hazard compared to the reference data. The total annual soil C input, including both birch and understory, was 283 g C m−2 yr−1. The proportion of understory annual C input was 35% of the total. Total annual belowground C input was 1.4-fold greater than that of aboveground.4. Our study indicated that the total annual belowground litter production was greater than that of the aboveground litter in a boreal deciduous forest stand. Therefore, more emphasis should be put to quantify the C cycling of both above- and belowground parts of different tree species as well as understory in boreal forests.

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.

连作杨树人工林细根寿命的代际差异及其影响因素

PDF HTML阅读 XML下载 导出引用 引用提醒 连作杨树人工林细根寿命的代际差异及其影响因素 DOI: 10.5846/stxb201612202624 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（31570618）；中国博士后科学基金项目（2015M572070）；山东省双一流奖补资金（SYL2017XTTD03）；山东省博士后创新基金项目 The difference in fine root lifespan between successive rotations of poplar plantation and the dominant causal factors 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:细根寿命是调控森林生产力形成的关键。通过在连作Ⅰ、Ⅱ代杨树人工林固定样地内埋设微根管，对杨树不同根序细根年度生长动态开展连续观测并进行生存分析。结果表明，杨树不同根序细根累积生存率存在显著差异，高级根（3-5级）寿命较长，其累积生存率显著高于1级和2级细根。杨树细根寿命存在显著的代际差异，连作Ⅱ代人工林活根量、死根量和细根总量均高于Ⅰ代林。连作Ⅱ代人工林细根中位值寿命为（90±16）d，显著低于Ⅰ代人工林（（102±22）d）。连作Ⅱ代林各根序细根数量、分布比例均高于Ⅰ代林，低级细根累积生存率低于Ⅰ代林而高级细根累积生存率显著高于Ⅰ代林。连作杨树人工林细根寿命显著受制于土壤环境，1级细根寿命与土壤速效氮相关性极显著（r=-0.861），2级细根寿命与土壤物理性状相关性较强且与土壤酚酸含量呈现极显著相关（r=0.870），高级根序细根寿命与土壤物理性质和养分状况等也具有一定相关性。连作杨树人工林土壤酚酸累积和养分有效性下降影响了细根寿命和周转，并进而造成净初级生产力损耗，相关结论为连作杨树人工林生产力衰退机理模型的建立提供了科学依据。 Abstract:The lifespan of fine roots plays an important role in forest productivity. On the basis of minirhizotron technology, this study focused on the annual dynamics of different order fine roots in successive rotation poplar plantations and analyzed their survival. The results showed that the cumulative survival rates of poplar fine roots were significantly different among root orders. The lifespan of higher order roots (3rd-5th order) was longer than that of lower order roots (1st-2nd order), and their cumulative survival rate was also higher. Furthermore, there was a significant difference in the lifespan of poplar fine roots between two plantations (the first and second generations). There were more live roots, dead roots, and total roots in the second rotation forest than in the first. The median lifespan of fine roots was 90±16 d in the second rotation poplar plantation, whereas it was 102±22 d in the first rotation plantation. The root number and the proportion of roots of each order in the second rotation poplar plantation were significantly higher than those in the first rotation plantation. However, the cumulative survival rate of lower order roots was significantly higher, whereas that of higher order roots was significantly lower, in the first rotation poplar plantation. The lifespan of poplar fine roots was responsive to soil environments, with the lifespan of the first order roots being significantly correlated with soil available nitrogen (r=-0.861) and that of the second order roots being significantly correlated with phenolic acid content (r=0.870). The lifespan of the higher order roots also showed some correlation with soil physical properties and nutrient conditions. The findings of this study indicate that the accumulation of phenolic acids and a decreased soil nutrient availability might influence fine root lifespan and turnover of poplar trees and lead to a loss of net primary productivity in poplar plantations, thereby providing an important insight into the mechanism of declining poplar plantation productivity. 参考文献 相似文献 引证文献

Fine root production and turnover of Pinus massoniana and their influencing factors in the Three Gorges Reservoir Area, China

In this study, the annual production and turnover rate of fine root of Pinus massoniana in Three Gorges Reservoir Area were calculated using sequential soil core,litterbag and compartment flux model methods, and the relationship between fine root production, turnover rate and factors was analyzed. The results showed that the annual mean biomass of <0.5, 0.5-1 and 1-2 mm fine root was 0.29, 0.59 and 0.76 t·hm-2, annual production was 0.13, 0.49, 0.37 t·hm-2, and annual turnover rate was 1.49, 1.01, 0.40 a-1, respectively. The effects of factors on production and turnover of fine roots with different diameters were different. Soil temperature and soil Ca content had significant effects on production and turnover of <0.5 mm fine roots, and soil temperature explained the variation of production and turnover by 32.8% and 25.0%, and soil Ca content explained by 65.6% and 73.1%, respectively. There was a positive relationship between fine root biomass and fine root production, and the biomass of fine root explained 41.0%, 41.1% and 54.5% of variation in fine root production for <0.5, 0.5-1 and 1-2 mm fine roots, respectively. P and K contents of fine roots correlated significantly with <0.5 mm fine root production, and explained 32.2% and 39.2% of the variation of <0.5 mm fine root production, respectively. The fine root with diameter <0.5 mm was most closely associated with soil factors, and soil temperature and soil Ca content were the main factors affecting fine root biomass.

Canopy management practices in mulberry: impact on fine and coarse roots

Canopy management practices viz. lopping, pruning, coppicing and pollarding in trees alter branch density, height, leaf area index and rooting pattern of the trees. The present study was conducted to quantify the impact of canopy management practices and intercropping on fine and coarse roots distribution in mulberry (Morus alba). In total, six treatments comprising of three management practices (pollarding, coppicing and lopping) and two cropping situations (intercropping and without intercropping) were evaluated. Vertical and lateral distribution of fine root biomass (FRB) was recorded through sequential core method in different seasons. Coarse root distribution and biomass was studied using excavation method. Results revealed that canopy management treatments viz., coppicing and pollarding reduced the FRB as compared to lopping treatment in both intercropped and non-intercropped situation. Results also revealed that majority of the fine root biomass (67.3%) was confined in 0–15 cm soil layer. All the canopy management treatments under non-intercropped plots showed higher production rate as compared to intercropped plots. Fine root turnover rate (yr−1) was highest (0.592) in lopping treatment in non-intercropped plots whereas, the minimum turnover rate was recorded in coppicing treatment (0.331) in non-intercropped plots. Coarse root biomass was highest in case of intercropped plots in all the three canopy management treatments. Pollarding + turmeric cultivation showed the maximum root biomass followed by lopping + turmeric intercropping treatment. The main and primary roots in all the treatments accounted for > 70% biomass except for coppicng + turmeric treatment, whereas secondary and tertiary roots contributed about 40% biomass. All the treatments showed a pronounced decrease in root biomass with increasing soil depth and 75–84% of the total root biomass (main + lateral roots) was allocated in the top 30 cm of the soil profile. From the study, it can be concluded that tree management practices have direct impact on fine and coarse root distribution and should be judiciously used for avoiding competition in intercropping situation.

Plant community composition influences fine root production and biomass allocation in perennial bioenergy cropping systems of the upper Midwest, USA

Fine roots play a key role in the global carbon (C) cycle because much of the C accumulating in soil is the result of fine root production and turnover. Here we explore the effect of plant community composition and diversity on fine root production in surface soils and plant biomass allocation to fine roots in six perennial cropping systems differing in composition and diversity planted as biofuel feedstocks. The six systems were established in 2008 at both a high and a moderate fertility site located in the upper Midwest, USA and included: switchgrass (Panicum virgatum), miscanthus (Miscanthus × giganteus), hybrid poplar (Populus nigra × P. maximowiczii ‘NM6), native grasses (a five-species assemblage of Andropogon gerardii, Elymus canadensis, P. virgatum, Schizachrium scoparium, and Sorghastrum nutans), an early successional system, and a restored prairie with 25 sown grass, legume, and forb species. For three years (2011–2013) at both sites ingrowth cores were deployed each spring; half were extracted at mid-season and the rest in late fall. Native grasses and restored prairie systems produced 31–77% more fine roots by mid-season compared to the other cropping systems at both sites. Miscanthus and hybrid poplars tended to have the lowest fine root production. The polyculture cropping systems allocated 39–94% more energy to the production of fine roots, with the exception of switchgrass at the low fertility site. Findings demonstrate a greater potential for diverse biofuel cropping systems to allocate C belowground to fine roots as compared to monocultures, with potential implications for soil C sequestration.

Fine Root Dynamics in Afromontane Forest and Adjacent Land Uses in the Northwest Ethiopian Highlands

Fine roots are a major pathway of C input into soils. The aim of this study was to quantify fine root stocks, production and turnover in natural forest and land use systems converted from forests in Ethiopia. The study was conducted in a remnant Afromontane forest, eucalyptus plantation and grass and cropland in NW Ethiopia. Fine root dynamics were investigated using three different methods: sequential coring, in-growth cores and in-growth nets. Soil cores for sequential analyses were taken in quarterly intervals, while in-growth cores and nets were harvested corresponding to 1-, 2-, 3-, 4-, 5-, 8- and 12-month interval. Fine root stocks averaged 564, 425, 56 and 46 g·m−2 in the forest, eucalyptus, grazing land and cropland ecosystems, respectively. The values decreased exponentially with increasing soil depth. In forest and eucalyptus, fine root biomass and necromass were highest in the dry season. Estimates of fine root production differed according to the method used. Fine root production based on in-growth coring averaged 468, 293, 70 and 52 g m−2·year−1. In general, land use conversion from forest to open lands reduced fine root production by 85–91%. The turnover rate of fine roots was 1.5 for forest and 2.1 for eucalyptus plantation.