Total Fine Root Research Articles

Effects of soil physical ameliorants on the growth and root morphology of Prunus yedoensis and Ginkgo biloba seedlings in compacted soils

ABSTRACT Soil compaction is prevalent in forest ecosystems, it alters the physical structure of the soil and impedes tree growth. Although ameliorants are known to enhance soil properties and positively influence tree growth, studies remain limited on the effects of potential factors on root development in compacted soils after amelioration. This study aimed to examine the effects of the physical ameliorant treatments BIOC (compaction + biochar) and ORGF (compaction + organic fertilizer) on the soil properties, growth, and root development of Prunus yedoensis and Ginkgo biloba seedlings in compacted soils. We found that ameliorant treatments improved physicochemical soil conditions, such as bulk density, porosity, permeability, pH, total carbon, and total nitrogen, which in turn influence seedling growth. Specifically, in P. yedoensis, the relative growth rate of height was significantly higher in BIOC (46.19 ± 3.47%) compared to the control (29.58 ± 3.22%). The ameliorants did not significantly affect root morphological traits; however, we found that the total fine root length was positively correlated with shoot biomass in G. biloba (R = 0.97), but not in P. yedoensis. Root length tended to increase in BIOC, with measurements of 288.12 ± 68.97 m for P. yedoensis and 65.96 ± 25.08 m for G. biloba, while the mean fine root diameter tended to decrease in ORGF (1.25 ± 0.04 mm) and BIOC (1.37 ± 0.08 mm) for G. biloba. We conclude that biochar and organic fertilizer positively affect both soil properties and plant growth, highlighting that enhanced root development through ameliorants can improve plant growth in compacted soil.

Intraspecific variation in fine root morphology of European beech: a root order-based analysis of phenotypic root morphospace

Fine roots are multifunctional organs that may change function with ageing or root branching events from primarily absorptive to resource transport and storage functions. It is not well understood, how fine root branching patterns and related root functional differentiation along the longitudinal root axis change with soil chemical and physical conditions. We examined the variation in fine root branching patterns (the relative frequency of 1st to 4th root orders) and root morphological and chemical traits of European beech trees with soil depth (topsoil vs. subsoil) and soil chemistry (five sites with acid to neutral/alkaline bedrock). Bedrock type and related soil chemistry had an only minor influence on branching patterns: base-poor, infertile sites showed no higher fine root branching than base-rich sites. The contribution of 1st-order root segments to total fine root length decreased at all sites from about 60% in the topsoil (including organic layer) to 45% in the lower subsoil. This change was associated with a decrease in specific root area and root N content and an increase in mean root diameter with soil depth, while root tissue density did not change consistently. We conclude that soil depth (which acts through soil physical and chemical drivers) influences the fine root branching patterns of beech much more than soil chemical variation across soil types. To examine whether changes in root function are indeed triggered by branching events or result from root ageing and diameter growth, spatially explicit root physiological and anatomical studies across root orders are needed.

Contrasting depth‐related fine root plastic responses to soil warming in a subtropical Chinese fir plantation

Abstract Warming‐induced soil drought, especially in topsoil, may enlarge the spatial mismatch between nutrients and water along the soil profile, which impedes the uptake of not only water but also nutrients by trees. Therefore, coordinating the acquisition of soil water and nutrients along the soil profile is an important strategy for trees to cope with global warming. This study examined soil depth‐related changes in nutrient concentrations, biomass and morphology of fine roots in a Chinese fir plantation after 3 years of large‐scale manipulative soil warming. Soil warming (ambient +4°C) increased fine root nitrogen (N) concentrations but decreased fine root phosphorus (P) concentrations across soil depths. Warming did not affect total fine root biomass and its vertical distribution. At the 0–10 cm depth, warming increased specific root length (SRL), specific root area (SRA), fine root diameter (RD) and root length density (RLD) but reduced root tissue density (RTD). In the 40–60 cm layer, warming reduced RD, SRL and RLD while increasing RTD mainly for roots of the 1–2 mm diameter class. Synthesis. We concluded that roots of Chinese fir plantations could adapt to warming‐induced moderate water stress through contrasting depth‐related root morphological adjustments, probably to optimize the acquisition of both soil water and nutrients. The results of this study are crucial for understanding the adaptation strategies of subtropical forests under future climate conditions.

Ecological stoichiometry of leaf-litter-fine roots in mixed plantations in mountainous area of Southern Ningxia, China.

The southern mountainous areas in Ningxia are representative regions of the Loess Plateau, with extremely fragile ecological environment. Large area of pure plantations established during the project of Grain for Green has suffered from poor nutrient availability and biodiversity loss, while planting mixed plantations is commonly consi-dered as an effective way to improve the ecological benefits. We selected Robinia pseudoacacia + Picea asperata mixed plantation, R. pseudoacacia + Armeniaca sibirica mixed plantation, A. sibirica pure plantation and R. pseudoa-cacia pure plantation located ina Ningnan mountainous area as test objects. Based on the theory and method of ecological stoichiometry, we measured the C, N and P contents of leaves, litter and fine roots to understand nutrient cycling characteristics of different plantations. The results showed that there was significant difference in foliar stoichiometry of each tree species within the four plantations. P. asperata leaves had the highest C content in the R. pseudoacacia + P. asperata mixed plantation, and R. pseudoacacia leaves had the highest N and P contents in the R. pseudoacacia + A. sibirica mixed plantation. N content of R. pseudoacacia and A. sibirica leaves was significantly higher in mixed plantation compared with that in pure plantation. There was no significant difference in litter biomass, litter C, N, P contents and stoichiometric ratios between the pure and mixed plantations of R. pseudoacacia. Litter biomass in A. sibirica pure plantation was significantly higher than that in R. pseudoacacia + A. sibirica mixed plantation, while litter C content was significantly lower than that in the mixed plantation. Fine root biomass decreased with increasing soil depth in the four plantations, with total fine root biomass being the highest in the R. pseudoacacia + A. sibirica mixed plantation. N content and N:P of fine roots in the R. pseudoacacia + A. sibirica mixed plantation were higher than those in R. pseudoacacia and A. sibirica pure plantations. There was significant negative correlation between N content in leaves and fine roots of R. pseudoacacia + A. sibirica mixed plantation. There were significant negative correlations between the N content of leaves and litter, as well as between the P content of leaves and fine roots in the R. pseudoacacia + P. asperata mixed plantation. P content between litter and fine roots in A. sibirica pure plantation was significantly negatively correlated. Nutrient status of mixed plantations was better than pure plantations in the Ningnan mountainous area, with the mixed plantation of R. pseudoacacia and A. sibirica being the best. Mixed planting reduced nutrient limitation on plant growth to a certain extent.

Is the Fine Root Tensile Strength Predictable from Structural and Morphological Traits across Mycorrhizal Types in Cool-Temperate Woody Species?

The mycorrhizal type affects the structure and functions of tree roots. Therefore, the mechanical traits of the roots of tree species with different types of mycorrhizal fungi may be linked to different root functional traits. Fine roots, in particular, are closely related to the root structure and are also important for slope protection. However, the relationship among the mycorrhizal types of trees, root mechanical traits, and root structure remains unclear. This study aims to investigate the link between fine root tensile strength (Tr) and root morphological and/or structural traits in temperate trees with different mycorrhizal types. We investigated the seedlings of 15 dominant tree species in the cool temperate forests of northern Japan. For each species, fine root Tr and other five common root morphological and structural traits were measured. There was a significant positive correlation between total fine root biomass and fine root Tr consistently, even in the analysis of mycorrhizal types (arbuscular mycorrhizal (AM), and ectomycorrhizae (EM)). Our findings indicate that the root structural trait is an important driver of fine root Tr, especially for AM and EM species, and suggest that including a plant-mycorrhizal framework in future work offers great potential to improve our understanding of forest restoration.

Fine root dynamics of Kandelia obovata, Rhizophora stylosa and Bruguiera gymnorrhiza in a mangrove environment in Okinawa, Japan

The present study investigates the fine root dynamics including comparison of fine root production, mortality and decomposition of Kandelia obovata (S., L.) Yong, Rhizophora stylosa Griff. and Bruguiera gymnorrhiza (L.) Lamk. in the Manko Wetland of Okinawa, Japan considering the importance of fine root to the ecosystem carbon dynamics. Our objective was to investigate seasonal dynamics of fine root of the three species and explore whether there is variation among species using sequential core and ingrowth core methods. The root systems were separated into living and dead mass fractions and these were subsequently separated as very fine roots (<0.5 mm) and fine roots (0.5—2 mm). Total fine root production of K. obovata, R. stylosa and B. gymnorrhiza ranged from 4.7 to 7.1 Mg ha −1 y−1, 1.7 to 3.6 Mg ha −1 y−1 and 2.9 to 4.9 Mg ha −1 y−1, respectively whereas mortality ranged 2.9 to 5.9 Mg ha −1 y−1, 0.6 to 2.3 Mg ha −1 y−1 and 0.8 to 3 Mg ha −1 y−1. The mean fine root turnover of K. obovata, R. stylosa and B. gymnorrhiza were estimated as 3.42, 2.78 and 3.37 y−1 having a longevity of 3.46, 4.32 and 3.56 months, respectively. The amount of decomposition through sequential core and ingrowth core methods for K. obovata, was estimated at 47 and 28 g m−2y−1, respectively, whereas for R. stylosa and B. gymnorrhiza these were 6 and 11 g m−2y−1, and 15 and 19 g m−2y−1, respectively. Significant variation of soil salinity, soil N, soil pH among three species plots was observed although the result was insignificant in different seasons. Using ingrowth core method, we observed significant correlations of fine root production with soil salinity and soil pH, but the results were insignificant with sequential core data. Finally, the significant effect of soil pH was found in the regression model as the predictor of fine root production. Although the seasonal pattern was absent in fine root production, the seasonal change in the biomass and necromass was obvious. The high amount of fine root necromass available can be a great source of organic matter in the forest for carbon and nutrient cycling.

Seasonal Variations of Fine Root Dynamics in Rubber-Flemingia macrophylla Intercropping System in Southwestern China.

Intercropping cover crops with trees enhance land productivity and improves the soil’s physio-chemical properties while reducing the negative environmental impact. However, there is a lack of quantitative information on the relationships between fine root biomass and available soil nutrients, e.g., nitrogen (N), phosphorus (P), and potassium (K), especially in the rubber-Flemingia macrophylla intercropping system. Therefore, this study was initiated to explore the seasonal variation in fine root biomass and available soil nutrients at different stand ages (12, 15, and 24 years) and management systems, i.e., rubber monoculture (mono) and rubber-Flemingia macrophylla intercropping. In this study, we sampled 900 soil cores over five seasonal intervals, representing one year of biomass. The results showed that the total fine root biomass was greater in 12-year-old rubber monoculture; the same trend was observed in soil nutrients P and K. Furthermore, total fine root biomass had a significant positive correlation with available N (p < 0.001) in rubber monoculture and intercropping systems. Thus, it suggests that fine root growth and accumulation is a function of available soil nutrients. Our results indicate that fine root biomass and soil nutrients (P and K) may be determined by the functional characteristics of dominant tree species rather than collective mixed-species intercropping and are closely linked to forest stand type, topographic and edaphic factors. However, further investigations are needed to understand interspecific and complementary interactions between intercrop species under the rubber-Flemingia macrophylla intercropping system.

Morphological adaptation of cocoa fine roots under shaded of langsat tree in exploring stony soil

Cocoa fine roots are responsive to changes in the soil environment to maximize nutrient and water absorption for plant growth. The presence of rock increases soil density and decreases available water content, promoting modification of fine root development. The purpose of this study was to clarify the effect of the physical properties of stony soil on the morphological properties of fine roots. In three land-use systems, soil samples were taken from four depths using a sample core measuring 385 cm3 in three land-use systems. Fine roots were extracted by the immersion method, to measure the length of fine roots from five classes of orders based on diameter. We notes, the bulk density of stony soil increases as the rock mass increases, and the depth increases. The available water content decreases with the increase in bulk density, and this decrease is more pronounced in the lower soil layer. Fine root length was found more in the lower order diameter class, decreasing soil moisture against the bulk density gradient. The bulk density in the topsoil layer reaches 1.71 g cm-3, increasing to 1.84 g cm-3 in the lower soil layer. It seems unreasonable, when compared to the general density of soil mass. Still, this result is solely due to the high fraction of rock with a higher density. Fine roots were dominated by orders 1 and 2 with root diameters < 0.25 mm and < 0.50 mm, reaching 70% of the total fine root length. Fine roots in this diameter class act as absorbent roots, acquiring water and nutrients from the soil.

Temporal dynamics of fine root production, mortality and turnover deviate across branch orders in a larch stand.

Fine roots play a key role in carbon, nutrient, and water biogeochemical cycles in forest ecosystems. However, inter-annual dynamics of fine root production, mortality, and turnover on the basis of long-term measurement have been less studied. Here, field scanning rhizotrons were employed for tracking fine root by branch order over a 6years period in a larch plantation. For total fine roots, from the first- to the fifth-order roots, annual root length production, length mortality, standing crops, and turnover rate varied up to 3.4, 2.3, 1.5, and 2.3-folds during the study period, respectively. The inter-annual variability of those roots indices in the first-order and the second-order roots were greater than that of the higher order (third- to fifth-order) roots. The turnover rate was markedly larger for the first-order roots than for the higher order roots, showing the greatest variability up to 20times. Seasonal dynamics of root length production followed a general concentrated pattern with peak typically occurring in June or July, whereas root length mortality followed a general bimodal mortality pattern with the dominant peak in May and the secondary peak in August or October. Furthermore, the seasonal patterns of root length production and mortality were similar across years, especially for the first-order and the second-order roots. These results from long-term observation were beneficial for reducing uncertainty of characterizing fine root demography in consideration of large variation among years. Our findings highlight it is important for better understanding of fine root dynamics and determining root demography through distinguishing observation years and root branch orders.

Fine Root Production and Soil Available Nutrients in Rubber Monoculture versus Rubber–Flemingia macrophylla Agroforestry

In the present study, we examined fine root production and soil available nutrients (N, P and K) across different soil depths in rubber monoculture and rubber–Flemingia macrophylla agroforestry of different stand ages. We used the ingrowth cores method and sampled 360 soil cores over four growth intervals, representing one year of growth for the present study. The results showed that root production and macronutrient concentrations generally decreased with increasing soil depth. Total fine root production was comparatively high in the youngest stand age (12 years) rubber monoculture; a similar trend was observed for the soil available P and K, but available N was greater in older than younger stand ages. Root growth and soil available P and K were all lower in the agroforestry system than the monoculture. Significant differences in fine root production with stand ages, management system and seasons suggest that fine root responses to the soil available nutrients are vital to understanding the precise response of above- and belowground biomass to environmental changes.

Is it necessary to apply chemical weed control in short-rotation poplar plantations on deep soil sites?

Chemical weed control has been widely applied in plantation forests around the world. However, understanding the long-term influence of weed control on stand growth and its underlying mechanisms is still limited. We conducted a six-year (2016–2021; an entire rotation) weed control study in Chinese white poplar (Populus tomentosa Carr.) plantations established using tall planting stock on a deep soil site, which is a typical afforestation mode for poplars in north China. Three treatments of chemical weed control degree were implemented: no weeding (W0), removing weeds within 50 cm distance from the tree row (W50) and removing all weeds on the ground (W150). Different tree growth indicators, soil water content (θ), tree root distribution, and soil physical properties were measured. There was no weed control degree effect on θ in 2017 (P = 0.4408) but significant θ difference (P = 0.0140) among treatments existed in 0–30 cm soil in 2021. Different degrees of weed control did not change soil physical properties (P > 0.05) after the long-term application of chemical weeding. There were no differences (P > 0.05) in all growth indicators. But the cumulative increments of tree diameter, height, stand volume index, and biomass at the end of the rotation in W150 were numerically 2–27% lower than W0 and 11–26% lower than W50. The total fine roots biomass increased with decreasing weed control degree, although the difference was non-significant (P > 0.05). The fine root distribution pattern indicated that there might be many fine roots below 200 cm depth. The tree growth response to weed control may be attributed to tall planting stock that avoids light competition from weeds and deep soil resource exploration by tree roots that alleviate competition by shallow weed roots. Consequently, it may be unnecessary to apply chemical weed control in poplar plantations established using tall planting stock on deep soil sites. Our findings provide guidance for the sustainable management of industrial plantation forests.

Ectomycorrhizal fungal community in mature white poplar plantation

Abstract: Ectomycorrhizal communities are rarely studied on seasonal basis, especially in poplar plantations. In this study we analysed the ectomycorrhizal community in a mature twenty-year-old white poplar (Populus alba L.) plantation during four consecutive seasons. Using morpho-anatomical and molecular identification 30 taxa of ectomycorrhizal fungi were recorded of which 15 were identified to the species level, 12 to the genus level, 2 to the family, and one morphotype of ectomycorrhizae remained unidentified. The most abundant among identified ectomycorrhizal fungi were: Inocybe griseovelata, Inocybe splendens, Tuber rufum, and Tomentella sp. 2, which together represented up to 50% of all ectomycorrhizal root tips. The number of ectomycorrhizal fungal taxa and the percentage of vital ectomycorrhizal root tips were highest in winter and spring, respectively. The diversity indices of ectomycorrhizae, number of vital ectomycorrhizal root tips, and total fine roots in the studied poplar plantation did not differ between seasons. Ectomycorrhizal fungi belonging to Inocybaceae family and the short-distance exploration strategy were dominant in all four seasons. On the other hand, the abundance of ectomycorrhizal root tips belonging to the medium-distance exploration strategy type was significantly higher in spring in comparison with autumn and winter.

Estimation of total fine root production using continuous inflow methods in tropical mangrove forest on Pohnpei Island, Micronesia: Fine root necromass accumulation is a substantial contributor to blue carbon stocks

AbstractFine root decomposition, mortality, and production are fundamental components of belowground carbon dynamics in mangrove ecosystems. Mangroves are highly productive ecosystems with huge carbon stocks; however, information on the dynamics of submerged fine roots in mangrove soils is limited. To estimate fine root production in several sites of mangrove communities on Pohnpei Island, Micronesia, we estimated continuous inflows using a simple mass balance model to combine ingrowth core and litterbag experimental results. According to our findings, previously reported mangrove fine root production values were severely underestimated because the fine root decomposition process was disregarded during the experimental period. We estimated that annual fine root production up to 0.3 m in depth ranged from 13.8 (Bruguiera gymnorrhiza in a landward plot) to 56.3 Mg ha−1 year−1 (B. gymnorrhiza in a seaward plot). However, comparing the fine root production with respect to the unit of stem cross‐section area increase in the sample tree, the fine root production of Rhizophora spp. was greater than that of other species. The annual fine root mortality and decomposition to annual fine root production was 70%–105% and 11%–52% of annual production, respectively. The annual fine root production estimated here was much higher than that previously reported. These findings begin to quantify the contribution and importance of highly productive mangrove fine roots for carbon sequestration in blue carbon ecosystems. Moreover, this study provides new insights into the organic carbon dynamics in mangrove soils with mangrove vegetation succession.

The Optimal Concentration of KH2PO4 Enhances Nutrient Uptake and Flower Production in Rose Plants via Enhanced Root Growth

Monopotassium phosphate is a widely used phosphorus and potassium fertiliser for ornamental plants, but it is not known what concentration will result in optimal flower production, root growth and nutrient uptake of rose plants. We compared potted rose plants fertilised with six different concentrations (0.0 as a water-only control, 1.0, 2.0, 3.0, 4.0 and 5.0 g·L−1) of an aqueous monopotassium phosphate solution as a combination of foliar and soil applications over two consecutive flowering cycles. Rose growth, flower production and nutrient accumulation responded differently to fertilisation with different concentrations of monopotassium phosphate. During the first flowering cycle, shoot and root dry weight, leaf chlorophyll content, flower diameter, total root length and surface area, and total fine root length significantly increased in response to increased monopotassium phosphate concentrations from 0.0 to 3.0 g·L−1 but decreased in response to fertilisation with 4.0 or 5.0 g·L−1 monopotassium phosphate. Similar trends were observed in shoot dry weight, leaf chlorophyll content, flower diameter and number, phosphorus and potassium accumulation during the second flowering cycle. According to quadratic equations derived from both flowering cycles, the optimal concentration of monopotassium phosphate, based on flower diameter and dry weight, as well as total phosphorus and potassium accumulation, was 2.6–3.0 g·L−1. Furthermore, total root length was significantly correlated with flower diameter, flower dry weight, and total phosphorus and potassium accumulation (p &lt; 0.05). These results indicated that fertilisation with optimal concentrations of monopotassium phosphate can increase rose growth, flower productivity and nutrient uptake through enhanced root growth.

Estimation of fine root production, mortality, and decomposition by using two core methods and litterbag experiments in a mangrove forest

AbstractMangrove forests are characterized by high rates of carbon sequestration, with much of this carbon being derived from fine roots. In this study, we sought to estimate the dynamics of the fine (&lt;2 mm) and small (≥2 mm) roots of Kandelia obovata, one of the mangrove forest species found on Okinawa Island, southern Japan, and to evaluate annual root production considering root decomposition estimated using root litterbags. To estimate root production and mortality, we applied two approaches, sequential soil core sampling and ingrowth core methods. We found that annual root production determined by sequential soil core sampling was 3.2 times higher than that estimated by ingrowth core methods. The annual production of fine roots (545 and 294 g m−2 year−1 for sequential soil core sampling and ingrowth core methods, respectively) was higher than that of small roots (536 and 44 g m−2 year−1 for sequential soil core sampling and ingrowth core methods, respectively). The results obtained using sequential soil core sampling indicated a high proportion of fine root necromass to total fine root mass (81%), most of which comprised very fine roots (&lt;0.5 mm). We also established that the decomposition ratio of fine roots was lower than that of small roots. Collectively, our observations indicate that the slow rate of decomposition and high rate of production of fine roots contribute significantly to the accumulation of fine root necromass, particularly that of very fine roots, in the mangrove forest.

Fine root biomass and necromass dynamics of Chinese fir plantations and natural secondary forests in subtropical China

Fine roots play a critical role in terrestrial carbon and nutrient cycling. Despite this, quantitative evaluation of the fine root dynamics in plantations and natural secondary forests is lacking. This study examined the dynamics of fine root biomass and necromass of Chinese fir plantations and natural secondary forests (5–41 years old) and employed primary forests as a reference in subtropical China. In the top 60-cm soil depth, the sum of fine root biomass of Chinese fir plantations and natural secondary forests initially increased and then decreased with stand development, attaining a peak in the 27–31-year age class. The total fine root biomass of natural secondary forests was significantly higher than that of Chinese fir plantations across all age classes. The total fine root biomass of primary forests was similar to that in the 38–41-year-old natural secondary forests and Chinese fir plantations. The total fine root necromass was higher in Chinese fir plantations than in natural secondary forests across all ages except in the youngest age class. The necromass to biomass ratio was significantly higher in Chinese fir plantations. Most of the fine root biomass resided in the topsoil (0–10 cm) for all stand types and ages. The higher fine root biomass in the secondary natural forests than in the Chinese fir plantation was most apparent in the topsoil. Across all age classes, the fine root biomass was positively correlated with stand basal area, mean diameter at breast height, and shrub cover, whereas the fine root necromass and the necromass to biomass ratio tended to be more consistent across measured stand characteristics. Our results highlight profound influences of forest management on fine root biomass and necromass and suggest that the low fine root biomass of Chinese fir plantations may have a negative impact on carbon and nutrient cycling in the subtropical forests.

Fine-root functional trait responses to experimental warming: a global meta-analysis.

Whether and how warming alters functional traits of absorptive plant roots remains to be answered across the globe. Tackling this question is crucial to better understanding terrestrial responses to climate change as fine-root traits drive many ecosystem processes. We carried out a detailed synthesis of fine-root trait responses to experimental warming by performing a meta-analysis of 964 paired observations from 177 publications. Warming increased fine-root biomass, production, respiration and nitrogen concentration as well as decreased root carbon : nitrogen ratio and nonstructural carbohydrates. Warming effects on fine-root biomass decreased with greater warming magnitude, especially in short-term experiments. Furthermore, the positive effect of warming on fine-root biomass was strongest in deeper soil horizons and in colder and drier regions. Total fine-root length, morphology, mortality, life span and turnover were unresponsive to warming. Our results highlight the significant changes in fine-root traits in response to warming as well as the importance of warming magnitude and duration in understanding fine-root responses. These changes have strong implications for global soil carbon stocks in a warmer world associated with increased root-derived carbon inputs into deeper soil horizons and increases in fine-root respiration.

Spatial–temporal variations of absorptive fine roots in the organic and soil layers of a Larix gmelinii forest

In the organic layer, absorptive fine roots of Larix gmelinii represent a significant proportion of the total fine-root biomass and can morphologically adjust during the growing season to optimize resource acquisition. Larix gmelinii is a foundational tree species in forests of northern China and Far-East Russia. A better understanding of the species’ belowground resource acquisition strategy is important for soil nutrient and carbon estimates. Here, we investigated seven traits of absorptive fine-roots at four depth levels, from the organic layer (organic, decomposed litter from dead plants) down to a soil depth of 30 cm in May, July and September of 2016. Biomass and functional traits of absorptive fine roots varied significantly, indicating the species ability to adjust its resource acquisition across the four depth layers. From the organic layer to deeper mineral soil layers, root diameter and tissue density increased, while specific root length decreased, in other words, roots become longer and thinner with increasing values of soil water and nutrient concentrations. At the same time, the average biomass and length of absorptive fine roots in the organic layer accounted for 14% and 16% of the total, respectively. With increasing soil depth, the averaged proportion of biomass and length density of absorptive fine roots to the total fine roots decreased significantly from almost 57 to 32%, and 80–62%, respectively. Finally, total soil nitrogen concentration showed the strongest link with absorptive fine-root traits, such as root diameter, specific root length, root standing biomass and length density. Our results indicate that absorptive fine roots in the organic layer play a crucial role in belowground resource acquisition and carbon cycle in a common and economical important species.

Grassland ecological restoration based on the relationship between vegetation and its below-ground habitat analysis in steppe coal mine area.

Coal mining activities have caused severe disturbances to the regional ecosystem and soil properties. Studying the relationship of vegetation and its below-ground habitat (RVBGH) is of great significance to the coal mine land ecological restoration. To identify the optimal thickness of the soil layer for mine land ecosystem recovery and characterize the changes of the reclaimed soil-vegetation ecosystem, we studied natural and reclaimed grassland at the coal mine of Baorixile, located in Hulunbuir Steppe, Northeastern China. The vegetation and its below-ground habitat (BGH), including "root mass" and soil properties in the soil profile (0-100cm), were surveyed in the natural and different year-reclaimed grassland. The "root mass" is the part of root system that has the most amounts of root hairs, which is the functional zone for plant growth. The RVBGH was identified by the "root mass" and plant water extraction depth, measured through the isotope δD and δ18O method. Firstly, the BGH of natural grassland was identified as a "double layer" vertical structure, with the "root mass" of 37.11±2.57% fine roots at 0-20cm range and 30.44±2.67% at 20-40cm range. The annual and perennial plant "root mass" was found at 0-20cm and 20-40cm depth, respectively. Secondly, an optimal thickness of the soil covering of 30-40cm was proposed for grassland reclamation. Thirdly, along the reclamation chronosequence, the values of the reclaimed vegetation properties (height, density, coverage and diversity) increased and a deep root system was established. The "root mass" increased from one layer to double layer and the amount of total fine roots increased from 1621±231.9 to 4459±456.0. Moreover, the reclaimed soil properties of organic matter, cation exchange capacity, available N and P also increased. The study proposed that vegetation restoration was significantly correlated with its BGH, suggesting that vegetation BGH recovery is crucial in ecological restoration.

Effects of warming and fertilization interacting with intraspecific competition on fine root traits of Picea asperata

Abstract Aims Competition, temperature and nutrient are the most important determinants of tree growth in the cold climate on the eastern Tibetan Plateau. Although many studies have reported their individual effects on tree growth, little is known about how the interactions of competition with fertilization and temperature affect root growth. We aim to test whether climate warming and fertilization promote competition and to explore the functional strategies of Picea asperata in response to the interactions of these factors. Methods We conducted a paired experiment including competition and non-competition treatments under elevated temperature (ET) and fertilization. We measured root traits, including the root tip number over the root surface (RTRS), the root branching events over the root surface (RBRS), the specific root length (SRL), the specific root area (SRA), the total fine root length and area (RL and RA), the root tips (RTs) and root branching (RB) events. These root traits are considered to be indicators of plant resource uptake capacity and root growth. The root biomass and the nutrient concentrations in the roots were also determined. Important Findings The results indicated that ET, fertilization and competition individually enhanced the nitrogen (N) and potassium (K) concentrations in fine roots, but they did not affect fine root biomass or root traits, including RL, RT, RA and RB. However, both temperature and fertilization, as well as their interaction, interacting with competition increased RL, RA, RT, RB and nutrient uptake. In addition, the SRL, SRA, RTRS and RBRS decreased under fertilization, the interaction between temperature and competition decreased SRL and SRA, while the other parameters were not affected by temperature or competition. These results indicate that P. asperata maintains a conservative nutrient strategy in response to competition, climate warming, fertilization and their interactions. Our results improve our understanding of the physiological and ecological adaptability of trees to global change.