Concentrations In Fine Roots Research Articles

增温和氮添加对杉木不同序级细根形态和化学性状的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 增温和氮添加对杉木不同序级细根形态和化学性状的影响 DOI: 10.5846/stxb202204291200 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金重点项目（31830014）；国家重点研发计划项目课题项目（2021YFD2200403） Effects of soil warming and nitrogen addition on the morphological and chemical characteristics of fine roots in different order classes of the Chinese fir Author: Affiliation: Fund Project: National Natural Science Foundation of China(31830014);Topics of state key R & D projects（2021YFD2200403） 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:全球气候变暖与氮（N）沉降是两个同时存在的全球变化主要因素，但目前关于二者的研究多以单因子为主。细根形态和化学性状等功能性状在促进植物养分获取和森林生物地球化学循环方面起着关键作用，但目前气候变暖、N沉降以及两者交互对细根形态和化学性状的影响尚不清楚。在福建三明森林生态系统国家野外科学观测研究站陈大观测点开展土壤增温与N添加双因子试验，包括对照（无增温，无氮添加）、低氮（+4gN m-2 a-1）、高氮（+8gN m-2 a-1）、增温（+5℃）、增温+低氮（+5℃，+4gN m-2 a-1）、增温+高氮（+5℃，+8gN m-2 a-1）六个处理，探讨增温与N添加对杉木（Cunninghamia Lanceolata）细根形态和化学性状的影响。结果表明：（1）增温显著增加了细根直径（D）。增温和N添加的交互作用对细根比根长（SRL）、比表面积（SRA）及组织密度（RTD）均存在显著影响，与对照相比，增温处理及增温+高氮处理均降低了细根SRL和SRA；不同处理间细根RTD无显著差异。N添加与序级交互作用对细根SRA存在显著影响，仅低氮添加显著增加了1级根SRA。（2）增温和N添加交互作用对细根碳（C）含量存在显著影响，与对照相比，仅增温+高氮处理显著增加了细根C含量。N添加与序级交互作用对细根C含量存在显著影响，仅在1级细根中，高氮添加的细根C含量要显著高于低氮添加。增温、N添加以及序级三者交互作用对细根N含量及碳氮比（C ： N）存在显著影响，与对照相比，低氮和高氮处理对细根N含量及C ： N影响因序级而异；增温处理、增温+低氮处理以及增温+高氮处理均显著提高了细根N含量，降低了细根C ： N；与高阶根相比，低阶根N含量和C ： N对单独增温处理及增温+低氮处理响应要更为敏感。以上结果表明，不同细根功能性状对增温、N添加及两者交互的响应存在差异，这种差异主要与细根序级和N添加水平有关；增温和N添加抑制了细根SRL和SRA，但促进了细根N含量并降低了细根C ： N，这将有助于理解亚热带地区森林地下养分循环以及C固存对全球环境变化的响应。 Abstract:Global warming and nitrogen deposition are two main global change drivers, often occurring simultaneously. However, most of related studies referred to only single factor. Fine root functional traits such as morphology and chemical properties play a key role in promoting plant nutrient acquisition and forest biogeochemistry cycling. The effects of climate warming, N deposition and their interactions on fine root morphology and chemical properties remain unclear. To explore the effects of warming and N addition on the morphological and chemical characteristics of fine roots of Cunninghamia Lanceolata. We conducted a two-factor experiment of soil warming and nitrogen addition, which consisted control (CT), low nitrogen treatment (LN), high nitrogen treatment (HN), warming treatment (W), warming and low nitrogen treatment (WLN), warming and high nitrogen treatment (WHN), at the Forest Ecosystem and Global Change Research Station of Fujian Normal University, Chenda, Sanming, Fujian Province. The results showed that:(1) the warming significantly increased fine root diameter (D). The interaction of warming and N addition had significant effects on the specific root length (SRL), specific surface area (SRA) and root tissue density (RTD) of fine roots. Compared with CT, the W and WHN reduced fine root SRL and SRA; there was no significant difference in RTD of fine roots among different treatments. The interaction of N addition and order had significant effects on fine root SRA. Low nitrogen addition only increased SRA of first order root significantly. (2) The interaction of warming and N addition had a significant effect on fine root C concentration, and only WHN significantly increased fine root C concentration. The interaction of N addition and order had significant effects on fine root concentration. The fine root C concentration of high N addition was significantly higher than that of low N addition. The interaction of warming, N addition and order had significant effects on fine root N concentration and C:N. Compared with CT, the effects of LN and HN on fine root N content and C:N varied with the order; The W, WLN and WHN significantly increased the fine root N concentration and decreased the fine root C:N. Compared with high-order root, low-order root N concentration and C:N were more sensitive to the effects of W and WLN. The results showed that the responses of fine root morphology and chemical characteristics to warming, N addition and their interaction were different, and the differences were mainly regulated by fine root branch order and N addition level; The warming and N addition promoted fine root N concentration and decreased fine root C:N, which would contribute to understand the subsurface nutrient cycling and the response of C sequestration to global environmental change in subtropical forests. 参考文献 相似文献 引证文献

Effect of the elevated ozone on greening tree species of urban: Alterations in C-N-P stoichiometry and nutrient stock allocation to leaves and fine roots

Anthropogenic ground-level ozone (O3) pollution can alter the phosphorus (P), carbon (C), and nitrogen (N) of terrestrial plants’ ecological stoichiometry, which in turn affects forest productivity, nutrient utilization, and carbon sink capacity. However, there is still quite a lot of uncertainty regarding the impact of high O3 levels on C-N-P stoichiometry in organs with a rapid turnover (i.e., fine roots and leaves) across varied functional types. This study investigated the effects of O3 on the stoichiometry of C-N-P nutrient allocation of stocks to various plant organs, with a special focus on tree species frequently employed for urban greening. The impact of O3 on C-N-P stoichiometry among different functional tree types was subsequently evaluated by reviewing the published literature. Under a pooling of all species, elevated O3 decreased and leaf C and P concentrations increased, thereby decreasing the leaf C: P ratio. Elevated O3 increased the N concentration in fine roots, thereby decreasing the C: N ratio, although no significant impact was observed in leaves. Elevated O3 significantly reduced the leaf stocks of C (CSleaf) and N (NSleaf), however, there was no observed variation in these stocks in fine roots. The content of P, C, and N in fine roots and leaves in evergreen broadleaf species exceeded those in deciduous species. Elevated O3 significantly reduced CSleaf, NSleaf, and PSleaf in deciduous broadleaf species, whereas there was a significant reduction for the same in evergreen species. The literature analysis further demonstrated a larger O3-induced increment in leaf P concentration in deciduous species as compared to evergreen species. Elevated O3 significantly increased the difference in C and N stocks between fine roots and leaves in deciduous broadleaf species, whereas this difference was observed to decrease in evergreen species. The results of this study can facilitate an improved understanding of ecological stoichiometric responses of urban greening tree species under O3 stress and the resulting nutrient use strategies.

Gypsum endemics accumulate excess nutrients in leaves as a potential constitutive strategy to grow in grazed extreme soils.

Extreme soils often have mineral nutrient imbalances compared to plant nutritional requirements and co‐occur in open areas where grazers thrive. Thus, plants must respond to both constraints, which can affect nutrient concentrations in all plant organs. Gypsum soil provides an excellent model system to study adaptations to extreme soils under current grazing practices as it harbours two groups of plant species that differ in their tolerance to gypsum soils and foliar composition. However, nutrient concentrations in organs other than leaves, and their individual responses to simulated herbivory, are still unknown in gypsum plants. We studied plant biomass, root mass ratio and nutrient partitioning among different organs (leaves, stems, coarse roots, fine roots) in five gypsum endemics and five generalists cultivated in gypsum and calcareous soils and subjected to different levels of simulated browsing. Gypsum endemics tended to have higher elemental concentration in leaves, stems and coarse roots than generalist species in both soil types, whereas both groups tended to show similar high concentrations in fine roots. This behaviour was especially clear with sulphur (S), which is found in excess in gypsum soils, and which endemics accumulated in leaves as sulphate (>50% of S). Moreover, plants subjected to clipping, regardless of their affinity to gypsum, were unable to compensate for biomass losses and showed similar elemental composition to unclipped plants. The accumulation of excess mineral nutrients by endemic species in aboveground organs may be a constitutive nutritional strategy in extreme soils and is potentially playing an anti‐herbivore role in grazed gypsum outcrops.

Whole-Tree Response of Non-Structural Carbohydrates, Carbon and Nitrogen Concentrations in Two Temperate Tree Species to 10-Year Nitrogen Fertilization

This study aimed to investigate the effects of long-term nitrogen fertilization on non-structural carbohydrates (NSC) and nitrogen (N) status and their interaction in mature trees at the whole-tree scale. Ten g N m−2 yr−1 of ammonium nitrate fertilizer were applied to 26-year-old Larix gmelinii Rupr. (larch) and Fraxinus mandschurica Rupr. (ash) trees in Northeastern China from 2002 to 2012. NSC, total carbon (C) and total N concentrations in different compartments were examined. For both species, concentrations of NSC and their components (soluble sugars and starch) tended to increase in aboveground organs but decrease in fine roots following N fertilization, with significant (p < 0.05) changes only observed in ash stems and larch roots. N fertilization increased N concentrations and decreased the C:N ratio in all organs, especially in foliage and roots, while the effects of fertilization on total C concentrations varied with tree species and organs. Concentrations of NSC (mainly reflected in soluble sugar) were generally negatively correlated with N concentration in fine roots but positively related to N concentration in aboveground woody organs in both control and fertilized treatments. However, fertilization strengthened this correlation in fine roots and weakened this relationship in aboveground organs. This study provides a decade-long insight into the effect of currently increasing N deposition on tree growth and function.

Quantification of Root Biomass in Post-Mining Areas in the Municipality of Capitão Poço – PA, Brazil

The present work aimed to quantify the concentrations and biomass stock of fine andthick roots, in three areas in the municipality of Capitão Poço-PA, Brazil. The areas used were degraded area, recovery area and native forest. For soil sampling, 24 trenches were opened, measuring 70 x 70 x 100 cm. In these trenches, soil samples were taken at depths 0-10, 10-20, 20-30, 30-40, 40-50, 50-60, 60-80 and 80-100 cm and sieving was carried out.All roots and other underground plant structures that remained in the sieve were collected by manual collection. The roots were separated into two diameter classes: fine roots ≤ 5 mm and thick roots > 5 mm, kiln dried and weighed.In the analysis, higherconcentrationsofthickand fine roots were observed in an area of native forest at depths of 0-10 and 10-20 cm. In the areas analyzed in this study, the root density in the topsoil of 0-10 cm was mainly composed of fine roots.In the three areas analyzed in this study, it was observed that from a depth of 10-20 cm there were decreases in theconcentrationsofthick roots. The area under recovery approached the area of native forest in the concentration of fine roots, demonstrating possible improvements in soil quality and recovery is probably actually taking place.

Nitrogen and Phosphorus Distribution and Relationship in Soils and Plants under Different Aged Chinese Fir Plantation

As essential nutrients for plant growth and development, the balance of nitrogen (N) and phosphorus (P) between soils and plants is a key component to ecosystem stability. In this study, we examined the distribution of nutrients in the soils and different organs of Chinese fir (Cunninghamia lanceolata) in Hunan Province, southern China. Additionally, we investigated the nutrient concentrations in soil layers (0–80 cm depth) and in plant organs, and the total biomass of 10-, 20-, and 30-year-old plantations. The results suggested that the nutrients in the soil were aggregated in the surface layer. The highest and lowest values of N concentrations in 0–80 cm soil layers and P concentrations in 0–40 cm soil layers were both in 30-year-old plantations and 20-year-old plantations, respectively. Nitrogen in the organs of Chinese fir in all plantations and P concentrations in the organs of 20- and 30-year-old trees decreased in the following order: leaves, fine roots, coarse roots, and stems. Total biomass (N and P pools of four organs) increased consistently with stand age increase, and N and P pools were the highest in leaves and stems, respectively. There were significant, positive correlations between N and P in the soil (0–80 cm), and organs, respectively, and also between N concentrations of fine roots and that of 0–10 and 10–20 cm soil, respectively. In Chinese fir plantations, concentrations of nutrients in specific tree organs and the soil were correlated positively, which can only partially explain the balance of nutrients within the plant–soil ecosystem. This study suggested that incorrect harvesting patterns may effectively deprive the forest ecosystem of valuable nutrients that would ordinarily have been returned to the soil.

Rates of soil respiration components in response to inorganic and organic fertilizers in an intensively-managed Moso bamboo forest

Fertilization is a common practice to increase forest productivity; however, the responses of soil respiration (RS) components to the application of inorganic and organic fertilizers and the associated mechanisms are not clear in subtropical forest ecosystems. In this field trial conducted within an intensively-managed Moso bamboo (Phyllostachys edulis) forest, we aimed to compare the effects of inorganic and organic fertilizers, and their combination on seasonal variations in RS components, i.e., heterotrophic (RH) and autotrophic (RA) respiration, and to establish the relations of RS components with soil properties. Fertilizer additions increased RH (P < 0.05), with the increase being greater with organic than with inorganic fertilizer. Fertilization also increased RA, but the effect was greater with inorganic fertilizer. Furthermore, fertilizer additions increased (P < 0.05) the concentrations of water-soluble organic C (WSOC) and microbial biomass C, invertase and β-glucosidase activities, as well as the biomass and N concentration of fine roots. Irrespective of fertilizer treatment, strong seasonal patterns were observed in both RS and RH, and an exponential relation (P < 0.01) was found between RS components (RH and RA) and soil temperature. Additionally, the Q10 for RH was higher (P < 0.05) in the inorganic than the organic fertilizer treatment. Although RS and RH showed no correlation with soil moisture content in any treatment, each of them was positively correlated with WSOC concentration and activities of invertase and β-glucosidase (P < 0.05). In the fertilized treatments, RA was positively related to β-glucosidase activities (P < 0.05) but not to the concentrations of WSOC or microbial biomass C. In conclusion, soil RA and RH in the subtropical Moso bamboo forest responded differently to the application of inorganic and organic fertilizers, indicating that separation of total RS into soil RH and RA is critically necessary to predict RS in subtropical forests under different fertilizer regimes.

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

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

The contrasting effects of nitrogen and phosphorus fertilizations on the growth of Cunninghamia lanceolata depend on the season in subtropical China

Phosphorus (P) and nitrogen (N) are the major limiting nutrients for plant growth in most ecosystems. However, it is unclear whether P fertilization exhibits higher effects on plant growth than N fertilization and whether the effects vary with season, since plant demands for N vs. P vary differently during different seasons. We seasonally measured N and P concentrations of fine roots, leaves, and soil as well as growth in Chinese fir (Cunninghamia lanceolata) plantations fertilized with P (5 g m−2 a−1) and/or N (5 g m−2 a−1 and 10 g m−2 a−1) over five years in subtropical China. Needle N and P concentrations were significantly influenced by P fertilization, whereas root N and P concentrations were significantly influenced by P fertilization and the interaction between P fertilization and season. Phosphorus fertilization generally decreased root N concentration in the warm season and increased P concentrations of needle and root in the cold season. Moreover, root P concentration with P fertilization was significantly higher during the cold season than during the warm season, regardless of N fertilization. Contrary to the cold season, in the case of high N fertilization, basal area increment was significantly lower with than without P fertilization during the warm season. Nitrogen fertilization in the warm season had a positive effect on basal area increment, contrary to the cold season. Contrary to N fertilization, P fertilization had a negative effect on basal area increment in the warm season, whereas it had a positive effect in the cold season. Phosphorus fertilization contributed more than N fertilization to basal area increment during both seasons. Moreover, root P concentration was the most crucial factor determining basal area increment during both seasons. The opposite effects of N and P fertilizations on plant growth depend on the season in the Chinese fir plantation, which suggested that the timing of P and N fertilizations should be considered for the Chinese fir plantations in subtropical areas.

Carbon and nutrient physiology in shrubs at the upper limits: a multispecies study

Abstract Aims Carbon and nutrient physiology of trees at their upper limits have been extensively studied, but those of shrubs at their upper limits have received much less attention. The aim of this study is to examine the general patterns of nonstructural carbohydrates (NSCs), nitrogen (N) and phosphorous (P) in shrubs at the upper limits, and to assess whether such patterns are similar to those in trees at the upper limits. Methods Across Eurasia, we measured the concentrations of soluble sugars, starch, total NSCs, N and P in leaves, branches and fine roots (&amp;lt;0.5 cm in diameter) of five shrub species growing at both the upper limits and lower elevations in both summer (peak growing season) and winter (dormancy season). Important Findings Neither elevation nor season had significant effects on tissue N and P concentrations, except for lower P concentrations in fine roots in winter than in summer. Total NSCs and soluble sugars in branches were significantly higher in winter than in summer. There were significant interactive effects between elevation and season for total NSCs, starch, soluble sugars and the ratio of soluble sugar to starch in fine roots, showing lower soluble sugars and starch in fine roots at the upper limits than at the lower elevations in winter but not in summer. These results suggest that the carbon physiology of roots in winter may play an important role in determining the upward distribution of shrubs, like that in the alpine tree-line trees.

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.

Seedling regeneration techniques affect root systems and the response of Quercus robur seedlings to water shortages

Regenerating oak seedlings by different methods impacts taproot architecture, root-to-shoot allometry and, potentially, soil water use and plant growth under water limitations. In the present study, Quercus robur (L.) seedlings regenerated by four different methods – sowing (acorn-sown seedlings), sowing followed by shoot clipping (coppiced), sowing followed by root-pruning (root-pruned), and container planting with the root plug intact (containerized) – were subjected to four water-shortage regimes – full watering and 75, 50, and 25% of full watering. These treatments were used to test the hypotheses that root morphology, anatomy and biochemistry varied among regeneration methods, and, thus, differentially affected plant responses to water-shortages. For most traits, the response to water shortage of acorn-sown and containerized seedlings was similar, and opposite to that of coppiced and root-pruned seedlings. Water shortage did not change tree allocation to total root biomass among regeneration methods but altered the partitioning between absorptive and structural roots within the root system. Acorn-sown and containerized seedlings produced more pioneer roots, and coppiced and root–pruned seedlings more highly-branched fine roots with greater specific root length and specific root surface area under greater water shortage. Thus, acorn-sown and containerized oaks appeared to be primed for water foraging, and coppiced and root-pruned oaks for water absorption efficiency in response to water shortage. Water shortage caused a reduction in nonstructural carbohydrate concentrations in fine roots of acorn-sown and containerized seedlings and in the taproot of coppiced and root-pruned seedlings. Results generally indicated that seedling response to water limitation depended on the regeneration method, highlighting the importance of root–to–shoot allometry, taproot development, and carbon reserve mobilization for plant functioning under water shortage. Acorn-sown and containerized oaks seedlings might be more suitable for forest regeneration in sites characterized by severe water shortage periods. The reduction of taproot starch reserves under strong water shortage may render root-pruned oak trees more susceptible to topsoil water deficit than acorn-sown trees. This work contributes to understand drought acclimation and to identify the most adequate forestry regeneration practices to adapt forest ecosystems to ongoing climatic changes.

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

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

Root Mass and Elemental Concentrations in an Irish Oak Woodland

Fine roots (&lt; 2 mm diameter) are key for nutrient and carbon cycling in forests but less well studied for oak than other European trees. To better understand controls on root mass and nutrient concentrations in oak stands, a study was conducted at Glendalough in Ireland. Roots were removed from soils and measured for biomass, length and nutrient concentrations along with soil nutrients. Fine root mass was 360 gm-2 and comparable to other oak stands. Whilst root N concentrations were high, P concentrations were low and N, P, K, Mg, but not C or Ca were at greater concentrations in fine roots compared to coarse (2-5 mm) roots. The root Ca:Al ratio suggested Al toxicity although this was less marked in organic-rich soils. Neither root mass nor root nutrient concentrations showed particularly strong correlations with soil nutrients or pH. Whilst this data agrees well with other similar studies, improved analysis by separating live and dead roots will further advance our understanding of controls on forest fine root dynamics.

Effect of Altitude on Nutrient Concentration, Nutrient Stock and Uptake in Fine Root of Sal (Shorea Robusta Gaertn.) Forest in Terai and Hill Areas of Eastern Nepal

The present study was conducted to understand the effect of altitude on the nutrient concentration, nutrient stock, and uptake in the fine root of the Terai Sal forest (TSF) and Hill Sal forest (HSF) in eastern Nepal. Annual mean fine root biomass in 0-30 cm soil depth was found higher in HSF (6.27 Mg ha-1) than TSF (5.05 Mg ha-1). Conversely, fine root production was higher in TSF (4.8 Mg ha-1 y-1) than HSF (4.12 Mg ha-1 y-1). Nitrogen, phosphorus, and potassium content in fine roots were slightly higher in TSF than HSF. Nutrient concentration in fine roots of smaller size (&lt;2 mm diameter) was nearly 1.2 times greater than that of larger size (2–5 mm diameter) in both forests. In HSF total stock of different nutrients (kg ha-1) in fine root was 55.62 N, 4.99 P, and 20.15 K whereas, these values were 49.49 N, 4.14 P, and 19.27 K only in TSF. However, total nutrient uptake (kg ha-1y-1) by fine root (both size classes) was greater in TSF (48.5 N, 4.3 P, and 18.6 K) than HSF (36.9 N, 3.3 P, and 13.5 K). The variability in fine root nutrient dynamics between these two forests was explained by the differences in fine root biomass and production which were influenced by the combined effect of varied altitude and season. The fine root, as being a greater source of organic matter, the information on its nutrient dynamics is inevitable for the management of soil nutrients in the forest ecosystem.

Elevated ozone prevents acquisition of available nitrogen due to smaller root surface area in poplar

Poplars are ecologically and economically important tree genus, sensitive to ozone (O3). This study aimed to investigate modifying effects of elevated O3 on poplar root response to nutrient addition. In pot experiment, young trees of an O3-sensitive Oxford poplar clone (Populus maximoviczii Henry × berolinensis Dippel) growing in soil with three levels of P (0, 40 and 80 kg ha−1) and two levels of N (0 and 80 kg ha−1) were exposed to three levels of O3 (ambient – AA, 1.5 x AA, 2.0 x AA) at a free air exposure facility. After one growing season, root biomass, fine root (<2 mm) nutrient concentrations and ratios, and fine root morphology were assessed. Nitrogen addition resulted in an up to +100.5% increase in coarse and fine root biomass under AA, and only up to +46.3% increase under 2.0 x AA. Elevated O3 and P addition had a positive effect, while N had a negative effect on P concentrations in fine roots. Nitrogen limitation for root growth expressed as a N:P ratio was more pronounced at elevated O3. Nitrogen addition increased root surface area per soil volume by +78.3% at AA and only by +9.9% at 2.0 x AA. Smaller root surface area per soil volume at elevated O3 prevented acquisition of available N, rendering N fertilization of young poplar plantations in such conditions economically and environmentally questionable.

VARIATIONS OF ELEMENT CONCENTRATIONS IN ROOTS OF DIFFERENT TREE SPECIES

ABSTRACT Element concentrations of roots play an important role for plant growth and below ground biochemical cycles in forest ecosystems. It can show a change among species. This research aimed to determine changes in the nutrient content for different root diameters of trees in the Belgrad forest. Natural species of Sessile oak (Quercus petraea L.), Scots pine (Pinus sylvestris L.), Austrian pine (Pinus nigra Arnold.), Turkish fir (Abies bornmuelleriana L.), and Oriental spruce (Picea orientalis L.) were studied. Root sampling was carried out by randomly collecting twenty soil samples within each species once every three months (from April 2007) over one year. Roots were classified by fine root ( 5mm) diameter classes. Total concentration of elements (K, Ca, P, Fe, Mg, Cu, Mn, Al, Ni, Zn, Na) in each root classes were determined. The macro elements Mg, K, and P and all microelements in the included species showed a tendency to decrease in concentration with increasing root diameters. Macro elements except K and P and microelements except Pb, Al, Zn, and Cu showed a significant temporal difference between species based on the root diameters. Al, Pb, Ni, Mn, and Fe showed different antagonistic relations with Ca, Mg, P, and K between species with regard to their concentration in fine roots. There was no significant negative correlation between small and coarse roots in species (except in oak species). The results have shown that nutrient storage characteristics differ between different species in the same site.

Root respiration and belowground carbon allocation respond to drought stress in a perennial grass (Bothriochloa ischaemum)

In order to accurately estimate the carbon (C) balance in arid and semi-arid grasslands, it is necessary to first understand how the demands of photosynthates and root carbon (C) are allocated in response to drought. To accomplish this goal, we used a 13C pulse labeling technique to assess correlations between root morphology and the amount of 13C in the root, which is a measure of respiration. We compared respiration changes via the excised root 13C of Bothriochloa ischaemum at various root excision times (i.e., 0, 6, 24, 48, 216, and 360 h after labeling). Our results showed that 13C and root respiration continued to increase until 216 h after labeling, and then they decreased after 360 h. Root respiration correlated significantly with the carbon labeled as being from the fine roots that were undergoing drought stress treatments. This indicates that later-photosynthates are the primary C source for root respiration. Fine root 13C positively correlated with fine root biomass and specific root length under serious drought conditions. This suggests that fine root growth is based primarily on recently derived photosynthates. Serious drought was shown to inflate the root/shoot ratio by increasing both the 13C and the biomass, which led to greater C allocation in the root system. Finally, the fine/coarse root ratios of 13C and biomass were greatest in the serious drought treatment. This suggests that fine roots have a higher C demand than coarse roots under drought stress. Fine root respiration was also found to stimulate new C demand in roots because the amount of 13C created during root respiration was positively correlated with tissue N concentration of fine roots.

Fine root contribution to the soil carbon stock of an agroforestry system in a Caatinga-Atlantic Forest transition zone

The objective of this work was to evaluate the distribution of fine roots and its influence on the soil organic carbon stock, at a depth of 20 cm, in a Grevillea robusta and Coffea arabica agroforestry system. The study was conducted in an agroforestry system established 15 years ago in a transition area of Caatinga and Atlantic Forest biomes in Brazil. G. robusta trees representing the most frequent diameter class were selected, and three distances of these trees (0, 0.75 and 1.50 m) and two soil collection depths (0–10 and 10–20 cm) were defined. The root samples were scanned and quantified using a software program. There was a general predominance of roots with a diameter of 0.6 mm at the shortest distance from the surface layer, while there was a predominance of roots with a diameter of 0.4 mm in the 10–20 cm layer. The root carbon stock at a distance of 0.75 m was higher at a depth of 0–10 cm (0.60 Mg ha-1). The soil organic carbon stock also showed higher results in the 0–10 cm layer compared to the 10–20 cm layer, although with significant variation only in the distance of 1.5 m. There was a higher concentration of fine roots in the topsoil, probably influenced by a greater availability of water and nutrients from plant residues. The soil carbon stock is not closely related to root density or root carbon stock. The data presented in this study do not provide a definitive conclusion.

Impacts of elevated CO2 on nitrogen uptake of cucumber plants and nitrogen cycling in a greenhouse soil

It remains unclear whether elevated CO2 would increase N uptake of vegetable and alleviate soil degradation via reducing N residual in greenhouse soils. This study investigated the effect of three CO2 concentrations 400 (ambient CO2), 800 (elevated CO2) and 1200 μmol mol−1 (super-elevated CO2) and two N application rates 0.06 (low N) and 0.24 g N kg−1 (high N) on N uptake of cucumber plants and N cycling in a greenhouse soil in open top chambers. Elevated CO2 increased the biomass and N concentration of fine roots in high N by 24% and 4%, respectively, indicating a greater improvement in N uptake efficiency. The improvement was greater under low N but to a lesser extent under super-elevated CO2. Elevated CO2 altered microbial community as indicated by decreased Shannon diversity, substrate richness and Shannon evenness when averaged N treatments possibly associated with the increased plant N uptake efficiency. Elevated CO2 and super-elevated CO2 tended to decrease gene abundances of soil bacterial amoA, nirS and nosZ in high N with increased plant N uptake and decreased concentrations of NH4+, NO2− and NO3− in soils resulting in less soil N loss. To conclude, moderate CO2 enrichment enhances N uptake efficiency in fine roots of cucumber plants and decreases soil N loss associated with decreased nitrification and denitrification under high N application in a greenhouse soil.