Fine Root Morphology Research Articles

Independent evolutionary changes in fine-root traits among main clades during the diversification of seed plants.

Changes in fine-root morphology are typically associated with transitions from the ancestral arbuscular mycorrhizal (AM) to the alternative ectomycorrhizal (ECM) or nonmycorrhizal (NM) associations. However, the modifications in root morphology may also coincide with new modifications in leaf hydraulics and growth habit during angiosperm diversification. These hypotheses have not been evaluated concurrently, and this limits our understanding of the causes of fine-root evolution. To explore the evolution of fine-root systems, we assembled a 600+ species database to reconstruct historical changes in seed plants over time. We utilise ancestral reconstruction approaches together with phylogenetically informed comparative analyses to test whether changes in fine-root traits were most strongly associated with mycorrhizal affiliation, leaf hydraulics or growth form. Our findings showed significant shifts in root diameter, specific root length and root tissue density as angiosperms diversified, largely independent from leaf changes or mycorrhizal affiliation. Growth form was the only factor associated with fine-root traits in statistical models including mycorrhizal association and leaf venation, suggesting substantial modifications in fine-root morphology during transitions from woody to nonwoody habits. Divergences in fine-root systems were crucial in the evolution of seed plant lineages, with important implications for ecological processes in terrestrial ecosystems.

Root growth of Eleuthero (Eleutherococcus senticosus [Rupr. & Maxim.] Maxim.) seedlings cultured with chitosan oligosaccharide addition under different light spectra

Eleuthero (Eleutherococcus senticosus [Ruprecht & Maximowicz] Maximowicz is an important understory species as well as a source of natural products in Asia. The natural source of Eleuthero has been over exploited for pharmacological use, but the manual restoration to rehabilitate its natural distribution has not yet been established. The root is one of the main underground organs in Eleuthero for the acquisition of pharmaceutical ingredients. Root growth also determines the seedling quality of this species for ecological restoration. In this study, Eleuthero seedlings were cultured for one growing cycle with chitosan oligosaccharide (CO) addition at rates of 0 and 25 ppm under artificial lightings by high-pressure sodium (HPS) lamps and two light-emitting diodes (LEDs) with photosynthetic photon flux density set to 94±5 μmol m-2. Light spectra of red (R): green (G): blue (B) ratios were measured to be 43.7:54.6:1.7, 43.8:47:9.2, and 72.7:13.3:14 for the HPS, LED-1, and LED-2 treatments, respectively. In autumn, no interactive effect was found between CO addition and light spectra treatments on any root parameters. Compared to the HPS treatment, the LED-1 treatment resulted in a greater root dry weight and morphology by over 30%. The CO addition caused an increase of root growth by 40-70%. Fine roots in diameter between 0-0.4 mm were the main root part that contributed to the length, surface area, and root tip number. Therefore, LED lighting with the R/G/B spectrum of 43.8:47:9.2 was suggested for the culture of Eleuthero seedlings with the purpose of promoting dry weight and morphology of fine roots.

Biomass, Morphology, and Dynamics of the Fine Root System Across a 3,000-M Elevation Gradient on Mt. Kilimanjaro.

Fine roots (≤2 mm) consume a large proportion of photosynthates and thus play a key role in the global carbon cycle, but our knowledge about fine root biomass, production, and turnover across environmental gradients is insufficient, especially in tropical ecosystems. Root system studies along elevation transects can produce valuable insights into root trait-environment relationships and may help to explore the evidence for a root economics spectrum (RES) that should represent a trait syndrome with a trade-off between resource acquisitive and conservative root traits. We studied fine root biomass, necromass, production, and mean fine root lifespan (the inverse of fine root turnover) of woody plants in six natural tropical ecosystems (savanna, four tropical mountain forest types, tropical alpine heathland) on the southern slope of Mt. Kilimanjaro (Tanzania) between 900 and 4,500 m a.s.l. Fine root biomass and necromass showed a unimodal pattern along the slope with a peak in the moist upper montane forest (~2,800 m), while fine root production varied little between savanna and upper montane forest to decrease toward the alpine zone. Root:shoot ratio (fine root biomass and production related to aboveground biomass) in the tropical montane forest increased exponentially with elevation, while it decreased with precipitation and soil nitrogen availability (decreasing soil C:N ratio). Mean fine root lifespan was lowest in the ecosystems with pronounced resource limitation (savanna at low elevation, alpine heathland at high elevation) and higher in the moist and cool forest belt (~1,800–3,700 m). The variation in root traits across the elevation gradient fits better with the concept of a multi-dimensional RES, as root tissue density and specific root length showed variable relations to each other, which does not agree with a simple trade-off between acquisitive and conservative root traits. In conclusion, despite large variation in fine root biomass, production, and morphology among the different plant species and ecosystems, a general belowground shift in carbohydrate partitioning is evident from 900 to 4,500 m a.s.l., suggesting that plant growth is increasingly limited by nutrient (probably N) shortage toward higher elevations.

Pioneer root invasion and fibrous root development into disturbed soil space observed with a flatbed scanner method

Fine roots with thick diameter preferentially elongated into disturbed soil space, indicating positive invasion of pioneer roots that recolonize distal root systems. Fine roots and their morphological traits are related to below-ground resource dynamics at physiological and ecological levels. Established approaches for investigating fine root dynamics inevitably cause artificial soil disturbance due to root excavation or instrument installation into the soil. Soil disturbance can have considerable effects on fine root dynamics. The aim of the present study was to clarify the temporal changes of morphological traits of fine roots produced after soil disturbance. The flatbed scanner method was employed in cypress (Chamaecyparis obtusa Endl.) and deciduous oak (Quercus serrata Thunb.) stands, and changes in length and diameter of elongated roots were measured for 4 years after soil disturbance. In both stands, specific trends of diameter and length production of fine roots were observed. Root length production increased extensively, and diameter was greater in an initial phase after soil disturbance. However, temporal patterns varied between the two stands. Soil disturbance affected fine root dynamics for a longer duration in the cypress stand, but more intensively in the oak stand. These results indicate that soil disturbance can affect fine root morphology and can induce invasion of thick fine roots, which are traditionally grouped as pioneer roots. Moreover, the results showed high length production continued for a longer period than that of larger diameter roots, suggesting recolonization of fine root systems by elongating pioneer roots followed by the branching of absorptive fibrous roots in order to recover root uptake capacity lost due to soil disturbance.

长白山白桦山杨次生林细根形态特征和解剖结构对氮沉降的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 长白山白桦山杨次生林细根形态特征和解剖结构对氮沉降的响应 DOI: 10.5846/stxb201807141528 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（41773075，41575137，31370494，31170421） Response of fine root morphology and anatomical structure of Betula platyphylla and Populus davidiana natural secondary forest to nitrogen deposition in Changbai Mountains Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:根系作为植物与土壤物质交换和养分循环的桥梁，长期以来一直是生态学研究的热点。于2017年7月植物生长季，对长白山模拟11年氮（N）沉降控制试验样地的白桦（Betula platyphylla）山杨（Populus davidiana）天然次生林进行了根系采样，并利用根序法研究了根系形态特征和解剖结构对不同梯度N添加处理的响应，旨在探求两物种根系之间潜在生态联系。本试验共设置了三个N添加梯度，分别为对照（CK，0 g N m-2 a-1）、低N处理（TL，2.5 g N m-2 a-1）和高N处理（TH，5.0 g N m-2 a-1）。研究结果如下：1） TL显著抑制白桦和山杨前三级细根皮层厚度的生长。白桦通过增加皮层细胞直径（一级根增加了72.77%，二级根增加了53.22%，三级根增加了39.96%）但减少皮层层数来降低皮层厚度，而山杨主要通过皮层细胞直径的减少（一级根下降了40.80%，二级根下降了28.17%）来降低其皮层厚度。2） TH显著抑制山杨前三级细根生长。主要通过增加皮层厚度（一级根增加了68.78%，二级根增加了50.81%，三级根增加了88.53%）以及降低导管横截面积来抑制吸收养分，从而达到影响生长的目的。3）白桦TH相比于TL细根直径呈抑制生长状态。其主要通过抑制中柱直径（一级根下降了17.61%，二级根下降了16.89%，三级根下降了20.62%）的生长来实现。以上结果表明，在同一立地条件下，白桦和山杨的细根对不同浓度N沉降的响应方式不同。 Abstract:As a bridge of material exchange and nutrient cycle between plant and soil, root system has been a research hot spot in ecology. The aim of this study was to explore the potential ecological relationship between the roots of two species. We carried out the research in the growing season in July 2017. The root system was collected in 11 years nitrogen (N) control simulation test sample of Betula platyphylla & Populus davidiana natural secondary forest in Changbai Mountains. The root sequence method was used to reveal responses of the root morphology and anatomical structure to different gradients of N addition. In the study, three N addition gradients were set, which were ambient environment (CK, 0.0 g N m-2 a-1), low nitrogen addition (TL, 2.5 g N m-2 a-1), and high nitrogen addition (TH, 5.0 g N m-2 a-1), respectively. The results were as follows. 1) The TL significantly inhibited growth of the cortical thickness of the first three levels of roots of Betula platyphylla and Populus davidiana. Betula platyphylla reduced cortical thickness by increasing cortical cell diameter (the primary root increased by 72.77%, the secondary root increased by 53.22%, and the third level root increased by 39.96%). While Populus davidiana reduced cortical thickness mainly by decreasing cortical cell diameter (the primary root and the secondary root decreased by 40.80% and 28.17%, respectively). 2) The TH significantly inhibited the growth of the first three levels of roots of Populus davidiana, which was inhibited mainly by increasing the thickness of the cortex (the primary root increased by 68.78%, the secondary root increased by 50.81%, and the third level root increased by 88.53%) and by decreasing the cross sectional area of the catheter so as to affect growth. 3) By comparing the TH with the TL, fine roots diameter of Betula platyphylla showed growth inhibition by inhibiting the growth of the stele diameter (the primary root decreased by 17.61%, the secondary root decreased by 16.89%, and the third level root decreased by 20.62%). The results indicate that the fine roots of Betula platyphylla and Populus davidiana respond differently to N deposition of different concentrations in the same site conditions. 参考文献 相似文献 引证文献

Plastic responses of fine root morphological traits of Castanopsis fabri and Castanopsis carlesii to short-term nitrogen addition

Nitrogen deposition will affect the morphology of fine roots and its absorption of nutrien-ts, resulting in changes nutrient cycling in terrestrial ecosystems. In order to understand the effects of nitrogen deposition on fine root morphological traits of Castanopsis fabri and C. carlesii, two ectomycorrhizas tree species, we carried out in situ experiment using the root bags method in an evergreen broadleaved forest in the subtropical zone. The results showed that the plastic responses of specific root length and specific root surface area of low-order roots (first to third order) to nitrogen addition was higher than that of high-order roots (fourth order). The plastic responses of root tissue density to nitrogen addition increased from the first-order to the fourth-order, while the average root diameter of each order had no significant plastic responses to nitrogen addition. There was a certain synergistic change between the plastic response of specific root length and specific surface area in the low order fine root and the plastic response of tissue density in the high order fine root. The specific root length, specific root surface area and root tissue density of the two species showed opposite plastic responses to nitrogen addition, indicating that different ectomycorrhizal tree species had different nutrient foraging strategies. C. fabri adopted rapid absorption strategy by increasing specific root length, specific root surface area, and proliferation rate of fine root length, while C. carlesii adopted a relatively conservative resource absorption strategy by increasing tissue density of fine roots.

Effects of long-term nitrogen addition and decreased precipitation on the fine root morphology and anatomy of the main tree species in a temperate forest

Fine root traits vary under increased nitrogen (N) deposition and decreased precipitation across root orders and species, and these differences reflect plant belowground carbon allocation and survival strategies. We aimed to investigate how fine roots respond to N deposition and precipitation changes and provide a database of related information. A long-term platform to explore the changes in fine root morphology and anatomy in response to N addition and decreased precipitation was established in a temperate forest in northern China. The response of Pinus koraiensis (PK) fine root diameter, stele diameter and stele-to-root ratio to N deposition differed from that of broadleaf species. Fine roots coordinated nutrient absorption with transportation by changing carbon allocation. Decreased precipitation caused Phellodendron amurense (PA) and Tilia amurensis (TA) to produce thinner fine roots with fast absorption capacity and PK and Fraxinus mandshurica (FM) to produce thicker fine roots with slow absorption capacity. The total absorptive capacity of the fine roots of Quercus mongolica (QM) had the smallest change. The interaction of N deposition with decreased precipitation on fine roots depends on tree species and may be inhibited or synergistic. This study provides insight into the variations in fine root dynamics among five tree species that are associated with environmental conditions and forecasts the trend of belowground carbon storage in boreal forests under multifactor climate change.

Variation in the morphology of fine roots in Cryptomeria japonica determined by branch order-based classification

This study assessed intraspecific variation in morphological traits of the fine root branch orders of Cryptomeria japonica, and identified variation in the diameter of the first three-order roots among species types with mycorrhiza, and the diameter of first-order roots at the family level. Diameter, length, and specific root length of branch order roots (up to the fourth-order) were measured in intact fine root systems collected in four C. japonica stands. Relationships between soil chemical properties and morphological traits of the first- to fourth-order roots were investigated. The diameter of roots of 52 tree species reported in previous studies was compared at species types with mycorrhiza and at family level. The diameter of first-order roots in C. japonica varied by 1.2 times among stands. Negative correlations between soil NH4+ content and specific root length of the second- and third-order roots were observed in C. japonica. The diameter of first- and second-order roots forming arbuscular mycorrhiza in coniferous trees were significantly higher than those of roots forming ectomycorrhiza in coniferous and broadleaf trees. The diameter of first-order roots in Cupressaceae were significantly larger than those of Pinaceae, Sapindaceae, Betulaceae, and Fagaceae. Clarifying intraspecific variation in morphological traits of C. japonica lower-order roots may contribute to understanding their responses to different site conditions such as soil inorganic nitrogen contents.

Variation in fine root traits reveals nutrient-specific acquisition strategies in agroforestry systems

Changes in root functional traits reveal important nutrient acquisition strategies, with well documented patterns in root trait expression within complex communities or along gradients of singular nutrients. In this field study, we investigate intra-root functional trait expression with six soil macro- and micro-nutrients in Theobroma cacao agroforestry systems. Using image, chemical, and spatial analysis, the fine root distribution, architecture, and morphology of T. cacao were compared to localized soil nutrients on two-dimensional soil profiles with conspecific and heterospecific neighbours. Fine-scale variation in soil nutrients was observed within the range of T. cacao root systems. Higher NH4+ and Ca2+ was associated with greater root length and biomass densities, coupled with greater investment to individual roots, expressed as increased fine root tissue density and diameter and lower specific root length. Conversely, NO3− had the opposite effect. Overall, roots tended towards higher acquisitive trait values when next to a shade tree. Plants generally employ several concomitant and at times opposing strategies for nutrient acquisition in heterogeneous soils. We show that fine-scale root plasticity is highly linked to localized nutrient-specific and neighbour-specific effects, driving patterns of nutrient acquisition in agroforestry systems.

Effects of precipitation change on fine root morphology and dynamics at a global scale: a meta-analysis

We compiled data from 495 observations and 103 papers and carried out a meta-analysis of the responses of fine root biomass, production, decomposition, and morphology to precipitation increases and decreases. In addition, we evaluated the effects of plant life form, soil depth, and experiment duration on the responses of fine roots to precipitation changes. Our results confirmed that decreased precipitation limited fine root diameter and accelerated turnover. Increased precipitation stimulated fine root elongation and enhanced the fine root accumulation. The responses of fine roots to precipitation changes varied among plants of different life forms. Tree fine root production and decomposition and non-tree fine root diameter varied most strongly under decreased precipitation. Specific root length of non-tree fine roots was much higher than that of tree fine roots under increased precipitation. Decreased precipitation limited the growth of fine roots in 20–40 cm deep soil, whereas increased precipitation promoted the growth of fine roots in both shallow and deep soil layers. The responses of fine roots to decreased precipitation were affected by experiment duration. Results filled the gap of evaluation data on the effect of precipitation change on fine root morphology and dynamics, which are useful for better predicting the C cycle under precipitation change.

Fine root morphology and growth in response to nitrogen addition through drip fertigation in a Populus × euramericana “Guariento” plantation over multiple years

Nitrogen addition through drip fertigation to a poplar plantation ( Populus × euramericana “Guariento”) promoted fine root growth only in the early period. The relationship between root growth and soil N content was positive in the first 2 years, but became negative in the third year when the soil N availability had substantially increased. Nitrogen (N) deficiency is common in forest soils, and N addition is sometimes applied in the case of intensive plantations. There is a need to better document the impact of N addition through the high-efficiency fertilization technique on fine root morphology and growth, given their importance for the uptake of nutrients and for tree growth. We aimed to quantitatively investigate the responses of fine roots in morphology and growth to N addition through surface drip fertigation over multiple years in a Populus × euramericana “Guariento” plantation. A field experiment that included four drip fertigation treatments with N addition levels (0, 60, 120, and 180 kg N ha−1 year−1) was conducted for three successive years. A coring method was used to sample soils and quantify the root morphological traits and soil N content along 0–60-cm profiles. The root biomass density, length, surface area, specific length, and tissue density were significantly higher in the N addition treatments than those in the control after the first year, but the positive effect decreased in the second year. In the third year, root biomass in the N addition treatments was even lower by 11–39% than that in the control. The relationship between root growth and soil N content was also positive in the first 2 years and negative in the third year. N addition promoted fine root growth mainly in the shallow soil and in the early period of experiment. The relationship between root growth and soil N content became negative in the third year when the soil N availability had substantially increased. It is suggested that fine roots adjust their growth and morphology in response to N availability varying along the soil profile and with the fertilization duration.

樟树(Cinnamomum camphora)幼苗细根形态对氮磷添加和幼苗密度的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 樟树(Cinnamomum camphora)幼苗细根形态对氮磷添加和幼苗密度的响应 DOI: 10.5846/stxb201809041884 作者: 作者单位: 华南农业大学林学与风景园林学院 作者简介: 通讯作者: 中图分类号: 基金项目: 中央财政林业科技推广示范项目（2015-GDTK-07） Responses of fine root morphology of Cinnamomum camphora seedlings to nitrogen and phosphorus additions and planting density Author: Affiliation: College of Forestry and Landscape Architecture,South China Agricultural University 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:全球氮沉降对森林生态系统结构和功能的影响已成为现代生态学研究热点之一，我国华南地区氮沉降的增长引起了土壤酸化和磷限制加剧等一系列生态问题。密度制约着植物个体对环境资源的吸收利用，是自然界中十分重要的选择压力之一。因此研究樟树（Cinnamomum camphora）幼苗的细根形态对氮磷添加和密度的响应，有利于了解亚热带树木根系对氮沉降和磷添加与林分密度的响应过程和机制，并为全球变化背景下樟树林生态系统的管理提供依据。本研究以1年生樟树幼苗为试验材料，选择氯化铵（NH4Cl）作为氮肥以模拟大气氮沉降，并且以二水合磷酸二氢钠（NaH2PO4·2H2O）模拟磷添加，氮磷处理设置4个水平，即对照、施N、施P和施N+P；种植密度设置10、20、40和80株/m2 4个水平。测定各处理樟树幼苗细根的根长、表面积、体积和根尖数，分析氮磷添加、密度和两者交互作用对樟树幼苗细根的影响。研究结果表明，与对照处理相比，N、P和N+P处理促进了幼苗细根长度、表面积、体积以及根尖数的增加。低密度条件下的N添加对幼苗根系形态的促进效果强于P添加。N+P处理对10、20、40株/m2幼苗根系形态的促进效果最佳，而各处理对80株/m2幼苗根系形态的促进效果均无显著性差异。随着种植密度的增大，幼苗细根长度、表面积、体积和根尖数均减少。樟树幼苗的细根长度、表面积、体积和根尖数在各密度间和不同氮磷添加处理间均有显著性差异，密度和氮磷处理间的交互作用对根系形态各指标均无显著影响。 Abstract:With the continuing deposition of atmospheric N and wide application of P fertilizer, N and P have become a major factor affecting the ecosystem C balance. Fine root morphological characteristics, such as the root length, surface area, volume, and tips, play a critical role in many functions, including nutrient absorption. Global N deposition and P addition induce changes in root morphology. Seedling density is an important factor affecting root morphology because of the enhanced resource competition among high density seedlings, which reflects the allocation ratio of photosynthetic C in the roots, and ultimately affects the overall plant C allocation balance. Understanding the effects of N and P additions and planting density on the fine root morphology is important to be able to improve fine root health. However, knowledge regarding the effects of N and P additions on the root morphology is limited, and it is still unclear how N and P additions and seedling density alter the fine root morphology of Cinnamomum camphora seedlings. In this study, the root morphology of C. camphora seedlings planted at different densities was evaluated, along with the root length, surface area, volume, and tips, in order to reveal the effects of N and P additions and plant density on the fine root morphological characteristics of this species. One-year-old C. camphora seedlings were used as test materials, and NH4Cl and NaH2PO4·2H2O were selected to simulate N deposition and P addition, respectively. N and P additions were performed with four different levels of treatment (control, N, P, and N+P), and seedlings were planted at four different densities (10, 20, 40, and 80 seedlings/m2). The results showed that the N, P, and N+P treatments increased the root length, surface area, volume, and tips of seedlings compared to those of the control treatment. The effect of N addition on root morphology was stronger than that of P addition under low planting densities. The N+P treatment had the greatest effect on the fine root morphology at densities of 10, 20, and 40 seedlings/m2, while there was no significant difference in the effect of each treatment at 80 seedlings/m2. With increased planting density, the length, surface area, volume, and tips of the seedling roots tended to decrease. The effects of different densities or treatments on the fine root length, surface area, volume, and tips of the seedlings were significantly different, but the interactive effect of density and N and P additions on the fine root morphology of the seedlings was not significant. 参考文献 相似文献 引证文献

Changes in quantity, morphology and nitrogen content of fine roots with stand development in a subalpine fir-wave forest

ABSTRACTTo determine the change in nutrient absorption capacity with stand development, we aimed to clarify the changes in fine root characteristics with stand development and stand characteristics. Stand characteristics (stand age, maximum tree height, tree density and basal area) and fine root characteristics were examined in three fir-wave stands that aged sequentially along the slope in a subalpine Abies forest in central Japan. The biomass, length, surface area and N content of fine roots did not change, but the specific root length (SRL) decreased with stand development, i.e. distance from the upper side of each transect. On the other hand, we observed an increase in fine root biomass with stand characteristics, i.e. maximum tree height and basal area of the Abies community, while a decrease in SRL was also observed. These changes resulted in an increase in surface area and N content of fine roots. However, the surface area of absorptive roots that were <0.5 mm in diameter did not change with stand characteristics. Thus, we suggest that the nutrient absorption capacity of the subalpine Abies community increased with aboveground biomass from the viewpoint of comprehensive activity of fine roots, but not from the viewpoint of fine root morphology. We further confirmed that the ratios of surface area and N content of fine roots to basal area decreased with stand development. Future research is needed to understand the actual effect of surface area and N content of fine roots on the maintenance of aboveground organs.

Fine-Root Responses of Populus tomentosa Forests to Stand Density

Stand density directly affects the distribution of ecological factors such as light, heat, and water in forest communities and changes the diversity and structure of undergrowth species, thereby affecting soil health. Fine roots can provide water and nutrients to plants rapidly in the fierce competition of soil resources, so as to get rid of environmental factors. This study examined the fine-root responses of the Populus tomentosa clone S86 to three stand densities (plant × row spacing: 2 × 2 m, 4 × 3 m, 4 × 5 m). We measured the biomass, morphology, and nitrogen content of lower- (1–3 order) and higher-order (&gt;3 order) fine roots, and analyzed soil chemical properties in 10–30 cm. The soil from the density (2 × 2 m) stands showed lower soil organic matter content, available nitrogen, available phosphorous, and available potassium than others. Obviously, lower and higher-order fine roots were different: biomass of the &gt;3 order accounted for 77–87% of the total biomass, 1–3-order fine-root diameter around 0.28–0.38 mm, while &gt;3-order fine root were 1.28–1.69 mm; the length of 1–3-order fine root was longer than the &gt;3 order, and root length density, specific root length, and nutrient content between the 1–3 and &gt;3 orders were different. At 2 × 2 m, 1–3-order fine-root biomass was the highest, 132.5 g/m3, and the 1–3-order fine-root length, diameter, surface, root length density was also the highest; at the same time, the 1–3-order fine-root total nitrogen and organic matter content was also the highest, while the &gt;3 order was highest under 4 × 3 m or 4 × 5 m. The findings of this study show that stand density affected the available nutrient content of the soil. When soil resources were poor, the biomass, morphology, and chemical content of fine roots were adjusted to increase the nutrient absorption rate, particularly in the lower-order roots.

Effect of Stand Age on Fine Root Biomass, Production and Morphology in Chinese Fir Plantations in Subtropical China

Despite the great importance of fine roots, which are referred to as roots smaller than 2 mm in diameter, in terms of carbon and nutrient cycling in terrestrial ecosystems, how fine root biomass, production, and turnover rate change with stand development remains poorly understood. Here we assessed the variations of fine root biomass, production, and morphology of trees and understory vegetation in Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) plantations at the ages of 7 years old, 17 years old and 25 years old in southern China, representing the sapling, pole and mature stage, respectively. Fine roots of trees and understory vegetation were sampled with sequential coring method to a depth of 60 cm and sliced into 4 layers (0–15, 15–30, 30–45 and 45–60 cm). Fine root biomass and necromass were highest in the pole stages among these three different aged Chinese fir plantations, although the significant differences were only detected for fine root necromass between 25-year-old and 7-year-old plantations. Fine root biomass of Chinese fir was heterogeneous in both temporal and spatial dimensions. Seasonal variation of fine root biomass in three age groups showed a similar pattern that the standing fine root biomass reached a peak in January and fell to the lowest in July. Vertically, the fine root biomass decreased with the increase of soil depth, but this extinction rate decreased with stand development. The effects of stand age on either total fine root length and surface area, or specific root length were not significant. However, the root tissue density increased significantly with Chinese fir stand ages, which suggested that the fine roots on Chinese fir may resort more to the mycorrhizal associations for the nutrient and water acquisition in the later stage of Chinese fir plantations. In addition to the stand age effect, the fine roots exhibited highly spatial and temporal variations in Chinese plantations, indicating different root foraging strategies for soil nutrient and water acquisition. Therefore, the fine root research not only helps to understand its role in carbon sequestration in terrestrial ecosystem under global climate change, but can also improve our understanding of nutrient management in forest ecosystem. At the same time, the research on the productivity of the Chinese fir growth stage provides guiding significance for the construction and management of Chinese fir.

Short-term effects of nitrogen and water treatments on fine root order morphology of Machilus pauhoi seedlings.

A factorial nitrogen and water addition experiment was carried out with one year-old Machilus pauhoi seedlings from Suichuan County, Jiangxi Province, with six treatments being established: two water levels with 80% and 40% of field moisture holding capacity and three nitrogen addition levels of 0, 50, 100 kg N·hm-2. Specific root length, specific root area, average diameter and tissue density of three fine root orders of M. pauhoi were measured to understand the main and interactive effects of short-term nitrogen addition and drought stress on root characters of M. pauhoi seedlings. The results showed that average fine root diameter and specific root length differed significantly among fine root orders. With the increases of root orders, the average root diameter increased, with the maximum being present in the third order (0.97 mm), but specific root length decreased, with the minimum being present in the third order (238.99 cm·g-1). No significant effects of nitrogen addition on specific root surface area, average fine root diameter, specific root length and root tissue density were observed. There were significant effects of water treatments on average fine root diameter, specific root length and root tissue density. Drought stress significantly increased average diameter of the third order fine roots of seedlings and decreased root tissue density of the first and second order fine roots. Specific root length of the third order fine roots in arid environments was significantly lower than that under the normal water supply condition. There was no interactive effects of nitrogen addition and drought stress on fine root morphology of M. pauhoi.

Morphology and longevity of different-order fine roots in poplar (Populus×euramericana) plantations with contrasting forest productivities

Fine roots play important roles in the allocation of forest net primary productivity. Here, to provide insights into the intrinsic and extrinsic factors affecting the root growth, we examined the morphology and longevity of different-order fine roots in two poplar (Populus × euramericana (Dode) Guinier) plantations with contrasting forest productivities. The results indicated that the biomass of fine roots decreased significantly as the root orders increased (P &lt; 0.05). In the plantation with relatively high productivity, the specific root length of the first- and second-order roots was significantly greater than that of the third- to fifth-order roots (P &lt; 0.05). Observations of minirhizotrons showed that roots of the third-order and higher lived longer than the first- and second-order roots. Compared with those in the plantation with relatively low productivity, the cumulative survival rate of the first-order roots was significantly higher in the plantation with relatively high productivity, while that of the third-order or higher roots was lower. The life-span of the first-order roots correlated negatively with soil available inorganic nitrogen, while that of the second-order roots correlated positively with the soil phenolic acid content. A Cox proportional hazards analysis revealed that soil conditions, root orders, season of root birth, and soil depth significantly affected fine-root longevity. These findings suggest that roots of different orders contribute unequally to the poplar plantation productivity.

A belowground perspective of temperate old-growth forests: Fine root system structure in beech primeval and production forests

Old-growth forests differ from managed forests by a generally higher biodiversity, larger carbon stores, and greater heterogeneity of aboveground structures. It is not known whether the aboveground structural diversity of old-growth forests is mirrored in root system structure, e.g. by greater root biomass, the occurrence of root gaps, and a different fine root morphology. We studied the fine root system of beech (roots <2 mm in diameter) in three development stages (initial, optimum, terminal) of a primeval beech (Fagus sylvatica) forest in the Slovakian Carpathians and compared it to a nearby beech production forest close to harvest. We conducted root coring to 30 cm depth in 16 plots (84 sampling locations) with subsequent detailed analysis of fine root bio- and necromass, and fine root morphology. Despite lower aboveground wood mass, the production forest had on average about 15% larger beech fine root biomass and necromass totals than the primeval forest, though the differences were not significant. Contrary to expectation, the spatial variation of fine root biomass in the 0–30 cm layer in the structurally diverse primeval forest was not higher than in the more homogeneous production forest. Also, fine root morphology did not differ between primeval and production forest.Across the three primeval forest stages, fine root biomass tended to peak in the optimum stage, but the difference was not significant, and no alteration in fine root morphology across the stages was detected. Fine root necromass increased significantly from the initial to the terminal stage, pointing at higher fine root mortality and/or reduced root decomposition in forest patches with many senescent trees and canopy gaps. Yet, soil fertility did not decrease toward the terminal stage of forest development. From the fine root biomass data, no root gaps could be detected in the terminal stage, perhaps due to rapid gap colonization by beech saplings. We conclude that the structural differences between the fine root systems of beech primeval and production forest were relatively small. Canopy heterogeneity seems to be a less important factor determining root distribution in the primeval forest than soil heterogeneity, which can be high in production forests as well.

Legacy effects of land-use modulate tree growth responses to climate extremes.

Climate change can impact forest ecosystem processes via individual tree and community responses. While the importance of land-use legacies in modulating these processes have been increasingly recognised, evidence of former land-use mediated climate-growth relationships remain rare. We analysed how differences in former land-use (i.e. forest continuity) affect the growth response of European beech to climate extremes. Here, using dendrochronological and fine root data, we show that ancient forests (forests with a long forest continuity) and recent forests (forests afforested on former farmland) clearly differ with regard to climate-growth relationships. We found that sensitivity to climatic extremes was lower for trees growing in ancient forests, as reflected by significantly lower growth reductions during adverse climatic conditions. Fine root morphology also differed significantly between the former land-use types: on average, trees with high specific root length (SRL) and specific root area (SRA) and low root tissue density (RTD) were associated with recent forests, whereas the opposite traits were characteristic of ancient forests. Moreover, we found that trees of ancient forests hold a larger fine root system than trees of recent forests. Our results demonstrate that land-use legacy-mediated modifications in the size and morphology of the fine root system act as a mechanism in regulating drought resistance of beech, emphasising the need to consider the 'ecological memory' of forests when assessing or predicting the sensitivity of forest ecosystems to global environmental change.

Interactions among plants, bacteria, and fungi reduce extracellular enzyme activities under long-term N fertilization.

Atmospheric nitrogen (N) deposition has enhanced soil carbon (C) stocks in temperate forests. Most research has posited that these soil C gains are driven primarily by shifts in fungal community composition with elevated N leading to declines in lignin degrading Basidiomycetes. Recent research, however, suggests that plants and soil microbes are dynamically intertwined, whereby plants send C subsidies to rhizosphere microbes to enhance enzyme production and the mobilization of N. Thus, under elevated N, trees may reduce belowground C allocation leading to cascading impacts on the ability of microbes to degrade soil organic matter through a shift in microbial species and/or a change in plant-microbe interactions. The objective of this study was to determine the extent to which couplings among plant, fungal, and bacterial responses to N fertilization alter the activity of enzymes that are the primary agents of soil decomposition. We measured fungal and bacterial community composition, root-microbial interactions, and extracellular enzyme activity in the rhizosphere, bulk, and organic horizon of soils sampled from a long-term (>25years), whole-watershed, N fertilization experiment at the Fernow Experimental Forest in West Virginia, USA. We observed significant declines in plant C investment to fine root biomass (24.7%), root morphology, and arbuscular mycorrhizal (AM) colonization (55.9%). Moreover, we found that declines in extracellular enzyme activity were significantly correlated with a shift in bacterial community composition, but not fungal community composition. This bacterial community shift was also correlated with reduced AM fungal colonization indicating that declines in plant investment belowground drive the response of bacterial community structure and function to N fertilization. Collectively, we find that enzyme activity responses to N fertilization are not solely driven by fungi, but instead reflect a whole ecosystem response, whereby declines in the strength of belowground C investment to gain N cascade through the soil environment.