Poplar Fine Roots Research Articles

Effects of poplar intercropping systems on reducing the concentration of different forms of inorganic nitrogen in the soil profile

AbstractThis study focused on understanding how different spacing arrangements of poplar (Populus deltoides)–wheat (Triticum aestivum) agroforestry systems and the processes of the tree and wheat roots in these systems impact the elimination efficiency of inorganic nitrogen from soil. Three planting systems were tested: a monoculture wheat system (control), a widely spaced wheat–poplar system (PWW) and a narrowly spaced wheat–poplar system (PWN). Soil and root samples were collected in four different soil layers (0–20, 20–40, 40–60, and 60–100 cm) at four different sampling sites (PWN: 0, 1.5, 2.5, and 3.5 m; PWW: 0, 1.5, 3.5, and 7 m from tree row, respectively). The nitrate–nitrogen (), ammonium–nitrogen (), and nitrite–nitrogen () in the soil samples were analyzed to determine the elimination efficiency of the different systems. The results indicated that the concentration and soil accumulation content reduction of inorganic nitrogen in the two intercropping systems, especially in the PWW system, were encouraging compared to those in the control system. The and concentration reductions and poplar fine root length density (FRLD) were higher at the sampling point near the poplar row, especially in surface soil (p < 0.05), but the distribution of the wheat FRLD decreased with soil depth and proximity to the poplar trunk. Furthermore, the poplar and wheat FRLD had significant positive relationships with the concentration reduction of inorganic nitrogen. In conclusion, poplar–agroforestry systems should be considered as an important method for controlling nonpoint pollution from farmland.

The Fine Root Distribution and Morphology of Mature White Poplar in Natural Temperate Riverside Forests under Periodically Flooded or Dry Hydrological Conditions

Fine roots are a key component of carbon turnover in the terrestrial environment. Therefore, their distribution allows for the estimation of areas of carbon in the soil. The vertical distribution of roots is the result of both the tree species and various environmental factors. Research on the architecture of root systems most often includes seedlings and young trees growing under experimental conditions; however, little is known about trees in their natural habitats. The aim of this study is to analyze the fine root distribution of mature white poplar trees in natural riverside temperate zone forests of Central Europe (Poland) periodically flooded and in dry hydrological conditions. The length, diameter, and area of the fine roots, as well as the specific root length (SRL) and specific root area (SRA) of white poplar were measured in three layers of the soil, 0–10 cm, 10–20 cm, and 20–30 cm depths, in three forest sites. Two of the sites experience periodic floods, and one has been without flooding for 80 years, due to the construction of a flood embankment. The highest values of the lengths and surface areas of the poplar fine roots were observed at a depth of 0–10 cm at all sites. Soil moisture was positively correlated with the analyzed root parameters. The presence of understory plant roots contributed to the reduction in the fine root length of poplar in the subsurface layer, compared to the site that was not affected by the presence of plants other than poplar. The distribution of fine roots, the most dynamic part of the plant root system, reflects the most active areas in the soil profile. The presented research will allow for a better understanding of the functioning of natural riverside ecosystems, as well as show the great adaptability of white poplar fine roots to various conditions in the soil.

Rhizosphere bacterial and fungal communities succession patterns related to growth of poplar fine roots

Understanding the succession patterns of microbial community along root growth provides deep insights into interaction between fine roots and microbes. In the study, we investigated this issue using fine roots from poplar trees and grouped these fine roots into three growth stages: newborn white roots (WR), mature yellow roots (YR) and aging brown roots (BR). Root surface traits were observed under a scanning electron microscopy (SEM). Adhered soils on roots of the three growth stages were grouped into the three soil compartments, correspondingly. The 16S rRNA and ITS1 region were sequenced for bacteria and fungi inhabiting rhizosphere soils, respectively. Phospholipid fatty acid (PLFA) technology was employed to examine the biomass of bacterial and fungal communities. The anatomical traits of fine roots show apparent differences among the WR, YR and BR. Both bacteria and fungi have 25 dominant genera with a relative abundance over 1%, of which, four genera of the bacteria (Bacillus, Burkholderia, Ralstonia and Dyella) differ in abundance among the WR, YR and BR soil compartments and four genera of the fungi (Fusarium, Chaetomium, Penicillium and Scleroderma) differ in abundance among these soil compartments. The operational taxonomic units (OTUs) showed the highest richness in the WR soil compartment for bacteria and in the YR soil compartment for fungi, indicating a different succession pattern between the bacterial and fungal communities. Furthermore, the biomass of bacterial community is larger than the fungal community according to PLFAs, and both decreased along fine root growth. The total carbon (TC) in the soil increases along root growth while the dissolved organic carbon (DOC) decreases. Redundancy analysis (RDA) shows a close correlation between twelve dominant bacteria genera and the total organic carbon (TOC), the readily oxidizable organic carbon (ROC) and DOC and ten dominant fungi genera with the TOC and ROC. In conclusion, our results indicate that fine roots growth has shaped the composition and structure of root associated bacterial and fungal communities.

Archaeal community succession with fine root growth in poplar plantation.

The archaeal community structure in the rhizosphere soils might change with root growth, which is of great importance for understanding the interaction between roots and microbes. According to root colors, three groups of rhizosphere soils from first-order fine roots of poplar trees (Populus × euramericana) were sampled, including rhizosphere soils surrounding newly born roots (white color, WR), mature roots (yellow color, YR) and aged roots (brown color, BR). Total microbial DNA was extracted from the soils associated with poplar fine roots. The specific primers were used to amplify the 16S rDNA V4-V5 region of soil archaea, and the Illumina MiSeq platform was used for high-throughput sequencing analysis. The results showed that the observed OTU (operational taxonomic unit) abundance of archaeal community in WR and BR rhizosphere soils were similar, while the OTU abundance in YR rhizosphere soil were lower. The WR and BR shared 134 OTUs of archea, the YR and BR shared 87 OTUs, and the WR and BR shared 90 OTUs. The Chao1 index and the ACE index of archaeal community in YR rhizosphere soil were significantly lower than those of WR and BR, while the Simpson index and the Shannon index of BR were significantly lower than WR to YR. Results from the PERMANOVA analysis showed that archaeal community compositions in WR and BR rhizosphere soils were significantly different. Species annotation showed that there were 12 genera of archea in three rhizosphere soils, five genera in WR, 10 genera in YR, and six genera in BR, respectively. The similarity of the archaeal community composition in poplar rhizosphere soils gradually decreased from WR to BR, with large differences among different growth stages of fine roots. The dominant genus was Candidatus_Nitrososphaera, with a relative abundance of more than 70%, indicating this archaea group might be closely related to poplar fine roots development.

连作杨树人工林细根寿命的代际差异及其影响因素

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

Composite poplars: a novel tool for ectomycorrhizal research

Key MessageComposite poplars were used for ectomycorrhiza formation. Structurally normal mycorrhizas of transgenic roots revealed better fungal sugar support. Targeting fluorescent proteins to peroxisomes allowed easy in planta visualization of successful transformation.A bottle neck in ectomycorrhizal research is the time demand for generation of transgenic plants. An alternative strategy for such root-centered research might be the formation of the so-called composite plants, where transgenic roots are formed by non-transgenic shoots. We have developed an Agrobacterium rhizogenes-mediated root transformation protocol using axenic Populus tremula × tremuloides and P. tremula × alba cuttings. When comparing four different bacterial strains, A. rhizogenes K599 turned out to be the most suitable for poplar transformation. Transgenic roots revealed only minor hairy root phenotype when plants were grown on agar plates with synthetic growth medium in the absence of a sugar source. When using different ectomycorrhizal fungi, formation of ectomycorrhizas by transgenic roots of composite poplars was not affected and mycorrhizas were anatomically indistinguishable from mycorrhizas of non-transgenic roots. Elevated trehalose content and marker gene expression, however, pointed towards somewhat better fungal carbon nutrition in ectomycorrhizas of transgenic compared to non-transgenic roots. Cell wall autofluorescence of poplar fine roots is an issue that can limit the use of fluorescent proteins as visual markers for in planta analysis, especially after ectomycorrhiza formation. By targeting marker proteins to peroxisomes, sensitive fluorescence detection, easily distinguishable from cell wall autofluorescence, was obtained for both poplar fine roots and ectomycorrhizas.

Root order-dependent seasonal dynamics in the carbon and nitrogen chemistry of poplar fine roots

Fine roots play an important role in above- and belowground carbon (C) allocation in forest ecosystems. However, few studies have focused on the seasonal dynamics of fine roots with different branching orders. The objective of this study is to provide insight to the seasonal heterogeneity in roots of different orders within root hierarchies of poplar trees under different soil conditions. Three plots were established in high (plantation A) and low (plantation B) soil nutrient conditions. Fine roots were sampled in each of four seasons throughout one year. All sampled roots were classified into one to five groups depending on their branching order, and the dry biomass of living roots and the concentrations of C, nitrogen (N) and total non-structural carbohydrate (TNC) were examined. Low order (first- to second-order) roots demonstrated more significant seasonal dynamics than high order roots, and the biomass of first-order fine roots was positively influenced by soil temperature and moisture while the biomass of second-order fine roots was negatively affected by soil nutrient conditions. The different responses of fine roots to environmental fluctuations implied a high division of root function, even within low order roots. The C and N chemistry of poplar fine roots also differed significantly with branching order; element concentrations were lower in low order roots. Principal component analysis indicated that root order explained 98.2% of the variation in fine root chemistry. Moreover, the first-order roots in plantation A had greater C but less TNC concentrations than those in plantation B, suggesting that C allocation in low order roots may be more responsive to soil nutrient conditions. The allocation of C and N also exhibited significant seasonal dynamics (p < 0.05); the TNC concentration was highest in winter, whereas C:N ratios were significantly lower in the summer and fall in each order of fine roots (p < 0.05). All these results suggest that branching order may be related to root growth and photoassimilate allocation, which should receive greater attention in future studies on C and N fluxes in forest ecosystems.

Interactive effects of phenolic acid and nitrogen on morphological traits of poplar (Populus &amp;times; euramericana &amp;lsquo;Neva&amp;rsquo;) fine roots

Aims The relationship between rhizosphere process and fine root growth is very close but still obscure. In poplar plantation, phenolic acid rhizodeposition and soil nutrient availability were considered as two dominant factors of forest productivity decline. It is very hard to separate them in the field and they might show an interactive effect on fine root growth. The objective of this study is to examine the influence of phenolic acids and nitrogen on branch orders of poplar fine roots and to give a deeper insight into how the ecological process on root-soil interface affected fine root growth as well as plantation productivity. Methods The cuttings of health annual poplar seedlings (I-107, Populus × euramericana ‘Neva’) serve as experiment materials, and were cultivated under nine conditions, including three concentration of phenolic acids at 0X, 0.5X, 1.0X (here, X represented the contents of phenolic acids in the soil of poplar plantation) and three concentration of nitrogen at 0 mmol·L, 10 mmol·L, 20 mmol·L, based on Hoagland solution. The roots were all separated from poplar seedlings after 35 days, and 30 percent of total fine roots of every treatment were taken as fine root samples. These fine roots were grouped according to 1 to 5 branch orders, and then the morphological traits of each group of fine roots were scanned via root analyzer system (WinRHIZO, Regent Instruments Company, Quebec, Canada) including total length, surface area, volume and average diameter. Meanwhile, the dry mass of fine root samples of every order was measured to calculate specific root length (SRL), root tissue density 朱婉芮等: 酚酸和氮素交互作用下欧美杨 107细根形态特征 1199 doi: 10.17521/cjpe.2015.0116 (RTD). All data were analyzed via SPSS 17.0 software, and interactive effect of phenolic acids and nitrogen on roots was analyzed through univariate process module. Principal component analysis (PCA) and redundancy analysis (RDA) were conducted via Canoco 4.5 software. Important findings Under the conditions without phenolic acids application, the fine roots growth was significantly inhibited in deficiency and higher nitrogen treatments, especially for 1–3 order roots. Only specific root length appeared decreased with nitrogen level, and other traits of fine roots did not demonstrate linear relationship with nitrogen concentrations. Compared to 0.5X phenolic acids treatment, 1.0X phenolic acids significantly promoted the diameter and volume of 1–2 order roots (p < 0.05). Both phenolic acids and nitrogen demonstrated influence on poplar fine root traits. However, the diameter and volume of 1–2 order roots were significantly affected by phenolic acids, while the total length and surface area of 4–5 order roots was affected by nitrogen. Two way ANOVA showed that phenolic acids and nitrogen made a synergistic or antagonistic effect on morphological building of fine roots. Furthermore, PCA and RDA indicated that the interactive effects of phenolic acids and nitrogen led to significant differences among 1–3 order, 4th order and 5th order of poplar fine roots. The PC1 explained about 60.9 percent of root morphological variance, which was related to foraging traits of roots. The PC2 explained 25.3 percent of variance, which was related to root building properties. The response of poplar roots to phenolic acids and nitrogen was closely related to root order, and nitrogen played more influence on poplar roots than phenolic acids. Thus, phenolic acids and nitrogen level would affect many properties of root morphology and foraging in rhizosphere soil of poplar plantation. But nitrogen availability would serve as a dominant factor influencing root growth, and soil nutrient management should be critical to productivity maintenance of poplar plantation.

Neglected carbon pools and fluxes in the soil balance of short-rotation woody biomass crops

The cultivation of dedicated bioenergy crops is being stimulated because of their potential to replace fossil fuels and to maintain or to sequester carbon (C) in the soil, and thus help to mitigate the rising atmospheric CO2 levels. There are, however, still a lot of inaccuracies with regard to the dynamics of C in the soil, and thus with the potential to sequester soil C in these bioenergy crops. Using experimental data observed at the intensively monitored short-rotation woody crops (SRWC) plantation of the POPFULL project, we demonstrate that frequently neglected C pools and fluxes can be of crucial importance for the soil C balance. We highlight three specific cases. First, C inputs into the soil due to weed roots may equal or exceed those due to poplar fine roots, especially during the establishment phase of the plantation. Secondly, harvesting influences the dynamics of above- and belowground C inputs, as well as the soil environment. Large amounts of C are stored in the belowground woody biomass, which represents a long-term C pool. Thirdly, spatial differences related to the planting design are an important source of error in the upscaling of soil variables. We call upon researchers to consider and measure these neglected C pools and fluxes.

Fine root biomass and turnover of two fast-growing poplar genotypes in a short-rotation coppice culture.

Background and aimsThe quantification of root dynamics remains a major challenge in ecological research because root sampling is laborious and prone to error due to unavoidable disturbance of the delicate soil-root interface. The objective of the present study was to quantify the distribution of the biomass and turnover of roots of poplars (Populus) and associated understory vegetation during the second growing season of a high-density short rotation coppice culture.MethodsRoots were manually picked from soil samples collected with a soil core from narrow (75 cm apart) and wide rows (150 cm apart) of the double-row planting system from two genetically contrasting poplar genotypes. Several methods of estimating root production and turnover were compared.ResultsPoplar fine root biomass was higher in the narrow rows than in the wide rows. In spite of genetic differences in above-ground biomass, annual fine root productivity was similar for both genotypes (ca. 44 g DM m−2 year−1). Weed root biomass was equally distributed over the ground surface, and root productivity was more than two times higher compared to poplar fine roots (ca. 109 g DM m−2 year−1).ConclusionsEarly in SRC plantation development, weeds result in significant root competition to the crop tree poplars, but may confer certain ecosystem services such as carbon input to soil and retention of available soil N until the trees fully occupy the site.

Relationship between genotype and soil environment during colonization of poplar roots by mycorrhizal and endophytic fungi

Poplars are among the few tree genera that can develop both ectomycorrhizal (ECM) and arbuscular (AM) associations; however, variable ratios of ECM/AM in dual mycorrhizal colonizations were observed in the roots of a variety of poplar species and hybrids. The objective of our study was to analyze the effect of internal and external factors on growth and dual AM and ECM colonization of poplar roots in three 12-15-year-old common gardens in Poland. We also analyzed the abundance of nonmycorrhizal fungal endophytes in the poplar roots. The Populus clones comprised black poplars (Populus deltoides and P. deltoides x Populus nigra), balsam poplars (Populus maximowiczii x Populus trichocarpa), and a hybrid of black and balsam poplars (P. deltoides x P. trichocarpa). Of the three sites that we studied, one was located in the vicinity of a copper smelter, where soil was contaminated with copper and lead. Poplar root tip abundance, mycorrhizal colonization, and soil fungi biomass were lower at this heavily polluted site. The total mycorrhizal colonization and the ratio of ECM and AM colonization differed among the study sites and according to soil depth. The influence of Populus genotype was significantly pronounced only within the individual study sites. The contribution of nonmycorrhizal fungal endophytes differed among the poplar clones and was higher at the polluted site than at the sites free of pollution. Our results indicate that poplar fine root abundance and AM and ECM symbiosis are influenced by environmental conditions. Further studies of different site conditions are required to characterize the utility of poplars for purposes such as the phytoremediation of polluted sites.

Relating Hybrid Poplar Fine Root Production, Soil Nutrients, and Hydrocarbon Contamination

ABSTRACT Quantifying the effects of hydrocarbon contamination on hybrid poplar fine root dynamics provides information about how well these trees tolerate the adverse conditions imposed by the presence of petroleum in the soil. The objective of this research was to investigate the relationship between the varying concentrations of total petroleum hydrocarbons (TPH) and nutrients across a hydrocarbon-contaminated site, and quantify the effects of these properties on the spatial and temporal patterns of fine root production of hybrid poplar (P. deltoides × P. petrowskyana C. V. Griffin) Twelve minirhizotron tubes were distributed across a TPH-contaminated site at Hendon, SK, Canada, and facilitated quantification of fine root production in areas of varying contamination levels. Residual hydrocarbon contamination was positively correlated with soil total C and N, which may suggest that the hydrocarbons remaining in the soil are associated with organic forms of these nutrients. Fine root production was stimulated by small amounts of hydrocarbon contamination at the field site. Nonlinear regression described fine root production as increasing linearly up to approximately 500 mg kg− 1 TPH, then remaining constant as contamination increased. Stimulation of hybrid poplar fine root production in hydrocarbon-contaminated soil could to lead to enhanced contaminant degradation as a result of stimulated microbial activity via a greater rhizosphere effect.

Impact of Ectomycorrhizal Colonization of Hybrid Poplar on the Remediation of Diesel‐Contaminated Soil

Infection by ectomycorrhizal (ECM) fungi may benefit hybrid poplar growing in contaminated soils by providing greater access to water and nutrients and possibly protecting the trees from direct contact with toxic contaminants. The objective of this research was to determine the effect of colonization of the ECM fungus Pisolithus tinctorius (Pers.) Coker & Couch on hybrid poplar fine root production, biomass and N and P uptake when grown in diesel-contaminated soil (5000 mg diesel fuel kg soil(-1)). Commercially available Mycogrow Tree Tabs were the source of inoculum. A minirhizotron camera was used to provide the data necessary for estimating fine root production. Colonization of hybrid poplar roots (P. deltoides x [P. laurifolia x P. nigra] cv. Walker) by P. tinctorius increased total fine root production in diesel-contaminated soil to 56.58 g m(-2) compared to 22.59 g m(-2) in the uncolonized, diesel-contaminated treatment. Hybrid poplar leaf N and P concentrations were significantly greater in the diesel-contaminated/ECM-colonized treatment compared to the diesel-contaminated/uncolonized treatment after 12 wk, while significantly less diesel fuel was recovered from the soil of the uncolonized treatment compared to the colonized treatment. Both planted treatments removed more contaminants from the soil than an unplanted control. Significantly greater concentrations of total petroleum hydrocarbons (TPH) were found sequestered in hybrid poplar root/fungal-sheath complexes from the colonized treatment compared to the roots of the uncolonized treatment. The results of this study indicate that over a 12-wk growth period, ECM colonization of hybrid poplar in diesel-contaminated soils increased fine root production and whole-plant biomass, but inhibited removal of TPH from the soil.

Nutrient Dynamics of Fine Roots in the Mixed Plantation of Poplar and Black Locust

The mixed plantation of poplar (Populus spp.) and black locust (Robinia pseudoacacia) is one of the typical mixed stands with nitrogen-fixing and non-nitrogen-fixing species. Interaction between the two species in the mixed stand is harmonious and productivity is high, making this kind of mixed plantation a very successful pattern on poor sandy sites in north China. In this study, the fine root decomposition of the two species was investigated in the mixed plantation of 27-year-old Canadian poplar (P. canadansis) and 22-year-old black locust on sandy sites along the Chaobai River in Beijing. Mechanism of harmonious interaction between the two species was observed in the view of the nutrient cycle of fine roots. Results showed that: (1) the fine root decomposition of Canadian poplar and black locust trees was different. Concentrations of N, Ca and Mg gradually increased and those of P and K gradually decreased in the fine roots of poplar during the period of decomposition. Concentrations of N, P and K gradually decreased in the fine roots of black locust during decomposition. The speed of nutrient decomposition in mixed fine roots of the two species fell between the speed of the two pure samples. (2) During decomposition, the annual return amount of N, K and Mg in fine roots of black locust was highest, followed by the mixed fine roots of the two species, and then the fine roots of poplar. (3) The increased return amount of N in mixed fine roots could improve the N nutrient condition of poplar trees. The return amount of P in poplar fine roots was greater than that of black locust, which could improve the P nutrient of black locust trees. The interaction of mutual supplements of N and P nutrient cycle of fine roots between these two species formed.

Carbohydrates in individual poplar fine roots: effects of root age and defoliation.

Late-summer starch accumulation in fine roots of poplars (Populus x canadensis Moench.) defoliated by gypsy moth (Lymantria dispar L.) lagged behind that in fine roots of undefoliated trees. If starch concentration declines with age, defoliation-induced changes in root system age structure could be partly responsible for this difference. To test this hypothesis, we measured fine-root starch and soluble sugar concentrations in roots of known age from trees in defoliated and undefoliated plots. There was a significant interaction between the effects of defoliation and root type (white, brown, or dead) on fine root soluble sugar concentration because of the high concentration of soluble sugars in white roots from trees in undefoliated plots. Both root starch and soluble sugar concentrations were variable among individuals of each age class. The population frequency distributions for starch and soluble sugar concentrations were both right-skewed, and fit by exponential functions. These data are most consistent with direct defoliation effects on a labile and dynamic pool of carbohydrates in poplar fine roots, rather than indirect defoliation effects on root system age structure.

Effect of coppicing on hybrid poplar fine root dynamics

Effect of coppicing on hybrid poplar fine root dynamics