A plane intersect method for estimating fine root productivity of trees from minirhizotron images

The advent of minirhizotrons more than a decade ago has made the careful and widespread study of fine root dynamics of trees possible. However, to this day, the estimation of fine root productivity in terms of mass production per unit of ground surface from the minirhizotron data remains hampered by the difficulty in transforming images of roots captured along a two-dimensional plane into estimates of root volume or mass within a soil volume. In this work, we propose that the date of fine root appearance and the diameter of fine roots are the most robust variables that can be obtained from minirhizotron measurements of tree roots and that these two variables should be the basis of productivity estimates. The method proposed for estimating fine root productivity expands the line intersect method of Van Wagner (1968) into a plane intersect method that permits, with the appropriate volumetric transformations and corrections for tube and slope angles, the estimation of fine root productivity per unit ground area for specific periods. Examples of calculations are presented for two datasets obtained within two different forested sites, as well as a comparison with a methodology based on camera depth-of-view. The main weakness of the plane intersect method is the assumption that all fine root segments are independent. The correction for the fraction of coarse particles also creates uncertainty in the final estimate.     

Genotypic variation in drought response of silver birch (Betula pendula Roth): leaf and root morphology and carbon partitioning

This study investigates the drought response of four genotypes of Betula pendula with a focus on leaf and root morphological traits, leaf phenology and carbon partitioning between shoot and root. Potted one-year-old clonal plants of four genotypes from regions with low to high annual rainfall (550–1270 mm year⁻¹) were subjected to drought periods of 12–14 weeks in two subsequent years. Well-watered control plants of the four genotypes differed significantly with respect to total leaf area per plant (LA) and specific leaf area (SLA), whereas differences in total fine root surface area (RA), root specific area (SRA), and the fine root:leaf mass ratio (FR:LM) were not significant. Highest LA and SLA were found in the clone originating from the driest environment. In complementary physiological investigations this clone was found to have the highest water use as well which was interpreted as competitive superiority in terms of water consumption. Drought resulted in an increase in SLA in all genotypes, and a decrease in LA. Leaf area reduction was more pronounced in the genotypes from high than in those from low rainfall origin. The ratio of total root to leaf surfaces remained more or less constant after drought application despite an increase in FR:LM. This is explained by a decrease in SRA resulting from a reduced abundance of very small fine rootlets (diameter <0.2 mm) in the drought-treated plants. The loss in total root surface area due to a reduction in finest root mass was compensated for by a relative increase in total root dry mass per plant. Comparison of results from the first and second drought period indicated a marked influence of timing of drought, root system size, and putative root limitation on plant drought response. We conclude that leaf and root morphology, the total leaf and root surfaces, and the morphological response to drought in birch are to a large extent under genetic control.     

微根管在细根研究中的应用

细根（直径≤2 mm）的周转在植物生态系统碳分配过程中具有重要意义.已往细根周转研究主要采用根钻法、分室模型法和内生长法等.这些方法由于不能直接观测到细根生长动态,导致细根周转估计不准确.微根管法是一种非破坏性野外观察细根动态的方法.本文从微根管的发展、功能、安装步骤、图像采集、参数计算、影响观测因素和存在问题等方面逐一进行介绍,并通过水曲柳和落叶松微根管细根观测实例介绍在细根周转过程研究中的应用. 结果表明,微根管可以比较精确地估计出细根长度、单位面积上根长密度、单位体积上根长密度、细根生长量、细根死亡量和细根周转等.微根管是一个观察细根生长、衰老、死亡和分解过程的有效工具.微根管观测精度主要取决于微根管安装的质量和数量、微根管取样间隔期和取样数量、微根管图像分析技术等.此外,土壤质地、石砾多少、微根管材料选择、减少光系统对根系的干扰等也是影响微根管测定精度的因素.如何提高微根管测定精度将成为今后微根管在细根研究中的主要问题.     

Plant density-dependent variations in bioactive markers and root yield in Australian-grown Salvia miltiorrhiza Bunge

The plant density‐dependent variations in the root yield and content, and the yield of biomarkers in Australian grown Salvia miltiorrhiza Bunge , a commonly used Chinese medicinal herb for the treatment of cardiovascular diseases, were investigated in a field trial involving six different plant densities. The key biomarker compounds cryptotanshinone, tanshinone I, tanshinone IIA, and salvianolic acid B were quantified by a validated RP‐HPLC method, and the root yields were determined per plant pair or unit area. There were significant variations (p<0.05) in the root yields and contents and the yields of the biomarkers between the different plant densities. Positive linear correlations were observed between the contents of the three tanshinones, whereas negative linear correlations were revealed between the contents of the tanshinones and salvianolic acid B. The highest root yield per plant pair was achieved when the plants were grown at 45×30 cm or 45×40 cm, whereas the highest root production par unit area was obtained for a plant density of 30×30 cm. The highest contents of the three tanshinones and the most abundant production of these tanshinones per unit area were achieved when the plants were grown at 30×30 cm. However, the highest content of salvianolic acid B was found for a density of 45×40 cm, while its highest yield per unit area was obtained for densities of 30×40 cm or 45×30 cm. The findings suggest that the plant density distinctly affects the root yield and content and the yield of tanshinones and salvianolic acid B in Australian grown S. miltiorrhiza, which may be used as a guide for developing optimal agricultural procedures for cultivating this herb.     

Tropical moist <Emphasis Type="Italic">Polylepis</Emphasis> stands at the treeline in East Bolivia: the effect of elevation on stand microclimate,above- and below-ground structure,and regeneration

We studied Polylepis forests along an elevational transect between 3,650 and 4,050 m a.s.l. at the treeline of the moist eastern cordillera in Bolivia to examine changes in above- and below-ground stand structure, leaf and root morphology, and regeneration in relation to stand microclimate. Field measurements and model predictions indicated relatively cold growth conditions of the Polylepis forests. Tree height, stem diameter, and basal area of the stands decreased markedly while stem density increased with elevation. Leaf morphology differed between the two occurring Polylepis species, and trees at the treeline had smaller leaves with higher specific leaf area. In contrast, fine root biomass increased from 37 g m⁻² at the lowermost stand to 234 g m⁻² at the treeline. Trees of the uppermost stand had higher specific root surface area and a much higher number of root tips per unit dry mass. Thus, root surface area and total number of root tips per unit ground area increased conspicuously from the lowermost stand to the treeline. Density of young growth inside the forest increased towards the treeline, while density in the open grassland decreased with elevation. Young growth originated from sexual reproduction at the lower forest but was comprised exclusively of root suckers at the treeline stand. We conclude that both the marked change in carbon allocation towards the root system, as well as the changes in root morphology with elevation indicate an adaptation to reduced nutrient supply under cold conditions of these Polylepis stands at the treeline in E Bolivia.

Root growth of potato crops on a marine-clay soil

Summary In 1982 and 1983 root samples were taken by auger from potato crops grown on marine clay in the Flevo-Polder. The roots increased their penetration depth throughout the periods of measurement, and ultimately reached depths between 80 cm and 100 cm below the hills. Between 50 and 60 days after emergence, decay of roots commenced, starting in the upper horizons. In the hill mean root length densities varied between 1 and 2 cm cm⁻³. Below the hills root density rarely exceeded 1 cm cm⁻³. The random variation in root density was equivalent to a coefficient of variation of 50%. There were significant effects of the position of sampling (relative to the centre of the plant) on root density; densities were usually lowest beneath the furrow. Depending on season and sampling date, total root length varied between 3.4 and 7.1 km m⁻², and root dry mass varied between 33 and 77 g m⁻². Representative figures for specific root length were 100–120 m g⁻¹ dry weight. About 90% of the root diameters were smaller than 0.44 mm; the most frequent class (35%) were roots with diameters between 0.12 and 0.20 mm.     

应用微根管法测定细根指标方法评述

树木细根(直径<2mm)在森林生态系统能量流动和物质循环中起着重要的作用。原有的细根生产周转研究中常采用的土钻法、内生长法、挖掘法、根室法和土柱法等,均不能直接观察到细根的动态变化。微根管法是一种非破坏性、可定点直接观察和研究植物根系的方法,为研究细根的生长、衰老、死亡、分解和再生长的过程提供了有效的工具,尤其适用于细根周转、寿命和分解等方面的研究。但该技术不能直接测定单位面积的细根生物量、细根化学组成及细根周转对土壤碳和养分循环的影响,需要与土钻法结合。本文就运用微根管法对细根生物量、生产、周转和寿命等指标的研究方法进行了评述。     

Indirect monitoring of root activity in soybean cultivars under contrasting moisture regimes by measuring electrical capacitance

The applicability of root electrical capacitance (EC) measurement for in situ investigation of root activity and drought tolerance was tested in soybean cultivars. Well-watered and drought-stressed plants were grown in pots with repeated EC measurements, followed terminally by harvest to determine root dry mass (RDM), shoot dry mass (SDM), root/shoot ratio (RSR) and leaf area (LA). EC measurement showed the cultivar differences in root growth and biomass production. EC increased till the beginning of flowering, then became nearly constant. Terminal EC was highly correlated with RDM for non-stressed (R ² = 0.844) and stressed plants (R ² = 0.936). Drought reduced the EC of cultivars by 28.8–50.5 %, consistently with the corresponding changes of SDM (25.5–49.1 %) and LA (23.6–51.5 %), but considerably exceeded the loss of RDM (12.6–47.3 %) in some cultivars. The reason is drought increased the RSR (by 3.9–21.9 %), leading to decreased water uptake, and thus EC per unit of RDM. This was confirmed by the significantly decreased slope of EC–RDM regression line from 0.437 to 0.317 nF g^?1 RDM calculated for well-watered and drought-stressed plants, respectively. As EC referred to root uptake activity, it was better indicator of the actual root status than RDM. EC measurement was adequate for monitoring the cultivar-specific differences in root growth and for estimation of biomass loss caused by drought. By supplementing the conventional methods, this in situ technique could be useful for various fields of agriculture, including cultivar selection or stress tolerance studies.     

The effects of clipping and soil moisture on leaf and root morphology and root respiration in two temperate and two tropical grasses

Numerous studies have explored the effect of environmental conditions on a number of plant physiological and structural traits, such as photosynthetic rate, shoot versus root biomass allocation, and leaf and root morphology. In contrast, there have been a few investigations of how those conditions may influence root respiration, even though this flux can represent a major component of carbon (C) pathway in plants. In this study, we examined the response of mass-specific root respiration (μmol CO₂ g⁻¹ s⁻¹), shoot and root biomass, and leaf photosynthesis to clipping and variable soil moisture in two C₃ (Festuca idahoensis Elmer., Poa pratensis L.) and two C₄ (Andropogon greenwayi Napper, and Sporobolus kentrophyllus K. Schum.) grass species. The C₃ and C₄ grasses were collected in Yellowstone National Park, USA and the Serengeti ecosystem, Africa, respectively, where they evolved under temporally variable soil moisture conditions and were exposed to frequent, often intense grazing. We also measured the influence of clipping and soil moisture on specific leaf area (SLA), a trait associated with moisture conservation, and specific root length (SRL), a trait associated with efficiency per unit mass of soil resource uptake. Clipping did not influence any plant trait, with the exception that it reduced the root to shoot ratio (R:S) and increased SRL in P. pratensis. In contrast to the null effect of clipping on specific root respiration, reduced soil moisture lowered specific root respiration in all four species. In addition, species differed in how leaf and root structural traits responded to lower available soil moisture. P. pratensis and A. greenwayi increased SLA, by 23% and 33%, respectively, and did not alter SRL. Conversely, S. kentrophyllus increased SRL by 42% and did not alter SLA. F. idahoensis responded to lower available soil moisture by increasing both SLA and SRL by 38% and 33%, respectively. These responses were species-specific strategies that did not coincide with photosynthetic pathway (C₃/C₄) or growth form. Thus, mass-specific root respiration responded uniformly among these four grass species to clipping (no effect) and increased soil moisture stress (decline), whereas the responses of other traits (i.e., R:S ratio, SLA, SRL) to the treatments, especially moisture availability, were species-specific. Consequently, the effects of either clipping or variation in soil moisture on the C budget of these four different grasses species were driven primarily by the plasticity of R:S ratios and the structural leaf and root traits of individual species, rather than variation in the response of mass-specific root respiration.     

Molecular mapping of genomic regions harbouring QTLs for root and yield traits in sorghum (Sorghum bicolor L. Moench)

Root system is a vital part of plants for absorbing soil moisture and nutrients and it influences the drought tolerance. Identification of the genomic regions harbouring quantitative trait loci (QTLs) for root and yield traits, and the linked markers can facilitate sorghum improvement through marker-assisted selection (MAS) besides the deeper understanding of the plant response to drought stress. A population of 184 recombinant inbred lines (RILs), derived from E36-1 × SPV570, along with parents were phenotyped for component traits of yield in field and root traits in an above ground rhizotron. High estimates of heritability and genetic advance for all the root traits and for most of the yield traits, presents high scope for improvement of these traits by simple selection. A linkage map constructed with 104 marker loci comprising 50 EST-SSRs, 34 non-genic nuclear SSRs and 20 SNPs, and QTL analysis was performed using composite interval mapping (CIM) approach. A total of eight and 20 QTLs were mapped for root and yield related traits respectively. The QTLs for root volume, root fresh weight and root dry weight were found co-localized on SBI-04, supported by a positive correlation among these traits. Hence, these traits can be improved using the same linked markers. The lack of overlap between the QTLs of component traits of root and yield suggested that these two sets of parameters are independent in their influence and the possibility of combining these two traits might enhance productivity of sorghum under receding moisture condition.     

Leaf and fine root carbon stocks and turnover are coupled across Arctic ecosystems

Estimates of vegetation carbon pools and their turnover rates are central to understanding and modelling ecosystem responses to climate change and their feedbacks to climate. In the Arctic, a region containing globally important stores of soil carbon, and where the most rapid climate change is expected over the coming century, plant communities have on average sixfold more biomass below ground than above ground, but knowledge of the root carbon pool sizes and turnover rates is limited. Here, we show that across eight plant communities, there is a significant positive relationship between leaf and fine root turnover rates (r² = 0.68, P < 0.05), and that the turnover rates of both leaf (r² = 0.63, P < 0.05) and fine root (r² = 0.55, P < 0.05) pools are strongly correlated with leaf area index (LAI, leaf area per unit ground area). This coupling of root and leaf dynamics supports the theory of a whole‐plant economics spectrum. We also show that the size of the fine root carbon pool initially increases linearly with increasing LAI, and then levels off at LAI = 1 m² m^?2, suggesting a functional balance between investment in leaves and fine roots at the whole community scale. These ecological relationships not only demonstrate close links between above and below‐ground plant carbon dynamics but also allow plant carbon pool sizes and their turnover rates to be predicted from the single readily quantifiable (and remotely sensed) parameter of LAI, including the possibility of estimating root data from satellites.     

A rhizotron to study root growth under flooded conditions tested with two wetland Cyperaceae

A new type of rhizotron is described that facilitates the study of root growth of inundated wetland plants. This rhizotron provides: (1) non-destructive root morphometric measurements during an experiment, (2) rhizotron-specific independent experimental units, (3) a water level of up to 45 cm above the soil surface, (4) easy access for planting, and (5) the ability to harvest at multiple soil depths. A removable back allows easy access for planting and harvesting at multiple soil depths. A gasket ensures a watertight seal. Detailed methods of construction allow researchers to construct and use similar rhizotrons for experimental research. Advantages and disadvantages of the new rhizotron type are discussed.Using the new rhizotron construction, growth response of the Cyperaceae species Eleocharis cellulosa and Rhynchospora tracyi from the Florida Everglades under different water levels and phosphate availabilities were investigated. Destructive and non-destructive analysis of development of above- and belowground biomass for the two species demonstrates that the two species differ in their response to alterations in water level, but show similarities in their response to phosphorus availability. While E. cellulosa showed larger increases in root density, root biomass, total shoot length, and shoot biomass with rising water level, the opposite was the case in R. tracyi. Both species produced more aboveground biomass with increasing phosphorus availability. Only E. cellulosa showed an increase in root density and a root biomass increase with high phosphorus availability. In R. tracyi, there was no significant increase in root biomass and root density with high phosphorus availability.     

Abscisic acid and gibberellin-like substances in roots and root nodules ofGlycine max

Summary The content of endogenous gibberellin (GA)-like substances of roots and root nodules of SOya, and GA production byRhizobium japonicum cultures, were investigated by a combined thin layer chromatographic (TLC)-dwarf pea epicotyl bioassay technique. GAs were more concentrated in root nodules than in the roots, totalling 1.34 and 0.16 nM GA₃ equivalents g⁻¹ dry wt. respectively. GA production byR. japonicum cultures was demonstrated (1.00 nM GA₃ equivalentsl ⁻¹) and comparison of the GA components of plant and bacterial culture medium extracts, suggested that rhizobial GA production may contribute to the nodule GA content. Cis-trans abscisic acid (ABA) was identified in root and nodule extracts by TLC-gas liquid chromatography (GLC), and amounted to 0.18 and 2.21 nM g⁻¹ dry wt. respectively, whereas 0.30 and 4.63 nM ABA equivalents g⁻¹ dry wt. were detected by a TLC-wheat embryo bioassay technique. ABA was not detected in extracts of bacterial cultures.     

Comparing simple root phenotyping methods on a core set of rice genotypes

Interest in belowground plant growth is increasing, especially in relation to arguments that shallow‐rooted cultivars are efficient at exploiting soil phosphorus while deep‐rooted ones will access water at depth. However, methods for assessing roots in large numbers of plants are diverse and direct comparisons of methods are rare. Three methods for measuring root growth traits were evaluated for utility in discriminating rice cultivars: soil‐filled rhizotrons, hydroponics and soil‐filled pots whose bottom was sealed with a non‐woven fabric (a potential method for assessing root penetration ability). A set of 38 rice genotypes including the OryzaSNP set of 20 cultivars, additional parents of mapping populations and products of marker‐assisted selection for root QTLs were assessed. A novel method of image analysis for assessing rooting angles from rhizotron photographs was employed. The non‐woven fabric was the easiest yet least discriminatory method, while the rhizotron was highly discriminatory and allowed the most traits to be measured but required more than three times the labour of the other methods. The hydroponics was both easy and discriminatory, allowed temporal measurements, but is most likely to suffer from artefacts. Image analysis of rhizotrons compared favourably to manual methods for discriminating between cultivars. Previous observations that cultivars from the indica subpopulation have shallower rooting angles than aus or japonica cultivars were confirmed in the rhizotrons, and indica and temperate japonicas had lower maximum root lengths in rhizotrons and hydroponics. It is concluded that rhizotrons are the preferred method for root screening, particularly since root angles can be assessed.     

The growth,activity and distribution of the fruit tree root system

Summary The paper reviews information, much of it obtained from studies using the East Malling root observation laboratories, on the growth and development of the fruit tree root system. The production of new white root varies from year-to-year, generally being highest in the early years. As trees age, woody roots constitute an increasing fraction of total root length although the contribution made by new root growth to the total root length of established trees is also affected by soil management, being higher for trees under grass than under herbicide. Soil management also affects the balance of short (lateral) to long (extension) roots; under grass there are more lateral roots.Calculation of the rate of water uptake per unit root length needed at various times in the year to meet transpirational demand, suggests that woody roots, which recent experimental work has shown to be capable of absorbing water, must be responsible for much of total water supply.Measurements of VA mycorrhizal infection in field-grown trees indicated, for part of the season, higher per cent infection in trees grown under irrigated grass than under herbicide management. It is suggested that this, which is associated with raised leaf phosphorus levels, may be due at least partly to higher numbers of lateral roots, the root type which becomes infected. The growth and functioning of the root system under field conditions depend upon the production and integration of a range of root types.     

Dependence of the aboveground CO2 exchange rate on tree size in field-grown hinoki cypress (Chamaecyparis obtusa)

The CO₂ exchange of the aboveground parts for five different-sized 17-year-old (as of 1991) hinoki cypress (Chamaecyparis obtusa) trees growing in the field was non-destructively measured over one year, using an open CO₂ exchange system. The CO₂ exchange of individual trees decreased with decreasing tree sizes, such as aboveground phytomass, leaf mass and leaf area. However, the CO₂ exchange abruptly decreased near the smallest-suppressed sample tree. The size dependence was well described by a generalized power function. The annual gross photosynthesis of individual trees was proportional to the square root of leaf mass or leaf area. The dependence of CO₂ exchange on annual phytomass increment was described by a simple power function with an exponent value less than unity, suggesting that CO₂ exchange per unit of phytomass increment was lower in larger-sized trees than in smaller-sized trees. The mean photosynthetic activity of a tree, i.e., gross photosynthesis per unit of leaf area, slightly increased to its highest value with decreasing leaf area and then decreased abruptly near the smallest sample tree. The maximum value of mean photosynthetic activity was estimated to be 2.85 kg CO₂ m⁻² year⁻¹ for a leaf area of 1.56 m² tree⁻¹. The ratio of mean photosynthetic activity to the maximum photosynthetic activity was the highest in an intermediate tree and decreased gradually toward larger-sized trees by ca. 60% and also decreased toward the smallest suppressed tree by ca. 35%.     

Estimating Root Production: Comparison of 11 Methods in Shortgrass Steppe and Review of Biases

Estimating root production has been difficult due to multiple potential biases associated with both old and new methods. This shortgrass steppe site is the only place we are aware of that can compare most methods including sequential coring, ingrowth cores, and ingrowth donuts, ¹⁴C pulse-isotope dilution, ¹⁴C pulse-isotope turnover, rhizotron windows, and minirhizotron, and indirect methods including nitrogen budget, carbon flux, simulation carbon flow model, and regression model. We used the studies at this site, other comparisons, a summary of potential directional biases, and different ways of calculating estimates in a logical, comparative approach of evaluating methods. Much of the literature for root production is based on sequential biomass coring, a method resulting in erroneous estimates. Root ingrowth estimates of production are generally conservative compared to minirhizotron and isotope turnover methods. The size of the ingrowth area may be the most important determinant of the underestimation. Estimates based on pulse-isotope dilution are also erroneous due to non-uniform labeling of tissues. Uniform labeling is not an assumption of the pulse-isotope turnover method, and this method has the least severe potential biases. Root production estimates from pulse-isotope turnover were lower than those using minirhizotron when the most common method of calculation was used. This agrees with literature concerning bomb ¹⁴C continuous-isotope labeling comparisons with minirhizotron, although some potential biases between isotope methods are different. However, good agreement between pulse-isotope turnover and minirhizotron were obtained when minirhizotron estimates were calculated from regression of decomposition versus production to equilibrium and when pulse-isotope turnover estimates were calculated from two-phase life-span regressions. This minirhizotron method bypasses biases associated with the artificial surface similar to root-cohort methods that may be practical only in mesic systems, and takes into account both short- and long-lived roots and corrects for soil-isotope contamination that the continuous-isotope labeling bomb ¹⁴C method is not able to account for. Comparisons of these direct methods are also made with four indirect methods.     

Recording,processing and analysis of grass root images from a rhizotron

To develop and test a system for computer-assisted image analysis, repeated video recordings of reed canary-grass roots (Phalaris arundinacea L.) were made in an 18-window rhizotron. The images were digitized and processed using a Unix computer and the Khoros software development environment.Two image sizes, 126×95 mm and 61×46 mm, both comprising 650 × 490 pixels, were compared. Among image processing techniques used were median filtering, segmentation and skeletonization. Root area and length in both the topsoil and subsoil were estimated using the two image sizes. The resolution (image size) strongly affected the calculated root lengths. The results were compared with root length measurements obtained manually.Statistically significant differences in root length and area in the topsoil were detected between the sampling dates using the computer-assisted methods. Possible sources of error and methods for reducing them are discussed.     

Some observations of the effects of mechanical impedance upon the ultrastructure of the root caps of barley

Summary The root apex of barley,Hordeum vulgare cv. Proctor, is a structure which undergoes a number of gross morphological and ultrastructural changes from the normal patterns of development when grown under a small degree of applied mechanical constraint (2 × 10⁴ Pa.). The root cap is generally smaller and thus does not confer to the root meristem the same degree of protection as caps growing in an uncompacted medium. Associated with this loss of peripheral cells is a reduction in the volume of mucigel in contact with the root apex.In many impeded caps, the planes of division in the calyptrogen are often neither transverse nor longitudinal. There is a reduction in both the number of amyloplasts and starch grains per amyloplast in the columella, but any statolith function of these must not be impaired since the root remains geotropically responsive. The patterns of accumulation of polysaccharide in the walls of peripheral cells as a result of Golgi activity are modified by mechanical impedance.     

Fine root dynamics in two tropical dry evergreen forests in southern India

Seasonality in fine root standing crop and production was studied in two tropical dry evergreen forests viz., Marakkanam reserve forest (MRF) and Puthupet sacred grove (PSG) in the Coromandel coast of India. The study extended from December 89 to December 91 in MRF and from August 90 to December 91 in PSG with sampling at every 2 months. Total fine interval. Mean fine root standing crop was 134 g m⁻² in MRF and 234 g m⁻² in PSG. root production was 104 g m⁻² yr⁻¹ in MRF and 117 g m⁻² yr⁻¹ in PSG. These estimates lie within the range for fine roots reported for various tropical forests. Rootmass showed a pronounced seasonal pattern with unimodal peaks obtained during December in the first year and from October–December in the second year in MRF. In PSG greater rootmass was noticed from June–October than other times of sampling. The total root mass in MRF ranged from 114 to 145 g m−2 at the 13 sampling dates in the three sites. The live biomass fraction of fine roots in MRF ranged from 46 to 203 g m⁻² and in PSG it ranged from 141 to 359 g mm⁻² during the study periods. The dead necromass fraction of fine roots ranged from 6 to 37 g m⁻² in MRF and from 12 to 66 g m⁻² in PSG. Fine root production peaked during December in both the forest sites. The necromass fraction of newly produced roots was negligible. Total N was slightly greater in PSG than in MRF. Whereas total P level was almost similar in both the sites. The study revealed that season and site characteristics influenced fine root system.