Variation In Root Biomass Research Articles

Variation in Root Biomass and Distribution Based on the Topography, Soil Properties, and Tree Influence Index: The Case of Mt. Duryun in Republic of Korea.

Root biomass and distribution are influenced by abiotic factors, such as topography and soil physicochemical properties, determining belowground productivity. Hence, we investigated the variation in root biomass and vertical root distribution based on the topography, soil physicochemical properties, and tree influence index, and their relationships, across soil depths (0-10 cm, 10-20 cm, and 20-30 cm) and topographical gradients in a warm-temperate forest in Mt. Duryun, Republic of Korea. Two contrasting research sites were established: a lower slope oriented at ≤3° and an upper slope with a slope of 30°. Each site comprised eleven 400 m2 sampling plots from which root samples from various diameter classes (<2 mm, 2-5 mm, 5-10 mm, and >10 mm) were collected. While the bulk density increased with soil depth in the lower slope, the organic matter, available phosphorus, Ca2+, and Mg2+ showed a reversed pattern. Linear mixed-effects models generally revealed significant negative correlations between root biomass and soil pH, total nitrogen, and cation exchange capacity, particularly in small roots (βstd = -1.03 to -1.51) and coarse roots (βstd = -6.30). Root biomass exhibited a 10-15% increase in the upper slope compared to the lower slope, particularly in fine (median = 52.0 g m2-65.64 g m2) and medium roots (median = 56.04 g m2-69.52 g m2) at a 0-20 cm soil depth. While no significant correlation between root biomass and the tree influence index was found on the lower slope, a different pattern was found on the upper slope. Our results indicate that the variation in root biomass and distribution can also be explained by the differences in the soil environment and topographical positions.

Effect of container size on yield and root morphology of different fruit crops

The experiment was conducted to standardize container gardening techniques for fruit crops, guava (Psidium guajava L), pomegranate (Punica granatum L.) and citrus (Citrus aurantifolia L) to meeting out the nutritional requirement of city dwellers. There was maximum average plant biomass (1072 g/plant) in guava and minimum (423g) in pomegranate. Maximum shoot biomass (1012.11g) was recorded in plant grown in 45 cm x 45 cm and minimum (402.78g/plant) in 30x30 cm container. Destructive method was used to extract the root mass for analysis significant variation in root biomass was also recorded, maximum root biomass (506.11g) in guava and minimum (239.86 g) in pomegranate, however root biomass was recorded significantly maximum (509.78 g) in 45 cm x 45 cm. Root to shoot ratio was recorded maximum (0.63) in Citrus crops. The root:shoot ratio had significant correlation with stem girth and negatively correlated with fruit weight, fruit yield and root hairs diameter. Collar diameter has significantly positive correlation with plant height, fruit weight and yield. The container size as well as growing media (substrate) influenced the plant growth, root and shoot biomass, fruit yield and root morphology remarkably.

Effect of canopy condition on Machilus nanmu seedling configuration and biomass allocation

The adaptation strategy of seedlings plays a decisive role in population regeneration. Machilus nanmu is a tree species belonging to Lauraceae, which is national class Ⅱ protected species and one of the dominant species in the evergreen broadleaved forest in Jinyun Mountain, Chongqing. Therefore, it is of great significance to understand the adaptation strategies of M. nanmu seedlings to maintain population regeneration and protect the biodiversity of evergreen broadleaved forest. We studied the temporal dynamics of early adaptation strategy of M. nanmu in Jinyun Mountain in Chongqing and its response to heterogeneous habitats from the perspective of morphology and biomass allocation. The seedlings of M. nanmu were classified into different age stages (stage 1: 1-3 a; stage 2: 4-6 a; stage 3: 7-9 a) under different canopy environments (gap/understory). Stem configurations (except branch angle) and leaf inclination angle of M. nanmu seedlings in the gap were significantly greater than understory at stages 2 and 3. Root configurations (except root diameter) and leaf area were significantly greater than that in the understory at stages 1 and 2. Specific leaf area in the gap was significantly smaller than understory at all three stages. Across all the conditions, biomass distribution was dominated by leaves. From the stage 2, stem biomass distribution of M. nanmu seedlings in the gap was increased, while root biomass distribution was decreased. There was no significant variation in root biomass of M. nanmu seedlings in the understory. The coordination among different organs of M. nanmu seedlings would help their adaptation to different habitats. Root and leaf of M. nanmu seedlings in the gap were significantly correlated, with the correlation changing from positive to negative as the age increased. While in the understory, there was significant positive correlation between root and stem, but no correlation between root and leaf. The slope of SMA equation of branch weight and branch length had significant difference under different canopy environments only at stage 3, while the slope of SMA equation of leaf and root biomass and configuration had no significant difference. Most of the SMA equation intercepts between biomass and configuration differed significantly at stage 2.

Root to shoot and carbon to nitrogen ratios of maize and soybean crops in the US Midwest

Abstract Root traits are important to crop functioning, yet there is little information about how root traits vary with shoot traits. Using a standardized protocol, we collected 160 soil cores (0−210 cm) across 10 locations, three years and multiple cropping systems (crops x management practices) in Iowa, USA. Maximum root biomass ranged from 1.2 to 2.8 Mg ha−1 in maize and 0.86 to 1.93 Mg ha−1 in soybean. The root:shoot (R:S) ratio ranged from 0.04 to 0.13 in maize and 0.09 to 0.26 in soybean. Maize produced 27 % more root biomass, 20 % longer roots, with 35 % higher carbon to nitrogen (C:N) ratio than soybean. In contrast, soybean had a 47 % greater R:S ratio than maize. The maize R:S ratio values were substantially lower than literature values, possibly due to differences in measurement methodologies, genotypes, and environment. In particular, we sampled at plant maturity rather than crop harvest to minimize the effect of senescence on measurements of shoots and roots. Maximum shoot biomass explained 70 % of the variation in root biomass, and the R:S ratio was positively correlated with the root C:N measured in both crops. Easily-measured environmental variables including temperature and precipitation were weakly associated with root traits. These results begin to fill an important knowledge gap that will enable better estimates of belowground net primary productivity and soil organic matter dynamics. Ultimately, the ability to explain variation in root mass production can be used to improve C and N budgets and modeling studies from crop to regional scales.

A historical and comparative review of 50 years of root data collection in Puerto Rico

AbstractFine roots play an important role in plant nutrition, as well as in carbon, water, and nutrient cycling. Fine roots account for a third of terrestrial net primary production (NPP), and inclusion of their structure and function in global carbon models should improve predictions of ecosystem responses to climate change. However, studies focusing on underground plant components are much less frequent than those on aboveground structure. This is more marked in the tropics, where one‐third of the planet's terrestrial NPP is produced. Some tropical forests have been more represented in the literature than others, as demonstrated in the collective studies in Puerto Rico. This Caribbean island's biodiversity, frequency of natural disturbances, ease of access to forests, and long‐term plots have created an ideal place for the study of tropical ecological processes. This literature review emphasizes 50 years of root research and patterns revealed around Puerto Rico. The data in this review were compiled from scientific publications, conference reports, symposiums, and raw data shared by some researches. Emergent patterns include the shallow distribution of fine roots, the great variation in root biomass among different forest types, little variation in root phosphorus concentrations, the slow recovery of root biomass after Hurricane Hugo, and the fact that most data on roots come from the wet tropical Luquillo Experimental Forest, causing other habitat types to be underrepresented. This review also shows the gaps in knowledge about fine roots in the island's ecosystems, which should be used to promote and guide future studies.Abstract in Spanish is available with online material.

Effects of plant productivity and species richness on the drought response of soil respiration in temperate grasslands.

Soil respiration plays a crucial role in global carbon cycling. While the response of soil respiration to abiotic drivers like soil temperature and moisture is fairly well understood, less is known about the effects of biotic drivers, such as plant above- and belowground productivity or plant diversity, and their interactions with abiotic drivers on soil respiration. Thus, current predictions of soil respiration to summer droughts might miss relevant biological drivers and their interactions with abiotic drivers. Since drought events are expected to increase in Central Europe in the future, we simulated early summer drought using rainout shelters at 19 grassland sites, which differed in plant productivity and species richness in central Germany in 2002 and 2003. We tested the potentially interacting effects of drought with biotic drivers, i.e. annual above-ground productivity, species richness and root biomass, on the drought response of soil respiration in temperate grasslands. In both years, drought led to a significant reduction in soil respiration. The drought-induced reduction in soil respiration was largely driven by the reduction in above-ground productivity in response to drought. The extent of the drought response of soil respiration was dependent on the species richness level of the site and this interacting effect was explainable by the variation in root biomass (root biomass and species richness were positively correlated). Our findings highlight the importance of biotic drivers for the quantification of the drought response of soil respiration in grasslands.

Mechanisms linking plant community properties to soil aggregate stability in an experimental grassland plant diversity gradient

Soil aggregate stability depends on plant community properties, such as functional group composition, diversity and biomass production. However, little is known about the relative importance of these drivers and the role of soil organisms in mediating plant community effects. We studied soil aggregate stability in an experimental grassland plant diversity gradient and considered several explanatory variables to mechanistically explain effects of plant diversity and plant functional group composition. Three soil aggregate stability measures (slaking, mechanical breakdown and microcracking) were considered in path analyses. Soil aggregate stability increased significantly from monocultures to plant species mixtures and in the presence of grasses, while it decreased in the presence of legumes, though effects differed somewhat between soil aggregate stability measures. Using path analysis plant community effects could be explained by variations in root biomass, soil microbial biomass, soil organic carbon concentrations (all positive relationships), and earthworm biomass (negative relationship with mechanical breakdown). The present study identified important drivers of plant community effects on soil aggregate stability. The effects of root biomass, soil microbial biomass, and soil organic carbon concentrations were largely consistent across plant diversity levels suggesting that the mechanisms identified are of general relevance.

Effects of forest floor organic layer and root biomass on soil respiration following boreal forest fire

Soil respiration and its spatial and temporal variation were studied at three boreal forest sites in central Saskatchewan, Canada, burned in 1998, 1989, and 1977. Soil respiration, soil temperature, and organic layer thickness were measured at 100 points in a grid pattern of 2 m × 2 m at each site in 2004 and 2005. The mean within-site spatial coefficient of variation was 35%, and the measurements were not spatially autocorrelated. We found no significant difference in variance between the two youngest sites (P &gt; 0.05), whereas the older site showed significantly lower variance (P &lt; 0.05). Soil respiration was not correlated with the forest floor organic layer thickness at any of the sites (R2 &lt; 0.1). Removal of the forest floor layer reduced the soil respiration by 17% to 38%, depending on the site. Thus, the respiration from the mineral soil seemed to contribute a major fraction of the total soil respiration (62%–83%). Soil respiration was positively linearly related to the fine root biomass (R2 = 0.63–0.85, P &lt; 0.05) at all sites. We conclude that variation in root biomass has a larger effect than differential forest floor organic layers on variation in soil respiration in young boreal postfire forests.

Improving Drought-Avoidance Root Traits in Chickpea (Cicer arietinum L.) -Current Status of Research at ICRISAT

Chickpea (Cicer arietinum L.), an important food legume grown in the semi-arid tropical and Mediterranean regions, suffers substantial yield loss due to drought at the end of the growing season (terminal drought), as the crop is largely grown rainfed in post-rainy season on progressively receding soil moisture conditions. Root traits have been identified to postpone dehydration (drought avoidance hereafter) under moisture stress. The root length density (RLD) in the relatively shallow soil layers and the maximum root depth (RDp) were found to positively influence the seed yield under terminal drought environments. Considerable progress has been made to improve the methodology for sampling and analysis of roots. Using a PVC cylinder technique, the mini-core collection (n=211) of chickpea germplasm was evaluated for a number of root traits, including root biomass, RLD and RDp. A few germplasm accessions were identified to have a more prolific root system than the previously identified germplasm line ICC 4958, the best-known source of high root biomass. The germplasm accession ICC 8261 was identified to have the best combination of both RLD and RDp. Molecular markers have been identified for one major quantitative trait locus (QTL) that accounts for about one-third of the variation in root biomass (as measured by total root dry matter) and RDp from study of recombinant inbred lines (RILs) derived from a cross between ICC 4958 and Annigeri. New RIL populations, developed from two other crosses (ICC 8261 × ICC 283 and ICC 4958 × ICC 1882) involving parents having larger variation for root traits than between Annigeri and ICC 4958, are being studied to identify additional QTLs for root traits. Marker-assisted breeding for improvement of root traits in chickpea is expected to promote the development of varieties with greater drought avoidance.

FINE ROOT BIOMASS AND PRODUCTION IN A SEMIARID MEXICAN SHRUBLAND

I describe the vertical distribution of root biomass and root productivity in a xeric shrubland of central Mexico. The effect of the soil nitrogen on root production was evaluated with a fertilization experiment. The highest percentage of roots was found at a depth of 40 to 60 cm. Monthly variation in root biomass for diameter class was significant. Fine and very fine roots were the most important fraction in terms of biomass and production. The highest production of fine root occurred in native soil versus the other treatments.

Contribution of root respiration to soil respiration in a C3/C4 mixed grassland

The spatial and temporal variations of soil respiration were studied from May 2004 to June 2005 in a C3/C4 mixed grassland of Japan. The linear regression relationship between soil respiration and root biomass was used to determine the contribution of root respiration to soil respiration. The highest soil respiration rate of 11.54 micro mol m-2 s-1 was found in August 2004 and the lowest soil respiration rate of 4.99 micro mol m-2 s-1 was found in April 2005. Within-site variation was smaller than seasonal change in soil respiration. Root biomass varied from 0.71 kg m-2 in August 2004 to 1.02 in May 2005. Within-site variation in root biomass was larger than seasonal variation. Root respiration rate was highest in August 2004 (5.7 micro mol m-2 s-1) and lowest in October 2004 (1.7 micro mol m-2 s-1 ). Microbial respiration rate was highest in August 2004 (5.8 micro mol m-2 s-1 ) and lowest in April 2005 (2.59 micro mol m-2 s-1 ). We estimated that the contribution of root respiration to soil respiration ranged from 31% in October to 51% in August of 2004, and from 45% to 49% from April to June 2005.

The effects of spatial pattern of nutrient supply on the early stages of growth in plant populations

Summary We report an experimental study of the effects of pattern of nutrient supply on the early stages of growth in populations of Cardamine hirsuta. Populations were grown with nutrients provided in one of four spatial patterns (three heterogeneous and one homogeneous). In the three heterogeneous treatments, nutrient‐rich and nutrient‐poor substrate patches of different sizes were set up in chequerboard patterns, with patches of each type accounting in total for half of the substrate, both by volume and area. All treatments provided the same total quantity of nutrients. After 31 days of growth, populations in the heterogeneous treatments had produced significantly more root, shoot and total biomass than those in homogeneous conditions. The coefficient of variation in shoot sizes, and the variation in root biomass per unit of substrate, were also significantly greater in populations growing under heterogeneous conditions. In the heterogeneous treatments significantly more than 50% of the biomass was located in nutrient‐rich patches, and this proportion increased significantly as patch size increased. In heterogeneous treatments, yield of plant parts from nutrient‐rich locations was significantly greater than that of plant parts in nutrient‐poor locations. It was also significantly greater than that recovered from equivalent locations in the homogeneous treatment. We conclude that the spatial configuration of nutrients significantly affects plant population yield, the spatial distribution of population biomass, and plant size hierarchy during the early stages of population growth, even when total nutrient supply is held constant. We predict that these early effects of heterogeneity will continue to have impacts, not only on size structure, but also on the spatial pattern of mortality and the overall level of mortality, at later stages of population growth.

Douglas-fir root biomass and rooting profile in relation to soils in a mid-elevation area (Beaujolais Mounts, France)

Douglas-fir is the main reforestation species in the French Massif Central area (14 000 ha), but little is known about its rooting strategy in different soil conditions. This information has important implications for the choice of better soils for settling Douglas-fir, and consequently limiting risks of failure, pests or diseases. As a result, the influence of edaphic conditions on rooting patterns of dominant Douglas-fir was studied over a large range of ecological conditions in a mid-elevation area of the French Massif Central (Beaujolais Mounts). Root systems were studied extensively using the trench profile wall technique and the sector method in 74 pure and evenly aged Douglas-fir stands. The stands were chosen as being representative of soil conditions among 165 stands in an auto-ecological study. The rooting patterns were related to seven typical soil profiles, and to root profile groups. Results stressed that edaphic constraints due to substratum and soil structures have a strong influence on root system morphology. Important variations in root biomass and vertical distribution were highlighted among soils. Small fine root biomass is maximal for soils with no major edaphic constraints. The vertical distribution of fine root biomass is positively correlated for some soil types with organic C, total N, and most cations. For some types it was negatively correlated with the amount of exchangeable aluminum and coarse fragments, and with constraining rock facies. Harsher soils however, showed no correlation between soil chemical variables and fine-root biomass. A practical implication is that Douglas-fir seems to be a pliable and adaptive species: variation in habit and root system biomass are considerable within a study area which was presumed uniform.

Investigating the relationship between neighbor root biomass and belowground competition: field evidence for symmetric competition belowground

Little is known about how small‐scale variation in neighbor biomass can influence the strength of root competition experienced by an individual plant. In this study, modified root exclusion tubes were used to vary the accessibility of the soil space surrounding Amaranthus retroflexus target plants to the neighboring plants. A gradient of root accessibility was created by drilling varying numbers of holes into standard root exclusion tubes, made of 15 cm diameter PVC pipe. Belowground competitive intensity, defined as biomass reduction due to root interactions alone, relative to growth in the absence of neighbors, was then measured along the resulting gradient of neighbor root densities. At low neighbor root abundances the strength of belowground competition was proportional to neighbor root biomass, consistent with prior evidence that belowground competition is symmetric. If belowground competition were asymmetric, neighbor roots should have had little effect on target plants when they are rare relative to those of the target plant. At higher neighbor root abundances, belowground competitive intensity should increase rapidly. The strong relationship found between neighbor root biomass and belowground competitive intensity suggests relatively small variations in root biomass could lead to large variations in belowground competition. Reduced belowground competition in areas with low root biomass could have important implications for the establishment and growth of poor belowground competitors, suggesting a mechanism by which species coexistence may occur despite extremely intense root competition.

A simulation model of the water uptake of a beech forest: testing variations in root biomass and distribution

AbstractA validated mathematical model was used to simulate the effects of roots biomass and distribution on the water uptake of a 120‐year old beech (Fagus silvatica L.) stand located at Solling (West Germany).The modell was based on the soil‐water movement equation including an extraction term to account for the water uptake of the root system. This extraction term varies with the meteorological conditions, root density and soil water potential.Root biomass values considered were: 500 kg. ha−‐1, 1000 kg. ha−‐1, 2000 kg. ha−‐1, 4000kg. ha−‐1 and 6000 kg. ha−‐1. For each of these values, five different distributions were tested. These ranged between a soil profile 0.40m deep with high root concentration to a 1.00m soil profile with idealized uniform root distribution. The model was run under two different rainfall conditions: i) an uncommon dry year (1971), (ii) a hypothetical normal year without a dry period.The model showed the fundamental importance of the root distribution under the given meteorological conditions. This was more evident when the root biomass was low and medium. A good root distribution throughout the profile allowed the forest to overcome long dry periods. With the maximum root biomass value the distribution had no effect on the forest water uptake.