Longevity and Turnover of Roots In the Shortgrass Steppe: Influence of Diameter and Depth (original) (raw)
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2008 Roumet et al Plant and Soil
This study examines whether root traits differed between three major plant families (Asteraceae, Fabaceae and Poaceae) and whether they are related to root respiration and exudation. Nine traits related to biomass allocation, root topology, morphology, chemical composition and mycorrhizal colonisation were examined for nine C 3 herbaceous species grown in controlled conditions. Poaceae differed from Fabaceae for the whole set of root traits examined except mycorrhizal colonisation, while Asteraceae showed intermediate characteristics. As compared to Fabaceae, Poaceae allocated more biomass to roots; showed a more sparsely branched root system with a small average root diameter, a high root dry matter content and a low nitrogen concentration. Root respiration was weakly related to root mass ratio and root dry matter content; no significant relationship was found between root functions and root architecture or morphology. This study shows that plant classification based on taxonomic affiliation reflects differences in root system traits and functions. Whole root system traits do not allow strong predictions of root respiration and exudation, perhaps because these processes are more linked to fine root than to whole root system traits.
Suites of root traits differ between annual and perennial species growing in the field
New Phytologist, 2006
Here, we tested whether root traits associated with resource acquisition and conservation differed between life histories (annuals, perennials) and families (Fabaceae, Asteraceae and Poaceae). • Root topology, morphology, chemistry and mycorrhizal colonization were measured on whole root systems of 18 field-grown herbaceous species grown and harvested in central Argentina.
Plant and Soil, 2003
Dependence of the properties of root systems on the size of the root system may alter conclusions about differences in plant growth in different environments and among species. To determine whether important root system properties changed as root systems aged and accumulated biomass, we measured three important properties of fine roots (tissue density, diameter, and C:N) and three biomass ratios (root:shoot, fine:coarse, and shallow:deep) of monocultures of 10 North American grassland species five times during their second and third years of growth. With increasing belowground biomass, root tissue density increased and diameter decreased. This may reflect cortical loss associated with the aging of roots. For non-legumes, fine root C:N decreased with increasing root biomass, associated with decreases in soil solution NO 3 − concentrations. No changes in fine root C:N were detected with increasing belowground biomass for the two legumes we studied. Among all 10 species, there were generally no changes in the relative amounts of biomass in coarse and fine roots, root:shoot, or the depth placement of fine roots in the soil profile as belowground biomass increased. Though further research is needed to separate the influence of root system size, age of the roots, and changes in nutrient availability, these factors will need to be considered when comparing root functional traits among species and treatments.
A non-destructive technique for studies of root distribution in relation to soil moisture
Agriculture, Ecosystems & Environment, 1991
Andr6n, O., Rajkai, K. and I~tterer, T., 1991. A non-destructive technique for studies of root distribution in relation to soil moisture. Agric. Ecosystems Environ., 34: 269-278. The minirhizotron technique is simple, non-destructive and can give detailed information on root growth dynamics. This method can easily be used to monitor the number of roots at several depth levels and in several experimental treatments. It was used in a field experiment on clay soil where winter wheat was subjected to different irrigation/fertilization combinations. Soil water content around the rhizotrons was measured at 6-cm depth intervals using a capacitance probe, which was gradually lowered into the minirhizotrons. The same depth intervals were used for making root observations, and moisture was measured shortly after making the root counts, resulting in a data set with a one-toone correspondence between root counts and soil water content. Estimates of soil water content were corrected for the soil cracking that occurred at low water contents. Other variables, e.g. changes in moisture over time and soil water tension, were calculated. Correlation and regression techniques were applied to variable pairs of the whole data set and subsets thereof. Potential applications, improvements and expansions of the technique are discussed.
Root-length densities of various annual crops following crops with contrasting root systems
Soil and Tillage Research, 2014
The aim of this study was to evaluate how soil structure and root-length densities of annual crops can be influenced by preceding crops. Three different annual field crops (spring wheat, Triticum aestivum L., winter barley, Hordeum vulgare L. and winter oilseed rape, Brassica napus L.) were cultivated either after two continuous years of chicory, Cichorium intybus L., a perennial taprooted fodder crop or after annual crops with fibrous root systems (oats, Avena sativa L. and tall fescue, Festuca arundinacea Schreb). Biopores of two diameter classes (2-5 mm and >5 mm) were quantified per unit surface area by visual classification in 45-145 cm soil depth. Root-length density was estimated by using the profile wall method or by image analysis of roots washed from monolith samples. After chicory, the number of large sized biopores per unit surface area in the subsoil was greater than after annual crops with fibrous root systems. When grown after chicory, the root-length densities of annual winter crops below 115 cm soil depth were greater than after fibrous precrops. It is concluded that cultivation of taprooted crops with the ability to create larger sized biopores allows subsequent crops to establish more roots in deep soil layers, with potentially greater access to nutrients and water from the subsoil. ß
Root growth and turnover in perennial forages as affected by management systems and soil depth
Plant and Soil, 2020
Aims Extensive knowledge of perennial forage root systems is essential, given their critical role in belowground C input. Methods Root length and diameter were quantified periodically from 2016 to 2018 with minirhizotrons in a field experiment with three forage management systems: mixture of timothy (Phleum pratense L.) and tall fescue (Festuca arundinacea Schreb.) fertilized with (i) dairy cattle slurry or (ii) calcic ammonium nitrate, and (iii) mixture of timothy, tall fescue, and alfalfa (Medicago sativa L.) without N fertilization. Root biomass was measured yearly by coring. Results Management systems with the two fertilization sources did not differ in root elongation, but the management system with alfalfa resulted in a slower root elongation after the first defoliation and a lower root mortality in the fall. Root length turnover was greater in the topsoil with dairy cattle slurry than with calcic ammonium nitrate. Fine roots dominated the surface soil and coarse roots the deeper soil layers. Conclusions Root growth and mortality were more contrasted between systems that differed by the presence of alfalfa than by fertilizer source. As many root characteristics are drivers of soil C storage, the choice of perennial species in mixtures appears as a key management factor for sustainable farming systems.
RESEARCH New Phytol. (2000), 147, 13–31 Global patterns of root turnover for terrestrial ecosystems
Root turnover is a critical component of ecosystem nutrient dynamics and carbon sequestration and is also an important sink for plant primary productivity. We tested global controls on root turnover across climatic gradients and for plant functional groups by using a database of 190 published studies. Root turnover rates increased exponentially with mean annual temperature for fine roots of grasslands (r# l 0.48) and forests (r# l 0.17) and for total root biomass in shrublands (r# l 0.55). On the basis of the best-fit exponential model, the Q "! for root turnover was 1.4 for forest small diameter roots (5 mm or less), 1.6 for grassland fine roots, and 1.9 for shrublands. Surprisingly, after accounting for temperature, there was no such global relationship between precipitation and root turnover. The slowest average turnover rates were observed for entire tree root systems (10% annually), followed by 34% for shrubland total roots, 53% for grassland fine roots, 55% for wetland fine roots, and 56% for forest fine roots. Root turnover decreased from tropical to high-latitude systems for all plant functional groups. To test whether global relationships can be used to predict interannual variability in root turnover, we evaluated 14 yr of published root turnover data from a shortgrass steppe site in northeastern Colorado, USA. At this site there was no correlation between interannual variability in mean annual temperature and root turnover. Rather, turnover was positively correlated with the ratio of growing season precipitation and maximum monthly temperature (r# l 0.61). We conclude that there are global patterns in rates of root turnover between plant groups and across climatic gradients but that these patterns cannot always be used for the successful prediction of the relationship of root turnover to climate change at a particular site. Aber JD, Melillo JM, Nadelhoffer KJ, McClaugherty CA, Pastor J. 1985. Fine root turnover in forest ecosystems in relation to quantity and form of nitrogen availability : a comparison of two methods. Oecologia 66 : 317-321. Aerts R, Bakker C, De Caluwe H. 1992. Root turnover as determinant of the cycling of C, N, and P in a dry heathland ecosystem. Biogeochemistry 15 : 175-190. Ares J. 1976. Dynamics of the root system of Blue Gramma. Journal of Range Management 29 : 208-213. Arneth A, Kelliher FM, McSeveny TM, Byers JN. 1998. Net ecosystem productivity, net primary productivity and ecosystem carbon sequestration in a Pinus radiata plantation subject to soil water deficit. Tree Physiology 18 : 785-793. Arthur MA, Fahey TJ. 1992. Biomass and nutrients in an Englemann spruce-subalpine fir forest in north central Colorado : pools, annual production, and internal cycling. Canadian Journal of Forest Research 22 : 315-325. Arunachalam A, Pandey HN, Tripathi RS, Maithani K.
Soil Depth Can Modify the Contribution of Root System Architecture to the Root Decomposition Rate
Forests
Aims: Changes in root system architecture (RSA) and soil depth affect the root decomposition rate. However, due to soil opacity, many variables of RSA have not been well studied or even measured. Methods: To investigate the effects of soil depth and the characteristics of RSA on the root decomposition rate, soil samples (Soil cores were collected in October 2020 from Cunninghamia lanceolata and Pinus taeda plantations, which were 40 years old) were obtained using a soil auger and had a diameter of 10 cm and a length of 60 cm. Samples were taken from six different soil depths, ranging from 0 to 60 cm with a 10 cm interval between each depth. The RSA in the in-situ soil cores was analyzed using computed tomography scans and Avizo. Results: Root volume and the number of root throats were significantly higher at the 0–10 cm soil depth than at the 10–60 cm soil depth, but root length was significantly lower at the 50–60 cm soil depth (p < 0.05). Structural equation modeling showed tha...