Fine-root seasonal pattern, production and turnover rate of European beech (Fagus sylvatica L.) stands in Italy Prealps: Possible implications of coppice conversion to high forest

The aim of this study was to investigate the possible effects of coppice conversion to high forest on the beech fine-root systems. We compared the seasonal pattern of live and dead fine-root mass (d<2 mm), production and turnover in three beech stands that differed in management practices. Tree density was higher in the 40-year-old coppice stand than in the stands that were converted from coppice to high forest in 1994 and 2004, respectively. We found that a reduction in tree density reduced the total fine-root biomass (Coppice stand, 353.8 g m-2; Conversion 1994 stand, 203.6 g m-2; Conversion 2004 stand, 176.2 g m-2) which continued to be characterised by a bimodal pattern with two major peaks, one in spring and one in early fall. Conversion to high forest may also affect the fine-root soil depth distribution. Both fine-root production and turnover rate were sensitive to management practices. They were lower in the Coppice stand (production 131.5 g m-2 year-1; turnover rate 0.41 year-1) than in the converted stands (1994 Conversion stand: production 232 g m-2 year-1, turnover rate 1.06 year-1; 2004 Conversion stand: production 164.2 g m-2 year-1, turnover rate 0.79 year-1)

Sowing Density: A Neglected Factor Fundamentally Affecting Root Distribution and Biomass Allocation of Field Grown Spring Barley (Hordeum Vulgare L.)

Studies on the function of root traits and the genetic variation in these traits are often conducted under controlled conditions using individual potted plants. Little is known about root growth under field conditions and how root traits are affected by agronomic practices in particular sowing density. We hypothesized that with increasing sowing density, root length density (root length per soil volume, cm cm−3) increases in the topsoil as well as specific root length (root length per root dry weight, cm g−1) due to greater investment in fine roots. Therefore, we studied two spring barley cultivars at ten different sowing densities (24–340 seeds m−2) in 2 consecutive years in a clay loam field in Germany and established sowing density dose-response curves for several root and shoot traits. We took soil cores for measuring roots up to a depth of 60 cm in and between plant rows (inter-row distance 21 cm). Root length density increased with increasing sowing density and was greatest in the plant row in the topsoil (0–10 cm). Greater sowing density increased specific root length partly through greater production of fine roots in the topsoil. Rooting depth (D50) of the major root axes (root diameter class 0.4–1.0 mm) was not affected. Root mass fraction decreased, while stem mass fraction increased with sowing density and over time. Leaf mass fraction was constant over sowing density but greater leaf area was realized through increased specific leaf area. Considering fertilization, we assume that light competition caused plants to grow more shoot mass at the cost of investment into roots, which is partly compensated by increased specific root length and shallow rooting. Increased biomass per area with greater densities suggest that density increases the efficiency of the cropping system, however, declines in harvest index at densities over 230 plants m−2 suggest that this efficiency did not translate into greater yield. We conclude that plant density is a modifier of root architecture and that root traits and their utility in breeding for greater productivity have to be understood in the context of high sowing densities

Effect of tree density on root distribution in Fagus sylvatica stands: a semi-automatic digitising device approach to trench wall method

5Knowledge of root profiles is essential for measuring and predicting ecosystem dynamics and function. In the present study, the effects of management practices on root (0.5 <= ø < 20 mm) spatial distribution were examined in a 40-year-old coppice stand (CpS 1968) and other two stands converted from coppice to thinned high forest in 1994 (CvS 1994) and 2004 (CvS 2004), respectively. The use of a semi-automatic digitising device approach was compared with a conventional root mapping method in order to estimate the time per person required from fieldwork to the final digital map. In July 2009, six trench walls per stand were established according to tree density, i.e. as equidistant as possible from all surrounding trees. Findings highlighted differences between the stands with CvS 1994 showing a lower number of small roots (2 <= ø < 5 mm), a higher mean cross-sectional area (CSA) of coarse roots (5 <= ø < 20 mm) and different root depth distribution as compared to CpS 1968 and CvS 2004 whose values were close to each other. The three diameter classes selected in this study showed significant relationships in terms of number of roots, scaling down from coarse- to small- and fine-roots. Forest management practices significantly affected only the number of small roots. The number of fine roots (0.5 <= ø < 2 mm) was isometrically related to their root length density (RLD, cm cm-3). No relationship occurred with RLD of very fine roots (ø < 0.5 mm). In conclusion, forest management practices in terms of conversion thinnings significantly affected belowground biomass distribution of beech forest in space and time. In particular, frequency of coarse roots was related to the stand tree density, frequency of small roots was related to the cutting age. Size of coarse roots was related to tree density but only several years after felling. The allometric relationship occurring between fineand small-roots highlighted how fine root number and RLD were only indirectly affected by forest management practices. These findings suggest that future investigations on the effect of forest thinning practices on fine-root traits like number, length and biomass several years after felling cannot ignore those on small roots.openDi Iorio, A.; Montagnoli, A.; Terzaghi, M.; Scippa, G.S.; Chiatante, D.DI IORIO, Antonino; Montagnoli, A.; Terzaghi, M.; Scippa, G. S.; Chiatante, Donat

Fine root growth and element concentrations of Norway spruce as affected by wood ash and liquid fertilisation

A field experiment to test various management practices of sustainable forestry was conducted in a Swiss spruce forest for two growing seasons. Treatments were a control (C), yearly application of 4000 kg ha−1 wood ash (A), daily irrigation with a steady state fertilisation as 'soptimal nutrition's (F) and irrigation with a water control (W). Samples were taken on a 5 × 5 m grid once a year with a soil corer to determine fine root biomass (≤ 2 mm) and soil pH of the topsoil. A subset of the fine root samples was further analysed for its nutrient composition by CN and ICP-AES analyses. The dynamics of root growth were observed with the aid of ingrowth-cores after 1, 1.5, and 2 years of treatment and the growth pattern was analysed in terms of biomass, tips, forks, length and root diameter of the samples. The A, F and also the W treatment resulted in a significant increase of soil pH in the topsoil. The fine root density increased over the two growing seasons, irrespective of the treatment. The root growth was only slightly different between the treatments with a initially faster growth under the A treatment. The W treatment reduced the number of root tips and forks, and the root length, while the A treatment increased the number of root tips, forks and the root length, but reduced the diameter. The differences between the three harvesting times (March 1999, October 1999, March 2000) of the ingrowth-cores stressed seasonal differences in root growth and the development of quasi 'ssteady state' root dynamics. The root turnover was not changed by the treatments. The elements in the fine roots were strongly affected by the treatments A and F and sometimes by W. Fine root N increased with the F treatment, while C concentrations decreased under the A, F and W treatments. The Ca and Mg concentrations were strongly enhanced by A but also by the F treatment. The K and P concentrations in the fine roots were improved by all three applications. Due to the pH increase Al, Fe and Mn concentrations in the fine roots were decreased by the A and F treatments. S and Zn concentrations showed inconsistent changes over the growing seasons. The results of this study were comparable with those of other studies in Europe and confirm the abilities of the fine roots as indicators of forest nutrition, to some extent more sensitive than the commonly used foliar analysi

Reconciling root plasticity and architectural ground rules in tree root growth models with voxel automata

Contacts: [email protected] models of tree root growth and function have to reconcile the architectural rules for coarse root topology with the dynamics of fine root growth (and decay) in order to predict the strategic plus opportunistic behaviour of a tree root system in a heterogeneous soil. We present an algorithm for a 3D model based on both local (soil voxel level) and global (tree level) controls of root growth, with development of structural roots as a consequence of fine root function, rather than as driver. The suggested allocation rules of carbon to fine root growth in each rooted voxel depend on the success in water uptake in this voxel during the previous day, relative to overall supply and demand at plant level. The allocated C in each voxel is then split into proliferation (within voxel growth) and extension into neighbouring voxels (colonisation), with scale-dependent thresholds and transfer coefficients. The fine root colonisation process defines a dynamic and spatially explicit demand for transport functions. C allocation to development of a coarse root infrastructure linking all rooted voxels depends on the apparent need for adjustment of root diameter to meet the topologically defined sap flow through this voxel during the previous day. The allometric properties of the coarse root system are maintained to be in line with fractal branching theory. The model can predict the dynamics of the shape and structure (fine root density, coarse root topology and biomass) of the root system either independently of soil conditions (purely genetically-driven) or including both the genetic and environmental effects of roots interacting with soil water supply and its external replenishment, linking in with existing water balance models. Sensitivity of the initial model to voxel dimensions was addressed through explicit scaling rules resulting in scale-independent parameters. The model was parameterised for two tree species: hybrid walnut (Juglans nigra x regia) and wild cherry (Prunus avium L.) using results of a pot experiment. The model satisfactorily predicted the root growth behaviour of the two species. The model is sparse in parameters and yet applicable to heterogeneous soils, and could easily be upgraded to include additional local influences on root growth (and decay) such as local success in nutrient uptake or dynamic soil physical propertie

Seasonal patterns of fine root production and turnover in a mature rubber tree (Hevea brasiliensis Müll. Arg.) stand- differentiation with soil depth and implications for soil carbon stocks

Fine root dynamics is a main driver of soil carbon stocks, particularly in tropical forests, yet major uncertainties still surround estimates of fine root production and turnover. This lack of knowledge is largely due to the fact that studying root dynamics in situ, particularly deep in the soil, remains highly challenging. We explored the interactions between fine root dynamics, soil depth, and rainfall in mature rubber trees (Hevea brasiliensis Müll. Arg.) exposed to sub-optimal edaphic and climatic conditions. A root observation access well was installed in northern Thailand to monitor root dynamics along a 4.5 m deep soil profile. Image-based measurements of root elongation and lifespan of individual roots were carried out at monthly intervals over 3 years. Soil depth was found to have a significant effect on root turnover. Surprisingly, root turnover increased with soil depth and root half-life was 16, 6&#8211;8, and only 4 months at 0.5, 1.0, 2.5, and 3.0 m deep, respectively (with the exception of roots at 4.5 m which had a half-life similar to that found between depths of 1.0 and 2.5 m). Within the first two meters of the soil profile, the highest rates of root emergence occurred about 3 months after the onset of the rainy season, while deeper in the soil, root emergence was not linked to the rainfall pattern. Root emergence was limited during leaf flushing (between March and May), particularly within the first two meters of the profile. Between soil depths of 0.5 and 2.0 m, root mortality appeared independent of variations in root emergence, but below 2.0 m, peaks in root emergence and death were synchronized. Shallow parts of the root system were more responsive to rainfall than their deeper counterparts. Increased root emergence in deep soil toward the onset of the dry season could correspond to a drought acclimation mechanism, with the relative importance of deep water capture increasing once rainfall ceased. The considerable soil depth regularly explored by fine roots, even though significantly less than in surface layers in terms of root length density and biomass, will impact strongly the evaluation of soil carbon stocks

Soil organic carbon and root distribution in a temperate arable agroforestry system

Aim To determine, for arable land in a temperate area, the effect of tree establishment and intercropping treatments, on the distribution of roots and soil organic carbon to a depth of 1.5 m. Methods A poplar (Populus sp.) silvoarable agroforestry experiment including arable controls was established on arable land in lowland England in 1992. The trees were intercropped with an arable rotation or bare fallow for the first 11 years, thereafter grass was allowed to establish. Coarse and fine root distributions (to depths of up to 1.5 m and up to 5 m from the trees) were measured in 1996, 2003, and 2011. The amount and type of soil carbon to 1.5 m depth was also measured in 2011. Results The trees, initially surrounded by arable crops rather than fallow, had a deeper coarse root distribution with less lateral expansion. In 2011, the combined length of tree and understorey vegetation roots was greater in the agroforestry treatments than the control, at depths below 0.9 m. Between 0 and 1.5 m depth, the fine root carbon in the agroforestry treatment (2.56 t ha-1) was 79% greater than that in the control (1.43 t ha-1). Although the soil organic carbon in the top 0.6 m under the trees (161 t C ha-1) was greater than in the control (142 t C ha-1), a tendency for smaller soil carbon levels beneath the trees at lower depths, meant that there was no overall tree effect when a 1.5 m soil depth was considered. From a limited sample, there was no tree effect on the proportion of recalcitrant soil organic carbon. Conclusions The observed decline in soil carbon beneath the trees at soil depths greater than 60 cm, if observed elsewhere, has important implication for assessments of the role of afforestation and agroforestry in sequestering carbon

Hydraulic factors limiting the use of subirrigation in fine textured soils : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Philosophy in Agricultural Engineering at Massey University

Subirrigation is a method of supplying water directly to the plant root zone under the ground surface by means of subsurfce drains which are also used to remove excess water from the root zone. Subsurface drainage systems are used to maintain appropriate levels of soil moisture in the root zone of a crop by managing the water table. Subirrigation is seen as being an economic alternative to conventional sprinkler irrigation systems on dairy farms where mole drainage systems are already installed. However, information on subirrigation of these fine textured soils is very limited. The primary focus of this study was to evaluate the hydraulic parameters limiting the use of subirrigation in fine textured soils. A field experiment was carried out on the Massey University No. 4 Dairy Farm in Palmerston North. During the study, a subsurface tile drainage system, with mole channels, was used to subirrigate 1248 m2 of Tokomaru silt loam soil. The depth of irrigation applied was 185.71mm (232 m3 of water added to the system). Time Domain Reflectometry (TDR) was used to measure the soil moisture content to a depth of 400mm at three positions, 5 m away from the drainage lateral and at three control points in an adjacent unirrigated plot. A theoretical daily water balance was developed for the irrigated plot and unirrigated control, based on the available weather data. The results from field experiment showed that sufficient water did not move from the drainage lateral to the moles. Reasons for this may include: (a) Not enough water applied, (b) Not enough pressure head was available to force water from the drainage lateral to the moles or (c) hydraulic conductivity of the backfill was too low. Having identified, from the field experiment, that the hydraulic connection between the lateral and mole was a potential problem, a bin model experiment was carried out in the hydraulic laboratory of the Agricultural Engineering Department. Two different backfill materials (gravel and tokomaru silt loam soil) were used with two mole positions in the bin relative to the drainage lateral. The flow rate and head losses through the system were measured for different applied pressure heads. The saturated hydraulic conductivity (Ksat) of the backfill materials were measured in the laboratory and were measured other relevant physical properties (bulk density, particle density and porosity). The bin model experiment showed that flow rate through the system increases as the pressure head increases for both gravel and Tokomaru silt loam soil backfills. The flow rate with gravel backfill was eight times more than the flow rate with Tokomaru silt loam soil. For a gravel backfill the efficiency of hydraulic connection between the lateral and moles must only be in the order of 2 to 3% for successful subirrigation. With a backfill of Tokomaru silt loam the efficiency of connection must be 10 to 20%. This may not be achieved in the field as the hydraulic conductivity of the backfill will be of a similar magnitude to the surrounding soil leading to significant water losses vertically downward as well as horizontally. It is recommended that further field studies be conducted using gravel backfill. Further laboratory studies using other alternative backfill materials are also suggested