Fine-roots dynamics, anatomy and carbon-nitrogen concentrations in relation to forest management and soil water content. Case studies in beech(Fagus sylvatica L.) and Turkey-oak (Quercus cerris L.) forests.

Uncertainties in estimates of fine root dynamics prevent a proper quantification of net primary productivity and belowground C allocation. Moreover, model studies for estimating carbon budgets are biased by the lack of fine roots datasets at forest stand level. This study shed some lights on fine root dynamics in two different Italian forests. In particular fine-root systems was investigated: 1) in three beech forest stands (Fagus sylvatica L.) located in Southern-Alps in relation to different forest management practices and age 2) in a mature Turkey-oak stand (Quercus cerris L.) located in the Southern Apennines in relation to soil moisture seasonal changes. Data from beech forests showed that conversion from coppice to high forest practice induced considerable variations in fine-root traits. Reduction of stand tree density induced a reduction of total fine-root mass and an increase of both production and turnover rate. Both fine-root production and turnover rate increased in converted stands. When fine-roots Carbon and Nitrogen contents were analyzed, their ratio was significantly lower in converted stands, supporting the finding of a higher turnover rate. A histological study was carried to assess if also anatomical changes occurred due to conversion practices. Anatomy on fine roots showed a higher percentage of xylem cells in conversion stands explaining the lowest carbon concentration. Turkey-oak fine-root biomass and length showed a bimodal pattern with a peak in summer and a peak in autumn. SRL had only one peak in summer. All fine root traits increased during the transition from the wet to dry season. These results indicate a pulse in root growth in order to increase the soil exploitation when soil water content is low. Moreover, during the summer period, Q. cerris change fine-root morphology leading an increase of fine root length per unit mass

Fine-roots dynamics, anatomy and carbon-nitrogen concentrations in relation to forest management and soil water content. Case studies in beech(Fagus sylvatica L.) and Turkey-oak (Quercus cerris L.) forests.

Uncertainties in estimates of fine root dynamics prevent a proper quantification of net primary productivity and belowground C allocation. Moreover, model studies for estimating carbon budgets are biased by the lack of fine roots datasets at forest stand level. This study shed some lights on fine root dynamics in two different Italian forests. In particular fine-root systems was investigated: 1) in three beech forest stands (Fagus sylvatica L.) located in Southern-Alps in relation to different forest management practices and age 2) in a mature Turkey-oak stand (Quercus cerris L.) located in the Southern Apennines in relation to soil moisture seasonal changes. Data from beech forests showed that conversion from coppice to high forest practice induced considerable variations in fine-root traits. Reduction of stand tree density induced a reduction of total fine-root mass and an increase of both production and turnover rate. Both fine-root production and turnover rate increased in converted stands. When fine-roots Carbon and Nitrogen contents were analyzed, their ratio was significantly lower in converted stands, supporting the finding of a higher turnover rate. A histological study was carried to assess if also anatomical changes occurred due to conversion practices. Anatomy on fine roots showed a higher percentage of xylem cells in conversion stands explaining the lowest carbon concentration. Turkey-oak fine-root biomass and length showed a bimodal pattern with a peak in summer and a peak in autumn. SRL had only one peak in summer. All fine root traits increased during the transition from the wet to dry season. These results indicate a pulse in root growth in order to increase the soil exploitation when soil water content is low. Moreover, during the summer period, Q. cerris change fine-root morphology leading an increase of fine root length per unit mass

Fine-root morphological and growth traits in a Turkey-oak stand in relation to seasonal changes in soil moisture in the Southern Apennines, Italy

We investigated the effects of seasonal changes in soil moisture on the morphological and growth traits of fine roots (<2 mm in diameter) in a mature Turkeyoak stand (Quercus cerris L.) in the Southern Apennines of Italy. Root samples (diameter: <0.5, 0.5\u20131.0, 1.0\u20131.5, and 1.5\u20132.0 mm) were collected with the Auger method. Mean annual fine-root mass and length on site was 443 g m!2 (oak fine roots 321 g m!2; other species 122 g m!2) and 3.18 km m!2 (oak fine roots 1.14 km m!2; other species 2.04 km m!2), respectively. Mean specific root length was 8.3 m g!1. All fine-root traits displayed a complex pattern that was significantly related to season. In the four diameter classes, both fineroot biomass and length peaked in summer when soil water content was the lowest and air temperature the highest of the season. Moreover, both fine-root biomass and length were inversely related with soil moisture (p < 0.001). The finest roots (<0.5 mm in diameter) constituted an important fraction of total fine-root length (79 %), but only 21 % of biomass. Only in this root class, consequent to change in mean diameter, specific root length peaked when soil water content was lowest showing an inverse relationship (p < 0.001). Furthermore, fine-root production and turnover decreased with increasing root diameter. These results suggest that changes in root length per unit mass, and pulses in root growth to exploit transient periods of low soil water content may enable trees to increase nutrient and water uptake under seasonal drought conditions

Ongoing modifications to root system architecture of Pinus ponderosa growing on a sloped site revealed by tree-ring analysis

Abstract Our knowledge of the root system architecture of trees is still incomplete, especially concerning how biomass partitioning is regulated to achieve an optimal, but often unequal, distribution of resources. In addition, our comprehension of root system architecture development as a result of the adaptation process is limited because most studies lack a temporal approach. To add to our understanding, we excavated 32-year-old Pinus ponderosa trees from a steep, forested site in northern Idaho USA. The root systems were discretized by a low magnetic field digitizer and along with AMAPmod software we examined their root traits (i.e. order category, topology, growth direction length, and volume) in four quadrants: downslope, upslope, windward, and leeward. On one tree, we analyzed tree rings to compare the ages of lateral roots relative to their parental root, and to assess the occurrence of compression wood. We found that, from their onset, first-order lateral roots have similar patterns of ring eccentricity suggesting an innate ability to respond to different mechanical forces; more root system was allocated downslope and to the windward quadrant. In addition, we noted that shallow roots, which all presented compression wood, appear to be the most important component of anchorage. Finally, we observed that lateral roots can change growth direction in response to mechanical forces, as well as produce new lateral roots at any development stage and wherever along their axis. These findings suggest that trees adjust their root spatial deployment in response to environmental conditions, these roots form compression wood to dissipate mechanical forces, and new lateral roots can arise anywhere and at any time on the existing system in apparent response to mechanical forces

Early pine root anatomy and primary and lateral root formation are affected by container size: implications in dry-summer climates

Although the presence of root anatomical structures of young Pinus ponderosa seedlings grown in containers of contrasting volume (164 vs. 7000 cm3) was similar, seedlings reared 60 days in the large container had more vascular cambium although the xylem thickness was similar. In addition, seedlings in large containers had nearly twice as many resin ducts within the vascular cambium as their cohorts in small containers. Taproot length closely matched container depth. Though lateral root emission rates were similar between container sizes, large container seedlings had more than 2X the number of lateral roots as those from small containers. These differences in morphophysiological characteristics may be important to seedling establishment on sites that experience dry summer conditions, or for seedlings destined to drier, harsher sites. Further work to elucidate the ramifications of these morphophysiological differences on seedling establishment is warranted

Estimating forest aboveground biomass by low density lidar data in mixed broad-leaved forests in the Italian Pre-Alps

Background: Estimation of forest biomass on the regional and global scale is of great importance. Many studies have demonstrated that lidar is an accurate tool for estimating forest aboveground biomass. However, results vary with forest types, terrain conditions and the quality of the lidar data. Methods: In this study, we investigated the utility of low density lidar data (<2 points∙m−2) for estimating forest aboveground biomass in the mountainous forests of northern Italy. As a study site we selected a 4 km2 area in the Valsassina mountains in Lombardy Region. The site is characterized by mixed and broad-leaved forests with variable stand densities and tree species compositions, being representative for the entire Pre-Alps region in terms of type of forest and geomorphology. We measured and determined tree height, DBH and tree species for 27 randomly located circular plots (radius =10 m) in May 2008. We used allometric equations to calculate total aboveground tree biomass and subsequently plot-level aboveground biomass (mg∙ha−1). Lidar data were collected in June 2004. Results: Our results indicate that low density lidar data can be used to estimate forest aboveground biomass with acceptable accuracies. The best height results show a R2 = 0.87 from final model and the root mean square error (RMSE) 1.02 m (8.3% of the mean). The best biomass model explained 59% of the variance in the field biomass. Leave-one-out cross validation yielded an RMSE of 30.6 mg∙ha−1 (20.9% of the mean). Conclusions: Low-density lidar data can be used to develop a forest aboveground biomass model from plot-level lidar height measurements with acceptable accuracies. In order to monitoring the National Forest Inventory, and respond to Kyoto protocol requirements, this analysis might be applied to a larger area. Keywords: LiDAR; Allometric equations; Plant height; Mixed fores

Reaction Wood Anatomical Traits and Hormonal Profiles in Poplar Bent Stem and Root

Reaction wood (RW) formation is an innate physiological response of woody plants to counteract mechanical constraints in nature, reinforce structure and redirect growth toward the vertical direction. Differences and/or similarities between stem and root response to mechanical constraints remain almost unknown especially in relation to phytohormones distribution and RW characteristics. Thus, Populus nigra stem and root subjected to static non-destructive mid-term bending treatment were analyzed. The distribution of tension and compression forces was firstly modeled along the main bent stem and root axis; then, anatomical features, chemical composition, and a complete auxin and cytokinin metabolite profiles of the stretched convex and compressed concave side of three different bent stem and root sectors were analyzed. The results showed that in bent stems RW was produced on the upper stretched convex side whereas in bent roots it was produced on the lower compressed concave side. Anatomical features and chemical analysis showed that bent stem RW was characterized by a low number of vessel, poor lignification, and high carbohydrate, and thus gelatinous layer in fiber cell wall. Conversely, in bent root, RW was characterized by high vessel number and area, without any significant variation in carbohydrate and lignin content. An antagonistic interaction of auxins and different cytokinin forms/conjugates seems to regulate critical aspects of RW formation/development in stem and root to facilitate upward/downward organ bending. The observed differences between the response stem and root to bending highlight how hormonal signaling is highly organ-dependent

Terrestrial laser scanning and low magnetic field digitization yield similar architectural coarse root traits for 32-year-old Pinus ponderosa trees

Background Understanding how trees develop their root systems is crucial for the comprehension of how wildland and urban forest ecosystems plastically respond to disturbances such as harvest, fire, and climate change. The interplay between the endogenously determined root traits and the response to environmental stimuli results in tree adaptations to biotic and abiotic factors, influencing stability, carbon allocation, and nutrient uptake. Combining the three-dimensional structure of the root system, with root morphological trait information promotes a robust understanding of root function and adaptation plasticity. Low Magnetic Field Digitization coupled with AMAPmod (botAnique et Modelisation de l’Architecture des Plantes) software has been the best-performing method for describing root system architecture and providing reliable measurements of coarse root traits, but the pace and scale of data collection remain difficult. Instrumentation and applications related to Terrestrial Laser Scanning (TLS) have advanced appreciably, and when coupled with Quantitative Structure Models (QSM), have shown some potential toward robust measurements of tree root systems. Here we compare, we believe for the first time, these two methodologies by analyzing the root system of 32-year-old Pinus ponderosa trees Results In general, at the total root system level and by root-order class, both methods yielded comparable values for the root traits volume, length, and number. QSM for each root trait was highly sensitive to the root size (i.e., input parameter PatchDiam) and models were optimized when discrete PatchDiam ranges were specified for each trait. When examining roots in the four cardinal direction sectors, we observed differences between methodologies for length and number depending on root order but not volume. Conclusions We believe that TLS and QSM could facilitate rapid data collection, perhaps in situ, while providing quantitative accuracy, especially at the total root system level. If more detailed measures of root system architecture are desired, a TLS method would benefit from additional cans at differing perspectives, avoiding gravitational displacement to the extent possible, while subsampling roots by hand to calibrate and validate QSM models. Despite some unresolved logistical challenges, our results suggest that future use of TLS may hold promise for quantifying tree root system architecture in a rapid, replicable manner

Fine-roots dynamics, anatomy and carbon-nitrogen concentrations in relation to forest management and soil water content. Case studies in beech(Fagus sylvatica L.) and Turkey-oak (Quercus cerris L.) forests.

Uncertainties in estimates of fine root dynamics prevent a proper quantification of net primary productivity and belowground C allocation. Moreover, model studies for estimating carbon budgets are biased by the lack of fine roots datasets at forest stand level. This study shed some lights on fine root dynamics in two different Italian forests. In particular fine-root systems was investigated: 1) in three beech forest stands (Fagus sylvatica L.) located in Southern-Alps in relation to different forest management practices and age 2) in a mature Turkey-oak stand (Quercus cerris L.) located in the Southern Apennines in relation to soil moisture seasonal changes. Data from beech forests showed that conversion from coppice to high forest practice induced considerable variations in fine-root traits. Reduction of stand tree density induced a reduction of total fine-root mass and an increase of both production and turnover rate. Both fine-root production and turnover rate increased in converted stands. When fine-roots Carbon and Nitrogen contents were analyzed, their ratio was significantly lower in converted stands, supporting the finding of a higher turnover rate. A histological study was carried to assess if also anatomical changes occurred due to conversion practices. Anatomy on fine roots showed a higher percentage of xylem cells in conversion stands explaining the lowest carbon concentration. Turkey-oak fine-root biomass and length showed a bimodal pattern with a peak in summer and a peak in autumn. SRL had only one peak in summer. All fine root traits increased during the transition from the wet to dry season. These results indicate a pulse in root growth in order to increase the soil exploitation when soil water content is low. Moreover, during the summer period, Q. cerris change fine-root morphology leading an increase of fine root length per unit mass

Plant Growth Promoting Microorganisms Useful for Soil Desalinization

The salinization of cultivable soils is a major issue that humankind will soon have to face [...