Tree Roots Research Articles

Understanding the risk of using herbicides for tree root removal into wastewater treatment plant performance

Adding herbicides to sewer lines, a common practice for controlling root intrusion in sewer pipes, may adversely impact downstream wastewater treatment by inhibiting nitrification and denitrification performance. This study investigated the effects of herbicides, namely diquat, triclopyr, and 2-methyl-4-chlorophenoxyacetic acid (MCPA)-dicamba, on these processes. Various parameters were monitored, including oxygen uptake rate (OUR), nutrients (NH3–N, TP, NO3–N, and NO2–N), chemical oxygen demand (COD), and herbicide concentrations. It was found that nitrification was not affected by OUR in the presence of each herbicide at various concentrations (1, 10, and 100 mg L−1). Additionally, MCPA-dicamba at various concentrations demonstrated minimal inhibition in the nitrification process compared to diquat and triclopyr. COD consumption was not affected by the presence of these herbicides. However, triclopyr significantly inhibited NO3–N formation in the denitrification process at various concentrations. Similar to nitrification process, both COD consumption and herbicide reduction concentration were not affected by the presence of herbicides during the denitrification process. Adenosine triphosphate measurements showed minimal impact on nitrification and denitrification processes when herbicides were present in the solution up to a concentration of 10 mg L−1. Tree root kill efficiency experiments were performed on Acacia melanoxylon. Considering the performance on nitrification and denitrification process, diquat emerged as the best herbicide option (concentration of 10 mg L−1), with a 91.24% root kill efficiency.

An experimental study on root-reinforced soil strength via a steel root analogue in unsaturated silty soil

AbstractLandslides due to catastrophic weather events, especially heavy rainfall, have risen significantly over the last several decades, causing significant damage and affecting the health and livelihoods of millions of people. Using tree roots to bio-engineer shallow slopes has been proven to be a cost-effective, sustainable measure and thus has gained increasing popularity. As slope failure often occurs under heavy precipitation, it is important to understand the mechanical interactions in the soil matrix surrounding a root to better estimate the reinforcement capacity of a root system, especially as the soil undergoes wetting from drier conditions. However, very few studies of root reinforcements have considered the effects of degree of saturation on behaviour. In this study, steel wires are used as a root analogue to explore the impact of root geometry, soil dilation and soil saturation on the pull-out behaviour of a root and three commonly used unsaturated soil strength models have been used to interpret the pull-out results. It was found that roots with larger diameter did not contribute to additional resistance. Also, a linear relationship between degree of saturation and pull-out strength was identified over a large range of suctions and one of the unsaturated soil strength models seemed to provide a more reasonable interpretation. The results will help future bioengineering slope design by improving the understanding of soil-root interface behaviour, including the effect of root diameter in slippage failure and greater emphasis on the importance of taking degree of saturation into account in unsaturated soil strength models.

Spatial distribution of tree and grassland fine roots in an alley cropping system

Alley cropping systems are known as more sustainable land use alternatives compared to monoculture cropland. In addition to the improvement of above-ground structures and creation of biotopes relevant to nature conservation, the improvement of resource development through various root systems plays a major role. We studied the interaction of the root systems in an alley cropping system combining permanent grassland and willows and at a reference grassland site. The system was established 12 years prior to our study on a site with a shallow groundwater table at 130 cm depth. We measured carbon stocks in the topsoil and determined the share of root-bound carbon relative to the total carbon pool and extracted soil cores up to a depth of 150 cm along a distance gradient to the trees and at a reference grassland site with no tree influence. The maximal rooting depth of the grassland roots increased with increasing distance to the tree lines and total root biomass was higher than under the grassland reference up to a distance of 2.5 m from the tree line. Tree roots extended up to a distance of 5.5 m from the trees and we could distinguish zones of tree root dominance very close to the trees, zones of grassland root dominance at distances ≥ 8.5 m and an interaction zone in between those two extremes. We conclude that alley cropping increases belowground biomass as compared to grassland and has therefore a higher potential to store carbon in the subsoil.

Analysis of Poplar’s (Populus nigra ita.) Root Systems for Quantifying Bio-Engineering Measures in New Zealand Pastoral Hill Country

Populus nigra ita. is an important tree species for preventing rainfall-triggered shallow landslides and hydraulic bank erosion in New Zealand. However, the quantification of its spatial root distribution and reinforcement remains challenging. The objective of this study is to calibrate and validate models for the spatial upscaling of root distribution and root reinforcement. The data were collected in a 26-year-old “Tasman” poplar stand at Ballantrae Hill Country Research Station in New Zealand. We assessed root distribution at different distances from the stem of four poplar trees and from eleven soil pits along a transect located in a sparse to densely planting poplar stand. 124 laboratory tensile tests and 66 field pullout tests on roots with diameters up to 0.04 m were carried out to estimate root mechanical properties. The results show that the spatial distribution of roots can be well predicted in trenches of individual tree root systems (R2 = 0.78), whereas it tends to overestimate root distribution when planting density was higher than 200 stems per hectare. The root reinforcement is underestimated within single tree root systems (R2 = 0.64), but it performs better for the data along the transect. In conclusion, our study provided a unique and detailed database for quantifying root distribution and reinforcement of poplars on a hillslope. The implementation of these models for the simulation of shallow landslides and hydraulic bank erosion is crucial for identifying hazardous zones and for the prioritization of bio-engineering measures in New Zealand catchments. Results from this study are useful in formulating a general guideline for the planning of bio-engineering measures considering the temporal dynamics of poplar’s growth and their effectiveness in sediment and erosion control.

Unmasking adaption of tree root structure in agroforestry Systems in Switzerland using GPR

The interest in agroforestry systems has increased considerably in recent years. The systems are more resilient to climate change and offer advantages related to soil health and biodiversity. Although the aboveground impacts of agroforestry systems are well known, the knowledge concerning root growth of trees remains limited.This study tested the applicability of a non-destructive investigation method, the ground penetrating radar (GPR), to detect tree roots. We mapped two 80-year-old pear trees in cropland and investigated the impact of tilled and no-tilled management on the root system architecture especially in deeper soils (>0.6 m).The root mapping method was successful, we determined the main roots of the tree up to a depth of 0.75 m. In addition, we found tillage significantly impacted root distribution. Tillage removed tree roots almost completely to a depth of 0.4 m. The bulk of the roots was present at a depth of 0.6 to 0.75 m (83% of the roots) in the tilled section, while it was found at 0.3 to 0.55 m (74%) in the no-tilled section. Detected roots indicated an overcompensation by additional roots in the tilled section that were not formed without tillage.Overall, we found agroforestry trees were rooting deeper, below the managed cropland and therefore colonise different soil layers. Thus, the potential volume of water and nutrient intake was enlarged, which might enhance the resilience of the combined production systems. In addition, our approach presents a method for future non-destructive and continuous monitoring of tree roots and their development.

The Use of Compost Tea in a Containerized Urban Tree Nursery Shows No Evident Benefits to Tree Growth or Mycorrhizal Colonization

Compost tea is a liquid organic amendment that has been reported to benefit plant growth and performance through positive effects on microbial communities and plant nutrition. However, few studies have demonstrated this for containerized plants produced in tree nurseries. Five common urban tree species (Acer negundo, Corymbia maculata, Ficus platypoda, Hymenosporum flavum, Jacaranda mimosifolia) were grown in a containerized experiment to investigate the effects of compost tea application on tree growth and root mycorrhizal colonization over six months. The microbial composition of compost tea was also determined with 16S (bacteria) and ITS1 (fungi) metabarcoding. No significant positive effect of compost tea on plant growth or root mycorrhizal colonization was observed. Roots of all tree species were colonized by one type of mycorrhizal fungi, ectomycorrhizae (ECM), or vesicular–arbuscular mycorrhizae (VAM). However, no relationship between the mycorrhizal colonization percentage and plant growth was detected. Thus, there was no evidence that a once-off application of compost tea had benefits for mycorrhizal colonization and growth of containerized trees in a nursery setting. Further research is needed to investigate whether any benefit from compost tea is evident once containerized trees are planted into urban landscapes where growth conditions may be more challenging.

Responses of fine-root biomass and production to drying depend on wetness and site nutrient regime in boreal forested peatland

IntroductionPeatlands are terrestrial-carbon hotspots, where changes in carbon pools and fluxes potentially caused by drying or warming may have significant feedbacks to climate change. In forested peatlands, fine-root biomass (FRB), and production (FRP) are important carbon pools and fluxes, but they and their depth distribution and plant functional type (PFT) composition are poorly known.MethodsWe studied the effects of persistent water-table level (WTL) drawdown on these characteristics in four forested boreal peatland site types that varied in soil nutrient and WTL regimes, ground vegetation and tree stand characteristics. Each site type was represented by a pair of one undrained and one drained site. Two pairs were nutrient-poor, Scots pine dominated sites, one very wet and one relatively dry in their undrained condition. The other two pairs were nutrient-rich, Norway spruce dominated sites, again one wetter and one drier in the undrained condition. FRB was estimated by separating and visually identifying roots from soil cores extending down to 50 cm depth. FRP was estimated using ingrowth cores covering the same depth, and the separated roots were identified using infrared spectroscopy.Results and discussionBoth FRB and FRP varied widely both within and among the different types of boreal forested peatland. In FRB, the clearest differences were seen in the two originally wettest sites, nutrient-poor tall-sedge pine fen and nutrient-rich herb-rich spruce swamp: FRB was smaller in the drained site compared to the undrained site in the pine fen, but the opposite was true in the spruce swamp. FRP was generally higher in the nutrient-poor, pine-dominated sites than the nutrient-rich, spruce-dominates sites. The depth distribution of FRB was more superficial than that of FRP, except for the most nutrient-rich spruce swamp. Tree and shrub roots dominated both FRB and FRP, except for the undrained pine fen, where graminoids and forbs dominated. Even there, these PFTs were replaced by trees and shrubs at the drained site. Site wetness and nutrient regime both thus clearly regulated FRB and FRP of the forested peatland site types studied, and both need to be considered when making any generalizations.

Climbing plants beat trees to soil nutrient patches

Charles Darwin reasoned that because climbing plants are freed from the need to be mechanically self-supporting, their stems can remain thin, elongate quickly, and efficiently colonize and display leaves in well-illuminated areas where trellises are available1. Herein, I report that this tremendous exploratory capacity also applies below-ground - roots of woody climbers (i.e., lianas) consistently beat tree roots to fertilized soil patches, apparently because lianas do not invest in thick roots. This claim is based on results of a greenhouse experiment in which individual seedlings (N = 5 individuals per species) of four liana and four tree species were planted in the centers of 60 x 15 cm rectangular sand-filled boxes. In the direction of a usually covered Plexiglas end wall, a nutrient gradient was established by adding increasing amounts of slow-release fertilizer in four 6 cm-wide vertical bands; no nutrients were added in the other direction. Entire plants were harvested by section when their first root reached the end wall. Roots from all four liana species reached the highly fertilized end of the planting box faster than all tree roots (Figure 1A; for statistical results, see the Supplementary Information). A Vitis rotundifolia root arrived after just 67 days, a Campsis radicans root after 84 days, another Vitis root after 91 days, and then a Wisteria sinensis root after 94 days, and the fastest root of Gelsemium sempervirens grew the 24 cm to the end wall in 149 days. In contrast to the liana species, the fastest tree roots reached the end wall in 235 days for Magnolia grandiflora, 253 days for Quercus hemisphaerica, 263 days for Nyssa sylvatica, and 272 days for Liquidambar styraciflua. This capacity to explore soil rapidly may help explain why lianas are such potent below-ground competitors2 and why their removal substantially increases tree growth rates3,4.

Impact of Deficit Irrigation on Growth and Water Relations of HLB-Affected Citrus Trees under Greenhouse Conditions

Huanglongbing (HLB) is a citrus disease that affects the growth of the fibrous roots of citrus trees. This means that HLB-affected trees may have reduced root volume and may impact water uptake. A greenhouse study was conducted from October 2019 to July 2021 at the Citrus Research and Education Center (CREC) in Lake Alfred, FL, to evaluate the growth and development of HLB-affected citrus trees under a deficit irrigation system. The objective was to assess the impact of deficit irrigation on tree growth, water availability, stem water potential (SWP), sap flow, and root growth of HLB-affected “cv. Valencia” (Citrus sinensis (L.)) orange trees on ‘Kuharske citrange’ rootstock (Citrus sinensis (L.) × Poncirus trifoliata) using an evapotranspiration (ET)-based irrigation schedule. The study hypothesized that HLB-affected citrus trees require less irrigation water to complete their biological functions than healthy citrus trees because of severe fibrous root loss. A total of 20 potted trees were either HLB-positive or non-HLB-affected, and one-half of the trees were subjected to deficit irrigation (80% ET) and the other half to full irrigation (100% ET). There was no significant difference in tree height in both years between HLB-affected trees irrigated at 80% ET and 100% ET. In general, there was no difference in SWP between the HLB-affected trees subjected to deficit irrigation and full irrigation. At 80% and 100% ET, non-HLB trees had greater sap flow than HLB-affected trees. Sap flow for the periods of March–April and June–July 2021 was comparable between HLB-affected trees at all irrigation rates. Maximum sap flow occurred between 11 and 16 h for HLB-affected trees during the three measurement periods. HLB-affected trees had an average water use of 1.6 mm day−1 compared to 2.1 mm day−1 for non-HLB trees. Healthy trees (non-HLB) used about 20% more water than HLB-affected trees, equivalent to 0.5 mm day−1. Thus, irrigating at 80% ET may be appropriate for achieving water savings in controlled environments for HLB-affected trees without causing water stress. However, since these results were conducted under greenhouse conditions in pots, a follow-up study is needed to validate these results under on-farm field conditions.

Pine root exploration of standing dead tree trunks: a short-cut biocycling process

Aim of study: To characterize the colonization of Pinus herrerae roots in trunks of dead standing trees and to evaluate the composition of roots and decomposing tissues of standing dead trees.
 Area of study. Jaguariaíva, Paraná state, Southern Brazil.
 Material and methods: This study evaluated root attributes in the soil, litter, and trunks of dead standing trees and the composition of wood and bark of trees. Root traits (length, mass mycorrhizal colonization, and mean nutrient concentrations), soil and organic layers, and mean nutrient concentrations of wood and bark for were analyzed by non-parametric test.
 Main results: Approximately 2 to 3.5 years after tree death, roots of adjacent trees in F and H horizon litter migrate into the wood/bark interface. Eight and a half years after tree death, roots of adjacent trees reached up to 3.3 m above the litter surface. At the wood/bark interface, a root mantle formed (length greater than 1 km m-2) with ~5% ectomycorrhizal colonization. Root presence in the wood/bark interface reduced P, K, and Fe concentration of dead wood and Zn concentration in bark.
 Research highlights: Our results indicate that roots of P. herrerae are capable of colonizing dead tree trunks as a nutrient resource pool. This nutrient acquisition mechanism may function as a shortcut in the biogeochemical cycling of nutrients in forest systems.

Nitrogen addition influences fine root growth and mycorrhizal symbiosis formation in trees with contrasting root morphology

Nitrogen (N) addition influences fine root growth and mycorrhizal symbiosis formation, the two dominant strategies for tree nutrient acquisition. Arbuscular mycorrhizae (AM) and ectomycorrhizae (ECM) are the two dominant types of mycorrhizal fungi that form symbioses with the roots of most trees. To reveal the divergent adaptive mechanisms and nutrient acquisition strategies of AM and ECM trees under N addition, we investigated the growth and nutrient acquisition of three dominant tree species in a subtropical forest with contrasting fine roots and mycorrhizal fungi symbioses. Castanopsis hystrix with thin fine roots forms associations with ECM. Michelia macclurei and Phoebe bournei with relatively thick fine roots form associations with AM. N addition facilitates the growth of AM trees more obvious than that of the EMC tree. Acid phosphatase activity was increased to overcome N addition-induced P deficiency. The increase in acid phosphatase activity in the rhizosphere of the ECM tree was greater than in AM trees. N addition decreased fine root length and mycorrhizal fungi colonization in all three tree species. The responses of fine roots and mycorrhizal fungi to N addition were species-specific: fine roots were more sensitive than mycorrhizal fungi for C. hystrix and P. bournei, while the opposite pattern (sensitivity of mycorrhiza > roots) was observed for M. macclurei. The divergent sensitivity of the two dominant nutrient acquisition strategies among tree species may facilitate ecological niche partitioning and inter-specific coexistence under limited nutrient availability.

Effects of poplar intercropping systems on reducing the concentration of different forms of inorganic nitrogen in the soil profile

AbstractThis study focused on understanding how different spacing arrangements of poplar (Populus deltoides)–wheat (Triticum aestivum) agroforestry systems and the processes of the tree and wheat roots in these systems impact the elimination efficiency of inorganic nitrogen from soil. Three planting systems were tested: a monoculture wheat system (control), a widely spaced wheat–poplar system (PWW) and a narrowly spaced wheat–poplar system (PWN). Soil and root samples were collected in four different soil layers (0–20, 20–40, 40–60, and 60–100 cm) at four different sampling sites (PWN: 0, 1.5, 2.5, and 3.5 m; PWW: 0, 1.5, 3.5, and 7 m from tree row, respectively). The nitrate–nitrogen (), ammonium–nitrogen (), and nitrite–nitrogen () in the soil samples were analyzed to determine the elimination efficiency of the different systems. The results indicated that the concentration and soil accumulation content reduction of inorganic nitrogen in the two intercropping systems, especially in the PWW system, were encouraging compared to those in the control system. The and concentration reductions and poplar fine root length density (FRLD) were higher at the sampling point near the poplar row, especially in surface soil (p < 0.05), but the distribution of the wheat FRLD decreased with soil depth and proximity to the poplar trunk. Furthermore, the poplar and wheat FRLD had significant positive relationships with the concentration reduction of inorganic nitrogen. In conclusion, poplar–agroforestry systems should be considered as an important method for controlling nonpoint pollution from farmland.

Long-Term Simulated Nitrogen Deposition Has Moderate Impacts on Soil Microbial Communities across Three Bioclimatic Domains of the Eastern Canadian Forest

The soil microbiome plays major roles in the below-ground processes and productivity of forest ecosystems. Atmospheric nitrogen (N) deposition is predicted to increase globally and might create disturbances in soil microbial communities, essentially by modifying soil chemistry. However, the impacts of higher N deposition on the soil microbiome in N-limited northern forests are still unclear. For 16 years, we simulated N deposition by adding ammonium nitrate at rates of 3 and 10 times the ambient N deposition directly into soils located in three bioclimatic domains of the eastern Canadian forest (i.e., sugar maple–yellow birch, balsam fir–white birch, and black spruce–feather moss). We identified changes in the microbial communities by isolating the DNA of the L, F, and H soil horizons, as well as by sequencing amplicons of the bacterial 16S rRNA gene and the fungal ITS region. We found that long-term increased N deposition had no effect on soil microbial diversity, but had moderate impacts on the composition of the bacterial and fungal communities. The most noticeable change was the increase in ectomycorrhizal fungi ASV abundance, potentially due to increased tree root growth on fertilized plots. Our work suggests that, in N-limited northern forests, extra N is rapidly mobilized by vegetation, thus minimizing impacts on the soil microbiome.

Weak phylogenetic and habitat effects on root trait variation of 218 Neotropical tree species

IntroductionTropical forests harbor a large diversity of closely related tree species that can thrive across habitats. This biodiversity has been found to correspond to large functional diversity in aboveground traits, and likely also relates to belowground trait variation. Globally, root trait (co-)variation is driven by different belowground resource strategies of species, environmental variation, and phylogeny; however, these patterns mostly reflect observations from temperate biomes and remain unconfirmed in tropical trees. We examine phylogenetic and environmental effects on root trait (co-)variation of trees across habitats in an Amazonian rainforest.MethodsRoots of 218 tree species from ten dominant families were sampled across three major habitats near Manaus, Brazil. We quantified five morphological and architectural root traits to (i) investigate how they reflected different resource strategies across species, (ii) compare them between families and superorders to test phylogenetic effects, and (iii) compare them between habitats to determine environmental effects on root trait expressions and variability.ResultsRoot traits discriminated species along a tradeoff between root diameter and root branching and, secondly, due to variation in root tissue density. Our results further show weak phylogenetic effects on tropical tree root variation, for example, families from the same superorder showed large divergence in their root traits, while those from different superorders often overlapped in their root morphology and architecture. Root traits differed significantly between habitats but habitat type had only little effect on overall root trait variation.DiscussionOur work suggests that the dimensions and drivers that underlie (co-)variation in tropical root traits may differ from global patterns defined by mostly temperate datasets. Due to (a)biotic environmental differences, different root trait dimensions may underlie the belowground functional diversity in (Neo)tropical forests, and we found little evidence for the strong phylogenetic conservatism observed in root traits in temperate biomes. We highlight important avenues for future research on tropical roots in order to determine the degree of, and shifts in functional diversity belowground as communities and environments change in tropical forests.

Ectomycorrhizal diversity, taxon-specific traits and root N uptake in temperate beech forests.

Roots of forest trees are colonized by a diverse spectrum of ectomycorrhizal (EM) fungal species differing in their nitrogen (N) acquisition abilities. Here, we hypothesized that root N gain is the result of EM fungal diversity or related to taxon-specific traits for N uptake. To test our hypotheses, we traced 15 N enrichment in fine roots, coarse roots and taxon-specific ectomycorrhizas in temperate beech forests in two regions and three seasons, feeding 1 mM NH4 NO3 labelled with either 15 NH4 + or 15 NO3 - . We morphotyped > 45 000 vital root tips and identified 51 of 53 detected EM species by sequencing. EM root tips exhibited strong, fungal taxon-specific variation in 15 N enrichment with higher NH4 + than NO3 - enrichment. The translocation of N into the upper parts of the root system increased with increasing EM fungal diversity. Across the growth season, influential EM species predicting root N gain were not identified, probably due to high temporal dynamics of the species composition of EM assemblages. Our results support that root N acquisition is related to EM fungal community-level traits and highlight the importance of EM diversity for tree N nutrition.

Tree root research in New Zealand: a retrospective ‘review’ with emphasis on soil reinforcement for soil conservation and wind firmness

Background: Trees and forests have been used in New Zealand to reduce erosion, particularly from rainfall–triggered landslides, gullying, and earthflows. Most New Zealand tree root research has been conducted during the life of the New Zealand Journal of Forestry Science, with much published in it. Methods: We undertook a retrospective ‘review’ of New Zealand tree root research focusing on soil reinforcement and its application for erosion control, slope stability assessment, and understanding tree stability in forests. The published and grey literature was searched using common search terms and relevant papers assessed. The international literature was not reviewed but helped provide context for the New Zealand studies. Results: Results were aggregated into broad topic areas and key findings summarised. Where multiple studies existed for a particular species, results are presented by species. Selected data are presented to enable inter-species comparisons, and the reader is directed to additional data or the original study. Conclusions: New Zealand tree root research has focused mostly on root description or simple measurements to support applied studies of root structure and function. Nonetheless, such research has made a valuable global contribution in addition to improving the understanding and management of New Zealand’s forests. Studies show that generally, exotic species outperform indigenous species for most empirical root metrics other than root tensile strength. A combination of both lateral and vertical roots provides the best soil reinforcement and contribution to slope stability. Future research should focus on acquiring more field data and improvements in dealing with spatial and temporal variability in model development. Practical tools for land managers to target the right places with the right vegetation (species, amount, density) are a pressing need as changing climate is changing the way we manage natural hazards like landslides, floods and wildfires.

Dendrogeomorphology in Evaluating Erosive Processes in an Urban Conservation Unit

Water erosion is a worldwide problem that has been depleting soils mainly in tropical regions, due to the greater volume of precipitated water. In this sense, recent prediction methods in tropical regions such as dendrogeomorphology are necessary and important to identify and date the influence and correlation between erosion processes and vegetation. This study aimed to understand and scale the erosive processes, through the annual historical recognition of the rate of soil loss and sedimentation, applying the concepts of dendrogeomorphology in the evaluation of the stem and roots of trees of the species of Anadenanthera macrocarpa and Schefflera morototoni, in a conservation unit in the Brazilian Cerrado. Trees were selected in the following soil level conditions: (i) having root exposure, (ii) no exposure (buried), and (iii) no change in soil level (control). Cross-dating was performed using the COFECHA software program, and the information applied in dating scars and abnormal radial growth periods were observed in exposed roots and associated with the beginning of erosion processes. The results indicated that the occurrence of the erosive processes ascertained by anatomical changes in the exposed roots and a most common erosive rains date from 2006, 2008, 2009, 2010, 2012, 2013, 2016 and 2017. While changes in the trunk growth ring width start from 1992, with similar years between the two species of 2013 and 2017. The highest soil accumulation rates were 18.6 mm/year, vertical losses were 500 mm per year and horizontal losses were 665 mm. Finally, there is a positive correlation between the number of scars and an abrupt increase in the growth rings of the exposed roots with the number of erosive rains.

Do highly anthropized hydrological conditions in marshes influence fish communities according to their life‐history strategies?

AbstractAlterations of natural hydrology in aquatic ecosystems are known to strongly impact the community composition of different taxa. Surprisingly, literature on the potential influence of hydrology on fish community composition is still very scarce in agricultural marshes, where canals represent one of the few remaining aquatic habitats. This study is aimed to address this research gap by monitoring fish communities in independent hydrological units differing in hydrology management over a 6 years period. We predicted variable fish responses to the hydrological context according to different life‐history strategies (opportunistic, equilibrium, or periodic species). Periodic and opportunistic species were the most frequently observed. Despite differences in hydrology between canals (but little variation over years), we found that hydrology explained only a very low proportion of variation in the composition of fish communities. In particular, the flooding duration of meadows in early spring did not influence the composition of fish communities, not even the abundance of periodic species expected to rely on such temporary habitats. Instead, fish communities were more influenced by local habitat variables (aquatic vegetation cover, turbidity, tree roots, and refuges under the canal banks). The hydrological management of most hydrological units for agricultural purposes (i.e., severe flood abatement in spring and shallow water depth in canals in summer) was found to be incompatible with conservation goals to promote more diverse fish communities between hydrological units. Therefore, we call for further investigations in similar habitats covering a larger range of hydrological conditions.

Development and growth of young black spruce (Picea mariana) trees under two different hydrological conditions

Large areas in boreal forests are classified as peatlands, characterized by organic soils with a high water table. Black spruce (Picea mariana (Mill.) B.S.P.) is one of the species capable of growing in this inauspicious environment, where an adaptation of the root system can be expected. We studied young black spruces growing in peat moss with two different hydrological conditions over a 19 years timespan: saturated and well-drained peat. We identified the initial and adventitious roots of the trees and compiled radial growth measurements of each root. The general growth pattern of the roots was identified and compared to the annual radial growth within the stem. We observed growth reductions during the first years after the planting shock, followed by a growth increase in the roots and stems for both hydrological conditions. The continuous formation of adventitious roots in trees growing in the saturated environment was the main adaptation noticed. The largest radial growth values were registered in the younger adventitious roots growing in saturated conditions. The lowest radial growth in the adventitious roots were registered in the well-drained condition. PCA analyses revealed the influence of root depth with regard to stem height and diameter at soil level. The black spruce trees displayed the required plasticity to form adventitious roots outside the range of the water table, allowing them a better access to oxygen and nutrients. This survival strategy implies to allocate a higher amount of energy to the root system instead of the aerial part of the tree in which overall productivity is low.

Resistance of domestic plum tree rootstocks against periodic overwatering of floodplain soils

This work investigates the effect of domestic plum rootstocks on the stability and productivity of Stanley plum plants. The main factor limiting the productivity of fruit crops in the floodplain soils of the foothill horticultural area of Krasnodar Oblast was found to be an unfavorable water-air regime of these soils in wet periods. The main geogenic factors that negatively affect the state and productivity of plum plants include the following: the presence of layers of low fertility and medium-clay granulometric composition in the soil profile. Depression and death of trees is promoted by prolonged overwatering of the upper part of the soil profile, caused by low filtration capacity of soil layers in combination with heavy granulometric composition and conditions of laying on the terrain (absence of horizontal surface runoff). A different degree of plum trees resistance to these unfavorable geogenic conditions depending on the type of rootstock was revealed. The lowest degree of depression under prolonged overwatering of the root-containing soil layer was observed in plum trees on the PK SK2 rootstock, which demonstrated the highest vegetative mass growth under the smallest number of dead plants. Stanley plum trees on rootstock AP1 were subjected to the greatest depression. The different degree of plum tree stability on different rootstocks is mainly related to the location of potentially active roots in the soil. The root system of plum trees on rootstock PK SK2 is characterized by the concentration of the main part (about 65 %) of potentially active roots in the upper soil layer of 0–40 cm. In plum trees on AP1 rootstock, potentially active roots penetrate to greater depths, with about 60% of the roots located in the soil layer of 40-80 cm. During wet periods and after abundant precipitation, when the soil below the 40 cm level is saturated with moisture, more than half of potentially active roots of plum trees on AP1 rootstock have to survive in unfavorable conditions.