Background / Purpose: Both light response and assimilation to internal CO2 concentration (A/Ci) c... more Background / Purpose: Both light response and assimilation to internal CO2 concentration (A/Ci) curves were developed along a soil metal load gradient. Main conclusion: Preliminary results indicate that compensation points differ significantly between Betla and Populus but not between the two Populus species. In addition, there were significant differences between the sites examined. These data, suggest that differences in resource allocation between growth and maintenance within the heterogeneous edaphic conditions of the urban context results in differing compensation points and hence carbon sequestration rates. Such data helps to define the value of urban forest and the point at which mitigation is necessary.
ABSTRACT Background/Question/Methods Allometric relationships of many forest species have been we... more ABSTRACT Background/Question/Methods Allometric relationships of many forest species have been well documented. As a result, there have been many attempts to generalize carbon sequestration across forest populations. However, such models must account for the temporary nature and variability of leaf biomass . Furthermore, these models do not generally account for biotic filters such as disturbance, insect/fungal/bacterial attacks and contamination of soil and water. Through both destructive sampling and LAI measurements we examined leaf biomass at four forest sites with varying levels of metal contamination and water availability. Results/Conclusions Our results indicate that soil metal loads and water availability affect LAI and leaf mass. The site with the lowest metal contamination and greatest water availability had an LAI of 2.85, and the site with the highest metal contamination and lowest water availability had an LAI of 1.6. The site with the highest metal contamination and lowest water availability had a per unit-leaf mass of 145.10g while the site with the lowest metal contamination and greatest water availability had a per unit-leaf mass of 128.1g. These data suggest that the site index at the microscale can play an important role in determining the carbon flux within an urban forest.
Restoration Notes have been a distinguishing feature of Ecological Restoration for more than 25 y... more Restoration Notes have been a distinguishing feature of Ecological Restoration for more than 25 years. This section is geared toward introducing innovative research, tools, technologies, programs, and ideas, as well as providing short-term research results and updates on ongoing efforts. Please direct submissions and inquiries to the editorial staff (ERjournal@ aesop.rutgers.edu).
Soil compaction, which is necessary to safely support sidewalks and pavement, conflicts with urba... more Soil compaction, which is necessary to safely support sidewalks and pavement, conflicts with urban trees' need for usable rooting space to support healthy tree growth. We have defined a rigid soil medium that will safely bear loads required by engineering standards yet still allow for rapid root exploration and growth. This was accomplished by forming a stone matrix and suspending soil within the matrix pores with the assistance of a hydrogel gluing agent. Initial studies using three stone types and various stone to soil ratios showed that the compacted stone-soil test medium (dry densities > 1700 kg/m3) increased root growth by a minimum of 320% over the compacted clay loam control (dry density of 1378 kg/m3). The proposed system can safely bear load demonstrated by California Bearing Ratios consistently exceeding 40. Discus- sion of a critical mixing ratio is presented as an approach for developing a specification for field installation.
We built a machine with a propeller capable of generating 33.5 m/s (75 mph) winds to determine th... more We built a machine with a propeller capable of generating 33.5 m/s (75 mph) winds to determine the influence of pruning dose and American National Standards Institute A300 pruning type on trunk movement of Quercus virginiana 'QVTIA' PP #11219, Highrise at various wind speeds. Trunk movement was regressed against wind speeds and pruning doses for each tree tested. Increasing wind speed increased trunk movement, and the magnitude of the increase depended on pruning dose and pruning type. Increasing pruning dose reduced trunk movement and the magnitude of the reduction was greater at higher wind speeds. The predicted trunk movement of thinned trees was statistically greater than movement of structurally pruned, raised, and lion's tailed trees at wind speeds of 20.1 m/s (45 mph) and was greater than all pruning types at 26.8 m/s (60 mph). There was no difference in movement among reduced, raised, structurally pruned, and lion's tailed trees; and there were no statistical...
. A Minolta SPAD-502 leaf chlorophyll meter was used for nondestructive data collection on the ch... more . A Minolta SPAD-502 leaf chlorophyll meter was used for nondestructive data collection on the chlorophyll and nitrogen (N) status of benjamin fig (Ficus benjamina) and cottonwood (Populus deltoides) to quantitatively evaluate foliage quality. The goal was to provide a specific calibration for interpreting SPAD data within a media study for each species. Triplicate SPAD readings were collected from each of six leaves, sampled from forty plants per species, then processed for foliar analysis. Leaf tissue disks were also collected directly over SPAD testing sites for chloro-phyll concentration measurement. Significant linear correlations were found between SPAD data and chlorophyll concentrations (r 2 = 0.90 in benjamin fig and r 2 = 0.91 for cottonwood). A significant, but lower correlation was found between SPAD data and N concentration. The SPAD-N correlations improved from the fifth month to the ninth month harvest (r 2 = 0.32 to 0.53 for benjamin fig and 0.26 to 0.42 for cottonwo...
In 1997, willow oak (Quercus phellos L.), swamp white oak (Quercus bicolor Willd.), and goldenrai... more In 1997, willow oak (Quercus phellos L.), swamp white oak (Quercus bicolor Willd.), and goldenraintree (Koelreuteria paniculata Laxm.) were planted in the right-of-way on Lorimer Street in Brooklyn, New York, U.S. This was one of the earliest commercial installations of the load-bearing stone-soil blends (hereafter called structural soil) developed at Cornell Universi- ty's Urban Horticulture Institute (Grabosky and Bassuk 1995). The north-south street segment bisects McCarren Park between Driggs Avenue and Bayard Street. Trees were planted as 5.1 to 7.6 cm (2 to 3 in) caliper trees on either side of the street. The west side trees were planted in a continuous trench of structural soil 0.6 m (2 ft) deep by 2.1 m (6.9 ft) wide down the entire block. The structural soil was used as the sidewalk base capped with concrete. Tree openings were 0.9 m by 1.5 m (3 × 5 ft), which were planted after paving and then covered by granite unit block pavers. The east side of the street was a tre...
Quercus robur seedlings were grown in compacted stone-soil mixes known to meet engineering standa... more Quercus robur seedlings were grown in compacted stone-soil mixes known to meet engineering standards for pavement base compaction and strength. Root penetration into these materials was greatly increased in comparison to an equally compacted clay loam, which was also a component of the test material. Oak root penetration in the clay loam decreased 50%, from 6 to 3 g dry root weight, as the bulk density increased from 1.24 to 1.55 Mg/m3. Severe root impedance was observed when clay loam bulk densities exceeded 1.5 Mg/m3 (90% standard AASHTO peak density),a situation produced after 20% of the standard compaction effort was imposed on the soil profile. At the standard AASHTO peak density for the clay loam (1.67 Mg/m3), which would be the norm in a sidewalk installation, root growth was entirely stopped. In contrast, structured stone-soil mixes compacted to 100% of their respective standard AASHTO peak densities (between 1.85 and 2.07 Mg/m3) did not restrict root penetration with mean r...
Three avenues of experimental observation detail aspects of plant available water holding capacit... more Three avenues of experimental observation detail aspects of plant available water holding capacity in compacted stone-soil media designed for urban tree establishment in paved situations. The various compacted media provided an estimated plant available moisture content of 7%-11% by volume, comparable to a loamy sand. Changes in aggregate and of soil influenced initial field capacity moisture content, but high matric potential moisture content was consistent, presumably as a reflection of the aggregate content of the designed system. A large portion of plant available moisture was weakly held in large voids, consistent with related infiltration and permeability data, and could be an influence in water storage and irrigation planning to use layers of designed soils in a layered pavement section for urban vegetation.
Branch diameter relative to the trunk diameter (aspect ratio) affected the extent of discolored a... more Branch diameter relative to the trunk diameter (aspect ratio) affected the extent of discolored and decayed wood in the trunk of seedling-propagated red maple (Acer rubrum L.) after branch removal. More discoloration resulted from removing codominant stems than removing branches that were small compared to the trunk. Removing limbs that originated from lateral buds resulted in the same amount of discoloration and decay as removing suppressed limbs that were once the leader. This result provides indirect evidence that a small codominant stem suppressed by pruning techniques designed to slow its growth rate can result in a branch protection zone at the union. There was no relation between the presence of a bark inclusion and decay 4 years after making pruning cuts. The importance of the branch protection zone (BPZ) in lim-iting trunk infection after branch injury or removal has been demonstrated (von Aufsess 1975, 1984; Shigo 1985). The BPZ is generally recognized as a three-dimension...
Background/Question/Methods Many forest understories of northeastern North America are heavily in... more Background/Question/Methods Many forest understories of northeastern North America are heavily invaded by shrubs. Given that nutrients are both limiting and distributed heterogeneously in the soil in these ecosystems, advantages for invasive species may come, in part, from greater efficiency in soil exploration. We tested this hypothesis by comparing root architectural traits associated with nutrient foraging in six species common in the Northeast (invasives: Berberis thunbergii, Lonicera maackii, Rubus phoenicolasius; natives: Viburnum dentatum, Lindera benzoin, Rubus allegeniensis). To characterize root architecture, we excavated and generated 3D renderings of complete, coarse root systems of 36 field-grown plants (six individuals per species). Topological and morphological parameters were derived from the resulting virtual plants, and supplemented with information on composition (C:N) and 2D structure of fine roots. Results/Conclusions Our preliminary results suggest that some ch...
Background/Question/Methods It is often under elevated resource conditions that invasive plants h... more Background/Question/Methods It is often under elevated resource conditions that invasive plants have performance advantages over co-occurring natives. When a resource is spatially heterogeneous, such as nutrients in forest soils, growth rate advantages may come from higher root system productivity in general and/or from greater responsiveness to nutrient patches (foraging precision) specifically. To determine if shrubs invasive in understory communities of northeastern North America respond to nutrient patches more strongly than do natives, we conducted a manipulative experiment with three invasive and three native species. In a non-competitive field setting, we grew eight young plants of each species (aged 2-3 yr initially) for one year, placing six ingrowth bags with sieved soil (controls, n=3) or soil amended with chopped grass (simulated patches, n=3) around each plant. We measured fine root growth and morphological characteristics in all ingrowth bags, as well as aboveground gr...
ABSTRACT Background/Question/Methods Berberis thunbergii, or Japanese barberry, is a clonal shrub... more ABSTRACT Background/Question/Methods Berberis thunbergii, or Japanese barberry, is a clonal shrub that has invaded numerous forests in the northeastern United States. Research we carried out over the past decade has shown that B. thunbergii alters soil properties and microbial communities, and that many of these effects persist after B. thunbergii is removed. These studies were performed in the field or greenhouse, and focused on characterizing soil nitrogen availability and mineralization, as well as microbial community structure (through phospholipid fatty acid analysis) and function (through extracellular enzyme activities). Most recently, we have investigated root architecture and functional traits, as well as belowground competitive dynamics in B. thunbergii and other shrub species. Our aim is to synthesize research on B. thunbergii interactions and effects belowground so as to more fully characterize the ecological legacies of its invasion for both microbial and plant communities. Results/Conclusions The most consistent edaphic changes that we have found in association with B. thunbergii colonization are increases in nitrate availability, nitrification rate, and pH. In addition, we have observed shifts in microbial community composition (primarily increases in bacteria:fungi) as well as decreases in the activity of several extracellular soil enzymes. Evidence from the field and greenhouse indicate that these changes persist for at least three years, though actual durations are likely much longer. Although several of our studies implicated leaf litter in raising soil nitrogen and initiating microbial community shifts, several lines of indirect evidence suggest that root litter and exudates also contribute to the observed shifts. In one study, we found that B. thunbergii roots have low C:N and morphological traits associated with rapid turnover, and in another study we found greater legacy effects in rhizosphere soil than in bulk soil. Our research has yielded some insight into the implications of B. thunbergii’s belowground legacies. Potentially as a result of increased nitrate availability, B. thunbergii and competing species both grew more rapidly in greenhouse soils that were previously conditioned by the invader. However, the stand structure and distribution of roots beneath B. thunbergii stands suggest that it can capitalize disproportionately on elevated soil nitrogen. In addition to leaving legacies that persist after plants are removed, B. thunbergii can thereby capitalize on soil feedbacks, ultimately contributing to its ability to form monocultures in forest understories.
Trees growing beneath electrical power lines are often subjected to heading cuts made during roun... more Trees growing beneath electrical power lines are often subjected to heading cuts made during roundover trimming. Heading cuts create wounds that allow decay to enter the branch, and a decay column will form if the tree does not contain it with compartmental reaction zones. The presence of a sizable decay column may predispose the leader to failure, especially when the tree has been converted from a roundover to a V-trim. The objectives of this study were to quantify the amount of decay in silver maples (Acer saccharinum L.) converted from roundover to V-trims and to develop models to allow utility arborists to estimate the extent of internal decay columns. Parent stems (leaders) were removed from converted trees, cut into 50 cm (20 in) sections, and measured for internal and external decay. Eighty percent of the leaders had internal decay columns beginning within 50 cm (20 in) of the heading cut and internal decay columns were found to be over 2 1 ⁄2 times longer than the length of external decay. Models are presented to predict the length and volume of internal decay from external measurements on the leader, including length of external decay.
... The three similarity models put forth by McMahon (1975) and Niklas'(1992) suggestion tha... more ... The three similarity models put forth by McMahon (1975) and Niklas'(1992) suggestion that branches and stems tran-sition between the models appear to best explain how tree stems and branches modify the relationship between lateral ... Alméras, T., A. Thibaut, and J. Gril. ...
The interactive effects of rooting volume and nutrient availability in a skeletal soil medium des... more The interactive effects of rooting volume and nutrient availability in a skeletal soil medium designed to meet street tree and pavement needs were observed in a containerized experiment. Benjamin fig (Ficus benjamina L.) was grown in a stone-soil blended skeletal soil material (CU-Soil ™) and compared to a loam soil. The same topsoil used as the soil component in the skeletal soil material was used as the sole component in the comparison soil-only treatment. Plants grown in the skeletal soil material had reduced leaf tissue N content and depressed growth compared with plants grown in non-diluted soil. No other mineral deficiencies were found. Leaf number, chlorophyll concentration, shoot weight, and root characteristics were all affected. Reduced growth from soil dilution could be offset by the provision of an enlarged rooting volume for root development. Large containers of skeletal soil were observed to have smaller root systems compared to equivalent net volumes of loam soil at the first two harvest dates of the study. By the end of the study, the large containers of skeletal soil were observed to have developed larger root systems compared to equivalent net volumes of loam soil; resulting in comparable leaf N levels and total plant dry matter. Plants in skeletal soil had lower shoot: root ratios at the end of the study. Investing resources to further root growth in times of nutrient shortages is a probable plant reaction as evidenced by differences in specific root length between treatments. The study allowed a method for directly partitioning the containerization effect by having equivalent amounts of soil over two volumes.
Allometric relationships for trunk, first order branches and associated foliage were developed to... more Allometric relationships for trunk, first order branches and associated foliage were developed to develop a repeatable pruning dose for wind interception studies on Quercus virginiana Mill ‘Cathedral’. Three trees were dissected to develop relationships. It was determined that leaf mass was linearly related to the basal area of the primary branch, consistent with pipe model expectations. A pruning dose for
... This formula has been used to derive the elastic similarity model (l∝r 2/3 ) (McMahon, 1975),... more ... This formula has been used to derive the elastic similarity model (l∝r 2/3 ) (McMahon, 1975), where l is tree height or branch length and r is the radius at the base; see Dahle and Grabosky (2009a) for a review of allometric modeling. ...
ABSTRACT Planting depth and irrigation can impact root and trunk growth following landscape insta... more ABSTRACT Planting depth and irrigation can impact root and trunk growth following landscape installation in various soil types; however, impact on lateral tree stability is unknown. Quercus virginiana Mill. trees were installed at four landscape planting depths into a well drained sandy soil and grown for six years under two irrigation regimes. There was no impact of planting depth on trunk diameter or height in the first five growing seasons after planting; however, trees irrigated regularly had 10mm larger trunk diameter than trees not irrigated. There was no impact of planting depth or irrigation on bending stress required to tilt trunks to 1°, 2° and 5° from vertical non-deformed start position six growing seasons after planting. Planting depth and irrigation also had no effect on diameter of the ten largest roots to a soil depth of 122cm, which might explain why bending stress required to pull trees was similar for all planting depth and irrigation treatments. However, trees planted deeper had deeper roots measured 115cm horizontally from trunk. Root cross-sectional area (CSA) 20–30 and 40–50cm deep was positively correlated with bending stress six growing seasons after planting. Trees planted deep had some roots that ascended toward soil surface at a steeper angle than trees planted shallow, and had a deeper root flare and more roots growing over the flare that could potentially form stem girdling roots. Diameter of roots over the flare was not impacted by planting depth; however, trees irrigated for the duration of the study had more roots over main flare roots than trees not irrigated. Irrigation increased root number (>5mm diameter) in the top 30cm soil profile. Irrigation had no impact on any other measured root parameter. Trees planted deeper settled down below soil surface more than shallow planted trees.
Background / Purpose: Both light response and assimilation to internal CO2 concentration (A/Ci) c... more Background / Purpose: Both light response and assimilation to internal CO2 concentration (A/Ci) curves were developed along a soil metal load gradient. Main conclusion: Preliminary results indicate that compensation points differ significantly between Betla and Populus but not between the two Populus species. In addition, there were significant differences between the sites examined. These data, suggest that differences in resource allocation between growth and maintenance within the heterogeneous edaphic conditions of the urban context results in differing compensation points and hence carbon sequestration rates. Such data helps to define the value of urban forest and the point at which mitigation is necessary.
ABSTRACT Background/Question/Methods Allometric relationships of many forest species have been we... more ABSTRACT Background/Question/Methods Allometric relationships of many forest species have been well documented. As a result, there have been many attempts to generalize carbon sequestration across forest populations. However, such models must account for the temporary nature and variability of leaf biomass . Furthermore, these models do not generally account for biotic filters such as disturbance, insect/fungal/bacterial attacks and contamination of soil and water. Through both destructive sampling and LAI measurements we examined leaf biomass at four forest sites with varying levels of metal contamination and water availability. Results/Conclusions Our results indicate that soil metal loads and water availability affect LAI and leaf mass. The site with the lowest metal contamination and greatest water availability had an LAI of 2.85, and the site with the highest metal contamination and lowest water availability had an LAI of 1.6. The site with the highest metal contamination and lowest water availability had a per unit-leaf mass of 145.10g while the site with the lowest metal contamination and greatest water availability had a per unit-leaf mass of 128.1g. These data suggest that the site index at the microscale can play an important role in determining the carbon flux within an urban forest.
Restoration Notes have been a distinguishing feature of Ecological Restoration for more than 25 y... more Restoration Notes have been a distinguishing feature of Ecological Restoration for more than 25 years. This section is geared toward introducing innovative research, tools, technologies, programs, and ideas, as well as providing short-term research results and updates on ongoing efforts. Please direct submissions and inquiries to the editorial staff (ERjournal@ aesop.rutgers.edu).
Soil compaction, which is necessary to safely support sidewalks and pavement, conflicts with urba... more Soil compaction, which is necessary to safely support sidewalks and pavement, conflicts with urban trees' need for usable rooting space to support healthy tree growth. We have defined a rigid soil medium that will safely bear loads required by engineering standards yet still allow for rapid root exploration and growth. This was accomplished by forming a stone matrix and suspending soil within the matrix pores with the assistance of a hydrogel gluing agent. Initial studies using three stone types and various stone to soil ratios showed that the compacted stone-soil test medium (dry densities > 1700 kg/m3) increased root growth by a minimum of 320% over the compacted clay loam control (dry density of 1378 kg/m3). The proposed system can safely bear load demonstrated by California Bearing Ratios consistently exceeding 40. Discus- sion of a critical mixing ratio is presented as an approach for developing a specification for field installation.
We built a machine with a propeller capable of generating 33.5 m/s (75 mph) winds to determine th... more We built a machine with a propeller capable of generating 33.5 m/s (75 mph) winds to determine the influence of pruning dose and American National Standards Institute A300 pruning type on trunk movement of Quercus virginiana 'QVTIA' PP #11219, Highrise at various wind speeds. Trunk movement was regressed against wind speeds and pruning doses for each tree tested. Increasing wind speed increased trunk movement, and the magnitude of the increase depended on pruning dose and pruning type. Increasing pruning dose reduced trunk movement and the magnitude of the reduction was greater at higher wind speeds. The predicted trunk movement of thinned trees was statistically greater than movement of structurally pruned, raised, and lion's tailed trees at wind speeds of 20.1 m/s (45 mph) and was greater than all pruning types at 26.8 m/s (60 mph). There was no difference in movement among reduced, raised, structurally pruned, and lion's tailed trees; and there were no statistical...
. A Minolta SPAD-502 leaf chlorophyll meter was used for nondestructive data collection on the ch... more . A Minolta SPAD-502 leaf chlorophyll meter was used for nondestructive data collection on the chlorophyll and nitrogen (N) status of benjamin fig (Ficus benjamina) and cottonwood (Populus deltoides) to quantitatively evaluate foliage quality. The goal was to provide a specific calibration for interpreting SPAD data within a media study for each species. Triplicate SPAD readings were collected from each of six leaves, sampled from forty plants per species, then processed for foliar analysis. Leaf tissue disks were also collected directly over SPAD testing sites for chloro-phyll concentration measurement. Significant linear correlations were found between SPAD data and chlorophyll concentrations (r 2 = 0.90 in benjamin fig and r 2 = 0.91 for cottonwood). A significant, but lower correlation was found between SPAD data and N concentration. The SPAD-N correlations improved from the fifth month to the ninth month harvest (r 2 = 0.32 to 0.53 for benjamin fig and 0.26 to 0.42 for cottonwo...
In 1997, willow oak (Quercus phellos L.), swamp white oak (Quercus bicolor Willd.), and goldenrai... more In 1997, willow oak (Quercus phellos L.), swamp white oak (Quercus bicolor Willd.), and goldenraintree (Koelreuteria paniculata Laxm.) were planted in the right-of-way on Lorimer Street in Brooklyn, New York, U.S. This was one of the earliest commercial installations of the load-bearing stone-soil blends (hereafter called structural soil) developed at Cornell Universi- ty's Urban Horticulture Institute (Grabosky and Bassuk 1995). The north-south street segment bisects McCarren Park between Driggs Avenue and Bayard Street. Trees were planted as 5.1 to 7.6 cm (2 to 3 in) caliper trees on either side of the street. The west side trees were planted in a continuous trench of structural soil 0.6 m (2 ft) deep by 2.1 m (6.9 ft) wide down the entire block. The structural soil was used as the sidewalk base capped with concrete. Tree openings were 0.9 m by 1.5 m (3 × 5 ft), which were planted after paving and then covered by granite unit block pavers. The east side of the street was a tre...
Quercus robur seedlings were grown in compacted stone-soil mixes known to meet engineering standa... more Quercus robur seedlings were grown in compacted stone-soil mixes known to meet engineering standards for pavement base compaction and strength. Root penetration into these materials was greatly increased in comparison to an equally compacted clay loam, which was also a component of the test material. Oak root penetration in the clay loam decreased 50%, from 6 to 3 g dry root weight, as the bulk density increased from 1.24 to 1.55 Mg/m3. Severe root impedance was observed when clay loam bulk densities exceeded 1.5 Mg/m3 (90% standard AASHTO peak density),a situation produced after 20% of the standard compaction effort was imposed on the soil profile. At the standard AASHTO peak density for the clay loam (1.67 Mg/m3), which would be the norm in a sidewalk installation, root growth was entirely stopped. In contrast, structured stone-soil mixes compacted to 100% of their respective standard AASHTO peak densities (between 1.85 and 2.07 Mg/m3) did not restrict root penetration with mean r...
Three avenues of experimental observation detail aspects of plant available water holding capacit... more Three avenues of experimental observation detail aspects of plant available water holding capacity in compacted stone-soil media designed for urban tree establishment in paved situations. The various compacted media provided an estimated plant available moisture content of 7%-11% by volume, comparable to a loamy sand. Changes in aggregate and of soil influenced initial field capacity moisture content, but high matric potential moisture content was consistent, presumably as a reflection of the aggregate content of the designed system. A large portion of plant available moisture was weakly held in large voids, consistent with related infiltration and permeability data, and could be an influence in water storage and irrigation planning to use layers of designed soils in a layered pavement section for urban vegetation.
Branch diameter relative to the trunk diameter (aspect ratio) affected the extent of discolored a... more Branch diameter relative to the trunk diameter (aspect ratio) affected the extent of discolored and decayed wood in the trunk of seedling-propagated red maple (Acer rubrum L.) after branch removal. More discoloration resulted from removing codominant stems than removing branches that were small compared to the trunk. Removing limbs that originated from lateral buds resulted in the same amount of discoloration and decay as removing suppressed limbs that were once the leader. This result provides indirect evidence that a small codominant stem suppressed by pruning techniques designed to slow its growth rate can result in a branch protection zone at the union. There was no relation between the presence of a bark inclusion and decay 4 years after making pruning cuts. The importance of the branch protection zone (BPZ) in lim-iting trunk infection after branch injury or removal has been demonstrated (von Aufsess 1975, 1984; Shigo 1985). The BPZ is generally recognized as a three-dimension...
Background/Question/Methods Many forest understories of northeastern North America are heavily in... more Background/Question/Methods Many forest understories of northeastern North America are heavily invaded by shrubs. Given that nutrients are both limiting and distributed heterogeneously in the soil in these ecosystems, advantages for invasive species may come, in part, from greater efficiency in soil exploration. We tested this hypothesis by comparing root architectural traits associated with nutrient foraging in six species common in the Northeast (invasives: Berberis thunbergii, Lonicera maackii, Rubus phoenicolasius; natives: Viburnum dentatum, Lindera benzoin, Rubus allegeniensis). To characterize root architecture, we excavated and generated 3D renderings of complete, coarse root systems of 36 field-grown plants (six individuals per species). Topological and morphological parameters were derived from the resulting virtual plants, and supplemented with information on composition (C:N) and 2D structure of fine roots. Results/Conclusions Our preliminary results suggest that some ch...
Background/Question/Methods It is often under elevated resource conditions that invasive plants h... more Background/Question/Methods It is often under elevated resource conditions that invasive plants have performance advantages over co-occurring natives. When a resource is spatially heterogeneous, such as nutrients in forest soils, growth rate advantages may come from higher root system productivity in general and/or from greater responsiveness to nutrient patches (foraging precision) specifically. To determine if shrubs invasive in understory communities of northeastern North America respond to nutrient patches more strongly than do natives, we conducted a manipulative experiment with three invasive and three native species. In a non-competitive field setting, we grew eight young plants of each species (aged 2-3 yr initially) for one year, placing six ingrowth bags with sieved soil (controls, n=3) or soil amended with chopped grass (simulated patches, n=3) around each plant. We measured fine root growth and morphological characteristics in all ingrowth bags, as well as aboveground gr...
ABSTRACT Background/Question/Methods Berberis thunbergii, or Japanese barberry, is a clonal shrub... more ABSTRACT Background/Question/Methods Berberis thunbergii, or Japanese barberry, is a clonal shrub that has invaded numerous forests in the northeastern United States. Research we carried out over the past decade has shown that B. thunbergii alters soil properties and microbial communities, and that many of these effects persist after B. thunbergii is removed. These studies were performed in the field or greenhouse, and focused on characterizing soil nitrogen availability and mineralization, as well as microbial community structure (through phospholipid fatty acid analysis) and function (through extracellular enzyme activities). Most recently, we have investigated root architecture and functional traits, as well as belowground competitive dynamics in B. thunbergii and other shrub species. Our aim is to synthesize research on B. thunbergii interactions and effects belowground so as to more fully characterize the ecological legacies of its invasion for both microbial and plant communities. Results/Conclusions The most consistent edaphic changes that we have found in association with B. thunbergii colonization are increases in nitrate availability, nitrification rate, and pH. In addition, we have observed shifts in microbial community composition (primarily increases in bacteria:fungi) as well as decreases in the activity of several extracellular soil enzymes. Evidence from the field and greenhouse indicate that these changes persist for at least three years, though actual durations are likely much longer. Although several of our studies implicated leaf litter in raising soil nitrogen and initiating microbial community shifts, several lines of indirect evidence suggest that root litter and exudates also contribute to the observed shifts. In one study, we found that B. thunbergii roots have low C:N and morphological traits associated with rapid turnover, and in another study we found greater legacy effects in rhizosphere soil than in bulk soil. Our research has yielded some insight into the implications of B. thunbergii’s belowground legacies. Potentially as a result of increased nitrate availability, B. thunbergii and competing species both grew more rapidly in greenhouse soils that were previously conditioned by the invader. However, the stand structure and distribution of roots beneath B. thunbergii stands suggest that it can capitalize disproportionately on elevated soil nitrogen. In addition to leaving legacies that persist after plants are removed, B. thunbergii can thereby capitalize on soil feedbacks, ultimately contributing to its ability to form monocultures in forest understories.
Trees growing beneath electrical power lines are often subjected to heading cuts made during roun... more Trees growing beneath electrical power lines are often subjected to heading cuts made during roundover trimming. Heading cuts create wounds that allow decay to enter the branch, and a decay column will form if the tree does not contain it with compartmental reaction zones. The presence of a sizable decay column may predispose the leader to failure, especially when the tree has been converted from a roundover to a V-trim. The objectives of this study were to quantify the amount of decay in silver maples (Acer saccharinum L.) converted from roundover to V-trims and to develop models to allow utility arborists to estimate the extent of internal decay columns. Parent stems (leaders) were removed from converted trees, cut into 50 cm (20 in) sections, and measured for internal and external decay. Eighty percent of the leaders had internal decay columns beginning within 50 cm (20 in) of the heading cut and internal decay columns were found to be over 2 1 ⁄2 times longer than the length of external decay. Models are presented to predict the length and volume of internal decay from external measurements on the leader, including length of external decay.
... The three similarity models put forth by McMahon (1975) and Niklas'(1992) suggestion tha... more ... The three similarity models put forth by McMahon (1975) and Niklas'(1992) suggestion that branches and stems tran-sition between the models appear to best explain how tree stems and branches modify the relationship between lateral ... Alméras, T., A. Thibaut, and J. Gril. ...
The interactive effects of rooting volume and nutrient availability in a skeletal soil medium des... more The interactive effects of rooting volume and nutrient availability in a skeletal soil medium designed to meet street tree and pavement needs were observed in a containerized experiment. Benjamin fig (Ficus benjamina L.) was grown in a stone-soil blended skeletal soil material (CU-Soil ™) and compared to a loam soil. The same topsoil used as the soil component in the skeletal soil material was used as the sole component in the comparison soil-only treatment. Plants grown in the skeletal soil material had reduced leaf tissue N content and depressed growth compared with plants grown in non-diluted soil. No other mineral deficiencies were found. Leaf number, chlorophyll concentration, shoot weight, and root characteristics were all affected. Reduced growth from soil dilution could be offset by the provision of an enlarged rooting volume for root development. Large containers of skeletal soil were observed to have smaller root systems compared to equivalent net volumes of loam soil at the first two harvest dates of the study. By the end of the study, the large containers of skeletal soil were observed to have developed larger root systems compared to equivalent net volumes of loam soil; resulting in comparable leaf N levels and total plant dry matter. Plants in skeletal soil had lower shoot: root ratios at the end of the study. Investing resources to further root growth in times of nutrient shortages is a probable plant reaction as evidenced by differences in specific root length between treatments. The study allowed a method for directly partitioning the containerization effect by having equivalent amounts of soil over two volumes.
Allometric relationships for trunk, first order branches and associated foliage were developed to... more Allometric relationships for trunk, first order branches and associated foliage were developed to develop a repeatable pruning dose for wind interception studies on Quercus virginiana Mill ‘Cathedral’. Three trees were dissected to develop relationships. It was determined that leaf mass was linearly related to the basal area of the primary branch, consistent with pipe model expectations. A pruning dose for
... This formula has been used to derive the elastic similarity model (l∝r 2/3 ) (McMahon, 1975),... more ... This formula has been used to derive the elastic similarity model (l∝r 2/3 ) (McMahon, 1975), where l is tree height or branch length and r is the radius at the base; see Dahle and Grabosky (2009a) for a review of allometric modeling. ...
ABSTRACT Planting depth and irrigation can impact root and trunk growth following landscape insta... more ABSTRACT Planting depth and irrigation can impact root and trunk growth following landscape installation in various soil types; however, impact on lateral tree stability is unknown. Quercus virginiana Mill. trees were installed at four landscape planting depths into a well drained sandy soil and grown for six years under two irrigation regimes. There was no impact of planting depth on trunk diameter or height in the first five growing seasons after planting; however, trees irrigated regularly had 10mm larger trunk diameter than trees not irrigated. There was no impact of planting depth or irrigation on bending stress required to tilt trunks to 1°, 2° and 5° from vertical non-deformed start position six growing seasons after planting. Planting depth and irrigation also had no effect on diameter of the ten largest roots to a soil depth of 122cm, which might explain why bending stress required to pull trees was similar for all planting depth and irrigation treatments. However, trees planted deeper had deeper roots measured 115cm horizontally from trunk. Root cross-sectional area (CSA) 20–30 and 40–50cm deep was positively correlated with bending stress six growing seasons after planting. Trees planted deep had some roots that ascended toward soil surface at a steeper angle than trees planted shallow, and had a deeper root flare and more roots growing over the flare that could potentially form stem girdling roots. Diameter of roots over the flare was not impacted by planting depth; however, trees irrigated for the duration of the study had more roots over main flare roots than trees not irrigated. Irrigation increased root number (>5mm diameter) in the top 30cm soil profile. Irrigation had no impact on any other measured root parameter. Trees planted deeper settled down below soil surface more than shallow planted trees.
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