Jason Grabosky

Soil metal concentrations and productivity of Betula populifolia (gray birch) as measured by field spectrometry and incremental annual growth in an abandoned urban Brownfield in New Jersey.

A forested brownfield within Liberty State Park, Jersey City, New Jersey, USA, has soils with arsenic, chromium, lead, zinc and vanadium at concentrations above those considered ambient for the area. Using both satellite imagery and field spectral measurements, this study examines plant productivity at the assemblage and individual specimen level. Longer term growth trends (basal area increase in tree cores) were also studied. Leaf chlorophyll content within the hardwood assemblage showed a threshold model for metal tolerance, decreasing significantly beyond a soil total metal load (TML) of 3.0. Biomass production (calculated with RG-Red/Green Ratio Index) in Betula populifolia (gray birch), the co-dominant tree species, had an inverse relationship with the Zn concentration in leaf tissue during the growing season. Growth of B. populifolia exhibited a significant relationship with TML. Assemblage level NDVI and individual tree NDVI also had significant decreases with increasing TML. Ecosystem function measured as plant production is impaired at a critical soil metal load.

Altered vegetative assemblage trajectories within an urban brownfield.

Recognizing the growing importance of both structure (maintenance of biodiversity) and function (fostering natural cycles) of urban ecologies, we examine coarse scale (herbaceous, shrub and forest) beta guild trajectory in an urban brownfield. The distribution of the pioneer forest assemblage dominated by Betula populifolia Marsh. and Populus spp. could be correlated positively with total soil metal load (arsenic, cadmium, chromium, copper, lead, zinc, lead and vanadium),whereas herbaceous and shrub guilds were negatively correlated. Distinct assemblage development trajectories above and below a critical soil metal threshold are demonstrated. In addition, we postulate that the translocation of metals into the plant tissue of several dominant species may provide a positive feedback loop, maintaining relatively high concentrations of metals in the litter and soil. Therefore assembly theory, which allows for the development of alternate stable states, may provide a better model for the establishment of restoration objectives on degraded urban sites.

Growth response of Ficus benjamina to limited soil volume and soil dilution in a skeletal soil container study

Abstract 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.

Nutrient foraging strategies are associated with productivity and population growth in forest shrubs

Background and Aims Temperate deciduous forest understoreys are experiencing widespread changes in community composition, concurrent with increases in rates of nitrogen supply. These shifts in plant abundance may be driven by interspecific differences in nutrient foraging (i.e. conservative vs. acquisitive strategies) and, thus, adaptation to contemporary nutrient loading conditions. This study sought to determine if interspecific differences in nutrient foraging could help explain patterns of shrub success and decline in eastern North American forests. Methods Using plants grown in a common garden, fine root traits associated with nutrient foraging were measured for six shrub species. Traits included the mean and skewness of the root diameter distribution, specific root length (SRL), C:N ratio, root tissue density, arbuscular mycorrhizal colonization and foraging precision. Above- and below-ground productivity were also determined for the same plants, and population growth rates were estimated using data from a long-term study of community dynamics. Root traits were compared among species and associations among root traits, measures of productivity and rates of population growth were evaluated. Key Results Species fell into groups having thick or thin root forms, which correspond to conservative vs. acquisitive nutrient foraging strategies. Interspecific variation in root morphology and tissue construction correlated with measures of productivity and rates of cover expansion. Of the four species with acquisitive traits, three were introduced species that have become invasive in recent decades, and the fourth was a weedy native. In contrast, the two species with conservative traits were historically dominant shrubs that have declined in abundance in eastern North American forests. Conclusions In forest understoreys of eastern North America, elevated nutrient availability may impose a filter on species success in addition to above-ground processes such as herbivory and overstorey canopy conditions. Shrubs that have root traits associated with rapid uptake of soil nutrients may be more likely to increase in abundance, while species without such traits may be less likely to keep pace with more productive species.

Root Growth Responses to Soil Amendment in an Urban Brownfield

Ecological Restoration Vol. 33, No. 1, 2015 ISSN 1522-4740 E-ISSN 1543-4079 ©2015 by the Board of Regents of the University of Wisconsin System. Root Growth Responses to Soil Amendment in an Urban Brownfield Frank J. Gallagher (Department of Landscape Architecture, Rutgers, The State University of New Jersey, New Brunswick, NJ), Joshua S. Caplan (corresponding author: Department of Ecology, Evolution & Natural Resources, Rutgers, The State University of New Jersey, New Brunswick, NJ 08901, jcaplan@aesop.rutgers.edu), Jennifer Adams Krumins (Department of Biology and Molecular Biology, Montclair State University, Montclair, NJ) and Jason C. Grabosky (Department of Ecology, Evolution & Natural Resources, Rutgers, The State University of New Jersey, New Brunswick, NJ).

Carbon stock in Korean larch plantations along a chronosequence in the Lesser Khingan Mountains, China

Carbon (C) dynamics are central to understanding ecosystem restoration effects within the context of Grain for Green Project (GGP). GGP stared in China since 2003 to improve the environment. Despite its importance, how total forest ecosystem C stock (FECS) develops following land-use changes from cropland to plantation is poorly understood, in particular the relationship of C allocation to pools. We quantified C pools in a chronosequence ranging from 0 to 48 years, using complete above- and below-ground harvests based on detailed field inventory. Stands were chosen along a succession sequence in managed plantations of Korean larch (Larix olgensis Henry.), a native planting species in the Lesser Khingan Mountains, Northeast of China. The FECS of Korean larch plantation (KLP) were dynamic across stand development, changing from 88.2 Mg·ha−1 at cropland, to 183.9 Mg·ha−1 as an average of forest C from 7-through 48-year-old plantation. In a 48-year-old mature KLP, vegetation comprises 48.63% of FECS and accounts for 67.66% of annual net C increment (ANCI). Soil is responsible for 38.19% and 13.53% of those, and with the remainders of 13.18% and 18.81% in down woody materials. Based on comparisons of our estimate to those of others, we conclude that afforestation of Korean larch plantation is a valid approach to sequester carbon.

Long-term Stability of Trace Element Concentrations in a Spontaneously Vegetated Urban Brownfield With Anthropogenic Soils

ABSTRACT Trace element (TE) contamination of soil is a persistent problem in urban environments, particularly hindering the reuse of abandoned land. While phytostabilization is a cost-effective approach to managing TE-contaminated soil, little is known about the effects of these practices on soil TE concentrations decades after plant establishment. This study analyzes soil data collected from 1995, 2005, and 2015 (28, 38, and 48 years since site abandonment) in a spontaneously vegetated urban brownfield contaminated with As, Cr, Cu, Pb, and Zn. No change in concentration of any of these TE in the upper 30 cm of soil at this site was observed from 1995 to 2005. However, from 2005 to 2015, As and Cr concentrations increased in the soil C1 horizon at this site (approximately 5- to 25-cm depth), whereas Cu, Pb, and Zn remained stable. We propose that the observed increases in As and Cr resulted from downward migration from the upper 5 cm of soil and subsequent immobilization in the C1 horizon. Increasing soil pH from 2005 to 2015 could have increased As and Cr solubility, while reducing Cu, Pb, and Zn solubility. In addition, significant correlations were found between the five TE and Fe or Mn, which are known to play a role in TE sorption. This study shows the ability of a phytostabilization site to retain some TE in its upper soil horizons for several decades following plant community establishment, although continued monitoring is needed to ensure soil conditions continue to favor stability.

Maintenance of photosynthesis by Betula populifolia in metal contaminated soils

Improving our understanding of plant responses to elevated trace metal concentrations under field conditions will enhance restoration and urban greening practices in settings with contaminated soils. This study examined the effects of trace metal pollution on the leaf gas exchange rates of mature, field-grown Betula populifolia Marsh. (gray birch) trees, additionally assessing whether elevated temperature and drought compounded the effects of trace metal contamination. The study compared B. populifolia growing in areas of comparatively high and low trace metal loads (HML and LML, respectively) within a former rail yard at Liberty State Park in Jersey City, New Jersey, USA. Gas exchange parameters were determined monthly from May through September in 2014 and 2015 using a portable photosynthesis system. The effects of drought and high temperature were assessed during a short heat wave in July 2015 and via a manipulative experiment, respectively. During a few of the measurement months, some parameters differed significantly between the LML and HML groups. However, when considered over the entire study period, no significant differences in biophysical parameters were observed between groups. The photosynthetic capacity of B. populifolia thus appears to be fairly robust across this sites steep gradient of trace metal contamination. Nonetheless, leaf mass per unit area was significantly lower in the HML group, indicating that metal loads affected resource allocation within trees. Also, immediately following the heat wave in 2015, intrinsic water use efficiency declined significantly in the HML group, suggesting that extreme climatic conditions can have a disproportionate effect on the physiological performance of plants growing in metal contaminated soils.

Beneath it all: Size, not origin, predicts belowground competitive ability in exotic and native shrubs1,2

Abstract Traits associated with root morphology and nutrient uptake rate may contribute to the competitive ability of invasive species by determining their access to soil nutrients and their ability to extract those resources. Here, we tested the hypotheses that (a) exotic woody shrubs would be superior belowground competitors for nitrogen in heterogeneous soil resulting from key aspects of root architecture and (b) larger plants would be superior belowground competitors. We tested these hypotheses using two native shrubs, Rubus allegheniensis and Viburnum dentatum, and two invasive exotic shrubs, Rubus phoenicolasius and Berberis thunbergii, all four of which can become abundant in plant communities in the eastern United States. We grew replicate plants from each species with interspecific competitors, with intraspecific competitors, and individually in a randomized layout in a greenhouse in two temporal blocks. Each experimental container had a central soil patch amended with 15N-labeled litter. We measured above- and belowground growth, root morphology, and nitrogen uptake to assess the effects of intra- and interspecific competition on plant growth and nitrogen uptake. All species grew better in the second temporal block, but we did not detect any differences in the competitive ability or root traits for exotic versus native species; rather, plant size was the key trait that predicted competitive effects. Both Rubus species, which capitalized on the extended growing season offered by our greenhouse conditions, were stronger competitors and typically larger plants than B. thunbergii and V. dentatum. Both Rubus species exerted measurable competitive effects on other species, resulting in decreased aboveground size of competitors by 50% or more relative to control plants, but did not routinely decrease 15N uptake or root biomass of competitors. When competing with Rubus, leaf C:N ratios of all species except R. phoenicolasius were greater than when grown alone, suggesting that large Rubus plants did decrease the total nitrogen available to competitors. Our data suggest that belowground competitive ability in shrubs may be more closely associated with plant size and growth rate than plant origin. In addition, plant species that exhibit plastic growth phenology, such as those in the genus Rubus, may gain a competitive advantage during years with warmer autumn months by extending their growing seasons, facilitating their invasion and establishment in new habitats.