Edward F. Loewenstein

Non-native plants in the understory of riparian forests across a land use gradient in the Southeast

As urbanization expands into rural areas, an increase in the number of non-native plant species at the urban-rural interface is expected due in large part to the increased availability of propagules from ornamental plantings. A study investigating the distribution of non-native plants in the understories of riparian forests across an urban-to-rural gradient north of Columbus, GA was initiated in 2003. A significantly greater number of non-native plant species occurred at the urban sites and at one site at the urban-rural interface, where 20 to 33% of the species encountered were non-native. In contrast, at the more rural sites non-native species comprised 4–14% of the total number of species. However, the importance values of non-native species as a whole did not change significantly across the land use gradient due to the high frequency and abundance of three non-native species (Ligustrum sinense, Lonicera japonica, and Microstegium vimineum) in the majority of the watersheds. Reductions in species richness and overstory reproduction associated with these non-natives could impact long-term forest structure and ecosystem function.

Genetic selection and fertilization provide increased nut production under walnut-agroforestry management

Eight years of nut data collected on 934 juvenile black walnut trees clearly demonstrates the value of mass selection as a means of increasing nut yields — number of nuts produced/tree/year ranged from 0 to 345. Furthermore, high variability in percentage kernel crackout and nut weight was observed in 130 select trees. Selection on the basis of these characteristics has the potential to lead to a several-fold increase in the quantity of usable kernels produced per hectare. An additional 48% gain in nut production is demonstrated using late-summer fertilization with NPK (13-13-13). Increases in nut yields could provide substantial increases in profit for the landowner and an enhancement in an already economically viable land-use alternative for individuals interested in making the transition from a cropping system to trees.

Comparison of carbon storage, carbon sequestration, and air pollution removal by protected and maintained urban forests in Alabama, USA

The Auburn University campus in Auburn, Alabama, USA, was the location for a case study to compare carbon storage, carbon sequestration, and air pollution (CO, O3, NO2, PM10, SO2) removal estimates between protected and maintained urban forests. Results were from a complete tree inventory and i-Tree Eco analysis of the 237 ha maintained and 5.5 ha protected areas of the campus. Trees in the maintained landscapes had an average diameter at breast height of 16.4 cm and basal area of 2.24 m2/ha when compared with 24.4 cm and 12.04 m2/ha for the protected area. The maintained landscapes were estimated to store 6652 kg of carbon per ha and sequester 291 kg/year/ha of carbon. The protected area was estimated to store 41,975 kg of carbon per ha and sequester 1758 kg/year/ha of carbon. Trees in the maintained areas removed 2970 kg/year of air pollution (12.5 kg/year/ha) compared with 560 kg/year for the protected area (102 kg/year/ha), which was 8 times the amount on a unit area basis compared with the maintained landscapes. The results demonstrate differences between maintained and protected forests and how important protected areas are in urban environments in enhancing carbon storage and sequestration and promoting air pollution removal.

Sediment dynamics following active management of a stream buffer zone: A case study

In this case study, change in sediment yield over a one year period was examined on paired watersheds (treated vs. reference) located in east Alabama. The effect of a partial cutting within a stream buffer zone (SBZ) on sediment yield was explored as well as the relative effects of pastoral, forested, and clearcut areas. During the no-harvest (calibration) period, upstream pastoral area generated much more sediment load per unit area than downstream forested sections during rainfall events. A partial cut within an SBZ changed the sediment pattern of downstream sections of the treatment watershed. On the treated sections, the observed sediment yield was higher than expected while there was no significant change in sediment yield from the pastoral area. Some of this increase was attributed to seasonal effects due to reduction in evapotranspiration. There was no change in the sediment yield pattern of the control watershed. The partial cut within the SBZ played a much more critical role than the stream road crossing as the sediment source. This study further shows that a holistic approach is needed to control sediment yield in mixed land use watersheds.

Comparing individual-tree approaches for predicting height growth of underplanted seedlings

Key messageIndividual-tree seeding height growth models developed using tree inventory data were comparable to those requiring the unique observation of point-based canopy structure data at each seedling.ContextQuantitative approaches describing the relationship between canopy structure and seedling growth can inform silvicultural decision making regarding the development of tree reproduction beneath a dominant forest canopy.AimsIndividual-tree seedling growth models with canopy structure predictors derived from tree inventory data have not been well-explored. This study compared a model framework fit using point-based measures of canopy structure observed at the seedling level to one fit using area-wide canopy structure variables derived from standard inventory plot data.MethodsSpecies-specific models predicting 5-year height growth were fit for cherrybark oak (Quercus pagoda Raf.), water oak (Quercus nigra L.), and yellow-poplar (Liriodendron tulipifera L.) underplanted within a canopy structure gradient created by silvicultural manipulation of a closed-canopy forest in Georgia, USA.ResultsThough the species varied in shade tolerance and growth rates, the general relationship between the predictor variables and height growth was similar among species and model type. Models highlight the importance of including predictor variables that describe seedling size along with openness and vertical structure of the forest canopy.ConclusionWhile the two model frameworks had comparable fit statistics, the one with predictors derived from tree inventory data may have enhanced utility as it can be directly integrated into existing individual-tree forest growth simulators.

13th Central Hardwoods Forest Conference

This conference was the 13th in a series of biennial meetings that have been hosted by numerous universities and research stations of the USDA Forest Service in the Central Hardwood forest region in the eastern United States. The purpose of the Conference has remained the same since its inception -- that is to provide a forum for the formal and informal exchange of information concerning the ecology, siliviculture, and management of the Central Hardwood forest by wide range of subjects was presented representing research efforts to understand this diverse forest resource. An especially noteworthy shift from previous conferences was the increase in oral and poster presentations related to forests in riparian zones and other wetlands and water quality issues. Altogether, there were 60 oral and 33 poster presentations accepted for this conference yielding these proceedings containing 58 peer-reviewed papers, 23 research notes, and 9 abstracts.