Catherine M. Mabry

Landscape and species-level distribution of morphological and life history traits in a temperate woodland flora

We developed a description of a central New Eng- land deciduous hardwood forest based on the distribution within the community of morphological and life history traits (N = 34) and environmental factors. Classification by TWINSPAN of 186 species based on morphological and life history traits identified six major functional groups of species largely corresponding to growth form. A data matrix of plots x traits was ordinated using PCA. Each of the resulting four PCA axes was associated with a major environmental gradi- ent: drainage, site exposure, disturbance due to past land use and degree of disturbance in the 1938 New England Hurricane (24.9, 19.8, 11.7 and 8.4% of the variation respectively). Two patterns suggested that a suite of potentially functional traits, rather than a few key characters (e.g. vital attributes), govern the distribution of species in this community: (1) each of the four axes was largely associated with a different group of traits and (2) each axis was associated with several traits that ap- peared to sort independently (i.e. not to co-occur within species). Evaluating one often-examined trait, there was no evidence that dispersal ability limited the colonization of species into secondary woodlands. We also found that landscape-scale abundance was associated with a small number of traits. Production of fleshy fruits and few diaspores per plant were positively associated with landscape-level abundance. Our results suggest that attempts to understand the overall struc- ture and function of this plant community based on a few key characters, such as dispersal ability, will meet with limited success. However, when focusing on one aspect of the com- munity, such as frequency across the landscape, relatively few characters may be important.

Diversifying Agricultural Catchments by Incorporating Tallgrass Prairie Buffer Strips

Crop production and prevailing farming practices have greatly reduced biodiversity and nearly eliminated native prairie in the central USA. Restoring small areas of prairie on cropland may increase plant biodiversity and native species abundance while benefiting the cropland. In Iowa, we incorporated buffer strips composed of prairie vegetation within catchments (0.5 ha to 3.2 ha land areas in which precipitation drained to a collection point at the slope bottom) used for corn (Zea mays) and soybean (Glycine max) production. We planted prairie buffer strips in three designs, varying the proportion of the catchment converted to buffer and/or the continuity of the buffer. Within the catchments, we determined the identity and percent cover of buffer strip plant species during 2008–2011 and of weed species in cropped areas during 2009–2011. We found 380% more species in 6 m2 of buffer strip than in 6 m2 of crop, indicating that the presence of buffer strips greatly increased catchment diversity. Plant community composition did not differ among the three buffer designs. Despite being surrounded by cropland, the buffer vegetation was dominated by native perennial species—the targeted vegetation type for both ecohydrological functions (e.g., erosion control) and native species conservation— within four years of establishment. Furthermore, weed species richness and prevalence did not differ between cropped areas of catchments with buffer strips and cropped areas of catchments without buffer strips. These results indicate that converting 10–20% of cropland to prairie buffer strips successfully reintroduced perennial species characteristic of native prairie without increasing weeds in adjacent crops.

Odonata Richness and Abundance in Relation to Vegetation Structure in Restored and Native Wetlands of the Prairie Pothole Region, USA

Over the past couple of decades, 2,200,000 ha of wetlands and grasslands have been restored in the prairie pothole region, USA. However, many restored and remnant wetlands in the region are dominated by two invasive plant species, reed canary grass (Phalaris arundinacea) and cattail (Typha spp.), which form dense monotypic stands. These restorations are usually evaluated as habitat for waterfowl and other birds; however, there is a need to evaluate their success for invertebrates. Odonata (dragonflies and damselflies) are ideal organisms to include in our evaluations of restored wetland habitat quality for both ecological and practical reasons. To examine the association between vegetation structure and odonate assemblages in shoreline vegetation of prairie pothole wetlands, we compared odonate richness and abundance in dense, monotypic stands to that of vegetation with diverse vertical structure. We also observed the use of these two different habitats by odonate species classified as “of conservation concern” in Iowa. Odonate species richness was substantially greater in the mixed-structure vegetation than in monotypic stands. A similar trend was found in odonate species with a “vulnerable” or “uncommon” conservation status. The number of occurrences of species of conservation concern was four times greater in mixed than in monotypic vegetation. A comparison of our data to those collected in the 1990s for one monotypic vegetation site further supported this conclusion. Many odonate species are targets for conservation and can readily benefit from wetland restoration and reconstruction if the sites are managed for proper vegetation structure.

A permanent plot study of vegetation and vegetation-site factors fifty-three years following disturbance in centralNew England, U.S.A.

AbstractPermanent plots, established at the Harvard Forest, Petersham, Massachusetts, U.S.A. in 1940 following the 1938 New England Hurricane, were resampled in order to examine the response of for...

An investigation of water nutrient levels associated with forest vegetation in highly altered landscapes

Stream pollution by nutrient loading is a chronic problem in the Midwest, United States, and greater impacts on water quality are expected as agricultural production and urban areas expand. Remnant riparian forests are critical for maintaining ecosystem functions in this landscape context, allowing water infiltration and capture of nutrients before they are lost from the system. Our objective was to identify linkages between riparian forest plant community composition and water quality in remnant forested headwater streams. We identified watersheds with embedded headwater streams in three land use categories: grazed, urban, and preserved. We assessed plant community composition and nutrient storage. We sampled the forest streams to monitor discharge rates and sediment, nitrogen (N), and phosphorus (P) loads. Herbaceous communities in preserved riparian forests had more native specialist species than urban or grazed sites. Plant N content was higher in preserved forests (17.6 kg ha−1 [15.7 lb ac−1]) than grazed (12.5 kg ha−1 [11.2 lb ac−1]) or urban forests (10.5 kg ha−1 [9.4 lb ac−1]). Conversely, stream water total N delivery was higher in urban watersheds (0.043 kg ha−1d−1[0.038 lb ac−1day−1]) than preserved (0.026 kg ha−1d−1 [0.023 lb ac−1day−1]) or grazed watersheds (0.02 kg ha−1d−1 [0.018 lb ac−1day−1]). Stream water nitrate (NO3-N) concentration and total P delivery were highest for streams in urban areas. The most pronounced differences for plant composition and stream discharge and pollutant loads were between preserved and urban forests. Seasonal patterns were variable. We detected a weak negative but seasonally important relationship between plant N content and stream water N. We did not detect a similar relationship for P, which may indicate saturation of this nutrient in the watershed system. Detailed knowledge about relationships between land use, plant community composition, and water quality outcomes could be used to target forest restoration efforts in landscapes highly impacted by humans.

Optimal Shrub Density for Bird Habitat in the Midwestern United States

Shrubs play a key role as bird habitat in eastern North America and are associated with a group of songbirds that are in sharp decline in the Midwest region, U.S.A. Savanna restoration throughout the region is a key priority for vegetation managers, and a priority goal is often to clear the understory of woody species encroachment, including shrubs. However, while the benefit of maintaining a shrub layer in restored savanna has been noted by wildlife managers, the degree to which native shrubs should be retained has not yet been quantified. In this study, I measured songbird occurrence in sites that met the criteria of savanna physiognomy and that have shrub cover ranging from 10 to ≥75%. The results indicated that the highest overall species richness and richness of species conservation concern occurred when shrub cover was ≤35%. This observation suggests that shrub cover in the range of 10–35% may be adequate to conserve declining shrub dependent bird species, while also meeting the objective of opening the understory desired by savanna restoration practitioners.

Restoration of herbaceous woodland plants: persistence, growth, and reproductive success of local and non-local propagules

Restoring the forest herbaceous layer in remnant forests throughout the Midwestern United States (U.S.) is limited by the lack of seed and propagules for many plant species. As a result, restorationists often have limited material to work with and must seek out plant material at a regional rather than a local scale, without knowing whether regional provenances are ecologically appropriate. We conducted greenhouse and field experiments to examine persistence, growth, and reproduction of three herbaceous perennials (wild ginger, Virginia waterleaf, and James’ sedge) that could be used for restoration. The greenhouse experiment represented a common garden and was conducted to identify whether there were genetic differences in morphological characters between local plants and non-local transplants from commercial nurseries. The two-year field study was conducted to determine whether any genetic differences noted in the greenhouse persisted in a natural setting, and also to determine what planting density (two or five individuals in a 0.25 m2 plot) would be sufficient for the plants to establish. In the greenhouse, growth and reproductive measures for non-local plants were generally equal to or greater than those of local plants. However, we found the reverse for many traits, particularly related to reproduction, in the field during year two. In natural field conditions local plants had equal or greater vegetative growth and reproduction than non-local plants, although both had similar persistence. Further, similar persistence and growth in low- and high-density field plots suggested that a limited number of transplants would be adequate for successful establishment of non-local transplant stock.

Survival, Reproductive Output, and Transplant Potential of Penstemon tubiflorus (Tube Penstemon)

ABSTRACT. Survival, reproductive output, and transplant success were studied for an Iowa population of Penstemon tubi- florus (tube penstemon), a species that is rare to uncommon through much of its range. The population was discovered in 2003 and is one of only 6 populations that have been documented in Iowa. I began monitoring the new population when 2 cohorts were permanently marked, the first in 2005 and the second in 2007. I estimated survival, flowering, and reproductive output. Then, I introduced greenhouse-grown transplants to 2 new sites and the original site. Survival data showed that P. tubiflorus is a short-lived perennial (approximately 50% survival after 3 years) with substantial variation in the percentage of individuals that flower in a given year. Recruitment over the 5 years of monitoring varied from zero to 26 individuals per year. Transplant survival was site-specific. However, high survival and robust reproduction output of transplants at one site indicated that there are additional suitable sites near the parent population and suggested that these sites remain unoccupied due to limited seed dispersal. While it is unlikely that pollinator limitation is the cause of low reproduction, further study is needed on the pollination syndrome of the Iowa populations of this and other Penstemon species. Future studies should investigate the possibility that the species is limited by site-specific factors that inhibit germination and the survival of small seedlings.

Stakeholders’ Perceptions of Native Plants and Local Ecotypes in Ecological Restoration

Many scientists and land managers recommend using local ecotypes for restoration projects. However, there is not a scientific consensus on what constitutes “local.” To gain information about production and use of locally sourced plant material, we surveyed two stakeholder groups, conservation professionals and nursery professionals, to learn if there were differences between these stakeholder groups in terms of use, sale, or perception of native and local ecotype plant material. Our survey results indicated that both conservation and nursery professionals are aware of the ecological and functional value of native plant communities, and are also familiar with associated plant sourcing issues. However, nursery professionals provide less local ecotype and source-certified plant material in their businesses than would meet the need expressed by conservation professionals for these materials. Conservation professionals also indicated that their organizations did not necessarily have specific guidelines for sourcing local ecotype native plant material. Although nursery professionals are aware of restoration techniques and the usefulness of local ecotypes, this does not appear to translate into provision of larger quantities of native, local ecotype, or source-certified plant material. We found that members of both stakeholder groups rely on trusted authorities and professional training for information, presenting an opportunity to reach both groups through combined workshops to encourage communication and facilitate availability of native plants for restoration.

Regional Genetic Differences in Forest Herbaceous Species

the ridges) plays a major role in controlling soil nutrient decomposition and availability. Results of this study confirm the suggestion by Krug et al. (2004) that ecological restoration initiatives in renosterveld old field should introduce native species in the furrows. This study provides evidence that the reported high soil nutrient content and soil moisture in the furrows compared to the ridges could explain why vegetation is successfully recolonizing on the furrows. Furrows increase restoration potential because they capture wind-dispersed seeds and create favorable germination conditions, which include improved water infiltration and soil moisture storage (van der Merwe and Kellner 1999). The study recommends that any future restoration efforts in renosterveld old fields should concentrate in the furrows rather than the ridges.