Survival Of Native Plants Research Articles

Effects of urban built-up patches on native plants in subtropical landscapes with ecological thresholds – A case study of Chongqing city

Abstract Urbanization has become a widespread social development trend in China. The size and configuration of urban built-up patches (UBPs) at a regional scale is presumed to be related to the extinction of rural and urban native plants in the landscape because of a tolerance threshold. The current study aimed to test the species area relationships in the heterogeneous space of UBPs vs. native plant taxa, which would enable examination of the tolerance thresholds of native plants to UBPs size and configuration. We investigated the types of land use, the patch configurations in the main region of Chongqing in western China, the statistics of native woody plants belonging to different species, and the life/growth forms found in sampling transects from four directions (east, west, north and south) along the rural-suburb-urban gradient. The size of UBPs has significant threshold effects on the native plant taxa, as well as the types of life/growth forms. Shrubs and deciduous plants are more resistant to the UBP size, followed by trees and evergreens. In addition, the smaller, more scattered, and rounder UBPs are related to more likely survival of native plants. The effect of the UBPs sizes in the landscape on native plants is negative, with critical thresholds ranging from 52.94% to 57.54% in a subtropical, mountainous megacity. Different plant taxa/life forms have different response thresholds. The influence of UBPs configurations on native plants can be positive or negative. The underlying mechanism of thresholds is thought to be caused by the accumulation of UBPs that form a matrix on the landscape.

Erratum to: Rhizobacterial Community Structures Associated with Native Plants Grown in Chilean Extreme Environments.

Chile is topographically and climatically diverse, with a wide array of diverse undisturbed ecosystems that include native plants that are highly adapted to local conditions. However, our understanding of the diversity, activity, and role of rhizobacteria associated with natural vegetation in undisturbed Chilean extreme ecosystems is very poor. In the present study, the combination of denaturing gradient gel electrophoresis and 454-pyrosequencing approaches was used to describe the rhizobacterial community structures of native plants grown in three representative Chilean extreme environments: Atacama Desert (ATA), Andes Mountains (AND), and Antarctic (ANT). Both molecular approaches revealed the presence of Proteobacteria, Bacteroidetes, and Actinobacteria as the dominant phyla in the rhizospheres of native plants. Lower numbers of operational taxonomic units (OTUs) were observed in rhizosphere soils from ATA compared with AND and ANT. Both approaches also showed differences in rhizobacterial community structures between extreme environments and between plant species. The differences among plant species grown in the same environment were attributed to the higher relative abundance of classes Gammaproteobacteria and Alphaproteobacteria. However, further studies are needed to determine which environmental factors regulate the structures of rhizobacterial communities, and how (or if) specific bacterial groups may contribute to the growth and survival of native plants in each Chilean extreme environments.

Rhizobacterial Community Structures Associated with Native Plants Grown in Chilean Extreme Environments.

Chile is topographically and climatically diverse, with a wide array of diverse undisturbed ecosystems that include native plants that are highly adapted to local conditions. However, our understanding of the diversity, activity, and role of rhizobacteria associated with natural vegetation in undisturbed Chilean extreme ecosystems is very poor. In the present study, the combination of denaturing gradient gel electrophoresis and 454-pyrosequencing approaches was used to describe the rhizobacterial community structures of native plants grown in three representative Chilean extreme environments: Atacama Desert (ATA), Andes Mountains (AND), and Antarctic (ANT). Both molecular approaches revealed the presence of Proteobacteria, Bacteroidetes, and Actinobacteria as the dominant phyla in the rhizospheres of native plants. Lower numbers of operational taxonomic units (OTUs) were observed in rhizosphere soils from ATA compared with AND and ANT. Both approaches also showed differences in rhizobacterial community structures between extreme environments and between plant species. The differences among plant species grown in the same environment were attributed to the higher relative abundance of classes Gammaproteobacteria and Alphaproteobacteria. However, further studies are needed to determine which environmental factors regulate the structures of rhizobacterial communities, and how (or if) specific bacterial groups may contribute to the growth and survival of native plants in each Chilean extreme environments.

Impacts of Carpobrotus edulis (L.) N.E.Br. on the germination, establishment and survival of native plants: a clue for assessing its competitive strength.

Does Carpobrotus edulis have an impact on native plants? How do C. edulis’ soil residual effects affect the maintenance of native populations? What is the extent of interspecific competition in its invasion process? In order to answer those questions, we established pure and mixed cultures of native species and C. edulis on soil collected from invaded and native areas of Mediterranean coastal dunes in the Iberian Peninsula. We examined the impact of the invader on the germination, growth and survival of seeds and adult plants of two native plant species (Malcolmia littorea (L.) R.Br, and Scabiosa atropurpurea L.) growing with ramets or seeds of C. edulis. Residual effects of C. edulis on soils affected the germination process and early growth of native plants in different ways, depending on plant species and density. Interspecific competition significantly reduced the germination and early growth of native plants but this result was soil, density, timing and plant species dependent. Also, at any density of adult individuals of C. edulis, established native adult plants were not competitive. Moreover, ramets of C. edulis had a lethal effect on native plants, which died in a short period of time. Even the presence of C. edulis seedlings prevents the recruitment of native species. In conclusion, C. edulis have strong negative impacts on the germination, growth and survival of the native species M. littorea and S. atropurpurea. These impacts were highly depended on the development stages of native and invasive plants. Our findings are crucial for new strategies of biodiversity conservation in coastal habitats.

Do white-tailed deer and the exotic plant garlic mustard interact to affect the growth and persistence of native forest plants?

Herbivores and invasive plants strongly affect the persistence of individual species and the overall composition of forest plant communities. Although their impacts are usually studied separately, they often co-occur with potential synergistic effects on native plants. We used a 2×2 experimental design replicated across five locations in southern Wisconsin to assess the separate and combined effects of herbivory by white-tailed deer (Odocoileus virginianus) and competition from the weedy invader Alliaria petiolata (garlic mustard) on five native species. Deer and Alliaria often reduce the growth and survival of native plants in these forests. A fenced exclosure erected at each site surrounded one of two pairs of adjacent plots densely occupied by Alliaria. We cleared one plot (in- and outside each exclosure) of Alliaria and then planted seedlings of the native species into all four plots. Species were chosen to display different functional traits (Aster lateriflorus/Symphyotrichum lateriflorum, Carex blanda, Geranium maculatum, Quercus rubra, and Uvularia grandiflora). We then monitored native seedling growth and survival for 13months. Deer access depressed survival and branching in Uvularia, growth in Geranium and Quercus, and tillering in Carex. The presence of Alliaria reduced height and tillering in Carex and Geranium but increased branching, reproduction, and survival in Uvularia. Thus, Alliaria may sometimes act to protect taxa like Uvularia sensitive to deer herbivory. Alliaria reduced the growth of Carex, Geranium, and Quercus significantly more in the absence of deer. Such interactive effects suggest that when deer do not restrict growth, plants grow larger to a point where Alliaria’s competitive effects increase. The impacts of both deer and Alliaria varied by species and trait. Species experiencing regional declines (e.g., oak seedlings and the lily, Uvularia) were more affected by deer than by Alliaria. Oak seedlings suffer particularly from Alliaria competition when deer are absent. Managers seeking to sustain deer-sensitive species should first work to reduce deer densities before seeking to control weedy plant invasions. Alliaria reduced growth more in species that tolerate deer browsing (Carex and Geranium). These differential responses argue for tailoring local deer and weedy plant control efforts to the taxa of concern. Deer and weedy plants have cumulative effects on native plant species. Interactions between their effects will become more important as their populations and impacts increase.

UPPER HUDSON RIVER ESTUARY (USA) FLOODPLAIN CHANGE OVER THE 20TH CENTURY

ABSTRACTDetailed surveys of the upper Hudson River Estuary and its floodplain from the early 1900s and digital mapping of the same areas today provide an opportunity to evaluate changes over the 20th century. This study uses a geographic information system to quantitatively compare water areas and islands mapped by the United States Army Corps of Engineers in 1907 and 1911 along an approximately 60‐km reach from Athens to Troy, NY, with the same features mapped in the late 20th century. The comparison shows a substantial decrease in total water area approximately 30% less than the 1907–1911 quantity, with secondary channels disproportionally affected (~70% less). The number and total area of islands has also dramatically decreased by approximately 65% and 85%, respectively. These changes primarily reflect the success of navigation improvement projects undertaken since the 19th century that transformed a shallow, island‐braided river in the study reach to one characterized by a deeper, single‐thread channel. Dredge spoils from the main channel were used to fill secondary channels and other backwater areas, a practice with implications for reproduction, growth and/or survival of native plants and animals. Published in 2011 by John Wiley & Sons, Ltd.