Microstegium Vimineum Research Articles

Effects of exotic plant species on soil properties in hardwood forests of New Jersey.

Two exotic plant species, Berberis thunbergii and Microstegium vimineum, recently have invaded deciduous hardwood forests in the Northeast. We examined changes in soil properties that maybe associated with this invasion in three parks in northern New Jersey. In each park, we collected soil and vegetation data along transects that were established across heavily infested areas and extended into uninvaded forest. The data were analyzed statistically by ANOVA and Canonical Correspondence Analysis (CCA). Significant differences were found between invaded and uninvadcd plots in both soil and vegetation characteristics. Invaded areas have fewer oaks (Quercus spp.) in the canopy, and lack the native understory shrubs (Vaccinium spp.). The pH of soils in the invaded areas is significantly higher than in the uninvaded areas, and the litter and organic horizons are thinner. The data cannot show that the exotic species have caused these changes. However, the occurrence of contrasting soils in adjacent areas of native vegetation, with no evidence of differences in land-use history between areas, suggests that such a cause-and-effect relationship exists. We propose a feedback loop involving the exotic plants, and the presence of earthworms to explain these dramatic soil differences.

A Comparison of Growth Efficiency of Plants on the East and West Sides of a Forest Canopy Gap

BARDEN, L. S. (Department of Biology, University of North Carolina at Charlotte, Charlotte, NC 28223). A comparison of growth efficiency of plants on the east and west sides of a forest canopy gap. Bull. Torrey Bot. Club 123:240-242. 1996.-The theoretical distribution of light in a circular forest canopy gap is symmetrically equal on the east and west sides of the gap. However, small plants on the west side of the gap receive maximum light in the morning when air temperature and vapor pressure deficit are relatively low, while plants on the east side receive maximum light in the afternoon when temperature and VPD are high. To test the hypothesis that plants on the west side of a gap are able to use light more efficiently, Microstegium vimineum, a shade-adapted annual grass, was grown in pots in a forest canopy gap, both in the actual open gap and in the extended gap. In the actual gap there was no difference in growth efficiency. However, in the extended gap growth efficiency was 39% greater on the west side than on the east side under equal light (integrated photon flux density). Thus, asymmetry of microclimate on the east and west sides of a canopy gap causes an east-west asymmetry in plant growth efficiency and may induce asymmetry in species composition of understory vegetation.

The Linear Relation between Stand Yield and Integrated Light in a Shade-Adapted Annual Grass

BARDEN, L. S. (Department of Biology, University of North Carolina at Charlotte, Charlotte, NC 28223). The linear relation between stand yield and integrated light in a shade-adapted annual grass. Bull. Torrey Bot. Club 123: 122-125. 1996.-Many ecology textbooks state that the photosynthetic response of plants to varying light is represented by the response of single leaves, which is a downward concave curve that often reaches saturation. Single leaves of the shade-adapted, annual grass, Microstegium vimineum (Trinius) A. Camus, saturate at 25% full sunlight. However, two field experiments showed that stand dry weight yield at the end of the growing season was a linear function of integrated light, rather than a downward concave saturation-type curve. The linear relation for M. vimineum stands concurs with results of several agricultural studies and may have implications for forest growth models that assume saturation-type response curves for whole trees or forest canopies.

Occurrence of Distinctive Cells in Leaves of C4Species in Arthraxon and Microstegium (Andropogoneae-Poaceae) and the Structural and Immunocytochemical Characterization of these Cells

Some C4 species in certain genera (e.g., Arundinella and Garnotia) within several tribes of the subfamily Panicoideae have bundle-sheath-like cells that are not associated with vascular tissue. These cells are known as distinctive cells (DCs) in the leaves. This article demonstrates that DCs also occur in the leaves of C4 species in the genera Arthraxon and Microstegium within the tribe Andropogoneae. DCs have not previously been recorded in this tribe. In leaves of Arthraxon hispidus, the DCs occur as single or multiple files in the mesophyll but their occurrence is rare. In leaves of Microstegium vimineum also, the DCs occur as single or multiple files, but an unusual feature, namely, bundle sheath cells (BSCs) that surround a single tracheary element, is often observed. The file of DCs in the two species did not extend continuously from the base to the tip of a leaf blade. A file of DCs ends, and then a vascular bundle with BSCs begins continuously, forming a longitudinal series. In the two species men...

Invasion of Microstegium vimineum (Poaceae), An Exotic, Annual, Shade-Tolerant, C 4 Grass, into a North Carolina Floodplain

Microstegium vimineum, an Asian annual C4 grass that is very shadetolerant, has invaded floodplains, streambanks and adjacent mesic slopes in the North Carolina Piedmont during the past 30 years. A 3-year study of its invasive characteristics revealed that M. vimineum is slow to invade undisturbed vegetation, but rapidly fills disturbed, mesic, shaded areas, such as streamsides where floods scour existing vegetation or sewer-line rights-of-way which are mown once a year. Its seeds remain viable for at least 3 years in the soil seedbank and rapidly germinate to produce a new cohort if a disturbance removes an existing cohort. On fertile floodplain sites, soil fertilization in March had no effect on seed production in October. When M. vimineum seeds were sown into existing vegetation, seed production was negatively correlated with soil potassium, calcium, silt and pH, probably because the more fertile sites also supported a denser ground vegetation layer. These qualities, in addition to its cleistogamous or apomictic reproduction, help explain how M. vimineum has spread throughout the eastern U.S. since its introduction approximately 70 years ago. INTRODUCTION Microstegium vimineum (Trin.) A. Camus is an annual grass species from Asia which recently invaded floodplains, streamsides and adjacent mesic slopes in the North Carolina Piedmont. It appears to be advancing into the existing ground cover of floodplains, which consists mainly of Japanese honeysuckle Lonicera japonica Thunberg. These two species often occur in dense monospecific stands which are separated by a strikingly narrow zone of mixing. This pattern of an introduced annual grass invading established stands of Japanese honeysuckle, a perennial woody vine which is known for its aggressiveness on fertile sites of the Carolinas (Bruner and Shearin, 1964), led me to ask the following questions: (1) Is M. vimineum invading undisturbed stands of L. japonica? (2) Does M. vimineum create a seedbank? (3) Can M. vimineum invade undisturbed stands of L. japonica if its seeds are sown in the stands in large numbers? (4) What environmental variables are related to success of M. vimineum sown in stands of L. japonica? (5) Does M. vimineum respond to an increase in essential soil elements with greater reproductive success? (6) Does M. vimineum alter the soil so as to inhibit growth of L. japonica? (7) What is the role of disturbance in the invasion of M. vimineum? Microstegium vimineum is in the tribe Andropogonae, subfamily Panicoideae. It was first collected in the United States in 1919 near Knoxville, Tennessee (Fairbrothers and Gray, 1972). By 1933 it had been collected in the mountains of western North Carolina (Blomquist, 1948; Fairbrothers and Gray, 1972) and by 1964 in 35 counties in North Carolina, primarily in the Piedmont (Radford et al., 1968). By 1972 the species had spread to at least 14 eastern states, from Florida to New Jersey and W to Ohio and Mississippi (Fairbrothers and Gray, 1972), and by 1978 to Arkansas (Smith, 1978). In Asia the species occurs in Japan, Korea, China, Ryukyus, Formosa, Malaysia, India and the Caucasus (Ohwi, 1984). Microstegium vimineum is unusual in that it is a C4 plant which, unlike typical C4 plants, is adapted to low light conditions (Brown, 1977, Winter et al., 1982). Under netting which transmitted 18% full sunlight, dry matter production was not significantly reduced from production in full sunlight; at 5% full sunlight, growth was 17% of that at full sunlight (Winter et al., 1982). Apparently, the C4 pathway itself has no inherent disadvantages, compared to the C3 pathway, under conditions of low light (Pearcy, 1983; Pearcy and Troughton, 1975).

Rates of Photosynthesis Relative to Activity of Photosynthetic Enzymes, Chlorophyll and Soluble Protein Content Among Ten C4 Species

Among 10 C4 species having a wide range in photosynthetic activity, the rates of photosynthesis/leaf area under high light were examined and compared with the chlorophyll and soluble protein content and the activities of several photosynthetic enzymes. The species examined were Digitaria sanguinalis, Echinochloa crus-galli, Microstegium vimineum, Panicum capillare, Panicum miliaceum, Paspalum dilatatum, Paspalum notatum, Pennisetum purpureum, Setaria lutescens, and Zea mays. The photosynthetic rates per unit leaf area ranged from 10 to 38 �mol CO2 fixed m-2 s-1. Among the 10 species there was a high degree of correlation of rate of photosynthesis/leaf area with soluble protein (r = 0.88), ribulose 1,5-bisphosphate carboxylase (r = 0.88) and pyruvate,PI dikinase (r = 0.94), but a lower correlation of photosynthetic rate/leaf area with phosphoenolpyruvate carboxylase (r = 0.74) and no significant correlation of photosynthetic rate/leaf area with chlorophyll content (r = 0.56). Among eight species of the NADP-malic enzyme C4 subgroup, there was a good correlation of photosynthetic ratelleaf area with NADP-malate dehydrogenase (r = 0.88) and NADP- malic enzyme (r = 0.92). Extractable activities of both the ribulose 1,5-bisphosphate carboxylase and the dikinase were generally close to the rate of photosynthesis. When comparing the activity per unit leaf area of one enzyme with another, generally a high degree of correlation was found among the species. The results suggest that a given C4 species tends to maintain a balance in the activities of several photosynthetic enzymes and that there is potential to estimate capacity for C4 photosynthesis under high light through determining activity of certain photosynthetic enzymes.

Microstegium vimineum, a shade adapted C 4 grass

Microstegium vimineum, a C 4 plant of the family Poaceae, is shown to be extremely adaptable to growing under shade conditions. The capacity for dry matter production of the species was similar from 18% to 100% full sunlight. Even at 5% full sunlight substantial growth occurred (17% of that at full sunlight). In comparison, growth of the C 4 species Digitaria sanguinalis and Sporobolus airoides declined rapidly below full sunlight with no growth occurring at 5% full sunlight. A number of measurements on leaves of M. vimineum grown under 5% of full sunlight versus full sunlight reflects the ability of this species to adapt to low light. Under low light there was a 2-fold increase in leaf area per leaf with an approx. 2-fold decrease in leaf thickness. The soluble protein/ chlorophyll ratio increased about 3.5-fold in the low light-grown plants due to an increase in chlorophyll/leaf area and a decrease in soluble protein/leaf area. Under both light regimes the plants had Kranz anatomy and high levels of phosphoenolpyruvate (PEP) carboxylase which are known features of C 4 plants. The results indicate that there are no inherent limitations in the C 4 mechanism or in the efficiency of energy utilization for carbon assimilation which prevents C 4 plants from adapting to low light conditions.