Lesser celandine (Ficaria verna Huds.), an invasive plant from Europe, is becoming widespread in river valleys throughout the northeastern United States and the Pacific Northwest. Its high rate of asexual bulbil and tuber production creates dense infestations threatening native spring ephemerals. Ficaria verna abundance and reproductive output (seeds, bulbils, and tubers) were examined in invaded transects spanning a disturbance gradient away from a river. Site characteristics (photosynthetically active radiation [PAR], soil pH, moisture, texture, and nutrients) were quantified to examine their roles in plant abundance and reproduction. A larger-scale study examined random transects not specifically chosen based on F. verna infestations. Soil characteristics and slope were hypothesized to drive F. verna abundance and reproduction; we also hypothesized that reproductive output and biomass would be highest at intermediate distances from rivers, where disturbances are infrequent. Ficaria verna abundance and reproductive output varied considerably by site; soil characteristics, rather than landscape placement, appeared to drive plant abundance and reproduction. Lower percent sand was associated with significantly higher F. verna stem density and bulbil and tuber production. CEC was significantly negatively related to F. verna biomass and tuber counts. In the larger-scale survey, slope and PAR were significantly negatively related to F. verna presence and percent cover, respectively. Overall, these findings suggest that soil texture and slope can help explain higher abundance and reproductive outputs. However, reproductive output and biomass were not significantly greater at intermediate distances, contrary to expectations. We did not observe any seed production in any of the plots, although we did see a few plants with seeds outside our study area in the second year, demonstrating a near-complete reliance on asexual reproduction in these populations. This study expands on the current limited understanding of F. verna and can help management by identifying areas likely to support dense infestations.

Understanding why ecological communities contain the species they do is a long-standing question in ecology. Two common mechanisms that affect the species found within communities are dispersal limitation and environmental filtering. Correctly identifying the relative influences of these mechanisms has important consequences for our understanding of community assembly. Here variable selection was used to identify the environmental variables that best predict tropical forest primate community similarity in four biogeographic regions: the Neotropics, Afrotropics, Madagascar and the island of Borneo in South-East Asia. The environmental variables included net primary productivity and altitude, as well as multiple temperature, precipitation and topsoil variables. Using the best environmental variables in each region, Mantel and partial Mantel tests were used to reanalyse data from a previously published study. The proportion of variance explained increased for each region. Despite increases, much of the variation remained unexplained for all regions (R2: Africa = 0.45, South America = 0.16, Madagascar = 0.28, Borneo = 0.10), likely due to different evolutionary and biogeographic histories within each region. Nonetheless, substantial variation among regions in the environmental variables that best predicted primate community similarity were documented. For example, none of the 14 environmental variables was included for all four regions, yet each variable was included for at least one region. Contrary to prior results, environmental filtering was an important assembly mechanism for primate communities in tropical forests worldwide. Geographic distance more strongly predicted African and South American communities whereas environmental distance more strongly predicted Malagasy and Bornean communities. These results suggest that dispersal limitation structures primate communities more strongly than environmental filtering in Africa and in South America whereas environmental filtering structures primate communities more strongly than dispersal limitation in Madagascar and Borneo. For communities defined by genera, environmental distance more strongly predicted primate communities than geographic distance in all four regions, which suggests that environmental filtering is a more influential assembly mechanism at the genus level. Therefore, a more nuanced consideration of environmental variables affects conclusions about the influences of environmental filtering and dispersal limitation on primate community structure.

Norflurazon [4-chloro-5-(methylamino)-2-(3-(trifluoromethyl)phenyl)-3(2H)-pyridazinone] persistence in five Georgia soils after application to the same plots in 1982 and 1983 was characterized by rapid initial degradation followed by slow loss of the herbicide. The rate of norflurazon loss at each location for each year was not affected by application rate (1.7 or 3.4 kg ai/ha). Relative rates of norflurazon loss were Dothan loamy sand ≥ Greenville sandy clay loam ≥ Rome gravelly clay loam = Appling coarse sanely loam > Bradson clay loam. The rate of dissipation was slower in 1983 than 1982 in the Greenville and Appling soils. Cool and/or dry environmental conditions combined with higher soil organic matter content caused slower herbicide loss. Norflurazon residue 1 yr after treatment in all soils was greater in 1983 than in 1982. Significant injury to grain sorghum [Sorghum bicolor (L.) Moench. ‘BR 64’) was observed in the spring of 1984 at all locations in all plots that were treated with norflurazon for the previous two seasons. The degree of injury corresponded to the concentration of norflurazon detected at that sampling date. Leaching did not appear to be an important method of norflurazon loss.

Response of grain sorghum [Sorghum bicolor (L.) Moench. ‘BR 64’] to norflurazon [4-chloro-5-(methylamino)-2-(3-(trifluoromethyl)phenyl)-3(2H)-pyridazinone] and fluridone {1-methyl-3-phenyl-5-[3-(trifluoromethyl) phenyl]-4(1H)pyridinone} and the effect of previous treatment on the persistence of herbicide activity in five soils were determined in the greenhouse. Relative phytotoxicity of fluridone in the soils was ordered as Greenville sandy clay loam > Appling coarse sandy loam > Dothan loamy sand = Rome gravelly clay loam > Bradson clay loam. Phytotoxicity of norflurazon was ordered as Greenville = Appling = Dothan > Rome > Bradson. Fluridone was more phytotoxic than norflurazon. Field soil that has been previously treated with norflurazon or fluridone (500 days earlier at 1.7 kg ai/ha) still had low concentrations of each herbicide present at the time of retreatment in the greenhouse. Previous treatment of norflurazon did not affect the rate of decline in activity in any of the soils compared to previously nontreated soils except for Appling. Significantly higher concentrations of norflurazon remained in all previously treated soils 297 days after treatment (DAT) compared to previously nontreated soil. Residual carryover of norflurazon was greater in the Bradson soil (2.8% O.M.) than soils having less than 2% O.M. Fluridone dissipation was significantly faster in previously treated soil than in previously nontreated soil, indicating enhanced microbial degradation of the herbicide.

Cogongrass is a highly invasive, perennial grass that is found on all continents, except Antarctica. It continues to spread at an alarming rate in the southeastern United States. Cogongrass has been reported from a wide array of habitats; however, soils from areas where cogongrass grows have never been characterized. Live cogongrass plants, herbarium specimens, and soil samples were collected from 53 cogongrass populations from across the 10 physiographic regions and land use areas in Mississippi. Cogongrass leaf and inflorescence morphology varied among sites, and plants were found in soils varying widely in texture (ranging from 28 to 86% sand, 3 to 48% silt, and 6 to 43% clay), organic matter content (ranging from 0.9 to 5.0%), pH (ranging from 4.4 to 8.0), and nutrient status: 6 to 190 kg ha−1 (15 to 470 lb A−1) of phosphorus (P), 46 to 734 kg ha−1 of potassium (K), 150 to 7,620 kg ha−1 of calcium (Ca), 26 to 1,090 kg ha−1 of magnesium (Mg), 1 to 190 kg ha−1 of zinc (Zn), 145 to 800 kg ha−1 of estimated sulfur (S) based on organic matter, and 57 to 300 kg ha−1 of sodium (Na). These soil parameters were highly variable among cogongrass populations, even within physiographic regions or land use areas, and encompassed much of the soil physiochemical diversity within the state. Soil characteristics were significantly correlated with leaf length (Ca, K, Mg, P, Zn, and percentage of sand and silt), leaf width (Ca, P, Mg, and percentage of sand and silt), the leaf length-to-width ratio (K and P), inflorescence length (Na, P, and pH), inflorescence width (S, organic matter, and pH), and the inflorescence length-to-width ratio (S and organic matter). These data indicate that cogongrass is able to establish, emerge, grow, and reproduce on a wide array of soils in Mississippi. This ability provides cogongrass an advantage over other plant species that are more limited in the soil types that support their growth.

Allelopathy has been suggested as a mechanism of interference in several weed species. Allelochemicals released from certain weed species influence the growth and yield of crop species. Several laboratory studies present circumstantial evidence of the occurrence of allelopathy as a causative agent in weed–crop agroecosystems. Field evidence, however, is still lacking. In this paper, the significance of field studies is argued in terms of a multifaceted approach to allelopathy, and mugwort is used as an example. Previous research demonstrated the allelopathic potential of mugwort; however, experiments were not carried out in a natural environment. Inderjit and Foy (1999) have demonstrated that chemical characteristics (pH, inorganic ions, and phenolics) of soil amended with mugwort leaf leachate were altered when compared to unamended soil. We have analyzed the mugwort-infested field soil and compared its chemical characteristics with those of amended soils. No definite trend, in terms of influence of mugwort on soil chemistry, was observed. Results indicate the importance of field studies in order to obtain ecologically relevant data from laboratory studies. Field situations are often complex in terms of the presence of interfering flora. Cyanobacteria, for example, play an important role in weed–crop interactions in rice paddy soils. Allelochemicals released from weed species present in the paddy field may influence nitrogen-fixing cyanobacteria in addition to their phytotoxic effects to the paddy crop. Significance of phytotoxic effects of weed species on crop growth, and N2-fixing potential of cyanobacteria in paddy soils is discussed.

Interest in the cultivation of goldenseal is increasing and this may have benefits for agriculture, human health, and conservation. To enable a better understanding of growing conditions, cultivation methods reported in the literature were reviewed, 21 natural goldenseal populations in the northern portion of its natural range in North America were described and analyzed in terms of population size and health, and 15 successful growers were interviewed on requirements for optimal cultivation. Growing conditions in the wild were compared to those reported in the cultivation literature. Summary of data from natural populations suggests goldenseal grows best in mixed hardwood forests, under 60–65% shade, in moist sandy loam soils high in organic matter, with pH 5.7 to 6.3. Similarly, review of the literature suggests that goldenseal grows best in moist, well-drained loams high in organic matter, with pH 5.5 to 6.5. Reported shade requirements vary but 47–80% shade is considered optimal. Growing conditions reported by growers were also consistent with the cultivation literature and similar to conditions of wild populations. Although optimal growing conditions are similar to those for many crops, goldenseal is relatively robust and can grow well in a variety of conditions including wet, predominantly sandy or clay soils with pH as low as 4.8 and as high as 7.8. Cultivation can utilize a ginseng crop infrastructure and goldenseal has been recommended as a rotation crop for ginseng. Commercial production of goldenseal is potentially advantageous because (1) it is an environmentally friendly crop; (2) it has been grown successfully far outside its natural range, is easy to grow, and is considered potentially profitable; and (3) it is relatively inexpensive, having low energy, land area, and fertilization requirements. Development of a sustainable crop may contribute to the protection of native wild germplasm, which can provide valuable material for crop improvement.