Long-term forest health monitoring programs are a valuable means of assessing the impacts of drivers and stressors and making projections about future structure and composition. A comprehensive, long-term forest monitoring program was established at the St. Croix National Scenic Riverway in 2007, and monitoring plots were revisited in 2013. Collectively, these plots spanned six forest types. Sugar maple forests, a climax type in the region, exhibited little change in the six-year interval between sampling periods. Substantial regeneration of Acer saccharum Marsh. and associated species suggests little change is expected in this type in the near future. In upland mixed hardwood-conifer forests, encroachment of Acer rubrum L. and Abies balsamea (L.) Mill. in the sapling and small tree layers was indicative of fire suppression and mesophication. Fire suppression was also evident in mixed conifer-red oak forests as plots in this forest type showed decreasing importance of Pinus spp. with increasing density and basal area of Quercus rubra L. These forests are in more well-drained soils than those of upland mixed hardwood/conifer forests; Q. rubra will likely become increasingly important in the coming decades. Mixed oak-aspen forests were in an earlier successional sere than the other five forest types, due to a high wind event in 2011; the high density of aspen observed here reflected clonal shoot growth in response to increased light availability. Both black ash-mixed hardwood forests and silver maple lowland forests supported a substantial amount of Fraxinus nigra Marsh., a species tolerant of saturated conditions. Major recruitment of several species occurred in black ash-mixed hardwood forests in the previous five to ten years and is likely a result of infrequent flooding and relatively shorter durations of inundation. The impending arrival of the emerald ash borer (Agrilis planipennis Fairmaire) poses one of the greatest threats in the St. Croix National Scenic Riverway, not only for the forests, but for the entire aquatic-terrestrial interface. As Fraxinus spp. trees begin to die, reduced evapotranspiration and increased flow velocity and water yield may result. Such changes may lead to increased sedimentation as well as decreased habitat quantity and quality for mussels and juvenile fish. Park managers should continue monitoring flow to help understand anticipated changes in riparian forests. In conifer forests, park staff should consider employing surrogate fire measures such as selective thinning and seedbed preparation, which can alter the successional pathways toward those of historic disturbance regimes. This strategy may facilitate northward migration of Quercus spp., Carya spp., and Pinus spp., as is anticipated as climate change continues.

The focus of this study was on seed germination and seedling growth of Pterocactus tuberosus, an endemic cactus inhabiting the Monte desert of Argentina, which possesses unusual winged seeds and geophytic habit. We evaluated the effects of water availability, temperature, and light on germination, and the influence of soil moisture on seedling growth. The effects of water potential were examined using 0, −0.1, −0.4, −0.7, and −1.0 MPa solutions. Temperature treatments included 15, 20, 25, 30, 35, 40, 20/10, 25/15, and 30/20 °C. To assess photoblastism, seeds were exposed to light or continuous darkness. Total germination, weighted germination percentages, and mean germination times were calculated. Plant size and biomass of 1- and 6-wk-old seedlings were determined under high, moderate, and low watering frequency treatments. Results showed that decreasing water potential affected germination, which was about 80% at 0 and −0.1 MPa, and then, decreased to almost complete inhibition at ≤ −0.7 MPa. Recovery of germination upon transfer to distilled water was successful, thus, suggesting that seeds maintain viability after exposure to reduced water potential. Seeds germinated under constant and fluctuating temperatures in the 15–35 °C range, with higher values between 20 °C and 35 °C, and marked inhibition at 15 °C and 40 °C. Germination occurred in darkness (58%) but was enhanced by light (84%). Both 1- and 6-wk-old seedlings grew substantially larger under high water availability but reduced their growth as the extent of the dry period increased. Similar proportion of biomass was allocated to roots and aerial parts, regardless of watering treatments, suggesting the relevance of the tuberous root as a water-storage organ. It appears that this root system may contribute to seedlings’ ability to withstand drought.

Laurel wilt disease is altering forests of the southeastern USA with widespread mortality to lauraceaous hosts, such as redbay (Persea borbonia (L.) Spreng.) and sassafras (Sassafras albidum (Nutt.) Nees). Sassafras is broadly distributed throughout the eastern USA and could serve as a pathway for laurel wilt disease spread into deciduous forests. The resulting invasion and widespread mortality of sassafras would affect these forests ecologically. In anticipation of this, we used preexisting vegetation data and the Forest Vegetation Simulator to predict future characteristics of invaded and noninvaded forests under two sassafras mortality scenarios, 33% and 99%. We calculated changes in total basal area and basal area of dominant species to assess the effects of invasion on forests of central Kentucky. We found that simulated sassafras mortality immediately resulted in significant declines to total basal area (0.87–2.32 m²/ha reductions) and also affected basal areas of selected species over time. Yellow poplar (Liriodendron tulipifera L.) and red maple (Acer rubrum L.) had the largest response to sassafras decline with long-term increases in basal area under both invasion scenarios. In contrast, the basal area of Quercus spp. as a whole only increased in the scenario with 99% sassafras mortality and only for a 15-yr period. Of the three oak species, black oak (Quercus velutina Lam.) was the only one to demonstrate significant long-term basal area increases, but again only within the 99% simulation. Our results suggest that if laurel wilt disease spreads north into deciduous forests, the resulting decline of sassafras will alter forest characteristics and affect ecological interactions, even at low levels of sassafras mortality.

Low levels of genetic variability, inbreeding, and limited gene flow are three possible threats to small, isolated plant populations as exemplified by Quercus hinckleyi C.H. Muller. J. This scrub oak species has survived over the past 10,000 years in a region in which the climate has become increasingly xeric. While more prevalent after the last ice age, its US range is now limited to a handful of populations in one county in West Texas. This study examines the genetic diversity of the relict metapopulation and resultant conservation implications. We used microsatellites to genotype a total of 204 ramets collected from three locations in Presidio County, TX, that represent all known occurrences of Q. hinckleyi. Analyses of eight loci were used to determine levels of genetic variability, population structure and clonal growth. Genetic diversity for the sampled plants was high: for the total metapopulation, the mean number of alleles (Na) was 17.875; the mean observed heterozygosity (H_o) was 0.807; and the mean expected heterozygosity (H_e) was 0.853. Allelic richness by locus and sample (Rs) ranged from 5.15 to 14.73. We found no evidence of inbreeding as measured by the fixation index, F_IS. Population structure analyses showed two distinct subpopulations with significant differentiation, as shown by G_ST (0.033, Bonferroni corrected P  =  0.001) and D_JOST (0.451, Bonferroni corrected P  =  0.001), unique alleles and genetic clustering. High clonality was discovered at the two smallest sites, with only seven unique genotypes among 58 ramets sampled. One clone was over 30 m across. Sexual reproduction appears to be present at the other sites, as indicated by less extensive cloning. Overall, we found that Q. hinckleyi is not genetically depauperate despite its rarity, although unique genets are reduced because of cloning. Asexual reproduction may in fact have allowed the small relict populations to survive extreme environmental change as their range has dwindled. The level of genetic diversity and differentiation among the remaining Q. hinckleyi sites warrants protection and preservation of all.

Morphological information was analyzed to evaluate whether Pithecellobium insigne, usually considered a synonym of Pithecellobium lanceolatum, is a different species. This question was addressed by a multivariate statistical analysis: cluster analysis, principal component analysis, and discriminant analysis using data obtained from herbarium specimens collected in Mexico, Central America, and northern South America. The results support P. insigne as a distinct species from P. lanceolatum. Significant differences with P. lanceolatum are: length of the floral bracts, length of the staminal tube, and thickness of the fruit. Pithecellobium insigne has the largest dimensions for all these features. Hybridization is possible and apparently takes place between both species in the Isthmus of Tehuantepec (Mexico), where populations of both species are parapatric and few specimens with intermediate characters were observed. A key to differentiate both taxa, as well as information about morphology, common names, ecology, conservation, and phenology of P. insigne is also included.

In the genus Nymphoides (floating-heart), at least six native and naturalized species are known to occur in the USA. Among the native species is Nymphoides humboldtiana, a species recently confirmed to reach its northern range limit in southern Texas. Plants similar in appearance to N. humboldtiana have been reported from Florida, where both white- and yellow-petaled variants have been identified as Nymphoides indica, a paleotropical species. We examined specimens using molecular (DNA) and morphological data to ascertain correct species identifications for the Florida plants. Sequence data from nuclear internal transcribed spacer and plastid trnK/matK regions indicated that Florida plants are not conspecific with N. humboldtiana, and that the white and yellow floral color variants attributed to N. indica actually represent separate species. We identified the white-petaled plants as N. indica, a likely escapee from the water garden trade in which the species is commonly grown. The yellow-petaled plants were identified by molecular data as Nymphoides grayana, and their identification was confirmed subsequently by morphological data. Nymphoides grayana is native to the Caribbean but was unknown previously in the USA. Because of the proximity of native N. grayana populations and the absence of this species in the water garden trade, we conclude that the Florida specimens arrived via a natural range expansion.

The validation of the fungal name Porogramme albocincta and five new records of poroid fungi to the Brazilian Amazonia are presented: Coriolopsis aspera, Coriolopsis hostmannii, Microporellus iguazuensis, Nigroporus macroporus, and Porogramme albocincta. A key to Porogramme species known for the Neotropics is provided.