Invasiveness potential of Miscanthus sinensis: implications for bioenergy production in the United States

Miscanthus sinensis (Anderss.) is a perennial grass species that has been grown widely as an ornamental since the late 1800s and is now being considered for bioenergy production in the United States. With its ability to be grown from seed and tolerate cold climates, this species offers practical advantages over current cultivars of the higher‐yielding hybrid species, M.×giganteus. Yet a large‐scale release of M. sinensis for bioenergy production in colder northern regions could result in new invasions into natural areas. We show, with reference to historical records and data collected in six wild US populations of M. sinensis in 2009, that ornamental varieties of this species have a long history of localized escape in the Eastern United States, primarily within the Appalachian region. To prevent further escape and gene flow, we recommend the development of sterile or functionally sterile varieties of M. sinensis or the restriction of its usage as a donor of genetic material to new sterile cultivars of M. ×giganteus. Other appropriate precautions for new biomass varieties include experimental demonstration of low invasiveness in the target region ahead of commercial production, along with postintroduction stewardship programs.     

Growth and fecundity of fertile Miscanthus × giganteus (“PowerCane”) compared to feral and ornamental Miscanthus sinensis in a common garden experiment: Implications for invasion

Perennial grasses are promising candidates for bioenergy crops, but species that can escape cultivation and establish self‐sustaining naturalized populations (feral) may have the potential to become invasive. Fertile Miscanthus × giganteus, known as “PowerCane,” is a new potential biofuel crop. Its parent species are ornamental, non‐native Miscanthus species that establish feral populations and are sometimes invasive in the USA. As a first step toward assessing the potential for “PowerCane” to become invasive, we documented its growth and fecundity relative to one of its parent species (Miscanthus sinensis) in competition with native and invasive grasses in common garden experiments located in Columbus, Ohio and Ames, Iowa, within the targeted range of biofuel cultivation. We conducted a 2‐year experiment to compare growth and reproduction among three Miscanthus biotypes—”PowerCane,” ornamental M. sinensis, and feral M. sinensis—at two locations. Single Miscanthus plants were subjected to competition with a native grass (Panicum virgatum), a weedy grass (Bromus inermis), or no competition. Response variables were aboveground biomass, number of shoots, basal area, and seed set. In Iowa, all Miscanthus plants died after the first winter, which was unusually cold, so no further results are reported from the Iowa site. In Ohio, we found significant differences among biotypes in growth and fecundity, as well as significant effects of competition. Interactions between these treatments were not significant. “PowerCane” performed as well or better than ornamental or feral M. sinensis in vegetative traits, but had much lower seed production, perhaps due to pollen limitation. In general, ornamental M. sinensis performed somewhat better than feral M. sinensis. Our findings suggest that feral populations of “PowerCane” could become established adjacent to biofuel production areas. Fertile Miscanthus × giganteus should be studied further to assess its potential to spread via seed production in large, sexually compatible populations.     

Can perennial dominant grass <Emphasis Type="Italic">Miscanthus sinensis</Emphasis> be nurse plant in recovery of degraded hilly land landscape in South China?

Perennial C₄ grasses, especially Miscanthus sinensis, are widely distributed in the degraded lands in South China. We transplanted native and exotic tree seedlings under the canopy of M. sinensis to assess the interaction (competition or facilitation) between dominant grass M. sinensis and tree seedlings. The results of growth, chlorophyll fluorescence, and ultrastructure showed that negative effects may be stronger in perennial dominant grass M. sinensis. Although M. sinensis buffered the air temperature, improved soil structure, and increased soil phosphorus content, these beneficial effects were outweighed by the detrimental effect, especially overshading. To ensure the establishment of target native species in M. sinensis communities in degraded lands of South China, restoration strategies should include removing aboveground vegetation, planting target species seedlings in openings to reduce the effects of canopy shading, and/or selecting competition-tolerant target species. Also, seedlings of exotic species used in restoration engineering cannot be directly planted under the canopy of M. sinensis.     

Testing appropriate habitat outside of historic range: The case of Amorpha herbacea var. crenulata (Fabaceae)

In the next century, safeguarding plant species against extinction from complete land conversion may require introducing species to novel locations. Although regulatory agencies caution against translocation outside of known historic ranges, when most wild populations and their habitats have been severely altered few viable options may be available for conserving rare plants. We introduced 345 endangered Amorpha herbacea var. crenulata along a pine rockland/transverse glade gradient with similar attributes to historically known occurrences for south Florida, USA, and monitored their survival and growth for five years. The experimental phase addressed: (1) Is the recipient site suitable for colonisation of this species despite hydrological manipulation in the region? (2) Can translocated plants grow equally well in four microhabitats along a gradient within the recipient site? We characterised soil water content, soil nutrient, and vegetation cover to assess the microhabitats at the recipient site. From 2006 to 2008 plants survived in all four microhabitats, but had highest survival in pineland. Translocated plants grew best in microhabitats with less grass cover and higher P content – the pineland and the restoration glade. Through 2008 we observed consistently higher soil water content with less total vegetation cover in pineland and significantly higher P content in the restoration glade.Using 2006–2008 data, we implemented the adaptive management phase, moving 20 plants from the lowest survival microhabitat to the highest survival microhabitat. This tactic improved the survival of plants by 2011, though growth rates of moved plants did not improve. Short-distance translocation, assessing environmental attributes related to plant survival and growth, quantifying similarity of soil, temperature, precipitation, and community as in this study are recommended to evaluate prospective introduction sites for translocations within or outside of range.     

Miscanthus sinensis grassland is an indicator plant community to predict forest regeneration and development on ski slopes in Japan

Most ski slopes in Japan are established by forest clearcutting, scraping off the ground surface and thereby artificial seeding in well-developed forests. Recently, some ski slopes have been abandoned owing to economical failure, and more skis resorts will go bankrupt. To restore abandoned ski slopes, therefore, we have to find out appropriate indicators to restore forest cover with low cost. Vegetation data were collected in Yuzawa, central Honshu, Japan (500–760 m elevation), where ski slopes are over-concentrated. To predict the possibility of forest development, relationships between tree stem density and vegetation characteristics were examined. Trees did not establish in areas where the introduced plant cover was more than 40%. Of native grasslands, Miscanthus sinensis grassland showed the highest stem density but did not show high species richness. In particular, stem density increased with increasing M. sinensis cover. To indicate advanced successional sere towards forests, therefore, M. sinensis cover is a more appropriate indicator rather than species richness.     

Structural characterization and analysis of the regeneration of woodlands dominated by Juniperus oxycedrus L. in west-central Spain

This work addresses the structural characterization of Juniperus oxycedrus-dominated woodlands in west-central Spain, as well as the analysis of the regeneration of this species in the presence of other species (mainly Quercus ilex) as a function of different environmental and land-use factors. The two densest populations of the species were sampled and different physiographic and land-use parameters were obtained. First, a structural characterization, specifically focused on regeneration, was carried out, based on the count of individuals and their classification according to their size (seedlings, saplings, or adults) and position (either beyond or below the canopy). The use of Generalized Linear Models (GLM) and Regression Trees permitted the identification and analysis of environmental and land-use variables significantly related to regeneration. Juniper woodlands in this part of Spain generally show a remarkable level of regeneration, although some significant differences were detected between the two existing populations. Of the factors studied, time since regeneration started, elevation, and soil rock surface cover influence J. oxycedrus regeneration at most of the individual classes considered, indicating the significance of these variables in this species regeneration. Canopy cover and depth of the organic layer and zone also affect several of the recruitment classes. Furthermore, radiation, the time elapsed since regeneration started, elevation, and aspect affect stand structure to a significant extent. The results of this study enlarge the knowledge on J. oxycedrus regeneration and woodland structure, providing helpful information for the conservation of these protected habitats.     

Novel Endophytic Nitrogen-Fixing Clostridia from the Grass Miscanthus sinensis as Revealed by Terminal Restriction Fragment Length Polymorphism Analysis

Anaerobic nitrogen-fixing consortia consisting of N₂-fixing clostridia and diverse nondiazotrophic bacteria were previously isolated from various gramineous plants (K. Minamisawa, K. Nishioka, T. Miyaki, B. Ye, T. Miyamoto, M. You, A. Saito, M. Saito, W. Barraquio, N. Teaumroong, T. Sein, and T. Tadashi, Appl. Environ. Microbiol. 70:3096-3102, 2004). For this work, clostridial populations and their phylogenetic structures in a stand of the grass Miscanthus sinensis in Japan were assessed by a 16S rRNA gene-targeted terminal restriction fragment length polymorphism (TRFLP) analysis combined with most-probable-number (MPN) counts. PCR primers and restriction enzymes were optimized for analyses of the plant clostridia. Clostridia were detected in strongly surface-sterilized leaves, stems, and roots of the plants at approximately 10⁴ to 10⁵ cells/g of fresh weight; they made up a large proportion of N₂-fixing bacterial populations, as determined by MPN counts associated with an acetylene reduction assay. Phylogenetic grouping by MPN-TRFLP analysis revealed that the clostridial populations belonged to group II of cluster XIVa and groups IV and V of cluster I; this result was supported by a culture-independent TRFLP analysis using direct DNA extraction from plants. When phylogenetic populations from M. sinensis and the soil around the plants were compared, group II clostridia were found to exist exclusively in M. sinensis.     

Reproductive challenges of a rare grass,Calamagrostis porteri subsp. insperata (Swallen) C. Greene: implications for habitat restoration

Background: Habitat management for reproductively challenged rare species is a problem when there is insufficient knowledge of their autecology. This study investigated reproductive failure in the rare grass Calamagrostis porteri ssp. insperata (Swallen) C. Greene (Reed bentgrass). Does the management recommendation of high light stimulate clonal growth, flowering, and seed production? Location: Shawnee National Forest, IL, USA, and in a greenhouse and an experimental garden at Southern Illinois University, Carbondale, IL, USA. Methods: Clones obtained from the three known Illinois populations were grown in a glasshouse under experimental light and soil moisture treatments. After 3 years, plants from the high light treatment were planted outside in an experimental garden where the light treatments were maintained for two more years. In the field, vegetative and flowering tiller density, canopy cover, and associated biotic and abiotic variables including abundance of co‐occurring plant species were monitored for 5 years. The overhead tree canopy was cleared over a portion of one population. Results: In the glasshouse, plants increased in size under high light and moist soil, and there were size differences among populations. Sixty‐six per cent (20 of 30) of the genets flowered when planted outdoors under full sunlight but did not produce seed. In the field, flowering only occurred in Calamagrostis growing in the cleared area, but no seed were produced. The plants in the flowering population were smaller than plants in the other two populations. The herbaceous community associated with Calamagrostis in the open diverged from the communities remaining under the shade. Conclusions: This study highlights the difficulty of managing reproductively challenged rare species. Calamagrostis populations can be managed to enhance clonal growth, but establishment of new populations would require translocation of vegetative material as it is highly unlikely that seed can be obtained.     

Improved Feedstock Option or Invasive Risk? Comparing Establishment and Productivity of Fertile <Emphasis Type="Italic">Miscanthus × giganteus</Emphasis> to <Emphasis Type="Italic">Miscanthus sinensis</Emphasis>

The perennial grass genus Miscanthus has great promise as biomass feedstock, but there are concerns about potential invasion outside production fields. While the sterile hybrid Miscanthus × giganteus is currently one of the leading feedstock options due to its low invasive potential, fertile varieties are being developed to reduce establishment costs, and their invasive risks need to be further assessed. We performed seed addition experiments in Ohio and Iowa, USA to examine the establishment, flowering, persistence, and shoot biomass per plot of a fertile M. × giganteus biotype (‘PowerCane’) and two Miscanthus sinensis biotypes, one feral, and one ornamental. Seeds were added to small, replicated plots in each of the 2 years under two seeding densities and two competition treatments, and plots were monitored for 2–3 years. The ‘PowerCane’ biotype established better, survived better, and produced greater amounts of biomass per plot than both M. sinensis biotypes. All three biotypes flowered by the second or third year after establishment, with inflorescences more numerous in ‘PowerCane’ and the Ornamental M. sinensis biotypes. Effects of seeding density and competition on these patterns were minor in most cases. Our research suggests that ‘PowerCane’ exhibits many traits shared by both biomass crops and invasive species: multi-year persistence, high biomass potential, and fertility. We suggest that the benefits of a seeded M. × giganteus should be carefully weighed against its increased invasive risk prior to deployment across the landscape.     

Predicting the Impacts of Climate Change on the Potential Distribution of Major Native Non-Food Bioenergy Plants in China

Planting non-food bioenergy crops on marginal lands is an alternative bioenergy development solution in China. Native non-food bioenergy plants are also considered to be a wise choice to reduce the threat of invasive plants. In this study, the impacts of climate change (a consensus of IPCC scenarios A2a for 2080) on the potential distribution of nine non-food bioenergy plants native to China (viz., Pistacia chinensis, Cornus wilsoniana, Xanthoceras sorbifolia, Vernicia fordii, Sapium sebiferum, Miscanthus sinensis, M. floridulus, M. sacchariflorus and Arundo donax) were analyzed using a MaxEnt species distribution model. The suitable habitats of the nine non-food plants were distributed in the regions east of the Mongolian Plateau and the Tibetan Plateau, where the arable land is primarily used for food production. Thus, the large-scale cultivation of those plants for energy production will have to rely on the marginal lands. The variables of “precipitation of the warmest quarter” and “annual mean temperature” were the most important bioclimatic variables for most of the nine plants according to the MaxEnt modeling results. Global warming in coming decades may result in a decrease in the extent of suitable habitat in the tropics but will have little effect on the total distribution area of each plant. The results indicated that it will be possible to grow these plants on marginal lands within these areas in the future. This work should be beneficial for the domestication and cultivation of those bioenergy plants and should facilitate land-use planning for bioenergy crops in China.     

Nuclear DNA content variation of three Miscanthus species in China

In order to estimate the variation in nuclear genome size in Miscanthus, flow cytometry of nuclei stained by propidium iodide was carried out using 36 populations of three Miscanthus species: M. lutarioriparius, M. sacchariflorus and M. sinensis, which were sampled from cold northern to warm and humid southern and central China, as well as near the sea level in eastern China to mountains in western China. The DNA content of diploid was 4.37 ± 0.02 pg/2C in M. lutarioriparius, 4.37 ± 0.01 pg/2C in M. sacchariflorus, and 5.37 ± 0.03 pg/2C in M. sinensis, respectively. There was no intraspecific variation in the three Miscanthus species at the diploid level, suggesting that the genome size was stable within species and the diverse environments did not induce variation in genome size at the diploid level. However, tetraploid populations were found in M. lutarioriparius and M. sacchariflorus, and their genome sizes were 8.56 and 8.54 pg, respectively, which are lower than expected values (8.74 pg), indicating the genome downsizing after polyploidization in the genus. Our results showed that the plant height of M. lutarioriparius was the highest one among the three species and the species was more closely related to M. sacchariflorus than M. sinensis. The intra-species genomic variation and inter-species differentiation in Miscanthus species provide important genetic and genomic information for the development of Miscanthus, especially for the endemic species, M. lutarioriparius, (together with Miscanthus × giganteus) which are now emerging as a key bio-energy crop because of their high yields and strong adaptability.     

Occurrence of adventitious sprouting in short-lived monocarpic herbs: a field study of 22 weedy species

Background and Aims

Adventitious sprouting from the hypocotyle and roots in monocarpic herbs has been confirmed in previous experimental studies as a means to avoid bud limitation after severe injury in annual and biennial plants. Data regarding the role of adventitious sprouting in natural populations, however, were lacking. The aim of the present study was to assess whether adventitious sprouting occurs in natural populations and how it is affected by plant size, plant injury, plant cover and environmental characteristics.

Methods

Data were sampled from 14 037 individual plants from 389 populations belonging to 22 annual and biennial species. Growth parameters were measured in individual plants, species composition and plant cover in communities were evaluated, and environmental characteristics were estimated using Ellenberg indicator values.

Key Results

It was confirmed that adventitious sprouting occurs in natural populations of all but five species examined. Adventitious sprouting was positively affected by plant size and plant injury. Environmental factors including availability of soil nitrogen were not shown to affect adventitious sprouting. Annual and biennial plants did not differ in sprouting, but upright annuals had a lower number of and longer adventitious shoots than prostrate annuals.

Conclusions

Adventitious bud formation is used to overcome meristem limitation when stem parts are lost due to injury, and thus resprouting in short-lived monocarps should not be overlooked.     

Genetic Analysis of Putative Triploid Miscanthus Hybrids and Tetraploid M. sacchariflorus Collected from Sympatric Populations of Kushima, Japan

Miscanthus ?×giganteus, a triploid hybrid between tetraploid M. sacchariflorus and diploid M. sinensis, has considerable potential as a bioenergy crop. Currently only one genotype is widely cultivated, increasing its vulnerability to diseases during production. Finding new hybrids is important to broaden genetic resources of M. ×giganteus. Three putative triploid hybrids were discovered in a sympatric population of tetraploid M. sacchariflorus and diploid M. sinensis in Kushima, Japan. The hybrid nature of the triploids was determined by morphological analysis and sequencing the ribosomal DNA internal transcribed spacer (ITS) region. The triploids had awns on their florets, which is a common characteristic of diploid M. sinensis, and sheath hairs, which is typical of tetraploid M. sacchariflorus. All triploids showed heterozygosity in their ribosomal DNA ITS sequences. Based on these results, it is confirmed that the triploids are hybrids and novel genotypes of M. ×giganteus. Natural crossing between tetraploid M. sacchariflorus × diploid M. sinensis may also lead to the production of tetraploid hybrids. ITS analysis of tetraploid plants showed that one maternal parent of the triploid hybrids, K-Ogi-1, had heterozygous ITS, which was different than the other analyzed tetraploid, M. sacchariflorus. Thus, K-Ogi-1 was likely of hybrid origin. These tetraploid hybrids can also be utilized as parents in M. ×giganteus breeding. Since all hybrids identified in this study had tetraploid M. sacchariflorus as maternal parents, collecting and analyzing seeds from tetraploid M. sacchariflorus in sympatric areas could be an effective strategy to identify natural Miscanthus hybrids that can be used as bioenergy crops.     

Soil fertility and herb facilitation mediated by Retama sphaerocarpa

Abstract. Woody legumes growing in dry climates can increase soil nutrient content and facilitate plant growth in their understorey. We investigated differences in soil fertility and herbaceous community in relation to the presence and absence of the legume Retama sphaerocarpa in a shrubland in a mediterranean type climate. The results showed a higher content of limiting nutrients for plant growth, such as phosphorus and nitrogen, under the R. sphaerocarpa canopy. Herbaceous biomass, cover and nitrogen content increased below the canopy. However, species richness and diversity were diminished in the presence of a dense canopy of R. sphaerocarpa. Nitrogen isotopic analysis did not indicate a clear relationship between symbiotic fixation in R. sphaerocarpa and nitrogen content of soil and plants under its canopy. Nevertheless, herbs growing in the understorey showed a linear correlation between foliar N content and ¹⁵N values. The existence of a dense shrub canopy induced a smaller monthly variation in herb richness, diversity and biomass, suggesting that it provides a stable microhabitat facilitating herbaceous vegetation establishment and growth. The ‘shelter’ effect was more important when environmental conditions became stressful for herbaceous plants.     

Scale‐dependence of environmental effects on species richness in oak savannas

Abstract. In order to investigate how scale (grain size) affects the relationships between species richness and environmental drivers (such as stress and disturbance), we collected 12 nested quadrats (from 0.25 m² to 1023 m²) from seven remnant oak savannas located in the floodplain of the Chippewa River in western Wisconsin, USA. Large and small‐scale richness were not significantly correlated, suggesting that small‐scale richness is not strongly controlled by sampling effects of the local species pool. Linear and curvilinear regressions between species richness and disturbance, canopy cover, biomass, and soil organic matter were dependent on sampling scale (grain size). Disturbance by fire was strongly related to richness at small scales, while tree canopy cover was strongly related to richness at larger scales. While there was some evidence suggesting the transition from disturbance to canopy effects occurs between 10 and 100 m², the transition was not particularly abrupt. The results cast doubt on the general importance of local species pools in affecting small‐scale richness as well as our ability to make generalizations that do not explicity include scale.     

Influence of community structure on the spatial distribution of critically endangered Dicerandra immaculata var. immaculata (Lamiaceae) at wild, introduced, and extirpated locations in Florida scrub

Community structure at local scales is a major factor controlling population and community dynamics of plant species. Dicerandra immaculata Lakela var. immaculata (Lamiaceae) is a critically endangered plant known only from a few locations in scrub habitat in Florida. Using seven sites where populations of D. immaculata were wild, introduced, and/or extirpated, we sought to answer the following questions: (1) how do habitat characteristics at locations supporting wild D. immaculata plants vary from random locations within the same habitat; (2) how do habitat characteristics differ between wild and extirpated populations; and (3) how do habitat characteristics differ between wild and introduced populations? At locations of wild D. immaculata, community structure had fewer woody stems, shorter understory vegetation, lower percent canopy coverage, and lower percent ground cover of detritus than random locations and locations with extirpated D. immaculata. In addition, bare ground decreased at extirpated locations because other plant species expanded their coverage, water saturation of the soil increased, diversity of shrubs decreased, and composition of the overstory changed compared to that of wild locations. Habitat characteristics associated with introduced plants were more similar to characteristics at randomly chosen locations than those with wild plants. However, introduced plants tended to occupy locations that had drier soil, a higher abundance of conspecifics, and a higher proportion of woody understory plants than that of random locations. Overall, gaps in the canopy and at ground level are likely essential for survival and recruitment of D. immaculata.     

Variation in soil respiration under the tree canopy in a temperate mixed forest,central China,under different soil water conditions

The forest canopy cover can directly and indirectly affect soil conditions and hence soil carbon emission through soil respiration. Little is known, however, on the effects of canopy cover on soil respiration under the canopy of different tree species and soil water conditions. We have examined the variation in soil respiration at different soil water conditions (dry <10 %, wet >20 %, v/v) under different tree canopy covers in comparison with the canopy interspace in a temperate coniferous (Pinus armandii Franch) and broadleaved (Quercus aliena var. acuteserrata) mixed forest in central China. The results show that soil respiration measured under tree canopy cover varied with canopy size and soil water content. Soil respiration under small-sized canopies of P. armandii (PS) was higher than that under large-sized (PL) canopies, but the difference was only significant under the dry soil condition. However, soil respiration under large-sized canopies of Q. aliena (QL) was significantly greater than that under small-sized (QS) canopies under both dry and wet soil conditions. The difference in soil respiration between differently sized canopies of Q. aliena (33.5–35.8 %) was significantly greater than that between differently sized canopies of P. armandii (2.4–8.1 %). Differences in soil respiration between inter-plant gaps and under QS canopies in both the dry and wet soil conditions were significant. Significant increases in soil respiration (9.7–32.2 %) during the transition from dry to wet conditions were found regardless of canopy size, but the increase of soil respiration was significantly lower under P. armandii canopies (9.7–17.7 %) than under Q. aliena canopies (25.9–31.5 %). Our findings that the canopy cover of different tree species influences soil respiration under different soil moisture conditions could provide useful information for parameterizing and/or calibrating carbon flux models, especially for spatially explicit carbon models.     

The effects of shrub patch sizes on the colonization of pioneer plants on the volcano Mount Koma,northern Japan

Vegetation recovery on Mount Koma, Hokkaido, Japan, has been slow after the catastrophic eruption in 1929, due to undeveloped soil and limited plant colonization. Nowadays, the seedling establishment is supported mostly by a nurse plant, Salix reinii forming shrub patches, facilitates the plant colonization. Although the effects of shrub patches should differ with patch sizes, the size effects have not been examined well. To examine the size effects, seed-sowing experiments were conducted on two common pioneer herbaceous species, Miscanthus sinensis and Polygonum sachalinense, in the field. The seed germination and seedling survival were monitored by the seeds sown into S. reinii patches (0.97 m²–4.12 m² in area) for 4 months during snow-free periods. Microenvironments altered by the patches were measured. Lab-experiments were performed to characterize the seed germination and seedling growth.Larger patches decreased light intensity and temperature more and increased litter and water content. The large patches promoted the seed germination of the two species. Interspecific interactions, examined by a seed mixture experiment, showed that the interaction increased the seed germination on M. sinensis and decreased that on P. sachalinense. On the lab-experiments at three temperatures (15, 20 and 25 °C), M. sinensis seeds germinated more at higher temperatures and obtained higher seedlings biomass. P. sachalinense germinated the seeds more at 20 °C and grew faster at lower temperatures. The total biomass of the two species was reduced by shade that intercepted 50% of light intensity. The seed germination and seedling growth of these two species became higher on litter with 2 cm in depth than on no litter. Soil water supported seed germination when the seeds of these two species were mixed while the water reduced the growth of P. sachalinense seedlings. Therefore, the dry soils were suitable for their growths. In all the treatments, P. sachalinense seedlings showed higher mortalities than M. sinensis.In conclusion, the large patches facilitated more to the colonization of pioneer plants via seed germination and growth. Large patches acted as a nursery supporting the natural regeneration in the disturbed area by improving litter accumulation, maintaining soil water, reducing strong light and/or protecting from heat.     

Soil organic C and nutrient contents under trees with different functional characteristics in seasonally dry tropical silvopastures

Aims

The selection of tree characteristics is critical for the outcome of the tree effects on soil fertility in silvopastoral pastures. This study aims to quantify the effects of trees on soil nutrient and C stocks, as well as assessing differences on the effects between legume (Albizia saman; Enterolobium cyclocarpum) and non-legume tree species (Tabebuia rosea; Guazuma ulmifolia).

Methods

In Central Nicaragua, soil was sampled (0–10 cm deep) in paired plots, under both a canopy and in open grassland, in 12 sites per tree species and analysed for organic C, total N stocks, available P and extractable K⁺, Ca²⁺ and Mg²⁺. To assess the effects of herbaceous composition and cattle to soil proprieties, we recorded the cover of plant groups and assessed the mass of dung in each plot.

Results

Soil organic C and N, available P and extractable K⁺ and Ca²⁺ were higher under the tree canopy than under paired open grassland. The basal area of trees was positively related with the canopy effect on soil variables, thus suggesting that the age or sizes of the trees are relevant factors associated with the content of soil C and nutrients. No specific effects related to the legume species group were detected.

Conclusions

Our results indicate that in fertile seasonally dry subtropical pastures, scattered trees have an overall effect on soil fertility, and that the magnitude of the effect depends more on the tree characteristics (i.e. basal area, crown area) than on whether the species is a legume or not.     

Microhabitat use by larvae and females of a rare barrens butterfly,frosted elfin (<Emphasis Type="Italic">Callophrys irus</Emphasis>)

The frosted elfin (Callophrys irus) is a localized and declining butterfly found in xeric open habitats maintained by disturbance. We described the effects of woody plant canopy cover, topography and host plant size and density on the quality of microhabitat of wild indigo (Baptisia tinctoria) host plants containing late instar frosted elfin larvae at four study sites in southeastern Massachusetts, United States. We also assessed whether females preferentially depositing eggs on host plants within specific microhabitats, therefore conferring greater survivorship to the larvae through the late-instar stage. We found that moderate amounts of canopy cover and large plant size characterized larvae-occupied host plants. In the absence of tree canopy cover, late instar larvae density remained low even when host plant density was high. However, females oviposited on wild indigo plants without regard to any of the vegetative or environmental variables we measured. These results indicate that canopy cover was an important characteristic of microhabitats containing late instar larvae, and late instar larvae occupancy was determined by suitable microhabitat conditions, and not female oviposition selection. Managing for canopy cover and microhabitat heterogeneity within relatively open habitats is recommended for the maintenance of frosted elfin populations.