The spread of transgenes and exotic germplasm from planted crops into wild or feral species is a difficult problem for public and regulatory acceptance of genetically engineered plants,particularly for wind-pollinated...The spread of transgenes and exotic germplasm from planted crops into wild or feral species is a difficult problem for public and regulatory acceptance of genetically engineered plants,particularly for wind-pollinated trees such as poplar.We report that overexpression of a poplar homolog of the floral repressor SHORT VEGETATIVE PHASE-LIKE(SVL),a homolog of the Arabidopsis MADS-box repressor SHORT VEGETATIVE PHASE(SVP),delayed the onset of flowering several years in three genotypes of field-grown transgenic poplars.Higher expression of SVL correlated with a delay in flowering onset and lower floral abundance,and did not cause morphologically obvious or statistically significant effects on leaf characteristics,tree form,or stem volume.Overexpression effects on reproductive and vegetative phenology in spring was modest and genotype-specific.Our results suggest that use of SVL and related floral repressors can be useful tools to enable a high level of containment for vegetatively propagated short-rotation woody energy or pulp crops.展开更多
Overstory basal area,ericaceous shrub cover(Kalmia latifolia L.and Rhododendron maximum L.),and fuels(i.e.,woody fuel loads and depths and O Horizon thickness) were assessed within Great Smoky Mountains National Park,...Overstory basal area,ericaceous shrub cover(Kalmia latifolia L.and Rhododendron maximum L.),and fuels(i.e.,woody fuel loads and depths and O Horizon thickness) were assessed within Great Smoky Mountains National Park,USA,in 2003-2004.Due to recent wildfire activity within the southern Appalachian Mountain region(including Great Smoky Mountains National Park),the potential spread and expansion of ericaceous shrubs,and the impacts of the hemlock woolly adelgid(Adelges tsugae Annand) on eastern hemlock(Tsuga canadensis(L.) Carrière),these same ecosystem components were again assessed in 2019.Elevation and moisture regime(xeric,intermediate,and mesic) were included in this assessment as potential influential factors.An evaluation of repeated measurements from 40 plots suggested that O Horizon thickness did not change significantly over the 16-year period,but increased as elevation increased,and moisture regime(xeric O Horizon thickness> mesic O Horizon thickness) was a significant,related factor.The sum of 1-,10-,and 100-h fuel loads(fuels less <7.6 cm diameter)increased,whereas woody fuel depth decreased over the16-year period.No significant changes in 1000-h fuel lo ads(>7.6 cm diameter),total woody fuel loads,ericaceous shrub cover,total basal area,or live T.canadensis basal area were observed.Live T.canadensis basal area decreased with increasing elevation.Dead,standing T.canadensis basal area increased from 2003-2019,and that increase was most pronounced as elevation increased on xeric and intermediate sites.Overall,we found that:1.hypothesized increases in total woody fuel loads and ericaceous shrub cover were not present;and 2.elevation and moisture regime were most related to observed changes in vegetation and fuel condition.展开更多
Recently the Journal of Mountain Science published three papers(Lumbres et al.2014;Jung et al.2015;Lumbres et al.2016)that compared selected taper models for bias and precision when estimating upper stem diameters for...Recently the Journal of Mountain Science published three papers(Lumbres et al.2014;Jung et al.2015;Lumbres et al.2016)that compared selected taper models for bias and precision when estimating upper stem diameters for various tree species.The purpose of this commentary is to point out the consequences of the choice of the variable to be predicted when fitting taper equations展开更多
Accurate prediction of stem diameter is an important prerequisite of forest management.In this study,an appropriate stem taper function was developed for upper stem diameter estimation of white birch(Betula platyphyll...Accurate prediction of stem diameter is an important prerequisite of forest management.In this study,an appropriate stem taper function was developed for upper stem diameter estimation of white birch(Betula platyphylla Sukaczev)in ten sub-regions of the Daxing’an Mountains,northeast China.Three commonly used taper functions were assessed using a diameter and height dataset comprising 1344 trees.A first-order continuous-time error structure accounted for the inherent autocorrelation.The segmented model of Max and Burkhart(For Sci 22:283–289,1976.https://doi.org/10.1093/fores tscie nce/22.3.283)and the variable exponent taper function of Kozak(For Chron 80:507–515,2004.https://doi.org/10.5558/tfc80507-4)described the data accurately.Owing to its lower multicollinearity,the Max and Burkhart(1976)model is recommended for diameter estimation at specific heights along the stem for the ten sub-regions.After comparison,the Max and Burkhart(1976)model was refitted using nonlinear mixed-effects techniques.Mixed-effects models would be used only when additional upper stem diameter measurements are available for calibration.Differences in region-specific taper functions were indicated by the method of the non-linear extra sum of squares.Therefore,the particular taper function should be adjusted accordingly for each sub-region in the Daxing’an Mountains.展开更多
Invasive plant species may alter soil characteristics or interact with the soil microbial community resulting in a competitive advantage.Our objectives were to determine:i)if invasive plant species alter soil properti...Invasive plant species may alter soil characteristics or interact with the soil microbial community resulting in a competitive advantage.Our objectives were to determine:i)if invasive plant species alter soil properties;and ii)the long-term effects of invasive plant species on soil properties and subsequent implications on ecological restoration efforts.We focused on Lespedeza cuneata,a plant that may be allelopathic.Soil samples were collected from four locations in Central Missouri,USA:an old-field with abundant L.cuneata,two reconstructed sites,and a remnant prairie that has never been plowed.Soil health indictors were used to characterize soil properties at these sites.Nearly every soil property differed significantly between the unplowed prairie reference site and the other three sites.The reconstructed sites,however,generally did not differ from the invaded old-field.These results indicate that the reconstructed prairies are not fully recovered.Although above-ground traits,such as the plant community structure,appear similar to the prairie,the soil microbial community structure still resembles that of an invaded old-field site.These results indicate that more time may be needed before soil microbial populations fully recover after invasive plant removal.展开更多
基金This project was supported by Biotechnology Risk Assessment Grant Program competitive grant no.2011-68005-30407 and 2010-33522-21736from the USDA National Institute of Food and Agriculture and Agricultural Research Service,National Science Foundation I/UCRC Center for Advanced Forestry(grant 0736283)+1 种基金USDA-IFAS(grant OREZ-FS671-R)the J.Frank Schmidt Charitable Foundation,and the TBGRC/GREAT TREES industrial cooperative at Oregon State University.
文摘The spread of transgenes and exotic germplasm from planted crops into wild or feral species is a difficult problem for public and regulatory acceptance of genetically engineered plants,particularly for wind-pollinated trees such as poplar.We report that overexpression of a poplar homolog of the floral repressor SHORT VEGETATIVE PHASE-LIKE(SVL),a homolog of the Arabidopsis MADS-box repressor SHORT VEGETATIVE PHASE(SVP),delayed the onset of flowering several years in three genotypes of field-grown transgenic poplars.Higher expression of SVL correlated with a delay in flowering onset and lower floral abundance,and did not cause morphologically obvious or statistically significant effects on leaf characteristics,tree form,or stem volume.Overexpression effects on reproductive and vegetative phenology in spring was modest and genotype-specific.Our results suggest that use of SVL and related floral repressors can be useful tools to enable a high level of containment for vegetatively propagated short-rotation woody energy or pulp crops.
基金This research is funded by the National Park Service (Task Agreement P19AC01059)。
文摘Overstory basal area,ericaceous shrub cover(Kalmia latifolia L.and Rhododendron maximum L.),and fuels(i.e.,woody fuel loads and depths and O Horizon thickness) were assessed within Great Smoky Mountains National Park,USA,in 2003-2004.Due to recent wildfire activity within the southern Appalachian Mountain region(including Great Smoky Mountains National Park),the potential spread and expansion of ericaceous shrubs,and the impacts of the hemlock woolly adelgid(Adelges tsugae Annand) on eastern hemlock(Tsuga canadensis(L.) Carrière),these same ecosystem components were again assessed in 2019.Elevation and moisture regime(xeric,intermediate,and mesic) were included in this assessment as potential influential factors.An evaluation of repeated measurements from 40 plots suggested that O Horizon thickness did not change significantly over the 16-year period,but increased as elevation increased,and moisture regime(xeric O Horizon thickness> mesic O Horizon thickness) was a significant,related factor.The sum of 1-,10-,and 100-h fuel loads(fuels less <7.6 cm diameter)increased,whereas woody fuel depth decreased over the16-year period.No significant changes in 1000-h fuel lo ads(>7.6 cm diameter),total woody fuel loads,ericaceous shrub cover,total basal area,or live T.canadensis basal area were observed.Live T.canadensis basal area decreased with increasing elevation.Dead,standing T.canadensis basal area increased from 2003-2019,and that increase was most pronounced as elevation increased on xeric and intermediate sites.Overall,we found that:1.hypothesized increases in total woody fuel loads and ericaceous shrub cover were not present;and 2.elevation and moisture regime were most related to observed changes in vegetation and fuel condition.
文摘Recently the Journal of Mountain Science published three papers(Lumbres et al.2014;Jung et al.2015;Lumbres et al.2016)that compared selected taper models for bias and precision when estimating upper stem diameters for various tree species.The purpose of this commentary is to point out the consequences of the choice of the variable to be predicted when fitting taper equations
基金fi nancially supported by the National Natural Science Foundation of China(31570624)Applied Technology Research and Development Plan Project of Heilongjiang Province(GA19C006)Fundamental Research Funds for Central Universities(2572019CP15).
文摘Accurate prediction of stem diameter is an important prerequisite of forest management.In this study,an appropriate stem taper function was developed for upper stem diameter estimation of white birch(Betula platyphylla Sukaczev)in ten sub-regions of the Daxing’an Mountains,northeast China.Three commonly used taper functions were assessed using a diameter and height dataset comprising 1344 trees.A first-order continuous-time error structure accounted for the inherent autocorrelation.The segmented model of Max and Burkhart(For Sci 22:283–289,1976.https://doi.org/10.1093/fores tscie nce/22.3.283)and the variable exponent taper function of Kozak(For Chron 80:507–515,2004.https://doi.org/10.5558/tfc80507-4)described the data accurately.Owing to its lower multicollinearity,the Max and Burkhart(1976)model is recommended for diameter estimation at specific heights along the stem for the ten sub-regions.After comparison,the Max and Burkhart(1976)model was refitted using nonlinear mixed-effects techniques.Mixed-effects models would be used only when additional upper stem diameter measurements are available for calibration.Differences in region-specific taper functions were indicated by the method of the non-linear extra sum of squares.Therefore,the particular taper function should be adjusted accordingly for each sub-region in the Daxing’an Mountains.
文摘Invasive plant species may alter soil characteristics or interact with the soil microbial community resulting in a competitive advantage.Our objectives were to determine:i)if invasive plant species alter soil properties;and ii)the long-term effects of invasive plant species on soil properties and subsequent implications on ecological restoration efforts.We focused on Lespedeza cuneata,a plant that may be allelopathic.Soil samples were collected from four locations in Central Missouri,USA:an old-field with abundant L.cuneata,two reconstructed sites,and a remnant prairie that has never been plowed.Soil health indictors were used to characterize soil properties at these sites.Nearly every soil property differed significantly between the unplowed prairie reference site and the other three sites.The reconstructed sites,however,generally did not differ from the invaded old-field.These results indicate that the reconstructed prairies are not fully recovered.Although above-ground traits,such as the plant community structure,appear similar to the prairie,the soil microbial community structure still resembles that of an invaded old-field site.These results indicate that more time may be needed before soil microbial populations fully recover after invasive plant removal.