The Experts below are selected from a list of 4197 Experts worldwide ranked by ideXlab platform
Om P. Rajora - One of the best experts on this subject based on the ideXlab platform.
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Effects of Silvicultural Practices on genetic diversity and population structure of white spruce in Saskatchewan
Tree Genetics & Genomes, 2013Co-Authors: Manphool S. Fageria, Om P. RajoraAbstract:Forest harvesting and renewal Practices using clearcut harvesting followed by artificial and natural regeneration (NR) may impact genetic diversity in subsequent forest tree populations. Plantations (PL) and phenotypic selections may exhibit lower genetic diversity than natural old growth (OG) and naturally-regenerated young populations because they may have a narrow genetic base. We used ten (six EST and four genomic) microsatellite loci, to reassess genetic impacts of Silvicultural Practices in white spruce (Picea glauca), previously assessed by using 51 RAPD markers by Rajora (1999). Allelic diversity at the genomic microsatellite loci was about three times higher than at the EST-derived microsatellite loci. Although the trends for microsatellite genetic diversity among different stands types were similar to that observed for RAPD markers, with natural OG stands showing the highest and tree improvement selections the lowest allelic and genotypic genetic diversity, no significant differences were observed for microsatellite genetic diversity among OG, young NR, PL and open-pollinated progeny of first-generation phenotypic selections (SEL). The inbreeding levels and genetic differentiation among populations within OG, NR and PL were also similar. However, phenotypic selections had somewhat different genetic constitution as they showed the highest genetic distances with OG, NR and SEL. On the other hand, the lowest genetic distances were observed between the OG and NR stands, which also had similar levels of genetic diversity. Our study suggests no significant negative impacts of harvesting and alternative reforestation Practices on microsatellite genetic diversity in white spruce and calls for using more than one marker type in assessing the genetic impacts of Silvicultural Practices in forest trees.
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Genetic biodiversity impacts of Silvicultural Practices and phenotypic selection in white spruce
Theoretical and Applied Genetics, 1999Co-Authors: Om P. RajoraAbstract:Forest-management Practices relying on natural and/or artificial regeneration and domestication can significantly affect genetic diversity. The aim of the present study was to determine and compare the genetic diversity of the pristine old-growth, naturally and artificially regenerated and phenotypically selected white spruce, and to determine the genetic-diversity impacts of Silvicultural Practices. Genetic diversity was determined and compared for 51 random amplified polymorphic DNA (RAPD) loci for the adjacent natural old-growth, naturally regenerated and planted white spruce stands at each of four sites, one oldest plantation and open-pollinated progeny of 30 phenotypic tree-improvement selections of white spruce from Saskatchewan. Each of the 420 white spruce individuals sampled was genetically unique. The old-growth stands had the highest, and the phenotypic selections the lowest, genetic diversity. The genetic diversity of the natural regeneration was comparable to that of the old-growth, whereas the genetic diversity of the plantations was comparable to that of the selections. On average, the genetic diversity of the old-growth and natural regeneration was significantly higher than that of the plantations and selections. The mean percent of loci polymorphic, the number of alleles per locus, the effective number of alleles per locus, heterozygosity, and Shannon’s index was 88.7, 83.8, 72.2 and 66.7; 1.89, 1.84, 1.72 and 1.67; 1.69, 1.62, 1.53 and 1.46; 0.381, 0.349, 0.297 and 0.259; and 0.548, 0.506, 0.431 and 0.381 for the old-growth stands; natural regeneration; plantations; and open-pollinated progeny of selections; respectively. Reduced genetic diversity in the plantations and selections suggest that their genetic base is relatively narrow, and should therefore be broadened in order to maintain genetic diversity, and sustainably manage and conserve white spruce genetic resources.
William P Fowler - One of the best experts on this subject based on the ideXlab platform.
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responses of benthic macroinvertebrates in small intermittent streams to Silvicultural Practices
Hydrobiologia, 1997Co-Authors: Arthur V Brown, Yolanda Aguila, Kristine B Brown, William P FowlerAbstract:We examined macroinvertebrate communities in small(0.1-1.0 m2) pools of intermittent streams (alwayscontainingsome water but without perennial flow) with small watersheds(2-6 ha) subjected to five types of forest harvest to assesspotential impacts of the different harvest methods. Bufferstrips10 m wide were left on each side of the streams. Each harvesttreatment was coupled with a similar unharvested referencestand.An incomplete block design included three 0.05 m2 vacuumsamples from each treatment paired with three from theadjacentreferences. There was a high degree of similarity amongreferencesfor parameters other than taxonomic composition (e.g.macroinvertebrate density, number of species, Shannondiversity,functional groups, etc.). Statistically significantdifferenceswere found between references and treatments and among harvestmethods but the responses varied among response variables(density,Shannon-Weiner diversity, species composition), differentspeciesassemblages (all invertebrates, chironomids,Ephemeroptera-Plecoptera-Trichoptera [EPT], isopods), andfunctional group categories (shredders, collector-gatherers).Wecollected 56 taxa, 7–16 per site, with low communitysimilarity(mean Jaccard‘s = 0.18, mean Bray-Curtis percentdissimilarity = 81). The most severe harvest treatmentsresultedin the highest diversities of total invertebrates in thesesmallspring pool communities.
Marcos A. Pedlowski - One of the best experts on this subject based on the ideXlab platform.
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Tropical forest management and Silvicultural Practices by small farmers in the Brazilian Amazon: recent farm-level evidence from Rondonia
Forest Ecology and Management, 2004Co-Authors: Percy M. Summers, John O. Browder, Marcos A. PedlowskiAbstract:This paper examines forest management and Silvicultural Practices of small colonist landholders in the western Brazilian Amazon state of Rondonia. Although recent colonists in the Amazon are widely acknowledged as key agents of tropical forest conversion, relatively little is known of their uses of primary and secondary forest patches and the degree to which these farmers plant trees as part of their land use strategies. Based on longitudinal survey data drawn from three different colonist settlements in 1992 and 2002, this paper explores the range of small farmer's uses of forests and fallows that may indicate future trends in forest management. We also examine the links between forest extraction and tree planting and the factors that may influence these Practices. We found that nearly 40% of the farmers surveyed regularly extract useful products from their forests. We examine the types and quantities of timber and non-timber forest products extracted by small farmers over this 10-year study period, and reasons given by them for managing or not managing their forest patches. Forest extractor households were characterized as having a smaller percentage of their land deforested and smaller cattle herds. In addition, we found that roughly 30% of the small farmers surveyed planted trees on their farms during this 10-year study period. Results of statistical analysis (ANOVA and chi square contingency tests) to identify factors that correlate with tree planting behavior indicate that tree planters own larger plots, reside longer on those plots, have a larger number of working age household members, and secure land titles. They were also more likely to participate in social organizations. We conclude that despite ongoing deforestation processes in the region, natural forest use is an important subsistence activity for many small farmers and that many farmers are planting and managing tree species for both short-term products and as long-term investments. # 2004 Published by Elsevier B.V.
Rafael Vivian - One of the best experts on this subject based on the ideXlab platform.
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atlantic forest tree species responses to Silvicultural Practices in a degraded pasture restoration plantation from leaf physiology to survival and initial growth
Forest Ecology and Management, 2014Co-Authors: Otavio Camargo Campoe, Claudia Iannelli, Jose Luiz Stape, Rachel L Cook, Joao Carlos Teixeira Mendes, Rafael VivianAbstract:Abstract Deforestation has led to ecosystem degradation in many tropical regions. Re-establishment of native tree species on degraded land presents challenges due to environmental stressors such as water and nutrient limitations, particularly from weed competition. Ecophysiological studies can help assess responses of native tree species to Silvicultural Practices and improve our understanding of processes that influence their establishment and growth. Silvicultural treatments borrowed from commercial tree plantations such as greater nutrient applications and complete weed control can improve best Silvicultural Practices in forest restoration. Two contrasting Silvicultural treatments, “traditional” based on common management Practices for reforestation of native trees and “intensive” based on commercial plantation silviculture, were evaluated based on tree mortality, biomass, photosynthesis, chlorophyll content, soluble proteins, and nutritional status of 20 native Brazilian species, 2.5 years after planting. Intensive silviculture increased tree survival by 20%, showed higher aboveground biomass from 13% to 7-fold and increased photosynthesis of ∼20% from 15.8 μmol m−2 s−1 to 18.7 μmol m−2 s−1, compared to traditional silviculture. Total soluble proteins were 14% higher with 6.7 μg cm−2 in intensive silviculture compared to 5.9 μg cm−2 under traditional silviculture. Eighty percent of trees showed greater N content, with a 13% higher average than under traditional silviculture (2.60 g m−2 versus 2.92 g m−2). Average values of chlorophyll A, B, and total were ∼8% higher under intensive silviculture, but not significantly different between treatments. Overall, intensive silviculture provided a positive impact on the restoration plantation. During the initial years of plantation establishment, intensive silviculture methods were effective in leading to significant increases in growth and survival.
Manphool S. Fageria - One of the best experts on this subject based on the ideXlab platform.
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Effects of Silvicultural Practices on genetic diversity and population structure of white spruce in Saskatchewan
Tree Genetics & Genomes, 2013Co-Authors: Manphool S. Fageria, Om P. RajoraAbstract:Forest harvesting and renewal Practices using clearcut harvesting followed by artificial and natural regeneration (NR) may impact genetic diversity in subsequent forest tree populations. Plantations (PL) and phenotypic selections may exhibit lower genetic diversity than natural old growth (OG) and naturally-regenerated young populations because they may have a narrow genetic base. We used ten (six EST and four genomic) microsatellite loci, to reassess genetic impacts of Silvicultural Practices in white spruce (Picea glauca), previously assessed by using 51 RAPD markers by Rajora (1999). Allelic diversity at the genomic microsatellite loci was about three times higher than at the EST-derived microsatellite loci. Although the trends for microsatellite genetic diversity among different stands types were similar to that observed for RAPD markers, with natural OG stands showing the highest and tree improvement selections the lowest allelic and genotypic genetic diversity, no significant differences were observed for microsatellite genetic diversity among OG, young NR, PL and open-pollinated progeny of first-generation phenotypic selections (SEL). The inbreeding levels and genetic differentiation among populations within OG, NR and PL were also similar. However, phenotypic selections had somewhat different genetic constitution as they showed the highest genetic distances with OG, NR and SEL. On the other hand, the lowest genetic distances were observed between the OG and NR stands, which also had similar levels of genetic diversity. Our study suggests no significant negative impacts of harvesting and alternative reforestation Practices on microsatellite genetic diversity in white spruce and calls for using more than one marker type in assessing the genetic impacts of Silvicultural Practices in forest trees.
