Graduate Thesis Or Dissertation

 

Evaluation of native and introduced plant species for revegetating Central Tunisian rangelands Public Deposited

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/47429d787

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  • The evaluations performed in this thesis were intended to provide a partial basis for the selection of species and varieties for reseeding Central Tunisian rangelands. The first evaluation determined the effects of four moisture regimes and two growth mediums on seedling emergence and early root and shoot development of eight plant species under greenhouse conditions. Seeds of Medicago laciniata (MELA), Hedysarum carnosum (HECA), H. spinosissimum (HESP), Argyrolobium uniflorum (ARUN), Oryzopsis miliacea (ORMI), and Dactylis glomerata [DAGL(TN)] were collected from indigenous sources in Central Tunisia. Seeds of Dactylis glomerata (Palestine) [DAGL(PN)] and Atriplex canescens (ATCA) were obtained from the United States. Days to 50% emergence and final emergence rates of all species were not affected by growth mediums and moisture regimes during the 15-day period. Days to 50% emergence ranged from 1 day for MELA to 9 days for ORMI. Roots of HESP penetrated deeper than the others in clay under all moisture regimes. Roots of DAGL(PN) and DAGL(TN) penetrated deeper when pots were allowed to dry 3 weeks before being watered than 1, 2 or 4 weeks. Root to shoot weight ratios for all species were higher in sand than in clay. Root depth and root to shoot weight ratio of ATCA increased as soil moisture decreased in both growth mediums. Root to shoot weight ratio of ARUN increased as water deficits increased in sand. Limited potential to develop root and shoot growth as water deficits increased was shown for HECA and ORMI. MELA, DAGL(PN and TN), and ARUN were suggested to revegetate sites with dry sand soils whereas HESP was recommended for revegetation sites with dry clay soils. In addition, DAGL(PN), DAGL(TN) and ATCA may also hold promise for reseeding clay soils. The second evaluation determined the adaptability of 142 selected grass and forb species and varieties to Central Tunisia (BRIKATE, SAYADA NORD and SBIBA). Mean densities of species and varieties were recorded at the end of each growing season. Several species and varieties failed to emerge in each site while others emerged but failed to survive through the second growing season. Few species and varieties survived through the second growing season in each site. Based on the mean densities recorded at the end of the second growing season for species and varieties which survived, species recommended for each area included: BRIKATE SITE: Scorpius myroculis, Plantago albicaulis, Medinago ciliaris, Hedysarum coronarium, Medysarum carnosum, SAYADA NORD SITE: Agropyron sibiricum, Agropyron desertorum "Nordan", Agropyron dasystachyum "Critana", Plantago albicaulis, Hedysarum coronarium, Medicago truncatula, SBIBA SITE: Agropyron elongatum "Largo", "Gose", Agropyron intermedium "Oahe", "Tegmar", "Trigo", Agropyron trachycaulum "Revenue", Agropyron sibiricum, Plantago albicaulis, Hedysarum coronarium, Trifolium vesiculosum, Hedysarum carnosum
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