Elaheh Fahimipour; Jamshid Ghorbani; Ghodratollah Heydari
Abstract
Soil seed bank has an important role in vegetation restoration following cessation of disturbance. In this study, the soil seed bank richness and diversity were investigated in semi-steppic rangeland with a history of land conversion into cultivation in Charmahal-Bakhtiari province. Land-use changes ...
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Soil seed bank has an important role in vegetation restoration following cessation of disturbance. In this study, the soil seed bank richness and diversity were investigated in semi-steppic rangeland with a history of land conversion into cultivation in Charmahal-Bakhtiari province. Land-use changes were identified in grassland and shrubland and then were classified into four groups according to the time since abandonment including < 5, 5-15, 15-25 and > 25 years. Aspect was considered in each group. Soil was sampled and seed bank was identified using seedling germination method in glasshouse. Then, seed bank richness and diversity indices were calculated. Results showed that in seed bank the number of perrenilas was greater than annuals. In both grassland and shrubland time since abandonment significantly influenced the soil seed bank richness and diversity. In grassland soil seed bank richness and diversity decreased with time of abandonment but in area with more than 25 yrs of abandonment seed abnk richness and diversity significantly increased. Aspect significantly affected both seed bank richness and diversity in shrubland. North slpoe showed fluctuation in seed bank richness and diversity during abandonment while an increase was found in west slope and a reduction in south and east slopes. In both sites the soil seed bank indices significantly increased shortly after abandonment (<5 yrs) but seed bank richness and diversity showed resilient in >25 yrs in grassland and >15 yrs in shrubland.
Hamidreza Mirdavoodi; Younes Asri; Gholamreza Goudarzi; Ali Famaheini
Abstract
Studying species diversity and analyzing of the relationships between plants, environmental factors and disturbance play an important role in studying the dynamics and management of ecosystems. We studied the species diversity patterns in relation to some physiographic factors and grazing along an altitudinal ...
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Studying species diversity and analyzing of the relationships between plants, environmental factors and disturbance play an important role in studying the dynamics and management of ecosystems. We studied the species diversity patterns in relation to some physiographic factors and grazing along an altitudinal gradient of 1000 meters and at different altitudes with 100-m intervals. The Margalef, Sheldon, and Shannon-Wiener indexes were used to assess richness, evenness and diversity, respectively. Partial Canonical Correspondence analysis was used to investigate the relationship between vegetation, physiographic factors (with an emphasis on altitude) and grazing. The study of the relationship between altitude and grazing showed a significant correlation between these two factors (P <0.01, R2 = 0.55). Results showed that increased species diversity and richness was observed at lower altitudes up to 2200 meters above sea level; however, at the altitude above 2200 m, the species diversity and richness decreased. This result is consistent with the mid-domain effect (MDE) hypothesis. Overgrazing at low altitudes has led to a shift in vegetation toward annual and ruderals species. The areas with intermediate grazing had the highest richness and diversity and the areas with high and low grazing intensity had the lowest richness and diversity. This result is consistent with the intermediate disturbance hypothesis. Species evenness also increased with increasing grazing intensity, although these changes were not significant (P> 0.05). Therefore, the changes in species diversity along ecological gradients cannot be evaluated without considering the grazing intensity.
Hamidreza Mirdavoodi; Adele Jalili; Ziba Jamzad; Ali Famaheini
Abstract
Classification of species in plant functional types (PFTs) according to Grime’s CSR theory has been found useful in understanding ecosystem functioning and processes and in quantifying variation along environmental gradients. The aim of this study was to assess variations in CSR strategies along ...
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Classification of species in plant functional types (PFTs) according to Grime’s CSR theory has been found useful in understanding ecosystem functioning and processes and in quantifying variation along environmental gradients. The aim of this study was to assess variations in CSR strategies along stress and grazing gradients in Meyghan playa of Arak. The strategy of plant species was determined according to the Grime’s CSR strategies, based on Pierce’s method. Random- Systematic design was applied to sampling. Two-way indicator species analysis (TWINSPAN) was applied to classification of the ecological plant groups, and partial canonical correspondence analysis (pCCA) was used to identify relationship between environment factors, disturbance and the plant groups studied, using the PC-ORD4.17 and CANOCO4.5 software, respectively. Among the factors that affect plant functional types and the structure of vegetation, soil salinity as a stress factor and grazing as a kind of disturbance were studied. Results showed that stress-tolerant peaked in conditions of high salinity. Competitors with a frequency of 14.3% were mostly present in conditions of low salinity and disturbance/light grazing. Ruderals with a frequency of 7.1% were mostly present in condition of overgrazing. The presences of competitor in protected areas with low soil salinity confirmed the theory of appearance of competitive strategy in low/stress-free areas and light/graze-free. Therefore, it may be possible to use Grimes’s PFTs for assessing environmental constraints and predicting whether a species with a specific strategy is likely to be positively or negatively affected by changes in environmental stress due, for instance, to climate change.
