RESUMEN
Seasonal changes in soil respiration (SR), soil temperature (ST) and soil moisture (SM) were compared between a barren land with no vegetation (control) and grassland dominated by Heteropogon contortus (L.) of a semi-arid eco-system during 2005-2006. A statistically significant (p<0.001) seasonal change in SR was observed between the two sites. The variation characteristics of soil CO2 efflux rates were observed during wet periods along precipitation gradients and it was consistently higher in grasslands than in control. A maximum soil CO2 efflux of 13.35 ± 0.33 Amol m-2 s-1 in grassland and 7.33 ± 0.8 Amol m-2 s-1 in control was observed during rainy season-II, i.e., from October to December, a minimum of 1.27 ± 0.2 Amol m-2 s-1 in grassland and 0.67 ± 0.5 Amol m-2 s-1 in control during summer season, i.e., from March to June. A positive significant relation observed between soil respiration and soil moisture (r2 above 0.8) and no significant relation was observed between soil CO2 efflux and soil temperature (r2 below 0.3). In water-limited semi-arid ecosystem, rewetting of the soil due to precipitation events triggered the increased pulses of soil respiration especially in grassland when compared to the barren land. The observed soil respiration rates during summer and after the subsequent precipitation events strongly indicated that the soil water-deficit conditions reduce the efflux both in barren land (control) and in grassland of semi-arid eco-system.
RESUMEN
Arid and semi-arid climates and antropojen effects have caused rapid deterioration of the natural resources in the watershed. The main objectives of the study were to determine the correlation between soil properties and flora and to examine some soil properties and floristic composition under natural forest and afforestration. The topographical, geological and stand viewing maps of the watershed belong to 1955 and 2006 years were eximaned in the study. According to this study, the 14.5% rate of black pine forest in 1955 increased to 35.8% in 2006. Degraded forest, degraded black pine and agricultural area decreased respectively to 5.7, 1.8 and 15.8% in 51 years. The richest families in the research area were Asteraceae, Fabaceae, Lamiaceae, Poaceae, Brassicaceae, Caryophyllaceae, Scrophulariaceae, Boraginaceae, Apiaceae and Rosaceae. The rate of the richest families was 71.75% in the total species, the remaining 22 families were scattered to 28.25% in proportion of species.