Skip to main content
Advanced Search

Filters: Tags: STEPPE (X) > Extensions: Citation (X)

3 results (22ms)   

View Results as: JSON ATOM CSV
A well-dated pollen record from a large lake located on the meadow?steppe ecotone provides a history of ecotone shift in response to monsoonal climate changes over the last 6000 years in the central Tibetan Plateau. The pollen record indicates that the ecotone shifted eastward during 6000?4900, 4400?3900, and 2800?1600 cal. yr BP when steppes occupied this region, whereas it shifted westward during the other intervals when the steppes were replaced by meadows. The quantitative reconstruction of paleoclimate derived from the pollen record shows that monsoon precipitation fluctuated around the present level over the last 6000 years in the central Tibetan Plateau. Three major drought episodes of 5600?4900, 4400?3900,...
Plants of four Great Basin grass species were grown from seed in two greenhouses at low (340 ? l l-1) and high (680 ? l l-1) CO2 concentration. In all four species, high CO2 promoted mean increases in the number of basal stems, leaf area, specific leaf weight and above-ground dry weight. High CO2 resulted in an increase in CO2 assimilation in two C3 grasses but not in a C4 grass, while all three species showed decreases in stomatal conductance. Mean increases of 60% in aboveground dry weight and 80% in water-use-efficiency are consistent with previously reported high CO2 effects on grasses. No consistent differential effects of high CO2 were observed when comparing annual vs perennial species. Global CO2 enrichment...
Water availability defines and is the most frequent control on processes in arid and semiarid ecosystems. Despite widespread recognition of the importance of water in dry areas, knowledge about key processes in the water balance is surprisingly limited. How water is partitioned between evaporation and transpiration is an area about which ecosystem ecologists have almost no information. We used a daily time step soil water model and 39 years of data to describe the ecohydrology of a shortgrass steppe and investigate how manipulation of soil and vegetation variables influenced the partitioning of water loss between evaporation and transpiration. Our results emphasize the overwhelming importance of two environmental...