Uzbekistan: Rehabilitation of Desert Rangelands Affected by Salinity, to Improve Food Security, Combat Desertification and Maintain the Natural Resource Base - Combating Desertification in Asia, Africa and the Middle East - page 244

closure and consequently increase the intrinsic water-use efficiency (Naoko et al.
Unpublished data). There was, however, no report that presented the response of the
d 13 C of leaf organic matter to the salinity
Carbon and oxygen isotope ratios were expressed by the following equation:

R sam

R std

• 13 Cor ￿ 18 O

D 1000 ./

R std

where R sam and R std represent the 13 C/ 12 Cor 18 O/ 16 O of the samples and standard,
respectively. PDB and VSMOW were used for the standards for d 13 Candd 18 O,
respectively.
The photosynthetic organ samples (leaves and short pieces of stems in the case
of aphyllous species) were oven-dried at 70 ı C for 48 h and finely ground. The
d 13 C in the organic samples was analyzed using a continuous flow system of an
elemental analyzer and an isotope ratio mass spectrometer (Flash 2000 and Delta S,
Thermo Fisher Scientific) at Field Science Education and Research Center, Kyoto
University, Japan.

3 Results and Grazing Management Implications

3.1 Spatio-Temporal Changes of Vegetation of Semi-desert

Rangelands Along a Grazing Gradient

The long term effect of grazing on semi-desert rangeland vegetation was studied
in proximity of a typical watering well located 25 km south-east of Zirabulak
Mountains in Karnabchul. Vegetation parameters (projective cover, density, green
biomass of perennials and above-, below ground biomass of annuals) were collected
in a radius of 3,000 m from the watering point.
Vegetation cover of study site is strongly affected by livestock grazing. Radial
attenuation of stocking and grazing pressure from the watering point (the so-called
piosphere effect, Lange 1969 ) resulted in changes in perennial and annual species
composition. Radial symmetry of grazing pressure is resulted in rapid changes of
vegetation community. The spatial variability that was observed shows gradients,
and is derived from intense grazing around water sources at the well site. Grazing-
driven changes in perennial and annual species composition in the closest areas and
intermediate distances from the focal point were demonstrated as presence/absence
of unpalatable/palatable species in plant composition.
The prevailing vegetation stratum of the study area is dominated by semi shrub
( Artemisia diffusa ) and perennial/annual herbaceous species (e.g. Carex pachystylis ,
Poa bulbosa , Bromus tectorum , Alyssum desertorum , Trigonella noeana ). Existing
physiognomy and floristic pattern of Karnabchul represents homogeneous type
of vegetation which is commonly described as Artemisia -ephemeral rangelands