The aim of this study was to investigate the spatial distribution patterns of soil seed bank of Stipagrostis pennata (Trin.) de Winter during different seasons in the Gurbantonggut Desert of north-west China.Results indicated that spatial patterns of the soil seed bank of S. pennata were similar to the distribution patterns of its associated standing vegetation, and there was a significant variation in soil seed densities among the different parts of the dunes.The highest soil seed density was found on the top of sampled dunes and in the soil of the underlayers of standing vegetation beds of S. pennata.The number of seeds stored in the soil decreased with distance from established stands of this grass species.Moreover, during secondary seed dispersal, which is air-borne in the windy season, a small proportion of seeds was also trapped by other plant species.Furthermore, the directional density distribution of seeds was strongly associated with the directions of the prevailing threshold wind (X6ms 1), and higher soil seed densities usually occurred on the leeward side of the vegetation stands.Based on these investigations, wind is, probably, the key factor in forming the spatial patterns of S. pennata seed banks in the region.On the other hand, grazing affected the quality and quantity of S. pennata seed storage, as a result of delayed development and the above-ground shoots being damaged by grazing.This occurred in spring to early summer, which is the most suitable growth season for the grass.Nevertheless, grazing had little influence on the spatial distribution patterns of the seed bank over all seasons.Germination trials showed that the percentage of viable soil seeds increased continuously throughout summer and autumn.The results also revealed the clear ecological characteristics influencing the population distribution of S. pennata.

A field experiment was conducted at the Haiyuan Experimental Station (36º34′N, 105º39′E), in a semiarid region of China, from 2000 to 2003 for rain-fed spring wheat (Triticum aestivum) production to maximize the utilization of low rainfall. This paper reports the two field cultivations of rainwater harvesting with a sowing in the furrow between film-covered ridges (SFFCR), and with a sowing in the holes on film-covered ridges (SHFCR). At the same time, the periods and indices of supplemental irrigation during the whole growth stage of rain-fed spring wheat were also studied. The periods of supplemental irrigation included the three-leaf stage (irrigated once), the elongation stage to flowering stage (irrigated twice), and the flowering stage to filling stage (irrigated once). The indices of supplemental irrigation during the whole growth stage of rain-fed spring wheat must reach over 59 and 40 mm in order to realize the 2250 and 2000kg ha 1 yield, respectively. This research also presented such a concept of efficient water saving supplemental irrigation, which was considered as a new index of water saving irrigation. The experimental result showed that the efficiency of water saving supplemental irrigation of field cultivation with SFFCR was 5.5-5.8%, and with SHFCR was 9.4-9.6%. The efficiency of water saving supplemental irrigation of field cultivation with SHFCR was improved by 40.4% in comparison with SFFCR. Consequently, in this region, the integration of rainwater harvesting and supplemental irrigation can play a crucial role in the improvement of rain-fed spring wheat yields and water use.

The recovery of vegetation cover following soil disturbance by the plateau zokor (Myospalax baileyi) was investigated from 2001 to 2004 in a subalpine meadow of the Qinghai-Tibet Plateau. Two adjacent plots were compared: one control community (undisturbed by zokors for over 5 years) and one disturbed community (with new mounds present before enclosure in year 2000). Vegetation on mounds tended to recover over time. Plant diversity, cover, biomass and density reached 88.5%, 87.9%, 73.1%, and 52.7% of the values for the control community, respectively, over the 4-year period when zokors were excluded. The edges around mounds showed a gradual increase in aboveground biomass and vegetation density from 2001 to 2004, which compensated for the lack of plant cover on the center of the mounds. The total number of species in the disturbed community increased from 15 in 2001 to 27 in 2004, and contained three alien species which were not found in the control plot, which contained 30 species. The average species diversity in mound sites (41.8) was generally higher than that of the control plot (1.7). It is probable that plateau zokors are important for maintaining or restoring the disturbance-dependent elements of native plant communities. In addition, zokor disturbance resulted in a significant change in soil particle size, increased soil water content from about 20% to 25% and soil organic carbon content from 108 to 114g/kg (0-20cm soil layer) after 4 years of restoration. The improvement in soil quality might be associated with the rate of vegetation recovery following zokor disturbance. Therefore, through modulation of vegetation recovery, plateau zokors might be said to act as ecosystem engineers in alpine meadows.

The objectives of this study were to: (1) characterize the evolutional tendency of the non-hydraulic root-sourced signal (NRS) from wheat wild relatives to its modern hexaploid species, and (2) test whether species sensitivity to the NRS was allied with their drought tolerance profiles. The NRS was judged to begin when there was a significant lowering of stomatal conductance without change in leaf relative water content (RWC). The lethal soil water content (LSWC) was operationally characterized as the soil water content (SWC) at the drying lethal point of wheat plants. The threshold of soil water content (TSWC) at which the NRS was triggered, and the LSWC differed amongst six wheat species. For "MO1" and "MO4" representing 'diploid' species, the TSWC and the LSWC were initiated successively at about 51% FWC (field water capacity) and about 30% FWC, respectively. Conversely, "Plateau 602" and "Longchun 8139-2" (modern hexaploid species) exhibited the TSWC and the LSWC between about 68% FWC and less than 14% FWC, a much wider threshold range (TR). Increasing TSWC was significantly correlated with decreasing LSWC (r=0.9464**). The widened TR from the TSWC to the LSWC was also significantly correlated with longer survival days (SD) and higher maintenance ratio of grain yield (MRGY), respectively (r=0.9411** and 0.8068*, respectively). Meanwhile, those species having higher TSWC had the least reduction ratio of stomatal conductance under the decreasing soil moisture from −0.2 to −1MPa. This suggests that advances in yield performance and drought tolerance would be made evolutionally by targeted selection for an earlier onset of NRS.

An improved Costanza model was developed to assess the health of the Jin he River Watershed ecosystem. The watershed is located at the center of the Huangtu Plateau in China and has suffered a severe disturbance in the last few decades. Three indicators including vigor, organization, and resilience were calculated respectively by merging ground-based observations with remotely sensed data on a watershed scale. Health indices of 12 topographic sub-watersheds were calculated using a modified Costanza formula. Health evaluated results indicated that sub-watersheds in the Huangtu mountain region were relatively healthy ecosystems with scores over 0.673. The sub-watersheds in the loess mountain and the loess gully regions, e.g., Jinghe, Heihe, and Honghe regions, scored moderately; their evaluated value ranged from 0.505 to 0.606. The two sub-watersheds in the loess gully region and all sub-watersheds in the loess hilly region scored the lowest, less than 0.50 and were considered unhealthy ecosystems. It can be argued that the loess hilly region and the loess gully regions should be in primary consideration for ecological protection and rehabilitation. This study provided a possible quantitative model for ecological planning and landscape management with respect to topographic conditions in this area.