Responses of soil fungal community to the sandy grassland restoration in Horqin Sandy Land, northern China.

Sandy grassland restoration is a vital process including re-structure of soils, restoration of vegetation, and soil functioning in arid and semi-arid regions. Soil fungal community is a complex and critical component of soil functioning and ecological balance due to its roles in organic matter decomposition and nutrient cycling following sandy grassland restoration. In this study, soil fungal community and its relationship with environmental factors were examined along a habitat gradient of sandy grassland restoration: mobile dunes (MD), semi-fixed dunes (SFD), fixed dunes (FD), and grassland (G). It was found that species abundance, richness, and diversity of fungal community increased along with the sandy grassland restoration. The sequences analysis suggested that most of the fungal species (68.4 %) belonged to the phylum of Ascomycota. The three predominant fungal species were Pleospora herbarum, Wickerhamomyces anomalus, and Deconica Montana, accounting for more than one fourth of all the 38 species. Geranomyces variabilis was the subdominant species in MD, Pseudogymnoascus destructans and Mortierella alpine were the subdominant species in SFD, and P. destructans and Fungi incertae sedis were the dominant species in FD and G. The result from redundancy analysis (RDA) and stepwise regression analysis indicated that the vegetation characteristics and soil properties explain a significant proportion of the variation in the fungal community, and aboveground biomass and C:N ratio are the key factors to determine soil fungal community composition during sandy grassland restoration. It was suggested that the restoration of sandy grassland combined with vegetation and soil properties improved the soil fungal diversity. Also, the dominant species was found to be alternative following the restoration of sandy grassland ecosystems.

[Physiological response of corn seedlings to changes of wind-sand flow strength].

Corn seedlings are often harmed by strong wind-sand in the spring in semi-arid wind-sand area of west of Northeast China. In order to understand physiological response mechanisms of the corn seedlings to wind-sand damage, the changes in MDA content, membrane permeability, protective enzymes activities and osmotic regulation substances at 0 (CK) , 6, 9, 12, 15 and 18 m . s-1 wind speed (wind-sand flow strength: 0, 1.00, 28.30, 63.28, 111.82 and 172.93 g . cm-1 . min-1, respectively) for 10 min duration were studied during the spring, 2013 in the Horqin Sand Land of Inner Mongolia. The results showed that effects of wind-sand flow blowing on the RWC of the corn seedling were lighter in the 6-12 m . s-1 treatments, but the RWC decreased by 19.0% and 18.7% in the 15 m . s-1 and 18 m . s-1 treatments compared to the CK, respectively. The MDA content tended to decline with increasing the wind-sand flow strength, and decreased by 35.0% and 39.0% in the 15 m . s-1 and 18 m . s-1 treatments compared to the CK, respectively. The membrane permeability increased significantly with increasing the wind-sand flow strength, and increased by 191.3% and 187.8% in the 15 m . s-1 and 18 m . s-1 treatments compared to the CK, respectively. With the increase of wind-sand flow strength, SOD activities decreased and changes of CAT activities were not significant, only POD activities increased significantly, which played an important role in the process of scavenging reactive oxygen species and protecting cell membrane against damage. For lighter water stress caused, by wind-sand flow blowing, proline and soluble sugar did not play any role in osmotic adjustment, but the proline content increased by 11.4% and 24.5% in the 15 m . s-1 and 18 m . s-1 treatments compared to the CK, respectively, which played an important role in osmotic adjustment.

[Effects of sand burial on growth and physiological process of Agriophyllum squarrosum seedlings in Horqin Sand Land of Inner Mongolia, North China].

In 2010-2011, a sand burial experiment was conducted on the Horqin Sand Land of Inner Mongolia to study the growth characteristics and physiological properties of Agriophyllum squarrosum seedlings under different depths of sand burial. The A. squarrosum seedlings had stronger tolerance against sand burial. The seedling growth could be severely inhibited when the burial depth exceeded seedling height, but some seedlings could still be survived when the burial depth exceeded 1.66 times of seedling height. When the burial depth did not exceed the seedling height, the seedling MDA content and membrane permeability had no significant change, but the lipid peroxidation was aggravated and the cell membrane was damaged with increasing burial depth. Under sand burial stress, the seedling SOD and POD activities and proline content increased significantly, while the seedling CAT activity and soluble sugar content deceased. Sand burial decreased the leaf photosynthetic area and damaged cell membrane, inducing the increase of seedling mortality and the inhibition of seedling growth. The increase of SOD and POD activities and proline content played a definite role in reducing the sand burial damage to A. squarrosum seedlings.

[Characteristics of Caragana microphylla sap flow and water consumption under different weather conditions on Horqin sandy land of northeast China].

Employing heat balance Dynamax packaged sap flow measuring system and automatic weather recording system, the sap flow of artificial Caragana microphylla community on Horqin sandy land of northeast China was monitored consecutively in 2006, and the photosynthetically effective radiation, air temperature, relative humidity and wind velocity were measured synchronously. According to the manual records of weather conditions, four most representative weather conditions were gathered up to analyze the relationships of C. microphylla sap flow and its single branch water consumption with test meteorological factors. The results showed that under high air temperature and intense radiation on sunny days, the diurnal variation of C. microphylla sap flow appeared a broad peak curve, so as to adapt the circumstance of drought and water shortage via lower transpiration. The diurnal variations of sap flow and its dominant affecting factors differed with weather conditions, and photosynthetically effective radiation was always the dominant factor affecting the sap flow. The variation of the sap flow was the result of comprehensive effects of multi-meteorological factors, and the overall variation trend of water consumption of single branch was declined in the order of sunny days > cloudy days > windy days > rainy days, with the mean value being 459, 310, 281 and 193 mg x d(-1), respectively.