[Inter- and intra-annual dynamics of vegetation litter at different habitats in Horqin Sandy Land, China.] / ç§‘å°”æ²æ²™åœ°ä¸åŒç”Ÿå¢ƒæ¤è¢«å‡‹è½ç‰©å¹´é™ åŠå¹´å† åŠ¨æ€.

As one of the important pathways of material and energy flow between plant and soil system, litterfall plays a key role in the process of vegetation and soil restoration in ecologically fragile region. To explore the inter- and intra-annual dynamics of litter production and related regulatory factors at different habitats in sandy land ecosystem, we investigated the litter production during nine continuous growing seasons, while the air temperature and precipitation were measured over mobile dune, fixed dune, and grassland in Horqin Sandy Land. The results showed that annual litter production at different habitants were in the order of mobile dune (9.01 g·m-2) ＜ fixed dune (67.46 g·m-2) ＜ grassland (119.55 g·m-2). The inter-annual dynamics of litterfall fluctuated significantly, with a double-peak curve in fixed dune and "W" curve in grassland. The intra-annual variation of litterfall exhibited a "U" curve at all the three habitats, with peaks appearing in April and September, respectively. Precipitation and temperature had significant effects on the intra-annul dynamics of litterfall production in fixed sand dune and grassland, but had no significant effect on the inter-annual dynamics of litter production at three habitats. Temperature was the major factor affecting the dynamics of the litter fall during the growing season in Horqin Sandy Land.

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.

[Germination and seedling growth of Artemisia halodendron under different incubation environments].

Artemisia halodendron is a dominant species in mobile and semi-mobile dunes of Horqin Sand Land. To investigate the germination character and seedling growth under different temperature and light conditions, the germination rate, germination index and growth of radicle and plumule were measured after treatments in laboratory and heating cabinet incubations. In the laboratory the light and temperature were near to nature condition, while in the heating cabinet it was kept at 25 degrees C with varying durations of light supply, including 24-, 12- and 0-hour light per day. Germination rate (66.6%) and germination index (19.1%) under laboratory condition were both significantly lower than in the heating cabinet (P < 0.05). In the heating cabinet, the germination rate under 0-hour light was 70.2%, which was insignificantly lower (P > 0.05) than under 12- and 24-hour light conditions (both 73.4%), and the germination index under 24-hour light was 28.2%, which was significantly (P < 0.05) lower than under 0- and 12-hour light conditions (31.3% and 30.8%, respectively). Radicle and plumule growth responded to light more readily than the seed germination rate and germination index during the process of germination, and the radicle growth was inhibited by darkness while promoted by light, and the plumule lengths under 0- and 12-hour light conditions were 2.81 cm and 1.51 cm, respectively, significantly higher than under 24-hour light (1.21 cm) and natural condition (1.27 cm). It was concluded that temperature was a main factor in seed germination, and seedling growth was mainly influenced by light regime.

[Ecological effect of plant root exudates and related affecting factors: a review].

The formation of plant root exudates is a vital physiological phenomenon in the metabolic processes of plant, and an important link of material turnover in "plant-soil" system. To study the plant root exudates is of significance in understanding the matter and energy flow, carbon and nitrogen balance, and improvement of primary production in terrestrial ecosystems. This paper reviewed the ecological effect of plant root exudates, such as the effect on plant physiological processes, soil microorganisms, soil matter turnover, and degradation of soil organic contaminants, and summarized the related affecting factors, including soil heavy metals and nutrient contents, soil moisture, light, and heat conditions, plant gene type, soil microorganisms, and input of exogenous organic contaminants. Based on the present research status of plant root exudates, the future research directions about the objects, methods, and effect assessment were prospected.