Search

Biological soil crusts (BSCs) serve important functions in conserving biodiversity and ecological service in arid and semi-arid regions. Afforestation on shifting sand dunes can induce the formation of BSC on topsoil, which can accelerate the restoration of a degraded ecosystem. However, the studies on microbial community succession along BSC development under sand-fixation plantations in desertification areas are limited. This paper investigated the soil properties, enzymatic activities, and bacterial and fungal community structures across an age sequence (0-, 10-, 22-, and 37-year-old) of BSCs under Caragana microphylla sand-fixation plantations in Horqin Sandy Land, Northeast China. The dynamics in the diversities and structures of soil bacterial and fungal communities were detected via the high-throughput sequencing of the 16S and ITS rRNA genes, respectively. The soil nutrients and enzymatic activities all linearly increased with the development of BSC; furthermore, soil enzymatic activity was more sensitive to BSC development than soil nutrients. The diversities of the bacterial and fungal communities gradually increased along BSC development. There was a significant difference in the structure of the bacterial/fungal communities of the moving sand dune and BSC sites, and similar microbial compositions among different BSC sites were found. The successions of microbial communities in the BSC were characterized as a sequential process consisting of an initial phase of the faster recoveries of dominant taxa, a subsequent slower development phase, and a final stable phase. The quantitative response to BSC development varied with the dominant taxa. The secondary successions of the microbial communities of the BSC were affected by soil factors, and soil moisture, available nutrients, nitrate reductase, and polyphenol oxidase were the main influencing factors. [ABSTRACT FROM AUTHOR]

Reforestation of native shrub on shifting sand dunes has been widely used for desertification control in semi-arid grassland in Northeast China. Previous studies have confirmed that plantation establishment facilitates fixing sand dunes, restoring vegetation, and improving soil properties, but very few have focused on the response of the soil fungal community. In this study, a chronosequence of Caragana microphylla (CM) shrub sand-fixation plantations (8-, 19-, and 33-year-old), non-vegetated shifting sand dunes (0 years), and adjacent natural CM forests (NCFs; 50-year-old) in the Horqin sandy land were selected as experimental sites. Soil properties including enzymatic activities were determined, and the composition and structure of the soil fungal community were investigated using the Illumina MiSeq sequencing technique based on the internal transcribed spacer (ITS) rDNA. This study aimed to (1) describe the response of the soil fungal community to revegetation onto a moving sand dune by planting a native shrub plantation; (2) determine the main soil factors driving the succession of the fungal community; and (3) discuss whether the soil fungal community can be restored to its original state by reforestation. The reforestation of CM significantly ameliorated soil properties, increased soil fungal diversity, and altered the composition and structure of the soil fungal community. Ascomycota, Basidiomycota, and Zoopagomycota were the dominant phyla in all sites. Ascomycota did not respond to plantation development, whereas the other two dominant phyla linearly increased or decreased with the plantation age. The relative abundance of dominant genera varied with sites and showed a waning and waxing characteristic. The composition and structure of the soil fungal community in the 33-year CM plantation were very close to that of the NCF, indicating the restorability of the soil fungal community. The succession of the soil fungal community was directly driven by soil properties, of which soil moisture, organic matter, total N, urease, and protease were the main affecting factors. [ABSTRACT FROM AUTHOR]

To determine the diversity of nitrogen-fixing and carbon-fixing microbial groups in aeolian sandy soil and the effects of sand-fixation plantation type on the structures of two microbial groups in the Horqin Sandy Land, we selected six representative sand-fixation vegetations with the same age, including Caragana microphylla, Artemisia halodendron, Salix gordejevii, Hedysarum fruticosum, Populus simonii, and Pinus sylvestris var. mongolica as well as their adjacent natural Ulmus pumila open forest as test objects to investigate the diversities and structures of nifH-and cbbL-carrying microbial communities in soil by high-throughput sequencing technique. The results showed that vegetation type significantly affected soil physical and chemical properties, microbiological activities, diversities and the main compositions of nitrogen-fixing and carbon-fixing microbial communities. The diversity of soil nitrogen-fixing microbial communities under S. gordejevii and P. simonii plantations and that of carbon-fixing microbial communities under P. sylvestris var. mongolica and P. simonii plantations were significantly higher than those of other plantations. Skermanella, Bradyrhizobium, Azospirillum, and Azohydromonas were dominant nitrogen-fixation genera, with the average relative abundance of 22.3%, 21.5%, 20.8%, and 17.8%, respectively. Soil carbon-fixation microbial communities were dominated by Pseudonocardia, Bradyrhizobium, Cupriavidus, and Mesorhizobium, with relative abundance of 22.4%, 18.5%, 10.5%, and 6.0%, respectively. Soil nitrogen-fixing microbial community under C. mirophylla plantation and carbon-fixing communities under S. gordejevii and P. simonii plantations were very close to those of natural U. pumila open forest. Soil organic matter, NH4+-N, and total phosphorus were the direct determining factors for nitrogen-fixing microbial community, while pH, soil moisture, and available phosphorus were main factors influencing carbon-fixing microbial community. These observations potentially provide the scientific foundations for evaluating the ecological benefits of revegetation practice in sandy lands. [ABSTRACT FROM AUTHOR]

A laboratory study was made on the germination characteristics of freshly-collected seeds of grass species at the Wulanaodu area of Keeqin Sandyland in Eastern Inner-Mongolia. Of the 15 species examined, 8 species including Clinelymus dahuricus, Cleistogenes squarrosa, Pappophorum boreale, Spodiopogon sibiricus, Phragmites communis, Chloris virgata, Arundinella hirta, Pennisetum alopecuroides had a germination rate of over 80%, but 4 species including Echinochloa hispidula, Hemarthria compressa, Tragus berteronianus and Setaria viridis had a value of less than 10%. Spodiopogon sibiricus, Eragrostis pilosa, Phragmites communis, Chloris virgata, Clinelymus dahuricus, Pappophorum boreale, Digitaria cilliaris and Cleistogenes squrrosa began to germinate within 1-3 days after the test began, while Setaria viridis, Tragus berteronianus and Hemarthria compressa failed to germinate in a period of more than 10 days. For the species such as Digitaria cilliaris, Echinochloa hispidula, Phragmites communis, Eragrostis pilosa and Spodiopogon sibiricus, their germination period was less than 10 days, while Clinelymus dahuricus and Pappophorum boreale had a germination period of more than 20 days. The days required for half the final germination rate to be reached were: 2 days for Chloris virgata, 3 days for Phragmites communis, 4 days for Spodiopogon sibiricus, 5 days for Clinelymus dahuricus and Cleistogenes squarrosa, 7 days for Arundinella hirta and Pappophorum boreale, and 10 days for Pennisetum alopecuriodes. Compared with the Sheffield region in Britain, the Wulanaodu area of Kerqin Sandyland had a higher proportion of annul grasses with a low germination rate and a longer germination period, and the perennial grasses at the Wulanaodu area had an approximately same germination rate, but a longer germination period. During germination, ruderals showed the potential for risk-sharring, and thus, they had a relatively higher disturbance-resistance capacity.