**3. Results**

#### **3.1 Community characteristics of different age** *C. microphylla* **plantation**

Ground vegetation communities within different aged *C. microphylla* plantation belonged to 10 families and 31 genera (**Table 1**), in which the Asteraceae (seven species), and Leguminosae (seven species) comprised the majority of plants, followed


#### **Table 1.**

*Community characteristics among 6 plots of* C. microphylla *plantation and control.*

*Evaluation of Soil Seed Banks in Different Aged* Caragana microphylla*… DOI: http://dx.doi.org/10.5772/intechopen.98712*

by the Gramineae (six species), the Chenopodiaceae (four species), and Convolvulacese (three species) in addition to Euphorbiaceae, Asclepiadaceae, and Zygophyllaceae that each comprised two species, and the Liliaceae and Polygalaceae that each constituted only one species. The species were divided into three kinds of life forms, including 3 shrubs or semi-shrubs (*Sophora alopecuroides*, *Caragana microphylla*, and *Lespedeza potaninii*), 11 annual plants, and 21 perennial herbaceous plants.

### **3.2 Species composition and seed density of SSB in different aged** *C. microphylla* **plantation**

There were 33 species of plants in the soil seed bank and 35 species of aboveground vegetation in all sample plots in the study area, among which 18 species of plants were found in both SBB and above-ground vegetation. Among the plots, 15 species only appeared in SSBs, while 17 species only appeared in the aboveground vegetation communities. A total of 33 plant species were identified in the study area that belonged to 13 families and 27 genera. The highest number of species were present in Gramineae (10) followed by Chenopodiaceae (7), and then Leguminosae (3) in addition to two species each for Asteraceae, Euphorbiaceae and Asclepiadaceae, and then one species each for Plantaginaceae, Zygophyllaceae, Rosaceae, Caryophyllaceae, Amaranthaceae, Convolvulacese, and Polygalaceae. In terms of plant life form, two species of semi-shrubs were identified (*Sophora alopecuroides* and *Lespedeza potaninii*), in addition to 11 perennial herbs and 20 species of one or two years herbaceous plants (**Table 2**).

In the semi-fixed sand dunes, there were 661.25 / m2 germinated seeds of the SSB consisting of 13 plant species that were dominated by *Setaria viridis* and *Digitaria ischaemum*, which accounting for 70.13% and 13.42% of plant community composition, respectively. In the 7 years *C. microphylla* plantation, there were 12,290.00<sup>m</sup><sup>2</sup> seeds comprising 21 plant species that were dominated by *Artemisia scoparia*. The SSB seed number decreased to 10,553.75<sup>m</sup><sup>2</sup> in the 16 years *C. microphylla* plantation, but there were 29 species that were mostly represented by nine species of Gramineae that accounted for 12.59% of the total plant composition. The SSB density of the 25 years *C. microphylla* plantation was 15,891.25<sup>m</sup><sup>2</sup> , which was highest among the SSB of *C. microphylla* plantation, although low species evenness was observed, with *Artemisia scoparia* accounting for 93.81% of the plants in these plots. The SSB density in the 37 years *C. microphylla* plantation was 6,260.00<sup>m</sup><sup>2</sup> , which was significantly lower than in other *C. microphylla* plantation. This decreased density in the oldest forest may be related to the types of species present in these plots and significantly reduced ground vegetation coverage (**Table 2**).

The average density of germinated seeds from SSBs in *C. microphylla* plantation was 11,248.75, with a total range from 6,262.00 - 15,891.25<sup>m</sup><sup>2</sup> . SSB seed numbers increased with forest age rapidly, followed by slight decreases with age after that. The mid-aged forests thus had the highest seed densities, while the density of the SSB in semi-fixed sand dunes was 661.25<sup>m</sup><sup>2</sup> . The difference equates to a 17-fold increase in seed density in planted area SSBs compared to non-planted areas (**Table 2**).

The densities of the SSB in *C. microphylla* plantation were lower than that of the natural grassland (19,788.75<sup>m</sup><sup>2</sup> ). However, there were less species in the SSB of the natural grassland (22), relative to the 16 and 37 years*C. microphylla* plantation (**Table 2**).

#### **3.3 Vertical distributions of species numbers of SSB in different aged** *C. microphylla* **plantation**

The vertical distribution of seeds within the SSB is an essential component for SSBs within degraded desert steppe ecosystems. With increasing age of


#### *Deserts and Desertification*

