Seasonal distribution and diversity of ground arthropods in microhabitats following a shrub plantation age sequence in desertified steppe.

In desertified regions, shrub-dominated patches are important microhabitats for ground arthropod assemblages. As shrub age increases, soil, vegetation and microbiological properties can change remarkably and spontaneously across seasons. However, relatively few studies have analyzed how ground arthropods respond to the microhabitats created by shrubs of different plantation ages across seasons. Using 6, 15, 24 and 36 year-old plantations of re-vegetated shrubs (Caragana koushinskii) in the desert steppe of northwestern China as a model system, we sampled ground arthropod communities using a pitfall trapping method in the microhabitats under shrubs and in the open areas between shrubs, during the spring, summer and autumn. The total ground arthropod assemblage was dominated by Carabidae, Melolonthidae, Curculionidae, Tenebrionidae and Formicidae that were affected by plantation age, seasonal changes, or the interaction between these factors, with the later two groups also influenced by microhabitat. Overall, a facilitative effect was observed, with more arthropods and a greater diversity found under shrubs as compared to open areas, but this was markedly affected by seasonal changes. There was a high degree of similarity in arthropod assemblages and diversity between microhabitats in summer and autumn. Shrub plantation age significantly influenced the distribution of the most abundant groups, and also the diversity indices of the ground arthropods. However, there was not an overall positive relationship between shrub age and arthropod abundance, richness or diversity index. The influence of plantation age on arthropod communities was also affected by seasonal changes. From spring through summer to autumn, community indices of ground arthropods tended to decline, and a high degree of similarity in these indices (with fluctuation) was observed among different ages of shrub plantation in autumn. Altogether the recovery of arthropod communities was markedly affected by seasonal variability, and they demonstrated distinctive communal fingerprints in different microhabitats for each plantation age stage

Characterization of the complete chloroplast genome of Ammopiptanthus mongolicus (Papilionoideae), a rare and Endangered plant to China

Ammopiptanthus mongolicus is a rare and Endangered plant of Ammopiptanthus (Papilionoideae) in China. It grows mainly in the arid and semi-arid regions. The complete chloroplast (cp) genome was assembled by Illumina paired-end reads data. The circular cp genome is 153,997 bp in size, including a large single copy (LSC) region of 83,957 bp, a small single copy (SSC) region of 18,008 bp and a pair of inverted repeat (IRs) regions of 26,016 bp. Besides, 5 genes possess a single intron, while another three genes ycf3, rps12, and clp have a couple of introns. The GC content of the entire A. mongolicus cp genome, LSC, SSC, and IR regions are 36.9, 34.6, 30.5, and 42.8%, respectively. Based on the concatenated coding sequences of cp PCGs, the phylogenetic analysis showed that A. mongolicus and A. nanus are closely related to each other within the family Leguminosae

Features of Plant Community and Driving Forces of Plant Community Succession in the Typical Desert Wetlands

Desert wetlands play a significant role in flood regulation, water purification, biodiversity maintenance, and regional ecological environment improvement. Vegetation is a key factor affecting wetland function and it is important to study the features of plant community and the driving forces of plant community succession. The Ningxia Habahu National Nature Reserve, a typical desert wetland ecosystem, was selected to study the features of wetland plant communities including plant density, biomass and frequency, and vegetation coverage, as well as the habitats, structural characteristics, species composition, dominant population structure, and other characteristics of different ecosystems. Data was collected using long-term fixed-point observation, sampling monitoring, and other methods. The results showed that the total plant density, total biomass, Magalef index and Shannon–Wiener index of the different desert wetlands in the reserve area were all relatively low, which was caused by the poor habitat and salinization of the arid environment. There was no significant difference between the root–shoot ratio of the wetland plants in the reserve area and that of the construct species of other ecosystems. The specific leaf area of the wetland plants was also not significantly different from that of the construct species of other ecosystems. Vegetation nitrogen-to-phosphorus (N/P) ratios were found to be the key driving force for the succession of plant community in the desert wetlands. These results not only provide underlying insights for the improvement of species diversity and ecological environment, but also provide a scientific basis for the sustainable protection and restoration of typical desert wetlands

Features of Plant Community and Driving Forces of Plant Community Succession in the Typical Desert Wetlands

Desert wetlands play a significant role in flood regulation, water purification, biodiversity maintenance, and regional ecological environment improvement. Vegetation is a key factor affecting wetland function and it is important to study the features of plant community and the driving forces of plant community succession. The Ningxia Habahu National Nature Reserve, a typical desert wetland ecosystem, was selected to study the features of wetland plant communities including plant density, biomass and frequency, and vegetation coverage, as well as the habitats, structural characteristics, species composition, dominant population structure, and other characteristics of different ecosystems. Data was collected using long-term fixed-point observation, sampling monitoring, and other methods. The results showed that the total plant density, total biomass, Magalef index and Shannon–Wiener index of the different desert wetlands in the reserve area were all relatively low, which was caused by the poor habitat and salinization of the arid environment. There was no significant difference between the root–shoot ratio of the wetland plants in the reserve area and that of the construct species of other ecosystems. The specific leaf area of the wetland plants was also not significantly different from that of the construct species of other ecosystems. Vegetation nitrogen-to-phosphorus (N/P) ratios were found to be the key driving force for the succession of plant community in the desert wetlands. These results not only provide underlying insights for the improvement of species diversity and ecological environment, but also provide a scientific basis for the sustainable protection and restoration of typical desert wetlands

A six-year grazing exclusion changed plant species diversity of a Stipa breviflora desert steppe community, northern China

Excluding grazers is one of most efficient ways to restore degraded grasslands in desert-steppe communities, but may negatively affect the recovery of plant species diversity. However, diversity differences between grazed and fenced grasslands in desert-steppe are poorly known. In a Stipa breviflora desert steppe community in Northern China, we established six plots to examine spatial patterns of plant species diversity under grazed and fenced conditions, respectively. We addressed three aspects of species diversity: (1) The logistic, exponential and power models were used to describe the species-area curve (SAR). Species richness, abundance and Shannon diversity values change differently with increasing sampling areas inside and outside of the fence. The best fitted model for SAR was the logistic model. Excluding grazers had a significant impact on the shape of SAR. (2) Variograms was applied to examine the spatial characteristics of plant species diversity. We found strong spatial autocorrelations in the diversity variables both inside and outside the fence. After grazing exclusion, the spatial heterogeneity decreased in species richness, increased in abundance and did not change in Shannon diversity. (3) We used variance partitioning to determine the relative contributions of spatial and environmental factors to plant species diversity patterns. Environmental factors explained the largest proportion of variation in species diversity, while spatial factors contributed little. Our results suggest that grazing enclosures decreased species diversity patterns and the spatial pattern of the S. breviflora desert steppe community was predictable

Means (±SEs) of total abundance, taxonomic richness, and Shannon’s diversity index of ground arthropods between microhabitats for each plantation age in different sampling periods.

<p>Means (±SEs) of total abundance, taxonomic richness, and Shannon’s diversity index of ground arthropods between microhabitats for each plantation age in different sampling periods.</p

RDA two-dimensional ordination diagram of the first two axes showing the relationship between the community composition of ground arthropods and environmental variables.

<p>RDA two-dimensional ordination diagram of the first two axes showing the relationship between the community composition of ground arthropods and environmental variables.</p

Comparison of Two Simulation Methods of the Temperature Vegetation Dryness Index (TVDI) for Drought Monitoring in Semi-Arid Regions of China

The Temperature Vegetation Dryness Index (TVDI), a drought monitoring index based on an empirical parameterization of the Land Surface Temperature (LST)–Normalized Difference Vegetation Index (NDVI) space, has been widely implemented in a variety of ecosystems worldwide because it does not depend on ancillary data. However, the simulation of dry/wet edges in the TVDI model can be problematic because remote sensing images do not have sufficient pixels to identify the wetness and dryness extremes of different vegetation coverages. In this study, an improvement in dry/wet edge simulation was proposed, and a comparison of the original TVDI and the modified Temperature Vegetation Dryness Index (TVDIm) was performed for drought monitoring in Ningxia Province, which is a typical semi-arid region in China. First, the difference between the land surface temperatures in day and night (∆LST) was used as an alternative to LST when building the TVDIm model. In addition, the wet edges were improved by removing outliers using a statistical method, and the dry edges were optimized by removing the “tail down” points in the NDVI range of 0.0–0.1. Here, the modeling process of TVDIm in 2005, one of recent extreme drought year is illustrated. The results show that both the TVDI and TVDIm can be used to monitor the temporal and spatial variations of drought, and the onset, duration, extent, and severity of drought can be reflected by TVDI and TVDIm maps. However, the magnitude of TVDI is higher than that of TVDIm, which could cause the TVDI-simulated drought condition to be elevated in normal years and underestimated in dry years. The TVDIm has higher coefficients of correlation with in situ meteorological drought index and agricultural drought statistical data than does the original TVDI, and it exhibits better performance in drought monitoring compared to that of the original TVDI in semi-arid regions of China

Precipitation and plant community-weighted mean traits determine total transpirable soil water in a desert grassland

The desert grassland has low precipitation, high evaporation and a limited soil water supply. Thus the tension between water shortage and sustainable vegetation restoration is increasingly evident. Change in total transpirable soil water (TTSW) reflects the water utilization and extraction capacity of plant communities, which are the basis for maintaining productivity and stability in communities, as well as the key ecological processes alleviating the above tension. Change in TTSW is influenced by precipitation, vegetation and soil. Quantifying the relative contribution of these factors to change in TTSW is key to the sustainable restoration of desert grassland. However, the current understanding of such effects remains limited. This study examined four typical plant communities in the Ningxia desert grassland, monitoring soil water content and evaluating plant community characteristics and diversity over three consecutive years. Using redundancy analysis and hierarchical partitioning methods, the influence of annual precipitation, vegetation (functional and species diversity, community characteristics) and soil physical properties on TTSW variation were investigated. Findings revealed: (1) The factors contributing to TTSW variation were annual precipitation (41 %-68 %,), vegetation (29 %-45 %), and soil physical properties (0 %-6.7 %). Specifically, community-weighted mean traits (CWM) and functional diversity (FD) explained TTSW variation by 24–37 % and 0.25–11 % respectively. In Gramineae communities, the influence of annual precipitation and vegetation on TTSW variation was consistent across soil depths. However, in degraded Sophora alopecuroides + Artemisia scoparia (SA) communities, the influence of vegetation (CWM, FD, community composition and community function) on TTSW variation was more pronounced in shallow soils (45 %) than in deeper soils (33 %), while annual precipitation effects were more substantial in the deep soil layers (66 %) than in the shallow soil layers (42 %). (2) Annual precipitation and CWM were the main biological and abiotic factors affecting TTSW. Interestingly, increased annual precipitation was negatively correlated with TTSW. Similarly, the primary controlling factor, CWM, also showed a significant negative relationship with TTSW. This relationship varied across community types and could be linear or quadratic, highlighting the need to understand the selection effects mediated by CWM in ensuring sustainable vegetation restoration. This research offers insights into the relationship between plant functional diversity and soil water retention function