Search Results (27)

Herbaceous vegetation under sand-fixing plantations is critical for ecosystem stability. Phosphorus (P) represents a key growth-limiting factor for plants in sandy soils, yet systematic understanding of P-cycling microbial communities including their composition, ecological functions, and responses to vegetation succession remains limited. We conducted cross-transplant experiments using dominant species from different successional stages under Caragana microphylla plantations in the Horqin Sandy Land, and assessed soil properties, enzyme activities, organic P mineralization and inorganic P solubilization rates, and phoD/gcd-harboring microbial communities. Encroachment by late-successional species increased soil nutrients, biological activities, phoD/gcd-microbial abundances, and soil P transformation rate, and restructured microbial communities while preserving core taxa. Soil properties (pH, electrical conductivity, organic matter, total nitrogen, total P, available potassium, available P, and NH₄⁺-N) significantly influenced phoD community composition. Notably, P availability was primarily driven by phoD-mediated organic P mineralization, with gcd-mediated solubilization playing a minor role. These changes enhanced alkaline phosphatase activity and P availability, promoting plant growth and new species colonization, thereby establishing a positive plant–soil–microbe feedback that drives succession. The identified dominant phoD/gcd taxa provide candidates for developing microbial inoculants to accelerate vegetation restoration. Full article

Establishing shrub plantations on mobile sand dunes is an effective strategy to combat desertification in semi-arid regions. Herbaceous communities developing beneath these plantations enhance ecosystem stability and improve revegetation outcomes. This study investigated the structural responses of soil bacterial communities, key functional genes (nifH, amoA, and phoD), and plant–soil–microbe interactions across a herbaceous vegetation succession gradient (initiation, early, middle, and stable stages) under Caragana microphylla sand-fixation plantations in the sandy Horqin Grassland. The results revealed that plant species richness, diversity, and biomass increased progressively with succession. Concurrent improvements in soil nutrients (organic matter, nitrogen, phosphorus, and potassium) and enzymatic activities (urease, protease, phosphatase, glucosidase, polyphenol oxidase, and dehydrogenase) were observed. The abundances of nifH, amoA, and phoD genes rose progressively with vegetation succession, contributing to enhanced soil nutrient levels. All dominant bacterial phyla and genera detected constituted shared taxa across successional stages, but their relative abundances shifted dynamically. Herbaceous succession facilitated rapid restoration of bacterial diversity, though structural recovery lagged, depending on the quantitative fluctuations of the dominant taxa. Soil pH, organic matter, electrical conductivity, total N, total P, available P, and available K all significantly influenced the soil bacterial community, with pH and organic matter being the most influential factors. These findings highlight plant–soil–microbe interactions as intrinsic drivers of vegetation succession in desertified ecosystems. Full article

Elucidating shrub ecohydrological adaptation is critical for optimizing vegetation-restoration strategies in arid regions and maintaining regional ecological stability. This study examined typical desert shrubs at the northern edge of the Mu Us Sand Land. During the growth peak season (July–September), we measured understory-soil δ¹⁸O, soil water content (SWC), leaf δ¹³C_p, stem δ¹⁸O, and gas-exchange rates, and evaluated shrub drought resistance and water-use efficiency using Mantel tests and principal component analysis (PCA). Based on the VPDB standard, the δ13Cp values of leaves ranked as follows: Caragana microphylla (−27.21‰) > Salix psammophila (−27.80‰) > Artemisia ordosica (−28.48‰). The results indicate that leaf δ¹³C_p and water δ¹⁸O are effective indicators of shrub water-use efficiency, reflecting Cᵢ/Cₐ dynamics and water-transport pathways, respectively. The three shrubs exhibit distinct water-use strategies: Caragana microphylla follows a conservative strategy that relies on deep-water sources and tight stomatal regulation; Salix psammophila shows an opportunistic strategy, responding to precipitation pulses and drawing from multiple soil layers; Artemisia ordosica displays a vulnerable, shallow-water-dependent strategy with high drought susceptibility. SWC was the primary driver of higher Long Water Use Efficiency (WUE), whereas Mean Air Temperature (MMAT) and Mean Relative Humidity (MMRH) exerted short-term regulation by modulating the vapor-pressure deficit (VPD). We conclude that desert-shrub water-use strategies form a complementary functional portfolio at the community scale. Vegetation restoration should prioritize high-WUE conservative species, complement them with opportunistic species, and use vulnerable species cautiously to optimize community water-use efficiency and ecosystem stability. Full article

Correctly understanding existing plantations and improving the cycles and effects of ecological restoration in sandy areas have become important scientific issues. Consequently, we selected different diameters at breast height (DBHs) for Populus spp. and Pinus sylvestris var. mongolica (P. sylvestris var. mongolica) and varying diameters at the base (DBs) of Caragana microphylla Lam. (C. microphylla) as research subjects in the sandy plantations in northwestern Liaoning Province. Soil samples were collected along a gradient at distances of 20 cm, 60 cm, and 120 cm from the tree base. Our objective was to investigate the connections among various afforestation species, DBHs or DBs (age), and soil nutrients. The results from our study area revealed that (1) the soil nutrient contents were extremely low; (2) the DBHs or DBs were not significantly related to soil exchangeable phosphorus (EP), total potassium (TK), or Pondus Hydrogenii (pH) but had a significant or moderately positive correlation with soil organic carbon (SOC), exchangeable potassium (EK), total nitrogen (TN), total carbon (TC), and total phosphorus (TP). The most significant relationship was with EK at a distance of 20 cm from the tree base; (3) the three afforestation species presented different trends in terms of the soil nutrient contents among the different distances from the tree base; and (4) the EK in the Populus spp. plantations was significantly greater than that in the P. sylvestris var. mongolica plantations and moderately significantly greater than that in the C. microphylla plantations. The pH levels in P. sylvestris var. mongolica plantations were significantly lower than those in Populus spp. plantations and C. microphylla plantations. Our study provides valuable insights into the synergistic development between sandy plantations and soil dynamics. This study provides important evidence for selecting suitable plant species for vegetation restoration and improvement efforts in sandy lands. Full article

Shrub encroachment is a global ecological issue. The changes in growth dynamics between shrub seedlings and herbs are pivotal in determining shrub encroachment, yet their response to varying rainfall regimes remains unclear. We conducted a precipitation manipulation experiment (three precipitation (P) amount treatments: P−25% (225 mm), P (300 mm), P+25% (375 mm); three drought interval treatments: DI4, DI6, DI8) on a mixture of Caragana microphylla (shrub) seedlings and four herbs (Neotrinia splendens, Campeiostachys dahurica, Lolium multiflorum and Medicago sativa), analyzing their ecophysiological and growth responses. The results showed the following: (1) Under P−25%, herb growth was inhibited, while shrub seedlings thrived. Compared to P, C. microphylla significantly increased by 138% in aboveground biomass (AGB), while herb AGB decreased by 10%. (2) Under P+25%, herbs exhibited superior growth to shrub seedlings. Compared to P, four herbs significantly increased by 53% in AGB, while C. microphylla growth did not significantly respond. (3) Under DI8, shrub seedlings exhibited superior growth compared to herbs. Compared to DI4, C. microphylla significantly increased by 90% in AGB, while herb growth did not significantly respond. Our results indicate that drier conditions suppressed herb growth while promoting shrubs. However, increased precipitation amounts stimulated herb growth but not shrubs. These results could explain the process of shrub encroachment and provide a theoretical basis for predicting the pattern of shrub expansion under future rainfall regimes. Full article

Environmental conditions can control the structure and composition of plant communities by changing the direction and intensity of plant–plant interactions. In extreme arid regions, accompanied by water and soil nutrient limitation, positive shrub–herb interactions may vary along an aridity gradient, leading to changes in the ecological consequences of shrub encroachment. We investigated the vegetation and soil within 60 shrub patches and their paired interspaces at 20 sites from the northeast to southwest desert steppe of Inner Mongolia, China, encroached by the Caragana microphylla shrub. The results show that aridity, soil organic matter (SOM), and soil total phosphorus (TP) were the main factors driving shrub–herb interactions. The positive shrub–herb interaction first increased and then decreased with increasing aridity (in the range of De Martonne Index (DMI) 0.54 to 1.85). The DMI indirectly affected shrub–herb interaction through TP, and the facilitation of shrubs on herbs coverage and biomass increased with the increase in TP. The SOM can directly affect the shrub–herbs interaction, and the facilitation of shrubs on herb diversity decreases with the increase in SOM. Our results indicate that the shrub–herb interaction changes along the environmental stress gradient; in general, shrubs have a positive effect on herbaceous communities along the aridity gradient. This study underscores the positive effects of shrubs on vegetation restoration in desert steppes, and changing environmental conditions by increasing precipitation, increasing TP content, and reducing SOM content can enhance the facilitation of shrub on herbs to accelerate the ecological restoration of degraded desert steppe. Full article

Background: The restoration of the degraded sandy grasslands in Hulun Buir is crucial for maintaining the local ecological balance and sustainable development. Caragana microphylla Lam., a shrub species widely employed in the restoration of sandy vegetation. It is essential to understand its impact on the understory vegetation and soil properties during this process. Methods: This study employed ANOVA, Pearson correlation, and redundancy analysis to systematically analyze the impact of C. microphylla on the three critical stages of desertified grassland vegetation recovery: semi-fixed dunes, fixed dunes, and sandy grasslands. It provided strategies for the restoration of desertified grassland vegetation and offered additional theoretical evidence for the role of vegetation in promoting the recovery of sandy lands. Results: (1) As the degree of vegetation recovery in desertified grasslands increases, the species richness of understory vegetation, Shannon–Wiener index, community height, and biomass also increase. Both the community height and biomass within shrublands are higher than outside, with species richness within the shrublands being higher than outside during the semi-fixed and fixed-sand land stages. (2) In both the 0~10 cm and 10~20 cm soil layers, soil water content showed an increasing trend, peaking in the sandy grassland stage (1.2%), and was higher within the shrublands than outside. The soil water content at 10~20 cm was higher than in the 0~10 cm layer. In both layers, clay and silt content gradually increased with the degree of vegetation recovery in the sandy land, and higher within the shrublands than outside, while the opposite was true for sand content. (3) In both soil layers, soil organic carbon gradually increased with the degree of vegetation recovery, peaking in the sandy grassland stage (4.12 g·kg⁻¹), and was higher within the shrublands than outside. Total nitrogen increased from the semi-fixed-sand land stage to the fixed-sand land stage, with higher levels within the shrublands than outside at all stages. Soil pH within the shrublands decreased as the degree of vegetation recovery increased. There was no significant change in the total phosphorus content. (4) In both soil layers, soil physicochemical characteristics accounted for 59.6% and 46.9% of the vegetation changes within and outside the shrublands, respectively, with the main influencing factors being the soil particle size, total nitrogen, soil water content, and soil organic carbon. Conclusions: In the process of sandy grassland restoration, C. microphylla facilitates the growth and development of vegetation by enhancing the underlying soil physicochemical properties, specifically regarding the soil particle size distribution, soil water content, soil organic carbon, and total nitrogen. Full article

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. Full article

Runoff and sediment (RAS) are important indicators of soil erosion in a watershed, playing a significant role in the migration of surface material and landform development. Previous studies have extensively documented the effects of trees, shrubs, herbs, and soil on runoff and sediment during erosive rainfall; however, the precise interactions among these factors and their influence on RAS yield within the vegetation hierarchy remain unclear. Using the random forest algorithm and the structural equation model, this research aimed to quantify the interaction of numerous variables within diverse vegetation hierarchies and how they affect RAS, as well as to identify critical indicators that influence RAS. The structural equation model results show that the grass properties have a direct effect on soil properties, and the grass properties and soil properties both affect the canopy properties directly; the soil properties and canopy properties are the main factors influencing runoff and sediment directly. In addition, the grass properties could affect RAS by influencing the soil properties indirectly, and the soil properties could also affect RAS indirectly by influencing the canopy properties. Height difference (HD) between two layers of vegetation had the highest weight of 1.043 among the canopy variables, showing that HD has a substantial effect on RAS. Among the soil properties, soil bulk density and maximum field capacity have a significant impact on RAS. We conclude that canopy properties have the greatest impact on RAS. In the future, more Caragana microphylla Lam and Robinia pseudoacacia Linn plants should be planted to prevent soil erosion. This study provides a scientific basis for vegetation planting management and soil erosion control on the Loess Plateau. Full article

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. Full article

Biodiversity is sensitive to climate change and human activity. Grazing management practices have a profound impact on plant species–genetic diversity in grassland and woodland communities. In this study, we explored the responses of species and genetic diversity to grazing in Ulmus pumila L. communities in the Hunshandak Sandy Land, analyzed the relationship between species and genetic diversity, and revealed the effects of climate factors on them. We found that the dominant species were Spiraea trilobata, Caragana microphylla and Artemisia intramongolica in U. pumila communities. Plant species richness in the banned grazing (BG) and seasonal grazing (SG) communities was significantly higher than that in the delayed grazing (DG) community. Plant Simpson’s diversity index showed a downward trend with increasing grazing duration. There was no difference in allelic richness in nuclear DNA (nrDNA) of U (U. pumila) and chloroplast DNA (cpDNA) of NU (other dominant species besides U. pumila) among grazing management types. The expected heterozygosity of U in nrDNA and cpDNA was significantly affected by grazing management, and the trend was BG > SG > DG. The genetic diversity of U was lower than that of NU. The genetic diversity characteristics of U in cpDNA were lower than those in nrDNA. The analysis of molecular variance (AMOVA) showed that 98.08% of the variation in U and 95.25% of the variation in NU was attributed within populations and the differences within grazing management types were 13.35% in U and 24.08% in NU (p < 0.001). The species richness of communities was positively correlated with the genetic diversity of U, NU and all dominant species (U + NU) in communities. The nineteen climatic variables together explained 94.24% and 79.08% of the total variation in U and NU genetic and species diversity. The mean temperature of the warmest quarter and temperature seasonality were the main factors affecting genetic diversity (p = 0.046; 0.01), while the maximum temperature of the warmest month was the main factor affecting species diversity (p = 0.05). Full article

To reveal the changes in the life history characteristics of grassland plants due to vegetation restoration, plant species and communities were analyzed for their competitor, stress tolerator, and ruderal (CSR) ecological strategies after the introduction of woody plants in the damaged steppe grassland and were compared with those in reference sites in Hulunbuir, Inner Mongolia. As a result, it was found that the introduction of the woody plants (Corethrodeneron fruticosum, Caragana microphylla, Populus canadensis, and Pinus sylvestris var. mongolica) into the damaged land greatly increased the plant species diversity and CSR eco-functional diversity as the succession progressed. The plant strategies of the temperate typical steppe (TTS) and woodland steppe (WS) in this Asian steppe are CSR and S/SR, respectively, which means that the plants are adapted to disturbances or stress. As the restoration time elapsed in the damaged lands exhibiting (R/CR) (Corispermum hyssopifolium), the ecological strategies were predicted to change in two ways: (1) →R/CSR (Cynanchum thesioides, Astragalus laxmannii, etc.) → CSR in places (TSS) (Galium verum var. asiaticum, Saussurea japonica, etc.) where only shrubs were introduced, and (2) → S/SR (Allium mongolicum, Ulmus pumila, etc.) → S/SR in sites (WS) (Ulmus pumila, Thalictrum squarrosum, etc.) where trees and shrubs were planted simultaneously. The results mean that the driving force that causes succession in the restoration of temperate grasslands is determined by the life-form (trees/shrubs) of the introduced woody plants. This means that for the restoration of these grasslands to be successful, it is necessary to introduce woody tree species at an early stage. Full article

Shrubs tended to increase their abundance as climatic aridity and grazing intensity increased in the Inner Mongolian grassland. Increasing shrub abundance was believed to be due to enhanced reproduction. However, the effects of climatic aridity and grazing on the sexual reproduction of shrubs in grassland remain largely unclear. In this study, we conducted field experiments with Caragana microphylla to examine the variation of sexual reproduction aspects (seed production, seed vigor, and sapling establishment) along a climatic aridity gradient (subhumid, semiarid, arid, and dry arid zones) and a grazing intensity gradient (fenced, mildly grazed, and severely grazed). We then quantified the population growth rate based on seed production and sapling establishment rates. Our objective was to evaluate whether sexual reproduction is the main mechanism for Caragana encroachment into grasslands. We found that climatic aridity decreased seed quantity and seed vigor but increased the sapling establishment rate of Caragana shrubs. Under ungrazed conditions, climatic aridity did not affect population growth rates, while under grazing conditions, increased aridity stresses reduced population growth rates. Grazing reduced seed production, sapling establishment, and population growth rates. Climatic aridity enhanced the negative effects of grazing on sexual reproduction, while grazing intensified the negative effects of aridity on the population growth of Caragana shrubs. In conclusion, climatic aridity, grazing, and their combined effects had negative effects on the sexual reproduction of Caragana shrubs. Therefore, sexual reproduction could not fully explain the increased abundance of shrubs with increasing aridity and grazing. Clonal reproduction might be of considerable importance for understanding the mechanism of shrub encroachment in grasslands. Full article

In recent years, grassland degradation has become a global ecological problem. The identification of degraded grassland species is of great significance for monitoring grassland ecological environments and accelerating grassland ecological restoration. In this study, a ground spectral measurement experiment of typical grass species in the typical temperate grassland of Inner Mongolia was performed. An SVC XHR-1024i spectrometer was used to obtain field measurements of the spectra of grass species in the typical grassland areas of the study region from 6–29 July 2021. The parametric characteristics of the grass species’ spectral data were extracted and analyzed. Then, the spectral characteristic parameters + vegetation index, first-order derivative (FD) and continuum removal (CR) datasets were constructed by using principal component analysis (PCA). Finally, the RF, SVM, BP, CNN and the improved CNN model were established to identify Stipa grandis (SG), Cleistogenes squarrosa (CS), Caragana microphylla Lam. (CL), Leymus chinensis (LC), Artemisia frigida (AF), Allium ramosum L. (AL) and Artemisia capillaris Thunb. (AT). This study aims to determine a high-precision identification method based on the measured spectrum and to lay a foundation for related research. The obtained research results show that in the identification results based on ground-measured spectral data, the overall accuracy of the RF model and SVM model identification for different input datasets is low, but the identification accuracies of the SVM model for AF and AL are more than 85%. The recognition result of the CNN model is generally worse than that of the BP neural network model, but its recognition accuracy for AL is higher, while the recognition effect of the BP neural network model for CL is better. The overall accuracy and average accuracy of the improved CNN model are all the highest, and the recognition accuracy of AF and CL is stable above 98%, but the recognition accuracy of CS needs to be improved. The improved CNN model in this study shows a relatively significant grass species recognition performance and has certain recognition advantages. The identification of degraded grassland species can provide important scientific references for the realization of normal functions of grassland ecosystems, the maintenance of grassland biodiversity richness, and the management and planning of grassland production and life. Full article

Remotely sensed images with low resolution can be effectively used for the large-area monitoring of vegetation restoration, but are unsuitable for accurate small-area monitoring. This limits researchers’ ability to study the composition of vegetation species and the biodiversity and ecosystem functions after ecological restoration. Therefore, this study uses LiDAR and hyperspectral data, develops a hierarchical classification method for classifying vegetation based on LiDAR technology, decision tree and a random forest classifier, and applies it to the eastern waste dump of the Heidaigou mining area in Inner Mongolia, China, which has been restored for around 15 years, to verify the effectiveness of the method. The results were as follows. (1) The intensity, height, and echo characteristics of LiDAR point cloud data and the spectral, vegetation indices, and texture features of hyperspectral image data effectively reflected the differences in vegetation species composition. (2) Vegetation indices had the highest contribution rate to the classification of vegetation species composition types, followed by height, while spectral data alone had a lower contribution rate. Therefore, it was necessary to screen the features of LiDAR and hyperspectral data before classifying vegetation. (3) The hierarchical classification method effectively distinguished the differences between trees (Populus spp., Pinus tabuliformis, Hippophae sp. (arbor), and Robinia pseudoacacia), shrubs (Amorpha fruticosa, Caragana microphylla + Hippophae sp. (shrub)), and grass species, with classification accuracy of 87.45% and a Kappa coefficient of 0.79, which was nearly 43% higher than an unsupervised classification and 10.7–22.7% higher than other supervised classification methods. In conclusion, the fusion of LiDAR and hyperspectral data can accurately and reliably estimate and classify vegetation structural parameters, and reveal the type, quantity, and diversity of vegetation, thus providing a sufficient basis for the assessment and improvement of vegetation after restoration. Full article