Vegetation Restoration Types Research Articles

Distributions and Influencing Factors of Soil Organic Carbon Fractions under Different Vegetation Restoration Conditions in a Subtropical Mountainous Area, SW China

Vegetation type is known to affect soil organic carbon (SOC) storage. However, the magnitudes and distributions of SOC sequestration and driving factors for different vegetation types are still largely unknown. Thus, we studied the changes in SOC fractions along soil profiles for different vegetation restoration types and their relationships with soil properties. We selected five vegetation types and collected soil samples from depth intervals of 0–10, 10–30, 30–60, and 60–90 cm. Five soil carbon fractions and the soil properties were tested to evaluate the soil carbon fraction distributions and influencing factors. Our results demonstrated that the concentrations of total organic carbon (TOC) and five carbon fractions were strongly affected by vegetation types and soil depths. The concentrations of all five soil carbon fractions in 0–10 cm depth were higher than those in the other three soil depths and generally increased with vegetation complexity. The Pearson correlations and redundancy analysis showed that the fractions of soil glomalin-related soil protein (GRSP) and Fe oxides as well as the soil bulk densities, were the most significant related to soil TOC levels and carbon fractions, which suggests that soil biochemical and physicochemical processes are among the most important mechanisms that contribute to SOC persistence. Considering the sensitive indices of the soil carbon variables and PCA results, soil permanganate oxidizable carbon (POXC) was considered to be the most sensitive index for differentiating the effects of vegetation types. These results provide important information regarding the distributions and driving factors of the carbon fractions that result from different vegetation restoration types and will help to improve our understanding of soil carbon sequestration during vegetation restoration processes.

Vegetation restoration improves soil hydrological properties by regulating soil physicochemical properties in the Loess Plateau, China

Soil hydrological properties play a key role in soil hydrological processes. However, the effect of long-term vegetation restoration on soil hydrological properties and the corresponding influencing mechanisms remains poorly understood. Here, three soil hydrological properties including saturated water-holding capacity (SWHC), field capacity (FC) and saturated hydraulic conductivity (Ks), as well as several basic soil properties in the Zhifanggou watershed of the Loess plateau were investigated. The variations in SWHC, FC and Ks under different vegetation restoration types and their dominant influencing factors were analyzed. Moreover, we collected available Ks data from peer-reviewed publications to determine the land use with the largest Ks across the entire Loess Plateau. The results showed that SWHC FC and Ks were increased after 20 years of vegetation restoration. The higher Ks was found in shrubland and forest in the whole Loess Plateau. Compared with cropland, Ks in shrubland was increased by 87.10% at 0–20 cm, 48.89% at 20–40 cm, and 18.37% at 40–100 cm, respectively, indicating that the impact of revegetation on Ks were most obvious in the upper soil layer. Bulk density (BD), total porosity (TP), capillary porosity (CP), noncapillary porosity (NCP) and soil organic matter (SOM) had a significant effect on SWHC, FC and Ks for different land-use types (P < 0.01). Soil porosity (i.e., TP, CP and NCP) and BD, soil chemical properties (i.e., SOM and pH), and soil particle composition explained 93.8%, 59.2%, and 13.4% of the total variance in soil hydrological properties (i.e., SWHC, FC and Ks), respectively. This indicates that soil porosity and BD are the dominant factors affecting soil hydrological properties. Moreover, soil particle composition played an important role in regulating Ks, with the contribution of 38.6%. The established pedotransfer function (PTF) of Ks using BD, clay and silt content had a better performance than two existing PTFs. This research provides a more systematic and comprehensive understanding of the soil hydrological effect of vegetation restoration in the Loess Plateau.

Topsoil carbon sequestration of vegetation restoration on the Loess Plateau

Vegetation restoration plays an important role in enhancing soil organic carbon (SOC) sequestration. However, there are diverse types of vegetation restoration with different SOC sequestration rates. Understanding the dynamic of SOC at topsoil (0–20 cm) and potential problems of the different types (i.e., woodlands, shrub lands, artificial grasslands, orchards, and abandoned lands) are important for future sustainable development. We surveyed 73 peer-reviewed studies conducted on the Chinese Loess Plateau from 2000 to 2019. The relative change in SOC stock under shrub lands, woodlands, and abandoned lands performed significantly and positively related to restoration time (P < 0.001). The rate was highest for shrub lands (0.55 ± 0.45 t ha−1 yr−1) compared to that of other restoration types. The Robinia pseudoacacia, a typical N-fixers, sequestrate more SOC (3.84% yr−1) than other tree species (1.18% yr−1). Orchards and artificial grasslands, however, were based on the relatively weak relations between restoration age and SOC stock with the low efficiency of SOC stock change (19.0 ± 32.1% and 20.2 ± 35.2% respectively overall time). The restoration age, initial SOC stock, and temperature significantly influenced the relative change in SOC stock (P < 0.001). In addition, the shrub lands remained inert to the temperature and precipitation (P > 0.05), indicating its wide adaptability on the Loess Plateau. We conclude that restoration types and environmental factors control SOC dynamic, and must be considered for the vegetation restoration types.

Effects of different vegetation restoration types on soil hydro-physical properties in the hilly region of the Loess Plateau, China

Context Severe soil erosion in the Chinese Loess Plateau and the resulting high sediment yield of the Yellow River have been important research topics. Aims Understanding the impacts of vegetation types on soil hydro-physical properties is essential for understanding regional runoff-sediment changes, soil and water conservation, and revegetation. Methods Three main plantation covers of the study area [natural restoration grassland (NG), artificial Prunus armeniaca forest (AP), and artificial Hippophae rhamnoides shrubland (AH) with 15 years of restoration] and Sorghum bicolor agricultural land as control (CK), were selected to compare their soil hydro-physical properties and infiltration capacity in the soil profile. Key results The bulk density was lower, and soil organic matter (SOM), the proportion of macro-aggregates (&gt;5 mm), mean weight diameter (MWD) of water-stable aggregates, and the initial infiltration and stable infiltration rate were higher in the AH plot compared to CK and the other two plots. The impacts of vegetation restoration on soil properties were mainly in the 0–60 cm layer. Infiltration rates changed mainly within 5 h and basically stabilised within 10 h, with even shorter times to reach stable infiltration in CK. The initial and stable infiltration rates were significant positively correlated (P &lt; 0.05) with macro-aggregate content, MWD, and SOM. Conclusions The AH and AP had greater impacts on soil hydro-properties than NG. The AH had the greatest positive effect on soil hydro-properties and soil and water conservation functions. Implications This study provides practical references for vegetation restoration measures assessment on the Loess Plateau or other similar regions.

Plant interactions control the carbon distribution of Dodonaea viscosa in karst regions.

Biomass and carbon (C) distribution are suggested as strategies of plant responses to resource stress. Understanding the distribution patterns of biomass and C is the key to vegetation restoration in fragile ecosystems, however, there is limited understanding of the intraspecific biomass and C distributions of shrubs resulting from plant interactions in karst areas. In this study, three vegetation restoration types, a Dodonaea viscosa monoculture (DM), a Eucalyptus maideni and D. viscosa mixed-species plantation (EDP) and a Pinus massoniana and D. viscosa mixed-species plantation (PDP), were selected to determine the effects of plant interactions on the variations in the C distributions of D. viscosa among the three vegetation restoration types following 7 years of restoration. The results showed that: (1) plant interactions decreased the leaf biomass fraction. The interaction of P. massoniana and D. viscosa decreased the branch biomass fraction and increased the stem and root biomass fraction, but not the interaction of E. maideni and D. viscosa. Plant interactions changed the C concentrations of stems and roots rather than those of leaves and branches. (2) Plant interactions affected the soil nutrients and forest characteristics significantly. Meanwhile, the biomass distribution was affected by soil total nitrogen, clumping index and gap fraction; the C concentrations were influenced by the leaf area index and soil total phosphorus. (3) The C storage proportions of all the components correlated significantly with the proportion of biomass. Our results suggested that both the biomass distribution and C concentration of D. viscosa were affected by plant interactions, however, the biomass fraction not the C concentration determines the C storage fraction characteristics for D. viscosa.

Hydrological and mechanical properties of loess landslides under different vegetation restoration types

Loess landslide is a common geological disaster in northern Shaanxi, which seriously affects people's life and property safety and social and economic development. The research on vegetation restoration types and hydrological and mechanical properties of loess landslides can provide basic data support for landslide stability prediction, and further provide reference for landslide prevention and treatment. In the present study, the loess landslide point of Zhang Zi Gou in Gan Quan County, Yan’an City was taken as the research object. On the basis of the existing natural condition data, the basic physical and mechanical properties and hydrological characteristics were obtained by collecting field landslide soil samples for indoor experimental analysis. The indoor analysis shows that the landslide is mainly distributed in dry land, medium coverage and low coverage grassland, indicating that the surface vegetation coverage can affect the stability of landslide. The worse the vegetation coverage, the more landslides occur. The void ratio and porosity of landslide soil decrease with the increase of dry density. The cohesion of natural soil is obviously higher than that of saturated soil, and the internal friction angle of natural soil is slightly lower than that of saturated soil. In general, due to the influence of water content, the shear strength of natural soil samples is higher than that of saturated soil samples. Therefore, in order to improve the accuracy of prediction and early warning system, it is necessary to consider the response of hydrological and mechanical properties of loess to vegetation restoration. The results provide basic data support for the establishment of loess landslide stability prediction system and provide reference for geological disaster management. Bangladesh J. Bot. 50(3): 795-801, 2021 (September) Special

Effects of vegetation restoration types on soil nutrients and soil erodibility regulated by slope positions on the Loess Plateau

Soil degradation is significantly increased driven by soil nutrient loss and soil erodibility, thus, hampering the sustainable development of the ecological environment and agricultural production. Vegetation restoration has been widely adopted to prevent soil degradation given its role in improving soil nutrients and soil erodibility. However, it is unclear which vegetation type has the best improving capacity from soil nutrient and soil erodibility perspectives. This study selected three vegetation restoration types of grasslands (GL), shrublands (SL), and forestlands (FL) along the five slope positions (i.e., top, upper, middle, lower, and foot slope), to investigate the effects of vegetation restoration types on soil nutrients and soil erodibility. All vegetation restoration types were restored for 20 years from croplands (CL). We used comprehensive soil nutrient index (CSNI) and comprehensive soil erodibility index (CSEI) formed by a weighted summation method to reflect the effect of vegetation restoration on the improving capacity of soil nutrient and erodibility. The results showed the vegetation types with the highest comprehensive soil quality index (CSQI) at the top, upper, middle, lower and foot slope were FL (1.92), FL (1.98), SL (2.15), FL (2.37) and GL (3.93), respectively. When only one vegetation type was considered on the entire slope, SL (0.59) and FL (0.59) had the highest CSNI, the SL had the lowest CSEI (0.34) and the highest CSQI (1.89). The CSNI was mainly influenced by soil structure stability index (SSSI), sand content, silt + clay particles, and CSEI was controlled by soil organic matter (SOM), macroaggregates and microaggregates. Moreover, the CSQI was influenced by pH, silt and clay content, and biome coverage (BC). The study suggested the SL were advised as the best vegetation restoration type on the whole slope from improving soil nutrients and soil erodibility.

Soil specific enzyme stoichiometry reflects nitrogen limitation of microorganisms under different types of vegetation restoration in the karst areas

Knowledge about resource limitations faced by soil microorganisms is crucial for understanding ecosystem functions and processes. In recent decades, vegetation restoration has been carried out in the degraded karst areas, leading to the alteration in the status of microbial resource limitation (MRL). However, mechanisms underlying MRL in different karst ecosystems remain poorly understood. Here we investigated MRL based on the theory of soil extracellular enzyme stoichiometry. Soil carbon (C), nitrogen (N), and phosphorus (P) acquiring enzyme activity (glucosidase, cellobiohydrolase, leucine aminopeptidase, urease and alkaline phosphatase) per unit microbial biomass carbon (MBCE) and per unit soil organic carbon (SOCE) of four main vegetation types (natural community, NC; ecological forest, EF; abandoned cropland, AC and economic plantation, EP) at 0–20 cm depth were measured in the karst areas in southwestern China. Significantly higher MBCE levels were found in EP than the other three vegetation types (p < 0.05), with EF having significantly higher SOCE than NC (p < 0.05), suggesting the highest metabolic activity and soil organic carbon (SOC) utilisation efficiency in EP and EF, respectively. C- and N-specific enzyme activity (MBCE and SOCE) were strongly negatively correlated with microbial biomass and soil C, N contents (p < 0.05), suggesting microbial resource requirement promotes the production of specific enzyme in resource-deficient ecosystems. Homeostasis analysis of microbial biomass C∶N and resources C∶N for all communities showed no homeostasis, indicating the microorganisms may be autotrophic to meet their N demands. In addition, the specific enzyme C∶N ratios were less than 1, the N∶P ratios were greater than 1, and vector angles were all less than 45° in all four types of vegetation restoration, indicating clear N limitation. A homeostasis analysis, as well as extracellular enzymatic stoichiometry and vector analysis, all suggested that soil microorganisms in the four vegetation types were nitrogen-limited, with NC most severely affected. Overall, we suggest that nitrogenous fertilisers should be added to restore the balance of elements while recovering the karst ecosystems.

Forestation delivers significantly more effective results in soil C and N sequestrations than natural succession on badly degraded areas: Evidence from the Central Loess Plateau case

Vegetation restoration is an important factor affecting soil carbon (C) and nitrogen (N) sequestration. However, the effects of the type of vegetation restoration on soil C and N sequestration varies owing to different environmental conditions. Therefore, additional studies should explore the effects of vegetation restoration type on soil C and N sequestration, especially between natural restoration and artificial afforestation. This study explored the differences in improving soil C and N sequestration between artificial forests (AF) and natural grasslands (NG) that had been converted from sloping cropland over 20 years since the implementation of GGP (Grain for Green Program) on the Central Loess Plateau, China. The results showed that NG and AF significantly increased the 0–20 cm soil organic carbon (SOC) content but had a minimal impact on the 20–100 cm SOC content after 20 years of vegetation restoration. In addition, the two vegetation restoration types significantly increased the 0–60 cm soil total nitrogen (STN) content, but they both had no significant effects on the 60–100 cm soil layer. Moreover, the C and N sequestration capacities of AF were higher than those of NG due to the AF had higher plant biomass and lower plant biomass C:N ratios compared to NG. The AF and NG both significantly increased the soil aggregate structure and stability following cropland conversions. Apart from soil aggregates playing a crucial role in affecting soil C and N sequestration, plant biomass and its C:N ratios also had the most substantial effects. The results suggested that soil aggregate stability and the quantity and quality of input organic matter have strongly influenced soil C and N sequestration post-restoration; moreover, N fixing species is more conducive to soil C and N sequestration and the artificial forests had higher C and N sequestration capacities than natural grasslands in the Loess Plateau, with a mean annual precipitation of 505 mm.

High-throughput Sequencing Analysis of Soil Bacterial Community in the Grain for Green Project Areas of the Loess Plateau

This study analyzed the characteristics of the soil bacterial community under different types of vegetation restoration, and explored the role of microorganisms in the vegetation restoration process, within the soil ecosystem of Grain for Green areas of the Loess Plateau. Typical artificial forest (artificial Robinia pseudoacacia forest, Pinus tabulaeformis forest), natural secondary forest, and grassland were selected as the research objects. High-throughput sequencing technology was used to analyze the α diversity and community structure of soil bacteria, and the correlation between soil environmental factors and bacterial communities. The Chinese National Ecosystem Research Network in Jixian County Station was chosen as the research area. The results showed that the bacterial communities of the five types of forest restoration comprised 25 phyla, 66 classes, 129 orders, 240 families, 392 genera, 760 species, and 2213 OTUs. There were significant differences in the abundance of bacterial communities, which could be ranked as follows: CD > CSL > CH2 > CH1 > YS. The dominant bacteria phyla in the different vegetation restoration types were Actinobacteria, Proteobacteria, Acidobacteria, and Chloroflexi. The relative abundances of natural secondary forest, grassland, and plantation were different, but not significantly. The relative abundances of α-Proteobacteria, β-Proteobacteria, and δ-Proteobacteria were higher in natural secondary forest soilthan in the soil of the other four restoration models, and the relative abundance was the lowest in grassland soil. The dominant bacteria were significantly correlated with soil pH and TN. Among them, TN was significantly positively correlated with Actinobacteria, pH was significantly positively correlated with Proteobacteria and negatively correlated with Actinobacteria, while Acidobacteria was significantly negatively correlated with soil pH and TN. PICRUSt analysis showed that the functional gene families were mainly related to 24 sub-functions, including cell motility, signal transduction mechanisms, amino acid transport and metabolism, as well as coenzyme transport and metabolism. These results can provide a good foundation for the evaluation of vegetation restoration in the Loess Plateau, as well as a scientific basis for the rational management of plantations.

Vegetation restoration types affect soil bacterial community composition and diversity in degraded lands in subtropical of China

Significant improvement of soil quality and biodiversity has been reported following vegetation restoration on the degraded lands in subtropical of China. However, so far the response of soil bacterial communities and drivers of their composition to differing vegetation restoration types are not well understood. In this study, we investigated soil physicochemical properties and bacterial communities in degraded land subjected to differing vegetation restoration types after 12 years of long‐term experiment. Restoration types included grassland, cropland, three differing plantation forests (orchard, coniferous forest, and coniferous forest with applied tillage), and control of degraded land. Bacterial community composition was examined using 16S rDNA sequencing. Result found that soil nutrient content includes soil organic carbon (SOC), total N (TN), available nitrogen (AN), available phosphorus (AP), and available potassium (AK) was improved after 12‐year restoration and the highest contents were found in cropland. However, soil pH was decreased after revegetation in the order degraded land &gt; grassland &gt; forestland &gt; cropland, and the soil C/N ratio was significantly decreased in cropland. Revegetation restoration significantly increased operational taxonomic units (OTUs), ACE, and Chao1 indices by 13.67–22.81%, 16.34–25.11%, and 14.66–24.00%, with relative abundances of bacterial phyla varying between the different vegetation types. Soil physicochemical properties (e.g. pH, SOC, TN, AN, AP, and AK) showed significant correlations with the majority of the dominant phyla. When degraded land was restored to cropland, soil C/N ratio decreased which promoted the growth of Actinobacteria. Revegetation with grassland and forest increased soil nutrient content and decreased pH, resulting in shifts in bacterial phyla favoring Proteobacteria and Acidobacteria. Our observations show that restoration of degraded land will lead to differing bacterial community compositions depending on the vegetation type.

Temperature and precipitation significantly influence the interactions between arbuscular mycorrhizal fungi and diazotrophs in karst ecosystems

Arbuscular mycorrhizal fungi (AMF) and diazotrophs have the potential for nutrient transfer and biological nitrogen fixation in ecosystems, respectively. However, their response to vegetation restoration remains unclear, especially under varying temperature and precipitation levels in karst ecosystems. This study aimed to understand the effects of three climatic levels within four natural and managed vegetation restoration types on the diversity and community composition of AMF and diazotrophs. The interactive effects of temperature, precipitation, and vegetation types affected AMF diversity, while diazotroph diversity was not affected. Under conditions of natural vegetation restoration, there was an increase in AMF diversity in response to increasing temperature and precipitation. AMF richness was higher in shrubland and mature forest than in cropland when temperatures were over 20 ℃ and precipitation was high. Thus, in terms of diversity, AMF were more responsive to changes in climatic conditions and vegetation recovery than diazotrophs. Both AMF and diazotroph community compositions were affected by temperature and vegetation type. The relative abundances of AMF groups (e.g., Gigaspora, Glomus, and Septoglomus) and diazotroph taxa (e.g., Frankia) increased at temperatures above 18 ℃. The relative abundances of the AMF genus Glomus and the diazotroph genus Bradyrhizobium in shrubland and mature forest were higher than those in cropland, while abundances of the AMF genus Septoglomus and diazotroph genus Anabaena increased in cropland. Network complexity increased with increasing temperature and precipitation between AMF and diazotroph taxa. Glomus and Bradyrhizobium showed the most links with other groups, confirming that the dominant genera perform well in the co-occurrence network. These results suggested high hydrothermal regions resist rapid nutrient decomposition by strengthening the interactions between AMF and diazotrophs, especially between the abundant groups Glomus and Bradyrhizobium. Management to increase AMF and diazotroph abundance during vegetation recovery in high climate level may stimulate nutrient absorption and transport.

Effect of Vegetation Restoration on Soil Hydrology in Karst Area of Southwest China: Inspiration from Barrel Planting Experiments

The purpose of this study was to explore the effects of different vegetation restoration types on soil hydrology characteristics in the Karst Plateau Gorge and to clarify the soil moisture (θ) use characteristics. A barrel experiment was conducted to monitor θ and the water potential (Ψ) of three vegetation types (Zanthoxylum bungeanum (ZB), Zea mays L. (ZM), and Sophora tonkinensis (ST), Abandoned land (AL)) was used as a control to explore θ use conditions of each vegetation type. A larger surface permeability led to lower moisture storage. The soil moisture storage showed the law of ZM &gt; ST &gt; AL &gt; ZB. The soil moisture storage also had obvious characteristics in dry-wet seasons. As a typical drought-tolerant crop, ZB responded more obviously to rainfall and had the highest effective replenishment amount and efficiency. Two processes were clearly involved in decreasing soil moisture, which could be divided into three stages of changes: a consumption period (CP), a moisture supplying period (SP), and a relatively stable period (RSP). CP occurred primarily in November to April, when θ was prone to water stress and required proper artificial replenishment. SP was characterized by limited rainfall replenishment in January and May, which significantly increased θ. During the rainy season, corresponding with RSP, θ fluctuated within a relatively stable range. At the end of the CP, the water shortage was more severe. In actual agricultural production, attention should be given to reasonable artificial recharge. This research aims to provide a theoretical basis for karst θ management.

Trade-off analyses of plant biomass and soil moisture relations on the Loess Plateau

Plant biomass is a crucial parameter for terrestrial ecosystem carbon cycling. Water plays a crucial role in biomass production, especially in arid and semi-arid regions. However, the trade-off relationships between the plant biomass and soil moisture have not been well investigated on the Loess Plateau. In our study, we synthesized 615 pairs of data to evaluate the trade-off between the plant biomass and soil moisture in different precipitation areas and vegetation restoration ages on the Loess Plateau using the quantitative trade-off method. The results showed that precipitation had the strongest effect on soil moisture content (SMC), and aboveground biomass (AGB) was controlled more by vegetation restoration type and elevation, whereas belowground biomass (BGB) was controlled more by vegetation restoration age and elevation. SMC had a higher relative benefit than AGB and BGB in most precipitation areas. In addition, vegetation restoration age is another critical variable to determine the trade-offs between AGB and SMC and between BGB and SMC. For forest, the minimum trade-off of restoration years was > 10 years, but it was < 10 years for shrubland and grassland. Because the trade-offs between AGB and SMC and between BGB and SMC revealed a large spatial change on the whole Loess Plateau, the vegetation in different precipitation areas should identify suitable management strategy to maintain benefits. Understanding the relationship between the plant biomass and soil moisture will improve our ability to sustainably manage vegetation construction and water resources.

The effects of different types of vegetation restoration on wind erosion prevention: a case study in Yanchi

Improving wind erosion prevention in the key ecological zones of sand fixation are closely linked to human welfare in China and Northern Eurasia. In this research, we studied the sand transport rate (STT), soil water content (SWC), and retention rate of the wind erosion prevention services (RR) in five experimental zones in Yanchi Country, including bare sandy land (BL), and four restoration zones with different types of vegetation restoration approaches, including artificial restored grassland with low-coverage (AGL), artificial restored grassland with high-coverage (AGH), artificial shrub land (AS), and naturally restored grassland (NG). The results showed that: (1) From 2006 to 2018, the STTs of the four restoration zones were lower than those of BL, and those of the AS were much lower than those of AGL, AGH, and NG; (2) in the rainy season, the SWCs of AS, NG, AGH, AGL, and BL were 3.01%, 2.80%, 2.79%, 2.68%, and 2.41% respectively. In the dry season, the SWCs of NG, BL, AGH, AHL, and AS were 2.86%, 2.93%, 3.00%, 3.08%, and 3.20%, respectively. The differences in the SWCs between the two seasons of BL were the largest (0.52%), while those of NG were the lowest (0.06%); (3) the annual average RRs in AS, AGH, NG, and AGL were 74.41%, 69.41%, 69.28%, and 61.64%, respectively, while the annual change of the RR in the NG was the smallest. This study reveals the effects of different types of vegetation restoration on wind erosion prevention in Yanchi country, thereby providing a scientific basis for policymakers to engage in effective vegetation restoration and formulate ecological protection policies.

Comparison of soil microbial community between reseeding grassland and natural grassland in Songnen Meadow

Microorganisms have important ecological functions in ecosystems. Reseeding is considered as one of the main strategies for preventing grassland degradation in China. However, the response of soil microbial community and diversity to reseeding grassland (RG) and natural grassland (NG) remains unclear, especially in the Songnen Meadow. In this study, the soil microbial community compositions of two vegetation restoration types (RG vs NG) were analyzed using a high-throughput sequencing technique. A total of 23,142 microbial OTUs were detected, phylogenetically derived from 11 known bacterial phyla. Soil advantage categories included Proteobacteria, Acidobacteria, Actinobacteria, and Bacteroidetes, which together accounted for > 78% of the all phyla in vegetation restoration. The soil microbial diversity was higher in RG than in NG. Two types of vegetation restoration had significantly different characteristics of soil microbial community (P < 0.001). Based on a molecular ecological network analysis, we found that the network in RG had a longer average path distance and modularity than in NG network, making it more resilient to environment changes. Meanwhile, the results of the canonical correspondence analysis and molecular ecological network analysis showed that soil pH (6.34 ± 0.35 in RG and 7.26 ± 0.28 in NG) was the main factor affecting soil microbial community structure, followed by soil moisture (SM) in the Songnen meadow, China. Besides, soil microbial community characteristics can vary significantly in different vegetation restoration. Thus, we suggested that it was necessary and reasonable for this area to popularize reseeding grassland in the future.

Changes of soil quality induced by different vegetation restoration in the collapsing gully erosion areas of southern China

Understanding the influence of collapsing gully management restoration on soil quality and function is essential to the protection of the regional ecological environment in the collapsing gully erosion area. The primary objective of this study was to construct soil quality index (SQI) to assess the influence of different vegetation restoration types on soil quality in collapsing gully restoration. The influence of five vegetation restoration types on soil properties was investigated by using a path analysis, a comprehensive soil quality index (SQI), and a general linear model (GLM). Vegetation restoration was shown to significantly increase the saturated hydraulic conductivity (Ks), mainly due to the effect of the physical parameters of bulk density, soil cohesion, and soil water content. Meanwhile, pH, Ks, soil organic matter (OM), and sand content were revealed as reasonable indicators to evaluate the influence of vegetation restoration on soil quality. Moreover, vegetation restoration was found to significantly improve the soil quality, with the highest SQI value for natural restoration mixed forest (NF), followed by replanted arboreal forest (RA) and replanted scrubland (RS), which were all significantly higher than the SQI value of the erosion area (EA) in the collapsing gully. Additionally, vegetation type explained the most substantial proportion of total variability (46.41%), and restoration time showed a positive correlation with SQI. The results of this study can provide a reference for the restoration and protection of the regional ecological environment in the collapsing gully area.

Effects of freeze-thaw cycles and soil moisture content on soil available micronutrients on aggregate scale in natural grassland and Chinese pine forestland on the Loess Plateau, China

Micronutrient presence and concentration are strongly influenced by soil aggregate size. Seasonal freeze-thaw patterns are known to modify soil aggregate distributions, thereby contributing to the transformation and redistribution of available soil micronutrients. Few studies, however, have evaluated the response of aggregate-associated available micronutrients to freeze-thaw cycles (FTCs) under different types of vegetation restoration. We designed a laboratory experiment to simulate the three typical types of ecosystems on the Loess Plateau in China (cropland, Chinese pine forestland, and natural grassland). In this experiment, we measured the effects of number of FTCs (0, 1, 3, and 9) and soil moisture content (SMC) (40 and 80% field capacity) on available micronutrients (Cu, Fe, Mn, and Zn) in bulk soil and three soil aggregate size classes. FTCs significantly increased available micronutrient content in bulk soil by increasing > 2000 μm aggregate-associated available micronutrient contents and decreasing < 250 μm aggregate-associated available micronutrient contents. In most cases, the influences of FTCs on bulk soil and aggregate-associated available micronutrient content were enhanced by increased SMC. Compared with cropland soil, the bulk soil available Cu, Fe, Mn, and Zn in natural grassland soil and available Cu in Chinese pine forestland soil were significantly increased. The increasing effects of FTCs on the available micronutrient content in cropland and natural grassland soils were larger than that in Chinese pine forestland soil. The results indicated that increasing FTCs and SMC was beneficial for alleviating available micronutrient deficiencies in soil, and natural grassland was better than Chinese pine forestland for increasing available micronutrients in this loess-derived soil.

Effects of vegetation restoration on soil quality in fragile karst ecosystems of southwest China.

Soil quality assessment is important for karst ecosystems where soil erosion is significant. A large amount of vegetation restoration has been implemented since the early 21st century in degraded karst areas across southwestern China. However, the impacts on soil quality of different restoration types rarely have been compared systematically. In the current study, we investigated the soil quality after a number of vegetation restoration projects as well as their adjacent cropland by analyzing soil samples. Six vegetation restoration types were evaluated, including one natural restoration (natural shrubland, protected for 13 years), three economic forests (4 years Eucalyptus robusta, 4 years Prunus salicina and 6 years Zenia insignis) and two mixed forests (1 year Juglans regia–crop and 13 years Toona sinensis-Pennisetum purpureum ). We evaluated the benefits of different restoration types more accurately by setting each adjacent cropland as the control and setting the variation between the corresponding restored and control site as the evaluation object so that the background differences of six sites could be eliminated. The results indicated that natural shrubland, Toona sinensis-Pennisetum purpureum and Zenia insignis were effective in improving soil quality index (SQI) in degraded karst cropland largely due to their higher SOC and TN content. The variation of SQI (VSQI) of natural shrubland was significantly higher than that in Eucalyptus robusta, Prunus salicina and Juglans regia-crop in total soil layer (0–30 cm) (P < 0.05), indicating natural shrubland had better capacity to improve soil quality. The boosting regression tree model revealed that vegetation restoration type explained 73.49% and restoration time explained 10.30% of the variation in VSQI, which confirmed that vegetation restoration type and restoration time are critical for achieving soil reserves. Therefore, it is vital to select appropriate vegetation type in restoration projects and recovery for a long time in order to achieve better soil quality. The current study provides a theoretical basis on which to assess the effects of different vegetation restoration types on the heterogeneous degraded karst areas.

Response of soil phosphorus fractions and fluxes to different vegetation restoration types in a subtropical mountain ecosystem

Soil phosphorus (P) improvement is one of the important aims of vegetation restoration. However, the effects of different vegetation restoration types on soil P cycling and the underlying mechanisms remain unclear. Together with vegetation structure and soil properties, we measured the soil P fractions and P transformation rates to evaluate the characteristics of ecologically relevant soil P fraction distributions and their dynamics for the most common vegetation restoration types in a subtropical mountain ecosystem (i.e., PF, Pinus forest; EF, Eucalyptus forest; SL, shrubland; and NSF, natural secondary forest). We found that water-extractable inorganic P (Pi), organic P (Po), and acid phosphatase activity (APA) were significantly higher in NSF than those in the other vegetation types (P < 0.01), together with the highest gross P mineralization rate (Pmin) and net P immobilization rate (Pimm), suggesting biological processes played a more important role in soil P cycling in the NSF. In contrast, the soil showed the lowest values of Pmin, Pimm, and APA in the EF compared to NSF and PF (P < 0.05), together with the highest P loss and the higher net P solubilization rate (Psol), indicating the greater importance of soil geochemical processes. Compared with the NSF and EF, geochemical and biological processes co-regulated soil P cycling in the PF and SL. However, the soil in the PF displayed higher P fluxes (Pmin, Pimm, Psol, and P loss) than those in the SL (P < 0.05), suggesting the soil had higher P flux magnitudes in the PF. Results of correlation analyses showed that the soil microbial community structure and activity played a more important role than plant community attributes and soil physicochemical properties in soil P fraction distribution and fluxes. In conclusion, soil P fraction distributions and their fluxes can be significantly influenced by vegetation restoration types. Land management strategies focusing on restoration of the soil microbial community may enhance soil P cycling and improve soil quality.