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Addressing the imbalance of the livestock–forage–environment system on the Qinghai–Tibet Plateau (QTP), the extensive replacement of natural grasslands with artificial grasslands has been pursued to enhance forage yield and quality. Recognizing their pivotal role in soil ecology, soil nematodes serve as sensitive indicators of the soil ecosystem structure and function. In this context, we embarked on a field investigation aimed at discerning the impact of varying artificial grasslands on soil nematode communities and food webs, with the intent of identifying an optimal forage species through the lens of soil nematode dynamics in the temperate steppe of the QTP. Our findings indicate that artificial grasslands, on the whole, tend to augment the soil nematode diversity—as reflected in the increased Margalef richness—and modify the community structure. Notable enhancements were observed in the abundance of bacterivores and omnivores, the fungivore and omnivore biomass carbon, and the connectance within fungal and bacterial channels. Specific insights reveal that grasslands established with Elymus nutans and Elymus sinosubmuticus notably boost the Margalef richness, omnivore biomass carbon, and both functional and structural metabolic footprints, with E. sinosubmuticus grasslands uniquely elevating the fungal channel connectivity. Elymus sibiricus grasslands, in particular, were associated with increased fungivore biomass carbon and metabolic footprints, as well as increased connectance in fungal and omnivore–predator channels. In summation, E. sibiricus, E. nutans, and E. sinosubmuticus emerge as superior choices for artificial grassland cultivation on the QTP, as suggested by soil nematode indicators. The adoption of mixed-species sowing incorporating these three candidates potentially offers enhanced benefits to the soil food web, although this hypothesis warrants further investigation. [ABSTRACT FROM AUTHOR]

The responses of dominant species to plant–soil feedback (PSF) are well established; however, the changes in the PSF of companion species remain unclear. This study aims to assess the direction and intensity of PSF, determine the main factors influencing it, and interpret the ecological significance of PSF in companion species within the context of grassland community succession. Three typical companion species, namely Artemisia sacrorum, Artemisia capillaris, and Artemisia giraldii, were planted in soils at three grassland community succession stages (early, middle, and late) on the Loess Plateau. Our results indicate that during both plant growth periods, the shoot biomass of A. sacrorum, A. capillaris, and A. giraldii in early- and late-stage soils was higher than that in the middle-stage soil, suggesting consistent growth of the three companion species during the two growth periods. However, plant growth simultaneously led to a reduction in soil nutrient content and microbial biomass, resulting in an overall decrease in the biomass of the three species, indicating a negative PSF effect in companion species. In conclusion, the negative PSF observed in all three associated species explains the temporary dominance of companion species during succession. This study enhances our understanding of the mechanisms driving PSF in community succession. [ABSTRACT FROM AUTHOR]

Background: Studying plant–soil feedback (PSF) is of great significance to understanding plant community dynamics. Aims: We aimed to determine the temporal variation in PSF at different stages of grassland community succession and the influencing factors. Methods: We conducted a 3‐year experiment to examine how PSF changes during different successional stages (early‐, mid‐ and late‐). Setaria viridis, Stipa bungeana and Bothriochloa ischaemum were selected as representative and dominant early‐, mid‐ and late‐species, respectively, in the semiarid grassland of the Loess Plateau, China. Results: The temporal variation in the PSF pattern was found to be species‐specific. Negative and neutral PSF patterns in early‐ and mid‐species, respectively, were found within the 3‐year growth periods. A positive PSF pattern for late‐species was found in the second growth period, and a negative PSF pattern was found in the third growth period. The shoot biomass of early‐species was overall positively correlated with soil nutrients and enzyme activity in the soil of the three species. However, the shoot biomass of late‐species was overall negatively correlated with soil nutrients and enzyme activity in early‐species soil. Conclusions: We suggest that the negative PSF of early‐species over the growing period explains why the advantage of these early colonizers is temporary. In contrast, the positive PSF of late‐species likely contributes to their successful colonization and the entire community succession process. Our results indicated that PSF plays an important role in the progression of plant community succession. [ABSTRACT FROM AUTHOR]

SUMMARY: Arbuscular mycorrhizal fungi (AMF) can improve plant nutrient acquisition, either by directly supplying nutrients to plants or by promoting soil organic matter mineralization, thereby affecting interspecific plant relationships in natural communities. We examined the mechanism by which the addition of P affects interspecific interactions between a C4 grass (Bothriochloa ischaemum, a dominant species in natural grasslands) and a C3 legume (Lespedeza davurica, a subordinate species in natural grasslands) via AMF and plant growth, by continuous 13C and 15N labelling, combined with soil enzyme analyses. The results of 15N labelling revealed that P addition affected the shoot uptake of N via AMF by B. ischaemum and L. davurica differently. Specifically, the addition of P significantly increased the shoot uptake of N via AMF by B. ischaemum but significantly decreased that by L. davurica. Interspecific plant interactions via AMF significantly facilitated the plant N uptake via AMF by B. ischaemum but significantly inhibited that by L. davurica under P‐limited soil conditions, whereas the opposite effect was observed in the case of excess P. This was consistent with the impact of interspecific plant interaction via AMF on arbuscular mycorrhizal (AM) benefit for plant growth. Our data indicate that the capability of plant N uptake via AMF is an important mechanism that influences interspecific relationships between C4 grasses and C3 legumes. Moreover, the effect of AMF on the activities of the soil enzymes responsible for N and P mineralization substantially contributed to the consequence of interspecific plant interaction via AMF for plant growth. [ABSTRACT FROM AUTHOR]

Artificial grasslands have been regarded as an effective method to improve grass production and quality, especially on the Qinghai–Tibet Plateau. Soil ecosystem multifunctionality (EMF) plays an important role in sustainable regional development. However, few studies have investigated the impacts of artificial grasslands on soil EMF. Here, we constructed single-species artificial grasslands in a natural temperate steppe and investigated soil microbial communities, abiotic factors (soil moisture and pH), and functions related to biogeochemical cycles to explore (1) how the transformation from temperate steppe to artificial grasslands affected soil EMF and (2) the roles of species and phylogenetic microbial diversities, microbial community composition, and abiotic factors in driving differences in soil EMF. Our results showed that artificial grasslands decreased soil EMF regardless of planting species; that the bacterial and fungal community composition contributed more to soil EMF prediction than species and phylogenetic diversities; and that microbial phylogenetic diversities were negatively associated with soil EMF. Soil pH played an important role in the effects of artificial grasslands on soil EMF—artificial grasslands increased soil pH, which was negatively associated with soil EMF. Overall, the benefits of establishing artificial grasslands, for example, higher grass production and quality, might be at the expense of soil EMF. Further studies should explore mixed-species artificial grasslands. [ABSTRACT FROM AUTHOR]

Global atmospheric nitrogen deposition significantly affects the nutrient cycling and C–N–P stoichiometry in ecosystems. Herein, a global meta-analysis was conducted based on 898 pairwise observations to analyze the impact of nitrogen addition on plant-soil-enzyme C–N–P stoichiometry and microbial nutrient limitation in different ecosystem types (cropland, grassland, and forest), nitrogen addition intensity (0–5, 5–10, and >10 g N m−2 yr−1) and duration (0–5, 5–10, and >10yr). Results showed that nitrogen addition significantly decreased plant C:N (shoot: 16.5%, root: 27.1%, litter: 16.5%), soil C:N (5.9%), enzyme C:P (1.2%), and enzyme N:P (5.1%), whereas significantly increased soil C:P (4.9%), enzyme C:N (7.1%), vector angle (4.4%), vector length (3.9%), and plant N:P (shoot: 24.1%, root: 23.8%, and litter: 13.5%). Furthermore, nitrogen addition mainly affected the enzyme C:N and vector length in grasslands. Additionally, the changes in C:N in plants, soil, and enzymes, and vector angle and length were higher at nitrogen addition intensity of >10 g N m−2 yr−1. The changes in C:N and C:P in plant and soil were higher at nitrogen addition duration of >10 yr. Finally, the N:P in shoot, soil and enzyme, and vector angle were strongly correlated with mean annual precipitation (MAP). In conclusion, nitrogen addition significantly reduced the C:N ratio in plants and soil and increased plant N:P, and microbial C and P limitation. These effects vary with the ecosystem type, MAP, and nitrogen addition intensity and duration. The results improve our understanding of the plant-soil-microbial nutrient cycling processes in terrestrial ecosystems under global nitrogen deposition. [Display omitted] • N addition reduced soil and plant C:N and increased plant N:P. • N addition increased microbial C limitation in grassland and P limitation in forests. • N addition intensity and duration weakened microbial P limitation. • Results help to understand terrestrial geochemical cycle under N deposition. [ABSTRACT FROM AUTHOR]

• A field warming experiment took place over 21 years on the Qinghai-Tibetan Plateau. • Warming increased the erodibility of topsoil but this effect weakened with depth. • Microbial activity and aboveground plant biomass decreased. • There were differences in the erodibility of shrubland and grassland soils. Terrestrial ecosystems are significantly impacted by global warming. To determine the effects of long-term warming on soil structure and erodibility in the Qinghai-Tibetan Plateau (China), a 21-year field warming experiment was conducted, where the soil response to temperature changes was investigated for two vegetation types (shrubland and grassland). The measured parameters included the fractal dimension (D v) of aggregates, mean weight diameter (MWD), geometric mean diameter (GMD), multifractal dimensions of particle size distribution [capacity dimension (D 0), information dimension (D 1), information dimension/capacity dimension ratio (D 1 / D 0), and correlation dimension (D 2)], and soil erodibility value (K). The results show that warming significantly increases the erodibility of the topsoil (0–2 cm). Among them, the larger particles (0.2–2 mm aggregates, sand) decreased, the K factor, D v , and multifractal dimension (D 0) increased, and the MWD and GMD of the soil aggregates decreased. Long-term warming affected the amounts of soil organic carbon, total nitrogen, and total phosphorus. Furthermore, warming weakened microbial activity and led to a reduction in the aboveground biomass of plants. With increasing soil depth, the effect of warming on the erodibility of underlying soil (2–12 cm) gradually weakened. Warming exhibited different effects on the erodibility of the shrubland and grassland because of their different soil aggregates and particle size distributions. These results confirm that long-term warming has obvious soil layering effects on different soil depths. Soil properties, plants, and microorganisms respond to warming and have direct or indirect effects on soil erodibility. The results of this study provide important insights into changes in soil structure and erodibility at high altitudes, especially under global warming. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ecological niches of different species were evaluated in a grassland community. • Shrubs and B. ischaemum showed advantages in stable grassland community. • Plant phosphorus, and C:N affected niche positively. • Rhizosphere SOC, TN, bacteria diversity affected niche negatively. • Niche was determined by bacterial diversity and plant below-ground carbon. To explore the primary factors affecting the ecological niches in a plant community, four dominant shrub species (Sophora viciifolia , Periploca sepium , Buddleja alternifolia , Clematis fruticosa) and six dominant grass species (Bothriochloa ischaemum , Artemisia sacrorum , Stipa bungeana , Cleistogenes squarrosa , Stipa grandis , Lespedeza bicolor) were selected from a stable grassland community in the Loess Plateau (China). The relative importance value and niche breadth were used as comprehensive quantitative indices to characterize the status, role, and degree of dominance of plant species in the community. We found that relative importance value and niche breadth were higher overall in shrub species than in most grass species, except B. ischaemum. Meanwhile, the relative importance value was significantly correlated with plant phosphorus concentration, plant carbon:nitrogen ratio, rhizosphere soil organic carbon, rhizosphere soil total nitrogen, rhizosphere soil total phosphorus, rhizosphere bacterial α-diversity. A stepwise regression analysis indicated that, among the plant and rhizosphere characteristics of these species, only their rhizosphere bacterial α-diversity and plant root carbon concentration primarily influence ecological niche patterns of these plant species in the community. In summary, our study reveals that shrub species occupy more advantageous ecological niches than grass species in a stable community due to the active rhizosphere interactions, providing a new opportunity to disentangle the mechanisms underlying the plant community assembly in grassland. [ABSTRACT FROM AUTHOR]

• Long-term warming experiment showed the changes in environmental contexts. • Soil microbes of two ecosystems responded differently to warming. • Plants mediated the effect of global warming on microbial responses. Exploring the feedback of the soil microbial community and associated processes to global warming represents a major global challenge. To date, the focus has been placed on the direct effects of warming on soil microbial communities, overlooking how concurrent changes in plant communities may mediate these effects. Additionally, few studies have examined long-term effects of warming in more than one environmental context. In the present study, we conducted a long-term simulated warming experiment to investigate how changes to the plant community within two different environmental contexts affect the responses of soil microorganisms and their respiration to warming. We analyzed the abundance, diversity, and community composition of plants and soil microbes, in addition to soil microbial interaction networks and soil microbial respiration, in two typical ecosystems of the Qinghai–Tibet Plateau. Following long-term warming, the soil microbial composition, structure, and interactions changed, and the shifts depended on the aboveground plant type. Specifically, the co-occurring networks containing different microbial communities tended to be more complex in a shrubland than in a grassland after warming, leading to higher carbon use efficiency. Additionally, long-term warming changed the structure of soil microbial communities, increasing the relative abundances of oligotrophic taxa in the shrubland but not in the grassland. The shifts in community structure and interaction patterns could be explained by vegetation community attributes, highlighting the strong effect of plants on soil microbial responses. These plant-mediated effects on community structure and interactions subsequently could explain changes in soil microbial respiration rates. Microbial respiration showed a positive response to elevated temperature in the grassland but no response to temperature in the shrubland. These results indicate that interactions between soil microbial communities and plant communities determine how soil microbes respond to global warming. Therefore, future research on soil microbial community composition and associated carbon feedbacks to the climate change should include plant-mediated effects, which can provide a scientific basis for effectively mitigating global warming. [ABSTRACT FROM AUTHOR]

• C:N:P stoichiometry in plants, soils, and enzymes varied with succession time. • Plant species showed a relatively strong homeostasis during secondary succession. • Rhizosphere stoichiometry differed among plant species and succession stages. • Enzyme is crucial than soil nutrients in determining plant tissue stoichiometries. Ecological stoichiometry is the study of the interaction and balance of multiple chemical elements in ecological processes. However, how ecological stoichiometric interactions among plants, soils, and enzymes in the rhizosphere affect secondary plant succession is largely unknown. In this study, we collected the dominant and main companion species Artemisia capillaris , A. sacrorum , and Stipa bungeana , along a secondary succession chronosequence (7, 12, 17, 22, and 32-year) following a cropland abandonment in the Loess Plateau, China. We measured the carbon (C), nitrogen (N) and phosphorus (P) concentrations of plant shoots and roots, as well as the concentrations of C, N, P, available N (aN), available P (aP), and the activity of one C-acquiring enzyme (β-glucosidase (BG)), two N-acquiring enzymes (N-acetylglucosaminidase (NAG), leucineaminopeptidase (LAP)), and one P-acquiring enzyme (alkaline phosphatase (AP)) found in the rhizospheric soil to explore the C:N:P stoichiometry that drives secondary plant succession. The C:P and N:P ratios in the shoots of dominant plant species significantly decreased to a minimum value at the 22-year site and then increased with plant secondary succession. Compared with the 7-year site, the rhizosphere soil C:P and N:P ratios, and enzyme N:P ratios (ln(NAG + LAP):ln(AP)) increased 103.6%, 72.0%, and 221.3%, respectively, but enzyme C:N ratios (ln(BG):ln(NAG + LAP)) decreased 48.2% in the dominant plant species at the 32-year site. Principal component analysis indicated that the stoichiometry characteristics of the plant-soil-enzyme continuum differed for each plant species and succession stage. Stoichiometric homeostasis indices for the plant species indicated a relatively strong homeostasis, while redundancy analysis revealed that the variations in soil BG, NAG, and AP activity and enzyme C:N ratio had significant effects on the stoichiometries and nutrient concentrations of the plant tissues. The results indicated that rhizosphere stoichiometry is a powerful tool for evaluating plant-soil interactions in terrestrial ecosystems and that the variation in rhizospheric soil enzyme activity driving the secondary succession of plants. [ABSTRACT FROM AUTHOR]

• Specific enzyme activities increased and then decreased along secondary succession. • Soil enzyme temperature sensitivities (Q 10) changed along succession in rhizosphere. • Q 10 at different temperature ranges differed in bulk soil, but not in rhizosphere. • Rhizosphere effects of enzyme activities changed to negative value with succession. The influence of plant secondary succession on soil enzyme activities has been increasingly recognized recently. However, the characteristics of specific enzyme activities and temperature sensitivity (Q 10) in the rhizosphere remain elusive. We collected rhizosphere and bulk soil samples from a secondary successional series (0, 7, 12, 17, 22, and 32 years after farmland abandonment, and a natural grassland reference) in a typical semi-arid ecosystems on the Loess Plateau of China. The potential activity of soil enzymes, including β-1,4-glucosidase (BG), β-1,4-N-acetylglucosaminidase (NAG), leucine aminopeptidase (LAP), and alkaline phosphatase (AP), was assayed at 37, 20 and 4 °C and expressed as activity per unit of soil organic carbon (specific enzyme activity). Q 10 values were calculated at 20–37 °C and 4–20 °C, respectively. The specific enzyme activities of BG, NAG, LAP and AP in bulk soil increased to a maximum at the 17-year site and then significantly decreased in older grasslands. In the rhizosphere, specific enzyme activities increased and then decreased along the successional gradient with significantly higher value at the 7-year site and the 17-year site. The Q 10 values of BG activity in bulk soil and the four enzyme's activities in rhizosphere soil were changed significantly along the successional gradients. In general, the Q 10 values at the two temperature ranges differed in bulk soil, but not in the rhizosphere soil. Along the plant successional gradient, the rhizosphere effects of specific enzyme activities gradually changed to negative values in the oldest sites. Our results indicate that plant secondary succession had different impacts on the enzyme activity and characteristics in the rhizosphere and bulk soil, and highlights the importance of temperature sensitivity and rhizosphere effects of enzyme activity along plant secondary successional gradients. [ABSTRACT FROM AUTHOR]

• Recovery years increased soil enzyme activity in the steppe and forest-steppe zone. • Recovery years decreased SOC stability in the steppe and forest-steppe zone. • The forest zone might have the most stable soil enzyme activity and SOC stability. • Key factors regulating these changes are different among the three vegetation zones. The effects of cropland abandonment on soil enzyme activity and soil organic carbon (SOC) stability, along with the driving factors, are poorly understood. Here, we aimed to systematically and comprehensively evaluate soil enzyme activity, SOC stability, and the associated driving factors in different vegetation zones after cropland abandonment on the Loess Plateau, China. We selected grasslands with different recovery times along a rainfall gradient encompassing the steppe zone (SZ), forest-steppe zone (FSZ), and forest zone (FZ). We measured and compared the changes in soil enzyme activity (saccharase, polyphenol oxidase, urease, phosphatase, and catalase) and SOC stability as a function of recovery time; we also evaluated the relationships between these two parameters. In SZ and FSZ, soil enzyme activity, fractions of oxidizable carbon (including very labile [C1], labile [C2], and less labile [C3]), and the carbon management index (CMI) increased with recovery time, whereas the SOC stability index (SI) decreased. Conversely, in FZ, polyphenol oxidase activity increased linearly, urease and catalase activities decreased linearly, and the change in saccharase activity was represented by a cubic equation regression. SI showed no obvious changes with recovery time, whereas C1, C2, and C3 initially decreased and then increased. Redundancy analysis showed that, in FSZ and FZ, soil enzyme activity, C1, C2, C3, and SI were influenced by vegetation diversity, coverage, and soil nutrient levels. In comparison, in SZ, these parameters were mainly influenced by soil nutrient levels. Soil enzyme activity was strongly correlated with C1 and C3 in SZ and FSZ, but not in FZ. Overall, in SZ and FSZ, soil enzyme activity increased with recovery time, whereas SOC stability decreased. In contrast, both parameters were relatively stable in FZ, which had higher mean annual precipitation and mean annual temperature. [ABSTRACT FROM AUTHOR]

• Recovery years increased soil microbial activity in the 0–20 cm soil layers. • Recovery years had smaller effect on soil microbial activity in the 30–50 cm layers. • Factors regulating microbial activity changes were different among the four layers. Cropland abandonment strongly affects plant-soil interactions. However, knowledge remains limited about how the production and diversity of plants and soil physicochemical parameters drive changes in soil microbial activity (such as microbial biomass, respiration, and enzyme activity) after cropland abandonment. Here, we investigated a grassland restoration chronosequence (0–30 years) to determine the dynamics of soil microbial biomass, respiration, and enzyme activity in the Loess Hilly, Region (China). Overall, cropland abandonment caused an increase in soil microbial activity primarily in the 0–20 cm soil layers. The metabolic quotient in the 0–10 cm layer decreased linearly with time since abandonment (recovery years). Structural equation models showed that recovery years directly and indirectly affected changes to soil microbial activity. Plant species richness, aboveground biomass, and soil organic carbon explained a large proportion of the variability in soil microbial activity in the 0–20 cm layer. However, the variability in soil microbial activity was mostly explained by plant species richness, belowground biomass, and soil total nitrogen in the 20–50 cm layers. Our results indicate that during recovery after cropland abandonment, changes in soil microbial activity are driven by plant characteristics and soil physicochemical parameters, with different drivers at different soil depths. [ABSTRACT FROM AUTHOR]

Beginning in the twentieth century, atmospheric deposition of N and P greatly increased in terrestrial ecosystems, including alpine grasslands. These inputs have profoundly affected soil microbial C and N cycles. Changes in the microbial environment are directly caused by changes in soil N and P availability and also indirectly through changes in vegetation in response to increased fertilization. The mechanisms involved in both the direct and indirect changes are not mutually exclusive and are poorly understood. Therefore, we investigated the responses of vegetation and soil microbes to a 9-year fertilization (N and P) experiment in an alpine grassland in the Qinghai–Tibetan Plateau in China. We found that N addition altered soil microbial community composition and processes regardless of P addition. To maintain stoichiometric homeostasis, soil microbes adjusted metabolic processes in response to changes in nutrient availability. High N availability enhanced microbial investment in C acquisition as indicated by β-1,4-Glucosidase activity. The abundance of microbial taxa that degrade labile C also increased. High N inputs also induced a proliferation of denitrifiers and increased the gaseous N loss potential. Partial least squares path modelling indicated that soil parameters (e.g., soil organic C and total N) and changes in the plant community played a key role in shaping soil microbial community structure and C and N cycling. Our results suggest that vegetation and stoichiometric differences between resource availability and soil microbial nutrient requirements collectively regulate the responses of soil microbial processes to N enrichment, which provides novel experimental insights into the mechanisms underlying the effects of nutrient inputs on microbial C and N cycles. Ultimately, our findings highlight the importance of plant traits in regulating microbial nutrient cycles, further promoting our comprehension about the mechanism of variation in the microbial nutrient cycles in an alpine grassland soils. • Microbial process was driven by stoichiometric relation between substrate and them. • Fertilization indirectly affects microbial processes mediated by vegetation. • Soil microbial community and functions correlated soil and plant parameters. [ABSTRACT FROM AUTHOR]

• Soil-specific enzyme activity are sensitive to vegetation restoration. • Recovery years increased specific enzyme activity per unit SOC in the 0–20 cm depth. • Recovery years decreased specific enzyme activity per unit MBC in 0–10 cm depth. • Soil-specific enzyme activity per unit SOC affected SOC stability negatively. It is well-established that changes to land use changes affect soil enzyme activity; however, little is known about the changes in soil specific enzyme activity per unit soil organic carbon (SOCE) and soil microbial biomass carbon (MBCE) after vegetation restoration in the arid and semi-arid regions of China. The objectives of this study were to investigate the effects of long-term vegetation restoration on soil specific enzyme activity and to elucidate the relationship between specific enzyme activity and soil organic carbon (SOC) stability in the Loess hilly region of China. We determined three enzymes (saccharase, urease, and phosphatase) activity at 0–50 cm soil depths in plots under vegetation restoration for different lengths of time and supporting different vegetation types (grassland, 2–30 recovery years; shrubland, 5–47 recovery years; and forestland, 5–56 recovery years). SOCE and the geometric mean of enzyme activity (GMEA) at 0–20 cm depth initially increased and then decreased, whereas overall MBCE at 0–10 cm depth decreased with time. Overall, SOCE and GMEA decreased with soil depth, and were significantly and negatively correlated with SOC stability index (SI). In comparison, the relationship between MBCE and SI was non-significant. Overall, our data showed that specific enzyme activity and GMEA responded to vegetation restoration, with SOCE and GMEA negatively impacting SOC stability. [ABSTRACT FROM AUTHOR]

• Microbial processes during secondary succession were studied on the Loess Plateau. • Microbial communities showed stoichiometric homeostasis during plant secondary succession. • Microbial metabolisms were co-limited by C and P during plant secondary succession. • Microbial activities were strongly affected by soil nutrient status. Soil microbial metabolism is vital for nutrient cycling and ecosystem stability. To quantify microbial metabolism and nutrient limitation during plant secondary succession, we measured soil physicochemical properties, microbial biomass, and four enzyme activities (β-1,4-glucosidase (BG), β-1,4- N -acetylglucosaminidase (NAG), L -leucine aminopeptidase (LAP), and alkaline phosphatase (AP)) and identified the changes of soil ecoenzymatic stoichiometry and microbial nutrient limitation along a secondary succession series in typical arid and semi-arid ecosystems on the Loess Plateau, China. Soil enzyme activities increased in the first 17a succession and then decreased with plant secondary succession. The ln(BG):ln(NAG + LAP) ratio and ln(BG):ln(AP) ratio showed a decreasing trend in the first 22a succession and then increased. Most soil nutrient contents and nutrient stoichiometry were significantly correlated with enzyme activities and enzymatic stoichiometry. Moreover, vector analysis of soil enzymes indicated that microbial community were co-limited by C and P during secondary succession. Linear regression of C:N and C:P between the soil nutrient and microbial community showed that soil microbial community maintained stoichiometry homeostasis during plant secondary succession. The threshold elemental ratio revealed that the microbial nutrient metabolisms were co-limited by N and P, particularly P during plant secondary succession. Therefore, microbial communities were co-limited by C, N, and P, particularly C and P during plant secondary succession, and the limitation was mainly associated with soil nutrient status. [ABSTRACT FROM AUTHOR]