Ecosystem services provide regulation, provisioning, support, and cultural benefits for human survival, but it needs to be clarified how the trade-off/synergy relationships can be used to optimize function. Based on the Web of Science (WOS) and China National Knowledge Infrastructure (CNKI) databases, we collected 254 articles on the ecosystem trade-offs/synergies and functional optimization. Through a systematic review of the literature, this paper summarized the research progress and landmark achievements from three aspects: trade-offs/synergies, functional optimization, and evaluation methods. The results indicated the following: (1) In terms of the number of articles published, there were no reports before 2005; from 2006 to 2022, the annual number of published papers increased from 1 to 72, showing an overall growth trend year by year. This mainly includes three stages: initial (1970–2005), slow development (2005–2014), and rapid development (2014–2022). (2) In terms of research areas, focus was placed mainly on Asia, North America, and Europe, accounting for 40.47%, 25.55%, and 15.07% of all regions, respectively. (3) In the future, it is necessary to focus on scientific issues such as the improvement of forest ecosystem functions, the trade-off/synergy relationships between services, the scale of spatiotemporal research, and the driving factors and evaluation methods for the management of rocky karst desertification. The aim is to provide a theoretical basis to optimize the forest ecosystem service functions.

Background: Leaf litter is the products of metabolism during the growth and development of plantation, and it is also an important component of nutrient cycling in plantation ecosystems. However, leaf litter chemistry and its effects on soil microorganisms in different ages, as well as the interactions between chemical components in leaf litter have been rarely reported. Based on this, this paper took Zanthoxylum planispinum var. dintanensis (hereafter Z. planispinum) plantations of 5–7, 10–12, 20–22, and 28–32 years old as the objects. By using one-way ANOVA, Pearson correlation analysis and redundancy analysis, we investigated leaf litter chemistry and its effects on soil microorganisms in different ages, and to reveal internal correlation of various chemical components in leaf litter, which can provide a scientific basis for the regulation of soil microbial activity in plantations. Results: The variation of organic carbon with plantation age was more stable compared to total nitrogen and phosphorus of leaf litter. Nitrogen resorption was stronger than phosphorus resorption efficiency in Z. planispinum, and resorption efficiencies of leaf nitrogen and phosphorus for different ages were lower than the global average. Total nitrogen was highly significantly positively correlated with lignin, and total potassium was significantly positively correlated with tannin, suggesting the increase of inorganic substances in leaf litter would promote the accumulation of secondary metabolites. The leaf litter chemical traits explained up to 72% of soil microorganisms, where lignin was positively correlated with fungi and negatively correlated with bacteria, indicating that fungi are able to decompose lower quality litter and can break down complex and stable organic compounds more rapidly than bacteria. The nutrient elements carbon and nitrogen in the leaf litter and their interrelationship also have a great impact on soil microorganisms, because carbon is not only the element that provides energy, but also the element with the largest content in the microbiota. Conclusions: The sustained increase in inorganic nutrients of leaf litter did not favor the decomposition of secondary metabolites, but rather inhibited the degradation of leaf litter. The significant positive effect of the leaf litter chemistry on soil microorganisms indicates the important role of leaf litter in promoting nutrient cycling in Z. planispinum plantations.

The study of soil ecological stoichiometry has mainly focused on surface soils. Exploring the nutrient content and stoichiometric characteristics of deep soils in karst areas helps us to understand the intrinsic relation mechanism and provides scientific evidence for making full use of fractured soil. We analyzed soil nutrient content, nutrient supply intensity, stoichiometric ratios, and their inter-relations at different soil depths in a karst plateau mountain area of China. Soil nutrient supply capacity was relatively low in the study area. The nitrogen and potassium supply capacity was highest in the surface layer, while phosphorus supply capacity was highest in deep soil. Carbon, nitrogen, phosphorus and potassium made varying contributions to the ecological stoichiometric ratios. Soil nitrogen and phosphorus were found to be deficient in the karst plateau mountain area of China. There was certain coordination between nutrient supply intensity and ecological stoichiometric ratios.

Plantations with different allocation patterns significantly affect soil elements, microorganisms, extracellular enzymes, and their stoichiometric characteristics. Rather than studying them as a continuum, this study used four common allocations of plantations: Zanthoxylum planispinum var. dintanensis (hereafter Z. planispinum) + Prunus salicina, Z. planispinum + Sophora tonkinensis, Z. planispinum + Arachis hypogaea, and Z. planispinum + Lonicera japonica plantations, as well as a single-stand Z. planispinum plantation as a control. Soil samples from depths of 0–10 and 10–20 cm at the five plantations were used to analyze the element stoichiometry, microorganisms and extracellular enzymes. (1) One-way analysis of variance (ANOVA) showed that the contents of soil organic carbon (C), nitrogen (N), phosphorus (P), and potassium (K) of Z. planispinum + L. japonica plantation were high, while those of calcium (Ca) and magnesium (Mg) were low compared to the Z. planispinum pure plantation; soil microbial and enzyme activities were also relatively high. Stoichiometric analysis showed that soil quality was good and nutrient contents were high compared to the other plantations, indicating that this was the optimal plantation. (2) Two-way ANOVA showed that stoichiometry was more influenced by plantation type than soil depth and their interaction, suggesting that plantation type significantly affected the ecosystem nutrient cycle; soil microbial biomass (MB) C:MBN:MBP was not sensitive to changes in planting, indicating that MBC:MBN:MBP was more stable than soil C:N:P, which can be used to diagnose ecosystem nutrient constraints. (3) Pearson’s correlation and standardized major axis analyses showed that there was no significant correlation between soil C:N:P and MBC:MBN:MBP ratios in this study; moreover, MBN:MBP had significant and extremely significant correlations with MBC:MBN and MBC:MBP. Fitting the internal stability model equation of soil nutrient elements and soil MBC, MBN, and MBP failed (p > 0.05), and the MBC, MBN, and MBP and their stoichiometric ratios showed an absolute steady state. This showed that, in karst areas with relative nutrient deficiency, soil microorganisms resisted environmental stress and showed a more stable stoichiometric ratio. Overall stoichiometric characteristics indicated that the Z. planispinum + L. japonica plantation performed best.

With a changing climate and socio-economic development, ecological problems are increasingly serious, research on ecosystem vulnerability and ecological resilience has become a hot topic of study for various institutions. Forests, the “lungs of the earth”, have also been damaged to varying degrees. In recent years, scholars have conducted numerous studies on the vulnerability and resilience of forest ecosystems, but there is a lack of a systematic elaboration of them. The results of a statistical analysis of 217 related documents show: (1) the number of studies published rises wave upon wave in time series, which indicates that this area of study is still at the stage of rising; (2) the research content is concentrated in four dimensions—ecosystem vulnerability assessment, ecosystem vulnerability model prediction, ecological resilience, and management strategies—among which the ecosystem vulnerability assessment research content mainly discusses the evaluation methods and models; (3) the research areas are mainly concentrated in China and the United States, with different degrees of distribution in European countries; and (4) the research institutions are mainly the educational institutions and forestry bureaus in various countries. In addition, this paper also reveals the frontier theory of forest ecosystem vulnerability and resilience research from three aspects—theoretical research, index system, and technical methods—puts forward the problems of current research, and suggests that a universally applicable framework for forest ecosystem vulnerability and resilience research should be built in the future, and theoretical research should be strengthened to comprehensively understand the characteristics of forest ecosystems so that sustainable management strategies can be proposed according to local conditions.