Improper disposal of coffee-processing by-products can cause environmental pollution, greenhouse gas emissions, and resource loss, whereas their reuse in coffee plantations may support sustainable production. This review systematically examines the material properties, stabilization methods, field application pathways, agronomic effects, quality responses, and environmental risks of coffee-pulp-type by-products in cultivation. Relevant studies published up to June 2026 were retrieved from Web of Science, Scopus, ScienceDirect, SpringerLink, Google Scholar, and CNKI and qualitatively synthesized along the soil–plant–quality continuum. Current evidence suggests that properly stabilized materials, applied at appropriate rates, can improve soil organic matter, structure, water and nutrient retention, microbial activity, plant growth, photosynthesis, and crop yield in plantations. They may also indirectly influence green bean quality by regulating sugars, amino acids, chlorogenic acids, and caffeine. However, these effects depend strongly on material properties, maturity, application rate, coffee genotype, soil and climatic conditions, and management practices. Excessive or insufficiently decomposed materials may cause soil acidification, phytotoxicity, oxygen depletion, nutrient imbalance, and yield–quality trade-offs. Overall, recycling within plantations can turn processing waste into farm inputs, reinforce on-farm carbon and nutrient cycles, ease disposal burdens, and advance BCG and wider circular-economy principles in practice.

Robusta coffee (Coffea canephora) possesses great industrial potential, whereas its intrinsic flavor defects compromise market competitiveness. Honey processing utilizing residual pulp and mucilage is capable of improving green coffee quality; nevertheless, the absence of quantitative research regarding graded pulp retention limits its industrial application. In this study, fermentation experiments with gradient retention of coffee cherry pulp were conducted to clarify the differential regulatory effects of varying coffee cherry pulp-retention amounts on physicochemical properties, functional components and volatile flavor precursor compounds of Hainan Robusta coffee. Quantitative scoring of coffee quality using international standard cup measuring instruments and the grey relational analysis was further employed to comprehensive quality assessment. Compared with the 0% coffee cherry pulp-retention treatment, all other treatments showed higher levels of selected functional components and volatile flavor precursor compounds. The 66% coffee cherry pulp-retention treatment enriched key roasting flavor substrates: sucrose, organic acids, pyrazines, and esters were increased by 8.74%, 26.58%, 80.66% and 30.18%, respectively. Meanwhile this treatment exhibited significantly lower protein and alkaloid contents than the 100% and 33% coffee cherry pulp-retention treatments, and significantly lower flavonoid content than the 0% and 33% coffee cherry pulp-retention treatments. This treatment exhibited remarkably excellent cup scores by 80.35 and superior comprehensive quality, outperforming the other treatments by 6.05–18.51%. This study identifies the optimal coffee cherry pulp-retention ratio for Robusta coffee post-harvest honey processing, providing theoretical basis and feasible technical references for the quality improvement, standardized processing and industrial promotion of local Robusta coffee.

Areca (Areca catechu L.) is an important economic crop in tropical regions, but excessive nitrogen application leads to low nitrogen fertilizer utilization efficiency (approximately 30%). Vanilla (Vanilla planifolia Andrews) can be intercropped with areca to enhance land use efficiency. However, the impact of combined nitrogen reduction and Arbuscular mycorrhizal fungi (AMF) inoculation on the intercropping system of areca and vanilla remains unclear. This study examined the impact of nitrogen reduction (at levels of conventional fertilization, a 30% reduction and a 60% reduction) and the inoculation of AMF on the photosynthetic characteristics, physiological metabolism, and nitrogen utilization within an areca and vanilla intercropping system, employing a two-factor experimental design. The nitrogen reduction significantly inhibited SPAD value (chlorophyll content) (decreased by 46.21%), net photosynthesis (Pn) (decreased by 71.13%), and transpiration rate (Tr) (decreased by 44.34%) of vanilla without inoculation of AMF, but had little effect on the photosynthesis of areca. Inoculation with AMF, notably Funneliformis mosseae, alleviated the adverse effects of reduced nitrogen on vanilla. The net photosynthesis and intercellular CO2 concentration (Ci) significantly increased by 76.23% and 69.48%, respectively. Additionally, the nitrogen uptake efficiency of the areca was improved, with root vitality increasing by 39.96%. Additionally, AMF enhanced the activities of acid phosphatase (ACP) (increased by 38.86% in vanilla) and nitrate reductase (NR) (increased by 53.77% in areca), promoting soil mineral nutrient activation and nitrogen metabolism. The nitrogen reduction combined with AMF inoculation can improve the nitrogen use efficiency of the areca and vanilla intercropping system, revealing its synergistic mechanism in the tropical intercropping system.

This study systematically investigated the response mechanisms of the rhizosphere microenvironment and physiological metabolism in an areca/vanilla intercropping system under three nitrogen reduction levels (conventional, 30% reduction, and 60% reduction) combined with inoculation of two arbuscular mycorrhizal fungi (AMF). The results showed that under 30% nitrogen reduction, inoculation with Claroideoglomus etunicatum significantly increased soil hydrolytic nitrogen by 26.29% (P < 0.05), this change directly drives the increase in nitrate reductase activity and photosynthetic pigment synthesis in plant leaves by optimizing the microenvironment of root nitrogen supply. Funneliformis mosseae increased soil organic matter by 10.93% (P < 0.05) by enriching the rhizosphere carbon source pool, reshaping the microbial interaction network, and indirectly promoting physiological metabolism related to root nutrient absorption. AMF exhibited species-specific regulation of soil enzyme activities. For instance, under conventional fertilization, Claroideoglomus etunicatum increased phosphatase activity by 25.68% (P < 0.05) by enhancing the biochemical microenvironment of organic phosphorus mineralization in the rhizosphere, thereby providing substrates for plant phosphorus metabolism. While under 60% nitrogen reduction, Funneliformis mosseae boosted urease activity by 64.46% (P < 0.05). This response stems from its induction of the enrichment of urease-producing bacterial communities in the rhizosphere, accelerating the conversion of organic nitrogen to alleviate nitrogen metabolic stress in plants under low nitrogen stress. Additionally, nitrogen reduction combined with AMF inoculation significantly promoted the accumulation of glomalin-related soil protein (GRSP). At 60% nitrogen reduction treatment, compared with the control group without AMF inoculation, the treatment group inoculated with Funneliformis mosseae showed a 5.16% (P < 0.05) increase in GRSP. This study demonstrates that AMF optimizes rhizosphere nutrient cycling (e.g., AMF (C.e) significantly increases hydrolytic nitrogen by 26.29% (P < 0.05) under 30% nitrogen reduction) and improves soil structure (e.g., AMF (F.m) promotes GRSP accumulation by 5.16% (P < 0.05), providing a theoretical basis for reducing fertilizer application and promoting sustainable intensification of tropical intercropping systems.

It is well established that root exudates play a crucial role in shaping the assembly of plant rhizosphere microbial communities. Nonetheless, our understanding of how different types of exudates influence the abundance of potential pathogens in soil remains insufficient. Investigating the effects of root exudates on soil-dwelling pathogenic fungi is imperative for a comprehensive understanding of plant-fungal interactions within soil ecosystems and for maintaining soil health. This study aimed to elucidate the effects of the principal components of root exudates-flavonoids (FLA), phenolic acids (PA), and organic acids (OA)-on soil microbial communities and soil properties, as well as to investigate their mechanisms of action on soil potential pathogenic fungi. The results demonstrated that the addition of these components significantly modified the composition and diversity of soil microbial communities, with OA treatment notably altering the composition of dominant microbial taxa. Furthermore, the introduction of these substances facilitated the proliferation of saprophytic fungi. Additionally, the incorporation of flavonoids, phenolic acids, and organic acids led to an increased abundance of potential pathogenic fungi in the soil, particularly in the FLA and PA treatments. It was observed that the addition of these substances enhanced soil fertility, pH, and antioxidant enzyme activity. Specifically, FLA and PA treatments reduced the abundance of dominant microbial taxa, whereas OA treatment altered the composition of these taxa. These findings suggest that the inclusion of flavonoids, phenolic acids, and organic acids could potentially augment the enrichment of soil potential pathogenic fungi by modulating soil properties and enzymatic activities. These results offer valuable insights into the interactions between plants and fungal communities in soil ecosystems and provide a scientific foundation for the management and maintenance of soil health.

Pandanus amaryllifolius Roxb. (pandan) and Cocos nucifera L. (coconut) are traditional economic crops widely cultivated in tropical and subtropical regions, with intercropping being common in South and Southeast Asia. However, the effect of intercropping with coconut on the growth and quality of pandan has received little attention at present. Therefore, a field experiment was conducted to evaluate the effects of intercropping modes on soil physicochemical properties, agronomic traits, photosynthetic characteristics, and volatile compound content of pandan. The results revealed that intercropping significantly enhanced soil moisture, leaf area, chlorophyll content, net photosynthetic characteristics, and carbon use efficiency of pandan. Furthermore, intercropping with coconut significantly enhanced the content of volatile compounds, including ketones, alcohols, esters, furanones, pyrroles, acids, and phenols. The increases in soil moisture, improvement in leaf structure, and enhancement of the photosynthetic process under intercropping were the primary drivers of the accumulation of volatile compounds, particularly key quality indicators such as 2-acetyl-1-pyrroline and phytol, in pandan leaves. These findings contribute to the identification of key regulatory factors for enhancing the growth and quality of pandan in intercropping mode.

Mulching cultivation with agricultural wastes is the main production pattern of coffee at present, but the effect of mulching cultivation on photosynthetic physiological processes of coffee plants is still not clear. Therefore, a randomized block design was adopted to establish a field experiment by one-year-old Coffee Canephora seedlings in this study. There were four types of mulch treatments, including non-mulch coffee waste (C), mulching coffee litter (L), mulching coffee cascara (cherry pericarp, P), and mulching coffee litter and cascara (LP) in this field experiment. Soil properties and microenvironment (e.g., moisture, temperature, pH, bulk density, organic matter content, alkali-hydrolyzed nitrogen content, available potassium content, and available potassium content), agronomic traits (e.g., specific leaf area, leaf area index, plant height, and relative chlorophyll content), and photosynthetic indices (e.g., photosynthesis, transpiration, respiration, stomatal conductance, intercellular CO2 concentration, water use efficiency, and carbon use efficiency) were investigated to determine the effects of different coffee waste mulches on the photosynthetic physiology of coffee seedlings. The results show that coffee litter and cascara mulch significantly reduced soil temperature by 0.42 or 0.33 °C, respectively, and coffee litter rather than cascara mulch significantly increased the soil’s available potassium content by 46.28%, although coffee waste mulch did not affect other soil properties or microenvironment indices; coffee cascara mulching significantly increased the specific leaf area and net and gross photosynthesis of coffee by 45.46%, 78.33%, and 91.72%, respectively, but the mulching treatments did not affect stomatal conductance, transpiration, or carbon use efficiency in this study. Additionally, coffee cascara mulching increased leaf respiration and net and gross water use efficiency by 109.34%, 80.54%, and 104.95%, respectively. The coffee cascara mulching alone had the most significant positive impact on the photosynthetic index, followed by a combination of litter and cascara, litter alone, and the control treatment. The observed variations in the coffee photosynthetic index may be attributed to the reduction of soil temperature caused by mulching treatments rather than the increase in soil nutrients content. These results indicate that coffee cascara mulching could effectively promote photosynthesis and the growth of coffee seedlings by improving the soil microenvironment.

Pandan (Pandanus amaryllifolius Roxb.) are one of the traditional food materials in Southeast Asian countries. However, there has long been a lack of understanding of the differences in volatile organic compounds (VOCs) of leaves at different growth periods. Gas chromatography-mass spectrometry (GC-MS) was used to identify and analyze VOCs in different leaf positions of Pandan in this study. The content of 2-Acetyl-1-pyrroline (2AP) was higher in L1-L3 and decreased with leaf growth, while squalene showed the opposite trend. The content of neophytadiene first increased and then decreased, reaching the highest in L15. L8 is the critical point at which the content of each major VOCs is balanced. Combining agronomic traits and VOCs content, leaves in L4-L25 position are suitable for harvesting. This study provides data support for scientific judgment of the harvesting site and time of Pandan, and provides theoretical basis for further utilization of VOCs of Pandan.

In recent decades, ecological cyclic cultivation models have attracted increasing attention, primarily because the decomposition of crop residues and litter enhances soil organic matter content, thereby altering the soil microenvironment and regulating the diversity and functions of soil microbial communities. However, the effects of different coffee waste mulching on the diversity of soil microbial communities and their functions are still unclear. Therefore, this study set up four kinds of covering treatments: uncovered coffee waste (C), covered coffee litter (L), covered coffee pericarp (P), and both covered coffee litter and pericarp (PL). The results showed that compared to the control, coffee pericarp mulching significantly increased the soil available potassium (SAK) content by 18.45% and alkali hydrolyzed N (SAN) content by 17.29%. Furthermore, coffee pericarp mulching significantly increased bacterial richness and diversity by 7.75 and 2.79%, respectively, while litter mulching had little effect on bacterial abundance and diversity was smaller. The pericarp mulching significantly increased the abundance of Proteus by 22.35% and the abundance of Chlamydomonas by 80.04%, but significantly decreased the abundance of Cyanobacteria by 68.38%, while the coffee litter mulching significantly increased the abundance of Chlamydomonas by 48.28%, but significantly decreased the abundance of Cyanobacteria by 73.98%. The increase in soil SAK promoted bacterial Anoxygenic_photoautotrophy, Nitrogen_respiration, Nitrate_respiration, Nitrite_respiration, and Denitrification functions. The above results indicate that the increase in available soil potassium and alkali hydrolyzed N content under coffee pericarp cover is the main reason for promoting the diversity and richness of bacterial community and promoting the changes in bacterial community structure and function. The use of coffee pericarps in coffee plantations for ecological recycling helps to improve the diversity of the soil microbial community and maintain the relative stability of the microbial community structure and function, promoting soil health conservation and the sustainable development of related industries.

The intercropping pattern promotes the sustainable development of efficient agriculture, especially cash crops, such as Areca catechu L. and Pandanus amaryllifolius Roxb. intercropping plantation in China. However, the mechanisms underlying intercropping pattern effects on soil microbial community diversity and composition are poorly understood. A monoculture and intercropping field experiment of the two crops was established to monitor the changes of soil physicochemical properties, enzyme activities, microbial (bacterial and fungal) diversity, and composition. Soil bacterial rather than fungal communities' diversity is more sensitive to intercropping pattern. The intercropping significantly decreased rhizospheric bacterial diversity of Areca catechu L. by 4.21%, and the decrease of soil nutrient content may be the main reason for the change of soil enzyme activity, bacterial community diversity, and composition structure under intercropping pattern. Supplementing nutrients to the soil of intercropping systems is conducive to maintain soil health and ecosystem functional stability in the tropical compound cultivation plantation.

咖啡是世界上闻名的饮料作物,长期单一化种植导致土壤生物功能退化,影响植株健康生长.间作槟榔是改善咖啡园土壤生物功能的有效措施,但作用机制尚不清楚.本文通过盆栽试验研究了咖啡间作槟榔对根际土壤生物和非生物学性状的影响.结果表明,间作增加了土壤速效养分含量,速效磷和速效钾含量分别显著增加58.24%和70.30%;相对于单作,间作模式改变了根际土壤细菌和真菌群落丰富度,真菌丰富度对种植模式的响应更显著;间作咖啡根际土壤细菌群落拥有更多独有的扩增子序列变异体(Amplicon Sequence Variants, ASV),而真菌独有ASV在间作模式下显著降低;根际土壤细菌和真菌属(如Pedomicrobium, Mycobacterium等)与咖啡植株生长显著相关;与咖啡单作相比,间作模式能够富集根际土壤中与养分循环(如Bradyrhizobium, Trichoderma, Bryobacter)和抑制植物病原菌(如Trichoderma, Penicillium, Streptomyces)相关的微生物群落,促进土壤养分释放和对潜在病原菌的抑制作用,促使植株健康生长.另外,间作模式下咖啡根际土壤能够富集与氮素循环和芳香化合物降解等功能相关的微生物.综上,咖啡间作槟榔可富集有益功能微生物,调控咖啡园土壤微生物群落结构和功能,缓解咖啡连作生物障碍.该研究为生产上应用复合栽培模式,助力咖啡绿色种植提供了理论依据.

Heterologous double-root grafting represents an effective strategy to mitigate challenges associated with continuous coffee cropping and reduce soil-borne diseases. However, its specific regulatory mechanism remains unclear. Therefore, a field experiment was conducted including six different grafting combinations for C. canephora cv. Robusta (Robusta) and Coffea Liberica (Liberica): Robusta scion with a homologous double root (R/RR), Liberica scion with a homologous double root (L/LL), Robusta scion with a heterologous double root (R/RL and L/RL), and Liberica scion with a heterologous double root (L/LR and R/LR); these combinations were conducted to clarify the effects of heterologous double-root grafting combinations on the root exudates and soil microbial diversity, structure, and function of Robusta and Liberica. The results demonstrated notable differences in root exudates, rhizosphere microbial structure, and function between Robusta and Liberica. Despite Liberica having lower diversity in its rhizosphere microbial communities and relatively higher levels of potential pathogenic bacteria, it showed stronger resistance to diseases. Roots of Robusta in heterologous double-root coffee seedlings significantly enhanced the secretion of resistance compounds, increased the relative abundance of potentially beneficial bacteria, and reduced the relative abundance of potential pathogenic fungi. This enhances the rhizosphere immunity of Robusta against soil-borne diseases. The results indicated that grafting onto Liberica roots can strengthen resistance mechanisms and enhance the rhizosphere immunity of Robusta, thereby mitigating challenges associated with continuous cropping.

香露兜为典型热带园艺作物,为研究其叶片最佳护色工艺,以香露兜叶片为试验材料,在单因素试验确定氯化钙为最佳护色剂以及处理时间、温度及其护色剂浓度范围的基础上,采用Box-Behnken法设计响应面试验对最佳护色工艺参数进行优化研究,确定香露兜叶片护色最佳工艺,为香露兜叶片加工护色提供技术方案.单因素试验结果表明:最佳护色剂为氯化钙,初步确定时间、温度、最佳护色剂浓度最适范围分别为20s～40s、55℃～65℃、0.60％～1.00％;响应面优化结果表明:时间32s、温度55℃、氯化钙浓度1.00％时护色效果最佳.通过最佳护色工艺处理的香露兜叶片可在一定时间内保持良好的色泽,且护色效果好,为香露兜叶片加工上的护色提供了一定的理论支撑.

以斑兰叶组培苗为材料,为探明最适宜斑兰叶增香的施肥配方,研究不同激素、微量元素对斑兰叶组培苗增香的影响.采用气相色谱-质谱联用技术(GC-MS)对斑兰叶的挥发性香气成分进行鉴定分析,并对结果进行主成分分析及聚类热图分析.结果显示:7 个不同处理的斑兰叶组培苗挥发性成分种类组成无显著差异,但挥发性成分含量差异显著(P<0.05).共分析鉴定出 21 种化合物,主要由醇类、吡咯类、酯类、酮类、呋喃类、呋喃酮类、酸类、烯烃类、酚类组成,其中角鲨烯、叶绿醇、2-乙酰-1-吡咯啉(2AP)、新植二烯、3-甲基-2-(5H)-呋喃酮、2,3-二氢苯并呋喃为主要香气挥发性成分.斑兰叶组培苗特征香气成分 2AP平均含量为(48.07±13.14)μg/g,其中处理 6(锌+组合肥)的 2AP含量最高,为 72.03 μg/g;处理 1(IBA+锌+组合肥)2AP含量最低,为 31.96 μg/g,表明处理 6 能显著提高特征性物质 2AP的含量.主成分分析表明,施用组合肥(碳酸氢铵+过磷酸钙+氯化钾)与施用清水存在较大差异,并且处理 2、处理 6 中主要挥发性成分为叶绿醇、2AP、3-甲基-2(5H)-呋喃酮、2,3-二氢苯并呋喃、新植二烯;处理 1、处理 5 中挥发性成分主要以油酸乙酯为主的酯类、2,4-叔丁基苯酚为主的酚类、丙酮醇为主的酮类等化合物;处理 3、处理 4、处理 7 中挥发性物质主要以角鲨烯为主.通过聚类分析发现,处理 6(锌+组合肥)中斑兰叶组培苗的挥发性香气成分均有较高的积累;而处理 1(IBA+锌+组合肥)中挥发性物质含量较少;其余处理对斑兰叶组培苗主要挥发性香气成分的影响较小.研究表明:采用硫酸锌浸泡和配施碳酸氢铵+过磷酸钙+氯化钾溶液优于其他处理组,有较好的增香效果.

Abstract method microwave power 12 Kw, drying time 13.33 min, and material thickness 1.92 cm. Under this condition, the measured value of the rehydration ratio of the microwave dried leaves was 4.46 ± 0.05 g·g− 1, which was close to the predicted value of 4.44 g·g− 1. At the same time, by analyzing the color, chlorophyll content, particle size, key volatile component content and other related quality indicators of microwave dried Pandan powder, it was concluded that the color difference △L of Pandan powder processed under this drying process was 10.55 ± 1.94, △a was − 0.20 ± 0.14, △C was 5.39 ± 2.94, the total chlorophyll content was 5.11 ± 0.06 mg·g− 1, the D50 of the powder was 92.73 ± 0.49µm, and the specific surface area was 205.70 ± 0.72 m2·kg− 1. The content of 2-acetyl-1-pyrroline was 0.07 ± 0.01 mg·g− 1, and the content of squalene was 2.28 ± 0.06 mg·g− 1. Its each index is better than oven drying powder. Compared with ordinary oven drying, the microwave drying powder optimized in this experiment had better color, emerald green, shiny, bright color, and smaller powder particles. The content of 2-acetyl-1-pyrroline and squalene was higher, which was better than that of ordinary oven drying.

Coffee is an important cash crop worldwide, but it has been plagued by serious continuous planting obstacles. Intercropping with Areca catechu could alleviate the continuous planting obstacle of coffee due to the diverse root secretions of Areca catechu. However, the mechanism of Areca catechu root secretion in alleviating coffee continuous planting obstacle is still unclear. The changes of coffee rhizosphere soil microbial compositions and functions were explored by adding simulated root secretions of Areca catechu, the primary intercropping plant species (i.e., amino acids, plant hormone, organic acids, phenolic acids, flavonoids and sugars) in current study. The results showed that the addition of coffee root exudates altered soil physicochemical properties, with significantly increasing the availability of potassium and organic matter contents as well as promoting soil enzyme activity. However, the addition of plant hormone, organic acids, or phenolic acids led to a decrease in the Shannon index of bacterial communities in continuously planted coffee rhizosphere soil (RS-CP). The inclusion of phenolic acids specifically caused the decrease of fungal Shannon index. Plant hormone, flavonoids, phenolic acids, and sugars increased the relative abundance of beneficial bacteria with reduced bacterial pathogens. Flavonoids and organic acids increased the relative abundance of potential fungal pathogen Fusarium. The polyphenol oxidase, dehydrogenase, urease, catalase, and pH were highly linked with bacterial community structure. Moreover, catalase, pH, and soil-available potassium were the main determinants of fungal communities. In conclusion, this study highlight that the addition of plant hormone, phenolic acids, and sugars could enhance enzyme activity, and promote synergistic interactions among microorganisms by enhancing the physicochemical properties of RS-CP, maintaining the soil functions in coffee continuous planting soil, which contribute to alleviate the obstacles associated with continuous coffee cultivation.

Pandanus amaryllifolius Roxb. is a special tropical spice crop resource with broad development prospects. It is widely cultivated under a Hevea brasiliensis (Willd. ex A. Juss.) Muell. Arg. canopy to improve the comprehensive benefits to Hevea brasiliensis plantations in Hainan Provence, China. However, the effects of intercropping with Hevea brasiliensis on the component number and relative contents of volatile substances in different categories in the Pandanus amaryllifolius leaves are still unknown. Therefore, a Hevea brasiliensis and Pandanus amaryllifolius intercropping experiment was set up to clarify the differences between several cultivated patterns on volatile substances in the Pandanus amaryllifolius leaves, and the key regulatory factors of volatile substances. The results showed that the soil pH was significantly decreased, while soil bulk density, alkali-hydrolyzable nitrogen and available phosphorus contents were significantly increased under the intercropping pattern. The component numbers of esters in volatile substances were increased by 6.20%, while the component numbers of ketones were decreased by 4.26% under the intercropping pattern. Compared with the Pandanus amaryllifolius monoculture, the relative contents of pyrroles, esters and furanones were significantly increased by 8.83%, 2.30% and 8.27%, respectively, while the relative contents of ketones, furans and hydrocarbons were decreased by 1.01%, 10.55% and 9.16% under the intercropping pattern, respectively. The relative contents of pyrroles, esters, furanones, ketones, furans and hydrocarbons were associated with changes in soil pH, soil available phosphorus content and air temperature. The results indicated that the reduction in soil pH and enhancement in soil-available phosphorus may be the main reasons for promoting the relative content of pyrroles and reducing the relative content of hydrocarbons under an intercropping pattern. Overall, Hevea brasiliensis intercropping with Pandanus amaryllifolius could not only improve soil properties, but also significantly increase the relative contents of the main volatile substances in Pandanus amaryllifolius leaves, which could provide a theoretical basis for the application and promotion of high-quality production patterns of Pandanus amaryllifolius.

As one of the characteristic spice crops in tropical areas of China, the content of aroma components is the key index to identify the quality of Pandanus amaryllifolius Roxb.（Pa）. Pa is suitable for planting under shade of Hevea brasiliensisr（Hb） forest in Hainan Island, China. However, the effect of Hb and Pa intercropping on the aroma component of the leaves of Pa has not been explored. Pot experiments were set up to compare the differences of soil physical and chemical properties and the types and content of aromatic composition in Pa leaves under intercropping and monoculture treatments. The intercropping mode significantly increased the soil bulk density by 13.63%, the content of soil alkali hydrolyzed nitrogen by 59.71%, the content of soil available phosphorus by 193.03%, the content of soil available potassium by 9.78% and the soil pH reduced by 1.00（P＜0.05）. A total of 10 categories and 68 aroma components were detected in the intercropping and monocropping treatments. Compared with monocropping treatment, intercropping significantly decreased the number of ketones by 56.52%, furans by 14.29%, furanones by 33.33%, hydrocarbons by 20.00% and phenols by 28.57%（P＜0.05）. Although furans significantly reduced the content of aroma components by 65.28%, hydrocarbons by 20.88% and ketones by 69.00%, they significantly increased the content of alcohol by 31.50%,pyrrole by 597.56%, esters by 122.78% and furanone by 96.89%（P＜0.05）. The decrease of soil pH was the main reason for the reduction of ketones, furans, furanones, hydrocarbons and phenols. Intercropping indirectly increased the content of alcohols, pyrroles and esters and reduced the content of furans and hydrocarbons by reducing pH, while increasing soil available phosphorus and alkali hydrolyzable nitrogen. Pyrrole compounds were the main aroma components of Pa,thus the intercropping mode could significantly promote the quality of Pa. The results of this study would have a positive effect on the optimization and promotion of the Hb intercropping Pa mode, and also conducive to promoting the income increase of farmers and the sustainable development of related industries.

The areca nut (Areca catechu L.) and pandan (Pandanus amaryllifolius Roxb.) intercropping cultivation system has been widely practiced to improve economic benefits and achieve the development of sustainable agriculture in Hainan Province, China. However, there is a lack of research on the relationships among soil properties, soil enzyme activities, and microbes in this cultivation system. Therefore, a random block field experiment of pandan intercropped with areca nut was established to investigate the effects of environmental factors on the diversity and functions of soil microbial communities in Lingshui county, Hainan Province. The diversity and composition of soil microbial communities under different cropping modes were compared using Illumina sequencing of 16S rRNA (bacteria) and ITS-1 rRNA (fungi) genes, and FAPROTAX and FUNGuild were used to analyze and predict the bacteria and fungi community functions, respectively. Correlation analysis and redundancy analysis were used to explore the responses of soil microbial communities to soil environmental factors. The results showed that the bacterial community was more sensitive to the areca nut and pandan intercropping system than the fungal community. The functional predictions of fungal microbial communities by FAPROTAX and FUNGuild indicated that chemoheterotrophy, aerobic chemoheterotrophy, and soil saprotroph were the most dominant functional communities. The intercropping of pandan in the areca nut plantation significantly enhanced the soil bacterial Ace and Chao indices by reducing the soil organic carbon (SOC) and total phosphorus (TP) content. In the intercropping system, urease (UE) and acid phosphatase were the key factors regulating the soil microbial community abundance. The dominant bacterial and fungal phyla, such as Firmicutes, Methylomirabilota, Proteobacteria, Actinobacteria, Chloroflexi, Verrucomicrobia, and Ascomycota significantly responded to the change in planting modes. Soil properties, such as UE, total nitrogen, and SOC had a significant stimulating effect on Proteobacteria, Chloroflexi, and Ascomycota. In summary, soil bacteria responded more significantly to the change in cropping modes than soil fungi and better reflected the changes in soil environmental factors, suggesting that intercropping with pandan positively affects soil microbial homeostasis in the long-term areca nut plantation.

Rhizosheaths are aggregated, sheath-like soils that physically adhere to root surface, and they form on herbaceous plant roots worldwide, especially in semiarid grasslands. Representing a strong root-soil-microbe interaction, the rhizosheaths are expected to have distinct soil organic carbon (SOC) signatures from rhizosphere soils of non-rhizosheath forming plants. However, such signatures remain unclear, which hinders our understanding of root effects on SOC cycling in grasslands. We compared SOC characteristics between rhizosheath and non-rhizosheath soils of eight herbaceous plant species, collected from a semiarid grassland of North China, using solid-state 13C nuclear magnetic resonance spectroscopy and biomarker analyses. We further examined the temporal dynamics of SOC characteristics of rhizosheath soils from early, middle, and late plant growth stages. Compared to non-rhizosheath SOC, rhizosheath SOC had more root inputs of both labile substrates (carbohydrates and free alkanoic acids) and relatively recalcitrant suberin- and lignin-derived compounds. Moreover, the labile inputs provided more substrates for microbial degradation of cutin-derived compounds. These indicators of labile substrate availability increased significantly from the early to late growth stages. Overall, our findings clarify the molecular characteristics of rhizosheath SOC and its temporal dynamics, both of which suggest a critical role of rhizosheath in shaping the rhizosphere microenvironment and regulating SOC cycling.