Oil tea Camellia, as a major cash and oil crop, has a high status in the forestry cultivation systems in China. To meet the current market demand for oil tea Camellia, its potential distribution and suitable soil condition was researched, to instruct its cultivation and popularization. The potential distribution of oil tea Camellia in China was predicted by the maximum entropy model, using global environmental and soil databases. Then, we collected 10-year literature data about oil tea Camellia soil and applied multiple imputation and factor modeling for an in-depth analysis of soil suitability for growing of oil tea Camellia. The prediction indicated that oil tea Camellia was mainly distributed in Hunan, Jiangxi, Zhejiang, Hainan, East Hubei, Southwest Anhui and most of Guangdong. Climatic factors were more influential than soil factors. The minimum temperature of the coldest month, mean temperature of the coldest quarter and annual precipitation were the most significant contributors to the habitat suitability distribution. In the cultivated area of oil tea Camellia, soil fertility was poor, organic matter was the most significant factor for the soil conditions. Based on climatic and soil factor analyses, our data suggest there is a great potential to spread the oil tea Camellia cultivation industry.

Camellia oleifera Abel., is an important woody plant, and its fruit contains high-quality edible oil. Production of C. oleifera has significantly expanded over the last 20 years in China. Due to the lack of appropriate information on nutrient management, its production has encountered low yield and low oil quality problems. As nitrogen (N) is an essential nutrient and the most abundant in C. oleifera tissues, the present study investigated effects of different ratios of nitrate (NO₃⁻) and ammonium (NH₄⁺) on the growth of a cultivar Xianglin 27 at the seedling stage. Uniform seedlings were grown in a soil-based substrate in containers and fertigated with solutions composed of six ratios of NO₃⁻ and NH₄⁺, respectively for five months. Results showed that C. oleifera prefers both NO₃⁻ and NH₄⁺ at a ratio of 1:1. Seedlings receiving this solution had the highest total N in leaves and total dry weight; elevated chrolophyll, soluble saccharide and protein contents as well as higher activities of peroxidase (POD), superoxide dismutase (SOD), nitrate reductase (NR), glutamine synthetase (GS), and glutamate synthase (GOGAT). Our study shows for the first time that N supply for producing C. oleifera should be an equal ratio of NO₃⁻ and NH₄⁺.

Increased nitrogen deposition is a key feature of global climate change, however, its effects on the structure and assembling mechanisms of the nitrogen-fixing bacteria present at the root surface remain to be elucidated. In this pursuit, we used NH₄NO₃ to simulate nitrogen deposition in a 10-year-old Camellia oleifera plantation, and set up four deposition treatments, including control N0 (0 kg N hm⁻² a⁻¹), low nitrogen N20 (20 kg N hm⁻² a⁻¹), medium nitrogen N40 (40 kg N hm⁻² a⁻¹) and high nitrogen N160 (160 kg N hm⁻² a⁻¹). The results showed that nitrogen deposition affected the soil nitrogen content and the structure of the nitrogen-fixing bacterial community. Low nitrogen deposition was conducive for nitrogen fixation in mature C. oleifera plantation. With increasing nitrogen deposition, the dominant soil nitrogen-fixing bacterial community shifted from Desulfobulbaceae to Bradyrhizobium. When nitrogen deposition was below 160 kg N hm⁻² a⁻¹, the soil organic matter content, total nitrogen content, nitrate nitrogen content, ammonium nitrogen content, urease activity, soil pH and nitrate reductase activity influenced the composition of the nitrogen-fixing bacterial community, but the stochastic process remained the dominant factor. The results indicate that the strains of Bradyrhizobium japonicum and Bradyrhizobium sp. ORS 285 can be used as indicator species for excessive nitrogen deposition.

High temperature and drought are the main factors restricting the increase in Camellia oleifera Abel production that can seriously harm its physiological and biochemical functions. This study aimed to explore the effect by which Ca²⁺ enhances the drought resistance of C. oleifera. Four-year-old potted plants of the ‘Xianglin 210’ variety were treated with four levels of CaCl₂ solution (0, 10, 20, and 40 mmol/L) and subjected to natural drought stress. The drought levels were categorized as CS (non-drought), LD (light drought), MD (moderate drought), and SD (severe drought). The effects of drought stress on the growth and physiological-biochemical characteristics of C. oleifera were measured. Under drought stress, spraying CaCl₂ solution on leaves could significantly increase the net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), endogenous hormone indoleacetic acid (IAA) content, abscisic acid (ABA) content, and gibberellic acid (GA) content in organs and tissues; enhance the superoxide dismutase (SOD) activity; and decrease the concentration of intercellular carbon dioxide (Ci) and number of dehiscence fruits. Spraying 10 mmol/L CaCl₂ effectively alleviates the damage of drought stress to tung oil trees. The study provides references for alleviating drought stress and increasing economic benefits in C. oleifera production.

Arbuscular mycorrhizal fungi (AMF) symbiosis has been shown to improve the ability to obtain nutrients and resist adverse environmental conditions. However, there are few studies on the functions of AMF in the absorption and accumulation of boron (B). Moreover, it is still unclear whether the root colonization rates of AMF are limited by B deficiency. In this study, Camellia oleifera seedlings were planted in normal and boron-deficient substrates, and the seedlings were inoculated with Funneliformis mosseae or left uninoculated. The growth and physiological indices of C. oleifera seedlings were determined. The results of this experiment indicate that AMF inoculation increased the plant biomass, B content, B accumulation, and antioxidant enzyme activity in both normal and boron-deficient C. oleifera seedlings. Furthermore, boron deficiency resulted in a decrease in the AMF root colonization efficiency and the inhibition of C. oleifera seedlings’ growth and physiological activity. These findings suggest that AMF inoculation could improve the resistance to B-deficiency stress. Additionally, the colonization efficiency of AMF was adversely affected by B deficiency; thus, AMF play a cooperative role with B in the growth and physiological functions of plants. The results provide a theoretical basis for taking measures to solve B-deficiency stress in C. oleifera and other plants’ cultivation.

Camellia oleifera, a prominent species of edible oil tree in China, depends on improved soil fertility for its sustainable growth. Although the application of bacterial manure has been demonstrated to enhance soil nutrient conditions, the specific contributions of endophytes within fertilizers and their interactions with soil microbial ecosystems remain inadequately explored. This study investigates the impact of organic fertilizers combined with three endophytes (CoT10, CoH27, and CoH17) on the physicochemical properties, enzymatic activities, and microbial diversity of soils in C. oleifera plantations. Findings indicate that the integration of endophytes with organic fertilizers significantly improved soil nutrient levels (including total nitrogen, total phosphorus, and hydrolysable nitrogen), enzymatic activities (such as phosphatase, amylase, and nitrate reductase), and microbial diversity compared to the application of organic fertilizer alone. Notably, the endophyte CoT10, when applied alone with organic fertilizer, resulted in increased levels of total nitrogen, total phosphorus, and hydrolysable nitrogen in the soil, as well as a marked enhancement in the activities of soil phosphatase, amylase, and nitrate reductase. Furthermore, the combination of CoT10 with other endophytes in organic fertilizer improved the functionality of the other microorganisms and the efficiency of organic fertilizer utilization. This study underscores the synergistic effects of endophytes and organic fertilizers, providing scientific insights and practical strategies for the sustainable cultivation of C. oleifera.