集约化柑橘种植抑制土壤磷循环微生物活性

Intensive Citrus Cultivation Suppresses Soil Phosphorus Cycling Microbial Activity

微生物是调节土壤磷循环的关键驱动力.阐明土壤解磷菌的微生物矿化过程对于提高植物养分吸收率和作物产量具有重要意义.通过测定柑橘园与毗邻的自然林地土壤编码碱性磷酸酶基因(phoD)丰度、解磷细菌群落多样性和土壤无机磷组分,探究柑橘种植对土壤微生物获取磷策略的影响机制.结果表明,柑橘种植导致土壤pH下降,土壤有效磷累积,ω(有效磷)平均值高达112 mg·kg^(−1),显著高于毗邻的自然林地(3.7 mg·kg^(−1)).柑橘种植也会影响土壤磷素组成,柑橘土壤含有较高的可溶态磷(CaCl_(2)-P)、柠檬酸提取态磷(Citrate-P)和矿物结合态磷(HCl-P).自然林地土壤各磷组分均显著低于柑橘土壤,而phoD基因丰度和碱性磷酸酶活性显著高于柑橘土壤.高通量测序结果表明,柑橘土壤解磷细菌Shannon指数(4.61)显著低于自然林地(5.35),群落结构也有别于自然林地.柑橘种植改变了土壤解磷菌的群落组成,自然林地变形菌门的相对丰度显著低于柑橘土壤.土壤有效磷含量与碱性磷酸酶活性呈显著负相关,表明土壤高磷累积抑制土壤解磷细菌的活性.柑橘种植改变了土壤微生物对磷的获取策略,在柑橘园中,土壤微生物主要依赖外源磷,而自然林地土壤微生物主要以微生物分泌碱性磷酸酶矿化有机磷来获取磷的方式满足其生长需求.

Soil microbes are key drivers in regulating the phosphorus cycle.Elucidating the microbial mineralization process of soil phosphorus-solubilizing bacteria is of great significance for improving nutrient uptake and yield of crops.This study investigated the mechanism by which citrus cultivation affects the soil microbial acquisition strategy for phosphorus by measuring the abundance of the phoD gene,microbial community diversity and structure,and soil phosphorus fractions in the soils of citrus orchards and adjacent natural forests.The results showed that citrus cultivation could lead to a decrease in soil pH and an accumulation of available phosphorus in the soil,with a content as high as 112 mg·kg^(−1),which was significantly higher than that of natural forests(3.7 mg·kg^(−1)).Citrus cultivation also affected the soil phosphorus fractions,with citrus soil having higher levels of soluble phosphorus(CaCl_(2)-P),citrate-extractable phosphorus(Citrate-P),and mineral-bound phosphorus(HCl-P).The phosphorus fractions of natural forest soils were significantly lower than those of citrus soils,whereas the phoD gene abundance and alkaline phosphatase activity were significantly higher in natural forest soils than in citrus soils.High-throughput sequencing results showed that the Shannon diversity index of phosphate-solubilizing bacteria in citrus soils was 4.61,which was significantly lower than that of natural forests(5.35).The microbial community structure in natural forests was also different from that of citrus soils.In addition,the microbial community composition of phosphate-solubilizing bacteria in citrus soils was also different from that of natural forests,with the relative abundance of Proteobacteria being lower in natural forest soils than in citrus soils.Therefore,citrus cultivation led to a shift of soil microbial acquisition strategy for phosphorus,with external phosphorus addition being the main strategy in citrus soils,whereas microbial mineralization of organic phosphorus was the main strategy in natural forest soils to meet their growth requirements.