The contamination of arable land with heavy metals, such as Cd, is a serious concern worldwide. Intercropping with Cd accumulators can be used for efficient safe crop production and phytoremediation of Cd-contaminated soil. However, the effect of intercropping on Cd uptake by main crops and accumulators varies among plant combinations. Rhizosphere interaction may mediate Cd uptake by intercropped plants, but the mechanism is unclear. Thus, in the present study, we aimed to examine the effect of rhizosphere interaction on Cd uptake by intercropping rice (Oryza sativa L.) with mugwort (Artemisia argyi Levl. et Vant.) in Cd-contaminated paddy soil. We grew O. sativa and A. argyi in pots designed to allow different levels of interaction: complete root interaction (no barrier), partial root interaction (nylon mesh barrier), and no root interaction (plastic film barrier). Our results indicated that both complete and partial root interaction increased the shoot and root mass of A. argyi, but did not decrease the shoot, root, and grain mass of O. sativa. Interspecific root interaction significantly increased the Cd content in the shoots, roots, and grains of O. sativa and the shoots of A. argyi. Increased content of total organic acids in the rhizosphere, which increased the content of available Cd, was a possible mechanism of increased Cd uptake in both plants under interspecific root interaction. Our findings demonstrate that an intercropping system can extract more Cd from contaminated soil than a monocropping system of either A. argyi or O. sativa. However, the intercropping system did not facilitate safe crop production because it substantially increased grain Cd content in O. sativa.

Phytoremediation is affected by physical and chemical properties of the soil such as soil pH, moisture, and nutrient content. Soil pH is a key element influencing Cd bioavailability and can be easily adjusted in agricultural practices. The soil pH level may relate to the effectiveness of phytoremediation; however, this has not been extensively investigated. In the current study, we evaluated the effect of Cd contamination level (0.56 and 0.92 mg/kg) and soil pH (5, 6, and 7) on Cd accumulation and allocation in Artemisia argyi, a fast-growing perennial crop. Our results indicated that higher soil Cd concentrations reduce A. argyi biomass, and the loss of the root mass was particularly significant. Higher soil pH decreased Cd content in stems and roots of A. argyi cultivated in moderately Cd-polluted soil, and increased Cd content in stems and roots of the plant grown in low Cd-polluted soil. Higher soil pH decreased the percentage of Cd distributed in the soluble fraction and cell walls and increased the percentage of Cd in the organelles of leaf cells for moderate soil Cd levels. The bioconcentration and translocation factor exceeded 4.0 and 1.0, respectively, across all tested treatments, indicating that A. argyi is a promising candidate for phytoremediation. Notably, the effects of soil pH on Cd accumulation and subcellular distribution in A. argyi differed between low and moderately Cd-contaminated soils. Adjustments to soil pH based on the degree of Cd contamination can enhance Cd extraction by A. argyi, thereby reducing the overall remediation cycle of cadmium-polluted paddy fields of South China.

Identifying ecosystem service trade-offs/synergies and their influencing factors are prerequisites for formulating scientific ecosystem management strategies. We selected Dongting Lake Area as the study area, quantified four key ESs dynamics, including food production (FP), soil conservation (SC), habitat quality (HQ) and ecological leisure (EL), identified relationships between paired ecosystem services using Spearman correlation coefficients, and analyzed how various drivers impact trade-offs and synergies by leveraging spatial panel data models; we also implemented ecosystem management zoning by superposition analysis on ecosystem services, the relationships between these services, and key drivers. The results showed that FC and SC displayed synergy before a trade-off over the period 2000–2022. The FP–HQ and HQ–EL initially displayed synergy, then trade-off, and then synergy again. Spatially, the spatial trade-off ratios of FP–HQ, SC–HQ, and HQ–EL exceeded the synergy ratios, and trade-off areas of FP–HQ, SC–HQ, and HQ–EL existed around Dongting Lake. The direct or indirect effects of DEM, slope, precipitation, and population density have the greatest effect on ecosystem service pairs. Furthermore, the DTLA was divided into ecological unbalance, soil conservation, habitat quality synergy, and ecological leisure areas. These finding may provide critical scientific insights into how to balance ecological conservation and socio-economic progress in the Dongting Lake Area.

Floodplain wetlands have a significant capacity for carbon sequestration but are vulnerable to land use changes. Poplars are extensively planted in wetlands due to the increasing demand for wood products and bioenergy. Although the large biomass of poplar may increase the carbon stock in wetlands, their high transpiration rates may reduce soil moisture, thereby improving the aeration and facilitating the oxidation of organic materials. Therefore, the impact of poplars on wetland carbon stock remains uncertain and unexplored. Here, we investigated the effects of poplar plantations on biomass carbon stock (BCS) and soil organic carbon (SOC) stock in Dongting Lake wetlands, China, using native Miscanthus lutarioriparius vegetation as a control. Our results indicated that the BCS of middle-aged and near-mature poplar plantations (36.47–81.34 t ha−1) was higher than that of M. lutarioriparius (8.31 t ha−1), and it increased with stand age. The SOC stock within the 0–60 cm depth in young, middle-aged, and near-mature poplar plantations (130.32–152.58 t ha−1) were higher than those in M. lutarioriparius (70.48 t ha−1), but they did not increase with stand age. The BCS was positively associated with soil bulk density, while SOC stock was negatively associated with soil sand content. Overall, our findings indicate that poplar plantations increase carbon stock in the Dongting Lake wetlands. Nevertheless, the long-term effect of poplar plantation on carbon sequestration in floodplain wetlands should be further investigated.