AimsPecan (Carya cathayensis Sarg.) is an important forest trees in China, the application of chemical pesticides for disease control has caused severe damage to the soil, including reduced fertility and disruption of microbial communities. Although Trichoderma treatment has been shown to promote plant growth and improve soil quality, its effects on the growth promotion of pecan and the impact on soil microbial communities and physicochemical properties remained unclear.MethodsIn this study, we investigated the impact of T. asperellum TCS007 spore suspension and its fermented crude extract on the growth and development of pecan seedlings. We also explored the effects of TCS007 treatment on the nutrients, enzyme activities, and microbial diversity in the rhizosphere soil of pecan seedlings during their three main growth stages.ResultsTreatment with TCS007 spore suspension or crude extract promoted the growth of pecan seedlings, with significantly higher levels of leaf hormones and defense enzyme activity compared to the control (CK). Moreover, the content of soil organic matter and ammonium nitrogen, as well as the activity of soil enzymes such as catalase and urease, were all significantly higher than CK after treatment, and the soil pH shifted from slightly acidic to slightly alkaline. The results indicated that TCS007 treatment significantly increased the richness of beneficial fungi and bacteria in the soil.ConclusionThe results demonstrated that TCS007 treatment significantly promoted the growth of pecan plants, increased enzyme activity and nutrient content in the soil, and improved the soil micro-ecological environment.

A study was conducted in the mountains of Magoebaskloof, Limpopo Province, where oak trees grow along the banks of the Broederstroom River. This study revealed that 22 nematode genera were associated with oak trees (Quercus robur). The most frequently occurring nematodes were Aphelenchus sp. (100%) and Plectus sp. (100%), followed by Helicotylenchus sp. (90%). This study examined the relationship between nematodes and the physicochemical properties of the soil using Pearson correlation. It uncovered that the organic matter content (OMC) had a negative correlation with the number of Panagrolaimus sp. (r = -0.770) and Hemicycliophora sp. (r = -0.674). Conversely, the sand percentage positively correlated (r = 0.695) with the number of Hemicycliophora sp. The clay content of the soil showed a positive correlation (r = 0.617) with the number of Ditylenchus. Soil pH demonstrated a significant negative correlation with Acrobeloides sp. (r = -0.877). The canonical correspondence analysis (CCA) explained 63.3% of the relationship between nematodes and soil physicochemical properties. The CCA results indicated that Ditylenchus exhibited a positive correlation with OMC, while the Panagrolaimus and Hemicycliophora species showed a negative correlation with OMC. The results indicated that none of the soil sample sites were under stress. The soil food web analysis revealed that most soil samples were nutrient-enriched with a low C/N ratio. In conclusion, this study revealed that oak trees harbor a high diversity of plant-parasitic and free-living nematodes. The results suggest that soil nematodes, particularly free-living bacterivores, such as Panagrolaimus, can indicate organic matter content in the soil.