Plant-Soil Mediated Effects of Long-Term Warming on Soil Nematodes of Alpine Meadows on the Qinghai-Tibetan Plateau

Simple Summary Global warming causes disturbances to grasslands and has a wide range of impacts on biodiversity and ecosystem processes worldwide. Soil nematodes are good indicators of climate change and are considered to be one of the important driving forces for the succession of plant communities. Therefore, understanding the relationship between soil nematodes and aboveground communities is particularly important under long-term warming. We selected an alpine meadow on the Qinghai-Tibetan Plateau and conducted a long-term artificial warming experiment with five different gradients. We found that both plant and soil nematode community composition were affected by long-term warming. In addition, plant diversity and community composition profoundly affect the diversity of soil nematode communities, thus reflecting the dynamic processes and evolution of soil ecosystems. Global warming is one of the most pressing environmental issues today. Our study aimed to investigate how warming affected plant and soil nematode communities in alpine meadows on the Qinghai-Tibetan Plateau over the past seven years. An artificial warming experiment with different gradients was conducted from 2011 to 2018, including temperature increases of 0 degrees C (CK), 0.53 degrees C (A), 1.15 degrees C (B), 2.07 degrees C (C), and 2.17 degrees C (D), respectively. Cyperaceae plants were shown to be eliminated by increasing temperature, and plant community composition tended to cluster differently under different warming gradients. The number of nematodes decreased with the increase in soil depth, and the majority of them were observed in the topsoil layer. The individual densities of soil nematodes were 197 ind.center dot 100 g(-1) dry soil at 10-20 cm and 188 ind.center dot 100 g(-1) dry soil at 20-30 cm in the A treatment, which was significantly higher than the CK (53 and 67 ind.center dot 100 g(-1) dry soil) (p < 0.05). The lowest relative abundance of bacterivore nematodes (Ba) was 31.31% in treatment A and reached the highest of 47.14% under the warming gradient of D (p < 0.05). The abundance of plant parasitic nematodes (Pp) was significantly reduced to 26.03% by excessive warming (2.17 degrees C increase) in comparison to CK (41.65%). The soil nematode community had the highest diversity with a 0.53 degrees C increase in soil temperature; 1.15 degrees C warming gradients were lower, and nematode communities tended to be simplified (p < 0.05). All nematode channel ratio (NCR) values were above 0.5, indicating that warming did not change the decomposition pathway of soil organic matter dominated by the bacterial channels. The Wasilewska Index (WI) in the D treatment increased significantly compared to other treatments (p < 0.05), indicating that the mineralized pathway of the food web was primarily involved with Ba and fungivores nematodes (Fu), which is conducive to the growth of micro-biophagous nematodes. The plant parasite index (PPI) decreased significantly in the D treatment compared with other treatments (p < 0.05), indicating that a high warming gradient caused a reduction in the maturity of Pp nematodes. The maturity index (MI) increased in the D treatment compared with A, B, and C treatments, indicating that overheating affected the nematode community in the later stage of succession and caused the soil to be less disturbed. A partial least squares path model (PLSPM) showed that warming indirectly affects Fu and Pp diversity by directly impacting the plant community as well as indirectly affecting Ba by directly affecting soil properties. In conclusion, plant diversity and community composition profoundly affect the soil nematode communities, thus reflecting the dynamic processes and evolution of soil ecosystems.

Automated summary

Global warming affects plant and soil nematode communities in alpine meadows on the Qinghai-Tibetan Plateau, and plant diversity and community composition play a significant role in shaping soil nematode communities.