Depth distribution of belowground net primary production across global biomes

The depth distribution of belowground net primary production (BNPP) has been unquantified globally, hindering our understanding of belowground carbon dynamics. We synthesize global observational data sets to infer the depth allocation of BNPP down to 2 m, and map depth-specific BNPP globally at 1 km resolution. We estimate that global average BNPP in the 0–20 soil layer is 1.1 Mg C ha–1 yr–1, accounting for >50% of total BNPP. Across the globe, the depth distribution of BNPP shows large variability, and more BNPP is allocated to deeper layers in hotter and drier regions. Edaphic, climatic and topographic properties (in the order of importance) can explain >80% of such variability in different soil depths; and the direction and magnitude of the influence of individual properties (e.g., precipitation and soil nutrient) are soil depth- and biome-dependent. Our results provide global benchmarks for predictions of whole-soil carbon profiles across global biomes.

Depth distribution of belowground net primary production across global biomes

The depth distribution of belowground net primary production (BNPP) has been unquantified globally, hindering our understanding of belowground carbon dynamics. We synthesize global observational data sets to infer the depth allocation of BNPP down to 2 m, and map depth-specific BNPP globally at 1 km resolution. We estimate that global average BNPP in the 0–20 soil layer is 1.1 Mg C ha–1 yr–1, accounting for >50% of total BNPP. Across the globe, the depth distribution of BNPP shows large variability, and more BNPP is allocated to deeper layers in hotter and drier regions. Edaphic, climatic and topographic properties (in the order of importance) can explain >80% of such variability in different soil depths; and the direction and magnitude of the influence of individual properties (e.g., precipitation and soil nutrient) are soil depth- and biome-dependent. Our results provide global benchmarks for predictions of whole-soil carbon profiles across global biomes.

Impacts of mixed-grazing on root biomass and belowground net primary production in a temperate desert steppe

The impacts of large herbivores on plant communities differ depending on the plants and the herbivores. Few studies have explored how herbivores influence root biomass. Root growth of vegetation was studied in the field with four treatments: sheep grazing alone (SG), cattle grazing alone (CG), mixed grazing with cattle and sheep (MG) and no grazing (CK). Live and total root biomasses were measured using the root ingrowth core and the drilling core, respectively. After 2 years of grazing, total root biomass showed a decreasing trend while live root biomass increased with time during the growing seasons. Belowground net primary production (BNPP) among the treatments varied from 166 ± 32 to 501 ± 88 g m −2 and root turnover rates (RTR) varied from 0.25 ± 0.05 to 0.70 ± 0.11 year −1 . SG had the greatest BNPP and RTR, while the CG had the smallest BNPP and RTR. BNPP and RTR of the MG treatment were between those of the CG and SG treatments. BNPP and RTR of the CK were similar to MG treatment. Compared with other treatments, CG had a greater impact on dominant tall grasses species in communities. SG could decrease community diversity. MG eliminated the disadvantages of single-species grazing and was beneficial to community diversity and stability.