[Carbon sequestration status of forest ecosystems in Ningxia Hui Autonomous Region].

Based on the data of Ningxia Hui Autonomous Region forest resources inventory, field investigation and laboratory analysis, this paper studied the carbon sequestration status of forest ecosystems in Ningxia region, estimated the carbon density and storage of forest ecosystems, and analyzed their spatial distribution characteristics. The results showed that the biomass of each forest vegetation component was in the order of arbor layer (46.64 Mg x hm(-2)) > litterfall layer (7.34 Mg x hm(-2)) > fine root layer (6.67 Mg x hm(-2)) > shrub-grass layer (0.73 Mg x hm(-2)). Spruce (115.43 Mg x hm(-2)) and Pinus tabuliformis (94.55 Mg x hm(-2)) had higher vegetation biomasses per unit area than other tree species. Over-mature forest had the highest arbor carbon density among the forests with different ages. However, the young forest had the highest arbor carbon storage (1.90 Tg C) due to its widest planted area. Overall, the average carbon density of forest ecosystems in Ningxia region was 265.74 Mg C x hm(-2), and the carbon storage was 43.54 Tg C. Carbon density and storage of vegetation were 27.24 Mg C x hm(-2) and 4.46 Tg C, respectively. Carbon storage in the soil was 8.76 times of that in the vegetation. In the southern part of Ningxia region, the forest carbon storage was higher than in the northern part, where the low C storage was mainly related to the small forest area and young forest age structure. With the improvement of forest age structure and the further implementation of forestry ecoengineering, the forest ecosystems in Ningxia region would achieve a huge carbon sequestration potential.

[Fine root biomass of four main vegetation types in Daluo Mountain of Ningxia, Northwest China].

By the method of soil core sampling, this paper studied the fine root biomass, soil water content, and soil bulk density in 0-40 cm soil layer of four main vegetation types (Picea crassifolia forest, Pinus tabulaeformis forest, deciduous shrubs, and desert grassland) in Daluo Mountain of Ningxia, and the fine root biomass in the 0-40 cm soil layer of P. crassifolia forests with the ages of 50-, 70-, and 100 a. The fine root biomass of the four vegetation types was mainly distributed in 0-20 cm soil layer, with the rank of P. tabulaeformis forest > P. crassifolia forest > deciduous shrubs > desert grassland, and the fine root biomass of P. tabulaeformis forest was significantly higher than that of the other three vegetation types. The fine root biomass of the P. crassifolia forests with different ages was 70 a > 100 a > 50 a, and there were no significant differences in the live fine root biomass ratio and dead fine root biomass ratio among the three P. crassifolia forests. The soil water content in the 0-40 cm soil layer of the four vegetation types was P. crassifolia forest > P. tabulaeformis forest > deciduous shrubs > desert grassland, while the soil bulk density followed an opposite pattern, and was significantly negatively correlated with the fine root biomass.