To reveal the changes in stoichiometry characteristics of leaf-litter-soil interactions of Haloxylon ammodendron plantations and their influencing mechanisms.

Using Haloxylon ammodendron plantations with different stand ages (3, 6, 11, 16 and 35 years old) in the Jilantai desert area of Inner Mongolia as the study objects, the changes in carbon (C), nitrogen (N), phosphorus (P) stoichiometry in Haloxylon ammodendron leaves, litter, and soil and their interrelationships were analyzed.

The results showed that: 1) Stand age had a significant effect on leaf, litter and soil C, N and P contents and stoichiometric ratios (P<0.05). The average carbon, nitrogen, and phosphorus contents of Haloxylon ammodendron leaves, litter, and soil were in the order of leaves > litter > soil. The C∶N, C∶P and N∶P were in the order of litter > leaves > soil; 2) At the depth of 0-20 cm, soil C∶N was significantly negatively correlated with leaf C∶N and C∶P, and extremely significantly negatively correlated with litter C∶P and N∶P; soil C∶P was significantly negatively correlated with leaf C∶N, C∶P, litter C∶P and N∶P; and soil N∶P was significantly negatively correlated with litter C∶P. Soil C∶N, C∶P, and N∶P were not significantly correlated with leaf/litter C∶N, C∶P, and N∶P at 20-60 cm soil depth; 3) Limiting factors for litter and leaves were inconsistent between shallow and deep soils. At the depth of 0-20 cm, soil C∶P and pH were important factors affecting nutrient content and stoichiometry of Haloxylon ammodendron leaves; soil C∶N and soil bulk density (BD) were important factors affecting nutrient content and stoichiometry of Haloxylon ammodendron litter. At the depth of 20-60 cm, soil total nitrogen (STN) and pH were important factors affecting nutrient content and stoichiometry of Haloxylon ammodendron leaves and litter, respectively.

The research results are beneficial for further clarifying the interaction patterns and mechanisms of carbon, nitrogen, and phosphorus in the leaf-litter-soil interactions of Haloxylon ammodendron plantations in desert areas.

To investigate the allocation patterns of carbon storage and carbon sequestration potential in Haloxylon ammodendron plantation ecosystems at different stand ages, and to elucidate the carbon sink function of Haloxylon forests in desert regions.

This study systematically analyzed ecosystem carbon stock allocation characteristics and its driving factors by using 3-30 a Haloxylon ammodendron in the Jilantai desert area.

The results showed that: 1) The carbon content in the branches, leaves and roots of Haloxylon ammodendron showed a trend of first increasing and then decreasing with stand ages. Stand ages had a significant impact on carbon content in various organs and soil of Haloxylon ammodendron plantations. The soil carbon content in Haloxylon ammodendron plantations had obvious vertical distribution characteristics. The soil carbon content in 3 a and 6 a Haloxylon ammodendron plantations gradually increased with soil depth, and soil carbon content in 11, 16 and 30 a Haloxylon ammodendron plantations decreased with increasing soil depth; 2) The biomass, carbon storage and soil carbon storage of various organs in shrub layer increase with stand age. Stand ages had a significant impact on biomass, carbon storage and soil carbon storage of various organs in the shrub layer (P < 0.05). The 0-100 cm soil carbon storage ranged from 1.17 to 7.82 t·hm^-2 of Haloxylon ammodendron plantations with different stand ages. The soil carbon storage of 3 a and 6 a Haloxylon ammodendron gradually increased with soil depth, and soil carbon storage of 11, 16, and 30 a Haloxylon ammodendron decreased with increasing soil depth; 3) The allocation proportion of Haloxylon ammodendron plantations ecosystem carbon stocks showed: soil layer > shrub layer > herb layer > litter layer, indicating that ecosystem carbon stocks were mainly concentrated in soil layer, with a carbon storage allocation ratio ranging from 84.06% to 95.73%; 4) Net primary productivity and annual carbon sequestration of Haloxylon ammodendron plantations increased with stand age. Among them, net primary productivity and annual carbon sequestration of shrub layer with 3 a and 6 a Haloxylon ammodendron plantations were greater than those of herbaceous layer, and net primary productivity and annual carbon sequestration of herbaceous layer with 11, 16 and 30 a Haloxylon ammodendron plantations were greater than those of shrub layer.

The establishment of Haloxylon ammodendron plantations in China's desert regions demonstrates significant carbon sequestration potential. The carbon storage capacity of these artificial Haloxylon ammodendron ecosystems exhibits pronounced age-dependent variation. Future assessments of carbon stocks in desert Haloxylon ammodendron plantations should therefore explicitly account for the differential impacts across stand ages.

This study aimed to investigate the biomass allocation pattern of four dominant shrubs, and to establish a prediction model for individual nutrient organ biomass, thus making an accurate assessment for biomass and carbon sequestration of plantations in the Jilantai salt lake area.

This study used four dominant shrubs (Hedysarum scoparium, Calligonum mongolicum, Haloxylon ammodendron and Tamarix chinensis) as research objects in the Jilantai salt lake area, and measured factors (plant height (H), basal diameter (D), crown width (C)) and their combination factors (CH, DH and D²H) were used as independent variables for optimal model fitting. We investigated the optimal biomass model for various nutrient organs and verified model fitting with accuracy.

1) 4 kinds of single dominant shrub biomass ranged from 28.19 to 43.44 kg in Jilantai salt lake area, with an average of 34.65 kg; Total biomass of single shrubs showed as follows: Hedysarum scoparium > Haloxylon ammodendron > Calligonum mongolicum > Tamarix chinensis; 2) The four dominant shrubs showed highly significant correlations between leaf biomass and branch biomass, leaf biomass and root biomass, and branch biomass and root biomass (P < 0.01); 3) Root-shoot ratios of four dominant shrubs ranged from 0.41 to 0.54, and the biomass of individual organs ranged from: branches > roots > leaves. The slopes of the fitted equations of the four dominant shrubs ranged from 0.78 to 1.23, with significant difference from 1, indicating that an allometric growth relationship between above- and underground biomass; 4) The R² values of different components shrub biomass prediction models were more than 0.825 for four dominant shrubs, and prediction accuracy of the optimal biomass model was more than 0.85, indicating good prediction accuracy.

The power and quadratic forms were optimal biomass models, and were suitable for an accurate estimation for biomass from specific tree species in Jilantai salt lake area.