Area closure is implemented in the Tigray region of Ethiopia as an effective management system to conserve natural resources in semi-arid areas. However, the growth rate of dwarf trees, such as Vachellia etbaica (Schweinf.) Kyal. & Boatwr., a dominant tree in plant communities in the region, is relatively low owing to the harsh natural environment. Many years of growth are required to produce sufficient biomass to enable provision of wood resources under a low growth rate. Limited information is available on the existing biomass and temporal change in the biomass of dwarf forest. This study focused on a V. etbaica stand in eastern Tigray, Ethiopia, to 1) derive a species site-specific allometric equation by destructive sampling of 20 trees, 2) estimate biomass from inventory data gathered in 2014 and 2017, and 3) calculate mean annual increment (MAI) from biomass change over a 3-year 4-month period to determine tree productivity. A survey plot (20 m×100 m) was established in an area closed for more than 20 years. For all V. etbaica individuals in the plot, diameter at ground level, diameter at 30 cm height above the ground, tree height, and crown size were measured. Three models for aboveground biomass (AGB), belowground biomass (BGB), and total biomass were developed from data for 20 individuals destructively sampled in 2014 and 2020. Assessment of the biomass models using the adjusted R², root mean square error, and corrected Akaike information criterion indicated that basal area at ground level and tree height improved the goodness of fit. Between 2014 and 2017, stand density declined by 2.6% from 1175 to 1145 individuals ha^–1, and crown coverage expanded by 9.0% from 3469.5 to 3780.8 m² ha^–1. Total biomass slightly increased from 16.70 to 18.42 Mg ha^–1 between the inventory years. From these two estimations, the MAI of AGB, BGB, and total biomass was calculated as 372, 148, and 516 kg ha^–1 year^–1, respectively. These results confirmed that the MAI in this study was extremely low in comparison with other reported examples. Considering the MAI of AGB and previous regional governmental data, annual biomass production may be sufficient to cover the fuelwood consumption for 194 individuals (or approximately 30 households). Eventually, the area-closure system will contribute to vegetation restoration; however, the policy may affect the livelihood of residents reliant on natural resources when vegetation with a low growth rate is a target of the system. Moreover, given that exploitation of woody resources is restricted by the system, other organic materials, such as animal feces, have been heavily exploited as an alternative fuel source instead of firewood. Rural communities require natural resources that can increase within a short period, while simultaneously conserving those resources. However, there is a limit to the rate of increase in woody biomass achievable by afforestation and forest management in semi-arid areas. Active introduction of alternative fuels, including further promotion of electrification and utilization of solar energy for rural areas, may be required to enable progress in the conservation of natural resources.