Spatial Distribution and Ecosytem Carbon Stock of Acacia decurrens Plantations in Guder Watershed of Awi Zone, Amhara Region, Northwest Ethiopia

Plantation forests, like Acacia decurrens , are even-aged stands deliberately established by humans, with their expansion largely driven by household demand for charcoal, soil fertility improvement, and efforts to rehabilite degraded lands. Despite its importance, the spatial distribution, LULC changes, and full ecosystem-level carbon stock potential of the species remain largely overlooked. Therefore, this study addressed these gaps by analyzing the spatial distribution, LULC changes, and carbon stock potential of A. decurrens plantations in the Guder Watershed, Northwest Ethiopia. Spatial distribution was assessed using Global Positioning System (GPS)-based presence-only data and geostatistical techniques, including Spatial Autocorrelation (Moran’s I) and Hotspot Analysis (Getis-Ord Gi*). LULC changes for 1991, 2002, and 2020 was mapped using supervised maximum likelihood classification of Landsat imagery and post-classification comparison. Carbon stocks was quantified through a field inventory and laboratory analysis. Tree diameter and height were measured to estimate AGB using allometric equations, while BGB was estimated using a root-to-shoot ratio applied to AGB. Litter and soil samples (0–30 cm depth) were collected from field plots and processed to determine organic carbon content and soil bulk density. Results showed significant spatial clustering of A. decurrens plantations (Moran’s I = 0.97), with hotspots (z > +2.58, 99% confidence level) clustered in the southern highlands and coldspots (z < -2.58) concentrated in the northern lowlands. Between 1991 and 2020, A.decurrens plantation cover increased by 15.28 percentage points (expanding from 10.70% to 25.98%), primarily replacing grassland, which declined by 13.73 percentage points (from 24.59% to 10.86%). The mean total ecosystem carbon stock was 140.16 t C ha⁻¹ (513.92 t CO₂e ha⁻¹). Although A. decurrens enhances carbon sequestration and ecological recovery, its spread into croplands and grasslands may threaten local biodiversity and food security, highlighting the need for balanced and sustainable land-use planning.