Uncertainties in carbon storage estimates for disturbance-prone dryland ecosystems hinder accurate assessments of their contribution to the global carbon budget. This study examines the effects of land-use change on carbon storage in an African savanna landscape, focusing on two major land-use change pathways: agricultural intensification and wildlife conservation, both of which alter disturbance regimes. By adapting tree inventory and soil sampling methods for dryland conditions, we quantified aboveground and belowground carbon in woody vegetation (AGC and BGC) and soil organic carbon (SOC) across these pathways in two vegetation types (scrub savanna and woodland savanna). We used Generalized Additive Mixed Models to assess the effects of multiple environmental drivers on AGC and whole-ecosystem carbon storage (C-total). Our findings revealed a pronounced variation in the vulnerability of carbon reservoirs to disturbance, depending on land-use change pathway and vegetation type. In scrub savanna vegetation, shrub AGC emerged as the most vulnerable carbon reservoir, declining on average by 56% along the conservation pathway and 90% along the intensification pathway compared to low-disturbance sites. In woodland savanna, tree AGC was most affected, decreasing on average by 95% along the intensification pathway. Unexpectedly, SOC stocks were often higher at greater disturbance levels, particularly under agricultural intensification, likely due to the preferential conversion of naturally carbon-richer soils for agriculture and the redistribution of AGC to SOC through megaherbivore browsing. Strong unimodal relationships between disturbance agents, such as megaherbivore browsing and woodcutting, and both AGC and C-total suggest that intermediate disturbance levels can enhance ecosystem-level carbon storage in disturbance-prone dryland ecosystems. These findings underline the importance of locally tailored management strategies-such as in carbon certification schemes-that reconcile disturbance regimes in drylands with carbon sequestration goals. Moreover, potential trade-offs between land-use objectives and carbon storage goals must be considered.

Indigenous vegetation fragments in agricultural landscapes are vulnerable to creeping edge effects and stochastic extinctions on top of the effects of historic land use and disturbance which have already resulted in significant changes to baselines. Agricultural intensification can potentially increase these threats through spillover of nutrients, water, and weeds, especially in dryland ecosystems which are naturally low in nitrogen and soil moisture. We use plot-based vegetation data and soil measurements of stable isotopes of nitrogen to test whether adjacent agricultural intensification increases plant invasions into dryland shrubland fragments in Canterbury, New Zealand. Nitrogen spillover was only associated with edges adjacent to intensive agriculture. Animal effluent was the most likely source. Edges adjacent to intensive agriculture had higher dominance by exotic species, higher exotic graminoid cover, and depressed native bryophyte cover immediately adjacent to the agricultural boundary. Changes in exotic cover were due to weedy species that dominate in areas of high disturbance and nutrients rather than pasture species moving over the fenced boundary. Spillover created more abrupt environmental and vegetation gradients at the edge but didn't change the extent of the edge, which typically transitioned to the fragment core at about 40-50 m from the fragment boundary. Hence, the core vegetation remained little affected by adjacent intensification. Spatial buffers to manage fertiliser and irrigation spillover will help prevent further degradation of edge communities adjacent to intensive agriculture. However, the longer term threat to the ecological integrity of the core area of these spatially isolated fragments is likely to be random extinction and vegetation succession. The loss of spatial linkages between vegetation patches and the mosaic of vegetation at different developmental stages means that many of the species that once made up the regional species pool will be lost from this landscape without intervention.