Introduction:

Oregano (Lippia graveolens H. B. K.) grows in semi-arid ecosystems. There is no information on the population dynamics of this species at the Tehuacán-Cuicatlán Biosphere Reserve (RBTC).

Objective:

To determine the vertical structure and spatial distribution of L. graveolens in five topographic conditions in the RBTC.

Materials and methods:

Ten sampling units were established in five topographic conditions (TC), where six plant height categories were defined. Density and structural variables were measured, from which IVI was obtained and population structure curves were constructed. The spatial distribution pattern was analyzed with the Ripley's transformed function (L (t) ).

Results and discussion:

TC1 showed population curve type IV (low frequency in the first, third and fourth height categories, high in the second and fifth categories, and low in the rest) with lower density (100 plants∙ha-1; 1.6 %) in category 6 (>251 cm), and higher density (1 840 plants∙ha-1; 29 %) in category 4 (151 a 200 cm). For TC2 to TC5, the curve was V-type (low frequency in the first category, gradual increase up to the intermediate category, and gradual decrease in the rest) with lower density (20 plants∙ha-1; 0.4 %) in category 6, and higher density (2 320 plants∙ha-1; 51 %) in category 4 which also had the highest IVI (92.8 to 126.1). Spatial distribution was aggregated in TC1 to TC4 and randomized in TC5.

Conclusions:

Topographic conditions influenced the vertical structure and spatial distribution of oregano.