COMPOSITION AND STRUCTURE OF A LOW SEMI-THORN SHRUBLAND IN NORTHEASTERN MEXICO

Abstract

Background: The plant community in southern Texas and the adjacent region in Mexico is Tamaulipan thornscrub (MET). However, the recently published proposals for quantitative hierarchical classifcation have evidenced the presence of more communities and the need for quantitative descriptions of these associations to determine their conservation status. Question: What is the structure and foristic composition of a semi-thorn shrubland in Reynosa's northwestern region? Studied species: Tamaulipan low semi-thorn scrubland. Study site and dates: Hills in Reynosa's northwestern region (Tamaulipas), Mexico. August 2018-July 2019. Methods: Abundance, height and coverage of each plant species were measured on 33 plots of 10 × 10 m. Horizontal structure was analyzed by Importance Value Index, vertical structure was estimated through a modifcation of the Pretzsch Index and in addition alpha diversity indices were calculated. tan Results: Richness was 55 species, within 54 genera and 25 families. The imporce values were centered mainly in small, spineless shrub species (Lippia graveolens, Calliandra conferta, Turnera diffusa and Krameria ramosissima). The vertical structure presented four defned strata with 50 % of species equally represented in all strata and the remaining 50 % restricted to a single stratum (A = 2.86, Amax = 5.39, Arel = 52.98 %). The species with the highest proportional density were distributed only in stratum IV (0-1.12 m). Conclusions: The community is a clearly defned low semi-thorn scrubland. The structural characteristics indicate that it can be a possible transition plant association between MET and piedmont scrub. This reinforces the proposals of the recently published classifcation systems.