Characterization and attributes of herbaceous vegetation in a Caatinga fragment in the State of Sergipe, Brazil

ABSTRACT Variations in environmental factors are expected to be responsible for the diversification of herbaceous plants in the Caatinga (dry forest). We analyzed the composition, floristic similarity and structure of the herbaceous vegetation in a Caatinga fragment in the municipality of Poço Verde, Sergipe State, Brazil. In addition, the influence of precipitation on richness among different Caatinga areas was evaluated. We installed 30 subplots and the floristic composition was complemented by collections made around these subplots. A total of 80 species were found, of which 43% are typically from disturbed areas of Caatinga. Among the Caatinga areas, precipitation did not explain the variation of richness; similarity values were determined by environmental heterogeneity. The parameters of Shannon-Wiener diversity and Pielou's evenness were within the range expected for Caatinga disturbed areas. Based on evidence supported by previous studies, we believe that human disturbance influences the composition and the structure of the studied herbaceous vegetation. Therefore, conservation actions are recommended.

摘要
环境因子的变异被认为是卡廷加（Caatinga，干旱森林）草本植物物种分化的驱动因素。本研究针对巴西塞尔希培州波索韦尔迪市境内的一片卡廷加植被片段，分析了其草本植被的组成、区系相似性与结构特征。此外，本研究还评估了降水对不同卡廷加区域物种丰富度的影响。研究共设置30个副样地，并通过在副样地周边开展标本采集工作以补充区系组成数据。本次调查共记录到80个物种，其中43%为卡廷加受干扰区域的典型物种。在不同卡廷加区域中，降水无法解释物种丰富度的变异；区系相似性值由环境异质性决定。香农-威纳多样性指数（Shannon-Wiener diversity）与皮尔洛均匀度指数（Pielou's evenness）的参数值均处于卡廷加受干扰区域的预期范围之内。基于既往研究的佐证证据，本研究认为人为干扰会对本次研究对象的草本植被组成与结构产生影响。因此，本研究建议开展针对性的保护行动。