Background: Andhra Pradesh, with approximately 23,044 km² of recorded forest area (28.92% geographic area), harbours a remarkable diversity of plant life concentrated primarily in dry deciduous formations of the Eastern Ghats and the Deccan Plateau. Despite floristic surveys conducted in major protected areas, a significant portion of the state’s forest landscape, particularly the less-accessible, non-gazetted ‘lesser-known’ forest fragments in the interior of Kurnool, Prakasam, Nellore, and parts of YSR Kadapa districts, remains inadequately documented. These dry deciduous forest patches, composed predominantly of tropical dry deciduous formations (Type 5A and 5B per Champion and Seth classification), host a unique assemblage of species, many of which are rare, endemic, or threatened, yet lack comprehensive scientific documentation that could inform their conservation management under the Biological Diversity Act 2002 and the Wildlife Protection Act 1972.

Objectives: This 24-month field study (June 2024 – May 2026) aimed to: (1) systematically enumerate all vascular plant species in five lesser-known dry deciduous forest patches across Kurnool, Prakasam, and Nellore districts of Andhra Pradesh; (2) compute phytosociological parameters (density, frequency, basal area, Importance Value Index) for tree species across 30 permanent vegetation plots; (3) assess species rarity using a multi-criteria rarity index incorporating distributional range, population size, and habitat specificity; (4) cross-reference all recorded taxa against the IUCN Red List, the Andhra Pradesh Biodiversity Board’s threatened species list, and the Botanical Survey of India (BSI) Deccan Regional Centre’s endemic plant database; and (5) provide the first baseline floristic inventory for these under-documented forest sites to guide conservation planning.

Methods: Field surveys were conducted seasonally across five study sites designated as: Site A (Gundlakamma Reserve Forest, Prakasam district), Site B (Lankamalleswara Reserve Forest, Kurnool district), Site C (Veligonda Hill Tract, Nellore district), Site D (Handri River Fringe Forest, Kurnool district), and Site E (Bandipalem-Dornala Forest Block, Prakasam district). Vegetation surveys used 30 systematically placed permanent plots (20 × 20 m) for trees (girth ≥ 10 cm at breast height), nested 5 × 5 m subplots for shrubs, and 1 × 1 m microplots for herbs. Species rarity was assessed using Rabinowitz’s seven forms of rarity framework (1981) [13], augmented by a Rarity Index (RI) score computed from range size, habitat breadth, and local population size. Statistical analyses included Shannon-Wiener diversity index (H’), Simpson’s dominance index (D), Pielou’s evenness (J’), and Sorensen’s similarity coefficient between sites.

Results: A total of 342 vascular plant species belonging to 245 genera and 78 families were recorded across the five study sites over the 24-month study period. Trees comprised 127 species (37.1%), shrubs 89 species (26.0%), herbs 108 species (31.6%), and climbers/lianas 18 species (5.3%). Fabaceae (34 species), Rubiaceae (22 species), Combretaceae (18 species), Euphorbiaceae (16 species), and Malvaceae (14 species) were the five most species-rich families. The most important tree species by IVI were Anogeissus latifolia (IVI = 48.6), Pterocarpus santalinus (IVI = 38.4), Hardwickia binata (IVI = 32.8), Chloroxylon swietenia (IVI = 28.6), and Terminalia pallida (IVI = 22.4). Shannon-Wiener diversity index (H’) ranged from 3.42 (Site D, lowest: riparian) to 4.28 (Site B, highest: Lankamalleswara). A total of 42 species were categorised as rare under the multi-criteria rarity assessment; 18 species were confirmed as IUCN-listed Threatened (Vulnerable, Endangered, or Critically Endangered); 12 species were recorded as endemic to the Eastern Ghats or Andhra Pradesh region, including 7 species new to the recorded flora of Kurnool and Prakasam districts.

Conclusion: The five lesser-known dry deciduous forest patches of south-central Andhra Pradesh harbour a floristically diverse and conservation-important assemblage of vascular plants that is poorly represented in existing protected area networks and biodiversity databases. Seven species documented for the first time in Kurnool and Prakasam districts represent significant range extensions that will require verification and formal reporting to the Botanical Survey of India. The prevalence of rare and threatened taxa, particularly Pterocarpus santalinus, Andrographis beddomei, and Ceropegia elegans, in these unprotected patches argues strongly for their inclusion in the State’s biodiversity management plans under the Biological Diversity Act (2002 and its 2023 amendment) and the Eco-Sensitive Area notification process. This study provides an urgently needed primary floristic baseline for conservation planning in a critically under-documented region of peninsular India’s dry deciduous biome.