Biodiversity and Abundance of Angiosperms Responding to Resilience Environments in the tidal range of Yuanjiang Dry-Hot Valley

Yuanjiang dry-hot valley is a poorly vegetated area and a fragile arid ecosystem. Although, in the past the valley was lushly forested, it has become a tropical montane savannah in recent decades. Nonetheless, it is unclear what controls plant species distribution in these kinds of dry-hot valleys. Clarifying this will be beneficial to sustainable ecosystem management in dry-hot valleys. This study explored the relationship between plant species and their living environments in the low land of this dry-hot valley. To achieve this, transects and plots were arranged along the river channel while alpha and beta indices were employed to observe the biodiversity change between species and environments. Estimated species, rarity, and abundance indices were also subscribed to examine the correlation among species, population size, and their living circumstances in terms of Species_estimated , Singletons , Uniques , ACE, ICE , and Chao2 . Fifty years of meteorological records including temperature and precipitation were collected for environmental reference . The results indicated that: (1) alpha diversity is higher when located closer to the river channel than from afar whereas beta diversity increases from the upper stream to the lower stream with Bray-Curtis < 0.500, but this condition is reversed in the transect perpendicular to the river; (2) total phosphorous (TP) and total potassium (TK) are increased when slope is declined, tending to be in the same direction as the total increase of nitrogen (TN) and organic matters (OM); (3) all measured nutrients are aggregated to the lower stream along with river flows, corresponding to an increased number of species; (4) water supply is the determinant factor for plant distribution while soil condition is the key decisive factor for water retention; (5) estimated species, rarity and abundance indices are significant on the sites that are closer to the river, thus strongly indicating heterogeneous of habitats and soil condition. (6) Fern species is screened as an indicator, thus representing the xeric environment in Yuanjiang dry-hot valley. Conclusively, plants are not flourished at low altitudes which are ascribed to high temperatures and low water supply. Therefore, attention and policy on microhabitat protection and environment management should be drawn and enforced exclusively for this valley.