INTERNATIONAL JOURNAL OF AGRICULTURE & BIOLOGY ISSN Print: 1560–8530; ISSN Online: 1814–9596 20–1553/2021/25–5–945–954 DOI: 10.17957/IJAB/15.1750 http://www.fspublishers.org Full Length Article To cite this paper: Alshahrani TS (2021). Existing status of Acacia woodlands in central Saudi Arabia: A case study in Hawtat Bani Tamim and Al Duwadmi. Intl J Agric Biol 25:945‒954 Existing Status of Acacia Woodlands in Central Saudi Arabia: A Case Study in Hawtat Bani Tamim and Al Duwadmi Thobayet Safar Alshahrani * Plant Production Department College of Food and Agriculture Sciences King Saud University P.O. Box 2460, Riyadh 11451, Saudi Arabia * For correspondence: talshahrani@ksu.edu.sa; thobayet@yahoo.com Received 27 October 2020; Accepted 02 January 2021; Published 16 April 2021 Abstract Acacia woodlands are ecologically important and it is necessary to understand its structures and dynamics to develop sustainable conservation strategies. This study aimed to provide baseline information on the composition and growth of Acacia woodlands in the Hawtat Bani Tamim and Al Duwadmi regions of central Saudi Arabia. Height, diameter at breast height, crown diameter, seedling density, and soil seed bank content of Acacia tree species were characterized for 27 remote, circular, 0.1-ha plots in both study areas. At Hawtat Bani Tamim, Acacia raddiana, A. tortilis, and A. ehrenbergiana accounted for 45.53, 37.5 and 16.96% of all species present there. Most DBH were in the 6–10 cm class. A. raddiana was the main species in most diameter classes. Most trees were 4.1–5.0 m tall and A. raddiana predominated in this height class. Acacia ehrenbergiana had 92.63% damaged seeds. At Al Duwadmi, A. raddiana represented 78.99% of all Acacia trees there. A. gerrardii and A. tortilis accounted for 11.93 and 9.07% of the species there, respectively. Most of the DBH values were in the 6–10 cm and 11–15 cm classes, and A. tortilis and A. raddiana were abundant in both classes. Most trees were in the 4.1–5 m height class, which was dominated by A. raddiana. A. ehrenbergiana had 88.26% damaged seeds. In both areas, there was a gradual decline in the number of trees in DBH classes > 35 cm. The Acacia species in the two areas showed a fair regeneration status. There were more seedlings than saplings and fewer saplings than trees. This baseline study could contribute towards future sustainability planning initiatives after other assessment studies have been conducted to identify changes in the Acacia woodlands of this region. © 2021 Friends Science Publishers Key words: Baseline; Crown diameter; DBH; Sapling; Seedling; Soil seed bank Introduction In Saudi Arabia, Acacia tree species are naturally distributed in small, low-density populations. Saudi Arabia is located in a desert belt region characterized by variable but very low amounts of rainfall and high temperatures. The Acacia woodlands in Saudi Arabia are undergoing intense grazing and logging for firewood and charcoal. A. tortilis is the preferred national fuelwood source. The level at which this species is being exploited far surpasses its ability to regenerate and meet the escalating demands of the local communities (Al-Abdulkader et al. 2004). Perturbations such as overgrazing and socioeconomic changes have caused severe rangeland and other forms of degradation in the interior of Saudi Arabia (Al-Rowaily et al. 2018). However, Acacia trees are palatable to herbivores and heavy browsing on them reduces their canopy cover and density (Noumi et al. 2010; Al-Rowaily et al. 2012). Extreme environmental conditions such as drought impede plant growth and survival. Nevertheless, Acacia species can survive and even thrive under such conditions. In desert ecosystems, Acacia trees improve soil nutrient status (Munzbergova and Ward 2002) and soil moisture (Ross and Burt 2015). Despite hindrances such as drought and temperature, root nodule bacteria nonetheless associate with Acacia species in central Saudi Arabia (Alshaharani and Shetta 2015). This mutualism may enhance soil fertility in arid and semiarid habitats (Zahran 1999). De Boever (2015) reported that in Tunisia, a single A. raddiana tree improved soil water availability in the top 40 cm soil layer by ≤175% inside and outside the canopy. A baseline or reference study evaluates degradation by comparison either with a previous state (FAO 2011) or with a contemporaneous reference condition (Thompson et al. 2013). In each case, the reference context must be derived from the same biome type in the same climate zone. The use of indicators such as shoot growth, soil seed banks, seedling abundance, or age structure of common woody plant species provides information regarding forest recovery in response to disturbances. Analyzing seedlings and young tree