Comparing distance-based methods of measuring plant density in an arid sparse scrubland: testing field and simulated sampling Hamid Jamali & Elham Ghehsareh Ardestani & Ataollah Ebrahimi & Fatemeh Pordel Received: 2 August 2019 /Accepted: 29 April 2020 # Springer Nature Switzerland AG 2020 Abstract Plant density is an important indicator of rangeland monitoring and management. In this paper, we aimed at comparing distance-based methods of den- sity measurement in field and in a simulated approach for two species of Astragalus verus Olivier and Astrag- alus albispinus Sirj. & Bornm with random and regular distribution pattern respectively. Then, we simulated a sampling scheme based on field measured statistics of the two species using Stochastic Geometry program and repeated the measurements using the same density methods. Moreover, the total individual plants of each species were counted in the sampling plots as the control method in Marjan rangelands of Iran during summer 2018. Results indicated that the best method for A. verus is nearest neighbor and point-centered quarter in field and simulated datasets in terms of both accuracy and precision respectively. For A. albispinus, the nearest neighbor and third closest individual were the best methods when compared with control in term of preci- sion and accuracy in the field respectively and third closet individual in simulated dataset in terms of both accuracy and precision compared with control, respectively. The results reveal that there is no statistically significant difference between the nearest neighbor and point-centered quarter for A. verus and third closest individual and nearest neighbor for A. albispinus when field/simulated datasets are compared with each other and con- trols. Therefore, we recommend using these dis- tance methods when this is a known species dis- tribution pattern, basic number per unit, and di- mensions of the unit as an alternative. Keywords Rangeland . Density estimation . Plotless methods . Astragalus verus Olivier . Astragalus albispinus Sirj. & Bornm . Spatial pattern Introduction Quantitative methods of plant surveying are essen- tial tools for monitoring and analyzing plant com- munities which are cornerstone of many ecological studies. Plant density is a significant attribute for interpretation of traits and for monitoring occurred changes in plant communities. Knowledge in plant density is vital for interpretation of plant reactions to ecological factors, measuring plant canopy cov- er, and estimating production and biomass of rangelands (Islam Khan et al. 2016). Plant density, the number of individuals in a given unit of area, is one of the most useful plant population characteristics because individuals are easily identified (Bonham 2013). Several methods are developed for Environ Monit Assess (2020) 192:343 https://doi.org/10.1007/s10661-020-08329-8 H. Jamali : E. Ghehsareh Ardestani (*) : A. Ebrahimi : F. Pordel Department of Rangeland and Watershed Management, Faculty of Natural Resources and Earth Sciences, Shahrekord University, Shahrekord 8818634141, Iran e-mail: elham.ghehsareh@nres.sku.ac.ir E. Ghehsareh Ardestani Central Laboratory, Shahrekord University, Shahrekord 8818634141, Iran