Zagros forests in western Iran have been impacted by severe fuelwood removal, traditional agricultural systems, non-timber products removal, and livestock grazing.These conditions have led to the forest area diminishing from 10 to 6 million hectares over the last six decades. This study was conducted to understand the consequences of livestock exclusion on understory plant diversity, forest tree regeneration, and soil physicochemical properties in semiarid forests. We selected four neighbouring areas, including those subject to livestock exclusion and to grazing, in the Zagros oak forests of Iran. Ten randomized sampling plots (400 m2) were established, and all plant species were recorded in each area. A soil physicochemical analysis indicated a significant improvement in soil nitrogen, phosphorous, potassium, and organic matter in the livestock exclusion area compared to the grazing area. The Shannon-Wiener diversity and species richness was also significantly higher in the livestock exclusion areas compared to the grazed. Grazing tolerant species like Poa bulbosa were abundant in grazing areas, while palatable and nitrogen-fixing species disappeared. The tree regeneration rate was significantly higher in the exclusion areas compared to the grazing areas, and its values were 0.079 and 0.006 per square metre in the exclusion and grazing areas, respectively. The results of the present study provided evidence that exclusion had a significant effect on improving soil chemical properties, understory plant diversity index, and sapling regeneration. However, the regeneration rates were still low, and therefore, livestock exclusion alone may not be enough to promote forest restoration. Therefore, to better understand plant diversity and tree regeneration in the Zagros forests, livestock exclusion and other factors such as soil seed bank and socio-economic status of people should be considered.

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The major objective of this study was to evaluate the effects of sand mining disturbances on the diversity of arbuscular mycorrhizal fungi (AMF). In addition, the proportional changes in the diversity of AMF to the distances from riverbanks were assessed. For this purpose, the riparian forest of the Maroon River, Iran was divided into three locations with a 200-meter wide zone in between. Thus, the locations studied were named Distance I (riverbank), Distance II (intermediate), and Distance III (farthest from riverbank). In each of these distances, 10 Tamarix arceuthoides and Populus euphratica of each species were randomly selected. At the same time, soil and root samples were collected from the rhizosphere of the tree species studied. Results indicated that totally 13 AMF species were observed in T. arceuthoides and 19 AMF species were recorded in P. euphratica rhizosphere belonging to 6 genera and 6 families. In these AMF species, Glomus segmentatum, G. geosporum, G. rubiforme, G. nanolumen, G. spinuliferum, Claroideoglomus drummondii, Gigaspora gigantea and Acaulospora paulinae appeared only in P. euphratica rhizosphere, while G. multiforum and Claroideoglomus claroideum were observed only in T. arceuthoides rhizosphere. Moreover, Distance II had the least AMF species both in T. arceuthoides and in P. euphratica rhizospheres, and also the least spore density and root colonization rate. Our results are important in that they provide a list of resistant AMF species that could be used in the conservation of biodiversity.

Basiri R., Moradi M., Kiani B., Maasumi Babaarabi M. (2018): Evaluation of distance methods for estimating population density in Populus euphratica Olivier natural stands (case study: Maroon riparian forests, Iran). J. For. Sci., 64: 230-244.The aim of this study was to determine the performance of distance methods in terms of accuracy, precision, bias, consumed time and sampling efficiency in the Maroon riparian forests, Iran. 40 estimators were used to evaluate the density of Populus euphratica Olivier trees in pure and mixed stands. Fifty quadrates (30 × 30 m) were established in each stand. To evaluate the accuracy, precision, bias, consumed time and efficiency of sampling techniques, relative root mean square error -RRMSE (%), coefficient of variation -CV (%), relative bias -RBIAS (%), t × RBIAS 2 , t × E 2 , where t is study time and E (%) is sampling error at a confidence level of 95%, and efficiency ratio between method j and k (Ef jk ) were used. A compound of three basic distance estimators sampling method and n-tree were the best in both stands according to all criteria for density estimation. Moreover, variable area transect by Parker (g = 3) and quadrat method were the best methods for density estimation only in pure stand, while the angle order-point-centred quarter method was superior in mixed stand. Regarding to the results, we recommend the use of compound of three basic distances (BDAV3) and basic distance-nearest neighbour (BDNN2) for density estimation of P. euphratica stands in riparian forests.

A study was conducted to investigate the effects of skid trail slope and traffic levels on soil disturbances at two soil depths (0−10 and 10−20 cm). The treatments were set at four traffic levels (2, 7, 12 and 20), two slope classes (<20% and >20%) and two soil depths (0−10 and 10−20 cm). Results show that skidder traffic, longitudinal slope and soil depth have significant effect on soil bulk density in skid trail. Comparison of average soil bulk density in different traffic levels shows that there are significant differences in average bulk density between different traffic levels and control (p<0.05). The average bulk densities in different slopes and soil depths are significantly increased with increase in traffic levels, maximized at 12 passes (p<0.05), but there are no significant differences between 12 and 20 passes. The interaction effects between traffic and soil depth are significant (F0.05,3=0.109, p<0.001). For all traffic treatments, there are significant differences in soil moisture content between the two slope classes and the two depths (p<0.001). However, the interaction effects between traffic levels and slope classes are not significant (p >0.05), although skidder traffic and slope affected soil moisture content.