Introduction: To preserve and restore natural habitats, before any work, sufficient information should be available on the effects of constituent plant species on environmental factors and their habitat needs. Identifying the constituent elements of the forest, is the most principled way to optimally manage its, because nutrients and soil microorganisms activities, especially in arid and semi-arid ecosystems, accumulate under the canopy, and these effects are also related to the size and extent of the canopy and cause changes in the various soil characteristics. So far, no research has been conducted on the various soil characteristics under and outside the canopy of the native and valuable species of Ziziphus spina-christi (L.) Desf. and Ziziphus nummularia (Burm.f.) Wight & Arn., as well as determining their soil quality index in these habitats. The purpose of the present study is to investigate the effect of their canopy cover on various soil properties so that, by better understanding and being aware of their impact on the soil and the causes of changes in their habitat, a general perspective can be provided to managers in the fields of natural resources.
Materials and Methods: 15 soil samples were randomly collected from the surface soil under the canopy and outside the canopy (control) of natural masses Z. spina-christi in Dashti and Z. nummularia in Dashtestan in Bushehr province in an eastward direction from a depth of 0 to 15 cm. To obtain a composite soil sample from under and outside the canopy of Z. spina-christi and Z. nummularia trees, soil samples taken from under and outside the canopy of all three trees (randomly) were thoroughly mixed together and converted into a composite sample, resulting in five composite soil samples from under the canopy and five composite soil samples from outside the canopy of Z. spina-christi and Z. nummularia trees. Using standard methods, the physical, chemical and biological properties of the soil were measured in the collected samples. Then, the normality of the some variables was confirmed by the Shapiro-Wilk test and the positions under and outside the canopy of the normal data of the two species, Z. spina-christi and Z. nummularia, were compared with the Independent T-test and the non-normal data with the non-parametric Mann-Whitney U test. Soil quality index was obtained based on three steps: determining the minimum data, giving a score to each of the data used, and merging and averaging the scores, and was analyzed as above.
Results: Under the canopy of the Z. spina-christi, Mn and Zn respectively, 202.8±9.3 and 49.2±1.46 (mg/kg), basal microbial 2.08±0.09 (mg CO2.gˉ¹ dm.24 hˉ¹) and Substrate-induced respiration 59.02±6.35 (mg CO2.100 gˉ¹ dm.hˉ¹), under the canopy of the Z. nummularia, saturated moisture 41.2±0.71 (%), Oc, 26.2±0.12 (%), N, 0.22±0.012 (%), and microbial biomass carbon 2.98±0.36 (mg biomass-C.100 gˉ¹dm), outside the canopy of Z. nummularia, Na, 4670±59.54 (mg/kg), were significantly more. Under the canopy of both species, pH, 7.38±0.04 and 7.64±0.06, P, 959.6±21.24 and 783±8.3 (mg/kg), nitrification potential 376.87±17.64 and 633.23±59.93 (µg N.gˉ¹dm.5hˉ¹), and SQI 8.74±0.04 and 8.8±0.15, respectively, were significantly more.
Conclusion: The exchange of nutrients, biological activities and soil quality index were higher under the canopy of Z. spina-christi and Z. nummularia trees. Therefore, the type of tree species and canopy cover can have different effects on different soil properties, and improve the their properties, it is necessary to maintain the vegetation cover of the area and, if necessary, restore it with native species. With continuous soil monitoring, at different time intervals, it is predicted that in the future it will be possible to more accurately assess the changes in the soil of their habitats and collect valuable information.