# Short-Term Effects of Pine Plantations on Vegetation and Soil in Northern Mongolia
## 4 Discussion
Optimal spacing at planting and during subsequent tending must balance several sometimes-competing factors. Stock ability, a concept of optimal growing space [57], depends upon species traits and site quality. Additionally, optimal planting density must consider competing vegetation to ensure that site resources are captured by the target planted species. Managing stand density at lower levels has been proposed as an adaptation to climate change-driven increases in aridity, which is an important consideration in Mongolia [48; 58]. Greater diversity and unique composition in the treatments compared to the undisturbed control suggested a link between resource heterogeneity and biodiversity [59] or legacy effects associated with different treatment changes in the understory plant community, which was partly supported by our study. The Shannon index was highly variable among treatments (Table 7) and generally indicated low species richness, which did not exceed 0.8156 in the BBS. Open conditions after the removal of previous stands provided an opportunity for non-forest understory species to establish. Changes in species composition and a stable existence of invasive plant species from different ecological groups tend to persist during the initial stage of forest plantation establishment [60]. The main living forms were mesophytes and xerophytes, which are quite fit for relatively barren soils and dry climate. Furthermore, the abundant herbaceous species with high plant coverage from steppe and forest meadow ecological groups were found not only in the STP and NFM, but also in other stands. This high proportion of herbaceous species adapted to the steppe and forest meadow ecosystem within planted forests, and their stable existence in the plantations, indicated a potential risk of replacing the Scots pine ecosystem with steppe ecosystems. Tree crowns produce shade and more appropriate microclimatic conditions for the growth of forest and forest meadow vegetation as they get bigger over time. Thus, comparisons of understory composition and biodiversity in plantations with other types of forests heavily depend on the plantation age. Forest management significantly affects forest soils, particular soil organic matter, a key component of sustainability [61; 62]. Soil is a crucial component in ecosystems, serving as a major storage and source of plant-available nutrients [8]. Change in the soil properties in our study mainly occurred in the top soil layers (0 to 20 cm). Significant increases in the soil bulk density (1.25 \(\pm\) 0.11 to 1.46 \(\pm\) 0.06 g cm\({}^{-3}\)), organic carbon (8.85 \(\pm\) 2.55 to 15.45 \(\pm\) 4.32 g kg\({}^{-1}\)), soil organic carbon stock (8.87 \(\pm\) 1.34 to 13.39 \(\pm\) 2.98 mg ha\({}^{-1}\)), available phosphorus (21.17 \(\pm\) 5.02 to 26.42 \(\pm\) 5.38 mg kg\({}^{-1}\)), and soil moisture (8.6 \(\pm\) 1.0 to 12.0 \(\pm\) 2.5%) were observed in plantations compared to NRS and NFM. The results of the assessments showed a slight increase in the soil temperature throughout the soil profile and a sharp decrease in the moisture content of the upper soil layer in the 2003 plantations. Restoration objectives include maintaining the pH levels between 7.5 and 8.2, enhancing soil organic matter to 30%-35%, sustaining electrical conductivity around 0.7-0.8, and demonstrating potential for improvement in all parameters through biological diversity strategies. Additional plots may gain from specific soil enrichment. Furthermore, we propose that a larger sample size be utilized to enhance the statistical significance, alongside temporal monitoring to evaluate seasonal fluctuations, the examination of additional environmental factors, and a comprehensive analysis of species composition.