Forage Species Identity Shapes Soil Biota in a Temperate Agroecosystem

Restoration of soil multifunctional indicators requires more than thirty years in degraded shrubland of a semi-arid mountainous ecosystem

Vegetation degradation in natural environments leads to considerable fluctuations in soil function indicators, particularly in the sensitive and delicate habitats of semi-arid regions. In this study, the dynamic of both litter and soil properties was examined in northern Iran, in sites with Crataegus melanocarpa and Berberis integerrima dominance. The chosen sites have been degraded in 1993 due to exploitation for fuel production. Litter and soil (0-10, 10-20 and 20-30 cm depths) samples were collected in sites that have been degraded [i.e., 10-years post-degradation (2003), 20-years post-degradation (2013), and 30-years post-degradation (2023)]. A site not to exposed to degradation (year 2023) was also included as a control. In total, 48 litter samples (4 study sites × 12 samples) and 144 soil samples (4 study sites × 3 depths × 12 samples) were collected. Our findings showed a significant reduction of approximately 60-70% in the chemical characteristics of the litter, such as phosphorus (P) and magnesium (Mg) after 10-years post-degradation (2003) compared to the control site. Soil fertility indicators were also reduced 2-6 times as a result of habitat degradation. Aligned with this, the biota population in the 10-year post-degradation site showed a decrease of 70-90% with respect to the control. Moreover, the densities of fungi and bacteria decreased by approximately 30%-70% and 45-80% respectively compared to the 30-year post-degraded site. The peak activation of soil enzymes including urease, acid phosphatase, arylsulfatase, and invertase was found in the site that was not subjected to degradation, being 3.5, 5.8, 6.7 and 6.7- times higher in comparison to the 10-year post-degradation site. Overall, the results showed that in the non-degraded ecosystems, the input of plant-based organic matter was accompanied by an increase in soil fertility, organism population and soil function. This pinpoints the importance of protecting plant species in these areas, while in degraded areas planting native species adapted to the region's climate and fertilization could significantly contribute to restoring these areas.

The effect of shrublands degradation intensity on soil organic matter-associated properties in a semi-arid ecosystem

Vegetation degradation can have significant effects on organic matter fractions as well as various soil characteristics. All these can lead to the changes in soil microbial communities, which are main drivers of nutrient cycles. This is especially important for mountainous ecosystems that are very sensitive and fragile habitats due to their climatic conditions, but less attention has been paid to them. Thus, Mirkola mountainous region (northern Iran) with semi-arid climate and vegetation being dominated by Crataegus and Berberis shrubs were investigated in this study. Sites with different intensities of vegetation degradation [light (60-70 % coverage), moderate (30-40 % coverage) and heavy (0-10 % coverage)] and also non-degraded control sites (90-100 % coverage) were selected. In order to avoid pseudoreplication, three plots, each with an area of 1 ha (100 m × 100 m), were used for each of the four studied habitats. Soil (in three soil depths at 0-10 cm, 10-20 cm and 20-30 cm) samples were collected from the corners and also the center (n = 5) of the plots using iron frames (30 × 30 cm). A total of 180 soil samples (4 habitats × 15 sample × 3 depths) were transferred to the laboratory. Labile and non-labile contents of soil organic matter (SOM) (C and N in soil particles and aggregates, C and N stocks, particulate and dissolved organic matter, hot-water extractable carbohydrate, C and N mineralization) were measured in each of these sites. Results showed that vegetation degradation might result in both labile and non-labile SOM losses. SOM and its associated properties were highest in the non-degraded sites, whereas, lower values were common under degraded areas. Based on the obtained data, vegetation cover can enhance the amount of organic matter entering the soil (especially in the surface layers) and formation of fertile islands in ecosystems. Accordingly, vegetation protection is emphasized to maintain stability and provide ecosystem services in mountainous semi-arid regions.

Vegetation degradation threatens soil health in a mountainous semi-arid region

Soil biological properties are good indicators for the evaluation of soil quality, introduced as key indicators in soil health, which is in line with the nutrient cycles in terrestrial ecosystems. To the best of the authors' knowledge, responses of belowground biota to habitat degradation have received little attention. The present study aimed to study the effect of different intensities of vegetation degradation [heavy (0-10% coverage), moderate (30-40% coverage) and light (60-70% coverage)] and non-degraded sites (as control; 90-100% coverage) in lands covered by Crataegus and Berberis shrubs on soil fauna, microbiota and microbial activities in the north of Iran. From each of these sites, 45 soil (30 × 30 cm area) samples were taken from 0 to 10 cm, 10-20 cm and 20-30 cm depths and 180 samples were transferred to the laboratory. According to principal component analysis, the studied habitats can be distinguished based on soil health and functional characteristics. In this regard, due to the more fertile soil in ecosystems without degradation, highest soil biological activities belonged to these areas. Following the increase in the intensity of degradation, the population of soil organisms and microbial activities are suppressed due to reduction of organic matter inputs, unsuitable soil microclimate, increase in soil erosion and finally depletion of soil nutrients. The results of this study indicate the dependence of soil quality on aboveground vegetation cover, especially in the topsoil, so the vegetation degradation can cause severe damages to soil health in semi-arid regions.