Seasonal dynamics in earthworm density, casting activity and soil nutrient cycling under Bermuda grass (Cynodon dactylon) in semiarid tropics, India

Litter and soil properties under woody and non-woody vegetation types: Implication for ecosystem management in a mountainous semi-arid landscape

There are contrasting reports about whether and how vegetation types influence litter and soil properties. Accurate and comprehensive assessment of the complex relationship between vegetation types, litter and soil characteristics in semi-arid mountain landscapes is almost unknown. Thus, the purpose of this research was to study the effects of (1) Carpinus orientalis Miller., (2) Crataegus melanocarpa M.B., (3) Rhamnus pallasii Fisch. and C.A.Mey, (4) Agropyron longiaristatum Boiss, (5) Bromus tomentolus Bioss. and (6) Hordeum vulgare L. on litter properties and soil physical, chemical, biochemical and biological features in northern Iran. A sampling of the organic layer (litter) and mineral soil (30 × 30 cm) from a depth of 0-10 cm was done for all characteristics in the summer season and for soil microclimate and biological characteristics in the summer and fall seasons. A total of 90 litter samples, 90 soil samples in summer and 90 soil samples in fall (6 vegetation types × 2 seasons × 15 samples) were taken from the area and transferred to the laboratory. Results showed that the Carpinus improved litter properties, soil organic matter contents, total N and available nutrients (P, K, Ca and Mg) and enzyme activities (urease, acid phosphatase, arylsulfatase and invertase). In addition, the population of earthworm groups (epigeic, anecic, and endogeic), acarina, collembola, nematodes, protozoa (especially in the fall season) and bacteria and fungi (especially in the summer season) under Carpinus significantly increased. Data analysis demonstrated higher soil fertility and biological activities in the woody vegetation, which can be assigned to the higher litter input and nutrients. Overall, the findings of this study showed that woody vegetation, especially Carpinus, can improve soil properties at high altitudes of mountainous, semi-arid sites that are often considered as especially fragile and sensitive ecosystems.

Soil function indicators are influenced by land use of different ages: A case study in a semi-arid region

Soil function refers to all the roles and services that the soil performs, and can be assessed by measuring physical, chemical and biological properties. In any case, studies on the state of fertility and biological activities are now emphasized as indicators of soil functions. Degradation of rangelands and their conversion to agricultural land is one of the most common land use changes in different parts of the world, with significant impacts on soil functions. Not much is known about the effects of land use change (especially rangeland to orchards of different ages) on soil function indicators in semi-arid areas. In the current study, the following five types of land covers were considered in a semi-arid region of northern Iran: (1) enclosured rangeland, (2) 10-year-old apple orchard, (3) 25-year-old apple orchard, (4) 10-year-old walnut orchard, and (5) 25-year-old walnut orchard. Results showed that the apple orchards (25-year-old) had a more fertile soil and a higher biological activity than the other land uses studied. Based on heat plots of soil properties under different land uses, the apple orchards (25-year-old) formed hot spots of soil functional indicators in the study area, followed by the walnut orchard (25-year-old) > enclosured rangeland > apple orchard (10-year-old) > walnut orchard (10-year-old). Although the conversion of natural lands (i.e., rangelands) to anthropogenic ones (i.e., orchards) is generally associated with negative feedbacks, tree species can be used (by creating forested rangeland or a combination of rangeland-agriculture) in areas with low soil function to improve soil conditions (in the long term).

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.

The effect of shrubland and grassland vegetation types on soil fauna and flora activities in a mountainous semi-arid landscape of Iran

The effect of vegetation types at mountainous sites on the relationships between soil biota and environmental variables applicable for the evaluation of soil quality and functions are barely studied and remain almost unknown. With the aim of studying the effect of shrubland and grassland plant coverings on soil fauna and flora activities, a mountainous semi-arid site in northern Iran (Diakooh) was selected for this research. Six vegetation types were selected with dominance in shrub and grassland coverage, i.e., (1) Crataegus microphylla CK. Koch., (2) Berberis integerrima Bunge, (3) Ribes uva-crispa L., (4) Prunus spinosa L., and with dominance in rangeland cover, i.e., (5) dominant Lecokia cretica (Lam.) DC., Orchis mascula L., Cardamine bulbifera (L.) Crantz, and (6) Fragaria vesca L. A total of 15 soil samples (30 × 30 × 10 cm) from each vegetation type were transferred to the laboratory. In addition, seasonal measurements (i.e. summer and autumn) were considered to achieve the temporal patterns of soil fauna and flora activities. Higher populations of soil earthworms (especially epigeic groups), acarina, collembola, nematode, and protozoa were found in the Crataegus site compared to other vegetation types with higher activities in the autumn season. Shrublands, especially with Crataegus cover, had increased activities of soil bacteria and fungi with higher abundances in the summer. Soils with higher fertility indicators and increased biota activities were attributed to the Crataegus and Berberis vegetation types by PCA. Overall, the findings of this study showed that shrubs can improve soil quality at high altitudes of mountainous, semi-arid sites that are often considered as especially fragile and sensitive ecosystems.