The Effect of Grazing Intensity on Properties of Mountain Steppe Pasture Vegetation and Soils

doi:10.21203/rs.3.rs-4942823/v1

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The Effect of Grazing Intensity on Properties of Mountain Steppe Pasture Vegetation and Soils

https://doi.org/10.21203/rs.3.rs-4942823/v1

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Purpose

Delivering sustainable management of mountain pasturelands with steppe vegetation is a concern to many nations including Armenia. Yet, to date, no unambiguous answer has been generated about the limiting impact domestic animal grazing has on the ecological status of such pastures. This research was designed to study the effect of different grazing management strategies (free grazing, reduced grazing, no grazing) on pastureland productivity including below-ground biomass and biodiversity, nutrient content of plants and soils.

Methods

ANOVA (Тukey’s test), Pearson correlation coefficient and the Redundancy analysis (RDA) was employed.

Results

The studies have indicated that livestock grazing has a strong impact upon biomass and diversity of plant groups., and the nutritive value of forages. Both below-ground biomass and root-to-shoot ratio are less dependen on the management strategy and increase the reduced grazing and free grazing sites. The effect of grazing on the nutrient contents of soils and vegetation is less pronounced; as a result of trampling the bulk density of soil and the contents of nitrogen, phosphorus, and potassium in above-ground and below-ground biomass increase.

Conclusions

The conducted studies and outcomes of grazing-imitation models allows us to conclude that regulation of grazing intensity and grazing regime in the ecosystems of mountain pasturelands are an effective approach to maintain and increase the capacity of natural fodder resources. The research results have already been used to develop measures to preserve the studied ecosystems.

Earth and environmental sciences/Ecology

Earth and environmental sciences/Environmental sciences

Free grazing

reduced grazing

no grazing

above-ground biomass

below-ground biomass

soils

Pasture degradation resulting from the effect of unfavorable soil-climatic and anthropogenic factors may lead to grave socio-economic and ecological aftermath (Lance et al. 2023). The published sources give controversial data on the effect of livestock grazing on pasture productivity and biodiversity. On the one hand, according to data from 47 separate studies, animal grazing on mountain meadows causes negative consequences for each resource territory (Vernon et al. 2022). A lack of measures for regulating grazing in conditions of a forecastable climate change decreases the productivity of plants and deteriorates the quality of fodder (Maestre et al. 2022). Overgrazing results in soil compaction (an increase in the bulk density of soil) and acceleration of erosive processes (Köbel et al. 2021). Due to decomposition and leaching, a change occurs in the structure of a pastureland plant community, the contents of soil carbon and soil nitrogen as well as C:N correlation (Dai et al. 2021; Vermeire et al. 2023, Abdalla et al. 2023). Intense grazing decreases the contents of soil biogenic elements (sodium, iron, zinc, and manganese) (Parissi et al. 2015). Intensification of grazing towards a water source in savanna ecosystems hampers the production of dry matter by herbaceous plants and disturbs the sustainability of pastures (Gebremedhn et al. 2023; Melak et al. 2019). At the same time, the negative effect of grazing on biomass and plant diversity in arid ecosystems with low-yielding capacity is more pronounced (Bilgili 2023; Herrero-Jáuregui et al. 2018). The research results for 98 arid sites of pastures located across six continents show lower parameters of carbon accumulation by soil in the case of free grazing (Maestre et al. 2022).

According to other investigations, neither plant biomass nor the contents of plant growth-regulating soil nutrients statistically differ between pastures exposed to intense grazing and those enjoying regulated forms of management. Grazing supports higher forage cover and the abundance of perennials and also favors the acceleration of flowering and growth rate and viability of forage species. (Sanderman et al. 2015). Cattle excreta speed up the mineralization of plant litter and serve as sources of total nitrogen, phosphorus, and organic carbon in soils (Yang et al. 2023). Grazing has a positive effect on the sustenance of plant litter (Kyriazopoulos et al. 2018), does not influence the concentrations of magnesium, sodium, potassium, and microelements, and increases the contents of soil nitrogen, sodium, copper, and iron (Parissi et al. 2015). The absence of grazing increases the organic carbon stocks in soils in a short-term prospect but decreases it in long-term prospects (Reinhart et al. 2021). Some of the authors suggest that though soil compaction is commonly regarded as an indicator of deterioration of its condition, insignificant compaction does notably decrease the mineralization of organic matter and finally augments its stocks (Reinhart et al. 2021; Yuting Lan et al. 2023). It is moderate grazing that maintains the maximal biomass of plant and nitrogen, phosphorus, and organic matter stocks at the expense of stimulation of biologically and geochemically determined turnover of biogenic elements between plants and soil (Deng et al. 2017; Song et al. 2023).

Agriculture is one of the major branches of Armenia’s economy, among the most significant issues being the growth of volumes of animal-based food production (Armstat, 2023). For this branch to develop, an increase in forage productivity is required; over 50% of meat, approximately 70% of milk, and almost 100% of wool the Republic produces annually, rest on the usage of forage crops. Low productivity of the livestock sector is explained precisely by the insufficiency of feed supply, which, in turn, may result from the poor condition of pastures (Armstat, 2023). The deterioration of pasture conditions is precisely associated with livestock grazing. Relative to Armenia’s mountain pastures with meadow vegetation, this aspect has been scarcely studied and therefore not always justified; there is no comprehensive answer to the question about the limiting role of grazing in pasture ecosystems. So, this paper considers research aimed at studying the effect of different grazing management strategies on dry mountain steppe ecosystems in the example of pastures of rural communities of Artashavan and Avan. The underlying 0-hypothesis of our studies is that livestock grazing does not influence the yielding capacity of agricultural crops. Issues to be discussed are as follows: (1) How does the grazing intensity impact plant biomass and biodiversity? (2) How does the grazing intensity impact nutrient contents of soils and plants? (3) Whether a decrease in grazing intensity is an effective approach to pasture restoration?

The yielded empiric data on pasture conditions, plant biomass, biodiversity, and the quality of vegetation and soils may be useful for safeguarding the sustainability of semi-arid pasture ecosystems to increase the volumes of natural forage resources, both local and global.

Study sites

The study objects are pastures of Artashavan and Avan rural communities located on south-eastern slope of Mt. Aragats (N 40°31′23″, E 44°11′43″; 4095 m a. s. l.) (Fig. 1).

This region with rugged topography is dominated by effusive rocks: basalts, basaltic andesites, tuffs, and lava tuffs forming on the surface multiple hills and hillocks alternating with small plateaus. In the rural communities, mountain black soils (Artashavan) and typical chestnut soils (Avan) are prevalent. The climate is moderate, with warm prolonged summer and cold winter. Air temperature in winter varies from + 0.5 to-4,30С, in summer from + 15.0 to -27,70С (2017–2023). The vegetation period spans from March through July. The mean annual temperature in the vegetation period varies from 10.3°С – 14.2°С reaching the maximum 23.3°С in July. Mean annual precipitation makes 362mm, 50% of which occurs during the vegetation period (Center of Hydrometeorology and Monitoring). The vegetation on Artashavan sites is represented predominantly by steppe plants involving elements of meadow vegetation; on Avan sites grass and forb-grass steppe vegetation is prevalent, with over 50% of herbs being desirable (tasty) enough. Ephemeral species e.g. Poa Bulbosa L., Colpodium humile (MB) Grisb., prevail in early spring, perennial legumes and forbs – at the beginning of summer. The dominant species are Bromus fibrosus E. Hack, Festuca sulcata E. Hack. Rizh., Hordeum crinitum Desf., Koeleria nitidula Vel., Agropyrum trichophorum Richt., A. cristatum (Schreb) P.B., Trifolium repense L., Onobrychis transcaucasica Grossh., Medicago sativa L., Nepeta Mussini Henke, Xeranthemum squarrosum Boiss. Artemisia austriaca Jack. and so on.

The study object selection was determined by the developed animal farming; historically, the study territory was used by the local populace as communal grasslands. The region accounts for some 2800 head of large horned cattle of the brown Caucasian breed and 6080 of the Balbas semi-rough-wool sheep (Armstat, 2023). Natural grasslands occupy an area of some 4600ha and are mainly of a mixed (dry steppe and meadow steppe) and true steppe type. For study sites to select, a reconnaissance survey was conducted with the participation of representatives of rural communities and managers having sufficient knowledge of historical and present-day grazing all across the study region. As a result, 3 categories of pastures were selected depending on grazing management systems: free grazing (FG), reduced grazing (RG), and no grazing (NG). The FG sites are the community’s property and are used both by the community and neighboring communities for the entire livestock population to graze from early spring to late autumn (Forage utilization percentage = > 50%) as NG sites serve fenced and grazing-protected private pastures attached to the village which are utilized as hayfields (FUP = 0%). The RG sites represent plots of land where grazing spans 3–4 months between July and October. Some general characteristics of these pasture sites are given in Table 1.

Table 1

General information regarding sites with three grazing management systems NG, RG and FG
Grazing	Coordinates	Altitude, m a.s.l	FUP	Area, ha	Altitude, degree.	Soils
Grazing	Coordinates	Altitude, m a.s.l	FUP	Area, ha	Altitude, degree.	Type	Soil horizon, m
Rural community of Artashavan
NG	N 40,413997 E 44,386365	1766	0	0,6	0	Mountain, chernozem-like soils of moderately wet steppes, not eroded, moderately stony	26
RG	N 40,413209 E 44,363138	1827	50	0,8	90		13
FG	N 40,414418 E 44,363601	1824	67	0,8	90		8.5
Rural community of Avan
NG	N 40,327009 E 44,151444	1579	0	0․35	180	Mountain chestnut soils of dry steppes, weakly eroded, moderately stony	25
RG	N 40,327422 E 44,151314	1601	42	0․46	180		30
FG	N 40,321109 E 44,155529	1501	74	0․4	135		13

Plant and soil sampling

The studies spanned three years (2022–2024). 288 samples of above-ground (AGB), 180 samples of below-ground biomass (BGB), and 108 soil samples were collected. On the selected FG, RG, and NG sites within the bounds of both communities, 2 permanent transects with a length of 40 m were laid per site. In May-June during the maximal productivity period, from the soil surface along each transect, every 5 m the above-ground biomass was cut off. The number of quadrants (1 m×1 m) from each transect made 8, i.e. 16 per site. Before the above-ground biomass cut-off, measurements were done of the vegetation height, then the biomass was partitioned into three basic functional groups: grasses, legumes, and forbs. The plants were dried in a drying oven at 65°С and then weighed. BGB was sampled from each plot by 5 quadrates (in all, 10), then washed out by running water. The isolated roots were dried and weighed. As the thickness of the soil horizon across the studied sites does not exceed 40 cm (Tabl.1), so through a vertical profile only one sample was collected (ISO 10381). On test sites, from each transect (40 m) 3 soil samples were collected with an area of 400 cm2 (0.20 m х 0.20 m). From а test site, 6 soil samples were collected which were then purged of plant residues, roots, stones, and other inclusions. The sampled soils were dried at 60–70°С for 48 hours, then ground, crushed, sieved through a 1mm diameter sieve (ISO 11464), averaged for mean samples preparing.

A total of 18 samples of soils, aboveground biomass and roots were analyzed. Samples collected from different test sites were analyzed separately. Key variables include the (1) characteristics of vegetation: height (H), above-ground biomass (AGB), including biomass of grasses (G), legumes (L), forbs (F), below-ground biomass (BGB), root-to-shoot ratio (R-S); (2) physicochemical properties of soil: humidity, bulk density and structure, organic carbon (OC), pH; (3) nutrients of plant (AGB, BGB) and soil: total nitrogen (N), soluble phosphorus (P) and potassium (K). For organic matter mineralization, the samples were boiled in sulfuric acid with a subsequent addition of hydrogen peroxide at a temperature not exceeding 4000C. The contents of soil nitrogen were determined by a modified Kjeldahl method (ISO 11261); phosphorus - by a modified spectrophotometric method of Truog (Truog, Meyer 1929; ISO 11263); potassium – by flame emission spectrometry with a pre-ashing of a sample to be analyzed (ISO 7485); organic carbon by Walkley-Black colorimetric method (FAO, 2019). The accuracy control (trueness and precision) of the measurement methods was done in compliance with ISO 5725:2023. To assure the accuracy of data generated while making measurements, C, N, P, and K-certified standard soils were used.

Data analysis

The data obtained are represented as a mean value standard error (SE). To reveal the difference between mean values, the one-way ANOVA (Analysis of Variance) was employed. If the impact of whatever factor in the plant community or soil was significant, the post-hoc Tukey’s test (HSD, Honestly Significant Difference) was used. The differences between mean values were considered significant at p < 0.05. This research employed the Pearson correlation coefficient and the Redundancy analysis (RDA) (Legendre et al. 2012). The entire statistical analysis was conducted using the SPSS Statistics v.17 and R.4.3.1 software.

The effects of grazing management on plant characteristics

Investigations into FG, RG, and NG sites across two rural communities of Artashavan and Avan show a significant effect of grazing on the study plant parameters. Significant differences are established between mean values of height, above-ground biomass, below-ground biomass, grasses, legumes, forbs, and root-to-shoot (Table 2, Fig. 2).

Table 2

The effects of grazing management strategies on plant biomass and community parameters (means + SE)
Sites/ management	Artashavan			Avan
Sites/ management	NG	RG	FG	NG	RG	FG
H, cm	33.93 ± 0.77a	22.90 ± 0.66b	11.76 ± 0.40c	38.15 ± 0.71a	24.38 ± 0.84b	5.53 ± 0.35c
AGB, g m^− 2	266.0 ± 9.2a	133.5 ± 4.3b	86.7 ± 2.8c	250.1 ± 12.1a	105.8 ± 5.0b	63.9 ± 3.1c
G, g m^− 2	106.5 ± 7.87a	43.96 ± 3.70b	19.19 ± 1.73c	108.60 ± 10.70a	41.41 ± 4.24b	10.10 ± 1.11c
L,g m^− 2	85.17 ± 8.59a	26.51 ± 2.49b	4.14 ± 0.50c	39.21 ± 5.70a	6.73 ± 0.96b	2.77 ± 0.62b
F, g m^− 2	74.26 ± 5.39a	62.99 ± 4.67a	63.40 ± 2.81a	102.24 ± 7.82a	57.61 ± 4.36b	51.02 ± 2.97b
BGB, g m^− 2	1857.0 ± 67.5a	2100.0 ± 62.87a	1145.1 ± 35.4b	1476.0 ± 49.3a	1512.0 ± 27.5a	1259.0 ± 49.4b
R:S	6.98 ± 0.36	15.73 ± 1.02	13.20 ± 0.68	5.90 ± 0.09	14.29 ± 0.021	19.70 ± 1.69
Different lowercase letters indicate significant differences in means among different grazing management (ANOVA, Tukey's test, significance level α < 0.05).

For all parameters, the difference between the three sites with different grazing is maximally significant (p < 0.001), with the exception of grass biomass in the RG and FG Artashavan sites (p = 0.128; F = 0.09). The height of vegetation cover is maximal during the peak of the vegetative period on NG sites Avan (56.1cm) and Artashavan (49.5cm), which is 1.5 times higher vs. RG management sites in both communities and respectively 6.9 and 2.9 times higher as compared with FG sites in both rural communities. Almost the same regularity is established for AGB: the biomass on the NG site in Avan is in excess of 2.4 and 3.9 times as compared to RG and FG sites. For Artashavan sites these values make 2.0 and 3.1, respectively. Of the studied plant groups, the strongest impact of grazing is exposed grasses and legumes. On average, the biomass of legumes, grasses, and forbs on FG versus NG sites Artashavan is lower 18.0; 7.3; and 1.5 times, respectively. A root-to-shoot is the highest on FG and RG sites. At the same time, the size of AGB, BGB, and root-to-shoot on all sites in Artashavan are always reliably higher as compared to Avan (6.98 and 5.90, respectively).

Redundancy analysis (RA) is used to test the response of plant community parameters and soil nutrient properties to grazing management strategies. Figure 3 clearly shows the relationships between soil nutrient variables, plant biomass and species, and different grazing strategies. The magnitude of the vectors in the ordinate space indicates the strength of the contribution of each variable, angles in between – and the strength of relations.

The parameters: height, AGB, grasses, legumes, forbs, and BGB are linearly interrelated, positively correlated with the NG management strategies, and negatively - with a root system. These variables explain the variance F1 = 75.83%. Soil nitrogen, phosphorus, and potassium strongly correlate with each other and RG plots and less strongly - with biomass and plant species. Organic carbon content correlates with FG, while no relationship with plant variables has been established for hydrogen. Soil variables explain F2 = 22.33% of the variance. Overall, factors F1 and F2 explain 98.17% of the variance (F = 6.77, p = 0.086) and are not linearly related (α > 0.05).

Effect of grazing management on soil and plants nutrient

The results of a three-year long research, parameters of soil, AGB and BGB are given in Table 3.

Table 3

The effect of grazing management on soil (depth: 0–20 cm), AGB and BGB quality parameters (mean ± SE)
Sites/ management	Artashavan			Avan
Sites/ management	NG	RG	FG	NG	RG	FG
Soil parameters
N, %	0.32 ± 0.03a	0.34 ± 0.01ab	0.40 ± 0.01b	0.34 ± 0.01a	0.34 ± 0.02a	0.43 ± 0.01b
P, %	0.34 ± 0.01a	0.45 ± 0.02b	0.46 ± 0.03b	0.30 ± 0.01a	0.39 ± 0.02b	0.43 ± 0.01b
K, %	0.35 ± 0.02a	0.38 ± 0.04ab	0.45 ± 0.01b	0.25 ± 0.01a	0.30 ± 0.03a	0.32 ± 0.01a
OC, %	2.36 ± 0.23a	2.48 ± 0.18a	2.91 ± 0.24a	1.64 ± 0.12a	2.38 ± 0.05b	2.52 ± 0.08b
pH	6.71 ± 0.07a	6.73 ± 0.03a	6.75 ± 0.04a	7.43 ± 0.07a	7.33 ± 0.09a	7.38 ± 0.07a
Above-ground biomass parameters
N, %	1.15 ± 0.04a	1.31 ± 0.06a	1.23 ± 0.04a	0.89 ± 0.03a	1.01 ± 0.05b	1.17 ± 0.01c
P, %	0.82 ± 0.01a	0.92 ± 0.01b	0.90 ± 0.02b	1.08 ± 0.02a	1.02 ± 0.02a	1.06 ± 0.02a
K, %	1.18 ± 0.03a	1.16 ± 0.02a	0.97 ± 0.03b	1.12 ± 0.05a	1.28 ± 0.01a	1.28 ± 0.04a
Below-ground biomass parameters
N, %	1.08 ± 0.03ab	1.14 ± 0.03a	1.03 ± 0.02b	0.89 ± 0.01a	1.01 ± 0.02b	1.13 ± 0.03c
P, %	0.88 ± 0.02a	0.88 ± 0.04a	1.09 ± 0.02b	1.01 ± 0.05a	1.02 ± 0.04a	1.13 ± 0.04a
K, %	0.40 ± 0.02a	0.37 ± 0.02ab	0.33 ± 0.01b	0.25 ± 0.01a	0.24 ± 0.01a	0.30 ± 0.01b
Different lowercase letters indicate significant differences in means among different grazing management (ANOVA, Tukey's test, significance level α < 0.05).

The concentration of soil nitrogen on the FG site in Artashavan statistically credibly exceeds that on NG sites by 1.21 times, and in Avan – 1.29 times. For phosphorus, these values make 1.37 and 1.42, respectively. Potassium concentration in FG versus NG soils in Artashavan is excessive at 1.29 times, and organic carbon in Avan − 1.54 times. In other cases, no significant differences are observed between the average values for different grazing areas, with the exception of total nitrogen (p < 0.001, F = 25.5) and organic carbon (p < 0.001, F = 28.3) in Avan, as well as phosphorus in Artashavan (p < 0.01, F = 8.9) and Avan (p < 0.001, F = 18.0) areas. For the rest of the substances, grazing management has had no considerable effect on soil properties; in contrast to plant parameters, the differences between mean values for soils are less significant. For different management strategies, significant differences between mean concentrations of nutrients in AGB are observed for Avan sites by total nitrogen (р<0,001, F = 63.3) and phosphorus (р<0,001, F = 13.0), for Artashavan sites – by potassium (р<0,001, F = 11.5); in BGB – total nitrogen (р<0,001, 32.1) and potassium (р<0,001, F = 13.0) (Avan) as well as phosphorus (р<0,001, F = 21.8) (Artashavan). It is worth noting, however, that no clear regularity regarding changes in concentrations of the studied parameters under different grazing strategies has been established; nitrogen contents in AGB on FG sites exceed those on NG sites 1.10–1.54 times, phosphorus contents in BGB is 1.12–1.23 times excessive. In the rest of cases, the concentrations of nutrients are lower or equal for sites under different grazing loads.

Pearson's correlation coefficient was calculated to identify relationships between soil nutrients and AGB and BGB under different grazing management strategies. At a significance level of α = 0.05, the nutrient content in the soil does not indicate a significant relationship with the content of AGB and BGB. The exception is the positive correlation of potassium content in the soils of the NG and AGB (K = 0.73) and BGB (K = 0.69) plots and the negative - in the FG plot in AGB (K = -0.75). Thus, the nutrient content of AGB does not always depend on the nutrient content of the soil. At the same time, the nutrient contents of AGB and BGB show good correlation; the Pearson correlation coefficient for nitrogen at the NG, RG, and FG sites is 0.64, 0.58, and 0.71, respectively; for phosphorus 0.55, 0.58, and 0.41; for potassium 0.80, -0.45, 0.41.

The relationship between soils, AGB, and BGB properties under different grazing strategies according to redundancy analysis (RDA2) is presented in Fig. 4.

The FG management strategy positively correlates with all studied quality parameters of AGB and BGB with the exception of potassium contents in the case of RG; plant root potassium negatively correlates with its contents in AGB. The parameters of plants make 76.18% dispersion; their contents in ABG and BGB show good correlation and also correlate well with FG and RG management strategies. The relationship between soil nutrients and a management strategy is less distinct. The contents of potassium in soils negatively correlate with those of potassium and nitrogen in plants. Soil variables account for 17.38% dispersion. Wholly, F1, and F2 factors explain 91.67% dispersion (F = 3.482, p-value = 0.002) and are linearly interrelated (α < 0.05).

Domestic livestock grazing is the dominant form of land use in mountain pasturelands with steppe vegetation. Studying the sites exposed to different grazing intensity across two rural communities of Armenia has indicated that a grazing management strategy produces a strong effect on the biomass and diversity of plant species. The difference between sites with different grazing management is maximally significant (р<0,001) with respect to such parameters as height, grasses, legumes, forbs, and AGB. They are linearly interrelated and positively correlate with the NG management strategy. The results obtained compared with published data; overgrazing affects the ecological functions and services of pastures (Vernon et al. 2022, Bilgili et al., 2023, Herrero-Jáuregui et al.2018), whereas both the overall vegetation cover and above-ground biomass significantly decrease as the number of grazing years increase (Lance et al. 2023; Yuting et al. 2023). Of the studied plant groups, grazing mostly impacts grass and legume biomass. Forb biomass is less dependent on a management strategy. This proves that grazing actively impacts the nutritive value of herbs because domestic herbivores in first term remove grasses and legumes as tasty (desirable) highly preferable species. In addition, legumes compare with grasses and forbs have a deeper root system (Apostolos et al. 2022), so grazing causes to poor aeration of legume roots and produces negative effects on these species. The observable reduction of tasty grasses abundance also agrees with data obtained for other semi-arid ecosystems (Hidalgo-Galvez et al. 2023, Sanaei et al. 2021). According to outcomes of a long-term, a 17 year-long field experiment on grazing management (grazing exclusion, continuous grazing, mowing and grazing, and rotational grazing), the above-ground biomass decreases significantly as grazing intensifies (Contosta et al. 2021; Yang, et al. 2023) i.e. intensive grazing throughout the studied mountain steppe region where climatic conditions hamper the development of plants (mostly across Avan sites), leads to a substantial reduction of grasses and legume biomass and finally - to deterioration of forage quality.

BGB is less dependent on a management strategy and increases on RG and FG sites. Constantly intensification of grazing causes the BGB growing due to decreasing the accumulation of biomass in above-ground parts of plants and an increasing in roots. RG sites show the highest values of R:S. Soil nutrients on NG sites to a lesser extent correlate both with plant biomass and AGB and BGB nutrients. Soil nitrogen, phosphorus, and potassium are closely related to RG sites, and organic carbon - to FG sites. The total content of soil nutrients is limited by nutrients processed via plant residues. The content of nitrogen and phosphorus in the above-ground biomass and roots on FG sites depend on concentrations of these elements in soils. In general, AGB and BGB parameters well correlated with each other and with FG and RG management strategies. Soil compaction on the studied sites also agrees with data on the analysis of mechanical properties of soils; bulk density of soils on NG, RG, and FG sites makes 0.95–1.15; 0.98–1.24; and 0.955–1.12 g/m3, respectively. Meanwhile, the FG and RG sections have the highest average values. The resulting data agree with published data; livestock grazing and trampling contribute to soil compaction; this suppresses seed maturation and decelerates AGB accumulation (Dai L et al.. 2023, Contosta et al., 2021, Pulido et al., 2018). In addition, trampling may increase the contents of total nitrogen and organic matter in soils, and livestock excreta – those of phosphorus compounds. According to the results obtained, in the case of FG management strategy the bulk density of soil and nutrient contents in AGB and BGB increase, while the effect of grazing on the contents of soil nutrients is insignificant.

To promote the methods of sustainable grazing management on the studied mountain pasturelands and identify the optimal regime of grazing (intensity and duration), model tests “grazing-imitation” were conducted. They differ from real-time grazing by the absence of cattle trampling-caused soil compaction. At the beginning of a vegetative period, throughout the no-grazing sites of Artashavan and Avan communities were isolated two plots, from which with a fortnight (twice a month) and with monthly intervals, at a height of 5cm the above-ground biomass (in three replications) was cut off, dried and weighed. The test results have indicated that the grazing exclusion regime with a monthly interval is more effective and lead to restore some 15% of plant biomass, i.e. a grazing exclusion regime may serve as an effective tool for recovering the natural environment of pastures and preserving their biodiversity.

Grazing by domestic herbivores is the most widespread management of mountain pasturelands with steppe vegetation. Studying three levels of grazing intensity (no grazing, regulated grazing, free grazing) have shown a substantial effect of grazing on productivity and diversity of plant groups. Variables such as height, above-ground biomass, biomass of grasses, legumes, and forbs are linearly interrelated and positively correlate with the NG management strategy, and below-ground biomass and root/shoot with RG and FG management strategies.

The strongest impact of grazing are exposed grasses and legumes which are preferable species for domestic herbivores. Grazing management has insignificant effect on soil properties. Soil nitrogen, phosphorus, and potassium are less related to the plant and plant group biomass.

As a result of trampling across FG sites the bulk density of soil and the content of nutrients in plants increase. The conducted studies and outcomes of imitation model tests suggested, that regulation of grazing intensity in mountain pastures with steppe vegetation is an effective approach to their restoration. The research results have already been used to develop measures to preserve the studied ecosystems and improve the quality of fodder resources.

Ethics approval and consent to participate

We approve and agree

Consent for publication

All authors agreed and approved the manuscript for publication in Ecological Processes

Availability of data and materials

The datasets generated and/or analyzed during the current study are available

from the corresponding author on reasonable request

Competing interests

The authors declare that they have no known competing financial interests

or personal relationships that could have appeared to influence the work reported in this paper

Funding

The article is funded by the RA MoESCS Higher Education and Science Committee

within the framework of research project No. 21T-4S237.

Authors' contributions

Conceptualization, formal analysis, investigation, preparing original draft Marine Navasardyan, Tatevik Sargsyan, Harutyun Daveyan. Writing, review and editing Gayane Babayan, Tatevik Sargsyan, Marine Navasardyan.

Acknowledgment

The work was supported by the RA MoESCS Higher Education and Science Committee, in the frames of the research project № 21Т-4С237.

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The Effect of Grazing Intensity on Properties of Mountain Steppe Pasture Vegetation and Soils

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Introduction

Material and methods

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Plant and soil sampling

Data analysis

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The effects of grazing management on plant characteristics

Effect of grazing management on soil and plants nutrient

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