Benefits of Short-Duration, High-Stocking Rate Opportunistic Grazing on Arid Rangelands During Favorable Conditions

The aim of this study was to assess the impact of short grazing periods with high-stocking density on vegetation during weather conditions favorable to plant growth. Continuous grazing is widely practiced in Tunisian arid rangelands and across most drylands and deserts of the Middle East and North Africa. In the early 1990s, the Tunisian government combined a variety of incentives and restrictions on rangeland grazing practices and initiated a national strategy for rangeland improvement. The strategy emphasizes grazing exclusion for three consecutive years, a practice known locally as gdel. At the end of this period, grazing is allowed with no restrictions or with some guidelines. However, these regulations created discontent among pastoral communities, mainly when local rainfall conditions result in a considerable quantity of green biomass. High stocking-density grazing for a short period would help satisfy pastoralist concerns and achieve the government’s strategic goal. This study was implemented in three arid rangeland types of southern Tunisia that have been under restricted grazing for 2 years. Each area in the study was grazed for short periods in late May (about 7 days) with a flock of 150 head of sheep. Measurements of vegetation cover, forage productivity, density, and species richness were taken before and after grazing. Our results suggest that perennial vegetation is more stable under grazing than annual vegetation. The presence of annual species would enhance rangeland vegetation cover and diversity and at the same time offers an opportunity for livestock to select a high-quality diet rich in protein. Opportunistic grazing, applied to heterogeneous rangelands in late spring and the beginning of the annual temperature increase, encouraged animals to select annual plants due to their higher palatability, higher digestibility, and water content rather than heavily grazing perennial species. Perennial biomass materials that die and do not fall through rapid biological decay tended to decline with increased period of placement, resulting in further oxidation to CO2 which affects photosynthetic performance negatively and may eventually cause plant death. Trampling from high-density stocking enhances the litterfall rates and removes the oxidized plant material. These findings may contribute to strategies for addressing the extreme climatic variations that threaten rangeland and livestock sustainability.

Effect of Grazing Management and Land Cover Types on Mineral-Associated Organic Carbon and Particulate Organic Carbon in a Semi-arid Rangelands in Kenya

BackgroundEnhancing soil organic carbon storage in areas under extensive livestock grazing has become a challenge in most arid and semi-arid rangelands in Sub-Saharan Africa. In Kenya for instance, continuous unplanned grazing in community lands has led to overgrazing and degradation of the rangelands. For decades, livestock production has shaped the landscape through various management practices. Grazing can be used to increase soil organic carbon (SOC) content but intensive use of land can lead to its depletion. This study was set out to elucidate the effect of two types of grazing management under varying land cover types on mineral-associated organic carbon (MAOC) and particulate organic carbon (POC) in the soil. The study was carried out in two ranches, Mpala Research Centre (controlled grazing) and Ilmotiok Community Group Ranch (continuous grazing). The experimental design was a completely randomized block design in split-plot arrangement with three replicates. The main plots were the grazing practices; (controlled grazing and continuous grazing); and sub-plots were the land cover types: (bare ground, patches of grasses, and mosaics of trees). These treatments were randomly selected and replicated three times. Three topographical positions (mid-slope, foot slope and bottom land) were used as a blocking factor.ResultsThe interaction had no significant effect on MAOC fraction in any soil depth interval. Controlled grazed zones significantly recorded higher organic carbon content (POC= 0.887% CC SD=0.49) compared to zones under continuous grazing (POC = 0.718% CC SD=0.3). Mosaic of trees (POC =1.15% CC, SD = 0.22) recorded the highest concentration of carbon followed by patches of grass (POC = 0.87% CC, SD= 0.37) and bare ground (POC = 0.38% CC SD = 0.12) had the least.ConclusionThis study shows that grazing practices as well as land cover types have a significant effect on POC but not on MAOC. Mosaic of trees under controlled grazing has higher POC whereas bareground under continuous grazing had the least POC. Destocking should be done under continuous grazed zones to reduce further loss of POC and MAOC and allow vegetation recovery.

Simulating Grazing Effects on Soil Organic Carbon Dynamics in Semi-arid Rangelands (Southern Iran)

Grazing is one of the main causes of rangeland degradation worldwide, due to the effects of overgrazing on vegetation cover and biodiversity. But few data are available on the effect of grazing intensity on the dynamics of soil organic carbon (SOC) and soil labile organic carbon (SLOC). So far, very few studies have addressed the modeling of SOC dynamics under different grazing intensities, and SLOC dynamics has not been modeled yet. In this study, we used the CENTURY model to select the most effective grazing management in terms of carbon sequestration (SOC and SLOC stocks) in semi-arid rangelands of Southern Iran. The effect of four different scenarios of grazing intensity was simulated: no grazing, light grazing (LG), moderate grazing (MG), and heavy grazing (HG). The results of long-term model simulations (2015–2100), indicated that SOC stocks will change by 2.7, 1.7, -23.4, and − 24.6% in the scenarios of exclusion, LG, MG, and HG respectively compared to 2014. With increasing grazing intensities, SLOC stocks in LG, MG, and HG scenarios significantly decreased compared to the no grazing scenario by 26.1, 59.6, and 70%, respectively. Thus, this study suggests recommending light grazing management for semi-arid rangelands of Iran and also SLOC as a suitable index for studying the effect of grazing on soil carbon.

Breeding and Genetics of Forages for Semi-Arid and Arid Rangelands

Rangelands are the Earth’s largest land type and provide the feed source for the extensive grazing of beef and dairy cattle (Bos taurus), sheep (Ovis aries), goat (Capra aegagrus hircus), horse (Equus ferus caballus), camel (Camelus spp [...]

Multifractal analysis of spatial heterogeneity in Spanish arid rangelands

<p>Rangeland and agricultural landscapes are complex and multifractal based on the interaction of biotic and abiotic factors such as soil, meteorology, and vegetation. The effects of land-uses on these areas modify their characteristics and dynamics.  The use of Normalized Difference Vegetation Index (NDVI) and NDVI anomalies (NDVIa) from satellite time series can effectively aid on understanding the differences among rangeland uses and types.</p><p>Multifractal detrended fluctuation analysis (MDFA) focuses on measuring variations of the moments of the absolute difference of their values at different scales. This allows us to use different multifractal exponent such as generalized Hurst exponent (H(q)), and the scaling exponent (ζ(q)) to characterize each area.</p><p>We collected the time series using satellite data of MODIS (MOD09Q1.006) from 2002 to 2019. Two areas from southeastern Spain (Murcia province) of 6.25 Km<sup>2</sup> were selected. Each area has 132 pixels with a spatial resolution of 250 x 250 m<sup>2</sup> and a temporal resolution of 8 days. The areas were selected to compare two types of arid rangeland. Area 1 (A1) is mainly covered by a mixed herbaceous cropland and grassland, Area 2 (A2) presents tree crops as well as a small patch of Mediterranean scrubland.</p><p>MDFA was used on every pixel of each area and H(q), and ζ(q) were plotted and compared. Our results report different exponent behaviours for diverse rangeland type or use. Within each area when different vegetation types are present MFDFA can allow us to distinguish among them such as in A2 where the pixels composing the river that crosses the area show less antipersistent character than the surrounding tree crops.<br>Comparing the scaling exponent of NDVI and NDVIa also suggest a difference of influence on the multifractal character of long-range correlations. This influence is much stronger in A4 than the three others, having their multifractal character due more heavily to probability density function.</p><p>We conclude that MDFA is a good tool to characterize arid rangelands spatial heterogeneity, particularly for rangeland with different vegetation types. It can be used to monitor and manage arid rangeland. It can be useful for policy-makers for short- and long-term solutions.</p><p><strong>Acknowledgements: </strong>The authors acknowledge the support of Project No. PGC2018-093854-B-I00 of the Ministerio de Ciencia Innovación y Universidades of Spain, “Garantía Juvenil” scholarship from Comunidad de Madrid, and the financial support from Boosting Agricultural Insurance based on Earth Observation data - BEACON project under agreement Nº 821964, funded under H2020EU, DT-SPACE-01-EO-2018-2020.</p>