Application of Geoinformation Technologies to Assess the Impact of Grazing and Fires on the Vegetation Cover of the North-Western Caspian Region

Pollen evidence for Late Pliocene – Early Pleistocene vegetation and climate change in the North Caucasus, North-Western Caspian Region

Background: Grasslands are heavily utilised for livestock agriculture and the resultant degradation through mismanagement contributes to an estimated 60% of this biome being permanently transformed. This study focused on the impact of fire and grazing in moist highland grasslands.Objectives: To determine the contribution of burning frequency and grazing intensity combined (for domestic livestock and indigenous ungulates) on vegetation structure heterogeneity and species diversity.Methods: Eight study sites under different management regimes were sampled over two summers. Vegetation structure characteristics and diversity data were collected monthly within multiple replicates in each study site. A disc pasture meter was used to assess standing biomass. Differences in vegetation structure characteristics, plant community composition and plant species assemblage structure across sites were statistically analysed using analyses of variance, indicator species analyses, multidimensional scaling ordinations and two-way cluster analyses.Results: The combination of heavy grazing and annual burning leads to a distinct plant community dominated by disturbance specialist species. Selective grazing by indigenous herbivores promotes a community of unpalatable species. This study illustrates that fenced indigenous herbivores, even at moderate stocking densities, have a greater detrimental impact on plant diversity and structure than do domestic livestock.Conclusion: Intensive grazing and burning have a detrimental impact on plant species diversity and structure. This also affects resultant palatability for grazing livestock and fenced game. To promote both grazing quality and ecological integrity we recommend a minimum sustainable ‘fodder capacity’ or standing phytomass of 5000 kg per large-animal unit per hectare for domestic livestock in moist highland grasslands.

Precise quantification of forest fire impacts is critical for management strategies in support of post-fire mitigation. In this regard, optical remote sensing imagery in combination with spectral unmixing has been widely used to measure fire severity by means of fractional cover of photosynthetic vegetation (PV), non-photosynthetic vegetation (NPV), charcoal (CH) and further ground components such as ash, bare soil and rocks. However, most unmixing analyses have made use of a single post-fire image without accounting for the pre-fire state. We aim to assess fire severity from Sentinel-2 data using a bi-temporal spectral unmixing analysis that provides a quantitative fire impact description and is oriented towards the process of change by including pre-fire and post-fire information. Unmixing was based on Random Forest Regression (RFR) modeling using synthetic training data from a bi-temporal spectral library. We describe fire severity as changes associated with the combustion of photosynthetic vegetation (PV–CH fraction) and dieback of photosynthetic vegetation (PV-NPV fraction). Unburned forest was mapped as stable photosynthetic vegetation (PV-PV fraction). We evaluated our approach on a forest fire that burned in a temperate forest region in eastern Germany in 2018. Independent validation was carried out based on reference fractions obtained from very high-resolution (VHR) imagery such as Plante Scope, SPOT6, orthophotos, aerial photos, and Google Earth. The results underline the effectiveness of our unmixing approach, with Root Mean Squared Errors (RMSE) of 0.072 for PV-CH, 0.09 for PV-NPV, and 0.08 for PV-PV fractions. Most of the errors were caused by spectral similarity between charcoal and shadow effects caused by trees, and the coloring of foliage and NPV in the late phenological season of the post-fire Sentinel-2 image. Based on the two-dimensional feature space of PV-CH and PV-NPV fractions, we calculated two metrics to characterize fire impacts: distance, an indicator of disturbance severity (sum of combustion and dieback), and angle, a measure of disturbance composition (gradient between combustion and dieback). Furthermore, we compared the fraction-based metrics with the difference Normalized Burn Ratio (dNBR). Since the dNBR is most sensitive to combustion and presence of charcoal, it does not fully characterize fire-related vegetation loss associated with dieback. The bi-temporal fraction-based indices provide more ecologically meaningful information on fire severity, particularly for regions that are less prone to severe wildfires such as Central Europe.

Grassland butterflies are undergoing worldwide population decline due to habitat loss and degradation. Rangelands in the Southern Great Plains can provide a habitat for grassland butterflies depending on management practices. Patch‐burn grazing is a management regime that involves burning portions of grazed pastures at different times. The combination of rotational fire and grazing creates a shifting mosaic of recently burned to older burned areas and lightly grazed to heavily grazed areas. However, the impact of fire and grazing on butterfly communities is complex and the effects of different management regimes on butterfly communities are not clear. We investigated the impact of time since prescribed fire and season of fire on butterfly communities in eight cattle‐grazed pastures, each with three burn units, in northern Oklahoma. Treatments included units burned in spring 2018, summer 2018, summer 2019, and spring 2020, with three replicates of each for a total of 12 burn units. Surveys were conducted three times per year in each burn unit in 2019 and 2020 using two standardised Pollard transects. A total of 909 butterflies and 35 species were observed. Species diversity varied by time since fire and season of fire, with spring‐burned sites having the lowest species diversity and summer‐burned sites having the highest. Dominant vegetation cover and blooming forb presence differed with time since fire and season of fire. Patch‐burn grazing creates a mosaic of successional vegetation stages which can benefit different butterfly species and support the overall community. Some species such as Cercyonis pegala , Danaus plexippus , and Atrytone arogos may benefit from fire every 1–2 years, while other species such as Echinargus isola may need longer times between fire treatments. Patch‐burn grazing regimes can support butterfly communities with species that need different fire return intervals by providing a mosaic of areas with different times since fire and associated grazing intensities.

African grasslands have developed under the impact of fire and grazing. There has been strong selection for grass plants to deter, escape and tolerate herbivory, and to escape and tolerate fire. It follows that the complete withdrawal of fire from those communities adapted to it and its replacement by heavy grazing, is not in the grazier's short or long term interests as strong selection for deterrents must result. It is proposed, then, that periodic burning in certain communities should become as legally obligatory as resting of veld.

Simulating the potential for ecological restoration of dryland forests in Mexico under different disturbance regimes

The relevance and practical significance of the research was due to the fact that in the North-Western Caspian region, in recent decades, due to natural and anthropogenic factors, a generally unfavorable environmental and socio-economic situation has developed. Despite the existing theoretical and practical developments of rational nature management in the Caspian region, some scientific provisions and zonal recommendations for the efficient use of agricultural land require a new understanding. The results of scientific research and the accumulated production experience convince us that in the system of adaptive agriculture in arid regions, it is necessary, first of all, to scientifically substantiate the selection of the most drought-resistant and highly productive crops that use the natural resource potential efficiently. The basis of the economy of the Republic of Kalmykia, as an agrarian subject of the Russian Federation, is agriculture with a highly developed animal husbandry with a specialization in beef cattle breeding and fine-wool sheep breeding. Further successful development of the agrarian sector of the economy in the context of an increasingly arid climate and the positioning of the republic as a promising region of Russia for the production of high-quality beef is only possible with the creation of a solid forage base on natural lands and arable lands. In the difficult ecological and economic conditions of the North-Western Caspian, one of the most acute problems is the increasing processes of land desertification, the preservation and reproduction of the fertility of zonal low-humus soil subtypes. For the successful functioning of the agro-industrial complex of Kalmykia, a comprehensive optimization of the water supply of the rural population, pasture animal husbandry and irrigated agriculture is necessary. A necessary condition for the successful development of agriculture in the region in the future is also a more complete information supply of domestic farmers with information about current trends in science and best practices, and the introduction of innovative research.

Fire is an important disturbance factor across a variety of vegetation zones and one of the major causes of geomorphological and ecological changes (Shakesby&Doerr, 2006). In the context of current and anticipated climate change, fire severity and frequency is expected to increase. The impact of fire in shaping the physical, chemical, biological characteristics of a soil surface is mediated by the interaction between climate factors, vegetation attributes and human activities. Depending on the size, duration and temperature reached, fire usually consumes the litter and vegetation cover. It consequently changes soil stability by enhancing rain-splash detachment, modifying infiltration and promoting soil erosion. Nonetheless, the long-term geomorphological effects of fire activity revealed by lake sediment records have been sparsely investigated in terms of both geographical coverage and range of environmental characteristics. Therefore, a better understanding of fire activity in a future warmer climate will be crucial in assessing and predicting landscape dynamics, feedback mechanisms and sensitivity to soil erosion with different fire behaviour.

Post-fire evolution of soil properties and vegetation cover in a Mediterranean heathland after experimental burning: A 3-year study

Tropical rainforests are recognized as one of the terrestrial tipping elements which could have profound impacts on the global climate, once their vegetation has transitioned into savanna or grassland states. While several studies investigated the savannization of, e.g., the Amazon rainforest, few studies considered the influence of fire. Fire is expected to potentially shift the savanna-forest boundary and hence impact the dynamical equilibrium between these two possible vegetation states under changing climate. To investigate the climate-induced hysteresis in pan-tropical forests and the impact of fire under future climate conditions, we employed the Earth system model CM2Mc, which is biophysically coupled to the fire-enabled state-of-the-art dynamic global vegetation model LPJmL. We conducted several simulation experiments where atmospheric CO_2 concentrations increased (impact phase) and decreased from the new state (recovery phase), each with and without enabling wildfires. We find a hysteresis of the biomass and vegetation cover in tropical forest systems, with a strong regional heterogeneity. After biomass loss along increasing atmospheric CO_2 concentrations and accompanied mean surface temperature increase of about 4 ^circ C (impact phase), the system does not recover completely into its original state on its return path, even though atmospheric CO_2 concentrations return to their original state. While not detecting large-scale tipping points, our results show a climate-induced hysteresis in tropical forest and lagged responses in forest recovery after the climate has returned to its original state. Wildfires slightly widen the climate-induced hysteresis in tropical forests and lead to a lagged response in forest recovery by ca. 30 years.

The effect of natural fires on the vegetation cover of steppe and forest-steppe zones in the south-east of European Russia (the middle course of the Volga River) has been evaluated. The research used methods of studying biosystems at organism, species, population and cenotic levels. The study revealed the possibility of regrowth of aboveground plant parts after fires, changes in the population structure of species, and resistance of populations and zonal plant communities to the effects of natural fires. The most vulnerable among zonal vegetation types are pine forests, feather-grass and petrophytic steppes. Frequency, intensity and area of natural fires in the Middle Volga region cause significant changes in the structure of vegetation cover and reduction of biodiversity. The results obtained in the study of the impact of fires on vegetation can be used in the planning and implementation of environmental and reforestation measures.

<p>Tropical rainforests are recognized as one of the terrestrial tipping elements which could have profound impacts on the global climate, once their vegetation has transitioned into savanna or grassland states. While several studies investigated the savannization of, e.g., the Amazon rainforest, few studies considered the influence of fire. Fire is expected to potentially shift the savanna-forest boundary and hence impact the dynamical equilibrium between these two possible vegetation states under changing climate. To investigate the climate-induced hysteresis in pan-tropical forests and the impact of fire under future climate conditions, we coupled the well established and comprehensively validated Dynamic Global Vegetation Model LPJmL5.0-FMS to the coupled climate model CM2Mc, which is based on the atmosphere model AM2 and the ocean model MOM5 (CM2Mc-LPJmL v1.0). In CM2Mc, we replaced the simple land surface model LaD with LPJmL and fully coupled the water and energy cycles. Exchanging LaD by LPJmL, and therefore switching from a static and prescribed vegetation to a dynamic vegetation, allows us to model important biosphere processes, including wildfire, tree mortality, permafrost, hydrological cycling, and the impacts of managed land (crop growth and irrigation).</p><p>With CM2Mc-LPJmL we conducted simulation experiments where atmospheric CO2 concentrations increased from a pre-industrial level up to 1280 ppm (impact phase) followed by a recovery phase where CO2 concentrations reach pre-industrial levels again. This experiment is performed with and without allowing for wildfires. We find a hysteresis of the biomass and vegetation cover in tropical forest systems, with a strong regional heterogeneity. After biomass loss along increasing atmospheric CO2 concentrations and accompanied mean surface temperature increase of about 4°C (impact phase), the system does not recover completely into its original state on its return path, even though atmospheric CO2 concentrations return to their original state. While not detecting large-scale tipping points, our results show a climate-induced hysteresis in tropical forest and lagged responses in forest recovery after the climate has returned to its original state. Wildfires slightly widen the climate-induced hysteresis in tropical forests and lead to a lagged response in forest recovery by ca. 30 years.</p>

The role of topkill in the differential response of savanna woody species to fire

Long-Term Effects of Fire on Sage Grouse Habitat

The Mediterranean forest ecosystem has a reputation for being subject to very high fire risks. In Algeria, this ecosystem is seriously threatened and suffers considerable damage every year due to wild and uncontrolled fires. Vegetation and soil are severely affected. The importance of the issues raises the need for a diagnosis of the vulnerability of soils subjected to fire and a reflection on the restoration of the quality of the burnt soils. Being aware of the consequences of the fires, we conducted a study on the impact of fires on the forest cover and, particularly, on the soil. The results showed that soil organic and mineral losses were greater than those of unburned soil, with erosion being 34 times higher. Sloping soils, after fire, degrade more quickly and becomemore vulnerable to erosion and drying out. A high frequency of fires alters the potential of the soil to such an extent that the resilience of the forest and soil could be compromised. The recurrence of fires creates a disturbance of vegetation and ground cover. Forest formations are degraded by fires and gradually replaced by secondary formations; the soil is often eroded. In some places, it has reached the threshold of irreversibility.