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Soil compaction causes substantial reduction in agriculture productivity and has always been of great distress for farmers. Intensive agriculture seems to be more crucial in causing compaction. High mechanical load, less crop diversification, intensive grazing, and irrigation methods lead to soil compaction. It is further exasperated when these factors are accompanied with low organic matter, animal trampling, engine vibrations, and tillage at high moisture contents. Soil compaction increases soil bulk density and soil strength, while decreases porosity, aggregate stability index, soil hydraulic conductivity, and nutrient availability, thus reduces soil health. Consequently, it lowers crop performance via stunted aboveground growth coupled with reduced root growth. This paper reviews the potential causes of compaction and its consequences that have been published in last two decades. Various morphological and physiological alterations in plant as result of soil compaction have also been discussed in this review.

Grazing can directly or indirectly influence carbon (C) inputs, turnover, and retention in grassland soil. However, relative to the plant response to grazing, belowground biota and process responses are more complex and often do not correlate with the aboveground responses. Ungulate grazing involves three mechanisms; defoliation (removal of plant shoot tissue), dung and urine return, and trampling. An evaluation of the relative roles of these mechanisms and their combinations in grazing can explain the causes of changes in grasslands, thereby explaining soil C sequestration in a steppe ecosystem. In this study, we examined changes in plant attributes, soil abiotic characteristics, and the soil microbial community in response to mowing (M), dung and urine addition (DU), simulated trampling (T), and their combinations by conducting a 3-yr experiment in a steppe ecosystem in Inner Mongolia, China. Most of the variation in the grazing effects on grasslands was explained by defoliation through decreased plant production and soil respiration and altered vegetation composition. Dung and urine return was second to defoliation in explaining grazing effects on grassland, and led to increasing plant C inputs to the soil, while simultaneously, potential loss of soil C due to the increase of the abundance of bacteria and soil respiration eventually accelerated soil C cycling. An interaction between defoliation and trampling on microbial growth was observed in our study: trampling increased the abundance of total bacteria, fungi, and arbuscular mycorrhizal fungi (AMF) only in the no-mowing plots. Trampling led to plant allocation to belowground tissues and increased the abundance of fungi and AMF, which are critical for soil C sequestration, and trampling with defoliation further decreased the abundance of soil microbes, which may decelerate soil C cycling and increase its retention time. These results indicate that defoliation and dung and urine return play major roles in explaining grazing effects on grassland systems, including plant, soil, and microbial parameters, but the trampling effects and the interaction between defoliation and trampling are two key factors that contribute to explaining the overall effects of grazing on soil C sequestration in a typical steppe ecosystem in Inner Mongolia.

Livestock grazing affects grassland stability, resilience, and productivity owing to trampling, foraging, and excretion. Over time, trampling influences a wide range of grassland components and can have lasting effects. Trampling helps maintain grassland health but may also cause its degradation. In a field experiment over two growing seasons, we simulated yak and sheep trampling at different intensities and investigated their effects on the reproductive and photosynthetic characteristics of Medicago ruthenica var . inschanica in a Tianzhu alpine meadow in Gansu Province, China. Our results show that simulated trampling inhibited the asexual and sexual reproduction and growth of M. ruthenica . The root surface area, root volume, root biomass, pod length, pod number per unit area, number of seeds per pod, thousand-seed weight, and seed yield were significantly reduced under simulated trampling in the upper 30 cm of soil ( P  < 0.05) but were not reduced in the deeper soil layers (> 30 cm). Light trampling by both yak and Tibetan sheep promoted photosynthesis, while heavy trampling by both species inhibited photosynthesis . Yak trampling inhibited photosynthesis more than Tibetan sheep trampling, and overall, the adverse effects of yak trampling on asexual and sexual reproduction and growth of M. ruthenica were greater than those of Tibetan sheep trampling. Thus, the effect of yak trampling is greater than the effect of trampling by Tibetan sheep, where the different trampling intensities of yak and Tibetan sheep can result in direct but varied influences on grasslands, potentially leading to grassland differentiation.

AIM: Biodiversity across the globe is heavily eroded by intensified management at local and landscape scales. Species communities of calcareous grasslands, which are among Europe's most diverse habitats, are severely threatened by the cessation of appropriate traditional management, loss of habitat connectivity and simplification of the surrounding landscape. However, our understanding of these often interrelated factors remains limited, in particular for trait‐mediated responses across taxa. Here, we test the independent effects of local management (grazing, mowing and abandonment), habitat connectivity (measured by a connectivity index) and landscape complexity (indicated by the percentage of arable land) on nine taxa: plants, butterflies, bees, grasshoppers, hoverflies, spiders, true bugs, rove beetles and leafhoppers on small semi‐natural calcareous grassland remnants (< 1 ha). LOCATION: Central Germany. METHODS: We use a joint analysis across taxa to identify general and trait‐mediated responses (body size and Red List status) in species richness, abundance and community composition. RESULTS: We identified three key drivers of local diversity patterns: First, an increasing proportion of arable land from 10% to 80% led to a 29% loss of overall species richness. Second, despite differences between taxa, increasing habitat connectivity generally enhanced species richness. Connectivity effects were more accentuated in the large species per taxon, which can be expected to be good dispersers. Finally, grazing reduced species richness and abundance much more than annual mowing or short‐term abandonment (5–15 years), in particular for red‐listed species. We attribute this to plant resource removal through overgrazing and trampling. MAIN CONCLUSIONS: For the conservation management of small calcareous grasslands, we advocate an alternating strategy of mowing or lenient grazing and short‐term abandonment, prioritizing connected fragments surrounded by diverse landscapes. Despite taxon‐specific responses, our study across nine taxa demonstrates universal, trait‐mediated effects of management, landscape complexity and connectivity on local biodiversity in fragmented communities.

Throughout the world, areas have been reserved for their exceptional environmental values, such as high biodiversity. Financial, political and community support for these protected areas is often dependent on visitation by nature-based tourists. This visitation inevitably creates environmental impacts, such as the construction and maintenance of roads, tracks and trails; trampling of vegetation and erosion of soils; and propagation of disturbance of resilient species, such as weeds. This creates tension between the conservation of environmental values and visitation. This review examines some of the main features of environmental impacts by nature-based tourists through a discussion of observational and manipulative studies. It explores the disturbance context and unravels the management implications of detecting impacts and understanding their causes. Regulation of access to visitor areas is a typical management response, qualified by the mode of access (e.g., vehicular, ambulatory). Managing access and associated impacts are reviewed in relation to roads, tracks and trails; wildlife viewing; and accommodations. Responses to visitor impacts, such as environmental education and sustainable tour experiences are explored. The review concludes with ten recommendations for further research in order to better resolve the tension between nature conservation and nature-based tourism.

Poaching is rapidly extirpating African forest elephants (Loxodonta cyclotis) from most of their historical range, leaving vast areas of elephant-free tropical forest Elephants are ecological engineers that create and maintain forest habitat; thus, their loss will have large consequences for the composition and structure of Afrotropical forests. Through a comprehensive literature review, we evaluated the roles of forest elephants in seed dispersal, nutrient recycling, and herbivory and physical damage to predict the cascading ecological effects of theirpopulation declines. Loss of seed dispersal by elephants will favor tree species disperse abiotically and by smaller dispersal agents, and tree species composition will depend on the downstream effects of changes in elephant nutrient cycling and browsing. Loss of trampling and herbivory of seedlings and saplings will result in high tree density with release from browsing pressures. Diminished seed dispersal by elephants and high stem density are likely to reduce the recruitment of large trees and thus increase homogeneity of forest structure and decrease carbon stocks. The loss of ecological services by forest elephants likely means Central African forests will be more like Neotropical forests, from which megafauna were extirpated thousands of years ago. Without intervention, as much as 96% of Central African forests will have modified species composition and structure as elephants are compressed into remaining protected areas. Stopping elephant poaching is an urgent first step to mitigating these effects, but long-term conservation will require land-use planning that incorporates elephant habitat into forested landscapes that are being rapidly transformed by industrial agriculture and logging. La caza furtiva está extirpando rápidamente a los elefantes africanos del bosque (Loxodonta cyclotis) de la mayor parte de su extensión histórica, lo que deja áreas extensas de bosque tropical libres de elefantes. Los elefantes son ingenieros ecológicos que crean y mantienen el habitat del bosque; por esto, su pérdida tendrá consecuencias para la composición y la estructura de los bosques afrotropicales. Por medio de una revisión exhaustiva de la literatura, evaluamos el papel de los elefantes del bosque en la dispersión de semillas, reciclaje de nutrientes, herbivoría, y daño físico para predecir los efectos ecológicos en cascada de la declinación de sus poblaciones. La falta de la dispersión de semillas realizada por elefantes favorecerá a las especies de árboles dispersadas abióticamente y por agentes dispersores más pequeños, y la composición de las especies de árboles dependerá de los efectos derivados de los cambios en el pastoreo y circulación de nutrientes de los elefantes. La ausencia de pisoteo y de la herbivoría de brotes y retoños resultará en una alta densidad de árboles conforme estas especies sean liberadas de la presión del pastoreo. La disminución en la dispersión de semillas por los elefantes y la alta densidad de tallos probablemente reduzcan el reclutamiento de árboles grandes, lo que incrementará la homogeneidad de la estructura del bosque y disminuirá las reservas de carbono. La pérdida de servicios ecológicos generados por elefantes probablemente implique que los bosques del centro de África sean más como los bosques neotropicales, en los que la megafauna fue extirpada hace miles de años. Sin una intervención, hasta el 96% de los bosques del centro de África tendrán una composición y estructura modificadas conforme los elefantes son restringidos dentro de las áreas protegidas. Detener la caza furtiva de elefantes es un primer paso urgente para mitigar estos efectos, pero la conservación a largo plazo requerirá una planeadón de uso de suelo que incorpore al habitat del elefante dentro de los paisajes boscosos que están siendo transformados rápidamente por la industria agrícola y maderera. 偷猎正在导致非洲森林象(Loxodonta cyclotis)从它们大部分的历史分布区消失，留下大片没有大象的热 带森林。大象是创造和维持森林生境的生态工程师，因此它们的消失会对非洲热带界森林的组成和结构产生很 大影响。通过全面的文献综述，我们评估了森林象在种子传播、营养循环、食草作用以及对森林的直接破坏中 的作用，以预测它们种群下降产生的生态级联效应。失去了大象对种子的传播,将有利于树种通过非生物途径和 更小型的传播者来传播种子，而树木种类的组成将取决于大象的营养循环和食草作用变化的下游效应。没有大 象来踩踏、取食幼苗和小树会导致树木密度増大，因为树木不再受到被取食的压力。大象对种子传播作用的下 降和树木密度的增高可能减少森林中大树的补充因此增加了森林结构的均质性，減少了碳储量。森林象带来的 生态服务功能衰退可能意味着中非森林将变得像几千年前巨型动物群灭绝了的新热带界森林。在没有干预的情 况下,随着大象的分布区收缩到剰余的保护区中,高达96%的中非森林的物种组成和结构会发生改变。要减缓 这些影响，刻不容缓的第一步是停止偷猎,但长期的保护还需要土地利用规划将大象的生境纳入到正在因农业产 业化和伐木而快速转化的森林景观中。

Overgrazing substantially contributes to global grassland degradation by decreasing plant community productivity and diversity through trampling, defoliation, and removal of nutrients. Arbuscular mycorrhizal (AM) fungi also play a critical role in plant community diversity, composition, and primary productivity, maintaining ecosystem functions. However, interactions between grazing disturbances, such as trampling and defoliation, and AM fungi in grassland communities are not well known. We examined influences of trampling, defoliation, and AM fungi on semiarid grassland plant community composition for 3 yr, by comparing all combinations of these factors. Benomyl fungicide was applied to reduce AM fungal abundance. Overgrazing typically resulted in reduced dominance of Stipa Krylovii, contributing to degradation of typical steppe grasslands. Our results indicated trampling generally had little effect on plant community composition, unless combined with defoliation or AM fungal suppression. Defoliation was the main component of grazing that promoted dominance of Potentilla acaulis over Stipa krylovii and Artemisia frigida, presumably by alleviating light limitation. In non-defoliated plots, AM fungi promoted A. frigida, with a concomitant reduction in S. krylovii growth compared to corresponding AM suppressed plots. Our results indicate AM fungi and defoliation jointly suppress S. krylovii biomass; however, prolonged defoliation weakens mycorrhizal influence on plant community composition. These findings give new insight into dominant plant species shifts in degraded semiarid grasslands.

This review regards the pressures and threats linked with the human use of European urban and suburban forests. They can be divided into the following major categories: urban development, fragmentation, and isolation of forests; human pressures on soil and vegetation (e.g., changes in vegetation due to trampling, environmental and especially air pollution); human pressures on animals (e.g., wildlife losses due to collisions, frequent presence of dogs accompanying the visitors); and other threats and damages (e.g., littering and acts of vandalism). The directions of negative relations between people and forests shown in this review draw attention to the high complexity of the discussed issues. Awareness of this complexity (when planning and implementing forest management) can limit or counteract conflicts arising from the use of urban and suburban forests by people. This is of particular importance in the era of progressing urbanization and the evolution of human needs regarding the use of forests.

Questions: Do the effects of grazing components on vegetation structure differ in their relative importance? Do components interact in their effect on vegetation? Location: San Jose department, Southern Campos, Uruguay. Methods: In a manipulative field experiment we simulated three different grazing components: trampling, defoliation and urine deposition, over 3 yr in a natural grassland. Defoliation was analysed through two intensity levels and two procedures: uniform and selective cutting. We evaluated the effects of grazing components on species diversity and composition, and frequency of plant functional types. Results: All simulated grazing components had at least some effect on vegetation structure. Additionally, both individual and interactive effects on vegetation attributes were detected. Our study indicates that the relative influence of each grazing component varied according to the attribute considered. N addition was the only treatment that affected plant diversity. Plant functional type composition, in turn, was affected mainly by trampling. N addition and trampling were the component that affected the frequency of the largest number of species. Defoliation selectivity showed effects both in terms of plant functional type and species composition. Exclosure treatment and defoliation intensity had slight effects on grassland structure. Conclusions: This study provides insight on the underlying mechanisms of some observed patterns of grazing on the Campos grasslands. Our results lead us to conclude that all grazing components have to be taken into account to understand vegetation dynamics subjected to grazing. Prevention of woody encroachment by grazing can be attributed to direct and indirect effects of trampling. Trampling should be taken into account to explain increaser species responses. However, mechanisms responsible for other general patterns remain less clear. The importance of selective defoliation in species replacement induced by grazing in these grasslands has yet to be clarified.

Herbivores are key drivers of vegetation dynamics in most ecosystems. However, the effect of high arctic herbivores on vegetation dynamics throughout a growing season is not well understood. In this study, we examine the impacts of a large dominant herbivore in the tundra ecosystem, the muskox, Ovibos moschatus, using exclosures established in a fen in high Arctic Greenland. Using weekly sampling throughout the growing season, we quantified the effects of muskox exclusion on aboveground plant biomass and on concentrations and pools of carbon and nitrogen, and explored the timing of peak biomass and nutrient pools. Excluding muskoxen profoundly changed plant abundances and dynamics of the fen, with more than a doubling of aboveground plant biomass and carbon and nitrogen pool sizes. Specifically, large increases in mosses and litter were observed, while graminoid biomass did not change significantly with exclusion of muskoxen. Excluding muskoxen advanced the peak of plant biomass, but also led to a more rapid decline, resulting in an earlier and shorter period of maximal plant biomass inside the exclosures. The largest impact of muskoxen on the arctic fen ecosystem seems to be through their trampling effects on the moss layer, which likely mediated most of the observed changes. This study demonstrates how quickly an ecosystem may respond to changes in the abundance of large herbivores and highlights their pivotal role in modifying vegetation dynamics and nutrient cycling in tundra ecosystems.