Patches Of Bare Ground Research Articles

Dam periodic storage drives the spatial pattern of vegetation towards banded evolution

Emerging and fragile ecosystems such as reservoir riparian zones are of increasing concern with the increasing number of damming projects worldwide. Current knowledge of riparian vegetation in reservoirs focuses on the individual and community level, with little understanding of spatial patterns and ecological processes at the landscape level. Here, we demonstrate the evolution process, evolution direction, and evolution mechanism of vegetation spatial patterns under persistent and periodic inundation disturbances in the reservoir riparian zone, through coupled analyses of landscape evolution and ecological processes, using continuous years of drone observation data in the riparian zones of two major reservoirs, Xiaowan and Nuozhadu of the Lancang River. We found that vegetation landscape evolution is driven by seed dispersal, environmental factors fluctuations, species tolerance differences, and competition for resource availability, showing a clear trend towards banded evolution. Ecological niche processes such as periodic wet-dry environmental filtering and interspecific competition dominated the formation of vegetation banding patches, and neutral processes of random seed dispersal dominated the areas where banding patches were formed. The water requirements of plants during the exposing period lead to a greater influence of environmental factors that are closely related to water, such as net rainfall, sunshine hours, groundwater storage, and soil moisture. Water redistribution between vegetated and bare ground patches is key to their formation and stability in the upper part of the riparian zone, where drought stress is severe, while in the lower part, vegetation is mainly affected by inundation stress during flooding periods. Therefore, riparian vegetation restoration is critical to maintain a certain area of bare ground patches for drought areas in the exposing period, in contrast to the emphasis on vegetation patch coverage. And it is possible to carry out spatial planning based on the development trend of the belt distribution, taking into account the flood and drought tolerance of the species as well as the fluctuating rhythms of the main factors, such as the rainfall, which is worth exploring further.

Finding food in a changing world: Small-scale foraging habitat preferences of an insectivorous passerine in the Alps.

Organisms living in high-elevation habitats are usually habitat specialists who occupy a narrow ecological niche. To envision the response of alpine species to a changing environment, it is fundamental to understand their habitat preferences on multiple spatial and temporal scales. However, information on small-scale habitat use is still widely lacking. We investigated the foraging habitat preferences of the migratory northern wheatear Oenanthe oenanthe during the entire presence at a breeding site in the central Alps. We repeatedly observed 121 adult and juvenile individuals. We applied Bayesian logistic regression models to investigate which habitat characteristics influenced foraging habitat selection on a fine spatial scale, and how habitat use varied temporally. Throughout their presence on the breeding grounds, northern wheatears showed a consistent preference for a mosaic of stones and bare ground patches with slow-growing, short vegetation. The proximity of marmot burrows was preferred, whereas dense and low woody vegetation was avoided. After arrival at the breeding site, short vegetation, preferably close to the snow, was favored. The preference for open habitat patches that provide access to prey underlines the critical role of small-scale habitat heterogeneity for northern wheatears. The strong and consistent preference for a habitat that is under pressure from land-use and climate change suggests that this alpine bird species may be sensitive to habitat loss, leading to a potential range contraction. We highlight the need to conserve habitat diversity on a small spatial scale to ensure the long-term availability of suitable habitat for northern wheatears in the Alps.

Effect of outdoor grazing-area access time and enrichment on space and pasture use, behaviour, health and growth traits of weaned rabbits.

Providing rabbits with a grassy outdoor area allows them to express a broad variety of specific behaviours such as grazing where grazeable herbage persists. However, rabbits that graze are also exposed to external stressors. Controlled outdoor access time may help preserve the grassland resource, while a hiding place may offer the rabbits a secure space. We focused on rabbit growth, health and behaviour according to outdoor access time and the presence of a hideout on a 30-m2 pasture area. We divided 144 rabbits into four groups (group of rabbits with 8 hours per day (H8) of access to pastures provided with an hideout (Y) (H8Y): n = 36; group of rabbits with 8 hours per day (H8) of access to pastures unprovided with an hideout (N) (H8N): n = 36; group of rabbits with 3 hours per day (H3) of access to pastures provided with an hideout (Y) (H3Y): n = 36; group of rabbits with 3 hours per day (H3) of access to pastures unprovided with an hideout (N) (H3N): n = 36) that differed in access time (H8, four replicates, eight hours a day from 0900 h to 1700 h; and H3, four replicates, three hours a day from 0900 h to 1200 h) and the presence of a hideout (presence of an hideout on the pasture (Y), four replicates, with a roof-shaped wooden hideout; and absence of an hideout on the pasture (N), four replicates, without). Rabbit growth and morbidity were measured weekly for each rabbit from 34 to 76 days of age. Rabbit behaviour was assessed on days 43, 60 and 74 by direct visual scanning. Available grassy biomass was evaluated on days 36, 54 and 77. We also measured the time rabbits took to enter and exit the mobile house and the level of corticosterone accumulated in their hair during the fattening period. There were no between-group differences in live weight (on average, 2 534 g at 76 days of age) and mortality rate (18.7%). The rabbits expressed a broad variety of specific behaviours, with grazing being the most frequent (30.9% of all the observed behaviours). Foraging behaviours including pawscraping and sniffing were more frequently observed in H3 rabbits than H8 rabbits (1.1 vs 0.3% and 8.4 vs 6.2%, respectively; P < 0.05). There was neither an access-time nor hideout presence effect on rabbit hair corticosterone levels or time to exit and enter the pens. Patches of bare ground were more frequent in H8 pastures than in H3 pastures (26.8 vs 15.6%, respectively; P < 0.05). Over the whole growing period, the biomass intake rate was higher in H3 than H8 and higher in N than Y (1.9 vs 0.9 g/rabbit/h and 1.8 vs 0.9 g/rabbit/h, respectively; P < 0.05). In conclusion, restricted access time tended to slow the reduction of the grass resource but had no detrimental effects on rabbit growth or health. Rabbits facing restricted access time adapted their grazing behaviour. A hideout helps rabbits cope with external stressors.

Contrasting effects of vineyard type, soil and landscape factors on ground‐ versus above‐ground‐nesting bees

Abstract Agricultural intensification and abandonment of traditional agricultural practices are main drivers of current insect declines. The resulting loss of feeding and nesting opportunities has led to a decrease in pollinator populations like wild bees. While the restoration of floral resources has been widely implemented in wild bee conservation, nesting resources, particularly for ground‐nesting species, are barely considered. We assessed wild bee diversity in a wine‐growing area in Germany in 15 study sites along a soil gradient and evaluated whether wild bees were distinctly affected by different vineyard types (vertically oriented, terraced, abandoned), local conditions (e.g. shrub and flower cover) and landscape factors in response to divergent nesting needs (above‐ground vs. ground‐nesting). We found that wild bees responded more strongly to the availability of nesting sites than to flower resources. While ground‐nesting bees were determined by the suitability of soil aspects for nesting irrespective of vineyard management types, above‐ground‐nesting bees profited from vineyard abandonment and shrub encroachment in vineyard fallows and were enhanced by the availability of semi‐natural habitats (SNHs) in the surrounding landscape. In contrast, floral resource availability in managed vineyards had only marginal effects on above‐ground‐nesting bees. Synthesis and applications: Life‐history traits like nesting strategies have long been neglected in wild bee conservation approaches, but proved to be highly relevant, especially for ground‐nesting bees. For this, agri‐environmental schemes can no longer solely focus on the restoration of floral resources, but should equally address nesting resources. Therefore, management efforts for enhancing wild bees in vineyard landscapes should aim at complementing nesting resources for ground‐nesting bees (e.g. exposed bare ground patches) and above‐ground‐nesting bees (e.g. woody elements, hedges) in addition to floral resources. At the landscape level, conserving heterogeneous landscapes at a mixture of actively managed vineyards and semi‐natural and woody elements is significant to maintain diverse bee communities.

New syntaxa of tundra vegetation in the Siberian sector of the Arctic

Vegetation of spotted dwarf shrub-sedge-moss and dwarf shrub-lichen communities in the southern tundra subzone of the Taymyr Peninsula is assigned to 3 associations, including 2 new ones. For comparison, we used previously published relevés of ass. Hierochloo alpinae–Hylocomietum splendentis Telyatnikov, Troeva, Ermokhina et Pristyazhnyuk 2019 with 2 subassociations and 3 variants, into which the authors combined spotted dwarf shrub-lichen-moss communities on sandy loam soils and dwarf shrub-lichen communities on sandy soils on the Gydanskii and Tazovskii Peninsulas. As a result of the revision of these syntaxa and their comparison with new materials from the Taymyr Peninsula, we have revised some syntaxonomic decisions. The zonal vegetation is assigned to 2 associations: ass. Carici arctisibiricae–Hylocomietum alaskani Matveyeva 1994 (with regular-cyclic horizontal structure: patches of bare ground – rims – small troughs) and a new ass. Arctagrostio latifoliae–Caricetum arctisibiricae Telyatnikov et al. ex Lavrinenko in Lapina et Lavrinenko ass. nov. hoc loco (with continuous sedge-moss cover) in the class Carici arctisibiricae–Hylocomietea alaskani Matveyeva et Lavrinenko 2023. Dwarf shrub-lichen communities on sandy soils are assigned to a new ass. Asahino chrysanthae–Salicetum nummulariae (Khitun in Telyatnikov et al. 2021) Lapina et Lavrinenko ass. nov. (stat. nov.) hoc loco in the class Loiseleurio procumbentis– Vaccinietea Eggler ex Schubert 1960.

Population survey and habitat selection of the European Nightjar (Caprimulgus europaeus L.) in the Győr-Gönyű sand steppes

This study investigated the habitat selection of the European Nightjar (Caprimulgus europaeus) during the breeding seasons of 2017 and 2018 in the Győr-Gönyű calcareous sand steppe area. In order to assess the habitat preferences of the European Nightjar, habitat characteristics around occupied territories were compared with unoccupied control plots. To characterize the surveyed territories, a total of nine variables related to landscape characteristics, vegetation structure, and composition were quantified. Multivariate methods (PCA and GLMs) were used to distinguish the main factors influencing habitat selection and to model the presence of the European Nightjar. A total of 25 occupied territories were surveyed in the study area in 2017, while 21 in 2018, all of which were characterized by mosaic-structured habitats. Based on our results, in the Gönyű sand steppes, a high probability of European Nightjar presence can be predicted in plots with a sufficient proportion of bare ground patches, higher lengths of forest edges, and the presence of grasslands near the territories.

Twenty-one year dynamics of vegetation from long-term plots in East European tundra

Twenty-one year dynamics of vegetation from long-term plots in East European tundra

Influence of Snowpack Cold Content on Seasonally Frozen Ground and Its Hydrologic Consequences: A Case Study From Niwot Ridge, CO

AbstractFrozen ground influences subsurface hydrology by reducing soil permeability, impeding infiltration, and inducing surface runoff. As the seasonal snowpack strongly controls the evolution of the ground thermal regime, it is necessary to represent the snowpack in models simulating frozen ground and its hydrologic consequences. Conventional understanding of the relationship between snowcover and frozen ground considers the snowpack as an insulator, shielding the ground from cold winter temperatures and thus inhibiting frozen ground. However, observations and modeling at Niwot Ridge, a seasonally snow‐covered alpine catchment in the headwaters of the Boulder Creek watershed, illustrate that snowpack cold content can promote and preserve frozen ground beneath the snowpack during the snowmelt season, unlike bare ground patches that thaw relatively rapidly due to exposure to solar radiation and warm spring temperatures. We present results from a coupled snowpack and subsurface thermo‐hydrologic model including freeze‐thaw processes that captures these contrasts reasonably well. Our results suggest that the cold snowpack at this site acts as a heat sink and promotes frozen ground, in contrast to the conventional understanding of the snowpack as an insulator. In the subalpine zone, infiltration simulations show that shallow freezing beneath snow‐covered ground has a much stronger effect on infiltration than shallow freezing beneath bare ground because the soil beneath the snow remained frozen during snowmelt, whereas bare patches thawed by the time they received excess snowmelt run‐on.

First Breeding Record of the European Robin Erithacus rubecula in Lebanon 2020

European Robin Erithacus rubecula has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion. The population trend appears to be increasing and the size is extremely large. For these reasons the species is evaluated as Least Concern. In Europe, the breeding population is estimated to number 58,700,000-90,500,000 pairs, which equates to 117,000,000-181,000,000 mature individuals. This species is found in forest undergrowth and edge, preferring conifer tracts in some parts of its range and deciduous woodland in others. It uses copses and adjacent open land, farmland woodlots, thickets along watercourses, hedgerows with some tall trees, orchards, gardens and parks and is also found in urban areas in parts of Europe. It requires cool shade, medium-height cover with perches, and patches of bare ground. Breeding occurs from early April to mid-June in the U.K., from the end of April to late July in central Europe and from mid-May in northern Russia and mid-April in southern Russia. On the 28th of April 2020, I was birdwatching in Horsh Ehden Nature Reserve Zgharta-Ehden District, north Lebanon when I encountered a couple of European Robins carrying insects to a nest in a hole in a big rock near the river. Following the birds, they entered the whole and went outside immediately watching me cautiously. I went to see what’s inside that rock and I saw the nest of the European Robin with 3 nestling inside of it. Later after 3 weeks I went again to see the nest I found the juveniles wandering around it. Reporting it to Dr Ghassan Ramadan Jaradi, it was accepted as a first breeding record of this species to Lebanon. Later on, I was able to identify many juvenile individuals near the same location.

Mixed evidence for the small‐island effect in a replicated colonisation experiment

AbstractAimPlant species richness increases with island/patch area, but the effect of spatial scale on the shape of the species‒area relationship remains debatable. We asked whether the small‐island effect (SIE; i.e. different relationship between island area and species richness on smaller compared to larger plots) occurs in plants naturally colonising extremely small de novo plots.LocationNorthern Europe.MethodsWe established 16 experimental plots with bare ground (two plots of each of eight sizes, from 2 to 0.01 m2) in each of four localities, and monitored colonisation of these plots by vascular plants from 2008 to 2010. We modelled species‒area relationships in these plots by linear and breakpoint regressions, and we analysed plant functional traits with respect to plot size.ResultsSmall‐seeded plants were over‐represented among the primary colonisers, and plant functional traits changed with plot size. On average, the number of plant species was six times greater in our largest (2 m2) than in our smallest (0.01 m2) plots. The SIE was observed in half of our analyses; the semi‐log models identified SIE more often than the log‐log models did (71.1% and 28.9% of all analyses respectively).ConclusionsThe evidence for the small‐island effect in boreal forest plants colonising patches of bare ground is mixed. Despite extremely small patch size and habitat uniformity, half of our data showed a “classic” species‒area relationship. Our findings hint that the probability of SIE occurrence increases with decreases in the species pool of primary colonisers and with decreases in the time from the beginning of colonisation. We suggest that the analysis of plant functional traits in study systems where SIE does occur be conducted to uncover the drivers of this interesting biogeographical phenomenon.

Habitat preferences of the Ortolan Bunting (Emberiza hortulana) in its prime wintering grounds, the cereal‐dominated Ethiopian Highlands

Agricultural intensification and land‐use changes are major factors impacting farmland biodiversity. The Ortolan BuntingEmberiza hortulanais the long‐distance trans‐Saharan migratory passerine that has undergone the most dramatic decline among all European farmland birds. The factors responsible for this decline may originate from the breeding grounds, migration stopovers and/or overwintering quarters. Very little is known about conditions on the species' wintering grounds, but a recent study has highlighted the utmost importance of the traditionally managed agroecosystems in the Ethiopian Highlands as a key wintering area, apparently harbouring as much as 90% of the world's Ortolan Bunting population. Using radiotracking and line transect surveys, this study aimed to provide fine‐grained information about species–habitat relationships in the Ortolan Bunting overwintering quarters. Our results showed the importance, at the landscape scale, of small‐scale agriculture, notably of traditionally managed, cereal‐dominated fields interspersed with semi‐natural structures. At a foraging‐site scale, on the other hand, patches of bare ground in combination with large areas of post‐harvesting stubble represented key habitat features. Stubbles provide an essential food resource and bare ground promotes ground foraging by enhancing food accessibility. The maintenance of a traditional agricultural economy will be essential to maintain the habitat potential for the Ortolan Buntings overwintering in the Ethiopian Highlands and will be instrumental in preserving its world population from further decline.

Socio‐psychological factors, beyond knowledge, predict people’s engagement in pollinator conservation

Abstract Nature conservation often depends on the behaviour of individuals, which can be driven by socio‐psychological factors such as a person's attitude, knowledge and identity. Despite extensive ecological research about pollinator declines, there has been almost no social research assessing the drivers of people's engagement in pollinator conservation. To address this gap, we used a large‐scale, online questionnaire in the United Kingdom, broadly framed around the Theory of Planned Behaviour. We received a total of 1,275 responses from a wide range of ages, incomes and education levels, despite a selection bias towards people with a pre‐existing interest in pollinators. A range of socio‐psychological factors predicted people's pollinator conservation actions and explained 45% of the variation. Respondents’ diversity of nature interactions and perceived behavioural control (feeling able to help pollinators) were consistently important predictors of people's pollinator conservation actions, whilst the importance of other socio‐psychological factors depended on the particular action. Notably, knowledge was far less important overall than people's perceptions and other socio‐psychological factors, highlighting a knowledge‐action gap. Further unexplained variation in people's behaviour could partly be due by structural and contextual factors, particularly regarding social norms around tidiness. From a practical perspective, our findings reveal three main insights. First, several simple, low‐cost pollinator conservation actions (reduced mowing, leaving areas unmown and creating patches of bare ground for ground‐nesting bees) are currently under‐utilised so should be priorities for pollinator conservation programmes. Second, strategies are needed to overcome reported practical barriers, for example by providing free resources (e.g. seeds of pollen‐ and nectar‐rich plants) and communicating simple beneficial actions that can be carried out with limited time, space and money. Third, knowledge is just one (relatively less important) factor that predicts pollinator conservation behaviour—other socio‐psychological factors provide potential pathways for increasing uptake, and structural and contextual limitations also need to be considered. In practice, this could be achieved by engaging, inspiring and empowering the public to help pollinators and to take responsibility for their local environment, for example through environmental education and community programmes facilitating public interest and involvement in the management of greenspace. A free Plain Language Summary can be found within the Supporting Information of this article.

Habitat selection of foraging male Great Snipes on floodplain meadows: importance of proximity to the lek, vegetation cover and bare ground

Drainage of wetlands and agricultural intensification has resulted in serious biodiversity loss in Europe, not least in grasslands. Consequently, many meadow birds have drastically declined, and the habitats they select for breeding currently rely on land management. However, the selection of habitats maintained by agriculture may contribute to reduced fitness and thus remain maladaptive for individuals, which makes conservation challenging. An understanding of the relationships between species’ habitat selection, food supply and land management in the context of species’ behaviour is therefore crucial for conservation. Lowland populations of Great Snipe Gallinago media are currently declining at a moderate rate, causing a conservation concern. We examined the daytime site selection (assumed as foraging sites) and food supply of radiotracked Great Snipe males breeding on a floodplain in NE Poland. Foraging sites were classified at micro‐ and macro‐scale levels using the logistic regression in a use–availability design. On the micro‐scale level, males selected moderate sward height and density, and a large amount of bare ground patches, and the importance of these increased as the breeding season progressed. On the macro‐scale level, these conditions were associated with (1) meadows mown twice per season and grazed thereafter (associated with the most abundant food resources – earthworms) and (2) extensively managed pastures, suggesting the importance of grazing. Abandoned or late‐mown meadows under agri‐environmental schemes (AES) were avoided by foraging males. However, parcels with delayed mowing offer safe breeding sites for females nesting close to leks, unlike land‐use types preferred by foraging males, which may act as an ecological trap. Effective conservation of Great Snipes on floodplain meadows requires precisely targeted AES schemes that will provide a mosaic of intensive and extensive land‐use patches in the vicinity of identified leks.

Native plant community recovery after Carpobrotus (ice plant) removal on an island — results of a 10‐year project

AbstractQuestionSpecies of the genus Carpobrotus, or ice plant, are succulent mat‐forming perennial herbs often introduced for soil stabilization. They are common in coastal environments and may thus threaten island biodiversity. While their effects are well known on soils, plant communities and associated fauna, the effects of Carpobrotus control on vegetation recovery are poorly documented. The aim of the paper is to describe plant community trajectories after Carpobrotus removal.LocationBagaud: a 58‐ha Mediterranean island, southern France.MethodsCarpobrotus and its litter were removed in 2011–2012. Follow‐up controls of germinations and resprouts were carried out from then on. Plant communities were surveyed every year two years before and seven years after Carpobrotus removal: on two ca. 0.5‐ha sites (one coastal and one inland) and in three native plant communities used as potential references. Differences in resprouts, vegetation parameters, and Bray–Curtis similarity indices between years were tested. Plant community dynamics was studied through a non‐metric multidimensional scaling and two recovery indices.ResultsThe removal of Carpobrotus and its litter led to the recovery of diverse native plant communities. To prevent Carpobrotus return and ensure success, follow‐up controls were necessary for a period of at least seven years, but the amount of work decreased with time. The plant community recovering on the coastal site quickly reached a composition and structure similar to that of non‐invaded coastal vegetation, although some slow‐growing native species remain underrepresented (e.g., Crithmum maritimum and Limonium pseudominutum). The plant community recovering on the inland site was still very different from the surrounding matorral vegetation because of its slow colonization dynamics, particularly in the presence of competitive herbaceous species.ConclusionBoth sites now provide diverse native plant communities with a more diversified composition and structure (plant heights, litter, bare ground patches) than the plant communities which used to be associated with Carpobrotus mats.

Shrinking opportunities for establishment of native annual forbs in fragmented grassy woodlands

AbstractQuestionsRepeat vegetation surveys in fragmented woodlands in southeast Australia show native and exotic annual plant species have different trajectories of abundance; native annuals are declining while exotic annuals are increasing. We ask: is the divergent species origin response due to fundamental differences in germination cues and/or “safe‐sites” for establishment?LocationTemperate grassy woodlands, southern Victoria, Australia.MethodsWe quantified patch type frequency in the field. Diurnal temperature effects on four native annual forbs and three exotic annual grasses were assessed in a laboratory germination trial. We used a glasshouse experiment to assess the effects of patch type (bare ground, tree litter, grass litter, moss mat) on the emergence and growth of two native and two exotic annuals.ResultsExotic annuals typically had higher and more rapid germination across a wider range of diurnal temperatures than native annuals. Emergence of native and exotic annuals was highest on bare ground patches but was suppressed by leaf litter and moss mat. Native annuals did not emerge from under a moss mat and germinated much less than exotics in all patch types. Seedling growth of native annuals was suppressed by tree litter whereas growth of exotic species was not suppressed by litter or the moss mat.ConclusionsThe regeneration niche of the native annual forb species we examined was typically narrower than that of exotic annual grasses. Many of the differences in response between native and exotic species may be due to seed traits such as seed mass; native annuals have much smaller seeds than exotic annual species. This likely affects the persistence, germination cues, co‐existence and restoration potential of native annuals in fragmented grassy woodlands that have lost their endogenous disturbance agents.

Landscape heterogeneity and management practices drive habitat preferences of wintering and breeding birds in intensively-managed fruit-tree plantations

Intensively-managed fruit-tree plantations consisting of low-stem trees have progressively replaced traditional high- and mid-stem orchards in Europe during the intensification of agriculture in the second part of the 20th century. Such perennial agricultural systems often form dense, homogeneous landscapes interspersed with open fields, urban areas and semi-natural structures. This observational study investigated the patterns driving landscape- and field-scale habitat preferences of bird communities in landscape units with varying fractions of intensively-managed fruit-tree plantations. At landscape scale, habitat homogeneity, notably a large proportion of fruit-tree plantations, had negative effects on both overall bird species richness and on the abundance of insectivorous birds. A higher proportion of semi-natural features, such as natural woody structures (hedgerows, isolated trees and forest patches) and marshes, positively affected overall bird species richness and abundance as well as insectivorous bird abundance. At field scale, we detected general, trait- and species-specific preferences for older trees during both winter and spring. In winter, leftover fruit is a crucial resource driving field selection by the avifauna. In spring, bird preferences for low and sparse ground vegetation were best explained by increased food accessibility for terrestrially foraging birds. Overall landscape heterogeneity as well as in situ management practices both matter to enhance bird habitat in fruit-tree plantations. Increasing the proportion of diverse semi-natural structures would promote wintering and breeding bird diversity and abundance. At field scale, conditions for birds can be improved by preserving older fruit-tree plantations and by maintaining patches of bare ground and short vegetation in the plantation inter-tree rows. However, given the current high-intensity management in most fruit-tree plantations in our study area, promoting natural features within the wider landscape matrix might represent a more cost-effective solution to enhance bird biodiversity in this agro-ecosystem.

High Arctic ecosystem states: Conceptual models of vegetation change to guide long-term monitoring and research

Vegetation change has consequences for terrestrial ecosystem structure and functioning and may involve climate feedbacks. Hence, when monitoring ecosystem states and changes thereof, the vegetation is often a primary monitoring target. Here, we summarize current understanding of vegetation change in the High Arctic—the World’s most rapidly warming region—in the context of ecosystem monitoring. To foster development of deployable monitoring strategies, we categorize different kinds of drivers (disturbances or stresses) of vegetation change either as pulse (i.e. drivers that occur as sudden and short events, though their effects may be long lasting) or press (i.e. drivers where change in conditions remains in place for a prolonged period, or slowly increases in pressure). To account for the great heterogeneity in vegetation responses to climate change and other drivers, we stress the need for increased use of ecosystem-specific conceptual models to guide monitoring and ecological studies in the Arctic. We discuss a conceptual model with three hypothesized alternative vegetation states characterized by mosses, herbaceous plants, and bare ground patches, respectively. We use moss-graminoid tundra of Svalbard as a case study to discuss the documented and potential impacts of different drivers on the possible transitions between those states. Our current understanding points to likely additive effects of herbivores and a warming climate, driving this ecosystem from a moss-dominated state with cool soils, shallow active layer and slow nutrient cycling to an ecosystem with warmer soil, deeper permafrost thaw, and faster nutrient cycling. Herbaceous-dominated vegetation and (patchy) bare ground would present two states in response to those drivers. Conceptual models are an operational tool to focus monitoring efforts towards management needs and identify the most pressing scientific questions. We promote greater use of conceptual models in conjunction with a state-and-transition framework in monitoring to ensure fit for purpose approaches. Defined expectations of the focal systems’ responses to different drivers also facilitate linking local and regional monitoring efforts to international initiatives, such as the Circumpolar Biodiversity Monitoring Program.

Management Techniques to Stimulate Oak Reproduction in Midwestern Oak Savanna Landscapes

Oak reproduction is often scarce or lacking in oak savannas under ecological restoration management, despite the fact that large canopy gaps created by the removal of invasive brush allow abundant sunlight to reach the ground surface. I conducted two experiments to investigate the effect of manipulating surface vegetation on the acorn-caching behavior of squirrels (gray squirrel Sciurus carolinensis; fox squirrel S. niger; or southern flying squirrel Glaucomys volans) and blue jays (Cyanocitta cristata). In Experiment 1, I created 10 × 10 m bare-ground patches prior to the time of acorn dispersal in restored white oak (Quercus alba) savanna and in adjacent unrestored brushy oak woods. I then compared oak seedling establishment in these bare patches the following summer to seedling establishment in unaltered tall vegetation. In Experiment 2, I used a combination of late-summer burning, tilling with an agricultural disc, and applying herbicide to create bare-ground patches adjacent to established oak woods, and then compared oak seedling establishment in these areas the following summer to that in burn-only, mow-only, and unaltered vegetation. In both experiments, oak seedling establishment was greater in areas denuded of ground vegetation. This agrees with previous research, which concluded that blue jays have a preference for storing acorns in areas of low to bare surface vegetation.

Зональная растительность равнинных восточноевропейских тундр

Зональная растительность равнинных восточноевропейских тундр

Root proliferation strategies and exploration of soil patchiness in arid communities

AbstractSoil patchiness is a key feature of arid rangelands. As root proliferation contributes to soil exploration and resource uptake, it is ecologically relevant to understand how species respond to soil heterogeneity and coexist. Campbell et al.'s influential 1991 hypothesis proposes that dominant species deploy root systems (scale) that maximize soil volume explored. Instead, subordinate species show accurate root systems that exclusively proliferate in nutrient‐rich patches (precision). After many experiments under controlled conditions, the generality of this hypothesis has been questioned but a field perspective is necessary to increase realism in the conceptual framework. We worked with a guild of perennial graminoid species inside a grazing exclosure in an arid Patagonian steppe, a model system for ecological studies in arid rangelands for four decades. We buried root traps in bare ground patches with sieved soil, with or without a pulse of nitrogen addition, to measure specific root biomass and precision at 6 and 18 months after burial. We also estimated scale (root density) in naturally established plants, and root decomposition in litter bags. Several species grew in root traps. Dominant species showed the highest root biomass (in both harvests) and scale. Subordinate species grew more frequently with nitrogen addition and showed lower biomass and scale. Similar total root biomass was found with and without nitrogen addition. Species differed in root decomposition, but correcting species biomass by decomposition did not change our conclusions. We did not find a relation between scale and precision, indicating that Campbell's hypothesis is probably not supported in this Patagonian steppe. Soil resource acquisition differences probably do not utterly explain the coexistence of dominant and subordinate species because the steppe is also affected by large herbivore grazing. We propose that root proliferation in this steppe is the result of the interaction between individual density in the community and specific root growth rates.