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Data from: Variability in community productivity: mediating effects of vegetation attributes

1. Plant productivity varies though time in response to environmental fluctuations. Reducing variability in productivity requires an improved understanding of how plant community attributes interact with environmental fluctuations to influence plant growth dynamics. We evaluated links between two community attributes, species diversity and abundance-weighted values of specific leaf area (SLA), and temporal variability in grassland productivity at patch (local) and aggregate (multi-patch) spatial scales. 2. Aggregate communities were created by combining patches of spatially-distinct communities of perennial plant species from grassland biodiversity experiments in Texas, USA. Inter-annual variability in aboveground net primary productivity (ANPP) of aggregate communities was analyzed as a function of two multiplicative components, mean temporal variability in the ANPP of patches and temporal synchrony in ANPP dynamics among patches. We used regression analyses to determine whether temporal variability in aggregate ANPP and its components were correlated with either species diversity or community-weighted SLA over 5 years. 3. Temporal variability in ANPP of aggregate communities was strongly correlated with temporal variability in patch ANPP. Increasing mean SLA reduced ANPP variability of aggregate communities by increasing mean productivity. Increased temporal changes in patch-scale SLA further reduced temporal variability in aggregate ANPP by reducing effects of precipitation fluctuations on productivity. Conversely, increasing species diversity over the narrow range measured increased temporal variability in aggregate ANPP. High diversity was associated with reduced dominance of temporally-stable C4 grasses. 4. Our results implicate means and patch-scale temporal dynamics in community SLA as potential indicators of variability in grassland primary productivity through time.

opencc-zeroDec 2012View details →

Data from: Postglacial climate and fire-mediated vegetation change on the western Olympic Peninsula, Washington

The mode and tempo of forest compositional change during periods of rapid climate change, including the potential for the fire regime to produce non-linear relationships between climate and vegetation, is a long-standing theme of forest ecological research. In the old conifer forests of the coastal Pacific Northwest, fire disturbances are sufficiently rare that their relation to climate and their ecological effects are poorly understood. We used a 14,700-year high-resolution sediment record from Yahoo Lake on the Olympic Peninsula to examine vegetation (landscape vegetation from pollen and local vegetation from macrofossils) and fire (landscape fire from total charcoal and local fire from charcoal peaks) in conjunction with independent records of climate. We hypothesized that the successional stage of the local forest will exhibit alternate stable states over a range of fire activity, that species turnover will increase abruptly above a certain level of fire activity and that both responses would be more gradual at the landscape scale than the local scale. Supporting these hypotheses, at the local scale we found strong evidence for alternate stable states of late vs. early successional communities and inertia of species turnover to changing fire activity. At the landscape scale, vegetation responded more gradually to changing fire activity. From 14,700 to 7000 years ago, high landscape vegetation turnover occurred along with high landscape fire activity, especially during the warm summers of the early Holocene. In several instances local species turned over completely following fire events but several centuries after climate change. In contrast, during the last 7000 years the local forest composition was dominated by late-successional species with little species turnover despite periods of moderate fire activity. We suggest that the relatively minor climate fluctuations of the past 7000 years were not sufficient to cause large-scale species turnover after fire. The Yahoo Lake fire and vegetation record of the early Holocene provides a model for dramatic ecosystem change following an anticipated shift to warmer summer temperatures.

Data from: Drivers of vegetative dormancy across herbaceous perennial plant species

Vegetative dormancy, that is the temporary absence of aboveground growth for ≥ 1 year, is paradoxical, because plants cannot photosynthesise or flower during dormant periods. We test ecological and evolutionary hypotheses for its widespread persistence. We show that dormancy has evolved numerous times. Most species displaying dormancy exhibit life‐history costs of sprouting, and of dormancy. Short‐lived and mycoheterotrophic species have higher proportions of dormant plants than long‐lived species and species with other nutritional modes. Foliage loss is associated with higher future dormancy levels, suggesting that carbon limitation promotes dormancy. Maximum dormancy duration is shorter under higher precipitation and at higher latitudes, the latter suggesting an important role for competition or herbivory. Study length affects estimates of some demographic parameters. Our results identify life historical and environmental drivers of dormancy. We also highlight the evolutionary importance of the little understood costs of sprouting and growth, latitudinal stress gradients and mixed nutritional modes.

opencc-zeroDec 2016View details →

Data from: Informative plot sizes in presence-absence sampling of forest floor vegetation

1. Plant communities are attracting increased interest in connection with forest and landscape inventories due to society's interest in ecosystem services. However, the acquisition of accurate information about plant communities poses several methodological challenges. Here we investigate the use of presence-absence sampling with the aim to monitor state and change of plant density. We study what plot sizes are informative, i.e. the estimators should have as high precision as possible. 2. Plant occurrences were modeled through different Poisson processes and tests were developed for assessing the plausibility of the model assumptions. Optimum plot sizes were determined by minimizing the variance of the estimators. While state estimators of similar kind as ours have been proposed in previous studies, our tests and change estimation procedures are new. 3. We found that the most informative plot size for state estimation is 1.6 divided by the plant density, i.e. if the true density is 1 plant per square meter the optimum plot size is 1.6 square meters. This is in accordance with previous findings. More importantly, the most informative plot size for change estimation was smaller and depended on the change patterns. We provide theoretical results as well as some empirical results based on data from the Swedish National Forest Inventory. 4. Use of too small or too large plots resulted in poor precision of the density (and density change) estimators. As a consequence, a range of different plot sizes would be required for jointly monitoring both common and rare plants using presence-absence sampling in monitoring programmes.

opencc-zeroMay 2020View details →

Data from: Structural complexity and large-sized trees explain shifting species richness and carbon relationship across vegetation types

1. It is prominently claimed that enhancing forest diversity would play a dual role of nature conservation and climate regulation. While the idea is intuitively appealing, studies show that species richness effects on aboveground carbon (AGC) are not always positive, but instead unpredictable especially across scales and complex terrestrial systems having large-diameter and tall-stature trees. Previous studies have further considered structural complexity and larger trees as determinants of AGC. Yet it remains unclear what drives differential diversity-AGC relationships across vegetation types. 2. Here, we test whether structural complexity and large-sized trees play an influential role in explaining shifting diversity-AGC relationships across vegetation types, using a 22.3 ha sampled dataset of 124 inventory plots in woodlands, gallery forests, tree/shrub savannahs and mixed plantations in West Africa. 3. Natural vegetation had greater species richness and structural complexity than mixed plantations, as expected. In addition, AGC was highest in gallery forests and mixed plantations, which is consistent with favorable environmental conditions in the former and high stocking densities and presence of fast-growing species in the latter. Significant interaction effects of species richness and vegetation on AGC revealed a vegetation-dependent species richness-AGC relationship: consistently, we found positive species richness-AGC relationship in both mixed plantations and woodlands, and nonsignificant patterns in gallery forests and tree/shrub savannah. Further, there was a vegetation-dependent mediation of structural complexity in linking species richness to AGC, with stronger positive structural complexity effects where species richness-AGC relationships were positive, and stronger positive large-sized trees' effect where species richness-AGC relationships were neutral. 4. Our study provides strong evidence of vegetation-dependent species richness-AGC relationships, which operated through differential mediation by structural complexity of the species richness and large trees' effects. We conclude that even higher species richness in diversified ecosystems may not always relate positively with AGC, and that neutral pattern may arise possibly as a result of larger dominant individual trees imposing a slow stand dynamic flux and overruling species richness effects.

Data from: Vegetation connectivity increases ant activity and potential for ant-provided biocontrol services in a tropical agroforest

In natural and managed systems, connections between trees are important structural resources for arboreal ant communities with ecosystem-level effects. However, ongoing agricultural intensification in agroforestry systems, which reduces shade trees and connectivity between trees and crop plants, may hinder ant recruitment rates to resources and pest control services provided by ants. We examined whether increasing connectivity between coffee plants and shade trees in coffee plantations increases ant activity and enhances biological control of the coffee berry borer, the most devastating insect pest of coffee. Further, we examined whether artificial connections buffer against the loss of vegetation connectivity in coffee plants located at larger distances from the nesting tree. We used string to connect Inga micheliana shade trees containing Azteca sericeasur ant nests to coffee plants to compare ant activity before and after placement of the strings, and measured borer removal by ants on coffee plants with and without strings. Ant activity significantly increased after the addition of strings on connected plants, but not on control plants. Borer removal by ants was also three times higher on connected plants after string placement. Greater distance from the nesting tree negatively influenced ant activity on control coffee plants, but not on connected plants, suggesting that connections between coffee plants and nest trees could potentially compensate for the negative effects that larger distances pose on ant activity. Our study shows that favoring connectivity at the local scale, by artificially adding connections, promotes ant activity and may increase pest removal in agroecosystems.

Data from: A decline in molluscan carbonate production driven by the loss of vegetated habitats encoded in the Holocene sedimentary record of the Gulf of Trieste

Carbonate sediments in non-vegetated habitats on the NE Adriatic shelf are dominated by shells of molluscs. However, the rate of carbonate molluscan production prior to the 20th century eutrophication and overfishing on this and other shelves remains unknown because (1) monitoring of ecosystems prior to the 20th century was scarce and (2) ecosystem history inferred from cores is masked by condensation and mixing. Here, based on geochronological dating of four bivalve species, carbonate production during the Holocene is assessed in the Gulf of Trieste, where algal and seagrass habitats underwent a major decline during the 20th century. Assemblages of sand-dwelling Gouldia minima and opportunistic Corbula gibba are time-averaged to > 1,000 years and C. gibba shells are older by >2,000 years than shells of co-occurring G. minima. This age difference is driven by temporally disjunct production of two species coupled with decimeter-scale mixing. Stratigraphic unmixing shows that Corbula gibba declined in abundance during the highstand phase and increased again in the 20th century. In contrast, one of the major contributors to carbonate sands, Gouldia minima, increased in abundance during the highstand phase, but declined to almost zero abundance over the past two centuries. G. minima and herbivorous gastropods associated with macroalgae or seagrasses are abundant in the top-core increments but are rare alive. Although G. minima is not limited to vegetated habitats, it is abundant in such habitats elsewhere in the Mediterranean Sea. This live-dead mismatch reflects the difference between highstand baseline communities (with soft-bottom vegetated zones and hard-bottom Arca beds) and present-day oligophotic communities with organic-loving species. Therefore, the decline in light penetration and the loss of vegetated habitats with high molluscan production traces back to the 19th century. More than 50% of the shells on the seafloor in the Gulf of Trieste reflect inactive production that was sourced by heterozoan carbonate factory in algal or seagrass habitats.

Data from: The influence of topography and soil phosphorus on the vegetation of Korup Forest Reserve, Cameroun

All living trees (≥ 30 cm gbh) were enumerated in 135 80×80 m plots, each subdivided into four 40×40 m subplots, and arranged along four 5 km transect lines in the Korup Forest Reserve, Cameroun. For each plot altitude, slope and the extent of permanent and seasonal swamps were recorded. Four hundred and eleven taxa were recognized of which 66% were identified to species. Mean tree density was 471 ha−1, basal area 27.6 m2 ha−1 and number of species per plot 75. The subfamily Caesalpinioideae (Leguminosae) was the most abundant family/subfamily in terms of basal area, but the Scytopetalaceae the most frequently represented, mainly on account ofOubanguia alata. Ten plots had at least three quarters of their area permanently swamped, and three, to a similar extent, were seasonally swamped. The ranges in sand, silt and clay content were 60–91, 0–24 and 4–20% respectively. The pH value, organic carbon content and nitrate-nitrogen concentration ranged between 4.0–5.8, 1.3–5.7% and 0–35 ppm respectively. The largest soil variations were in available phosphorus, range 2–29 ppm, and potassium, 38–375 ppm. Correspondence analysis ordination of all plots showed a major indirect floristic gradient correlated with increasing altitude, slope and soil phosphorus and potassium. Removal of the topographic effect by separate re-ordinations of four groups of plots at low, middle (2) and high altitude/slopes highlighted a strong correlation of the main floristic gradients of the middle altitude/slope groups with the concentration of available soil phosphorus. Direct gradient analysis using all plots with respect to available soil phosphorus concentration confirmed the indirect analyses. Individual species response to phosphorus were also shown by direct comparisons in the vegetation on plots of high and low available soil phosphorus concentration. Low available phosphorus soils (≤ 5 ppm) are strongly associated with species of the subfamily Caesalpinioideae, especially of the tribes Amherstieae and Detarieae. It is suggested that this result is probably due to the ability of these particular legume tribes to form associations with ectotrophic mycorrhizae.

Data from: The role of plant-soil feedbacks in stabilizing a reindeer-induced vegetation shift in subarctic tundra

1.Herbivory can drive vegetation into different states of productivity and community composition, and these changes may be stable over time due to historical contingency effects. Interactions with abiotic and biotic soil components can contribute to such long‐term legacies in plant communities through stabilizing positive feedbacks. 2.We studied the role of plant‐soil feedbacks in maintaining vegetation changes caused by historical (~1350‐1900 AD) reindeer herding in northern Sweden. These historical milking grounds (HMGs) consist of meadow plant communities formed in naturally nutrient poor heath or naturally nutrient rich shrub‐dominated vegetation, and are still clearly visible in the landscape, a century after active use ceased. 3.We selected two phytometer species: the forb Potentilla crantzii as representative of HMG vegetation, and the dwarf shrub Betula nana, as representative of control vegetation. We grew both species under glasshouse conditions on soils derived from replicated HMG and paired control plots, using live soils and sterilized (γ‐radiation)‐inoculated soils, to separate between biotic and abiotic soil effects. 4.A net negative plant‐soil feedback for B. nana biomass in its home (i.e., control) soil and a net positive feedback for P. crantzii in its home (i.e., HMG) soil in heath habitat was partly driven by the soil biotic community. However, abiotic differences in mineral nitrogen (N) concentrations between control and HMG soils were a stronger driver of differences in plant growth. Positive feedbacks maintaining a high mineral nutrient availability are thus important, especially in nutrient poor habitats. 5.The positive plant responses to higher soil mineral N concentrations, combined with positive biotic plant‐soil feedbacks, might shift the competitive balance in favour of typical HMG plant species, thereby contributing to stability of HMG plant communities. Our data indicate that herbivore‐driven changes in the interactions between plants and both biotic and abiotic components of the soil persist over long temporal scales.

opencc-zeroMar 2020View details →

Substrate quality drives fungal necromass decay and decomposer community structure under contrasting vegetation types

1. Fungal mycelium is increasingly recognized as a central component of soil biogeochemical cycling, yet our current understanding of the ecological controls on fungal necromass decomposition is limited to single sites and vegetation types. 2. By deploying common fungal necromass substrates in a temperate oak savannah and hardwood forest in the midwestern USA, we assessed the generality of the rate at which high- and low-quality fungal necromass decomposes; further, we investigated how the decomposer 'necrobiome' varies both across and within sites under vegetation types dominated by either arbuscular (AM) or ectomycorrhizal (EM) plants. 3. The effects of necromass quality on decay rate were robust to site and vegetation type differences, with high-quality fungal necromass decomposing, on average, 2.5 times faster during the initial stages of decay. Across vegetation types, bacterial and fungal communities present on decaying necromass differed from bulk soil microbial communities and were influenced by necromass quality. Moulds, yeasts and copiotrophic bacteria consistently dominated the necrobiome of high-quality fungal substrates. 4. Synthesis: We show that regardless of differences in decay environments, high-quality fungal substrates decompose faster and support different types of decomposer microorganisms when compared with low-quality fungal tissues. These findings help to refine our theoretical understanding of the dominant factors affecting fast cycling components of soil organic matter (SOM) and the microbial communities associated with rapid decay.

zenodo32/100

Bed morphology adjustment under the impact of a near-bank emergent model vegetation patch: implications for urban channel restoration

The dataset (including videos) are uploaded to support the research study Bed morphology adjustment under the impact of a near-bank emergent model vegetation patch: implications for urban channel restoration

opencc-by-4.0Dec 2021View details →

opencc-zeroDec 2016View details →

Data from: Vegetation cover in relation to socioeconomic factors in a tropical city assessed from sub-meter resolution imagery

Fine-scale information about urban vegetation and social-ecological relationships is crucial to inform both urban planning and ecological research, and high spatial resolution imagery is a valuable tool for assessing urban areas. However, urban ecology and remote sensing have largely focused on cities in temperate zones. Our goal was to characterize urban vegetation cover with sub-meter resolution aerial imagery, and identify social-ecological relationships of urban vegetation patterns in a tropical city, the San Juan Metropolitan Area, Puerto Rico. Our specific objectives were to: i) map vegetation cover using sub-meter spatial resolution (0.3 m) imagery; ii) quantify the amount of residential and non-residential vegetation; and iii) investigate the relationship between patterns of urban vegetation versus socioeconomic and environmental factors. We found that 61% of the San Juan Metropolitan Area was green, and that our combination of high spatial resolution imagery and object-based classification was highly successful for extracting vegetation cover in a moist tropical city (97% accuracy). In addition, simple spatial pattern analysis allowed us to separate residential from non-residential vegetation with 76% accuracy, and patterns of residential and non-residential vegetation varied greatly across the city. Both socioeconomic (e.g., population density, building age, detached homes) and environmental variables (e.g., topography) were important in explaining variations in vegetation cover in our spatial regression models. However, important socioeconomic drivers found in cities in temperate zones, such as income and home value, were not important in San Juan. Climatic and cultural differences between tropical and temperate cities may result in different social-ecological relationships. Our study provides novel information for local land use planners, highlights the value of high spatial resolution remote sensing data to advance ecological research and urban planning in tropical cities, and emphasizes the need for more studies in tropical cities.

Data from: Arctic fungal communities associated with roots of Bistorta vivipara do not respond to the same fine-scale edaphic gradients as the above-ground vegetation

Soil conditions and microclimate are important determinants of the fine-scale distribution of plant species in the Arctic, creating locally heterogeneous vegetation. We hypothesize that root-associated fungal (RAF) communities respond to the same fine-scale environmental gradients as the aboveground vegetation, creating a coherent pattern between aboveground vegetation and RAF. We explored how RAF communities of the ectomycorrhizal (ECM) plant Bistorta vivipara and aboveground vegetation structure of arctic plants were affected by biotic and abiotic variables at 0.3–3.0-m scales. RAF communities were determined using pyrosequencing. Composition and spatial structure of RAF and aboveground vegetation in relation to collected biotic and abiotic variables were analysed by ordination and semi-variance analyses. The vegetation was spatially structured along soil C and N gradients, whereas RAF lacked significant spatial structure. A weak relationship between RAF community composition and the cover of two ECM plants, B. vivipara and S. polaris, was found, and RAF richness increased with host root length and root weight. Results suggest that the fine-scale spatial structure of RAF communities of B. vivipara and the aboveground vegetation are driven by different factors. At fine spatial scales, neighbouring ECM plants may affect RAF community composition, whereas soil nutrients gradients structure the vegetation.

opencc-zeroDec 2010View details →

Data from: Evolution of Dendrocolaptes platyrostris (Aves: Furnariidae) between the South American open vegetation corridor and the Atlantic forest

The open vegetation corridor of South America is a region dominated by savanna biomes. It contains forests, i.e. riverine forests, that may act as corridors for rainforest specialist between the open vegetation corridor and its neighboring biomes, the Amazonian and Atlantic forests. A prediction for this scenario is that populations of rainforest specialists in the open vegetation corridor and in the forested biomes show no significant genetic divergence. We addressed this hypothesis by studying plumage and genetic variation of the Planalto woodcreeper Dendrocolaptes platyrostris Spix (1824) (Aves: Furnariidae), a forest specialist that occurs in both the open habitat and in the Atlantic forest. Our questions are: (1) is there any evidence of genetic continuity between populations of the open habitat and the Atlantic forest? and (2) is plumage variation congruent with patterns of neutral genetic structure or with ecological factors related to habitat type? We used cytochrome b and mtDNA control region sequences to show that D. platyrostris is monophyletic and that presents substantial intraspecific differentiation. We found two areas of plumage stability: one associated to Cerrado and the other associated to southern Atlantic Forest. Multiple Mantel tests showed that most of the plumage variation followed transition of habitats but not phylogeographic gaps, suggesting that selection may be related to the evolution of the species plumage. Results were not compatible with the idea that forest specialist in the open vegetation corridor and in the Atlantic forest are linked at the population level because birds from each region were not part of the same genetic unit. Divergence in the presence of gene flow across the ecotone between both regions might explain our results. Also, our findings indicate that the southern Atlantic forest may have been significantly affected by Pleistocene climatic alteration, but that those events did not cause local extinction of most taxa, as occurred in other regions of the globe where forests were significantly affected by global glaciations. Finally, our results neither supported subspecies nor regions of stability of plumage as species.

opencc-zeroDec 2013View details →

Data from: Vegetation patterns in small boreal streams relate to ice and winter floods

1. In-stream and riparian vegetation is species-rich, productive and dynamic. Its patterns in small boreal streams are largely driven by seasonal flow regimes. Traditionally, flow-related processes during the growing season, particularly the spring flood, have been seen as the most important, whereas vegetation has been viewed as being dormant and 'less affected' during winter. 2. Riparian and in-stream vegetation was inventoried during the summers 2011‒2013 in eight reaches of northern Swedish streams. Along each reach the ice formation was surveyed during winter by visual inspections and with permanently placed cameras. We then evaluated the potential effects of ice regimes and winter flooding on riparian and in-stream vegetation during 3 years by relating the abundance of winter floods caused by anchor-ice to the cover, composition and biomass of vegetation. 3. We found that the numbers of winter floods were higher along reaches with anchor-ice formation than in reaches without. We also found that species diversity of riparian vegetation was higher in the reaches with anchor-ice. This resulted from a lower cover of riparian dwarf shrubs and a higher cover of graminoids and forbs along reaches with anchor-ice. We also found a lower cover of in-stream algae but a higher cover of bryophytes in anchor-ice reaches. These patterns were consistent throughout the study period although there were interannual differences in temperature, water levels and ice cover. 4. During our study period, we encountered an average of 20 shifts per winter between freezing and thawing, while there was an average of 10 shifts per winter during 1960‒1990. This indicates a warming climate in high latitudes. Higher temperatures and more shifts between freezing and thawing may initially increase ice dynamics. However, with further increases in mean temperature ice production should eventually decrease. 5. Synthesis. Ice and winter floods caused by anchor-ice appear to be important disturbance agents that allow less competitive species to establish along small boreal streams. If ice dynamics is reduced, the composition and production of riparian and in-stream vegetation may be changed, with possible consequences for the entire stream ecosystem.

opencc-zeroDec 2016View details →

Data from: Vegetation recovery in tidal marshes reveals critical slowing down under increased inundation

A declining rate of recovery following disturbance has been proposed as an important early warning for impending tipping points in complex systems. Despite extensive theoretical and laboratory studies, this 'critical slowing down' remains largely untested in the complex settings of real-world ecosystems. Here, we provide both observational and experimental support of critical slowing down along natural stress gradients in tidal marsh ecosystems. Time series of aerial images of European marsh development reveal a consistent lengthening of recovery time as inundation stress increases. We corroborate this finding with transplantation experiments in European and North American tidal marshes. In particular, our results emphasize the power of direct observational or experimental measures of recovery over indirect statistical signatures, such as spatial variance or autocorrelation. Our results indicate that the phenomenon of critical slowing down can provide a powerful tool to probe the resilience of natural ecosystems.

Data from: Herbivory and competition of Tibetan steppe vegetation in winter pasture: effects of livestock exclosure and plateau pika reduction

Rangeland degradation has been identified as a serious concern in alpine regions of western China on the Qinghai-Tibetan plateau (QTP). Numerous government-sponsored programs have been initiated, including many that feature long-term grazing prohibitions and some that call for eliminating pastoralism altogether. As well, government programs have long favored eliminating plateau pikas (Ochotona curzoniae), assumed to contribute to degraded conditions. However, vegetation on the QTP evolved in the presence of herbivory, suggesting that deleterious effects from grazing are, to some extent, compensated for by reduced plant-plant competition. We examined the dynamics of common steppe ecosystem species as well as physical indicators of rangeland stress by excluding livestock and reducing pika abundance on experimental plots, and following responses for 4 years. We established 12 fenced livestock exclosures within pastures grazed during winter by local pastoralists, and removed pikas on half of these. We established paired, permanent vegetation plots within and outside exclosures and measured indices of erosion and biomass of common plant species. We observed modest restoration of physical site conditions (reduced bare soil, erosion, greater vegetation cover) with both livestock exclusion and pika reduction. As expected in areas protected from grazing, we observed a reduction in annual productivity of plant species avoided by livestock and assumed to compete poorly when protected from grazing. Contrary to expectation, we observed similar reductions in annual productivity among palatable, perennial graminoids under livestock exclusion. The dominant grass, Stipa purpurea, displayed evidence of density-dependent growth, suggesting that intra-specific competition exerted a regulatory effect on annual production in the absence of grazing. Complete grazing bans on winter pastures in steppe habitats on the QTP may assist in the recovery of highly eroded pastures, but may not increase annual vegetative production.

Data from: Chronic anthropogenic disturbance drives the biological impoverishment of the Brazilian Caatinga vegetation

1. In addition to acute transformations of ecosystems caused by deforestation, old-growth forests worldwide are being increasingly altered by low-intensity but chronic human disturbance. Overgrazing and the continuous extraction of forest products are important drivers of chronic disturbance, which can lead to the gradual local extinction of species and the alteration of vegetation structure. 2. We tested this hypothesis in the Brazilian Caatinga vegetation, one of the most species-rich and populated semi-arid regions of the world. Using a multi-model averaging approach we examined the impact of five recognized indicators of chronic disturbance (i.e. proximity to urban centre, houses, roads, density of people and livestock) on the diversity, abundance and evenness of 30 woody plant communities. We separately tested the response of seedlings, saplings, and adults to identify the ontogenetic stages that are most susceptible to chronic disturbance. 3. We recorded over 11 000 individuals belonging to 51 plant species. As expected, most indicators of chronic disturbance were negatively related to species diversity and stem abundance, with a variable effect on community evenness. The density of people and livestock were the main factors driving changes in plant communities, with a stronger negative impact on seedling and sapling diversities. Species composition also varied significantly with disturbance indicators, irrespective of ontogeny. 4. Our results show the potential negative impact that chronic disturbance can have on Caatinga plant assemblages and highlight the fact that disturbance resulting from an extractivism-based and subsistence economy are probably driving old-growth forest stands towards shrub-dominated secondary stands. 5. Synthesis and applications. These findings indicate that chronic disturbance should not continue to be neglected and we argue for (1) research and rural programs able to support better practices in terms of land use and sustainable exploitation of forest resources, (2) improved governance and law enforcement to shift extractivism towards sustainable standards, and (3) expanding the coverage and effective implementation of strictly protected areas.

opencc-zeroDec 2013View details →

Data from: Climate change will increase savannas at the expense of forests and treeless vegetation in tropical and subtropical Americas

1. Transition areas between biomes are particularly sensitive to environmental changes. Our understanding of the impacts of ongoing climate change on terrestrial ecosystems has significantly increased during the last years. However, it is largely unknown how climatic change will affect transitions among major vegetation types. 2. We modelled the distribution of three alternative states (forest, savanna and treeless areas) in the tropical and subtropical Americas by means of climate-niche modelling. We studied how such distribution will change by the year 2070 by using 17 downscaled and calibrated global climate models from the Coupled Model Intercomparison Project Phase 5 and the latest scenarios provided by the 5th Assessment Report of the IPCC. 3. Our results support the savannization of the tropical and subtropical Americas because of climate change, with an increase in savannas mainly at the expense of forests. 4. Our models predict an important geographical shift in the current distribution of transition areas between forest and savannas, which is much less pronounced in the case of those between savannas and treeless areas. Largest shifts, up to 600 km northward, are predicted in the forest–savanna transitions located in the eastern Amazon. 5. Our findings indicate that climate change will promote a shift towards more unstable states: the extent of the transition areas will notably increase, and largely stable forest areas are predicted to shrink dramatically. 6. Synthesis. Our work explores dimensions of the impact of climate change on biomes that have received little attention so far. Our results indicate that climate change will not only affect the extent of savanna, forest and treeless areas in the tropical and subtropical Americas, but also will: (i) promote a significant geographical shift and an increase of the extent of transition areas between biomes and (ii) decrease the stability of the equilibrium between forest, savanna and treeless areas, yielding a more unpredictable system.

Data from: Predicting bird phenology from space: satellite-derived vegetation green-up signal uncovers spatial variation in phenological synchrony between birds and their environment

Population-level studies of how tit species (Parus spp.) track the changing phenology of their caterpillar food source have provided a model system allowing inference into how populations can adjust to changing climates, but are often limited because they implicitly assume all individuals experience similar environments. Ecologists are increasingly using satellite-derived data to quantify aspects of animals' environments, but so far studies examining phenology have generally done so at large spatial scales. Considering the scale at which individuals experience their environment is likely to be key if we are to understand the ecological and evolutionary processes acting on reproductive phenology within populations. Here, we use time series of satellite images, with a resolution of 240 m, to quantify spatial variation in vegetation green-up for a 385-ha mixed-deciduous woodland. Using data spanning 13 years, we demonstrate that annual population-level measures of the timing of peak abundance of winter moth larvae (Operophtera brumata) and the timing of egg laying in great tits (Parus major) and blue tits (Cyanistes caeruleus) is related to satellite-derived spring vegetation phenology. We go on to show that timing of local vegetation green-up significantly explained individual differences in tit reproductive phenology within the population, and that the degree of synchrony between bird and vegetation phenology showed marked spatial variation across the woodland. Areas of high oak tree (Quercus robur) and hazel (Corylus avellana) density showed the strongest match between remote-sensed vegetation phenology and reproductive phenology in both species. Marked within-population variation in the extent to which phenology of different trophic levels match suggests that more attention should be given to small-scale processes when exploring the causes and consequences of phenological matching. We discuss how use of remotely sensed data to study within-population variation could broaden the scale and scope of studies exploring phenological synchrony between organisms and their environment.