Effets des pratiques sylvicoles sur les traits fonctionnels des communautés végétales de friches arbustives

Différents modes de réhabilitation forestière des sites agricoles abandonnés peuvent affecter la diversité végétale des sites. L’analyse des traits fonctionnels des plantes pourrait permettre de révéler l’effet des différentes pratiques sylvicoles suggérées. L’étude porte sur deux communautés de friches arbustives ayant reçu la plantation de trois espèces d’arbres feuillus. La préparation des sites par un débroussaillement total ou par bande, combinés ou non d’herbicide offre l’occasion de mesurer l’effet de ces traitements sur la distribution des traits fonctionnels des communautés végétales après onze ans. Les résultats d’une analyse du 4e coin montrent un effet des traitements sur les traits fonctionnels des communautés et ce, davantage sur le site où la transmission de la lumière est supérieure. Un débroussaillement par bande permet un recul successionnel moins grand que total, avec la présence de plusieurs traits fonctionnels liés aux espèces de fin de succession tels que les phanérophytes et les espèces à semences de plus grande taille Un débroussaillement total résulte plutôt en une présence accrue des espèces exogènes et des intolérantes à la lumière. L’application d’herbicide influence peu la distribution des traits mais augmente la croissance du noyer noir lors de débroussaillement total et dans une moindre mesure lors de débroussaillement en bande. Le peu de différenciation significative de survie et de croissance en hauteur des arbres entre les traitements permet de proposer un débroussaillement par bande plutôt que total, afin de diminuer le recul successionnel, tout en nécessitant un moins grand recours à l’herbicide.

Do the Golden-winged Warbler and Blue-winged Warbler Exhibit Species-specific Differences in their Breeding Habitat Use?

We compared habitat features of Golden-winged Warbler (Vermivora chrysoptera) territories in the presence and absence of the Blue-winged Warbler (V. cyanoptera) on reclaimed coal mines in southeastern Kentucky, USA. Our objective was to determine whether there are species specific differences in habitat that can be manipulated to encourage population persistence of the Golden-winged Warbler. When compared with Blue-winged Warblers, Golden-winged Warblers established territories at higher elevations and with greater percentages of grass and canopy cover. Mean territory size (minimum convex polygon) was 1.3 ha (se = 0.1) for Golden-winged Warbler in absence of Blue-winged Warbler, 1.7 ha (se = 0.3) for Golden-winged Warbler coexisting with Blue-winged Warbler, and 2.1 ha (se = 0.3) for Blue-winged Warbler. Territory overlap occurred within and between species (18 of n = 73 territories, 24.7%). All Golden-winged and Blue-winged Warblers established territories that included an edge between reclaimed mine land and mature forest, as opposed to establishing territories in open grassland/shrubland habitat. The mean distance territories extended from a forest edge was 28.0 m (se = 3.8) for Golden-winged Warbler in absence of Blue-winged Warbler, 44.7 m (se = 5.7) for Golden-winged Warbler coexisting with Blue-winged Warbler, and 33.1 m (se = 6.1) for Blue-winged Warbler. Neither territory size nor distances to forest edges differed significantly between Golden-winged Warbler in presence or absence of Blue-winged Warbler. According to Monte Carlo analyses, orchardgrass (Dactylis glomerata), green ash (Fraxinus pennsylvanica) seedlings and saplings, and black locust (Robinia pseudoacacia) saplings were indicative of sites with only Golden-winged Warblers. Sericea lespedeza, goldenrod (Solidago spp.), clematis vine (Clematis spp.), and blackberry (Rubus spp.) were indicative of sites where both species occurred. Our findings complement recent genetic studies and add another factor for examining Golden-winged Warbler population decline. Further, information from our study will aid land managers in manipulating habitat for the Golden-winged Warbler.

Variables associated with nest survival of Golden-winged Warblers (Vermivora chrysoptera) among vegetation communities commonly used for nesting

Among shrubland- and young forest-nesting bird species in North America, Golden-winged Warblers (Vermivora chrysoptera) are one of the most rapidly declining partly because of limited nesting habitat. Creation and management of high quality vegetation communities used for nesting are needed to reduce declines. Thus, we examined whether common characteristics could be managed across much of the Golden-winged Warbler’s breeding range to increase daily survival rate (DSR) of nests. We monitored 388 nests on 62 sites throughout Minnesota, Wisconsin, New York, North Carolina, Pennsylvania, Tennessee, and West Virginia. We evaluated competing DSR models in spatial-temporal (dominant vegetation type, population segment, state, and year), intraseasonal (nest stage and time-within-season), and vegetation model suites. The best-supported DSR models among the three model suites suggested potential associations between daily survival rate of nests and state, time-within-season, percent grass and Rubus cover within 1 m of the nest, and distance to later successional forest edge. Overall, grass cover (negative association with DSR above 50%) and Rubus cover (DSR lowest at about 30%) within 1 m of the nest and distance to later successional forest edge (negative association with DSR) may represent common management targets across our states for increasing Golden-winged Warbler DSR, particularly in the Appalachian Mountains population segment. Context-specific adjustments to management strategies, such as in wetlands or areas of overlap with Blue-winged Warblers (Vermivora cyanoptera), may be necessary to increase DSR for Golden-winged Warblers.

The effects of cattle grazing on plant-pollinator communities in a fragmented Mediterranean landscape

The main aims of this study were to assess grazing impacts on bee communities in fragmented mediterranean shrubland (phrygana) and woodland habitats that also experience frequent wildfires, and to explain the mechanisms by which these impacts occur. Fieldwork was carried out in 1999 and 2000 on Mount Carmel, in northern Israel, a known hot-spot for bee diversity. Habitats with a range of post-burn ages and varying intensities of cattle grazing were surveyed by transect recording, grazing levels, and the diversity and abundance of both flowers and bees were measured. The species richness of both bees and flowers were highest at moderate to high grazing intensities, and path-analysis indicated that the effects of both grazing and fire on bee diversity were mediated mainly through changes in flower diversity, herb flowers being more important than shrubs. The abundance of bees increased with intensified grazing pressure even at the highest levels surveyed. Surprisingly though, changes in bee abundance at high grazing levels were not caused directly by changes in flower cover. The variation in bee abundance may have been due to higher numbers of solitary bees from the family Halictidae in grazed sites, where compacted ground (nesting resource) and composites (forage resource) were abundant. The effects of grazing on plants were clearest in the intermediate-aged sites, where cattle inhibited the growth of some of the dominant shrubs, creating or maintaining more open patches where light-demanding herbs could grow, thus allowing a diverse flora to develop. Overall, bee communities benefit from a relatively high level of grazing in phrygana. Although bee and flower diversity may decrease under very heavy grazing, the present levels of grazing on Mount Carmel appear to have only beneficial effects on the bee community.

Land-atmosphere energy exchange in Arctic tundra and boreal forest: available data and feedbacks to climate

This paper summarizes and analyses available data on the surface energy balance of Arctic tundra and boreal forest. The complex interactions between ecosystems and their surface energy balance are also examined, including climatically induced shifts in ecosystem type that might amplify or reduce the effects of potential climatic change. High latitudes are characterized by large annual changes in solar input. Albedo decreases strongly from winter, when the surface is snow-covered, to summer, especially in nonforested regions such as Arctic tundra and boreal wetlands. Evapotranspiration (QE) of high-latitude ecosystems is less than from a freely evaporating surface and decreases late in the season, when soil moisture declines, indicating stomatal control over QE, particularly in evergreen forests. Evergreen conifer forests have a canopy conductance half that of deciduous forests and consequently lower QE and higher sensible heat flux (QH). There is a broad overlap in energy partitioning between Arctic and boreal ecosystems, although Arctic ecosystems and light taiga generally have higher ground heat flux because there is less leaf and stem area to shade the ground surface, and the thermal gradient from the surface to permafrost is steeper. Permafrost creates a strong heat sink in summer that reduces surface temperature and therefore heat flux to the atmosphere. Loss of permafrost would therefore amplify climatic warming. If warming caused an increase in productivity and leaf area, or fire caused a shift from evergreen to deciduous forest, this would increase QE and reduce QH. Potential future shifts in vegetation would have varying climate feedbacks, with largest effects caused by shifts from boreal conifer to shrubland or deciduous forest (or vice versa) and from Arctic coastal to wet tundra. An increase of logging activity in the boreal forests appears to reduce QE by roughly 50% with little change in QH, while the ground heat flux is strongly enhanced.

Pollen-based biome reconstructions for Latin America at 0, 6000 and 18000 radiocarbon years

The biomisation method is used to reconstruct Latin American vegetation at 6000±500 and 18 000±1000 radiocarbon years before present (14C yr BP) from pollen data. Tests using modern pollen data from 381 samples derived from 287 locations broadly reproduce potential natural vegetation. The strong temperature gradient associated with the Andes is recorded by a transition from high altitude cool grass/shrubland and cool mixed forest to mid-altitude cool temperate rain forest, to tropical dry, seasonal and rain forest at low altitudes. Reconstructed biomes from a number of sites do not match the potential vegetation due to local factors such as human impact, methodological artefacts and mechanisms of pollen representivity of the parent vegetation.

Mid-late Holocene environmental change and human activities in the northern Apennines, Italy

Radiocarbon-dated palaeoecological records from the upland zone of the northern Apennines spanning the Mid-Late Holocene (last 7000 years) have been evaluated using established criteria for detecting anthropogenic impact on the landscape and environment. The integrated palaeoecological records across the study area collectively indicate human interference with natural vegetation succession and landscape modification from at least the Middle Neolithic. These activities resulted in the progressive decline of Abies, Ulmus, Fraxinus and Tilia, and the spread of Fagus, from ∼7000 cal BP, accompanied at various times by evidence for biomass burning, soil erosion, the expansion of shrubland and herbaceous taxa, and the possible cultivation of Olea, Juglans and Castanea. Comparison of these data with the archaeological scheme for the region, and the climate history of the central-western Mediterranean, has revealed that the palaeoecological records broadly support the archaeological evidence, but suggest that several key vegetation changes also coincide with important periods of climate change, especially at ∼7800–5000 cal BP.

Palaeovegetation in China during the late Quaternary: Biome reconstructions based on a global scheme of plant functional types

Two previous reconstructions of palaeovegetation across the whole of China were performed using a simple classification of plant functional types (PFTs). Now a more explicit, global PFT classification scheme has been developed, and a substantial number of additional pollen records have become available. Here we apply the global scheme of PFTs to a comprehensive set of pollen records available from China to test the applicability of the global scheme of PFTs in China, and to obtain a well-founded reconstruction of changing palaeovegetation patterns. A total of 806 pollen surface samples, 188 mid-Holocene (MH, 6000 14C yr BP) and 50 last glacial maximum (LGM, 18,000 14C yr BP) pollen records were used to reconstruct vegetation patterns in China, based on a new global classification system of PFTs and a standard numerical technique for biome assignment (biomization). The biome reconstruction based on pollen surface samples showed convincing agreement with present potential natural vegetation. Coherent patterns of change in biome distribution between MH, LGM and present are observed. In the MH, cold and cool-temperate evergreen needleleaf forests and mixed forests, temperate deciduous broadleaf forest, and warm-temperate evergreen broadleaf and mixed forest in eastern China were shifted northward by 200–500 km. Cold-deciduous forest in northeastern China was replaced by cold evergreen needleleaf forest while in central northern China, cold-deciduous forest was present at some sites now occupied by temperate grassland and desert. The forest–grassland boundary was 200–300 km west of its present position. Temperate xerophytic shrubland, temperate grassland and desert covered a large area on the Tibetan Plateau, but the area of tundra was reduced. Treeline was 300–500 m higher than present in Tibet. These changes imply generally warmer winters, longer growing seasons and more precipitation during the MH. Westward shifts of the forest–shrubland–grassland and grassland–desert boundaries imply greater moisture availability in the MH, consistent with a stronger summer monsoon. During the LGM, in contrast, cold-deciduous forest, cool-temperate evergreen needleleaf forest, cool mixed forests, warm-temperate evergreen broadleaf and mixed forest in eastern China were displaced to the south by 300–1000 km, while temperate deciduous broadleaf forest, pure warm-temperate evergreen forest, tropical semi-evergreen and evergreen broadleaf forests were restricted or absent from the mainland of southern China, implying colder winters than present. Strong shifts of temperate xerophytic shrubland, temperate grassland and desert to the south and east in northern and western China and on the Tibetan Plateau imply drier conditions than present.

Pollen-based reconstructions of biome distributions for Australia, Southeast Asia and the Pacific (SEAPAC region) at 0,6000 and 18,000 14C yr B.P.

Aim  This paper documents reconstructions of the vegetation patterns in Australia, Southeast Asia and the Pacific (SEAPAC region) in the mid-Holocene and at the last glacial maximum (LGM). Methods  Vegetation patterns were reconstructed from pollen data using an objective biomization scheme based on plant functional types. The biomization scheme was first tested using 535 modern pollen samples from 377 sites, and then applied unchanged to fossil pollen samples dating to 6000 ± 500 or 18,000 ± 1000 14C yr bp. Results  1. Tests using surface pollen sample sites showed that the biomization scheme is capable of reproducing the modern broad-scale patterns of vegetation distribution. The north–south gradient in temperature, reflected in transitions from cool evergreen needleleaf forest in the extreme south through temperate rain forest or wet sclerophyll forest (WSFW) and into tropical forests, is well reconstructed. The transitions from xerophytic through sclerophyll woodlands and open forests to closed-canopy forests, which reflect the gradient in plant available moisture from the continental interior towards the coast, are reconstructed with less geographical precision but nevertheless the broad-scale pattern emerges. 2. Differences between the modern and mid-Holocene vegetation patterns in mainland Australia are comparatively small and reflect changes in moisture availability rather than temperature. In south-eastern Australia some sites show a shift towards more moisture-stressed vegetation in the mid-Holocene with xerophytic woods/scrub and temperate sclerophyll woodland and shrubland at sites characterized today by WSFW or warm-temperate rain forest (WTRF). However, sites in the Snowy Mountains, on the Southern Tablelands and east of the Great Dividing Range have more moisture-demanding vegetation in the mid-Holocene than today. South-western Australia was slightly drier than today. The single site in north-western Australia also shows conditions drier than today in the mid-Holocene. Changes in the tropics are also comparatively small, but the presence of WTRF and tropical deciduous broadleaf forest and woodland in the mid-Holocene, in sites occupied today by cool-temperate rain forest, indicate warmer conditions. 3. Expansion of xerophytic vegetation in the south and tropical deciduous broadleaf forest and woodland in the north indicate drier conditions across mainland Australia at the LGM. None of these changes are informative about the degree of cooling. However the evidence from the tropics, showing lowering of the treeline and forest belts, indicates that conditions were between 1 and 9 °C (depending on elevation) colder. The encroachment of tropical deciduous broadleaf forest and woodland into lowland evergreen broadleaf forest implies greater aridity. Main conclusions  This study provides the first continental-scale reconstruction of mid-Holocene and LGM vegetation patterns from Australia, Southeast Asia and the Pacific (SEAPAC region) using an objective biomization scheme. These data will provide a benchmark for evaluation of palaeoclimate simulations within the framework of the Palaeoclimate Modelling Intercomparison Project.

Land use and climate change impacts on soil organic carbon stocks in semi-arid Spain

Purpose The sensitivity of soil organic carbon to global change drivers, according to the depth profile, is receiving increasing attention because of its importance in the global carbon cycle and its potential feedback to climate change. A better knowledge of the vertical distribution of SOC and its controlling factors—the aim of this study—will help scientists predict the consequences of global change. Materials and methods The study area was the Murcia Province (S.E. Spain) under semiarid Mediterranean conditions. The database used consists of 312 soil profiles collected in a systematic grid, each 12 km2 covering a total area of 11,004 km2. Statistical analysis to study the relationships between SOC concentration and control factors in different soil use scenarios was conducted at fixed depths of 0–20, 20–40, 40–60, and 60–100 cm. Results and discussion SOC concentration in the top 40 cm ranged between 6.1 and 31.5 g kg−1, with significant differences according to land use, soil type and lithology, while below this depth, no differences were observed (SOC concentration 2.1–6.8 g kg−1). The ANOVA showed that land use was the most important factor controlling SOC concentration in the 0–40 cm depth. Significant differences were found in the relative importance of environmental and textural factors according to land use and soil depth. In forestland, mean annual precipitation and texture were the main predictors of SOC, while in cropland and shrubland, the main predictors were mean annual temperature and lithology. Total SOC stored in the top 1 m in the region was about 79 Tg with a low mean density of 7.18 kg Cm−3. The vertical distribution of SOC was shallower in forestland and deeper in cropland. A reduction in rainfall would lead to SOC decrease in forestland and shrubland, and an increase of mean annual temperature would adversely affect SOC in croplands and shrubland. With increasing depth, the relative importance of climatic factors decreases and texture becomes more important in controlling SOC in all land uses. Conclusions Due to climate change, impacts will be much greater in surface SOC, the strategies for C sequestration should be focused on subsoil sequestration, which was hindered in forestland due to bedrock limitations to soil depth. In these conditions, sequestration in cropland through appropriate management practices is recommended.

Late Würm and Early-Middle Holocene environmental change and human activities in the Northern Apennines, Italy

An enhanced radiocarbon-dated pollen-stratigraphical record from Rovegno (Liguria, 812m asl), northern Apennines (Italy), has provided a history of vegetation succession from before 17,056-16,621 cal yrs BP to the present day. The record indicates the transition from open Pinus woodland to Artemisia dominated grassland, and finally Juniperus shrubland during the late Würm. This is succeeded by Betula and Pinus woodland, and the expansion of thermophilous taxa, namely Abies, Corylus and Quercus during the Late Würm Lateglacial Interstadial. The ‘Younger Dryas’ is possibly represented by an increase in Betula and Artemisia. During the early Holocene, mixed coniferous-deciduous woodland is dominant with Quercus, as well as Abies, Fagus and Corylus. Fagus woodland becomes established sometime before 6488-6318 cal yrs BP, but never becomes a major component of the woodland cover. Throughout the middle Holocene, Abies woodland fl uctuates, with marked declines between 6488-6318 cal yrs BP and 5287-4835 cal yrs BP, although the cause remains uncertain. Finally, the paper evaluates the application of non-pollen palynomorphs, especially coprophilous fungal spores, at Prato Spilla ‘A’ (Emilia Romagna) and concludes that greater caution must be used when interpreting middle Holocene human activity based upon pollen data alone

Terrestrial biosphere changes over the last 120 kyr

A new global synthesis and biomization of long (> 40 kyr) pollen-data records is presented and used with sim- ulations from the HadCM3 and FAMOUS climate models and the BIOME4 vegetation model to analyse the dynamics of the global terrestrial biosphere and carbon storage over the last glacial–interglacial cycle. Simulated biome distribu- tions using BIOME4 driven by HadCM3 and FAMOUS at the global scale over time generally agree well with those in- ferred from pollen data. Global average areas of grassland and dry shrubland, desert, and tundra biomes show large- scale increases during the Last Glacial Maximum, between ca. 64 and 74 ka BP and cool substages of Marine Isotope Stage 5, at the expense of the tropical forest, warm-temperate forest, and temperate forest biomes. These changes are re- flected in BIOME4 simulations of global net primary pro- ductivity, showing good agreement between the two models. Such changes are likely to affect terrestrial carbon storage, which in turn influences the stable carbon isotopic composi- tion of seawater as terrestrial carbon is depleted in 13C.

Validação de bioindicadores de recuperação de áreas degradadas por minerações de bauxita em Poços de Caldas, MG

Pós-graduação em Geociências e Meio Ambiente - IGCE

Inventário da araneofauna (Arachnida, Araneae) do Parque Nacional de Sete Cidades, Piauí, Brasil

Foi realizado o inventário da araneofauna do Parque Nacional de Sete Cidades (municípios de Brasileira e Piracuruca, Piauí), utilizando amostragem padronizada para permitir comparações entre as assembléias de aranhas de seis fitofisionomias existentes na área de estudo e obter estimativas de riqueza. Utilizaram-se dados oriundos amostragem com armadilhas de queda (PTF), extratores de Winkler (WIN), guarda-chuva entomológico (GCE), rede de varredura (RV) e coletas manuais noturnas (MN), totalizando 1386 amostras; além do exame de todos os demais espécimes já coletados na área de estudo (n=1166). As análises estatísticas foram realizadas utilizando-se os dados obtidos com GCE, RV e MN. Ao todo, foram coletados 14.890 indivíduos (4491 adultos), segregados em 364 espécies. Destas, 72 foram determinadas a nível específico, 62 são novos registros para a área de estudo, 2 são novos registros para o Brasil e 48 foram reconhecidas como espécies novas por especialistas. A aplicação dos métodos GCE, RV e MN resultou em 11.085 aranhas, pertencentes a 303 espécies. As estimativas de riqueza variaram entre 355 (Bootstrap) e 467 (Jack 2). Entretanto o estimador que apresentou maior tendência a atingir a assíntota foi Chao 2 (403 spp.). A riqueza observada foi maior na mata seca semi-decídua (131 spp.), seguida pela mata de galeria (104 spp.), campo limpo (102 spp.), cerradão (91 spp.), cerrado típico (88 spp.) e cerrado rupestre (78 spp.). A eficiência dos métodos de coleta exibiu variação de acordo com a fitofisionomia onde o método foi aplicado, destacando-se a elevada eficiência da rede de varredura em áreas abertas. A composição de espécies variou entre as fitofisionomias e pode ser, em parte, explicada pela complexidade estrutural das áreas em questão. Os resultados das análises de agrupamento sugerem que em condições de dominância elevada, estes testes sejam realizados com coeficientes que utilizem dados qualitativos, a fim de anular-se o efeito da escolha do coeficiente e/ou a necessidade de transformação dos dados. De maneira geral, a araneofauna do Parque Nacional de Sete Cidades não segue padrões de agrupamento como sugerido para as análises botânicas, em que fitofisionomias campestre, savânicas e florestais são agrupadas.

A new ant species of Oxyepoecus (Hymenoptera: Formicidae: Myrmicinae), with the description of Oxyepoecus browni gyne and new records for the genus

We describe a new species of Oxyepoecus Santschi, 1926, Oxyepoecus regularis sp. nov., based on workers and a gyne collected in "Caatinga Arbórea" (Arboreal Shrubland) in Milagres and "Mata Seca" (Dry Forest) in Boa Vista do Tupim, both in the state of Bahia, Brazil. The gyne of Oxyepoecus browni Albuquerque & Brandão, 2004, collected in the same leaf litter ant survey, is also described. In addition, we present new records for Oxyepoecus species in Northeastern Brazil.