Tall Shrubland Research Articles

Vegetation Monitoring and Post-Fire Recovery: A Case Study in the Centre Inland of Portugal

Wildfires are a major environmental issue that have an impact on land degradation. Remote sensing spectral indices provide valuable information for short-term mitigation and rehabilitation after wildfires. A study area in the Centre inland of Portugal occupied with Maritime pine and Eucalypts forests and affected by wildfires in 2003, 2017 and 2020 was used. The aims of the study were twofold: (1) to compute the Normalized Difference Vegetation Index (NDVI) and with forest inventory data derivate a Maritime pine production model, differentiate evergreen coniferous forests (e.g., Maritime pine), evergreen broadleaved forests (e.g., Eucalypts), and shrubland, and monitor vegetation and its post-fire recovery; and (2) to compute the Normalized Burn Ratio (NBR) difference between pre-fire and post-fire dates for burn severity levels assessment. The plots of a previous forest inventory were used to follow the NDVI values in 2007 and from 2020 to 2022. An aerial coverage in 2007 and the Sentinel-2 imagery in 2020–2022 were used. Linear models fitted maritime pine production with the transformed NDVI by age, showing a fitting efficiency of 60%. The stratification of cover types by stand development stage and fire occurrence was possible using the NDVI time curve, which also showed the impact of fire and of low precipitation. Cover types were ranked by decreasing NDVI values as follows: mature Eucalypts plantations, young Maritime pine regeneration, mature Maritime pine, young Eucalypts plantations, Strawberry tree shrubland, Eucalypts plantations post-fire, Maritime pine post-fire, tall shrubland, and short shrubland. Vegetation post-fire recovery was lower in higher burn severity level areas. Maritime pine areas have lost their natural regeneration capability due to the wildfires’ short cycles. Spectral indices were effective tools to differentiate cover types and assist in the evaluation of forest and shrubland conditions.

Influence of human activities, social and environmental variables on the behavior of guanacos in Southern Andean Precordillera (Argentina)

ABSTRACT Human disturbance, social interactions and habitat constraints usually influence the behavior of wild ungulates. Poaching and habitat degradation are threats to the guanaco, a native South-American herbivore adapted to arid environments. Flight and vigilance behaviors, and guanaco–observer distances, were seasonally surveyed in mountain Andean environments, inside a protected area and surroundings. Field surveys and GIS analyses estimated environmental variables. Linear mixed models estimated probability of the mentioned behaviors and distance based on predictions about influences of human disturbance, social interactions, environmental constraints, and their changes over time. Flight and vigilance behaviors and guanaco–observer distance were higher in less protected landscapes, and near urban sites. Flight probability and guanaco–observer distance decreased over the years, being this distance shorter within the protected area. Flight decreased in summer, while vigilance increased. Vigilance was higher in groups with young, and lower in larger groups. Flight and vigilance behaviors were lower in slopes and higher in tall shrublands. These results are in agreement with hypotheses of risk-allocation, learning habituation, fitness maximization, risk detection strategy and foraging hypothesis. Social and environmental influences on guanaco behavior will probably prevail over anthropogenic influences insofar as current efforts to discourage disruptive activities are maintained in these mountain environments.

Is livestock grazing a key factor for changing vegetation patterns in lime rich coastal dunes in the Netherlands?

In 1990, livestock grazing was introduced in Meijendel, a 1800 ha lime-rich coastal dune area, at a density of 0.06–0.07 LLU.ha-1.year−1 (1:12–18 ha) to counteract encroachment of tall grasses and shrubland on dune grassland and increase the bare sand area. Monitoring was based on four digital orthophotos (1975–1990–2001-2009) with a high spatial resolution (pixel size 25 × 25 cm). The changes were tested using Generalized Estimating Equations. Habitat changes occurred, but contradicting our hypothesis, there was no significant impact from the grazing on bare sand, grassland or shrubland within 11 and 19 years post livestock introduction. (1) After several decennia of decreasing bare sand, there was a significant increase between 2001 and 2009, irrespective of livestock presence. (2) The changes in grasslands and shrublands are independent of the livestock, but dependent on distance to the coast. (3) Bare sand and shrub cover determine the space left for the dune grasslands. It appears other factors than livestock grazing must have induced the changes. Changes in climate conditions and nitrogen load might have stimulated bare sand. An interaction with the end of Marram planting in 1990 cannot be concluded from available data. The disease-led reduction of rabbit grazing from the mid-1950s led to an expansion of the dominant shrub Hippophae rhamnoides. However, Hippophae shrubland typically regresses to grasslands on its collapse after 25–40 years. Tree species like Crataegus, Betula and Quercus will gradually dominate the landscape for far longer. Active removal of these indigenous species is necessary to prevent future loss of dune grasslands.

Seasonal and Long-Term Changes to Active-Layer Temperatures after Tall Shrubland Expansion and Succession in Arctic Tundra

Vegetation, active-layer soils, and snow cover regulate energy exchange between the atmosphere and permafrost. Therefore, interactions between changes to tundra vegetation and soil thermal regime will fundamentally affect permafrost in a warmer world. We recorded soil temperatures for approximately 1 year in a Siberian Low Arctic landscape with a known history of alder (Alnus) shrub expansion on disturbed microsites in patterned ground. We recorded near-surface soil temperatures and measured physical properties of soils and vegetation on sorted-circle microsites in four stages of shrubland development: (1) tundra lacking tall shrubs; (2) shrub colonization zones; (3) mature shrublands; and (4) paludified, long-established shrublands with thick soil organic layers. Summer soil temperatures declined with increasing shrub cover and soil organic thickness; shrub colonization suppressed cryoturbation, facilitating the development of continuous vegetation and a surface organic mat on circles. Compared to open tundra, mature shrubs cooled soils by up to 9 °C during summer, but warmed soils by greater than 10 °C in winter presumably because they developed highly insulative snowpacks. Paludified shrublands had the coldest summer active layers, but winter soil temperatures were much colder than mature shrublands and were similar to earlier stages. Our results indicate that although tall shrub establishment dramatically warms winter soils within decades, much of this warming is transient at paludification-prone sites because the buildup of wet peat favors cooling in winter and the stature and snow-trapping capacity of shrubs diminish over time. In the ecosystem we studied, shrub expansion has contrasting effects on active-layer temperatures both seasonally and over longer timescales due to successional processes.

Effects of biological legacies and herbivory on fuels and flammability traits: A long‐term experimental study of alternative stable states

Summary Ecological memory, often determined by the extent and type of retained biological legacies present following disturbance, may produce persistent landscape patterns. However, after fire, the persistence or switch to an alternative state may depend on the complex interplay of ecological memory (biological legacies) and potential effects of new external factors influencing the post‐fire environment. The current study assesses both the strength of ecological memory resulting from biological legacies of pre‐burn vegetation types as well as post‐fire effects of livestock. Following a severe fire in 1999, we set up a network of long‐term exclosures to examine the effects of legacies and cumulative herbivory by cattle on fuel types, amounts, distribution, flammability and microenvironmental conditions in two post‐fire communities representing alternative fire‐driven states: pyrophobic Nothofagus pumilio subalpine forests and pyrophytic Nothofagus antarctica tall shrublands in northwestern Patagonia, Argentina. Our results show that the retained post‐disturbance legacies of tall shrublands and subalpine forests largely determine fuel and flammability traits of the post‐fire plant communities 16 years after fire. The importance of biological legacies retained from the unburned plant communities was reflected by the substantially higher amounts of total fine fuel, greater vertical and horizontal fuel continuity and the higher temperatures reached during experimental tissue combustion at post‐fire shrubland compared to post‐fire forest sites. We show that herbivores may produce antagonistic effects on flammability by decreasing tissue ignitability, total fine fuel and litter depth, and disrupting the vertical and horizontal fine fuel continuity, therefore reducing the probability of fire propagation. However, cattle can increase ratios of dead to live fine fuels, reduce soil moisture, and inhibit tree height growth to canopy size, consequently impeding the development of a closed pyrophobic forest canopy. Synthesis. Our results support the hypothesis that biological legacies, most importantly the dominance by pyrophytic woody plants that resprout vigorously vs. the dominance by pyrophobic obligate seeders, favour fuel and flammability characteristics at the community level which reinforce the mechanisms maintaining pyrophytic shrublands vs. pyrophobic forests. Herbivory by introduced cattle can partially blur sharp pyrophobic/pyrophytic state boundaries by promoting the development of novel post‐fire transitional states.

Management of Biodiversity in Australia

The concept of holistic ecosystem research, termed community-physiology, has gradually developed over the last 150 years. The discipline of community-physiology investigates the physico-chemical processes that determine the structure, growth and biodiversity of plant communities (with associated consumers and decomposers), both above and below ground, in space and time, from the tropical north to the temperate south of Australia. These physico-chemical processes (aerodynamic fluxes — frictional, thermal, evaporative ± atmospheric salinity — plus available soil water and soil nutrients) need to be clearly enunciated and integrated in ‘ecosystem models’ in order to predict the effect of perturbations (such as Global Warming, nutrient pollution, invasive biota, fire, overgrazing, etc.) on Australian ecosystems. An increase in global temperatures of 2 o C is predicted to affect the development of the foliage covers of overstorey and understorey strata resulting in open-forests —> woodlands —> open-woodlands —> tall shrublands —> low shrublands throughout Australia. In order to conserve Australian biota for posterity, community-physiologists, ecosystem modelers and environmental impact ecologists must have a deep understanding of the eco-physiology of producers, consumers and decomposers that compose an ecosystem and how these organisms interact with the continually-changing physico-chemical processes in the atmosphere and soil, in space and time.

Regional and landscape-scale variability of Landsat-observed vegetation dynamics in northwest Siberian tundra

Widespread increases in Arctic tundra productivity have been documented for decades using coarse-scale satellite observations, but finer-scale observations indicate that changes have been very uneven, with a high degree of landscape- and regional-scale heterogeneity. Here we analyze time-series of the Normalized Difference Vegetation Index (NDVI) observed by Landsat (1984–2012), to assess landscape- and regional-scale variability of tundra vegetation dynamics in the northwest Siberian Low Arctic, a little-studied region with varied soils, landscape histories, and permafrost attributes. We also estimate spatio-temporal rates of land-cover change associated with expansion of tall alder (Alnus) shrublands, by integrating Landsat time-series with very-high-resolution imagery dating to the mid-1960s. We compiled Landsat time-series for eleven widely-distributed landscapes, and performed linear regression of NDVI values on a per-pixel basis. We found positive net NDVI trends (‘greening’) in nine of eleven landscapes. Net greening occurred in alder shrublands in all landscapes, and strong greening tended to correspond to shrublands that developed since the 1960s. Much of the spatial variability of greening within landscapes was linked to landscape physiography and permafrost attributes, while between-landscape variability largely corresponded to differences in surficial geology. We conclude that continued increases in tundra productivity in the region are likely in upland tundra landscapes with fine-textured, cryoturbated soils; these areas currently tend to support discontinuous vegetation cover, but are highly susceptible to rapid increases in vegetation cover, as well as land-cover changes associated with the development of tall shrublands.

Fuel vertical structure affects fire sustainability and behaviour of prescribed burning in Spartium junceum shrublands

Prescribed burning is increasingly recommended to control encroaching shrublands in the Mediterranean area. The aims of this paper are to analyze the fuel structural characteristics of Spartium junceum and how they influence fire behaviour during prescribed burning. Two winter–spring prescribed burns were conducted in 2009 and 2011. Fuel load and structure of S. junceum shrubs were assessed using the Cube Method, and shrub 3-D models were built using the FIRE PARADOX FUEL MANAGER software. Allometric equations to estimate S. junceum fuel load were developed. During burning, thermocouples measured temperature variations, which were then analyzed relative to fuel characteristics. Fuel load components and distribution were strictly related to shrub height; in tall shrubs, most of the fine fuel was more than 1.5 m aboveground. Due to fuel vertical discontinuity, not all shrubs were burned in the fires, but wind increased fire sustainment and fuel consumption. Maximum temperatures (over 800 °C) and residence times were positively related to fuel load. S. junceum tall shrublands represent high hazard formations due to their elevated fuel load, mostly in fine fuel fractions. Vertical discontinuity among fuel strata limits fire propagation in mild weather conditions. Winter–spring prescribed burning cannot eliminate S. junceum shrublands, but do create shrub cover discontinuity. As S. junceum has fire-adapted morphological traits, a single burn is insufficient to control it.

Synergistic influences of introduced herbivores and fire on vegetation change in northern Patagonia, Argentina

Question: We investigated how cattle and European hares, the two most widespread exotic herbivores in Patagonia, affect species composition, life-form composition and community structure during the first 6 years of vegetation recovery following severe burning of fire-resistant subalpine forests and fireprone tall shrublands. We asked how the effects of introduced herbivores on post-fire plant community attributes affect flammability of the vegetation. Location: Nahuel Huapi National Park, northwest Patagonia, Argentina Methods: We installed fenced plots to exclude livestock and European hares from severely burned subalpine forests of Nothofagus pumilio and adjacent tall shrublands of N. antarctica. The former is an obligate seed reproducer, whereas the latter and all other woody dominants of the shrubland vigorously resprout after burning. Results: Repeated measures ANOVA of annual measurements over the 20012006 period indicate that cattle and hare exclusion had significant but complex effects on the cover of graminoids, forbs, climber species and woody species in the two burned community types. Significant interactions between the effects of cattle and hares varied by plant life forms between the two communities, which implies that their synergistic effects are community dependent. Conclusions: Following severe fires, the combined effects of cattle and hares inhibit forest recovery and favour transition to shrublands dominated by resprouting woody species. This herbivore-induced trend in vegetation structure is consistent with the hypothesis that the effects of exotic herbivores at recently burned sites contribute to an increase in the overall flammability of the Patagonian landscape.

Phenomorphology and ecomorphological characters of Maytenus senegalensis L. Shrublands in the Iberian Peninsula: A comparison with other Mediterranean plant communities

This work sets out to establish ecomorphological and phenomorphological patterns in the constituent flora of an Iberian Maytenus senegalensis plant community in order to relate it with or separate it from other types of Mediterranean vegetation. This plant community contains tall shrubs, scrubs, palms and vines of a variety of families. Typical ecomorphological adaptations to the Mediterranean climate were observed in the community studied: an abundance of thorny species or species with tomentose leaves and photosynthetic stems, small leaves and a high presence of species with organs capable of post-fire regeneration. However, the community also showed hybrid characteristics between scrubland (predominantly malacophyllous leaves lasting 9 months on average and low biomass) and tall shrubland communities (predominance of phanerophytes up to 3 m in height, predominantly smooth bark, periodical reposition of leaves, mean lifespan of plants 25 years and mainly fleshy fruit). The community also presents an outstanding quantity of amphiphytes (29%). From a phenological point of view, the formation of buds in winter, flowering in spring, summer–autumn seed dispersal and leaf shedding in summer are typical of other Mediterranean communities, while fructification and growth lasting three seasons, as in the case of Maytenus shrubland, is not. The RVA phenophasic index (balance between reproductive and vegetative phenophases) with values of 0.4–2 shows an intermediate value between typical shrubland (0.3–1) and forest community (1–2) values. The APC index (period of phenophasic activity of the community) differentiates it from others, since it remains at 100% for seven months, three of which are winter months. Phenophasic patterns (overlapping, or not, of flower bud formation, flowering and growth) show how similar M. senegalensis shrubland is to forests because of the absence of phenophase pattern type A (characteristic in open-scrublands); in addition, we have detected a new pattern (type G), still regarded as exclusive to M. senegalensis. As regards the existence of coenomorphs (group of species with similar morpho-functional strategies), the studied community showed much greater diversity than other communities studied to date, with an Strategies Richness index (SRi) of 0.79 (11 groups covering the 14 species existing), pointing to the co-existence of a great variety of eco-phenomorphological strategies, each with a successful response to the same ecological conditions. Finally, some of the species in the community, e.g. Asparagus horridus, Chamaerops humilis and M. senegalensis, stand out because of their unique ecomorphological and phenological characteristics.

Effects of fire on the vegetation of a lowland heathland in North-western Italy

This study focuses on the effect of fire on lowland heathlands at the extreme southern edge of their European distribution (Vauda Nature Reserve, NW Italy). Forty-nine plots (50 m radius) were surveyed between 1999 and 2006. Each year, fire occurrences were recorded and per cent cover of four vegetation types (grassland, heath, low shrubland, and tall shrubland) was estimated in each plot. Vascular plant species richness was also recorded in 255, 1 m2 quadrats. After a fire, grassland vegetation expanded, but then declined rapidly as heath and shrubland recovered: 7 years after a fire, tall shrubland encroached on to more than 40% of the plots, and grassland declined from 50% to 20% cover. Between 1999 and 2006, Betula pendula shrubland greatly expanded, while grassland decreased over most of the Reserve, even where fire frequency was high. Tall shrubland had low plant diversity and was dominated by widespread species of lower conservation value. By contrast, early successional vegetation (grassland and low shrubland) had higher richness and more narrowly distributed species, indication that the development of tall shrubland causes significant species loss in the heathland. Italian lowland heathlands are characterized by high rates of shrubland encroachment that threatens both habitat and species diversity. Burning frequencies of once in 3–6 years seem appropriate in this habitat, but burning alone might not suffice without actions to increase herbivore grazing.

Relação entre o conhecimento local, atributos químicos e físicos do solo e uso das terras

O conhecimento dos agricultores sobre o uso das terras pode auxiliar no levantamento de solos. Este trabalho foi realizado na Fazenda Americana, Norte do Estado de Minas Gerais, com o objetivo de relacionar o conhecimento local do ambiente com os atributos químicos e físicos do solo e com o Sistema de Capacidade de Uso das Terras para fins de reforma agrária. Por meio do conhecimento local, foram identificados sete ambientes: baixada, vereda, chapada, tabuleiro, carrasco, tabuleiro misto e espigão. O conhecimento local sobre o uso das terras mostrou estreita relação com o Sistema de Capacidade de Uso, constituindo uma ferramenta para o parcelamento das terras para fins de reforma agrária.

Gibson Desert birds: responses to drought and plenty

There is little information on the response of birds to rainfall in the Australian arid zone. Counts of birds between 1988 and 1992 on paired 1-km2 quadrats representing major landform and vegetation types in the Gibson Desert revealed significant changes in species richness, community composition and abundance during increasing drought and following drought-breaking high rainfall. Species considered sedentary or resident (sedentary—resident), which were insectivorous or carnivorous, declined in abundance as the drought progressed, with at least one species, Rufous-crowned Emu-wren (Stipiturus ruficeps), apparently disappearing from the quadrats and not reappearing following heavy rainfall. Irruptive species, which were granivorous, nectarivorous or insectivorous, included species first recorded after heavy rainfall. Some species often considered to be nomadic, such as White-fronted (Phylidonyris albifrons) and Pied (Certhionyx variegatus) Honeyeaters, appeared to be both sedentary—resident and irruptive. Most species were recorded in more than one quadrat-pair; a few were recorded only in Mulga (Acacia aneura) tall shrubland—Common Bronzewing (Phaps chalcoptera), Boobook Owl (Ninox novaeseelandiae), Spotted Nightjar (Eurostopodus argus), Ground Cuckoo-Shrike (Coracina maxima) and Inland Thornbill (Acanthiza apicalis). Breeding activity showed a strong correlation with rainfall, with more breeding occurring in spring than the previous autumn.

Territory quality, survival and reproductive success in southern emu‐wrens Stipiturus malachurus

Multi‐factor analyses of territory quality in relation to fitness components of adults are rare, especially in non‐migratory species. I studied the influence of multiple attributes of territory quality (habitat type and the abundance of food and predators) on the reproductive success and survival of a threatened Australian passerine, the southern emu‐wren Stipiturus malachurus. The abundance of frequently‐selected prey types (lepidoptera, diptera, hemiptera and larvae) varied significantly across territories according to habitat type. Reproductive success (number of offspring fledged) was highest in territories containing a greater proportion of tall shrubland, which had the highest insect abundance of any habitat. Closed heathland and sedge/rushland also had high food abundance compared to other habitat types, but higher fledging success occurred only within closed heathland, possibly because predator density was lower in this habitat type. High snake density was associated with reduced adult survival during the breeding season and a lower probability of nest success. In sedge/rushland, any benefits of prey abundance may therefore be offset by a high density of predators. Emu‐wren age and size were unrelated to breeding output of pairs, suggesting that ecological factors may swamp effects of individual quality on emu‐wren fitness components. Preservation of tall shrubland and closed heathland habitats appear to be of key conservation priority for emu‐wrens.

LANDSCAPE INFLUENCES ON OCCURRENCE AND SPREAD OF WILDFIRES IN PATAGONIAN FORESTS AND SHRUBLANDS

Spatial heterogeneity of vegetation types and the abiotic environment can influence the occurrence and spread of wildfires, but in some landscapes the importance of these effects varies under conditions of severe fire weather. In the northern Patagonian landscape of forests and shrublands we examined the effects of vegetation type (tall forest vs. tall shrubland) and abiotic factors (elevation, topography, and precipitation) on fire occurrence at a broad scale and on fire spread at a fine scale. We used satellite images (1985-1999) and aerial photography (1950-1999) to map fires in relation to pre-burn vegetation type and abiotic factors. Fire extent is greatest at intermediate elevations and locations of intermediate precipitation. Fire extent is limited by lack of fuel quantity at the lower end of the precipitation gradient and by infrequent or insufficient fuel desiccation at the upper end. Tall shrublands are proportionally more affected by fire than are adjacent mesic forests of Nothofagus dombeyi and N. pumilio. Patches of subalpine forests often tend to serve as natural fire breaks, except under the most severe fire weather. Tall shrublands are dominated by species that resprout vigorously so that fuels quickly recover. In contrast, forests are dominated by species dependent on seed reproduction that sometimes fails after severe fires so that shrublands tend to replace burned forests. The greater propensity of shrublands to burn is a positive feedback that is favorable to fire and that accelerates the replacement of forest by shrublands. Infrequently occurring severe weather is important in the burning of otherwise relatively fire-resistant subalpine forests. Past burning, associated both with drought and early forest clearing, expanded shrublands at the expense of forests so that in the modern landscape an increase in anthropogenic ignitions and the positive feedback of fire and shrublands are synergistically accelerating conversion from forest to shrubland.

Last glacial to Holocene evolution of semi-arid rangelands in southeastern Australia

Pollen sequences from playa lakes in the Darling Anabranch dunefields of southwestern New South Wales record vegetation changes over the last glacial period and into the Holocene. This interval was one of marked taxonomic and structural reorganization, with the plant communities that became established after the last glacial maximum (LGM; ~24-18 ka) distinct from those that had prevailed over the build-up to full glacial conditions (~70-24 ka). The glacial period was characterized by a gradual reduction of woodland and tall shrubland cover. Recolonization of the dunefields involved a similar, gradual succession from herbfields and low shrublands to tall shrublands and, finally, woodlands. These changes are likely to have been driven by climatic change, particularly fluctuations in temperature, precipitation and atmospheric CO2, as global climate systems entered and emerged from the last glaciation.

Avifaunal changes revealed in Quaternary deposits near Waitomo Caves, North Island, New Zealand

Late Pleistocene (23 000–10 000 14C yr BP) and Holocene (10 000 14C yr – present BP) avifaunas are described from the Henry Lambert and associated passages in Gardners Gut Cave, Waitomo Caves, North Island, New Zealand. Nine radiocarbon dates on bones and three uranium series dates on speleothems support the dating of the sites. These data are augmented by six new dates and reanalysis of the avifaunas from F1c Cave, also in the Waitomo karst. A distinctive Pleistocene avifauna characterised by the moa Euryapteryx curtus and Pachyornis mappini and the North Island goose (Cnemiornis gracilis) with common associates including New Zealand coot (Fulica prisca), North Island takahe (Porphyrio mantelli), Finsch's duck (Euryanas finschi), and North Island kokako (Callaeas wilsoni) was present. The presence of kokako, saddleback (Philesturnus rufusater), and robin (Petroica longipes) in the Pleistocene deposits and the absence of grassland taxa such as pipit (Anthus novaeseelandiae) and quail (Coturnix novaezelandiae) indicate that the vegetation about Gardners Gut Cave included tall shrubland and probably lacked much grassland, even over the Last Glacial Maximum. The Holocene at Waitomo was characterised by a moa fauna dominated by Anomalopteryx didiformis, although both Euryapteryx curtus and Pachyornis mappini persisted in small numbers. The frequent occurrence of kakapo (Strigops habroptilus), weka (Gallirallus australis), and brown teal (Anas chlorotis) typifies Holocene avifaunas; Cnemiornis and Fulica are unknown from Holocene deposits in the area.

Landscape changes and breeding bird assemblages in northwestern Portugal: the role of fire

Fire is a major driving force of landscape change in the Mediterranean region. The objectives of this paper were to explore the implications of landscape change and wildfires in a region of northwestern Portugal for the diversity of breeding birds. Land use cover for the years 1958, 1968, 1983 and 1995 was obtained from aerial photography for a study area of 3700 ha. Breeding bird assemblages in each of six land use categories were characterized in 1998 using point counts. The main landscape changes in the study area across the 40 years were a decrease in the area of agricultural land and low shrublands (respectively 29% and 48%) and an increase in forests and tall shrublands (both over 95%). Bird assemblages showed increased richness and diversity across the gradient: low shrublands → tall shrublands → conifer → mixed → deciduous → agricultural areas. Many of the species with narrow niche breadth (specialists) were associated with agricultural areas and deciduous forests. In spite of the low diversity of burned areas (mostly shrublands) a few specialist species depend on this habitat. Thus, the current fire regime probably contributes to maintaining bird diversity at the landscape level. There was an inverse relationship between landscape diversity and estimated bird diversity across the last 40 years. Landscape management actions to preserve bird diversity should focus on the maintenance of agricultural land and deciduous forests. In parallel, a wider use of prescribed burning and grazing is suggested. This would contribute to maintaining low shrublands in the landscape, useful both as an habitat for some bird species and as fuel breaks for preventing the occurrence of large wildfires.

Temporal (1958-1995) pattern of change in a cultural landscape of northwestern Portugal: implications for fire occurrence

In this paper we test the hypothesis that landscape changes in a region of Northern Portugal (Minho) in the last 40 years could be predicted from socioeconomic and political history. The major predicted changes were related to agricultural abandonment and afforestation. We further predicted that these changes contributed to increased fire risk. Analysis of aerial photography for the years 1958, 1968, 1983 and 1995 in a study area of 3700 ha revealed a significant decline in agricultural areas and low shrublands and an increase in tall shrublands and forests. This represented a 20–40% increase in fuel accumulation at a landscape level, suggesting that the abandonment of farming activities is a major driving force of increasing fire occurrence in the region. With one exception, all the predictions were partly or totally confirmed. This study confirms that socioeconomic factors might explain a significant part of the variation in landscape composition across time, in the Mediterranean region.

Native grasslands and the stabilization of earthwork archaeological sites on the middle Missouri River, North Dakota

Site condition and management practices at six Missouri River archaeological sites are reviewed and the condition of the sites compared between observations in 1993 and 1998. Earthwork sites in a cover of prairie or pasture grasses that have been mown for interpretation purposes have become more infested with ground squirrels. Tall prairie or shrubland obscures site features but these animals are less numerous on sites with such cover. One mown site in an urban area had no ground squirrels, suggesting that the animals had been removed by local urban dwellers or their cats and had no chance to re-invade. The long-term stability of archaeological sites can best be achieved by allowing native prairie grasses to grow tall, leaving only small samples of the site area open, or by control of ground squirrel numbers.