Climate sets the limits to plant growth but does climate determine the global distribution of major biomes? I suggest methods for evaluating whether vegetation is largely climate or consumer-controlled, focusing on large mammal herbivores and fire as influential consumers. Large parts of the world appear not to be at equilibrium with climate. Consumer-controlled ecosystems are ancient and diverse. Their distinctive ecology warrants special attention.

Abbreviations: DGVM = Dynamic Global Vegetation Model; HSS = Hanston et al. (1960).

Question: What are the major vegetation units in the Arctic, what is their composition, and how are they distributed among major bioclimate subzones and countries?

Location: The Arctic tundra region, north of the tree line.

Methods: A photo-interpretive approach was used to delineate the vegetation onto an Advanced Very High Resolution Radiometer (AVHRR) base image. Mapping experts within nine Arctic regions prepared draft maps using geographic information technology (ArcInfo) of their portion of the Arctic, and these were later synthesized to make the final map. Area analysis of the map was done according to bioclimate subzones, and country. The integrated mapping procedures resulted in other maps of vegetation, topography, soils, landscapes, lake cover, substrate pH, and above-ground biomass.

Results: The final map was published at 1:7 500 000 scale map. Within the Arctic (total area = 7.11 × 106 km²), about 5.05 × 10⁶ km² is vegetated. The remainder is ice covered. The map legend generally portrays the zonal vegetation within each map polygon. About 26% of the vegetated area is erect shrublands, 18% peaty graminoid tundras, 13% mountain complexes, 12% barrens, 11% mineral graminoid tundras, 11% prostrate-shrub tundras, and 7% wetlands. Canada has by far the most terrain in the High Arctic mostly associated with abundant barren types and prostrate dwarf-shrub tundra, whereas Russia has the largest area in the Low Arctic, predominantly low-shrub tundra.

Conclusions: The CAVM is the first vegetation map of an entire global biome at a comparable resolution. The consistent treatment of the vegetation across the circumpolar Arctic, abundant ancillary material, and digital database should promote the application to numerous land-use, and climate-change applications and will make updating the map relatively easy.

Nomenclature: US Department of Agriculture Plants Database (USDA-NRCS 2004) for all plant names. Nomenclature of syntaxa is in accordance with Weber (2000).

Abbreviations: AVHRR = Advanced Very High Resolution Radiometer; CAVM = Circumpolar Arctic Vegetation Map; CIR = False colour-infrared; DCW = Digital Chart of the World; PAF = Panarctic Flora initiative.

Question: What is the composition, ecology and distribution of the main plant communities on Santiago Island?

Location: Santiago Island (Cape Verde archipelago).

Methods: 308 plots were established using a stratified sampling system according to habitat type; random sampling was employed in each habitat type. Floristic and ecological (topographic, edaphic, climatic and land use) data were collected and analysed using classification and ordination methods and regression analysis.

Results: The classification results led to the recognition of ten plant communities. Ordination pointed to the importance of altitudinal gradient, slope angle and soil moisture in vegetation variation, as well as some categories of land use, land form or soil type. Regression analysis of sample distributions in ordination space and altitude, according to the two main types of slope aspect – leeward vs. windward – produced altitude differences of ca. 100 m. Variation in rainfall proved more effective at lower altitudes, resulting in the differentiation of more vegetation belts. Slope angle proved to be more important for vegetation differentiation when values exceeded 40°, particularly at medium and higher altitudes. Plant communities are mainly dominated by herbaceous annual species, many of which are exotic.

Conclusions: Two main phyto-ecological zones can be distinguished: a xerophilous zone (up to 300/400 m) and a mesophilous zone (above 300/400 m). The zonal communities (four mesophilous and three xerophilous) were distributed in altitudinal belts (mainly reflected in a precipitation gradient); different altitudinal ranges were estimated for these communities according to aspect. The two hygrophilous and one psammophilous communities presented an azonal distribution.

Nomenclature: Hansen & Sunding (1993); Brochmann et al. (1997); Paiva et al. (eds.) (1995), Diniz et al. (eds.) (2002).

Questions: How do physical microsite conditions of microsites affect germination and seedling survival in different successional stages? Do different species germinate in similar microsites in a given successional stage?

Location: Coleman Glacier foreland, Mount Baker, Washington State, USA.

Methods: Two methods were used to characterize safe sites. 1. Grids of 300 10 cm × 10 cm plots were located in four different age classes on the foreland. 2. 105 pairs of plots, with and without seedlings of Abies amabilis, were located in each age class. For each plot we identified all seedlings and all individuals < 1 m tall. Microsite characteristics such as topography and presence of rocks or woody debris were noted for each plot. Microsite characteristics were compared between plots with and without each species. In addition we examined the effect of distance from seed sources on the presence of Alnus viridis seeds and seedlings in a newly disturbed area.

Results: In early successional sites, seedlings of several species were positively associated with depressions and presence of rocks, and negatively associated with ridges. Patterns were generally consistent among species. In later succession, seedlings were not significantly associated with any microsite characteristics. For Alnus viridis, seed density decreased with distance from seed sources but seedling density did not.

Conclusions: Because of harsh conditions in early succession, physical microsites are important, and most species have similar microsite requirements. In later succession, physical microsites characteristics are not as important and are more variable. Microsites appear to be more important than seed rain in controlling the distribution of Alnus viridis in early succession.

Nomenclature: Kartesz (1999).

Question: How do properties of different vegetation components vary along ecotones of semi-deciduous forest islands, and can the depth of edge influence (DEI) of the components be detected using a novel combination of analyses?

Location: Comoé National Park (CNP), NE Ivory Coast.

Methods: Along eight transects at semi-deciduous forest islands tree individuals > 20 cm DBH were mapped. At one transect, tree and shrub individuals down to 1 cm DBH were measured and cover of species was estimated. Split moving window dissimilarity analysis (SMWDA) and moving window regression analysis (MWRA) were combined to detect statistical significance of borders in multivariate vegetation data along continuous transects, to determine the width of associated ecotones, and, thus, the DEI towards the forest interior.

Results: For trees > 20 cm DBH, a distinct boundary formation was detected, dominated by the semi-fire resistant tree species Anogeissus leiocarpus. The median of DEI towards the forest interior was 55 m. Ecotone detection with all species present revealed an interlocked sequence of ecotones for grasses, herbs, woody climbers, shrubs and trees, with each of these ecotones being narrower than the overall ecotone. DEI ranged from 10 m for grasses up to 120 m for trees and shrubs.

Conclusions: The coherent set of analyses applied proved to be an objective method for detecting borders and the width of associated ecotones. The patterns found may be explained by successional processes at the forest-savanna border. The DEI measured for the forest islands in the nearly undisturbed semi-natural system of the CNP is of relevance to concepts of core-area analysis and the protection of forest interior species in semi-deciduous forests in tropical West Africa.

Nomenclature: Lebrun & Storck (1991–1997).

Abbreviations: CNP = Comoé National Park; DEI = Depth of edge influence; MWRA = Moving window regression analysis; SED = Squared Euclidean distance; SMWDA = Split moving window dissimilarity analysis.

Question: Bush encroachment (i.e. an increase in density of woody plants often unpalatable to domestic livestock) is a serious problem in many savannas and threatens the livelihood of many pastoralists. Can we derive a better understanding of the factors causing bush encroachment by investigating the scale dependency of patterns and processes in savannas?

Location: An arid savanna in the Khomas Hochland, Namibia.

Methods: Patterns of bush, grass, and soil nutrient distribution were surveyed on several scales along a rainfall gradient, with emphasis on intraspecific interactions within the dominant woody species, Acacia reficiens.

Results: Savannas can be interpreted as patch-dynamic systems where landscapes are composed of many patches (a few ha in size) in different states of transition between grassy and woody dominance.

Conclusions: In arid savannas, this patchiness is driven both by rainfall that is highly variable in space and time and by inter-tree competition. Within the paradigm of patch-dynamic savannas, bush encroachment is part of a cyclical succession between open savanna and woody dominance. The conversion from a patch of open savanna to a bush-encroached area is initiated by the spatial and temporal overlap of several (localized) rainfall events sufficient for Acacia germination and establishment. With time, growth and self-thinning will transform the bush-encroached area into a mature Acacia stand and eventually into open savanna again. Patchiness is sustained due to the local rarity (and patchiness) of rainfall sufficient for germination of woody plants as well as by plant-soil interactions.

Nomenclature: Dyer (1975, 1976); Ross (1979); Gibbs-Russell et al. (1991).

Question: Following a volcanic eruption of ca. 232 AD, known as the Taupo eruption, the emergent conifer Libocedrus bidwillii expanded on Mt. Hauhungatahi, upwards above the current tree-line, and downwards into the mixed montane forest. We ask: (1) if current age-structures at different altitudes support the patterns predicted by the temporal stand replacement model, with cohort senescence and progressively depleting recruitment at ca. 600 year intervals (average cohort age) since the eruption: and (2) if the case history of the population sheds light on the persistence of mixed conifer-hardwood forests in general.

Location: Mt. Hauhungatahi, Tongariro National Park, New Zealand.

Methods: The species composition and structure of seven stands covering the altitudinal range of Libocedrus bidwillii, were quantified. Libocedrus trees were cored, and regression equations used to predict ages. Cohorts were identified.

Results: Libocedrus densities and basal areas, and the abundance of seedlings and saplings, peaked at different altitudes. At the species' lower limits there has been no recruitment for ca. 550 years, and the angiosperm Weinmannia racemosa has gained dominance. In the tree line and sub-alpine forest stands, a low level of continuous regeneration has been boosted by periodic cohort recruitment following exogenous disturbances.

Conclusions: In the montane zone, the Libocedrus age structure, and its replacement by Weinmannia, are consistent with a model of depleting cohorts separated by ca. 600 years since the Taupo eruption. At higher altitudes more frequent disturbances and reduced competition have allowed Libocedrus persistence. Comparison with other studies suggests long-term relationships between gymnosperms and angiosperms are mediated by the scale and frequency of disturbance.

Nomenclature: Indigenous gymnosperms and dicotyledons: Allan (1961) except as modified in Connor & Edgar (1987); monocots: Moore & Edgar (1970); pteridophytes: Brownsey & Smith-Dodsworth (1989).

Question: In semi-arid systems, rainfall gradients can cause plant-plant interactions to shift from negative to positive or vice versa. However, the importance of a second major abiotic factor, soil nutrients, has rarely been considered. We consider different combinations of both factors and ask: do net adult-seedling interactions become less competitive and more facilitative with increasing overall abiotic harshness?

Location: Succulent Karoo, Western Cape, South Africa.

Methods: We examined the interactions between seedlings and adult shrubs at two sites. Sites differ in rainfall, and each contain two habitats: Nutrient-rich mounds associated with underground termitaria and a relatively nutrient-poor matrix. We carried out a spatial pattern analysis of community-wide seedling-adult associations. We then conducted field and greenhouse experiments to test the effects of soil and the presence of neighbouring shrubs on the growth and survival of six seedling species.

Results: At the higher rainfall site, both competitive and facilitative effects of adults on seedlings were found but did not differ by habitat, despite the more benign conditions in the mound habitat. At the lower rainfall site, adult shrubs generally had neutral effects on seedlings in the matrix habitat. In the nutrient-rich mound habitat, however, adult shrubs had strong and consistently competitive effects on seedlings.

Conclusion: Seedling-adult interactions could not be predicted by a simple overall gradient of abiotic harshness, demonstrating the need for more complex, mechanistic models to predict plant-plant interactions. We suggest that rainfall and soil nutrients affect seedling-adult relations through their interactive effects on the life-history attributes of the species involved.

Nomenclature: Germishuizen & Meyer (2003).

Questions: What is the relationship between alpine vegetation patterns and climate? And how do alpine vegetation patterns respond to climate changes?

Location: Tibetan Plateau, southwestern China. The total area is 2 500 000 km² with an average altitude over 4000 m.

Methods: The geographic distribution of vegetation types on the Tibetan Plateau was simulated based on climatology using a small set of plant functional types (PFTs) embedded in the biogeochemistry-biography model BIOME4. The paleoclimate for the early Holocene was used to explore the possibility of simulating past vegetation patterns. Changes in vegetation patterns were simulated assuming continuous exponential increase in atmospheric CO₂ concentration, based on a transient ocean-atmosphere simulation including sulfate aerosol effects during the 21st century.

Results: Forest, shrub steppe, alpine steppe and alpine meadow extended while no desert vegetation developed under the warmer and humid climate of the early Holocene. In the future climate scenario, the simulated tree line is farther north in most sectors than at present. There are also major northward shifts of alpine meadows and a reduction in shrub-dominated montane steppe. The boundary between montane desert and alpine desert will be farther to the south than today. The area of alpine desert would decrease, that of montane desert would increase.

Conclusions: The outline of changes in vegetation distribution was captured with the simulation. Increased CO₂ concentration would potentially lead to big changes in alpine ecosystems.

A number of investigators have interpreted the slope of a linear production-resource relationship as a measure of efficiency of resource utilization. However, this is rarely true and may lead to incorrect conclusions. Here, by means of simple mathematical equations and conceptual definitions, we point out the theoretical differences between slope and efficiency. While a slope represents the change in the dependent variable per unit change in the independent variable, efficiency expresses the amount of output produced by a unit amount of input. Practical implications of using slopes as indicators of resource-use efficiency are less important as the resource amount increases. Slopes may be used as indicators of the sensitivity of production to changes in input, which is by itself an interesting property of biological systems. Finally, production function intercepts determine whether the efficiency will decrease, increase, or remain constant as resources increase.

The Ginkgo software is a subset of the VegAna (for Vegetation edition and Analysis) package that contains three programs named Quercus, Fagus and Yucca. Ginkgo is a multivariate analysis tool; it is oriented mainly towards ordination and classification of ecological data. Quercus is a relevé table editor; it handles community data to perform a phytosociological analysis. Fagus is a floristic citation editor; it can handle data coming from field surveys, bibliographic sources or collections. Yucca is a cartographic tool; it allows plotting distributions of taxa or syntaxa.

VegAna is produced by the Department of Vegetal Biology, University of Barcelona. The general project is directed by Xavier Font I Castell, the Ginkgo module by Francesc Oliva I Cuyàs. Programmers are Miquel De Cáceres and Richard Garcia. This review deals primarily with Ginkgo.