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This paper examines morphological plasticity of clonal plants of contrasting habitats and of contrasting architectures in response to nutrient supply. The hypotheses were tested that plants from rich habitats possess greater plasticity in response to variation in resource supply than species from poor habitats, and that rhizomatous species are less plastic in their response than stoloniferous species. Two sympodial rhizomatous herbs (Carex flacca, C. hirta) and two monopodial stoloniferous herbs (Trifolium fragiferum, T. repens) were subjected to four levels of nutrient supply in a garden experiment. One of the two species of each genus (C. hirta, T. repens) is from fertile and the other from infertile habitats. We measured 1) whole plant characters: total plant dry weight, number of modules (product of a single apical meristem) and number of ramets; 2) ramet characters: ramet leaf area and ramet height; and 3) spacer characters: branches per module, length per module and length per module internode. All measured characters in the Trifolium species significantly responded to treatment: the values for all measured characters increased with higher levels of fertilization. The differences in plant characters between fertilization levels were larger in Trifolium repens than in T. fragiferum in terms of whole plant characters, ramet characters and stolon internode length. The two Carex species did not differ in their responses to treatment in terms of most characters measured. In ramet characters and in some whole plant characters the species from fertile habitats were more plastic than those from infertile habitats. In spacer characters this pattern was not found. Foraging could not be demonstrated unequivocally. Morphological plasticity in the stoloniferous (Trifolium) species was much larger than in the rhizomatous (Carex) species. This seems in accordance with a foremost storage function of rhizomes, as against a foremost explorative function of stolons.

Inland dunes in northwestern Europe support a number of dry vegetation types. These ecosystems are poor in nutrients and it has been suggested that accumulation of nutrients triggers succession in such systems.

Seedling performance, morphology, and leaf characteristics of evergreen tree species from different successional stages of Chinese broadleaved evergreen forests were studied in four simulated gap environments: in 100, 55, 33, and 18% of full sunlight. The first two represent the light regimes of clearings (gaps secondarily become more open due to human activity and natural erosion). The hypothesis was tested that early-successional species achieve their greatest seedling size in clearings and contrast in this respect with late-successional species. Late-successional species were expected to show a stronger morphological response (leaf/root ratio) to clearings than early-successional ones. The results provided some evidence in support of these hypotheses with one exception, namely that late-successional Castanopsis fargesii appeared to be a highly sun-tolerant species. It is suggested that Castanopsis seedlings are competitive in large gaps and clearings.

An analysis is given of the growth form composition of the flora of the Canary Islands based on a checklist published by Hansen & Sunding (1985) and the authors' field studies. Results are compared with similar data available from Israel and California. Special attention is given to endemism, the Mediterranean-wides and introduced species, as well as to some special plant features such as succulence, spinescence and fleshy fruits. Long-distance dispersal is stressed as the mechanism by which the Canaries obtained their flora. The growth-form composition of the Canaries is discussed in the context of the prevailing present-day environmental conditions, not in the context of climatic conditions in geological time. Characteristic features are the low percentages of endemic and even of indigenous annuals, the high percentage of chamaephytes (many of whom are endemic), the strong development of arborescence, the richness in leaf succulents, and the paucity of spines.

Using a combination of mathematical modeling and field studies we showed that in dense stands of growing herbaceous plants the vertical pattern of leaf nitrogen distribution resembles the pattern of mean light attenuation in the stand and hence tends to maximize total daily photosynthetic carbon gain of the whole stand. Flowering represents a strong sink of nitrogen away from the photosynthetic apparatus and in herbs like Solidago altissima it induces leaf shedding. We studied both the effect of nitrogen reallocation and leaf shedding on the whole canopy photosynthesis and changes in leaf nitrogen distributions in stands moving from the growing to the flowering stage. Despite a decrease in leaf area index and total nitrogen available for photosynthesis in the flowering stand, the leaf nitrogen distribution here also leads to an almost maximum canopy photosynthesis. In both the growing and the flowering stands the leaf area index was higher than calculated optimum values. It is pointed out that this should not necessarily be interpreted as ‘non-adaptive’.

The amount of photosynthetically-active photon flux density incident upon a leaf and the nitrogen content of that leaf strongly affect the photosynthetic carbon gain of that leaf. Therefore, the canopy structure of a stand, affecting the light climate in the canopy, and the leaf nitrogen distribution pattern in the canopy, affect the carbon gain of the whole canopy. This review discusses the results of studies directed to this problem and obtained so far in open and in dense canopies of stands of herbaceous, monocotyledonous or dicotyledonous, plants in their growing or flowering stages. It is found that the leaf nitrogen distribution pattern in the canopy is vertically non-uniform, and in dense stands more strongly so than in open stands. The leaf nitrogen distribution pattern in most canopies closely approaches an optimal pattern in that it maximizes whole canopy potential carbon gain as calculated for the actual total leaf nitrogen content and leaf area index of the stand. The resulting increase in potential carbon gain as compared to a uniform leaf nitrogen distribution pattern is considerable and it is larger in dense stands than in open stands. For at least some dense stands simulation studies show that with the available total leaf nitrogen content, whole canopy carbon gains could still be considerable higher had a lower leaf area index been developed.

A succulent is a plant with water storing tissue, but succulence clearly is a quality that can be possessed to a higher or lesser degree. This paper gives a definition of succulence and discusses problems concerning Delf's measure of succulence. A new measure, Succulence Quotient, is proposed. It measures the amount of water that a plant can store at the expenditure of one gram of organic matter. We demonstrate this measure on a number of plants from the Namib desert, southern Africa, and compare it with the measured caloric values of the plant tissues. We also discuss life cycles of desert succulents in terms of utilizable and structural biomass and water. We contrast the concepts of growth form, life form and life strategy, and propose, on the basis of life cycle characteristics, an outline classification of life strategies of desert succulents. One detail of this outline classification is further worked out and illustrated for succulents from the Namib desert.

Various types of grasslands in the Netherlands were catagorized by their structure: phytomass and leaf area were measured in arbitrarily chosen vegetation layers with width intervals of 2.5, 5, 10 or 20 cm, depending on the height of the sward. Data were standardized for fixed width of layers (layer width set), and for equal numbers of layers of varying width (layer number set). Data were clustered by Ward's method as well as ordinated by Principal Components Analysis (PCA). The cluster method revealed 6 groups; those of the layer number sets could be contrasted in their vertical built-up of leaf area index (LAI) — and phytomass profiles and could be characterized ecologically. The ordinations confirmed the findings of the cluster analyses. In our data grassland structure varied mainly along a gradient from constant and sufficient to strongly varying soil water supply during the growing season, and a gradient in soil nutrients from rich to poor. Sites with constant water supply appeared more often nutrient-rich and those with a varying water supply more often poor in nutrients.

A comparison is made between floristic and structural-physiognomic classifications of a tropical dry, semi-evergreen forest and thicket vegetation of south-eastern India. The classifications are strikingly similar in their main groupings which are ecologically meaningful; the differences between the classifications are virtually limited to allocation of some stands to different subcommunities. It is concluded that the use of structural-physiognomic criteria allows a detailed and ecologically significant classification of vegetation. Fairly advanced calculation facilities are necessary, however, to reach such a classification, since the structural-physiognomic differences between the resulting groupings are largely of a quantitative and not of a qualitative nature. This is a consequence of the general occurrence in all stands of the vegetation of the very great majority of the characters used in this study.

A transect in grassland vegetation in the southern part of the Netherlands showing both a very gradual and a more marked transition in species composition, was sampled as regards species frequency and a number of soil variables. Clustering (TABORD) and Principal Component Analysis revealed the two types of vegetation boundaries, a strong, rigid and a weak, gradual boundary, and the gradient situation in the transect. Species performance curves were tested for Gaussian form, but less than half of the species showed this form even though limits for acceptance were mild. The few species showing a Gaussian response curve clearly illustrate the two types of vegetation boundaries in this transect in agreement with Whittaker's model for such boundaries.

A Monte Carlo method based on Ripley's K function-a cumulative function related to the number of plants encountered at different distances from other plants-is used to test the null hypothesis of random distribution of shrub clumps in a desert dwarf shrub community in Namaqualand, South Africa, where Psilocaulon arenosum is the dominant shrub. The method takes into account the apparent regularity of pattern caused by the finite size (up to 2 m diameter) of the clumps. It is shown that the clump centres are significantly aggregated (compared to random expectation) at distances on the order of 1 m. Such aggregation is expected, as a simple result of regeneration near to seed sources, if the time between catastrophic droughts is short in relation to the time required for development of a non-aggregated or regular pattern determined by moisture competition. No significant regulatiry was detected at distances of 3 m or less. One subplot showed regularity above 3 m, but this pattern was not shown by the other subplot and may not be a competition effect. These results support a hypothesis of aggregation caused by regeneration pattern decaying slowly toward randomness as larger individuals compete.