Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

The Theory of Island Biogeography

This book is the second of two volumes in a series on terrestrial and marine comparisons, focusing on the temporal complement of the earlier spatial analysis of patchiness and pattern (Levin et al. 1993). The issue of the relationships among pattern, scale, and patchiness has been framed forcefully in John Steele’s writings of two decades (e.g., Steele 1978). There is no pattern without an observational frame. In the words of Nietzsche, “There are no facts… only interpretations.”

https://esajournals.onlinelibrary.wiley.com/doi/pdf/10.2307/1941447

The Problem of Pattern and Scale in Ecology: The Robert H. MacArthur Award Lecture

The metacommunity concept is an important way to think about linkages between different spatial scales in ecology. Here we review current understanding about this concept. We first investigate issues related to its definition as a set of local communities that are linked by dispersal of multiple potentially interacting species. We then identify four paradigms for metacommunities: the patch-dynamic view, the species-sorting view, the mass effects view and the neutral view, that each emphasizes different processes of potential importance in metacommunities. These have somewhat distinct intellectual histories and we discuss elements related to their potential future synthesis. We then use this framework to discuss why the concept is useful in modifying existing ecological thinking and illustrate this with a number of both theoretical and empirical examples. As ecologists strive to understand increasingly complex mechanisms and strive to work across multiple scales of spatio-temporal organization, concepts like the metacommunity can provide important insights that frequently contrast with those that would be obtained with more conventional approaches based on local communities alone.

/pdf/the-metacommunity-concept-a-framework-for-multi-scale-4dcjhfvx5w.pdf

The metacommunity concept: a framework for multi-scale community ecology

SUMMARY
1According to ‘Gause's hypothesis’ a corollary of the process of evolution by natural selection is that in a community at equilibrium every species must occupy a different niche. Many botanists have found this idea improbable because they have ignored the processes of regeneration in plant communities.
2Most plant communities are longer-lived than their constituent individual plants. When an individual dies, it may or may not be replaced by an individual of the same species. It is this replacement stage which is all-important to the argument presented.
3Several mechanisms not involving regeneration also contribute to the maintenance of species-richness:


(a). differences in life-form coupled with the inability of larger plants to exhaust or cut off all resources, also the development of dependence-relationships,
(b) differences in phenology coupled with tolerance of suppression,
(c) fluctuations in the environment coupled with relatively small differences in competitive ability between many species,
(d) the ability of certain species-pairs to form stable mixtures because of a balance of intraspecific competition against interspecific competition,
(e) the production of substances more toxic to the producer-species than to the other species,
(f) differences in the primary limiting mineral nutrients or pore-sizes in the soil for neighbouring plants of different soecies, and
(g) differences in the competitive abilities of species dependent on their physiological age coupled with the uneven-age structure of many populations.


4The mechanisms listed above do not go far to explain the indefinite persistence in mixture of the many species in the most species-rich communities known.
5In contrast there seem to be almost limitless possibilities for differences between species in their requirements for regeneration, i.e. the replacement of the individual plants of one generation by those of the next. This idea is illustrated for tree species and it is emphasized that foresters were the first by a wide margin to appreciate its importance.
6The processes involved in the successful invasion of a gap by a given plant species and some characters of the gap that may be important are summarized in Table 2.
7The definition of a plant's niche requires recognition of four components:


(a) the habitat niche,
(b) the life-form niche,
(c) the phenological niche, and
(d) the regeneration niche.


8A brief account is given of the patterns of regeneration in different kinds of plant community to provide a background for studies of differentiation in the regeneration niche.
9All stages in the regeneration-cycle are potentially important and examples of differentiation between species are given for each of the following stages:


(a) Production of viable seed (including the sub-stages of flowering, pollination and seed-set),
(b) dispersal, in space and time,
(c) germination,
(d) establishment, and
(e) further development of the immature plant.


10In the concluding discussion emphasis is placed on the following themes:


(a) the kinds of work needed in future to prove or disprove that differentiation in the regeneration niche is the major explanation of the maintenance of species-richness in plant communities,
(b) the relation of the present thesis to published ideas on the origin of phenological spread,
(c) the relevance of the present thesis to the discussion on the presence of continua in vegetation,
(d) the co-incidence of the present thesis and the emerging ideas of evolutionists about differentiation of angiosperm taxa, and
(e) the importance of regeneration-studies for conservation.

The maintenance of species-richness in plant communities: the importance of the regeneration niche

The continued increase in the atmospheric concentration of carbon dioxide due to anthropogenic emissions is predicted to lead to significant changes in climate. About half of the current emissions are being absorbed by the ocean and by land ecosystems, but this absorption is sensitive to climate as well as to atmospheric carbon dioxide concentrations, creating a feedback loop. General circulation models have generally excluded the feedback between climate and the biosphere, using static vegetation distributions and CO2 concentrations from simple carbon-cycle models that do not include climate change. Here we present results from a fully coupled, three-dimensional carbon–climate model, indicating that carbon-cycle feedbacks could significantly accelerate climate change over the twenty-first century. We find that under a 'business as usual' scenario, the terrestrial biosphere acts as an overall carbon sink until about 2050, but turns into a source thereafter. By 2100, the ocean uptake rate of 5 Gt C yr-1 is balanced by the terrestrial carbon source, and atmospheric CO2 concentrations are 250 p.p.m.v. higher in our fully coupled simulation than in uncoupled carbon models, resulting in a global-mean warming of 5.5 K, as compared to 4 K without the carbon-cycle feedback.

/pdf/acceleration-of-global-warming-due-to-carbon-cycle-feedbacks-3788793i7v.pdf

Acceleration of global warming due to carbon-cycle feedbacks in a coupled climate model

On the wetter slope s of the highest tropical mountains, wherever man' s depradations are not in evidence, a continuous forest cover may be found from sea level to an altitude of about 4000 m. With increase in altitude the forest becomes markedly changed in character. Most obviously it decreases in height from about 45 m to about 2 m, but there are also many changes in the representation of life forms and in the physiognomy of the plants. Very frequently these changes are relatively sharp over narrow altitudinal bands so that it is practicable to recognize four major formation types with relatively narrow

Control of Forest Growth and Distribution on Wet Tropical Mountains: with Special Reference to Mineral Nutrition

Light is widely considered to be the most important factor limiting the performance of plants on the floors of forests and woodlands, but the roles of nutrient availability and water supply remain poorly defined. We seek to predict the types of forest in which root competition affects seedling performance, and the types of plants that respond most strongly to release from root competition. We then test our predictions by reviewing experiments in which tree seedlings and forest herbs are released from belowground competition, usually by cutting trenches to sever the roots of surrounding trees. First, we provide a worldwide review of changes in canopy form and fine-root mass along gradients of soil fertility and seasonal drought, keeping in mind the stages of forest development. Our review shows that penetration of light is least in forests on moist soils providing large amounts of major nutrients. The changes are far more complex than those considered by allocation models. Dry woodlands typically allow 20 ...

Impacts of root competition in forests and woodlands: a theoretical framework and review of experiments

Ecologists interested in seed size have generally contrasted functional groups of plants but, recently, some have focussed on explaining the large range of seed size found within a functional group. A potentially important theoretical advance was the idea that seed number–seedling survival tradeoffs could explain the coexistence of species, in particular colonization–competition tradeoffs where smaller-seeded species are superior colonizers and larger-seeded species are superior competitors. However, recent models have placed limits on the potential of this approach, chiefly by showing that the asymmetry of competition must be strong. Also, although there is evidence from studies within functional groups that seed size does trade off against number of seeds and dispersal of those seeds, and that seed size is correlated with competitive ability among seedlings and tolerance of hazards during establishment, the available evidence suggests that SNSS tradeoffs do not make possible long-term coexistence without other forms of niche differentiation.

Peter J. Grubb

Papers

The maintenance of species-richness in plant communities: the importance of the regeneration niche

Control of Forest Growth and Distribution on Wet Tropical Mountains: with Special Reference to Mineral Nutrition

Impacts of root competition in forests and woodlands: a theoretical framework and review of experiments

Colonization, tolerance, competition and seed-size variation within functional groups

A comparison of montane and lowland rain forest in ecuador