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

Humans are altering the composition of biological communities through a variety of activities that increase rates of species invasions and species extinctions, at all scales, from local to global. These changes in components of the Earth's biodiversity cause concern for ethical and aesthetic reasons, but they also have a strong potential to alter ecosystem properties and the goods and services they provide to humanity. Ecological experiments, observations, and theoretical developments show that ecosystem properties depend greatly on biodiversity in terms of the functional characteristics of organisms present in the ecosystem and the distribution and abundance of those organisms over space and time. Species effects act in concert with the effects of climate, resource availability, and disturbance regimes in influencing ecosystem properties. Human activities can modify all of the above factors; here we focus on modification of these biotic controls. The scientific community has come to a broad consensus on many aspects of the re- lationship between biodiversity and ecosystem functioning, including many points relevant to management of ecosystems. Further progress will require integration of knowledge about biotic and abiotic controls on ecosystem properties, how ecological communities are struc- tured, and the forces driving species extinctions and invasions. To strengthen links to policy and management, we also need to integrate our ecological knowledge with understanding of the social and economic constraints of potential management practices. Understanding this complexity, while taking strong steps to minimize current losses of species, is necessary for responsible management of Earth's ecosystems and the diverse biota they contain.

/pdf/effects-of-biodiversity-on-ecosystem-functioning-a-consensus-13j8vabcus.pdf

Effects of biodiversity on ecosystem functioning: a consensus of current knowledge

A doubling in global food demand projected for the next 50 years poses huge challenges for the sustainability both of food production and of terrestrial and aquatic ecosystems and the services they provide to society. Agriculturalists are the principal managers of global useable lands and will shape, perhaps irreversibly, the surface of the Earth in the coming decades. New incentives and policies for ensuring the sustainability of agriculture and ecosystem services will be crucial if we are to meet the demands of improving yields without compromising environmental integrity or public health.

/pdf/agricultural-sustainability-and-intensive-production-1h98l920tu.pdf

Agricultural sustainability and intensive production practices

Bringing together leaf trait data spanning 2,548 species and 175 sites we describe, for the first time at global scale, a universal spectrum of leaf economics consisting of key chemical, structural and physiological properties. The spectrum runs from quick to slow return on investments of nutrients and dry mass in leaves, and operates largely independently of growth form, plant functional type or biome. Categories along the spectrum would, in general, describe leaf economic variation at the global scale better than plant functional types, because functional types overlap substantially in their leaf traits. Overall, modulation of leaf traits and trait relationships by climate is surprisingly modest, although some striking and significant patterns can be seen. Reliable quantification of the leaf economics spectrum and its interaction with climate will prove valuable for modelling nutrient fluxes and vegetation boundaries under changing land-use and climate.

/pdf/the-worldwide-leaf-economics-spectrum-1uikdmil76.pdf

The worldwide leaf economics spectrum

We discuss the physical and enzymatic bases of carbone isotope discrimination during photosynthesis, noting how knowledge of discrimination can be used to provide additional insight into photosynthetic metabolism and the environmental influences on that process

Carbon Isotope Discrimination and Photosynthesis

The partitioning of nitrogen deposition among soil, litter, below- and above-ground biomass of trees and understory vegetation was investigated in a 15-year-old Picea abies (L.) Karst. plantation in the Fichtelgebirge, Germany, by labeling with 62 mg of15N tracer per square meter in March 1991. Ammonium and nitrate depositions were simulated on five plots each, by labeling with either15N-NH4
+ or15N-NO3
−, and the15N pulse was followed during two successive growing seasons (1991 and 1992). Total recovery rates of the15N tracer in the entire stand ranged between 93 and 102% for both nitrogen forms in 1991, and 82% in June 1992. δ5 N ratios increased rapidly in all compartments of the ecosystem. Roots and soils (to 65 cm depth) showed significant15N enrichments for both15N-treatments compared to reference plots. Newly grown spruce tissues were more enriched than older ones, but the most enriched δ15N values were found in the understory vegetation. Although spruce trees were a much larger pool (1860 g biomass/m2) than understory vegetation (Vaccinium myrtillus 333 g/m2, Calluna vulgaris 142 g/m2, Deschampsia flexuosa 22 g/m2), the ericaceous shrubs and the perennial grass were a much greater sink for the15N label. Eight months after labeling, 9% of the ammonium and 15% of the nitrate label were found in the understory. P.abies retained only 3% of the15N-ammonium and 7% of the15N-nitrate. The main sink for both15N tracers was the soil, where 87% of the ammonium and 79% of the nitrate tracer were found. The organic soil horizon (5-0 cm depth) contained 63% of the15N-ammonium and 46% of the15N -nitrate suggesting strong immobilization by microorganisms of both N forms. Eight months after tracer application, about 16% of both15N-tracers was found below 25 cm soil depth. This 16% corresponds well to a 20% decrease in the recovery of both15N tracers after 15 months and indicates a total loss out of the ecosystem. Highly enriched δ15N values were found in fruit bodies of fungi growing in reference lots (no15N addition), although soils did not show increased δ15N ratios. No transfer of15N-tracer between fungi and spruce or understory vegetation was apparent yet.

Partitioning of 15N-labeled ammonium and nitrate among soil, litter, below- and above-ground biomass of trees and understory in a 15-year-old Picea abies plantation

The response of stomata to a gradual increase in temperature at increasing plant water stress was studied in a hot desert habitat (Negev, Israel) in the field, but under controlled temperature and humidity conditions. Four native species (Zygophyllum dumosum, Artemisia herba-alba, Hammada scoparia, Reaumuria negevensis) and one cultivated plant (Prunus armeniaca) were used in these studies. The stomatal response to temperature was compared with the response in well-irrigated plants of the same species.At low water stress, the diffusion resistance for water vapour decreased in response to a gradual increase in temperature. Transpiration increased accordingly. This response was reversible. All species responded in the same way. The opening of stomata with increasing temperature was apparently independent of the stomatal response regulated by atmospheric humidity. At high plant water stress, the stomatal response was reversed, i.e., the stomata closed when temperature was gradually increased. This stomatal closure was also independent of the closure regulated by atmospheric humidity. The plant water potential at which the stomatal response to temperature was reversed, differed among the species investigated.

Stomatal responses to changes in temperature at increasing water stress.

Biodiversity and ecosystem processes.

Biomass distribution and diurnal CO2 uptake under natural conditions were investigated on Picea abies in a mountainous climate (Solling, Northwest Germany). Spruce has a remarkable variability in leaf characteristics. Even on a single branch in the lower sun crown, needle dry weight and surface area change considerably from the branch base to the tip and accoring to exposure. Only about 18% of the total biomass of the tree was current year's growth, about 40% of the needles were 4 years and older reaching a maximal age of 12 years. The main growing zone was at the border of upper shade and lower sun crown and the main accumulation of dry weight was at a greater tree height than was observed for maximal growth of needle numbers or surface area. The annual, new growth shifted toward the upper sun crown. Maximal daily CO2 uptake was highest in the lower sun crown on days with variable cloud cover when temperatures were moderate and water vapor pressure deficits were low. Also the annual CO2 uptake was highest in the lower sun crown, where 4-year-old and older needles contributed about 35% to the annual CO2 uptake of the tree. Current year growth contributed about 15% of the total CO2 gain. The upper and lower sun crowns produce about 70% of the total carbon gain. The carbon balance of spruce and the distribution of the production process in relation to needle age and crown level are discussed.

Spacial distribution of photosynthetic capacity and performance in a mountain spruce forest of Northern Germany : I. Biomass distribution and daily CO2 uptake in different crown layers.

These studies use starch synthesis mutants to quantify the contribution of assimilatory starch to whole plant growth and form. Arabidopsis thaliana (L.) Heynh plants were used with null plastid phosphoglucomutase (T Caspar, SC Huber, CR Sommerville, [1986] Plant Physiol 79; 1-7) or 7% of wild-type ADP-glucose pyrophosphorylase (T-P Lin, T Caspar, CR Sommerville, J Preiss [1988] Plant Physiol 88; 1175-1179). The daily turnover of starch and the rate of biomass increase in the mutants and the wild type were investigated during growth in a 14 hour light/10 hour dark cycle in high irradiance (600 micromoles per square meter per second) and nitrogen (6 millimolar NH(4)NO(3)), in high irradiance and low nitrogen (0.1 millimolar NH(4)NO(3)) or in low irradiance (80 micromoles per square meter per second) and high nitrogen. There is some variability in the data, but the following conclusions can be drawn. Growth was slow in the absence of starch turnover. In high nitrogen conditions, about 1 mole of carbon per gram dry weight per day was incorporated additionally into structural biomass for every one mole of carbon turned over as starch per gram dry weight per day. In low nitrogen, the gain was much lower. This indicates that temporary storage of photosynthate is important for rapid growth in high nitrogen, but not in low nitrogen when carbohydrate is in excess. Starch-deficient plants showed the usual decrease of the shoot/root ratio in low nitrogen and increase of the ratio in low light. This shows that adjustment of plant form to nitrogen nutrition and irradiance is not mediated via regulation of photosynthate partitioning in the leaf. Starch deficient plants had lower shoot/root ratios than the wild type and the nitrogen concentration in their leaves was increased. It is discussed how interactions between carbohydrate allocation, respiration and growth at the organ and whole plant level generate these changes. We conclude that mutants with a decreased capacity to carry out a particular partial process provide a powerful tool to disect complex mutually interacting systems, and define and quantify causal interactions at the level of whole plant growth.

Ernst Detlef Schulze

Papers

Partitioning of 15N-labeled ammonium and nitrate among soil, litter, below- and above-ground biomass of trees and understory in a 15-year-old Picea abies plantation

Stomatal responses to changes in temperature at increasing water stress.

Biodiversity and ecosystem processes.

Spacial distribution of photosynthetic capacity and performance in a mountain spruce forest of Northern Germany : I. Biomass distribution and daily CO2 uptake in different crown layers.

A Quantification of the Significance of Assimilatory Starch for Growth of Arabidopsis thaliana L. Heynh.