Ernst Detlef Schulze

Bio: Ernst Detlef Schulze is an academic researcher from Max Planck Society. The author has contributed to research in topics: Biodiversity & Ecosystem. The author has an hindex of 133, co-authored 670 publications receiving 69504 citations. Previous affiliations of Ernst Detlef Schulze include University of Idaho & University of Utah.

Climatic control of stand thinning in unmanaged spruce forests of the southern Taiga in European Russia

Abstract: The demography of Picea abies trees was studied over a period of about 30 yr on permanent plots in six forest types of an unmanaged forest located in a forest reserve of the Southern Taiga, NW of Moscow. This study encompassed a broad range of conditions that are typical for old growth spruce forests in the boreal region, including sites with a high water table and well drained sites, podzolic soils, acidic soils and organic soils. At all sites stand density, tree height, breast height diameter and age has been periodically recorded since 1968. Tree density ranged between 178 and 1035 trees ha −1 for spruce and between 232 and 1168 trees ha −1 for the whole stand, including mainly Betula and Populus . Biomass ranged between 5.4 and 170 t dw ha −1 for spruce and between 33 to 198 t dw ha −1 for the whole stand. Averaged over a long period of time, biomass did not change with stand density according to the self-thinning rule. In fact, on most sites biomass remained almost constant in the long term, while stand density decreased. The study demonstrates that the loss of living trees was not regulated by competitive interactions between trees, but by disturbances caused by climatic events. Dry years caused losses of minor and younger trees without affecting biomass. In contrast, periodic storms resulted in a loss of biomass without affecting density, except for extreme events, where the whole stand may fall. Dry years followed by wet years enhance the effect on stand density. Since mainly younger trees were lost, the apparent average age of the stand increased more than real time (20% for Picea ). Average mortality was 2.8 ± 0.5% yr −1 for spruce. Thus, the forest is turned over once every 160–180 yr by disturbances. The demography of dead trees shows that the rate of decay depends on the way the tree died. Storm causes uprooting and stem breakage, where living trees fall to the forest floor and decay with a mean residence time ( t 1/2 ) of about16 yr (decomposition rate constant k d = 0.042 yr −1 ). This contrasts with trees that die by drought or insect damage, and which remain as standing dead trees with a mean residence time of 3–13 yr until they are brought to ground, mainly by wind. These standing dead trees require an additional mean residence time of about 22 yr for decay on the ground ( k d = 0.031) . In conclusion, we demonstrate that, rather than competitive interactions, it is climate extremes, namely drought, rapid changes of dry years followed by wet years, and storm that determine stand structure, biomass and density, which then affect the net exchange with the atmosphere. The climatic effects are difficult to predict, because the sensitivity of a stand to climate extremes depends on the past history. This may range from no effect, if the stand was recovering from an earlier drought and exhibited a relatively low density, to a total collapse of canopies, if drought reduces stand density to an extent that other climatic extremes (especially wind) may cause further damage. DOI: 10.1034/j.1600-0889.2002.01344.x

Contrasting effects of intraspecific trait variation on trait-based niches and performance of legumes in plant mixtures.

Abstract: Niche differentiation, assumed to be a key mechanism of species coexistence, requires that species differ in their functional traits. So far it remains unclear to which extent trait plasticity leads to niche shifts of species at higher plant diversity, thereby increasing or decreasing niche overlap between species. To analyse this question it is convenient to measure niches indirectly via the variation in resource-uptake traits rather than directly via the resources used. We provisionally call these indirectly measured niches trait-based niches. We studied shoot- and leaf-morphological characteristics in seven legume species in monoculture and multi-species mixture in experimental grassland. Legume species varied in the extent of trait variation in response to plant diversity. Trait plasticity led to significant shifts in species niches in multiple dimensions. Single-species niches in several traits associated with height growth and filling of canopy space were expanded, while other niche dimensions were compressed or did not change with plant diversity. Niche separation among legumes decreased in dimensions related to height growth and space filling, but increased in dimensions related to leaf size and morphology. The total extent of occupied niche space was larger in mixture than in the combined monocultures for dimensions related to leaf morphology and smaller for dimensions related to whole-plant architecture. Taller growth, greater space filling and greater plasticity in shoot height were positively, while larger values and greater plasticity in specific leaf area were negatively related with increased performance of species in mixture. Our study shows that trait variation in response to plant diversity shifts species niches along trait axes. Plastically increased niche differentiation is restricted to niche dimensions that are apparently not related to size-dependent differences between species, but functional equivalence (convergence in height growth) rather than complementarity (divergence in traits associated with light acquisition) explains increased performance of legumes in mixture.

Environmental regulation of surface conductance for evaporation from vegetation

Abstract: We examine conductances for evaporation from both vegetation and soil in response to environmental variables. Data from a vertically-structured pristine forest ofNothofagusare presented as an example of the effects of biodiversity on the scaling of conductances between tiers of plant organisation. Available data sets of maximum leaf stomatal conductances(g lmax ) and bulk vegetation surface conductances (G smax ) are compared. Overall, the ratio G smax /g lmax is consistently close to 3 for seven major vegetation types of diverse structure. An analytical model accounts for this close relationship, and in particular how G smax is conservative against changes in leaf area index because of the compensating decrease in plant canopy transpiration and increase in soil evaporation as leaf area index diminishes. The model is also successfully tested by comparison with canopy conductances of emergent trees measured in the Nothofagusforest. The constraint of vegetation surface conductance and evaporation via environmental regulation by irradiance, air saturation deficit and root zone water supply are discussed.

Environmental control of crassulacean acid metabolism in Welwitschia mirabilis Hook. Fil. in its range of natural distribution in the Namib desert

Abstract: Within the area of its natural distribution in South West Africa, Welwitschia mirabilis has a less negative δ13C value than C3 plants and a more negative δ13C value than C4 species. This indicates that Welwitschia m. assimilates CO2 partially via CAM when growing in its natural habitat. The difference between the δ13C values of Welwitschia m. and of the C3 species is significant in the savanna, whereas it is only small and statistically not significant in the grassland zone. The proportion of CO2 fixed via CAM is largest in the coastal desert zone. There was no correlation between the δ13C values and the Cl- or ash content of the tissue. Thus, CAM in Welwitschia m. seems not to be induced by salt stress. There is no change in the δ13C values along the persistent Welwitschia m. leaf. The present data indicate that on a broad geographical scale in the area of distribution temperature regime, and water stress as a modifying factor, determine CAM in Welwitschia m. The ecological implications are discussed by comparing the behaviour of Welwitschia m. with other CAM, C3 and C4 species of the accompanying flora.

Carbon uptake and respiration in above-ground parts of a Larix decidua x leptolepis tree

Abstract: Shade needles of hybrid larch (Larix decidua × leptolepis) had the same rates of photosynthesis as sun needles per dry weight and nitrogen, and a similar leaf conductance under conditions of light saturation at ambient CO2 (Amax). However, on an area basis, Amax and specific leaf weight were lower in shade than in sun needles. Stomata of sun needles limited CO2 uptake at light saturation by about 20%, but under natural conditions of light in the shade crown, shade needles operated in a range of saturating internal CO2 without stomatal limitation of CO2 uptake. In both needle types, stomata responded similarly to changes in light, but shade needles were more sensitive to changes in vapor pressure deficit than sun needles. Despite a high photosynthetic capacity, the ambient light conditions reduced the mean daily (in summer) and annual carbon gain of shade needles to less than 50% of that in sun needles. In sun needles, the transpiration per carbon gain was about 220 mol mol−1 on an annual basis. The carbon budget of branches was determined from the photosynthetic rate, the needle biomass and respiration, the latter of which was (per growth and on a carbon basis) 1.6 mol mol−1 year−1 in branch and stem wood. In shade branches carbon gains exceeded carbon costs (growth + respiration) by only a factor of 1.6 compared with 3.5 in sun branches. The carbon balance of sun branches was 5 times higher per needle biomass of a branch or 9 times higher on a branch length basis than shade branches. The shade foliage (including the shaded near-stem sun foliage) only contributed approximately 23% to the total annual carbon gain of the tree.

The Theory of Island Biogeography

Abstract: 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

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

Abstract: 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.

Agricultural sustainability and intensive production practices

Abstract: 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.

The worldwide leaf economics spectrum

Abstract: 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.

Carbon Isotope Discrimination and Photosynthesis

Abstract: 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