Abstract. While land use is known to be a major driver of biodiversity loss, it is generally difficult to quantify land-use intensity. As a consequence, studies often use a qualitative approach and contrast different land-use categories, or use structural ecosystem attributes as a proxy for land-use intensity. In this paper we compared these different approaches with two quantitative approaches using forest management as an example. We carried out detailed biodiversity assessments of ten different groups of organisms, ranging from fungi and plants to arthropods and birds; in 12 different forest stands of four forest types in three regions of Southern Germany. We compared the explanatory power of the categorical approach to the explanatory power of (1) stand structural attributes, (2) stand structural complexity indices, (3) measures of forest 'naturalness', and (4) a recently developed quantitative descriptors of land-use intensity in forests, Silvicultural Management Intensity (SMI).The diversities of many taxa differed between the different land-use categories but the explanatory power of the categorical approach strongly decreased when using jackknifing. Single structural attributes explained differences in biodiversity for some taxa which were illustrative for proximate mechanisms underlying biodiversity changes. Stand structural complexity indices i.e., combinations of single structural attributes, showed higher explanatory power than single structural attributes but explained less variation in biodiversity among stands than land-use intensity measures. SMI was negatively correlated with forest 'naturalness', and, for many groups of organisms, increasing SMI decreased biodiversity, but trophic guilds responded differently. Some guilds, such as wood-and bark living fungi, saprophytic arthropods, herbivores, canopy predators and breeding birds showed a clear negative response to increasing land-use intensity, while for others such as plants there was no relationship. Some guilds, such as mosses and ground dwelling predators appeared to even benefit from increased land-use intensity. Using a quantitative measure of land-use intensity can thus help to understand even more subtle relationships between human impact and the diversity of organisms. Measures such as SMI seem to be useful tools for quantifying land-use intensity in forests and may be applied to biodiversity data of different forest ecosystems worldwide.

The population sizes of 10 sympatric grasshopper species in an example grassland biotope were quantitatively determined using their species-specific song patterns. The numbers of singing males, the diurnal song activity, the song quality, the audible distance for the different species, and their sex proportion provided the basis for the calculation of grasshopper numbers. By this, densities and species compositions could be estimated simultaneously. The calculated numbers were strongly supported by the results of direct catches in small areas. For assessment of the quality of biotopes and their subbiotopes, the numerical proportion between euryoecious and xerophilic grasshoppers (independent of the species) was calculated and proved to be an excellent parameter. This provided a rapid, well-reproducible, and detailed method to measure the eutrophication of grassland habitats. With this method, we could also quantitatively assess the effects of protective measures.

The population sizes of 10 sympatric grasshopper species in an example grassland biotope were quantitatively determined using their species‐specific song patterns. The numbers of singing males, the diurnal song activity, the song quality, the audible distance for the different species, and their sex proportion provided the basis for the calculation of grasshopper numbers. By this, densities and species compositions could be estimated simultaneously. The calculated numbers were strongly supported by the results of direct catches in small areas. For assessment of the quality of biotopes and their sub‐biotopes, the numerical proportion between euryoecious and xerophilic grasshoppers (independent of the species) was calculated and proved to be an excellent parameter. This provided a rapid, well‐reproducible, and detailed method to measure the eutrophication of grassland habitats. With this method, we could also quantitatively assess the effects of protective measures.

ABSTRACT. Measurements of spectral scalar irradiance were made in a shallow estuarine system during a phytoplankton bloom in summer 1994. High concentrations of dissolved organic matter (DOM) and pigments resulted in strong attenuation of light within the upper 1 m of the water column. Spectral analysis showed an increase in the ratio of far-red p 7 0 0 nm) irradiance to total photosynthetically available radiation (PAR) as depth increased. Under these conditions it is expected that state transition may occur, as far-red light is preferentially absorbed by Photosystem 1 (PSI). Measurements of fluorescence emission at 77K from natural phytoplankton samples as well as from laboratory-grown unialgal cultures showed that redistribution of excitation energy between the photosystems occurred in response to changes in the spectral light environment. Exposure to the far-red-enriched lower euphotic zone induced State 1 (whereby more light energy was directed towards Photosystem 2, PS2), whereas algae reverted to State 2 (redirection of light energy away from PS2) at the surface or after exposure to near-dark conditions at the bottom of the euphotic zone. Differences in the kinetics of state transition between green algae and cyanobacteria together with estimation of the wind-induced mixing time of the water column are discussed with respect to photoacclimation. For both natural phytoplankton and laboratory cultures, state transition occurred on a time scale equal to or faster than the time required for 1 vertical mixing cycle. The faster response of cyanobacteria to changes in spectral irradiance in the water column may be an important factor contributing to cyanobacterial dominance in hypertrophic waters under light-limited conditions.

Various processes in the output pathway of the circadian clock are thought to act as important clock targets resulting in the circadian rhythms of photosynthesis observed in various algae. Examples of such processes are synchronization of the cell cycle, pigmentation, and light or dark reaction of photosynthesis. The newly detected, robust photosynthetic circadian rhythm in the red macroalga Kappaphycus alvarezii was investigated in more detail with respect to rhythmically changing components within the photosynthetic apparatus. The following major results were obtained; (1) The growing tips of Kappaphycus (0 -2 cm) were found to exhibit a diurnal and circadian rhythm of nuclear division like many other algal species, (2) The circadian photosynthetic rhythm was apparent in the actively growing and dividing tip portions (0 -2 cm) as well as in older portions (2 -4 cm) with little remaining mitotic activity. The Kappaphycus rhythm seems therefore to be independent of the cell cycle, at least in the older portions of the thallus, (3) During real (L : D cycle) or subjective (LL) dark phases, net photosynthetic capacity (P max ) dropped drastically in young (tip) parts of the thallus, and a, the 'light affinity' parameter, decreased likewise. The net result of these two changes was an increase in the light saturation point, E k . Dark respiration did not change rhythmically from one circadian maximum to the next circadian minimum. DF/F m ' dropped during real and subjective night phases, while non-photochemical quenching (NPQ) increased. Low temperature (77 K) emission spectra with an excitation wavelength of 580 nm exhibited a larger increase of the 720 : 685 nm as well as the 720 : 696 nm emission quotients compared with spectra at 440 nm excitation for samples harvested in the middle of the subjective dark phase indicating changes in energy trapping from the phycobilisomes to the photosystems.