Library

Notes: Summary 1. It has been reported that when the vegetarian Bush hyrax Heterohyrax and the Rock hyrax Procavia are allopatric they occupy an almost identical niche, while when sympatric they differ in feeding behaviour. To investigate whether indeed a displacement in feeding behaviour takes place where Procavia johnstoni and Heterohyrax brucei occur sympatrically, the feeding characteristics of three (two H. brucei, one P. johnstoni)allopatric family groups and four (two of each species) sympatric family groups living on five kopjes in the Serengeti were studied and compared. 2. The vegetation of these five kopjes was surveyed. It was divided into four classes (grass, forb, bush, tree), the plant species identified and the indices of diversity and similarity calculated. The plant biomass was roughly quantified through a foliage density (f.d.) factor and the seasonal variation of vegetation recorded. The number of plant species ranged from 65 to 95 (Fig. 4). The closer the kopjes are geographically, the greater the resemblance in their plant species composition (Fig. 6). Although bushes and trees comprise the fewest plant species (15–27%) they form the highest foliage density values (65–85%; Table 1, Fig. 5).There is a substantial variation of plant species diversity. A significant correlation exists between the diversity indices and crown cover, but there is no correlation between diversity indices and a) kopje area or b) the quotient of total number of hits per transect length. Grasses, forbs and small bushes observe more or less the rainfall pattern, while other bushes, and trees, never completely lose their leaves (Fig. 7). 3. The behaviour of individuals in the groups was regularly observed and recorded in the wet and dry seasons. a) H. brucei was observed feeding on 64 plant species (Annex A) but 2\2-11 species formed 90% of the animals' staple diet. There is a high correlation (r s=0.90) between the comparative abundance of vegetation (measured by f.d.) and the proportions of the four vegetation classes eaten by H. brucei (Fig. 8). All four family groups fed roughly in proportion to the foliage density, yet showed preference for certain plant species. They browsed predominantly on bushes and trees in the wet (81%) and dry (92%) seasons (Fig. 11), but showed a tendency to eat more grass and browse less in the wet season. There are marked differences in feeding between the family groups, due to selective preferences and the vegetation composition in the respective kopjes (Table 2, Fig. 10). b) P. johnstoni was observed feeding on 79 plant species (Annex A). The animals have a high seasonal adaptability: in the wet season they showed a high preference for grasses (78%), but in the dry season when grasses became parched and poor in quality they browsed (57%) extensively (Fig. 11), and more or less in proportion to the foliage density of each vegetation class (Fig. 9). P. johnstoni must go outside the kopje to graze. Around one kopje the cropped grass area was very marked, its size varying with rainfall (Figs. 12 and 13). a) Competition for food could occur especially in the dry season when both species browse. However, no evidence could be found for a competition-induced displacement here. 4. Almost no aggressive behaviour was observed between the species. 5. Both P. johnstoni and H. brucei have morning and evening feeding activity peaks in the wet and dry seasons, the evening one always being higher (Fig. 14). There was no indication in sympatric groups of any activity shift induced by the presence of the other species. Evidence on the social character of group feeding and the guarding function of the territorial ♂ ♂ is presented. 6. The results obtained are compared with those of other authors. There is no indication of niche segregation in sympatric kopjes. Possible climatic and other reasons for regional sympatry are discussed. The advantage of selecting food items rich in protein and energy and low in fibre content are considered and food competitors listed.

Notes: Abstract. Four time-dependent greenhouse warming experiments were performed with the same global coupled atmosphere-ocean model, but with each simulation using initial conditions from different ”snapshots" of the control run climate. The radiative forcing – the increase in equivalent CO2 concentrations from 1985–2035 specified in the Intergovernmental Panel on Climate Change (IPCC) scenario A – was identical in all four 50-year integrations. This approach to climate change experiments is called the Monte Carlo technique and is analogous to a similar experimental set-up used in the field of extended range weather forecasting. Despite the limitation of a very small sample size, this approach enables the estimation of both a mean response and the ”between-experiment" variability, information which is not available from a single integration. The use of multiple realizations provides insights into the stability of the response, both spatially, seasonally and in terms of different climate variables. The results indicate that the time evolution of the global mean warming signal is strongly dependent on the initial state of the climate system. While the individual members of the ensemble show considerable variation in the pattern and amplitude of near-surface temperature change after 50 years, the ensemble mean climate change pattern closely resembles that obtained in a 100-year integration performed with the same model. In global mean terms, the climate change signals for near surface temperature, the hydrological cycle and sea level significantly exceed the variability among the members of the ensemble. Due to the high internal variability of the modelled climate system, the estimated detection time of the global mean temperature change signal is uncertain by at least one decade. While the ensemble mean surface temperature and sea level fields show regionally significant responses to greenhouse-gas forcing, it is not possible to identify a significant response in the precipitation and soil moisture fields, variables which are spatially noisy and characterized by large variability between the individual integrations.

Notes: Abstract. Due to restrictions in the available computing resources and a lack of suitable observational data, transient climate change experiments with global coupled ocean-atmosphere models have been started from an initial state at equilibrium with the present day forcing. The historical development of greenhouse gas forcing from the onset of industrialization until the present has therefore been neglected. Studies with simplified models have shown that this "cold start" error leads to a serious underestimation of the anthropogenic global warming. In the present study, a 150-year integration has been carried out with a global coupled ocean-atmosphere model starting from the greenhouse gas concentration observed in 1935, i.e., at an early time of industrialization. The model was forced with observed greenhouse gas concentrations up to 1985, and with the equivalent CO2 concentrations stipulated in Scenario A ("Business as Usual") of the Intergovernmental Panel on Climate Change from 1985 to 2085. The early starting date alleviates some of the cold start problems. The global mean near surface temperature change in 2085 is about 0.3 K (ca. 10%) higher in the early industrialization experiment than in an integration with the same model and identical Scenario A greenhouse gas forcing, but with a start date in 1985. Comparisons between the experiments with early and late start dates show considerable differences in the amplitude of the regional climate change patterns, particularly for sea level. The early industrialization experiment can be used to obtain a first estimate of the detection time for a greenhouse-gas-induced near-surface temperature signal. Detection time estimates are obtained using globally and zonally averaged data from the experiment and a long control run, as well as principal component time series describing the evolution of the dominant signal and noise modes. The latter approach yields the earliest detection time (in the decade 1990–2000) for the time-evolving near-surface temperature signal. For global-mean temperatures or for temperatures averaged between 45° N and 45° S, the signal detection times are in the decades 2015–2025 and 2005–2015, respectively. The reduction of the "cold start" error in the early industrialization experiment makes it possible to separate the near-surface temperature signal from the noise about one decade earlier than in the experiment starting in 1985. We stress that these detection times are only valid in the context of the coupled model's internally-generated natural variability, which possibly underestimates low frequency fluctuations and does not incorporate the variance associated with changes in external forcing factors, such as anthropogenic sulfate aerosols, solar variability or volcanic dust.

Notes: Abstract Four time-dependent greenhouse warming experiments were performed with the same global coupled atmosphere-ocean model, but with each simulation using initial conditions from different “snapshots” of the control run climate. The radiative forcing — the increase in equivalent CO2 concentrations from 1985–2035 specified in the Intergovernmental Panel on Climate Change (IPCC) scenario A — was identical in all four 50-year integrations. This approach to climate change experiments is called the Monte Carlo technique and is analogous to a similar experimental set-up used in the field of extended range weather forecasting. Despite the limitation of a very small sample size, this approach enables the estimation of both a mean response and the “between-experiment” variability, information which is not available from a single integration. The use of multiple realizations provides insights into the stability of the response, both spatially, seasonally and in terms of different climate variables. The results indicate that the time evolution of the global mean warming signal is strongly dependent on the initial state of the climate system. While the individual members of the ensemble show considerable variation in the pattern and amplitude of near-surface temperature change after 50 years, the ensemble mean climate change pattern closely resembles that obtained in a 100-year integration performed with the same model. In global mean terms, the climate change signals for near surface temperature, the hydrological cycle and sea level significantly exceed the variability among the members of the ensemble. Due to the high internal variability of the modelled climate system, the estimated detection time of the global mean temperature change signal is uncertain by at least one decade. While the ensemble mean surface temperature and sea level fields show regionally significant responses to greenhouse-gas forcing, it is not possible to identify a significant response in the precipitation and soil moisture fields, variables which are spatially noisy and characterized by large variability between the individual integrations.

Notes: Abstract Due to restrictions in the available computing resources and a lack of suitable observational data, transient climate change experiments with global coupled ocean-atmosphere models have been started from an initial state at equilibrium with the present day forcing. The historical development of greenhouse gas forcing from the onset of industrialization until the present has therefore been neglected. Studies with simplified models have shown that this “cold start” error leads to a serious underestimation of the anthropogenic global warming. In the present study, a 150-year integration has been carried out with a global coupled ocean-atmosphere model starting from the greenhouse gas concentration observed in 1935, i.e., at an early time of industrialization. The model was forced with observed greenhouse gas concentrations up to 1985, and with the equivalent C02 concentrations stipulated in Scenario A (“Business as Usual”) of the Intergovernmental Panel on Climate Change from 1985 to 2085. The early starting date alleviates some of the cold start problems. The global mean near surface temperature change in 2085 is about 0.3 K (ca. 10%) higher in the early industrialization experiment than in an integration with the same model and identical Scenario A greenhouse gas forcing, but with a start date in 1985. Comparisons between the experiments with early and late start dates show considerable differences in the amplitude of the regional climate change patterns, particularly for sea level. The early industrialization experiment can be used to obtain a first estimate of the detection time for a greenhouse-gas-induced near-surface temperature signal. Detection time estimates are obtained using globally and zonally averaged data from the experiment and a long control run, as well as principal component time series describing the evolution of the dominant signal and noise modes. The latter approach yields the earliest detection time (in the decade 1990–2000) for the time-evolving near-surface temperature signal. For global-mean temperatures or for temperatures averaged between 45°N and 45°S, the signal detection times are in the decades 2015–2025 and 2005–2015, respectively. The reduction of the “cold start” error in the early industrialization experiment makes it possible to separate the near-surface temperature signal from the noise about one decade earlier than in the experiment starting in 1985. We stress that these detection times are only valid in the context of the coupled model's internally-generated natural variability, which possibly underestimates low frequency fluctuations and does not incorporate the variance associated with changes in external forcing factors, such as anthropogenic sulfate aerosols, solar variability or volcanic dust.

Notes: Abstract By TPD it could be shown that hydrogen desorption of a reduced NiY-zeolite stoichiometrically corresponds to the decrease of reduction degree. Therefore, the reason for hydrogen abstraction should be a partial reoxidation of Ni0.

Notes: Abstract We quantified the extent of communal suckling in the cavy Galea musteloides. Six groups of animals were held in large indoor enclosures and suckling behavior was recorded over 113 h of observation. The groups contained 2–6 lactating females and 3–14 sucking pups. Due to the relative synchronization of births, 73% of the pups present in each group during lactation were non-offspring. Each of the 22 lactating females in the six groups suckled non-offspring in addition to her own offspring. On average, females suckled 86% of non-offspring present in their groups. Thus, 98% of all pups (n = 47) received milk from non-mothers. Although suckling frequencies were significantly higher for mothers with their own individual offspring than with non-offspring individuals, females invested more total time suckling all non-offspring than did suckling just their own; this was possible because for each mother many more non-offspring than offspring pups were present during lactation. Suckling bouts were significantly longer for mothers with their own individual offspring than with non-offspring individuals. The proportion of non-offspring suckling of mothers correlated negatively with the proportion of own young among the pups of a group. Non-offspring suckling did not affect future reproduction of females. Our observations demonstrate extensive practice of communal suckling in G. musteloides under laboratory conditions. Probably because all mothers of a group participated more or less equally in communal suckling behavior, the obvious cost of giving energetically expensive milk to non-offspring did not result in reduced (future) reproductive success. Potential benefits directly involved with communal suckling are unclear. More indirectly, communal suckling as well as birth synchrony might contribute to the formation of advantageous multi-litter kindergardens.

Notes: Abstract We quantified the extent of communal suckling in the cavy Galea musteloides. Six groups of animals were held in large indoor enclosures and suckling behavior was recorded over 113 h of observation. The groups contained 2–6 lactating females and 3–14 sucking pups. Due to the relative synchronization of births, 73% of the pups present in each group during lactation were non-offspring. Each of the 22 lactating females in the six groups suckled non-offspring in addition to her own offspring. On average, females suckled 86% of non-offspring present in their groups. Thus, 98% of all pups (n = 47) received milk from non-mothers. Although suckling frequencies were significantly higher for mothers with their own individual offspring than with non-offspring individuals, females invested more total time suckling all non-offspring than did suckling just their own; this was possible because for each mother many more non-offspring than offspring pups were present during lactation. Suckling bouts were significantly longer for mothers with their own individual offspring than with non-offspring individuals. The proportion of non-offspring suckling of mothers correlated negatively with the proportion of own young among the pups of a group. Non-offspring suckling did not affect future reproduction of females. Our observations demonstrate extensive practice of communal suckling in G. musteloides under laboratory conditions. Probably because all mothers of a group participated more or less equally in communal suckling behavior, the obvious cost of giving energetically expensive milk to non-offspring did not result in reduced (future) reproductive success. Potential benefits directly involved with communal suckling are unclear. More indirectly, communal suckling as well as birth synchrony might contribute to the formation of advantageous multi-litter kindergardens.

Notes: Im Rahmen einer Übersicht werden für einige der z. Z. wichtigsten Prozesse zur Gewinnung von Süßwasser aus dem Meer die verfahrenstechnischen und wirtschaftlichen Probleme aufgezeigt. Intensiver behandelt werden die mehrstufige Entspannungsverdampfung, Langrohrverdampfung, Kristallisationsverfahren und das Verfahren der umgekehrten Osmose.