Carbon-cycling changes during regeneration of a decinduous broadleaf forest after clear-cutting II. Aboveground net production

Growth and death rates of aboveground plant parts were measured in a mature forest and four different-aged deciduous broadleaf forests regeneratede after clear-cutting, with special reference to rates for woody parts (stems and branches) of different diameters (ø) in rerms of the pipe model theory (Shinozaki et al., 1964). The total biomass increment of woody parts of trees higher than 1.3 m varied within a range of 2.1-4.6 ton ha^?1 yr^?1, the increase beingdue largely to the growth of canopy trees exposed to direct sunlight. Biomass increments of small (ø<1 cm) and medium (1≤ø<5 cm) woody parts were negligibly small except in the youngest forest, and changes in aboveground woody biomass with forest age after clear-cutting mainly resulted from accumulation of large (5 cm<ø) woody parts of canopy trees. Biomass loss of trees due to death and grazing increased with forest age from 4.0 to 8.3 ton ha^?1 yr^?1. Recovery of leaf and small wood falls was observed at the early stage of regeneration, while large wood falls increased during regeneration. Flower and fruit fall was markedly higher in the mature forest than in the other four forest types. Mortality of woody parts became higher with forest age and was 20, 5.0 and 0.46% yr^?1 for small, medium and large parts, respectively, at the mature stage. Aboveground net production of the forest was in therange 7.6-13.3 ton ha^?1 yr^?1 with the undergrowth vegetation lower than 1.3 m being 0.4-1.4 ton ha^?1 yr^?1. Production recovered rapidly at an early stage of regeneration and was highest in mature forest.     

Production ecology of phyto- and zooplankton in a eutrophic pond dominated byChaoborus flavicans (Diptera: Chaobolidae)

Primary production of phytoplankton and secondary production of a daphnid and a chaoborid were studied in a small eutrophic pond. The gross primary production of phytoplankton was 290 gC m⁻² per 9 months during April–December. Regression analysis showed that the gross primary production was related to the incident solar radiation and the chlorophylla concentration and not to either total phosphorus or total inorganic nitrogen concentration. The mean chlorophylla concentration (14.2 mg m⁻³), however, was about half the expected value upon phosphorus loading of this pond. The mean zooplankton biomass was 1.60 g dry weight m⁻², of whichDaphnia rosea and cyclopoid copepods amounted to 0.69 g dry weight m⁻² and 0.61 g dry weight m⁻², respectively. The production ofD. rosea was high during May–July and October and the level for the whole 9 months was 22.6 g dry weight m⁻².Chaoborus flavicans produced 10 complete and one incomplete cohorts per year. Two consecutive cohorts overlapped during the growing season. The maximum density, the mean biomass, and the production were 19,100 m⁻², 0.81 g dry weight m⁻², and 11.7 g dry weight m⁻²yr⁻¹, respectively. As no fish was present in this pond, the emerging biomass amounted to 69% of larval production. The production ofC. flavicans larvae was high in comparison with zooplankton production during August–September, when the larvae possibly fed not only on zooplankton but also algae.     

Studies on the life history of the population of an evergreen herb,Pyrola japonica,on the forest floor in a warm temperate region

Photosynthetic and respiratory activities and gross production in relation to temperature conditions were investigated in the population of an evergreen herb,Pyrola japonica, growing on the floor of a deciduous forest in the warm temperate region of central Japan. Analysis of the temperature-photosynthesis relationship ofP. japonica leaves during the growing season indicated distinct seasonal changes in the temperature optimum for photosynthesis. This population was found to be acclimatable to ambient air temperatures exceeding 15C, but this acclimation became less pronounced under thermal conditions below 15 C. This plant possessed narrow photosynthetic optima in the warm season but wide optima in the cold season. The shape of the temperature-respiration curve did not vary significantly with the months except for April. The Q₁₀ for respiration between 10 C and 20 C was calculated to be 1.93–2.65. Annual dry matter loss associated with respiration was estimated to amount to 159.1 g d.w.m⁻² based on the measurements of the seasonal changes in the respiratory activity of each organ. Gross production of this population was estimated to be 219.3 g d.w.m⁻² year⁻¹ as the sum total of the net production (60.2 g d.w.m⁻²year⁻¹) and the respiration. Monthly gross production was high in the early growing season, and low and stable in winter.     

Atmospheric input of inorganic nitrogen to the Western Mediterranean

Bulk inorganic nitrogen deposition was monitored over a period of 3 years at the Bavella Pass (Corsica, France). Annual fluxes range between 126 and 150mol.m^–2.d-^–1, increasing slightly with annual rainfall. Natural background average concentrations of rain water and associated fluxes were estimated from a classification of rain events into natural (Oceanic and Saharan), polluted and composite. Long range transport of incoming polluted air masses increases the atmospheric wet nitrogen input by at least a factor of 1.6 in this Mediterranean area. Extrapolation of atmospheric dissolved inorganic nitrogen input to the Western Mediterranean leads to fluxes of 80 to l00mol.m^–2.d-^–1. This atmospheric input is in the same order of magnitude as the inorganic nitrogen riverine input. As a consequence, the nitrogen budget for the Mediterranean has had to be reassessed. Atmospheric wet inorganic nitrogen input is of noticeable importance to marine Mediterranean ecosystems, representing on average 10 to 25% of new production in the Western Basin, with values of up to 60% in oligotrophic zones.     

Microcalorimetric investigations on human leukemia cells--Molt 4

Heat production by leukemia cells Molt 4, growing in suspensions with 1 and 3 x 10(5) cells/ml for 4 days, was studied by microcalorimetry. Heat production rates were related to cell growth, glucose consumption, lactate production and cellular ATP-content. The results show that the time course of heat dissipation is dependent on initial cell number. However, observed thermal power maxima were fairly identical in all experiments. Heat production rates per cell were similar during the initial phase of the study independently of initial cell number, while higher cell densities resulted in significantly lower rate of heat production. Glycolytic conversion of glucose into lactate is nearly stoichiometric. Our results indicate a relationship between heat production and amounts of glucose and lactate in the medium. ATP concentration in cells decreased after 24 hours of culture.     

旱地作物生态工程的设计

旱地作物生态工程是运用生态学和系统科学的原理和方法而设计和组建的旱地作物生产工艺体系。它把作物及其环境作为一个系统,统筹兼顾,相互协调,全面安排,综合利用。其最终目标是建立高效的,相对平衡的旱地作物生态系统。工程的最大特点在于它的整体性和综合性。它是作物先进生产技术的科学组装     

EVOLUTION OF FLORAL TRAITS IN A HERMAPHRODITIC PLANT: FIELD MEASUREMENTS OF HERITABILITIES AND GENETIC CORRELATIONS

Genetic variances, heritabilities, and genetic correlations of floral traits were measured in the monocarpic perennial Ipomopsis aggregata (Polemoniaceae). A paternal half-sib design was employed to generate seeds in each of four years, and seeds were planted back in the field near the parental site. The progeny were followed for up to eight years to estimate quantitative genetic parameters subject to natural levels of environmental variation over the entire life cycle. Narrow-sense heritabilities of 0.2–0.8 were detected for the morphometric traits of corolla length, corolla width, stigma position, and anther position. The proportion of time spent by the protandrous flowers in the pistillate phase (“proportion pistillate”) also exhibited detectable heritability of near 0.3. In contrast, heritability estimates for nectar reward traits were low and not significantly different from zero, due to high environmental variance between and within flowering years. The estimates of genetic parameters were combined with phenotypic selection gradients to predict evolutionary responses to selection mediated by the hummingbird pollinators. One trait, corolla width, showed the potential for a rapid response to ongoing selection through male function, as it experienced both direct selection, by influencing pollen export, and relatively high heritability. Predicted responses were lower for proportion pistillate and corolla length, even though these traits also experienced direct selection. Stigma position was expected to respond positively to indirect selection of proportion pistillate but negatively to selection of corolla length, with the net effect sensitive to variation in the selection estimates. Anther position also was not directly selected but could respond to indirect selection of genetically correlated traits.     

Comparison of wild type and genetically engineered nuclear polyhedrosis viruses of Autographa californica for mortality, virus replication and polyhedra production in Trichoplusia ni larvae

Virus replication and polyhedra production of two polyhedron-positive recombinant nuclear polyhedrosis viruses of Autographa californica, AcJHE.KK and AcAaIT which encode juvenile hormone esterase and scorpion toxin, respectively, were compared with those of a plaque purified wild-type nuclear polyhedrosis virus, AcMNPV-C6, in Trichoplusia ni larvae. Though average times required to kill the T. ni larvae increased with the age of the larvae, killing time by either recombinant virus was significantly shorter than that by wild-type virus. Killing time was reduced ca. 30% for AcAaIT-infected larvae and 5 to 8% for AcJHE.KK-infected larvae as compared to that for AcMNPV-C6-infected larvae. The average weight of larvae infected with AcAaIT was significantly lower than that of larvae infected with AcJHE.KK and AcMNPV-C6. The mean numbers of polyhedra produced in each larva inoculated with AcAaIT and AcJHE.KK were ca. 20% and 60%, respectively, of those for AcMNPV-C6. Total virus titers in AcMNPV-C6-infected larvae were significantly higher than those in AcJHE.KK- and AcAaIT-infected larvae until 2 days post infection.     

Growth response of Bolboschoenus maritimus ssp. maritimus and B. maritimus ssp. compactus to different trophic conditions

Bolboschoenus maritimus (L.) Palla (=Scirpus maritimus L.) forms extensive stands in the littoral zone of small fishponds and as a weed in rice and maize fields. Within the species, two subspecies are distinguished: Bolboschoenus maritimus subsp. maritimus, B. maritimus subsp. compactus. They differ in ecology, especially in their relationships with trophic conditions and salinity of habitats. To determine growth response of these two types to different nutrient levels, we compared their seasonal development under experimental cultivation at four controlled nutrient levels. Some differences between the subspecies were found to be stable, regardless of nutrient level, namely greater amount of smaller underground tubers and more extensive rhizome system in subsp. compactus compared to less numerous larger tubers and simpler rhizome system in subsp. maritimus. In response to trophic conditions,the plants of subsp. compactus were more resistant to the conditions of the highest trophic level than those of subsp. maritimus, which were stressed. This demonstrates better adaptability and spreading ability of B. maritimus subsp. compactus at high trophic levels.