The dwarfed conifer forests occurring on the coastal terraces of Mendocino County, California, are oligotrophic communities containing edaphic endemics as dominants. Species distributions and community characteristics are traced along a gradient in podzolization of the soils from these pygmy conifer stands on highly weathered terrace spodosols, to redwood stands on weakly developed slope spodsols. Vegetation stature, canopy closure, species richness, litter biomass and pH generally decrease along the gradient as podzolization and nutrient impoverishment increase, whereas soil organic matter and available water capacity tend to be highest at the gradient extremes. Analyses of pygmy forest soils show low levels of macro— and micro—nutrients, and high levels of exchangeable aluminum. When ordinations of stands based on vegetational data are compared with rankings based on environmental data, changes in pH of the soil A horizon are found to correlate most highly with vegetation changes. Nutrient loss and acidification, initiated by varying rates of soil weathering in the pygmy forest region, may be aggravated, in the case of pygmy forest soils, by a series of feedback effects, including solubilization of possibly toxic amounts of aluminum by low pH, which may contribute to the observed plant stunting and shrinking pools of nutrients in the biomass. A ranking of stands along a soil nutrient gradient, based on field observations and presence data for species, correlated successively less strongly with ordinations computed by similarity—projection, Bray—Curtis method, importance—projection, principal components analysis, and factor analysis. Although these ordinations were expected to produce distortions in the interstand relations due to the modal and even polymodal nature of species response curves and to the presence of species not spanning the range of the data set, additional distortions due to variability in sample data were also highlighted.

Three soils having different chemical and physical properties were flooded with deionized water and used as bottom soils for greenhouse microponds. The submerged soils supplied sufficient nutrients to the overlying waters to sustain algal growth for 489 days in two successive floodings of 219 and 270 days each. Differences in electrical conductivity, pH, and nutrient concentration were observed among the three soils and a control nutrient solution. During the first flooding, indigenous algae prevailed in the soil systems, but during the second flooding the dominant algal genera were less diversified. In a companion study, in which perennial ryegrass (Lolium perenne L.) was grown in the same three soils, the grass yields per kilogram of soil could not be related to the ash-free biomass yields per kilogram of soil in the microponds. Algal growth could not be predicted from soil characteristics or solution composition, or the productivity of cropped soils, but the study showed that submerged soils can be a sole source of algal nutrients.

The wet tundra near Barrow, Alaska, is dominated by three species of graminoids: Dupontia fischeri, Carex aquatilis, and Eriophorum angustifolium. Root production, root turnover, and root distribution patterns of these three species were studied by direct observations of growing roots and by analysis of whole, interconnected tiller systems dug from the soil. Root weight per unit length and density of individual tillers were also measured in the field. Production of new roots was found to be strongly correlated with age of individual tillers, each species having a distinctive pattern and phenology. Root turnover rates also varied considerably; the range is from an annual turnover in E. angustifolium to 6—8(10) yr in C. aquatis. An estimated of root turnover on an ecosystem basis is about 100 g ° m— ² ° yr— ², or 25% of the live root biomass. Species with the shallowest and longest lived roots have the greatest weight per unit length of root, and vice versa. Each species has a characteristic root distribution pattern with depth and in relation to the progress of soil thaw.

Biotic and abiotic pathways of incident energy are rarely considered together in comparable detail, so little is known about whether energy or carbon relations remain constant in contrasting energy environments. An experiment to determine the fates of energy and carbon in cheatgrass (Bromus tectorum L.) was carried out on steep (40°) north— and south—facing slopes on a small earth mound, using many small lysimeters to emulate swards of cheatgrass. Meteorological conditions and energy fluxes that were measured included air and soil temperatures, relative humidity, wind speed, incoming and reflected shortwave radiation, net all—wave radiation, heat flux to the soil, and evaporation and transpiration separately. The fate of photosynthetically fixed carbon during spring growth (31 March to 31 May) was determined by separation of the plant tissues into mineral nutrients, ash, crude protein, crude fat, crude fiber, and nitrogen—free extract (NFE) (the proximate analysis scheme routinely used for feed analysis) for roots, shoots, and seeds separately. Temperatures and humidities were not notably different between slopes. However, all terms in the radiation balances were significantly larger on the south exposure, and the sensible heat flux to the atmosphere on the south exposure was much greater than on the north. The energy—saturated south exposure was subjected to water stresses much earlier than the north exposure. Total transpired water, the fraction of energy used to transpire water, and soil water content simultaneously showed an abrupt decrease in slope at about 10% soil water content (—14 bars average water potential) in the 60—cm lysimeter soil profile, indicating a rather sudden decrease in water availability to the plants. This change occurred near day 30 on the south exposure, and near day 45 on the north exposure, implying that water was readily available to the north exposure for about 2 wk longer than on the south exposure. Root and seed production were both about 30% greater on the north exposure than on the south, but shoot production was not different. Heats of combustion (caloric content) differed between roots, shoots, and seeds, but not between exposures. Total production and total energy fixation were not statistically different on the two exposures, because the greater biomass and variability of the shoots overwhelmed the statistically significant differences in roots and seeds. Incident shortwave radiation was very much greater on the south exposure than on the north, so the south exposure was much less efficient in converting solar energy into chemical energy stored in plant tissues. The clearest difference in carbon pathways occurred for crude protein in shoot tissues at the end of the growing season (23 g m— ² on the north compared to 30 g m— ² on the south). Since both exposures began the growing season with 33 g m— ², shoot protein was translocated to other tissues during the season, to a greater extent on the north exposure than on the south. The crude fiber and NFE (g m— ²) in seed tissues were both greater on the north exposure, reflecting only a greater total seed biomass; but for roots and shoots there were no appreciable differences between exposures other than crude protein. The average individual seed weight was only about 10% heavier on the north exposure, although the north produced more than a third more total seed biomass. The composition of an average seed indicated that the difference in seed weight was caused primarily by about 8% more NFE in north exposure seeds, probably starches in the endosperm. By contrast, the crude protein in an average seed was almost identical between slopes–possibly a very important compensation for seedling size and vigor. Homeostasis (self—regulation) was evident as a gradation decreasing in the order seed viability (very strongly homeostatic) > seed composition (strong) > shoot and root composition (moderately strong) > average seed weight = shoot production (moderate) > seed number = mineral content (weak) > total root and seed production (no detectable homeostasis).

With the exception of sediment deposited close to land, organic matter in marine sediments is derived mainly from planktonic debris from the local biomass. Since planktonic material is principally composed of proteins and carbohydrates (hemicellulose), it is of interest to compare the pathway of organic decay in a marine sediment with that of a terrestrial soil where lignin and cellulose is the chief organic input.The article briefly summarizes the present state of knowledge on early diagenesis of organic matter in marine soils. Information is based on the authors studies on distribution of amino acids and sugars in marine sediments deposited under reducing and oxidizing conditions. It is concluded that diagenesis is controlled by (i) biological degradation at the sediment-water interface, (ii) organic condensations, (iii) organic-metal ion interactions, and (iv) organicmineral interactions.

In the present paper, distribution of nitrogen in different plant compartments and in the top 20 cm soil from three grassland sites for a 3-year period at the time of peak standing crop has been studied. The sites represent short-grass, mixed-grass, and tall-grass prairies located, respectively, in Colorado, South Dakota, and Oklahoma. Partitioning, uptake, transfers, and release of nitrogen in the above-ground and below-ground compartments were evaluated with respect to the abiotic factors. A positive linear relationship was found with the total nitrogen content in shoots (g m−2) and the annual precipitation as well as with the annual actual evapotranspiration. On the other hand, a negative linear relationship was found with the nitrogen per gram dry weight in shoots, and the annual precipitation and evapotranspiration. Inter-seasonal and inter-site variations in the nitrogen content (g m−2) in different plant compartments indicated significant differences. The short-grass and mixed-grass prairies indicated greater nitrogen content in the above-ground and below-ground plant tissues as compared to the tall-grass prairie. However the total nitrogen content in shoots from the tall-grass prairie was greater than that of short-grass or mixed-grass prairies which was mainly due to greater shoot biomass in the tall-grass prairie. The major portion of nitrogen (over 90 per cent) in the system was retained in the soil while a fraction of nitrogen (4–8 per cent) resided in the biological material. The distribution of nitrogen in different plant compartments, the uptake, transfer, and release of nitrogen with respect to abiotic factors have been discussed in detail.

Net primary productivity and distribution of mixed grassland plant communities in western North Dakota were studied. The semiarid continental climate supports several grassland types, delimited on the bases of topography and substratum. The dominant species and herbage (shoot) production (mean of 2 yr) of stands located on what were classified as silty range sites included, on rolling upland, (1) Stipa viridula (128 g m— ²), Stipa comata (128 g m— ²), and (3) Bouteloua gracilis (110 g m— ²); on ravine slopes, (4) Stipa spartea—forbs (135 g m— ²) and (5) Andropogon spp. (126 g m— ²). On sandy range sites were found, in shallower ravine bottoms and at bases of slopes, (6) Sporobolus heterolepis—Stipa spartea (160 g m— ²) and (7) Sporobolus heterolepis (185 g m— ²); on slopes with very sandy soils, (8) A. scoparius—Stipa spartea (132 g m— ²), (9) A. scoparius—forbs (107 g m— ²), and (10) A. scoparius (119 g m— ²). The highest annual herbage production was measured in Stand 7 (200 g m— ²) and the lowest in Stand 3 (77 g m— ²). Root mass ranged from 6230 g m— ² (Stand 7) to 3030 g m— ² (Stand 9). Annual root production could not be measured but was estimated to be equivalent to herbage production. Variation in herbage production between sites and between years was attributed to differences in soil moisture and fertility (especially the latter in sites with sandy soils). Fresh mulch was highest in the Stipa—dominated sites (288—320 g m— ²) and lowest in Andropogon— and Bouteloua—dominated stands (212—234 g m— ²). The highest fresh mulch decay constant and shortest equilibrium time were determined to occur in sites dominated by Sporobolus heterolepis, and the converse for Stipa—dominated sites. Chlorophyll values ranged from 78 mg m— ² (Stand 3) to 542 mg m— ² (Stand 7); variation depended on plant morphology and phenology as well as biomass. Maximum efficiency in herbage production occurred later in the year for stands with a large warm—season component (Sporobolus heterolepis an Andropogon spp.) than in sites dominated by cool—season grasses (Stipa spp.). On an annual basis, Stand 7 was most efficient (0.12%) and Stand 3 least (0.06%). The interrelationships between drought tolerance, phenology (cool— vs. warm—season development), physiology, and production are discussed.