Eville Gorham

Litter production in forests of the world

Publisher Summary In this chapter, the litter production in forests of the world is discussed. The study of quantitative aspects of litter–fall is an important part of forest ecology, dealing with a major pathway for both energy and nutrient transfer in ecosystem. This chapter collates the available data on the quantity of litter produced by forests in different parts of the world. It demonstrates the importance of litter–fall in the nutrient cycle of the forest, and the significance in soil development is investigated in the types of forest humus layer. Harvest methods are used to commercially utilize litter. The various sources, selection criteria, arrangement, and presentation of data are provided. The annual production of leaf and total litter by forests of the world are tabulated. The detailed litter separation components, percentage of non–leaf litter in different climates, understory litter, mineral material, and organic material are also described. Major factors affecting litter–fall are evergreen gymnosperms and deciduous angiosperms, and the environment. The proposed treatments for litter–fall are also discussed. The seasonal litter–fall of in forests is graphically represented and the dry weight of standing crops of leaves on an annual production basis is tabulated.

Magnitude and significance of carbon burial in lakes, reservoirs, and peatlands

Globally, lakes are currently accumulating organic carbon (OC) at an estimated annual rate of about 42 Tgṁyr −1 . Most of the OC in all but the most oligotrophic of these lakes is autochthonous, produced by primary production in the lakes. The sediments of reservoirs accumulate an additional 160 Tg annually, and peatlands contribute 96 Tg annually. These three carbon pools collectively cover less than 2% of the Earth9s surface and constitute a carbon sink of about 300 Tgṁyr −1 . Although the oceans cover 71% of the Earth9s surface, they accumulate OC at a rate of only about 100 Tgṁyr −1 .

Environmental Factors Controlling Methane Emissions from Peatlands in Northern Minnesota

Controls on methane emission from peatlands in northern Minnesota were investigated by correlation to environmental variables and by field manipulation. From September 1988 through September 1990, methane flux measurements were made at weekly to monthly intervals at six sites in the Marcell Experimental Forest, northern Minnesota (two open bog sites, two forested bog sites, a poor fen, and a fen lagg). Flux was related to water table position and peat temperature with simple correlations at individual sites and multiple regression on all sites together. The effect of water table was also investigated experimentally in “bog corrals” (open-ended metal enclosures set in the peat) in which water table was artificially raised to the surface in the driest peatland. Temperature largely controlled variation in flux within individual ecosystems at Marcell, but hydrology distinguished between-site variation. Water table position, peat temperature, and degree of peat humification explained 91% of the variance in log CH4 flux, predicted annual methane emission from individual wetlands successfully, and predicted the change in flux due to the water table manipulation. Raising the water table in the bog corrals by an average of 6 cm in autumn 1989 and 10 cm in summer 1990 increased emission by 2.5x and 2.2x, respectively. Just as expanding the scale of investigation from a single habitat in a wetland to several wetlands necessitates incorporation of additional variables to explain flux (water table, peat characteristics), modeling flux from several wetland regions, if possible, will require the addition of climate parameters.

Influence of Lake Surface Area and Depth Upon Thermal Stratification and the Depth of the Summer Thermocline

Among the important physical characteristics of a lake are whether it stratifies seasonally, and if so, the depth to which wind-mixing is limited by the stratification. It is generally known that sufficiently shallow lakes tend to remain isothermal throughout the year and that the depth of the thermocline in stratified lakes correlates positively with the surface area of the lake. Observations from lakes in several different regions of the temperate zone of the northern hemisphere show that whether a lake stratifies depends on both the maximum depth and the surface area of the lake, whereas the depth of the thermocline depends primarily on the surface area. A modification of previously published scaling arguments provides a plausible theoretical basis for some of this behavior. These arguments account for additional shear-induced mixing associated with the fundamental internal seiche in small lakes and with near-inertial motion in big lakes. For lakes of cross-basin diameter less than 5,000 m (surface area less than 25 km2), an estimate of the depth of the thermocline, h, at the time of maximum heat content is given by: h≅2.0(τgΔρ)1/2L1/2 where τ is the wind stress associated with late summer storms, Δp is the density contrast between epilimnion and hypolimnion typical for lakes in that region near the time of maximum heat content, g is the gravitational acceleration, and L is the square root of the surface area of the lake. A consistent set of units must be employed.

The Influence and Importance of Daily Weather Conditions in the Supply of Chloride, Sulphate and Other Ions to Fresh Waters from Atmospheric Precipitation

This paper deals with chemical analyses for hydrogen, sodium, potassium, calcium, chloride, sulphate and nitrate ions in daily precipitation samples collected in the English Lake District, and examines the correlations of these analyses with (a ) one another, ( b) the amount of precipitation, (c) wind direction, (d) wind velocity, and (e) temperature. Highly significant correlations are found between estimates for H, K, Ca, NO3 and SO4 ions, and atmospheric pollution appears to supply much of the sulphate in Lake District rain, since it comes largely as sulphuric acid from the south-east. The correlation between Na and Cl is also extremely close, with the proportion between the two ions very similar to that in sea water. Since these two ions are supplied mainly from the south-west, in amounts which are greatly increased by high winds, sea spray may be inferred as the principal source. Nevertheless, evidence is presented for some small supply from atmospheric pollution, and it is furthermore suggested that mixed droplets of sea salt and sulphuric acid may, upon abstraction of moisture by freezing or evaporation, release gaseous hydrogen chloride to the air and so alter the balance of Na and Cl in precipitation. The supply of Na and Cl is also considerably higher in cold than in warm weather, a phenomenon possibly connected with stormier conditions and greater evaporation over the Atlantic Ocean. The atmospheric contribution of ions to natural waters via precipitation is shown to be of great importance, in particular to bog pools, to upland tarns on hard rocks, and to the soil solution in highly organic mor humus layers overlying heavily leached hillside soils. Sodium and chloride in most surface waters appear to be almost wholly supplied by sea spray, while calcium and magnesium bicarbonates are the main products of soil weathering. A net loss of rain acids is evident in all soil waters, although some may be more acid than normal rain water owing to considerable concentration by evaporation. The soil waters are relatively rich in potassium, presumably supplied from decaying vegetation.

Shoot height, weight and standing crop in relation to density of monospecific plant stands

DESPITE great differences in architecture and supporting tissue, monospecific stands of single-stemmed plants ranging in size from a moss to a tree follow a simple rule relating shoot dry weight and standing crop to density. We describe here an equation for this relationship which remains true for almost any fully occupied plant stand dominated by a single species.

On the acidity and salinity of rain

Abstract Analyses of pH, Na, K, Ca, Mg, HCO 3 , Cl, SO 4 , NO 3 , and PO 4 are recorded for forty-two rain samples collected in the English Lake District between 14 May and 23 October 1954. NaCl was often an important constituent, and the main source of Na, Mg, and Cl appeared to be sea-spray. SO 4 was clearly correlated with soot, and free H 4 SO 4 frequently accounted for an appreciable proportion of total ions. Ca, K, and SO 4 were correlated to some extent. HCO 3 was absent from more than half the samples. NO 3 and PO 4 were usually low in concentration. Sea-spray influence appeared greatest in autumn, while industrial pollution reached its highest concentration in spring. The ecological significance of the ions in rain is pointed out.

BIOTIC FEEDBACKS IN THE WARMING OF THE EARTH

A positive correlation exists between temperature and atmospheric concentrations of carbon dioxide and methane over the last 220,000 years of glacial history, including two glacial and three interglacial periods. A similar correlation exists for the Little Ice Age and for contemporary data. Although the dominant processes responsible may be different over the three time periods, a warming trend, once established, appears to be consistently reinforced through the further accumulation of heat-trapping gases in the atmosphere; a cooling trend is reinforced by a reduction in the release of heat-trapping gases. Over relatively short periods of years to decades, the correspondence between temperature and greenhouse gas concentrations may be due largely to changes in the metabolism of terrestrial ecosystems, whose respiration, including microbial respiration in soils, responds more sensitively, and with a greater total effect, to changes in temperature than does gross photosynthesis. Despite the importance of positive feedbacks and the recent rise in surface temperatures, terrestrial ecosystems seem to have been accumulating carbon over the last decades. The mechanisms responsible are thought to include increased nitrogen mobilization as a result of human activities, and two negative feedbacks: CO2 fertilization and the warming of the earth, itself, which is thought to lead to an accumulation of carbon on land through increased mineralization of nutrients and, as a result, increased plant growth. The relative importance of these mechanisms is unknown, but collectively they appear to have been more important over the last century than a positive feedback through warming-enhanced respiration. The recent rate of increase in temperature, however, leads to concern that we are entering a new phase in climate, one in which the enhanced greenhouse effect is emerging as the dominant influence on the temperature of the earth. Two observations support this concern. One is the negative correlation between temperature and global uptake of carbon by terrestrial ecosystems. The second is the positive correlation between temperature and the heat-trapping gas content of the atmosphere. While CO2 fertilization or nitrogen mobilization (either directly or through a warming-enhanced mineralization) may partially counter the effects of a warming-enhanced respiration, the effect of temperature on the metabolism of terrestrial ecosystems suggests that these processes will not entirely compensate for emissions of carbon resulting directly from industrial and land-use practices and indirectly from the warming itself. The magnitude of the positive feedback, releasing additional CO2, CH4, and N2O, is potentially large enough to affect the rate of warming significantly.

Peatland restoration: A brief assessment with special reference to Sphagnum bogs.

Recent literature on peatland restorationindicates as a general goal repairing orrebuilding ecosystems by restoringecosystem structure, trophic organization,biodiversity, and functions to thosecharacteristic of the type of peatland towhich the damaged ecosystem belonged, or atleast to an earlier successional stage.Attainment requires provision of anappropriate hydrological regime,manipulating surface topography, improvingmicroclimate, adding appropriate diaspores,manipulating base status where necessary,fertilizing in some cases, excludinginappropriate invaders, adaptively managingthrough at least one flood/drought cycle toensure sustainability, and monitoring on ascale of decades. Several matchingconditions favoring or opposing restorationare suggested.In the restoration of peatlands, successeshave generally been those of short-termrepair. Periods of restoration have beenmuch too short to ensure progression to, oreven well toward, a fully functionalpeatland reasonably compatible with thepristine state of similar peatlandselsewhere, although with altered surfacepatterns.Long-term monitoring ofpeatland-restoration projects is essentialfor a better understanding of how to carryout such restoration successfully.Paleoecology is suggested as anunderutilized tool in peatlandrestoration.

ON THE CHEMICAL COMPOSITION OF SOME WATERS FROM THE MOOR HOUSE NATURE RESERVE

The analysis of bog waters has a two-fold value. Firstly, it is of some intrinsic interest to elucidate the chemical composition of waters isolated from the mineral soil by organic deposits, and deriving their entire mineral supply from atmospheric precipitation. Secondly, the poverty of raised and blanket bogs in mineral nutrients is undoubtedly an important factor in determining their floras; and vegetation patterns can often be associated in a general way with water composition. This paper records the amounts of eleven constituents in various natural waters from the new Pennine Nature Reserve at Moor House - chiefly from pools on the blanket peats at Bog Hill, now under intensive investigation by the Nature Conservancy. DESCRIPTION OF THE AREA Moor House lies at an altitude of about 1800 ft. (550 m.) in the northern Pennine uplands, with a rainfall of about 64 in. (162 cm.), an average annual temperature of 44? F. (6.7? C.) and an average relative humidity of 86 per cent (all data for 1953 only). It is surrounded by moorland and blanket bog vegetation, on peat overlying drift or carboniferous rock with limestone bands. Burning and grazing have affected the plant communities, which in general resemble those described by Pearsall (1941) from the Stainmore district a little to the south. Among the least disturbed areas is Bog Hill, a slight elevation blanketed by deep peat and bearing a community dominated by Sphagnum acutifolium (agg., including rubellum and nemoreum), Calluna vulgaris and Eriophorum vaginatum, with Trichophorum caespitosum locally abundant. The Sphagnum cover is fairly continuous, with several small pools dotted about its surface. These most frequently contain Sphagnum cuspidatum and Eriophorum angustifolium, with the alga Chlorobotrys sometimes forming a scum at the bottom. In certain pools Drepanocladus fluitans is quite plentiful, in others the liverwort Gymnocolea inflata. Sphagnum papillosum is often abundant at the pool margins. METHODS Water samples were obtained on two occasions in 1954, following a dry spell (May 18th) and during wet weather (August 2nd). The bog pools sampled ranged in size from about 1 to 15 ft. (0.3 m. to 4.5 m.) across, and up to about 18 in. (46 cm.) deep. Collections were made and stored in polythene bottles, the waters being filtered through Whatman 541 papers (washed with three volumes of distilled water and one volume of sample) within a day or two of collection. pH was determined by glass electrode, and specific conductivity by a bright platinum cell and Mullard bridge. Calcium and magnesium were estimated by versenate titration with ammonium purpurate and eriochrome black T as indicators; samples coloured by humus were evaporated to dryness with a few drops of hydrogen peroxide and taken up in dilute hydrochloric acid. Sodium and potassium were measured by EEL flame photometer,