Forests temperate

Table 1 Range of biomass and productivity for temperate forests, temperate grasslands, and moist to wet...

Temperate forest Temperate grassland Tropical forest... 

The availability of reactive nitrogen limits photosynthesis in a wide variety of terrestrial and marine ecosystems. Nitrogen limitation is particularly common in temperate and boreal forests, temperate grasslands, and Arctic and subalpine tundra, and in estuaries and coastal marine ecosystems in temperate zones.Introduction of relatively large external inputs of the nutrient must be expected to change the productivity of affected ecosystems, as well as the modes of their nitrogen storage and composition of their species. 

In a temperate forest ecosystem on Isle Royale, Michigan, ecologists found that it takes 762 pounds (346 kg) of plant food to support every 59 pounds (27 kg) of moose, and that 59 pounds of moose are required to support every one pound (0.45 kg) of wolf. The basic point is that massive amounts of energy do not flow from one trophic level to the next energy is lost at each stage of the food chain, so there are more plants than herbivores and more herbivores than carnivores. 

Several studies, based on models, examined the effects of land-use change on the global carbon cycle and conclude that there is a net release of carbon due to land clearing. However, the results and conclusions of these studies are based on assumed sizes of vegetation carbon pools which are inputs to the models. For example, Melillo et al. 24) concluded that boreal and temperate deciduous forests of the northern hemisphere are net sources of atmospheric carbon. Their analysis used values for carbon density derived by Whittaker and Likens 19) from work by Rodin and Bazilevich (27). Rodin and Bazilevich extrapolated results of small, unrelated studies in Europe and the USSR to estimate total biomass of Eurasian boreal and temperate deciduous forests. Their estimates have since been extrapolated to forests worldwide and are used often today. 

Negligible quantities of wood may be removed when tropical forests are cut for shifting cultivation or pasture conversion. In contrast to the temperate coniferous forests of the Northwest USA, only small quantities of wood are usually exported as a result of timber operations in tropical evergreen forests. In... 

Temperate Coniferous Forest Coastal redwood USA Primary 1150-3200 28... 

Temperate Deciduous Forest Global Average Primary 174 89... 

Soil surface temperature of slash fires in tropical and temperate forests... 

Figure 6. An undisturbed primary temperate coniferous forest in the Pacific Northwest, USA (Olympic National Park). The nutrient balance of this forest is in a relative equilibrium with elemental inputs closely approximating elemental losses.

Figure 7. Another temperate coniferous forest site of the Pacific Northwest, USA following clearcutting and slash burning. Severe levels of deforestation result in large quantities of nutrient losses through wood export, biomass burning and accelerated erosion and leaching losses. (Photograph is by courtesy of Dian L. Cummings. ...

Tropical forests and savannas are the primary source of C emissions that originate from biomass burning (73, 75). However, temperate forests are also sources of atmospheric carbon. Harmon et al. (77) reported that conversion of primary temperate forests to younger, second-growth forests lead to increases in atmospheric CO2 levels, due to losses in long-term carbon storage within these forests. They ascertained that timber exploitation of 5 million hectares of primaiy forests in the Pacific Northwest of North America during the past century has resulted in the addition of 1,500 Tg of C to the atmosphere. 

Crotnack, Jr., K. Delwiche, C.C. McNabb, D.H. In Symbiotic Nitrogen Fixation in the Management of Temperate Forests Gordon, J.C. Wheeler, C.T. Perry, D.A., Eds. Forest Research Laboratory, Oregon State University, Corvallis, OR, 1979 pp 210-223. 

Alfisols Bt horizon with moderate base saturation Temperate deciduous forests... 

Ultisols Low base saturation and Bt horizon Tropical to temperate, often forested... 

Discuss how physical weathering operates in each of the following environments (1) sea shore, (2) hot desert, (3) temperate forest. 

Aggradation or degradation of biomass or soil reservoirs may also produce effects that appear to be fractionation. This is because the elemental ratios in vegetation or soil reservoirs can be very different from those of bedrock. Sufficiently large and rapid changes in these reservoirs are sometimes evident in river chemistry. For example, the uptake and release of potassium in association with the seasonal growth and loss of leaves can affect the composition of streams that drain temperate deciduous forests (Likens et al, 1977 Vitousek, 1977). 

Sedjo, R. A. (1992). Temperate forest ecosystems in the global carbon cycle, Ambio, 21, 274-277. 

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