Biomass aboveground

Biomass Redistribution Associated with Deforestation and Fire. The influence of deforestation on biogeochemical cycles is dependent upon a number of factors associated with the unique characteristics of the ecosystem (climate, soils, topography, etc), the quantity of the total nutrient pool stored in aboveground biomass (Table II), and the level of disturbance (i.e. the degree of canopy removal, soil disturbance, and the quantity of wood or other forest products exported from the site). The quantity of biomass consumed by one or more slash fires following deforestation can also dramatically increase nutrient losses, influence post fire plant succession, and hence, postfire biogeochemical cycles. 

Table II. Total aboveground biomass (Mg ha ) in selected forests of the world.

The burning of slash following deforestation, whether intentional or unintentional, results in far greater direct and indirect losses of nutrients than deforestation alone. This is particularly true in many tropical forests where only a small fraction (if any) of the aboveground biomass is removed prior to burning. Carbon losses from slash fires in the tropical dry forest were 4-5 fold greater than C losses from wood export (Table IV) (55). Slash fires in tropical dry forests resulted in N losses of 428-500 kg ha whereas fuel wood export of the relatively N-poor coarse woody debris amounted to approximately 41 kg N ha" Losses of P increase with increasing fire severity. P losses of 10-77 kg ha" as a result of severe fires is not uncommon (Table TV) (53, 58, 60). 

In full-season soybeans and sunflowers planted into desiccated green rye, the elimination of tillage and the presence of rye mulch reduced aboveground biomass of C. album, A. artemisiifolia, and A. retroflexus 99,... 

CAGB Aboveground biomass. AGB and densities determined 49 days after test initiation. 

We can see that trees are major contributors to the plant biomass of this ecosystem. They account for 60% of the root and 98% of the aboveground biomass. The monitoring results showed also that the grasses provide a larger part of the annual... 

The differences in amounts and distribution of total biomass reinforce the hypothesis of nutrient availability, especially P, being the overriding determinant for biomass development. Forests with similar amounts of aboveground biomass can differ up to 100 Mg ha"i in total biomass when the belowground component is also measured (Table 4.2). The biomass contribution of roots can vary between 9 to 20% in those forests. Root/shoot ratios can range between 6 and 33, suggesting that belowground biomass may be allocated to increase nutrient and/or water uptake. 

Table 4.2 Belowground and aboveground biomass, percent contribution of belowground and root/shoot ratios in terra firme forests.

A comparison of these data with those of an Amazonian forest shows that the aerial biomass of the trees of a cerrado sensu stricto in central Brazil may be only 8 to 22% of that of an Amazonian forest, and the basal area only 10 to 26% (Table 5.3). This difference in biomass reflects directly on the nutrient pools in the biomass. A comparison of the data reported by Klinge et al. (1995) for the aboveground biomass and nutrient stock in two inundation forests in the Ilha de Marchantaria with the data for a cerrado sensu stricto from central Brazil (Silva 1990) illustrates how nutritionally poor the cerrado is in quantitative terms. The proportions of stock of essential nutrients in the tree biomass of cerrado are 7 to 16% for P, 1.7 to 4.6% for K, 0.83 to 3.09% for Ca, and 3.5 to 7.4% for Mg. Thus Ca, K, and Mg seem to be much more deficient in the cerrados than P. We have no corresponding data for the stock of nutrients in the root biomass of trees for comparison among the two ecosystems. This comparison is only illustrative of two specific sites. Estimates of aboveground biomass for the Amazonian forests may vary... 

Brown, S., and A. E. Lugo. 1992. Aboveground biomass estimates for tropical moist forests of the Brazilian Amazon. Interciencia 170an-Feb) 8-18. 

Fig. 7.4 Aboveground biomass and roots (0-15 cm soil depth) of 3-year-old stands of 4 indigenous tree species Terminalia amazonia, Hieronyma alchomeoides, Albizia guachapele, and Virola koschnyi, grown in pure plots, and a mixture of the 4 species at La Selva Biological Station, Costa Rica.

Fig. 9.1 Aboveground biomass estimates for Amazonian secondary forests, (a). Data for 0 to 20-year-old forests, (b). Data for 0 to 80-year-old forests. The data points for forests that are 60 years and older all come from a single study of secondary forests on abandoned agricultural clearings in the Upper Rio Negro region of Venezuela (Saldarriaga et al. 1988). Other sources of data are Aide 1993 Alves et al. 1997 Brown et al. 1992 Fearnside and Guimaraes 1996 Guimaraes and Fearnside unpublished manuscript, Moutinho 1998b Nepstad 1989 Salomao et al. 1998 Uhl et al. 1988.

Table 9.1 Total nutrient stocks in mature and secondary forest aboveground biomass and in the upper 20 cm (meant 1 SD)of Oxisol (Haplustox) soils within the Fazenda Vitoria, Paragominas, Brazil.

Table 11.3 Estimates of total aboveground biomass in Amazonia, sampling areas up to 1 ha...

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