The fertility capability soil classification system: Interpretation, applicability and modification

Metal Accumulation in 5 Native Plants Growing on Abandoned Cu-Tailings Ponds

“…Regarding exchangeable cations, Ca was the most abundant among alkaline-earth cations followed by Mg, K and Na. K contents in almost all the samples were lower than 0.2 cmol (+) kg -1 revealing a deficiency of this element [21]. The average cation exchange capacity observed as 4.39 cmol (+) kg -1 .…”

Vulnerability of tropical forest ecosystems and forest dependent communities to droughts

“…Therefore, the relationships between NPP and precipitation levels were further explored within each of the three soil texture classes especially since they represent more than half (59%) of the soil textures found in the humid tropics. Sanchez et al (1982) reported that generally 45% of the humid tropical soils are clayey, 23% loamy, 16% loamy over clayey, 13% sandy, 1% sandy over loamy and 2% organic. The results of the remaining nine soil texture classes, with no significant relationships between precipitation levels and NPP, suggest that ~41% of the terrestrial areas are less vulnerable to drought.…”

“…Data do not exist, however, to answer the second question due to a lack of data on how much productivity capacity is harvested by people from forests where the field plots are located. The second question can be indirectly explored heuristically by estimating how much productivity is no longer available for harvest by local communities due to droughts and where data were aggregated by each of the three soil textures classes that account for 59% of the soils in the humid tropics (Sanchez 1982). It allows us to explore the impact of droughts on productivity level for the most common soil textures found in the tropics.…”

“…This experiment showed that two years of continuous rainfall exclusion (50% reduction in throughfall reaching the soil) resulted in a modeled prediction of an average decrease of 13-14% in GPP and 40-45% decrease in GPP during the dry period of the year. In contrast, forests growing on clay textured soils (which accounts for 45% of the total terrestrial 509 area of humid tropics; Sanchez et al 1982) were at risk to lose NPP if precipitation increased 510 (perhaps the clays become waterlogged) (see Figure 3). For the clay textured soils, no data points 511 were available for forests growing below 2000 mm yr -1 in our database to determine how 512 productivity levels would respond to lower precipitation levels.…”

“…Of 12 soil textural classes, forests growing on three textural classes (i.e., sand, sandy loam and clay) had productivity levels changing in response to precipitation levels. Since these three textural classes are found in over half of the tropical forest sites (Sanchez et al 1982), relationships between NPP and precipitation (e.g., NPP per precipitation amounts) were examined to search for any potential trends and/or thresholds. A by-product of this exercise generated an estimate of the potential drought impact on productivity as well on the amount of productivity capacity available for harvest by humans.…”