Nutrient input–output budgets of tropical forest ecosystems: a review

Abstract

Atmospheric gains and hydrologic losses of calcium, magnesium, potassium, phosphorus and nitrogen for 25 tropical forest sites on a variety of geological substrates are reviewed. The data set comprised 19 lowland and six montane sites. Twenty studies were subjected to further analysis after initial quality control. These were subdivided into forests on (1) very infertile soils (N = 5), (2) (moderately) infertile soils (N = 5), (3) moderately fertile soils (N = 4) and (4) fertile soils (N = 4). Two studies pertaining to large river basins were treated separately. Although variation in nutrient fluxes was large, reflecting both natural and methodological factors, scatter plots of annual calcium, magnesium and potassium losses v. annual runoff for small catchment areas revealed four groups with characteristic nutrient export patterns that corresponded closely with soil fertility levels. Element losses from the two large basins were much higher than those recorded for small basins in the same areas and were interpreted in terms of depths of weathering front, river incision and root network. Phosphorus accumulated in virtually all cases, reflecting the low mobility of the element. Nitrogen budgets were generally very incomplete. There is a need for more and careful studies of tropical forest nutrient budgets, especially for nitrogen. Standardization of methodology is essential if comparability of results is to be improved.

Ecological feedbacks following deforestation create the potential for a catastrophic ecosystem shift in tropical dry forest

“…This study demonstrates that P losses are compounded by the postdisturbance decrease in P input from atmospheric deposition. Our estimates of P deposition in rainfall (0.26-0.81 kg/ha per year) are comparable to those from other tropical systems (26)(27)(28)(29)(30) and are consistent with the few existing measurements showing P enrichment in throughfall (27,30). Our data support a positive feedback between inorganic P deposition and vegetation: the presence of the canopy augments the amount of P deposited by throughfall to the forest floor.…”

Litterfall, precipitation and nutrient fluxes in a secondary lowland rain forest in Ile-Ife, Nigeria

“…Th roughfall estimate of 77% of annual rainfall of 1078.6 mm in this study is slightly lower than the range for lowland (Bruijnzeel 1990); Malayan forest, 78.8% (Manokanran 1979), Bornean and Brunei rain forest, 81 -83% (Sinun et al 1992) and a plot within this forest, 78.8% (Muoghalu & Oakhumen 2000). It is however very similar to 55 to 88% reported by Brasell & Sinclair (1983) for an Australian rain forest.…”

Precipitation partitioning and related nutrient fluxes in a subtropical forest in Okinawa, Japan

“…Xu et al stemflow are modified mainly through the processes of washoff of materials deposited during the previous period without rain, and by leaching of nutrient from plants, and absorption of ions from the rain [34,36]. The actual nutrient balances depend on forest type, rainfall excess and soil types and may reflect different patterns of behavior in nutrients in different ecosystems [5,8,24,30].…”