Proton Budget for a Japanese Cedar Forest Ecosystem

The proton budget for a Japanese cedar (Cryptomeria japonica) forest in Gunma Prefecture, Japan, was studied by estimating biogeochemical fluxes. The proton budgets were estimated for three individual compartments of the ecosystem: vegetation canopy, and the upper (O horizon + 0–10 cm) and lower (10–100 cm) soil layers. The dominant proton sources in the compartments were atmospheric deposition (1.2 kmol ha^?1 yr^?1), nitrification (5.1 kmol, ha^?1 yr^?1) and base-cation uptake by vegetation (8.0 kmol, ha^?1 yr^?1) respectively. These proton sources were neutralized almost completely within the individual compartments mainly by base-cation release from the canopy or the soil. The sum of internal proton sources was five times as large as that of external ones. Nitrogen input from the atmosphere was 2.2 kmol ha^?1 yr^?1, whereas its output from the lower soil layer was 3.9 kmol ha^?1 yr^?1, indicating that a net loss of nitrogen occurred in the ecosystem. However, this did not cause the acidification of soil leachates because of a sufficient release rate of base cations from the soil.     

Manure application has an effect on the carbon budget of a managed grassland in southern Hokkaido,Japan

Abstract

The carbon (C) budget of managed grassland in a cool-temperate region of Japan was estimated using a combination of eddy covariance and the biometric method for five years, to evaluate the effect of manure application. Chemical fertilizer was applied to the fertilizer (F) plot at a rate of 79 ± 20 kg N ha^?1 yr^?1. In the manure (M) plot, dairy cattle manure was applied at a rate of 10 Mg fresh matter ha^?1 yr^?1 (1923 ± 407 kg C ha^?1 yr^?1, 159 ± 68 kg N ha^?1 yr^?1). There was no significant difference in seasonal gross primary production (GPP) and harvest between the treatment plots, indicating that both fertilizer and manure can increase the biomass production. Annual net ecosystem production (NEP) and ecosystem respiration (RE) was significantly different between the treatment plots. The difference in RE, and between M and F plots approximates heterotrophic respiration of manure (RHm), which ranged from 0.9 to 1.3 Mg C ha^?1 yr^?1. Average annual RHm was 1.1 ± 0.4 Mg C ha^?1 yr^?1, and accounted for 56% of the total amount of applied manure C. The annual net biome production (NBP) in the M plot (from 0.0 to 1.5 Mg C ha^?1 yr^?1) was significantly higher than in the F plot (?1.4 to 0.5 Mg C ha^?1 yr^?1). The long-term effect of manure application combined with chemical fertilizer did not reduce grass production compared with chemical fertilizer only; however, manure application decreased the NEP throughout manure decomposition, and long-term manure application enhanced the NBP.     

Carbon stock and deposition in phytomass of the Russian forests

Russian forests occupy an area of 771 Mha with a wood volume of 81.6 × 10⁹ m³. In this paper we estimate the carbon (C) storage and annual C deposition in living vegetation for stands of different age groups according to information in the Russian National Forest Inventory (NFI). Conversion of root C storage into phytomass was based on phytomass/storage ratios calculated from data from 1900 test areas in the different forest regions of Russia. We developed these conversion ratios for different phytomass fractions, namely: stems, branches, roots and foliage, for different forest forming species. Of the total forest area (771 Mha), C storage in the living phytomass is 35.07 Pg C. Total annual C deposition in forest vegetation is estimated at 213.2 Tg C. We considered the role of the main forest forming species in the C cycle of the forest vegetation taking into account the actual structure of the Russian forests.     

Calculating critical loads of acid deposition with PROFILE — A steady-state soil chemistry model

A steady state soil chemistry model was used to calculate the critical load of acidity for forest soils and surface waters at Lake GÄrdsjön in S.W. Sweden. The critical load of all acid precursors (potential acidity) for the forest soil is 1.64 kmol_c ha^?1 yr^?1, and 1.225 kmol_c ha^?1 yr^?1 for surface waters. For the most sensitive receptor, the critical load is exceeded by 1.0 kmol_c ha^?1 yr^?1, and a 80% reduction in S deposition is required, if N deposition remains unchanged. The critical load is largely affected by the present immobilization of N in the terrestrial ecosystem which is higher than the base cation uptake. The model, PROFILE, is based on mass balance calculations for the different soil layers. From measurable soil properties, PROFILE reproduces the present stream water composition as well as present soil solution chemistry. The model calculates the weathering rate from independent geophysical properties such as soil texture and mineral composition.     

Nature and Magnitude of Atmospheric Fluxes of Total Inorganic Nitrogen and Other Inorganic Species to the Tampa Bay Watershed, FL, USA

We estimated the total inorganic fluxes of nitrogen (N), sulfur (S), chloride (Cl^?, sodium (Na⁺, calcium (Ca²⁺, magnesium (Mg²⁺, potassium (K⁺ and hydronium (H⁺. The resistance deposition algorithm that is programmed as part of the CALMET/CALPUFF modeling system was used to generate spatially-distributed deposition velocities, which were then combined with measurements of urban and rural concentrations of gas and particle species to obtain dry deposition rates. Wet deposition rates for each species were determined from rainfall concentrations and amounts available from the National Acid Deposition Program (NADP) monitoring network databases. The estimated total inorganic nitrogen deposition to the Tampa Bay watershed (excluding Tampa Bay) was 17 kg-N ha^?1 yr^?1 or 9,700 metric tons yr^?1, and the ratio of dry to wet deposition rates was ～2.3 for inorganic nitrogen. The largest contributors to the total N flux were ammonia (NH₃ and nitrogen oxides (NO _x at 4.6 kg-N ha^?1 yr^?1 and 5.1 kg-N ha^?1 yr^?1, respectively. Averaged wet deposition rates were 2.3 and 2.7 kg-N ha^?1 yr^?1 for NH₄ ⁺ and NO₃ ^?, respectively.     

Atmospheric Deposition of Acidifying Components to a Japanese Cedar Forest

One-year field measurements were conducted in a Japanese cedar (Cryptomeria japonica) forest, located in Gunma Prefecture, Japan. On the basis of the meteorological and atmospheric concentration data, the dry deposition of SO₂, HNO₃, NO₂ and HCl was estimated using the inferential method. The annual dry deposition of H⁺ was estimated at 721 eq ha^?1yr^?1, which was 40% larger than the measured annual wet deposition of H⁺ (514 eq ha^?1yr^?1). Therefore, dry deposition is an important pathway for the atmospheric input of H⁺ to the forest in the study site. The contribution of each gas to the dry deposition of H⁺ was as follows: SO₂, 25%; HNO₃, 32%; NO₂, 10%; and HCl, 33%. The extremely high contribution of HCl appeared to be caused by the high emission intensity of HCl due to waste incineration in the site region. The differences between estimated deposition and throughfall and stemflow measurements indicated that about 80% of the total deposition of H⁺ was taken up by the canopy.     

Potential hazards of lime application in a damaged pine forest ecosystem in Berlin,Germany

Ninety percent of the pines (P. Sylvestris) in the forests of Berlin (West) are classified as damaged. Needle and leaf analyses do not indicate nutrient deficiencies. In site of high S-inputs (55 kg ha^?1 yr^?1 with throughfall) total acid inputs are moderate (2.4 kmol ha^?1 yr^?1) due to their neutralization by carbonatic dusts. Heavy metal depositions have led to accumulations in the forest floor (e.g. Pb 150 mg kg^?1, Cd 0.5 mg kg^?1). The dominating soil type, a cambic arenosol (Ustipsamment) is strongly acidified (pH 3.2 – 4.0) and poor in available nutrients. On an experimental plot, the application of dolomitic lime (6.1 tons ha^?1) and fertilizer (145 kg ha^?1 K₂SO₄) led to a significant increase m pH and base saturation in the top 10 cm of the mineral soil after 2 yr. The data on element fluxes give evidence for increased mineralization rates, enhanced heavy metal accumulation in the forest floor and increased soil solution concentrations of potentially hazardous substances (Al, Cd, NO₃). The lime application is discussed in terms of site specific effects on ecosystem stability and groundwater quality.     

Impacts of longterm conservation measures on ecosystem services in Northwest Ethiopia

A Soil Conservation Research Program (SCRP) has been on-going in Anjeni Watershed, Amhara Region, Ethiopia since the 1980s, focussing particularly on soil-based, graded fanya juu terraces. This study was carried out to examine the long-term impacts of these soil and water conservation measures in improving ecosystem services. A comparative analysis was made with a non-treated 100 ha adjacent watershed (Zikrie). The Revised Universal Soil Loss Equation (RUSLE) was used in a geographic information system (GIS) to quantify soil loss. Representative soil samples were taken 30 cm deep soil pits in the loss and deposition zones in the terraced Anjeni and topo-sequential soil samples on both watersheds. Laboratory analysis was carried out at the National Soil Testing Laboratory (NSTL) of Ethiopia. Soil texture, pH and OC were analyzed for the 91 soil samples. A GIS analysis of the RUSLE factors was made on a 5 m grid cell basis. The mean annual soil loss rate in Anjeni was estimated to be 37 t ha^-1 yr^-1, while that of the adjacent non-conserved Zikrie was 45 t ha^-1 yr^-1. The total estimated soil loss in Anjeni watershed was 4214 t yr^-1. River valleys in the Anjeni watershed had the maximum mean annual estimated soil loss hazard (86 t ha^-1 yr^-1). Cultivated land had medium mean annual estimated soil loss (44 t ha^-1 yr^-1) due to the soil conservation works. Supporting the soil-based graded fanya juu terraces with biological soil conservation measures is important for the stability of the ecosystem.     

Structure and biomass of larch stands regenerating naturally after clearcut logging

Variations in the succession following cutting of a herbaceousLarix sibirica Ledeb. phytocoenosis along the southern boundary of boreal forests in southern Siberia and in Eastern Hentey, Mongolia, were studied. Morphometric methods were used to determine the dimensional hierarchies of coenopopulation individuals. Structure and productivity of the aboveground components including standing wood, herbaceous cover and litter were studied. The maximum aboveground phytomass was measured as 212.3 Mg ha^?1 (oven dry mass). The highest total aboveground biomass productivity rate of aLarix sibirica phytocoenosis located at its southern limit exceeds 7 Mg ha^?1 per year. The maximum annual phytomass increment was found to be 4.4 Mg ha^?1 for the overstorey trees, 2.1 Mg ha^?1, for the herbaceous layer and 0.7 Mg ha^?1 for forest litter.     

Effects of nitrogen deposition on the acidification of terrestrial and aquatic ecosystems

The concentration of ammonium and nitrate in precipitation has increased during this century. The deposition of N compounds (wet + dry) is reaching 30 to 40 kg ha^?1yr^?1 in many areas in Central Europe and above 20 kg in the southern parts of Scandinavia. In extreme situations throughfall data indicate depositions above 60 kg ha^?1yr^?1 in Central Europe and above 40 kg ha^?1yr^?1 in south Sweden. Very high depositions are observed on slopes at forest edges and adjacent to areas with animal farms and manure spreading. In areas with low N deposition almost all deposited N (>95%) will be absorbed in the tree canopies or in the soil. In areas with high deposition an increased outflow is observed which in some cases reach 10 to 15 kg ha-lyr-1. The increased output is an indication of N saturation of the ecosystem and it leads to acidification effects in soils, soilwater, groundwater and surface waters.     

Estimation of the Maximum Critical Load for Sulfur in South Korea

The maximum critical load of sulfur and its exceedance by the sulfur deposition of 1994–1997 were mapped for South Korea with a spatial resolution of 11 × 14 km using the steady-state mass balance method. The Korean soil and geological maps were used as basis for the estimations of the critical alkalinity leaching and the weathering rate of base cations. The normalized difference vegetation index data obtained from the Advanced Very High Resolution Radiometer (AVHRR) together with the observed primary productivity of plants were used for the estimation of the critical uptake of base cations. Wet deposition of the non-sea-salt base cations was derived from measured base cation concentrations in precipitation, precipitation rate and air concentration of total suspended particulate while dry deposition of base cations was estimated using the inferential technique using scavenging ratios. The predominant ranges of base cation weathering, uptake and deposition were estimated to be of 200 – 600 eq ha^?1 yr^?1, 200 – 400 eq ha^?1 yr^?1 and 400 – 600 eq ha^?1 yr^?1, respectively. Critical alkalinity leaching was mainly in the range of 1000 – 2000 eq ha^?1 yr^?1 due to relatively high value of precipitation runoff. Exceedance of sulfur critical load was found at 40 % of the ecosystems considered mainly in the southeastern part of Korea, and about 60 % of Korea ecosystems were sustainable against sulfur acidity loadings.     

Deposition Patterns of SO4 2−, NO3 − and H+ in the Brazilian Territory

SO₄ ^2?, NO₃ ^? and H⁺ depositions are estimated in the Brazilian territory based on the existing rainfall chemical data and on annual rainfall distribution over the whole territory. Local and regional depositions are estimated. Rainfall chemical data over the Braziliian territory shows that the average pH values are usually low (between 4.0 and 5.5). These values are observed in the tropical Amazon forest as well as in urban areas. However, the rainwater acidity in the tropical forests are due to organic acids naturally produced by the vegetation while in urban areas the acidity is mainly due to acidic anion deposition (NO₃ ^? and SO₄ ^2?). In some Amazonian areas, the average input values through rainfall for NO₃ ^? is about 0.06 keq.ha.yr^?1 and for SO₄ ^2? is between 0.23 and 0.54 keq.ha^?1.yr^?1. On the other hand, in some urban centers, such as São Paulo, values of .072 keq.ha^?1.yr^?1 for NO₃ ^? and 1.16 keq.ha^?1.yr^?1 of SO₄ ^2? are found and in sites where sulfate sources (coal mining) are present, as for the area of Florianópolis, values as high as 5.59 keq.ha^?1.yr^?1 for SO₄ ^2? are found.     

Trace element release from forest floor can be monitored by ion exchange resin tubes

Risk assessment of heavy metal input into forest ecosystems requires information about metal fluxes from the forest floor (organic layer) into the mineral soil. Common methods for the monitoring of element fluxes are generally time‐consuming and expensive. Additionally, the reliability of the results is in part contested especially for trace elements, showing very low concentrations which are sometimes even below analytical detection limit. We used ion exchange resin tubes installed below the forest floor to determine heavy metal and As fluxes at 25 forest monitoring sites in Germany. Chloride tracer experiments and the comparison of our data with throughfall and lysimeter data, determined within the Level II monitoring network, proved the accuracy of our method. Mean trace element fluxes based on the resin method were 50 g As ha^–1 yr^–1, 2 g Cd ha^–1 yr^–1, 168 g Cu ha^–1 yr^–1, 176 g Ni ha^–1 yr^–1, and 186 g Pb ha^–1 yr^–1.The results show that the organic layer may change into a source of heavy metals after emission has decreased.     

Studies of Atmospheric Nitrogen Deposition in a Mire of the German National Park Hochharz Mountains Using Two Different Methods

The purpose of this study was to determine the nitrogen (N) deposition in a mire of the German National Park Hochharz Mountains in regard to different input pathways of open area and forest stand deposition. High N deposition rates strongly affect the development and growth of mires in general. For determination of the open area N deposition two methods were applied: the bulk deposition method and the Integral Total Nitrogen Input (ITNI) method. This method is based on the ¹⁵N isotope dilution technique and was adapted at this study to evaluate its applicability for natural ecosystems as well as to compare with the traditional bulk method. The forest stand deposition included canopy throughfall, stemflow and fog was measured by means of bulk collectors. On the test site, bulk deposition measurements showed an input of 27 kg N ha^{? 1} yr^{? 1} in the open area and 47 kg N ha^{? 1} yr^{? 1} in the forest stand. The higher N input in the forest stand is caused by interception of fog by the canopy. N concentrations in fog were up to more than six times higher than in rain. The ITNI system yielded a total N deposition of 30 kg N ha^{? 1} yr^{? 1} on average in the open area. The small differences between the two simultaneously applied measuring techniques were caused by a minimum biomass development of the autochthonous plant Calamagrostis villosa in the ITNI system. With increasing biomass production the influence of plants on the atmospheric N input also increased. It can be concluded that the ITNI system is beneficial for the application in a natural ecosystem when using more robust and biomass producing plants. The measured atmospheric N deposition exceeds the critical load for nutrient poor mires and represents therefore a potential risk for the continuity of this ecosystem.     

Soil carbon sequestration in China through agricultural intensification,and restoration of degraded and desertified ecosystems

The industrial emission of carbon (C) in China in 2000 was about 1 Pg yr⁻¹, which may surpass that of the United States (1ċ84 Pg C) by 2020. China's large land area, similar in size to that of the United States, comprises 124 Mha of cropland, 400 Mha of grazing land and 134 Mha of forestland. Terrestrial C pool of China comprises about 35–60 Pg in the forest and 120–186 Pg in soils. Soil degradation is a major issue affecting 145 Mha by different degradative processes, of which 126 Mha are prone to accelerated soil erosion. Total annual loss by erosion is estimated at 5ċ5 Pg of soil and 15ċ9 Tg of soil organic carbon (SOC). Erosion‐induced emission of C into the atmosphere may be 32–64 Tg yr⁻¹. The SOC pool progressively declined from the 1930s to 1980s in soils of northern China and slightly increased in those of southern China because of change in land use. Management practices that lead to depletion of the SOC stock are cultivation of upland soils, negative nutrient balance in cropland, residue removal, and soil degradation by accelerated soil erosion and salinization and the like. Agricultural practices that enhance the SOC stock include conversion of upland to rice paddies, integrated nutrient management based on liberal use of biosolids and compost, crop rotations that return large quantities of biomass, and conservation‐effective systems. Adoption of recommended management practices can increase SOC concentration in puddled soil, red soil, loess soils, and salt‐affected soils. In addition, soil restoration has a potential to sequester SOC. Total potential of soil C sequestration in China is 105–198 Tg C yr⁻¹ of SOC and 7–138 Tg C yr⁻¹ for soil inorganic carbon (SIC). The accumulative potential of soil C sequestration of 11 Pg at an average rate of 224 Tg yr⁻¹ may be realized by 2050. Soil C sequestration potential can offset about 20 per cent of the annual industrial emissions in China. Copyright © 2002 John Wiley & Sons, Ltd.     

Elevational Patterns of Acid Deposition into a Forest and Nitrogen Saturation on Mt. Oyama, Japan

Virgin fir trees have been dying on Mt. Oyama, which is located in the southwestern part of Kanto Plain, although the frequency of death seems to be reducing recently. We report elevational patterns of acid deposition in precipitation and throughfall under fir and cedar canopies and nitrogen saturation in the forest ecosystem on Mt. Oyama. The deposition fluxes of major inorganic ions in precipitation were nearly constant regardless of elevation except for hydrogen and ammonium ions, whereas the deposition fluxes of all major inorganic ions in throughfall among cedar increased. The 5-year average of annual nitrate deposition in precipitation from 1994 to 1998 showed 19.3 – 23.5 kg ha^?1 yr^?1 (annual inorganic total N deposition: 9.6 – 10.7 kgN ha^?1 yr^?1) at four sites ranging in elevation from 500 to 1252 m, whereas the deposition in both cedar and fir throughfall was over 6 times greater than that in precipitation. The average soil surface nitrate concentration in 1998 was 140 µg g^?1 (the range: 21.1 – 429 µg g^?1, n=80) and the 7-year average of nitrate concentration in stream water from 1992 to 1998 was 4.81 mg L^?1 (the range: 2.38 – 20.6 mg L^?1, n=317). Our results indicate that nitrogen saturation is occurring in the forest ecosystem because of high N deposition, probably via acid fog, on Mt. Oyama.     

Multiple measurements constrain estimates of net carbon exchange by a Eucalyptus forest

Net ecosystem exchange of carbon (F_NEE) was estimated for a temperate broadleaf, evergreen eucalypt forest ecosystem at Tumbarumba in south-eastern Australia to investigate the processes controlling forest carbon sinks and their response to climate. Measurements at a range of temporal and spatial scales were used to make three different estimates of F_NEE based on: (1) the difference between fluxes of carbon input by photosynthesis and output by autotrophic plus heterotrophic respiration, (2) changes over time in the carbon pools in the above- and below-ground biomass, soil and litter, and (3) micrometeorological flux measurements that provide a continuous estimate of the net exchange. A rigorous comparison of aggregated component fluxes and the net eddy fluxes within a flux tower source area was achieved based on an inventory of the site and a detailed sampling strategy. Measurements replicated in space and time provided mean values, confidence limits and patterns of variation of carbon pools and fluxes that allowed comparisons within known limits of uncertainty. As a result of comparisons between nighttime eddy flux and chamber measurements of respiration, a revised micrometeorological method was developed for estimating nighttime carbon flux using flux tower measurements. Uncertainty in the final estimate of F_NEE was reduced through mutual constraints of each of these measurement approaches. F_NEE for the period October 2001–September 2002, with average rainfall, was an uptake of 6.7 (5.1–8.3) tC ha^?1 yr^?1 estimated from component fluxes, and 5.4 (3.0–7.5) tC ha^?1 yr^?1 estimated from the revised eddy flux method. Biomass increment was 4.5 (3.7–5.4) tC ha^?1 yr^?1 and the remaining 0.9–2.2 tC ha^?1 yr^?1 could represent a carbon sink in the soil and litter pools or lie within the confidence limits of the measured fluxes. F_NEE was reduced to ?0.1 to 2.4 tC ha^?1 yr^?1 during a period of drought and insect disturbance in October 2002–September 2003, with biomass increment being the main component reduced. The forest is a large carbon sink compared with other forest ecosystems, but this is subject to high-annual variability in response to climate variability and disturbance.     

Average critical loads for nitrogen and sulfur and its use in acidification abatement policy in the Netherlands

Atmospheric deposition of N and S on terrestrial and aquatic ecosystems causes effects induced by eutrophication and acidification. Effects of eutrophication include forest damage, NO₃ pollution of groundwater and vegetation changes in forests, heathlands and surface waters due to an excess of N. Effects of acidification include forest damage, groundwater pollution, and loss of fish populations due to Al mobilization. Critical loads (deposition levels) for N and S on terrestrial and aquatic ecosystems in the Netherlands related to these effects have been derived by empirical data and steady-state acidification models. Critical loads of N generally vary between 500 and 1500 mol _c ha^?1 yr^?1 for forests, heathlands and surface waters and between 1500 and 3600 for phreatic groundwaters. Critical loads of total acid (S and N) vary between 300 to 500 mol _c ha^?1 yr^?1 for phreatic groundwaters and surface waters and between 1100 to 1700 mol ha^?1 yr^?1 for forests. On the basis of the various critical loads a deposition target for total acid of 1400 mol _c ha^?1 yr^?1 has been set in the Netherlands from which the N input should be less than 1000 mol _c ha^?1 yr^?1. This level, to be reached in the year 2010, implies an emission reduction of 80–90% in SO₂, NO _x and NH₃ in the Netherlands and of about 30% in neighboring countries compared to 1980 emissions.     

Influence of acid deposition on element cycling in mature sugar maple forest,Algoma, Canada

Forestry studies were undertaken within the Turkey Lakes Watershed to determine the impact of long-range transport of air pollutants on biogeochemical processes in old-growth sugar maple forest on shallow Precambrian-derived till soils in the Algoma District of Ontario, Canada. Distributions of organic matter and macroelements were determined in the tree- and field-layer vegetation, the forest floor and the mineral soil of the study site. Annual tree growth was largely offset by mortality, resulting in a relatively stable standing stock of ca. 245 t ha^?1. Annual aboveground litter production averaged 3.7 t ha^?1 yr^?1, chiefly in the form of deciduous leaf fall. The average pH of the precipitation (4.3) was reduced considerably by contact with the forest canopy. Throughfall was enriched with other elements, principally K and, to a lesser extent, Ca and Mg. The cationic composition of the forest-floor percolates, on the other hand, was dominated primarily by Ca and only to a lesser extent by Mg and K. The stand receives moderate acid deposition, mainly from average inputs of 33–36 kg ha^?1 yr^?1 of SO₄ ^2? and 24–29 kg ha^?1 yr^?1 of NO₃ ^? distributed throughout the year. Atmospheric inputs add to substantial natural NO₃ ^? production, notably within the forest floor and upper mineral soil, and contribute to leaching of bases, principally Ca and Mg, from the rooting zone. Active recycling of elements together with weathering of primary minerals should assist in preserving the base status of the site.     

Effects of nitrogen and phosphorus fertilization on the ratio of activities of carbon-acquiring to nitrogen-acquiring enzymes in a primary lowland tropical rainforest in Borneo,Malaysia

ABSTRACT

Previous meta-analyses revealed that the ratio of activities of carbon (C)-acquiring enzyme to nitrogen (N)-acquiring enzymes in tropical forest ecosystems was nearly identical to those in other ecosystems, despite of the N-rich condition in tropical forests. This could be explained by microbes in tropical forest soils, which require a large amount of N to produce N-rich acid phosphatase (AP) for catalyzation of the organic form of phosphorus (P) and compensation for poor P availability in soils. Based on this idea, we hypothesized that experimental P fertilization would reduce the allocation to N-acquiring enzymes compared with that of C-acquiring enzymes, i.e. that it would increase the ratios of activities of β-1,4-glucosidase (BG) to β-1,4-acetylglucosaminidase (NAG) and leucine aminopeptidase (LAP). We tested this hypothesis using an experimental fertilization site with factorial N (100 kg ha^?1 yr^?1) and P (50 kg ha^?1 yr^?1) addition in a primary tropical lowland forest in Bornean Malaysia, where our earlier work demonstrated that P fertilization reduced AP activity. Contrary to our hypothesis, the BG:NAG and BG:(NAG + LAP) ratios were not altered by either N or P fertilizations. This result indicated that AP production was not a reason for the maintenance of a relatively high investment in N-acquiring enzyme at our study site. Rather, NAG and LAP production was likely driven by C acquisition, rather than N acquisition, as the target substrates contained C as well as N. This idea was supported by the fact that neither the BG:NAG ratio nor the BG:(NAG + LAP) ratio was elevated by N addition. We propose that the ratios of activities of BG to NAG and LAP do not necessarily indicate the ratio of C:N acquisition, at least in our N-rich tropical forest ecosystem.