Throughfall pH Research Articles

Throughfall and stemflow nutrient flux in deodar and oak forests, Garhwal Himalaya, India

Abstract A study to understand the throughfall and stemflow chemistry under deodar and oak forests of Garhwal Himalaya was conducted during 2014–2015. Total rainfall during experimental period was 1473.8 mm and estimated interception loss was 34.018% for deodar forest, 24.85% for oak forest. Stemflow represented the minimum proportion of gross rainfall, i.e. 0.321% in deodar forest and 0.463% in oak forest. pH of throughfall and stemflow in both deodar (6.087 and 6.47 respectively) and oak forests (6.75 and 7.03 respectively) was significantly more acidic than the gross rainfall (7.15). Electrical conductivity was recorded higher in deodar stemflow (231.89 μs/cm) and throughfall (102.75 μs/cm) compared to oak forest (172.92 μs/cm and 83.83 μs/cm respectively). Net nutrient leaching and stemflow were considerably higher from oak forest than deodar forest. Oak forest has better water yield capacity than deodar forest as the interception loss was higher in deodar forest. The idea of sustainable agriculture may be possible surrounding such forests as the need for chemical fertilizer and water can be met by the nutrient-rich soil, available soil moisture and surface water.

Formation of Soil Chemical Environment in Coastal Pinus thunbergii Parlatore Forest in Southwestern Japan

We investigated the chemical properties of precipitation and litter fall, and their effects on soil chemistry, in a coastal forest consisting of pure Pinus thunbergii stands, Pinus-dominated stands with broadleaf trees in the understory, mixed stands of Pinus and evergreen broadleaf trees, and evergreen broadleaf stands. Throughfall pH in the pure Pinus stand was significantly lower than those in the other three stands, and the soil in the pure Pinus stand was determined to be acidic (pH = ca. 5.0). In Pinus-dominated stands with broadleaf species in the understory, precipitation had a neutralizing effect in the foliage of broadleaf species in the understory of the Pinus stand and the pH levels of their surface mineral soil were significantly higher than those in the pure Pinus stand. The soil pH level was low in the pure Pinus stand, and then increased with an increasing dominance of broadleaf species in the understory. The soil pH was lowered with an increasing dominance of broadleaf species in the canopy layer. A litter layer consisting of decomposable litter of broadleaf species with low C/N ratio acidified precipitation that was deposited as throughfall on the litter surface. Nitrates in the soil-extracted water from the mixed stand and from the evergreen broadleaf stand were significantly higher than the nitrates of stands with high dominance of Pinus. Higher nitrogen flux in the mixed stand and in the evergreen broadleaf stand, as well as a lower C/N ratio of the litter of broadleaf species, accelerated nitrogen accumulation in the soil in stands with high broadleaf species dominance in the canopy compared to the Pinus-dominated stand. Thus, the accumulation of nitrogen in the soil through litter fall is a possible factor that promotes succession from Pinus stands to evergreen broadleaf stands.

Influence of forest tree species composition on bryophytic diversity in mixed and pure pine (Pinus sylvestris L.) and oak (Quercus petraea (Matt.) Liebl.) stands

Abstract The effects of mixed stands on biodiversity are increasingly being studied since they are supposed to offer higher habitat heterogeneity. Nevertheless, for tree-associated diversity, including epiphytes and terricolous species near tree trunks, few studies exist, and still fewer compare mixed stands with each corresponding pure tree species stand. We evaluated and quantified the influence of forest composition on tree-associated bryophyte diversity (species richness, abundance, composition) in mixed and pure oak-pine stands in a French lowland forest. The main explanatory variables for bryophyte diversity at tree-level were the identity of the phorophyte tree species and the mixture type (pure versus mixed). At the plot level, the main explanatory variable was the stand type (pure oak, pure pine and mixed). We also explored the role of other variables including the chemistry of the bryophyte substrates (soil, bark) and water supply (stemflow, throughfall), as well as stand abundance variables (basal area, interfering plant cover). We analyzed data with Generalized Linear Models under Bayesian statistics, to take into account the spatial autocorrelation between plots and any under- or over-dispersion of our data. At the tree-level, bryophyte richness and abundance were higher on oak than on pine. Pine bryophyte richness was higher in mixed compared to pure stands, whereas for oak, mixed stands did not enhance bryophyte richness. At the plot level, mixed stands hosted bryophyte communities of similar richness to those in pure oak stands, whereas pure pine stands were clearly poorer. Our exploratory models suggested strong effects of water supply chemistry (stemflow and throughfall pH or conductivity) and basal area; the latter had a strong quadratic effect on epiphytic richness at the plot level. In terms of composition, three species were more likely to be found on pine phorophytes, seven species clearly occurred more frequently on oaks. Some species were more likely to be associated to pine in mixed than in pure stands, and one species was found more often under pines in pure stands. Therefore, bryophyte diversity at the landscape level should benefit from the simultaneous presence of the three stand composition types – pure oak, pure pine and mixed stands.

Atmospheric deposition in coniferous and deciduous tree stands in Poland

The objective of this study was to assess the transformation of precipitation in terms of quantity and chemical composition following contact with the crown layer in tree stands with varied species composition, to investigate the effect of four predominant forest-forming species (pine, spruce, beech, and oak) on the amount and composition of precipitation reaching forest soils, and to determine the sources of pollution in atmospheric precipitation in forest areas in Poland.The amount and chemical composition (pH, electric conductivity, alkalinity, and chloride, nitrate, sulfate, phosphate, ammonium, calcium, magnesium, sodium, potassium, iron aluminum, manganese, zinc, copper, total nitrogen, and dissolved organic carbon contents) of atmospheric (bulk, BP) and throughfall (TF) precipitation were studied from January to December 2010 on twelve forest monitoring plots representative of Polish conditions. The study results provided the basis for the determination of the fluxes of pollutants in the forest areas of Poland and allowed the comparison of such fluxes with values provided in the literature for European forest areas. The transformation of precipitation in the canopy was compared for different tree stands. The fluxes of substances in an open field and under canopy were influenced by the location of the plot, including the regional meteorological conditions (precipitation amounts), vicinity of the sea (effect of marine aerosols), and local level of anthropogenic pollution. Differences between the plots were higher in TF than in BP. The impact of the vegetation cover on the chemical composition of precipitation depended on the region of the country and dominant species in a given tree stand. Coniferous species tended to cause acidification of precipitation, whereas deciduous species increased the pH of TF. Pine and oak stands enriched precipitation with components that leached from the canopy (potassium, manganese, magnesium) to a higher degree than spruce and beech stands.

Increase of fast nutrient cycling in grassland microcosms through insect herbivory depends on plant functional composition and species diversity

Nutrient cycling in terrestrial ecosystems is affected by various factors such as plant diversity and insect herbivory. While several studies suggest insect herbivory to depend on plant diversity, their interacting effect on nutrient cycling is unclear.In a greenhouse experiment with grassland microcosms of one to six plant species of two functional groups (grasses and legumes), we tested the influence of plant species richness (diversity) and functional composition on plant community biomass production, insect foliar herbivory, soil microbial biomass, and nutrient concentrations in throughfall. To manipulate herbivory, zero, three or six generalist grasshoppers (Chorthippus parallelus) were added to the plant communities.Increasing plant species richness increased shoot biomass and grasshopper performance, without significantly affecting root biomass or insect herbivory. Plant functional composition affected all of these parameters, e.g. legume communities showed the highest shoot biomass, the lowest grasshopper performance and suffered the least herbivory. Nutrient concentrations (dissolved mineral N, PO4‐P, SO4‐S) and pH in throughfall increased with herbivory. PO4‐P and pH increases were positively affected by plant diversity, especially under high herbivore pressure. Plant functional composition affected several throughfall variables, sometimes fully explaining diversity effects. Increasing plant diversity tended to increase soil microbial biomass, but only under high herbivore pressure. Faeces quantities strongly correlated with changes in pH and PO4‐P; frass may therefore be an important driver of throughfall pH and a main source of PO4‐P released from living plants. Our results indicate that insect herbivory may significantly influence fast nutrient cycling processes in natural communities, particularly so in managed grasslands.

Long-Term Annual and Seasonal Patterns of Acidic Deposition and Stream Water Quality in a Great Smoky Mountains High-Elevation Watershed

The recovery potential of stream acidification from years of acidic deposition is dependent on biogeochemical processes and varies among different acid-sensitive regions. Studies that investigate long-term trends and seasonal variability of stream chemistry in the context of atmospheric deposition and watershed setting provide crucial assessments on governing biogeochemical processes. In this study, water chemistries were investigated in Noland Divide watershed (NDW), a high-elevation watershed in the Great Smoky Mountains National Park (GRSM) of the southern Appalachian region. Monitoring data from 1991 to 2007 for deposition and stream water chemistries were statistically analyzed for long-term trends and seasonal patterns by using Seasonal Kendall Tau tests. Precipitation declined over this study period, where throughfall (TF) declined significantly by 5.76 cm year−1. Precipitation patterns play a key role in the fate and transport of acid pollutants. On a monthly volume-weighted basis, pH of TF and wet deposition, and stream water did not significantly change over time remaining around 4.3, 4.7, and 5.8, respectively. Per NDW area, TF SO42- flux declined 356.16 eq year−1 and SO42- concentrations did not change significantly over time. Stream SO42- remained about 30 μeq L−1 exhibiting no long-term trends or seasonal patterns. SO42- retention was generally greater during drier months. TF monthly volume-weighted NH4+ and NO3- concentrations significantly increased by 0.80 μeq L−1 year−1 and 1.24 μeq L−1 year−1, respectively. TF NH4+ fluxes increased by 95.76 eq year−1. Most of NH4+ was retained in the watershed, and NO3- retention was much lower than NH4+. Stream monthly volume-weighted NO3- concentrations and fluxes significantly declined by 0.56 μeq L−1 year−1 and 139.56 eq year−1, respectively. Overall, in NDW, inorganic nitrogen was exported before 1999 and retained since then, presumably from forest regrowth after Frazer fir die-off in the 1970s from balsam wooly adelgid infestation. Stream export of NO3- was greater during winter than summer months. During the period from 1999 to 2007, stream base cations did not exhibit significant changes, apparently regulated by soil supply. Statistical models predicting stream pH, ANC, SO42-, and NO3- concentrations were largely correlated with stream discharge and number of dry days between precipitation events and SO42- deposition. Dependent on precipitation, governing biogeochemical processes in NDW appear to be SO42- adsorption, nitrification, and NO3- forest uptake. This study provided essential information to aid the GRSM management for developing predictive models of the future water quality and potential impacts from climate change.

The Chemical Properties of Water in <i>Pinus</i><i> koraiensis</i> Plantation at Mountainous Region in Heilongjiang Province

In this paper, the Pinus koraiensis plantation at mountainous region in Heilongjiang Province is the research object. Four different types of water in Pinus koraiensis plantation including rainfall, throughfall, stemflow and runoff are respectively selected to study the influence of Pinus koraiensis plantation on the water quality from May to November of 2004. The indicator included pH, Do, TURB, TDS, COND, ORP, K, Na, Ca, Mg, Cu, Zn, Mn and Fe. The results show that the chemical properties of rainfall have been changed after it passing through forest canopy. The value of pH, Do and ORP in throughfall are lower than those of rainfall, the value of TURB and TDS increase obviously, 3.2 and 6.4 times higher than the rainfall. The concentrations of Na, Ca and Zn in the throughfall are lower than those in the rainfall but other metal elements show higher concentrations. The value of pH and Do in stemflow are lower than other water. The element contents in stemflow increase greatly except Cu. The values of pH, TURB, TDS and COND in the runoff are higher than those in stemflow, throughfall and rainfall. The variance of pH and Do don’t change significantly, and the variance coefficients of pH and Do are lower in rainfall, throughfall, stemflow and runoff. The value of TURB, TDS and COND vary remarkably, and the variance coefficients of which are higher. The leaching coefficient of throughfall is in the following order: K>Mg>Mn>Fe>Cu>Na>Zn>Ca. The leaching coefficient of stemflow is in the order of Fe>Mn>Mg>K>Na>Ca>Cu>Zn. After atmospheric precipitation passing through the Pinus koraiensis plantation, the value of pH in the throughfall, stemflow and runoff increase gradually closer to neutral, which shows that the Pinus koraiensis plantation have good buffer function to the acidification of the water.

Hydrogeochemical effects of secondary forest in Guangxi Nongla karst areas in China

Rainfall, throughfall, stemflow and spring were studied in a secondary forest during a wet season from April to August in 2006. Some of the chemicals in throughfall, stemflow and spring were increased in contrast with incident rainfall. Specifically, Cl−, HCO3−, Na+ and Ca2+ were leached negatively in throughfall, but K+ and Mg2+ were leached positively. In stemflow, Cl− and Na+ were leached negatively, the others were leached positively and their concentrations were higher than those in throughfall. Total carbon, organic carbon and inorganic carbon in throughfall and stemflow were increased as rainfall went through the secondary forest. The concentration of free CO2 in rainfall was lower than both, throughfall and stemflow; the relationship between total acidity and free CO2 was linear. pH of throughfall and stemflow , such as maximum, minimum and mean, were lower than that of rainfall and the extent of pH in spring was changed minimally. We came to a conclusion that rainfall via the secondary forest can lead to further erosion, accelerate the biogeochemical cycle in epikarst zone, enhance the effective state of alkali elements in the soil, supply vegetation with more nutrients and advance vegetation’s growth and succession, which are reasonably sufficient to form a stable karst ecosystem.

The Effect of Stand Age on Throughfall Chemistry in Spruce Stands in the Potok Dupniański Catchment in the Silesian Beskid Mountains, Southern Poland

The chemical composition of throughfall depends on the age of the Norway spruce (Picea abies Karst) stands and season of the year. The pH of throughfall decreased and the amount of hydrogen ion in throughfall deposited to the soil increased with increasing age of spruce stands, especially in the winter season. Concentrations of K+, H+, SO42−, Mn2+, and NH4+ in throughfall were higher than bulk precipitation for the whole year and K+, H+, and Mn2+ concentrations were higher in throughfall in winter and the growing season. This indicates that these ions were washed out or washed from the surface of needles and/or the bark, and that NO3−, NH4+, Ca2+, Mg2+, Fe2+, and Zn2+ were absorbed in the canopy. The effect of high nitrogen deposition, above critical loads, and an increase in the amount of sulfur and in the sum of the strong acids (S-SO42− and N-NO3−) that reached the soil with throughfall may have implications for the vitality of spruce stands, especially in older age classes. The application of Principal Component Analysis (PCA) has led to identification of five factors responsible for the data structure (“mineral dust”, “acidic emissions”, “heavy metals-dust particles”, “ammonium [NH4+]”, and “H+”). They explain more than 60% of the total variance system. The strong positive correlation between stand age class and ionic concentrations in throughfall occurs for all year and the winter period for ions within the following categories: “acidic emissions”, SO42− + NO3−; “heavy metals-dust particles”, Fe2+ + Mn2+ + Zn2+; “mineral dust”, Na+ + K+ + Ca+2 + Mg2+; “NH4+”; and “H+”. The strength of the relationship decreases in the growing period, probably due to processes occurring in the canopy (adsorption, leaching, etc.).

乗鞍高原の森林生態系における物質循環―１．林内降水の化学特性と季節変化―

Because of precipitation serves as a major vehicle of nutrient input into the forest ecosystem, the accurate measurement of its volume and ion concentration is of prime importance in an evaluation of any bio-geochemical cycle. Therefore, chemistry of the precipitation and throughfall of forest ecosystem was investigated in the Norikura Highlands. The investigation period was from January, 2003 to October, 2006. The throughfall volume in growing season and dormant season were 86 % and 93 % of the precipitation volume. Throughfall pH increased with increasing K+ concentration showed that H+ was held within the canopy by cation exchange reaction. And the concentration level of K+, Mg2+ and Ca2+ in the throughfall was much higher than that in the precipitation. It was the cause of canopy leaching. In growing season, proportions of canopy leaching of K+, Mg2+ and Ca2+ were 95 %, 70 % and 43 % of the throughfall deposition respectively. At Coniferous site, the flux of dry deposition was higher in dormant season than growing season. It is suggested that aerosol of the atmosphere and leaf area might be influenced.

Liquid and Chemical Fluxes in Precipitation, Throughfall and Stemflow: Observations from a Deciduous Forest and a Red Pine Plantation in the Midwestern U.S.A.

Wet deposition (WD), throughfall (TF) and stemflow (SF) measurements undertaken in a deciduous forest show 85% of the WD liquid flux is observed as TF and approximately 2% as SF. TF and SF were observed to be enriched in base cations and accordingly had an average pH of 6.1 and 5.9, respectively relative to a WD pH of 5.1. The seasonal variability of TF pH below the deciduous canopies was more pronounced than that of WD though both exhibited a growing season maximum, and there is evidence that the seasonal variability of TF pH below the pines is inverted relative to the deciduous canopies likely due to enhanced dust capture and buffering by calcium carbonate. TF ion concentrations differed significantly between deciduous and pine canopies during the growing season, and there is some evidence that variation in sky view factor of 0.18–0.22 is sufficient to manifest statistically differing TF composition below sugar maples. The total atmospheric flux of inorganic nitrogen to the forest is approximately 14–18 kg-N ha−1 yr−1 with approximately half taken up by the canopy. Associated experiments designed to quantify uncertainties in the nutrient fluxes included laboratory tests of the Aerochem automated wet-dry sampler. These experiments indicate the delay in initiating sample collection is less than half a minute for rainfall rates above 1 cm h−1, but may increase substantially for lower precipitation rates.

산성 강우에 의한 수목의 쇠퇴현상(I) - 음이온을 중심으로 -

대기오염으로 인하여 산성비의 영향을 받고 있는 공단지역과 도시 근교 지역, 농촌 지역으로 나누어 각 산림지역 내에 있는 임외우와 수관 통과우에 대한 강우의 pH, EC 및 이온특성, 대기중 <TEX>$SO_2,\;NO_2$</TEX>의 농도, 해송림의 쇠퇴도를 분석하였다. 도시 근교 및 농촌 지역의 임외우는 <TEX>$pH\;5.29{\sim}5.76$</TEX>으로 공단지역보다 높게 나타났다. 수관 통과우는 공단 지역(온산, 농소)이 <TEX>$pH\;4.64{\sim}4.98$</TEX>, 도시 근교 지역(진주)이 <TEX>$pH\;4.87{\sim}5.13$</TEX>이었으며 전기전도도는 농촌 지역이나 도시 근교 지역보다 공단 지역이 높게 조사되었다. 임외우와 수관 통과의 음이온 중 <TEX>$SO_4^{2-}$</TEX>는 공단 지역이 농촌지역에 비해 각각 3배, 8배 이상 높게 나타났다. 해송의 쇠퇴도와 강우의 음이온 성분간의 상관분석을 실시한 결과는 해송의 쇠퇴도와 강우의 pH(r=-0.8374), pH와 <TEX>$Cl^-$</TEX>(r=-0.9324)이온 간에는 부의 상관이 나타났다. This study was carried out to analyze pH, Electrical conductivity(EC), cation and anion on rainfall and throughfall raining at industrial area(Onsan and Nongso of Ulsan city), suburban area(Myeongsek-myeon of Jinju city) and rural area(Haman and Changyoung-gun), and to investigate <TEX>$SO_2\;and\;NO_2$</TEX> concentration in the air of industrial area and rural area, and to survey degree of decline of Pinus thunbergii growing at each area. The rainfall pH was higher than the throughfall pH at the all surveyed areas. The rainfall pH and throughfall pH was <TEX>$4.76{\sim}5.15\;and\;4.64{\sim}4.98,\;4.95{\sim}5.30\;and\;4.87{\sim}5.13,\;5.29{\sim}5.76\;and\;5.12{\sim}5.73$</TEX> at the industrial area, suburban area and rural area, respectively. The EC of rainfall and throughfall was <TEX>$13.64{\sim}17.22\;and\;41.60{\sim}103.59,\;4.18{\sim}8.65\;and\;17.02{\sim}23.89,\;4.09{\sim}6.65\;and\;13.75{\sim}21.44$</TEX> at the industrial area, suburban area and rural area, respectively. Generally EC at the industrial area was higher than those of suburban area and rural area. In the correlation analysis among Degree of decline on Pinus thunbergii and ingredients of rainfall, it showed that there was a negative correlation between Degree of decline and pH. There was a positive correlation between pH and <TEX>$Cl^-$</TEX> respectively.

The Effectiveness of Canopy Trees to Reduce Rainfall Acidity in the Industrial Area at Medan

The term of acid rain is referred to the mean rainfall with a pH less than 5,65. The element of Sox and Nox are the major sources of aid rain. These two elements are oxidized into SO4 and NO3 respectively in the air. Sulfate and Nitrate are water soluble and the primary sources of hydrogen ions in acid precipitation. Rain passing through a tree canopy may lose or gain mineral elements trough some combination of natural process of absorption and leaching. By this process, the canopy may reduce rainfall acidity and negatif effects of the acid rain which will enter into the soil. Due to characteristic differences among tree canopies, a study to evaluate effectiveness of the trees in reducing rainfall acidity was done. In this study, rainfall and troughfall were collected every single rain and the pH measure by portable pH-meter. Based on data collection during 3 months in Medan Industrial Estate, it found that the mean pH of rainfall was 5,15. The highest pH of throughfall was found from Gnetum gnemon, that was 5,70; following by Mimusops elengi, Filicium decipiens, Acacia mangium, and the lowest was Nephelium lappacum. G. Gnemon was able to reduce 11% of rainfall acidity, but N. Lappacum caused 13% increasing rainfall acidity. In this study, the main source of rainfall acidity was hidrogen from sulfate acid (54%), following by chloride acid (30%), and nitrate acid (16%).

Patterns of canopy interception and throughfall along a topographic sequence for black spruce dominated forest ecosystems in northwestern Ontario

A 3-year (1993–1995) study was conducted to describe both the spatial (within- and between-site) and temporal (monthly) patterns associated with canopy interception, throughfall, and net forest water along a black spruce (Picea mariana (Mill.) BSP) topo-sequence situated in northwestern Ontario. This site array included (1) an upland, well-drained, mineral soil site; (2) a poorly drained, midslope, wet mineral site; and (3) a treed wetland on organic (peat) soil. Bulk precipitation (BP) and throughfall (TF) were collected, on an event basis (63 events, over 4800 samples analyzed), using standard collecting devices and analyzed for total Kjeldahl nitrogen (TKN), ammonium (NH4+), nitrate (NO3–), total phosphorus (TP), potassium (K), calcium (Ca), and magnesium (Mg). Comparison of BP and TF data suggested that an enrichment of K (190%), Mg (115%), and Ca (70%) occurred during canopy interactions. On the other hand, inorganic nitrogen (NH4+: –73%; NO3–: –47%), and to a lesser extent TP (–35%), rates declined. TKN, however, remained the same, suggesting that inorganic N reductions were offset by organic N inputs. Downward shifts in pH were also detected for TF (4.45–4.48), as compared with the pH of BP (4.52–4.80). Although all study sites received similar rainfall amounts, the more productive sites (i.e., carrying greater foliar mass, higher leaf area index) had lower TF volumes (i.e., higher interception rates) but higher macronutrient returns to the forest floor. This increase in macronutrient deposition was directly related to substantial increases in nutrient concentrations, which, in turn, suggested a greater degree of canopy interaction and (or) leaching on these sites. Throughfall pH, however, was not significantly different across the three study sites. With respect to temporal patterns, the major cations (K+, Ca2+, Mg2+) demonstrated an increasing trend in concentration levels in TF as the season progressed to a maximum in October. TKN and TP concentrations, on the other hand, maintained relatively stable levels throughout the summer, peaking in September, but dropping substantially in October as metabolic processes slowed and the supply of these nutrients to the foliage was reduced. Even with the increase in base cation concentration, throughfall pH shifted downward to 4.3 or below by late fall.

Interception loss, throughfall and stemflow chemistry in pine and oak forests in northeastern Mexico.

Interception loss, gross precipitation, throughfall and stemflow solution chemistry beneath pine (Pinus pseudostrobus Lindl.), oak (Quercus sp.) and pine-oak natural forest canopies in northeastern Mexico were measured. Coefficients of variation for throughfall were 12% in pine and oak canopies and 17% in the mixed pine-oak canopy. The variability of stemflow averaged 66, 126 and 73% for pine, oak and the mixed pine-oak canopies, respectively. Linear regression analysis of net versus gross precipitation for the three canopies showed highly significant correlations (r = 0.974-0.984). Total precipitation during the experimental period was 974 mm and estimated interception loss was 19.2, 13.6 and 23% for the pine, oak and pine-oak canopies, respectively. Stemflow did not occur following rainfall events of less than 4 mm and, in all canopies, stemflow represented a minimal proportion of gross precipitation (0.60, 0.50 and 0.03% for pine, oak and pine-oak, respectively). Throughfall pH in pine (6.2), oak (6.3) and pine-oak (6.3) canopies was significantly more acidic than gross precipitation (6.6). Stemflow pH ranged from 3.7 (pine) to 6.0 (oak). The pine-oak canopy registered the highest throughfall and stemflow electrical conductivities, 104 and 188 microS cm(-1), respectively. Net nutrient leaching of K, Mg, Na, Fe, Mn and Zn was significantly higher from the pine-oak canopy than from the pure pine and oak canopies. Mean depositions of Ca and Cu in throughfall behaved similarly among the three types of canopies. A greater proportion of Zn in gross precipitation was absorbed by the oak canopy than by the pine and pine-oak canopies. Enrichment factors beneath the pine-oak canopy relative to gross precipitation varied from 1.2 to 3.2 for macro-nutrients (Ca, K, Mg and Na) and from 1.4 to 3.1 for micro-nutrients (Cu, Fe, Mn and Zn). Stemflow depositions of Ca, K, Mg and Cu were higher in the pine-oak canopy, whereas stemflow depositions of Na, Fe, Mn and Zn were higher in the pine canopy.

Chemical Modification of Rain Water by Alnus japonica Wetland Forest in Kiritapp Mire, Eastern Hokkaido, Japan

A survey was made of seasonal changes in pH and electronic conductivity (EC) of precipitation in Alnus japonica (Thunb.) Steud. forest in Kiritapp mire, Hokkaido, Japan. The average pH of throughfall and stem flow was higher than that of bulk deposition. When the pH of bulk deposition exceeded 5.5, however, pH of throughfall and stem flow was lower than that of bulk deposition. The EC of stem flow was always higher than throughfall, and that of throughfall higher than that of bulk deposition. The EC of stem flow was highest during the first defoliation period of A. japonica. On the other hand, the differences in the EC of throughfall and bulk deposition was very few just after the first defoliation period of A. japonica. This implies that the chemical properties of throughfall and stem flow are strongly affected by the phenology of the plants.

The influence of basic aerosols on throughfall fluxes of sulfate, ammonium and nitrate in three oak stands along a distance gradient from a lime quarry

Three oak stands (Quercus petraea and Quercus robur) in the Weinviertel, Lower Austria, located along a distance gradient from a lime quarry, were studied to determine the effects of basic aerosols on the deposition of ammonium, nitrate and sulfate. Higher concentrations of limestone aerosols in the vicinity of the quarry are suggested by higher Ca2+ fluxes and pH in throughfall and precipitation. The ammonium/nitrate ratio in throughfall decreases with distance from the quarry, though monitoring of NH3 and NO2 concentrations in the air with passive samplers shows the opposite trend. These findings support the theory of discrimination against NH3 in dry deposition due to the presence of Ca 2+ particles on leaf surfaces resulting from limestone aerosols. Higher sulfate deposition near the quarry is consistent with higher atmospheric SO2 concentrations and co-deposition between calcium and sulfate.

Canopy modification of precipitation chemistry in deciduous and coniferous forests affected by acidic deposition

Abstract Ionic concentrations and fluxes of throughfall and precipitation were measured during a period of 3 y in a deciduous stand (Df-site) and a coniferous stand (Cf-site) affected by acidic precipitation in the north-western part of Toma-komai in Hokkaido. Throughfall pH at the Df-site was higher than precipitation pH in many cases, indicating that the deciduous canopy neutralized a proton in acidic precipitation. In contrast, pH in throughfall at the Cf-site fluctuated independently of the acidity of precipitation without any significant difference between pH in throughfall and that in precipitation. Concentrations of SO4 2-, K+, Na+, Cl- in throughfall were higher than in precipitation at both sites, especially during the growing period (from June to October), and the magnitude of increment at the Cf-site was larger than that at the Df-site. Na+ and Cl- in net throughfall flux (throughfall flux minus precipitation flux) for both sites were markedly affected by sea salt, while other ions in net throughfall flux were supplied by non sea salt, namely, external terrestrial, biological and anthropogenic materials and internal sources of living leaves. Net throughfall flux of protons showed that proton consumption on the leaf surface was a major process of canopy modification. At the Df-site, the absolute value of net H+ flux during the growing period (from June to October) was almost equivalent to that of K+ and HCO3 -, suggesting that the mechanism of H+ consumption during canopy modification was closely dependent upon K+ release from internal sources of foliage and surface reactions which were controlled by bicarbonate and/or weak organic acid equilibrium. Annual proton consumption in deciduous and coniferous canopies were 0.53 and 0.28 kmolc ha-1 y-1 respectively, and these values corresponded to about 80 and 44% of the proton load as wet deposition, respectively. The smaller value of proton consumption at the Cf-site compared with the Df-site may reflect the high capturing efficiency of the coniferous canopy which acts as a collector of dry acidic deposition, especially non sea salt SO4 2-.

Throughfall chemistry of ponderosa pine exposed to wet and dry acidic deposition, drought, ozone, and nitric acid

Throughfall chemistry was studied in ponderosa pine (Pinusponderosa Laws.) seedlings exposed to wet and dry acidic deposition, ozone (O3), drought, and nitric acid (HNO3) in open-top chambers in the Sierra Nevada of California from 1988 to 1990. Seven acid rain events (pH 3.5, 4.4, and 5.3) occurred during each growing season. Acidity of the simulated rain treatments had little effect on net throughfall fluxes except for greater net SO42− content in throughfall of the pH 3.5 treatment. Electrical conductivity and NO3− and NH4+ content of throughfall were significantly higher in the NF150 treatment (1.5 × ambient O3) than in the charcoal-filtered (CF) or non-charcoal-filtered (NF) treatments in all 3 years. Throughfall acidity in the NF150 treatment was higher than that in the CF or NF treatment during the last 2 years of the study. Effects of the NF150 treatment on throughfall chemistry were attributed primarily to deposition of HNO3 from higher N oxides produced by the air-supplied O3 generator. The concentration of HNO3 in the NF150 chambers was typical for forests in the United States, but only 26% as high as that at Tanbark Flat in the Los Angeles Air Basin. We estimated that co-generated HNO3 contributed 0.5% of the total N in current-year foliage of seedlings in the NF150 treatment. Irrigation treatment did not have a significant effect on throughfall chemistry except for a slightly greater decrease in throughfall pH in the well-watered plants compared with the drought-stressed plants in the pH 5.3 rain treatment in 1989. Absolute values for electrical conductivity and NO3− and NH4+ content in throughfall tended to be higher with greater particulate dry deposition (45–55% removed versus 90% removed by filtration) in 1989 and 1990, but differences were not statistically significant.

Changes in bulk precipitation reactivity throughout the vegetation/soil continuum in a Trachpogon savanna (Venezuela)

Abstract The reactivity of bulk precipitation moving into the soil of a bush island Trachypogon savanna throughout a forest grove and the herbaceous layer was analyzed during four consecutive years. In the forest grove, there was a significant decrease of annual hydrogen (H+) content (meq/ha) of 44–75% as rainfall leached through the canopy, whereas the bulk throughfall pH in the grass layer was similar to the bulk precipitation pH. As throughfall passed throughout the soil profile of the grove, the H+ content decreased 87–70%. Results evidenced a buffering capacity of the system when bulk precipitation was acid during the last measured year. The savanna system retained 92–93% of H+ input from the bulk precipitation indicating that a redistribution of H+ ocurred instead of a net input or net loss. Canopy neutralization of bulk precipitation appears to take place in the grove canopy mainly by organic and bicarbonate salts.