Modelling of Nutrient Emissions in River Systems – MONERIS – Methods and Background

MONERIS is a semi‐empirical, conceptual model, which has gained international acceptance as a robust meso‐ to macro scale model for nutrient emissions. MONERIS is used to calculate nitrogen (N) and phosphorus (P) emissions into surface waters, in‐stream retention, and resulting loads, on a river catchment scale. This paper provides the first (i) comprehensive overview of the model structure (both the original elements and the new additions), (ii) depiction of the algorithms used for all pathways, and for retention in surface waters, and (iii) illustration of the monthly disaggregation of emissions and the implementation of measures. The model can be used for different climatic conditions, long term historical studies, and for future development scenarios. The minimum validated spatial resolution is 50 km², with a temporal resolution of yearly or monthly time steps. The model considers seven emission pathways (atmospheric deposition on surface waters, overland flow, erosion, tile drainage, groundwater, emissions from sealed urban areas, and point sources), and six emission sources (natural background, fertilizer application, nitrogen atmospheric deposition on arable land and other areas, urban sources, and point sources); and these are calculated separately for different land‐uses. The pathway and source‐related approach is a prerequisite for the implementation of measures to reduce non‐point and point‐source emissions. Therefore, we have modified MONERIS by the addition of a “management alternative” tool which can identify the potential effectiveness of nutrient reduction measures. MONERIS is an appropriate tool for addressing the scientific and political aspects of river basin management in support of a good surface water quality. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Nitrogen retention in the riparian zone of catchments underlain by discontinuous permafrost

1. Riparian zones function as important ecotones that reduce nitrate concentration in groundwater and inputs into streams. In the boreal forest of interior Alaska, permafrost confines subsurface flow through the riparian zone to shallow organic horizons, where plant uptake of nitrate and denitrification are typically high. 2. In this study, riparian zone nitrogen retention was examined in a high permafrost catchment (approximately 53% of land area underlain by permafrost) and a low permafrost catchment (approximately 3%). To estimate the contribution of the riparian zone to catchment nitrogen retention, we analysed groundwater chemistry using an end‐member mixing model. 3. Stream nitrate concentration was over twofold greater in the low permafrost catchment than the high permafrost catchment. Riparian groundwater was not significantly different between catchments, averaging 13 μm overall. Nitrogen retention, measured using the end‐member mixing model, averaged 0.75 and 0.22 mmol N m^?2 day^?1 in low and high permafrost catchments, respectively, over the summer. The retention rate of nitrogen in the riparian zone was 10–15% of the export in stream flow. 4. Our results indicate that the riparian zone functions as an important sink for groundwater nitrate and dissolved organic carbon (DOC). However, differences in stream nitrate and DOC concentrations between catchments cannot be explained by solute inputs from riparian groundwater to the stream and differences between streams are probably attributable to deeper groundwater inputs or flows from springs that bypass the riparian zone.     

Effects of upstream lakes and nutrient limitation on periphytic biomass and nitrogen fixation in oligotrophic, subalpine streams

1. We conducted bioassays of nutrient limitation to understand how macronutrients and the position of streams relative to lakes control nitrogen (N₂) fixation and periphytic biomass in three oligotrophic Rocky Mountain catchments. We measured periphytic chlorophyll‐a (chl‐a) and nitrogen‐fixation responses to nitrogen (N) and phosphorus (P) additions using nutrient‐diffusing substrata at 19 stream study sites, located above and below lakes within the study catchments. 2. We found that periphytic chl‐a was significantly co‐limited by N and P at 13 of the 19 sites, with sole limitation by P observed at another four sites, and no nutrient response at the final two sites. On average, the addition of N, P and N + P stimulated chl‐a 35%, 114% and 700% above control values respectively. The addition of P alone stimulated nitrogen fixation by 2500% at five of the 19 sites. The addition of N, either with or without simultaneous P addition, suppressed nitrogen fixation by 73% at nine of the 19 sites. 3. Lake outlet streams were warmer and had higher dissolved organic carbon concentrations than inlet streams and those further upstream, but position relative to lakes did not affect chl‐a and nitrogen fixation in the absence of nutrient additions. Chl‐a response to nutrient additions did not change along the length of the study streams, but nitrogen fixation was suppressed more strongly by N, and stimulated more strongly by P, at lower altitude sites. The responses of chl‐a and nitrogen fixation to nutrients were not affected by location relative to lakes. Some variation in responses to nutrients could be explained by nitrate and/or total N concentration. 4. Periphytic chl‐a and nitrogen fixation were affected by nutrient supply, but responses to nutrients were independent of stream position in the landscape relative to lakes. Understanding interactions between nutrient supply, nitrogen fixation and chl‐a may help predict periphytic responses to future perturbations of oligotrophic streams, such as the deposition of atmospheric N.     

氮沉降下西南山地针叶林根际和非根际土壤微生物养分限制特征差异

长期氮(N)沉降诱导了土壤养分失衡, 深刻影响着森林生态系统养分循环过程、生态功能及其可持续发展。前期研究发现N沉降下西南森林树木生长受到不同程度的磷(P)限制, 而土壤微生物是否表现出与植物养分限制特征协同的响应仍未明确。基于此, 该研究以西南山地典型人工针叶林——华山松(Pinus armandii)林为对象, 通过野外原位模拟N沉降实验, 测定了土壤有效养分供给、土壤微生物生物量(碳(C)、N、P)含量以及胞外酶活性, 结合生态酶化学计量的3种模型(比值模型、矢量分析模型与阈值元素比率模型)验证森林根际/非根际土壤中微生物是否受P养分限制。结果表明: (1) N添加下两个土壤位置(根际和非根际土壤)酸性磷酸酶(AP)活性分别显著升高52.5%和53.2%, 导致土壤酶活性N:P分别降低7.8%和4.8%; (2)矢量模型分析发现N添加下两个土壤位置的矢量角度均大于45°, 根际土壤和非根际土壤的矢量角度分别为52.2°和49.0°; (3) N添加下两个土壤位置C:P阈值(TER_C:P)显著降低, 导致C:P阈值与土壤有效C:P的比值(TER_C:P/Av_C:P)远小于1, 且根际土壤表现更明显。综上所述, 3个模型均表明N沉降加剧了土壤微生物代谢的P限制, 且根际土壤微生物P限制程度更强, 这与土壤和微生物养分含量及其化学计量特征密切相关。该研究结果可为全球气候变化下森林生态系统的适应性管理提供重要科学依据。     

Plasticity in photosynthetic response to nutrient supply of seedlings from a mixed conifer‐angiosperm forest

Abstract We measured the plasticity of the response of photosynthesis to nutrient supply in seedlings of the dominant four conifer and broadleaved angiosperm tree species from an indigenous forest in South‐westland, New Zealand. We hypothesized that the response of conifers to differing nutrient supply would be less than the response for the angiosperms because of greater adaptation to low fertility conditions. In Prumnopitys ferruginea (D. Don) de Laub. the maximum velocity of electron transport, J_max, doubled with a 10‐fold increase in concentration of nitrogen supply. In Dacrydium cupressinum Lamb. the maximum velocity of carboxylation, V_cmax, doubled with a 10‐fold increase in phosphorus supply. In contrast, photosynthetic capacity for the angiosperm species Weinmannia racemosa L.f. was affected only by the interaction of nitrogen and phosphorus and photosynthetic capacity of Metrosideros umbellata Cav. was not affected by nutrient supply. The response of the conifers to increasing availability of nutrient suggests greater plasticity in photosynthetic capacity, a characteristic not generally associated with adaptation to soil infertility, thus invalidating our hypothesis. Our data suggest that photosynthetic response to nutrient supply cannot be broadly generalized between the two functional groups.     

Phosphatase activity and nitrogen fixation reflect species differences,not nutrient trading or nutrient balance,across tropical rainforest trees

A fundamental biogeochemical paradox is that nitrogen‐rich tropical forests contain abundant nitrogen‐fixing trees, which support a globally significant tropical carbon sink. One explanation for this pattern holds that nitrogen‐fixing trees can overcome phosphorus limitation in tropical forests by synthesizing phosphatase enzymes to acquire soil organic phosphorus, but empirical evidence remains scarce. We evaluated whether nitrogen fixation and phosphatase activity are linked across 97 trees from seven species, and tested two hypotheses for explaining investment in nutrient strategies: trading nitrogen‐for‐phosphorus or balancing nutrient demand. Both strategies varied across species but were not explained by nitrogen‐for‐phosphorus trading or nutrient balance. This indicates that (1) studies of these nutrient strategies require broad sampling within and across species, (2) factors other than nutrient trading must be invoked to resolve the paradox of tropical nitrogen fixation, and (3) nitrogen‐fixing trees cannot provide a positive nitrogen‐phosphorus‐carbon feedback to alleviate nutrient limitation of the tropical carbon sink.     

Groundwater influence on the water balance and nutrient budget of a small natural wetland in Northeastern Victoria,Australia

Despite the critical role of water movement in the nutrient dynamics of wetlands, few wetland studies of nutrient imports, exports and cycling have been based on comprehensive water balance studies. In particular, many investigations have underestimated the importance and role of groundwater movement. Nutrient loads entering and leaving a 2 ha reed swamp in the Kiewa Valley, North-east Victoria showed the swamp to be a nutrient source within the landscape under both base flow and storm flow conditions. During a dry period between February 1994 and January 1995 the wetland itself exported 230 kg of Total Nitrogen (115 kg ha⁻¹ yr⁻¹) and 24 kg of Total Phosphorus (12 kg⁻¹ ha⁻¹ yr⁻¹). Investigations confirmed that the wetland was a significant discharge area, and that groundwater accounted for 97% of the surface water and 50% of the Total Nitrogen and Total Phosphorus load leaving the system. A further 30% of Total Nitrogen and 26% of Total Phosphorus leaving the wetland was not attributable to rain/dust, surface water inputs or groundwater, and most likely resulted from the flushing of previously stored nitrogen and phosphorus. A fire which burnt most of the wetland area in September 1994 had little immediate impact on nutrient loads leaving the system. The study illustrates the complexity of assessing the nutrient dynamics and hydrology of natural wetlands, and raises questions with respect to the use of such systems for the interception of diffuse source nutrient loads within rural catchments.     

Limiting nutrients for periphyton growth in sub-alpine, forest, agricultural and urban streams

1. Nutrient-diffusing artificial substrata were used in summer and autumn to assess limiting nutrients for periphytic algal growth in streams draining sub-alpine, forested, agricultural and urban catchments in eastern Victoria, Australia. 2. Chlorophyll a density was primarily limited by nitrogen in most cases; often phosphorus was secondarily limiting. One sub-alpine, one forest and one agricultural stream were primarily phosphorus limited in at least one season. Added trace elements and vitamins did not increase chlorophyll density. 3. The dominant filamentous algal genera did not differ greatly between various nutrient enrichments. However, the relative abundance of Stigeodanium spp. was sometimes increased on substrata containing the limiting nutrient. 4. The results suggest that nutrient limitation is a widespread phenomenon in Victorian streams, and that limiting nutrients can be inferred from stream-water nitrogen to phosphorus ratios in many instances.     

Site fertility and leaf nutrients of sympatric evergreen and deciduous species of Quercus in central coastal California

Leaf and soil nutrient levels interact with and may each influence the other. We hypothesize that to the extent soil fertility influences the nutritional state of trees, soil fertility should correlate with summer leaf nutrient levels, whereas to the extent that trees influence soil nutrient levels, the quality of leaf litterfall should correlate with soil fertility. We examined these correlations for five sympatric oak species (genus Quercus) in central coastal California. Soil fertility, including both nitrogen and especially phosphorus, correlated significantly with summer leaf nutrient levels. In contrast, phosphorus, but not nitrogen, in the leaf litterfall correlated positively with soil nutrients. These results suggest that soil nitrogen and phosphorus influence tree nutrient levels and that leaf phosphorus, but not leaf nitrogen, influence soil fertility under the trees. Feedback between the soil and the tree for phosphorus, but not nitrogen, is apparently significant and caused by species-specific differences in leaf quality and not by litterfall quality differences within a species. We also compared functional differences between the evergreen and deciduous oak species at our study site. There were no differences in soil nitrogen and only small differences for soil phosphorus between the phenological types. Differences in leaf nutrient concentration were much more pronounced, with the evergreen species having substantially lower levels of both nitrogen and phosphorus. Evergreen species conserved more phosphorus, but not more nitrogen, than the deciduous species, but there was no consistent relationship between retranslocation and either soil nitrogen or phosphorus. These results do not support the hypothesis that evergreenness is an adaptation to low soil fertility in this system.     

Soluble nitrogen and phosphorus excretion of exotic freshwater mussels (Dreissena spp.): potential impacts for nutrient remineralisation in western Lake Erie

1. Recent increases in phytoplankton biomass and the recurrence of cyanobacterial blooms in western Lake Erie, concomitant with a shift from a community dominated by zebra mussels (Dreissena polymorpha) to one dominated by quagga mussels (D. bugensis), led us to test for differences in ammonia‐nitrogen and phosphate‐phosphorus excretion rates of these two species of invasive molluscs. 2. We found significant differences in excretion rate both between size classes within a taxon and between taxa, with zebra mussels generally having greater nutrient excretion rates than quagga mussels. Combining measured excretion rates with measurements of mussel soft‐tissue dry weight and shell length, we developed nutrient excretion equations allowing estimation of nutrient excretion by dreissenids. 3. Comparing dreissenid ammonia and phosphate excretion with that of the crustacean zooplankton, we demonstrated that the mussels add to nitrogen and phosphorus remineralisation, shortening nitrogen and phosphorus turnover times, and, importantly, modify the nitrogen and phosphorus cycles in Lake Erie. The increased nutrient flux from dreissenids may facilitate phytoplankton growth and cyanobacterial blooms in well‐mixed and/or shallow areas of western Lake Erie.     

贵州喀斯特山区不同海拔花椒人工林土壤质量评价

阐明贵州喀斯特山区花椒人工林的土壤养分含量及其质量综合指数至关重要。以不同海拔样地的土壤为研究对象,采用土壤农业化学、环境矿物学技术对矿质元素等进行分析。结果表明:不同样地土壤的pH值呈显著差异,随海拔增加表现为升高—降低的变化趋势;最低海拔(594m,HJ1)与最高海拔(884m,HJ5)样地的土壤有机碳、总氮、速效氮总体显著高于中间3个海拔样地(660m、705m、778m,HJ2—HJ4),总磷与速效磷的变化则相反;除大量元素外,矿质元素在不同海拔花椒林地之间变化规律不明显,其中总硫、铅、镉、硒等元素表现为最高海拔样地急剧升高的趋势;氮、磷与其他矿质元素之间表现出一定的显著性相关,表明其关系密切;土壤质量综合指数为HJ5(2.16)HJ3(0.43)HJ4(0.19)HJ1(-0.21)HJ2(-2.60),表明高海拔花椒林地表层土壤质量总体优于低海拔,揭示了土壤养分随海拔变化表现出分异规律。土壤管理上应同时施用有机肥和矿质元素肥料,提高土壤养分供给能力和利用效率。以上结论可为贵州喀斯特山区花椒林养分管理和可持续经营工作提供借鉴和参考。     

Export of DOM from Boreal Catchments: Impacts of Land Use Cover and Climate

Dissolved organic matter (DOM) is an important fraction in carbon (C) and nutrient budgets for aquatic ecosystems and can have broad effects on food webs and nutrient cycling. To look at the role land use cover and climate might play in DOM transport from the boreal region, the export of total organic carbon (TOC), total organic nitrogen (TON) and dissolved organic phosphorus (DOP) was estimated for Finnish main rivers and their sub-catchments, altogether 86 catchments, situated between latitudes 60° N and 69° N and covering 297,322 km², 88% of the total area of Finland. On an average, 94% of the TOC, 90% of the total nitrogen (TN) and 40% of the total phosphorus (TP) in Finnish rivers was in a dissolved form. The majority of the DOM export from Finnish catchments consists of organic C. The TOC export increased with increasing peatland proportion (r = 0.39, p = 0.003), while TON export increased with the increasing percentage of agricultural land (r = 0.60, p <0.001). Although upstream lakes covered only on average 9% of the catchment area, they were the most important predictor for TOC, TON and DOP export (r = −0.83, r = −0.82 and r = −0.61, respectively). The higher the upstream lake percentage, the lower the export indicating organic matter retention in lakes.     

Influence of land use on stream ecosystem function in a Mediterranean catchment

1. Due to the hierarchical organization of stream networks, land use changes occurring at larger spatial scales (i.e. the catchment) can affect physical, chemical and biological characteristics at lower spatial scales, ultimately altering stream structure and function. Anthropogenic effects on streams have primarily been documented using structural metrics such as water chemistry, channel alteration and algal biomass. Functional parameters, including metrics of nutrient retention and metabolism, are now being widely used as indicators of stream condition. 2. Within this hierarchical context, we used a multivariate approach to examine how structural and functional (i.e. nutrient retention and metabolism) attributes of streams are related to catchment variables, including land use. The study was done in 13 streams located within a single Mediterranean catchment, but draining sub‐catchments with contrasting land use. 3. At the catchment scale, results showed two contrasting land use gradients: (i) from forested‐ to urban‐dominated catchments and (ii) from low to moderate agricultural‐dominated catchments. Variation in structural and functional parameters was strongly related to these land use gradients. Specifically, NH₄⁺ demand (measured as the uptake velocity, V_f) decreased along the gradient from forested‐ to urban‐dominated catchments primarily in response to increases in stream nutrient concentrations [NH₄⁺, dissolved organic nitrogen (DON) and carbon (DOC)]. Both primary production and respiration increased along the gradient of agricultural development in response to increases in algal biomass (chlorophyll a). Soluble reactive phosphorus demand was not related to any of the land use gradients. 4. Our results illustrate the connections among factors operating at different spatial scales (i.e. from catchments to streams) and their distinct influence on stream ecosystem function. Managers should take into consideration these connections when designing stream management and restoration plans. Because ecologically successful stream management and restoration is expected to restore function as well as structure to streams, the use of appropriate measures of functional processes is required. Nutrient retention and metabolism parameters are good candidates to fill this gap.     

Estimation of long-term variation in nutrient loads from the Hii River by comparing the change in observed and calculated loads in the catchments

To study the long-term change in nutrient loads from the Hii River to Lake Shinji, water samples were taken repeatedly over a year in 1983/1984 and again in 2001/2002. Annual total nitrogen (TN) loads, estimated from observations of water quality and river flow, increased from 860 to 920 t with a corresponding increase in NO₃–N concentration during the cool season. In contrast, total phosphorus (TP) loads decreased from 96 to 62 t. Annual TN and TP loads, calculated using emission factors and annual statistics for the catchments, showed a tendency to decline from 1986 to 2002. No source could be identified which would result in the increase in TN in the catchments, therefore, the increase in observed TN loads was considered to originate in other areas. Atmospheric nitrogen deposition transported from long distances has elevated the sum of NH₄–N and NO₃–N concentration in rainwater in the cool season. Therefore, it was considered that this resulted in the increase in TN loads in the Hii River.     

两种立地条件下麻栎人工林地上部分养分的积累和分配

麻栎(Quercus acutissima)是一种分布广、用途大、耐干旱瘠薄的乔木树种, 掌握其生长规律和养分利用特性对麻栎人工林的科学经营十分必要。对安徽省滁州市红琊山林场两种立地条件下的麻栎人工林的生长和养分状况进行了对比研究, 结果表明: 在土壤含石量较高、养分含量较少的立地条件下, 12年生的麻栎人工林地上部分生物量为49 180.2 kg·hm^-2; 林木养分总累积量为633.9 kg·hm^-2, 其中N、P、K、Ca、Mg的累积量分别为119.9、18.7、88.5、368.6和38.2 kg·hm^-2。在土壤含石量较少、养分含量较高的立地条件下, 12年生麻栎人工林地上部分生物量为90 774.8 kg·hm^-2; 林木养分总累积量为993.6 kg·hm^-2, 其中N、P、K、Ca、Mg的累积量分别为203.5、23.0、146.9、553.6和66.6 kg·hm^-2。所以, 立地条件对麻栎生长和养分累积具有显著影响。较差立地条件下的麻栎对土壤养分的富集系数较大, 但其凋落物的养分含量较低。研究显示, 麻栎可以通过养分奢侈吸收、提高养分内循环、减少养分损失等途径来适应低养分环境。     

Identifying and ameliorating nutrient limitations to reconstructing a forest ecosystem on mined land

Nutrient deficiency is commonly a limiting factor in reconstructing ecosystems on disturbed areas such as mines, quarries, and construction sites. An open‐cut coal mine in southeastern Australia is being used as a model to explore strategies for reconstructing a sustainable forest ecosystem on a spoil substrate. This study aimed to identify the nutrients limiting forest establishment and ways of ameliorating these. A pot trial, using two endemic Myrtaceae tree species, found that nitrogen was the most growth‐limiting nutrient followed by phosphorus. To overcome these spoil nutrient deficiencies, a field trial compared the application of forest topsoil to the addition of two rates of inorganic fertilizer, gypsum, or biosolids on the response of a range of native forest plant species directly seeded into the substrate. Only biosolids significantly increased total nitrogen levels in the spoil. However, all treatments significantly decreased spoil pH, thereby increasing nutrient availability. Topsoil produced the highest plant density of native species due to contributions from its seed bank. Biosolids increased growth of Corymbia maculata. The higher rate of fertilizer addition improved seedling establishment of Mimosaceae and the survival of Myrtaceae species. High nutrient treatments increased weed and grass densities, which may have reduced the nutrient benefit for native species. In conclusion, biosolids and the high rate of fertilizer application ameliorated the nitrogen and phosphorus deficiency of spoil to support growth and survival of reintroduced native species. However, potential benefits were attenuated by competition from accompanying weed growth that could be managed by implementing a control program.     

Phosphorus Limitation in Boreal Forests: Effects of Aluminum and Iron Accumulation in the Humus Layer

Plant growth in boreal forests is generally considered to be predominantly nitrogen (N) limited, but forested groundwater discharge areas may be exceptions. In this study, we conducted tests to determine whether highly productive forested groundwater discharge areas generally differ from adjacent groundwater recharge areas in terms of humus chemistry and the availability of phosphorus (P) and N to plants. We investigated six forested sites, divided into groundwater discharge and adjacent groundwater recharge areas, in northern Sweden. The humus layers of the forested groundwater discharge areas were clearly distinguished from the adjacent groundwater recharge areas by having higher acid-digestible calcium (Ca) and/or aluminium (Al) and iron (Fe) content and higher organic P and N content. Soil solution inorganic N (NH₄ ⁺ and NO₃ ⁻) and pH were higher in the groundwater discharge areas than in the groundwater recharge areas. The organic P content showed a positive linear relationship to the Al and Fe content in the humus layer, indicating that organic P is associated with Al and Fe compounds in the humus. A plant bioassay using humus substrate from one groundwater discharge area and the adjacent groundwater recharge area found that plants grown in groundwater discharge area humus (with a high P-fixation capacity) increased their biomass upon P fertilization, whereas no growth response was found for N additions. By contrast, plants grown in humus from the groundwater recharge area did not respond to added P unless N was added too. This study suggests that groundwater discharge can affect the nutrient availability of N and P both directly, via increased P fixation due to the redistribution of Al and Fe, and indirectly, via the inflow of groundwater high in Ca and alkalinity, maintaining a high pH in the humus layer that favors in situ N turnover processes. Received 2 March 2001; Accepted 9 November 2001.     

Growth ofAgrostis capillaris andDeschampsia flexuosa in relation to decomposition of and nutrient release by Sitka spruce litter

Summary Bags containing Sitka spruce litter (0, 15, 50 g) were placed in flower pots and covered with sand. Pots were watered at weekly intervals with nutrient solutions with and without nitrogen and with and without phosphorus. Decomposition was measured by carbon dioxide evolution from pots without plants. Neither added nitrogen nor added phosphorus had any marked effect on the rate of decomposition, which amounted to 14% loss of carbon in a year. The two grass species responded similarly to fertilizer; 72% of added nitrogen and 90% of added phosphorus were recovered in plant parts.A. capillaris captured nutrients more effectively from spruce litter than didD. flexuosa, recovering 13% of the phosphorus in the litter but only 5% of the nitrogen. Neither uptake of nitrogen nor uptake of phosphorus was enhanced in plants receiving fertilizer additions of the other nutrient.