Data from: Patterns of nitrogen-fixing tree abundance in forests across Asia and America
Menge, Duncan N.L. ; Chisholm, Ryan A. ; Davies, Stuart J. ; Abu Salim, Kamariah ; Allen, David ; Alvarez, Mauricio ; Bourg, Norm ; Brockelman, Warren Y. ; Bunyavejchewin, Sarayudh ; Butt, Nathalie ; Ouden, Jan den; Jansen, Patrick - \ 2019
Determinants of plant community diversity and structure - Forest - Smithsonian ForestGEO - legume - symbiosis - nutrient limitation - nitrogen fixation
Symbiotic nitrogen (N)‐fixing trees can provide large quantities of new N to ecosystems, but only if they are sufficiently abundant. The overall abundance and latitudinal abundance distributions of N‐fixing trees are well characterised in the Americas, but less well outside the Americas. Here, we characterised the abundance of N‐fixing trees in a network of forest plots spanning five continents, ~5,000 tree species and ~4 million trees. The majority of the plots (86%) were in America or Asia. In addition, we examined whether the observed pattern of abundance of N‐fixing trees was correlated with mean annual temperature and precipitation. Outside the tropics, N‐fixing trees were consistently rare in the forest plots we examined. Within the tropics, N‐fixing trees were abundant in American but not Asian forest plots (~7% versus ~1% of basal area and stems). This disparity was not explained by mean annual temperature or precipitation. Our finding of low N‐fixing tree abundance in the Asian tropics casts some doubt on recent high estimates of N fixation rates in this region, which do not account for disparities in N‐fixing tree abundance between the Asian and American tropics. Synthesis. Inputs of nitrogen to forests depend on symbiotic nitrogen fixation, which is constrained by the abundance of N‐fixing trees. By analysing a large dataset of ~4 million trees, we found that N‐fixing trees were consistently rare in the Asian tropics as well as across higher latitudes in Asia, America and Europe. The rarity of N‐fixing trees in the Asian tropics compared with the American tropics might stem from lower intrinsic N limitation in Asian tropical forests, although direct support for any mechanism is lacking. The paucity of N‐fixing trees throughout Asian forests suggests that N inputs to the Asian tropics might be lower than previously thought.
Patterns of nitrogen-fixing tree abundance in forests across Asia and America
Menge, Duncan N.L. ; Chisholm, Ryan A. ; Davies, Stuart J. ; Abu Salim, Kamariah ; Allen, David ; Alvarez, Mauricio ; Bourg, Norm ; Brockelman, Warren Y. ; Bunyavejchewin, Sarayudh ; Butt, Nathalie ; Cao, Min ; Chanthorn, Wirong ; Chao, Wei Chun ; Clay, Keith ; Condit, Richard ; Cordell, Susan ; Silva, João Batista da; Dattaraja, H.S. ; Andrade, Ana Cristina Segalin de; Oliveira, Alexandre A. de; Ouden, Jan den; Drescher, Michael ; Fletcher, Christine ; Giardina, Christian P. ; Savitri Gunatilleke, C.V. ; Gunatilleke, I.A.U.N. ; Hau, Billy C.H. ; He, Fangliang ; Howe, Robert ; Hsieh, Chang Fu ; Hubbell, Stephen P. ; Inman-Narahari, Faith M. ; Jansen, Patrick A. ; Johnson, Daniel J. ; Kong, Lee Sing ; Král, Kamil ; Ku, Chen Chia ; Lai, Jiangshan ; Larson, Andrew J. ; Li, Xiankun ; Li, Yide ; Lin, Luxiang ; Lin, Yi Ching ; Liu, Shirong ; Lum, Shawn K.Y. ; Lutz, James A. ; Ma, Keping ; Malhi, Yadvinder ; McMahon, Sean ; McShea, William ; Mi, Xiangcheng ; Morecroft, Michael ; Myers, Jonathan A. ; Nathalang, Anuttara ; Novotny, Vojtech ; Ong, Perry ; Orwig, David A. ; Ostertag, Rebecca ; Parker, Geoffrey ; Phillips, Richard P. ; Abd. Rahman, Kassim ; Sack, Lawren ; Sang, Weiguo ; Shen, Guochun ; Shringi, Ankur ; Shue, Jessica ; Su, Sheng Hsin ; Sukumar, Raman ; Fang Sun, I. ; Suresh, H.S. ; Tan, Sylvester ; Thomas, Sean C. ; Toko, Pagi S. ; Valencia, Renato ; Vallejo, Martha I. ; Vicentini, Alberto ; Vrška, Tomáš ; Wang, Bin ; Wang, Xihua ; Weiblen, George D. ; Wolf, Amy ; Xu, Han ; Yap, Sandra ; Zhu, Li ; Fung, Tak - \ 2019
Journal of Ecology 107 (2019)6. - ISSN 0022-0477 - p. 2598 - 2610.
forest - legume - nitrogen fixation - nutrient limitation - Smithsonian ForestGEO - symbiosis
Symbiotic nitrogen (N)-fixing trees can provide large quantities of new N to ecosystems, but only if they are sufficiently abundant. The overall abundance and latitudinal abundance distributions of N-fixing trees are well characterised in the Americas, but less well outside the Americas. Here, we characterised the abundance of N-fixing trees in a network of forest plots spanning five continents, ~5,000 tree species and ~4 million trees. The majority of the plots (86%) were in America or Asia. In addition, we examined whether the observed pattern of abundance of N-fixing trees was correlated with mean annual temperature and precipitation. Outside the tropics, N-fixing trees were consistently rare in the forest plots we examined. Within the tropics, N-fixing trees were abundant in American but not Asian forest plots (~7% versus ~1% of basal area and stems). This disparity was not explained by mean annual temperature or precipitation. Our finding of low N-fixing tree abundance in the Asian tropics casts some doubt on recent high estimates of N fixation rates in this region, which do not account for disparities in N-fixing tree abundance between the Asian and American tropics. Synthesis. Inputs of nitrogen to forests depend on symbiotic nitrogen fixation, which is constrained by the abundance of N-fixing trees. By analysing a large dataset of ~4 million trees, we found that N-fixing trees were consistently rare in the Asian tropics as well as across higher latitudes in Asia, America and Europe. The rarity of N-fixing trees in the Asian tropics compared with the American tropics might stem from lower intrinsic N limitation in Asian tropical forests, although direct support for any mechanism is lacking. The paucity of N-fixing trees throughout Asian forests suggests that N inputs to the Asian tropics might be lower than previously thought.
Planetary boundaries: guiding human development on a changing planet
Steffen, W. ; Richardson, K. ; Rockström, J. ; Cornell, S.E. ; Fetzer, I. ; Bennett, E. ; Biggs, R. ; Vries, W. de - \ 2015
Science 347 (2015)6223. - ISSN 0036-8075
environmental flow requirements - early-warning signals - safe operating space - functional diversity - critical transitions - nutrient limitation - marine-environment - biodiversity loss - climate - water
The planetary boundaries framework defines a safe operating space for humanity based on the intrinsic biophysical processes that regulate the stability of the Earth System. Here, we revise and update the planetary boundaries framework, with a focus on the underpinning biophysical science, based on targeted input from expert research communities and on more general scientific advances over the past 5 years. Several of the boundaries now have a two-tier approach, reflecting the importance of cross-scale interactions and the regional-level heterogeneity of the processes that underpin the boundaries. Two core boundaries—climate change and biosphere integrity—have been identified, each of which has the potential on its own to drive the Earth System into a new state should they be substantially and persistently transgressed.
Does functional trait diversity predict aboveground biomass and productivity of tropical forests? Testing three alternative hypotheses
Finegan, B. ; Peña Claros, M. ; Oliviera, A. de; Alarcón, A. ; Ascarrunz, N. ; Bret-Harte, M.S. ; Carreño-Rocabado, G. ; Casanoves, F. ; Díaz, S. ; Eguiguren Velepucha, P. ; Fernandez, F. ; Licona, J.C. ; Lorenzo, L. ; Salgado Negret, B. ; Vaz, M. ; Poorter, L. - \ 2015
Journal of Ecology 103 (2015)1. - ISSN 0022-0477 - p. 191 - 201.
net primary production - basin-wide variations - rican rain-forest - amazon forest - growth-rates - nutrient limitation - economics spectrum - species richness - plant diversity - tree
Tropical forests are globally important, but it is not clear whether biodiversity enhances carbon storage and sequestration in them. We tested this relationship focusing on components of functional trait biodiversity as predictors. Data are presented for three rain forests in Bolivia, Brazil and Costa Rica. Initial above-ground biomass and biomass increments of survivors, recruits and survivors + recruits (total) were estimated for trees =10 cm d.b.h. in 62 and 21 1.0-ha plots, respectively. We determined relationships of biomass increments to initial standing biomass (AGBi), biomass-weighted community mean values (CWM) of eight functional traits and four functional trait variety indices (functional richness, functional evenness, functional diversity and functional dispersion). The forest continuum sampled ranged from ‘slow’ stands dominated by trees with tough tissues and high AGBi, to ‘fast’ stands dominated by trees with soft, nutrient-rich leaves, lighter woods and lower AGBi. We tested whether AGBi and biomass increments were related to the CWM trait values of the dominant species in the system (the biomass ratio hypothesis), to the variety of functional trait values (the niche complementarity hypothesis), or in the case of biomass increments, simply to initial standing biomass (the green soup hypothesis). CWMs were reasonable bivariate predictors of AGBi and biomass increments, with CWM specific leaf area SLA, CWM leaf nitrogen content, CWM force to tear the leaf, CWM maximum adult height Hmax and CWM wood specific gravity the most important. AGBi was also a reasonable predictor of the three measures of biomass increment. In best-fit multiple regression models, CWMHmax was the most important predictor of initial standing biomass AGBi. Only leaf traits were selected in the best models for biomass increment; CWM SLA was the most important predictor, with the expected positive relationship. There were no relationships of functional variety indices to biomass increments, and AGBi was the only predictor for biomass increments from recruits. Synthesis. We found no support for the niche complementarity hypothesis and support for the green soup hypothesis only for biomass increments of recruits. We have strong support for the biomass ratio hypothesis. CWMHmax is a strong driver of ecosystem biomass and carbon storage and CWM SLA, and other CWM leaf traits are especially important for biomass increments and carbon sequestration.
Food quality dominates the impact of food quantity on Daphnia life history: possible implications for re-oligotrophication
Sarpe, D. ; Senerpont Domis, L.N. de; Declerck, S.A.J. ; Donk, E. van; Ibelings, B.W. - \ 2014
Inland Waters : Journal of the International Society of Limnology 4 (2014)4. - ISSN 2044-2041 - p. 363 - 368.
phosphorus limitation - nutrient limitation - long-term - lakes - carbon - eutrophication - growth
The elemental composition of phytoplankton is highly variable compared to the relatively narrow stoichiometry of zooplankton grazers. Using a full factorial design, we tested the effects of alterations in algal elemental composition (i.e., food quality) combined with food quantity on the life history of a Daphnia galeata clone from Lake IJsselmeer. Lower food quality reduced survival, growth, and reproduction. Food quantity became important at high food quality only. The strong effect of food quality indicates the potential for a stoichiometric bottleneck in Lake IJsselmeer, resulting in less high quality food for higher trophic levels as a result of re-oligotrophication.
Savanna grass nitrogen to phosphorous ratio estimation using field spectroscopy and the potential for estimation with imaging spectroscopy
Ramoelo, A. ; Skidmore, A.K. ; Schlerf, M. ; Heitkonig, I.M.A. ; Mathieu, R. ; Cho, M.A. - \ 2013
International Journal of applied Earth Observation and Geoinformation 23 (2013). - ISSN 0303-2434 - p. 334 - 343.
least-squares regression - band-depth analysis - red edge position - n-p ratios - nutrient limitation - reflectance spectra - absorption features - vegetation indexes - mineral-nutrition - continuum removal
Determining the foliar N:P ratio provides a tool for understanding nutrient limitation on plant production and consequently for the feeding patterns of herbivores. In order to understand the nutrient limitation at landscape scale, remote sensing techniques offer that opportunity. The objective of this study is to investigate the utility of field spectroscopy and a potential of hyperspectral mapper (HyMap) spectra to estimate foliar N:P ratio. Field spectral measurements were undertaken, and grass samples were collected for foliar N and P extraction. The foliar N:P ratio prediction models were developed using partial least square regression (PLSR) with original spectra and transformed spectra for field and the resampled field spectra to HyMap. Spectral transformations included the continuum removal (CR), water removal (WR), first difference derivative (FD) and log transformation (Log(1/R)). The results showed that CR and WR spectra in combination with PLSR predicted foliar N:P ratio with higher accuracy as compared to FD and R, using field spectra. For HyMap spectral analysis, addition to CR and WR, FD achieved higher estimation accuracy. The performance of FD, CR and WR spectra were attributed to their ability to minimize sensor and water effects on the fresh leaf spectra, respectively. The study demonstrated a potential to predict foliar N:P ratio using field and HyMap simulated spectra and shortwave infrared (SWIR) found to be highly sensitive to foliar N:P ratio. The study recommends the prediction of foliar N:P ratio at landscape level using airborne hyperspectral data and could be used by the resource managers, park managers, farmers and ecologists to understand the feeding patterns, resource selection and distribution of herbivores (i.e. wild and livestock).
Carotenoid and fatty acid metabolism in nitrogen-starved Dunaliella salina, a unicellular green microalga
Lamers, P.P. ; Janssen, M. ; Vos, R.C.H. de; Bino, R.J. ; Wijffels, R.H. - \ 2012
Journal of Biotechnology 162 (2012)1. - ISSN 0168-1656 - p. 21 - 27.
beta-carotene - biochemical-composition - nutrient limitation - low-temperature - high light - accumulation - bardawil - alga - induction - stress
Nitrogen availability and light intensity affect ß-carotene overproduction in the green alga Dunaliella salina. Following a previous study on high-light stress, we here report on the effect of nitrogen depletion on the growth characteristics and ß-carotene as well as fatty acid metabolism of D. salina under a constant light regime in a turbidostat. Upon nitrogen depletion, the biomass yield on absorbed light approximately doubled, due to a transient increase in cell division rate, swelling of the cells and a linear increase of the density of the cells. Simultaneously, ß-carotene started to accumulate up to a final intracellular concentration of 14 mg LCV-1 (i.e. 2.7% of AFDW). This ß-carotene production accounted for 6% of the increased density of the cells, indicating that other biochemical constituents accumulated as well. Since D. salina accumulates ß-carotene in lipid globules, we also determined the fatty acid content and composition of D. salina. The intracellular concentration of the total fatty acid pool did not change significantly during nitrogen starvation, indicating that ß-carotene and total fatty acid accumulation were unrelated, similar to what was found previously for high-light treated cells. However, for both high-light and nitrogen stress, ß-carotene accumulation negatively correlated with the degree of unsaturation of the total fatty acid pool and, within the individual fatty acids, correlated positively with oleic acid biosynthesis, suggesting that oleic acid may be a key component of the lipid-globule-localized triacylglycerols and thereby in ß-carotene accumulation.
Leaf economics traits predict litter decomposition of tropical plants and differ among land use types
Bakker, M.A. ; Carreño Rocabado, G. ; Poorter, L. - \ 2011
Functional Ecology 25 (2011)3. - ISSN 0269-8463 - p. 473 - 483.
old-field succession - rain-forest - nutrient limitation - functional traits - central argentina - grasslands - rates - ecosystems - worldwide - spectrum
1. Decomposition is a key ecosystem process that determines nutrient and carbon cycling. Individual leaf and litter characteristics are good predictors of decomposition rates within biomes worldwide, but knowledge of which traits are the best predictors for tropical species remains scarce. Also, the effect of a species’ position on the leaf economics spectrum (LES) and regeneration light requirements on decomposition rate are, until now, unknown. In addition, land use change is the most immediate and widespread global change driver, with potentially significant consequences for decomposition. 2. Here we evaluate 14 leaf and litter traits, and litter decomposition rates of 23 plant species from three different land use types (mature forest, secondary forest and agricultural field) in the moist tropics of lowland Bolivia. 3. Leaf and litter traits were closely associated and showed, in line with the LES, a slow–fast continuum ranging from species with tough, well-protected leaves (high leaf density, leaf dry matter content, force to punch and litter C : N ratio) to species with cheap, productive leaves [high specific leaf area (SLA) and nutrient concentrations in leaves and litter]. 4. Fresh green leaf traits were better predictors of decomposition rate than litter traits, and leaf nitrogen concentration (LNC) was a better predictor of decomposition than leaf phosphorus concentration, despite the widely held belief that tropical forests are P-limited. 5. Multiple regression analysis showed that LNC, SLA and chlorophyll content per unit leaf area had positive effects on decomposition, explaining together 65–69% of the variation. Species position on the LES and regeneration light requirements were also positively related to decomposition. 6. Plant communities from agricultural fields had significantly higher LNC and SLA than communities from mature forest and secondary forest. Species from agricultural fields had higher average decomposition rates than species from other ecosystems and tended to be at the fast end of the LES. 7. Both individual traits of living leaves and species’ position on the LES persist in litter, so that leaves lead influential afterlifes, affecting decomposition, nutrient and carbon cycling
Climate is a stronger driver of tree and forest growth rates than soil and disturbance
Toledo, M. ; Poorter, L. ; Peña-Claros, M. ; Alarcón, A. ; Balcázar, J. ; Leaño, C. ; Licona, J.C. ; Llanque, O. ; Vroomans, V. ; Zuidema, P. ; Bongers, F. - \ 2011
Journal of Ecology 99 (2011)1. - ISSN 0022-0477 - p. 254 - 264.
tropical rain-forest - long-term plots - diameter increment - amazonian forests - french-guiana - phosphorus fertilization - silvicultural treatments - nutrient limitation - neotropical forest - carbon dynamics
1. Essential resources such as water, nutrients and light vary over space and time and plant growth rates are expected to vary accordingly. We examined the effects of climate, soil and logging disturbances on diameter growth rates at the tree and stand level, using 165 1-ha permanent sample plots distributed across Bolivian tropical lowland forests. 2. We predicted that growth rates would be higher in humid than in dry forests, higher in nutrient-rich than nutrient-poor forests and higher in logged than non-logged forests. 3. Across the 165 plots we found positive basal area increases at the stand level, which agree with the generally reported biomass increases in tropical forests. 4. Multiple regression analysis demonstrated that climate variables, in particular water availability, were the strongest drivers of tree growth. More rainfall, a shorter and less intense dry period and higher temperatures led to higher tree growth rates. 5. Tree growth increased modestly with soil fertility and basal area growth was greatest at intermediate soil fertility. Surprisingly, tree growth showed little or no relationship with total soil nitrogen or plant available soil phosphorus. 6. Growth rates increased in logged plots just after logging, but this effect disappeared after 6 years. 7. Synthesis. Climate is the strongest driver of spatial variation in tree growth, and climate change may therefore have large consequences for forest productivity and carbon sequestration. The negative impact of decreased rainfall and increased rainfall seasonality on tree growth might be partly offset by the positive impact of increased temperature in these forests.
Future challenges to microbial food safety
Havelaar, A.H. ; Brul, S. ; Jong, A.E.I. de; Jonge, R. de; Zwietering, M.H. ; Kuile, B.H. ter - \ 2010
International Journal of Food Microbiology 139 (2010)Suppl. 1. - ISSN 0168-1605 - p. S79 - S94.
escherichia-coli o157-h7 - infectious intestinal disease - sentinel general practices - under-reporting rate - bacillus-subtilis - salmonella-enterica - foodborne disease - domestic environment - gastrointestinal illness - nutrient limitation
Despite significant efforts by all parties involved, there is still a considerable burden of foodborne illness, in which micro-organisms play a prominent role. Microbes can enter the food chain at different steps, are highly versatile and can adapt to the environment allowing survival, growth and production of toxic compounds. This sets them apart from chemical agents and thus their study from food toxicology. We summarize the discussions of a conference organized by the Dutch Food and Consumer Products Safety Authority and the European Food Safety Authority. The goal of the conference was to discuss new challenges to food safety that are caused by micro-organisms as well as strategies and methodologies to counter these. Management of food safety is based on generally accepted principles of Hazard Analysis Critical Control Points and of Good Manufacturing Practices. However, a more pro-active, science-based approach is required, starting with the ability to predict where problems might arise by applying the risk analysis framework. Developments that may influence food safety in the future occur on different scales (from global to molecular) and in different time frames (from decades to less than a minute). This necessitates development of new risk assessment approaches, taking the impact of different drivers of change into account. We provide an overview of drivers that may affect food safety and their potential impact on foodborne pathogens and human disease risks. We conclude that many drivers may result in increased food safety risks, requiring active governmental policy setting and anticipation by food industries whereas other drivers may decrease food safety risks. Monitoring of contamination in the food chain, combined with surveillance of human illness and epidemiological investigations of outbreaks and sporadic cases continue to be important sources of information. New approaches in human illness surveillance include the use of molecular markers for improved outbreak detection and source attribution, sero-epidemiology and disease burden estimation. Current developments in molecular techniques make it possible to rapidly assemble information on the genome of various isolates of microbial species of concern. Such information can be used to develop new tracking and tracing methods, and to investigate the behavior of micro-organisms under environmentally relevant stress conditions. These novel tools and insight need to be applied to objectives for food safety strategies, as well as to models that predict microbial behavior. In addition, the increasing complexity of the global food systems necessitates improved communication between all parties involved: scientists, risk assessors and risk managers, as well as consumers
Global assessment of nitrogen deposition effects on terrestrial plant diversity: a synthesis
Bobbink, R. ; Hicks, K. ; Galloway, J. ; Spranger, T. ; Alkemade, R. ; Ashmore, M.R. ; Bustamante, M. ; Cinderby, S. ; Davidson, E. ; Dentener, F. ; Emmett, B. ; Erisman, J.W. ; Fenn, M. ; Gilliam, F. ; Nordin, A. ; Pardo, L. ; Vries, W. de - \ 2010
Ecological Applications 20 (2010)1. - ISSN 1051-0761 - p. 30 - 59.
simulated environmental-change - arctic polar semidesert - western united-states - long-term - n-deposition - nutrient limitation - critical loads - racomitrium-lanuginosum - atmospheric deposition - southern california
Atmospheric nitrogen (N) deposition is a recognized threat to plant diversity in temperate and northern parts of Europe and North America. This paper assesses evidence from field experiments for N deposition effects and thresholds for terrestrial plant diversity protection across a latitudinal range of main categories of ecosystems, from arctic and boreal systems to tropical forests. Current thinking on the mechanisms of N deposition effects on plant diversity, the global distribution of G200 ecoregions, and current and future (2030) estimates of atmospheric N-deposition rates are then used to identify the risks to plant diversity in all major ecosystem types now and in the future. This synthesis paper clearly shows that N accumulation is the main driver of changes to species composition across the whole range of different ecosystem types by driving the competitive interactions that lead to composition change and/or making conditions unfavorable for some species. Other effects such as direct toxicity of nitrogen gases and aerosols, long-term negative effects of increased ammonium and ammonia availability, soil-mediated effects of acidification, and secondary stress and disturbance are more ecosystem- and site-specific and often play a supporting role. N deposition effects in mediterranean ecosystems have now been identified, leading to a first estimate of an effect threshold. Importantly, ecosystems thought of as not N limited, such as tropical and subtropical systems, may be more vulnerable in the regeneration phase, in situations where heterogeneity in N availability is reduced by atmospheric N deposition, on sandy soils, or in montane areas. Critical loads are effect thresholds for N deposition, and the critical load concept has helped European governments make progress toward reducing N loads on sensitive ecosystems. More needs to be done in Europe and North America, especially for the more sensitive ecosystem types, including several ecosystems of high conservation importance. The results of this assessment show that the vulnerable regions outside Europe and North America which have not received enough attention are ecoregions in eastern and southern Asia (China, India), an important part of the mediterranean ecoregion (California, southern Europe), and in the coming decades several subtropical and tropical parts of Latin America and Africa. Reductions in plant diversity by increased atmospheric N deposition may be more widespread than first thought, and more targeted studies are required in low background areas, especially in the G200 ecoregions.
Fen-meadow succession in relation to spatial and temporal differences in hydrological and soil conditions
Hoek, D. van der; Sykora, K.V. - \ 2006
Applied Vegetation Science 9 (2006)2. - ISSN 1402-2001 - p. 185 - 194.
nutrient limitation - vegetation - netherlands - management - phosphorus - nitrogen - wetland - wet
Question: In fen meadows with Junco-Molinion plant communities, falling groundwater levels may not lead to a boosted above-ground biomass production if limitation of nutrients persists. Instead, depending on drainage intensity and microtopography, acidification may trigger a shift into drier and more nutrient-poor plant communities. Location: Nature reserve, central Netherlands, 5 m a.s.l. Methods: Long-term study (1988-1997) in a fen meadow along a gradient in drainage intensity at different scales. Results: Above-ground biomass increased only slightly over ten years, despite a lower summer groundwater table. The accountable factors were probably a limited availability of nutrients (K in the higher well-drained plots, P in the intermediate plots and N in the lower hardly drained plots), plus removal of hay. Junco-Molinion species increased in dry sites and Parvocaricetea species increased in wet sites, presumably primarily because of soil acidification occurring when rainwater becomes more influential than base-rich groundwater. The extent of the shift in species composition depends primarily on the drainage intensity and secondarily on microtopography. Local hydrological measures have largely failed to restore wetter and more basic-rich conditions. Conclusions: Acidification and nutrient removal, leaching and immobilization resulted in the succession towards Junco-Molinion at the cost of Calthion palustris elements. Lower in the gradient this change was reduced by the presence of buffered groundwater in slightly drained sites. To conserve the typical plant communities of the Junco-Molinion to Calthion gradient in the long term, further acidification must be prevented, for example by inundation with base-rich surface water.
Nutritional constraints in ombrotrophic Sphagnum plants under increasing atmospheric nitrogen deposition in Europe
Bragazza, L. ; Tahvanainen, T. ; Kutnar, L. ; Rydin, H. ; Limpens, J. ; Hajek, M. ; Grosvernier, P. ; Hansen, I. ; Lacumin, P. ; Gerdol, R. - \ 2004
New Phytologist 163 (2004)3. - ISSN 0028-646X - p. 609 - 616.
nutrient limitation - n-deposition - bog vegetation - raised bogs - growth - co2 - water - wet - acidification - accumulation
We studied the effects of increasing levels of atmospheric nitrogen (N) deposition on nutrient limitation of ombrotrophic Sphagnum plants. • Fifteen mires in 11 European countries were selected across a natural gradient of bulk atmospheric N deposition from 0.1 to 2 g/m2 year-1. Nutritional constraints were assessed based on nutrient ratios of N, phosphorus (P), and potassium (K) in Sphagnum plants collected in hummocks (i.e. relatively drier microhabitats) and in lawns (i.e. relatively wetter microhabitats). • Nutrient ratios in Sphagnum plants increased steeply at low atmospheric N input, but above a threshold of N deposition of c. 1 g/m2 year-1 the N : P and N : K ratios tended to saturation. Increasing atmospheric N deposition was also accompanied by a reduced retention of Ca and Mg in Sphagnum plants and a decreased stem volumetric density in hummock Sphagnum plants. • We suggest a critical load of N deposition in Europe of 1 g/m2 year-1 above which Sphagnum plants change from being N-limited to be K + P colimited, at N : P > 30 and N : K > 3.
Changes in soil and vegetation during dune slack succession
Sykora, K.V. ; Bogert, J.C.J.M. van den; Berendse, F. - \ 2004
Journal of Vegetation Science 15 (2004)2. - ISSN 1100-9233 - p. 209 - 218.
nutrient limitation - accumulation - communities - pedogenesis - dynamics - decline
Many rare plant species occur in Dutch wet dune slacks, particularly in the Junco baltici-Schoenetum nigricantis. For nature management it is important to understand the processes controlling the presence of these basiphilous early successional communities, which is why we investigated vegetation and soil development during succession in coastal dune slacks. We compared 12 chronosequential stages of 0, 2, 4, 9, 10, 13, 25, 30, 43, 60, 70 and 85 yr in five different dune slack systems. In four of these locations turf had earlier been removed in order to restore the basiphilous pioneer stage. The main variation in the vegetation is related to the acidification/soil enrichment gradient and the salinity/maritime gradient. During succession, organic matter accumulates and acidification takes place. Maritime influence can buffer the soil and postpone the succession of basiphilous pioneer communities for many years. A significant correlation with age was found for 18 variables. Multiple regressions predicted changes in the vegetation (dependent variables: biomass, cover of Salix repens, Calamagrostis epigejos and Schoenus nigricans) as a function of acidification, organic matter accumulation, increase in available P and presence of Na in the soil. We conclude that natural ageing of the vegetation and the associated process of accumulation of biomass drive succession in this hydrosere. The underlying soil processes are acidification and organic matter accumulation. During succession dominance shifts from S. nigricans to S. repens or C. epigejos. Maintenance of the pioneer character of the habitat is only possible by local intervention or by natural or man-induced dune forming. The effect of sod-stripping depends on the environmental conditions and, in case of acidification, success is limited. Succession can be postponed by mowing