Publikationen
Es wurden 8 Publikationen gefunden
Wilcke, W. (2021): Litterfall in Andean forests: Quantity, composition, and environmental drivers. In: Randall W. Myster (eds.): The Andean Cloud Forest ( ), Springer Nature Switzerland, Basel, Switzerland, 89-110.
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DOI: 10.1007/978-3-030-57344-7_5
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Abstract:
Abstract:
Litterfall is the most easily and most frequently measured part of net primary productivity (NPP) of forests. It has been shown that litterfall accounts for about one third of total NPP and thus serves as a proxy for the total productivity of forests. Moreover, litterfall carries nutrients from the forest canopy to the soil and therefore is also a major vector of nutrient cycling. I reviewed the published literature about litterfall rates and chemical properties in Andean forests and found reports from 44 forest sites, which I evaluated together with unpublished data from 12 sites in a lower montane forest in Ecuador. I found many more reports from tropical (52 sites) than from temperate Andean forests (4 sites). In the humid tropical north Andes, litterfall showed a hump-shaped elevational distribution. It increased from premontane to lower montane forests and decreased to upper montane forests. The tropical lower montane forest had a similar productivity than tropical lowland forests. The litterfall of the temperate southern beech forests was similar to that of the tropical upper montane forests. The C/N and C/P ratios of litterfall decreased with increasing elevation, while the N/P ratios were not correlated with elevation. This illustrates that the forests become increasingly nutrient efficient with increasing elevation, while there is no indication of a general change in the kind of nutrient limitation. There was a negative correlation between litterfall and soil organic layer thickness (r = −0.61, p < 0.001) illustrating that the organic matter input via litterfall is a less important driver of organic matter accumulation on top of the mineral soil than other, mainly abiotic properties including temperature and soil waterlogging. My evaluation suggests that there are systematic relationships between abiotic conditions and litterfall, which could be used to predict litterfall in the Andes. However, the data coverage particularly of the southern Andes (Bolivia, Chile, Argentina), the Andean dry forests, and the widespread tree plantations is poor. The observed elevational influence on litterfall in the humid tropical Andes suggests that the forest productivity will likely respond to climate change driving the vegetation belts to higher elevation with an unknown overall effect on C sequestration of these forests.
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Keywords: |
nutrient cycle |
elevational gradient |
macronutrients |
Aboveground forest productivity |
Fine litter production |
Homeier, J.; Báez, S.; Hertel, D. & Leuschner, C. 2017: Tropical Forest Ecosystem Responses to Increasing Nutrient Availability. (Frontiers Media SA).
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Abstract:
Abstract:
Deforestation and land use change have led to a strong reduction of tropical forest cover during the last decades. Climate change will amplify the pressure to the remaining refuges in the next years. In addition, tropical regions are facing increasing atmospheric inputs of nutrients, which will have unknown consequences for the structure and functioning of these systems, no matter if they are within protected areas or not. Even remote areas are expected to receive rising amounts of nutrients.
The effects of higher rates of atmospheric nutrient deposition on the biological diversity and ecosystem functioning of tropical ecosystems are poorly understood and our knowledge of nutrient fluxes and nutrient limitation in tropical forest ecosystems is still limited. Yet, it will be of paramount importance to know the effects of increased nutrient availability to conserve these ecosystems with their biological and functional diversity.
During the last years, research efforts have more and more focused on the understanding of the role of nutrients in tropical ecosystems and several coordinated projects have been established that study the effects of experimental nutrient addition.
This Research Topic combines results from experiments and from observational studies with the aim to review and conclude on our current knowledge on the role of additional nutrients in ecosystems.
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Keywords: |
nutrients |
NUMEX |
nutrient cycle |
Nutrient deposition |
nutrient additions |
Schob, S. (2014): Concentration-Discharge Hysteresis Effects of BOD, COD, Nitrate and Turbidity during Storm Flow Events in the Paramo of Southern Ecuador University of Giessen - Institute of Landscape Ecology and Resources Management, bachelor thesis
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Abstract:
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Future climate and land use change may have a great impact on essential ecosystem functions such as carbon storage and water supply of the Andean p´aramo ecosystem. As hydrogeochemical processes in the p´aramo and possible reactions to these changes are still largely unknown, nutrient fluxes during storm flow events in a
p´aramo catchment in the Cajas National Park of south Ecuador were studied. From February to June 2014, discharge and stream concentrations of biochemical oxygen demand (BOD), chemical oxygen demand (COD), turbidity and nitrate (NO3-N) were monitored in five minute intervals in the Quinuas River. In order to study the catchment’s response to rainfall events, rotational patterns of concentration-discharge hysteresis effects were analysed. In total, 35 events were suitable for analysing hysteresis effects of BOD, COD, and turbidity. Nitrate concentrations were studied in 20 events. Precipitation events led to an increase of concentration of all parameters. Hysteresis patterns showed a high consistency. COD, turbidity, and nitrate rotated mainly clockwise, BOD counterclockwise. Therefore, a fast response of the sources of COD, nitrate, and turbidity is suggested. This might be mainly due to a fast subsurface flow through the upper organic soil horizons. BOD sources, mainly soil surface and litter layer, predominate later in the
storm flow event
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Keywords: |
hydrochemistry |
hydrological processes |
nutrient cycle |
indirect land use change (ILUC) |
Camenzind, T.; Homeier, J.; Dietrich, K.; Hempel, S.; Hertel, D.; Krohn, A.; Leuschner, C.; Oelmann, Y.; Olsson, P.A.; Suarez, J.P. & Rillig, M.C. (2016): Opposing effects of nitrogen versus phosphorus additions on mycorrhizal fungal abundance along an elevational gradient in tropical montane forests. Soil Biology & Biochemistry 94, 37-47.
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DOI: 10.1016/j.soilbio.2015.11.011
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Abstract:
Abstract:
Studies in temperate systems provide evidence that the abundance of arbuscular mycorrhizal fungal (AMF) depends on soil nutrient availability, which is mainly explained in the context of resource stoichiometry and differential plant biomass allocation. We applied this concept to an understudied ecosystem – tropical montane forest – analyzing root and AMF abundance along an elevational gradient with decreasing nutrient availability, combined with responses to nitrogen (N) versus phosphorus (P) additions. At three sites from 1000 to 3000 m above sea-level we analyzed fine root length, AMF root colonization as well as extraradical AMF biomass (neutral lipid fatty acid 16:1?5, hyphal length and spore counts) in a nutrient manipulation experiment. We found a significant increase in root length as well as intra- and extraradical AMF abundance with elevation. Overall, P additions significantly increased, whereas N additions decreased AMF abundance, with differential though nonsystematic changes along the elevational gradient. Strongest effects were clearly observed at the intermediate site. These findings suggest a general dependency of roots and AMF on nutrient availability, though responses to N and P additions differed from previous studies in temperate systems. In the context of future nutrient depositions, results suggest diverging responses of AMF abundance depending on site characteristics.
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Keywords: |
NUMEX |
Bombuscaro |
AM fungi |
arbuscular mycorrhiza |
nutrient cycle |
Nutrient deposition |
Spöri, E. (2015): Phosphatase Activity in Soil of an Ecuadorian Tropical Montane Rainforest University of Tuebingen, bachelor thesis
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Abstract:
Abstract:
Ecosystems worldwide face increasing nutrient depositions mainly caused by anthropogenic processes. In particular, tropical ecosystems react sensitively to altering nutrient supply. The deposition of nutrients might influence the nutrient cycles, primarily of N and P in tropical montane rainforests. Increased nutrient supply leads to an enhanced biomass production and therefore other nutrients become limited for plants and microorganisms.
For this reason, the aim of this thesis is to study the response of phosphatase activity (PA) on moderate fertilization along an altitudinal gradient in a tropical montane rainforest in South Ecuador. The experiment was conducted on the NUMEX study sites including three different elevation levels 1000, 2000 and 3000m a.s.l. The different plots were treated with N, P, N+P to simulate increased nutrient depositions and one control plot. Further, organic layer and mineral soil was sampled and phosphomono- and phosphodiesterase activity (PMEA and PDEA) were determined.
The N fertilized plots showed only small effects compared to the control; presumably due to low amounts of added fertilizer. PA in the P addition plots showed reduced activity compared to the control with significant results of PMEA in the organic layer of the study sites on 2000 and 3000m a.s.l. The reason might be sufficient quantities of inorganic P which suppresses the production of phosphatases. Further, PA in N+P plots showed lower PA compared to the control than in the P addition plots. This effect could be caused through the dominating inhibitory effect of P in contrast to the stimulating effect of N on PA. Altitudinal differences were observed comparing the control plots at different elevation levels (1000, 2000 and 3000m a.s.l.). The results for the organic layer showed increasing PA along the altitudinal gradient with the lowest PA at 1000m a.s.l. The findings are contrary to the present literature which states that lowland tropical forests are characterized by high decomposition rates coming up with high PA. The findings cannot support this hypothesis; therefore more research is needed in the studied area in South Ecuador.
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Keywords: |
NUMEX |
nutrient cycle |
Kotowska, M. & Werner, F.A. (2013): Environmental controls over methane emissions from bromeliad phytotelmata: The role of phosphorus and nitrogen availability, temperature, and water content. GLOBAL BIOGEOCHEMICAL CYCLES 27, 1-8.
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DOI: 10.1002/2013GB004612
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Abstract:
Abstract:
Tank bromeliads are common epiphytic plants throughout neotropical forests that store
signi?cant amounts of water in phytotelmata (tanks) formed by highly modi?ed leafs.
Methanogenic archaea in these tanks have recently been identi?ed as a signi?cant source of
atmospheric methane. We address the effects of environmental drivers (temperature, tank
water content, sodium phosphate [P], and urea [N] addition) on methane production in
anaerobically incubated bromeliad slurry and emissions from intact bromeliad tanks in
montane Ecuador. N addition ? 1 mg g 1 had a signi?cantly positive effect on headspace
methane concentrations in incubation jars while P addition did not affect methane
production at any dosage (? 1 mg g 1 ). Tank bromeliads (Tillandsia complanata) cultivated
in situ showed signi?cantly increased ef?uxes of methane in response to the addition of
26 mg N addition per tank but not to lower dosage of N or any dosage of P (? 5.2 mg plant 1 ).
There was no signi?cant interaction between N and P addition. The brevity of the
stimulatory effect of N addition on plant methane ef?uxes (1–2 days) points at N
competition by other microorganisms or bromeliads. Methane ef?ux from plants closely
followed within-day temperature ?uctuations over 24 h cycles, yet the dependency of
temperature was not exponential as typical for terrestrial wetlands but instead linear. In
simulated drought, methane emission from bromeliad tanks was maintained with minimum
amounts of water and regained after a short lag phase of approximately 24 h. Our results
suggest that methanogens in bromeliads are primarily limited by N and that direct effects of
global change (increasing temperature and seasonality, remote fertilization) on bromeliad
methane emissions are of moderate scale.
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Keywords: |
nutrients |
gas emission |
NUMEX |
N-cycle |
nitrogen |
Gas exchange |
phosphorus |
nutrient manipulation |
nutrient limitation |
phosphorus availability |
nutrient cycle |
methane |
Wullaert, H.; Bigalke, M.; Homeier, J.; Cumbicus Torres, N.; Valarezo, C. & Wilcke, W. (2013): Short-term response of the Ca cycle of a montane forest in Ecuador to low experimental CaCl2 additions. Journal of Plant Nutrition and Soil Science 176(6), 892-903.
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DOI: 10.1002/jpln.201300146
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Abstract:
Abstract:
The tropical montane forests of the E Andean cordillera in Ecuador receive episodic Sahara dust inputs particularly increasing Ca deposition. We added CaCl2 to isolate the effect of Ca deposition by Sahara dust to tropical montane forest from the simultaneously occurring pH effect. We examined components of the Ca cycle at four control plots and four plots with added Ca (2 × 5 kg ha–1 Ca annually as CaCl2) in a random arrangement. Between August 2007 and December 2009 (four applications of Ca), we determined Ca concentrations and fluxes in litter leachate, mineral soil solution (0.15 and 0.30 m depths), throughfall, and fine litterfall and Al concentrations and speciation in soil solutions. After 1 y of Ca addition, we assessed fine-root biomass, leaf area, and tree growth. Only < 3% of the applied Ca leached below the acid organic layer (pH 3.5–4.8). The added CaCl2 did not change electrical conductivity in the root zone after 2 y. In the second year of fertilization, Ca retention in the canopy of the Ca treatment tended to decrease relative to the control. After 2 y, 21% of the applied Ca was recycled to soil with throughfall and litterfall. One year after the first Ca addition, fine-root biomass had decreased significantly. Decreasing fine-root biomass might be attributed to a direct or an indirect beneficial effect of Ca on the soil decomposer community. Because of almost complete association of Al with dissolved organic matter and high free Ca2+ : Al3+ activity ratios in solution of all plots, Al toxicity was unlikely. We conclude that the added Ca was retained in the system and had beneficial effects on some plants.
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Keywords: |
tree growth |
NUMEX |
roots |
calcium |
aluminium |
nutrient cycle |
Wullaert, H.; Homeier, J.; Valarezo, C. & Wilcke, W. (2010): Response of the N and P cycles of an old-growth montane forest in Ecuador to experimental low-level N and P amendments. Forest Ecology and Management 260, 1435-1445.
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DOI: 10.1016/j.foreco.2010.07.021
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Abstract:
Abstract:
Atmospheric nitrogen (N) and phosphorus (P) depositions are expected to increase in the tropics as a
consequence of increasing human activities in the next decades. In the literature, it is frequently assumed
that tropical montane forests are N-limited, while tropical lowland forests are P-limited. In a low-level N
and P addition experiment, we determined the short-term response of N and P cycles in a north Andean
montane forest on Palaeozoic shists and metasandstones at an elevation of 2100m a.s.l. to increased N
and P inputs. We evaluated experimental N, P and N+ P additions (50 kg ha−1 yr−1 of N, 10 kg ha−1 yr−1
of P and 50 kg + 10 kg ha−1 yr−1 of N and P, respectively) and an untreated control in a fourfold replicated
randomized block design. We collected litter leachate, mineral soil solution (0.15 and 0.30m depths),
throughfall and litterfall before the treatment began (August 2007) until 16 months after the first nutrient
application (April 2009). Less than 10 and 1% of the applied N and P, respectively, leached below the
organic layer which contained almost all roots and no significant leaching losses of N and P occurred
to below 0.15m mineral soil depth. Deposited N and P from the atmosphere in dry and wet form were
retained in the canopy of the control treatment using a canopy budget model. Nitrogen and P retention
by the canopy were reduced and N and P fluxes in throughfall and litterfall increased in their respective
treatments. The increase in N and P fluxes in throughfall after fertilization was equivalent to 2.5% of the
applied N and 2% of the applied P. The fluxes of N and P in litterfall were up to 15% and 3%, respectively,
higher in the N and N+ P than in the control treatments. We conclude that the expected elevated N and P
deposition in the tropics will be retained in the ecosystem, at least in the short term and hence, N and P
concentrations in stream water will not increase. Our results suggest that in the studied tropical montane
forest ecosystem on Palaeozoic bedrock, N and P are co-limiting the growth of organisms in the canopy
and organic layer.
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Keywords: |
tropical montane forest |
nutrient cycle |
leaching losses |
N deposition |
P deposition |
environmental change |