1,721,003 research outputs found
Importance of canopy herbivores to dissolved and particulate organic matter fluxes to the forest floor
No full textFew studies deal with the origin and contribution of organic matter (OM) fluxes from forest canopies to the variability of DOM and nutrient dynamics in the forest floor. Recent studies indicate a microbial and phytophages origin of OM in the throughfall of temperate forest ecosystems and reported inputs of dissolved (< 0.45 mu m) organic carbon (DOC) with throughfall range between 40 and 160 kg C ha(-1) year(-1). Data on particulate organic matter (0.45 mu m < POM < 2 mm) associated with throughfall fluxes are rare and not often considered in terrestrial ecosystem element budgets. Using field and laboratory experiments, we investigated the direct effects of canopy infestation by two functional groups of herbivores (sap and leaf feeders) on dissolved and particulate organic matter fluxes in throughfall and their impact on forest floor processes. Throughfall fluxes of particulate amino-nitrogen beneath infested spruce were about 60% and those of bexosecarbon beneath infested hardwood trees up to 70% higher compared to uninfested control trees. Corresponding fluxes to filtered samples showed no statistically significant differences. In column irrigation experiments, different levels of aphid infestation (uninfested, moderately, heavy infested) were simulated by adding honeydew to the irrigation solution. Forest floor solution chemistry from forest floor showed a significant reduction in NH4-N and NO3-N fluxes, slightly reduced DON fluxes and significantly increased CO2 effluxes following honeydew application. We suggest that the amount of POM compounds transported with throughfall solution and its subsequent effects on forest floor processes depend on the herbivore functional group and on the level of infestation. From both a quantitative and qualitative point of view, our data indicate that herbivory-mediated organic matter in particulate and dissolved forms contribute considerably to the overall throughfall input of organic substances into the forest floor. (c) 2004 Elsevier B.V. All rights reserved
Impact of a pine lappet (Dendrolimus pini) mass outbreak on C and N fluxes to the forest floor and soil microbial properties in a Scots pine forest in Germany
No full textHerbivorous insect infestations significantly alter element and nutrient cycling in forests, thus directly and indirectly affecting ecosystem functioning. In this paper, we report on the herbivore-mediated transfer of carbon (C) and nitrogen (N) from the canopy to the forest floor and its influence on soil microbial activity during a pine tappet (Dendrolimus pini L.) infestation. Over the course of 6 months, we followed C and N fluxes in bulk deposition, throughfall, and green fall (green needle debris dropped during herbivory) together with solid frass (insect faeces) in an 80-year-old Scots pine (Pinits silvestris L.) forest. Compared with the control, herbivore defoliation significantly doubled throughfall inputs of total and dissolved organic C and N over the study period. Frass plus green-fall C and N fluxes peaked in June-July at 110 kg C.ha(-1) and 2.3 kg N.ha(-1), respectively. Randomized intervention analysis revealed no significant effects of herbivory on soil microbial properties, except for adenylate energy charge, which showed slightly higher values under herbivory. This study demonstrates the importance of canopy herbivory on overall C and N inputs to forest ecosystems, particularly in altering the timing and quality of the organic material reaching the forest floor and potentially affecting belowground processes.erman Research Foundation, DFG [MI 927/1-1
Soil microbiochemical properties as indicators for success of heathland restoration after military disturbance
No full textDecline of heathlands in Central Europe raises the question of successful restoration of degraded heathlands. We examined the impact of different restoration techniques oil soil microbial biomass carbon (C(mic)) and nitrogen (N(mic)) and enzyme activity on an abandoned military training site in the Luneburger Heaths. The aim was to determine which technique resulted in typical heathland soil conditions. The training site was ill use for about 50 years. Vegetation and soils were degraded in large areas. Restoration actions were: (1) spreading of heath plaggen (sods, containing the organic layer and a few centimetres mineral soil), (2) spreading of heath plaggen and grass seeds (Festuca filiformis Pourr.). (3) spreading of F. filiformis-seeds and (4) succession (episodical tree removal). Ten years after restoration. we measured pH, bulk density, abundance of roots, soil organic carbon (SOC), nitrogen (N(1)), phosphorus (P(1)) C(mic), N(mic) and acid phosphatase activity (AcP) in the first 10cm of the mineral soil. Four restoration treatments were compared with one reference site. The reference site is heathland located near the training site, where no military actions took place. At all disturbed sites, bulk density and pH proved to be higher than oil the reference site. Relative to the reference site, SOC storage reached from 37 to 91 per cent, regeneration of N(1) was slightly lower. In contrast to the advanced development of SOC and Nt, the regeneration of C(mic) and N(mic) was much lower (15-44 per cent). The succession site showed a low pool of SOC, Nt, C(mic) and N(mic), but microbial ratios indicated a less disturbed C- and N-cycle. AcP pronounced differences in nutrient demand between disturbed sites and reference. On this base, recommendations for restoration management were given. Copyright (C) 2008 John Wiley & Soils, Ltd
Emissions of organo-metal compounds via the leachate and gas pathway from two differently pre-treated municipal waste materials - A landfill reactor study
No full textDue to their broad industrial production and use as PVC-stabilisers, agro-chemicals and anti-fouling agents, organo-metal compounds are widely distributed throughout the terrestrial and marine biogeosphere. Here, we focused on the emission dynamics of various organo-metal compounds (e.g., di,- tri-, tetra-methyl tin, di-methyl mercury, tetra-methyl lead) from two different kinds of pre-treated mass waste, namely mechanically-biologically pre-treated municipal solid waste (MBP MSW) and municipal waste incineration ash (MWIA). In landfill simulation reactors, the emission of the organo-metal compounds via the leachate and gas pathway was observed over a period of 5 months simulating different environmental conditions (anaerobic with underlying soil layer/aerated/anaerobic). Both waste materials differ significantly in their initial amounts of organo-metal compounds and their environmental behaviour with regard to the accumulation and depletion rates within the solid material during incubation. For tri-methyl tin, the highest release rates in leachates were found in the incineration ash treatments, where anaerobic conditions in combination with underlying soil material significantly promoted its formation. Concerning the gas pathway, anaerobic conditions considerably favour the emission of organo-metal compounds (tetra-methyl tin, di-methyl mercury, tetra-methyl lead) in both the MBP material and especially in the incineration ash. (c) 2006 Elsevier Ltd. All rights reserved
Canopy herbivory altering C to N ratios and soil input patterns of different organic matter fractions in a Scots pine forest
No full textHerbivorous insects can affect ecological processes in forested ecosystems such as nutrient and matter cycling especially during outbreak situations. However, the knowledge about their contribution to the quality and flows of energy and matter in forests is still imperfect. In this paper we report on the herbivore-affected C to N ratios in different fractions of organic matter cascading from the canopy to the forest floor during a pine lappet (Dendrolimus pini L.) mass infestation. Throughout a four months period we monitored the C and N fluxes with throughfall, and the C/N ratios of insect excrements (faeces) and pine needles in an 80-year-old Scots pine forest. Compared to the control, herbivore defoliation significantly magnifies C and N input fluxes by two to three times amounting to 95 kg TOC and 5.9 kg TN ha−1 in addition. Concurrently NO3-N fluxes diminished and the C/N ratios in throughfall solutions increased during peaking frass activity. Compared to fresh needle biomass, the C/N ratios in insect faeces triple during peaking frass activity resulting in values between 70 and 100. This study demonstrates the importance of herbivorous insect’s pests on element cycling as they act as a short-time phenomenon altering the nutrient quality and quantity reaching the forest floor and potentially affecting below-ground processes
Insect herbivory, organic matter deposition and effects on belowground organic matter fluxes in a central European oak forest
Full text linkApart from the forest floor, the canopy of forested ecosystems functions as the second most important source for dissolved and particulate fractions of organic and inorganic C and N compounds. However, under mass outbreak situations of insect herbivores this flux path of organic matter is considerably intensified clearly exceeding C and N fluxes from the forest floor. In this paper we report on herbivore-altered C and N fluxes from the canopy to the forest floor and effects on forest floor nutrient fluxes during severe defoliating herbivory of the winter moth (Operophtera brumata) and the mottled umber moth (Eranis defoliaria) in an oak forest in Germany. Over the course of 6.5 months we followed the C and N fluxes with bulk deposition, throughfall solution, insect frass deposits (green-fall together with insect faeces) and with forest floor solution in an 117-yr-old oak (Quercus petraea) forest. Compared to the control, herbivore defoliation significantly enhanced throughfall inputs of total and dissolved organic carbon and nitrogen by a factor of 3 and 2.5 (for TOC and DOC), and by 1.4 and 1.3 times (for TNb and DNb), respectively. Frass plus green-fall C and N fluxes peaked in May with 592 kg C ha(-1) and 33.5 kg N ha(-1) representing 79.6% (for C) and 78.3% (for N) of the total C and N input over 2.5 months. The quantitative and qualitative C and N input via faeces and litter deposition significantly differ between the insect affected and non-affected site. However, the C and N fluxes with throughfall did not significantly correlate with forest floor leachates. In this context, forest floor fluxes of TOC, DOC and NO3-N were significantly lower at the infested site compared to the control, whereas fluxes of NH4-N together with DON were significantly higher. The study demonstrates the importance of linking the population and associated frass dynamics of herbivorous insects with the cycling of nutrients and organic matter in forest ecosystems, highlighting the remarkable alterations in the timing, amounts and nature of organic matter dynamics on the ecosystem level. Consequently, the ecology of phytophagous insects allows partly to explain temporal-spatial alterations in nutrient cycling and thus ecosystem functioning.German Research Foundation (DFG) [MI 927/1-3
Late Holocene human impact and environmental change inferred from a multi-proxy lake sediment record in the Loja region, southeastern Ecuador
No full textLate Holocene human impact and environmental changes were reconstructed from a sediment core of the Laguna Daniel Alvarez (2200 m asl) located on the outskirts of the city of Loja, southeastern Ecuador. Palaeoenvironmental changes were investigated by pollen, spore, algae and charcoal analysis in combination with X-Ray Fluorescence (XRF) scanning and element analysis of delta C-13, Total Organic Carbon (TOC), Total Nitrogen (TN) and radiocarbon dating. This multi-proxy study provides in detail the settlement history in the inner-Andean dry valley in southern Ecuador over the last ca. 1400 years. Between 630 and 1470 AD, Zea mays was intensively cultivated around the studied lake by the native Palta culture in the Loja region. After ca. 1470 AD, Z. mays cultivation collapsed, accompanied by an increase in fallow vegetation, such as Mimosa and Poaceae, probably as a result of the Inca invasion and occupation from 1463 to 1531 AD in southern Ecuador. After ca. 1570 AD, Amaranthaceae/Chenopodiaceae markedly increased, reflecting the beginning of the Spanish Conquest. In 1531 AD, Loja became Spanish and, during the first ca. 100 years of the Spanish regime, Loja developed into the fortified capital of the province. In the 17th century, crop growing strongly declined due to the diminished indigenous population that probably suffered from new diseases introduced by the Spanish invaders. Pinus and Eucalyptus as well as Plantago lanceolata were introduced in the Loja region about 220 years ago. (C) 2013 Elsevier Ltd and INQUA. All rights reserved.Deutsche Forschungsgemeinschaft (DFG) [FOR 402/D1
Drought tolerance of emerging European silver fir seedlings (Abies alba Mill.) does not follow geographic gradients
Full text linkAbstract One of silviculture's primary objectives is converting monospecific into diverse forest stands comprising climate-tolerant species, aiming to mitigate global change. In practice, this is often achieved by enrichment planting or seeding of species, currently not occurring in the specific area. Silver fir ( Abies alba ) is considered one of the European native species regarded as climate tolerant. The species, therefore recently received increasing attention in research and forestry in the context of climate change adaptation. The intra-specific variation in drought tolerance has been intensively studied in Abies alba adult trees, but not in seedlings. Here, we explore the potential of Abies alba seedlings to withstand simulated summer droughts in central Europe. A climate chamber experiment was conducted, examining the resistance to and recovery from drought of silver fir seedlings of four provenances representing a geographic West–East gradient in Europe. Seedlings were exposed to two 30-day drought scenarios of differing severity under controlled conditions. We measured biomass partitioning patterns and individual photosynthetic efficiency. Growth and maximum photosynthetic efficiency were unaffected by intermediate drought. Intense drought significantly reduced the maximum photosynthetic efficiency of all provenances. Seedlings of the easternmost provenance showed the greatest biomass across all treatments; however, they failed to recover from drought. Our findings show that differences in drought susceptibility of emerging Abies alba seedlings do not follow geographic gradients
Influence of Rhizobia Inoculation on Biomass Gain and Tissue Nitrogen Content of Leucaena leucocephala Seedlings under Drought
Full text linkAnticipated increases in the frequency of heat waves and drought spells may have negative effects on the ability of leguminous trees to fix nitrogen (N). In seedlings of Leucaena leucocephala inoculated with Mesorhizobium loti or Rhizobium tropici, we investigated how the developmental stage and a short drought influenced overall biomass and the accumulation of carbon and N in plant tissues. In early developmental stages, the number of nodules and nodule biomass were correlated with total plant biomass and δ15N, and nodules and roots contributed 33%–35% of the seedling total N. Seedlings associated with R. tropici fixed more N and exhibited higher overall biomass compared with M. loti seedlings. Four and a half months after inoculation (140 days after inoculation, DAI), a short (15-day) drought inhibited seedling growth and caused a decline in total plant N, with the smallest decline in R. tropici seedlings. After 15 days of drought, i.e., 155 DAI, the nodules had accumulated proline, but the total amino acid concentration did not change. Our results indicate that N-fixation is independent of seedlings growth. In addition, R. tropici is a better choice than M. loti as a symbiont for Leucaena seedlings for forest restoration and agroforestry applications under increasingly drier conditions
Land Use Effects on Carbon and Nutrient Fluxes in Soils
Full text linkLand-use and management influence the coupled carbon and nutrients cycles in soils. However, studies that investigate carbon and nutrient cycling in multiple land-uses over multiple study regions with distinct environmental conditions and across broad management gradients are scarce. Therefore, many questions regarding management, biotic and abiotic effects on carbon and nutrient cycling, remain open in real-world ecosystems. Some of these research questions are: i) how forest properties affect soil respiration: through their effects on soil properties or on climatic conditions?, ii) how grassland management influences soil respiration, and that is the role of plant diversity? and iii) what is the relative importance of direct and indirect effects of grassland management on nutrient leaching, and how are the indirect effects mediated by soil, plant and microbial properties? In this thesis, I measured in-situ soil respiration and nutrient (nitrate, ammonium, phosphate and sulphate) leaching in 150 forests and 150 grasslands over three temperate regions in Germany. In-situ soil respiration was measured with soda-lime method as single measurements over long periods (3-7 days), in early summer in 2018 and 2019. Nutrient leaching was determined at 10 cm soil depth with a resin method as the cumulative downward flux over a year (from spring 2018 to spring 2019). The main objectives of my Thesis were to: i) determine management effects on these two major soil functions, ii) determine their main biotic and abiotic drivers, and iii) compare these carbon and nutrient fluxes between the two land-use types
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