Search results for "Biomas"
showing 10 items of 980 documents
Responses of decomposer community to root-isolation and addition of slash
2001
Abstract We studied the causal relationships between forest harvesting and the soil decomposer community focusing on suppression of energy inputs from trees to the soil through root–mycorrhizal network and increased energy input to the soil in the form of slash left on site. We hypothesised that both of these factors would affect the decomposer community, since the soil food web has been regarded as a system in which the amount of resources controls the numbers of consumers. To study the importance of these factors without changes in microclimate, like in sunshine and shade, taking place in clear-felled areas, the experiment was performed in a mature spruce ( Picea abies (L.) Karst.) forest…
Soil carbon quality and nitrogen fertilization structure bacterial communities with predictable responses of major bacterial phyla
2014
Abstract Agricultural practices affect the soil ecosystem in multiple ways and the soil microbial communities represent an integrated and dynamic measure of soil status. Our aim was to test whether the soil bacterial community and the relative abundance of major bacterial phyla responded predictably to long-term organic amendments representing different carbon qualities (peat and straw) in combination with nitrogen fertilization levels and if certain bacterial groups were indicative of specific treatments. We hypothesized that the long-term treatments had created distinctly different ecological niches for soil bacteria, suitable for either fast-growing copiotrophic bacteria, or slow-growing…
Influence of carbon and nutrient additions on a decomposer food chain and the growth of pine seedlings in microcosms
2001
Abstract Because of N deposition plant production is becoming increasingly limited by other nutrients in boreal forests. At the same time more C is suggested to become available for below-ground food webs because of enhanced CO2 fixation. We studied the effects of carbon and nutrient addition on a fungus–nematode food chain and on the growth of mycorrhizal or nonmycorrhizal pine seedlings (Pinus sylvestris L.) in microcosms with N-rich mineral soil and a humus layer. The role of the food chain and mycorrhizal fungi for pine growth was tested in a smaller set-up. The total pine biomass was not N-limited at the scale of two experimental growing seasons. In accordance with established knowledg…
Top predators, mesopredators and their prey: interference ecosystems along bioclimatic productivity gradients
2010
1. The Mesopredator Release Hypothesis (MRH) suggests that top predator suppression of mesopredators is a key ecosystem function with cascading impacts on herbivore prey, but it remains to be shown that this top-down cascade impacts the large-scale structure of ecosystems. 2. The Exploitation Ecosystems Hypothesis (EEH) predicts that regional ecosystem structures are determined by top-down exploitation and bottom-up productivity. In contrast to MRH, EEH assumes that interference among predators has a negligible impact on the structure of ecosystems with three trophic levels. 3. We use the recolonization of a top predator in a three-level boreal ecosystem as a natural experiment to test if l…
Functional diversity of decomposer organisms in relation to primary production
1998
Abstract The term `biodiversity' is claimed to lack connections to a serious scientific background. In this work, we approached the concept of biodiversity from a functional point of view by asking: “At what level of the ecological organization (species, trophic species/feeding guilds, trophic levels etc.) should reduction in biodiversity matter to bring about visible changes in ecosystem performance?” We investigate the concepts of `functional diversity' and `ecosystem performance' in relation to feeding habits (such as fungivory, detritivory etc.) of soil fauna and plant growth. After analysing the results of a number of microcosm studies, we came into the following conclusions: (i) troph…
Plant litter decomposition and microbial characteristics in volcanic soils (Mt Etna, Sicily) at different stages of development
2006
Soils at different developmental stages were sampled from eight sites on the slopes of Mt Etna, Sicily (Italy) and characterized for total C, microbial biomass and microbial respiration. The values of these parameters were greatest for the most developed soils, but differences in recent management and site characteristics limited analysis of trends with soil development across the eight sites. The decomposition kinetics of both intact leaf litter and the water-insoluble fraction of leaf litter from three common species on Etna [Etnean broom (Genista aetnensis), European chestnut (Castanea sativa), and Corsican pine (Pinus nigra)] were determined in four of the soils (the two with the smalle…
Retrieval and assessment of CO2 uptake by mediterranean ecosystems using remote sensing and
2014
Photosynthesis is a process by which carbon and energy enter ecosystems. The knowledge of where,when, and how carbon dioxide (CO2) is exchanged between terrestrial ecosystems and atmosphere is crucial to close the Earth's carbon budget and predict feedbacks in a likely warming climate. Gross photosynthesis (uptake of CO2) by vegetation is responsible for the gross primary production (GPP) of the ecosystem. Normally GPP refers to the sum of the photosynthesis by all leaves measured at the ecosystem scale. John Monteith proposed in 1972 a simple approach that has become the paradigm for understanding GPP. It considers GPP as proportional to the incident short wave radiation (PAR), the fractio…
Surface soil moisture retrieval using L-band SMAP SAR data and its validation
2016
Surface soil moisture was retrieved globally by systematically correcting for the effects of vegetation and soil surface roughness. The retrieval is enabled by employing physical-models of radar forward scattering for individual vegetation types to account for vegetation scattering and absorption, and by constraining the surface roughness effect using time-series observations. The L-band SMAP multi-polarized (HH/VV/HV) σ° data acquired globally every three days were used from mid-April to early July, 2015. Assessment was conducted over 13 rigorously-chosen core validation sites covering a wide range of biomass types, biomass amount, and soil conditions. The soil moisture retrieval reached a…
Responses of microbial food web to increased allochthonous DOM in an oligotrophic subarctic lake
2013
Climate-induced changes in catchment area vegetation and runoff alter the quality and quantity of carbon that enters lakes, with implications for food webs in recipient water bodies. The effect of dissolved organic matter (DOM) on the ratio between heterotrophic and autotrophic biomass and productivity was studied in a subarctic, clear water lake in northern Finland. In a mesocosm experiment, natural DOM from a subarctic bog and a boreal lake was added to the lake water, doubling the initial dissolved organic carbon (DOC) concentration. Optical indices sug- gested that the subarctic DOM addition was more bioavailable, which was in line with the greater increase in bacterial biomass and prod…
Meiofauna ratios as environmental indicators in the profundal depths of large lakes.
1995
Two sets of samples from Lake Paijanne and one from Lake Ladoga were used to examine the relations between the meiofauna and environmental variables. The most obvious indicators of an unpolluted environment were, in order of importance, the true meiofauna/total meiofauna ratio, the proportion of Aeolosomatidae, the proportion of Harpacticoida (excluding C. staphylinus), the meiofauna/macrofauna biomass ratio, the proportion of Naididae and the A. crassa + P. schmeili/true meiofauna ratio. Conversely, the clearest indicators of a polluted environment were the proportion of resting stages of Cyclopinae, the Nematoda/non-resting Copepoda ratio, and the proportions of Tubificidae, Oligochaeta, …