Christian Kampichler

Plot-scale spatial patterns of soil water content, pH, substrate-induced respiration and N mineralization in a temperate coniferous forest

Samples of two perpendicular transects from an even-aged Norway spruce Picea abies forest . were used for geostatistical analysis of forest floor water content WC , pH, substrate-induced . . respiration SIR, a measure of microbial biomass , and N mineralization Nmin . Nmin data did not fulfil the stationarity assumptions of geostatistics and had to be detrended prior to analysis. All variables exhibited spatial structure. The degree of spatial dependence was generally high .60%-95% . pH and SIR were isotropically distributed; WC and Nmin were anisotropic. Three . different scales of spatial variability were detected at the site. 1 A fine-scale pattern with ranges - 1 m that was attributed to retarded decomposition, poor chemical and structural diversity of P. . abies litter, and lacking bioturbatic activity of earthworms. 2 A mesoscale pattern was indicated by sinoidal periodicity of most variograms, with inflection points every 1.0-1.5 m. This

Long-term dynamics and interrelationships of soil Collembola and microorganisms in an arable landscape following land use change

Abstract An arable landscape (150 ha) comprising a broad variety of soil types had been cultivated conventionally for many years. A small section had been intensively managed (hops), while another had been used as grassland. For 2 years at the beginning of our study, all arable land was cultivated with cereals only. After that, management was changed to integrated or organic farming, grassland or fallow land. Within a group of sites representing the variety of soil types and management systems, the development of soil microorganisms and Collembola was monitored every spring during an 8-year period. The microbial biomass compared to initial conditions under uniform management increased, particularly in land that had been set aside. General Collembola abundance slightly decreased, except for areas that had been converted to integrated farming. Protaphorura armata and Lepidocyrtus cyaneus decreased over the entire area, whereas the Isotoma viridis group was positively affected by conversion to integrated farming. Although recorded only once per year, the main results were comparable to data recorded in this area at higher temporal or spatial resolution. Nevertheless, site conditions may influence the reactions of soil organisms to land use change, and should be taken into account for evaluation. Biota resident in the upper 0–10 cm of the soil reflected current management practice, whereas those at greater soil depth reflected instead management history and soil properties. The microbial biomass and abundance of selected Collembola taxa were modeled using artificial intelligence methods (regression trees). Land management type was the most important factor determining soil biota performance. The variation of Collembola abundance depended additionally on microbial biomass. When supported by a sufficiently large data set, regression trees are powerful tools for explaining complex non-linear relationships. Finally, suggestions for the sampling design in future long-term studies at the landscape scale are given.

Use of enclosed model ecosystems in soil ecology: a bias towards laboratory research

Enclosed model ecosystems, or microcosms, have become a major research tool in soil ecology. Due to the speed, statistical power and mechanistic insights attainable with laboratory-based microcosm experiments, these have added considerably to our ecological knowledge. However, soil ecologists agree that, due to problems of scale and artificiality, microcosm research should be carried out in the context of appropriately scaled field model ecosystems (e.g. mesocosms). This paper aims at clarifying the terminology of enclosed model ecosystems as well as determining and discussing the frequency with which laboratory and field model ecosystems are used in current soil-ecological research. Among 92 model ecosystem studies published from 1993 to 1998 in soil biological journals, only 19 were performed in the field. Laboratory microcosms are, on average, significantly smaller and experiment duration is significantly shorter than in field model ecosystem studies. They are easier to maintain and allow for a larger number of experiments in a unit of time. We argue that the bias towards laboratory research is mainly caused by the growing demand for publications with high-impact ratings in an increasingly competitive scientific world and by the fact that an increasing emphasis is being placed on subjects where research can be carried out very quickly.

INTERACTIVE EFFECTS OF PLANT SPECIES DIVERSITY AND ELEVATED CO2 ON SOIL BIOTA AND NUTRIENT CYCLING

Terrestrial ecosystems consist of mutually dependent producer and decomposer subsystems, but not much is known on how their interactions are modified by plant diversity and elevated atmospheric CO2 concentrations. Factorially manipulating grassland plant species diversity and atmospheric CO2 concentrations for five years, we tested whether high diversity or elevated CO2 sustain larger or more active soil communities, affect soil aggregation, water dynamics, or nutrient cycling, and whether plant diversity and elevated CO2 interact. Nitrogen (N) and phosphorus (P) pools, symbiotic N2 fixation, plant litter quality, soil moisture, soil physical structure, soil nematode, collembola and acari communities, soil microbial biomass and microflora community structure (phospholipid fatty acid [PLFA] profiles), soil enzyme activities, and rates of C fluxes to soils were measured. No increases in soil C fluxes or the biomass, number, or activity of soil organisms were detected at high plant diversity; soil H2O and aggregation remained unaltered. Elevated CO2 affected the ecosystem primarily by improving plant and soil water status by reducing leaf conductance, whereas changes in C cycling appeared to be of subordinate importance. Slowed-down soil drying cycles resulted in lower soil aggregation under elevated CO2. Collembola benefited from extra soil moisture under elevated CO2, whereas other faunal groups did not respond. Diversity effects and interactions with elevated CO2 may have been absent because soil responses were mainly driven by community-level processes such as rates of organic C input and water use; these drivers were not changed by plant diversity manipulations, possibly because our species diversity gradient did not extend below five species and because functional type composition remained unaltered. Our findings demonstrate that global change can affect soil aggregation, and we advocate that soil aggregation should be considered as a dynamic property that may respond to environmental changes and feed back on other ecosystem functions.

Limits to the bioindication potential of Collembola in environmental impact analysis: a case study of forest soil-liming and fertilization

Abstract We tested the suitability of the collembolan community as a bioindicator for assessing the effects of forest soil-liming and fertilization on the belowground decomposer community. Our investigation was based on a 5-year survey that took place in a German oak-hornbeam and spruce forest in which amelioration measures took place in 1988, 1994 and 1995, with chemical parameters and Collembola being sampled between 1993 and 1997. To address these questions, we applied new methods which have not yet, to our knowledge, been used in biomonitoring studies on forest soils. We used a time-lag analysis for the detection of directional change and a regression-tree induction to show the relationship between Collembola and soil factors. Soil parameters changed considerably after the onset of liming and fertilization. However, no change was detected in community composition over time, nor was there a relationship between Collembola and soil parameters that would make possible the development of a model with at least a moderate predictive success. Taking into account the effort invested in this study (5-year sampling period, identification of 35,000xa0Collembola, 99xa0species, 1,170xa0chemical analyses), we question the suitability of collembolan communities as a bioindicator for forest disturbance.

Improved quantification of active soil microfauna by a "counting crew"

Abstractu2002Recently, a comparative study revealed that the predominately used most probable number (MPN) method yields seriously biased estimates for active soil ciliates (Protozoa). The direct counting method, in contrast, gave reliable and reproducible data with a high level of discrimination between the invstigated sites between the investigated sites. However, this method requires that fresh soil samples are used, limiting its versatility. In order to overcome this problem a team (counting crew) of 13 people was trained to carry out direct counts of soil microfauna simultaneously. The densities of active ciliates, rotifers, nematodes and tardigrades in the litter layer of a spruce stand were assessed by the direct counting technique. It could be shown that there was no significant influence of individual crew members on ciliate, rotifer or nematode numbers. The ciliate abundance did not vary significantly in the bulk sample with time of day. A significant increase in active ciliates was observed when counts took longer than 90u2009min. Comparing our results to literature data obtained by diverse extraction methods revealed that the direct counting method is very efficient for microscopic soil metazoa as well. If a counting crew is available, more precise and realistic data on active soil microfauna can be obtained.