Soil management is fundamental to all agricultural systems and fertilization practices have contributed substantially to the impressive increases in food production. Despite the pivotal role of soil microorganisms in agro-ecosystems, we still have a limited understanding of the complex response of the soil microbiota to organic and mineral fertilization in the very long-term. Here, we report the effects of different fertilization regimes (mineral, organic and combined mineral and organic fertilization), carried out for more than a century, on the structure and activity of the soil microbiome. Organic matter content, nutrient concentrations, and microbial biomass carbon were significantly increased by mineral, and even more strongly by organic fertilization. Pyrosequencing revealed significant differences between the structures of bacterial and fungal soil communities associated to each fertilization regime. Organic fertilization increased bacterial diversity, and stimulated microbial groups (Firmicutes, Proteobacteria, and Zygomycota) that are known to prefer nutrient-rich environments, and that are involved in the degradation of complex organic compounds. In contrast, soils not receiving manure harbored distinct microbial communities enriched in oligotrophic organisms adapted to nutrient-limited environments, as Acidobacteria. The fertilization regime also affected the relative abundances of plant beneficial and detrimental microbial taxa, which may influence productivity and stability of the agroecosystem. As expected, the activity of microbial exoenzymes involved in carbon, nitrogen, and phosphorous mineralization were enhanced by both types of fertilization. However, in contrast to comparable studies, the highest chitinase and phosphatase activities were observed in the solely mineral fertilized soil. Interestingly, these two enzymes showed also a particular high biomass-specific activities and a strong negative relation with soil pH. As many soil parameters are known to change slowly, the particularity of unchanged fertilization treatments since 1902 allows a profound assessment of linkages between management and abiotic as well as biotic soil parameters. Our study revealed that pH and TOC were the majors, while nitrogen and phosphorous pools were minors, drivers for structure and activity of the soil microbial community. Due to the long-term treatments studied, our findings likely represent permanent and stable, rather than transient, responses of soil microbial communities to fertilization.

Climate change and land‐use change are considered as the most important threats to ecosystems. Both factors can be expected to have interacting influences on ecosystem functions directly and indirectly via changes in biodiversity. Knowledge about these interactions is limited due to a lack of experiments which investigate climate change effects under different land‐use scenarios. Among the processes involved in ecosystem responses to global change, in particular, those occurring in soils or related to biotic interactions and microevolution were underinvestigated in previous experiments. Examinations of these relationships require spatial and temporal scales which go beyond those realized in the majority of ecological field experiments. We introduce a new research facility, the Global Change Experimental Facility (GCEF), which was designed to investigate the consequences of a future climate scenario for ecosystem functioning in different land‐use types on large field plots (400 m2). Climate manipulation is based on projections for the period of 2070–2100 with an increased temperature and a changed precipitation pattern consisting of reduced precipitation in summer and increased precipitation in spring and autumn. We subject five different land‐use types (two farming systems, three grasslands), differing in land‐use intensity, to ambient and future climatic conditions. The use of automated roofs and side panels to passively increase night temperatures results in an average increase in daily mean temperature by 0.55°C accompanied by a stronger increase in minimum temperatures (up to 1.14°C in average) with longer frost‐free periods and an increase in growing degree days by 5.2%. The combined use of mobile roofs and irrigation systems allows the reduction (in summer by ~20%) and increase in rainfall (in spring and autumn by ~10%) according to future scenarios superimposed on the ambient variation in precipitation. The large plot size and the technical configuration allow the establishment of realistic land‐use scenarios and long‐term observations of responses of ecosystem functions and community dynamics on relevant temporal and spatial scales. Thus, the GCEF provides a well‐suited platform for the interdisciplinary research on the consequences of climate change under different land‐use scenarios.

This study assessed specific peaks obtained by diffuse reflectance Fourier transform mid‐infrared spectroscopy (DRIFTS) for characterizing the soil organic matter (SOM) composition of a Haplic Chernozem. Soils were collected from the Static Fertilization Experiment, Bad Lauchstädt, Germany, during 5 years from the farmyard manure (FYM), mineral fertilizer (NPK), combination (FYM + NPK) and no fertilizer (Control) treatments. Soils were extracted with hot water (HWE), and fractionated by size and density. Bulk soil and fractions were analysed by DRIFTS. Peak areas at 2930, 1620, 1530 and 1159 cm−1 were selected as a range of organic functional groups (with limited mineral interference), integrated with a local baseline (corrected peak area) and each was divided by the summed area of the four peaks (relative peak area). Positive correlations between carbon (C) in fractions representing labile OM (<1.8 g cm−3, 1.8–2.0 g cm−3, CHWE) and the corrected peak area at 2930 cm−1 (3010–2800 cm−1) in the bulk soil indicated that this aliphatic peak corresponded to the more labile C compounds. Negative correlations between the same fractions and the corrected area of the predominantly aromatic peak at 1620 cm−1 (1660–1580 cm−1) in the bulk soil suggested a relationship with more stable SOM compounds. All relative peak areas were significantly affected by fertilizer treatment, with an increasing relative peak area at 2930 cm−1 in FYM compared with non‐FYM treatments. The ratio of the peaks at 1620 and 2930 cm−1 was positively correlated with the ratio of stable C (sum of C in >1.8 g cm−3 and clay fractions) to labile C (C content of <1.8 g cm−3 fraction) and thus taken as an indicator of SOM stability. The DRIFTS peak area method reflected changes in SOM quality and composition under long‐term management as measured by size and density fractionation, indicating heterogeneous chemical composition of the latter. Further, the DRIFTS analysis of undiluted soil samples can be used to assess SOM composition in small sample sets if specular reflection and mineral interferences are considered.

Using data from long‐term experiments at the Loess‐Chernozem site, Bad Lauchstädt und 12 other European sites, the carbon (C) and nitrogen (N) dynamics in soils, the determination of decomposable soil organic matter (SOM), the effect on yield of SOM as well as carbon and nitrogen balances are discussed. Both C and N in SOM have to be divided into an inert and a decomposable fraction. The inert C is strongly correlated with clay content, while most changes in both C and N occur in the readily decomposable fraction. In the experiments considered the latter ranges between 0.2 to 0.6% C and 0.02 to 0.06% N. The annual changes of the Corg content amount only to about 0.01% Corg corresponding to 500 kg/ha, even under extreme changes of the fertilizing system. Hot water extractable C (Chwe) has proved to be an appropriate criterion for the calculation of the decomposable C and thus for the N release from soil. Different methods to maintain a SOM balance are compared and first guideline values for an agronomically and ecologically justified SOM content of arable soils are recommended. In arable soils the exceeding of an upper Corg value influences neither crop yield nor the C and N balance in a positive way. In terms of ecology and environment, set‐aside‐programmes or fallows in a crop rotation affect the balances negatively. Atmospheric N deposition can amount to about 50 kg/ha·yr.

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Leaf litter decomposition is the key ecological process that determines the sustainability of managed forest ecosystems, however very few studies hitherto have investigated this process with respect to silvicultural management practices. The aims of the present study were to investigate the effects of forest management practices on leaf litter decomposition rates, nutrient dynamics (C, N, Mg, K, Ca, P) and the activity of ligninolytic enzymes. We approached these questions using a 473 day long litterbag experiment. We found that age-class beech and spruce forests (high forest management intensity) had significantly higher decomposition rates and nutrient release (most nutrients) than unmanaged deciduous forest reserves (P<0.05). The site with near-to-nature forest management (low forest management intensity) exhibited no significant differences in litter decomposition rate, C release, lignin decomposition, and C/N, lignin/N and ligninolytic enzyme patterns compared to the unmanaged deciduous forest reserves, but most nutrient dynamics examined in this study were significantly faster under such near-to-nature forest management practices. Analyzing the activities of ligninolytic enzymes provided evidence that different forest system management practices affect litter decomposition by changing microbial enzyme activities, at least over the investigated time frame of 473 days (laccase, P<0.0001; manganese peroxidase (MnP), P = 0.0260). Our results also indicate that lignin decomposition is the rate limiting step in leaf litter decomposition and that MnP is one of the key oxidative enzymes of litter degradation. We demonstrate here that forest system management practices can significantly affect important ecological processes and services such as decomposition and nutrient cycling.