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What would current ecosystems be like without the impact of mankind? This question, which is critical for ecosystem management, has long remained unanswered due to a lack of present-day data from truly undisturbed ecosystems. Using mountaineering techniques, we accessed pristine relict ecosystems in the Peruvian Andes to provide this baseline data and compared it with the surrounding accessible and disturbed landscape. We show that natural ecosystems and human impact in the high Andes are radically different from preconceived ideas. Vegetation of these ‘lost worlds’ was dominated by plant species previously unknown to science that have become extinct in nearby human-affected ecosystems. Furthermore, natural vegetation had greater plant biomass with potentially as much as ten times more forest, but lower plant diversity. Contrary to our expectations, soils showed relatively little degradation when compared within a vegetation type, but differed mainly between forest and grassland ecosystems. At the landscape level, a presumed large-scale forest reduction resulted in a nowadays more acidic soilscape with higher carbon storage, partly ameliorating carbon loss through deforestation. Human impact in the high Andes, thus, had mixed effects on biodiversity, while soils and carbon stocks would have been mainly indirectly affected through a suggested large-scale vegetation change.

Type and rate of fertilizers influence the level of soil organic carbon (C org ) and total nitrogen (N t ) markedly, but the effect on partitioning of C and N into different pools is open to question. Objectives were to investigate the impact of fertilizer type and rate on labile, intermediate and passive C and N pools in a sandy Cambisol at Darmstadt, Germany, after 27 years of different fertilization treatments. The six treatments were: straw incorporation plus application of mineral fertilizer (MSI) and application of farmyard manure (FYM) each at high (140-150 kg N ha −1 year −1 ), medium (100 kg N ha −1 year −1 ) and low (50-60 kg N ha −1 year −1 ) rates. Soil microbial biomass C (C mic ) and N (N mic ) and C and net N mineralization (266 days incubation at 10°C and 50% waterfilled pore space) were determined. Soils (0-25 cm) of MSI treatments had significantly (p≤0.05) lower C mic stocks (308-361 kg ha −1 ) than soils of FYM treatments (404-520 kg ha −1 ). Differences in N mic stocks were less pronounced. After 266 days, mineralized C (1130-1820 kg ha −1 ) and N (90-125 kg ha −1 ) had significantly increased with fertilizer rate. The application of an exponential two-pool model showed that very labile pools (turnover times: 17 and 9 days for C and N, respectively) were small (1.3-1.8% of C org and 0.5-1.0% of N t ) and not influenced by type or rate of fertilizer. Stocks of the modeled labile C and N pools (turnover times: 462 and 153 days for C and N, respectively) were not influenced by the type of fertilizer but depended significantly on the application rate and ranged from 7 to 13% of C org and from 4 to 5% of N t . In contrast, the size of the calculated intermediate C pool was greater for the FYM treatments, and depended significantly on the interaction of fertilizer type and rate. The intermediate N pool was unaffected by fertilizer type or rate. Passive C and N pools, as experimentally revealed by oxidation with disodium peroxodisulfate (Na 2 S 2 O 8 ), were independent of the treatments. Overall, labile and intermediate pools were affected differently by the fertilizer type and the application rate.

Grasslands are very important regionally and globally because they store large amounts of carbon (C) and nitrogen (N) and provide food for grazing animals. Intensive degradation of alpine grasslands in recent decades has mainly impacted the upper root-mat/soil horizon, with severe consequences for nutrient uptake in these nutrient-limited ecosystems. We used 15 N labeling to identify the role of individual soil layers for N-uptake by Kobresia pygmaea-the dominating plant in the degraded Tibetan pasture ecosystems. We hypothesized a very efficient N-uptake corresponding mainly to the vertical distribution of living roots (topsoil > subsoil). We assume that K. pygmaea develops a very dense root-mat, which has to be maintained by small aboveground biomass, to enable this efficient N-uptake. Consequently, a higher N-investment into roots compared to shoots was hypothesized. The 15 N recovery in whole plants ($70%) indicated very efficient N-uptake from the upper injection depths (0-5 cm). The highest 15 N amounts were recovered in root biomass, whereby 15 N recovery in roots strongly decreased with depth. In contrast, 15 N recovery in shoots was generally low ($18%) and independent of the 15 N injection depth. This clearly shows that the low N demand of Kobresia shoots can be easily covered by N-uptake from any depth. Less living root biomass in lower versus upper soil was compensated by a higher specific activity of roots for N-uptake. The 15 N allocation into roots was on average 1.7 times higher than that into shoots, which agreed well with the very high R/S ratio. Increasing root biomass is an efficient strategy of K. pygmaea to compete for belowground resources at depths and periods with available resources. This implies high C-costs to maintain root biomass ($6.0 kg DM m -2 ), which must be covered by a very low amount of photosynthetically active shoots (0.3 kg DM m -2 ). It also suggests that Kobresia grasslands react extremely

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