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Abstract Soils contain significantly more carbon than the atmosphere, hence we should understand how best to stabilize it. Unfortunately, the role of human interventions on soil organic carbon (SOC) persistence in the Anthropocene remains vague, lacking adequate sites that allow unbiased direct comparisons of pristine and human influenced soils. Here we present data from a unique study system in the High Andes that guarantees pristineness of the reference sites by physical inaccessibility through vertical cliffs. By comparing the isotopic signatures of SOC, mineral related carbon stabilization, and soil nutrient status across grazed versus pristine soils, we provide counterintuitive evidence that thousands of years of pastoralism increased soil C persistence. Mineral associated organic carbon (MAOC) was significantly higher in pastures. Land use increased poorly crystalline minerals (PCM’s), of which aluminum correlated best with MAOC. On the other hand, human’s acceleration of weathering led to acidification and higher losses of cations. This highlights a dilemma of lower soil quality but higher persistence of SOC due to millennia of pastoralism. The dynamics of soil genesis in the Anthropocene needs better understanding, but if human-induced weathering proves generally to promote soil carbon persistence it will need to be included in climate—soil feedback projections.

The Tibetan Kobresia pastures store 2.5% of the world’s soil organic carbon. Here the authors show that soil degradation and microbial shifts may irreversibly diminish the carbon sink function and accelerate nutrient losses.

Abstract 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.

Antecedentes: Las hierbas terrestres son un elemento florístico importante de los bosques tropicales; sin embargo, aún es escasa la investigación centrada en este grupo de plantas. Pregunta: ¿Cuáles son los patrones de distribución de especies de angiospermas herbáceas a lo largo de gradientes de altitud y de perturbación en el Cofre de Perote, centro de Veracruz, México? Especies de estudio: Angiospermas herbáceas terrestres. Sitio de estudio y años de estudio: Vertiente este del Cofre de Perote, centro de Veracruz, México; desde 2012 hasta 2014. Métodos: Establecimos un gradiente altitudinal (40 a 3,520 m), donde realizamos un muestreo florístico en ocho sitios de estudio dentro de pisos altitudinales de aproximadamente 500 m cada uno. Registramos la presencia de angiospermas herbáceas terrestres dentro de 135 parcelas de 20 × 20 m, distribuidas en bosques maduros, degradados, secundarios, así como vegetación azonal. Se analizó la riqueza de especies, la composición florística y luego comparamos los datos resultantes entre los diferentes pisos altitudinales y los grados de perturbación del bosque. Resultados: Se registraron 264 especies de plantas, 31 endémicas de México y tres amenazadas. Esta riqueza representa 5.7 % de la flora de herbáceas angiospermas en Veracruz. Los pisos altitudinales con mayor riqueza de especies fueron 2,500 m (76) y 1,500 m (52). En la mayoría de los casos, los bosques secundarios tuvieron la mayor riqueza de especies en el gradiente altitudinal, mientras que los bosques maduros tuvieron menos especies. Conclusiones: La riqueza de especies observada, incluyendo elementos endémicos, resalta la importancia de esta zona para la conservación de plantas, que se encuentra amenazada por el cambio de uso del suelo. Además, sugerimos que la variación de la vegetación formada por bosques maduros, perturbados y secundarios es aceptable (e inevitable) y puede incluso incrementar la riqueza de especies.

Terrestrial herbs are important elements of tropical forests; however, there is a lack of research on their diversity patterns and how they respond to different intensities of forest-use. The aim of this study was to analyze the diversity of herbaceous angiosperms along gradients of elevation (50 m to 3500 m) and forest-use intensity on the eastern slopes of the Cofre de Perote, Veracruz, Mexico. We recorded the occurrence of all herbaceous angiosperm species within 120 plots of 20 m x 20 m each. The plots were located at eight study locations separated by ~500 m in elevation and within three different habitats that differ in forest-use intensity: old-growth, degraded, and secondary forest. We analyzed species richness and floristic composition of herb communities among different elevations and habitats. Of the 264 plant species recorded, 31 are endemic to Mexico. Both α- and γ-diversity display a hump-shaped relation to elevation peaking at 2500 m and 3000 m, respectively. The relative contribution of between-habitat β-diversity to γ-diversity also showed a unimodal hump whereas within-habitat β-diversity declined with elevation. Forest-use intensity did not affect α-diversity, but β-diversity was high between old-growth and secondary forests. Overall, γ-diversity peaked at 2500 m (72 species), driven mainly by high within- and among-habitat β-diversity. We infer that this belt is highly sensitive to anthropogenic disturbance and forest-use intensification. At 3100 m, high γ-diversity (50 species) was driven by high α- and within-habitat β-diversity. There, losing a specific forest area might be compensated if similar assemblages occur in nearby areas. The high β-diversity and endemism suggest that mixes of different habitats are needed to sustain high γ-richness of terrestrial herbs along this elevational gradient.

Forest soils contribute ca. 70% to the global soil organic carbon (SOC) pool and thus are an important element of the global carbon cycle. Forests also harbour a large part of the global terrestrial biodiversity. It is not clear, however, whether tree species diversity affects SOC. By measuring the carbon concentration of different soil particle size fractions separately, we were able to distinguish between effects of fine particle content and tree species composition on the SOC pool in old-growth broad-leaved forest plots along a tree diversity gradient (1-, 3- and 5-species). Variation in clay content explained part of the observed SOC increase from monospecific to mixed forests, but we show that the carbon concentration per unit clay or fine silt in the subsoil was by 30–35% higher in mixed than monospecific stands indicating a significant species identity or species diversity effect on C stabilization. Underlying causes may be differences in fine root biomass and turnover, in leaf litter decomposition rate among the tree species, and/or species-specific rhizosphere effects on soil. Our findings may have important implications for forestry offering management options through preference of mixed stands that could increase forest SOC pools and mitigate climate warming.