A Multi-Perspective Assessment Method with a Dynamic Benchmark for Human Activity Impacts on Alpine Ecosystem under Climate Change

Intense human activities and rapid climate changes both have obvious impacts on alpine ecosystems. However, the magnitudes and directions of the impacts by these two drivers remain uncertain due to a lack of a reasonable assessment method to distinguish between them. The impact of natural resilience is also generally included in the dynamics of a disturbed ecosystem and is liable to be mixed into the impact of human activity. It is urgent that we quantitatively discriminate human activity impacts on the ecosystem under climate change, especially for fast-developing alpine regions. Here, we propose an assessment method to determine human activity impacts under a dynamic climate, taking the potential net primary production (NPP) of an ecosystem as a benchmark. The potential NPP (NPPP) series under the changing climate was retrieved by an improved integrated biosphere simulator based on the initial disturbed ecosystem status of the assessment period. The actual NPP (NPPA) series monitored by remote sensing was considered as the results derived from the joint impacts of climate change, natural resilience and human activity. Then, the impact of human activity was quantified as the difference between the NPPP and NPPA. The contributions of human activity and natural forces to ecosystem NPP dynamics were then calculated separately and employed to explore the dominant driver(s). This assessment method was demonstrated in a typical alpine ecosystem in Northwest China. The results indicate that this method capably revealed the positive impacts of local afforestation and land-use optimization and the negative impacts caused by grazing during the assessment period of 2001–2017. This assessment method provides a quantitative reference for assessing the performances of ecological protections or human damage to alpine ecosystems at the regional scale.

High Mountains Becoming Wetter While Deserts Getting Drier in Xinjiang, China since the 1980s

Climate change has been thought to drive the accelerated expansion of global drylands. However, many studies reveal that Arid Central Asia (ACA) has been warming and wetting in recent decades, representing an anomalous response to global climate change. Given that ACA is composed of complex ecosystems and landforms, it is not clear whether or not this trend is uniform in this topographically heterogenous region. Here, we integrate the Google Earth Engine and ERA5-Land reanalysis data to study the trend of changes, since the 1980s, in temperature and precipitation in the Tianshan Mountains and the surrounding deserts, collectively referred to as the Tianshan and Desert Ecozone, which is in Northwest China. Our results show that only 20.4% of this area is becoming both warmer and wetter, which occurs mainly in the altitudes above 2800 m (Tianshan Ecozone). All three alpine ecosystems (coniferous forests, alpine meadow, and nival zone) in the Tianshan Ecozone exhibit similar warming and wetting trends, including of elevation-dependent wetting on the specific altitude range. In contrast, the low-lying oasis where human activities are mostly concentrated is undergoing warming and drying, which will face a greater threat of drought projected under three emissions scenarios (SSP1-2.6, SSP2-4.5, and SSP5-8.5). These results highlight the importance of considering the differences of climate change in different altitude gradients and different ecosystems when studying climate change in drylands.

Decoupling of Carbon and Nitrogen Under Elevated CO2 in a Typical Alpine Ecosystem

Aims: Vegetation in high-altitude regions is hypothesized to be more responsive to increasing atmospheric CO2 concentrations due to low CO2 partial pressure. However, this hypothesis and the underlying mechanisms driving this response at an ecosystem scale are poorly understood. We aimed to exploring the biomass allocation and plant carbon-nitrogen relationships in response to elevated CO2 in a Tibet meadow.Methods: Here, a 5-year manipulation experiment was conducted in an alpine meadow (4585 m above sea level) to explore the responses of plant carbon (C), nitrogen (N) and biomass dynamics, as well as their allocation schemes, to elevated CO2 and N fertilization.Results: Elevated CO2 alone significantly enhanced aboveground plant biomass by 98.03 %, exhibiting a stronger CO2 fertilization effect than the global average level (20 %) for grasslands. In contrast to the belowground parts, elevated CO2 caused disproportionally aboveground tissues increment in association with C and N accumulation. These results suggest a potential C limitation for plant growth in alpine ecosystems. N fertilization alleviates the N constraints on CO2 fertilization effects, which strengthened C sequestration capacity for the aboveground plant tissues. Moreover, our results indicate a decoupling between C and N cycles in alpine ecosystems in the face of elevated CO2, especially in the N-enrichment environments.Conclusions: Overall, this study shows a high sensitivity of aboveground plant biomass and decoupled C-N relationships under elevated CO2 for high-elevation alpine ecosystems, highlighting the need to incorporate altitude effects into Earth System Models in predicting C cycle feedback to climate changes.

Assessing and Projecting Surface Air Temperature Conditions Required To Sustain Permafrost in Japan

Permafrost covers a wide area of the Northern Hemisphere, including high-altitude mountainous areas even at mid-low latitudes. There is concern that the thawing of mountain permafrost can cause slope instability and substantially impact alpine ecosystems. However, permafrost in mountainous areas is difficult to observe, and detailed analyses have not been performed on its current distribution and future changes. Here, we show that the surface air temperature required to sustain Japan's mountain permafrost is estimated to decrease rapidly at present; most mountain permafrost in Japan is projected to disappear by the second half of the 21st century, and disappear very quickly in some places from approximately 2020–2030, regardless of climate scenarios. Our projections indicate that climate change has a considerable impact on mountain environments and that even if climate stabilization is achieved, Japan's mountain permafrost may almost disappear. It is important to consider measures to adapt to the changing mountain environment.

Insights on Ethiopian montane ground beetles biodiversity: Taxonomic study of afro-alpine and sub-alpine Trechini (Coleoptera: Carabidae: Trechinae)

Based on collaborative work of a French-Ethiopian team, we investigated the diversity and distribution of Ethiopian trechine beetles (Carabidae, Trechini), in the sub-alpine and afro-alpine ecosystems. Four new genera, three new subgenera and eighteen new species are described from Ethiopian Highland environments: Trechus (Abyssinotus) subgen. nov. (type species: salomon sp. nov.) and Trechus (Abyssinotus) sabae sp. nov. (Mount Choke, Amhara), Trechus (s. str.) lalibelae sp. nov. (Abuna Yusef Mountains, Amhara), T. (s. str.) habeshaicus sp. nov. (Menz-Guassa Plateau, Amhara), Trechus (s. str.) kosso sp. nov. (Bale Mountains, Oromia), Deuveopsis gen. nov. (type species: lobeliae sp. nov.) (Mount Choke, Amhara), Deuveopsis (Abayopsis) subgen. nov. (type species: basilewskianus Geginat, 2008) (Mount Choke, Amhara), Aethiopsis gen. nov. (type species: chioriae sp. nov.) (Abuna Yusef Mountains, Amhara), Aethiopsis abunaensis sp. nov. (Abuna Yusef Mountains, Amhara), Aethiopsis wolloi sp. nov. (Abuna Yusef Mountains, Amhara), Aethiopsis lastaensis sp. nov. (Abuna Yusef Mountains, Amhara), Aethiopsis meneliki sp. nov. (Delanta Mountains, Amhara), Aethiopsis delantae sp. nov. (Delanta Mountains, Amhara), Aethiopsis guassaensis sp. nov. (Menz-Guassa Plateau, Amhara), Afrotrechus gen. nov. (type species: afroalpinus sp. nov.) (Mount Choke, Amhara), Afrotrechus abyssinicus sp. nov. (Mount Choke, Amhara), Afrotrechus (Abyssiniopsis) subgen. nov. (type species: amharicus (Ortuño and Novoa, 2011) comb. nov.) (Mount Choke, Amhara), Afrotrechus (Abyssiniopsis) bunae sp. nov. (Belleta Forest, Oromia), Nilotrechus gen. nov. (type species: reebae sp. nov.) (Mount Choke, Amhara), Nilotrechus niloticus sp. nov. (Mount Choke, Amhara). New data and informations are provided for previously described species: Trechus (A.) dimorphicus Pawlowski, 2001 comb. nov., Trechus (A.) chokensis Pawlowski, 2001 comb. nov., Trechus (A.) gigas Pawlowski, 2001 comb.nov., and Trechus (s. str.) bipartitus Raffray, 1885, sublaevis Raffray, 1885 and aethiopicus Alluaud, 1918. The putative phylogenetic affinities of the different genera are discussed. Considerations about microspeciation and endemism on Mount Choke are proposed.

Projections of surface air temperature required to sustain permafrost and importance of adaptation to climate change in the Daisetsu Mountains, Japan

Permafrost is known to occur in high mountainous areas such as the Daisetsu Mountains in Japan, which are located at the southernmost limit of the permafrost distribution in the world. In this study, areas with climatic conditions suitable for sustaining permafrost in the Daisetsu Mountains are projected using bias-corrected and downscaled climate model outputs and statistical relationships between surface air temperatures and permafrost areas. Using freezing and thawing indices, the size of the area in the Daisetsu Mountains where climatic conditions were suitable for permafrost were estimated to be approximately 150 km2 in 2010. Under the RCP8.5 scenario, this area is projected to decrease to about 30 km2 by 2050 and it is projected to disappear by around 2070. Under the RCP2.6 scenario, the area is projected to decrease to approximately 20 km2 by 2100. The degradation of mountain permafrost could potentially affect the stability of trekking trails due to slope displacement, and it may also have deleterious effects on current alpine ecosystems. It is therefore important to accurately monitor changes in the mountain ecosystem environment and to implement measures to adapt to an environment that is projected to change significantly in the future.

Lowland plant migrations into alpine ecosystems amplify soil carbon loss under climate warming

Climate warming is releasing carbon from soils around the world1–3, constituting a positive climate feedback. Warming is also causing species to expand their ranges into new ecosystems4–9. Yet, in most ecosystems, whether range expanding species will amplify or buffer expected soil carbon loss is unknown10. Here we used alpine grasslands as a model system to determine whether the establishment of herbaceous lowland plants in alpine ecosystems influences short–term soil carbon storage under warming. We found that warming (< 1 year) led to negligible alpine soil carbon loss, but its effects became significant and 52% ± 31% (mean ± 95% CIs) larger after lowland plants were introduced at low density into the ecosystem. We present evidence that soil carbon loss likely occurred via lowland plants increasing rates of root exudation, soil microbial respiration and CO2 release. Our findings suggest that warming–induced range expansions of herbaceous plants may yield a rapid positive climate feedback in this system, and that plant range expansions among herbaceous communities may be an overlooked mediator of warming effects on carbon dynamics.