Warming increases soil carbon input in a Sibiraea angustata-dominated alpine shrub ecosystem

Aims Plant-derived carbon (C) inputs via foliar litter, root litter and root exudates are key drivers of soil organic C stocks. However, the responses of these three input pathways to climate warming have rarely been studied in alpine shrublands. Methods By employing a three-year warming experiment (increased by1.3 ℃), we investigated the effects of warming on the relative C contributions from foliar litter, root litter and root exudates from Sibiraea angustata, a dominant shrub species in an alpine shrubland on the eastern Qinghai-Tibetan Plateau. Important Findings The soil organic C inputs from foliar litter, root litter and root exudates were 77.45, 90.58 and 26.94 g C m -2, respectively. Warming only slightly increased the soil organic C inputs from foliar litter and root litter by 8.04 and 11.13 g C m -2, but significantly increased the root exudate C input by 15.40 g C m -2. Warming significantly increased the relative C contributions of root exudates to total C inputs by 4.6% but slightly decreased those of foliar litter and root litter by 2.5% and 2.1%, respectively. Our results highlight that climate warming may stimulate plant-derived C inputs into soils mainly through root exudates rather than litter in alpine shrublands on the Qinghai-Tibetan Plateau.

Relative use of xeric boreal habitats by shrews (Sorex spp.)

Few studies have explicitly examined habitat use by shrews (Sorex spp.) in the boreal forest of western North America. We conducted pitfall trapping in six common xeric habitat types in Yukon, Canada, to determine their relative use by shrews. The overall capture rate was 0.47 shrews per 100 trap nights (TN), with a total sampling effort of 3652 TN. Cinereus shrews (Sorex cinereus; 0.25 per 100 TN) were the most common species, followed by dusky shrews (Sorex monticolus; 0.14 per 100 TN) and American pygmy shrews (Sorex hoyi; 0.08 per 100 TN). Shrew capture rates and species richness was low in all habitat types sampled. Cinereus shrews were captured in similar numbers in boreal mixedwood forest and alpine shrub habitats, and rarely in other lowland forest habitat types. Dusky shrews were captured largely in alpine shrub habitats, while pygmy shrews were captured only in lowland forest habitat types. The relative use of alpine shrub habitat by cinereus shrews and dusky shrews was not expected. Our data was limited by low captures; however, we provide a first approximation of the relative use of common forest types and subalpine shrub habitat in the boreal forest of northwestern Canada.

Soil Biological Community and Chemical Characteristics of Evergreen and Deciduous Shrub Islands in an Alpine Shrub Meadow

Aim Global change is driving shrub expansion in alpine and Arctic tundra, increasing the size and number of shrub islands. This phenomenon can directly affect the vegetation microclimate and indirectly affect biogeochemical cycling. However, it is unclear how shrub island formation, with a shift in dominant vegetation from graminoids to deciduous or evergreen shrub islands, affects the alpine biochemical cycling of carbon, nitrogen, phosphorus and decomposer diversity and activity. Methods Two dominant shrub species in the alpine shrub meadow in the eastern Tibetan Plateau were selected. Rhododendron lapponicum (RL) represents evergreen shrubs, and Sorbus rufopilosa (SR) represents deciduous shrubs. Soil fauna community diversity, soil microbial biomass, extracellular enzyme activity and enzyme stoichiometry of the organic soil layer (OL) and mineral soil layer (ML) were determined. Results Presence of shrub islands significantly affected nutrient cycling and microbial processes. Compared with the SR shrub island, the RL shrub island featured lower soil total nitrogen and microbial biomass carbon; lower total microbial phospholipid fatty acid, Gram-negative bacteria and total bacteria contents; and higher enzyme activities of β-glucosidase, cellobiohydrolase, β-N-acetylglucosaminidase, peroxidase and polyphenol oxidase. The OL response was greater than the ML response, especially in terms of enzyme activities. Conclusion Evergreen and deciduous shrub islands in an alpine shrub meadow had differences in soil biological communities and nutrient cycling, we suspect the OL was more sensitive than the ML to the shrub expansion in the alpine tundra.

A Hierarchical Analysis On Ecosystem Classification of Land

Background: The ecosystem classification of land (ECL) has been studied for a couple of decades, from the beginning of the perfect organism system “top-down” approach to a reversed “bottom-up” approach, defining micro-ecological unit. After reviewing two study cases of the ecosystem classification of land, the ecosystem classification framework implements in different ecoregions were examined and analyzed. Results: Theoretically, Bailey’s upper levels ECL (1995) was applied to the United States, and world continents. China's Eco-geographic classification was most likely fitted into Bailey’s Ecosystem Classification regime. With a binary decision tree analysis, it demonstrated that the top-level, Domain has an empty entity between the US and China ecoregion framework. Based on the biogeoclimate condition, vegetation distribution, landform, and plant species feature, classified HIIC1 into two subsections ( labeled as i, ii ), and delineated iia of QiLian Mountain East Alpine Shrub and Alpine Tundra ecozone into iia-1 and iia-2 zone.Conclusions: 1) The Plateau Domain 500 should be added into the top-level Bailey’s ecoregion framework, coordinately it includes HI and HII Divisions, and humid, dub-humid, semiarid, and arid provinces. 2) Two case comparisons recommend using a practical approach, objectively defined ecosystem classification for the lower-level ECLs in matter of time and project cost.