| 1. |
- Ehlers, Todd A., et al.
(författare)
-
Past, present, and future geo-biosphere interactions on the Tibetan Plateau and implications for permafrost
- 2022
-
Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252. ; 234
-
Tidskriftsartikel (refereegranskat)abstract
- Interactions between the atmosphere, biosphere, cryosphere, hydrosphere, and geosphere are most active in the critical zone, a region extending from the tops of trees to the top of unweathered bedrock. Changes in one or more of these spheres can result in a cascade of changes throughout the system in ways that are often poorly understood. Here we investigate how past and present climate change have impacted permafrost, hydrology, and ecosystems on the Tibetan Plateau. We do this by compiling existing climate, hydrologic, cryosphere, biosphere, and geologic studies documenting change over decadal to glacial-interglacial timescales and longer. Our emphasis is on showing present-day trends in environmental change and how plateau ecosystems have largely flourished under warmer and wetter periods in the geologic past. We identify two future pathways that could lead to either a favorable greening or unfavorable degradation and desiccation of plateau ecosystems. Both paths are plausible given the available evidence. We contend that the key to which pathway future generations experience lies in what, if any, human intervention measures are implemented. We conclude with suggested management strategies that can be implemented to facilitate a future greening of the Tibetan Plateau.
|
|
| 2. |
- Li, Xiaojuan, et al.
(författare)
-
Climate and soil properties drive soil organic and inorganic carbon patterns across a latitudinal gradient in southwestern China
- 2023
-
Ingår i: Journal of Soils and Sediments. - : Springer Science and Business Media LLC. - 1614-7480 .- 1439-0108. ; 23:1, s. 91-102
-
Tidskriftsartikel (refereegranskat)abstract
- PurposeDrylands account for 47.2% of land area and contain 15.5% of global carbon (C). However, the variation in organic and inorganic C stocks across latitudinal gradients in arid and semiarid shrubland ecosystems remains understudied, and we lack in-depth understanding of the main drivers of C variation at this spatial scale.MethodsHere, we sampled soils from 95 sites across a latitudinal gradient to explore both the latitudinal patterns and potential drivers of soil organic carbon density (SOCD) and soil inorganic carbon density (SICD). We also assessed variation in SOCD and SICD down the soil profile, by sampling soils at four depths (0 – 10 cm, 10 – 20 cm, 20 – 30 cm, and 30 – 50 cm).ResultBoth SOCD and SICD exhibited a binomial relationship with latitude (P < 0.01). Soil properties accounted for the greatest variation in SOCD, with the most important explanatory factor being exchangeable calcium, followed by mean annual temperature, pH, plant diversity, and silt content. Soil pH and plant diversity were more important in explaining variation in SOCD in the subsoil (> 20 cm depth) than the topsoil. For SICD, soil properties explained the greatest variation at all depths. Soil pH explained the most variance in SICD, followed by exchangeable calcium and mean annual temperature in the topsoil (i.e., 0 – 10 cm and 10 – 20 cm). In the subsoil (i.e., 20 – 30 cm and 30 – 50 cm), exchangeable calcium was the most important predictor, followed by soil organic carbon, mean annual temperature, and pH.ConclusionOur study shows that soil properties are a strong predictor of latitudinal patterns of soil organic and inorganic C in arid and semiarid shrubland ecosystems. We also identified differences in potential drivers of SOCD and SICD with depth, advancing our understanding of large-scale patterns of C storage in arid and semiarid soils.
|
|
| 3. |
- Li, Xiaona, et al.
(författare)
-
Biochar increases soil microbial biomass but has variable effects on microbial diversity : A meta-analysis
- 2020
-
Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697. ; 749
-
Tidskriftsartikel (refereegranskat)abstract
- Biochar has been extensively studied as a soil amendment for carbon sequestration and for improving soil quality; however, a systematic understanding of the responses of soil microbial biomass and diversity to biochar addition is lacking. Here, a meta-analysis of 999 paired data points from 194 studies shows that biochar increases microbial biomass but has variable effects on microbial diversity. Generally, the effects of biochar on microbial biomass are dependent on biochar properties, while that on microbial diversity is dependent on soil properties. The application of biochar, particularly that produced under low temperature and from nutrient-rich feedstocks, could better increase soil microbial biomass (based on phospholipid fatty acid analysis (MBCPLFA)) and diversity. The increases of total microbial biomass with biochar addition are greater in the field than in laboratory studies, in sandy than in clay soils, and when measured by fumigation-extraction (MBCFE) than by MBCPLFA. The bacterial biomass only significantly increases in laboratory studies and fungal biomass only in soils with pH ≤ 7.5 and soil organic carbon ≤30 g kg−1. The increases in total microbial diversity with biochar addition were greater in acidic and sandy soils with low soil organic carbon content and in laboratory incubation studies. In addition, long-term and low-rate addition of biochar always increases microbial diversity. To better guide the use of biochar as a soil amendment, we suggest that establishing long-term and field studies, using a standard method for measuring microbial communities, on different soil types should be our emphasis in future research.
|
|
| 4. |
- Li, Xiaojuan, et al.
(författare)
-
Latitudinal patterns of light and heavy organic matter fractions in arid and semi-arid soils
- 2022
-
Ingår i: Catena. - : Elsevier BV. - 0341-8162. ; 215
-
Tidskriftsartikel (refereegranskat)abstract
- Semi-arid and arid ecosystems are important for the global C cycle. Despite this, it remains unclear how organic matter fractions vary across latitudinal gradients, and what drives this variation, in dry ecosystems. In this study, we sampled soils from 100 sites across a latitudinal gradient in the dry valleys of southwestern China to explore the latitudinal patterns of light fraction organic matter (LFOM) and heavy fraction organic matter (HFOM) at two soil depths (0–10 cm and 10–20 cm). Across the studied gradient, HFOM accounted for a larger fraction of soil organic matter than LFOM. LFOM increased exponentially with increasing latitude at both 0–10 cm and 10–20 cm depths. Heavy fraction organic C increased linearly with increasing latitude at both depths, while heavy fraction organic N only increased with latitude in soils from 10 to 20 cm depth. Latitudinal patterns of LFOM were mainly explained by climate, with the most important driver being mean annual temperature, followed by mean annual precipitation. Soil physicochemical factors – in particular cation exchange capacity and silt content – explained the most variation in HFOM. Total microbial biomass was also important in explaining variation in HFOM, especially in the 10–20 cm soil layer. Overall, our results shed light on the spatial distribution of organic matter fractions in arid and semi-arid regions. We also identify candidate drivers of the variation in LFOM and HFOM in arid and semi-arid regions, finding that climate primarily explains variation in LFOM while soil physiochemistry primarily explains variation in HFOM.
|
|
| 5. |
|
|
