Carbon use efficiency of terrestrial ecosystems in desert/grassland biome transition zone: A case in Ningxia province, northwest China

AbstractCarbon use efficiency (CUE), one of the most important eco-physiological parameters, represents the capacity of plants to transform carbon into new biomass. Understanding the variations and controls of CUE is crucial for regional carbon assessment. Here, we used 15-years of continuous remote sensing data to examine the variations of CUE across broad geographic and climatic gradients in China. The results showed that the vegetation CUE was averaged to 0.54 ± 0.11 with minor interannual variation. However, the CUE greatly varied with geographic gradients and ecosystem types. Forests have a lower CUE than grasslands and croplands. Evergreen needleleaf forests have a higher CUE than other forest types. Climate factors (mean annual temperature (MAT), precipitation (MAP) and the index of water availability (IWA)) dominantly regulated the spatial variations of CUE. The CUE exhibited a linear decrease with enhanced MAT and MAP and a parabolic response to the IWA. Furthermore, the responses of CUE to environmental change varied with individual ecosystem type. In contrast, precipitation exerted strong control on CUE in grassland, while in forest and cropland, the CUE was mainly controlled by the available water. This study identifies the variations and response of CUE to environmental drivers in China, which will be valuable for the regional assessment of carbon cycling dynamics under future climate change.

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Supplementary material to "Global variability of carbon use efficiency in terrestrial ecosystems"

10.5194/bg-2019-37-supplement ◽

2019 ◽

Author(s):

Xiaolu Tang ◽

Nuno Carvalhais ◽

Catarina Moura ◽

Bernhard Ahrens ◽

Sujan Koirala ◽

...

Keyword(s):

Terrestrial Ecosystems ◽

Carbon Use Efficiency ◽

Use Efficiency ◽

Supplementary Material

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Increasing microbial carbon use efficiency with nitrogen addition resulting from plant-mineral interaction

10.5194/egusphere-egu21-845 ◽

2021 ◽

Author(s):

Xuehui Feng ◽

Jie Hu ◽

Yuanhe Yang ◽

Leiyi Chen

Keyword(s):

Microbial Growth ◽

Global Environmental Change ◽

Terrestrial Ecosystems ◽

Metabolic Parameter ◽

N Availability ◽

Microbial Physiology ◽

Soil C ◽

Carbon Use Efficiency ◽

N Input ◽

Use Efficiency

Elucidating the&#160;mechanisms underlying the changes in microbial physiology under anthropogenic nitrogen (N) input&#160;is of fundamental importance for understanding the carbon-N interaction under global environmental change. Carbon use efficiency (CUE), the ratio of microbial growth to assimilation, represents&#160;a critical&#160;microbial metabolic parameter&#160;that&#160;controls the fate of soil C.&#160;Despite the recognized importance of mineral protection&#160;as a driver of soil C cycling in terrestrial ecosystems, little is known on how mineral-organic association&#160;will modulate the response of microbial CUE to increasing N availability. Here, by combining a 6-year N&#8208;manipulation experiment and 18O isotope incubation, mineral analysis and a two-pool C decomposition model, we evaluate how N-induced modification in mineral protection affect the changes in microbial growth, respiration and CUE. Our results showed&#160;that microbial CUE increased under N enrichment due to the enhanced microbial growth and decreased respiration. Such changes&#160;in microbial physiology further led to a significant decrease in&#160;CO2-C release from the slow C pool&#160;under high N&#160;input. More importantly, the disruption in mineral-organic association induced by elevated root exudates is the foremost reason for the enhanced&#160;microbial growth and CUE&#160;under high N input. Taken together, these findings provide an empirical evidence for the linkage between soil&#160;mineral protection&#160;and&#160;microbial physiology, and highlight the need to consider the plant-mineralogy-microbial&#160;interactions&#160;in Earth system models to improve the prediction of soil C fate under global N deposition.

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Spatial and Temporal Changes in the Normalized Difference Vegetation Index and Their Driving Factors in the Desert/Grassland Biome Transition Zone of the Sahel Region of Africa

Remote Sensing ◽

10.3390/rs12244119 ◽

2020 ◽

Vol 12 (24) ◽

pp. 4119

Author(s):

Shupu Wu ◽

Xin Gao ◽

Jiaqiang Lei ◽

Na Zhou ◽

Yongdong Wang

Keyword(s):

Climate Change ◽

Transition Zone ◽

Human Activities ◽

Vegetation Index ◽

Normalized Difference Vegetation Index ◽

Climate Factors ◽

Desert Grassland ◽

Temperature And Precipitation ◽

Grassland Biome ◽

Sahel Region

The ecological system of the desert/grassland biome transition zone is fragile and extremely sensitive to climate change and human activities. Analyzing the relationships between vegetation, climate factors (precipitation and temperature), and human activities in this zone can inform us about vegetation succession rules and driving mechanisms. Here, we used Landsat series images to study changes in the normalized difference vegetation index (NDVI) over this zone in the Sahel region of Africa. We selected 6315 sampling points for machine-learning training, across four types: desert, desert/grassland biome transition zone, grassland, and water bodies. We then extracted the range of the desert/grassland biome transition zone using the random forest method. We used Global Inventory Monitoring and Modelling Studies (GIMMS) data and the fifth-generation atmospheric reanalysis of the European Centre for Medium-Range Weather Forecasts (ERA5) meteorological assimilation data to explore the spatiotemporal characteristics of NDVI and climatic factors (temperature and precipitation). We used the multiple regression residual method to analyze the contributions of human activities and climate change to NDVI. The cellular automation (CA)-Markov model was used to predict the spatial position of the desert/grassland biome transition zone. From 1982 to 2015, the NDVI and temperature increased; no distinct trend was found for precipitation. The climate change and NDVI change trends both showed spatial stratified heterogeneity. Temperature and precipitation had a significant impact on NDVI in the desert/grassland biome transition zone; precipitation and NDVI were positively correlated, and temperature and NDVI were negatively correlated. Both human activities and climate factors influenced vegetation changes. The contribution rates of human activities and climate factors to the increase in vegetation were 97.7% and 48.1%, respectively. Human activities and climate factors together contributed 47.5% to this increase. The CA-Markov model predicted that the area of the desert/grassland biome transition zone in the Sahel region will expand northward and southward in the next 30 years.

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