Global terrestrial ecosystems absorbed carbon at a rate of 1-4 Pgyr-1 during the 1980s and 1990s, offsetting 10-60 per cent of the fossil-fuel emissions1,2. The regional patterns and causes of terrestrial carbon sources and sinks, however, remain uncertain. With increasing scientific and political interest in regional aspects of the global carbon cycle, there is a strong impetus to better understand the carbon balance of China. This is not only because China is the world's most populous country and the largest emitter of fossil-fuel CO2 into the atmosphere', but also because it has experienced regionally distinct land-use histories and climate trends, which together control the carbon budget of its ecosystems. Here we analyse the current terrestrial carbon balance of China and its driving mechanisms during the 1980s and 1990s using three different methods: biomass and soil carbon inventories extrapolated by satellite greenness measurements, ecosystem models and atmospheric inversions. The three methods produce similar estimates of a net carbon sink in the range of 0.19-0.26 Pg carbon (PgC) per year, which is smaller than that in the conterminous United States but comparable to that in geographic Europe. We find that northeast China is a net source of CO2 to the atmosphere owing to overharvesting and degradation of forests. By contrast, southern China accounts for more than 65 per cent of the carbon sink, which can be attributed to regional climate change, large-scale plantation programmes active since the 1980s and shrub recovery. Shrub recovery is identified as the most uncertain factor contributing to the carbon sink. Our data and model results together indicate that China's terrestrial ecosystems absorbed 28-37 per cent of its cumulated fossil carbon emissions during the 1980s and 1990s.

http://image.sciencenet.cn/olddata/kexue.com.cn/upload/blog/file/2009/12/20091221221338237882.pdf

The carbon balance of terrestrial ecosystems in China

https://faculty.washington.edu/stevehar/rangeland%20degradation.pdf

Rangeland degradation on the Qinghai-Tibetan plateau: A review of the evidence of its magnitude and causes

Changes to forest production drivers (light, water, temperature, and site nutrient) over the last 55 years have been documented in peer-reviewed literature. The main objective of this paper is to review documented evidence of the impacts of climate change trends on forest productivity since the middle of the 20th century. We first present a concise overview of the climate controls of forest production, provide evidence of how the main controls have changed in the last 55 years, followed by a core section outlining our findings of observed and documented impacts on forest productivity and a brief discussion of the complications of interpreting trends in net primary production (NPP). At finer spatial scales, a trend is difficult to decipher, but globally, based on both satellite and ground-based data, climatic changes seemed to have a generally positive impact on forest productivity when water was not limiting. Of the 49 papers reporting forest production levels we reviewed, 37 showed a positive growth trend, five a negative trend, three reported both a positive and a negative trend for different time periods, one reported a positive and no trend for different geographic areas, and two reported no trend. Forests occupy 52% of the Earth’s land surface and tend to occupy more temperature and radiation-limited environments. Less than 7% of forests are in strongly water-limited systems. The combined and interacting effects of temperature, radiation, and precipitation changes with the positive effect of CO2, the negative effects of O3 and other pollutants, and the presently positive effects of N will not be elucidated with experimental manipulation of one or a few factors at a time. Assessments of the greening of the biosphere depend on both accurate measurements of rates (net ecosystem exchange, NPP), how much is stored at the ecosystem level (net ecosystem production) and quantification of disturbances rates on final net biome production.

/pdf/impacts-of-climate-change-on-natural-forest-productivity-49rtnvdj6k.pdf

Impacts of climate change on natural forest productivity – evidence since the middle of the 20th century

China has experienced rapid urbanization and dramatic economic growth since its reform process started in late 1978. In this article, we present evidence for a significant urbanization effect on climate based on analysis of impacts of land-use changes on surface temperature in southeast China, where rapid urbanization has occurred. Our estimated warming of mean surface temperature of 0.05°C per decade attributable to urbanization is much larger than previous estimates for other periods and locations. The spatial pattern and magnitude of our estimate are consistent with those of urbanization characterized by changes in the percentage of urban population and in satellite-measured greenness.

/pdf/evidence-for-a-significant-urbanization-effect-on-climate-in-mz9tftrs54.pdf

Evidence for a significant urbanization effect on climate in China

Leaf nitrogen and phosphorus stoichiometry of Chinese terrestrial plants was studied based on a national data set including 753 species across the country. Geometric means were calculated for functional groups based on life form, phylogeny and photosynthetic pathway, as well as for all 753 species. The relationships between leaf N and P stoichiometric traits and latitude (and temperature) were analysed. The geometric means of leaf N, P, and N : P ratio for the 753 species were 18.6 and 1.21 mg g(-1) and 14.4, respectively. With increasing latitude (decreasing mean annual temperature, MAT), leaf N and P increased, but the N : P ratio did not show significant changes. Although patterns of leaf N, P and N : P ratios across the functional groups were generally consistent with those reported previously, the overall N : P ratio of China's flora was considerably higher than the global averages, probably caused by a greater shortage of soil P in China than elsewhere. The relationships between leaf N, P and N : P ratio and latitude (and MAT) also suggested the existence of broad biogeographical patterns of these leaf traits in Chinese flora.

https://nph.onlinelibrary.wiley.com/doi/epdf/10.1111/j.1469-8137.2005.01530.x

Leaf nitrogen and phosphorus stoichiometry across 753 terrestrial plant species in China

[1] In this paper, we analyzed interannual variations of normalized difference vegetation index (NDVI) and their relationships with climatic variables (temperature and precipitation) and human activity in China between 1982 and 1999. Monthly and seasonal NDVI increased significantly at both the country and biome scales over the study period. NDVI shows the largest increase (14.4% during the 18 years and a trend of 0.0018 yr−1) over 85.9% of the total study area in spring and the smallest increase (5.2% with a trend of 0.0012 yr−1) over 72.2% of the area in summer. The NDVI trends show a marked heterogeneity corresponding to regional and seasonal variations in climates. There is about a 3-month lag for the period between the maximum trend in temperature (February) and that in NDVI (April or May) at the country and biome scales. Human activity (urbanization and agricultural practices) also played an important role in influencing the NDVI trends over some regions. Rapid urbanization resulted in a sharp decrease in NDVI in the Yangtze River and Pearl River deltas, while irrigation and fertilization may have contributed to the increased NDVI in the North China plain.

/pdf/interannual-variations-of-monthly-and-seasonal-normalized-4ad2v7sm9x.pdf

Interannual variations of monthly and seasonal normalized difference vegetation index (NDVI) in China from 1982 to 1999

Knapp and Smith (1) suggested that interannual variability in aboveground net primary production (ANPP) is not related to fluctuations in precipitation, based on analysis of data from 11 Long-Term Ecological Research sites across North America. This finding, if applicable to other regions, is crucial to climate change research, because it may necessitate revisions of projections of ecosystem responses to climate change (2, 3). To examine the relationship between variability in net primary production (NPP) and precipitation at a broad scale, a longterm normalized difference vegetation index (NDVI) data set derived from the Advanced Very High Resolution Radiometer (AVHRR) of the National Oceanic and Atmospheric Administration (NOAA), coupled with a historical climate data set, should constitute a useful and powerful data source, because NDVI data are strongly correlated with terrestrial NPP and are frequently used as NPP predictors (4, 5). We used an annual mean NDVI data set over China to quantify temporal NPP variability relative to precipitation variation, and used coefficient of variation (CV) to express the magnitude of interannual variability in NDVI and precipitation. We then calculated CVs of these two variables for each pixel, with a resolution of 0.1° latitude by 0.1° longitude, for five biome groups across China—forest, grassland, desert, alpine vegetation, and cropland (6 )—using 1982 to 1999 NDVI and precipitation data compiled in China (7 ). We assumed that interannual variability in NDVI or NPP was related to temporal variability in precipitation if the correlation between CVs for NDVI or NPP and precipitation were identified as statistically significant. The CV value of NDVI for these five biome groups showed a large spatial variation, with a mean CV of 8.3% for the forest biome group, 10.4% for grasslands, 24.6% for desert areas, 12.7% for alpine vegetation, and 9.3 % for cropland. The largest variation occurred in the desert bi

/pdf/interannual-variability-in-net-primary-production-and-1co9wqyj0t.pdf

Interannual Variability in Net Primary Production and Precipitation

Climate-related increases in terrestrial vegetation activity in the northern regions of the Northern Hemisphere have been identified by recent satellite based studies How- ever, evidence for this increase from ground observations is very limited In the current study, we used a time series data set for the Normalized Difference Vegetation Index (NDVI) for the growing season (April to October) from 1982 to 1999, along with historical climate data, to analyse year to year variations in vegetation activity and to explore the relationship between the growing season NDVI and climatic variables in China Vegetation activity, as measured by NDVI, increased in 81% of the study area, with significant gains in 27% of the region The magnitude of the mean growing season NDVI for the 1980s and the 1990s was not significantly different The increase in NDVI corresponded to an increase in temperature on the national scale, while regional variations in NDVI appeared to be related to precipitation The NDVI trend showed a large spatial heterogeneity, possibly associated with changes in regional climate, land use and vegetation type Our study suggests that agricultural practices caused an increase in NDVI in some regions, and rapid urbanization on the east coast resulted in a sharp decrease in NDVI since the 1980s

/pdf/variation-in-a-satellite-based-vegetation-index-in-relation-1as7qaiuim.pdf

Wei Ji

Papers

Interannual variations of monthly and seasonal normalized difference vegetation index (NDVI) in China from 1982 to 1999

Interannual Variability in Net Primary Production and Precipitation

Variation in a satellite-based vegetation index in relation to climate in China

Lake restoration from impoldering: impact of land conversion on riparian landscape in Honghu Lake area, Central Yangtze