Detecting One-Hundred-Year Environmental Changes in Western China Using Seven-Year Repeat Photography

Due to its diverse, wondrous plants and unique topography, Western China has drawn great attention from explorers and naturalists from the Western World. Among them, Ernest Henry Wilson (1876 –1930), known as ‘Chinese’ Wilson, travelled to Western China five times from 1899 to 1918. He took more than 1,000 photos during his travels. These valuable photos illustrated the natural and social environment of Western China a century ago. Since 1997, we had collected E.H. Wilson's old pictures, and then since 2004, along the expedition route of E.H. Wilson, we took 7 years to repeat photographing 250 of these old pictures. Comparing Wilson's photos with ours, we found an obvious warming trend over the 100 years, not only in specific areas but throughout the entire Western China. Such warming trend manifested in phenology changes, community shifts and melting snow in alpine mountains. In this study, we also noted remarkable vegetation changes. Out of 62 picture pairs were related to vegetation change, 39 indicated vegetation has changed to the better condition, 17 for degraded vegetation and six for no obvious change. Also in these photos at a century interval, we found not only rapid urbanization in Western China, but also the disappearance of traditional cultures. Through such comparisons, we should not only be amazed about the significant environmental changes through time in Western China, but also consider its implications for protecting environment while meeting the economic development beyond such changes

EFFECTS OF LIVESTOCK EXCLUSION ON VEGETATION AND SOIL PROPERTIES UNDER TWO TOPOGRAPHIC HABITATS IN AN ALPINE MEADOW ON THE EASTERN QINGHAI-TIBETAN PLATEAU

Long-term overgrazing has resulted in grassland deterioration and even desertification on the eastern Qinghai-Tibetan Plateau. In this paper, we examined the characteristics of vegetation and soil properties in the fivestock-excluded pastures and the adjacent grazed pastures under two topographic habitats (the flat valley and the south-facing slope). Seven-year exclusion of livestock has enhanced aboveground live biomass, root biomass and litter accumulation. Livestock exclusion has also increased soil bulk density and soil water content, soil organic C concentration, total N concentration and its transformation rate, and soil microbial activity. The results showed that livestock exclusion has facilitated vegetation recovery and improved physical, chemical and biological properties of soil. However, livestock exclusion has significantly decreased graminoid biomass accumulation, especially on the flat valley, the biodiversity also significantly decreased there. The results suggested that long-term livestock exclusion was disadvantageous for palatable forage production and biodiversity protection on the flat valley. Compared to the flat valley, the grassland on the south-facing slope was under more severe degradation, and the reversion was in a slower process. Thus, the optimal grassland management in the livestock-excluded pasture on the flat valley should include a low or moderate grazing intensity or adopt an alternate grazing system, but more effective and even longer livestock exclusion practice should be taken on the south-facing slope

Seasonal and interannual dynamics of soil microbial biomass and available nitrogen in an alpine meadow in the eastern part of Qinghai-Tibet Plateau, China

Soil microbial activity varies seasonally in frozen alpine soils during cold seasons and plays a crucial role in available N pool accumulation in soil. The intra- and interannual patterns of microbial and nutrient dynamics reflect the influences of changing weather factors, and thus provide important insights into the biogeochemical cycles and ecological functions of ecosystems. We documented the seasonal and interannual dynamics of soil microbial and available N in an alpine meadow in the eastern part of Qinghai-Tibet Plateau, China, between April 2011 and October 2013. Soil was collected in the middle of each month and analyzed for water content, microbial biomass C (MBC) and N (MBN), dissolved organic C and N, and inorganic N. Soil microbial community composition was measured by the dilutionplate method. Fungi and actinomycetes dominated the microbial community during the nongrowing seasons, and the proportion of bacteria increased considerably during the early growing seasons. Trends of consistently increasing MBC and available N pools were observed during the nongrowing seasons. MBC sharply declined during soil thaw and was accompanied by a peak in available N pool. Induced by changes in soil temperatures, significant shifts in the structures and functions of microbial communities were observed during the winter-spring transition and largely contributed to microbial reduction. The divergent seasonal dynamics of different N forms showed a complementary nutrient supply pattern during the growing season. Similarities between the interannual dynamics of microbial biomass and available N pools were observed, and soil temperature and water conditions were the primary environmental factors driving interannual fluctuations. Owing to the changes in climate, seasonal soil microbial activities and nutrient supply patterns are expected to change further, and these changes may have crucial implications for the productivity and biodiversity of alpine ecosystems

The combined effects of warming and drying suppress CO2 and N2O emission rates in an alpine meadow of the eastern Tibetan Plateau

The eastern Tibetan Plateau has become increasingly warmer and drier since the 1990s. Such warming and drying has a great impact on ecosystem processes on the eastern Tibetan Plateau. To determine their combined effects on CO2 and N2O emission rates, we conducted a field manipulative experiment in an alpine meadow of the eastern Tibetan Plateau during the growing season of 2009. The experiment showed that warming manipulation increased soil temperature by 1 A degrees C, and drying manipulation decreased soil water content by 6.8 %. We found that by counteracting the effect of low temperature in the area, experimental warming significantly increased soil microbial biomass, the number of bacteria, fungi, actinomycetes, ammonifying bacteria, nitrobacteria and denitrifying bacteria, and facilitated the emission rates of CO2 and N2O by 33.4 and 31.5 %, respectively. However, decreased precipitation further aggravated soil water stress and inhibited the numbers of these organisms, and reduced the emission rates of CO2 and N2O by 47.4 and 37.9 %, respectively. So decreased soil water content tended to offset the positive effect of warming. Compared to the positive effects of warming, decreased soil water content was shown in our study to have even greater impact on the eastern Tibetan Plateau during the growing season. Therefore, inhibition of CO2 and N2O emission rates (32.3 and 29.3 %, respectively) by warming and drying will intensify if the combined effects of these climatic trends persist in the region

EFFECTS OF LIVESTOCK EXCLUSION ON VEGETATION AND SOIL PROPERTIES UNDER TWO TOPOGRAPHIC HABITATS IN AN ALPINE MEADOW ON THE EASTERN QINGHAI-TIBETAN PLATEAU

Long-term overgrazing has resulted in grassland deterioration and even desertification on the eastern Qinghai-Tibetan Plateau. In this paper, we examined the characteristics of vegetation and soil properties in the fivestock-excluded pastures and the adjacent grazed pastures under two topographic habitats (the flat valley and the south-facing slope). Seven-year exclusion of livestock has enhanced aboveground live biomass, root biomass and litter accumulation. Livestock exclusion has also increased soil bulk density and soil water content, soil organic C concentration, total N concentration and its transformation rate, and soil microbial activity. The results showed that livestock exclusion has facilitated vegetation recovery and improved physical, chemical and biological properties of soil. However, livestock exclusion has significantly decreased graminoid biomass accumulation, especially on the flat valley, the biodiversity also significantly decreased there. The results suggested that long-term livestock exclusion was disadvantageous for palatable forage production and biodiversity protection on the flat valley. Compared to the flat valley, the grassland on the south-facing slope was under more severe degradation, and the reversion was in a slower process. Thus, the optimal grassland management in the livestock-excluded pasture on the flat valley should include a low or moderate grazing intensity or adopt an alternate grazing system, but more effective and even longer livestock exclusion practice should be taken on the south-facing slope

Improving Phenology Representation of Deciduous Forests in the Community Land Model: Evaluation and Modification Using Long‐Term Observations in China

Abstract Phenology is an important factor indicating environmental changes and regulates the variations of carbon, water, and energy exchange. However, phenology models exhibit large uncertainties due to limited understanding of its mechanisms. In this study, we modified deciduous phenology scheme based on the evaluation of different phenological models using long‐term observations at Chinese Ecosystem Research Network with CLM4.5. The alternating leaf unfolding model and summer‐influenced autumn leaf falling model that we proposed, performed best in simulating leaf‐unfolding and leaf‐falling. Compared with the observed and remote‐sensed phenology, the modified model could better simulate the phenological dates at the site and regional scale. Moreover, the modified model improved the simulation of gross primary productivity (GPP) by decreasing the errors of modeled carbon uptake duration and amplitude. Furthermore, the advance in leaf‐unfolding slowed down from 0.20 days/year during 1981–2015 to 0.11 days/year during 2016–2100 under RCP4.5 because of the slowdown of climate warming, but the delay in leaf‐falling changed little. By the last decade of the twenty‐first century, the leaf‐unfolding would advance (8 days) and leaf‐falling would delay (16 days). The subtropical region had large interannual variation (IAV) in leaf‐unfolding because of the high sensitivity to temperature. The phenological dates IAV in the cold temperate region increased due to enhanced temperature IAV. We suggest that the deciduous phenology models, especially the leaf‐falling process, used in Community Land Model need to be improved to reduce the errors in predicting phenology and carbon flux in the future

Unchanged and recovered forests, degraded grasslands in Western China.

<p><b>A:</b> In Huanglong. Latitude and longitude: 32°44.742′N, 103°49.803′E. Elevation: 3197 m. Note that a calcified landscape with a dense coniferous forest in the historical photo. After one hundred years, the landscape has almost remained the same. <b>B:</b> By the Jinhua Bridge. Latitude and longitude: 29°40.766′N, 102°59.279′E. Elevation: 1148 m. Note that the almost flat top of Mt.Wawu with a piece of farmland on the right side in the historical photo. After one hundred years, the farmlands and the mountain slopes have been fully covered by tall forests of <i>Cryptomeria fortunei</i>. <b>C:</b> Daping Village of Xinxing Township. Latitude and longitude: 29°53.221′N, 102°00.967′E. Elevation: 3724 m. Note that an alpine grassland in south slope of Mt.Yajiageng in the historical photo. The grassland has degraded greatly and many places on the slope have become naked without vegetation due to overgrazing.</p