Dynamics of iron and aluminum storages in a subtropical forest headwater stream

The forest headwater streams are important hubs for connecting terrestrial and aquatic ecosystems,with plant litter and sediments as the major carriers for material migrations;however,until now we knew little about the dynamics of trace elements such as iron(Fe)and aluminum(Al)in forest headwater streams.Here,we quantitatively identified the spatiotemporal dynamics of Fe and Al storages in plant litter and sediments and their influencing factors in a subtropical forest headwater stream,and assessed the potential pollution risk.The results showed that:(1)the mean concentrations of Fe and Al in plant litter(sediments)were 5.48 and 8.46(7.39 and 47.47)g·kg^(-1),and the mean storages of Fe and Al in plant litter(sediments)were 0.26 and 0.43(749.04 and 5030.90)g·m^(-2),respectively;(2)the storages of Fe and Al in plant litter and sediments significantly fluctuated from January to December,and showed a decreasing pattern from the source to mouth;and(3)storages of Fe and Al had no significant correlation with riparian forest type and the present of tributary and the Fe and Al storages in plant litter were mainly affected by water temperature and water alkalinity,and their storages in sediments were mainly affected by water temperature and frequency of rainfall;and(4)there were no anthropogenic pollution in Fe and Al in the forest headwater stream.Our study revealed the primary factors of concentrations and storages of Fe and Al in plant litter and sediments in a forest headwater stream,which will improve our understanding of the role of headwater streams in forest nutrient storage and cycling along with hydrological processes.

Ecosystem changes revealed by land cover in the three-river headwaters region of Qinghai,China(1990–2015)

The Three-River Headwaters Region(TRHR) of Qinghai Province, in the Tibetan Plateau of China, is the main source of the Yangtze, Yellow, and Lancang rivers, and is very significant to the security of freshwater resources for China and southeastern Asia. It is a critical ecological region of China for its ecological functions, and has been changed or even degraded in recent decades owing to climate change and human pressure. To effectively protect and restore the degraded ecosystems, the Chinese government initiated a series of ecological conservation projects in TRHR. It is essential to quantitatively assess ecosystem changes and their relationship to driving factors for indepth understanding of long-term changes of ecosystems and effects of ecological restoration policies and offer practical insights for ecological restoration. Here, land cover data has been interpreted with the series data of Landsat during 1990–2015. The patterns of different ecosystems and their developing process have been derived from land cover change. The results show that ecosystem types in TRHR include forest, grassland, cropland,wetland, artificial surface and barren land, accounting for 4.51%, 70.80%, 0.15%, 9.47%, 0.16% and 14.90%,respectively. Barren land converted to wetland was the significant ecosystem change from 1990 to 2015. Increases in temperature and precipitation and implementation of ecological rehabilitation helped maintain relatively stable ecosystem patterns. It is necessary to continue ecological projects to improve and/or maintain the ecosystems in TRHR because there is still a risk of land degradation under increasing climate change and human activity.

Changes in Grassland Ecosystem Service Values in the Three-River Headwaters Region,China

[Method] This study aimed to assess the changes in grassland ecosystem Service values in the Three-River Headwaters Region of China, the source of the Yangtze, Yellow （Huang He） and Lantsang （Mekong） rivers. [Method] Biophysical values of four services were monetized within the region, including water regulation, air quality regulation, climate regulation and soil conservation. [Result] The total ESVs were 884.97×10^8 Yuan, 1 302.06×10^8 Yuan and 1 299.49×10^8 Yuan in 2000, 2005 and 2008, respectively. The amount of value per unit area experienced a steep increase from 2000 to 2005（18.10×10^4 Yuan/km2）, and then remained almost unchanged from 2005 to 2008 （-0.31×10^4 Yuan/km2）. The ESV tended to decline from the southeastern to the northwestern. ESV in the eastern and central part increased faster than that in the south-central and western part of the TRHR from 2000 to 2008. It could be seen that the ecosystem condition of grassland in the TRHR improved signifi- cantly over the study period of 2000-2008. [Conelusion] The results provided good information to assess the effectiveness of current ecological protection measures in the TRHR and support regional sustainable management policies.

Synthesis Analysis of Soil Erosion for Three-River Headwater Region Based on GIS

In this paper,based on the common soil erosion model,the Three-River Headwaters region was select for study object. GIS methods are applied to conduct Semi-quantitative assessment for different types of soil erosion,and some results are concluded. The water erosion occurs in High Mountain and extra-high mountain of Yushu,Nangqian,Banma and Jiuzhi County in the southeast and south of the Three-River Headwaters region. The degree of erosion is prone to topography,precipitation,river and human activity. The freeze-thaw erosion mainly distributes in the northwest of the Three-River Headwaters region. The area of middle and above middle erosion degree accounts for roughly 50%.

Quantitative Allocation Analysis of "Raising by Planting" System Combining Fruits and Poultry for Mountainous Region in Headwaters of Dongjiang River

[Objective] The aim was to promote nutrient cycling and utilization in the mountain＇s system combining fruits and poultry and to control non-point source pollution produced from swine raising and navel orange planting in headwaters of Dongjiang River. [Method] The quantitative analysis was mainly conducted for the so called ＂raising by planting＂ which is about material cycle in ＂pig-methane-fruit-fish＂ model and energy cascade utilization, based on relationship between excreted amount by livestock and the utilized quantity in Xinlin Farm in Longtang Town, Dingnan County, Jiangxi Province. [Result] Considering N requirement by fruit trees, a navel orange orchard （1 mu） could support about 2.72 pigs, the equipped biogas pool （1.88 m3） could support 1 166.67 kg of duckweeds and a fish pond could support 25.57 grass carps. In contrast, a satsuma orchard （1 mu） could support about 1.96 pigs, the equipped biogas pool （1.35 m3） could support 841.53 kg duckweeds and the fish pond could support 18.44 grass carps. [Conclusion] The results provided scientific references for quantitative allocation of members in ＂pig-methane-fruit-fish＂ model when popularized in headwaters of Dongjiang River.

Grassland degradation in the ＂Three-River Headwaters＂ region, Qinghai Province

Supported by MSS images in the mid and late 1970s,TM images in the early 1990s and TM/ETM images in 2004,grassland degradation in the＂Three-River Headwaters＂region （TRH region）was interpreted through analysis on RS images in two time series,then the spatial and temporal characteristics of grassland degradation in the TRH region were analyzed since the 1970s.The results showed that grassland degradation in the TRH region was a continuous change process which had large affected area and long time scale,and rapidly strengthen phenomenon did not exist in the 1990s as a whole.Grassland degradation pattern in the TRH region took shape initially in the mid and late 1970s.Since the 1970s,this degradation process has taken place continuously,obviously characterizing different rules in different regions.In humid and semi-humid meadow region,grassland firstly fragmentized, then vegetation coverage decreased continuously,and finally＂black-soil-patch＂degraded grassland was formed.But in semi-arid and arid steppe region,the vegetation coverage decreased continuously,and finally desertification was formed.Because grassland degradation had obviously regional differences in the TRH region,it could be regionalized into 7 zones, and each zone had different characteristics in type,grade,scale and time process of grassland degradation.

Assessing the effects of vegetation and precipitation on soil erosion in the Three-River Headwaters Region of the Qinghai-Tibet Plateau,China

Soil erosion in the Three-River Headwaters Region(TRHR)of the Qinghai-Tibet Plateau in China has a significant impact on local economic development and ecological environment.Vegetation and precipitation are considered to be the main factors for the variation in soil erosion.However,it is a big challenge to analyze the impacts of precipitation and vegetation respectively as well as their combined effects on soil erosion from the pixel scale.To assess the influences of vegetation and precipitation on the variation of soil erosion from 2005 to 2015,we employed the Revised Universal Soil Loss Equation(RUSLE)model to evaluate soil erosion in the TRHR,and then developed a method using the Logarithmic Mean Divisia Index model(LMDI)which can exponentially decompose the influencing factors,to calculate the contribution values of the vegetation cover factor(C factor)and the rainfall erosivity factor(R factor)to the variation of soil erosion from the pixel scale.In general,soil erosion in the TRHR was alleviated from 2005 to 2015,of which about 54.95%of the area where soil erosion decreased was caused by the combined effects of the C factor and the R factor,and 41.31%was caused by the change in the R factor.There were relatively few areas with increased soil erosion modulus,of which 64.10%of the area where soil erosion increased was caused by the change in the C factor,and 23.88%was caused by the combined effects of the C factor and the R factor.Therefore,the combined effects of the C factor and the R factor were regarded as the main driving force for the decrease of soil erosion,while the C factor was the dominant factor for the increase of soil erosion.The area with decreased soil erosion caused by the C factor(12.10×10^3 km^2)was larger than the area with increased soil erosion caused by the C factor(8.30×10^3 km^2),which indicated that vegetation had a positive effect on soil erosion.This study generally put forward a new method for quantitative assessment of the impacts of the influencing factors on soil erosion,and also provided a scientific basis for the regional control of soil erosion.

Changing Spring Phenology Dates in the Three-Rivers Headwater Region of the Tibetan Plateau during 1960–2013

The variation of the vegetation growing season in the Three-Rivers Headwater Region of the Tibetan Plateau has recently become a controversial topic. One issue is that the estimated local trend in the start of the vegetation growing season(SOS)based on remote sensing data is easily affected by outliers because this data series is short. In this study, we determine that the spring minimum temperature is the most influential factor for SOS. The significant negative linear relationship between the two variables in the region is evaluated using Moderate Resolution Imaging Spectroradiometer–Normalized Difference Vegetation Index data for 2000–13. We then reconstruct the SOS time series based on the temperature data for 1960–2013.The regional mean SOS shows an advancing trend of 1.42 d(10 yr)during 1960–2013, with the SOS occurring on the 160th and 151st days in 1960 and 2013, respectively. The advancing trend enhances to 6.04 d(10 yr)during the past 14 years. The spatiotemporal variations of the reconstructed SOS data are similar to those deduced from remote sensing data during the past 14 years. The latter exhibit an even larger regional mean trend of SOS [7.98 d(10 yr)] during 2000–13. The Arctic Oscillation is found to have significantly influenced the changing SOS, especially for the eastern part of the region,during 2000–13.

Hydrological effects of alpine permafrost in the headwaters of the Urumqi River,Tianshan Mountains

Against the background of climate change, alpine permafrost active layers have shown a gradual thickening trend and the hydrothermal conditions have undergone significant changes in the Tianshan Mountains and the Qinghai-Tibet Plateau, China. At the ice-free cirque basins in the headwaters of the Urumqi River （hereafter referred to as the Ice-Free Cirque） in eastern Tianshan, China, the hydrological effects of the alpine permafrost active layers appear to have also exhibited sig- nificant changes recently. The increasing trend of local precipitation is clear in May and June. The onset of winter and spring snowmelt runoff clearly lags behind increases of air temperature, and the runoff peak appears near the beginning of the melting season, which results in the spring rtmoff increasing. In summer, runoff decreases strongly and the maximum runoff occurs earlier. In our analysis of meteorological and hydrologic data from 1959 to 2010, the runoffand precipitation changes are significantly correlated. In the initial stage of runoff, the runoff-producing process is mainly under the control of the soil water content and soil temperature in the 0-30 cm active layers. Spring precipitation and snowmelt water are mainly involved in the processes of infiltration and evaporation while some melt water infiltrates into the seasonal thawed layer and stays above the frozen layers. During the strong ablation period in summer, the runoff-generating process is mainly controlled by soil water content in the active layers deeper than 60 cm. In the active layer, precipitation and sea- sonal snowmelt water infiltrates, migrates, collects, and then forms runoff.

Quantifying impacts of climate and human activities on the grassland in the Three-River Headwater Region after two phases of Ecological Project

The Three-River Headwater Region(TRHR)of China is a typical representative of the alpine environment in the Central Asian plateau and the alpine grassland in the world.Grassland degradation is one of its serious eco-logical problems.The purpose of this study is to quantify the joint impacts of climate and human activities on grassland changes in TRHR after two phases of Ecological Conservation and Construction Project(Ecological Project).Grassland vegetation coverage is selected as an indicator for analyzing grassland changes.We adopt Sen+Mann-Kendall trend analysis,residual trend analysis and correlation analysis methods to analyze the trends in spatial-temporal changes and driving factors of grassland in TRHR from 2000 to 2019.The results show that:(1)The grassland has been mainly restored,and the degraded grassland area only accounts for 1.66%of TRHR.After the implementation of the first phase of the Ecological Project,the percentage of restored grassland area has significantly increased from 8.82%to 24.57%,and slightly decreased during the second phase.(2)The establish-ment of national nature reserves and the implementation of the Ecological Project have changed the situation that“the grassland inside the reserve is worse than that outside the reserve”.(3)Grassland restoration is mainly af-fected by the joint effects of climate and human activities.Nevertheless,grassland degradation is mainly affected by human activities such as overgrazing and grassland reclamation.All of these findings can enrich our under-standing of grassland restoration in TRHR.Artificial measures have certain limitations in promoting grassland restoration.Natural restoration should be considered when human beings strengthen ecological conservation and transform their production and life styles.

A method for determining vegetation growth process using remote sensing data: A case study in the Three-River Headwaters Region, China

Accurate measurements of the associated vegetation phenological dynamics are crucial for understanding the relationship between climate change and terrestrial ecosystems. However, at present, most vegetation phenological calculations are based on a single algorithm or method. Because of the spatial, temporal, and ecological complexity of the vegetation growth processes, a single algorithm or method for monitoring all these processes has been indicated to be elusive. Therefore, in this study, from the perspective of plant growth characteristics, we established a method to remotely determine the start of the growth season(SOG) and the end of the growth season(EOG), in which the maximum relative change rate of the normalized difference vegetation index(NDVI) corresponds to the SOG, and the next minimum absolute change rate of the NDVI corresponds to the EOG. Taking the Three-River Headwaters Region in 2000–2013 as an example, we ascertained the spatiotemporal and vertical characteristics of its vegetation phenological changes. Then, in contrast to the actual air temperature data, observed data and other related studies, we found that the SOG and EOG calculated by the proposed method is closer to the time corresponding to the air temperature, and the trends of the SOG and EOG calculated by the proposed method are in good agreement with other relevant studies. Meantime, the error of the SOG between the calculated and observed in this study is smaller than that in other studies.

The complex nonlinear systems with fractal as well as chaotic dynamics of annual runoff processes in the three headwaters of the Tarim River

This paper attempted to identify fractal and chaotic characteristics of the annual runoff processes in headwaters of the Tarim River.Methods of fractal analyses were used to explore several aspects of the temporal changes from 1957 to 2002.The main findings are as follows:(1) The annual runoff processes of the three headwaters of the Tarim River are com-plex nonlinear systems with fractal as well as chaotic dynamics.(2) The correlation dimensions of attractor derived from the time series of the annual runoff for the Hotan,Yarkand and Aksu rivers are all greater than 3.0 and non-integral,implying that all three rivers are chaotic dynamical systems that are sensitive to initial conditions,and the dynamic modeling of their annual runoff process requires at least four independent variables.(3) The time series of annual runoff in each river presents a long-term correlation characteristic.The Hurst exponent for the period of 1989 to 2002 suggests that we may expect to see an increasing trend in the annual runoff of the Aksu and Yarkand rivers in the years after 2002,but a decreasing tendency for the Hotan River in the same period.

Research on Hydraulic Block Scenarios in the Land Conservation Zone of the Headwaters Area of Jinshu Bay

[Objective] The aim was to study the hydraulic block scenarios in the water source land conservation zone in Jinshu Bay so as to ensure the water quality in the water sources in Jinshu Bay.[Method] By dint of one dimension water amount and water quality mode in the river net in Taihu,the water flow movement characteristics and pollutants transportation rules in the water sources areas in Jinshu Bay under five kinds of hydraulic block scenarios were compared and discussed.[Result] After demolishing the temporary soil dam in the water source conservation zone in Jinshu Bay,water amount and pollutants increased and water quality deteriorated.It was necessary to take certain hydraulic power to block and control the pollutants in the preservation area;after demolishing the dam,there was less water amount and pollutants.The water quality improved significantly.The hydraulic block facility in the preservation area and its surroundings were all releasing and not introducing;the one along the mouth of the river of Mentianji Gang,Jinshugang and Longtanggang were introducing and not releasing,which only restricted poor-quality water in Beijing-Hangzhou Canal and Huguang Canal flowing into the conservation zone.The water into the conservation zone was all from Gonghu.The water mobility within the conservation zone was good.The regional water quality improved to the largest scale.[Conclusion] Judging from the water flow movement characteristics and pollutants transportation rules in Jinshu Bay,the fifth proposal was more appropriate.

Chemical Characteristics of Stream Draining fromDudu Glacier: An Alpine Meltwater Stream inGanga Headwater, Garhwal Himalaya

The EC (electrical conductivity), pH and concentrations of major anions, cations and dissolved silica were determined in the stream meltwater draining from the glacier. Stream meltwater samples were sampled during June and October 1997 from Dudu glacier, Bhngirathi valley, Garhwal Himalaya. This study is an attempt to reveal the hydrochemical processes operating in the glacialized regime of Garhwal Himalaya. The results show that the abundance order of cations and anions in the meltwater is c(Ca2+ )>c(Na+ )>c(Mg2+ ) >c(K+ ) and c(SO42- ) >c>(HCO3-) >c(NO3- ) >c(CI- ). The rock weathering is the most important mechanism controlling the water chemistry in the basin. Pyrite oxidation and carbonation are the main hydrogen ion supply reactions contributing to the chemical weathering in the basin. There is a distinct difference between the solute concentrations in samples collected during June and October.

Long-term ecological compensation policies and practices in China:Insights from the Three Rivers Headwaters Area

Using the Three Rivers Headwaters Area in China as a pilot project, this study has investigated the effectiveness of the ecological compensation policies and practices have implemented in this area over the past decade. Major issues have encountered during the implementation process, including the formidable extent of grassland degradation, the comprehensive nature of measures needed to restore the ecosystem, and the time needed to achieve these goals. These issues are discussed, and remedial measures proposed. They include: drafting regulations giving the Three Rivers Headwaters Area ecological protection, setting aside funds for ecological compensation and establishing a national park, using an ecological assets accounting methodology for financial reporting purposes, designing a science-based approach for conducting the livestock husbandry population migration, enhancing the oversight capacity for all aspects of the ecological compensation process, and making an overall plan to promote the harmonious development of this area together with other regions in Qinghai Province.

Winter Rain versus Snow in Headwater Catchments: Responses of an Unconfined Pumice Aquifer, South-Central Oregon, USA

Winter precipitation in two headwaters catchments (elevation ~1600 m) in the rain shadow of the Cascades volcanic arc in south-central Oregon normally falls as snow. However, in water year 2015, winter precipitation fell mainly as rain. An eight year study of the unconfined pumice aquifer allowed inter-annual comparison of groundwater recharge during the freshet and discharge during the growing season. During these water years precipitation ranged from 67% (WY2014) to 132% (WY2017) of the 30 year average, and included the rain dominated winter of WY2015 when precipitation during the water year was 98% of the 30 year average. Change in storage in the pumice aquifer was estimated from thickness of the pumice deposit and depth to water table from the ground surface. Measurements were made where 1) the pumice aquifer was exposed at the surface;2) where the aquifer was partially eroded and overlain by either alluvium or lacustrine glassy silt to fine sand;3) fens where the partially eroded aquifer was overlain by peat;and 4) monitoring wells drilled through the pumice aquifer into bedrock. In all settings, groundwater storage in the pumice aquifer following the rain-dominated winter of WY2015 was similar or less than storage following the drought of WY2014 when winter precipitation fell as snow. Storage at the end of WY2014 and WY2015 was the least observed in the eight year study. Winter-time rain during WY2015 produced runoff rather than storage in snow pack. Runoff conveyed from the catchments by flow in stream reaches normally dry from late summer through the winter months. Rain-dominated winter precipitation stresses the perched pumice aquifer. Winter storms starting as rain and turning late to snow and ground-freezing temperatures lead to runoff during the next rain-dominated precipitation event. These patterns produced stream flow in channels that are commonly dry during the winter, reduced near-surface groundwater storage in the pumice aquifer, muted springtime freshet, and stressing of groundwater-dependent ecosystems, forage in meadows, and forest health.

Study on the Status and Topographic Heterogeneity of the Headwater Region of the Three Rivers

The ecological environment of the Three-River Headwater Region is primitive and unique,and sensitive and complex to external influences.The Three-River Headwater Region is the largest nature reserve in China,and is also a nature reserve with the highest concentration of biodiversity in the world's high-altitude areas,so the protection of ecological diversity in this region is particularly important.Ecological diversity is the material basis on which the entire humanity depends to survive and develop.It not only provides humans with basic needs such as food,energy and materials,and is also extremely important for maintaining ecological balance,regulating the climate and promoting the sustainable development of the region.Studying the topographical heterogeneity of the region is first of all a true grasp of the topography of the region,which has certain guiding significance for people's production and life.In addition,studying the impact of topographical heterogeneity on the climate of the region will help to study the formation and variation of regional climate.

Post-depositional modification of NO_3 in snow layers at East Antarctica and atthe headwater of Urumqi River

Acidic species, such as Nitrate, in polar snow and firn layers are “reversibly” deposited, and are sufficiently volatile to undergo significant post depositional exchange between snow/firn and the atmosphere. Through comparison of the snowpit and snowpack nitrate concentrations from central East Antarctica and the headwater of rumqi River, we conclude that the nitrate peaks in the uppermost surface snow layers in central Antarctica are not related to an atmospheric signal and must account for post depositional effects. Such effects, however, are not found in the surface snowpack nitrate profiles from the headwater of rumqi River. Two reasons may account for the post depositional difference. At first, nitrate in the polar snow and firn layers appears to be hydrated ion, which can be taken up by the atmosphere, while at the headwater of rumqi River it seems mainly as mineral ion, which assembles the behavior of aerosol derived species that are “irreversibly” deposited and do not undergo significant post depositional exchange with the atmosphere. Secondly, the chemical features of the snow and ice on the Antarctica are mainly determined by wet deposition, to the contrary, dry deposition is more significant at the headwater of rumqi River than that on the East Antarctic Plateau.

Hydrological Controls on Nutrient Exportation from Old-Growth Evergreen Rainforests and <i>Eucalyptus nitens</i>Plantation in Headwater Catchments at Southern Chile

Soil cover disturbances have a direct effect on biogeochemistry, potentially enhancing nutrient loss, land degradation and associated changes in ecosystem services and livelihood support. The objective of this study was to assess how canopy affected throughfall chemistry and how hydrology affected stream nutrient load responses in two watersheds dominated by native old-growth evergreen rainforest (NF) and exotic plantation of Eucalyptus nitens (EP), located at the Coastal mountain range of southern Chile (40&deg;S). We measured nitrogen (NO3-N, NH4-N, Organic-N, Total-N) and total phosphorus (Total-P) at catchment discharge, and δ18O in throughfall precipitation and stream discharge in both catchments, in order to separate throughfall (or new water) contributions during storm events. It was hypothesized that all nutrients showed an increase in concentration as discharge increased (or enhanced hydrological access), in EP;but not in NF. Our results indicated that Organic-N, Total-N and Total-P concentrations were positively related to discharge. However, NO3<sup style="margin-left:-7px;">--N showed a negative correlation with catchment discharge. Organic-N and Total-P showed a flush during storm events;the opposite was observed for NO3<sup style="margin-left:-7px;">--N. However, this behavior suggested that NO3<sup style="margin-left:-7px;">--N was being retained by charged particles or soil micro biota, whether Organic-N was flushed as it was more concentrated in big pore water that was not tightly attached, compared with NO3<sup style="margin-left:-7px;">--N.