Zoige Plateau Research Articles

A new method for perceiving origins of international important Ramsar wetland ecological habitat scenes in China

A tentative and interesting experiment was conducted for perceiving the origins of international important Ramsar wetland ecological habitat scenes (WEHS) in China. Four different categories of international importance wetlands in the Ramsar list, including DongZhai Harbor inter-tidal mangrove wetland in Hainan Province, Lashi Lake alpine peat wetland in Yunnan Province, Zoige plateau freshwater lake wetland in Sichuan Province and Yancheng coastal saline wetland in Jiangsu Province, in China were investigated. The spatial envelope (SE) algorithm was used to extract the ecological features of the WEHS. The multi-resolution spectral functions of the SE algorithm in the spatial-frequency domain were rearranged to be approximately orthogonal. The original ecological image was transferred through such optimized channels and some valid features were obtained, which can be used to represent the WEHS. The principal component analysis algorithm was used to extract the principal components from these optimum characteristics. Three kinds of nonlinear recognition methods including conditional maximum entropy regression, multi-class support vector machine (SVM) and scaled conjugate gradient multi-layer perceptron were used to determine the logical ecological habitat attributions using the obtained principal components. The first-ranking perceiving accuracy and mean average precision (mAP) scores achieved 70% and 0.791 by using the multi-class SVM, respectively. The results demonstrated that the proposed methods could be preliminarily used to perceive the origins of the typical WEHS in China.

A comparison study on empirical microwave soil moisture downscaling methods based on the integration of microwave-optical/IR data on the Tibetan Plateau

Soil moisture plays a vital role in land surface energy and the water cycle. Microwave remote sensing is widely used because of the physically based relationship between the land surface emission observed and soil moisture. However, the application of retrieved soil moisture data is restricted by its coarse spatial resolution. To overcome this weakness, downscaling methods should be developed to disaggregate coarse resolution microwave soil moisture data to fine resolution. The traditional method is the microwave-optical/IR synergistic approach, in which land surface temperature, vegetation index, and surface albedo are key parameters. Five purely empirical methods based on the triangle feature are selected in this study. To evaluate their performance on downscaling microwave soil moisture, these methods are applied to the Zoige Plateau in China using the Advanced Microwave Scanning Radiometer on the Earth Observing System (AMSR-E) Land Parameter Retrieval Model (LPRM) soil moisture product and Moderate Resolution Imaging Spectroradiometer (MODIS) optical/IR products. The coarse-resolution AMSR-E LPRM soil moisture data are disaggregated into the high resolution of the MODIS product, and the surface soil moisture measurements of the Maqu soil moisture observation network located in the plateau are used to validate the downscaling results. Results show that (1) the relationship models used in these methods can generally capture the variation in soil moisture, with R2 around 0.6, but have a relatively high uncertainty under conditions of high soil moisture; (2) the methods can provide high-resolution soil moisture distribution, but the downscaled soil moisture presents a low level correlation with field measurements at different spatial and temporal scales. This comparative study provides insight into the performance of popular purely empirical downscaling methods on enhancing the spatial resolution of soil moisture on the Tibetan Plateau. Although synergistic methods can improve the spatial resolution of AMSR-E soil moisture data, additional studies are needed to exclude the uncertainty from AMSR-E soil moisture estimation, the low sensitivity of the relationship model under high soil moisture, and the spatial representativeness difference between coarse pixels and point measurement.

Higher recent peat C accumulation than that during the Holocene on the Zoige Plateau

In order to understand the carbon fate of alpine peatlands under climate change, this study aimed to measure carbon accumulation in recent decades and that during the Holocene at seven representative peat sites on the Zoige Plateau using empirical peat core data (14C and 137CS) and modeling approaches. The observed apparent carbon accumulation rate over the past 50 years was 75 (35–123) g C m−2yr−1, nearly four times that of 19 (7–30) g C m−2 yr−1over the whole Holocene. With decomposition history included in consideration by using modeling approaches, the average expected peat carbon accumulation rate was still nearly 1.6 times that of the modeled net carbon uptake rate of peats accumulated over the whole Holocene, though exceptions were found for Denahequ and Hongyuan peat cores with extremely low water table levels. The newly accumulated peat carbon of the Zoige Plateau amounted to 0.4 Tg C yr−1 (1 Tg = 1012 g) during recent decades. Overall, the effect of climate warming on recent C accumulation of peatlands on the Zoige Plateau is dependent on their water conditions. The peat C storage on the alpine Plateau is threatened by human activities (drainage) and continuous climate change with increasing temperature and decreasing precipitation which cause dryness of peatlands.

Soil cellulase activity and fungal community responses to wetland degradation in the Zoige Plateau, China

Four soil types (peat, marsh, meadow, and sandy) in the Zoige Plateau of China are associated with the severity of wetland degradation. The effects of wetland degradation on the structure and abundance of fungal communities and cellulase activity were assessed in these 4 soil types at 3 depths using DGGE (Denatured Gradient Gel Electrophoresis), qPCR (Quantitative Real-time PCR), and 3,5-dinitrosalicylic acid assays. Cellulase activity and abundance of the fungal community declined in parallel to the level of wetland degradation (from least to most disturbed). DGGE analysis indicated a major shift in composition of fungal communities among the 4 soil types consistent with the level of degradation. Water content (WC), organic carbon (OC), total nitrogen (TN), total phosphorus (TP), available nitrogen (AN), and available phosphorus (AP) were strongly correlated with cellulase activity and the structure and abundance of the fungal community. The results indicate that soil physicochemical properties (WC, OC, TN, TP, AN, and AP), cellulase activity, and diversity and abundance of fungal communities are sensitive indicators of the relative level of wetland degradation. WC was the major factor involved in Zoige wetland degradation and lower WC levels contributed to declines in the abundance and diversity of the fungal community and reduction in cellulase activity.

Effects of soil warming, rainfall reduction and water table level on CH4 emissions from the Zoige peatland in China

The Zoige Plateau features approximately 4605 km2 of peatlands, making it the largest peatland area in China. This area stored 2.9 Pg peat during the Holocene, yet little is known about methane (CH4) emissions from this region. In this study, we designed a mesocosm experiment to measure CH4 emissions during the growing seasons of 2009–2010 under different scenarios involving soil warming, 20% reduction in rainfall and changes in the water table level. Our results showed that CH4 emissions were higher in 2009 than in 2010 under all experimental conditions. Average soil temperature was approximately 11.4 °C under control conditions, 13.3 °C under soil warming conditions, 12.7 °C with 20% rainfall reduction, and 13.4 °C under combined conditions of soil warming and 20% reduced rainfall. For the single factor effect, soil warming treatment increased average CH4 emissions by 28%, while rainfall reduction increased it by 30%; however, neither increase was statistically significant. In contrast, the combined effect of soil warming and rainfall reduction significantly decreased CH4 emissions by an average of 58%. Extending this result across the entire peatland area in the Zoige Plateau translates into approximately 5.3 Gg of CH4 uptake per year. These results suggest that a drier and warmer Zoige Plateau will become a CH4 sink. Our study also found a positive relationship between water table level and CH4 emissions. Average CH4 emissions decreased by approximately 82% as water drawdown varied from 0 (0.94 mg CH4 m−2 h−1) to −50 cm (0.17 mg CH4 m−2 h−1). When we simultaneously examined the effect of all three factors of water table level, soil warming and rainfall reduction on CH4 emissions, we found soil warming and rainfall effect on CH4 emissions varied with water table levels. However, none of the three factors significantly affected CH4 emissions at a water table depth of 30 cm below peat depth.

青藏高原东北部5000年来气候变化与若尔盖湿地历史生态学研究进展

PDF HTML阅读 XML下载 导出引用 引用提醒 青藏高原东北部5000年来气候变化与若尔盖湿地历史生态学研究进展 DOI: 10.5846/stxb201308052023 作者: 作者单位: 中国科学院成都生物研究所;中国科学院若尔盖泥炭与全球变化研究站,中国科学院成都生物研究所;中国科学院若尔盖泥炭与全球变化研究站; 国际山地综合发展中心,西北农林科技大学;中国科学院若尔盖泥炭与全球变化研究站,中国科学院成都生物研究所,中国科学院成都生物研究所,西北农林科技大学,中国科学院若尔盖泥炭与全球变化研究站,中国科学院成都山地灾害与环境研究所,中国科学院成都生物研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国际科技合作项目（S2013GI0408）；国家青年自然科学基金（31100348）；教育部新世纪优秀人才支持计划（NCET-12-0477）；教育部高等学校博士学科点专项科研基金（20120204110011） The 5000-year climate change of northeastern Qinghai-Tibetan Plateau and historical ecology of Zoige wetlands Author: Affiliation: Chengdu Institute of Biology, CAS;Zoige Peatland and Global Change Research Station, CAS,,,Chengdu Institute of Biology, CAS;Zoige Peatland and Global Change Research Station, CAS,,,,,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:全球变化背景下古气候学的研究越来越受到关注。利用多年来的文献记载和自然证据，对青藏高原东北部气候变化进行重建。并以若尔盖湿地为例，梳理了区域5000 a来气候变化对湿地植被类型、泥炭沼泽发育和文化发展产生的影响，探讨了气候变化、文化发展、沼泽发育三者之间可能具有的相互关系。指出青藏高原东北部5000-3000 a B.P.之间气候较为暖湿，其平均温度要高出现在2 ℃左右；3000 a B.P.至今为气候干冷期，其中1000 a B.P.左右是过去5000 a中最寒冷时期，近1000 a来气温呈缓慢回升趋势。区域的气候变化决定了植被类型，对泥炭沼泽的形成和发育发挥了重要作用，对文明进程的影响主要体现在气候变化通过影响沼泽的演替，从而改变人类活动的范围与早期文明的形成，同时人类的过度活动也在一定程度上影响了沼泽的分布格局及动态。但气候变化、沼泽发育和文化发展三者之间的关系有赖于多因素耦合，其具体机理有待更深入的研究。 Abstract:Paleoclimatology is attached more and more importance by climate and ecological scientists. As the strengthening of the monsoon activity, the middle Holocene (6.0-5.0ka B.P.) became an important reference era of Paleoclimate Modeling Intercomparison Project (PMIP). In addition, the northeastern Qinghai-Tibetan Plateau was focused by its climatic sensibility and ecological vulnerability. In this paper, we used the data from Qinghai Lake, Zoige plateau and the source area of Yellow River to present the trends of 5000-year climate change on northeastern Qinghai-Tibetan Plateau. Then taking Zoige wetlands as an example, we reviewed studies about the impact of climate change on vegetation types, peat development and civilization evolution, and discussed the possible interaction among them. According to our analyses, the climate on the northeastern Qinghai-Tibetan Plateau was warm and humid from 5.0 to 3.0 ka B.P., with an average temperature 2℃ higher than the present. In this period, the dominant macrophanerophyte was mainly coniferous tree and the major herbage type was sedge. Moreover, thick peat accumulation was found due to the warm and humid climate. However, the climate turned into dry and cold since then to 1.0 ka B.P., with an extremely cold event around 1ka B.P.. The coniferous forest had been shrinking from highland to lowland because of fading Indian monsoon, wetlands developed very slowly and the civilization was also influenced. Meanwhile, human activities also slightly limited the development of wetlands due to the increasing population of Di-Qiang ancient people. We deduced that there existed a roughly synchronous resonance between climate change and the phenomenon of nomad migrated southward or eastward periodically. It is worth mentioning that Medieval Warm Period was observed in this era, following the prosperity of The tea-horse trade and the appearance of agricultural production by Uigur in Gansu Corridor. In recent 1000 years, due to the relatively warming climate, though not very steady, the coniferous forest and the wetland developed slightly again. In recent 100 years, the abrupt warming was introduced by increasing GHGs, the precipitation was decreased relatively. The area of Zoige wetlands decreased by a half due to drainage from 60s to the early 80s, then the shrinkage of wetlands was mainly due to climate warming, especially the abrupt warming of recent ten years. In short, the regional climate change determined vegetation types and affected the formation and development of wetlands. Climate change also impacted civilization, which altered the scope of human activity and early establishment of civilization. Meanwhile, human activities also affected the distribution and dynamics of wetlands. The interaction among climate change, wetland development and civilization course, however, depend on coupling of different factors. Furthermore, it is urgent to carry out researches about integrated adaptation and related technology on alpine's ecosystem to mitigate the climate change, as well as establishing a sustainable management system of Qinghai-Tibetan Plateau. 参考文献 相似文献 引证文献

Aerobic methanotroph diversity in Riganqiao peatlands on the Qinghai–Tibetan Plateau

The Zoige Plateau is characterized by its high altitude, low latitude and low annual mean temperature of approximately 1°C and is a major source of atmospheric methane in the Qinghai-Tibetan Plateau. Methanotrophs play an important role in the global cycling of CH4, but the diversity, identity and activity of methanotrophs in this region are poorly characterized. Soils were collected from hummocks and hollows in the Riganqiao peatland and the methanotroph community was analysed by qPCR and sequencing methane monooxygenase (pmoA and mmoX) genes. The pmoA genes ranged between 10(7) and 10(8) copies g(-1) fresh soil, with a somewhat greater abundance in hummocks than hollows. The pmoA genes were analysed by amplicon pyrosequencing and the mmoX genes by cloning and sequencing. Methylocystis species were found to be the most abundant methanotrophs, but numerous clades were present including three novel pmoA and three novel mmoX clusters. There were differences between the methanotroph communities in the hummocks and hollows, with the most significant being an increased abundance of uncultivated type Ib methanotrophs in the hollows. The results indicate that aerobic methanotrophs are abundant in Riganqiao peatland and include previously undetected clades in this geographically isolated and distinctive environment.

Landscape pattern evolution processes of alpine wetlands and their driving factors in the Zoige Plateau of China

Zoige Plateau wetlands are located in the northeastern corner of the Qinghai-Tibet Plateau. The landscape pattern evolution processes in the Zoige Plateau and their driving factors were identified by analyzing the dynamic changes in landscape modification and conversion and their dynamic rates of alpine wetlands over the past four decades. The results showed that the landscape conversion between wetlands and non-wetlands mainly occurred during the period from 1966 to 1986. The marsh wetland area converted from lake and river wetlands was larger because of swamping compared to other wetland landscapes. Meanwhile, the larger area of marsh wetlands was also converted to lake wetlands more than other types of wetlands. The modification processes mainly occurred among natural wetland landscapes in the first three periods. Obvious conversions were observed between wetland and non-wetland landscapes (i.e., forestland, grassland, and other landscapes) in the Zoige Plateau. These natural wetland landscapes such as river, lake and marsh wetlands showed a net loss over the past four decades, whereas artificial wetland landscapes (i.e., paddy field and reservoir and pond wetlands) showed a net decrease. The annual dynamic rate of the whole wetland landscape was 0.72%, in which the annual dynamic rate of river wetlands was the highest, followed by lake wetlands, while marsh wetlands had the lowest dynamic rate. The integrated landscape dynamic rate showed a decreasing trend in the first three periods. The changes in wetland landscape patterns were comprehensively controlled by natural factors and human activities, especially human activities play an important role in changing wetland landscape patterns.

Effects of Alpine Wetland Landscapes on Regional Climate on the Zoige Plateau of China

The differences in the air temperature, precipitation, evaporation, and relative humidity between wetlands and nonwetlands were analyzed to investigate the effects of alpine wetlands on regional climate. Meanwhile, the changes in precipitation and surface runoff fluxes before and after the typical wetland degradation were discussed, and the effects of wetland degradation on soil organic carbon were assessed. Correlation and regression analyses were applied to exhibit the relationships between wetland landscape areas and meteorological factors. Our results showed that the cooling effects of wetlands on ambient environment were very obvious, and soil temperature could be higher in the area with less surrounding wetland area. The evaporation capacity and relative humidity in wetlands were higher compared to the surrounding non-wetlands. Precipitation and surface runoff flux decreased due to serious wetland degradation, indicating that wetland degradation or expansion had close relation with regional precipitation. Once peat soils were converted to meadow soils or Aeolian sandy soils, soil organic carbon (SOC) would decline linearly. Correlation and regression analyses showed that there were significant correlations between wetland landscape areas and the annual average air temperature, the average air temperature in growing seasons, and the evaporation in growing seasons (P<0.05).

Estimating the Maximal Light Use Efficiency for Different Vegetation through the CASA Model Combined with Time-Series Remote Sensing Data and Ground Measurements

Maximal light use efficiency (LUE) is an important ecological index of a vegetation essential attribute, and a key parameter of the LUE-based model for estimating large-scale vegetation productivity by remote sensing technology. However, although currently used in different models there still exists extensive controversy. This paper takes the Zoige Plateau in China as a case area to develop a new approach for estimating the maximal LUEs for different vegetation. Based on an existing land cover map and MODIS NDVI product, the linear unmixing method with a moving window was adopted to estimate the time-series NDVI for different end members in a MODIS NDVI pixel; then Particle Swarm Optimizer (PSO) was applied to search for the optimization of LUE retrievals through the CASA (Carnegie-Ames-Stanford Approach) model combined with time-series NDVI and ground measurements. The derived maximal LUEs present significant differences among various vegetation types. These are 0.669 gC·MJ−1, 0.450 gC·MJ−1 and 0.126 gC·MJ−1 for the xerophilous grasslands with high, moderate and low vegetation fraction respectively, 0.192 gC·MJ−1 for the hygrophilous grasslands, and 0.125 gC·MJ−1 for the helobious grasslands. The field validation shows that the estimated net primary productivity (NPP) by the derived maximal LUE is closely related to the ground references, with R2 of 0.8698 and root-mean-square error (RMSE) of 59.37 gC·m−2·a−1. This indicates that the default set in the CASA model is not suitable for NPP estimation for the regional mountain area. The derived maximal LUEs can significantly improve the capability of NPP mapping, and open up the perspective for long-term monitoring of vegetation ecological health and ecosystem productivity by combining the LUE-based model with remote sensing observations.

Estimation of storage and density of organic carbon in peatlands of China

Based on the results of the National Survey of Peat Resources (1983–1985) and the investigation results on the peatlands of China, the storage and density of the organic carbon in the peatlands of China were estimated. The total organic carbon storage (OCS) of the peatlands in China, including bare peatlands and buried peatlands, are 1.503 × 109 t, unevenly distributed over 30 provincial level administrative units and 16 climatic zones. Peatland organic carbon storage (POCS) in Sichuan (6.45 × 108 t) and Yunnan provinces (2.91 × 108 t) is the highest, accounting for 62.29% of the total POCS. Humid zone of plateau has the highest POCS of 7.14 × 108 t, especially in the Zoige Plateau, where the POCS is 6.30 × 108 t, accounting for 41.92% of the total POCS of China. The organic carbon density (OCD) of the peatlands in China mostly ranges from 80 kg/m3 to 140 kg/m3, and the range of the maximum is 270–360 kg/m3, and the minimum is less than 80 kg/m3. Divided by the Yanshan Mountain, Taihang Mountains and Hengduan Mountains, the peatland oganic carbon density (POCD) is lower on the northwestern side than that on the southeastern side. Jiangxi Province has the highest POCD due to the ancient buried peatlands. The OCD of the bare peatlands is mostly in the range of 60–150 kg/m3, and that of the buried peatlands is more than 100 kg/m3. In the bare peatlands, the OCD generally increases from the surface layer to the below surface layer, and then decreases with the depth. Although the peatlands area in China is small, the OCS per unit area is far higher than the other soil types, so peatlands protection can effectively mitigate climate change.

Palaeoclimate reconstruction based on pollen records from the Tangke and Riganqiao peat sections in the Zoige Plateau, China

Palynological analysis was performed to characterize the Holocene paleoflora of China's Zoige Plateau and the implications for the plateau's palaeoclimate, using the Tangke and Riganqiao peat sections. Atomic mass spectrometry 14C dates and modern surface soil pollen materials were used to reconstruct the palaeoclimate parameters. From 7940 to 6420 cal. BP, the climate under which the Tangke section formed was slightly warm and humid; from 6420 to 6030 cal. BP, the climate was warm and humid; from 6030 to 3790 cal. BP, the climate was slightly cold and dry; from 3790 to 1580 cal. BP, the climate was cold and dry; and from 1580 cal. BP to the present, the climate was very warm and humid. From 7320 to 6955 cal. BP, the climate under which the Riganqiao section formed was warm and humid; from 6955 to 5467 cal. BP, the climate was very cold and dry; from 3641 to 5467 cal. BP, the climate was slightly cold and dry; from 2337 to 3641 cal. BP, the climate was warm and slightly humid; and from 2337 to 615 cal. BP, the climate was warm and slightly humid. Several cold and dry events have therefore occurred since 8000 cal. BP in both sections. There is a close relationship between peat mire development and paleoenvironmental change during the five periods recorded in the two sections.

Overlooked? The Growing Threat of Desertification

Overlooked? The Growing Threat of Desertification Julian Zhu modes of subsistence. As livestock herders raise increasingly larger herds, areas which cannot sustain the amount of grazing needed to raise such large groups of animals begin the transfor- mation (Dong 2010). Healthy root systems play a key role in increasing soil’s water-holding ca- pacity and in holding soil down against high winds. As such, overgrazing directly threat- ens the natural resilience of soil against desert spread because it disturbs these root systems. In a similar fashion, marsh draining to make space for new agriculture and grazing land on the Zoige Plateau decreases the land’s ability to “Sustainable grazing requires significantly reduced livestock herd sizes on the part of herders or far stricter regulation of rangeland usage on the part of government” sustain life in the long-term, because doing so kills the area’s native plant life and disrupts the balance of the soil, which in turn leads to soil degradation and loss of long-tern fertility. Elsewhere, similar land use issues threaten a different environment. Karst is a type of land characterized by significant subterranean drain- age and low levels of surface water (Chen et al., 2009). Karst land covers 15% of the world’s land area and houses 1 billion people. Karst areas are highly delicate and have only a small band of agriculturally-usable soil between the surface and bedrock, making these regions extremely susceptible to rock desertification. As in the Zoige Plateau, intensive agriculture or over- grazing can leave soil vulnerable to dispersal by wind, leaving only non-arable rock. In karst B erkeley S cientific J ournal S ave or D estroy • S pring 2012 • V olume 16 • I ssue 2 • 1 B S J For many, the story of a threatened environment and our roles as caretakers of a fragile Earth has become a mainstay of modern liberal rhetoric, perhaps to the point of weariness. Whereas many citizens have become more and more knowledge- able of environmental issues such as air pollution, climate change, and overfishing, other significant environmental problems – especially those that disproportionately affect developing countries – are overlooked, regardless of their urgency. Desertification, defined broadly as the transfor- mation of productive land to infertile desert (pri- marily in arid and semi-arid regions), is one such problem, and one which threatens to undermine the long-term economic stability of many devel- oping countries. At first, the issue of desertification seems simple enough. As land becomes overworked – through intensive agriculture, overgrazing, or poor re- source management – its ability to sustain plant life deteriorates, leading to the transformation of arable land to desert. That said, however, framing desertification as purely the result of human er- ror doesn’t capture the whole picture. While hu- man action does indeed contribute heavily to des- ert spread, the economic forces that govern these actions, as well as environmental factors beyond human control, play significant roles in deserti- fication, and only through an understanding of both the economic and environmental issues of desertification can meaningful efforts be made to halt its spread. On a geophysical level, desertification is primarily the product of soil degradation and conflicts over land usage. Aeolian desertification, or deserti- fication caused when windborne sand settles in previously arable regions, is a serious problem in semi-arid regions such as the Zoige plateau China, where desertified lands have expanded at a com- pounded annual rate of 4.07% from 1975 to 2005 (Dong 2010). For many people in the region, agri- culture and livestock husbandry are the primary

Analysis on Relationship between Wetland Landscape and Environmental Factors in Zoige Plateau Based on DCCA

Analysis on Relationship between Wetland Landscape and Environmental Factors in Zoige Plateau Based on DCCA

Changes in ecosystem service values in Zoige Plateau, China

Climate change and human activities in high-altitude, cold pasture areas with fragile environments can cause land use changes that significantly affect ecosystem services and functions. Our study investigated changes in ecosystem services in response to land use changes caused mainly by climate change and human activities on the Zoige Plateau, a region in the eastern fringe of the Tibetan Plateau with large areas of grassland and wetland. The aim was to provide guidance for sustainable management of high, cold pasture areas. We used remote sensing to evaluate land use changes, and then applied a fast method for evaluating ecological service values in 1975, 1990, and 2005. The value of ecosystem services dropped from 61.46×109yuan in 1975 to 58.61×109yuan in 2005, exhibiting an accelerating rate of decrease, mainly due to the degradation of wetlands and, to a lesser extent, high-cover grassland. Waste treatment and water supply were the two largest service functions, contributing about 42% of the total service value. The results suggest that future land use planning should emphasize the protection of wetlands, high-cover grassland, and woodland, which have the highest ecosystem service values and showed the greatest degradation during the study period.

Methane Fluxes from Alpine Wetlands of Zoige Plateau in Relation to Water Regime and Vegetation under Two Scales

Methane fluxes in alpine ecosystems remain insufficiently studied, especially in terms of the magnitude, temporal, and spatial patterns. To quantify the mean methane emission of alpine ecosystems, methane fluxes were measured among six ecosystems and microsites within each ecosystem at Zoige National Wetland Reserve. The average methane emission from Zoige Plateau was 2.25 mg CH4 m(-2) h(-1), which fell into the range of methane emission rate reported by a number of studies in other alpine wetlands. Prevailing ecosystem types had important impacts on the methane flux on the landscape scale. In the wet ecosystems, the microsites had different methane emissions resulting from the differences in the depth of water table and associated vegetation characteristics. The identification of the microsites based on their vegetation characteristics thus allows upscaling of methane emissions in these ecosystems. However, in the dry ecosystems showing even methane uptake, the spatial variation in the methane fluxes was low and the vegetation has a poor predicative value for the methane fluxes. There, the soil porosity linked to the gas diffusion rate in soil would be the key factor explaining methane fluxes.

Modeling CH_4 Emissions from Natural Wetlands——Model Modification and Validation

Wetlands are one of the most important sources of atmospheric CH4, but the quantity of this source is still highly uncertain. We developed a biogeophysical model called CH4MODwetland to simulate CH4 emissions from natural wetlands based on CH4MOD that simulates CH4 emissions from irrigated rice paddies. The development of CH4MODwetland focused on the supply of methanogenic substrates, the process of vegetation growth, and the variation of soil redox potential that differ from the rice paddy. CH4MODwetland was validated against independent datasets from Sanjiang Plain and Zoige Plateau. Model validation showed that the observed seasonal and interannual variations of CH4 emissions from marshland in northeastern China were well captured, but that from peatland in southwest plateau of China were less well; Nevertheless, modeled seasonal amount of CH4 emissions agreed observed well in the two places, yielding an R2 of 0.96 (n=7, p<0.001); The root-mean-squared error, mean deviation, and model efficiency between modeled and observed values are 14.1%， -6.7%, and 0.95, respectively.

Aeolian desertification and its causes in the Zoige Plateau of China’s Qinghai–Tibetan Plateau

Studies and efforts to control aeolian desertification in China have focused on the arid and semiarid lands in the north. However, the aeolian desertification that is occurring on the high-altitude Qinghai–Tibetan Plateau, which has a cold and humid climate, has received attention only in recent years. In this paper, we report the results of monitoring this aeolian desertification between 1975 and 2005 and of our analysis of its causes on the Zoige Plateau, which is located in the northeastern part of China’s Qinghai–Tibetan Plateau. Aeolian desertified lands expanded at a compound annual rate of 4.07% between 1975 and 2005. They expanded most rapidly between 1975 and 1990, at an annual rate of 7.73%. Factors responsible for this expansion include increasing temperature, decreasing precipitation, over-grazing, drainage of water systems, and land reclamation for agriculture. Increasing temperature, over-grazing, and the drainage of water systems were the key factors. The climatic variations between 1975 and 2005 were not sufficient by themselves to lead to aeolian desertification. Human disturbances such as over-grazing and drainage of water systems must thus have been primarily responsible for the observed changes, and human behavior must be adjusted to control the expansion of aeolian desertification and rehabilitate the desertified lands.

Application of Apack software on analyzing spatial pattern of wetland landscape on the Zoige Plateau

以2000年的遥感影像为数据源，基于Apack软件运用景观格局指数数量方法研究了若尔盖高原高寒湿地的景观空间分布格局特征及其空间异质性特征。结果表明：2000年若尔盖高原湿地率为9.7％，其中沼泽湿地景观是主要景观组分，占湿地景观面积的96.32%；若尔盖高原湿地的景观多样性指数和均匀度都很小，聚集度较高，景观破碎化水平低，几何形状复杂，自相似性差。在5县域中，若尔盖县湿地景观的面积和湿地率最大，阿坝县和碌曲县所占比例较小；红原县的斑块数最多，碌曲县最少，但平均斑块面积以若尔盖县最大，阿坝县最小。各县湿地景观组分的比例分配差异大，但均以沼泽湿地景观为主要景观类型，且湿地景观聚集度高，破碎化水平低，几何形状复杂。在区域尺度上若尔盖高原湿地以自然湿地景观为主，且具有高度的空间异质性特征。

Influence of ENSO on multi‐annual temperature variations at Hongyuan, NE Qinghai‐Tibet plateau: evidence from δ13C of spruce tree rings

AbstractInfluence of ENSO on global temperature variations has aroused wide attention. However, little is known about this effect at regions where different monsoons prevail. In this study, we measured δ13C of spruce trees (picea likiangensis var. rubescens) and reconstructed temperature variations during the past 270 years at Hongyuan, the Zoige plateau where Indian summer monsoon (ISM) dominates. Temperature variation inferred from δ13Ctreering at the Zoige plateau shows anti‐teleconnection on multi‐annual timescales to the sea‐surface temperature (SST) anomaly in the Niño3 region (SSTANiño3 for short) which has been widely used as an indicator of the “El Niño–South Oscillation” (ENSO). We speculate that the ENSO may modulate the regional surface temperature by influencing the intensity of the ISM, which affects the influx of warm/moist air mass to the study region and subsequently changes the latent heating. On multi‐annual scales, when the SSTANiño3 is high (low), the ISM is weak (strong), monsoon precipitation decreases (increase), the latent heating is weakened (strengthened) and surface air temperature is lower (higher). Copyright © 2009 Royal Meteorological Society