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1.
It is well known that forest carbon or sink projects have not been included in theClean Development Mechanism (CDM), one of the flexible mechanisms created under the Kyoto Protocol. The main concern for postponing sink projects is related to issues of methodology and integrity. Project eligibility needs to be judged in a transparent manner if they are real, measurable,provide long-term benefits to mitigate climate change, and provide additional benefits to those thatwould occur in the absence of a certified project. One of the biggest challenges in implementing sink projects is fire risks and the associated biophysical and socio-economic underlying causes. This study attempts to assess fire probability and use it as a tool to estimate fire risk in carbon sink projects. Fire risks may not only threatenongoing projects but may also cause leakage of carbon stocks in other areas, especially in pro-tected areas. This exercise was carried out in the Berbak National Park located in Jambi Province, Sumatra, Indonesia and the surrounding areas. Fire probability is associated with (i) the means by which access to a given area is possible, and (ii) vegetation type or fuel load. Although most fires were intentionally ignited, fire escape iscommon and is enhanced by long spell of dry weather. When this occurs, secondary road was themost frequently used means, and it was certainly the case during 1997/1998 big fires when dam-age to natural vegetation (natural and secondary forests) was substantial. Burnt natural vegetationwas 120000 ha or 95% of the total burnt areas, and released more than 7 Mt of carbon into the atmosphere.  相似文献   

2.
火作为森林生态系统重要的自然干扰因子之一,对森林的碳动态有着不可忽视的影响.本研究使用CENTURY模型模拟了大兴安岭呼中林区兴安落叶松林的碳收支对不同强度火烧的响应.结果表明:在不同强度火烧后,土壤总碳库呈先升后降再逐渐恢复的变化趋势,而林分生物碳库则先降后升,其中,林分细小组分碳库的恢复速度明显快于大组分,各碳库的波动程度随火烧强度的增大而增大.森林植被的净初级生产力(NPP)和土壤异养呼吸在火后均先降后升,但NPP的恢复快于土壤异养呼吸,二者的动态变化改变了林分的碳源/汇作用.轻微火烧后,兴安落叶松林仍表现为弱碳汇,并很快恢复到火前水平;其他强度的火烧使兴安落叶松林在短期内(9~12年)表现为碳源,随后逐渐转为碳汇.较低强度的林火不仅可以促进落叶松林的更新、减少死可燃物,也不会对林分的碳汇功能造成太大影响;高强度的严重林火对土壤和林木碳库造成严重损失,延缓森林的恢复,并可使林分表现为较长时间的碳源.  相似文献   

3.
Wildfire is the major natural agent of disturbance in interior Alaska. We examined the magnitude of human impact on fire by comparing fire regime between individual 1-km2 grid cells designated for fire suppression with lands where fires are allowed to burn naturally. Two-thirds of interior Alaska has an essentially natural fire regime, with few human ignitions, negligible suppression activity, and many large lightning-caused fires. In the 17% of land that is designated for fire suppression due to its proximity to communities and roads, there was a 50% reduction in the proportion of area burned from 1992–2001, relative to areas without suppression. The remaining 16% of land serves as a buffer, receives some suppression, and has an intermediate fire regime. Even though there were 50 times more fires and the fire season began two months earlier in lands designated for suppression, most of these fires were lit by people and remained small because fires tended to occur at times and places less favorable for fire spread and were more accessible to fire fighters compared to lands not designated for suppression. Even in the absence of fire suppression, human-caused fires were less likely to exceed 400 ha compared to lightning-caused fires. Fire suppression reduced area burned in all fuel types but was somewhat more effective in less flammable (non-forest) vegetation. Alaska’s fire policy of focusing suppression efforts on a small proportion of the fire-prone region maximizes the ecological and social benefits associated with fire-dependent ecosystem services, while minimizing the social and ecological costs of suppression. Application of this policy to other areas would require well-informed managers and stakeholders to make difficult decisions about the relative costs and benefits of fire across ecologically and culturally variable landscapes.  相似文献   

4.
The high-latitude terrestrial carbon sink: a model analysis   总被引:7,自引:1,他引:6  
A dynamic, global vegetation model, hybrid v4.1 ( Friend et al. 1997 ), was driven by transient climate output from the UK Hadley Centre GCM (HadCM2) with the IS92a scenario of increasing atmospheric CO2 equivalent, sulphate aerosols and predicted patterns of atmospheric N deposition. Changes in areas of vegetation types and carbon storage in biomass and soils were predicted for areas north of 50°N from 1860 to 2100. Hybrid is a combined biogeochemical, biophysical and biogeographical model of natural, potential ecosystems. The effect of periodic boreal forest fires was assessed by adding a simple stochastic fire model. Hybrid represents plant physiological and soil processes regulating the carbon, water and N cycles and competition between individuals of parameterized generalized plant types. The latter were combined to represent tundra, temperate grassland, temperate/mixed forest and coniferous forest. The model simulated the current areas and estimated carbon stocks in the four vegetation types. It was predicted that land areas above 50°N (about 23% of the vegetated global land area) are currently accumulating about 0.4 PgC y?1 (about 30% of the estimated global terrestrial sink) and that this sink could grow to 0.8–1.0 PgC y?1 by the second half of the next century and persist undiminished until 2100. This sink was due mainly to an increase in forest productivity and biomass in response to increasing atmospheric CO2, temperature and N deposition, and includes an estimate of the effect of boreal forest fire, which was estimated to diminish the sink approximately by the amount of carbon emitted to the atmosphere during fires. Averaged over the region, N deposition contributed about 18% to the sink by the 2080 s. As expected, climate change (temperature, precipitation, solar radiation and saturation pressure deficit) and N deposition without increasing atmospheric CO2 produced a carbon source. Forest areas expanded both south and north, halving the current tundra area by 2100. This expansion contributed about 30% to the sink by the 2090 s. Tundra areas which were not invaded by forest fluctuated from sink to source. It was concluded that a high latitude carbon sink exists at present and, even assuming little effect of N deposition, no forest expansion and continued boreal forest fires, the sink is likely to persist at its current level for a century.  相似文献   

5.
Fire is an important disturbance agent in Myanmar impacting several ecosystems. In this study, we quantify the factors impacting vegetation fires in protected and non-protected areas of Myanmar. Satellite datasets in conjunction with biophysical and anthropogenic factors were used in a spatial framework to map the causative factors of fires. Specifically, we used the frequency ratio method to assess the contribution of each causative factor to overall fire susceptibility at a 1km scale. Results suggested the mean fire density in non-protected areas was two times higher than the protected areas. Fire-land cover partition analysis suggested dominant fire occurrences in the savannas (protected areas) and woody savannas (non-protected areas). The five major fire causative factors in protected areas in descending order include population density, land cover, tree cover percent, travel time from nearest city and temperature. In contrast, the causative factors in non-protected areas were population density, tree cover percent, travel time from nearest city, temperature and elevation. The fire susceptibility analysis showed distinct spatial patterns with central Myanmar as a hot spot of vegetation fires. Results from propensity score matching suggested that forests within protected areas have 11% less fires than non-protected areas. Overall, our results identify important causative factors of fire useful to address broad scale fire risk concerns at a landscape scale in Myanmar.  相似文献   

6.
A new fire model is proposed which estimates areas burnt on a macro‐scale (10–100 km). It consists of three parts: evaluation of fire danger due to climatic conditions, estimation of the number of fires and the extent of the area burnt. The model can operate on three time steps, daily, monthly and yearly, and interacts with a Dynamic Global Vegetation Model (DGVM), thereby providing an important forcing for natural competition. Fire danger is related to number of dry days and amplitude of daily temperature during these days. The number of fires during fire days varies with human population density. Areas burnt are calculated based on average wind speed, available fuel and fire duration. The model has been incorporated into the Lund‐Potsdam‐Jena Dynamic Global Vegetation Model (LPJ‐DGVM) and has been tested for peninsular Spain. LPJ‐DGVM was modified to allow bi‐directional feedback between fire disturbance and vegetation dynamics. The number of fires and areas burnt were simulated for the period 1974–94 and compared against observations. The model produced realistic results, which are well correlated, both spatially and temporally, with the fire statistics. Therefore, a relatively simple mechanistic fire model can be used to reproduce fire regime patterns in human‐ dominated ecosystems over a large region and a long time period.  相似文献   

7.
不同区域森林火灾对生态因子的响应及其概率模型   总被引:3,自引:0,他引:3  
李晓炜  赵刚  于秀波  于强 《生态学报》2013,33(4):1219-1229
火灾是影响森林生态系统过程的重要干扰之一,其对森林生态系统内各生态因子的响应各不相同.由于植被状况及生态环境的不同,森林火灾的时空分布特征在中国不同植被气候类型内表现不同,根据植被气候类型分类系统,将中国主要森林火灾地区划分为4个区域:东北(冷温带松林)、华北(落叶阔叶林)、东南(常绿阔叶林)和西南(热带雨林),应用遥感监测数据和地面环境数据,以时空变量、生态因子(植被生长变化指数、湿度等)为可选自变量,应用半参数化Logistic回归模型,就森林火险对不同生态影响因子的响应规律进行了分析,建立了基于生态因子的着火概率模型和大火蔓延概率模型,通过模拟及实际数据散点图、火险概率图,评估了模型应用价值.结果表明,土壤湿度及植被含水量在落叶阔叶林、常绿阔叶林、热带雨林地区对着火概率影响显著.在4个植被气候区内,土壤及凋落物湿度对大火蔓延的作用较小.在冷温带松林、落叶阔叶林、常绿阔叶林地区,植被生长的年内变化对火灾发生的影响显著,在常绿阔叶林地区,年内植被生长变化对大火蔓延的作用较小.森林火险概率与各生态因子的相关关系主要呈现出非线性.不同植被气候区内,火险概率受不同生态因子组合的影响,这与不同区域的植被状况及生态环境不同有关.在不同植被气候类型,应用时空变量、生态因子建立半参数化logistic回归模型,进行着火概率和大火蔓延概率的模拟具有可行性和实际应用能力.为进一步分析森林生态系统与火灾之间的动态关系、展开生态系统火灾干扰研究提供了理论基础.  相似文献   

8.

Background

Forecasting the effects of global changes on high altitude ecosystems requires an understanding of the long-term relationships between biota and forcing factors to identify resilience thresholds. Fire is a crucial forcing factor: both fuel build-up from land-abandonment in European mountains, and more droughts linked to global warming are likely to increase fire risks.

Methods

To assess the vegetation response to fire on a millennium time-scale, we analyzed evidence of stand-to-local vegetation dynamics derived from sedimentary plant macroremains from two subalpine lakes. Paleobotanical reconstructions at high temporal resolution, together with a fire frequency reconstruction inferred from sedimentary charcoal, were analyzed by Superposed Epoch Analysis to model plant behavior before, during and after fire events.

Principal Findings

We show that fuel build-up from arolla pine (Pinus cembra) always precedes fires, which is immediately followed by a rapid increase of birch (Betula sp.), then by ericaceous species after 25–75 years, and by herbs after 50–100 years. European larch (Larix decidua), which is the natural co-dominant species of subalpine forests with Pinus cembra, is not sensitive to fire, while the abundance of Pinus cembra is altered within a 150-year period after fires. A long-term trend in vegetation dynamics is apparent, wherein species that abound later in succession are the functional drivers, loading the environment with fuel for fires. This system can only be functional if fires are mainly driven by external factors (e.g. climate), with the mean interval between fires being longer than the minimum time required to reach the late successional stage, here 150 years.

Conclusion

Current global warming conditions which increase drought occurrences, combined with the abandonment of land in European mountain areas, creates ideal ecological conditions for the ignition and the spread of fire. A fire return interval of less than 150 years would threaten the dominant species and might override the resilience of subalpine forests.  相似文献   

9.
Forest fires are a significant and natural element of the circumboreal forest. Fire activity is strongly linked to weather, and increased fire activity due to climate change is anticipated or arguably has already occurred. Recent studies suggest a doubling of area burned along with a 50% increase in fire occurrence in parts of the circumboreal by the end of this century. Fire management agencies' ability to cope with these increases in fire activity is limited, as these organizations operate with a narrow margin between success and failure; a disproportionate number of fires may escape initial attack under a warmer climate, resulting in an increase in area burned that will be much greater than the corresponding increase in fire weather severity. There may be only a decade or two before increased fire activity means fire management agencies cannot maintain their current levels of effectiveness.  相似文献   

10.
寒温带湿地在维护区域生态平衡方面发挥着重要作用.火是湿地的重要干扰因子.重度火烧会导致湿地生态功能明显退化.火后植被恢复,特别是火后早期植被的恢复是生态系统功能恢复的前提和基础.本文对火后湿地植被恢复影响因子的国内外研究进展进行了综述.寒温带湿地火后植被恢复受到火强度、火面积、火前植被类型、物种更新特性、立地条件等多因子的制约.寒温带湿地火后恢复的长期监测、植被恢复的关键影响因子、冻土层在植被恢复过程中的作用、植被恢复的理论与技术将是今后研究的重要方向.  相似文献   

11.
Fire is a natural ecological force in the cerrado. However, the increasing use of fire by people means that conservation areas are subject to frequent burns. The aim of this study was to assess the potential of fire in an ecological reserve in the Brazilian savannas (cerrado) of central Brazil. Data about vegetation type, topography, climate, and fuel characteristics were input into the fire prediction models BEHAVE and FARSITE to simulate fire behavior during different weather conditions and from different entry points into the conservation area. The results indicated that there is a higher probability of fire entry from particular border regions as a result of the fuel characteristics. The presence of invasive grasses, such as Melinis minutiflora, within parts of the reserve also significantly affected the pattern of fire spread. Wind speed greatly increased the spread and extent of fire. The study showed that significant improvements in modeling fire behavior in savannas still need to be made. This study was the initial stage in the development of a decision support system for fire management in the cerrado.  相似文献   

12.
Fire is a major determinant of vegetation structure worldwide, and structural vegetation change following fire exclusion is well documented throughout Australia. Such changes include the displacement of treeless ecosystems by forest and the transition of open forest to rainforest. These changes displace essential habitat for myriad plant and animal species and are likely drivers of localised species extinctions. Despite these potential consequences, research identifying the spatial extent of fire‐excluded ecosystems is largely absent from the ecological literature. This study identifies the spatial and temporal extent of fire exclusion in Byron Shire in north‐east New South Wales. GIS analysis compared modern fire history with recommended fire intervals for the maintenance of fire‐dependent vegetation types. Fire exclusion (low‐frequency fire) vastly exceeded high‐frequency fire, comprising 99.1% of areas affected by inappropriate fire frequency. Most fire‐dependent vegetation was fire‐excluded, with less than 10% within recommended fire interval thresholds. Most affected areas were fire‐excluded for multiple recommended fire‐return cycles, increasing the likelihood of vegetation change and localised extinctions. These findings demonstrate the operation of a major threatening process affecting Byron Shire's biodiversity that has previously been little recognised. A growing body of ecological literature suggests that irreversible change to fire‐excluded vegetation is likely wherever plant growth resources are sufficient to enable transition. Irreversible vegetation change and rapid species declines have been reported for several communities in Byron Shire, and there is compelling evidence that further change may be widespread. With increasing time since fire, efforts to restore these sites may be complicated by encroaching trees resistant to removal by fire alone and the difficulties of reintroducing low‐intensity understorey fires where the flammable understorey has been lost through shading. Further research into the impacts of fire exclusion is urgently required, as is the reinstatement of fire to fire‐excluded vegetation to prevent ongoing displacement of fire‐dependent biodiversity values.  相似文献   

13.
Abstract Fire is often used as a management tool in fire‐prone communities to reduce fuel loads with the intention of reducing the severity and extent of unplanned fires, often resulting in the increased occurrence of fire in the dry sclerophyll vegetation of Australia. This study examined the effects of fire frequency (length of the inter‐fire interval) on the reproductive output of seven plant species in the Proteaceae, including obligate seeding shrubs (Hakea teretifolia, Petrophile pulchella), resprouting shrubs (Banksia spinulosa, Isopogon anemonifolius, Lambertia formosa) and resprouting trees (Banksia serrata, Xylomelum pyriforme). Reproductive output (measured as either number of confructescences or follicles) and relative size were estimated for 100 individuals at each of five sample sites, covering a range of past fire frequencies over 26 years including repeated short inter‐fire intervals. Patterns in reproductive output (after standardizing for size) were related to the life‐history attributes of the species. In areas that had experienced short inter‐fire intervals, obligate seeders had greater reproductive output compared with longer intervals, and the reproductive output of resprouting shrubs was less. Fire frequency did not affect reproductive output of the resprouting trees. The decreased reproductive output of the resprouting shrubs could be due to the allocation of resources to regrowth following fire rather than to reproduction. It is less clear what process resulted in the increased reproductive output of obligate seeders in high fire frequency areas, but it could be due to the most recent fires being more patchy in the areas experiencing shorter inter‐fire intervals, or it may have resulted from the selection for early reproduction in the high fire frequency areas. These results highlight the need to take into account past fire frequency at a site, in addition to time since the last fire, when planning prescribed fires.  相似文献   

14.
15.
Aim We tested the hypothesis that anthropogenic fires favour the successful establishment of alien annual species to the detriment of natives in the Chilean coastal matorral. Location Valparaíso Region, central Chile. Methods We sampled seed rain, seedbank emergence and establishment of species in four paired burned and unburned areas and compared (using GLMM) fire resistance and propagule arrival of alien and native species. To assess the relative importance of seed dispersal and seedbank survival in explaining plant establishment after fire, we compared seed rain and seedbank structure with post‐fire vegetation using ordination analyses. Results Fire did not change the proportion of alien species in the coastal matorral. However, fire increased the number of annual species (natives and aliens) of which 87% were aliens. Fire reduced the alien seedbank and not the native seedbank, but alien species remained dominant in burned soil samples (66% of the total species richness). Seed rain was higher for alien annuals than for native annuals or perennials, thus contributing to their establishment after fire. Nevertheless, seed rain was less important than seedbank survival in explaining plant establishment in burned areas. Main conclusions Anthropogenic fires favoured alien and native annuals. Thus, fire did not increase the alien/native ratio but increased the richness of alien species. The successful establishment of alien annuals was attributable to their ability to maintain rich seedbanks in burned areas and to the greater propagule arrival compared to native species. The native seedbank also survived fire, indicating that the herbaceous community has become highly resilient after centuries of human disturbances. Our results demonstrate that fire is a relevant factor for the maintenance of alien‐dominated grasslands in the matorral and highlight the importance of considering the interactive effect of seed rain and seedbank survival to understand plant invasion patterns in fire‐prone ecosystems.  相似文献   

16.
Abstract. In seasonally dry regions of the world fire is a recurring disturbance but little is known of how fire interacts with granite outcrop vegetation. We hypothesize that the floristic composition in granite vegetation, usually attributed to the edaphic environment, may also reflect the impact of disturbances such as fire. Dramatic differences in floristic composition and cover over 13 years and two fires were observed in vegetation on a Western Australian granite outcrop. This was very marked in the first year following the two fires, with annuals and geophytes showing the greatest turnover of species. Even among the perennial shrubs there was considerable turnover in a number of obligate seeders. After the first fire the number of species declined for woody perennials, herbaceous perennials and annuals, remained unchanged for perennial grasses and sedges, and varied with highest richness 4 yr after fire for geophytes. Demographic studies of two endemic woody obligate seeders and three endemic mallee eucalypt resprouters similarly showed dramatic differences within and between species in seedling recruitment following the two fires. Fire does have a significant impact on the floristic composition of semi‐arid granite outcrop vegetation communities. Studies on other granite outcrop systems are needed to test the generality of this conclusion.  相似文献   

17.
林火直接破坏森林资源,改变森林的结构与功能,影响局地甚至全球气候状况并威胁人类生命和财产安全,在气候变暖背景下林火将更加频发,因此开展林火预测/预报研究至关重要。利用MODIS (Moderate-resolution Imaging Spectroradiometer)的温度异常/火产品(MOD14A1)获取逐日林火数据,分析了2001-2018年中国西南地区林火时空分布特征;采用随机森林算法,综合考虑气象、地形、可燃物状况及植被等林火驱动因子,构建了中国西南地区干、湿季林火发生预测模型,系统分析了西南地区干湿季林火发生的主要驱动因子。结果表明:(1)中国西南地区林火主要集中分布于云南大部、四川西南部及贵州南部地区,并呈集聚分布特征;林火多发于干季,占林火发生总次数的96.5%,年林火发生次数呈阶段性变化特征,2001-2014年呈现显著增加趋势,随后表现为不显著减少趋势;(2)构建的干、湿季林火发生预测模型能较准确地模拟林火发生状况:训练期模型准确率分别处于82.94%-83.99%与85.12%-90.31%之间,AUC (Area Under Curve)值分别处于0.908-0.914与0.922-0.965之间;测试期模型准确率分别为79.73%和83.27%,AUC值分别为0.886和0.855;(3)海拔是西南地区林火发生最关键的限制因子,林火多集中于中海拔区,而在低海拔和高海拔地区林火不易发生,这与人类活动密切相关。当日的气象条件是干季林火发生次重要的驱动因子,可燃物的温湿度状况则是湿季林火发生次重要的驱动因子。FWI系统指标(Fire Weather Index)在西南地区有较好的适用性且对于区域干湿季林火发生均有重要的影响,因此在西南地区林火预测/预报工作中有必要引入FWI系统指标。  相似文献   

18.
林火是森林生态系统的重要影响因子,建立科学准确的林火预测预报模型对林火管理工作至关重要。本研究以不同气象因子为主要预测变量,基于Logistic回归和广义线性混合效应模型建立福建省林火发生预测模型,通过对比Logistic基础模型和广义线性混合效应模型的拟合度和预测精度,研究混合效应模型在林火预报中的适用性。结果表明: Logistic基础模型的受试者工作特征曲线下面积(AUC)值为0.664,验证准确率为60.4%。添加随机效应后,模型的拟合和检验精度均获得了提升。其中,考虑行政区划和海拔差异效应的两水平混合效应模型的表现最优,其AUC值和验证准确率分别比基础模型提升0.057和6.0%。用此混合效应模型对福建省各地区的林火发生概率进行预测的结果表明,福建省西北部和南部为林火中高发区域,西南部和东部为林火低发区域,与实际观测的火点分布一致。混合效应模型在数据拟合和林火发生预测方面均优于Logistic基础模型,可作为林火预测和管理的重要工具。  相似文献   

19.
火干扰与生态系统的碳循环   总被引:18,自引:0,他引:18  
吕爱锋  田汉勤  刘永强 《生态学报》2005,25(10):2734-2743
火干扰是陆地生态系统碳循环的重要影响因子。它改变着整个系统的碳循环过程与碳分布格局。正确评估火干扰在碳循环过程中的作用,对推进全球碳循环研究有着重要的意义。从4个方面系统的回顾了火干扰对碳循环的影响过程及其研究方法:(1)火烧过程中含碳痕量气体排放的估算;(2)火烧迹地恢复过程中净第一性生产力(NPP)与土壤呼吸的变化;(3)火干扰对生态系统碳源/汇的影响;(4)模型方法在火干扰与生态系统碳循环研究中的应用。目前火灾碳排量的估算方法业已成熟,但进行更精确的估算必须基于对受干扰生态系统的性质以及火势的时空变异性质的准确理解;相比之下,对于间接的、更为重要的影响,即对火烧迹地恢复过程中碳循环变化的研究则显不足。由于数据缺乏,现有研究大多限于对碳循环某一方面的观测与定量描述,缺乏全面的机理性分析。对此,实地观测、模型模拟与遥感观测的跨尺度集成将成为未来火干扰研究的一个主要方向。  相似文献   

20.
There is increasing consensus that the global climate will continue to warm over the next century. The biodiversity-rich Amazon forest is a region of growing concern because many global climate model (GCM) scenarios of climate change forecast reduced precipitation and, in some cases, coupled vegetation models predict dieback of the forest. To date, fires have generally been spatially co-located with road networks and associated human land use because almost all fires in this region are anthropogenic in origin. Climate change, if severe enough, could alter this situation, potentially changing the fire regime to one of increased fire frequency and severity for vast portions of the Amazon forest. High moisture contents and dense canopies have historically made Amazonian forests extremely resistant to fire spread. Climate will affect the fire situation in the Amazon directly, through changes in temperature and precipitation, and indirectly, through climate-forced changes in vegetation composition and structure. The frequency of drought will be a prime determinant of both how often forest fires occur and how extensive they become. Fire risk management needs to take into account landscape configuration, land cover types and forest disturbance history as well as climate and weather. Maintaining large blocks of unsettled forest is critical for managing landscape level fire in the Amazon. The Amazon has resisted previous climate changes and should adapt to future climates as well if landscapes can be managed to maintain natural fire regimes in the majority of forest remnants.  相似文献   

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