Vegetation dynamics

植被动态
  • 文章类型: Journal Article
    监测陆地国家公园(TNP)的植被动态对于确保可持续的环境管理和减轻了解自然和保护区内气候变化影响的短期和长期干扰的潜在负面影响至关重要。这项研究旨在通过首先将其分类到苏门答腊地区来监测印度尼西亚TNP的植被动态,Jawa,加里曼丹,苏拉威西岛,和印度尼西亚东部,然后在GEE云计算平台上应用2000年至2022年的现成MODISEVI时间序列图像(MOD13Q1)。具体来说,这项研究利用森的坡度调查了绿化和褐变的趋势,通过分析最大和最小EVI值来考虑季节性,并通过比较年度时间序列和长期EVI中值来评估异常年份。研究结果表明,大多数TNP的绿化趋势显着增加,除了DanauSentarum,从2000年到2022年。季节性分析表明,大多数TNP在雨季和旱季结束时表现出高峰和低谷的绿色,分别,随着植被对降水的响应增加和减少。在所有地区都发现了受气候变化影响的季节性异常。为了提高TNPs的适应能力,建议的措施包括积极植树造林和实施辅助自然再生,加强基本管理任务的执行,森林火灾管理。
    Monitoring vegetation dynamics in terrestrial national parks (TNPs) is crucial for ensuring sustainable environmental management and mitigating the potential negative impacts of short- and long-term disturbances understanding the effect of climate change within natural and protected areas. This study aims to monitor the vegetation dynamics of TNPs in Indonesia by first categorizing them into the regions of Sumatra, Jawa, Kalimantan, Sulawesi, and Eastern Indonesia and then applying ready-to-use MODIS EVI time-series imageries (MOD13Q1) taken from 2000 to 2022 on the GEE cloud-computing platform. Specifically, this research investigates the greening and browning fraction trends using Sen\'s slope, considers seasonality by analyzing the maximum and minimum EVI values, and assesses anomalous years by comparing the annual time series and long-term median EVI value. The findings reveal significantly increasing greening trends in most TNPs, except Danau Sentarum, from 2000 to 2022. The seasonality analysis shows that most TNPs exhibit peak and trough greenness at the end of the rainy and dry seasons, respectively, as the vegetation response to precipitation increases and decreases. Anomalies in seasonality that is affected by climate change was detected in all of the regions. To increase TNPs resilience, suggested measures include active reforestation and implementation of Assisted Natural Regeneration, strengthen the enforcement of fundamental managerial task, and forest fire management.
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  • 文章类型: Journal Article
    由于火势加剧,火灾引起的植被组成变化正在导致生态系统服务发生变化,这可能威胁到其未来的可持续性。火灾复发,特别是,可能是影响火灾易发生态系统中生态系统服务恢复力的关键驱动力。这项研究评估了火灾复发的影响,二十四年来,关于十大调控的潜在供应能力,供应,利益相关者和专家选择作为关键服务的文化服务。我们评估了四个火灾易发景观中的火灾影响,这些景观主要由具有不同功能特征的物种对火的反应(即,专性播种机与繁殖物种)。通过使用Landsat图像对土地使用和土地覆盖(LULC)类别进行监督分类,估计了与火灾复发有关的潜在供应能力的趋势,与适应当地社会生态环境的生态系统服务能力矩阵相关。在以播种机为主的景观中,火灾复发中断了传统上与成熟森林覆盖相关的服务的潜在供应能力(即,气候调节的潜在供应能力下降的预测概率,木材,木材燃料,蘑菇生产,旅游,景观美学,和文化遗产发生了高火灾复发)。在以繁殖物种为主的景观中,火灾复发的影响在火灾后的短期得到了部分缓冲,并且没有发现变化趋势的实质性差异(即,在不考虑火灾复发的情况下,生态系统服务的潜在供应能力的预测概率相等)。我们发现了与火灾复发相关的生态系统服务供应的两个新机会:牲畜和蜂蜜生产,尤其是在播种机为主的地方。这些发现提供了有价值的信息,旨在恢复火灾后生态系统服务潜在供应,以部分抵消社会生态系统的损失。当火灾后恢复的主要目标是在火灾易发生态系统中保持生态系统服务恢复力时,建立以促进繁殖物种为重点的管理策略,可以帮助减轻火灾导致的供应能力损失。
    Fire-induced changes in vegetation composition due to fire-regime intensification are leading to alterations in ecosystem services that might threaten their future sustainability. Fire recurrence, in particular, could be a key driver shaping ecosystem service resilience in fire-prone ecosystems. This study evaluates the impact of fire recurrence, over twenty-four years, on the potential supply capacity of ten regulating, provisioning, and cultural services selected as critical services by stakeholders and experts. We assessed fire effects in four fire-prone landscapes dominated by species with different functional-traits response to fire (i.e., obligate seeder vs resprouter species). Trends in the potential supply capacity linked to fire recurrence were estimated by applying a supervised classification of Land Use and Land Cover (LULC) classes performed using Landsat imagery, associated to an ecosystem service capacity matrix adapted to the local socio-ecological context. In landscapes dominated by seeders, fire recurrence broke off the potential supply capacity of services traditionally associated to mature forest cover (i.e., the predicted probability of a decrease in the potential supply capacity of climate regulation, timber, wood fuel, mushroom production, tourism, landscape aesthetic, and cultural heritage occurred with high fire recurrence). In landscapes dominated by resprouter species, the effect of fire recurrence was partially buffered in the short-term after fire and no substantial differences in trends of change were found (i.e., equal predicted probability in the potential supply capacity of ecosystem services regardless of fire recurrence). We detected two new opportunities for ecosystems service supply associated to fire recurrence: livestock and honey production, especially in sites dominated by seeders. These findings provide valuable information aiming at recovering post-fire ecosystem service potential supply to partially counterbalance the loss in the socio-ecological system. When the main post-fire restoration goal is preserving ecosystem service resilience in fire-prone ecosystems, establishing management strategies focused on promoting resprouter species could aid mitigating the fire-driven loss of their supply capacity.
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  • 文章类型: Journal Article
    自2012年以来,“山体开挖与城市建设”(MECC)项目已在中国黄土高原广泛实施,通过平整黄土山顶以填充山谷,将沟渠转变为平坦的土地,以进行城市扩张。然而,这种前所未有的人类活动对其未知的潜在生态影响引起了广泛的争议。定量评估MECC项目对植被的影响是生态管理和恢复的关键。以黄土高原最大的MECC项目区为例,延安新区(YND),作为研究区域,本研究利用2009年至2023年的多时相归一化差异植被指数(NDVI)时间序列,调查了MECC项目实施前后植被动态的时空格局,并探讨了植被动态对大规模MECC项目的响应。结果表明,由于MECC项目,YND的植被动态表现出显著的时空异质性,受项目影响地区的植被破坏迅速,恢复缓慢。植被破坏仅发生在项目影响区域,其中84%的地区在10年内开始复苏,表明大规模MECC项目对区域植被的影响有限。植被动态与MECC项目具有很强的相关性,说明项目影响区植被的破坏和恢复主要受人为控制,这突出了有针对性的生态政策的重要性。具体来说,MECC项目在土地创建期间对植物种群结构造成了局部人为破坏,但是通过城市化实现了植被的再生和合理配置,逐步形成新的平衡生态环境。这些发现将有助于全面了解植被对此类大规模工程活动的反应,并帮助地方政府采取促进植被恢复的项目或政策。
    Since 2012, the \"Mountain Excavation and City Construction\" (MECC) project has been implemented extensively on the Loess Plateau of China, transforming gullies into flat land for urban sprawl by leveling loess hilltops to fill in valleys. However, this unprecedented human activity has caused widespread controversy over its unknown potential ecological impacts. Quantitative assessment of the impacts of the MECC project on the vegetation is key to ecological management and restoration. Taking the largest MECC project area on the Loess Plateau, Yan\'an New District (YND), as the study area, this study investigated the spatiotemporal pattern of vegetation dynamics before and after the implementation of the MECC project using a multitemporal normalized difference vegetation index (NDVI) time series from 2009 to 2023 and explored the response of vegetation dynamics to the large-scale MECC project. The results showed that the vegetation dynamics in the YND exhibited significant spatial and temporal heterogeneity due to the MECC project, with the vegetation in the project-affected areas showing rapid damage followed by slow recovery. Vegetation damage occurred only in the project-affected area, and 84 % of these areas began recovery within 10 years, indicating the limited impact of the large-scale MECC project on the regional vegetation. The strong correlation between vegetation dynamics and the MECC project suggested that the destruction and recovery of vegetation in the project-affected areas was mainly under anthropogenic control, which highlights the importance of targeted ecological policies. Specifically, the MECC project induced local anthropogenic damage to the plant population structure during the land creation period, but regeneration and rational allocation of the vegetation were achieved through urbanization, gradually forming a new balanced ecological environment. These findings will contribute to a full understanding of the response of vegetation to such large-scale engineering activities and help local governments adopt projects or policies that facilitate vegetation recovery.
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  • 文章类型: Journal Article
    一个关键的生理指标被称为水利用效率(WUE)(Foley等人。)评估水损失和碳吸收之间的权衡。碳和水的耦合机制,能量平衡,生态系统中的水文循环过程受到气候变化的影响,植被动态,和土地利用变化。在这项研究中,我们采用了森趋势分析,Mann-Kendall测试,土地利用转移矩阵,和多元线性回归分析,研究中国WUE的区域和时间动态及其对气候变化和土地利用转移变化的反应。根据调查结果,从2000年到2017年,中国的年平均WUE为0.998gC/mm·m2。在九大流域中,大陆盆地的WUE最低(0.529gC/mm·m2),西南流域的WUE最高(0.691gC/mm·m2),珠江流域和东南江流域的WUE最高(1.184gC/mm·m2)。海河流域和黄河流域是WUE高架的重点区域。森林有最大的WUE(1.134gC/mm·m2;在九个主要流域中),其次是灌木(1.109gC/mm·m2)。植被动态变化对WUE的影响高于气候变化和土地利用变化,当气候变化的贡献,植被动态变化,和WUE的土地利用变化是分开的。影响WUE变化的最大气候因子为VPD(28.04%±3.98%),而在植被动态因素中,NDVI(33.75%±6.90%)和LAI(22.21%±2.11%)的贡献最大。从高植被到低植被的过渡导致WUE相对下降,反之亦然,根据2000-2017年中国土地利用变化数据。土地利用变化对WUE变化产生了积极影响。这项研究的结果可能有助于中国选择合适的区域植物覆盖和可持续管理当地水资源。
    A crucial physiological indicator known as water use efficiency (WUE) (Foley et al.) assesses the trade-off between water loss and carbon uptake. The carbon and water coupling mechanisms, energy balance, and hydrological cycle processes in the ecosystem are impacted by climate change, vegetation dynamics, and land use change. In this study, we employed Sen trend analysis, the Mann-Kendall test, the land-use transfer matrix, and multiple linear regression analysis to investigate the regional and temporal dynamics of WUE and its reaction to climate change and land-use transfer changes in China. According to the findings, the annual average WUE in China was 0.998 gC/mm·m2 from 2000 to 2017. Of the nine major river basins, the Continental Basin had the lowest WUE (0.529 gC/mm·m2), and the Southwest River Basin had the highest WUE (0.691 gC/mm·m2), while the Pearl River Basin and the Southeast River Basin had the highest WUEs (1.184 gC/mm·m2). The Haihe River Basin and the Yellow River Basin were the key regions with elevated WUE. Forest had the greatest WUE (1.134 gC/mm·m2; out of the nine major river basins), followed by shrub (1.109 gC/mm·m2). Vegetation dynamics changes had a higher impact on WUE than climate change and land use changes, when the contributions of climate change, vegetation dynamics changes, and land use changes to WUE were separated. The largest climatic factor influencing variations in WUE was VPD (28.04% ± 3.98%), whereas among the vegetation dynamics factors, NDVI (33.75% ± 6.90%) and LAI (22.21% ± 2.11%) contributed the most. The transition from high to low vegetation cover led to a relative decrease in WUE, and vice versa, according to data on land use change in China from 2000 to 2017. Land use change made a positive impact to WUE change. The findings of this study may be helpful in China for choosing a suitable regional plant cover and managing local water resources sustainably.
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  • 文章类型: Journal Article
    了解植被生长的基本机制对于提高我们对植被生长如何响应其周围环境的认识具有重要意义。从而有利于预测未来的植被生长和指导环境管理。然而,人类对植被生长的影响,尤其是它的年内变化,仍然是一个知识差距。夜灯(NL)已被证明是表征人类活动的有效指标,但是使用季节性NL观测,对年度内植被生长的潜在改善知之甚少。为了解决这个差距,我们通过建立植被生长的多元线性回归模型(由归一化植被指数表示,NDVI)具有人为因素(此处由NL观测表明)和三个气候因素,即,温度,水供应,和太阳辐射使用主成分回归(PCR)方法。结果表明,NL观测显着改善了我们对全球年内植被生长的理解。模型可解释性,即,PCR模型的调整后的R2度量,考虑到NL观测值,平均相对提高了54%,中值为11%。这样的改善发生在整个调查像素的82%中。我们发现,在NL和NDVI趋势都很大的地区,模型解释能力的提高是显著的,除了两个趋势都是负面的。在国家一级,模型解释力的改进随着GDP的减少而增加,说明中等偏下收入国家比高收入国家有更大的改善。我们的发现强调了在植被生长中考虑人类活动(此处由NL表示)的重要性,为解释年内植被生长提供了新的见解。
    Understanding the underlying mechanism of vegetation growth is of great significance to improve our knowledge of how vegetation growth responds to its surrounding environment, thereby benefiting the prediction of future vegetation growth and guiding environmental management. However, human impacts on vegetation growth, especially its intra-annual variability, still represent a knowledge gap. Night Lights (NL) have been demonstrated as an effective indicator to characterize human activities, but little is known about the potential improvement of intra-annual vegetation growth using seasonal NL observations. To address this gap, we investigated and quantified the explainability improvement of intra-annual vegetation growth by establishing a multiple linear regression model for vegetation growth (indicated by Normalized Difference Vegetation Index, NDVI) with human factor (indicated by NL observations here) and three climatic factors, i.e., temperature, water availability, and solar radiation using the Principal Components Regression (PCR) method. Results indicate that NL observations significantly improve our understanding of intra-annual vegetation growth globally. Model explainability, i.e., adjusted R2 metric of the PCR model, was comparatively improved by 54 % on average with a median value of 11 % when taking NL observations into consideration. Such improvement occurred in 82 % of the whole investigation pixels. We found that the improvement of model explanatory power was significant in regions where both NL and NDVI trends were large, except for the case where both of their trends were negative. At the country-level, the improvement of model explanatory power increases as GDP decreases, illustrating a greater improvement in a lower middle-income country than that in a high-income country. Our findings emphasize the importance of considering human activities (indicated by NL here) in vegetation growth, offering novel insights into the explanation of intra-annual vegetation growth.
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  • 文章类型: Journal Article
    这项研究评估了2000年至2023年巴基斯坦植被动态与气候变化之间的关系。利用高分辨率Landsat数据进行归一化植被指数(NDVI)评估,与来自CHIRPS和ERA5数据集的气候变量相结合,我们的方法利用谷歌地球引擎(GEE)进行高效处理。它结合了统计方法,包括线性回归,Mann-Kendall趋势测试,森的斜率估计器,偏相关,和交叉小波变换分析。这些发现强调了NDVI的显著时空变化,平均每年增加0.00197(p<0.0001)。这一积极趋势伴随着降水量增加0.4801毫米/年(p=0.0016)。相比之下,我们的分析记录到温度略有下降(-0.01011°C/年,p<0.05)和太阳辐射减少(-0.27526W/m2/年,p<0.05)。值得注意的是,交叉小波变换分析强调了NDVI与气候因子之间的显著相干性,揭示了同步波动和明显滞后关系的时期。这项分析特别强调了降水是植被生长的主要驱动力,说明了它在巴基斯坦各个地区的关键影响。此外,分析揭示了不同的季节模式,表明植被健康在季风季节反应最灵敏,与季节性降水的峰值密切相关。我们的调查揭示了巴基斯坦植被健康与气候因素之间的复杂关联,不同地区的差异。通过交叉小波分析,我们已经确定了不同的相干性和相位关系,突出了气候驱动因素对植被模式的关键影响。这些见解对于制定区域气候适应战略以及在面对持续的气候变化时告知可持续的农业和环境管理实践至关重要。
    This study assesses the relationships between vegetation dynamics and climatic variations in Pakistan from 2000 to 2023. Employing high-resolution Landsat data for Normalized Difference Vegetation Index (NDVI) assessments, integrated with climate variables from CHIRPS and ERA5 datasets, our approach leverages Google Earth Engine (GEE) for efficient processing. It combines statistical methodologies, including linear regression, Mann-Kendall trend tests, Sen\'s slope estimator, partial correlation, and cross wavelet transform analyses. The findings highlight significant spatial and temporal variations in NDVI, with an annual increase averaging 0.00197 per year (p < 0.0001). This positive trend is coupled with an increase in precipitation by 0.4801 mm/year (p = 0.0016). In contrast, our analysis recorded a slight decrease in temperature (- 0.01011 °C/year, p < 0.05) and a reduction in solar radiation (- 0.27526 W/m2/year, p < 0.05). Notably, cross-wavelet transform analysis underscored significant coherence between NDVI and climatic factors, revealing periods of synchronized fluctuations and distinct lagged relationships. This analysis particularly highlighted precipitation as a primary driver of vegetation growth, illustrating its crucial impact across various Pakistani regions. Moreover, the analysis revealed distinct seasonal patterns, indicating that vegetation health is most responsive during the monsoon season, correlating strongly with peaks in seasonal precipitation. Our investigation has revealed Pakistan\'s complex association between vegetation health and climatic factors, which varies across different regions. Through cross-wavelet analysis, we have identified distinct coherence and phase relationships that highlight the critical influence of climatic drivers on vegetation patterns. These insights are crucial for developing regional climate adaptation strategies and informing sustainable agricultural and environmental management practices in the face of ongoing climatic changes.
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  • 文章类型: Journal Article
    自发现以来,太阳诱导的叶绿素荧光(SIF)已用于表征植被光合作用,是监测植被动态的有效工具。它对气象干旱的反应增强了我们对面临缺水的植物的生态后果和适应机制的理解,为更有效的资源管理和减缓气候变化的努力提供信息。本研究调查了SIF的时空格局,并研究了黄河流域(YRB)植被SIF对气象干旱的响应。研究结果表明,整个黄河流域的SIF从东南到西北逐渐下降,总体增加-从2001年的0.1083Wm-2μm-1sr-1增加到2019年的0.1468Wm-2μm-1sr-1。大约96%的YRB表现出SIF上升趋势,这些领域的75%达到统计意义。4个月时间尺度的标准化降水蒸散指数(SPEI-4),基于梁-克莱曼信息流方法,被确定为最合适的干旱指数,巧妙地描述影响SIF变化的因果关系。随着干旱加剧,SPEI-4指数明显偏离基线,导致SIF值降至最低值;随后,随着干旱的减轻,它倾向于基线,SIF值开始逐渐增加,最终恢复到接近年度最大值。关键发现是SIF与SPEI的变异性在早期生长季节相对明显,与草原和农田相比,森林表现出更好的恢复力。植被SIF对SPEI的响应性,有利于建立有效的干旱预警系统,促进水资源的合理规划,从而减轻气候变化的影响。
    Solar-induced chlorophyll fluorescence (SIF) has been used since its discovery to characterize vegetation photosynthesis and is an effective tool for monitoring vegetation dynamics. Its response to meteorological drought enhances our comprehension of the ecological consequences and adaptive mechanisms of plants facing water scarcity, informing more efficient resource management and efforts in mitigating climate change. This study investigates the spatial and temporal patterns of SIF and examines how vegetation SIF in the Yellow River Basin (YRB) responds to meteorological drought. The findings reveal a gradual southeast-to-northwest decline in SIF across the Yellow River Basin, with an overall increase-from 0.1083 W m-2μm-1sr-1 in 2001 to 0.1468 W m-2μm-1sr-1 in 2019. Approximately 96% of the YRB manifests an upward SIF trend, with 75% of these areas reaching statistical significance. The Standardized Precipitation Evapotranspiration Index (SPEI) at a time scale of 4 months (The SPEI-4), based on the Liang-Kleeman information flow method, is identified as the most suitable drought index, adeptly characterizing the causal relationship influencing SIF variations. As drought intensified, the SPEI-4 index markedly deviated from the baseline, resulting in a decrease in SIF values to their lowest value; subsequently, as drought lessened, it gravitated towards the baseline, and SIF values began to gradually increase, eventually recovering to near their annual maximum. The key finding is that the variability of SIF with SPEI is relatively pronounced in the early growing season, with forests demonstrating superior resilience compared to grasslands and croplands. The responsiveness of vegetation SIF to SPEI can facilitate the establishment of effective drought early warning systems and promote the rational planning of water resources, thereby mitigating the impacts of climate change.
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  • 文章类型: Journal Article
    基于过程的森林模型结合了生物,物理,和化学过程的理解,以模拟森林动态作为系统的新兴属性。因此,它们是研究气候变化对森林生态系统影响的宝贵工具。具体来说,它们允许测试有关长期生态系统动态的假设,并提供评估气候情景对未来森林发展的影响的手段。因此,在过去的几十年中,已经进行了许多本地规模的模拟研究,以评估气候变化对森林的影响。这些研究应用了适合当地条件的最佳可用模型,由当地专家进行参数化和评估。然而,迄今为止,这个关于气候变化应对的知识宝库仍然没有得到充分的探索,因为缺少一个一致和统一的本地模型模拟数据集。这里,我们的目标是(i)在一个共同的数据库中汇编现有的关于欧洲气候变化下森林发展的本地模拟,(Ii)将它们与一组共同的输出变量相协调,和(iii)为每个模拟位置提供辅助环境变量的标准化向量,以帮助后续调查。我们的欧洲标准和景观级森林模拟数据集包含超过110万次模拟运行,代表遍布欧洲的13,000多个独特地点的1.35亿次模拟年。协调数据,以一致地描述林分结构(主导高度)方面的森林发展,组成(优势种,混合物种),和功能(叶面积指数)。提供的辅助变量包括一致的每日气候信息(温度、降水,辐射,蒸汽压力不足)以及当地现场条件信息(土壤深度,土壤物理性质,土壤持水能力,植物可用氮)。本数据集有助于跨模型和位置的分析,为了更好地利用本地模拟中包含的有价值的信息来提供大规模的政策支持,以及促进对气候变化对欧洲森林生态系统影响的更深入了解。
    Process-based forest models combine biological, physical, and chemical process understanding to simulate forest dynamics as an emergent property of the system. As such, they are valuable tools to investigate the effects of climate change on forest ecosystems. Specifically, they allow testing of hypotheses regarding long-term ecosystem dynamics and provide means to assess the impacts of climate scenarios on future forest development. As a consequence, numerous local-scale simulation studies have been conducted over the past decades to assess the impacts of climate change on forests. These studies apply the best available models tailored to local conditions, parameterized and evaluated by local experts. However, this treasure trove of knowledge on climate change responses remains underexplored to date, as a consistent and harmonized dataset of local model simulations is missing. Here, our objectives were (i) to compile existing local simulations on forest development under climate change in Europe in a common database, (ii) to harmonize them to a common suite of output variables, and (iii) to provide a standardized vector of auxiliary environmental variables for each simulated location to aid subsequent investigations. Our dataset of European stand- and landscape-level forest simulations contains over 1.1 million simulation runs representing 135 million simulation years for more than 13,000 unique locations spread across Europe. The data were harmonized to consistently describe forest development in terms of stand structure (dominant height), composition (dominant species, admixed species), and functioning (leaf area index). Auxiliary variables provided include consistent daily climate information (temperature, precipitation, radiation, vapor pressure deficit) as well as information on local site conditions (soil depth, soil physical properties, soil water holding capacity, plant-available nitrogen). The present dataset facilitates analyses across models and locations, with the aim to better harness the valuable information contained in local simulations for large-scale policy support, and for fostering a deeper understanding of the effects of climate change on forest ecosystems in Europe.
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  • 文章类型: Journal Article
    在降水量<400毫米的干旱和半干旱地区,蒸散量(ET)约占降水量的80%,是流域的主要用水户。然而,近年来的植被绿化将通过影响根系中的土壤水分来增加ET并加剧该地区的干旱。植被变化是区域性和空间异质性的,因此,为了表征植被动态下的ET变化,有必要扩大ET模拟的空间尺度。然而,广泛使用的蒸散模拟模型,例如Shuttleworth-Wallace模型(SW模型),在反映垂直(即,土壤深度)和水平(即,植被动态)方向。在现场抽样的基础上,构建了结构方程模型(SEM),我们发现植被动态不仅直接影响蒸散,但也间接影响不同深度的土壤水分。在此基础上,我们定义了草地植被带的加权系数为0.85和0.15,林草散布区0.3、0.15、0.20、0.25、0.10,林地为0.20、0.55、0.25,分别,基于SEM结果。在不同的植被类型区域内定义了不同的土壤水分加权系数,改进的SW模型称为S-W-α。将仿真结果与实测数据进行比较,S-W-α将该区域的ET模拟精度提高了33.92%,并且改进的ET空间趋势可以响应植被的动态变化。用改进的S-W-α替换块式使用TOPMODEL和Muskingum-Cunge方法模式(BTOP模型)中的ET模块,结果表明,改进模型的仿真精度提高了25%,在费率期和验证期内,纳什都高于75%,实现了模型从点尺度到流域尺度的扩展。改进后的模型可为生态脆弱地区的蒸散模拟和生态系统健康管理提供技术支持。
    In arid and semi-arid areas with <400 mm of precipitation, evapotranspiration (ET) accounts for about 80% of precipitation and is the main water consumer in the watershed. However, vegetation greening in recent years will increase ET and exacerbate the aridity of the area by affecting soil moisture in the root system. Vegetation changes are regional and spatially heterogeneous, therefore, in order to characterize ET changes under vegetation dynamics, it is necessary to expand the spatial scale of ET simulation. However, widely used evapotranspiration simulation models, such as the Shuttleworth-Wallace model (SW model), are deficient in reflecting the direct and indirect effects of vertical (i.e., soil depths) and horizontal (i.e., vegetation dynamics) directions. Based on field sampling and constructed structural equation model (SEM), we found that vegetation dynamics affect evapotranspiration not only directly, but also indirectly by affecting soil moisture at different depths. On this basis, we defined the weighting coefficients of 0.85 and 0.15 for grassland vegetation zones, 0.3, 0.15, 0.20, 0.25, 0.10 for forest-grass interspersed zones, and 0.20, 0.55, 0.25 for forested zones, respectively, based on the SEM results. Different soil moisture weighting coefficients were defined within different vegetation type zones and the improved SW model is called S-W-α. Comparing the simulation results with the measured data, S-W-α improved the ET simulation accuracy in this region by 33.92% and the improved ET spatial trend can respond to the dynamic changes of vegetation. Replacing the ET module in the Block-wise use of TOPMODEL and Muskingum-Cunge method mode (BTOP model) with the modified S-W-α, the results show that the simulation accuracy of the improved model is increased by 25%, and the Nash is higher than 75% for both the rate period and the validation period, which realizes the extension of the model from the point scale to the basin scale. The modified model may provide technical support for simulation of evapotranspiration and management of ecosystem health in ecologically fragile areas.
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  • 文章类型: Journal Article
    评估气候变化和人类活动的相对重要性对于制定区域土地利用的可持续管理政策非常重要。在这项研究中,多个遥感数据集,即CHIRPS(气候危害组红外降水与站数据)降水,MODIS地表温度(LST),增强植被指数(EVI),潜在蒸散量(PET),土壤水分(SM),WorldPop,并对夜间光线进行了分析,以研究气候变化(CC)和区域人类活动(HA)对2000年至2022年印度东部植被动态的影响。气候和人为因素的相对影响是在非参数统计的基础上评估的,即曼-肯德尔和森的斜率估计器。降水和LST的显着空间和海拔依赖性变化是明显的。高海拔地区的年平均气温升高(0.22°C/年,p<0.05)和过去二十年冬季降水减少,而西孟加拉邦北部和西南部地区的年平均降水量增加(17.3毫米/年,p<0.05)和轻微的降温趋势。温度和降水趋势共同影响EVI分布。虽然LST和EVI之间存在负空间相关性,降水与EVI呈正相关且较强(R2=0.83,p<0.05)。相关的水文气候参数是EVI的有力驱动因素,由此,在西南地区的PET导致显著较低的SM。CC和HA对EVI的相对重要性也在空间上变化。在加尔各答主要城市附近,并得到夜间光照和人口密度数据的证实,植被覆盖的变化显然由HA(87%)主导。相比之下,在该州较高的北部地区以及东南部,CC成为EVI的主要驱动因素(70-85%)。我们的发现为整个州脆弱的社会水文气候系统的未来可持续性提供了政策依据。
    Assessing the relative importance of climate change and human activities is important in developing sustainable management policies for regional land use. In this study, multiple remote sensing datasets, i.e. CHIRPS (Climate Hazard Group InfraRed Precipitation with Station Data) precipitation, MODIS Land Surface Temperature (LST), Enhanced Vegetation Index (EVI), Potential Evapotranspiration (PET), Soil Moisture (SM), WorldPop, and nighttime light have been analyzed to investigate the effect that climate change (CC) and regional human activities (HA) have on vegetation dynamics in eastern India for the period 2000 to 2022. The relative influence of climate and anthropogenic factors is evaluated on the basis of non-parametric statistics i.e., Mann-Kendall and Sen\'s slope estimator. Significant spatial and elevation-dependent variations in precipitation and LST are evident. Areas at higher elevations exhibit increased mean annual temperatures (0.22 °C/year, p < 0.05) and reduced winter precipitation over the last two decades, while the northern and southwest parts of West Bengal witnessed increased mean annual precipitation (17.3 mm/year, p < 0.05) and a slight cooling trend. Temperature and precipitation trends are shown to collectively impact EVI distribution. While there is a negative spatial correlation between LST and EVI, the relationship between precipitation and EVI is positive and stronger (R2 = 0.83, p < 0.05). Associated hydroclimatic parameters are potent drivers of EVI, whereby PET in the southwestern regions leads to markedly lower SM. The relative importance of CC and HA on EVI also varies spatially. Near the major conurbation of Kolkata, and confirmed by nighttime light and population density data, changes in vegetation cover are very clearly dominated by HA (87%). In contrast, CC emerges as the dominant driver of EVI (70-85%) in the higher elevation northern regions of the state but also in the southeast. Our findings inform policy regarding the future sustainability of vulnerable socio-hydroclimatic systems across the entire state.
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