湿地植被生物量是衡量湿地生态系统健康状况的重要指标，其估算方法研究一直是湿地领域的研究热点。传统的植被地上生物量测算主要依靠样方调查，对于复杂湿地生态系统存在一定的局限，而随着遥感估算方法的发展，湿地植被生物量的研究实现了长期、动态且大尺度的监测。本文在查阅和分析国内外相关文献的基础上，以遥感数据为主要数据源，阐述了基于光学、合成孔径雷达（SAR）、激光雷达（Lidar）以及多源协同遥感数据反演湿地植物地上生物量的理论基础及计算原理，总结了其研究进展，分析了其适用性，继而从湿地植被生物量监测类型的拓展、多源遥感数据的融合、遥感数据的同化以及遥感机理模型发展等方面出发，对植物生物量研究的发展趋势进行了深入探讨。

Wetland vegetation biomass is a key factor to measure the fitness of wetland ecosystem. How to estimate biomass is one of the most hotspot topics in the wetland research. The general methods of estimating the vegetation aboveground biomass mainly depended on quadrat, which is limited when dealing with complicated wetland ecosystem. With the progress of remote sensing, the observation of wetland vegetation biomass has turned into a long-lasting, dynamic and largescale manner. After analyzing a large amount of related references, we illustrated theoretical basis and calculation principle of the estimation of wetland vegetation aboveground biomass, based on optical remote sensing image, SAR data, Lidar data and multisource, using remote sensing data as data source. We summarized the research progress, analyzed the applicability and limitation of the methods. Then, we described the developing trend in study on wetland vegetation biomass in several aspects, such as expanding the monitoring type of wetland vegetation biomass, integrating the multisource remote sensing data, assimilating the remote sensing data and developing the remote sensing mechanism models.

基于Sentinel-2植被指数,应用回归分析法分析了鄱阳湖碟形子湖泊（常湖池）的苔草（Carex）群落生物量与植被指数的关系,并探讨了高程水位和气温变化对其的影响。研究结果表明：（1）10种常用的植被指数中,土壤调节植被指数（Soil Adjusted Vegetation Index,SAVI）是常湖池苔草春季生长中后期（3月22日至5月5日）地上生物量估算的最佳植被指数,SAVI构建的三次多项式是常湖池苔草地上生物量最优遥感估算模型,其均方根误差为73.91 g/m²,预测吻合度为71.90%,苔草生物量分布总体表现为自湖心到湖岸逐渐增加。（2）3月22日（春季苔草生长中期）和5月5日（春季苔草生长后期）苔草的地上总生物量分别为1.06×10⁵ kg和3.28×10⁵ kg,单位面积苔草生物量分别为77.56 g/m²和208.44 g/m²,这与鄱阳湖其他子湖单位面积生物量一般低于300 g/m²相一致。（3）常湖池苔草生长受高程、水位和气温多重要素综合影响。3月底常湖池13.47 m高程（黄海高程,参考星子站水位,下同）以下苔草植株矮小,生物量积累较少;13.47 m高程以上区域受前期低温胁迫,生物量增长缓慢。随着气温回暖,出露区域的苔草生物量逐渐积累,并随高程增加而增长。

The relationship between community biomass of spring <em>Carex</em> and Sentinel-2 derived vegetation indices (VIs) was analyzed using regression analysis in one of dish-shaped lakes (i.e. Changhuchi) of Poyang Lake. In addition, the effects of elevation, water level, and temperature changes on community biomass were also examined. The results showed that: (1) Among the 10 commonly used VIs, Soil Adjusted Vegetation Index (SAVI) is the most appropriate VI for spring <em>Carex</em> biomass estimation of Changhuchi Lake from March 22^nd to May 5^th. The cubic polynomial parameterized by SAVI was an optimal biomass estimation model with the root mean square error of 73.91 g/m² and the predicted coincidence of 71.90%. Spatially, the biomass of spring <em>Carex</em> community generally increased from the central part to lakeshore. (2) On March 22^nd (normally in the middle of growth) and May 5^th (the end of growth), the total aboveground biomass of spring <em>Carex</em> grass was 1.06&#x000D7;10⁵ kg and 3.28&#x000D7;10⁵ kg, respectively, along with the biomass per unit area of 77.56 g/m² and 208.44 g/m², respectively. Our estimates were basically in line with the previously reported upper limit of 300 g/m² in other sub-lakes within Poyang Lake. (3) The growth of spring <em>Carex</em> in Changhuchi Lake is jointly affected by elevation, water level and air temperature. At the end of March, the area below 13.47 m (Yellow Sea Datum) in Changhuchi Lake is generally flooded, hence with dwarf plants and less biomass accumulation. For the regions above 13.47 m, the biomass is also at a low level due to low temperature and short dormancy. As the temperature rises, the biomass of spring <em>Carex</em> in the whole exposed area of Changhuchi Lake gradually accumulates with larger per unit area biomass at the higher elevations.

在气候变化、人类活动导致流域水循环改变、极端水文事件频发的背景下,从江湖关系角度分析鄱阳湖水文节律变化规律,对于维护流域水安全具有重要意义。利用1951~2011年湖区4站及湖口站水文实测资料,采用统计分析及水文过程分析方法,对湖泊水文节律在2003~2011年与1980~2002年发生的显著变化及其与长江水量交换的关系进行研究。结果表明：2003~2011年,湖泊因涨、退水阶段水位均偏低,进而枯水阶段延长,同时丰水阶段缩短,湖泊水文节律整体呈现洪旱急转情势;近年来江湖水量交换的变化是造成湖泊水文节律变化的主要原因。

Watershed hydrological cycle has been changed along with the intensifying frequency of extreme water events due to the influence of climate change and human activities. Poyang Lake, the largest freshwater lake in China, is a lake naturally connected with the Changjiang River. The complicated river-lake interactions impact the hydrological rhythm of lake, which will further influence water security associated with flood control, drinking water usage, water pollution and water ecology in the lake basin. In the case, it is of great importance for maintaining watershed water security to understand the characteristics of hydrological rhythm variation in terms of river-lake interactions. In this study, temporal variation of hydrological rhythm in Poyang Lake and the associated water exchange with the Changjiang River were analyzed based on the measured hydrological data of 4 gauge stations in Poyang Lake area along with other data from the Hukou station at the intersection between the Changjiang River and Poyang Lake in 1951-2011. The major findings are shown as follows: the span of dry season increased since water level remains low in November and April. Meanwhile, the span of flood season decreased in 2000s. The lower water level in rising season and retreating season make Poyang Lake rising later but falling earlier than they did in 1980-2002, thus shortening the conversion time of the lake from flood situation to dry situation. Further, the peak flow in the annual hydrograph has been shifted. The primary cause of hydrological rhythm variation is the water exchange between the main stream of the Changjiang River and Poyang Lake. In 2000s, changes in the water level of the Changjiang River altered the interaction between the river and Poyang Lake through the slope of water surface, disturbing the lake basin hydrological processes and resulted in disordering of hydrological rhythm in Poyang Lake. The increasing discharge from the lake to the river in retreating season lead to the lake enter dry season earlier. And the declining water level of Changjiang River in rising season lead to the addition of lake water continued to leak river, thus the lake rose slowly. For the reasons given above, the variation of water supplement of Poyang Lake on the Changjiang River mainstream in 2000s altered the hydrological rhythm in Poyang Lake. Results of this study improve our understanding of Poyang Lake hydrological rhythm consequences of river-lake relationship changes, and it provides knowledge for long-term planning for effectively restoring nature's innate rhythms for sustainability and productivity in the Poyang Lake Basin. In addition, the results will help further explore the coordinate and healthy river-lake relationships.

针对鄱阳湖湿地植被长期变化的科学问题,本文基于谷歌地球引擎(GEE)遥感大数据平台和CART分类回归树算法提取鄱阳湖2000—2017年涨水期、丰水期、退水期和枯水期的年时序植被分布范围,阐明其时空变化特征;在此基础上,结合水位数据分析湿地植被与水文情势变化之间的响应关系。结果表明,①2000—2017年,枯水期、涨水期、丰水期和退水期鄱阳湖湿地植被平均面积分别为846.35、679.03、172.35、508.63km²。②2000—2017年,不同水位期鄱阳湖湿地植被总面积均呈增加趋势,并有向湖心演变的趋势。③鄱阳湖植被面积受水位影响显著,水位与植被面积呈负相关,降水异常(如极端降水或严重干旱)是导致植被面积明显偏离平均面积的主导因素。本文结论有助于鄱阳湖湿地生态系统的健康诊断,对鄱阳湖湿地保护和修复政策的制定具有科学参考意义。

In order to solve the scientific problem of long-term vegetation evolution in Poyang Lake, this paper extracts the annual vegetation distribution range of the rising water period, the high water period, the receding water period and the low water period from 2000 to 2017 based on the Google Earth Engine(GEE) remote sensing big data platform and CART classification regression tree algorithm, and expounds the spatio-time characteristics of the vegetation change. On this basis,It combines with water level data, the response relationship between wetland vegetation and hydrological regime is analyzed. The results show that: ①The average vegetation area of Poyang Lake wetland during the low water period, the rising water period, the high water period and the receding water period from 2000 to 2017 is 846.35km²、679.03km²、172.35km²、508.63km². ②From 2000 to 2017, the total vegetation area of Poyang Lake wetland increased at different water levels and tended to evolve towards the center of the lake. ③The vegetation area of Poyang Lake is significantly affected by water level, and the water level is negatively correlated with the vegetation area. The precipitation anomaly (such as extreme precipitation or severe drought) is the main factor leading to the significant deviation of the average vegetation area. The results of this study have scientific reference significance for the formulation of wetland protection and restoration policies in Poyang Lake.

水淹状况是湿地植被动态的重要影响因素。该研究基于谷歌地球引擎(GEE)平台, 利用2000-03-01至2020-02-29所有覆盖研究区域的MODIS遥感影像数据, 分析20年间水淹频率(IF)、增强型植被指数(EVI)的时空变化以及湿地植被对IF变化的响应, 得出以下结论: (1) 20年来鄱阳湖水文节律发生了明显改变, 高IF (IF &gt; 75%)水域面积呈现下降趋势, 从2000年1 435.3 km²下降至2019年的510.25 km², 降幅为64.45%; (2)区域平均EVI呈显著上升趋势, 植被扩张主要集中在中部IF下降区域; (3)分析不同总水淹频率区域中平均EVI年际变化, 发现EVI与水淹状况的变化趋势相似, 2009年之后鄱阳湖水域面积萎缩趋势缓解, EVI增长速度出现下降; (4)鄱阳湖湿地植被主要沿水域面积萎缩方向扩张, 基于像元统计20年间IF与EVI的变化趋势, 发现它们在空间分布上高度吻合, 这种空间异质性进一步证实水淹状况起到调节植被动态变化的作用。

<p id="p00010"><i><strong>Aims</strong></i> Inundation frequency (<i>IF</i>) is an important influencing factor on dynamics of wetland vegetation. This study analyzed the temporal and spatial variations of <i>IF</i> and enhanced vegetation index (<i>EVI</i>) of wetland vegetation and their correlation in Poyang Lake, so as to maintain the stability of wetland ecosystem.</p> <p id="p00015"><i><strong>Methods</strong></i> In view of the significant seasonal changes of Poyang Lake, its impact on wetland vegetation needs to be analyzed with a high temporal resolution method. Based on MODIS image data from 2000-03-01 to 2020-02-29, this study mapped the annual water inundation frequency of Poyang Lake, analyzed the temporal and spatial variations of <i>EVI</i> under different flooding conditions, and explored the response of <i>EVI</i> of wetland vegetation to changes in flooding conditions.</p> <p id="p00020"><i><strong>Important findings</strong></i> The following conclusions are drawn: (1) The hydrological rhythm of Poyang Lake has changed significantly in the past 20 years. The water area with high inundation frequency (<i>IF &gt;</i>75%) decreased from 1 435.3 km² in 2000 to 510.25 km² in 2019, with a decrement of 64.45%. (2) The regional average <i>EVI</i> showed a significant upward trend. Vegetation expansion was mainly concentrated in the middle region of Poyang Lake which was also the main region of<i> IF</i> declining. (3) By analyzing the changes of average<i> EVI</i> value under different total <i>IF</i> regions, it was found that the variation trend of <i>IF</i> was similar to that of <i>EVI</i>. After 2009, the shrinking trend of the Poyang Lake water area was alleviated, and the growth rate of <i>EVI</i> decreased. (4) In the past 20 years, the changing trend of <i>IF</i> and <i>EVI</i> in Poyang Lake was highly consistent in spatial distribution. Wetland vegetation was mainly expanded along the decreasing direction of water area. This spatial heterogeneity further confirms that hydrological variation plays a role in regulating vegetation dynamics.</p>