On the use of leaf water to determine plant water source: A proof of concept

Source water apportionment studies using the dual isotopes of oxygen and hydrogen have revolutionized our understanding of ecohydrology. But despite these developments—mostly over the past decade—many technical problems still exist in terms of linking xylem water to its soil water and groundwater sources. This is mainly due to sampling issues and possible fractionation of xylem water. Here we explore whether or not leaf water alone can be used to quantify the blend of rainfall event inputs from which the leaf water originates. Leaf water has historically been avoided in plant water uptake studies due to the extreme fractionation processes at the leaf surface. In our proof of concept work we embrace those processes and use the well-known Craig and Gordon model to map leaf water back to its individual precipitation event water sources. We also employ a Bayesian uncertainty estimation approach to quantify source apportionment uncertainties. We show this using a controlled, vegetated lysimeter experiment where we were able to use leaf water to correctly identify the mean seasonal rainfall that was taken up by the plant, with an uncertainty typically within ± 1‰ for δ¹⁸O. While not appropriate for all source water studies, this work shows that leaf water isotope composition may provide a new, relatively un-intrusive method for addressing questions about the plant water source.     

Effects of Larval Settlement and Post-Settlement Mortality on the Distribution Pattern and Abundance of the Spirorbid Tube Worm Neodexiospira brasiliensis (Grube) (Polychaeta) Living on Seagrass Leaves

Abstract. The role of larval settlement, post-settlement mortality and competition with a red algae in determining the patterns of abundance and distribution of the spirorbid tube worm Neodexiospira brasiliensis (Grube) (Polychaeta: Spirorbidae) on leaves of three seagrass species: Zostera marina Linnaeus, Zostera asiatica Miki and Phyllospadix iwatensis Makino were examined in Aininkap, Akkeshi Bay, Akkeshi, Hokkaido, Japan. Field collections of seagrass shoots were made at about 1-week intervals. The density of newly settled larvae (< 0.3 mm in tube diameter) increased significantly on Z. asiatica and P. iwatensis , but not on Z. marina during the sampling period. It was highest on Z. asiatica among the three seagrass species, followed by P. iwatensis and Z. marina . Newly settled larvae occurred more on the basal part of younger leaves of each seagrass species. Mortality tended to be high on Z. marina , followed by Z. asiatica and P. iwatensis , although the differences were not great. Size-specific mortality showed the existence of high mortality in early post-settlement stages on Z. asiatica and P. iwatenisis . Relatively high mortality was also suffered by individuals with a tube diameter over 1.5 mm. Growth in tube diameter of N. brasiliensis was slower on P. iwatensis than on the other two seagrasses. The effect of a calcareous red algae on larval settlement was investigated with removal experiments; however, no effect of red algae was detected. Patterns in the distribution and abundance of N. brasiliensis on leaves of three seagrass species resulted from the heterogeneity of larval settlement rather than from post-settlement mortality or competition with red algae. Different densities of larval settlement among the three seagrass species or on a leaf are likely to relate to larval behaviour, such as negative phototaxis.     

基于网络药理学探讨荷叶抗非酒精性脂肪肝的作用机制

目的：基于网络药理学探讨荷叶抗非酒精性脂肪肝（NAFLD）的作用机制。方法：利用TCMSP平台和Swiss Target Prediction 等数据库搜集荷叶活性成分和作用靶点。通过GeneCard、GenCLiP3数据库获取NAFLD的相关靶点,利用Cytoscape 3.8.2 软件构建荷叶成分-疾病-靶点蛋白网络。使用STRING数据库和Cytoscape 3.8.2 软件构建蛋白质-蛋白质相互作用（PPI）网络,进行基因本体（GO）功能与京都基因与基因组百科全书（KEGG）通路富集分析。结果：获得荷叶活性成分15种,潜在靶点441个,疾病相关靶点1316个,成分-疾病-靶点161个。PPI网络显示,丝氨酸/苏氨酸蛋白激酶、白细胞介素6、肿瘤抑制基因 p53、血管内皮生长因子、肿瘤坏死因子等靶点与荷叶抗NAFLD的关系最密切。GO功能主要有药物的反应、凋亡过程的负调控、胞液、核浆、细胞质、线粒体酶结合、细胞因子活性、转录因子结合等。KEGG通路主要涉及乙型肝炎、癌症的途径、肿瘤坏死因子（TNF）信号通路、Toll样受体信号通路、NOD样受体信号通路、缺氧诱导因子-1信号通路等。结论：荷叶通过调控161个靶点参与TNF信号通路、Toll样受体信号通路、NOD样受体信号通路等作用于NAFLD。     

科尔沁沙地沙质草地与固定沙丘植物群落结构对极端干旱的响应

为了探究沙地植物群落结构特征对极端干旱的响应,通过野外模拟试验开展了极端干旱(生长季减雨60％与干旱60 d)对沙质草地和固定沙丘植物群落丰富度、地上生物量和叶性状等群落结构特征影响的研究.结果表明:(1)生境变化对植物群落地上生物量和叶干物质含量(LDMC)具有显著影响(P＜0.05),草地地上生物量和LDMC显著高...     

地表覆盖分类数据对区域森林叶面积指数反演的影响

以江西省吉安市为研究区,将5种全球地表覆盖分类数据(包括美国地质调查局(USGS)、马里兰大学(UMD)和波士顿大学(BU)生成的3套数据和欧洲生成的2套数据)以及由TM影像生成的区域地表覆盖分类数据,分别与MODIS1km反射率资料结合,利用基于4尺度几何光学模型的LAI反演方法生成研究区的LAI。在1km和4km两种尺度上将反演的LAI与TM资料生成的LAI进行比较,评价地表覆盖分类数据对LAI反演结果的影响。结果表明,TM和欧洲太空局的GLOBCOVER地表覆盖分类数据用于反演LAI的结果较好,在1km尺度上,反演的LAI与统计模型估算的TMLAI相关的R2分别为0.44和0.40,在4km尺度上的R2分别为0.57和0.54;其次为波士顿大学的MODIS地表覆盖分类数据,据其反演的LAI与TMLAI相关的R2在1km和4km尺度上分别为0.38和0.51;而马里兰大学的UMD和欧洲的GLC2000地表覆盖分类数据会导致反演的LAI存在较大误差,据其反演的LAI与TMLAI之间的一致性较差,在1km和4km两种尺度上平均偏低20%左右;LAI的反演结果对聚集度系数具有强的敏感性。该研究表明,为了提高区域/全球LAI反演精度,需要有高质量的地表覆盖分类数据。     

海草凋落叶的溶解有机物的释放及其生物地球化学意义

Dissolved organic matter(DOM) represents a significant source of nutrients that supports the microbial-based food web in seagrass ecosystems. However, there is little information on how the various fractions of DOM from seagrass leaves contributed to the coastal biogeochemical cycles. To address this gap, we carried out a 30-day laboratory chamber experiment on tropical seagrasses Thalassia hemprichii and Enhalus acoroides. After 30 days of incubation, on average 22% carbon(C), 70% nitrogen(N) and 38% phosphorus(P) of these two species of seagrass leaf litter was released. The average leached dissolved organic carbon(DOC), dissolved organic nitrogen(DON) and dissolved organic phosphorus(DOP) of these two species of seagrass leaf litter accounted for 55%, 95% and 65% of the total C, N and P lost, respectively. In the absence of microbes, about 75% of the total amount of DOC, monosaccharides(MCHO), DON and DOP were quickly released via leaching from both seagrass species in the first 9 days. Subsequently, little DOM was released during the remainder of the experiment. The leaching rates of DOC, DON and DOP were approximately 110, 40 and 0.70 μmol/(g·d). Leaching rates of DOM were attributed to the nonstructural carbohydrates and other labile organic matter within the seagrass leaf. Thalassia hemprichii leached more DOC, DOP and MCHO than E. acoroides. In contrast, E. acoroides leached higher concentrations of DON than T. hemprichii, with the overall leachate also having a higher DON: DOP ratio. These results indicate that there is an overall higher amount of DOM leachate from T. hemprichii than that of E. acoroides that is available to the seagrass ecosystem. According to the logarithmic model for DOM release and the in situ leaf litter production(the Xincun Bay, South China Sea), the seagrass leaf litter of these two seagrass species could release approximately 4×10~3 mol/d DOC, 1.4×10~3 mol/d DON and 25 mol/d DOP into the seawater. In addition to providing readily available nutrients for the microbial food web, the remaining particulate organic matter(POM)from the litter would also enter microbial remineralization processes. What is not remineralized from either DOM or POM fractions has potential to contribute to the permanent carbon stocks.     

The interactive climate and vegetation along the Pole-Equator belts simulated by a global coupled model

The interaction between climate and vegetation along four Pole-Equator-Pole （PEP） belts were explored using a global two-way coupled model, AVIM-GOALS, which links the ecophysiological processes at the land surface with the general circulation model （GCM）. The PEP belts are important in linking the climate change with the variation of sea and land, including terrestrial ecosystems. Previous PEP belts studies have mainly focused on the paleoclimate variation and its reconstruction. This study analyzes and discusses the interaction between modern climate and vegetation represented by leaf area index （LAI） and net primary production （NPP）. The results show that the simulated LAI variation, corresponding to the observed LAI variation, agrees with the peak-valley variation of precipitation in these belts. The annual mean NPP simulated by the coupled model is also consistent with PIK NPP data in its overall variation trend along the four belts, which is a good example to promote global ecological studies by coupling the climate and vegetation models. A large discrepancy between the simulated and estimated LAI emerges to the south of 15°N along PEP 3 and to the south of 18°S in PEP 1S, and the discrepancy for the simulated NPP and PIK data in the two regions is relatively smaller in contrast to the LAI difference. Precipitation is a key factor affecting vegetation variation, and the overall trend of LAI and NPP corresponds more obviously to precipitation variation than temperature change along most parts of these PEP belts.     

Dynamic factor analysis of long-term growth trends of the intertidal seagrass Thalassia hemprichii in southern Taiwan

We examined environmental factors which are most responsible for the 8-year temporal dynamics of the intertidal seagrass Thalassia hemprichii in southern Taiwan. A dynamic factor analysis (DFA), a dimension-reduction technique, was applied to identify common trends in a multivariate time series and the relationships between this series and interacting environmental variables. The results of dynamic factor models (DFMs) showed that the leaf growth rate of the seagrass was mainly influenced by salinity (Sal), tidal range (TR), turbidity (K), and a common trend representing an unexplained variability in the observed time series. Sal was the primary variable that explained the temporal dynamics of the leaf growth rate compared to TR and K. K and TR had larger influences on the leaf growth rate in low- than in high-elevation beds. In addition to K, TR, and Sal, UV-B radiation (UV-B), sediment depth (SD), and a common trend accounted for long-term temporal variations of the above-ground biomass. Thus, K, TR, Sal, UV-B, and SD are the predominant environmental variables that described temporal growth variations of the intertidal seagrass T. hemprichii in southern Taiwan. In addition to environmental variables, human activities may be contributing to negative impacts on the seagrass beds; this human interference may have been responsible for the unexplained common trend in the DFMs. Due to successfully applying the DFA to analyze complicated ecological and environmental data in this study, important environmental variables and impacts of human activities along the coast should be taken into account when managing a coastal environment for the conservation of intertidal seagrass beds.     

海南常见红树植物叶片脂肪酸组成

脂肪酸的组成分析对认识红树植物脂肪酸资源、红树林生态系统内部的营养关系、食物网的结构,以及红树植物对生境的适应等具有重要参考价值。本研究分析了海南岛铁炉港和清澜港两个港湾的红海榄(Rhizophora stylosa)、杯萼海桑(Sonneratia alba)、木果楝(Xylocarpus granatum)、角果木(Ceriops tagal)、榄李(Lumnitzera racemosa)、木榄(Bruguiera gymnorrhiza)和正红树(Rhizophora apiculata)等7种不同红树植物叶片中脂肪酸的组成及含量。在样品中共检测出25种脂肪酸,其中月桂酸、棕榈酸和肉豆蔻酸等8种存在于所有样品中。样品中含量最高的饱和脂肪酸均为棕榈酸(占比44.32%),其次为硬脂酸(占比7.74%),不饱和脂肪酸含量较高的有油酸(占比7.61%)、亚油酸(占比9.81%)和二十碳烯酸(占比12.16%)。植物样品的脂肪酸不饱和指数为0.24～1.13。除木果楝和清澜港采集的木榄样品外,其余样品种的不饱和脂肪酸含量均低于饱和脂肪酸。铁炉港的红海榄、杯萼海桑、角果木和榄李4种植物叶...     

混合像元聚集指数研究及尺度分析

本文提出了一种新的混合像元聚集指数计算方法。该方法基于高分辨率遥感数据,采用方向孔隙率公式和线性混合模型相结合的方法,详细描述了混合像元内部由于植被覆盖度(FVC)、端元聚集指数以及叶倾角分布等引起的尺度差异。利用模拟数据进行初步敏感性分析,将计算得到的混合像元聚集指数与所占面积比例最大的端元聚集指数进行比较,结果表明端元聚集指数的不均一性对计算结果影响最大,由此得到的混合像元聚集指数较最大面积端元聚集指数下降了55%;植被覆盖度的不均一性影响次之,可使聚集指数降低43%;植被叶倾角分布(G函数)的空间异质性影响最小,约12%。敏感性分析的结果同时也证明了对于空间异质性较强的混合像元进行尺度差异修正的必要性。利用本文中提出的混合像元聚集指数方法有望在提高低分辨率叶面积指数反演中发挥重要作用。