Historical forest biomass dynamics modelled with Landsat spectral trajectories

Estimation of forest aboveground biomass (AGB) is informative of the role of forest ecosystems in local and global carbon budgets. There is a need to retrospectively estimate biomass in order to establish a historical baseline and enable reporting of change. In this research, we used temporal spectral trajectories to inform on forest successional development status in support of modelling and mapping of historic AGB for Mediterranean pines in central Spain. AGB generated with ground plot data from the Spanish National Forest Inventory (NFI), representing two collection periods (1990 and 2000), are linked with static and dynamic spectral data as captured by Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper Plus (ETM+) sensors over a 25 year period (1984–2009). The importance of forest structural complexity on the relationship between AGB and spectral vegetation indices is revealed by the analysis of wavelet transforms. Two-dimensional (2D) wavelet transforms support the identification of spectral trajectory patterns of forest stands that in turn, are associated with traits of individual NFI plots, using a flexible algorithm sensitive to capturing time series similarity. Single-date spectral indices, temporal trajectories, and temporal derivatives associated with succession are used as input variables to non-parametric decision trees for modelling, estimation, and mapping of AGB and carbon sinks over the entire study area. Results indicate that patterns of change found in Normalized Difference Vegetation Index (NDVI) values are associated and relate well to classes of forest AGB. The Tasseled Cap Angle (TCA) index was found to be strongly related with forest density, although the related patterns of change had little relation with variability in historic AGB. By scaling biomass models through small (∼2.5 ha) spatial objects defined by spectral homogeneity, the AGB dynamics in the period 1990–2000 are mapped (70% accuracy when validated with plot values of change), revealing an increase of 18% in AGB irregularly distributed over 814 km² of pines. The accumulation of C calculated in AGB was on average 0.65 t ha⁻¹ y⁻¹, equivalent to a fixation of 2.38 t ha⁻¹ y⁻¹ of carbon dioxide.     

森林地上生物量的极化相干层析估计方法

基于微波的后向散射系数估计森林地上生物量(AGB)易受后向散射系数饱和的影响,而利用森林高度,根据生长方程估计AGB,却没有考虑和AGB密切相关的林分密度、树种组成、林层垂直分布等空间结构特征的作用,针对这些问题,提出一种基于极化相干层析(Polarization Coherence Tomography,PCT)技术的AGB估计方法。基于德国宇航局(DLR)机载SAR系统(ESAR)获取的特劳斯坦(Traunstein)试验区L-波段极化干涉SAR(PolInSAR)数据,通过对具有不同AGB水平的典型林分的相对反射率函数曲线的分析,定义了9个与AGB具有相关性的特征参数。然后基于20个林分的实测AGB数据,以林分尺度上这9个特征参数的平均值为自变量,以实测林分平均AGB为因变量,采用逐步回归分析法构建了AGB估测模型,并对该模型进行评价,对影响模型估计精度的因素进行分析,结果表明,由PCT提取的相对反射率函数特征参数对AGB很敏感,充分利用相对反射率函数信息可提高AGB估计精度。     

Possible mixotrophy of pigmented nanoflagellates: Microbial plankton biomass, primary production and phytoplankton growth in the NW Iberian upwelling in spring

Microbial plankton biomass, primary production (PP) and phytoplankton growth rates (μ) were estimated along the NW Iberian margin during an upwelling relaxation event. Although the interaction between wind forcing and coastline singularities caused high spatial variability in PP (0.4-8.4 g C m⁻² d⁻¹), two domains (coastal and oceanic) could be distinguished regarding microbial plankton biomass and μ. At the coastal domain, with higher influence of upwelling, diatoms showed an important contribution (27 ± 17%) to total autotrophic biomass (AB). Nonetheless, AB was dominated by autotrophic nanoflagellates (ANF) at both realms, accounting for 62 ± 16% and 89 ± 6% of the integrated AB at the coastal and oceanic domain respectively. AB and heterotrophic biomass (HB) were significantly higher at the oceanic than at the coastal domain, with both biomasses covarying according to HB:AB = 0.33. Whereas the low phytoplankton carbon to chlorophyll a ratio (C_ph:chl a = 38 ± 3) and the high μ = 0.54 ± 0.09 d⁻¹ registered at the coastal stations suggest that phytoplankton was not nutrient limited at this domain, the values (C_ph:chl a = 157 ± 8; μ = 0.17 ± 0.02 d⁻¹) recorded at the oceanic domain point to severe nutrient limitation. However, the high Fv/Fm fluorescence ratios (0.56 ± 0.09) measured at the sea surface in the oceanic domain suggest that nutrient limitation did not occur. To reconcile these two apparently opposite views, it is suggested the occurrence of mixotrophic nutrition of ANF, with heterotrophic nutrition supplying about 75% of carbon requirements.     

青岛岩礁海藻附植动物的区系组成和季节动态

于2007年11月～2008年10月对青岛太平角岩石潮间带鼠尾藻附植动物进行了连续12个月的逐月采样调查,并根据蜈蚣藻、角叉菜、扇形叉枝藻、海蒿子和叉节藻等海藻生长期的不同而在不同月份对其分别进行了采样,研究了附植动物的类群组成、丰度、生物量及其季节动态。所有海藻样品共鉴定出附植动物16个类群。鼠尾藻附植动物的年平均丰度为606ind/gdwtalgae,优势类群为线虫和桡足类,其次是腹足类和多毛类。鼠尾藻附植动物的平均丰度最高值出现在4月,最低值出现在7月。鼠尾藻附植动物的年平均生物量为282×103μg/g dwt algae,最高值出现在6月,最低值为2月。其他海藻附植动物的类群数、丰度、生物量均低于鼠尾藻。海藻附植动物的优势类群及其丰度和生物量在不同月份和不同海藻之间均显著不同。相对于海水理化因子季节变化的影响,不同海藻生长型形态的复杂性及同一种海藻随生长周期而发生的形态变化对附植动物的区系组成和季节动态的影响可能占居更主要地位。     

植物激素对裂殖壶菌生长与DHA含量的影响

研究了6种植物激素(BA、GA、KT、IBA、NAA和IAA)对裂殖壶菌OUC175生长和DHA含量的影响。结果显示,在适宜的浓度条件下,6种植物激素都能不同程度提高裂殖壶菌生长速度和DHA含量,但是浓度过高产生抑制作用。6种植物激素对裂殖壶菌生物量和DHA含量的适宜浓度分别是:BA,3mg/L;KT,10mg/L;GA,1mg/L;IBA,3mg/L;NAA,6mg/L;IAA,3mg/L。BA在添加量3mg/L时,裂殖壶菌的生物量和DHA含量分别比对照组提高27.1%和30.0%。     

加权最小二乘相位解缠的一种改进

基于最小二乘相位解缠原理,针对现有的加权和不加权最小二乘在残差点过多时计算结果平滑问题,提出利用相位导数变化图对其进行加权改进。结合真实数据,通过现有的加权与不加权最小二乘算法的比较和分析,证明该改进算法能有效处理残差点过多的情况,解缠精度高,解缠结果更可靠。     

Carbon pools in an arid shrubland in Chile under natural and afforested conditions

The pattern of carbon (C) allocation among the different pools is an important ecosystem structural feature, which can be modified as a result of changes in environmental conditions that can occur gradually (e.g., climatic change) or abruptly (e.g., management practices). This study quantified the C pools of plant biomass, litter and soil in an arid shrubland in Chile, comparing the natural condition (moderately disturbed by grazing) vs. the afforested condition (two-year-old plantation with Acacia saligna (Labill.) H.L. Wendl.), each represented by a 60 ha plot. To estimate plant biomass, allometric functions were constructed for the four dominant woody species, based on the volume according to their shape, which showed high correlation (R² > 0.73). The soil was the largest C pool in both natural and afforested conditions (89% and 94%, respectively) and was significantly lower in the afforested than natural condition at all five soil depths. The natural condition had in total 36.5 ton (t) C ha⁻¹ compared to 21.1 t C ha⁻¹ in the afforested condition, mainly due to C loss during soil preparation, prior to plantation of A. saligna. These measurements serve as an important baseline to assess long-term effects of afforestation on ecosystem C pools.     

北方荒漠及荒漠化地区草地地上生物量空间分布特征

 北方典型荒漠及荒漠化地区草地地上生物量的空间分布特征对揭示中国陆地生态系统的碳储量具有重要意义,同时对于了解区域尺度上畜牧业发展潜力、生物多样性现状、以及生态系统稳定性具有一定的作用。利用北方典型荒漠及荒漠化地区144个草地样点的植被地上生物量数据,分析地上生物量的空间分布特征及其与多年平均降水量、多年平均温度、海拔高度等环境因素的相关关系。结果表明,北方典型荒漠及荒漠化地区草地单位面积地上生物量的空间分布高度异质,在5.5~371.2 g·m-2之间波动,平均地上生物量为83.3 g·m-2。北方典型荒漠及荒漠化地区草地地上生物量在经向和纬向上的分布均有明显的规律性。相关分析显示,植被地上生物量与纬度之间呈显著的负相关关系(P<0.05),与经度之间呈显著正相关关系(P<0.001)。草地地上生物量与年降水量之间存在显著的正相关关系(P<0.001),但和海拔高度、年平均温度之间无显著相关性,这意味着水分条件是导致北方典型荒漠及荒漠化地区草地地上生物量空间分异的重要因素。