联合GF-6和Sentinel-2红边波段的森林地上生物量反演

光谱反射率能反映地物差异,是森林地上生物量（Aboveground Biomass,AGB）遥感反演的理论基础。红边波段处于近红外与红光波段交界处快速变化的区域,能对植被冠层结构和叶绿素含量的微小变化做出快速反应,对植被生长状况较敏感。研究以GF-6和Sentinel-2多光谱影像作为数据源,结合野外调查AGB数据,构建落叶松和樟子松AGB线性和非线性估测模型,通过比较模型精度选择最优模型进行森林AGB反演和空间分布制图。结果表明：GF-6和Sentinel-2影像红边波段反射率与落叶松、樟子松AGB均呈显著相关（P<0.05）,红边波段对AGB估测较敏感。多变量估测模型整体估测效果优于单变量模型,所有模型中多元线性回归模型取得了最优的决定系数（落叶松R²=0.66,樟子松R²=0.65）和最低的均方根误差（落叶松RMSE=31.45 t/hm²,樟子松RMSE=54.77 t/hm²）。相比单个数据源,联合GF-6和Sentinel-2影像构建的多元线性回归模型估测效果得到了显著提升,模型RMSE对于落叶松和樟子松AGB估测分别最大降低了22.9%和11.2%。增加红边波段进行AGB估测能显著提高模型估测精度,三组数据源分别加入红边波段信息后进行建模,模型RMSE得到了显著降低。GF-6拥有800 km观测幅宽和高效的重访周期,可以快速地提供大尺度时间序列数据,在森林地上生物量反演和动态监测方面有着很大潜力。     

基于LULUCF温室气体清单编制的浙江省杉木林生物量换算因子

以杉木林为研究对象,在12个县市选取浙江省2009年CFI体系的95个杉木林样地,根据样地平均木,在样地外围相似地段确定解析木共计95株,联立树高曲线方程和生物量模型,同时使用已公开发表的20个杉木生物量模型进行估算,由单株累加获得CFI系统样地的生物量,计算样地生物量与蓄积之比即BEF,建立BEF与林分蓄积之间的关系.根据2009年浙江省CFI体系数据,推算全省杉木林BEF为0.7453t/m3,杉木林总生物量为3721.54万t,不确定性为5.739％;使用IPCC(1996)的碳密度缺省值(0.50)计,生长1 m3杉木吸收CO2 1.3663 t.     

The illusion of nature: perception and the reality of natural landscapes,as illustrated by vertebrate fauna in the Northern Territory,Australia

Biomass figures are compared for common native vertebrate species and common non‐native vertebrate species (including fish, amphibian, reptile, bird and mammal species) across the Northern Territory, an area of ostensibly, largely unmodified natural system. The total biomass of the considered non‐native species very substantially surpasses that of the common native vertebrate species considered; hence, the perception that this is a largely intact natural system is, to some extent, an illusion. This preponderance of biomass of non‐native species may help explain the increasing evidence of ecosystem stress and decline of native species. An integrity index based on the relative biomass of native and non‐native species may provide insight into the status and trends of ecological systems across different regions.     

Twenty‐first‐century climate change impacts on marine animal biomass and ecosystem structure across ocean basins

Climate change effects on marine ecosystems include impacts on primary production, ocean temperature, species distributions, and abundance at local to global scales. These changes will significantly alter marine ecosystem structure and function with associated socio‐economic impacts on ecosystem services, marine fisheries, and fishery‐dependent societies. Yet how these changes may play out among ocean basins over the 21st century remains unclear, with most projections coming from single ecosystem models that do not adequately capture the range of model uncertainty. We address this by using six marine ecosystem models within the Fisheries and Marine Ecosystem Model Intercomparison Project (Fish‐MIP) to analyze responses of marine animal biomass in all major ocean basins to contrasting climate change scenarios. Under a high emissions scenario (RCP8.5), total marine animal biomass declined by an ensemble mean of 15%–30% (±12%–17%) in the North and South Atlantic and Pacific, and the Indian Ocean by 2100, whereas polar ocean basins experienced a 20%–80% (±35%–200%) increase. Uncertainty and model disagreement were greatest in the Arctic and smallest in the South Pacific Ocean. Projected changes were reduced under a low (RCP2.6) emissions scenario. Under RCP2.6 and RCP8.5, biomass projections were highly correlated with changes in net primary production and negatively correlated with projected sea surface temperature increases across all ocean basins except the polar oceans. Ecosystem structure was projected to shift as animal biomass concentrated in different size‐classes across ocean basins and emissions scenarios. We highlight that climate change mitigation measures could moderate the impacts on marine animal biomass by reducing biomass declines in the Pacific, Atlantic, and Indian Ocean basins. The range of individual model projections emphasizes the importance of using an ensemble approach in assessing uncertainty of future change.     

Strategies for the production of cell wall‐deconstructing enzymes in lignocellulosic biomass and their utilization for biofuel production

Microbial cell wall‐deconstructing enzymes are widely used in the food, wine, pulp and paper, textile, and detergent industries and will be heavily utilized by cellulosic biorefineries in the production of fuels and chemicals. Due to their ability to use freely available solar energy, genetically engineered bioenergy crops provide an attractive alternative to microbial bioreactors for the production of cell wall‐deconstructing enzymes. This review article summarizes the efforts made within the last decade on the production of cell wall‐deconstructing enzymes in planta for use in the deconstruction of lignocellulosic biomass. A number of strategies have been employed to increase enzyme yields and limit negative impacts on plant growth and development including targeting heterologous enzymes into specific subcellular compartments using signal peptides, using tissue‐specific or inducible promoters to limit the expression of enzymes to certain portions of the plant or certain times, and fusion of amplification sequences upstream of the coding region to enhance expression. We also summarize methods that have been used to access and maintain activity of plant‐generated enzymes when used in conjunction with thermochemical pretreatments for the production of lignocellulosic biofuels.     

Energy density and its variation in space limit species richness of boreal forest birds

Aim An area’s ability to support species may be dependent not only on the total amount of available energy it contains but also on energy density (i.e. available energy per unit area). Acknowledging these two aspects of energy availability may increase mechanistic understanding of how increased energy availability results in increased species richness. We studied the relationship between energy density, its variation in space and boreal forest bird species richness and investigated two possible mechanisms: (1) metabolic constraints of organisms, and (2) increased resource availability for specialists. Location Protected areas in Finland’s boreal forest. Methods We tested whether bird species richness was best determined by total energy availability in an area or by energy density and its variation within the area, before and after including bird abundance in the models. We evaluated two main explanatory variables: tree growth reflecting the rate of energy production and tree volume as a measure of biomass. In addition, we modelled individual species’ responses to energy density and its variation, and evaluated the prediction of the metabolic constraints hypothesis that small species are limited by energy density whereas large species are limited by total energy availability in the area. Results Energy density and its variation were good predictors of species richness: together with abundance they explained 84% of variation in species richness (compared with 74% for abundance alone). Pure metabolic constraints were unlikely to explain this relationship. Instead, the mechanism probably involved increased habitat heterogeneity benefiting specialist species. Total energy availability was also an important factor determining species richness but its effect was indirect via abundance. Main conclusions Our results corroborate the importance of energy availability as a driver of species richness in forest bird communities, and they indicate that energy density and its variation in the landscape strongly influence species richness even after accounting for abundance.     

The Effect of Tillage and Mesorelief on the Structure of Soil Microbial Cenoses

The investigation of soil microbial cenoses in cultivated catenas and in virgin soils at the foot of catenas showed that the structure of these microbiocenoses depends on the type of the vegetation cover, the characteristics of mesorelief, and the degree of soil tillage. The microbiocenoses were found to be dominated by the fungal mycelium. The proportion of bacteria and fungal spores was higher and the seasonal variations in the soil microbial communities were more distinct in the cultivated than in the virgin swamp and forest soils. The type of mesorelief was found to appreciably influence microbial populations in the top humus-rich horizons of the cultivated soils and not in the mineral soil horizons.     

Soil microbial biomass and respiration measurements: An automated technique based on infra-red gas analysis

An automated system for continuous soil respiration and microbial biomass measurements based on Infra Red Gas Analysis was constructed. The switching device is computer controlled and allows hourly measurements of up to 24 samples when switching intervals of 2.5 min are selected. This allows the use of the substrate-induced respiration method for biomass determination. A software package to run the system was developed.