土壤水分条件对亚麻生长发育的影响

采用随机区组设计，三次重复，研究了土壤湿度对亚麻生长发育的影响，在生育期间定期取样，分别测定干物重、CAT、POD活性及叶绿素含量，并在收获后分析种子包衣对高度、工艺长度、萌果数、分枝数、原茎数、纤维重及出麻率的影响。结果表明：高水份条件利于亚麻的生长发育，能有效提高CAT和POD的活性，增加抗病抗害能力，促进干物质的积累，在一定程度上提高了亚麻出麻率。     

气候变化背景下中国陆地水循环时空演变

水循环是气候系统各子系统相互作用过程中一个最活跃的枢纽,受气候变化影响显著。本文采用观测和多套再分析数据,系统分析了1979年以来中国及各大流域大气水汽含量、降水、蒸散发和地表径流等水循环要素年际变化。研究发现,1979-2018年,中国陆地整层大气水汽含量和水汽收支呈显著上升趋势;水汽收支除在松花江和西南诸河略有下降,其余流域均呈上升趋势;降水除西北诸河流域呈现显著上升趋势外,其余流域变化不显著;蒸散发整体呈微弱增加,但南方大部流域呈现显著的减小趋势;除西北诸河径流显著上升趋势外,北方大部分流域地表径流呈现减少趋势,而南方流域的径流变化趋势复杂多样。相对1979-2000年,21世纪以来中国年平均气温上升约0.63℃,年降水量、大气水汽含量分别增加0.5%和1.2%,水汽总输入和输出量均减小,降水再循环率增加10.9%。进入21世纪,中国陆地水资源一级分区内循环均较前20 a活跃,降水再循环率除松花江和辽河流域外,均有所增加。其中,海河、黄河、淮河和西北诸河流域的水汽和蒸发形成的降水都有所增加;辽河流域蒸发形成的降水有所增加,但输入水汽减少导致流域降水减少最多;松花江、长江、珠江和西南诸河流域蒸发形成的降水增加,输入水汽减少导致降水略有减少;东南诸河蒸发形成的降水略有增加,但整体变化不大。     

Effect of atmospheric stability on the growth of surface gravity waves

In this paper we study the effect of atmospheric stability on the growth of surface gravity waves. To that end we numerically solved the Taylor-Goldstein equation for wind profiles which deviate from a logarithmic form because stratification affects the turbulent momentum transport. Using Charnock's relation for the roughness height z ₀ of the wind profile, it is argued that the growth rate of the wave depends on the dimensionless phase velocity c/u _* (where u _* is the friction velocity) and a measure of the effect of atmospheric stability, namely the dimensionless Obukhov length gL/u _* ², whereas it only depends weakly on gz _t /u _* ² (where z _t is the roughness height of the temperature profile). Remarkably for a given value of u _* /c, the growth rate is larger for a stable stratification (L > 0) than for an unstable one (L < 0). We explain why this is the case. If, on the other hand, one considers the growth rate as a function of c/U ₁₀ (where U ₁₀ is the windspeed at 10 m), the situation reverses for c/U ₁₀ < 1. For practical application in wave prediction models, we propose a new parameterization of the growth rate of the waves which is an improvement of the Snyder et al. (1981) proposal because the effect of stability is taken into account.     

土壤水分条件对冬小麦生长发育及产量构成影响研究

通过2011-2013年中国气象局固城生态环境与农业气象试验站冬小麦种植试验,利用冬小麦不同生育期土壤湿度、根长密度、株高、绿叶面积和产量等资料,研究不同土壤水分条件对河北固城冬小麦生长发育和产量构成的影响。结果表明：2011-2012年固城站冬小麦0-50 cm土壤相对湿度>50%为冬小麦适宜土壤湿度。2012-2013年固城站冬小麦各生育期0-80 cm土壤相对湿度<55%时,尽管80-120 cm土壤相对湿度为55%-80%,但冬小麦根系和产量构成要素均较小。冬小麦各生育期0-80 cm土壤相对湿度为55%-70%时,冬小麦根系总量最多,则冬小麦生长发育最好,产量构成要素均较好,总产量最高。冬小麦各生育期0-120 cm土壤相对湿度<55%时,冬小麦根系总量最小,且根系集中分布的深度也较浅,总产量最小。冬小麦各生育期0-120 cm土壤相对湿度>80%时,冬小麦根系总量较多,但总体产量比0-80 cm土壤相对湿度为55%-70%时低。     

Integrated estimates of global terrestrial carbon sequestration

Assessing the contribution of terrestrial carbon sequestration to climate change mitigation requires integration across scientific and disciplinary boundaries. A comprehensive analysis incorporating ecologic, geographic and economic data was used to develop terrestrial carbon sequestration estimates for agricultural soil carbon, reforestation and pasture management. These estimates were applied in the MiniCAM integrated assessment model to evaluate mitigation strategies within policy and technology scenarios aimed at achieving atmospheric greenhouse gas stabilization by 2100. Terrestrial sequestration reaches a peak rate of 0.5–0.7 GtC yr⁻¹ in mid-century with contributions from agricultural soils (0.21 GtC yr⁻¹), reforestation (0.31 GtC yr⁻¹) and pasture (0.15 GtC yr⁻¹). Sequestration rates vary over time and with different technology and policy scenarios. The combined contribution of terrestrial sequestration over the next century ranges from 23 to 41 GtC.     

Potential impact of land use change on land productivity dynamics with focus on land degradation in a sub-humid terrestrial ecosystem

The aim of this study was to generate a land productivity dynamics (LPD) map of a degraded catchment located in sub-humid terrestrial ecosystem via a land degradation assessment using three indicators, namely land use and land cover, land productivity, and soil organic carbon density. The study was carried out in two adjacent microcatchments located in Gediz River Basin and conducted between 2001 and 2015. For this purpose, Landsat satellite images were used to determine changing of land use and land cover and vegetation density. In addition, 319 soil samples were collected from surface and subsurface soil depths to detect soil organic carbon density of the study area in May 2015. According to the study results, in more than 23% of the catchments’ area of approx. 3896 ha, land productivity is observed to decline while about 24% shows early signs of decline level. Some of these areas used under agricultural cropping, overgrazed pasture, and artificial areas showed evidence of soil erosion problem. Only very small area of the catchment shows stable and increasing land productivity dynamics trend during the 14-year period.     

Effect of thermal stratification on the growth of the internal boundary layer

The growth of a two-dimensional internal boundary layer (IBL), which develops when a neutral or unstably stratified flow over a uniform terrain encounters a step-change in surface roughness, is numerically investigated by a higher-order turbulence closure theory. It is found that the thickness of the IBL increases as ~ x ⁿ, where x is the downstream distance from the roughness-transition line. For a given set of upstream conditions, the value of the exponent n depends only on the Monin-Obukhov length L, and it is approximately independent of the roughness-change parameter M = In (z01/z02). At large fetches, increases markedly with increasing instability.NRC-NAS Resident Research Associate at AFCRL, 1973–74     

不同生育期水分胁迫对玉米光合特性的影响

利用遮雨棚以夏玉米为对象进行水分胁迫大田试验,通过分析玉米叶片光合测量数据,研究不同生育期水分胁迫对玉米光合特性的影响,为定量分析不同水分胁迫程度对玉米生育的可能机理提供数据和初步的理论支持.结果表明:土壤水分下降会使玉米叶片的光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)降低,而胞间CO2浓度(Ci)和水分利用效率(WUE)会增加;Pn随着光照强度的增加而增加,且随着水分胁迫强度增强,Pn增加速率降低;干旱胁迫会改变Pn、Tr日变化规律,并且对拔节期光合作用的抑制小于成熟期;WUE与Pn存在极显著的正相关关系,与Tr、Ci及Gs存在显著的负相关关系.     

播期对不同类型水稻生长及产量构成因素的影响

通过分期播种,研究了不同播期对水稻生长和产量的影响.通过测定不同播期水稻抽穗期和成熟期的叶绿素、可溶性糖和氮的质量分数,分析不同播期对水稻生长的影响.结果表明Ⅰ期为两优培九和6两优9386最适宜播期,Ⅱ期为Ⅱ优084最适宜播期.播期对水稻单株穗数、每穗粒数、结实率、千粒重均有影响,尤其是对两优培九的结实率、6两优9386的每穗粒数有显著影响.研究结果可为合理利用南方气候资源、合理安排播栽播期、提高水稻产量提供理论依据和技术指导.     

Implications of uncertain future fossil energy resources on bioenergy use and terrestrial carbon emissions

The magnitude and character of the global resource base of fossil fuels is a key determinant of the evolution of the future global energy system and corresponding fossil fuel carbon emissions. What is less well understood is the potential magnitude of impact of the availability of fossil fuels, due to the interaction with biomass energy, on agriculture, land use, ecosystems and therefore carbon emissions from land-use change. This paper explores these links and implications. We show that if oil resources are limited, then the consequently higher price for liquids induces both the use of coal-to-liquids technology deployment, but also enhanced production of bioenergy crops particularly in a business-as-usual scenario. This in turn implies greater pressure to convert unmanaged ecosystems to produce bioenergy, and higher rates of terrestrial carbon emissions from land use.     

Future changes of the terrestrial ecosystem based on a dynamic vegetation model driven with RCP8.5 climate projections from 19 GCMs

Future changes of terrestrial ecosystems due to changes in atmospheric CO₂ concentration and climate are subject to a large degree of uncertainty, especially for vegetation in the Tropics. Here, we evaluate the natural vegetation response to projected future changes using an improved version of a dynamic vegetation model (CLM-CN-DV) driven with climate change projections from 19 global climate models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5). The simulated equilibrium vegetation distribution under historical climate (1981–2000) has been compared with that under the projected future climate (2081–2100) scenario for Representative Concentration Pathway 8.5 (RCP8.5) to qualitatively assess how natural potential vegetation might change in the future. With one outlier excluded, the ensemble average of vegetation changes corresponding to climates of 18 GCMs shows a poleward shift of forests in northern Eurasia and North America, which is consistent with findings from previous studies. It also shows a general “upgrade” of vegetation type in the Tropics and most of the temperate zones, in the form of deciduous trees and shrubs taking over C3 grass in Europe and broadleaf deciduous trees taking over C4 grasses in Central Africa and the Amazon. LAI and NPP are projected to increase in the high latitudes, southeastern Asia, southeastern North America, and Central Africa. This results from CO₂ fertilization, enhanced water use efficiency, and in the extra-tropics warming. However, both LAI and NPP are projected to decrease in the Amazon due to drought. The competing impacts of climate change and CO₂ fertilization lead to large uncertainties in the projection of future vegetation changes in the Tropics.     

Greening the terrestrial biosphere: simulated feedbacks on atmospheric heat and energy circulation

Much research focuses on how the terrestrial biosphere influences climate through changes in surface albedo (reflectivity), stomatal conductance and leaf area index (LAI). By using a fully-coupled GCM (HadCM3LC), our research objective was to induce an increase in the growth of global vegetation to isolate the effect of increased LAI on atmospheric exchange of heat and moisture. Our Control simulation had a mean global net primary production (NPP) of 56.3 GtCyr^?1 which is half that of our scenario value of 115.1 GtCyr^?1. LAI and latent energy (Q _E) were simulated to increase globally, except in areas around Antarctica. A highly productive biosphere promotes mid-latitude mean surface cooling of ~2.5°C in the summer, and surface warming of ~1.0°C in the winter. The former response is primarily the result of reduced Bowen ratio (i.e. increased production of Q _E) in combination with small increases in planetary albedo. Response in winter temperature is likely due to decreased planetary albedo that in turn permits a greater amount of solar radiation to reach the Earth’s surface. Energy balance calculations show that between 75° and 90°N latitude, an additional 2.4 Wm^?2 of surface heat must be advected into the region to maintain energy balance, and ultimately causes high northern latitudes to warm by up to 3°C. We postulate that large increases in Q _E promoted by increased growth of terrestrial vegetation could contribute to greater surface-to-atmosphere exchange and convection. Our high growth simulation shows that convective rainfall substantially increases across three latitudinal bands relative to Control; in the tropics, across the monsoonal belt, and in mid-latitude temperate regions. Our theoretical research has implications for applied climatology; in the modeling of past “hot-house” climates, in explaining the greening of northern latitudes in modern-day times, and for predicting future changes in surface temperature with continued increases in atmospheric CO₂.     

Estimation of critical levels of climate change influence on the natural terrestrial ecosystems on the territory of Russia

Developed are the axiomatics and criteria for estimating the critical levels of climate change influence on the natural terrestrial ecosystems based on the revelation of key climate-dependent environmental elements and model analysis of their variations. Developed is an empirical statistical vegetation model for the territory of Russia considering 15 vegetation zones including five ones in the permafrost zone. The model was used to estimate the proximity of the climate impact on the natural terrestrial ecosystems to the critical level for several climate projections.     

CMIP6模式对亚洲陆地生态系统的模拟评估与预估

基于国际耦合模式比较计划第六阶段（CMIP6）模式模拟以及观测数据,评估了9个CMIP6模式对亚洲地区叶面积指数（LAI)、总初级生产力（GPP）和净初级生产力（NPP）的模拟性能。模拟评估结果表明,9个CMIP6模式能够较好地模拟出亚洲地区陆地生态系统LAI、GPP和NPP的时空分布特征。综合来看,多模式集合（MME）模拟效果最佳,其模拟的LAI、GPP和NPP与观测的空间相关系数分别达到0.90、0.81和0.89,均方根误差在0.5左右。在此基础上,利用MME结果进一步预估了亚洲地区陆地生态系统在SSP1-2.6、SSP2-4.5和SSP5-8.5情景下的未来变化。总体而言,亚洲地区LAI、GPP和NPP到21世纪末都呈现上升趋势。其中,温室气体高排放情景下的上升趋势大于温室气体低排放情景下的上升趋势,亚洲中高纬度地区的增幅大于低纬度地区的增幅。从区域平均来看,到21世纪末期,与当今气候态相比,北亚LAI、GPP和NPP的增幅最大,其在SSP5-8.5情景下分别增加68%、106%和90%;东南亚增幅最小,分别为15%、34%和39%。在SSP1-2.6情景下,北亚LAI、GPP和NPP在21世纪末的增幅分别为23%、29%和26%;东南亚分别为3%、10%和11%,意味着未来全球变暖背景下亚洲区域陆地生态系统变绿和固碳幅度加强。     

Potential future changes in water limitations of the terrestrial biosphere

This study explores the effects of atmospheric CO₂ enrichment and climate change on soil moisture (W _r ) and biome-level water limitation (L _TA), using a dynamic global vegetation and water balance model forced by five different scenarios of change in temperature, precipitation, radiation, and atmospheric CO₂ concentration, all based on the same IS92a emission scenario. L _TA is defined as an index that quantifies the degree to which transpiration and photosynthesis are co-limited by soil water shortage (high values indicate low water limitation). Soil moisture decreases in many regions by 2071–2100 compared to 1961–1990, though the regional pattern of change differs substantially among the scenarios due primarily to differences in GCM-specific precipitation changes. In terms of L _TA, ecosystems in northern temperate latitudes are at greatest risk of increasing water limitation, while in most other latitudes L _TA tends to increase (but again varies the regional pattern of change among the scenarios). The frequently opposite direction of change in W _r and L _TA suggests that decreases in W _r are not necessarily felt by actual vegetation, which is attributable mainly to the physiological vegetation response to elevated CO₂. Without this beneficial effect, the sign of change in L _TA would be reversed from predominantly positive to predominantly negative.     

Climatic change and the broad-scale distribution of terrestrial ecosystem complexes

The broad-scale distribution of terrestrial ecosystem complexes is determined in large part by climate and can be altered by climatic change due to natural causes or due to human activities such as those leading to increasing atmospheric CO₂ concentration. Classifications that recognize the dependence of natural vegetation on climate provide one means of constructing maps to display the impact of climatic change on the geography of major vegetation zones. A world map of the Holdridge Life-Zone Classification, developed from approximately 8,000 meteorological records, is compared with a Holdridge Map with average temperature increments simulated by a. model of climate under elevated atmospheric CO₂ concentration. The largest changes are indicated at high latitudes, where the simulated temperature increase is largest and the temperature intervals defining life zones are smallest. Boreal Forest Zones are replaced by either Cool Temperate Forest or Cool Temperate Steppe, depending on average precipitation. Changes in the tropics are smaller; however, in some regions, Subtropical Moist Forest is replaced by Tropical Dry Forest.Research supported by the National Science Foundation's Ecosystem Studies Program under Interagency Agreement Nos. DEB81-15316 and DEB83-15185.     

Net primary production of terrestrial ecosystems from 2000 to 2009

The CASA (Carnegie-Ames-Stanford) ecosystem model has been used to estimate monthly carbon fluxes in terrestrial ecosystems from 2000 to 2009, with global data inputs from NASA??s Terra Moderate Resolution Imaging Spectroradiometer (MODIS) vegetation cover mapping. Net primary production (NPP) flux for atmospheric carbon dioxide has varied slightly from year-to-year, but was predicted to have increased over short multi-year periods in the regions of the high-latitude Northern Hemisphere, South Asia, Central Africa, and the western Amazon since the year 2000. These CASA results for global NPP were found to be in contrast to other recently published modeling trends for terrestrial NPP with high sensitivity to regional drying patterns. Nonetheless, periodic declines in regional NPP were predicted by CASA for the southern and western Untied States, the southern Amazon, and southern and eastern Africa. NPP in tropical forest zones was examined in greater detail to discover lower annual production values than previously reported in many global models across the tropical rainforest zones, likely due to the enhanced detection of lower production ecosystems replacing primary rainforest.