Historical Changes and Multi-scenario Prediction of Land Use and Terrestrial Ecosystem Carbon Storage in China

Terrestrial carbon storage(CS)plays a crucial role in achieving carbon balance and mitigating global climate change.This study employs the Shared Socioeconomic Pathways and Representative Concentration Pathways(SSPs-RCPs)published by the Intergovernmental Panel on Climate Change(IPCC)and incorporates the Policy Control Scenario(PCS)regulated by China’s land management policies.The Future Land Use Simulation(FLUS)model is employed to generate a 1 km resolution land use/cover change(LUCC)dataset for China in 2030 and 2060.Based on the carbon density dataset of China’s terrestrial ecosystems,the study analyses CS changes and their relationship with land use changes spanning from 1990 to 2060.The findings indicate that the quantitative changes in land use in China from 1990 to 2020 are characterised by a reduction in the area proportion of cropland and grassland,along with an increase in the impervious surface and forest area.This changing trend is projected to continue under the PCS from 2020 to 2060.Under the SSPs-RCPs scenario,the proportion of cropland and impervious surface predominantly increases,while the proportions of forest and grassland continuously decrease.Carbon loss in China’s carbon storage from 1990 to 2020 amounted to 0.53×10^(12)kg,primarily due to the reduced area of cropland and grassland.In the SSPs-RCPs scenario,more significant carbon loss occurs,reaching a peak of8.07×10^(12)kg in the SSP4-RCP3.4 scenario.Carbon loss is mainly concentrated in the southeastern coastal area and the Beijing-TianjinHebei(BTH)region of China,with urbanisation and deforestation identified as the primary drivers.In the future,it is advisable to enhance the protection of forests and grassland while stabilising cropland areas and improving the intensity of urban land.These research findings offer valuable data support for China’s land management policy,land space optimisation,and the achievement of dual-carbon targets.

Demographic changes in China’s forests from 1998 to 2018

Background: Tree demography is an essential indicator of various forest ecosystem services, and understanding its changes is critical for the sustainable management of forests. During the past four decades, China implemented unprecedented forest restoration projects, which altered tree demography by increasing the number of trees and introducing new species. However, it remains unclear how species composition has changed in China in response to the past forest restoration and demographical processes.Methods: We applied Forest Stability Index(FSI) and the relative change of FSI(%FSI) to describe the population dynamics of tree species and structure in China since 1998, using field-survey data collected from over 200,000plot-records from the 6th to 9th National Forest Inventories(NFIs).Results: The overall populations of both natural and planted forests have grown rapidly from 1998 to 2018, while the range of changes in the relative tree density was more variable for natural forests(ranging from-8.53% to42.46%) than for planted forests(ranging from-1.01% to 13.31%). The populations declined only in some of the tree species, including Betula platyphylla, Ulmus pumila, and Robinia pseudoacacia. In contrast, the populations of trees in the largest size-class either remained stable or expanded.Conclusions: Tree density of China?s forests(both natural and planted forests) generally expanded and the overall populations increased in most size classes, with greater increases occurred in planted forests. In contrasting to the global decline trends of large diameter trees, here we found no apparent decline for trees in the largest size-class in China, highlighting China?s success in improving forest health and forest adaptations to climate change. We advocate for more studies to reveal the mechanisms of the changes in tree demography, which will help to improve forest ecosystem services such as the carbon sequestration capacity.

The Pursuit of Fallacy in Density Functional Theory: The Quest for Exchange and Correlation, the Rigorous Treatment of Exchange in the Kohn-Sham Formalism and the Continuing Search for Correlation

As pointed out in the paper preceding this one, in the case of functionals whose independent variable must obey conditions of integral normalization, conventional functional differentiation, defined in terms of an arbitrary test function, is generally inapplicable and functional derivatives with respect to the density must be evaluated through the alternative and widely used limiting procedure based on the Dirac delta function. This leads to the determination of the rate of change of the dependent variable with respect to its independent variable at each isolated pair, , that may not be part of a functional (a set of ordered pairs). This extends the concept of functional derivative to expectation values of operators with respect to wave functions leading to a density even if the wave functions (and expectation values) do not form functionals. This new formulation of functional differentiation forms the basis for the study of the mathematical integrity of a number of concepts in density functional theory (DFT) such as the existence of a universal functional of the density, of orbital-free density functional theory, the derivative discontinuity of the exchange and correlation functional and the extension of DFT to open systems characterized by densities with fractional normalization. It is shown that no universal functional exists but, rather, a universal process based only on the density and independent of the possible existence of a potential, leads to unique functionals of the density determined through the minimization procedure of the constrained search. The mathematical integrity of two methodologies proposed for the treatment of the Coulomb interaction, the self-interaction free method and the optimized effective potential method is examined and the methodologies are compared in terms of numerical calculations. As emerges from this analysis, the optimized effective potential method is found to be numerically approximate but formally invalid, contrary to the rigorously exact results of the self-interaction-free method.

The changes of preoperative bone mineral density of patients with nonfunctional pituitary adenoma

Objective To evaluate the bone mineral density (BMD) alteration of patients with nonfunctional pituitary adenoma in Chinese mainland and further to investigate the relevant factors of BMD changes. Methods 31 patients with nonfunctional adenoma and 255 healthy controls were enrolled in this study between December 2007 and May 2008.

Change of probability density distributions of summer temperatures in different climate zones

Extreme events have become increasingly frequent worldwide which are reflected in diverse changes in the shape of the temperature probability density function.However,few studies have paid attention to the heterogeneity of temperature at the scale of climate zones.Here,we use the ERA5-land data set to explore interdecadal summer temperature changes and the distribution across different climate zones from 1981 to 2019.Comparing the minimum(Tmin)and maximum(Tmax)temperature of 1982–1991 and 2010–2019,the results imply that Tmin and Tmax in summer maintained a notable upward trend over the past 40 years,especially Tmin.The effects of a simple shift toward a warmer climate contributed most to all climate zones,while the standard deviation,skewness and kurtosis had minor effects on extreme temperature except for tropics.Quantile analysis shows that the probability of extreme events in all climate zones is increasing in frequency and intensity,especially Tmin and Tmax in temperate climate zone.Understanding diverse reasons for climate change can assist us with taking different measures to address extreme climate in distinct climate zones.

Spatial-Temporal Changes of Soil Organic Carbon During Vegetation Recovery at Ziwuling, China

To probe the processes and mechanisms of soil organic carbon (SOC) changes during forest recovery, a 150-yearchronosequence study on SOC was conducted for various vegetation succession stages at the Ziwuling area, in the centralpart of the Loess Plateau, China. Results showed that during the 150 years of local vegetation rehabilitation SOC increasedsignificantly (P < 0.05) over time in the initial period of 55-59 years, but slightly decreased afterwards. Average SOCdensities for the 0-100 cm layer of farmland, grassland, shrubland and forest were 4.46, 5.05, 9.95, and 7.49 kg C m-3,respectively. The decrease in SOC from 60 to 150 years of abandonment implied that the soil carbon pool was a sink forCO2 before the shrubland stage and became a source in the later period. This change resulted from the spatially variedcomposition and structure of the vegetation. Vegetation recovery had a maximum effect on the surface (0-20 cm) SOCpool. It. was concluded that vegetation recovery on the Loess Plateau could result in significantly increased sequestrationof atmospheric CO2 in soil and vegetation, which was ecologically important for mitigating the increase of atmosphericconcentration of CO2 and for ameliorating the local eco-environment.

A New Kind of Shape-stabilized Phase Change Materials

Based on the lowest melting point and Schroeder’s theoretical calculation formula,nano- modified organic composite phase change materials（PCMs）were prepared.The phase transition temperature and the latent heat of the materials were 24℃and 172 J/g,respectively.A new shape-stabilized phase change materials were prepared,using high density polyethylene as supporting material.The PCM kept the shape when temperature was higher than melting point.Thus,it can directly contact with heat transfer media.The structure,morphology and thermal behavior of PCM were analyzed by FTIR,SEM and DSC.

The Impact of Land Use Change for Greenhouse Gas Inventories and State-Level Climate Mediation Policy: A GIS Methodology Applied to Connecticut

Greenhouse gas (GHG) inventories conducted at state and regional levels serve to quantify long-term emissions trends and set benchmarks against which to evaluate the effectiveness of state government-mandated emissions reductions. GHG inventories which incompletely account for land use, land change, and forestry (LUCF) due to insufficient measurement tools discount the value of terrestrial carbon (C) sinks. In consequence, sink preservation is often omitted from regional land use planning. This paper proposes an accounting methodology which estimates foregone C sequestration derived LUCF change in the southern New England State of Connecticut (CT). The Natural Capital Project’s InVEST program provided a template for modeling C storage and sequestration for CT’s land class categories. LandSat mapping of long-term land cover patterns in CT conducted by CLEAR at the University of CT served as input data for InVEST computer modeling of C sequestration, both realized and foregone due to LUCF. The results showed that: 1) Land converted from high C density forestland to low density C land cover classes reduced the rate of C sequestration loss at 4.62 times the rate of forest reduction. Forest loss of 3.83% over twenty-five years was responsible for foregone C sequestration equivalent to 17.68% of total 2010 sequestration. 2) Accumulating C stocks pushed total annual sequestration from a 1985 baseline level of 866 MMTCO2 to 1116 MMTCO2 by 2010—a 250 MMTCO2 increment. 3) C sequestration from forest loss since 1985 would have yielded additional sequestration of 53.74 MMTCO2 by 2010. By 2002, foregone yield surpassed CT’s annual fossil fuel emissions, currently at 40 MMTCO2. 4) Preservation of forest C stocks over time becomes the determining factor for influencing biomass C sequestration levels. Deciduous forests have a preponderant influence on CO2 budgets. The ground-up methodology to quantify land-based C sequestration presented here demonstrates the influence of forest biomass in state-level C mitigation efforts useful to climate-oriented policy makers.

Challenges and Opportunities of On-farm Tree Planting as an Alternative Wood Source on Mt. Marsabit, Northern Kenya： Towards Mitigating Climate Change

Constraints and probable pathway towards increasing tree density and diversity within farmlands as a means of reducing human dependency on Mt. Marsabit forest for wood are addressed. The forest provides a carbon sink to counteract the risks and hazards associated with climate change. A structured questionnaire was administered to a sample of 205 respondents that were selected from a population of 3075 farming households using a systematic random sampling procedure. While majority of the farms （53%） had low tree density （1-10 trees）, only 8% of the farms had high density （≥ 20 trees）. About 50% and 15% farms had Grevelia robusta and Eucalyptus cammudelensis, which were grown for timber production, respectively. Broad leafed trees, like Croton megalocarpus and Moringa stenoptella had been established in 17% of the farmlands, respectively. With only 20% of the households having a fence around the crop fields, coupled by widely inter-household sharing of crop residues for grazing, tree browsing by livestock was a constraint to tree establishment. The challenges present an opportunity to establish governance structures and processes for communal responsibility and management of tree resources in the farms. A plausible approach entails the Adaptive Collaborative Management （ACM） as a process that facilitates to experiential learning and negotiation for probable actions and policies in management of natural resources.

基于“自然-社会”视角的陕西省土地利用变化碳核算与演变格局分析

土地利用变化对碳源-汇有着重要的影响,在全球碳循环中扮演着重要的角色。为揭示土地利用变化对碳平衡的影响,以陕西省为研究区,基于资源清查、土壤调查、能源消费等多源数据,利用簿记模型和GIS软件核算了该省2002-2022年社会间接碳排放和自然直接碳储量,并引入夜间灯光数据反演,揭示了不同地类及地类内部的碳密度差异与时空格局演变。结果表明:1)陕西省土地利用类型空间特征明显,林地和耕地占全省面积71.7%,2022年与2002年相比建设用地、林地、水域面积分别增加2.67×10^(5)、1.05×10^(6)、7.73×10^(3) hm^(2),耕地、草地、未利用地面积分别减少7.76×10^(5)、3.75×10^(5)、1.73×10^(5) hm^(2);2)研究期间陕西省土地利用相关碳吸收与碳排放严重失衡,土地利用相关年均碳汇量为4.98×10^(6) t,与林地面积的扩大及固碳能力的提升有关,年均碳排放量为3.10×10^(7) t,增长了7倍,与高排放能源的消耗有关;3)研究期间陕西省碳汇量在2007年后开始由负增长变为正增长,2017年后增长速度变快,碳排放量则一直处于高速增长,但受生态保护和减排政策等影响2017年后排放趋于稳定;4)研究期间陕西省地均碳密度表现为陕南秦巴山地>关中平原地区>陕北黄土高原,增长较为稳定的碳密度>60 t·hm^(−2)的地块主要集中在安康与商洛、汉中交界一带,碳排放区域主要集中在关中平原一带和陕西西北部,并在栅格单元空间上呈现扩张趋势。研究还发现,固碳主要依靠林地碳汇,当前陕西省碳排放趋于稳定,如何提升林草地的固碳能力将成为“双碳”目标实现的关键问题。

基于形状改变能密度的岩石强度准则研究

分析砂岩在常规三轴压缩试验过程中弹性应变能密度、体积改变能密度和形状改变能密度的演化规律,根据峰值形状改变能密度与围压的线性变化关系建立形状改变能密度岩石强度准则。结果表明:(1)体积改变能密度与形状改变能密度,在峰前阶段逐渐增加,峰后急剧下降;(2)形状改变能密度强度准则参数物理意义明确,且可通过参数变换转化为经典的Hoek-Brown准则;(3)形状改变能密度强度准则计算结果与8种不同类型岩石的常规三轴压缩试验结果基本一致,验证了准则的精确性和适用性。

基于APSIM模型的未来气候变化对干旱区雨养春小麦播期和种植密度的影响

气候变化评估对智慧农业的影响至关重要。通过2010—2017年实测陇中地区小麦田间数据对APSIM (Agricultural Production Systems sIMulator)模型进行参数校正和验证,结合CMIP5(Coupled Model Intercomparison Project 5)模式的未来气候情景数据和验证后的APSIM模型对播期和种植密度变化下的小麦产量及生物量进行模拟。结果表明,APSIM模型在调参验证后,模拟精度较高;在气候变化情景下,增加种植密度处理春小麦产量和生物量较高,提前播种处理春小麦产量和生物量较高;增加种植密度且早播处理有利于产量形成。未来气候变化情景下,播种密度为237 kg·hm^(-2)、播种日期为3月10日时,可提高4%的春小麦籽粒产量。模拟结果可为未来气候变化下的甘肃陇中旱区雨养小麦播期及种植密度管理提供借鉴。

基于圆台波浪形换热管的潜热储热单元性能分析

为提高潜热储热单元(latent heat storage unit,LHSU)的储热性能,提出了三种优化换热管结构的新型LHSU,分别为圆台形换热管潜热储热单元、波浪形换热管潜热储热单元和圆台波浪形换热管潜热储热单元(frustum wavy heat transfer tube latent heat storage unit,FW-LHSU)。基于数值模拟方法,比较了传统圆柱形换热管潜热储热单元(cylindrical heat transfer tube latent heat storage unit,C-LHSU)和三种新型LHSU的储热性能。此外,针对FW-LHSU研究了换热管壁面倾斜角度对储热性能的影响。结果发现,所提出的三种新型换热管结构均能增强储热性能,其中FW-LHSU储热效果最好,与C-LHSU相比,FW-LHSU的熔化时间缩短了32.64%,储热速率密度提高了48.1%。当增加FW-LHSU的换热管壁面倾斜角度时,其储热性能可进一步提高。当换热管倾斜角度从2°增加到8°时,FW-LHSU的储热时间可缩短37.00%、储热速率密度可提高48.44%。

考虑扰动影响的修正Duncan-Chang模型

根据中国ISO标准砂在不同条件下的三轴试验资料,发现相对密实度对砂土强度和变形特性有显著影响.基于扰动状态概念(DSC)理论,以砂土相对密实度为扰动参量,建立统一扰动度函数表达式;根据试验结果,建立参数K和峰值强度与统一扰动度之间的函数关系式,提出考虑扰动影响的修正Duncan-Chang模型.给定砂土材料参数d、g以及初始状态下的Duncan-Chang模型参数,通过该修正模型可以对任意扰动度下的砂土应力-应变关系进行预测.试验验证表明,修正Duncan-Chang模型可以较好地反映相应扰动状态下砂土的应力-应变关系.

聚氨酯型固-固相变储能材料对沥青调温效果的影响研究

聚氨酯型固-固相变储能材料可以有效提高沥青的相变储能能力,从而在调节路面温度的同时,减小温度波动。基于上述背景,针对聚氨酯型固-固相变储能材料对沥青调温效果的影响展开研究。确定相变材料的分类标准,并分别研究其储能原理及具体应用情况,完成对聚氨酯型固-固相变储能材料特性的分析。在此基础上,定义周期性储热边界条件,根据沥青调温过程中内聚能密度的变化形式,推导相变储能材料的能量变化规律,从而确定聚氨酯型固-固相变储能材料对沥青调温效果的影响能力。

基于WorldView-3遥感影像的福田红树林碳储量年际变化

红树林是热带亚热带地区特有的滨海蓝碳生态系统,然而其碳储量动态变化却鲜有报道。该文以深圳福田红树林为研究对象,基于2017年获取的WorldView-3高分辨率遥感影像以及地面样本点,采用面向对象的随机森林分类方法识别红树林优势群落冠层,反演并计算得到深圳福田红树林各优势群落面积。进一步,基于2017年、2020年和2023年3个时间段红树林群落实地调查数据,计算各优势群落碳储量,进而获得福田红树林群落碳储量空间分布及年际动态变化。结果表明:(1)随机森林算法的冠层识别总体精度为82.29%,Kappa系数为0.77;福田红树林分布面积为93.84 hm 2,其中秋茄(Kandelia obovata)分布面积最大(49.96 hm 2),白骨壤(Avicennia marina)、海桑(Sonneratia caseolaris)、无瓣海桑(S.apetala)、木榄(Bruguiera gymnorhiza)的面积依次为26.23、8.90、6.52、0.50 hm 2。(2)秋茄群落总碳储量最高,其次是白骨壤、海桑和无瓣海桑,木榄群落总碳储量最低。无瓣海桑和海桑的群落碳密度呈上升趋势且无瓣海桑群落碳密度在五个优势群落中最高,秋茄群落碳密度先升后降,白骨壤群落碳密度呈下降趋势,木榄群落碳密度变化不明显。总体而言,福田红树林优势群落碳储量在2017—2023年间变化不大,秋茄、无瓣海桑和海桑群落碳固存能力较强,白骨壤群落的碳密度逐年减少,而木榄群落碳密度相对稳定。该研究结果为评估福田红树林各优势群落固碳能力提供了数据基础,并对后续红树林恢复与管理提供科学依据。

贵州省土地利用变化频数分布及驱动因素

[目的]研究贵州省土地利用动态转移变化频数的空间格局及驱动因素,为该区土地调查工作与相关政策提供理论参考。[方法]基于2000—2020年贵州省土地利用数据,采用土地利用变化频数统计、核密度分析、空间自相关性等方法分析贵州省土地利用变化频率的时空分布特征,并借助地理探测器对其影响因素进行研究。[结果](1)贵州省2000—2020年土地利用变化频数中土地发生变化的面积仅为2%,但资金和人力的投入却相对较高,因此两者的投入关系极不协调。(2)贵州省2000—2020年土地利用变化频数中已变化的土地在空间分布上具有显著的空间异质性。(3)贵州省2000—2020年已变化土地核密度结果呈现“西高东低”的分布特征,土地变化1次的分布密度最大,土地变化3次的分布密度最小。(4)贵州省2000—2020年已变化土地和未变化土地皆呈显著空间集聚特征,已变化热点区域为赫章、大方等,未变化热点区域为威宁、从江等地区。(5)2000—2020年贵州省土地利用变化频数驱动因素的交互探测结果显示,坡度和坡向的交互作用对贵州省土地利用变化频数空间分异的解释力最强。[结论]贵州省土地利用变化频率分布具有显著的空间异质性,应建立贵州省土地利用变化频数监管机制,实现有效利用社会资源和减轻社会财政负担。

脑血管病患者介入术后脑灰质和白质密度变化及其与神经功能缺损程度的相关性

目的:探究脑血管病患者介入术后大脑灰质和白质密度变化情况以及大脑灰质和白质密度变化及其与神经功能缺损程度的相关性。方法:选择2019年3月至2022年3月我院收治的缺血性脑血管病接受介入手术的163例患者作为研究对象,依据美国国立卫生研究院卒中量表(NIHSS)评分对神经功能缺损程度进行分组,分为轻度神经功能缺损组(53例)、中度神经功能缺损组(61例)、重度神经功能缺损组(49例)。多因素Logistic回归分析重度神经功能缺损的重要影响因素。分层交互检验判断脑灰质和白质密度差对神经功能缺损的影响。绘制验证脑灰质和白质密度差对神经功能缺损严重程度的受试者操作特征(ROC)曲线。回归方程y=1-1/(1+e^(-z))预测模型,ROC曲线下面积(AUC)、一致性指数评价模型的区分度和准确性。结果:超敏C反应蛋白、白细胞、中性粒细胞、S100钙结合蛋白B、脑灰质和白质密度差等是重度神经功能缺损的独立危险因素(P<0.05)。脑灰质和白质密度差与神经功能缺损程度具有正相关性。当脑灰质和白质密度差≥14.08 HU时,脑血管病患者介入术后出现重度神经功能缺损的概率显著提升。经Bootstrap自抽样,预测模型区分度、准确度较好。结论:介入术后,脑灰质和白质密度变化与脑血管病患者神经功能缺损严重程度紧密相关,轻中度脑血管病患者介入术后脑灰质和白质密度逐渐下降,而重度患者则逐渐增加。

基于LV-DBSCAN算法的大坝安全监测数据异常检测

大坝安全监测数据原始序列中常存在异常测值,极大影响了大坝安全监测资料分析的可靠性和准确性。为此,在分析异常值特性及传统异常检测方法优缺点的基础上,分别从局部与整体角度研究监测数据异常检测方法。首先针对多重局部异常系数法要求数据序列较长且数据等时间间距等缺陷,提出了局部变化异常系数法(LV)及局部方法与整体方法协同判别策略;进一步引入密度聚类算法(DBSCAN),提出了兼顾数据整体与局部特性的LV-DBSCAN异常检测方法。以某混凝土重力坝两垂线测点顺流向位移监测数据为实例,对比分析了不同方法在不同类型数据集上的检测精度。研究结果表明,所提LV-DBSCAN方法适用性更广,准确率更高,误判率更低。