分类： 物理学 >> 核物理学 提交时间： 2023-06-01 合作期刊: 《Nuclear Science and Techniques》
摘要：Nuclear nonproliferation is of critical importance for global security. Dangerous fissile materials including highly enriched uranium and weapons-grade plutonium are especially important to detect. Active interrogation techniques may result in much better sensitivity but are difficult with conventional portal monitors that rely on detecting thermal neutrons. Also, most conventional portal monitoring systems rely on 3 He, which has a finite and continually decreasing supply. By designing a highly segmented array of organic scintillators, we posit that we can accurately and quickly identify fissile materials, including weapons-grade plutonium and highly enriched uranium, being smuggled. We propose a new design for a fast-neutron detector that overcomes the limitations of the current generation of portal monitors. MCNP6 simulations have been performed in conjunction with the UMPBT statistical model to determine the sensitivity limitations of the proposed detector. Results suggest that the proposed detector may be 10 times more efficient than current-generation thermal neutron detectors and may be able to positively identify a 81 mg 235 U source in as little as 192 seconds utilizing active interrogation techniques.
分类： 物理学 >> 核物理学 提交时间： 2023-06-01
摘要：Compton camera-based prompt gamma (PG) imaging has been proposed for range verification during proton
therapy. However, a deviation between the PG and dose distributions, as well as the difference between the
reconstructed PG and exact values, limit the effectiveness of the approach in accurate range monitoring during
clinical applications. The aim of the study was to realize a PG-based dose reconstruction with a Compton
camera, thereby further improving the prediction accuracy of in-vivo range verification and providing a novel
method for beam monitoring during proton therapy. In this paper, we present an approach based on a subsetdriven origin ensemble with resolution recovery (SD-OE-RR) and a double evolutionary algorithm (DEA) to reconstruct the dose depth profile (DDP) from the gamma events obtained by a Cadmium-Zinc-Telluride
(CZT) Compton camera with limited position and energy resolution. Simulations of proton pencil beams with
clinical particle rate irradiating phantoms made of different materials and the CT-based thoracic phantom were
used to evaluate the feasibility of the proposed method. The results show that for the monoenergetic proton
pencil beam irradiating homogeneous-material box phantom, the accuracy of the reconstructed DDP was within
0.3 mm for range prediction and within 5.2% for dose prediction. In particular, for 1.6-Gy irradiation in the
therapy simulation of thoracic tumors, the range deviation of the reconstructed spread-out Bragg peak was
within 0.8 mm, and the relative dose deviation in the peak area was less than 7% compared to the exact values.
The results demonstrate the potential and feasibility of the proposed method in future Compton-based accurate
dose reconstruction and range verification during proton therapy.
分类： 物理学 >> 核物理学 提交时间： 2023-05-31
Xu,Miaofu
Zhang,Xiangzhen
Ye,Rui
Wang,Jincan
Bian,Xiaojuan
Gao,Yao
Li,Minxian
Chen,Fusan
Yang,Xiaochen
Ge,Rui
摘要：A 3W1 superconducting wiggler (SCW) with the pole gap of 68 mm was successfully tested and installed in a BEPC II storage ring in November, 2019. The goal of zero liquid helium consumption was achieved, and the cryogenic system exhibited a 12% residual cooling capacity (approximately 0.69 W @4.2K). The 3W1-SCW was set to operate at 2.49 T and has been operating for more than seven months. Three instances of magnet quenching occurred during the normal operation. The evaporated helium gas can be recycled to the helium gas recycling system when the pressure in the helium tank is higher than the parameter value（the setpoint of the presssur value is 1.2 bara）. The cryogenic system can be recovered within 4 h if sufficient liquid helium is available to inject into the cryostat.
分类： 物理学 >> 核物理学 提交时间： 2023-05-31
摘要：Theoretical uncertainties of single proton transfer cross sections of the (3He,d) and (d,3He) reactions
due to the uncertainties of the entrance- and exit-channel optical model potentials are examined with the
30Si(3He,d)31P, 13B(d,3He)12Be, and 34S(3He,d)35Cl reactions at incident energies of 25 MeV, 46 MeV, and
25 MeV, respectively within the framework of distorted wave Born approximation. Differential cross sections
at the first peaks in the angular distributions of these reactions are found to be uncertain within around 5% due
to the uncertainties of the optical model potentials from an result of 20000 times of calculations with the optical
potential parameters randomly sampled. This amount of uncertainties is found to be nearly independent of the
angular momentum transfer and the target masses within the studied range of incident energies. Uncertainties
of the single proton spectroscopic factors obtained by matching the theoretical and experimental cross sections
at different scattering angles are also discussed.
分类： 物理学 >> 核物理学 提交时间： 2023-05-31
Guan Yongjing
Chen Wu
Wang Shenzhen
Hua Yuxin
Jing Qiaoyan
Liu Zhiyong
Huang Chunping
Wang Deyu
Wang Huijuan
He Xianwen
Mario De Cesare
Cui Liangjia
He Hua
Fan Kaidi
Guo Zichen
摘要：The spatial distributions of 239+240Pu and 137Cs in soils from Longji Rice Terraces were investigated to evaluate soil erosion. The activity concentrations of 239+240Pu and 137Cs in the surface soils of the paddy fields were in the range of 0.089-0.734 and 1.80-7.88 mBq/g, respectively. The activities of 239+240Pu and 137Cs showed very similar distribution trends, first increasing and then decreasing with increasing elevation. The 240Pu/239Pu atom ratios in the surface soils ranged from 0.162–0.232. The activities of 239+240Pu and 137Cs in the soil cores tended to be uniformly distributed within the plowed layer and declined exponentially below this depth. The mean soil erosion rates of Longji Rice Terraces estimated by 239+240Pu and 137Cs tracer methods were 5.44 t/(ha·a) and 5.16 t/(ha·a), respectively, which demonstrated that plutonium can replace 137Cs as an ideal tracer for soil erosion research in the future. Landform features are the main factors affecting the distribution of plutonium and 137Cs as well as soil erosion in the Longji Rice Terraces.
分类： 物理学 >> 核物理学 提交时间： 2023-05-31
摘要：In this work we perform a Bayesian inference of the crust-core transition density ρt of neutron stars based upon the neutron-star radius and the neutron-skin thickness data within a thermodynamical method. The uniform and Gaussian distributions for the ρt prior are adopted in the Bayesian approach. It has a larger probability to have values higher than 0.1 fm 3 for ρt as the uniform prior and the neutron-star radius data are used. We found that this is controlled by the curvature Ksym of the nuclear symmetry energy. This phenomenon will not happen if Ksym is not extremely negative, i.e., Ksym > -200 MeV. The obtained ρt is 0.075+0.005-0.01fm^3 at 68% confifidence level when both the neutron-star radius and the neutron-skin thickness data are taken into account. The strongly anti-correlations between ρt and the slope L, curvature of the nuclear symmetry energy are observed. The dependence of the three L-Ksym correlations predicted in the literature on the crust-core density and pressure is quantitatively investigated. The most probable value of 0.08 fm^3 for ρt is obtained from the L-Ksym relation raised by Holt et al. and the larger values are preferred by the other two relations.
分类： 物理学 >> 核物理学 提交时间： 2023-05-31
摘要：A simulation code, GOAT, is developed to simulate single-bunch intensity-dependent effects and their interplay in the proton ring (pRing) of the Electron-Ion Collider in China (EicC) project. GOAT is a scalable and portable macroparticle tracking code written in Python and coded by object-oriented programming technology. It allows for transverse and longitudinal tracking, including impedance, space charge effect, electron cloud effect, and beam-beam interaction. In this paper, physical models and numerical approaches for the four types of high-intensity effects, together with the benchmark results obtained through other simulation codes or theories, are presented and discussed. In addition, a numerical application of the cross-talk simulation between the beam-beam interaction and transverse impedance is shown, and a dipole instability is observed below the respective instability threshold. Different mitigation measures implemented in the code are used to suppress the instability. The flexibility, completeness, and advancement demonstrate that GOAT is a powerful tool for beam dynamics studies in the EicC project or other high-intensity accelerators.
分类： 物理学 >> 核物理学 提交时间： 2023-05-31
摘要：Bonner多球谱仪(BBS)求解中子能谱是一个复杂的多维模型，需要使用复杂的优化算法求解第一类Fredholm积分方程。针对极大似然期望最大化(MLEM)算法容易陷入局部最优，粒子群优化(PSO)算法易得到粒子飞行方向和步长不合理，导致迭代无效，影响效率和精度的问题，提出了一种改进的PSO-MLEM算法用于中子能谱展开。利用动态加速因子平衡全局和局部搜索能力，提高算法的收敛速度和精度。首先，采用蒙特卡罗方法对BBS进行模拟，得到BBS的响应函数和计数率。模拟计数率时，采用了国际原子能机构403号技术报告中的4个参考光谱作为蒙特卡罗方法的输入参数。采用PSO-MLEM算法对中子能谱展开，通过展开能谱与参考能谱的差异进行验证。最后，利用BBS对252Cf中子源进行测量，并采用PSO-MLEM算法展开实验中子谱。与最大熵反卷积(MAXED)、PSO和MLEM算法相比，PSO-MLEM算法参数更少，并自动调整动态加速因子以解决局部最优问题。PSO-MLEM算法的收敛速度分别是MLEM和PSO算法的1.4倍和3.1倍。与PSO、MLEM和MAXED算法相比，PSO-MLEM算法的相关系数分别提高了33.1%、33.5%和1.9%，相对平均误差分别降低了98.2%、97.8%和67.4%。
分类： 物理学 >> 核物理学 提交时间： 2023-05-31
摘要：lead-shielded HPGe detector and offline g–ray spectra of the residual product were used to measure the cross-section (CS) and ratios of isomeric CS (sm/sg) in 134Xe(n,2n)133m,gXe reactions at different energies including 13.5, 13.8, 14.1, 14.4, and 14.8 MeV, relative to 93Nb(n,2n)92mNb reaction CS. The target was high-purity natural Xe gas under high pressure. T(d,n)4He reaction was used to produce neutrons. The TALYS code (1.95 version) for nuclear reactions was used for calculations along with the default parameters and various nuclear level density models. The uncertainties present in the measured CS data were thoroughly analyzed using the covariance analysis method. The results were subsequently compared to the theoretical values, evaluation data, and previous experimental findings. Thus, the CS data of the 134Xe(n,2n)133mXe and 134Xe(n,2n)133gXe reactions and the corresponding isomeric CS ratios at 13.5,13.8 and 14.1 MeV neutron energies are reported for the first time. This work advances our knowledge of pre-equilibrium emission in the (n,2n) reaction channel by resolving inconsistencies in Xe data.
分类： 物理学 >> 核物理学 提交时间： 2023-05-31
摘要：The properties of exotic nuclei are the focus of the present research. Two-neutron halo structures of neutron-rich 17,19B were experimentally confirmed. We studied the formation mechanism of halo phenomena in 17, 19B using the complex momentum representation method applied to deformation and continuum coupling. By examining the evolution of the weakly bound and resonant levels near the Fermi surface, s–d orbital reversals and certain prolate deformations were observed. In addition, by analyzing the evolution of the occupation probabilities and density distributions occupied by valence neutrons, we found that the ground state of 15B did not exhibit a halo, and the ground states of 17B and 19B exhibited halos at 0.6≤β2≤0.7 and 0.3≤β2≤0.7, respectively. The low-l components in the valence levels that are weakly bound or embedded in the continuous spectrum lead to halo formation.
分类： 医学、药学 >> 临床医学 提交时间： 2023-05-31 合作期刊: 《中国全科医学》
摘要：背景 浙江省嵊州市自 2022 年 8 月起开展医疗保险门诊支付方式改革，通过实施总额预算、更新人头费测算标准、改进激励约束机制等政策逐步开展按人头付费改革，激励基层医疗卫生机构提供适宜的基本医疗服务，降低基层医疗费用支出，促进医疗保险基金的可持续发展。目的 分析浙江省嵊州市基本医疗保险门诊按人头付费政策对基层医疗卫生机构费用的影响机制，为完善相关支付制度提供参考。方法 于 2022 年 4—7 月，以“capitation”“medical costs”等为英文检索词，以“按人头付费”“医疗费用”等为中文检索词，检索 2000-01-01至 2022-07-31 PubMed、Web of Science、中国知网、万方数据知识服务平台等数据库中与按人头付费相关的文献，同时梳理嵊州市实行按人头付费相关的政策文件、政府报告及新闻报道等；于 2022 年 9—12 月，对嵊州市按人头付费政策制定与实施者代表进行个人访谈（n=13）。采用系统动力学方法对浙江省嵊州市门诊总额预算下按人头付费改革政策对费用的影响机制进行定性分析。结果 将嵊州市本轮医疗保险支付方式改革的政策绘制成因果关系图，得到 5条反馈回路。结果显示：按人头总额预算政策的实行能激励基层医疗卫生机构为居民提供规范的医疗服务，促进提高基层签约率，从而控制医疗费用支出；科学的人头费用标准能够激励基层医疗卫生机构自主控制医疗费用；提高医疗保险报销比例，可以切实减轻患者就医负担；完善绩效考核制度，有利于持续提升基层医疗卫生机构服务能力；加强信息共享机制的建设，实现数据共享互通，能整体性地提高居民的健康水平。结论 实施按人头付费改革配合多项政策措施，能够提高基层签约率和就诊率，拓宽医疗保险基金来源，保证医疗保险基金的可持续性，提高基层医疗卫生机构的医疗水平和服务能力，改善居民健康状况，最终有利于改善慢性病的防治效果。
分类： 生物学 >> 昆虫学 提交时间： 2023-05-30 合作期刊: 《干旱区研究》
摘要：为明确民勤温性荒漠草原拟步甲昆虫群落多样性及其时间动态，于2021年4—10月采用巴氏罐诱法对甘肃省民勤县砾质、沙质与盐土荒漠草地拟步甲科昆虫群落进行系统调查。（1）本次调查共捕获拟步甲科昆虫8492头，分属于8属10种，其中姬小胸鳖甲（Microdera elegans）和多毛宽漠甲（Sternoplax setosa setosa）为优势种，分别占总个体数的26.88%和25.07%，波氏真土甲（Eumylada potanini）为砾质荒漠草地的特有种。（2）3个亚类荒漠草地拟步甲昆虫物种数和个体数在7月达到峰值，10月降到最低。（3）砾质荒漠草地和沙质荒漠草地的拟步甲群落多度和香农多样性指数显著高于盐土荒漠草地（P＜0.05）；盐土荒漠草地的拟步甲群落丰富度显著高于沙质荒漠草地（P＜0.05）。（4）相关性分析表明，拟步甲群落的丰度指数与植被群落高度、土壤含水量和植被盖度呈显著负相关（P<0.05）；拟步甲丰度指数与植被香农多样性指数和植被丰富度呈显著正相关（P<0.05）。荒漠草原的植被组成单一，促使拟步甲群落组成简单；相对于盐土荒漠草地和沙质荒漠草地，砾质荒漠草地中植被香农多样性指数和植被丰富度较高，砾质荒漠草地中拟步甲物种也最丰
分类： 地球科学 >> 地理学 提交时间： 2023-05-30 合作期刊: 《干旱区研究》
摘要：：构建干旱区生态安全格局有利于促进区域生态系统服务供应与需求之间的动态平衡。以干旱区开都-孔雀河流域为研究区，利用InVEST模型、RWEQ模型和Getis-Ord Gi*模型分析生态供给源地，以土地利用程度、地均GDP、人口密度和夜间灯光指数分析生态需求源地，并基于最小累积阻力模型确定供给源地与需求源地之间的生态廊道，从而构建研究区生态安全格局。研究结果表明：（1）开都-孔雀河流域生态供给源地14个，占研究区面积的21.46%，重点生态需求源地共9个斑块，占流域总面积4.63%；生态廊道126条，重要廊道17条，总长度654.68km；生态节点65个，重点生态节点24个。（2）开都-孔雀河流域生态系统服务供给与需求空间错位明显，高供给区域与高需求区域呈现出以城镇边界为分界线的明显特征。（3）结合研究区自然地理特征和景观生态系统服务流动性，运用阻力面模型，构建“两核心、两片区、三横四纵多节点”的开都-孔雀河流域生态安全格局可为保障区域生态系统服务功能和可持续发展政策的制定提供科学参考。
分类： 地球科学 >> 地理学 提交时间： 2023-05-30 合作期刊: 《干旱区研究》
摘要：利用CASA 模型（Carnegie-Ames-Stanford Approach）模拟石羊河流域2000—2020 年植被净初级生产力（NPP），分析流域NPP的时空变化特征、稳定性和未来变化趋势，并从气候因素、地形因素和人类活动因素3个方面探讨对NPP的变化影响。结果表明：（1）2000—2020年石羊河流域植被NPP多年平均值为291.01 g C·m-2·a-1，呈不显著增加趋势，空间分布呈南高北低的分布格局。（2）2000年以来植被NPP呈增加趋势的区域占总面积的86.4%，其中极显著增加和显著增加的区域分别占6.7%和10.1%。（3）NPP变化在中等波动以上（变异系数Cv≥0.25）的区域所占比例为50.4%。（4）从未来变化趋势看，石羊河流域植被NPP恢复的持续性较弱，呈增加并反持续的地区所占比例达到57.1%。（5）流域的植被NPP变化与气温、降水均成正相关，对气温的响应更为敏感。NPP随海拔高度和坡度增加呈现增大后减小趋势，近年来流域实施的一系列人工造林、退耕还林还草等措施对植被NPP的增加具有明显促进作用。
分类： 生物学 >> 生态学 提交时间： 2023-05-30 合作期刊: 《干旱区研究》
摘要：替代稳态下的荒漠生态系统生态弹性反映了系统承受环境干扰后的恢复能力，这对认识荒漠生态系统过程具有重要的理论意义。当前研究主要集中在湖泊和森林生态系统，而有关荒漠生态系统弹性的研究普遍未考虑替代稳态，也鲜有考虑弹性的时间变化。本研究以阜康北部的古尔班通古特沙漠南缘至沙漠腹地样带为例，运用2001年1月至2020年12月的MODIS全球植被指数遥感数据，采用BFAST（Breaks for Additive Season and Trend）和状态空间建模对数据进行处理和提取，通过不同状态的退出时间量化得出不同时段替代稳态条件下的生态弹性，同时根据计算结果分析了该地区生态弹性时空演变特征及其影响机制。研究结果表明：（1）研究区弹性+和弹性-整体呈现先下降后上升的趋势，但沙漠边缘至腹地空间差异显著。（2）生态弹性对降水变化存在滞后响应。（3）降水季节变化的差异会降低降水量与生态弹性之间的相关性。综上所述，生态弹性的空间分布总体受降水格局控制，但立地条件导致的植被空间异质性增加了生态弹性空间分布的复杂性，而生态弹性与降水变化的关系取决于植被群落构成、植物对降水变化响应、降水量变化趋势和季节分布。本研究在认识荒漠生态系统功能稳定性维持机制以及荒漠生态保护和修复方面具有重要的理论与实践意义。
分类： 地球科学 >> 地理学 提交时间： 2023-05-30 合作期刊: 《干旱区研究》
摘要：为实现农牧交错带生态用地与生产用地的协调发展，提升区域生态功能，以张家口坝上地区为例，构建土地利用转移矩阵，利用地理集中度和地理探测器模型，揭示生态用地与生产用地时空变化、转换特征和驱动因素。结果表明：（1）2000—2020年，张家口坝上地区生态用地规模增加了5.41%，表现为先增后减的变化趋势，生产用地规模减少了6.89%，表现为先减后增的变化趋势。（2）生态用地和生产用地之间相互转换频繁，生产用地向生态用地转换了21.23×104 hm2，转换数量逐渐减少，自然条件较好地区（降雨量多、海拔低和坡度缓等）的生产用地开始向生态用地转换；生态用地向生产用地转换了12.47×104 hm2，转换数量逐渐增加，且自然条件较恶劣地区的生态用地开始向生产用地转变。（3）土壤有机质、人均耕地面积和坡度等是影响生产用地向生态用地转换的主要因素，土壤有机质与人均耕地面积的交互作用解释力最大；土壤有机质含量低、人均耕地面积多、坡度6°～15°和年均降雨量低于400 mm的地区容易发生生产用地向生态用地转变。坡度、年均降雨量和人均耕地面积等是影响生态用地向生产用地转变的主要因素，坡度与地貌类型的交互作用解释力最大；在坡度2°～6°较缓区、年均降雨量大于400mm、人均耕地面积少的地区容易发生生态用地向生产用地转变。研究区近年来出现生态用地向生产用地的转换应引起重视。
分类： 生物学 >> 植物学 提交时间： 2023-05-30 合作期刊: 《干旱区研究》
摘要：研究典型株型沙生灌丛周围的流场分布，旨在为干旱、半干旱地区合理选择不同株型的防风沙植被提供理论依据。本文利用FLUENT软件对3类典型株型（坛形、梭形、帚形）灌丛周围的流场进行数值模拟，分析不同植株形态对风沙流的影响，并加以风洞试验验证，结果表明：（1）3类株型周围流场可分为5个区，且株后均存在3个涡流。受涡流强度的影响，在积沙初始阶段，梭形、帚形植株主要在株后6~7 H处积沙，而坛形植株在3 H附近积沙。（2）受植株最大侧影面积高度层的影响，3类株型灌丛株后1 H处的风速极小值依次出现在0.3 m、0.4 m、0.8 m高度处，最优防护高度依次为0.2~0.4 m、0.3~0.6 m、0.8~1 m。3类株型株后的空气动力学粗糙度逐渐减小，且坛形的粗糙度明显高于其他株型。（3）3类株型在-2~10 H范围内均可有效降低风速，株后近地表区防风效益表现为坛形＞梭形＞帚形，而中高空区防风效益均随株距增加而减小。（4）在T=10 s时，3类植株周围总积沙长度分别为8.5 H、6H、4.5 H，梭梭、沙拐枣分别在距入口5~5.5 m、4.5~6 m处存在不同程度的风蚀现象。对比其他植株，白刺（Nitrariasphaerocarpa）具有较好的阻沙效果，在防风固沙工程建设中建议将其与梭梭（Haloxylon ammodendron）、沙拐枣（Cal⁃ligonum mongolicum）结合，既能发挥白刺的阻沙作用，又可利用梭梭、沙拐枣较好的中高空防风效果。
分类： 生物学 >> 植物学 提交时间： 2023-05-30 合作期刊: 《干旱区研究》
摘要：植被群丛的稳定对于群落演替乃至区域生态系统安全发挥着关键作用。受气候变化和人类活动影响，长梗扁桃（Amygdalus pedunculata）自然群丛退化严重，面积不断减少，亟需保护。本研究基于浑善达克沙地长梗扁桃群丛35个样方的数据，通过典范对应分析（Canonical Correspondence Analusis，CCA）揭示了长梗扁桃群丛分布的驱动因子以及不同群丛特征与环境因子之间的关系。研究发现，基于立地条件的差异，长梗扁桃群丛可分为4种类型：群丛Ⅰ，长梗扁桃-蒙古韭（Allium mongolicum）；群丛Ⅱ，长梗扁桃-西北针茅（Stipa sareptana var. krylovii）-冷蒿（Artemisia frigida）；群丛Ⅲ，长梗扁桃-画眉草（Eragrostis pilosa）；群丛Ⅳ，榆树（Ulmus pumila）-长梗扁桃-蒙古虫实（Corispermum mongolicum）。大尺度上，温度和海拔是影响长梗扁桃群丛分布的主要环境因子，贡献率分别为13.2%和11.4%。小尺度上，10~20 cm和20~30 cm土壤有机质和海拔是影响群丛结构特征的关键因素。群从Ⅱ和群从Ⅲ的结构特征对土壤因子响应较为敏感，海拔是群丛Ⅰ和群丛Ⅳ结构特征的主要影响因子。本研究明确了温度、土壤和海拔是浑善达克沙地长梗扁桃群丛的主要环境影响因子，而关于土壤和气候对于群丛的交叉影响还有待进一步研究。
分类： 农、林、牧、渔 >> 土壤学 提交时间： 2023-05-30 合作期刊: 《干旱区研究》
摘要：为探究荒漠灌丛及其伴生种对灌丛下土壤粒径、养分空间异质性的影响，以西鄂尔多斯国家级自然保护区内沙冬青（Ammopiptanthus mongolicus）-霸王（Sarcozygium xanthoxylon）混生群落、单株沙冬青为研究对象，以周围无植被覆盖的裸沙地为对照（CK），对比分析不同灌丛分布类型下土壤粒度特征、养分积累变化及养分与粒度组成的作用关系。结果表明：（1）单株沙冬青土壤黏粒、粉粒、细砂的体积百分含量较沙冬青-霸王分别增加0.8%、0.8%、0.71%。随灌丛种类减少，土壤粒径依次变细，分选性变差，分形维数变小，土壤颗粒分布逐渐不对称，颗粒组成向细粒物质集中。（2）土壤有机质、碱解氮含量随灌丛种类的增多分别增加了1.85 g·kg-1、8.18 mg·kg-1。单株沙冬青对有机质、速效磷的富集作用较沙冬青-霸王更强，对碱解氮的积累效果较沙冬青-霸王稍差。（3）沙冬青-霸王土壤速效磷含量与细砂含量呈显著正相关（P<0.05），沙冬青土壤碱解氮、速效钾与粗砂呈显著正相关（P<0.05）。沙冬青-霸王、沙冬青可有效促进土壤颗粒细粒化、显著改善土壤养分，但伴生种霸王的存在降低了沙冬青对有机质和速效磷的富集作用。
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