Sunny Slopes Research Articles

Tree-to-Shrub Shift Benefits the Survival of Quercus mongolica Fisch. ex Ledeb. at the Xeric Timberline

Woody species are either trees or shrubs, with the exception of approximately 9.2% “trub” species exhibiting both tree and shrub growth forms. Little is known thus far about the ecological importance of plant growth-form plasticity under a drying climate. Quercus mongolica Fisch. ex Ledeb., a dominant tree species of temperate forests in East Asia, typically shows tree-to-shrub growth-form shifts at the xeric timberline and is suitable to test whether growth-form plasticity can physiologically benefit plant drought acclimation. We quantified the tree architecture, drought stress, physiological drought tolerance, and nonstructural carbohydrates of Q. mongolica trees and shrubs on the opposite slope of the same mountain at the xeric timberline in July 2018. Compared with Q. mongolica trees on shady slopes, the shrubs on sunny slopes had less available water to use and were more severely threatened by drought. Moreover, the shrubs had stronger tolerance to drought but still tended to have less nonstructural carbohydrate accumulation. The tree-to-shrub shift effectively benefits the survival of Q. mongolica under a dry climate and may strongly contribute to forest dynamics and even fire regimes under climate drying, especially for sensitive ecosystems such as the xeric timberline, which will be vulnerable under future climate change scenarios.

Frost heave modelling of the sunny-shady slope effect with moisture-heat-mechanical coupling considering solar radiation

The sunny-shady slope effect on structures in cold regions is significant due to solar radiation, which threatens structural stability. Solar radiation is rarely considered in modelling frost heave, and its effects on the moisture-heat transfer of frozen soil and structural deformation are unclear. Here, a frost heave model with moisture-heat-mechanical coupling, solar radiation and self-shadowing is presented; its accuracy is verified through comparison with field monitoring data of a canal. Then, the coupling development of the moisture-heat transfer, stress-deformation and differential frost heave progression of differently oriented canals are analyzed. Finally, the effects of solar radiation on the soil frost heave and frost damage mechanism of canals with the sunny-shady slope effect are discussed. The freezing depth is shallower and the water content, deformation, and tensile stress are lower for sunny than for shady slopes. As the canal orientation varies from east-west to north–south, the differences in the freezing characteristics decrease to 0, and the frost damage time of shady slopes is gradually delayed; the opposite occurs for sunny slopes. The developments in structural surface temperature, moisture-heat transfer in frozen soil and structural deformation are consistent with solar radiation and air temperature changes, emphasizing solar radiation’s contribution to structure frost heave. The uneven, asynchronous, asymmetrical frost heave and melting deformation of linings in sunny and shady slopes are the causes of canal damage. This model investigates interactions among solar radiation-diurnal temperature-frozen soil-structures and offers a theoretical basis for using solar energy to reduce frost heave in seasonally frozen regions.

Numerical evaluation for cooling performance of a composite measure on expressway embankment with shady and sunny slopes in permafrost regions

As an efficient engineering measure for protecting permafrost from thawing, the composite measure composed of L-shaped two-phase closed thermosyphons (TPCTs), insulation board and crushed-rock revetments (CRs) is applied to the low-grade highway in the Qinghai-Tibet Plateau. However, it is uncertain whether this composite measure can be available for an expressway embankment with wide bituminous pavement and strict deformation requirement, and the deformation performance of the embankment with composite measure is the key factor controlling safe operation. In this study, a hydro-thermo-mechanical coupled model for the expressway embankment combined with the composite measure is developed, the working process and mechanism of L-shaped TPCTs, insulation board and CRs are analyzed, respectively, and the cooling and reinforcing effects of the composite measure for the embankment with shady and sunny slopes are evaluated. The numerical results show that: (1) The working process and mechanism of L-shaped TPCTs, insulation board and CRs are different. (2) The composite measure can not only prevent the permafrost degradation, but also relieve the asymmetric geotemperature and moisture distributions caused by shady-sunny slope effect. (3) The composite measure can significantly reduce the embankment deformation, reliably alleviate the deformation difference and reinforce the stability of the expressway embankment in permafrost regions.

不同坡向川西亚高山林木竞争与叶片表型可塑性的关系研究

PDF HTML阅读 XML下载 导出引用 引用提醒 不同坡向川西亚高山林木竞争与叶片表型可塑性的关系研究 DOI: 10.5846/stxb202009172425 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划项目（2017YFC0505003） Relationships between competition intensity and leaf phenotypic plasticity of woody plants in subalpine forests on different slope directions Author: Affiliation: Fund Project: 2017YFC0505003 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:表型可塑性是植物生长响应外界环境变化的重要表现形式，体现了植物个体在环境胁迫下的适合度。但是关于植物表型可塑性的驱动机制仍然存在很多争议。为了探讨植物表型可塑性的影响因素，以四川省阿坝藏族羌族自治州位于同一海拔梯度但坡向相反的天然次生林为研究对象，分析了不同坡向竞争强度与10种树木叶片功能性状表型可塑性的关系的差异。研究发现：（1）研究样地中阴坡水分和养分资源优于阳坡；（2）阴坡上林木平均种内和种间竞争强度高于阳坡，阴坡上林木种内竞争强度随着树木个体大小的增加而显著性减少，阳坡上林木种内竞争强度却随着个体大小的增加而增加；（3）阴坡上叶片表型可塑性高于阳坡，表型可塑性随着个体大小的增加而增加，在阳坡上却随着个体大小增加而降低。这些结果表明阴坡上水分等资源环境条件优于阳坡，林木生长受到环境资源限制较少。在林木生长过程中，较高的竞争强度引起的资源重叠加剧，尤其是种内竞争强度的变化，从而导致了阴坡上较高的叶片表型可塑性。因为较高的竞争强度，随着林木个体大小的增加，树木需要更高的可塑性赢得竞争优势来获取更多的资源支持生长。但是在阳坡上，资源相对缺乏，环境资源对树木生长的限制降低了叶片表型的可塑性，因为环境资源的限制，随着树木个体大小的增加越容易受到资源限制的影响，因此阳坡上表型可塑性随着个体大小的增加而降低。研究说明，阴坡上叶片表型可塑性主要受到竞争强度的影响，而阳坡上则主要受环境资源的限制。 Abstract:Phenotypic plasticity is an indicator of the responses of plant growth and development to environmental changes, which reflects the fitness of plant individuals under environmental stress. However, the driving mechanism of plant phenotypic plasticity is still controversial. To explore the impacts of environmental conditions and competition on the phenotypic plasticity of leaf traits in trees, we surveyed two secondary forests with different slope directions in the Ngawa (Aba) Tibetan and Qiang Autonomous Prefecture in western Sichuan, China and analyzed the difference in the relationship between competition intensity and phenotypic plasticity of 10 tree species leaf functional traits between shade and sunny slopes. Results show that:(1) water and nutrient availabilities were greater on shade slope than those on sunny slope. (2) Mean intraspecific and interspecific competitions of tree species on shade slope were higher than those on sunny slope; intraspecific competition intensity decreased with the increases of individual tree size on shade slope, but it increased along with the increase of individual size on sunny slope. (3) The leaf traits include specific leaf area (SLA), leaf carbon content (C), leaf nitrogen content (N), leaf phosphorus content (P), leaf kalium content (K), leaf carbon-phosphorus ratio (CPR), leaf carbon-nitrogen ratio (CNR), and leaf nitrogen-phosphorus ratio (NPR). Phenotypic plasticity of all eight measured leaf traits on shade slope was higher than on sunny slope. Phenotypic plasticity of leaf traits increased with the increase of individual tree size on shade slope, but decreased with the increase of individual size on sunny slope. These findings suggest that the environmental resources of community on shade slope were greater than on sunny slope. The growth of forest trees was less restricted by the availability of environmental resources on shade slope, where higher competition intensity led to the intensification of resource overlap, especially the high intraspecific competition intensity, ultimately resulted in the higher phenotypic plasticity of leaf traits on shade slope. Because of higher competition intensity, with the increase of individual size, trees need higher phenotypic plasticity to gain competitive advantage and obtain more resources to support growth. However, because resources were relatively poor, the limitation of the availability of environmental resources reduced to the lower phenotypic plasticity of leave traits on sunny slope. Due to the limitation of the availability of environmental resources, with the increase of individual size, trees were more likely to suffer resource constraints. Therefore, phenotypic plasticity of leaf traits on sunny slope decreased with the increase of tree individual size. To summary, our study demonstrated that leaf phenotypic plasticity was mainly affected by competition intensity on the shade slope, while it was mainly limited by the availability of environmental resources on the sunny slope. 参考文献 相似文献 引证文献

内蒙古大青山国家级自然保护区植被归一化指数时空变化及其与环境因子的关系

PDF HTML阅读 XML下载 导出引用 引用提醒 内蒙古大青山国家级自然保护区植被归一化指数时空变化及其与环境因子的关系 DOI: 10.5846/stxb202108072161 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 内蒙古自治区科技重大专项项目（zdzx2018060，2019ZD007）；内蒙古自治区退耕还林生态效益监测项目 Spatio-temporal variation of NDVI and influencing factors in the Daqing Mountain National Nature Reserve, Inner Mongolia Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:选取2000-2020年MODIS影像的归一化指数（NDVI）数据及同期的气象数据，采用趋势分析、变异系数、相关分析等方法，从海拔、坡度和坡向的角度分析了内蒙古大青山国家级自然保护区生长季NDVI的时空变化特征，并进一步探讨了NDVI时空变化与气候因子的相关性。结果表明：（1）2000-2020年，内蒙古大青山国家级自然保护区植被总体覆盖状况良好且呈增长趋势，增长速率为0.058/10a；（2）保护区NDVI空间分布呈现出西部低、东部高的从西到东逐渐增加的特征。保护区生长季NDVI均值随着海拔的升高而明显增加，随着坡度的增加呈缓慢增加趋势，在不同坡向上，生长季NDVI均值大小依次为阴坡 > 半阴坡 > 半阳坡 > 阳坡；（3）从NDVI变化趋势分析来看，2000-2020年大青山自然保护区植被覆盖改善的面积占总面积的61.75%，其中，显著改善、极显著改善面积分别占总面积的41.13%、20.62%，基本保持不变的面积占总面积的38.17%，退化面积占总面积的0.07%。在空间分布上，NDVI显著、极显著增加的区域主要分布在保护区西部和东部，中部以变化不显著为主。保护区各功能区NDVI变化趋势看，NDVI极显著增加、显著增加面积百分比大小顺序为实验区 > 核心区 > 缓冲区；（4）2000-2020年，稳定性整体表现为"不同波动变化并存，较低、中等和较高波动变化居多，低波动和高波动变化面积占比相对较小"的特点，高波动变化区域主要分布在保护区西部、中部和实验区，人为影响和降水量是影响稳定性的主要驱动因素；（5）大青山自然保护区生长季NDVI与年均降水量以正相关为主，正相关面积比例达到99.79%，与温度相关性不显著为主，不显著面积占总面积的97.91%，降水量是影响大青山自然保护区植被覆盖的最主要气象因子。 Abstract:Based on the Normalized Difference Vegetation Index (NDVI) data of Moderate Resolution Imaging Spectroradiometer (MODIS) image and the relative meteorological data from 2000 to 2020, the temporal and spatial variation characteristics of NDVI in the growing season of Daqing Mountain National Nature Reserve in Inner Mongolia are analyzed from the perspective of elevation, slope and slope aspect by using the methods of trend analysis, coefficient of variation and correlation analysis. The correlation between temporal and spatial variation of NDVI and climate factors was further explored. The results show that:(1) The overall vegetation coverage of Daqing Mountain National Nature Reserve was good and growing from 2000 to 2020, with a growth rate of 0.058/10a. (2) The spatial distribution of the NDVI shows the characteristics of low in the west and high in the east, and gradually increasing from west to east of the reserve. With the increase of elevation, the mean value of NDVI in the growing season of the reserve increased significantly, but increased slowly with the increase of the slope. In different slope aspects, the mean value of NDVI in growing season was shady slope > semi-shady slope > semi-sunny slope > sunny slope. (3) From the analysis of NDVI change trend in 2000-2020, the area of vegetation coverage improvement in Daqing Mountain National Nature Reserve accounted for 61.75% of the total area, of which the areas of significant improvement and extremely significant improvement accounted for 41.13% and 20.62% of the total area, respectively, the area basically unchanged accounted for 38.17% of the total area, and the degraded area accounted for 0.07% of the total area. In terms of spatial distribution, the areas with the significant and extremely significant increase in NDVI were mainly distributed in the west and east of the reserve, and the change was not significant in the middle. According to the changing trend of NDVI in each functional area of the reserve, the NDVI increased significantly, and the area percentage increased significantly in the order of experimental zone > core zone > buffer zone. (4) From 2000 to 2020, the overall performance of stability is characterized by the coexistence of different fluctuations, the majority of low, medium and high fluctuations, and the proportion of low and high fluctuations being relatively small. The high fluctuations are mainly distributed in the western and central areas of the reserve and the experimental zone, and human disturbance and precipitation are the main driving factors. (5) The average annual maximum NDVI in the growing season of Daqing Mountain National Nature Reserve is mainly positively correlated with the average annual precipitation, and the proportion of the positive correlation area reaches 99.79%. It is mainly insignificant with temperature, and the insignificant area accounts for 97.91% of the total area. Precipitation is the main meteorological factor affecting the vegetation coverage of Daqing Mountain National Nature Reserve. 参考文献 相似文献 引证文献

鹞落坪国家级自然保护区草本植物多样性及空间分布

鹞落坪国家级自然保护区草本植物多样性及空间分布

秦岭山地碳中和空间服务范围及其模拟预测

PDF HTML阅读 XML下载 导出引用 引用提醒 秦岭山地碳中和空间服务范围及其模拟预测 DOI: 10.5846/stxb202112053440 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学青年基金项目（42071285）；国家自然科学基金项目（41771576）；陕西省自然科学科学基金项目（2021JQ-818）；咸阳师范学院青年骨干教师培养基金项目（XSYGG201902） Spatial service scope and simulation prediction of carbon neutralization in Qinling mountains Author: Affiliation: Fund Project: The National Natural Science Foundation of China (General Program, Key Program, Major Research Plan) 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:在当前碳中和背景下，秦岭山地碳中和的量化及其空间服务范围的测算对于碳中和合理规划和快速实现具有重要意义。采用IUEMS （Intelligent Urban Ecosystem Management System）系统对秦岭山地的固碳量进行核算，利用DMSP/OLS （Defense Meteorological Satellite Program/Operational Linescan System）和NPP-VIIRS （Net Primary Productivity-Visible infrared Imaging Radiometer）夜间灯光数据和各地市的能源消耗数据通过模型拟合对秦岭山地碳排放量进行空间量化，基于固碳量和碳排放量得到秦岭山地空间碳中和量。利用PLUS （Patch-generating Land Use Simulation Model）模型模拟了2030和2050年的碳中和空间分布，结合常见气体扩散系数计算得到常温常压下秦岭山地碳中和对周边区域的服务范围。结果表明：2000-2020年秦岭山地固碳量呈现上升的趋势，大部分区域不同时间尺度上的固碳速率呈正向趋势，空间上秦岭山地中西部区域固碳量整体较大；对秦岭固碳量影响较大的地形特征为海拔1200m左右、斜坡、半阳坡和半阴坡；研究区内碳排放量空间上整体较低，碳排放低值区面积占到了秦岭总面积的90%，碳排放较大区域主要位于秦岭北坡的城区区域，时间上碳排放量最大值为先增加后减少的变化趋势；2000-2050年秦岭山地碳汇服务范围为174-262.63km，服务范围在空间上呈逐渐扩大趋势，2030年后其扩大程度将略有减少。 Abstract:Under the current background of carbon neutralization, the quantification of carbon neutralization in Qinling mountains and the calculation of its spatial service scope are of great significance for rational planning and rapid realization of carbon neutralization. Intelligent Urban Ecosystem Management System (IUEMS) was used to calculate the amount of carbon sequestration in the Qinling mountains. The spatial quantification of carbon emissions in the Qinling mountains was carried out by fitting the model with the data of night light and energy consumption of various cities. Based on carbon sequestration and carbon emissions, the spatial carbon neutralization of Qinling mountains was obtained. PLUS (The patch-generating Land Use Simulation Model) was used to simulate the spatial distribution of carbon sequestration in 2030 and 2050. Combined with the diffusion coefficients of common gases, the service scope of carbon neutralization for surrounding regions in Qinling mountains was obtained. The results showed that the carbon sequestration in the Qinling mountains showed an upward trend from 2000 to 2020, and the carbon sequestration rate in most regions showed a positive trend at different time scales. The carbon sequestration in the central and western regions of the Qinling mountains was larger in space. The topographic features that have great influence on the carbon sequestration in the Qinling mountains were slope, half sunny slope and half shady slope with an altitude of about 1200 m. In the study area, the overall spatial carbon emission was low, and the area with low carbon emission value accounted for 90% of the total area of the Qinling mountains. The area with large carbon emission was mainly located in the urban area of the northern slope of the Qinling mountains. In terms of time, the maximum carbon emission increased first and then decreased. From 2000 to 2050, the service range of carbon sink in Qinling mountains is 174-262.63 km, and the service range is gradually expanding in space, and the expansion degree will decrease slightly after 2030. 参考文献 相似文献 引证文献

横断山区龙蜥属(Diploderma)物种生境偏好和形态分化

PDF HTML阅读 XML下载 导出引用 引用提醒 横断山区龙蜥属(Diploderma)物种生境偏好和形态分化 DOI: 10.5846/stxb202104160986 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 生态环境部"生物多样性调查与评估"项目（2019HJ2096001006）；第二次青藏高原综合科学考察研究项目（2019QZKK04020202，2019QZKK050100503） Habitat preference and morphological differentiation of Diploderma in Hengduan Mountainous Region Author: Affiliation: Fund Project: The Biodiversity Survey and Assessment Project of the Ministry of Ecology and Environment, China (2019HJ2096001006) to Yin QI and Feng XIE. The Second Tibetan Plateau Scientific Expedition and Research Program (2019QZKK04020202, 2019QZKK050100503). 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:横断山区是全球25个生物多样性热点之一，其生态安全和生物多样性保护备受国内外关注。经济社会发展给横断山区特有龙蜥属动物带来许多新的挑战，大量原始生境被道路修建和水电工程彻底破坏，有些物种甚至在局部地区灭绝。因此及时开展龙蜥保护生态学相关研究，对准确制定保护行动计划非常关键。生境偏好与形态分化是保护生态学研究的重要内容。采用样线和样方法，对横断山区9个龙蜥属物种生境因子进行了测量。同时借助野外标本采集和标本馆标本测量，对19个龙蜥属物种进行了形态量化。采用广义线性混合模型（Generalized Linear Mixed Model，GLMM）和基于系统发育的广义最小二乘法（Phylogenetic Generalized Least-Squares，PGLS）对龙蜥生境偏好和形态学分化进行了分析。结果表明，来自不同生境的龙蜥对生境因子具有特殊的偏好。灌丛型龙蜥更偏好石块灌丛、阳坡、较陡、平均石块粒径较大、温度适中的生境，偏好生境中往往有两头毛（Incarvillea arguta）分布；林地型龙蜥偏好乔木、较陡的上坡位和植被覆盖率高的生境，偏好生境中往往有红花羊蹄甲（Bauhinia×blakeana）分布。从形态分化方面看，灌丛型和林地型龙蜥在体型大小和运动形态方面均发生了明显地分化，对雄性而言，林地型龙蜥尾长、鼻眼距、第4指长以及第4趾爪长大于灌丛型龙蜥，而灌丛型龙蜥吻长和胫骨长大于林地型龙蜥。对雌性而言，尾长、头长、吻长、鼻眼距、第4指长、第4趾长以及第4趾爪长均为林地型龙蜥大于灌丛型。研究为横断山区龙蜥生境偏好和形态分化提供了直接证据，有助于理解龙蜥对干热河谷生境的适应策略，同时为科学制定龙蜥保护计划提供重要支撑。 Abstract:Hengduan Mountainous Region (HMR) is one of the top 25th biodiversity hotspots in the world, and its ecological security and biodiversity conservation have increasingly attracted much attention from China and other countries. Economic and social development has brought many new challenges to the survival of Diploderma, the endemic species of the HMR. The original habitats of several Diploderma species have completely been destroyed because of road construction and hydropower projects, and what made us worrying was some species that have become extinct in local areas. Therefore, timely research on the conservation ecology of Diploderma is very important and urgent to the design of conservation plan. Habitat preference and morphological differentiation are important contents of conservation ecology research. In this study, the habitat factors including habitat type, vegetation coverage, vegetation height, stone size, distance road, interference factor, slope direction, slope position, gradient, temperature, and humidity of 9 Diploderma species in HMR were measured by line and square to transect. At the same time, the morphological characters of 19 Diploderma species were quantified using field sampling and herbarium specimen. Habitat preference and morphological differentiation were analyzed using Generalized Linear Mixed Model (GLMM) and Phylogenetic Generalized least-squares (PGLS). The results showed that Diploderma from different habitat types had special preferences for habitat factors. The species distributed in shrub preferred the habitats with stone, brush, steeper sunny slopes, large stone size, and suitable temperature (25-35℃), with Incarvillea arguta. The species distributed in forest preferred the habitats with big trees, steeper hill and high vegetation coverage, with Bauhinia×blakeana. Our results also showed much differentiation in body size and locomotion characters between shrub-type and forest-type lizard. For males, forest distributing species possessed large size in tail length, nose-eye distance, 4th finger length and claw length of the 4th toe compared with shrub distribution species, meanwhile snout length and shin length were just the opposite. While for females, forest distribution species possessed large size in tail length, head length, snout length, nose-eye distance, 4th finger length, 4th toe length and claw length of the 4th toe compared with shrub distribution species. Taken together, our study provides direct evidence for habitat preference and morphological differentiation of the endemic lizards' species in HMR, while it would greatly contribute to the understanding of adaptation tactics towards the dry-hot valley habitat in Diploderma, as well as provide important support for the design of conservation plan. 参考文献 相似文献 引证文献

Impacts of 1-Aminocyclopropane-1-Carboxylic Acid as a Late Post-Bloom Thinner on Fruit Set, Yield, and Fruit Quality in “Gala” and “Fuji” Apples

A few post-bloom thinners are available for apple (Malus domestica Borkh.) and the prospects for additional thinners appear to be limited. Application of blossom thinners may present a risk of overthining in the areas where weather is less predictable. Thus, we studied the impacts of various rates of 1-aminocyclopropane-1-carboxylic acid (ACC) in three strains of “Fuji” apple and different rates of ACC and one rate of Ethrel in “Buckeye Gala” apple, when fruitlet diameter was about 20 mm, on fruit set, yield and fruit quality attributes at harvest, and return bloom in southwest Idaho in the Intermountain West region, USA. In 2013, application of Ethrel at 300 mg·L-1 did not affect fruit set, fruit weight, diameter (D), length(L), or L/D ratio 34 days after application, or yield, fruit weight, color, russet, and starch degradation pattern (SDP) at harvest, while application of ACC at 150 mg·L-1 or higher reduced fruit set by 19% to 34% in “Buckeye Gala” apple. In this cultivar, application of ACC at 350 mg·L-1 significantly increased fruit weight, diameter and length 34 days after application, and increased fruit weight, color, and SDP at harvest time. Application of ACC at all rates reduced total yield per tree in “Buckeye Gala”. Application of ACC at 300 mg·L-1 significantly reduced fruit set but applications of 150 mg·L-1 or 300 mg·L-1 ACC did not affect yield or quality attributes of “Sun Fuji” apple in Sunny Slope area in 2013. Application of ACC reduced fruit set and slightly increased fruit size in “Top Export Fuji” in 2013. Application of ACC at 600 mg·L-1 significantly reduced fruit set in “Aztec Fuji” apple in 2014. Application of ACC in a season never reduced bloom density (return bloom) of the next season. Overall, we conclude that ACC is an excellent tool as a late-season post-bloom fruit thinner and can be effective when applied fruitlet diameter is about 20 mm.

Effect of Cultivation Methods on Seed Yield Traits, Oil Yield, and Fatty Acid Compositions of Cultivated Paeonia ostii

Paeonia ostii is recognized as an important oilseed tree peony species with potential as a raw material source for cosmetic and health care products, strong seed setting capacity, high seed oil yield, and abundant omega-3 polyunsaturated fatty acids. P. ostii, commonly called Fengdan, is widely cultivated in China. The cultivation method difference has an important influence on the oil-use feature, which is a key index for evaluating the quality of oilseed crops. This study aimed to select an optimal cultivation method to provide the first reference data for high-yield and high-quality seed oil harvesting and to facilitate the understanding of the quality difference in the formation mechanism of seed oil in cultivated P. ostii. This study selected five representative cultivation methods, open field cultivation, sunny slope cultivation, shady slope cultivation, understory intercropping cultivation, and high-altitude cultivation, and investigated the influence of cultivation method differences on the oil-use feature based on the three aspects of seed yield traits, oil yield, and fatty acid compositions. Six seed yield traits (fruit pod length, fruit pod width, fruit pod thickness, number of fruit pods per plant, 1000-grain weight, and seed yield per plant) and oil yield reached the maximum values of 7.75 cm, 6.99 cm, 1.57 cm, 11.33, 290.45 g, 85.8 g, and 30.41%, respectively, using the understory intercropping cultivation method. Fatty acid compositions were mainly identified as α-linolenic acid, linoleic acid, oleic acid, stearic acid, and palmitic acid, with significant content differences among different cultivation methods (P < 0.05). Functional component α-linolenic acid and total amounts of unsaturated fatty acids reached the maximum values of 46.85% and 65.23%, respectively, with high-altitude cultivation and understory intercropping cultivation. The seed yield traits, oil yield, and total amounts of unsaturated fatty acids were optimal with the understory intercropping cultivation method, whereas high-altitude cultivation was conducive to the accumulation of α-linolenic acid. Understory intercropping cultivation with appropriate altitude increases is recommended as a preponderant cultivation method for high-yield and high-quality seed oil harvesting for this crop.

How Does Spring Phenology Respond to Climate Change in Ecologically Fragile Grassland? A Case Study from the Northeast Qinghai-Tibet Plateau

Vegetation phenology is an important indicator of global climate change, and the response of grassland phenology to climate change is particularly sensitive in ecologically fragile areas. To enhance the ecological security of the Tibetan Plateau, it is crucial to determine the relationship between fluctuations in the start of the growing season (SOS) and the response to environmental factors. We investigated the trends of the intra-annual (ten-day) and interannual spatiotemporal dynamics of the SOS on the Northeast Qinghai-Tibet Plateau (NQTP) from 2000–2020 with MOD09GA data. We identified the response relationships with environmental factors (climate, terrain) using the maximum value composite method and the Savitzky–Golay filtering and dynamic threshold method. The SOS was concentrated from the 110th to 150th days; the average annual SOS was on the 128th day, with a spatial pattern of “early in the east and late in the west”. The overall trend of the SOS was advanced (45.48%); the regions with the advanced trend were mainly distributed in the eastern part of the NQTP. The regions with a delayed SOS were mainly concentrated in the higher-altitude regions in the southwest (38.31%). The temperature, precipitation and SOS exhibited a reverse fluctuation trend around the midpoint of 2010. Precipitation affected the SOS earlier than temperature. When temperature became a limitation of the SOS, precipitation had a more significant regulatory effect on the SOS. The SOS and aspect, slope and altitude were distributed in axisymmetric, pyramidal and inverted pyramidal shapes, respectively. The SOS on shaded slopes was earlier and more intensive than that on sunny slopes. With increasing slope, the area of the SOS decreased, and it occurred later. The SOS area was largest at 4500–5000 m and decreased at lower and higher altitude intervals. The SOS occurred later as altitude increased.

Spatiotemporal change and driving factors of the Eco-Environment quality in the Yangtze River Basin from 2001 to 2019

The Yangtze River Basin has a wide range and complicated topography. In recent years, under the background of climate and land cover change, the ecological response of the whole ecological quality of the Yangtze River Basin is still unknown. To reveal the spatiotemporal changes in ecological quality in the Yangtze River Basin from 2001 to 2019 and their relationship with environmental and topographical factors, this study used the Google Earth Engine (GEE) platform to calculate the remote sensing ecological index (RSEI) based on the Moderate-resolution Imaging Spectroradiometer (MODIS) product image set, combined with the digital elevation data set and statistical yearbook. The data evaluated the ecological quality of the Yangtze River Basin and analyzed its causes. The results showed that: 1) the average RSEI of the Yangtze River Basin showed an overall upward trend, the growth rate was 0.027 (year−1), and the variation ranged from 0.5 to 0.568. The overall ecological quality rank was mainly neutral and slightly good. 2) The ecological quality of 85.7% of the Yangtze River Basin remains stable. A total of 11.2% of the regional ecological quality is improving, and 3.1% of the regional ecological quality is declining. Areas with reduced ecological quality are concentrated in the Hengduan Mountains. The dominant LST factor drives the deterioration of its ecological quality at a rate of −1.06 (year−1). The areas with improved ecological quality are concentrated in the upper and middle reaches of the Yangtze River. The dominant WET factor drives its ecological quality to improve at a rate of 0.27 (year−1). 3) From the perspective of topography, the ecological quality of the Yangtze River basin shows a wave-like decline and first rises and then falls in elevation and slope (the elevation is bounded by 2000 m and 6000 m, and the slope is bounded by 15°.). The average RSEI of the Yangtze River Basin is the highest on the northwest slope (0.554), and the ecological quality of sunny slopes is generally higher than that of shady slopes. The research shows that from 2001 to 2019, the overall ecological quality of the Yangtze River Basin has improved and evolved, but the ecological quality of the Hengduan Mountains has declined. Therefore, implementing different ecological protection policies in different regions is an important strategy for enhancing the stability of the ecosystem.

Altitude and landslide scale regulated the assembly of grassland communities on landslides during the recovery process after the magnitude 8.0 Wenchuan earthquake, China

Earthquakes are one of the worst natural disasters, causing environmental fluctuations and ecosystem degradation. Previous studies have evaluated the macro-characteristics of vegetation recovery after earthquakes. However, the internal mechanisms driving community assembly and diversity remain poorly understood. This study was located in Longxi-Hongkou National Natural Reserve, China. We investigated the current vegetation status of typical large-scale landslides in regions with the highest intensity of earthquake damage in the area affected by the 2008 magnitude 8.0 earthquake, and studied the community assembly using phylogenetic methods. Relationships between community assembly and influencing factors were carried out using generalized linear models (GLMs) and redundancy analysis (RDA). Our findings suggested that the communities in areas of larger landslides were dominated by herbs 11 years after the earthquake and had not yet regenerated to the original community. The average net relatedness index (NRI) and nearest taxon index (NTI) of the communities were 0.293 and 0.482, respectively, which were higher than those of the null model. These results showed a clustered phylogenetic pattern and suggested that the community assembly process in the early regeneration stage after the earthquake supported the environmental filtering hypothesis. Altitude negatively impacted species diversity, NRI, NTI and phylogenetic diversity. This result suggested that the community assembly process was more dependent on abiotic regulation than biotic regulation at high altitudes after earthquakes. Species diversity, NRI, NTI and phylogenetic diversity were also impacted by landslide intensity; however, the responses to landslide intensity were not completely equivalent for landslides of varying widths and lengths. Slope aspect impacted the phylogenetic diversity of the regenerating community after the earthquake; that is, the sunny slopes had higher phylogenetic diversity than the shady slopes. Soil type, soil organic carbon, soil nitrogen, soil moisture, and soil phosphorous impacted community assembly. Collectively, This work showed evidence supporting the abiotic regulation of community assembly after earthquakes and reported the key abiotic influencing factors. It is important for a general understanding of community assembly after strong disturbances in temperate forests and beyond and can also provide a theoretical basis for ecological restoration engineering design.

Spatiotemporal Monitoring of Soil CO2 Efflux in a Subtropical Forest during the Dry Season Based on Field Observations and Remote Sensing Imagery

The CO2 efflux from forest soil (FCO2) is one of the largest components of the global carbon cycle. Accurate estimation of FCO2 can help us better understand the carbon cycle in forested areas and precisely predict future climate change. However, the scarcity of field-measured FCO2 data in the subtropical forested area greatly limits our understanding of FCO2 dynamics at regional and global scales. This study used an automatic cavity ring-down spectrophotometer (CRDS) analyzer to measure FCO2 in a typical subtropical forest of southern China in the dry season. We found that the measured FCO2 at two experimental areas experienced similar temporal trends in the dry season and reached the minima around December, whereas the mean FCO2 differed apparently across the two areas (9.05 vs. 5.03 g C m−2 day−1) during the dry season. Moreover, we found that both abiotic (soil temperature and moisture) and biotic (vegetation productivity) factors are significantly and positively correlated, respectively, with the FCO2 variation during the study period. Furthermore, a machine-learning random forest model (RF model) that incorporates remote sensing data is developed and used to predict the FCO2 pattern in the subtropical forest, and the topographic effects on spatiotemporal patterns of FCO2 were further investigated. The model evaluation indicated that the proposed model illustrated high prediction accuracy for the training and testing dataset. Based on the proposed model, the spatiotemporal patterns of FCO2 in the forested watershed that encloses the two monitoring sites were mapped. Results showed that the spatial distribution of FCO2 is obviously affected by topography: the high FCO2 values mainly occur in relatively high altitudinal areas, in slopes of 10–25°, and in sunny slopes. The results emphasized that future studies should consider topographical effects when simulating FCO2 in subtropical forests. Overall, our study unraveled the spatiotemporal variations of FCO2 and their driving factors in a subtropical forest of southern China in the dry season, and demonstrated that the proposed RF model in combination with remote sensing data can be a useful tool for predicting FCO2 in forested areas, particularly in subtropical and tropical forest ecosystems.

Characteristics and prevention mechanisms of artificial slope instability in the Chinese Loess Plateau

Numerous artificial slopes emerged in the watersheds of the Chinese Loess Plateau (LP) after the Gully Land Consolidation project (GLCP) that cut slopes to create farmland in the gully, which had incurred instabilities over time and could potentially resulted in soil erosion and geological hazard. This paper explored the characteristics and prevention mechanisms of artificial slope instability after the GLCP with field investigation in a typical watershed and the Back Propagation Neural Network (BPNN) method. The results showed that: (1) 439 instabilities induced by infiltration and erosion were found in 79 artificial slopes. (2) The difference of soil moisture and failure mode resulted in the instability degree of shady slope and lower slope were significantly higher than that of sunny slope and upper slope. (3) Among the surface condition factors, slope instability volume was significantly influenced by gradient, soil compactness, height and soil shear strength. Platform instability volume had great connection with soil compactness and its shear strength. (4) A “Drain-Improve-Green-Reinforce (DIGR)” system was proposed as the prevention mechanism for artificial slope instability, which included drainage system, soil improvement, vegetation protection, and reinforcement engineering. Taken together, this research provides the scientific reference for a better understanding and prevention of artificial slope instability, which would contribute to ensuring GLCP effectiveness and ecological security in the LP.

InVEST Model-Based Spatiotemporal Analysis of Water Supply Services in the Zhangcheng District

The Zhangcheng District is critically responsible for protecting water resources, preserving sand sources, and improving the ecological environment in Beijing. Quantitative evaluation and research on the ecosystem water supply services in this area are beneficial for developing conservation planning and establishing ecological compensation mechanisms in water conservation areas. In this paper, based on the land use, meteorological, soil, and field observation data of the research area, the InVEST water yield model is used to estimate the water supply of the ecosystem in the Zhangcheng District. The model quantitatively analyzes the spatiotemporal distribution characteristics of water supply services in the basin and the influence of different topographic factors. The results show that the average supply of ecosystem water in the Zhangcheng District is approximately 45 mm, and there is a degree of spatial heterogeneity. The total water supply in the Zhangcheng District is relatively small. The water resource supply in the southwest is relatively small, the rainfall in mountainous forest areas in the southeast is high, its water supply is higher, and the supply of forest land water is relatively high. The high-value areas are mainly distributed at 1500 to 3500 m and 15°~40°; the water supply on the sunny slope is greater than that on the shady slope. With the increase in altitude and slope, the water supply in the basin tends to increase first and then decrease.

Long-term thermal stability and settlement of heat pipe-protected highway embankment in warm permafrost regions

Warm permafrost is a challenging geological material for infrastructure engineering. This study presents the observed damage, ground temperature, and settlement at varying depths from three-year continuous monitoring of two selected highway embankment segments along the Qinghai-Tibet Highway in warm permafrost areas, including one conventional embankment and the other with heat pipes on the sunny slope side. Field monitoring data reveal that the embankment settlement mainly results from thaw consolidation of warm permafrost, and the permafrost table beneath a conventional embankment is concave-shaped due to the polythermal effects of asphalt pavement. In contrast, the permafrost table underneath the embankment equipped with heat pipes on the sunny side is convex-shaped due to heat pipes' cooling effects. The different causes of longitudinal cracks on the two embankment surfaces were uncovered based on field observed data. Results of coupled hydro-thermal-mechanical model simulation considering climate warming show that while the configurations of heat pipes on both sides of the embankment can generally ensure the long-term thermal stability and limit the differential settlement across the road surface, the one with slanted heat pipes delivers the best performance and is recommended for future applications. Results from this study, including field monitoring data and recommended heat pipe configuration, will be of value for the construction and maintenance of transportation infrastructure in warm permafrost regions.

Aboveground biomass estimation of black locust planted forests with aspect variable using machine learning regression algorithms

An accurate estimation of forest aboveground biomass (AGB) is important for carbon accounting and afforestation policy making, and the aspect factors that affect forest stand growth are important to the accuracy of AGB estimation. In this study, aspect was incorporated as a variable into three machine learning algorithms (MLAs) (support vector machine (SVM), artificial neural network (ANN) and random forest (RF)), to estimate the AGB of black locust (Robinia pseudoacacia) planted forests in 96 field plots with four different aspects (sunny slope, semi-sunny slope, semi-shady slope and shady slope). The results showed that in the models incorporating aspect variables, the increase in accuracy varied from 36.72% to 41.23% for 29 validation plots based on R2. The A-RF model (RF with aspect variable), which had the highest R2 (0.8519) and lowest RMSE and rRMSE (12.552 Mg/ha and 0.175) was considered optimal for AGB estimation of black locust planted forests. The overestimation of sunny and shady slopes, and the underestimation of semi-sunny and semi-shady slopes are reduced by incorporating the aspect variable. Areas with lower AGB values mainly occur on sunny and shady slopes, and areas with higher AGB values mainly occur on semi-sunny and semi-shady slopes. Overall, our study demonstrates that the introduction of the aspect variable provided the model with a basis for the effects of different growth conditions of black locust planted forests on different aspects, which can improve the accuracy of AGB estimation.

Functional traits of Fagaceae plants in shady and sunny slopes in karst degraded tiankeng.

In the negative terrain habitat of the karst degraded tiankeng, the shady and sunny slopes are dramatically different, which results in substantial variations in plant communities. With the degraded tiankeng Shenxiantang in Zhanyi, Yunnan as an example, we explored the functional traits of Fagaceae plants in the shady and sunny slopes, which would help reveal the value of tiankeng as species diversity conservation pool. The results showed that soil nutrients in the shady slope were more than those in the sunny slope. Leaf area, specific leaf area and leaf dry weight of Faga-ceae plants in the shady slope were significantly larger than those in the sunny slope. Leaf thickness was significantly lower than that in the sunny slope. Dry matter content of leaves was less than that of the sunny slope. The main environmental factors affecting functional traits of Fagaceae plants in the shady slope were soil total potassium concentration and soil moisture, while soil total phosphorus concentration was the key factor in the sunny slope. The extent of variation of leaf functional traits in shady slope was less than that in the sunny slope. Fagaceae plants mainly adapted to the shady slope habitat by changing the leaf dry weight to increase photosynthetic rate and carbon accumulation abi-lity. Sunny slope obtained more resource by keeping smaller specific leaf area and increasing the extent of variation of the leaf area. The succession rate of plant community in the shady slope of the degraded tiankeng Shenxiantang was significantly faster than that in the sunny slope. The dominance of Fagaceae plants gradually decreased in the shady slope, but remained to be the constructive species in the sunny slope.

Burrow characteristics and ecological significance of Marmota himalayana in the northeastern Qinghai-Tibetan Plateau.

Burrows provide burrowing animals with a place to hibernate, reproduce, and avoid predators and harsh weather conditions and thus have a vital impact on their survival. However, the general physical characteristics and ecological functions of Marmota himalayana burrows as well as whether there are differences in burrow traits under different terrains (e.g., sunny slopes, shady slopes, and flat areas) are not well understood. From July to August 2019 (warm season), we used unmanned aerial vehicles to fly at low altitudes and slow speeds to locate 131 M. himalayana burrows (45 on shaded slopes, 51 on sunny slopes, and 35 on flat areas) in the northeastern Qinghai‐Tibetan Plateau region. We then measured the physical characteristics (burrow density, entrance size, first tunnel length, volume, orientation, and plant characteristics near the burrow entrance) of these burrows on site. We found that terrain had a substantial influence on burrow density, orientation, and entrance size and on the angle of the burrow entrance; species richness had a substantial impact on path density and tunnel volume. The physical parameters of the M. himalayana burrows showed that they function to protect the marmots from natural enemies and bad weather, provide good drainage, and maintain a stable microclimate around the entrance. We discuss the ability of burrowing animals (e.g., M. himalayana) to adapt to the external environment based on their burrow characteristics.