Soil water response to precipitation in different microtopographies on the semi-arid Loess Plateau,China

Soil water is an important factor restricting afforestation on the semi-arid Loess Plateau.The microtopography of the loess slope has changed the distribution pattern of soil water on the slope.To improve water utilization efficiency and optimize afforestation configuration patterns,the relationship between soil water and precipitation at micro-topographic scale must be studied.We used time series analysis to study the temporal variation of soil water and its response to precipitation in four kinds of micro-topographies and undisturbed slope on loess slopes.Micro-topographies significantly influenced soil water distribution and dynamics on the slopes.Soil water stored in the platform,sinkhole,and ephemeral gully influenced subsequent soil water for 4 weeks,whereas soil water stored in the scarp and undisturbed slope could influence soil water for 2 weeks.It took 12 weeks,10 weeks,18 weeks,6 weeks,and 12 weeks for precipitation to reach the deeper soil layer in the platform,sinkhole,scarp,ephemeral gully,and undisturbed slope,respectively.These soil water characteristics in different micro-topographies are vital factors that should be taken into consideration when undertaking afforestation on the Loess Plateau.     

中国观赏芍药表型多样性解析与资源评价

【目的】明确中国观赏芍药品种资源多样性水平,并从切花品种农艺性状角度分析资源特点,为种质收集、利用与创新提供理论依据。【方法】采集来自4个主要栽培地的346个中国观赏芍药品种,从品种资源整体和不同栽培地品种两个方面对采集的表型性状进行频率分布统计、变异系数计算和多样性指数计算,并进行聚类分析。【结果】我国观赏芍药品种多个性状多样性丰富,二元性状、有序多态性状和无序多态性状的多样性指数为0.29—1.90,数值性状的多样性指数为1.90—2.08。二元性状、有序多态性状和无序多态性中,花色和花型多样性指数最高,分别为1.90和1.88,其次是花蕾颜色（1.46）和雄蕊瓣化程度（1.42）。数值性状中,株高和茎长多样性指数最高,分别为2.08和2.07,其次是蕾径（2.04）、花径（2.04）和花高（2.01）,仅茎粗（1.99）和花梗长（1.90）多样性指数小于2。株高和茎长呈正态分布,株高介于38.50—100.50 cm,茎长介于43.19—120.00 cm;蕾径、花径、花高、茎粗和花梗长等5个指标呈非正态分布,蕾径偏大,分布介于1.22—3.99cm;花径变异系数最小,为15.6...     

Plant regeneration functional groups modulate the response to fire of soil enzyme activities in a Mediterranean shrubland

Soil enzymes are critical to soil nutrient cycling function but knowledge on the factors that control their response to major disturbances such as wildfires remains very limited. We evaluated the effect of fire-related plant functional traits (resprouting and seeding) on the resistance and resilience to fire of two soil enzyme activities involved in phosphorus and carbon cycling (acid phosphatase and β-glucosidase) in a Mediterranean shrublands in SE Spain. Using experimental fires, we compared four types of shrubland microsites: SS (vegetation patches dominated by seeder species), RR (patches dominated by resprouter species), SR (patches co-dominated by seeder and resprouter species), and IP (shrub interpatches). We assessed pre- and post-fire activities of the target soil enzymes, available P, soil organic C, and plant cover dynamics over three years after the fire. Post-fire regeneration functional groups (resprouter, seeder) modulated both pre- and post-fire activity of acid phosphatase and β-glucosidase, with higher activity in RR and SR patches than in SS patches and IP. However, we found no major differences in enzyme resistance and resilience between microsite types, except for a trend towards less resilience in SS patches. Fire similarly reduced the activity of both enzymes. However, acid phosphatase and β-glucosidase showed contrasting post-fire dynamics. While β-glucosidase proved to be rather resilient to fire, fully recovering three years after fire, acid phosphatase showed no signs of recovery in that period. Overall, the results indicate a positive influence of resprouter species on soil enzyme activity that is very resistant to fire. Long-lasting decrease in acid phosphatase activity probably resulted from the combined effect of P availability and post-fire drought. Our results provide insights on how plant functional traits modulate soil biochemical and microbiological response to fire in Mediterranean fire-prone shrublands.     

现代月季F_1群体的繁育系统分析

为研究现代月季F1群体的繁育系统,了解其传粉授粉方法及生殖方式和过程。本研究以现代月季F1群体为研究对象,测量花粉生活力、柱头可授性、花粉量-胚珠比、杂交指数等指标。结果显示,现代月季F1群体一年多次开花,单花开放分为6个阶段。群体表型具明显的性状分离,导致其在繁育系统上有一定程度的差异性。花粉生活力整体较低,在花朵开放期内都检测到柱头可授性,但其强度不同,呈现一定程度的雌雄蕊异熟。根据花粉量-胚珠比的测定结果,月季群体的P/O值差异较大,在528.3~13638.2之间,杂交指数为4,二者测定结果相一致符合,属于异交为主,自交部分亲和且需要传粉者。研究结果表明重瓣性对于开花过程及传粉授粉影响很大,使得群体内繁育系统出现较大差异;现代月季F1群体属于异交为主,部分自交亲和的类型;进一步杂交育种工作中,在群体中选择杂交指数较高的植株进行试验。     

锌钾营养对温室无土栽培番茄生理和品质的影响

以番茄品种丰收为试材,在封闭式循环无土栽培系统下研究锌肥和钾肥对番茄植株生长、光合特性、产量和品质的影响。结果表明,增施锌肥、钾肥均能提高番茄植株的株高、茎粗、叶片数;提高番茄净光合速率、蒸腾速率等光合指标;番茄果实VC、可溶性糖、可溶性固形物、可滴定酸含量及糖酸比均增加,单果质量和单株产量显著提高,其中钾肥对番茄生长、产量和品质的影响高于锌肥,锌肥和钾肥同施的效果优于单独施用。     

国内外茶叶农药最大残留限量标准对比分析及建议

为探究茶叶农药最大残留限量标准现状,对比了我国《食品安全国家标准食品中农药最大残留限量》(GB 2763—2019)中涉及茶叶的农药最大残留限量指标与欧盟及日本制定的农药最大残留限量指标,分析了中国与欧盟及日本茶叶中农药最大残留限量指标的差异,提出了我国茶园农药的使用和管控建议,以期为茶叶安全优质生产提供理论参考。     

Research on landscape quality of country parks in Beijing as based on visual and audible senses

Construction of Chinese country parks has been developing quickly in recent years, but less effort has been made in the field of esthetic quantitative evaluation of landscape of the country parks. Based on the theories of landscape esthetics and psychology, this paper constructs a landscape quality evaluation model for the country parks by means of SBE and SD methods, with which the authors of the paper carried out the research on and evaluation of the landscape quality of four selected country parks outside the Fifth Ring Road in Beijing. The purpose of this paper is to further put forward suggestions for a better development of the landscape of the four country parks in order to bring their landscape and recreation functions into full play. The findings of this paper indicate that both natural and artificial landscape characteristics exercise either positive or negative influences on landscape quality; among them the effect of vitality, color richness, senses of both joy and beauty are the key elements affecting the attraction of the country park's landscape. Country parks boast with special significance because of their localism, naturalness and tranquility. These advantages are fully shown in their sufficient space for waterscape construction and conspicuous effect on landscape as reflected from the green belts previously constructed. Nevertheless, three major problems existed in the country parks including insipid color, over artificialized parkways, and peripheral high-rise buildings in the nearby neighborhood that have also given rise to visual interference. Recommendations for relevant landscape construction and protection of the country parks are suggested.     

The effects of three regeneration harvest methods on plant diversity and soil characteristics in the southern Appalachians

We evaluated the effects of three regeneration harvest methods on plant diversity and soil resource availability in mixed-hardwood ecosystems. The study area is in the Wine Spring Creek watershed on the Nantahala National Forest of the Southern Appalachian Mountains in western North Carolina. The regeneration treatments were: an irregular, two-aged shelterwood cut (2A), with 5.0 m²/ha residual basal area; a shelterwood cut (SW), with 9.0 m²/ha residual basal area; a group selection cut (GS), with 0.10–0.20 ha openings and 25% overstory removal on area basis at first entry; fourth, the control, consisted of two uncut sites (UC). Each harvest treatment was replicated three times across the landscape in similar plant community types. Within each treatment area, permanent plots were marked and inventoried for overstory, midstory, and herbaceous layer plants. In each permanent plot, we collected soil samples in winter (December–March) to reduce temporal variation due to vegetation phenological stage and rainfall events. We analyzed soil samples for extractable calcium (Ca), magnesium (Mg), potassium (K), cation exchange capacity (CEC), pH, bulk density, A-horizon depth, total carbon (C), and nitrogen (N). Species diversity of overstory, understory, and herbaceous layer species was evaluated using species richness (S), Shannon–Wiener's index of diversity (H′), and Pielou's evenness index (E). We used direct gradient analysis (non-metric multidimensional scaling, NMS) to explore the changes in vegetation–site relationships among herbaceous layer abundance, and soil characteristics and overstory basal area between pre-harvest (1994) and post-harvest (2000). Twelve minor overstory species were cut from the 2A treatments and nine species were cut from the SW treatments. Thus, it is not surprising that S and H′ were reduced in the overstory on the heavily cut sites. However, most of these species sprouted from cut stumps and were substantially more abundant in the midstory layer after harvest than before. For the midstory, we found higher S and H′ on the harvested treatments than the control; however, H′ did not differ significantly among the harvest treatments. We measured an increase in herbaceous layer H′ on the more heavily cut treatments (2A and SW) after harvest. We found an increase in average distance in the NMS ordination among sites in 2000 compared to 1994, which suggests greater herbaceous species diversity after harvest. However, we did not see a clear separation among harvest treatments in the NMS ordination.     

南方红壤区自然灾害刚弹韧性社会评估——以福建省长汀县为例

[目的]探索建设更加强健、有效的自然灾害刚弹韧性社会途径,为南方红壤区防范化解重大自然灾害风险提供科学参考。[方法]以南方红壤区典型受灾区福建省长汀县为例,从刚性抵御、弹性管控、韧性恢复3个维度构建了指标体系,利用熵权TOPSIS模型和耦合协调度模型定量评价了2006—2019年长汀县的自然灾害刚弹韧性社会综合水平及一级指标间的耦合协调性,并进行障碍度因子分析。[结果](1)长汀县的自然灾害刚弹韧性社会水平经历了由缓慢下降到显著增长的演化过程,在2006—2019年增长了0.461 6,总体呈现显著增长趋势。(2)长汀县自然灾害刚弹韧性社会的刚性抵御水平、弹性管控水平和韧性恢复水平总体呈现显著增长趋势,仅韧性恢复指数在2006—2010年呈明显下降趋势,由0.402 0下降至0.280 9。(3)在各项评价指标中,灾害监测能力、治安管理水平、第三产业比重、碳储存能力的下降以及水源涵养功能的减退是限制长汀县自然灾害刚弹韧性社会发展的关键因素。[结论]从刚性抵御、弹性管控、韧性恢复3个维度对南方红壤区进行评估能较为有效、准确地反映该地区的自然灾害刚弹韧性社会综合水平。同时,应补齐发展短板,...     

Changes in enzyme activities of spruce (Picea balfouriana) forest soil as related to burning in the eastern Qinghai-Tibetan Plateau

The effect of forest fire on soil enzyme activity of spruce (Picea balfouriana) forest in the eastern Qinghai-Tibetan Plateau was assessed. Six specific enzymes were chosen for investigation: invertase, acid phosphatase, proteinase, catalase, peroxidase and polyphenoloxidase. It was found that the activities of invertase and proteinase were reduced by burning, but the activities of acid phosphatase, polyphenoloxidase and peroxidase increased. Meanwhile, burning significantly (P < 0.05) resulted in the decrease of concentrations of available N and K of 0–20 cm depth layer soil, and significantly (P < 0.05) decreased concentrations of organic matter content, total N and P, as well as available N, P and K in soil at both 20–40 and 40–60 cm depths except for available P at 20–40 cm soil depth. These results illustrated that burning could influence the enzyme activities and chemical properties of soil not only of upper but also lower soil layers. Correlation analysis indicated that invertase activities in 0–20 cm depth layer soil were significantly positively correlated with organic matter, total N and P, as well as available N and P. Furthermore, all six enzymes studied were sensitive to fire disturbance, and thus could be used as indicators of soil quality. Our study also showed that soil enzyme activities were associated with soil depth, decreasing from top to bottom in both burned and unburned spruce forests. The distribution pattern of soil enzyme activities suggested that the rate of organic matter decomposition and nutrient cycling depended on soil depth, which had important structural and functional characteristics in nutrient cycling dynamics and implications in plantation nutrient management. The finding that burning effects on enzyme activities and soil properties between different soil layers were homogenized was attributed to the 8-years’ regeneration of forest after burning.