宁夏土地利用碳排放强度时空变化与效应

[目的] 土地利用变化是影响碳排放和环境质量的重要驱动力之一。研究土地利用碳排放时空格局变化与效应,为制定低碳发展策略提供理论依据。[方法] 基于灰色理论和生态承载系数,利用1980—2020年宁夏回族自治区22个县区土地利用和能源消耗数据,分析了土地利用变化与碳排放强度变化及效应。[结果] ①碳排放变化量与土地利用变化之间具有密切的关联性。其中,建设用地与碳排放的关联度最大,为0.95。②1980—2020年宁夏土地利用类型碳排放量净增加了5.24×10⁷ t,增幅625.43%。建设用地面积以年均4.42%的速率增长,碳排放量增幅达2 385.85%;草地面积减少了2.95×10⁵ hm²,碳汇量减少了5.80×10⁴ t;林地对碳汇的贡献超过75%,且随林地面积的不断增大而增加。③1980—2020年宁夏土地利用碳排放强度以年均0.25 t/hm²的速率增大,中度及以上等级覆盖面积逐渐增大,在空间上形成沿黄城市碳排放强度高于中、南部的分布格局。④宁夏各县区碳排放生态承载系数空间差异明显,碳生态容量表现出北弱南强的分布格局。[结论] 1980—2020年宁夏土地利用碳排放强度逐渐增大,北部沿黄河各县区碳生态容量逐渐减小,中南部县区碳生态容量增大,但减排压力较大。建议优化建设用地空间格局,增加混交林面积,增强森林碳汇能力。     

1980-2020年洞庭湖流域土地利用变化及其碳效应

[目的] 探查粮食主产区土地利用变化规律及其碳效应,为土地利用结构调整及低碳经济发展提供依据。[方法] 基于1980,2000,2020年3期土地利用现状数据,在网格采样法、土地利用动态度模型、碳排放系数法以及空间自相关分析模型支持下,揭示1980年以来洞庭湖流域土地利用变化规律及其碳效应的空间异质性特征。[结果] ①洞庭湖流域土地利用阶段性变化。1980—2000年综合动态度为0.02%,其中动态度最大的是建设用地,未利用地次之。2000—2020年综合动态度增至0.18%,建设用地面积增长加快。②净碳效应表现为碳汇,但由1980年的5.93×10⁷ t下降到2020年2.82×10⁷ t,而由土地利用变化引起的碳效应呈现碳排放变化量大于碳汇变化量特点,并导致净碳排放量增加了6.08×10⁵ t,且空间上净碳排放相对高值区呈“H”型分布特点,低值区逐渐扩张。③洞庭湖流域集水小区净碳排放的空间自相关性特征显著。1980—2000年主要聚集类型为高—高型和低—低型,低—高型分布零散,2000—2020年高—高型分布更加集中连片,低—低型主要在湘江流域北部。[结论] 在洞庭湖流域,应坚持“碳增汇,碳减排”定位,保持林地的碳汇稳定状态,科学引导高碳排放土地的开发利用,并依据空间自相关特点关注不同集水区的碳排放“同化”作用。     

长江中下游典型区域土地利用碳排放风险——以江西省九江市为例

[目的]定量测算江西省九江市土地利用碳排放,揭示其时空演变特征,并估算土地利用碳排放风险,为九江市构建绿色低碳土地利用方式提供科学参考。[方法]采用土地利用碳排放系数法测度2000—2020年九江市土地利用碳排放和时空变化规律,并从网格化的视角,利用碳排放风险指数识别各县区碳排放风险,基于对数平均迪式指数(LMDI)模型,分析土地利用碳排放的影响因素。[结果] 2000—2020年九江市土地利用净碳排放量呈递增趋势,年均增幅为13.75%,建设用地是主要碳源,占碳排放量的90%以上,林地是主要碳汇。九江市净碳排放量呈现“东北高,西南低”的空间分布特征,森林覆盖率好的武宁县、修水县一直处于碳汇功能,濂溪区、浔阳区、湖口县、瑞昌市的碳排放量占九江市净碳排放量的95%以上。九江市土地利用碳排放风险整体偏低,并呈现“东北高,西南低”的分布特征,长江沿岸县区濂溪区、浔阳区和柴桑区处于高度碳排放风险区。经济发展水平是碳排放增加的主要因素,能源消费强度则是抑制碳排放的关键因素。[结论] 2000—2020年九江市土地利用碳排放大幅增加,应控制新增碳源用地,优化土地利用结构,并积极探索低碳绿色能源利用...     

基于土地利用变化的新疆塔城地区碳排放特征分析

[目的]分析新疆塔城地区1980—2020年的碳排放变化时空特征及效应,为科学制定区域碳减排措施及低碳调控政策提供依据。[方法]基于1980—2020年土地利用变化数据,计算了塔城地区碳排放量和碳吸收量,并采用碳足迹和碳生态承载力评估了碳排放效应。[结果](1)1980—2020年,塔城地区净碳排放量表现出明显的增加趋势,其中耕地和建设用地的不断扩张是导致塔城地区碳排放量增加的主要诱因,而林地面积的持续减少是造成塔城地区碳吸收量减少的关键因素;(2)在空间分布上,沙湾县和乌苏市是塔城地区的主要碳源区,解释了塔城地区净碳排放的67.20%,和丰县和额敏县解释了塔城地区净碳排放量的20.89%,托里县是塔城地区的主要碳汇区;(3)在碳排放效应方面,2000年前塔城地区绝大多数区域都表现为生态盈余,但2000年后开始出现碳排放的生态赤字。[结论]当前,沙湾县、乌苏市及和丰县,存在明显的生态赤字,是未来塔城地区碳减排的重点控制区域。     

2000-2020年淮南矿区土地利用变化对碳源/碳汇时空格局的影响

[目的]分析淮南矿区2000—2020年土地利用碳源/碳汇时空格局分布特征,为淮南市国土空间规划及未来低碳调控政策制定提供依据。[方法]以淮南矿区为研究对象,选取2000,2010,2020年3期土地利用数据,以格网尺度量化不同土地利用变化发展阶段下碳源/碳汇/碳排放的时空格局,基于冷热点分析碳源/碳汇/碳排放的空间格局。[结果](1)2000—2020年,土地利用类型由单一用地为主转换多种土地利用类型同时发生,其中,建设用地面积增大,导致碳源效应增强,碳汇效应相对减弱,碳排放量持续增加,碳源年增加量为2.76×10⁶ t,碳汇年增加量仅为130 t,碳排放年增加量为2.76×10⁶ t;(2)碳源和碳排放空间分布特征基本一致,中部建成区和西北矿区是碳源和碳排放的主要集中区,碳汇主要聚集在东部、西部边缘区和西部部分矿区;(3)中部建成区是碳源和碳排放的显著热点、热点区域,以显著热点变化特征为主;显著冷点和冷点主要分布在研究区东部、西部边缘区域和西北部分矿区。[结论]淮南矿区的碳减排和低碳效应需要着重关注北部大面积的平原耕地区域,控制该区域矿区...     

沱江流域土地利用碳平衡与人类活动强度的关系

[目的] 研究土地利用碳平衡与人类活动强度间的协同关系,为沱江流域的区域协同碳减排规划及实现中国“碳达峰、碳中和”目标提供参考。[方法] 基于2000—2020年土地利用及社会经济数据,使用碳排放经济贡献系数、碳生态承载系数、人类活动强度指标,耦合协调度模型及回归分析方法,核算了沱江流域土地利用碳排放量并分析了土地利用碳平衡与人类活动强度的时空演变特征及其协同关系。[结果] 研究表明,2000—2020年沱江流域碳排放量增加了5.13×10⁷ t,其中建设用地碳排放量占90%以上;碳吸收量变化不大,主要来自林地,呈现先减后增的趋势;净碳排放增长率呈下降趋势。各区县的土地利用碳平衡协调度均在提升,但70%以上的区域处于失调衰退状态。沱江流域人类活动强度整体处于中等强度水平,空间上从北向南呈现“低—高—低—高”的格局。[结论] 人类活动强度与人均GDP、人均碳排放均存在显著的正相关关系。土地利用碳平衡协调度与人类活动强度的负相关关系随着技术进步与能源利用效率的提高而降低。提高碳汇能力与碳生产力是改善区域土地利用碳平衡协调水平的有效途径。     

碳达峰背景下遵义市土地利用转型的生态环境效应及预测

[目的]研究土地利用转型的生态环境效应及其发展趋势,为促进土地利用转型、低碳循环发展及实现“双碳”目标提供依据。[方法]基于贵州省遵义市2005,2010,2015,2020年4期的土地利用数据,运用空间分析技术,对该区土地利用转型的生态环境效应及其发展趋势进行研究。[结果](1)2005—2020年土地转型主要表现为碳汇用地之间的相互转换,以及碳汇用地向碳源用地转型。(2)净碳排放量由2005年的5.99×10⁵ t增加到2020年的9.87×10⁶ t,增加了9.27×10⁶ t,增幅达1 548.15%。但增量却呈逐渐减少的趋势,增幅也逐渐降低。(3)遵义市生态系统服务价值量由2005年的7.64×10¹⁰元增加到2020年的7.73×10¹⁰元,呈波动上升趋势,共增加了9.14×10⁸元,增长率为1.2%。(4)通过灰色预测模型得出遵义市未来净碳排放量和生态系统服务价值量会持续增加,且都呈规律上升趋势。[结论]遵义市在生态环境方面仍面临着不小的压力...     

基于PLUS-InVEST模型的珠三角碳储量时空演变与预测

[目的] 探究珠三角地区2005-2020年土地利用变化及其对碳储量的影响,并对2035年珠三角的土地利用格局和碳储量进行模拟预测,以期为珠三角地区"双碳"目标下的国土空间规划和生态决策提供科学依据。[方法] 基于2005-2020年4期土地利用数据,以珠三角城市群为研究区域,采用PLUS模型和InVEST模型对该区的土地利用变化和碳储量演变进行分析,并预测其2035年土地利用空间格局和碳储量变化趋势。[结果] ①2005-2020年,珠三角地区碳储量先增加后减少,林地、建设用地和未利用地增多促进碳储量增长了4.82×10⁷ t,耕地、草地和水域减少导致碳储量减少了5.10×10⁷ t。②预计2035年,随着建设用地和林地的增加,该区碳储量较2020年增长5.75×10⁷ t,生态环境向好发展。③该区碳储量表现出"四周高,中部低"的空间分布格局,与土地利用空间分布具有显著一致性,即碳储量高值区集中在林地、耕地和草地,碳储量低值区集聚在建设用地。[结论] 随着未来城市发展需要,政府部门应进行土地综合开发利用,采取生物、工程技术等生态修复措施,提升区域固碳能力,助力实现碳中和目标。     

基于InVEST-PLUS模型的郑州市碳储量时空演变及空间自相关分析

[目的] 陆地生态系统碳储量的主要驱动因素之一是土地利用变化,以“过去—现在—未来”的逻辑,分析河南省郑州市土地利用与碳储量时空演变之间响应关系,为实现城市的生态安全可持续发展提供参考。[方法] 首先基于GIS和InVEST模型,对2005—2020年碳储量时空分布进行定量评估,然后结合PLUS模型,模拟2050年自然发展情景和生态保护情景下土地利用和碳储量时空变化特征;并辅以莫兰指数和热点分析在格网尺度下评估其空间关联程度。[结果] ①2005—2020年,耕地不断调整为建设用地,累计转入1 004.98 km²,致使郑州市土地利用结构发生显著变化,生态保护情景下生态用地减少趋势相对自然发展情景得到较好改善。②受城镇化快速扩张的影响,2005,2020年郑州市碳储量分别为6.59×10⁷,5.67×10⁷ t,15 a间高碳密度地类用地转移,碳储量空间分布呈“西高东低,南北中等,中部低”的特点,自然发展情景和生态保护情景下碳储量变化分别减少了8.27×10⁶ t和1.80×10⁶ t,其中耕地发挥着重要碳汇作用。③碳储量空间分布上具有集聚性,冷热点分布不均,生态保护情景下热点破碎化程度缓和。巩义市和登封市始终为碳储量集聚程度较高区域。[结论] 碳储量时空分布特征与土地利用结构变化密切相关,郑州市未来土地利用规划应适当采取生态保护措施,优化土地利用格局,增强生态系统固碳能力。     

河南省土地利用碳源/汇及其变化分析

土地利用变化及其碳源/汇状况是影响区域碳循环的重要因素.该文构建了土地利用碳源/汇研究的理论框架和计算模型;采用1999-2008年河南省的能源消费、土地利用等数据.对河南省不同土地利用方式的碳源/汇状况及其强度进行了分析.结果表明:(1)河南省土地利用碳排放呈明显增加趋势,其中建设用地和农用地是主要的碳排放源;2003年以来河南省城市建设用地加速扩张,造成建设用地碳排放量的大幅增加;(2)河南省土地利用碳吸收呈缓慢增长趋势,其中农作物是最主要的碳汇;(3)建设用地碳排放强度最大,为56.46 t/(h㎡·a),而耕地的碳汇能力最强,为9.17t/(h㎡·a).(4)1999年以来,地均碳排放强度呈加速增长趋势,而同时期单位GDP碳排放强度则呈下降趋势.     

低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响

【目的】以富士（Fuji）、 秦冠（Qinguan）嫁接在平邑甜茶（Malus hupehensis Rehd.）上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水（ZZ）、 低氮正常水（DZ）、 正常氮干旱（ZG）、 低氮干旱（DG）。氮素和水分均设置两个水平,分别为正常氮（6 mmol/L NO-3-N）、 低氮（0.3 mmol/LNO-3-N）、 正常供水（保持盆中砂子相对含水量为饱和含水量的80%~85%）、 干旱处理（保持盆中砂子相对含水量为饱和含水量的60%~65%）。【结果】富士和秦冠的生物量（茎和叶）、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）,并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）; 氮、 钾元素含量在植株各部位的分布顺序依次是叶＞根＞茎,磷元素则是根＞叶＞茎;光合氮素利用效率（PNUE）和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水（DZ）处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱（DG）处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。     

Pasture Vegetation Elemental Analysis by Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing.     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Macroinvertebrates in North American tallgrass prairie soils: effects of fire, mowing, and fertilization on density and biomass

The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils.     

Variation in quality parameters between and within 14 Nordic tree fruit and berry species

Abstract

A 3-year study was carried out to investigate quality parameters in 14 tree fruit and berry species grown in southern Norway. The species were blueberry, apple, aronia, sour cherry, sweet cherry, red raspberry, strawberry, blackcurrant, gooseberry, red currant and elderberry, harvested along with wild bilberry, cloudberry and lingonberry. Significant differences between species were identified for all quality parameters. The coefficient of variation between species was lowest for pH (12.5%), dry matter (18.9%) and soluble solids (25.3%), followed by titratable acids (59.3%), total phenolics (83.8%), antioxidant capacity FRAP (85.7%) and antiradical power by the DPPH-assay (97.8%), total monomeric anthocyanins (132%) and ascorbic acid (137%). Average coefficient of variation within species were lower and ranged from 4 (pH) to 62% (ascorbic acid). Only the FRAP values were significantly affected by harvesting year with lower levels in 2004 than in 2005 and 2006. There were significant interactions between species and harvesting year for dry matter, soluble solids, pH, ascorbic acid and FRAP. The results indicate generic ranges in composition within species independent upon growing location and climate, and the composition of the tree fruits and berries is not likely to deviate from these ranges. It is concluded that desirable composition of tree fruits and berries and their products should primarily be achieved by selection among species rather than searching fors broadened variation within individual species.     

Potassium Fixation and Release Characteristics in Rhizosphere and Nonrhizosphere Soils for a Rapeseed–Rice Cropping Sequence

Potassium (K) fixation and release in soil are important factors in the long-term sustainability of a cropping system. Changes in K concentration and characteristics of K fixation and release in rhizosphere and nonrhizosphere soils in the rapeseed (Brassica napus L.)–rice (Oryza sativa L.) rotation were investigated using a rhizobox system. The concentrations of different forms of K in both rhizosphere and nonrhizosphere soils decreased with plants compared to without plants, regardless of K fertilizer application. Potassium uptake by crops mainly came from the rhizosphere soil. In the treatment without K fertilizer (–K), the main form of K supplied by the soil to the crops was 1.0 mol L^?1 nitric acid (HNO₃) nonextractable K, followed by nonexchangeable K, and then exchangeable K. In the treatment with K fertilizer (+K), the main K forms supplied by the soil to the crops were exchangeable K and nonexchangeable K. The amount and rate of K fixation after one cycle of the rapeseed–rice rotation was greater in rhizosphere soil than in nonrhizosphere soil. The amount and rate of K fixation of soil in the +K treatment were significantly less than in the –K treatment. The cumulative amounts of K released with 1.0 mol L^?1 ammonium acetate (NH₄OAc) and 1.0 mol L^?1 HNO₃ extraction increased with the increasing numbers of extractions, but the K-releasing power of soil by successive extraction decreased gradually and finally became almost constant. The release of K was less in rhizosphere soil than in nonrhizosphere soil. The release of K in the +K treatment was similar to that in the –K treatment in rhizosphere soil, but the K release in nonrhizosphere soil was greater with the +K than the –K treatment. Overall, the information obtained in this study will be helpful in formulating more precise K fertilizer recommendations for certain soils.     

Electron donor and pH relationships for biologically enhanced dissolution of chlorinated solvent DNAPL in groundwater

Biologically enhanced dissolution offers a method to speed removal of chlorinated solvent dense non-aqueous-phase liquid (DNAPL) sources such as tetrachloroethene (PCE) and trichoroethene (TCE) from aquifers. Bioremediation is accomplished by adding an electron donor to the source zone where fermentation to intermediates leading to acetic acid and hydrogen results. The hydrogen and possibly acetic acid are used by dehalogenating bacteria to convert PCE and TCE to ethene and hydrochloric acid. Reductive dehalogenation is thus an acid forming process, and sufficient alkalinity must be present to maintain a near neutral pH. The bicarbonate alkalinity required to maintain pH above 6.5 is a function of the electron donor: 800 mg/L of bicarbonate alkalinity is sufficient to achieve about 1.2 mM TCE dechlorination with glucose, 1.7 mM with lactate, and a much higher 3.3 mM with formate. Laboratory studies indicate that in mixed culture, formate can be used as an electron donor for complete conversion to ethene, contrary to pure cultures studies indicating it cannot. Various strategies can be used to add electron donor to an aquifer for DNAPL dehalogenation while minimizing pH problems and excessive electron donor usage, including use of injection-extraction wells, dual recirculation wells, and nested injection-extraction wells.     

Biodiversity and ecogeography of wild Lactuca spp. in some European countries

Staff members of the Department of Botany of Palacký University in Olomouc and Gene Bank Department – Workplace Olomouc, Research Institute of Crop Production in Prague, Czech Republic, conducted an expedition in seven European countries (Austria, Czech Republic, France, Germany, Italy, the Netherlands, Switzerland) in August/September 1999 to collect wild Lactuca spp. germplasm and study its geographic distribution, ecology and biodiversity. During the mission, more than 600 locations were visited resulting in the collection of 602 seed samples (accessions) of wild Lactuca species and 13 seed samples of related genera (Chondrilla and Mycelis). Lactuca serriola f. serriola, L. serriola f. integrifolia, L. saligna and L. viminea subsp. chondrilliflora were prevalent in southern Europe (Italy, France), however, only L. serriola was common in central and western Europe (Austria, Czech Republic, Germany, Netherlands, Switzerland). The greatest diversity of Lactuca species was found in France, where also the most seed samples (165) were collected. The most characteristic habitats with a high density of Lactuca spp. populations were observed along roads and highways, grassy ditches, ruderal communities, and dust-heaps. Natural infections by powdery mildew (Erysiphe cichoracearum) and downy mildew (Bremia lactucae) on some wild Lactuca spp. were observed. Recent observations concerning the geographic distribution, population structure, habitats, and natural occurrence of diseases of Lactuca spp. are discussed. This assemblage of genetic resources of Lactuca spp. can serve as the basis of future studies of species diversification, spatial population structure, plant microevolution, domestication processes, and genetic variability of host-parasite interactions.     

Responses of native legume desert trees used for reforestation in the Sonoran Desert to plant growth-promoting microorganisms in screen house

Three slow-growing legume trees used for desert reforestation and urban gardening in the Sonoran Desert of Northwestern Mexico and the Southwestern USA were evaluated whether their growth can be promoted by inoculation with plant growth-promoting bacteria (Azospirillum brasilense and Bacillus pumilus), unidentified arbuscular mycorrhizal (AM) fungi (mainly Glomus sp.), and supplementation with common compost under regular screenhouse cultivation common to these trees in nurseries. Mesquite amargo (Prosopis articulata) and yellow palo verde (Parkinsonia microphylla) had different positive responses to several of the parameters tested while blue palo verde (Parkinsonia florida) did not respond. Survival of all tree species was over 80% and survival of mesquite was almost 100% after 10 months of cultivation. Inoculation with growth-promoting microorganisms induced significant effects on the leaf gas exchange of these trees, measured as transpiration and diffusive resistance, when these trees were cultivated without water restrictions.     

Increase in auxiliary photoprotective photosynthetic pigments in wheat seedlings induced by Azospirillum brasilense

Inoculation of wheat seedlings with the plant growth-promoting bacterium Azospirillum brasilense Cd was immobilized in alginate microbeads and, without applying any stress, significantly increased the quantity of several photosynthetic pigments, such as chlorophyll a, chlorophyll b, and the auxiliary photoprotective pigments violaxanthin, zeaxanthin, antheroxanthin, lutein, neoxanthin, and β-carotene. This resulted in greener plants with no apparent visible stress. After monitoring the quantity of photosynthetic pigments for 4 weeks, we observed that inoculated plants had higher quantities of pigments in shoot and stem. The greatest difference in the quantity of all pigments between inoculated and noninoculated plants occurred in the first week of growth. Regardless of treatment, the quantity of pigments in stems was three to four times less than the quantity of these pigments in shoots. Application of Azospirillum, either as liquid inoculant or as alginate microbeads, did not alter the positive effect of the bacteria on pigment production or the positive response of the plants towards A. brasilense Cd inoculation.