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[目的] 探寻城镇化快速发展条件下作为生态示范村的陕西省米脂县高西沟村的土地利用转型特征,为陕北黄土高原地区的乡村“三生”空间可持续发展提供参考。 [方法] 通过土地利用动态度、土地利用转移矩阵分析高西沟1953—2022年的“三生”空间特征,并结合实地调研对村域多年“三生”空间格局演变特征及对应的空间治理优化策略展开分析。 [结果] ①1953—2022年,高西沟生产空间呈减小趋势,生活空间和生态空间呈增大趋势。1953—1973年,生态空间变化幅度最大,绿地生态空间从12.07 hm2增加到100.33 hm2,其他生态空间从12.07 hm2减小到100.33 hm2,生产空间逐渐减小,从145.67 hm2减小到110.07 hm2。1986—2022年,生产空间减少了42.4 hm2,生活空间增加了5 hm2,生态空间增加了37.39 hm2。 ②1986—2022年,高西沟“三生”空间转型体现在绿地生态空间和农村生活空间的增加,农业生产空间、其他生态空间和水域生态空间的减少。有67.83 hm2的农业生产空间和59.95 hm2的其他生态空间转化为绿地生态空间,而部分绿地生态空间转化为农业生产空间和农村生活空间,其转移面积分别为21.20和3.22 hm2。 ③高西沟针对生产空间效益不足的问题,采取改变广种薄收的耕种方式,大幅提高粮食产量,改变单一的农业生产状况,实现多种经营模式并存的举措;针对生活空间品质低下的问题,采取全力抓牢基建,量力新建家园,鼓励青年外出,从事其他产业的举措;针对生态空间破坏严重的问题,采取控制水土流失,退耕还林还草,打造旅游文化,推广生态风光的举措。 [结论] 根据早期“三生”空间的主要问题,高西沟做出适宜的优化策略,提高土地利用率,扩大林草面积,使绿地生态空间达到80%。农林牧的高效发展,生产、生活、生态的全面改善,使高西沟成为黄土丘陵区的生态示范代表。 相似文献
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南方稻区绿肥生态服务功能及生态价值评估研究 总被引：9，自引：4，他引：5
为探究我国南方稻区绿肥种植的生态服务价值,本文以我国南方稻区农田引入绿肥紫云英为例,界定了稻田种植紫云英的生态服务功能,并运用实际市场法、替代市场法和虚拟市场法等研究方法,构建了绿肥生态价值评估的理论模型,核算了绿肥的生态服务价值,得到了以下研究结论：1）南方稻区绿肥生态服务功能主要涉及调节和支持两类,调节服务包括气体调节、水分涵养和土壤保持3种功能,支持服务则包括土壤有机质累积和土壤营养物质循环两种功能;对应地,南方稻区农田轮作冬绿肥紫云英的生态价值也被界定为以上5种。2）南方稻区冬闲田种植紫云英在一个轮作周期中能够产生1.125万元·hm-2的生态价值,其中,气体调节价值最大,为0.380万元·hm-2,其次是土壤有机质累积价值,为0.279万元·hm-2,营养物质循环价值和土壤保持价值分别为0.204万元·hm-2和0.214万元·hm-2,土壤水分涵养价值最小,为0.048万元·hm-2。3）南方稻区绿肥种植投入成本为0.173万元·hm-2,绿肥种植所产生的生态价值是种植投入成本的6.5倍。研究表明农田冬种绿肥紫云英的生态服务价值是客观存在的。该研究为南方稻区绿肥引入冬闲田后生态价值的评估提供了较为科学的研究方法和基础参数,同时,也为未来政府制定绿肥种植的生态补偿机制提供了理论依据。 相似文献
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西北干旱区绿洲县域3类空间冲突分析与模拟 总被引：1，自引：1，他引：0
[目的] 对西北干旱区绿洲县域3类空间冲突进行分析与模拟,为该区国土空间合理布局、区域可持续发展提供科学参考。[方法] 以西北干旱区绿洲县域——新疆麦盖提县为研究区,基于土地利用主导功能构建空间分类体系,将国土空间划分为城镇、农业与生态空间;根据景观格局指数构建空间冲突测度模型探讨2009—2019年空间冲突水平演变特征;通过CA-Markov模型预测2024年空间布局并分析冲突强度变化特征。[结果] ①3类空间呈现“两增一减”的变化动态,城镇空间面积呈逐年递增趋势,由1 537.74 hm2增加至4 582.24 hm2;农业空间由84 670.06 hm2增加至107 447.66 hm2;生态空间面积减少25 822.69 hm2。②2009—2019年空间冲突强度显著增强,中等空间冲突、较高空间冲突与高空间冲突评价单元所占比例分别增加了50.41%,13.45%,0.53%。③2024年城镇空间、农业空间将分别增加2 981.19和4 285.96 hm2,生态空间将减少7 267.16 hm2;冲突水平以所占比例为60.24%的中等空间冲突为主。[结论] 2009—2019年城镇空间、农业空间逐年增加、生态空间逐年递减,各类空间的无序变化导致空间冲突强度整体增强,通过预测2024年3类空间变化趋势与2009—2019年保持一致,并以中等空间冲突为主。 相似文献
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[目的] 评估土地利用变化与生态系统服务价值损益之间的关联效应,为制定适宜的土地干预政策提供科学依据。[方法] 基于5期额尔齐斯河流域土地利用数据以及CLUE-S模型,量化土地利用变化下流域生态系统服务价值损益时空演变规律。[结果] ①2000—2018年额尔齐斯河流域草地和林地持续地转化为其他土地,耕地面积大幅度增长;到2030年,流域耕地面积的比例将上升4.92%(1 502.48 km2上升到4 070 km2),而林地呈现快速下降趋势,所占比例将下降7.18%(由7 547.26 km2减少到5 424.36 km2)。②额尔齐斯河流域生态系统服务价值由2000年的518.16亿元增长到2018年的1 832.44亿元,到2030年,生态系统服务价值处于波动下降趋势(2030年为1 777.86亿元); ③林地和草地被耕地所占用,导致额尔齐斯河流域生态系统服务价值损失预计达到108.80亿元,依次为：草地转换损失(34.39亿元)>林地转换损失(28.49亿元)>水域转换损失(18.31亿元)。④额尔齐斯河流域生态系统服务价值损益空间分布呈现“北高南低”的发展格局,价值损益在全局和局部上均呈现显著的正向空间自相关。[结论] 人为因素导致大量生态用地被占用,生态系统服务价值下降且损益空间异质性显著,需要进一步采取有效的生态保护与补偿政策推动农牧户生计转型,减小对自然环境的依赖性。 相似文献
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当前农业生产“空间错位、功能错乱”问题严重,优化耕地果园布局,实现耕地下山果树上山,对改善耕地质量、优化耕地空间布局具有重要意义。该研究以林果业为主导农业的江西省赣州市寻乌县为例,在耕-果空间错位矛盾下,以耕地质量评价为基础,耦合地形空间与地理学定义划定“山上山下”以识别耕-果错位空间,在矛盾优化原则下应用GIS技术构建空间决策模型协调优化果园与耕地的空间布局。研究表明：1）寻乌县耕地细碎,质量评价结果为Ⅰ级的耕地面积为2227.02 hm2,占总耕地面积的24.17%;Ⅴ级面积为671.70 hm2,占7.29%;地形空间划分的“山下”空间占24.06%,“山上”空间占48.19%。 2）以“山上山下”为分区标准,在耕地适宜性评价结果下初划耕地空间为保护区与拟调区,初划林果空间为宜耕区、宜果区与保留区,拟调区与宜耕区为耕-果发生错位的空间,耕地错位面积1221.77 hm2,果园错位面积5169.39 hm2。3）按矛盾协调原则在空间决策模型下优化耕-果错位空间,最终结果为1247.25 hm2的“山下”果园调为耕地,1221.77 hm2的“山上”耕地调整为果园。研究结果优化了耕-果空间布局,提高了耕地质量,可为当前“山上”换“山下”优化耕地布局工作提供参考与理论依据。 相似文献
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[目的] 分析露天矿集中区土地利用时空变化特征,为开展露天矿区生态环境监测提供科学参考。[方法] 以河北省唐山市长山沟露天矿集中区为研究对象,基于2003,2010,2015和2019年4期Google Earth影像,进行土地利用遥感分类,使用ArcGIS软件计算土地利用转移矩阵,分析露天矿集中区土地利用时空变化特征及原因。[结果] ①2003—2015年,研究区内绿地面积减少了169.61 hm2,占总面积的6.30%,裸地和工业场地面积分别增加了184.73和60.46 hm2,占总面积的6.86%和2.25%;部分耕地被占用;在空间上以绿地转为裸地和工业场地为主。②2015—2019年,研究区内绿地面积减少了61.05 hm2,占总面积的2.27%,工业场地面积增加了43.90 hm2,占总面积的1.63%,其他地类面积变化不大;空间上绿地与裸地和工业场地相互转化,总面积变化不大。[结论] 露天矿集中区开采前期大量绿地被占用,植被破坏与土地资源占用现象较为严重,生态环境受到了严重的影响。开采后期由于加强了矿山生态修复治理,“边开采,边治理”模式的治理效果已初步体现。 相似文献
7.
陕西黄土台塬区土地系统变化特征分析 总被引：1，自引：1，他引：0
基于GIS和RS支持,采用土地利用变化系列指标对陕西黄土台塬区1985-2010年土地利用变化特征进行了分析。结果表明,2010年黄土台塬区耕地984337.30 hm2,草地143030.47 hm2,建设用地105871.35 hm2,分别占总面积77.89%,11.32%和8.38%;研究时段内耕地、草地、林地、水域依次减少20866.61,11065.22,1186.44和748.96 hm2,分别比1985年减少了2.08%,7.18%,4.60%和11.64%;建设用地增加33902.8 hm2,为1985年的47.11%;建设占用耕地26668.8 hm2,占建设用地转入流的96.26%;草地转耕地18923.9 hm2,占草地转出流的93.24%;1985-1990年土地系统较为稳定,综合动态度为0.52;1990-1995土地利用变化活跃,综合动态度达到3.60,其后逐渐降低,到2005-2010降低为1.16,土地系统趋于稳定。空间上,耕地转建设用地在城镇周边幅度较大,草地和耕地互转主要在渭南台塬东部、咸阳塬北部以及宝鸡台塬区。 相似文献
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[目的] 研究如何精准提取净耕地利用信息,为农田管理与耕地科学利用提供理论支持。[方法] 基于灰色系统理论提出净耕地预测思路,以典型粮食产区挠力河流域为研究区,在土地利用变更调查数据支持下,运用净耕地系数、突变检测模型、灰色动态模型（GM）等数理模型,提取并验证净耕地（包括旱地和水田）利用信息。[结果] 挠力河流域土地利用斑块面积变化表现出显著的“灰色”特征,对20 hm2等额面积区间的非旱地和非水田斑块面积累加处理,可增强数据列的规律性特征;GM （1,1）灰色系统模型和多项式预测方法均可较为准确地提取非旱地和非水田面积信息。2018年,挠力河流域旱地和水田的净面积分别是1.06×106 hm2和3.87×105 hm2,对应的净系数为97.65%和98.07%。[结论] 耕地斑块面积变化具有灰色特征,可采用灰色系统理论进行净耕地面积预测。 相似文献
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丹江上游商洛市畜禽粪便排放量与耕地污染负荷分析 总被引：1，自引：0，他引：1
南水北调中线上游水源地保护与水质持续安全一直是研究的重点之一。商洛市辖商州区、丹凤县和商南县被规划为丹江流域上游“水源地安全保护区”。掌握该地区畜牧养殖业发展情况、估算畜禽粪便的排放量、分析该地区常用耕地对畜禽粪便及其污染物的消纳能力、评估畜禽粪便可能造成的污染风险等是科学管控畜牧养殖业和有效实施水源地保护的基础性研究。目前,该地区尚无这些方面具体的成果和资料。本研究采用畜禽粪便排泄系数方法,估算了丹江上游流域自上游至下游的商洛市辖商州区、丹凤县、商南县2014—2016年各类畜禽粪便排放量,依据3区县的常年耕地面积分析了畜禽粪便猪粪当量耕地负荷,确定了当前商洛地区畜禽粪便猪粪当量最大适宜耕地负荷标准,并评估了3区县畜禽粪便耕地负荷的污染风险。结果表明：1）商州区、丹凤县和商南县年度平均畜禽粪便排放量猪粪当量分别为5.732×105 t·a-1、9.321×105 t·a-1和1.274×106 t·a-1;其中猪与禽的粪便占到总粪便排放量的68.06%。2）3区县畜禽粪便排放量猪粪当量耕地负荷依次为27.04 t·hm-2·a-1、76.72 t·hm-2·a-1和90.10 t·hm-2·a-1。3）商洛市畜禽粪便排放量猪粪当量最大适宜耕地负荷标准为61.22 t·hm-2·a-1。4）3区县畜禽粪便耕地负荷的污染风险警报级别分别是：商州区为Ⅱ级,稍有污染风险;丹凤县和商南县均为Ⅳ级,有较严重的污染风险。5）商州区、丹凤县和商南县的总氮平均耕地负荷分别为159 kg·hm-2·a-1、450 kg·hm-2·a-1和530 kg·hm-2·a-1,总磷平均耕地负荷分别是51 kg·hm-2·a-1、179kg·hm-2·a-1和199 kg·hm-2·a-1,生化需氧量平均耕地负荷分别为716 kg·hm-2·a-1、2 275 kg·hm-2·a-1和2 595kg·hm-2·a-1,化学需氧量平均耕地负荷分别为768 kg·hm-2·a-1、2 345 kg·hm-2·a-1和2 667 kg·hm-2·a-1,NH3-N平均耕地负荷分别为65 kg·hm-2·a-1、201 kg·hm-2·a-1和232 kg·hm-2·a-1。总之,商洛市商州区、丹凤县和商南县的畜禽养殖总量大,养殖结构不合理;商洛市常用耕地面积相对较少,畜禽粪便的耕地负荷及其污染物负荷均较大,且形成自上游到下游急剧增加的态势;商洛市超量污染物排放会造成氮素和磷素等成分的淋溶和流失,对于南水北调水源地的水质安全构成较大的潜在威胁。 相似文献
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抚仙湖流域生态用地时空演变及其驱动因素 总被引：1，自引：1，他引：0
[目的] 研究生态用地时空演变规律及形成机制，为维持区域生态平衡和保障生态文明建设提供科学参考。[方法] 运用土地利用变化幅度、洛伦兹曲线、基尼系数、回归分析及GIS技术等方法，分析2010-2018年抚仙湖流域生态用地时空演变特征及其形成机理。[结果] ①抚仙湖流域生态用地以耕地、林地和水域及水利设施用地为主。8 a来，耕地面积减少5.15 km2，林地面积减少1.94 km2，草地面积减少0.81 km2，园地面积减少0.19 km2，其他土地面积减少1.40 km2，水域及水利设施用地面积增加0.03 km2。②流域各种生态用地空间分布差异较大，耕地、林地空间分布较均匀，洛伦兹曲线比较靠近绝对均匀线，基尼系数居0~0.25之间。草地、园地、水域及水利设施用地和其他土地分布相对集中，洛伦兹曲线下凹程度较大，基尼系数多处于0.5之上。生态用地空间分布不均的趋势有所加强。③从驱动机制来看，导致流域生态用地时空变化的主要驱动因素为人口密度、城镇化水平、政策、到主要公路距离、到水域距离、到城镇建成区距离。[结论] 研究时段内，抚仙湖流域生态用地时空变化较显著，其变化是自然条件、社会经济条件及空间区位条件多种因素协同作用的结果。 相似文献
11.
低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响 总被引：2，自引：2，他引：0
【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。 相似文献
12.
Aleš Lebeda Ivana Doležalová Eva Křístková Barbora Mieslerová 《Genetic Resources and Crop Evolution》2001,48(2):153-164
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. 相似文献
13.
Kyle Devey Michael Mucalo Gordon Rajendram Joseph Lane 《Communications in Soil Science and Plant Analysis》2015,46(4):72-80
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. 相似文献
14.
Thomas Larsen Jesper Luxhøi Jakob Magid Lars Stoumann Jensen Paul Henning Krogh 《Biology and Fertility of Soils》2007,44(1):59-68
We have studied the effect of anaerobically digested (ADMSW) and composted municipal solid waste (CMSW) on mineralization
and foodweb dynamics to verify the hypothesis that ADMSW would immobilize N right after addition to soil in contrast to addition
with CMSW. Another hypothesis was that the mesofauna (enchytraeids and microarthropods) would stimulate N release from the
decomposer community. We measured excretion of -N and urea-N from the mesofauna and hypothesized that enchytraeids would release urea. ADMSW and CMSW were amended to pots
with sandy loam and barley. The pots were divided into treatments with or without mesofauna. Mesofauna, plant N and biomass,
soil N and ergosterol (fungal biomass) were measured over a 113-day period of four equidistant samplings. Soil respiration,
N mineralization and N release by the mesofauna were modelled from concurrent studies. ADMSW- and CMSW-treated soils initially
(<20 days) immobilized N. The amendments did not increase plant growth substantially, and this was probably due to N-limitation
in the early stages of plant growth. Enchytraeid abundance was about three times higher in ADMSW- than CMSW-treated soils,
indicating that ADMSW contained more labile compounds, bacteria, and microfauna. The mesofauna did not affect N-content, but
the cumulated -N excreted by the mesofauna was estimated to be substantial and about one-fifth of total plant N in ADMSW. An explanation
for this discrepancy might be that in the absence of the mesofauna, other members of the detrivore and microbivore community
performed the mesofauna’s function. Neither enchytraeids nor microarthropods excreted urea. 相似文献
15.
《中国生态农业学报》2014,(6)
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, 相似文献
16.
《中国生态农业学报》2014,(7)
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, 相似文献
17.
《中国生态农业学报》2014,(8)
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, 相似文献
18.
M.A. Callaham Jr. J.M. BlairT.C. Todd D.J. KitchenM.R. Whiles 《Soil biology & biochemistry》2003,35(8):1079-1093
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. 相似文献
19.
I.L. Boyd 《Biological conservation》2010,143(7):1664-1674
“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options. 相似文献
20.
Soil-profile distribution of primary and secondary plant-available nutrients under conventional and no tillage 总被引：1，自引：0，他引：1
Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate. 相似文献