基于Google Earth Engine 分析黄土高原植被覆盖变化及原因

为探明黄土高原植被覆盖时空变化及其原因,基于Google Earth Engine(GEE),采用Landsat Surface Reflectance data(陆地卫星地表反射率数据)分 析了黄土高原1987~2015 年间植被覆盖度的时空变化规律,并借助累积量斜率变化率方法对引起植被覆盖度变化的气候和人为因素进行了量化分析. 结果表明:黄土高原年均植被覆盖度由1987年的41.78%增加到2015年的53.23%,增速为0.38%/a(P&lt;0.05).其中,1987~1999年年均植被覆盖度变化趋势 不显著(P&gt;0.05);而退耕还林还草工程实施以来(2000~2015 年),年均植被覆盖度显著增加(P&lt;0.05),增速达到0.59%/a.由像元尺度分析,黄土高原72.93% 的区域植被覆盖度呈增加趋势,其中38.31%的区域增加趋势显著(P&lt;0.05).植被覆盖度的变化受气候和人为因素的共同影响,以1987~1999 年为基准期, 气候变化和人类活动对黄土高原2000~2015年间植被覆盖度变化的相对贡献率分别为23.77%、76.23%,人类活动为引起黄土高原植被覆盖度变化的主 要原因.退耕还林还草工程极大地改善了黄土高原的植被覆盖状况,但是城市的扩张使得部分地区的植被覆盖呈显著退化现象.</p

生物炭施用下中国农田土壤N2O 排放的Meta 分析

为明确施加生物炭对中国农田土壤N2O 排放的影响和主要控制因素, 以公开发表的试验数据为研究 对象, 采用Meta-analysis 法定量分析了施加生物炭条件下, 气候、土壤性质、田间管理方式、生物炭性质与施 加量对土壤N2O 排放的影响, 并对各影响因素进行通径分析。结果表明, 当年降雨量&ge;600 mm 时, 生物炭显 著降低土壤N2O 排放量(P&lt;0.05), 且随年降雨量的增加而增强; 当年日照时数大于1 000 h 时, 生物炭对土壤 N2O 的减排效果随年日照时数的增加而减弱。当土壤pH&ge;6.5 时, 生物炭对土壤N2O 的减排效果随土壤pH 的增加呈先增后减趋势; 在壤土中施加生物炭对N2O 的减排效果显著(P&lt;0.05), 而砂土和黏土不显著 (P&gt;0.05)。生物炭对覆膜土壤N2O 的减排效果优于不覆膜土壤; 生物炭对土壤N2O 的减排效果随施氮肥量增 加而减弱, 而随生物炭比表面积的增加而增强。当生物炭C/N 处于30~500 时, 生物炭施用下土壤N2O 排放量 显著降低(P&lt;0.05); 当生物炭施加量处于20~160 thm2 时, 生物炭对土壤N2O 的减排效果随施加量增加而增 强。生物炭对土壤N2O 减排的影响存在显著的区域性特征, 对华南、华东、华中和东北地区影响显著(P&lt;0.05), 而对西北地区不显著(P&gt;0.05); 施氮肥量、生物炭施加量、年均温和年降雨量是影响生物炭减排效果的最主要 因素, 这些因素的相互作用共同影响生物炭对土壤N2O 的减排效果。该研究可为生物炭在我国农区的推广应 用和农田N2O 减排提供参考。</p

垄膜沟灌对旱区农田土壤盐分及硝态氮运移特征的影响

引黄水量的执行性削减加剧了河套灌区农业水资源的紧缺程度及土壤次生盐渍化问题。采取 合 理 的节水灌溉模式对缓解河套灌区农业用水紧张、改良盐渍化土壤、营造适宜作物生长的土壤环境具有重要 意义。为明晰垄膜沟灌对河套灌区土壤盐分及硝态氮运移特征的影响及调控效果，通 过４次 田 间 沟 灌 试 验，对比研究了高水、中水、低水及高肥、低肥６个组合处理条件下土壤盐分以及土壤硝态氮的变化特征。 结果表明：垄膜沟灌条件下灌水量对土壤全盐量的影响高于施肥量，中水处理土壤全盐量始终维持在一个 适宜且稳定的水平。灌水量和施肥量对土壤硝态氮含量均有不同程度的影响，中、低水处理后期硝态氮的 淋溶显著低于高水处理。垄膜沟灌种植模式下中水低肥处理增加了土壤水分的有效性，抑制了土壤反盐， 减少了垄上硝态氮的淋溶，在节水节肥的基础上为作物的生长发育提供了一个适宜的土壤环境，利于生物 量的累积及最终产量的形成，在一定程度上解决了河套灌区引黄灌溉配额减少与漫灌洗盐方式严重浪费 水资源之间的矛盾，为当地垄膜沟灌技术的推广提供了一定的理论依据与技术支撑。</div

基于 Google Earth Engine 分析黄土高原植被覆盖变化及原因

为探明黄土高原植被覆盖时空变化及其原因,基于 Google Earth Engine(GEE),采用 Landsat Surface Reflectance data(陆地卫星地表反射率数据)分 析了黄土高原 1987~2015 年间植被覆盖度的时空变化规律,并借助累积量斜率变化率方法对引起植被覆盖度变化的气候和人为因素进行了量化分析. 结果表明:黄土高原年均植被覆盖度由 1987 年的 41.78%增加到 2015 年的 53.23%,增速为 0.38%/a(P&lt;0.05).其中,1987~1999 年年均植被覆盖度变化趋势 不显著(P&gt;0.05);而退耕还林还草工程实施以来(2000~2015 年),年均植被覆盖度显著增加(P&lt;0.05),增速达到 0.59%/a.由像元尺度分析,黄土高原 72.93% 的区域植被覆盖度呈增加趋势,其中 38.31%的区域增加趋势显著(P&lt;0.05).植被覆盖度的变化受气候和人为因素的共同影响,以 1987~1999 年为基准期, 气候变化和人类活动对黄土高原 2000~2015 年间植被覆盖度变化的相对贡献率分别为 23.77%、76.23%,人类活动为引起黄土高原植被覆盖度变化的主 要原因.退耕还林还草工程极大地改善了黄土高原的植被覆盖状况,但是城市的扩张使得部分地区的植被覆盖呈显著退化现象. </div

Aripiprazole versus other atypical antipsychotics for schizophrenia

BACKGROUND: In most western industrialised countries, second generation (atypical) antipsychotics are recommended as first line drug treatments for people with schizophrenia. In this review we specifically examine how the efficacy and tolerability of one such agent - aripiprazole - differs from that of other comparable second generation antipsychotics. OBJECTIVES: To evaluate the effects of aripiprazole compared with other atypical antipsychotics for people with schizophrenia and schizophrenia-like psychoses. SEARCH METHODS: We searched the Cochrane Schizophrenia Group Trials Register (November 2011), inspected references of all identified studies for further trials, and contacted relevant pharmaceutical companies, drug approval agencies and authors of trials for additional information. SELECTION CRITERIA: We included all randomised clinical trials (RCTs) comparing aripiprazole (oral) with oral and parenteral forms of amisulpride, clozapine, olanzapine, quetiapine, risperidone, sertindole, ziprasidone or zotepine for people with schizophrenia or schizophrenia-like psychoses. DATA COLLECTION AND ANALYSIS: We extracted data independently. For dichotomous data we calculated risk ratios (RR) and their 95% confidence intervals (CI) on an intention-to-treat basis based on a random-effects model. Where possible, we calculated illustrative comparative risks for primary outcomes. For continuous data, we calculated mean differences (MD), again based on a random-effects model. We assessed risk of bias for each included study. MAIN RESULTS: We included 12 trials involving 6389 patients. Aripiprazole was compared to olanzapine, risperidone and ziprasidone. All trials were sponsored by an interested drug manufacturer. The overall number of participants leaving studies early was 30% to 40%, limiting validity (no differences between groups).When compared with olanzapine no differences were apparent for global state (no clinically important change: n = 703, 1 RCT, RR short-term 1.00 95% CI 0.81 to 1.22; n = 317, 1 RCT, RR medium-term 1.08 95% CI 0.95 to 1.22) but mental state tended to favour olanzapine (n = 1360, 3 RCTs, MD total Positive and Negative Syndrome Scale (PANSS) 4.68 95% CI 2.21 to 7.16). There was no significant difference in extrapyramidal symptoms (n = 529, 2 RCTs, RR 0.99 95% CI 0.62 to 1.59) but fewer in the aripiprazole group had increased cholesterol levels (n = 223, 1 RCT, RR 0.32 95% CI 0.19 to 0.54) or weight gain of 7% or more of total body weight (n = 1095, 3 RCTs, RR 0.39 95% CI 0.28 to 0.54).When compared with risperidone, aripiprazole showed no advantage in terms of global state (n = 384, 2 RCTs, RR no important improvement 1.14 95% CI 0.81 to 1.60) or mental state (n = 372, 2 RCTs, MD total PANSS 1.50 95% CI -2.96 to 5.96).One study compared aripiprazole with ziprasidone (n = 247) and both the groups reported similar change in the global state (n = 247, 1 RCT, MD average change in Clinical Global Impression-Severity (CGI-S) score -0.03 95% CI -0.28 to 0.22) and mental state (n = 247, 1 RCT, MD change PANSS -3.00 95% CI -7.29 to 1.29).When compared with any one of several new generation antipsychotic drugs the aripiprazole group showed improvement in global state in energy (n = 523, 1 RCT, RR 0.69 95% CI 0.56 to 0.84), mood (n = 523, 1 RCT, RR 0.77 95% CI 0.65 to 0.92), negative symptoms (n = 523, 1 RCT, RR 0.82 95% CI 0.68 to 0.99), somnolence (n = 523, 1 RCT, RR 0.80 95% CI 0.69 to 0.93) and weight gain (n = 523, 1 RCT, RR 0.84 95% CI 0.76 to 0.94). Significantly more people given aripiprazole reported symptoms of nausea (n = 2881, 3 RCTs, RR 3.13 95% CI 2.12 to 4.61) but weight gain (7% or more of total body weight) was less common in people allocated aripiprazole (n = 330, 1 RCT, RR 0.35 95% CI 0.19 to 0.64). Aripiprazole may have value in aggression but data are limited. This will be the focus of another review. AUTHORS' CONCLUSIONS: Information on all comparisons are of limited quality, are incomplete and problematic to apply clinically. Aripiprazole is an antipsychotic drug with a variant but not absent adverse effect profile. Long-term data are sparse and there is considerable scope for another update of this review as new data emerges from the many Chinese studies as well as from ongoing larger, independent pragmatic trials