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    黄土高原生态分区及概况

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    黄土高原地域广阔,水土流失区域差异显著。为了有效治理水土流失,评估水土流失治理技术和模式及生态恢复建设工 程的成效性,需要对黄土高原进行区域划分。依据自然条件、水土流失治理技术和模式的区域性特征及差异,基于国家基础地 理信息系统数据的县级行政界,对其进行合并,进行生态分区的划分,并分别统计其气候、地形地貌、植被特征及水土流失现状, 以期为黄土高原水土流失治理技术和模式的改良优化提供依据。主要结论如下: ( 1) 黄土高原分为黄土高塬沟壑区,黄土丘陵 沟壑区,沙地和农灌区,土石山区及河谷平原区。其中黄土高塬沟壑区和黄土丘陵沟壑区分别划分为两个副区。( 2) 黄土高原 的气候、植被、水土流失具有明显的分区差异。降水和植被覆盖度自东南向西北递减,二者在空间分布上具有很好的一致性,降 水量大的分区,植被覆盖度也高。在年际变化方面,丘陵沟壑区 B2 副区降水量呈增加趋势,其他分区呈减小趋势,变化均不显 著。80 年代以来,黄土高原和各生态分区的植被覆盖度均逐渐增加,黄土丘陵沟壑区的增加量最大。各分区的面平均气温均 呈非显著增加趋势,90 年代以来增温明显。( 3) 1970 年以来,黄土高原侵蚀产沙强度减弱趋势显著,至 2002&mdash;2015 年,多年平 均输沙模数在 0.13&mdash;3924 t km-2 a-1之间,侵蚀强度最大为中度侵蚀( 2500&mdash;5000 t km-2 a-1 ) ,但面积较小,主要分布于第二高塬 沟壑区的泾河流域。</div

    黄土丘陵沟壑区治沟造地土壤快速培肥效应

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    为了在黄土区新垦土地上快速有效地构建优质耕作层,缓解黄土高原耕地数量和质量退化问题。该研究以一次 性工程化措施快速构建优质耕作层为目标,选取黄土丘陵沟壑区治沟造地完成的沟道新构造土地为研究区域,利用 3a 连 续的田间定位试验,探索以木本泥炭、生物炭等为主的外源有机物质,配合腐熟秸秆和化肥等措施,研究不同耕作层构 建模式下对黄土区培肥土壤、改善土壤结构、提高土地生产力及作物产量的影响。结果表明:添加木本泥炭,配合腐熟 秸秆,辅以生物激发调节剂处理下可快速提高土壤有机质和易氧化碳等养分含量,增加土壤团聚体数量及稳定性,维持 较高的土壤养分含量,且不存在重金属超标的风险,最终增加玉米籽粒产量,2016&mdash;2018 年连续 3a 较对照分别增产 17.5%、 28.6%、1.0%。耕层土壤物理、化学等性质得以显著改善,土地生产力显著提升。因此,木本泥炭+生物激发调节剂+腐 熟秸秆+化肥是黄土区一次性工程化快速构建优质耕作层的最佳施用模式。</div

    黄土丘陵区草地植被群落优势种叶片 功能性状对氮磷添加的响应

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    以黄土丘陵区草地植被群落 3 种优势种白羊草、长芒草和达乌里胡枝子为对象,采 用裂区试验设计,设置 0、 50 和 100 kg N&middot;hm-2&middot;a-1 3 个氮处理和 0、 40 和 80 kg P2O5&middot;hm-2&middot; a-1 3 个磷处理,于生长旺盛期测定了各植物的叶长、叶宽、比叶面积、叶片干物质含量、叶片 氮、磷含量和氮磷比等指标,分析不同优势种叶片功能性状对氮磷添加的响应差异.结果表 明: 与未施肥相比, 50 和 100 kg N&middot;hm-2&middot;a-1 处理下白羊草叶长和叶宽分别显著增加 35.3% 和 64.4%,而长芒草仅有叶长显著增加 58.8%,达乌里胡枝子仅有叶宽显著增加 33.9%,但三 者叶片干物质含量分别显著降低 10.7%、 15.3%和 11.2%,白羊草和长芒草叶片氮含量分别显 著增加 23.0%和 99.2%,氮磷比分别显著增加 45.8%和 96.9%; 40 和 80 kg P2O5&middot;hm-2&middot;a-1处 理下达乌里胡枝子叶长、叶宽和比叶面积分别显著增加 56.9%、 41.4%和 19.6%,叶片干物质 含量显著下降 14.9%,三者叶片磷含量分别显著增加 96.7%、 110.9%和 238.4%,氮磷比分别显 著降低 45.8%、 42.8%和 53.7%.50 kg N&middot;hm-2&middot;a-1 处理下,与未施磷相比, 40 和 80 kg P2O5&middot; hm-2&middot;a-1 处理后仅达乌里胡枝子叶长和叶宽显著增大, 3 种植物叶片磷含量显著增加,白羊 草和长芒草叶片氮含量显著降低; 100 kg N&middot;hm-2&middot;a-1 处理下,施磷后白羊草和长芒草叶长、 达乌里胡枝子叶宽显著增大,三者叶片磷含量显著增加,白羊草叶片氮含量显著降低.综上表 明, 3 个优势种植物叶片功能性状对短期氮磷添加的响应存在明显差异,这些差异与物种属性 和施肥水平有关,不同优势种对氮磷添加响应的差异对维持草地群落多样性和稳定性具有重 要作用.</div

    黄土丘陵区植被恢复模式对土壤碳组分的影响

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    为认识黄土丘陵区不同恢复模式对土壤碳组分的影响规律,寻找可以反映植被恢复过程中的土壤碳库质量 因子,以纸坊沟流域蟠龙山上6种恢复30年的植被恢复样地为研究对象,选取坡耕地和区域顶级群落侧柏林(Platy- cladusorientailisL.)为对照,分析了植被恢复过程中土壤有机碳(SOC)、重铬酸钾易氧化态碳(ROC)、高锰酸钾易氧 化态碳(LOC)、非活性有机碳(NLOC)、微生物量碳(MBC)、水 溶 性 有 机 碳(DOC)、盐 浸 提 有 机 碳(SEOC)、热 水 浸 提 有机碳(HWEC)、热水浸提碳水化合物(HWC)的变化特征。结果表明:坡耕地由于不合理的利用方式,土壤碳组分含 量较低,不同植被恢复显著增加了土壤活性碳组分,TOC,ROC,LOC,NLOC,MBC,SEOC,DOC,HWEC和 HWC的 含量分别较坡耕地增加了109%~228%,153%~338%,94%~212%,102%~271%,109%~142%,117%~288%, 66%~149%,166%~279%和128%~217%,但是和天然侧柏林相比分别低了 55.4% ~72.4%,57.2% ~75.3%, 50.1%~69.0%,59.9%~78.2%,60.2%~65.9%,6.7%~48.6%,2.2%~35.1%,40.1%~58.3%和55.6%~67.8%, 混交林具有较高的碳组分含量,表明混交林恢复模式效果相对好于草地和纯林。不同恢复模式各碳组分和同一恢复 模式中不同碳组分敏感性差异较大,并非所有碳组分的敏感性均高于 TOC,在采用土壤碳组分作为土壤质量指标时 应根据不同恢复模式选择相应指标。</div

    密植栽培模式对渭北旱塬苹果树生长的影响

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    为了提高渭北旱塬苹果园的经济效益,以盛果期乔砧密植园为对照,将相同树龄的矮砧密植园和半矮化砧 密植园的留果量保留为同一水平,监测不同砧穗组合密植园的树体生长状况。结果表明:矮砧密植园和半矮化砧 密植园的叶面积指数较乔砧密植园分别降低30.47%和23.98%,叶片蒸腾速率分别降低7.56%和5.84%,叶片光合 速率则分别提高17.36%和9.88%。矮砧密植园、半矮化砧密植园的树体生长量小,但果实产量与乔砧密植园的基 本一致。矮砧密植园、半矮化砧密植园的果园产值较乔砧密植园分别提高了8.58%和7.43%。说明矮砧密植和半 矮化砧密植可提高果园产值,因此渭北旱塬应积极推广苹果矮砧密植和半矮化砧密植栽培。</div

    生物炭添加对半干旱区土壤细菌群落的影响

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    以半干旱区固原生态试验站生物炭修复 4a 的表层土壤为对象,采用高通量测序技术研究了不同添加类型(槐树皮生物炭、锯末生物炭)和比例 (1%、3%、5%,质量百分比)的生物炭对土壤细菌多样性及群落结构的影响.结果表明,生物炭应用提高了土壤细菌群落的多样性,锯末生物炭优于槐树皮 生物炭,且 3%锯末生物炭对细菌群落的多样性影响最佳,其香农指数为 6.22;优势门主要为放线菌门(Actinobacteria)、变形菌门(Proteobacteria)、绿弯菌 门(Chloroflexi)、酸杆菌门(Acidobacteria)和 Saccharibacteria,相对丰度共占 76.80%~85.31%;优势纲有放线菌纲(Actinobacteria)、&alpha;-变形菌纲 (Alphaproteobacteria)、酸杆菌纲(Acidobacteria),其相对丰度占 48.13%~57.08%;属水平上,施加生物炭增加了芽孢杆菌属(Bacillus)、硝化螺旋菌属 (Nitrospira)的相对丰度,降低了土微菌属(Pedomicrobium)、根瘤菌属(Rhizobium)的相对丰度;层级聚类及冗余分析(RDA)发现,施加生物炭对细菌群落结 构有影响,其中,微生物量碳、含水率、铵态氮、有机碳对细菌群落结构的影响较大.细菌优势门与环境因子相关性热图分析表明,铵态氮与放线菌门、 绿弯菌门呈显著相关性.铵态氮是影响细菌群落的主要理化因子.</p

    2001—2017 年黄土高原实际蒸散发的时空格局

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    为了给全面评估黄土高原地区大规模实施退耕还林还草的生态效应提供依据, 基于 NASA 发布的空间分辨率为 500 m 的MOD16A2 蒸散发数据产品,分析了黄土高原以及黄河中游典型流域 2001&mdash;2017 年实际蒸散发量时空变化特征。结果表明: 黄土高原年均实际蒸散发量从西北向东南递增,多年平均季节蒸散发量空间分布格局与年平均蒸散发量分布格局基本一致, 季节蒸散发量由大到小顺序为夏季>秋季>春季>冬季; 实施退耕还林还草工程以来, 黄土高原年均蒸散发量以 8.23 mm /a 的速率显著增加, 多年平均蒸散发量为 278.71 mm; 黄河中游各典型支流 2001&mdash;2017 年蒸散发量均呈现增加的趋势, 延河流域增速最大( 为 12.96 mm / a) ,皇甫川流域增速最小( 为 4.34 mm /a) ; 不同流域实际蒸散发量差异较大,渭河干流年均蒸散发量最大( 为 388.26 mm) ,皇甫川流域年均蒸散发量最小( 为 153.71 mm) 。 &nbsp;</p

    Effects of shrub species on soil nitrogen mineralization in the desert-loess transition zone

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    Shrubs play a vital role in ecosystem restoration in the desert transition zone, which suffers intensive desertification, land degradation, and nitrogen (N) limitation. To evaluate the effects of different shrub species on soil N availability, transformation, and their seasonal dynamics, we determined mineral N contents and mineralization rates in soils under three common shrub species (Artemisia ordosica Krasch., Caragana korshinskii Kom., and Salix psanunophila C.) and in bare land during the growing season in the desert-loess transition zone in northwestern China. The average contents of soil nitrate N and mineral N were 153% and 55% greater, respectively, and cumulative net N nitrification and mineralization were 101.2 and 121.0 mg N m-2 higher, respectively, in soils beneath C. korshinskii than in bare land (P &lt; 0.05) at the 0-10 cm depth over the growing season. The net N mineralization rate in 0-10 cm depth was significantly higher in soils under C. korshinskii than that in bare land during 21 Jun-23 Jul and 23 Aug-15 Oct of the growing season. However, C. korshinskii did not influence soil N metrics at the 10-20 cm depth. The incorporation of A. ordosica and S. psanunophila into bare land did not influence soil N availability or transformation rates. Our results demonstrated that C. korshinskii was more preferable than A. ordosica and S. psanunophila in ameliorating soil N cycling in the desert-loess transition zone.</p

    Response of aggregate associated organic carbon, nitrogen and phosphorous to re-vegetation in agro-pastoral ecotone of northern China

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    The agro-pastoral ecotone is an ecologically fragile transition zone and suffers from extensive human-induced land-use changes. To understand how soil organic carbon (OC) and nutrients will respond to re-vegetation practices in such an ecotone zone, we present the response of OC, nitrogen (N) and phosphorus (P) in both bulk soils and water-stable aggregates to typical re-vegetation patterns in an agro-pastoral ecotone of northern China. Three re-vegetation patterns, i.e., cropland converted to natural grassland, woodland and artificial grassland at different times (6 to 40 years), were selected. The paired croplands were also selected as the control for each re-vegetation pattern. The measured soil metrics include the proportions of each type of water-stable aggregate, the mean weight diameter and geometric mean diameter of the aggregates, and the concentrations of OC, N and P in bulk soils and each aggregate fraction. The results showed that the three re-vegetation patterns significantly increased the mass proportion of macro-aggregates, the values of mean weight diameter and geometric mean diameter, and the concentrations of OC and N in topsoils (0-10 cm). The accumulation of OC and N in bulk soils was mainly due to the accumulation in macro-aggregates. Furthermore, increases in OC and N were greater after conversion to legume vegetation than to non-legume vegetation, and were highest at approximately 20 years after the conversion. However, concentrations of P in bulk soils and aggregates were similar among the three re-vegetation patterns and the three aggregate fractions, and were minimally affected by the conversion. These results highlighted the potential of legume vegetation to increase OC and N in surface soils and aggregates, and indicated no response of soil P to re-vegetation in an agro-pastoral ecotone of northern China.</p

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    Institute of Soil and Water Conservation,Chinese Academy of Sciences and Ministry of Water Resources
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