不同时间尺度胡杨液流速率与土壤因子的关系

为揭示土壤因子对胡杨液流的影响是否存在时间尺度差异，对库姆塔格沙漠东南部胡杨液流速率及20、50、100、150和200 cm土层的土壤含水量（soil water content，SWC）、土壤温度（soil temperature，Ts）进行持续 5个月的同步观测。结果表明，月尺度下，SWC_200cm是胡杨液流速率变化的主要影响因子，单独能解释94.9%的液流速率变化；日尺度下，Ts_200cm、SWC_50cm、SWC_20cm、SWC_200cm4个因子可以共同解释胡杨93.2%的液流速率变化，其中，Ts_200cm可以解释液流速率变化的90.3%，对胡杨液流速率影响最大；小时尺度下，Ts_200cm对胡杨液流的影响最大，可以解释液流速率变化的51.6%。随着时间尺度的扩大，对液流速率变化的影响因子由多变少，可靠性由小变大。由此表明，根据土壤含水量及土壤温度预测小时尺度胡杨液流速率需要较多的参数，且可靠性较小；而预测月尺度液流速率需要较少的参数，且可靠性较大。因此，预测月尺度胡杨液流速率更为合适。     

乌鲁木齐周边典型荒漠草地群落物种多样性及生物量关系研究

为探讨荒漠草地群落物种多样性及生物量分配，本研究采用样方法对乌鲁木齐市周边典型荒漠草地群落物种多样性与生物量的关系进行研究。结果表明：乌鲁木齐周边典型荒漠草地群落物种组成单一，群落平均高度、盖度、密度、生物量呈现显著性差异(P<0.05)；0～50cm土层中，群落地下生物量除梭梭群落均随着土层深度增加而逐渐减小，梭梭群落则呈先增加后降低的趋势；植物群落呈异速生长模式，拟合方程为：y=231.375×e^{0.003 3x}(R²=0.714 8)；凋落物生物量与地下生物量之间呈线性关系，拟合方程为：y=13.818x+259.812(R²=0.616 1)；地上生物量与物种多样性之间呈单峰变化曲线，对应方程为：y=-5.210 4x²+0.004 5x+0.369 9(R²=0.307 1，P<0.01)，群落地下生物量与物种多样性之间关系表现出极显著的线性相关，对应方程为：y=3.073 5x+0.678 2(R²=0.543 4，P<0.05)。本研究结果可为退化荒漠草地的恢复及生物多样性保护、生态系统功能维持与恢复提供基础数据。     

荒漠草原灌丛转变过程土壤呼吸动态变化及其影响因素研究

探析荒漠草原向灌丛转变过程土壤呼吸动态及其影响因素，对确定干旱半干旱生态系统碳“源”/“汇”状态具有重要意义。本研究以宁夏东部荒漠草原-灌丛镶嵌体为研究对象，选取荒漠草地、草地边缘、灌丛边缘、灌丛地为研究样地，开展各样地微生境(植丛与空斑)下土壤呼吸(Rs)及相关土壤性质研究，结果表明：随着荒漠草原向灌丛地转变，土壤呼吸日动态与季节动态呈上升趋势，季节动态在7月达到峰值(P<0.05)，灌丛地显著高出荒漠草地42.4%；土壤温度为转变过程土壤呼吸日动态的主要影响因子，温度和水分共同影响(R²介于0.44~0.80)土壤呼吸季节动态；回归分析和主成分分析表明，土壤呼吸与全碳、全氮、微生物生物量碳、生物量氮、土壤有机碳呈显著负相关(P<0.01)，与硝态氮呈显著正相关(P<0.05)。综上，近30年灌丛转变过程促使土壤二氧化碳通量增加，加速荒漠草原有机碳养分消耗。     

荒漠草原区显热通量变化特征及源区分布

对荒漠草原下垫面显热通量的时空特征分析对于提高区域水热交换规律认识和了解其在气候变化中的作用有重要意义。本研究基于内蒙古荒漠草原2021年5—12月的大孔径闪烁仪观测与相应的气象、环境观测资料，分析了荒漠草原区不同时间尺度显热通量变化特征及其源区分布。结果表明：大气不稳定条件下显热通量日变化曲线呈单峰型，相比于晴天，多云和阴天的日变化存在无规律波动；显热通量季节变化明显，5月以后不断减少；通量源区按照闪烁仪光径走向朝上风向延伸分布，越靠近光径对通量贡献能力越大；受稳定度、风速风向和下垫面植被特征共同影响，各时间尺度的通量源区特征不同，源区范围日变化与大气稳定度变化基本一致，研究期间11月源区面积最大，7月最小，相差约70 000 m²,整个生长季的通量贡献区小于非生长季；大气稳定度和风向是影响通量源区分布的重要因素。     

Grazing alters sandy soil greenhouse gas emissions in a sand-binding area of the Hobq Desert,China

Deserts are sensitive to environmental changes caused by human interference and are prone to degradation. Revegetation can promote the reversal of desertification and the subsequent formation of fixed sand. However, the effects of grazing, which can cause the ground-surface conditions of fixed sand to further deteriorate and result in re-desertification, on the greenhouse gas (GHG) fluxes from soils remain unknown. Herein, we investigated GHG fluxes in the Hobq Desert, Inner Mongolia Autonomous Region of China, at the mobile (desertified), fixed (vegetated), and grazed (re-desertified) sites from January 2018 to December 2019. We analyzed the response mechanism of GHG fluxes to micrometeorological factors and the variation in global warming potential (GWP). CO₂ was emitted at an average rate of 4.2, 3.7, and 1.1 mmol/(m²•h) and N₂O was emitted at an average rate of 0.19, 0.15, and 0.09 µmol/(m²•h) at the grazed, fixed, and mobile sites, respectively. Mean CH₄ consumption was as follows: fixed site (2.9 µmol/(m²•h))>grazed site (2.7 µmol/(m²•h))>mobile site (1.1 µmol/(m²•h)). GHG fluxes varied seasonally, and soil temperature (10 cm) and soil water content (30 cm) were the key micrometeorological factors affecting the fluxes. The changes in the plant and soil characteristics caused by grazing resulted in increased soil CO₂ and N₂O emissions and decreased CH₄ absorption. Grazing also significantly increased the GWP of the soil (P<0.05). This study demonstrates that grazing on revegetated sandy soil can cause re-desertification and significantly increase soil carbon and nitrogen leakage. These findings could be used to formulate informed policies on the management and utilization of desert ecosystems.     

草地和荒漠生态系统生物土壤结皮对土壤养分及酶活性的影响

为探讨在草地和荒漠生态系统中生物土壤结皮(Biological soli crusts, BSCs)对土壤养分及酶活性的影响，本研究选取国内外30篇中英文文献当中11个指标进行Meta分析，通过亚组分析对草地与荒漠两种生态系统下不同类型BSCs对土壤养分及酶活性的影响，并通过土壤养分恢复指数(NRI)和随机森林分析对其影响程度做出统一评价。结果表明：在荒漠生态系统中BSCs对NRI的作用大于在草地生态系统中；地衣结皮>混合结皮>苔藓结皮>藻结皮。并且通过随机森林分析和对年平均降雨量(MAP)与年平均温度(MAT)的拟合回归分析发现磷酸酶、脲酶和蔗糖酶对NRI贡献显著高于其余所选指标，其中磷酸酶与MAP、蔗糖酶与MAT均呈极显著正相关关系，而脲酶与MAP,磷酸酶与MAT均呈显著负相关关系。在今后的研究中，可以考虑将不同生态系统与BSCs类型匹配，从而更有效的利用BSCs进行土地退化和荒漠化的治理。     

Competition,spatial pattern,and regeneration of Haloxylon ammodendron and Haloxylon persicum communities in the Gurbantunggut Desert,Northwest China

Competition, spatial pattern, and regeneration are important factors affecting community composition, structure, and dynamics. In this study, we surveyed 300 quadrats from three dunes (i.e., fixed dunes, semifixed dunes, and mobile dunes) in the Gurbantunggut Desert, Northwest China, from late May to early June in 2021. The intraspecific and interspecific competition, spatial pattern, and regeneration of Haloxylon ammodendron and Haloxylon persicum were studied using the Hegyi competition index and point pattern analysis methods. The results showed that the optimal competition distance of the objective tree in the H. ammodendron and H. persicum communities was 6 m. The intraspecific and interspecific competition of H. ammodendron was the greatest in fixed dunes, while the competition intensity of H. persicum in semifixed dunes and mobile dunes was greater than that in fixed dunes. The order of competition intensity of the two populations was seedlings>saplings>adults, and the competition intensity gradually decreased with the increase in plant diameter. The spatial distribution pattern of the three life stages of H. ammodendron and H. persicum was random, and there were no correlations between seedlings and saplings, adults and saplings, and seedlings and adults. The density of regenerated seedlings and saplings of H. ammodendron in the three dunes followed the order of fixed dunes>semifixed dunes>mobile dunes, and that of H. persicum in the three dunes followed the order of mobile dunes>semifixed dunes>fixed dunes. Therefore, when artificially planting H. ammodendron and H. persicum for sand control, the planting interval should be 6 m, and seedlings should be planted next to adults to minimize the competition between plants, which can promote the renewal of H. ammodendron and H. persicum and the stabilization of the ecosystem.     

Human use of the sand dune ecosystem in the semiarid zone of the Rajasthan Desert,India

Sand dunes form one of the most fragile terrestrial ecosystems. in Rajasthan they have a diverse vegetation and are often utilized by considerable human and livestock populations. a thorough knowledge of the resource utilization by the human and animal populations is essential if the future potential of the ecosystem and its physical stability under changing environmental conditions are to be accurately assessed. This study examines the socio-economic aspect of land degradation at four sites in Churu and Jhunjhunu districts, northwest Rajasthan. an attempt is made to assess the socioeconomic factors leading to land degradation. Data on human use of the Rajasthan (Thar) Desert semiarid ecosystem were collected through individual interviews, group discussions and field measurements. the present exploitation of soil and vegetation resources, possible future biomass deficiency, its impact on sustainable development and role in land degradation are examined. The average number of people in each household in the study area, and the number of livestock each household maintains are too high to allow a satisfactory income to be sustained. the annual income of 50-90 per cent of households was less than 10 000 rupees ($US 1 = 17 rupees in 1987). Sale and consumption of milk, wool, surplus animals and wood provide livelihood, supplemented with income from wage labour. Rain-fed marginal land cultivation produces poor yields and the per capita production is too low to justify the huge soil erosion losses occurring. the number of goats, sheep and cattle owned by the inhabitants has increased tremendously in recent years. Stocking rates vary from 1.63 to 12.08 animals per hectare. the grazing pressure during the dry season, when forage availability decreases, reaches 34.9 animals per hectare. as a result of overgrazing, The land productivity has decreased considerably. the annual fodder deficit values in the study area are enormous. Demand for fuelwood at all the study sites is increasing, yet available forests have already largely been cut down. the distance travelled to collect fuelwood has been increasing, whereas the amount and quality of fuelwood is decreasing. Use of cattle dung to supplement fuelwood during the summer dry season and in drought periods has been decreasing due to low fodder availability and high livestock mortality. Human numbers are increasing, and livestock numbers are also multiplying (except in drought periods) and consequently the available resources are decreasing. Soil erosion and desertification will continue to increase during the next decade unless effective counter measures are undertaken.     

腾格里沙漠东北缘飞播植物群落土壤水分特征

[目的]研究腾格里沙漠东北缘1992年飞播造林区主要植物群落土壤水分特征,为区域人工固沙植被合理建设与管理提供理论依据。[方法]采用环刀法测定研究区4种不同植物群落不同坡位200 cm深度土壤含水量,分析其土壤水分分布、变异性及土壤贮水亏缺度。[结果](1)不同植物群落土壤平均含水量呈现：花棒群落(0.57%)>沙拐枣群落(0.55%)>花棒+沙拐枣群落(0.51%)>沙拐枣+花棒群落(0.51%),花棒群落土壤含水量与花棒+沙拐枣群落和沙拐枣+花棒群落之间具有显著差异(p<0.05),不同坡位平均土壤含水量均呈现出：坡底>坡中>坡顶的趋势。花棒和沙拐枣组合的植被群落土壤水分垂直变异性以及随坡位的变异性小于花棒群落和沙拐枣群落。(2)不同植物群落200 cm深度土壤总贮水量变化范围为15.45～17.79 mm,土壤贮水量随土层深度变化趋势与土壤含水量一致。(3)不同植物群落土壤贮水亏缺度呈现：花棒+沙拐枣群落(97.74%)>沙拐枣+花棒群落(97.62%)>花棒群落(97.48%)>沙拐枣群落(97.44%)。[结论]研究区土壤...     

降水变化和氮沉降对荒漠草原土壤丛枝菌根真菌群落结构的影响

降水变化和氮沉降是影响植物、微生物和土壤环境变化的两个重要方面。尽管丛枝菌根（AM）真菌在陆地生态系统中起着至关重要的作用，但人们对降水变化和氮添加如何交互影响AM真菌群落仍知之甚少。本研究以短花针茅荒漠草原为研究对象，采用裂区设计，主区为自然降雨(CK)、增雨30%(W)和减雨30%(R)三个水分梯度，副区为0(N0)，30(N30)，50(N50)和100(N100) kg?hm-2?a-1 四个氮素梯度共12个处理，通过高通量测序分析了土壤中AM真菌群落的多样性和组成。结果发现，水分处理对土壤AM真菌的Alpha多样性有促进作用，氮素处理抑制了土壤AM真菌的Alpha多样性，水分增加和氮素添加的交互作用促进了AM真菌的Alpha多样性增加，并改变了土壤AM真菌群落组成。水分和氮素刺激了各功能型植物生物量的增加，氮添加使多年生杂草和半灌木、小半灌木生物量显著增加，多年生禾草生物量显著减少。此外，多型孢子菌科的相对丰度与一二年生植物和半灌木、小半灌木生物量呈显著正相关，一二年生植物和半灌木、小半灌木生物量在氮添加和增雨处理下增加。本研究证明了AM真菌群落在短期气候变化下的稳定性。此外，AM真菌在科水平上的丰度与各生活型植物地上生物量的相关性证明了地上和地下生态系统的连通性。