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.     

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。     

探索生命极限的模式生物——南极土壤自由生活线虫Plectus murrayi及其环境适应性特征

针对土壤自由生活线虫的环境适应性及其生态功能研究一直是土壤动物学和生态学的核心内容之一。前期研究表明南极土壤自由生活线虫能够在极端干旱的土壤中生存，尤其是线虫的优势种群之一——Plectus murrayi, 在生理生态水平上均表现出独特的适应性。土壤自由生活线虫Plectus murrayi是仅在南极麦克默多山谷（McMurdo Dry Valleys, MDV）发现的主要陆生生物之一，目前已在多领域成为研究极端环境下生态学以及生物学的模式生物。本文旨在综述其系统发育、分布、生命周期和实验室发育的最新研究，以及其在遗传水平上的耐冷冻和耐干燥性，结合南极沙漠土壤的特殊生态系统，阐述其对于探索生命极限的意义。基于P. murrayi在南极麦克默多山谷土壤的生境分布，与其他南极自由生活线虫相比，P. murrayi喜欢相对较高的湿度和较低的盐度土壤生境。由于全球气候变暖，南极麦克默多山谷的温度和湿度不断增加，P. murrayi极可能成为南极沙漠中的主要陆生动物。通过对P. murrayi的研究，能够探索其适应和功能基因之间的新联系，这些基因在理解细胞对极端微环境的抗逆性有着至关重要的作用，具有长远的农业以及医学利用价值。未来对南极麦克默多山谷土壤环境压力的短期和长期响应的研究，有助于揭示细胞对环境干旱、寒冷的耐受和修复作用，探明生物进化与生态系统复杂性之间的关系，以及不同微环境在塑造更复杂系统重的群落中的作用。