Subjects: Geosciences >> Other Disciplines of Geosciences submitted time 2019-09-11 Cooperative journals: 《干旱区研究》
Abstract：以渭河流域为研究区，获取流域内21个气象站1978—2002年20 cm口径蒸发皿和1985—2015年E-601型蒸发器日观测资料，采用线性回归模型重构各站点蒸发皿蒸发数据资料，Mann-Kendall趋势检验与空间插值法分析流域蒸发皿蒸发量的时空变换特征，敏感性分析法定量评估各气象要素对蒸发皿蒸发量变化的贡献。结果表明：流域多年平均蒸发皿蒸发能力低于黄河流域的平均水平，蒸发皿蒸发量介于1 015.5~1 705.6 mm，其空间分布状况表现为由北向南逐渐减少；年蒸发皿蒸发量总体呈增加趋势，变化率为1.371 mm·a-1；蒸发皿蒸发量对实际水汽压最敏感；气温是影响蒸发皿蒸发量的主导因子，其贡献率为304.5%。
Subjects: Biology >> Ecology submitted time 2017-02-09 Cooperative journals: 《生态学报》
Abstract：以陕西省29个县（市）39个样点的刺槐、辽东栎和油松林为研究对象，分析比较不同树种乔木叶片、凋落物与土壤N、P化学计量特征及其与经纬度、海拔、年均温度和年降水等环境因子间关系的异同以及三者之间可能存在的关系，以期为认识陕西省主要森林树种养分限制状况、制定合理的植被管理和恢复措施提供理论依据。结果表明：3树种叶片N、P含量及比值均为刺槐 > 辽东栎 > 油松，与叶片相比，凋落物中N、P含量变化幅度较小，为刺槐 > 辽东栎 > 油松，N：P比值为油松 > 辽东栎 > 刺槐。10-20 cm与0-10 cm土层相比，3树种中除辽东栎中P含量差异不显著外，其它指标N、P含量及N：P比值均显著下降（P < 0.05）。刺槐、辽东栎和油松叶片N、P含量与土壤N、P含量均没有显著相关性，以刺槐、辽东栎和油松3种植物叶片为总体来说，P含量与土壤P含量显著正相关（P< 0.05）。叶片N、P含量均大致表现出随着年均温度和年降水的增加而增加，随着经纬度的增加而降低的趋势，这一点在刺槐叶中最为明显。凋落物N含量随着年均温度和年降水的增加而增加，随着纬度和经度的增加而降低；P含量随着年降水和经度的增加而降低；N：P比值随着年均温度和年降水的增加而增加，随着纬度的增加而降低。研究区内，土壤N、P含量随着纬度、海拔的增加和年均温度、年降水、经度的降低而增加，N：P比值则呈相反的趋势。3树种土壤N、P含量及N：P比值中，P含量比N含量受环境影响更大，且0-10 cm和10-20 cm土层N、P含量及N：P比值与各环境因子的关系基本一致。
Subjects: Biology >> Ecology submitted time 2017-02-09 Cooperative journals: 《生态学报》
Abstract：土壤有机碳和全氮的分布与矿化是退化草地封育后土壤生态效应研究的重要内容和指标。结合野外调查和室内培养实验，研究了半干旱黄土区不同封育年限草地土壤有机碳和全氮的含量变化及其矿化特征。结果表明，封育对半干旱黄土区退化草地土壤有机碳和全氮的影响主要体现在0-40 cm土层，封育超过17a后，封育年限的影响逐渐减弱。封育显著增加了土壤有机碳矿化速率和Cmin/C0，封育对有机碳矿化速率的影响与封育年限和土层深度无关，而对Cmin/C0的影响则与封育年限和土层深度有关。封育显著提高了0-40 cm土层土壤氮素矿化速率，但是降低了40-80 cm土层土壤氮矿化速率，并且降低了0-80 cm土层Nmin/N0。碳氮矿化速率与有机碳和全氮之间显著相关，而与碳氮比之间的相关性较小。这些结果表明，退化草地封育后土壤碳氮元素的转化主要受土层深度、封育年限以及土壤碳氮含量的影响。
Subjects: Biology >> Botany >> Plant ecology, plant geography submitted time 2016-05-03
Abstract： Aims Carbon sequestration is the basic function and most primary service of forest ecosystems, and plays a vital role in mitigating the global climate change. However, carbon storage and allocation in forest ecosystems have been less studied at regional scales than for forest stands, and the results are subject to uncertainty due to inconsistent methodologies. Here, we aimed at relatively accurate estimates of forest carbon storage and sequestration rate at a provincial scale (regional) based on plot surveys of both stand biomass and soils over the province. Methods Based on the area and distribution of major forest types, 212 sampling plots, covering different age classes and originality (natural/planted), were surveyed in Gansu Province in northern China. Field investigations were conducted for vegetation layers (trees, shrubs, herbs and litter), soil profiles, and sampling of both plant materials and soils for laboratory analyses. Regional carbon storage was calculated by up-scaling the carbon densities of all forest types with their corresponding areas. Carbon sequestration rate was estimated by referring the reports of national forest inventory for different periods. Important findings Forest carbon storage at the provincial scale was 612.43 Tg C, including 179.04 Tg C in vegetation biomass and 433.39 Tg C in soil organic materials. Specifically, natural forests contributed largely and stored 501.42 Tg C, approximately 4.52 times that of the plantations. Vegetation carbon density in both natural forests and plantations showed increasing trend with the increase in age classes, and the natural forest showed a higher value than the plantation at the same age class. Soil carbon density also increased along the age classes in natural forests, whereas the highest value in plantations appeared at pre-mature stage. Weighted average of regional vegetation carbon density was 72.43 Mg C?hm–2, with 90.52 and 33.79 Mg C?hm–2 in natural forest and plantations, respectively. In 1996, vegetation biomass stored 132.47 and 12.81 Tg C in natural forests and plantations, respectively, and the values increased to 152.41 and 26.63 Tg C in 2011, with the mean carbon sequestration rates of 1.33 and 0.92 Tg C?a–1. Given that young and middle-aged forests account for a large proportion (62.28%) of the total forest area, they are expected to exert substantial potential of carbon sequestration in the province.
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