若尔盖盆地沙漠化驱动机制

作为世界上最大的高寒泥炭沼泽湿地,若尔盖盆地是黄河水源的重要补给区,素有黄河"蓄水池"之称.作为生态敏感区,在自然环境和不合理的人为活动的影响下,若尔盖盆地出现了湿地萎缩、草场退化、沙地增加等一系列严重的生态环境问题.本文通过分析若尔盖盆地沙漠化现状及其驱动因素,进而阐述和分析沙漠化驱动机制.结果表明:若尔盖盆地广泛分布的古风沙沉积物是现代沙漠化的沙物质来源,地表致密草皮层的机械破坏,使下伏松散的古风沙沉积物暴露,是形成沙漠化的关键一步;随后在风蚀、雨水冲刷及生物因素的共同作用下,松散的古风沙沉积物被侵蚀,引起草皮层坍塌,导致古沙丘活化,风沙活动加剧,形成风沙沉积;若尔盖沙漠化是人为因素与自然因素共同作用的结果,其中人为因素是其主导驱动因素,鼠类活动和热融沉陷、滑塌是沙漠化的诱发因素.     

Canopy rainfall storage capacity as affected by sub‐alpine grassland degradation in the Qinghai–Tibetan Plateau,China

Grassland degradation resulting from global climate change, overgrazing, and rodent damage is expected to influence the magnitude of canopy hydrological fluxes because of reduced vegetation biomass and changed species composition. The objectives of this study were to estimate herbaceous canopy rainfall storage capacity (S) along three different stages of sub‐alpine grassland degradation (non‐degraded, lightly degraded and moderately degraded) in the Qinghai–Tibetan Plateau, China, and relate changes in S to canopy properties. An artificial wetting method and the water budget balance method, using rain simulations, were used for estimating S. Grassland degradation significantly reduced S. In non‐degraded, lightly degraded and moderately degraded grasslands, S estimated using the artificial wetting method were 0.612 ± 0.08 mm, 0.289 ± 0.04 mm, and 0.217 ± 0.01 mm, respectively; S estimated using the water budget balance method were 0.979 ± 0.32 mm, 0.493 ± 0.13 mm, and 0.419 ± 0.09 mm, respectively. These changes could be explained by accompanying changes in above‐ground biomass and leaf area index, as well as changes in species composition. Species‐specific rainfall storage capacity varied by a factor of 2.7 among the investigated species, with graminoids having the lowest values. Leaf area index was more correlated to S than was canopy coverage. Converting fresh weight of non‐leaf tissues into effective leaf area of the corresponding species and then introducing a coefficient of leaf area according to the specific storage capacity of leaves improved the linear relationship between S and leaf area index. Copyright © 2011 John Wiley & Sons, Ltd.     

Effect of mixture sowing on biomass allocation in the artificially-planted pastures,Southeastern Tibetan

Artificial planting is an important measure to promote the restoration of degraded grassland and protect the ecological environment. The objectives of the current study were to investigate the allocation pattern between aboveground biomass(AGB) and belowground biomass(BGB) in different seeding types of artificially-planted pastures. We explored the variation in biomass and the relationship between above-and belowground biomass in four artificiallyplanted pastures with one species from Elymus nutans Griseb(EN, perennial), Elymus sibiricus Linn(ES, perennial), Medicago sativa Linn(MS, perennial), and Avena sativa Linn(AS, annual) and in six artificially-planted communities with mixtures of two species by seeding ratio 1:1 from the abovementioned grasses(EN + AS, MS + AS, EN + ES, MS + EN, MS + ES, AS + ES) in 2015 and 2016. The results showed that E. nutans is the most productive species with the highest biomass production among the single crops. MS + ES was the most productive group in 2015, while the group with the highest biomass production changed to AS + ES in 2016. AGB was positively correlated to BGB in the surface soil layer in the first year, but positively related to BGB in the subsoil layer in the second year. In the early stageof artificial grassland succession, plants allocated more biomass to aboveground parts, with a root to shoot(R/S) ratio of 1.98. The slope of the log-log relationship between AGB and BGB was 1.07 in 2016, which is consistent with the isometric theory. Different sowing patterns strongly affected the accumulation and allocation of biomass in artificiallyplanted grassland, E. sibiricus was the suitable plant in the alpine regions, which will be conducive to understanding vegetation restoration and plant interactions in the future.     

草地生态系统碳循环研究评述

本文就目前草地生态系统碳循环研究的主要问题进行了综述,重点阐述了四个方面的内容：1、草地生态系统碳贮量,包括植被及土壤碳贮量,草地NPP及生物量的分布特征和测定;2、草地土壤呼吸,认为其是草地碳循环中最主要的环节,是目前研究的重点;3、气候及人类活动（开垦和放牧等）对草地生态系统碳循环的影响;4、二氧化碳增加对草地碳循环的可能影响,并对研究工作中的难点做了简要评述。     

Detecting the storage and change on topsoil organic carbon in grasslands of Inner Mongolia from 1980s to 2010s

Soil carbon sequestration and potential has been a focal issue in global carbon research. Under the background of global change, the estimation of the size as well as its change of soil organic carbon（SOC） storage is of great importance. Based on soil data from the second national soil survey and field survey during 2011–2012, by using the regression method between sampling soil data and remote sensing data, this paper aimed to investigate spatial distribution and changes of topsoil（0–20 cm） organic carbon storage in grasslands of Inner Mongolia between the 1980 s and 2010 s. The results showed that：（1） the SOC storage in grasslands of Inner Mongolia between the 1980 s and 2010 s was estimated to be 2.05 and 2.17 Pg C, with an average density of 3.48 and 3.69 kg C·m–2, respectively. The SOC storage was mainly distributed in the typical steppe and meadow steppe, which accounted for over 98% of the total SOC storage. The spatial distribution showed a decreased trend from the meadow steppe, typical steppe to the desert steppe, corresponding to the temperature and precipitation gradient.（2） SOC changes during 1982–2012 were estimated to be 0.12 Pg C, at 7.00 g C·m–2·yr–1, which didn＇t show a significant change, indicating that SOC storage in grasslands of Inner Mongolia remained relatively stable over this period. However, topsoil organic carbon showed different trends of carbon source/sink during the past three decades. Meadow steppe and typical steppe had sequestered 0.15 and 0.03 Pg C, respectively, served as a carbon sink; while desert steppe lost 0.06 Pg C, served as a carbon source. It appears that SOC storage in grassland ecosystem may respond differently to climate change, related to vegetation type, regional climate type and grazing intensity. These results might give advice to decision makers on adopting suitable countermeasures for sustainable grassland utilization and protection.     

新疆伊犁河流域草地类型特征及其生态服务价值研究

以新疆伊犁河流域为研究对象,采用Costanza生态系统服务价值计算公式,参照谢高地等人的中国草地生态系统服务单位面积价值,分析了伊犁河流域草地类型特征和生态系统服务价值。研究结果表明,新疆伊犁河流域草地资源丰富,草地面积占土地总面积的60.88%以上,草地产草量及载畜能力均处于全疆最好水平,其中山地草甸类草地面积最大,占草地可利用面积的27.91%。草地生态系统每年的服务价值为200.47亿元,山地草甸类草地、温性草甸草原类以及温性草原类草地生态服务价值达145.3亿元,占到全流域草地总生态服务价值的72.48%,是草地生态服务价值的主体部分,流域生态系统服务性功能远大于生产性功能。总体看来,伊犁河流域草地生态服务价值山间盆地、丘陵区较高;而平原区相对较低。草地存在退化现象,1985—2005年间草地生态服务价值有所下降。     

CLM4.5在西北农牧交错带盐池站的模拟性能评估

农牧交错带具有草地、裸地、农田大面积相互镶嵌的独特下垫面,其地表水热过程变化复杂,亟需深入研究。利用宁夏盐池站2017年实际观测资料,对陆面过程模式CLM4.5的模拟性能进行检验。结果表明,在复杂下垫面下,CLM4.5仍能较好地模拟出草地的地面反射辐射、地面长波辐射和净辐射以及0~10 cm土壤含水量和温度的变化特征,但模拟值与观测值还存在一定偏差。CLM4.5能模拟出辐射通量的日变化特征,除5月外,地面反射辐射模拟值与观测值之间的偏差较小。地面长波辐射模拟值白天偏高,净辐射观测值与模拟值的相关系数为0.99,均方根误差为22.50 W·m^-2。土壤含水量观测值与模拟值的相关系数达0.83,但模拟值偏低,且模式对降雨后土壤含水量变化过程的模拟性能有待提高。土壤温度模拟值的日变化特征较为明显,观测值与模拟值的相关系数为0.98,均方根误差为2.82℃。     

黄土高原地区退耕还林还草模式案例研究——以宁夏原州区为例

对地处黄河上游、黄土高原西北部、水土流失严重并以贫困著称的宁夏原州区退耕还林还草模式进行研究。通过与原州区有关部门座谈、6个村的典型调查、偶遇抽样的农户问卷调查,在对调查记录和取得的73份有效问卷进行分析的基础上,总结了该区退耕还林还草的模式、工程实施的现状;分析该区退耕还林（草）工程实施过程中模式选择带来的一些问题;最后,提出了相应建议。旨在对新形势下巩固已经取得的退耕还林还草成果,进一步推进退耕还林还草等生态建设,提供实践方面的案例剖析。     

2004－2014年河西走廊荒漠化草地生态系统服务价值估算

草地是干旱、半干旱区面积占优势的生态系统,在时间尺度上对其进行生态系统服务价值评估是判断区域生态系统处于改善或退化的主要途径。基于野外调查和遥感分类解译划分的河西走廊荒漠化草地基础数据,首次建立了河西走廊不同类型、不同程度荒漠化草地生态系统服务价值计算和修正方案,评估了第三次（2004年）、第四次（2009年）和第五次（2014年）荒漠化监测期河西走廊荒漠化草地生态系统服务价值动态变化及服务价值结构。结果表明：（1）2004—2014年间河西走廊草地荒漠化呈现轻微逆转趋势,荒漠化草地面积由519.7万 hm²减少至357.7万 hm²;（2）10年间河西走廊荒漠化草地生态系统服务总价值以损失为主,损失量达209亿元;（3）河西走廊荒漠化草地生态系统服务总价值在时空分布、荒漠化类型和程度方面存在显著差异;（4）河西走廊荒漠化草地生态系统服务倾向于气候调节、净化环境和水文调节功能。     

基于稀疏样点的蒙古国产草量估算方法研究

产草量是衡量草原生产力和诊断草原健康状况的指标,是草地资源管理的重要依据。近年来,遥感数据结合地面实测数据建模已成为产草量估算的重要手段。充足的实测样点信息是产草量遥感建模估算的基础。受境外采样多重因素的制约,蒙古国产草量估算研究中无法获取足够且分布均匀的实测样点,估产模型的精度受到影响,这一问题目前尚未发现有好的解决方法。本研究选取中蒙铁路沿线（蒙古段）两侧200 km缓冲区作为研究区,针对产草量遥感估算中野外样点稀少且分布不均的问题,引入P-BSHADE方法,基于多年NDVI数据和获取的少量地面实测样点数据,考虑草地分布的非均匀性以及样点之间的相关性,对均匀分布的模拟样点处的产草量数据进行插值实验。结果显示,P-BSHADE法的插值效果优于Kriging法,可得到均匀分布于研究区的样点。基于以上实测样点和插值样点,结合NDVI、EVI、PsnNet 3种植被指数进行遥感建模,最优模型精度达到80%,精度优于已有相关研究。选取其中最优的基于NDVI的指数模型对研究区2000—2019年产草量进行反演,获得的产草量空间格局与年际变化与已有研究结果趋势吻合,进一步印证了结果的可靠性和插值方法的可行性。本研究通过插值的方式改善数据源从而提高估算模型精度是一种全新的思路与尝试,对于“一带一路”等境外区域资源环境监测具有借鉴意义。