Soil carbon increases with long-term cattle stocking in northern temperate grasslands

Grassland management aimed at enhancing carbon (C) in soil is an important tool in mitigation of rising atmospheric CO₂, yet little is known of how grassland soil C changes with livestock stocking rate (SR). We relate soil organic and inorganic C mass (t ha⁻¹ to 60 cm depth) with cattle stocking over periods of 7–27 year for 32 paddocks distributed across nine community pastures in the mixed-grass prairie of Saskatchewan, Canada. Initial analysis comparing Akaike information criterion models showed that cattle SR explained a greater proportion of variance in soil C, particularly soil organic C, than rainfall. Soil organic C mass increased with cattle SR (R² = .293; p = .001), even when the latter was normalized to account for differences in vegetation composition and growing conditions among pastures. Normalized SR varied from 0.49 to 2.30 times recommended levels, over which SOC increased from 24.7 to 57.4 t ha⁻¹. Increases in soil organic C under greater stocking coincided with increased abundance of introduced vegetation, particularly the rhizomatous grass Poa pratensis. Inorganic soil C accounted for 34.6% of total soil C, being particularly large below 30 cm soil depth, but did not vary with stocking rate. These findings indicate that both organic and inorganic C are important pools of C in northern temperate grassland soils, with soil organic C positively associated with long-term cattle SR. Further studies are recommended to understand more fully the mechanisms regulating grazing impacts on soil C mass in northern temperate grasslands.     

基于实地和遥感调查的离子型轻稀土尾砂土壤侵蚀对植被修复措施响应

稀土开采产生大量尾砂,导致严重土壤侵蚀,伴生水质和地质灾害,评价植被修复措施对稀土尾砂土壤侵蚀治理效果可为措施优选提供理论依据。以寻乌县离子型轻稀土尾砂区为研究区,基于1982—2015年GIMMS NDVI 3 g、DEM等遥感和尾砂理化性状现场调查数据,采用空间代时间方法,结合RUSLE模型及其全微分公式探究不同修复年限土壤侵蚀量对植被修复措施的响应机理。结果表明:1982—2015年研究区土壤侵蚀模数显著下降,倾向率为-60 t/(km~2·10a),突变年份为2008年;在植被修复措施实施年(2008年)前后,多年平均土壤侵蚀量减幅超过60%;土壤侵蚀模数呈现上升、平稳、上升、平稳、上升和下降的阶段性变化,与NDVI时程变化呈负相关;水土保持措施、植被覆盖、土壤可蚀性和降雨变化对土壤侵蚀量减小的贡献率分别为33.18%,32.19%,19.95%,13.19%。植被修复过程中,矿区土壤侵蚀量减少的主要影响因子为水土保持措施因子和植被覆盖因子。     

农业气象灾害对我国粮食生产的影响——基于八大经济区的面板数据回归

随着全球气候变暖的加剧,气象灾害频发对世界各国的农业生产构成了巨大威胁。本文基于投入产出理论,通过分析我国八大经济区域1997-2018 年农业生产状况的面板数据,着重考虑了农业气象灾害对不同地区粮食生产的影响程度,并基于分析结果提出了相应的建议。     

岷江上游典型流域植被水文效应模拟

该文通过研究现有土地覆盖下水文分布的空间格局,及不同植被类型集水区内降雨与径流间的关系,来揭示森林生态系统与水文动态之间相互作用的机制,从而为岷江上游的生态环境评价和区域生态环境保护及恢复提供理论依据和科学指导.在前人研究的基础上,结合先进的地理信息系统和遥感技术,构建岷江流域植被水文模型.模型以水文子模块TOPMODEL为中心,由山地小气候模型MTCLIM和林冠截留模型为其提供水文学参数,研究中水文循环过程涉及植被截留、(实际)蒸散发、降雨入渗和土壤水分动态等.最后将模型应用于岷江上游典型支流——杂古脑流域,对其1995年7—9月的径流特征进行了模拟分析.结果显示,7—9月日径流量总体趋势表现为逐渐降低,径流量对降水响应敏感,基本反映了杂古脑流域雨季的径流变化特征.     

基于Sentinel-2卫星数据的埃及地区蝗灾监测

【目的】 蝗灾突发性强,传统地面调查及生物学模型方法在时间、空间上不能满足精准防控的需求,且对历史数据依赖度高,利用高分辨率遥感数据监测蝗虫栖息生境的变化,从而实现蝗灾及时、快速监测,对治蝗防蝗具有重要意义。【方法】 文章以埃及南部蝗灾常发区为研究区,基于Sentinel-2卫星数据和地面气象数据、土地利用数据、行政区划数据等,监测植被生长季植被指数及植被覆盖度变化,实现埃及地区蝗虫发生地、发生程度的快速评估。【结果】 2019年6—7月,埃及南部植被覆盖区蝗灾受灾面积比例约为12%,中度及重度以上面积不超6%,整体受灾不严重。【结论】 不依赖于历史数据,从短期植被覆盖度变化入手,可以动态监测蝗灾变化,总体时效性较强、效果较好。     

TM影像VI提取植被信息技术研究

应用规一化植被指数（ＮＤＶＩ）、土壤调节植被指数（ＳＡＶＩ）和修正后的土壤调节植被指数（ＭＳＡＶＩ）,研究了ＴＭ影像植被信息的提取技术。结果表明,ＳＡＶＩ较之ＮＤＶＩ和ＭＳＡＶＩ,消除土壤背景影响和适应植被密度变化的能力更强,是植被信息提取效果较好的植被指数。使用ＳＡＶＩ,关键是要确定一个合适的土壤调节参数Ｌ,以最大限度地消除土壤背景的影响,ＳＡＶＩ提出时推荐的最佳Ｌ值（０．５）应用于卫片处理有很大局限性;基于研究结果,本文给出了适于不同植被条件卫片处理的最佳Ｌ取值。     

不同发育阶段杉木人工林林下植被的多样性

为揭示不同发育阶段杉木人工林林下植被多样性的变化规律,对福建三明莘口教学林场不同发育阶段杉木人工林（幼龄林、成龄林和过熟林）林下植被的种类、数量、丰富度、盖度、高度等指标进行调查。结果表明：不同发育阶段杉木人工林林下植被物种丰富度（ S）差异不大,个体丰富度（ N）差异较大,表现为成龄林（478个）＞过熟林（308个）＞幼龄林（223个）;幼龄林林下植被以玉叶金花等耐阴树种占优势,成龄林及过熟林中网脉酸藤子、毛冬青等喜阳植物重要地位明显上升,在各发育阶段均处于优势地位的物种如裸花紫珠、杜茎山、狗脊蕨、江南卷柏等,可以考虑作为恢复林分物种多样性的启动物种;随着林分的发育,林下植被Simpson指数（ D）、 Shannon-Wiener指数（ H）、 Pielou均匀度指数（ J′）和生态优势度指数（ DMc ）均表现为先升高后降低的趋势。可见林下植被的物种多样性与杉木林分的生长发育阶段密切相关,及时进行抚育间伐是提高杉木人工林林下植被物种多样性和维持生态系统稳定性的有效途径。     

Status of aquatic and riparian biodiversity in artificial lake ecosystems with and without management for recreational fisheries: Implications for conservation

1. Humanity is facing a biodiversity crisis, with freshwater-associated biodiversity in a particularly dire state. Novel ecosystems created through human use of mineral resources, such as gravel pit lakes, can provide substitute habitats for the conservation of freshwater and riparian biodiversity. Many of these artificial ecosystems are subject to a high intensity of recreational use, however, which may limit their biodiversity potential.
2. The species richness of several taxa (plants, amphibians, dragonflies, damselflies, waterfowl, and songbirds) was assessed and a range of taxonomic biodiversity metrics were compared between gravel pit lakes managed for recreational fisheries (n = 16) and unmanaged reference lakes (n = 10), controlling for non-fishing-related environmental variation.
3. The average species richness of all the taxa examined was similar among lakes in both lake types and no substantial differences in species composition were found when examining the pooled species inventory. Similarly, there were no differences between lake types in the presence of rare species and in the Simpson diversity index across all of the taxa assessed.
4. Variation in species richness among lakes was correlated with woody habitat, lake morphology (surface area and steepness), and land use, but was not correlated with the presence of recreational fisheries. Thus, non-fishing-related environmental variables had stronger effects on local species presence than recreational fisheries management or the presence of recreational anglers.
5. Collectively, no evidence was found that anglers and recreational fisheries management constrain the development of aquatic and riparian biodiversity in gravel pit lakes in the study region; however, the conservation of species diversity in gravel pit lakes could benefit from an increasing reliance on habitat enhancement activities.

     

间伐对华北土石山区油松林生长及其林下植被发育的影响

间伐是森林经营的主要措施之一,研究间伐对森林生态系统的影响对其可持续发展具有深远意义。对河北省木兰围场国有林场管理局北沟林场4块油松人工林样地分别进行46.6%,56.2%,67.1%的3个强度间伐以及对照处理,通过植被群落调查,研究不同间伐强度后油松林生长及其林下植被发育。结果表明:油松林分经不同强度抚育间伐后单木胸径、树高、冠幅和生物量均显著高于对照,且随间伐强度增大而增加,但单位面积蓄积量随间伐强度增大而减小;弱度、中度间伐能够增加林下植物种类,提高林下植物丰富度、多样性和均匀度指数,但是强度间伐后林下植物种类并不会增多,此现象符合"中度干扰假说";林分经不同强度间伐后,林下植被优势种各异;随着间伐强度的增大,林下植被生物量增加。综上,合理的间伐能够促进林分生长及其林下植被发育,研究区选择56.2%左右的间伐强度最优。     

湘中紫色丘陵区不同植被类型根际与非根际土壤理化特征

[目的]探索湘中紫色丘陵区不同植被类型根际与非根际土壤的理化特征,为湘中地区生态修复提供理论依据。[方法]以典型抽样方法调查湘中丘陵区草丛(G)、草灌(GS)、灌木(S)和乔灌(AS)4种典型植被,研究其根际与非根际土壤理化性质的差异,通过典型相关分析揭示根际与非根际土壤理化指标间的耦合关系。[结果]研究区草丛和灌木根际土壤中细砂粒(0.25~0.05mm)含量分别显著(p0.05)低于乔灌63.84%和76.97%;粉粒(0.02~0.002mm)含量表现为草和灌木分别显著高于乔灌的38.48%和37.66%。根际土壤0.25~0.05mm微团聚体含量均表现为乔灌高于其他植被,0.02~0.002mm微团聚体含量均表现为灌木高于其他植被。草灌与灌木非根际土壤有机质含量显著(p0.05)低于根际土壤148.05%和121.92%,灌木和草灌根际土壤有机质含量显著(p0.05)高于乔灌土壤84.28%和92.08%;草灌根际土壤全氮含量显著(p0.05)高于非根际土壤83.33%,草灌根际土壤碱解氮含量显著(p0.05)高于乔灌土壤200.83%;不同植被类型根际/非根际土壤磷含量差异不明显,总体来看,同一植被根际土壤全磷含量低于非根际土壤,而有效磷表现为乔灌最低;乔灌根际土壤速效钾含量分别显著(p0.05)低于草丛和草灌土壤125.15%和137.71%,除草灌外,其余植被类型根际土壤全钾含量均低于非根际土壤。典范相关分析表明土壤有机质和全量养分含量,2~1,1~0.5,0.25~0.05mm土粒含量,2~1,1~0.5mm团聚体3组理化性状间相互关系密切。[结论]改善土壤理化性质,促进湘中丘陵地区生态恢复,应注重协调土壤养分、颗粒组成及团聚体之间的耦合关系。