岷江上游油松与云杉人工林土壤微生物生物量及其影响因素

以立地条件和营林方式相同的约30a林龄油松与云杉人工纯林为对象,测定地表微气候、土壤理化性质以及微生物生物量C、N、P(MBC、MBN、MBP),揭示林分结构、土壤性质与微生物生物量间的关系,以及两林分间的差异性。结果表明:两个林分地表环境荫湿,土壤肥力较低,土壤微生物生物量低,林地土壤碳积累低,土壤生态服务功能不强。相对而言,云杉林比油松林相对湿度大而地表温度低、林地土壤肥力高、土壤微生物生物量高,因此更有利于林地土壤生态服务功能的恢复。综合分析发现,林分结构、土壤养分状况及地表小气候影响着土壤微生物生物量与肥力转换过程,降低乔木冠层密度可以改善地表小气候,为有机物分解与养分归还创造良好的条件,从而改善土壤肥力与林地土壤生态服务功能。     

西安城市绿地生态功能研究

通过调查,将西安市片状绿地按种植结构分为乔灌草、乔草、灌草、乔木、灌木和草坪6种类型,并定点定时测定绿地中心和对照点的光强、湿度、温度、噪音、空气中细菌数.结果表明,在片状绿地中,除草坪外,其他绿地均具有一定的遮荫效应,不同结构绿地遮荫效应依次为灌木＞乔灌草＞乔草＞灌草＞乔木＞草坪;各绿地也有明显的降温效应,降温效应依次为乔灌草＞乔木＞灌木＞乔草＞灌草＞草坪;各绿地还有一定的增湿效应,增湿效应依次为乔草＞乔灌草＞乔木＞灌木＞灌草＞草坪;各绿地也具有降噪效应,降噪效应依次为乔灌草＞乔草＞乔木＞灌草＞灌木＞草坪;各绿地在灭菌方面也有明显的作用,灭菌效应依次为乔灌草＞乔草＞乔木＞灌草＞灌木＞草坪.相同种植结构的绿地中复层结构绿地的生态效益均大于单层结构的绿地.最后,根据以上结论提出了提高城市绿地生态功能的措施.     

丹霞地貌沟谷生态效应

以广东省丹霞山为研究实例,探讨丹霞地貌特殊的沟谷生态效应.结果表明,丹霞地貌的特殊沟谷生态效应体现在以下两个方面:第一是丹霞地貌演变过程中形成了众多石峰隆起和沟谷凹陷,特殊的地貌环境使得沟谷中的生态因子与其它非丹霞地貌开阔区域产生差异,小气候相对封闭,水湿条件极好,为喜高温高湿的热带物种提供了较好的生存环境;沟谷所处位置的地理环境,如四周崖壁的光滑程度会影响到太阳光反射到沟谷的光强,这些都会对沟谷中的温湿度产生影响.第二是丹霞地貌特殊的生态条件,为沟谷地带孕育出一批热带性较强的分类群提供了可能,与相近纬度的诸多植被相比,丹霞地貌植物区系热带性明显增强,热带分布区类型所占比重比同纬度区域要大10%以上,大多数沟谷中热带性物种分布现象比较明显,藤本分布较多,蕨类植物也较丰富,耐水湿的植物区系发育良好;这实际上造成了植物水平分布上的移位,使中亚热带区域中分布有南亚热带甚至热带区域的物种,出现了由于其特殊的沟谷地貌效应而形成的与其地貌条件保持协调和平衡的演替顶级群落类型,称为地貌顶级群落.     

南亚热带森林演替过程中小气候的改变及对气候变化的响应

区域水热格局变化和系统演替深刻影响森林内部小气候,不同演替阶段森林内部水热环境对气候变化的响应和反馈作用有待进一步认识和评估。以南亚热带地区的3种不同演替阶段代表性森林生态系统统(人工恢复的马尾松针叶林(Pinus massoniana coniferous forest,PF)、马尾松针阔叶混交林(mixed Pinus massoniana/broad-leaved forest,MF)和季风常绿阔叶林(monsoon evergreen broad-leaved forest,MEBF))为研究对象,通过分析其林内小气候林型间差异以及时间序列上的动态变化,探讨森林系统内部水热环境的改变机理。结果表明:演替驱动下,随着PF→MF→MEBF的正向发展,林内温度条件如气温、土壤温度逐渐降低,林内相对湿度、土壤层及凋落物含水量等水分状况逐步升高。不同林型在"雨热同期"的南亚热带地区其"降温效应"有差,演替初期的PF干、湿季"降温效应"分别为7.9%和3.6%,中期MF分别为11.6%和6.4%,顶级群落MEBF干、湿季"降温效应"可达15.7%和10.5%。总体上,随演替"降温增湿"效应越来越显著,且"降温"表现为干季更明显,而"增湿"表现为湿季明显。此外,演替驱动下后期森林对高温及土壤温度的调节作用更为突出。时间序列上,区域降水趋于"极端化"的格局影响下,森林生态系统的水分固持能力下降。主要表现为:自1984年以来,3种林型0—50cm土壤含水量均呈显著降低的趋势(P0.001),且湿季土壤含水量下降速率高于干季,林型间在全年及湿季均为MFMEBFPF,干季为MEBFMFPF。虽然研究期间3种林型林内气温、土壤温度无明显趋势性变化,但顶级群落MEBF林内相对湿度(P=0.021)、凋落物自然状态下含水量(P=0.003)在年际尺度上均呈现显著下降的趋势。与土壤含水量干、湿季下降速率的格局一致,二者也均为湿季大于干季。研究认为,成熟森林可能在当前南亚热带区域气候变化及水热格局改变背景影响下更为敏感和脆弱。     

Species turnover in ant assemblages is greater horizontally than vertically in the world's tallest tropical forest

Abiotic and biotic factors structure species assembly in ecosystems both horizontally and vertically. However, the way community composition changes along comparable horizontal and vertical distances in complex three‐dimensional habitats, and the factors driving these patterns, remains poorly understood. By sampling ant assemblages at comparable vertical and horizontal spatial scales in a tropical rainforest, we tested hypotheses that predicted differences in vertical and horizontal turnover explained by different drivers in vertical and horizontal space. These drivers included environmental filtering, such as microclimate (temperature, humidity, and photosynthetic photon flux density) and microhabitat connectivity (leaf area), which are structured differently across vertical and horizontal space. We found that both ant abundance and richness decreased significantly with increasing vertical height. Although the dissimilarity between ant assemblages increased with vertical distance, indicating a clear distance‐decay pattern, the dissimilarity was higher horizontally where it appeared independent of distance. The pronounced horizontal and vertical structuring of ant assemblages across short distances is likely explained by a combination of microclimate and microhabitat connectivity. Our results demonstrate the importance of considering three‐dimensional spatial variation in local assemblages and reveal how highly diverse communities can be supported by complex habitats.     

上海南京东路热舒适分析与评价

为探析夏热冬冷地区城市街道的空间因子对小气候与人体热舒适的影响及相互作用规律,通过对上海南京东路步行街中典型的风景园林空间按顶面遮蔽方式分为4种空间类型下的12个测点进行冬夏两季小气候实测及热舒适问卷调查,分析不同顶面遮蔽对风景园林小气候风湿热的影响差异,并结合热舒适评价指标的计算和使用者热舒适问卷,评价不同顶面遮蔽空间下人体热舒适感受。结果显示：1）根据热舒适问卷,建筑遮蔽区位于街道北侧的悬挑区在冬季最舒适,夏季最舒适的是树荫全遮蔽区;2）通过改善空间遮蔽程度与类型,根据风向与距街道十字交叉口的距离合理进行街道设计可以对街道中的太阳辐射与风环境产生显著影响,从而改善街道热舒适;3）采用生理等效温度（PET）指标计算的热中性范围冬季是16.90~28.95℃,夏季是9.05~22.57℃;4）PET评价在高温季节低估了风速对热舒适的影响,提出了基于问卷的热舒适预测方程。可为未来城市街道的舒适性规划建设提供经验与参考。     

小麦与蚕豆间作系统施氮对蚕豆赤斑病发生和冠层微气候的影响

通过田间小区试验,设N₀(0 kg·hm^-2)、N₁(45 kg·hm^-2)、N₂(90 kg·hm^-2)、N₃(135 kg·hm^-2)4个施氮水平,研究不同施氮水平下小麦与蚕豆间作对蚕豆赤斑病发生和冠层微气候的影响,探讨间作系统氮肥调控下冠层微气候变化及其与蚕豆赤斑病发生的关系.结果表明: 施氮提高了蚕豆单、间作种植模式下蚕豆赤斑病发病盛期的病情指数,增幅27.2%～58.0%,增加了病情进展曲线下面积(AUDPC),增幅15.0%～101.8%,N₃水平下赤斑病病情指数和AUDPC最高.施氮使蚕豆冠层温度降低0.2～1.1 ℃,冠层透光率降低1.7%～29.7%,冠层相对湿度增加0.5%～28.7%.与单作相比,间作蚕豆赤斑病病情指数显著降低36.3%～48.1%,AUDPC显著降低44.0%～53.6%,冠层温度和透光率分别提高2.1%～8.7%和12.0%～53.8%,相对湿度降低11.6%～31.6%.相关分析表明,冠层温度和透光率与赤斑病病情指数呈显著负相关,而湿度与病情指数呈显著正相关.表明高氮恶化了冠层微气候环境,加重了蚕豆赤斑病的发生和危害,而间作对蚕豆冠层微气候的改善是控制蚕豆赤斑病发展的重要原因.     

On metapopulations and microrefugia: palaeoecological insights

We highlight the importance of microrefugia in the light of population migration and genetic drift by synthesizing lessons learnt from metapopulation and palaeoecological studies. The concept of microrefugia is considered as a long‐term variant of conventional metapopulations, in which microclimatic stability supersedes gene flow in determining species survival. Not all species can maintain populations in microrefugia. Life history traits such as small body size, the capacity for asexual reproduction, and species with light genetic loads favour survival. Microrefugia will facilitate faster rates of species responses to climate change than envisioned in diffusion models, and potentially provide a means to alleviate the negative effects posed by natural or anthropogenic barriers to migration. Predictive models based on relatively coarse‐grained approaches that ignore microrefugia will lead to overestimates of extinction risk. Microrefugia should be identified and conserved, not for the species they contain, as these are likely to turn over with time, but as an important component of landscape diversity that will provide a safe haven for species not yet identified as at risk.