Silvopastoralism in the Alps: Native plant species selection under different grazing pressure

To evaluate the suitability of wood pastures as a managing tool in subalpine regions it is essential to know more about the influence of grazing on the ground vegetation. This study assessed native plant species selection by cattle at different stocking rates, feeding habits and site preferences of cattle. Based on the results, conclusions concerning the value of silvopastoral systems in the Alps were drawn. A field study on six different wood pasture areas, grazed by cattle at different stocking rates, was accompanied by an experiment on three adjoining areas of 0.51 ha each, stocked with either three, six, or nine heifers. Plant species were recorded in plots of 20 cm × 20 cm before and after grazing, and the intensity of grazing on each species was assessed. At low stocking rates, grasses and tall species were most intensely grazed, while at higher stocking rates the intake of forbs and small species increased. Since no relationship was found between nutritional value and species preference, other factors such as accessibility of a plant seem to be important for the feeding preferences of cattle. The preference for grasses at low and medium stocking rates suggests that an increased growth of forbs might lead to an increase in plant species diversity.     

Wood density as a proxy of drought-induced forest dieback in silver fir

Drought-induced dieback is a matter of global concern. It has been widely reported and could compromise the climate warming mitigation potential of forests. That is why we need reliable early-warning proxies to achieve better forecasts of forest dieback and tree death. Tree-ring data can provide some of these needed proxies. Here I propose considering minimum (MND) and maximum (MXD) wood density values as proxies of tree vulnerability against drought. This hypothesis is evaluated in silver fir (Abies alba) forests from the western Spanish Pyrenees showing ongoing dieback processes after the severe 1985 drought. MXD increased in response to warm summer conditions in 1985 whereas MND increased in response to growing-season water deficit in 1986. The average between prior MXD (MXD_t-1) and subsequent MND (MND_t) could be used to detect severe drought impacts and forecast dieback.     

珠穆朗玛峰国家自然保护区蕨类植物区系研究

在野外实地调查和室内标本整理以及查阅文献的基础上,对珠穆朗玛峰自然保护区蕨类植物区系进行研究,为探讨喜马拉雅植物区系的起源以及该区生物多样性的保护提供资料。结果表明:(1)珠穆朗玛峰自然保护区共有蕨类植物193种,隶属于31科59属,其中优势科为鳞毛蕨科(51种)、水龙骨科(41种)、蹄盖蕨科(22种)、铁角蕨科(10种),优势属为耳蕨属(27种)、鳞毛蕨属(20种)、瓦韦属(17种)。(2)科的分布区类型有8种,以泛热带分布型(55.56%)为主;属的分布区类型有14种,以泛热带分布型(23.81%)、中国-喜马拉雅分布型(19.05%)为主;蕨类植物以土生(55.88%)为主,石生(24.35%)和附生(21.76%)也占有一定比例,缺乏水生蕨类。(3)珠穆朗玛峰自然保护区蕨类植物区系成分与南迦巴瓦峰地区联系最为密切,其次为横断山地区和尼泊尔,与九塞沟自然保护区、秦岭地区有一定的联系,与西双版纳地区的关系较为疏远。     

中国天然林资源保护工程综合评价指标体系与评估方法

天然林资源是国家重要的战略资源与生态资源,在维护国土生态安全、应对气候变化、保护生物多样性等方面发挥着不可替代的重要作用。作为覆盖范围最广、投资规模最大的天然林资源保护工程（简称天保工程）自2000年正式启动以来,对长江上游、黄河上中游地区以及东北、内蒙古、新疆、海南等重点国有林区的森林资源保护修复、区域生态环境改善及经济社会可持续发展等多方面都产生了巨大、深远影响。天保工程二期于2020年结束,全面定量评估天保工程的生态、经济和社会综合效益和国内外的巨大影响,可为全面推进我国天然林资源保护修复提供科技支撑,为后续政策修订提供决策依据。本文基于空间信息技术、样地调查、生态站观测、比较分析等手段,构建了适用于天保工程的综合评价指标体系与评估方法,涵盖森林资源、生态效益、社会经济效益、生态修复措施和政策设计5个方面,对全面贯彻落实国家生态文明战略和《天然林保护修复制度方案》具有重要的现实意义和深远历史意义,为开展全国性的重大生态工程评估提供借鉴和参考。     

40年岷山地区白河自然保护区川金丝猴的生境格局动态

好的生境质量是野生动物生存和繁衍的必备条件,生境质量的变化将对动物的生存产生深远影响,定量客观的评估生境变迁过程显得尤为必要。川金丝猴作为我国一级保护动物,评定其生境质量变化过程有利于制定有效的保护措施。3S技术的不断发展与广泛应用为研究川金丝猴生境格局的动态变化提供了有利的工具。以岷山白河自然保护区为例,利用陆地资源卫星的MSS/TM/OLI遥感影像,并基于专家知识的决策树分类方法对遥感影像进行分类,获取了5个时期的覆被类型空间分布图;根据NDVI与郁闭度的相关性获取了研究区郁闭度的时空变化信息。然后,通过对野外观测数据的数理统计与空间分析,获取了川金丝猴的生活习性特征,并结合AHP方法构建了川金丝猴生境质量的评价体系,对5个时期的生境质量进行了评价,最后定量分析了40年来川金丝猴的生境格局的动态变化趋势。研究表明,近40年来白河自然保护区内及周边的生境经历了由良好到不断恶化,再到逐渐恢复的过程,其中最适宜和适宜生境呈现先降低后逐渐升高的趋势,而不适宜和勉强适宜则表现为先增加后减小的趋势。1975—1982年时段内,各生境等级变化剧烈,尤以最适宜和不适宜等级变化显著,生境质量整体呈恶化趋势;1982—1994年,各生境等级变化剧烈程度较前一时期有所缓和,生境质量得到较大改善,呈良性发展趋势;1994—2003年时段内,研究区内生境质量进一步改善,环境恶化状况得到了缓解;2003—2014年时间段内整体质量改善的速度明显减缓,生境质量达到平衡状态。除1975—2014时段外,前4个时段的各综合变化指标呈现递减趋势,前期生境等级变化剧烈,后期趋缓。气候变化和人为干扰为导致生境变化的主要因素,其中20世纪80年代生境变化与气候变化关系密切,而20世纪90年代之后人为干扰因素明显增加。研究有助于理解气候变化与人为干扰背景下,川金丝猴生境格局时空变化特征,为野生濒危动物生境保护管理和政策制定提供科学依据。     

森林生态系统的水源涵养功能及其计量方法

为全面认识与正确评价森林生态系统的水源涵养功能,本文探讨了其概念、表现形式及其计量方法,认为：1）森林的水源涵养功能是一个动态、综合的概念,随着人们对森林水文作用认识的不断深入,其内涵不断丰富扩大,因此森林的水源涵养功能概念存在狭义和广义之分;2）森林的水源涵养功能（广义）有多种表现形式,包括拦蓄降水、调节径流、影响降雨和净化水质等,不过其具体表现形式与研究对象、研究目的以及研究尺度有关;3）目前森林拦蓄降水功能的计量方法主要有土壤蓄水能力法、水量平衡法、年径流量法和多因子回归法等8种,不过这些方法都存在一定的局限性,实际应用中需要综合考虑。     

Ecology of seed germination of eight non-pioneer tree species from a tropical seasonal rain forest in southwest China

We compared various aspects of the seed biology of eight non-pioneer tree species from a tropical seasonal rain forest in Xishuangbanna, SW China, that differ in time of dispersal, size and fresh seed moisture content (MC). Seeds were tested for germination under laboratory conditions after dehydration to different moisture levels and under 3.5, 10 and 30% solar irradiances in neutral-shade houses. For six species, germination was also compared in forest understory (3.5% light) and center of a forest gap (32.5% light). Under continuous dehydration over activated silica gel, 100% of seeds of four species had lost the ability to germinate after 48 h, and those of all species except Castanopsis hystrix (decreased from >90 to 30% germination) had lost the ability to germinate after 120 h. Four species did not differ in final germination percentages at the three irradiances (i.e. uniform germination). However, final germination percentages of Horsfieldia pandurifolia and Litsea pierrei var. szemaois were significantly lower in 30% than in 10 or 3.5% light, and seeds of Antiaris toxicaria and C. hystrix germinated to higher percentages in 30 and 10% than in 3.5% light. Mean time to germination (MTG) of the eight species (forest and shade house data combined) ranged from 5–5 days for Pometia tomentosa to 72–207days for L. pierrei; MTG for four species was ≤21 days. There was no obvious relationship between relative desiccation resistance and either time of dispersal, MTG or uniformity of germination at the three light levels, or between seed size and MC or MTG. However, the relationship between seed MC at maturity (25–60% fresh mass basis) and MC at 50% loss of seed viability (12.4–42.5%) was significant. Seven of the species fit Garwood’s (Ecol Monogr 53:159–181, 1983) rapid-rainy germination syndrome and one, L. pierrei, either her delayed-rainy or intermediate-dry germination syndrome. However, fresh, non-dehydrated seeds of all eight species germinated in ≤30 days at constant 30°C in light.     

达赉湖自然保护区疣鼻天鹅繁殖行为初步观察

2006年8～11月和2007年4～8月,在内蒙古达赉湖国家级自然保护区对疣鼻天鹅(Cygnus olor)的繁殖数量、繁殖行为及迁飞时间进行研究.结果显示,疣鼻天鹅通常4月初迁来,10月底迁离,居留期长达196 d左右(n=3).4月下旬开始求偶,时间一般为上午进行,没有固定求偶地点,每次求偶所需时间平均172 s(n=8).主要依靠炫耀行为来保卫和标记领域.2006与2007年的繁殖种群数量均为12只(6对),2006年育成幼鸟数分别为4、2、4、3、6、3只;2007年仅有3对繁殖成功,幼鸟数分别为4、4、5只.     

Evaluation of CuO oxidation parameters for determining the source and stage of lignin degradation in soil

The composition of phenols and other aromatic compounds in organic and mineral soil horizons and their respective source vegetation from different climatic zones of the Canadian Prairies were analyzed using CuO oxidation and gas chromatography-mass spectrometry (GC-MS) to investigate the stage of lignin degradation. Parameters based on the CuO oxidation products were calculated for the soils and corresponding vegetation to determine the lignin sources and to monitor the lignin degradation. In addition to the widely used lignin monomer parameters, parameters resulting from lignin-derived phenolic dimers are used for the first time to assess lignin degradation in soils. The composition of lignin-derived phenols (S/V, C/V) in soil closely matches the composition observed in their respective source plants (grass, Aspen, Pine) reflecting the preservation of characteristic lignin patterns in soils. Degradation parameters based on lignin phenols and benzenes derived from tannins or other phenolic biomolecules indicate a progressive degradation from the vegetation to the soil horizons. In addition to commonly used lignin monomer indicators, parameters based on the lignin dimers are applied. Lignin degradation is found to be lowest in the Pine forest, intermediate in the grassland soils and highest in the Aspen-grassland transition soil. Degradation parameters based on non-lignin aromatic derivatives (3,5-dihydroxybenzoic acid, benzenepolycarboxylic acids) demonstrate a similar trend. The lignin from samples in the cooler climate (Black Chernozems) is observed to be more oxidized than in the soils from the warmer climate (Brown Chernozems) suggesting that abiotic processes may be in involved in the alteration of lignin and other phenolic biomolecules in soils. The results indicate that the comparative analysis of CuO oxidation products of soils and source vegetation is a valuable tool to assess the sources and degradation of lignin in soils.     

不同稀有种处理对双向指示种分析分类结果影响的比较

为探讨不同稀有种处理对TWINSPAN分类结果的影响,以北京小龙门林场华北落叶松林调查数据为例,采用2×2列联表比较了剔除频度＜5%、盖度＜5%的稀有种前后TWINSPAN分类结果的异同,同时结合引入的DBI重点对比了最佳分类等级的吻合性。结果表明：(1)在相同的分类终止原则下,剔除稀有种前后的最大分类结果分别分为12、11个群落类型;(2)基于结合系数r,剔除稀有种前后TWINSPAN在低分类等级的结果差异较大,随着分类等级的增加,二者的吻合度增大,表明稀有种对低分类等级的结果影响较为明显;(3)引入的DBI适用于确定TWINSPAN分类的最佳分类等级,尽管剔除稀有种前后的最佳分类等级不同,但分类结果的吻合度较高。因此,在TWINSPAN分类应用中,建议引入DBI指数辅助确定最佳分类等级,同时取低分类等级结果时必须做删除稀有种处理。