蒙古栎林生态系统的水分循环与养分循环关系

本文从群体水平上研究了蒙古栎林生态系统中的水分循环与养分循环的关系。结果表明,降雨是系统养分的重要输入。降雨对林冠的淋洗淋溶作用有助于养分的归还及缩短养分循环的途径。蒙古栎树干茎流量大,且其中含有的养分元素较多,从而使蒙古栎的根系能获得更多的水分与养分,有助于适应干旱、瘠薄的立地环境。径流是系统的水分输出,也是养分输出。蒙古栎林的下渗流约占整个径流的90％,且养分元素含量较低,从而有助于养分的积累。降雨在蒙古栎林内的分配格局不一,导致系统养分积累的明显差异。本文还探讨了干扰对养分循环与水分循环的影响。结果表明,采伐森林导致水分分配的变化,也使系统的养分发生亏损。只有把养分循环与水分循环结合起来,才能较完整地评价森林的生态功能。     

森林生态系统的水文调节功能及生态学机制研究进展

森林水文调节功能是森林所实现的重要服务功能之一,可是由于森林资源被无节制的开采利用,导致人们不断遭受森林破环所带来的洪旱灾害。因此关于森林生态水文功能研究已成为生态学和水文学的研究重点之一。近年来,国内外对森林水文调节过程及其生态学机制进行了广泛深入的研究,所以文章从森林的水文过程出发,对林冠截留、树干流、凋落物层截留、林地水分涵养和蒸发蒸腾及其影响因子的国内外研究现状进行了归纳分析,研究认为林地各冠层均能够截留降雨,降低雨水动能,从而减少地表径流的产生和对地表的冲击;凋落物层能蓄留水分、抑制蒸散、减缓地表径流;而树干流改变降雨水平空间格局,影响水分入渗以及土壤水源涵养。森林结构复杂,明显改变了降雨分配过程,而森林水文过程及调节功能又受到森林结构的制约,因此定量定性探讨森林生态系统的结构、过程与水文调节功能之间关系,是未来森林生态水文功能研究的重点。     

气温变化对西南山区流域森林水文效应影响的模拟

为了揭示气温变化对西南山区流域森林水文效应的影响,用生物物理/动态植被模型SSiB4/TRIFFID与流域地形指数水文模型TOPMODEL的耦合模型SSiB4T/TRIFFID模拟了西南山区长江上游梭磨河流域森林水文效应对气温变化的响应,分析了气温变化对植被不同演替阶段的流域总径流和总蒸发以及冠层截流蒸发、植被蒸腾和土壤蒸发的影响。结果表明,（1）梭磨河流域森林（常绿针叶林）蒸腾与草和灌木差异小,森林蒸腾潜热比草和灌木仅高1~4 W.m-2,森林冠层截留蒸发高于草和灌木,但土壤蒸发明显低于草和灌木覆盖,森林覆盖流域总蒸发低于草和灌木覆盖甚至低于裸土蒸发,因此增加了流域总径流量,但森林增加径流的作用随土壤蒸发的减小而减小。（2）气温减小1℃将通过减小森林冠层截留蒸发和蒸腾而使森林增加流域总径流量的作用增加;相反,气温增加将增加森林冠层截留蒸发和蒸腾而使森林增加总径流量的作用减小。（3）当温度增加4℃,由于森林总蒸发较草和灌木明显增加,对于较高的土壤蒸发,森林增加总径流量的作用已不明显;对于较低的土壤蒸发,森林减小了流域总径流量。     

基于SSiB4T/TRIFFID模拟的森林植被与流域径流量关系研究

为了揭示森林植被与流域径流量关系的空间分异规律,用生物物理/动态植被模式SSiB4/TRIFFID与流域水文模型TOPMODEL的耦合模式SSiB4T/TRIFFID进行青弋江流域和西南亚高山区的梭磨河流域各种气候情景的植被演替和碳水循环模拟。根据模拟结果并结合森林集水区试验结果,分析森林植被对流域径流量的影响。模拟结果表明,不存在水分胁迫时,在草地、灌木和森林3种植被类型中,森林蒸腾、冠层截留蒸发、蒸散和叶面积指数对温度变化最敏感;存在水分胁迫时,森林蒸腾、冠层截留蒸发、蒸散和叶面积指数对降水的变化最敏感。控制试验结果表明,青弋江流域阔叶林在植被向平衡态演替过程中取得支配地位,森林、灌木和草地蒸散分别为742.2、588.6和546.2 mm·a~(-1),森林蒸散明显大于灌木和草地,森林减小了径流量。梭磨河流域针叶林在植被向平衡态演替过程中取得支配地位,森林、苔原灌木和草地蒸散分别为387.8、444.3和387.5 mm·a~(-1),森林蒸散低于苔原灌木,森林增加了径流量。但随着温度增加,由于森林蒸散增加幅度明显大于苔原灌木和C3草地,森林蒸散逐渐大于苔原灌木,森林从增加径流量转变为减小径流量。对于湿润地区,随着温度增加,森林从增加径流量转变为对径流量没有明显影响和减小径流量。对于半湿润和半干旱地区,随着降水的减小,森林蒸散减小幅度明显大于灌木和草地,森林对径流量的影响随着降水量的减小而减小。气候的垂直地带性和水平地带性分布对森林植被与流域径流量关系的空间变化起着重要的控制作用。     

氮沉降对森林土壤碳收支机制的影响

森林土壤储存着全球陆地生态系统大约45%的碳,在维持全球碳平衡方面具有重要的作用。不断加剧的全球氮沉降对森林生态系统碳循环和碳吸存产生了深刻的影响,进而改变了森林生态系统的生产力和生物量积累。本文以欧洲和北美温带地区开展的有关氮沉降对森林生态系统影响的研究为基础,提炼出最可能决定加氮影响碳输入、输出效应方向和大小的因素：凋落物分解、细根周转、外生菌根真菌、土壤呼吸及可溶性有机碳淋失,并探讨了森林生态系统碳动态对氮沉降响应的不确定性。陆地生态系统碳氮循环密切相关,由于氮循环的复杂性,尽管以往碳循环研究都考虑了氮对碳循环的限制作用,但在碳氮循环耦合机理方面的研究还比较少见。在未来研究中,应通过探寻森林土壤碳氮相互作用特征,及土壤微生物、土壤酶等与土壤碳氮过程的互动机制,来增进氮沉降对森林碳储量和碳通量的理解。     

干扰对森林凋落物分解影响的研究现状及展望

凋落物分解是森林生态系统物质循环和能量流动的核心环节。干扰能够影响凋落物分解速率和养分循环,进而改变森林生态系统的结构、功能及过程。文章通过整理干扰对森林凋落物分解影响的研究成果,从凋落物质与量、微环境及分解者类群等方面阐述了干扰对森林凋落物分解的影响机制,并分析现有研究的不足,为未来合理经营森林,增加适度干扰提供一定的理论依据。现有的研究表明,间伐等干扰会显著减少森林凋落物产量,改变凋落物化学特性并促进凋落物分解;干扰对凋落物分解环境的影响主要表现于对温湿度的调节,间伐能增加林内贯穿雨量,从而对湿度有显著提升作用;干扰对土壤动物的短期负面影响较为显著,而对微生物种类和数量则显著提高,从而有效地促进凋落物的分解,这主要归因于干扰改变了微环境与凋落物底物的质量;干扰通过改变土壤条件进而影响相关微生物分解酶的活性,酶活性越高,分解越迅速。干扰对林分结构、分解环境等影响因素的改变与凋落物分解之间的关系错综复杂,其中的机制与机理仍有待明晰;不同方式及程度干扰对森林恢复过程中凋落物分解模式的研究尚有待加深;建立干扰梯度以研究森林地上部分对地下部分的调控及反馈应受到重视;如何进行合理的森林经营以促进凋落物分解也需进一步研究。     

不同理论方程模拟华南桉树人工林蒸散量的比较

森林生态系统蒸散作为生态系统中的重要生态过程,联系着生态系统的水分平衡和能量平衡,并与养分循环密切相关.以雷州半岛桉树人工林纪家、河头林场为研究样地,在样地调查的基础上,对林地有关气象因子、土壤水文生态因子作了近4 a的定位观测.选取TURC公式、Penman-Monteith方程(PM)和周国逸公式作为代表,三者分别以温度为指标、以辐射与能量转换为驱动因子和以物理过程为主导的蒸散量理论计算方法.并将理论计算结果同水量平衡法估算结果进行比较.结果表明,尽管各种计算方法的结果均存在一定的波动性,但是其波动的原因是不一样的.对于PM方程而言,结果对所选参数有一定的依赖性.对于周国逸公式来说,在计算较小时间尺度(≤1 a)蒸散量时可能会出现一定的波动,波动的原因可能在于参数的时间尺度匹配问题.对于TURC公式,计算结果波动的根本原因在于其公式的经验局限性.理论计算值同水量平衡估算结果比较说明,三者均可以在一定程度上反映系统的年蒸散量.比较而言,周国逸公式计算结果的波动性范围较小,较适用于热带、亚热带森林生态系统蒸散量的计算.     

荒漠草原典型植物群落枯落物生态水文功能

在退化荒漠草原生态系统恢复过程中,枯落物是联系植被和土壤物质循环与能量流动的重要中间环节,且发挥着重要的生态水文功能。通过调查荒漠草原5种典型植物群落（蒙古冰草群落、甘草群落、赖草群落、杂类草群落和沙蒿群落）枯落物蓄积量、持水性能、对降雨的截留和对土壤水分蒸发的抑制作用,分析了荒漠草原不同植被类型枯落物的生态水文功能。结果表明：枯落物蓄积量和最大持水量均为蒙古冰草群落〉甘草群落〉赖草群落〉杂类草群落〉沙蒿群落;5种群落枯落物层对降雨的截留量在3.36～5.27 mm,截留率在3.40%～6.82%,枯落物对降雨的截留量与降雨量呈正相关,而降雨量与截留率呈负相关,且枯落物对降雨的截留具有显著的季节变化规律。在不同枯落物覆盖下,枯落物对土壤的抑制效应也存在显著差异,0.5~2 cm覆盖厚度比不盖枯落物土壤水分蒸发减少了19.25%～76.82%,枯落物层减少土壤水分蒸发效应随枯落物层厚度增大而增加。枯落物的蓄积与覆盖对土壤水分的运移和蓄存产生明显的生物学作用,已经成为荒漠草原最重要的生态过程之一。     

基于实测站点的区域森林水源涵养量空间化方法综述

在全球气候变暖、人口增加和淡水资源紧张等多重压力下,水资源存储和保护至关重要,森林水源涵养是对降雨的截留、存储和调控,是调节气候、存储水资源的重要过程。已有的大尺度水源涵养量研究多是基于水文或遥感模型估算,缺乏基于站点实测数据的大尺度区域水源涵养量空间化方法的系统研究。该研究提出了基于实测站点的大尺度区域森林水源涵养量空间化框架,总结了林冠层、枯落物层、土壤层和森林水源涵养量的影响因子及其影响方式;在此基础上,综述了结合影响因子的站点空间化方法,总结了森林水源涵养量空间化存在的问题;最后,指出了站点空间化过程中辅助变量选择、分区分模型空间化、森林水源涵养量动态变化等方面的未来研究方向。     

估算区域蒸发的能量法研究

本文介绍了有关估算区域尺度蒸发的模型研究.通过对我国分别为1878(?),318161,866559km~2的三个区域蒸发的估算,验证了Budyko能量模型的适用性.用该模型分别计算的三个区域蒸发结果与相应区域实测结果比较表明,Budyko的能量模型可以应用于我国不同气候条件和较大尺度区域蒸发的估算.本文对数据处理和区域选择也进行了研究.     

杉木观光木混交林群落的能量生态

对杉木观光木混交林群落能量的研究结果表明：混交林中观光木地上部分灰分含量以皮最高,而杉则以叶最高,两者GCV（干重热值）和AFCV（去灰分热值）均以叶为最高;观光木、杉木地下各部分的灰分含量均随径级的减小而增加,GCV均以粗根最高,细根最低;观光木的平均灰分含量高于杉木,但GCV和AFCV均低于杉木;从乔木层、灌木层到草本层,灰分含量依次增加,GCV和AFCV则依次降低,混交林群落的能量现存量公占群落的很小一部分,而其能量年净增量、归还量和净固定量却占有一定比重,混交林群落的太阳能转化率为1.57%,而纯林为1.44%,表明杉观混交林是一种能量生产力较高和维持地力能力较强的杉阔混交类型。同时,混交林的能量累积比大于纯林,能量流动速率则低于纯林;乔木层的能量累积比高于林下植被,能量流动速率则低于林下植被,从能量的角度看,构建合理的群落结构必须选择高能量累积比的乔木层树种,同时须促进能量流动速率快的林下植被的发育以维持和提高地力。     

Self-organization of tropical seasonal rain forest in southwest China

How to measure development of ecosystems is both a theoretical and practical question in ecology. Species richness and biomass accumulation are familiar figures of merit, but they cannot be instant watched. Self-organization is a tacit character. However, methods to measure the degree of self-organization of ecosystem are problematic. To this end Lin et al. (2009) have devised indicators of energy capture and dissipation so that self-organization defined via maximum energy dissipation can be quantified easily. Here the method is used to analyze long-term data (2004-2006) of a tropical seasonal rain forest included in the ChinaFLUX program. Three years of average self-organization values were clearly separated by seasonal variation. Reflection and long wave radiation are the main two pathways of energy loss. For tropical seasonal rain forest studied, long wave radiation contributed most to energy loss, and was negatively correlated with energy capture ability (Rn/DR). The nocturnal difference between canopy and air temperatures had a strong negative correlation with the long wave radiation loss ratio. However, the long wave radiation loss ratio was slightly lower than the reflection loss ratio in rainy season, when values were very low. Precipitation and wind had significant impact on energy dissipation ability in the hot dry season, but the correlation coefficients between precipitation and wind with thermal response numbers (TRNs) were very low. The results indicated that the self-organization estimation system based on “maximum energy dissipation theory” is applicable for tropical forest.     

珠江口红树林硫的累积和循环研究

主要研究了珠江口红树林硫的累积和循环特点，并探讨其对土壤中硫累积的影响．结果表明，珠江口五个红树群落硫的贮存量平均为１７０．４２ｋｇ／ｈｍ２；在群落硫元素的生物循环中，年存留量平均为１７．６０１ｋｇ／ｈｍ２，年归还量平均为３５．６０３ｋｇ／ｈｍ２，年吸收量平均为５３．２０４ｋｇ／ｈｍ２，周转期为３－８ａ，富集率均大于１．选定浅海沉积物的平均含硫量作为林下土壤成土母质的本底含硫量，估算红树植物生长后土壤含硫量的变化，并与群落硫的年归还量作比较．红树林对其林下土壤硫的累积作用有两方面，一是对海水硫的生物选择吸收与归还，二是为海水中的ＳＯ４（２－）为黄铁矿提供有机还原剂和嫌气微生物的能源，尤以后者的作用更重要．     

Suspended particulates in the Irish Sea and feeding conditions for fish larvae

The size distributions (2 to 160 m equivalent spherical diameter) of suspended particulate material sampled on two cruises along a transect in the Irish Sea in 1988 are described in relation to hydrographic conditions, chlorophylla concentration and carbon to nitrogen ratios. Particulates were more abundant and larger size modes in the distribution were more evident, in the upper mixed layer of stratified water than in areas where the water column was fully mixed. The detrital content was estimated at 52% of total particulate matter above the thermocline in stratified regions and at around 97% at mixed water sites. In stratified regions the predominance of larger sized phytoplankton and lower levels of detritus is argued to support a more direct and efficient transfer of energy to fish larvae via larger sizes of copepods. Conversely, in mixed areas of high detrital loading the smaller size spectrum of particulates incorporates a less efficient transfer of energy through bacterial cycling and smaller copepods.     

东北过伐林灌木层物种多样性与林分因子的典型相关分析

研究林分特征尤其是经营上可以控制的因子对生物多样性的影响，将有助于制定合理的经营措施来维持和保护生物多样性，本文作者以我国东北过伐林区3种典型天然林类型为对象，采用典型相关分析方法，研究影响灌木层物种多样性的主要因子。结果表明：影响灌木层物种多样性的主要因子包括土壤含水率，树种多样性和林分密度；灌木层多样性组的变异被林分组第一典型变量解释的比例为68.32%,仍有31.68%的变异不能得到解释。     

Nutrients in soil solution following selective logging of a humid tropical ‘terra firme’ forest north of Manaus,Brazil

Sustainable use of the Amazon forest for timber production is conditioned by the effect of logging on the system's nutrient cycling. This paper reports the results of a soil moisture and soil water chemistry monitoring campaign before and immediately after a selective logging which removed 35 m³ wood/ha. Soil moisture was measured using tensiometers, and soil water chemistry using suction samplers in five disturbance classes: tractor tracks, clearing centres, clearing edges, forest edges and untouched forest. The results show that the soil under the tractor tracks and clearings contained more moisture than under the untouched forest. The suction samplers extracted substantially more nitrate, ammonium, calcium, magnesium and potassium from the clearing centres, the tractor tracks and the clearing edges than from the forest sites. The results are explained in terms of altered microbial activity, changes in crown interception and uptake by roots.     

Forest Edges as Nutrient and Pollutant Concentrators: Potential Synergisms between Fragmentation, Forest Canopies, and the Atmosphere

Abstract: Forest fragmentation leads to a dramatic increase in forest edge, and these edges may function as traps and concentrators for wind-borne nutrients and pollutants. We assessed the influence of forest edges on atmospheric deposition and subsequent inputs to the forest floor in deciduous-forest fragments in the eastern United States. To quantify these inputs, we collected throughfall—water that has passed through the forest canopy—from edge and interior zones of forests adjacent to open fields. During the 1995 growing season, atmospheric input (wet and dry deposition) of sulfur to forest edge zones was elevated compared with input to forest interiors. Throughfall fluxes of dissolved inorganic nitrogen and calcium were also greater at edges than interiors. The mean edge increases ranged from 17% to 56% for the nutrients and pollutants we measured. When we manipulated the structure of forest edges by removing all vegetation below half the canopy height, throughfall flux in the edge zone declined sharply and was less than that of the respective interior zone. Changing the vegetation structure of the edge also shifted the zone of highest throughfall flux farther into the interior of the forest. Our data suggest that forest edges can function both as significant traps for airborne nutrients and pollutants from adjoining agricultural or urban landscapes and effective concentrators of below-canopy chemical fluxes. These enhanced fluxes may have cascading effects on soil-nutrient cycling, microbial activity, seedling dominance, and other ecological processes near forest edges.     

Biological weighting of ultraviolet (280–400 nm) induced mortality in marine zooplankton and fish. I. Atlantic cod (Gadus morhua) eggs

In the Gulf of St. Lawrence, Canada, productivity-determining biophysical interactions occur in the upper 0 to 30 m of the water column. The eggs and larvae of several commercially important marine invertebrates and fishes (e.g. Gadus morhua L.) are found in this layer. Measurements of the diffuse attenuation coefficients for ultraviolet-B radiation (280 to 320 nm, UV-B) at various locations in this geographic region indicated maximum 10% depths (the depth to which 10% of the surface energy penetrates at a given wavelength) of 3 to 4 m at a wavelength of 310 nm. This represents a significant percentage of the summer mixed-layer water column: organisms residing in this layer are exposed to UV-B radiation. Laboratory experiments using a Xenon-arc-lamp based solar simulator revealed that cod embryos exposed to UV-B exhibited high wavelength-dependent mortality. The strongest effects occurred under exposures to wavelengths below 312 nm. This susceptibility was also dependent upon developmental stage; mortality was particularly high during gastrulation. At the shorter wavelengths (<305 nm) UV-B-induced mortality was strongly dose-dependent, and not significantly influenced by dose-rate. The biological weighting function (BWF) derived for UV-B-induced mortality in cod eggs is similar to that reported for naked DNA – suggesting that the mortality is a direct result of DNA damage. There was no evidence of a detrimental effect of ultraviolet-A radiation (320 to 400 nm). Calculations based upon the BWF indicate that, under current noon surface irradiance, 50% of cod eggs located at or very near (within 10 cm) the ocean surface will be dead after 42 h of exposure. Under solar spectral irradiance simulating a 20% decrease in ozone layer thickness, this time drops to 32 h. These are first-order estimates based upon surface irradiance taken at a time of day during which the values would be maximal. Nonetheless, they illustrate the relative changes in UV-B impacts that will result from ozone layer depletions expected over the coming decades. It is also important to point out that variability in cloud cover, water quality, and vertical distribution and displacement of cod eggs and larvae within the mixed layer, can all have a greater effect on the flux of UV-B radiation to which fish eggs are exposed than will ozone layer depletion at these latitudes. Received: 2 March 1998 / Accepted: 18 December 1998