大兴安岭北部森林景观对气候变化的响应

将森林景观模型LANDIS和林窗模型LINKAGES相结合,模拟气候变化对大兴安岭森林景观的影响,并比较分析了气候变化对森林景观的直接影响与通过火干扰改变所产生的影响.结果表明:维持当前气候和火干扰情景的条件下,森林景观保持动态平衡,兴安落叶松占据优势树种地位,未来气候情景下,兴安落叶松和偃松的分布面积降低,白桦、山杨、甜杨和钻天柳等阔叶树以及樟子松的分布面积增加,森林景观的破碎化和多样性增加;气候变化对森林景观的影响具有时滞性和长期性,气候变暖有利于大部分树种(兴安落叶松除外)的生长,火干扰增加使山杨、甜杨和钻天柳等分布面积增加,使兴安落叶松、樟子松和偃松的分布面积明显降低;火干扰增加对森林景观的影响几乎与气候变化的直接影响同等重要,其加剧了气候变化对森林组成、森林景观破碎化和森林景观多样性的直接影响.     

气候变化和林火干扰对大兴安岭林区地上生物量影响的动态模拟

预测森林地上生物量对气候变化和林火干扰的响应是陆地生态系统碳循环研究的重要内容,气温、降水等因素的改变和气候变暖导致林火干扰强度的变化将会影响森林生态系统的碳库动态.东北森林作为我国森林的重要组成部分,对气候变化和林火干扰的响应逐渐显现.本文运用LANDIS PRO模型,模拟气候变化对大兴安岭森林地上生物量的影响,并比较分析了气候变暖对森林地上生物量的直接影响与通过林火干扰强度改变所产生的影响.结果表明: 未来气候变暖和火干扰增强情景下,森林地上生物量增加;当前气候条件和火干扰下,研究区森林地上生物量为(97.14±5.78) t·hm^-2;在B1F2预案下,森林地上生物量均值为(97.93±5.83) t·hm^-2;在A2F3预案下,景观水平第100～150和150～200年模拟时期内的森林地上生物量均值较高,分别为(100.02±3.76)和(110.56±4.08) t·hm^-2.与当前火干扰相比,CF2预案(当前火干扰增加30%)在一定时期使景观水平地上生物量增加(0.56±1.45) t·hm^-2,CF3预案(当前火干扰增加230%)在整个模拟阶段使地上生物量减少(7.39±1.79) t·hm^-2.针叶、阔叶树种对气候变暖的响应存在差异,兴安落叶松和白桦生物量随气候变暖表现为降低趋势,而樟子松、云杉和山杨的地上生物量则随气候变暖表现出不同程度的增加;气候变暖对针阔树种的直接影响具有时滞性,针叶树种响应时间比阔叶树种迟25～50年.研究区森林对高CO₂排放情景下气候变暖和高强度火干扰的共同作用较为敏感,未来将明显改变研究区森林生态系统的树种组成和结构.     

空间异质性对样地数据空间外推的影响

应用模型结合的方法模拟了3个空间异质性等级预案下反应变量(气候变化下景观水平的树种分布面积)的变化情况,并分析模拟结果在预案之间的差异性,探讨了环境空间异质性对样地观测到的树种对气候变化响应向更大空间尺度外推的影响.结果表明：空间异质性在一般情况下对样地数据向土地类型尺度外推没有影响,而对样地尺度外推到海拔带尺度的影响则有较复杂的情况.对于对气候变化不敏感的树种以及非地带性树种,空间异质性对样地数据向海拔带尺度外推没有影响;对于大多数对气候变化敏感的地带性树种而言,空间异质性对样地数据向海拔带尺度外推则有影响.     

大兴安岭呼中林区虫害与火干扰交互作用的长期模拟

虫害和林火是森林生态系统的两种主要干扰类型,各种干扰在大时空尺度上存在一定的交互作用.本文采用空间直观景观模型LANDIS模拟虫害和林火在300年内的交互作用.结果表明:虫害干扰降低了细可燃物载量,提高了模拟前期(0～100 a)和中期(100～200 a)的粗可燃物载量,降低了模拟前期和中期的林火频率,不同干扰预案模拟后期(200～300 a)火烧频率的结果比较接近;虫害干扰降低了模拟前期和后期的火烧强度,增加了模拟中期的火烧强度,提高了模拟中期的森林火险等级,降低了模拟前期和后期的火险等级.人类灭火可增加虫害的发生面积,因此建议森林管理部门采取适当的防虫措施,不可只注重灭火,可以采取可燃物去除和计划火烧等方式管理林火,促进森林生态系统的可持续发展.     

水曲柳幼苗根系对土壤养分和水分空间异质性的反应

通过沙培试验方法,研究了温室条件下水曲柳幼苗在施肥和浇水区,非施肥和非浇水区中根系生长,生物量分布,地下部分与地上部分关系,细根直径等特征。结果表明,土壤养分和水分的空间异质性对水曲柳幼苗根系生长和分布有明显影响。在施肥区和浇水区根系生长快,密度大,生物量高,而在非施肥和非浇水区根系生长受到抑制,根系密度小,生物量低,与非施肥区相比,施肥区细根直径下降,有利于根系对养分和水分的运输,但是在非浇水区     

施氮量对小麦叶片硝酸还原酶活性、一氧化氮含量和气体交换的影响

研究了不同施氮量对冬小麦分蘖到抽穗期叶片硝酸还原酶(NR)活性、一氧化氮(NO)含量、气体交换参数和籽粒产量的影响.结果表明:叶片光合速率（P_n）、蒸腾速率（T_r）、瞬时水分利用效率（IWUE）和产量均随施氮量的增加呈先升高后降低的趋势,在180 kg·hm^-2氮处理时达到最高.随施氮量的增加,叶片NR活性提高; 在分蘖期和拔节期,叶片NR活性与NO含量呈显著线性相关（R²≥0.68,n=15）,NO含量和气孔导度（G_s）呈显著正二次相关（R²≥0.43,n=15）;低氮处理下,NR活性较低使叶片NO含量维持在较低水平,促进气孔开放,高氮处理下,NR活性较高使叶片NO含量增加,诱导气孔关闭;在抽穗期叶片NR活性和NO含量无显著相关关系,虽然NO含量和G_s也呈显著正二次相关（R²≥0.36,n=15）,但不能通过施氮提高NR活性来影响叶片NO含量,进而调节叶片气孔行为.合理施氮使小麦叶片NO含量维持在较低水平,可提高叶片G_s、T_r和IWUE,增强作物抗旱能力,促进光合作用,提高小麦产量.     

景观空间异质性对生态系统服务形成与供给的影响

景观空间异质性与生态系统服务的关系极为密切,适当调整景观空间异质性有助于生态系统服务的持续形成与稳定供给。研究景观空间异质性和生态系统服务形成与供给之间的相互影响作用及响应机制具有重要的理论与现实意义,是保护生物多样性、管理生态系统服务与优化景观空间配置的基础。现有研究大多在不同尺度上探讨了景观格局与生态过程或生态系统服务间的相互影响关系,而缺乏景观格局-生态过程-生态系统服务三者间有效联结等方面的研究。景观空间异质性是怎样直接或间接地作用于生态系统服务形成与供给的,目前还没有一个较为明确的解释。因此,通过分析国内外文献,回顾了景观格局或景观空间异质性与生态系统服务之间关系的研究进展、研究内容和研究方法;从景观组成、景观构型的变化入手,讨论了景观空间异质性对生态系统服务形成与供给的影响及其强度,并认为景观组成异质性变化能够直接影响生态系统服务,而景观构型异质性变化会通过改变生态过程而间接影响生态系统服务;阐述了景观空间异质性在影响生态系统服务形成与供给的同时,也使生态系统服务在空间上产生了异质性分布,并从自然因素和人为因素两个方面对其进行解释;强调了尺度问题在景观空间异质性与生态系统服务研究中的重要性;最后,明确了对生态系统服务形成与供给的景观空间异质性影响研究不仅有助于生态系统服务的维持与调节,也能更深层次地揭示其中的生态学意义。     

夜间增温对冬小麦根系生长和土壤养分有效性的影响

气候变暖存在明显的昼夜不对称性,夜间气温升高幅度显著高于白天.本研究采用夜间被动式增温系统,于2009-2010年在我国冬小麦主产区（石家庄、徐州、许昌和镇江）进行全生育期田间增温试验,研究了土壤pH值、速效养分和抽穗期冬小麦根系对夜间增温的响应.结果表明： 与不增温对照相比,夜间增温显著降低了土壤pH值和速效养分含量,并在一定程度上提高了根系干质量和根冠比.冬小麦整个生育期,夜间增温分别使石家庄、徐州、许昌和镇江试验点土壤pH值平均降低0.4%、0.4%、0.7%和0.9%,碱解氮含量平均降低8.1%、8.1%、7.1%和6.0%,速效磷含量平均降低15.7%、12.1%、19.6%和25.8%;速效钾含量平均降低11.5%、7.6%、7.6%和10.1%.增温处理下,石家庄、徐州和镇江试验点抽穗期冬小麦根系干质量分别平均增加31.5%、27.0%和14.5%;石家庄、许昌和镇江试验点抽穗期冬小麦根冠比分别平均提高23.8%、13.7%和9.7%.夜间增温可能通过改变土壤化学特性影响土壤养分供应和冬小麦生长     

夜间增温对冬小麦根系生长和土壤养分有效性的影响

气候变暖存在明显的昼夜不对称性,夜间气温升高幅度显著高于白天.本研究采用夜间被动式增温系统,于2009-2010年在我国冬小麦主产区（石家庄、徐州、许昌和镇江）进行全生育期田间增温试验,研究了土壤pH值、速效养分和抽穗期冬小麦根系对夜间增温的响应.结果表明： 与不增温对照相比,夜间增温显著降低了土壤pH值和速效养分含量,并在一定程度上提高了根系干质量和根冠比.冬小麦整个生育期,夜间增温分别使石家庄、徐州、许昌和镇江试验点土壤pH值平均降低0.4%、0.4%、0.7%和0.9%,碱解氮含量平均降低8.1%、8.1%、7.1%和6.0%,速效磷含量平均降低15.7%、12.1%、19.6%和25.8%;速效钾含量平均降低11.5%、7.6%、7.6%和10.1%.增温处理下,石家庄、徐州和镇江试验点抽穗期冬小麦根系干质量分别平均增加31.5%、27.0%和14.5%;石家庄、许昌和镇江试验点抽穗期冬小麦根冠比分别平均提高23.8%、13.7%和9.7%.夜间增温可能通过改变土壤化学特性影响土壤养分供应和冬小麦生长     

空间直观景观模型LANDIS在大兴安岭呼中林区的应用

应用空间直观景观模型(LANDIS),研究有采伐和无采伐预案下大兴安岭呼中林区的森林景观的长期变化。用APACK计算每一个物种及各年龄级的分布面积。为了研究物种分布格局的变化,计算了物种分布的聚集度指数。研究结果如下：(1)在无采伐预案下。火干扰模式为低频率大面积高强度火烧;在有采伐预下,火干扰模式为高频率小面积低强度火烧;(2)在无采伐预案下,火会造成各种群分布面积的强烈波动,但是对种群的年龄结构没有很大影响;在有采伐预案下,火对种群分布面积和年龄结构都没有很大的影响;(3)采伐能完全改变各种群的年龄结构。降低种群分布的聚集度,但是对各种群的分布面积并没有很大影响;(4)在有采伐预案下,各种群为增长型种群,增长量通过采伐取走,群落处于演替的干扰顶极状态;在无采伐预案下,各种群为稳定型种群(樟子松和偃松除外),大面积高强度火烧使群落产生较大的波动。结果表明,在呼中林业局,在没有人为干扰情况下,火干扰是森林景观变化的主导因素。自从有了人为干扰,采伐开始逐渐取代火干扰成为影响森林景观变化的主导因素。空间直观景观模型的一个挑战是模型的验证。由于缺乏详细的空间数据及模型模拟中的随机性,很难通过模型模拟结果与实地调查或遥感数据的比较进行验证。通过对火模拟、物种分布和物种组成的生态或生物学实现对模型进行验证。     

Effects of wind erosion on the spatial heterogeneity of soil nutrients in two desert grassland communities

Wind is known to affect the spatial heterogeneity of soil resources in arid and semiarid systems, but multi-year, quantified observations are largely absent. We studied the effects of wind erosion on the spatial distribution of soil organic carbon (SOC) and other soil nutrients at the Jornada Experimental Range, in southern New Mexico. Enhanced wind erosion was encouraged by grass cover reduction in a Sporobolus-mesquite dominated site (SM) and a Bouteloua-mesquite dominated site (BM). The scale and magnitude of spatial dependence for the soil analytes were quantified using geostatistical analyses. Results of this study show that soil organic matter related analytes such as SOC, TN, N_avail, and SO₄ ^2- are among the first to be eroded and redistributed; cations such as Ca²⁺ and Mg²⁺ may not be removed and redistributed significantly; and other ions such as K⁺, Na⁺ and Cl⁻ showed no discernible pattern of change. Geostatistics show that wind appeared to increase the scale of spatial autocorrelation, but decrease the scale of spatial dependence of most soil analytes over 2–3 windy seasons. In the wind enhanced plot of the SM site, up to 99% of the spatial dependence of SOC was autocorrelated at the distance of 1.45 m before the initiation of wind erosion, but the spatial dependence dropped significantly to only 60% at a larger autocorrelation distance of 2.76 m after three windy seasons. Similar but less significant changes were observed for SOC in the BM site. Despite the differential effects of wind on the soil analytes, we conclude that the overall results of wind on the grass cover reduction plots are the disappearance of small, strong fertile islands, which may be related to grasses; and the reinforcement of large fertile islands, which are likely related to mesquite shrubs. In addition, the change of the spatial patterns of SOC and other soil nutrients induced by enhanced wind erosion may persist and reinforce soil islands associated with shrubs, thus allowing a positive feedback for further desertification in this arid grassland.     

Vertical distribution of fine roots in relation to soil factors in Pinus tabulaeformis Carr. forest of the Loess Plateau of China

Growth and vertical distribution of fine root closely depend on soil resource availability. Better understanding of relationships of root profile with vertical distribution of available soil resource and soil characteristics can allow ecologists to predict the fine root distribution on the scales ranging from individual plants to vegetation communities. The objective of the study was to understand the fine root mass density (FRMD), fine root length density (FRLD), fine root area density (FRAD), mean root diameter and specific root length (SRL), vertical distribution in soil profile and their relation with soil environment factors in semiarid and arid Loess Plateau of China. The vertical fine root distribution and soil bulk density, soil moisture and soil inorganic N in 0-60 cm soil profile (0–15, 15–30, 30–45 and 45–60 cm intervals) were investigated by soil coring methods in three Pinus tabulaeformis Carr. forests chosen at three locations. The fine root density parameters (FRMD, FRLD and FRAD) and SRL peaked in the most upper soil layer (0–15 cm interval) and decreased with increased soil depth. The results provided a strong support that soil water rather than soil inorganic N is a key control on fine root distribution in the Loess Plateau. With increased soil moisture, the root mass, length and SRL increased and the mean root diameter decreased. The effects of soil bulk density on the fine root parameters were consistent with those of the soil water. An unexpected result was obtained about the relationships between soil organic N and the root distributions and occurrences because of no differences among the soil depth intervals in soil inorganic N content. It might be associated with severe soil water deficit limiting soil nitrogen utilization efficiency in arid Loess Plateau.     

Species interactions at the level of fine roots in the field: influence of soil nutrient heterogeneity and plant size

Interference at the level of fine roots in the field was studied by detailed examination of fine root distribution in small soil patches. To capture roots as they occur in natural three-dimensional soil space, we used a freezing and slicing technique for microscale root mapping. The location of individual roots intersecting a sliced soil core surface was digitized and the identity of shrub and grass roots was established by a chemical technique. Soil patches were created midway between the shrub, Artemisia tridentata, and one of two tussock grasses, Pseudoroegneria spicata or Agropyron desertorum. Some soil patches were enriched with nutrients and others given only deionized water (control); in addition, patches were located between plants of different size combination (large shrubs with small tussock grasses and small shrubs with large tussock grasses). The abundance of shrub and grass roots sharing soil patches and the inter-root distances of individual fine roots were measured. Total average rooting density in patches varied among these different treatment combinations by only a factor of 2, but the proportion of shrub and grass roots in the patches varied sixfold. For the shrub, the species of grass roots sharing the patches had a pronounced influence on shrub root density; shrub roots were more abundant if the patch was shared with Pseudoroegneria roots than if shared with Agropyron roots. The relative size of plants whose roots shared the soil patches also influenced the proportion of shrub and grass roots; larger plants were able to place more roots in the patches than were the smaller plants. In the nutrient-enriched patches, these influences of grass species and size combination were amplified. At the millimeter- to centimeter-scale within patches, shrub and grass roots tended to segregate, i.e., avoid each other, based on nearest-neighbor distances. At this scale, there was no indication that the species-specific interactions were the result of resource competition, since there were no obvious patterns between the proportion of shrub and grass roots of the two species combinations with microsite nutrient concentrations. Other potential mechanisms are discussed. Interference at the fine-root level, and its species-specific character, is likely an influential component of competitive success, but one that is not easily assessed.     

Biomass, morphology and nutrient contents of fine roots in four Norway spruce stands

Fine root systems may respond to soil chemical conditions, but contrasting results have been obtained from field studies in non-manipulated forests with distinct soil chemical properties. We investigated biomass, necromass, live/dead ratios, morphology and nutrient concentrations of fine roots (<2 mm) in four mature Norway spruce (Picea abies [L.] Karst.) stands of south-east Germany, encompassing variations in soil chemical properties and climate. All stands were established on acidic soils (pH (CaCl₂) range 2.8–3.8 in the humus layer), two of the four stands had molar ratios in soil solution below 1 and one of the four stands had received a liming treatment 22 years before the study. Soil cores down to 40 cm mineral soil depth were taken in autumn and separated into four fractions: humus layer, 0–10 cm, 10–20 cm and 20–40 cm. We found no indications of negative effects of N availability on fine root properties despite large variations in inorganic N seepage fluxes (4–34 kg N ha⁻¹ yr⁻¹), suggesting that the variation in N deposition between 17 and 26 kg N ha⁻¹ yr⁻¹ does not affect the fine root system of Norway spruce. Fine root biomass was largest in the humus layer and increased with the amount of organic matter stored in the humus layer, indicating that the vertical pattern of fine roots is largely affected by the thickness of this horizon. Only two stands showed significant differences in fine root biomass of the mineral soil which can be explained by differences in soil chemical conditions. The stand with the lowest total biomass had the lowest Ca/Al ratio of 0.1 in seepage, however, Al, Ca, Mg and K concentrations of fine roots were not different among the stands. The Ca/Al ratio in seepage might be a less reliable stress parameter because another stand also had Ca/Al ratios in seepage far below the critical value of 1.0 without any signs of fine root damages. Large differences in the live/dead ratio were positively correlated with the Mn concentration of live fine roots from the mineral soil. This relationship was attributed to faster decay of dead fine roots because Mn is known as an essential element of lignin degrading enzymes. It is questionable if the live/dead ratio can be used as a vitality parameter of fine roots since both longevity of fine roots and decay of root litter may affect this parameter. Morphological properties were different in the humus layer of one stand that was limed in 1983, indicating that a single lime dose of 3–4 Mg ha⁻¹ has a long-lasting effect on fine root architecture of Norway spruce. Almost no differences were found in morphological properties in the mineral soil among the stands, but vertical patterns were apparently different. Two stands with high base saturation in the subsoil showed a vertical decrease in specific root length and specific root tip density whereas the other two stands showed an opposite pattern or no effect. Our results suggest that proliferation of fine roots increased with decreasing base saturation in the subsoil of Norway spruce stands.     

空间异质性定量研究理论与方法

通过变异函数对空间异质性定量研究进行了讨论．结果表明,空间异质性定量研究应从空间特征和空间比较两方面去考虑．对空间特征,着重讨论怎样应用变异函数将空间异质性分解成各定量组分;确定空间异质性程度;探测空间异质性变化的尺度．对空间比较,怎样对同一变量和不同变量用变异函数比较空间异质性时的统计检验;采用标准化变异函数比较同一地点上的不同变量的空间异质性．最后通过阔叶红松景观中林型和土壤类型的空间异质定量研究实例验证了上述理论与方法．     

细根对竹林-阔叶林界面两侧土壤养分异质性形成的贡献

土壤养分异质性是竹林-阔叶林界面(bamboo and broad-leaved forest interface, 以下简称竹阔界面)的重要特征, 细根生长、周转和分解影响土壤养分供应能力, 但其在竹阔界面养分异质性形成中的贡献尚不清楚。该文选取竹阔界面两侧的毛竹(Phyllostachys pubescens)林和常绿阔叶林为研究对象, 开展土壤养分(C、N、P)含量、细根生物量及周转、细根分解及养分回归等指标的对比研究。结果表明: (1)竹阔界面两侧毛竹林和常绿阔叶林土壤养分差异明显, 毛竹林0-60 cm土壤有机碳(SOC)和土壤总氮(STN)含量分别为20.51和0.53 g·kg^-1, 常绿阔叶林0-60 cm土壤有机碳(SOC)和土壤总氮(STN)含量分别为13.42和0.26 g·kg^-1, 前者比后者分别高出34.53%和50.35%, 但毛竹林土壤全磷(STP)含量低于常绿阔叶林25.54%; (2)竹阔界面两侧细根生物量、养分密度及养分回归量差异明显, 毛竹林细根生物量高达1201.60 g·m^-2, 是常绿阔叶林的5.86倍; 养分密度分别为591.42 g C·m^-2、5.44 g N·m^-2、0.25 g P·m^-2, 分别是常绿阔叶林的6.12倍、3.77倍和3.11倍; 年均养分回归量分别为278.54 g C·m^-2·a^-1、2.36 g N·m^-2·a^-1、0.11 g P·m^-2·a^-1, 是常绿阔叶林的6.93倍、4.29倍和3.67倍; (3)细根对界面两侧土壤SOC、STN异质性形成的年均潜在贡献分别为76.79%和28.33%, 但对STP异质性形成起减缓作用, 贡献率为6.17%。这些结果说明毛竹扩张可以改变常绿阔叶林土壤的养分状况, 且细根对不同养分的异质性形成贡献不一致, 是土壤SOC、STN异质性形成的重要原因。     

Fluctuations of the soil environment and fine root growth in a young Sitka spruce plantation

Summary From soil cores extracted at 5 day intervals from 3 May to 6 August it was found that the biomass of fine roots in a Sitka spruce plantation, 14 years old, fluctuated with maxima in late May and mid July. The earlier peak coincides with increasing soil temperatures during a period of high incident precipitation and the latter developed when the soil profile was rewetted. Fine root biomass and soil moisture tension (SMT) were significantly and negatively correlated in three of four soil horizons. Root mortality occurred whenever incident precipitation failed to maintain soil moisture tension near zero. In the very open pored horizons the critical SMT for root death was unexpected small, <0.1 bars; in the peat horizons it wasc 0.2 bars.     

Spatial and temporal heterogeneity in soil nutrient supply measured usingin situ ion-exchange resin bags

Summary Data are presented which illustrate the range of ion values obtained from soil solutions eluted fromin situ ion exchange resin bags in grazed and ungrazed grassland soils sampled in the summer and early autumn. Overall, higher levels of cations were being supplied in both the grazed and ungrazed plots in the autumn compared with during the summer. Variation in ion levels reflected spatial heterogeneity in ion supply in these soils. This variation was correlated with the distribution and abundance of the dominant plants and soil surface microtopography. The use ofin situ ion exchange resin bags allow an understanding of short-term temporal and spatial heterogeneity in ion supply.