密度制约对宝天曼落叶阔叶林锐齿栎死亡前后分布格局的影响

为了在温带和亚热带的过渡带中验证森林树木死亡是否受密度制约的影响, 我们在宝天曼国家级自然保护区选择1个100 m×100 m的暖温带落叶阔叶林样地, 用双变量函数g(r)(the pair-correlation function)研究了锐齿栎(Quercus aliena var. acuteserrata)死亡前(活树和枯木统称为死亡前树木)和死亡后(活树为死亡后树木)的分布格局。把样地中的锐齿栎分为幼树(1 cm ≤ DBH<10 cm)、小树(10 cm ≤ DBH<20 cm)和成年树(DBH≥20 cm)3个不同的生长阶段来研究密度制约对空间分布格局的影响机制。结果表明: (1)死亡前锐齿栎在r>5 m尺度呈聚集分布, 死亡后幼树(1 cm≤DBH<10 cm)和成年树(DBH≥20 cm)在1-25 m尺度呈现随机分布, 死亡后小树(10 cm≤DBH< 20 cm)在r<1.5 m和2.5-4.5 m的尺度为随机分布, 在r>5 m的尺度呈聚集分布; (2)采用随机标签零模型和案例-对照设计的方法, 排除生境异质性影响后, 将幼树和小树的分布格局作为案例, 将成年树的分布格局作为对照, 并代表生境异质性的作用, 通过小径级树木与成年树分布格局的对比发现, 密度制约效应对死亡前后的锐齿栎分布格局均具有影响; (3)幼树和小树在成年树周围的分布死亡前为显著聚集分布格局, 死亡后剩余树木的聚集强度下降; 随着与成年树之间距离的增加, 死亡后的幼树(仅包括现存的活树)逐渐向随机分布格局演替。本研究初步表明锐齿栎空间格局受生境异质性的影响并呈现出显著的聚集效应, 排除生境异质性影响后, 锐齿栎死亡前后的空间格局受到密度制约的影响, 这一结果为Janzen-Connell假说提供了支持。     

Distribution,community characteristics and classification of Stipa tianschanica var. gobica steppe in China

戈壁针茅(Stipa tianschanica var. gobica)草原主要分布于荒漠草原区的石质丘陵或石质山坡, 向东可以分布在典型草原区的石质丘陵或山地, 向西也可以分布在荒漠区的石质山坡上。该研究调查了中国戈壁针茅草原的主要植被类型, 通过对115个样地的样方数据分析, 量化描述了这一草原类型的主要植物群落特征。结果表明, 中国戈壁针茅草原共有维管植物272种, 隶属于38科127属; 其中裸子植物3种, 隶属于1科1属; 被子植物269种, 隶属于37科126属, 物种数大于等于10种的科为: 菊科、禾本科、豆科、蔷薇科、百合科、藜科、石竹科; 戈壁针茅草原植物区系的生活型谱以地面芽植物为主, 共178种植物, 占总种数的65.44%; 水分生态类型以旱生植物为主, 共120种, 占总种数的44.12%; 植物区系地理成分上以东古北极分布种和亚洲中部分布种(含其变型)最多, 分别为82种和80种, 占总种数的30.14%和29.41%; 盖度等级划分上以0.1%-1.0%的盖度最多, 共174种, 占总种数的63.97%; 恒有度等级划分上以I级(0-20%)的物种数最多, 共258种植物, 占所有植物种数的94.85%。基于群落调查数据, 按照群落-外貌分类原则, 将戈壁针茅群系划分为8个群丛组106个群丛。     

喀斯特常绿落叶阔叶林个体死亡对空间格局及种间关联性的影响

树木死亡作为森林生态系统中一个重要的生态学过程,研究其如何影响物种的空间分布格局及种间关联性,可以为揭示树木死亡机制及群落动态变化规律提供重要参考。本研究根据木论25 hm²喀斯特常绿落叶阔叶林动态监测样地两次木本植物调查数据,采用点格局分析方法,分析了树木死亡前后空间格局和种间关系的变化。结果表明: 样地内个体死亡前后主要表现为聚集分布,但死亡后聚集分布的物种比例较死亡前略微下降,小尺度上呈现随机分布的物种比例有所增加,个体的死亡呈非随机性死亡。在物种水平上,13个优势种的死树和活树之间在0～30 m各尺度上呈显著正关联,表明样地内优势物种个体之间种内和种间竞争作用不激烈;树木死亡前后种间关联性主要为正关联,且大部分物种种间关系在死亡前后并未发生变化,表明群落已发展到相对稳定的阶段;死亡后,在1～30 m尺度上表现为正关联的物种对比例有所增加,负关联和无关联的物种对在大部分尺度上有所减少,说明个体死亡发生后,各个物种之间的竞争压力在一定程度上有所缓解。     

秦岭中段不同坡向锐齿栎种子雨、土壤种子库与幼苗更新

以秦岭中段不同坡向(阳坡、半阳坡、半阴坡及阴坡)锐齿栎天然林为对象,对锐齿栎种子雨、种子库的数量、质量动态以及幼苗发育过程进行研究.结果表明: 锐齿栎种子雨一般从8月中旬开始,9月中下旬到10月上旬达到高峰期,11月中上旬结束;不同坡向的种子雨降落历程、发生时间和组成不同;半阳坡种子雨强度最大,为134.13粒·m^-2,其余大小依次为阳坡、半阴坡、阴坡;阳坡种子雨降落时间最早、持续时间最长,高峰期持续时间也最长,阴坡种子雨降落时间最晚、持续时间最短,高峰期持续时间也最短;种子活力及成熟种子占其种子雨的比例大小顺序为半阳坡>阳坡>半阴坡>阴坡.从种子雨降落结束到翌年8月,各坡向土壤种子库总储量大小顺序均为半阳坡>阳坡>半阴坡>阴坡;各坡向的土壤种子库中成熟、未成熟、被啃食种子数量和种子活力均随时间变化呈递减趋势,而霉烂种子数量增加;各坡向土壤种子库中的种子均主要集中在枯落物层,其次为0~2 cm土层,而在2~5 cm土层中只有极少量种子存在.4种坡向中锐齿栎幼苗的密度差异显著,半阳坡幼苗最多,其余依次是阳坡、半阴坡和阴坡.半阳坡更适合锐齿栎种子的萌发和幼苗生长.     

秦岭优势乔木锐齿槲栎的空间分布格局及种内关联

为探究锐齿槲栎种群的空间分布特征及关联性,本研究以秦岭皇冠暖温性落叶阔叶林25 hm²森林样地内优势树种锐齿槲栎为对象,采用成对相关函数g(r)对其空间格局及其种内关联性进行了研究。结果表明: 锐齿槲栎径级结构呈“双峰”型,幼树(1 cm≤胸径DBH＜5 cm)个体数较多,种群呈增长型结构,更新良好;中树(15 cm≤DBH＜25 cm)比大树(25 cm≤DBH＜35 cm)、老树(DBH≥35 cm)的个体数略多,但远少于幼树和小树(5 cm≤DBH＜15 cm)。锐齿槲栎空间分布具有明显的海拔依赖性,主要分布在中高海拔地区。完全空间随机零模型分析表明,各径级个体在＜60 m的大尺度范围聚集分布。使用异质泊松模型剔除生境异质性分析表明,各径级的个体转变为大尺度的随机分布,表明树种的分布明显受到生境变化的影响。在＜40 m的小尺度范围内,径级差距小的个体间的空间关联性为正关联,径级差距大的个体间的空间关联性转变为负关联和无关联;在＞40 m的大尺度范围内,大径级个体间的空间关联性为正关联,而幼树和其他径级个体间的空间关联性为负关联或无关联。锐齿槲栎自身生物学特性和环境异质性是种群空间格局形成的重要原因。     

山西省南方红豆杉自然分布与群落生态学特征

南方红豆杉为国家Ⅰ级重点保护植物,山西省东南部为其自然分布最北界.本文调查了南方红豆杉在山西省的野生分布,对其进行了群落划分、物种多样性、结构特征和竞争特性的研究.结果表明: 山西省南方红豆杉主要形成南方红豆杉+鹅耳枥群落、南方红豆杉-荆条群落、南方红豆杉-海州常山群落和南方红豆杉+栓皮栎群落,集中分布于陵川县磨河和阳城县蟒河自然保护区,其他地区均为散生;群落垂直结构明显,南方红豆杉已进入主林层,混交林林冠层高8~10 m,纯林高5～6 m;群落间的总体物种多样性指数和均匀度指数存在显著差异.南方红豆杉植株矮小,平均高5.16 m,乔木层、演替层分别占43.4%和56.6%,更新层缺乏;胸径＜16 cm的个体占67.6%,胸径32～40 cm的个体占4.0%,幼苗稀少,仅发现4株幼苗;大量的小径级个体虽可保证南方红豆杉在一定时间内维持稳定的种群结构,但幼苗缺失必将引起未来种群的衰退.山西省野生南方红豆杉分布相对集中,多数是小径级个体,导致其种内竞争激烈,种内竞争强度占61.8%;鹅耳枥和栓皮栎是研究地区的主要组成树种,对南方红豆杉造成的种间竞争压力最大.     

Change of growth characters and carbon stocks in plantations of Pinus sylvestris var. mongolica in Saihanba,Hebei, China

Aims Pinus sylvestris var. mongolica is one of the main afforestation tree species in North China. It is important to study the characters of growth and carbon (C) sequestration, which can provide scientific basis for the sustainable management. Therefore, our study aims at quantifying the growth characters and C sequestration in these middle-aged plantations, and to investigate the effect of diameter at breast height (DBH) on those dynamics. Methods We selected a middle-aged P. sylvestris var. mongolica plantation as our permanent experimental plot, which is located in Saihanba, Hebei Province, China. DBH and height of all stands in this plot were measured in 2006 and 2016. Based on the anatomical trees and allometric equation, we calculated C density and sequestration from 2006 to 2016. We also analyzed C sequestration in different DBH groups in the study area. Important findings Our results showed that the carbon sink of those middle-age (age between 28 and 38 years old) plantation would be enhanced in future, and there were differences in characters of growth and C sequestration among DBH groups. The decadal increment rate of DBH and height were 4.19% and 1.97%, and the increment rate was the lowest in the 0-10 cm DBH class. The mortality rate of the plantation was 8.39%, with 7.82% mortality occurred in 0-10 cm tree size class. The forest stands biomass carbon stocks in 2006 and 2016 were 59.04 and 109.64 t?hm^-2, respectively, and almost 87.1% of the carbon stocks were in the middle DBH-class, even though the number of trees only accounted for nearly 59.2%. The small class’s number of trees accounted for 39.1%, while the carbon stocks accounted for 8.3%. Our results also demonstrate that forests in Saihanba would continue to act as a carbon sink in the coming years. The variations among DBH groups highlights that the diameter class should be taken into consideration while assess the ecological efficiency and carbon sequestration capacity in a certain area.     

穿透雨减少下锐齿栎叶片光合色素季节动态及其反射光谱响应

通过林地穿透雨排除的方法模拟降雨减少,测定河南宝天曼自然保护区锐齿栎叶片光合色素含量与反射光谱的季节变化,对减雨处理造成的光合色素变化及其反射光谱的变化进行了定量分析,并探讨了水分控制条件下反射光谱对叶片光合色素变化的响应机制.结果表明: 锐齿栎叶片的光合色素含量和色素比率均呈现明显的季节变化.减雨样地与对照样地叶片的光合色素含量和比率在生长季的各个时期存在差异,其中,叶片叶绿素b(Chl b)含量的差异显著,说明Chl b对减雨处理的敏感性最高,叶片类胡萝卜素(Car)含量的差异较小,说明Car对减雨处理的敏感性相对较弱.550 nm处的光谱反射率对色素季节变化的响应最敏感,以其构造的简单比值指数(SR_750,550)与叶片Chl a、Chl b、总Chl和Car含量的正相关关系显著,光化学反射指数(PRI)与叶片Car/Chl的负相关关系显著.550 nm处的光谱反射率对减雨处理造成的色素变化响应最为敏感.SR_750,550对减雨处理造成的叶片Chl a、Chl b和总Chl的含量变化表现敏感(P<0.01),对Chl a/b的变化不敏感.PRI对减雨处理造成的叶片Car/Chl变化表现敏感(P<0.01).     

中国戈壁针茅草原的分布、群落特征和分类

戈壁针茅(Stipa tianschanica var. gobica)草原主要分布于荒漠草原区的石质丘陵或石质山坡, 向东可以分布在典型草原区的石质丘陵或山地, 向西也可以分布在荒漠区的石质山坡上。该研究调查了中国戈壁针茅草原的主要植被类型, 通过对115个样地的样方数据分析, 量化描述了这一草原类型的主要植物群落特征。结果表明, 中国戈壁针茅草原共有维管植物272种, 隶属于38科127属; 其中裸子植物3种, 隶属于1科1属; 被子植物269种, 隶属于37科126属, 物种数大于等于10种的科为: 菊科、禾本科、豆科、蔷薇科、百合科、藜科、石竹科; 戈壁针茅草原植物区系的生活型谱以地面芽植物为主, 共178种植物, 占总种数的65.44%; 水分生态类型以旱生植物为主, 共120种, 占总种数的44.12%; 植物区系地理成分上以东古北极分布种和亚洲中部分布种(含其变型)最多, 分别为82种和80种, 占总种数的30.14%和29.41%; 盖度等级划分上以0.1%-1.0%的盖度最多, 共174种, 占总种数的63.97%; 恒有度等级划分上以I级(0-20%)的物种数最多, 共258种植物, 占所有植物种数的94.85%。基于群落调查数据, 按照群落-外貌分类原则, 将戈壁针茅群系划分为8个群丛组106个群丛。     

Effects of night warming on the uptake of inorganic nitrogen by two dominant species in subalpine coniferous forests

Aims Plant roots play a critical role in the uptake of nutrients, and nitrogen (N) absorption is considered as the first step and a pivotal process in N metabolism of plants. Our objective was to better understand the absorption of two major inorganic N forms (NH₄⁺ and NO₃^-) in subalpine coniferous forests under global warming Methods Experimental warming using infrared heater was applied to two dominant species in subalpine coniferous forests of Sichuan, China, Picea asperata and Abies fargesiivar. faxoniana. The non-invasive micromeasurement technology was used to investigate the effects of warming on the uptake rates of NH₄⁺ and NO₃^- and the potential interactions between these two ions.Important findings Results showed that the maximal net root uptake of NH₄⁺ and NO₃^-occurred at a distance of 17-18 mm and 17 mm from root tips, respectively for P. asperata. and at a distance of 11 mm and 11.5 mm from root tips respectively for A. fargesiivar. faxoniana. Experimental warming elevated the uptake rates of NH₄⁺ and NO₃^- in both species, but the interactions between NH₄⁺ and NO₃^- differed between the two species. While NO₃^- uptake was inhibited in the presence of NH₄⁺ for both P. asperataand A. fargesiivar. faxoniana, net NH₄⁺ uptake was promoted by NO₃^- supply only in P. asperata roots under experimental warming.     

Plant nutrient dynamics and stoichiometric homeostasis of invasive species Spartina alterniflora and native Cyperus malaccensis var. brevifolius in the Minjiang River estuarine wetlands

Aims Stoichiometric homeostasis is an important mechanism in maintaining ecosystem structure, function, and stability. The invasion of exotic species, Spartina alterniflora, has largely threatened the structure and function of native ecosystems in the Minjiang River estuarine wetland. However, how S. alterniflora invasion affect plant stoichiometric homeostasis is largely unknown. This could enhance our understanding on wetland ecosystem stability and expand the applications of ecological stoichiometry theory.
Methods Nitrogen (N) and phosphorus (P) contents of plant organs and soils in the S. alterniflora, Cyperus malaccensis var. brevifolius, and S. alterniflora-C. malaccensis var. brevifolius mixture were measured, and the homeostatic index (H) was calculated according to the stoichiometric homeostasis theory.
Important findings Our results showed that the invasion of S. alterniflora significantly increased soil N:P ratio (p < 0.05), but did not affect soil N or P contents. The N and P contents of leaf and stem were the highest for S. alterniflora, and those of the stem were the highest for C. malaccensis var. brevifolius. At the ecosystem level, the average of homeostatic index (H) of N (H_N, 25.31) was larger than those of P (H_P, 10.33) and N:P (H_N:P, 2.50). At the organ level, root H_N was significantly larger than stem H_N (p < 0.05) and sheath H_N:P was greater than root H_N:P (p < 0.05), while there was no significant difference for H_P among root, stem, leaf, and sheath (p > 0.05). As for species, root H_N of S. alterniflora was significantly larger than that of C. malaccensis var. brevifolius in the mixture community (p < 0.05). In the monoculture, stem H_N:P of S. alterniflora was significantly higher than that of C. malaccensis var. brevifolius (p < 0.05). Furthermore, root H_N, leaf H_N and sheath H_N of S. alterniflora in the mixed community was significantly larger than that of S. alterniflora in the monoculture (p < 0.05), suggesting that S. alterniflora invasions increased their stoichiometric homeostasis. Meanwhile, the stoichiometric homeostasis of invasive and native plants were influenced by multiple factors, such as nutrients, organs, vegetation, and invasion. However, larger homeostasis was found in S. alterniflora than in C. malaccensis var. brevifolius in some particular organs either in mixture or monoculture communities. Therefore, the successful invasion of S. alterniflora may result from higher homeostatic index than the native species, C. malaccensis var. brevifolius.     

Effects of nitrogen addition on soil respiration in shrublands in Mt. Dongling,Beijing, China

Aims Soil respiration from terrestrial ecosystems is an important component of terrestrial carbon budgets. Compared to forests, natural or semi-natural shrublands are mostly distributed in nutrient-poor sites, and usually considered to be relatively vulnerable to environmental changes. Increased nitrogen (N) input to ecosystems may remarkably influence soil respiration in shrublands. So far the effects of N deposition on shrubland soil respiration are poorly understood. The aim of this study is to investigate the soil respiration of Vitex negundo var. heterophylla and Spiraea salicifolia shrublands and their response to N deposition. Methods We carried out a N enrichment experiment in V. negundo var. heterophylla and S. salicifolia shrublands in Mt. Dongling, Beijing, with four N addition levels (N₀, control, 0; N₁, low N, 20 kg N·hm^-2·a^-1; N₂, medium N, 50 kg N·hm^-2·a^-1 and N₃, high N, 100 kg N·hm^-2·a^-1). Respiration was measured from 2012-2013 within all treatments.Important findings Under natural conditions, annual total and heterotrophic respiration were 5.91 and 4.23, 5.76 and 3.53 t C·hm^-2·a^-1 for the V. negundo var. heterophylla and S. salicifolia shrublands, respectively and both were not affected by short-term N addition. In both shrubland types, soil respiration rate exhibited significant exponential relationships with soil temperature. Temperature sensitivity (Q₁₀) of total soil respiration in V. negundo var. heterophylla and S. salicifolia shrublands ranged from 1.44 to 1.58 and 1.43 to 1.98, and Q₁₀ of heterotrophic soil respiration ranged from 1.38 to 2.11 and 1.49 to 1.88, respectively. Short-term N addition decreased only autotrophic respiration rate during the growing season, but had no significant effects on total and heterotrophic soil respiration in V. negundo var. heterophylla shrubland. In contrast, N addition enhanced the heterotrophic soil respiration rate and did not influence autotrophic and total soil respiration in S. salicifolia shrubland.     

Community characteristics and spatial distribution of dominant tree species in a deciduous broad-leaved forest of Muzhaling,Henan, China

Aims The objective of this paper is to quantify the species composition and spatial distribution pattern in a deciduous broad-leaved forest in temperate to subtropical ecological transition zone.
Methods In this study, a 3-hm² forest was selected in the temperate to subtropical ecological transition zone to analyze the community species composition, structure of diameter at breast height, community classification and spatial distribution pattern of dominant tree species.
Important findings Our results showed that in the plot there were 85 species, 52 genera and 31 families, mainly composed of Betulaceae, Celastraceae, Caprifoliaceae, Salicaceae and Aceraceae. Quercus aliena var. acuteserrata and Pinus armandii are dominant species of the community tree layer. The rare species and occasional species accounted for 20.0% and 28.24% of total species respectively. Size distribution of all species showed an invert J-shape, which indicates that the community is in a stable and normal growth status. Using multiple regression trees, the community in this plot can be divided into four categories: 1) Quercus aliena var. acuteserrata + Pinus armandii + Litsea tsinlingensis + Cerasus clarofolia + Lindera obtusiloba; 2) Quercus aliena var. acuteserrata + Salix chaenomeloides + Sorbus hupehensis; 3) Quercus aliena var. acuteserrata + Ailanthus altissima + Cerasus clarofolia + Litsea tsinlingensis; 4) Quercus aliena var. acuteserrata + Fraxinus chinensis + Litsea tsinlingensis + Philadelphus incanus. Under the completely random distribution model, the main species in the plot display clustered distributions, with the different species occurring in different habitat types, showing obvious terrain habitat preferences. However, under the heterogeneous Poisson distribution model, these species at different scales are distributed randomly or regularly. This study helps to understand the plant community species composition of the Muzhaling World Geopark, community structure and community distribution. The results show that the terrain habitat heterogeneity is an important factor influencing the spatial distribution of the species. The present work improves the understanding of plant community in Muzhaling World Geopark, and provides technical reference for biodiversity conservation and forest management of this area.     

Simulation on the light-response curves of electron transport rate of Quercus variabilis and Robinia pseudoacacia leaves in the Xiaolangdi area,China

为了比较直角双曲线模型、非直角双曲线模型与叶子飘模型的优缺点, 研究阴生叶和阳生叶电子传递速率的差异, 探讨环境/生物因素对电子传递速率等参数的影响, 该文采用LI-6400XT荧光测定系统对黄河小浪底栓皮栎(Quercus variabilis)、刺槐(Robinia pseudoacacia)叶片电子传递速率-光响应(J-I)曲线进行了测定, 利用直角双曲线模型、非直角双曲线模型和叶子飘模型对J-I曲线进行了拟合。结果表明, 3种模型对叶片J-I曲线拟合的决定系数(R ²)在0.96以上, 叶子飘模型的R ²最高(> 0.99)。直角双曲线模型和非直角双曲线模型无法模拟植物叶片光系统II动力学下调现象, 且不能得出饱和光强(I_sat); 直角双曲线模型对最大电子传递速率(J_max)的模拟明显大于实测值; 叶子飘模型能很好地模拟光系统II动力学下调现象, 得出的J_max和I_sat均最接近实测值。对阴生叶和阳生叶J-I曲线研究发现, 栓皮栎、刺槐阴生叶的J_max分别低于阳生叶25.0%和18.0%, 阳生叶的I_sat分别高于阴生叶26.0%和10.1%。栓皮栎和刺槐J_max与气温显著正相关; 刺槐I_sat与气温、土壤水分含量和净光合速率具有显著的正相关关系; 栓皮栎和刺槐J-I曲线初始斜率α均与净光合速率呈显著负相关关系。     

Population structure and spatial pattern of Caragana tibetica communities in Nei Mongol shrub-encroached grassland

Aims The community structure and function of the shrub-encroached grassland, as well as its formation mechanism, is one of hot scientific problems in vegetation science. The spatial pattern analysis is an important means for studying plant population interactions and the relationships between plant population and environment. The shrub-encroached grassland is one major vegetation type in Nei Mongol. Knowledge on the spatial pattern of shrub can improve our understanding on adaptive characteristics of shrub to steppe environment.
Methods We chose Caragana tibetica encroached grassland distributed in Ordos City as research objects. The spatial position of each C. tibetica individual in 64 m × 64 m study plot was determined by a method of “three-distance location method”, and then the spatial pattern and intraspecific associations of C. tibetica individuals was analyzed with the point pattern analysis.
Important findings The results showed that C. tibetica population was at the rising stage. The mature individuals showed a uniform distribution at the scale of less than 3.7 m, subsequently exhibiting a random distribution with an increased scale. The juvenile individuals showed an aggregation distribution at the scale of 0.3-20.4 m, but a uniform distribution at other scales. The dead C. tibetica individuals were distributed aggregately at the scale from 0.7 to 1.4 m, but randomly at other scales. An indistinctive positive association was found for live C. tibetica individuals to dead individuals at the scale of less than 9.9 m, but no associations was found between them at other scales. The mature individuals negatively interacted with juveniles at the scale of larger than 2.2 m, but unassociated at the other scales.     

松栎林天然更新模拟与不确定性分析

森林天然更新的复杂性和不确定性是森林生态系统动态预测中的关键问题。本研究引入贝叶斯技术和全局敏感性分析,构建基于竞争、气候和地形3类因子的秦岭松栎林天然更新模型。备选模型形式以泊松(Poisson)模型、负二项(negative binomial,NB)模型、零膨胀泊松(zero-inflated Poisson,ZIP)模型和零膨胀负二项(zero-inflated negative binomial,ZINB)模型为基础。同时,根据模型参数传递的不确定性量化分析结果,阐释影响森林更新小概率事件的主导因子。结果表明: ZINB模型在油松和锐齿栎更新模拟中均优于其他模型。林分总断面积、光截留、坡位和生长季最低温是影响松栎林中油松天然更新的最关键因子;而林分总断面积、坡向与海拔的组合、年均温和最热季节降水量则是影响松栎林中锐齿栎天然更新的关键因子。油松更新模拟中,各类因子对模型输出的不确定性贡献率从小到大依次为: 竞争因子(25%)＜气候因子(29%)＜地形因子(46%);锐齿栎更新模拟中为: 气候因子(12%)＜竞争因子(24%)＜地形因子(64%)。油松天然更新数量对生长季最低温和最干季节降水量为正响应,对最干季节均温为负响应;锐齿栎天然更新数量对年均温、生长季最低温和最热季节降水量为正响应,对最干季节均温为负响应。基于贝叶斯技术的ZINB模型可以量化森林更新的影响因子,并解释参数传递的不确定性,是预测森林天然更新的有力工具。     

长白山阔叶红松林3个常见树种径向生长的影响因素

为探究树木径向生长的影响因子,基于对长白山阔叶红松林25 hm²样地中3个常见树种红松、紫椴、蒙古栎连续5年的生长环监测数据,分析各树种的季节生长变化,比较树种间的生长速率差异,并分析初始径级、邻体树木竞争、土壤、地形因素等对不同树种径向生长的作用.结果表明: 3个树种径向生长的季节变化趋势一致,树木于5月末开始生长,7月是生长旺盛期,8月底生长开始减缓,于10月中下旬停止生长.3个树种的径向相对生长率存在显著差异,蒙古栎相对径向生长率显著高于红松和紫椴,该差异在小、中径级个体中表现更为显著.3个树种径向生长的主要影响因子不同,邻体树木的竞争显著抑制了红松和蒙古栎的径向生长,而紫椴的径向生长主要受初始径级、土壤和地形等因子的影响.     

Distribution and species diversity patterns of Vitex negundo var. heterophylla shrublands in North China

生境差异是影响植物群落及其物种多样性分布格局的重要因素。该研究基于370个荆条(Vitex negundo var. heterophylla)灌丛的野外调查样方, 结合多元回归树(MRT)、显著性分析、Pearson相关分析等技术手段, 分析了华北地区荆条灌丛及其物种多样性的空间分布格局。结果表明: 荆条灌丛的经纬度均跨越10°以上, 可分为高、中、低纬度分布区; 分布海拔则从117 m至1 248 m跨越了1 000 m以上, 也可分为高、中、低海拔分布区。所有分布区中荆条灌丛草本层的Shannon-Wiener指数、Simpson指数和均匀度指数均高于灌木层。灌木层物种多样性随着纬度的降低而降低, 随着海拔的升高而降低; 草本层相反, 物种多样性随着纬度降低而升高, 随着海拔升高而升高。灌木层和草本层的物种丰富度(Shannon-Wiener指数)与水、热、地形等环境因子显著相关, 其中灌木层物种多样性随着气温、坡位升高而显著减少, 随着降水的增加而显著增加;草本层则相反。     

Variations and interrelationships of foliar hydraulic and photosynthetic traits for Larix gmelinii

Aims Variations and potential trade-offs of leaf hydraulic and photosynthetic traits are essential for assessing and predicting the effect of climate change on tree survival, growth and distribution. Our aims were to examine variations and interrelationships of leaf hydraulic and photosynthetic traits in response to changes in site conditions for Dahurian larch (Larix gmelinii)—a dominant tree species in Chinese boreal forests.Methods This study was conducted at the Maoershan Forest Ecosystem Research Station. A transect of 27 year-old Dahurian larch plantation was established that consisted of five plots extending from the valley to the ridge of a slope. The predawn leaf water potential (Ψ_pre), area- and mass-based leaf hydraulic conductance (K_area and K_mass, respectively), resistance to embolism capacity (P₅₀), leaf mass per area (LMA), net photosynthetic rate (A), and leaf nitrogen content (N) were measured in August 2016.Important findings The Ψ_pre, K_area, K_mass, P₅₀, A, LMA, and N all varied significantly among the plots (p < 0.05), indicating significant intra-specific variations in these traits in response to the changes in site conditions. The P₅₀ was significantly (p < 0.05) correlated with Ψ_pre, K_area or K_mass, suggesting that a trade-off between hydraulic efficiency and safety exist within the species to some degree. There were significant (p < 0.05) pairwise correlations between A, LMA, and N. Nevertheless, there was no significant (p < 0.05) correlation between the measured photosynthetic traits and hydraulic traits. We concluded that the intra-specific variations and multiple interrelationships of the leaf hydraulic and photosynthetic traits for the larch reflect the plasticity of its leaf traits and strategies of its survival and growth as a result of its acclimation to diverse site conditions.     

河北塞罕坝樟子松径向生长动态变化及其与气象因子的关系

树木是森林生态系统的基本组成, 其生长受气象因子的影响, 基于此, 该研究通过监测樟子松(Pinus sylvestris var. mongolica)的径向生长, 研究樟子松生长日动态规律、季节动态规律及其与气象因子的关系, 探讨河北塞罕坝地区樟子松森林生态系统对气候变化的响应机制。此外, 以往研究树木生长大多数基于树轮年代学, 缺少短期树木径向生长动态的研究。该研究利用径向生长记录仪监测河北塞罕坝机械林场内樟子松连续3年(2016-2018)的树干径向动态变化。结果表明: 由于树干的水分吸收与蒸腾作用, 樟子松树干径向昼夜变化呈现季节性规律, 可划分为4个阶段: 春季萌动期、夏季生长期、秋冬交替期和冬季休眠期。塞罕坝樟子松树干径向生长开始于每年4月初; 4月初至5月中旬为水分恢复阶段; 5月中旬至7月中旬为快速生长阶段; 7月中旬至10月中旬为缓慢生长阶段; 10月中、下旬生长趋于停止, 并有树干径向收缩现象。以一天为时间尺度, 在快速生长阶段(5月初至7月中旬)樟子松径向生长主要受空气温度的影响; 缓慢生长阶段(7月中旬至10月下旬)降水量、空气温度均影响樟子松径向生长。以15天为时间尺度, 温度对樟子松径向生长的影响显著。结果显示樟子松的生长动态规律及其影响因子, 为未来樟子松生理研究提供参考时间节点, 同时在极端低温与干旱的情况下, 为半干旱地区樟子松的生长状态提供参考依据。