Regeneration pattern analysis of Quercus liaotungensis in a temperate forest using two-dimensional wavelet analysis

This paper introduces the two-dimensional (2D) wavelet analysis as a general interrogative technique for the detection of spatial structure in lattice data. The 2D wavelet analysis detects components of hierarchical structure and displays the locational information of the components. Patches and gaps of different spatial scales in graphical presentation of wavelet coefficients can be linked to the local ecological processes that determine patterns at stand or landscape scales. Derived from the 2D wavelet transform function, the calculation of wavelet variance can reduce the four-dimensional data of wavelet coefficients to a two-dimensional wavelet variance function and quantify the contribution of the given scale to the overall pattern. We illustrate the use of the 2D wavelet analysis by analyzing two simulated patterns and identifying the regeneration pattern of the Quercus liaotungensis in a warm temperate forest in north China. Our results indicate that the recruitment of Q. liaotungensis occurs in an overlapping area between the patch of adult and canopy gap at scales of 45 m×45 m–70 m×70 m and 20 m×20 m–30 m×30 m. The regeneration pattern of Q. liaotungensis can be mainly ascribed to a trade-off between two ecological processes: recruitment around parent trees and the physiological light requirements of seedlings and saplings. Our results provide a general portrayal of the regeneration pattern for the dispersal-limited and shade-intolerant Quercus species. We find that the two-dimensional wavelet analysis efficiently characterizes the scale-specific pattern of Q. liaotungensis at different life-history stages.     

Regeneration pattern analysis of Quercus Iiaotungensis in a temperate forest using two-dimensional wavelet analysis

This paper introduces the two-dimensional (2D) wavelet analysis as a general interrogative technique for the detection of spatial structure in lattice data. The 2D wavelet analysis detects components of hierarchical structure and displays the locational information of the components. Patches and gaps of different spatial scales in graphical presentation of wavelet coefficients can be linked to the local ecological processes that determine patterns at stand or landscape scales. Derived from the 2D wavelet transform function, the calculation of wavelet variance can reduce the four-dimensional data of wavelet coefficients to a two-dimensional wavelet variance function and quantify the contribution of the given scale to the overall pattern. We illustrate the use of the 2D wavelet analysis by analyzing two simulated patterns and identifying the regeneration pattern of the Quercus liaotungensis in a warm temperate forest in north China. Our results indicate that the recruitment of Q. liaotungensis occurs in an overlapping area between the patch of adult and canopy gap at scales of 45m×45m-70m×70 m and 20m×20m-30m×30m. The regeneration pattern of Q. liaotungensis can be mainly ascribed to a trade-off between two ecological processes: recruitment around parent trees and the physiological light requirements of seedlings and saplings. Our results provide a general portrayal of the regeneration pattern for the dispersal-limited and shade-intolerant Quercus species. We find that the two-dimensional wavelet analysis efficiently characterizes the scale-specific pattern of Q. liaotungensis at different life-history stages.     

Ecological application of wavelet analysis in the scaling of spatial distribution patterns of Ceratoides ewersmanniana

Ecological experiments are usually conducted on small scales, but the ecological and environmental issues are usually on large scales. Hence, there is a clear need of scaling. Namely, when we deal with patterns and processes on larger scales, a special connection needs to be established on the small scales that we are familiar with. Here we presented a wavelet analysis method that could build relationships between spatial distribution patterns on different scales. With this method, we also studied how spatial heterogeneity and distribution patterns changed with the scale. We investigated the distribution and the habitat of C. ewersmanniana in two plots (200 m × 200 m; the distance between these two plots is 15 km) at Mosuowan desert. The results demonstrated that spatial heterogeneity and distribution patterns were incorporated into larger scales when the wavelet scale varied from one (5 m) to four (20 m). However, if the wavelet scale was above five (25 m), the spatial distribution patterns varied placidly, the oscillation frequency of landforms stabilized at 110 m, and the dynamic quantity period of C. ewersmanniana stabilized at 115–125 m. We also identified signal mutation points with wavelet analysis and verified the heterogeneity degree of local space with position variance. We found that position variance decomposed the distribution patterns on large scales into small sampling plots, and the position with the largest variance also had the strongest heterogeneity. In a word, the wavelet analysis method could scale-up spatial distribution patterns and habitat heterogeneity. With this method and other methods derived from this one, such as wavelet scale, wavelet variance, position variance and extremely direct-viewing graphs, wavelet analysis could be widely applied in solving the scaling problem in ecological and environmental studies.     

桥山林区麻栎种群不同发育阶段空间格局及关联性

为探究麻栎种群不同发育阶段的空间分布特征及关联性,以黄土高原南部桥山林区麻栎天然次生林为研究对象,用L(r)函数对麻栎种群不同发育阶段空间分布特征及关联性进行分析。结果表明:(1)样地内麻栎种群各发育阶段数量结构均为不规则倒"J"型,种群结构稳定,能实现持续更新。(2)麻栎种群总体的空间分布特征受生境异质性影响较大,纯林样地中,种群在0—10 m尺度上表现为高强度聚集分布,5—35 m尺度表现为低强度聚集;混交林样地中,0—5 m尺度上表现为高强度聚集分布,5—35 m尺度上则表现为低强度聚集分布。(3)随着种群的发育及尺度的增大,麻栎种群空间聚集强度减弱,纯林样地内,麻栎幼苗在0—6 m的小尺度表现为聚集分布,6—12 m尺度上表现为随机分布;幼树在各尺度上均表现为聚集分布;中龄树与成龄树在各尺度上均表现为随机分布。混交林样地中,仅幼苗在0—6 m尺度上表现为聚集分布,其余各阶段在各尺度下均趋于随机分布。(4)种群不同发育阶段不同尺度空间关联性不同,纯林样地中,幼苗与幼树在1—2 m小尺度上呈负相关,幼树与中龄树在8 m尺度呈正相关,其余各生长阶段之间在任意尺度上均无关联性;混交林样地中,幼树与中龄树在2—12 m尺度上表现为正相关,其余各生长阶段之间在各尺度上均无关联。在未来的森林经营中,应对不同发育阶段、不同生境的种群进行不同抚育措施,促进种群良性发育。     

辽东栎幼苗根系形态特征对环境梯度的响应

以辽东栎(Quercus liaotungensis)在陕西不同分布区:秦岭北坡(太白)、黄土高原南部(黄龙)和黄土高原中部(延安)为研究地点并设置样地,对1—5年生辽东栎幼苗的根系形态指标进行测定,分析辽东栎幼苗根系形态特征及其与环境因子的关系。结果表明:由秦岭北坡到黄土高原中部,黄龙地区辽东栎幼苗根系在发育前期(1—2年)低于太白和延安,总体上黄龙地区幼苗根系总长度、表面积、总体积、根尖数、平均直径、组织密度和单株生物量高于太白和延安地区。在太白地区,辽东栎幼苗根系表面积、总体积和平均直径较小,根系分岔数较大,幼苗根系主要通过提高分岔数来拓展自己的营养空间以适应环境;在黄龙和延安地区,幼苗根系表面积、总体积和平均直径较大,根系分岔数较小,幼苗根系主要是通过根系的伸长生长适应胁迫环境。3个地区辽东栎幼苗根系总长度、表面积、总体积、根尖数和分岔数随年龄的增长呈线性函数变化格局,均可用线性函数方程y=ax+b(a0,P0.05)进行描述。冗余分析表明幼苗根系分岔数、总长度、比根长和根尖数与土壤速效磷、硝态氮、速效钾、降雨量、石砾含量和速效氮呈正相关;与较高的土壤pH值、年均温和夏季气温呈负相关。未来辽东栎林抚育经营中,含石砾的湿润土壤生境更有利于辽东栎幼苗根系生长。     

Spatial patterns and associations in a Quercus‐Betula forest in northern China

Question: Are species‐specific regeneration strategies and competition the dominant processes facilitating species coexistence in a Quercus liaotungensis dominated temperate deciduous forest? Location: Dongling Mountains, North China, 1300 m a.s.l. Methods: Ripley's K‐function was used to characterize the spatial patterns and spatial associations of two dominant tree species, Quercus liaotungensis and Betula dahurica, and a common subcanopy species, Acer mono, at different growth stages (adult, sapling, seedling). Results: Seedlings, saplings and adults of all three species exhibited clumped distributions at most spatial scales. Quercus seedlings and saplings were positively associated with conspecific adult trees and spatially independent of dead trees suggesting that seed dispersal and vegetative regeneration influenced the spatial patterning of Quercus trees. Betula seedlings and saplings were positively associated with both live and dead trees of conspecific adults at small scales (<5 m) but negatively associated with live and dead trees of other species indicating sprouting as an important mechanism of reproduction. Saplings of Acer had a strong spatial dependence on the distribution of conspecific adult trees indicating its limited seed dispersal range. Negative associations between adult trees of Betula and Quercus demonstrated interspecific competition at local scales (<5 m). Conclusions: Different regeneration strategies among the three species play an important role in regulating their spatial distribution patterns, while competition between individuals of Betula and Quercus at the adult stage also contributes to spatial patterning of these communities. The recruitment limitations of Betula and Quercus may affect the persistence of these species and the long‐term dynamics of the forest.     

小波分析方法在心叶驼绒藜(Ceratoides ewersmanniana)空间格局尺度推绎研究中的应用

以古尔班通古特沙漠南缘莫索湾沙地选取相隔15km的两个200m×200m样地,以建群种心叶驼绒藜(Ceratoides ewersmanniana)及其生境地形为研究对象,应用小波分析定量研究了多尺度上空间格局的推绎以及空间异质性、空间格局依赖于尺度的变化关系。研究发现：小波分析尺度由1(5m)变化到4(20m)时,两个样地小尺度上的异质性和格局被合并到更大的尺度上,当小波分析的尺度大于等于5(25m)时,两个样地的格局变化平稳,对应地形（丘顶、丘坡、丘底）的基频稳定在110m左右,心叶驼绒藜的数量动态变化周期稳定在115～125m之间。结果表明：小波分析对信号整体特征的提取作用实现了小尺度上的信息到大尺度上的聚合。结合小波分析对信号突变点的检测,利用位置方差检验局部空间异质性程度,发现位置方差将大尺度上的格局分解到每个取样小样方,位置方差最大的地点对应的异质性也最强,实现了大尺度上的信息到小尺度上的分解。总结认为应用小波分析可以实现对空间格局的尺度推绎,具有对植被、环境的分布格局以及异质性有双重度量作用,由小波系数以及由其衍生的小波方差、位置方差来实现这种度量,图形表现直观,优越性明显。     

Regeneration in subalpine coniferous forests

The regeneration process of a subalpine coniferous forest, a mixed forest ofTsuga diversifolia (dominant species),Abies veitchii, Abies mariessi, andPicea jezoensis var.hondoensis, was studied on the basis of annual ring data. The age class distribution was discontinuous and four age groups occurred in the study plot (30m×30m). The canopy layer was a mosaic of patches (83.8–133.7 m² patch area), which had different mean ages. The recruitment of canopy trees was carried out only by advance regeneration in the plot. The diameter growth ofAbies andPicea exceeded diameter growth ofTsuga in the gap.Abies lived for 200–300 years and their trunks were susceptible to heart rot.Picea lived for 300–400 years andTsuga for more than 400 years. The regeneration process derived from the analysis of the plot consisted of three phases leading to the development of a even-aged patch; (1) the establishment of saplings before a gap opening, (2) the opening of a gap in the canopy and repair of the canopy by advance regenerated saplings dominated by rapid growth species,Abies andPicea, and (3) the dying off of canopy trees as each species reached the end of its life-span, resulting in pure patches of long-livedTsuga.     

Two-dimensional pattern analysis on dominant species and community in subalpine meadow of Luya Mountain, Shanxi Province, China

The spatial pattern analysis of population and community is important to understand community structure and has become one key topic in modern plant ecology. There are many techniques for analyzing one-dimensional pattern in ecological literature. Two-dimensional pattern analysis is better than one-dimensional analysis in the study on community spatial characteristics and structure. However, it is hard to analyze these two-dimensional patterns due to poor effective methodology. The two-dimensional sampling using two transects that meet at right angles was applied to get quadrat data in this work. And then the data from the two transects were analyzed separately by one-dimensional pattern analysis method, two-term local quadrat variance. The length, width, and area of patches at different scales of pattern for populations were obtained from the analysis. For community pattern, detrended correspondence analysis (DCA) was employed to summarize the species information firstly, and then the first DCA axis scores were analyzed to check its pattern. The application of this method to the pattern analysis on dominant populations and community for subalpine meadow (Comm. Polygonum viviparum + Carex rigescens + Kobresia bellardii) in the Luya mountains showed that it could release the characteristics of spatial pattern clearly and was a very effective technique. The method is easy to use and saves time with obvious advantages, compared with the two-dimensional pattern analysis methods presented in the literatures. In the study meadow, the patterns of the main dominant species, Polygonum viviparum, Carex rigescens, and Kobresia bellardii, were apparent and comparatively regular in shape with large areas of patches at the same scale compared with other species such as Festuca sp. and Thalictrum petaloideum. There were two or three scales of patterns for each plant population studied. This was related to population features, the interaction with environmental factors, and their dominant position in the community. The two scales of patterns for the meadow community were clear. The pattern of community was closely correlated with that of the main dominant species. The patches of dominant species were inter-distributed and overlapped, and formed the community pattern together. This is beneficial for utilization of resources, and keeping the community stable. __________ Translated from Acta Ecologica Sinica, 2005, 25(6): 1264–1268 [译自: 生态学报]     

辽东栎林内不同小生境下幼树植冠构型分析

以黄土高原黄龙山林区辽东栎林内3个小生境（林下、林隙、林缘）下辽东栎天然更新幼树为研究对象,采用典型抽样法对辽东栎幼树侧枝、叶片和树冠的空间分布状况以及生物量分配状况进行调查分析,探讨微生境与幼树植冠构型特征的关系,明确辽东栎幼树对不同小生境的适应策略,为栎林经营和林分结构优化提供理论依据。结果显示：（1）3种生境下辽东栎幼树构型发生了可塑性变化,林下幼树树冠层次比较单一,林隙与林缘的幼树树冠层次更加丰富。（2）由林下至林缘,幼树的树高、枝下高呈逐渐减小的趋势,而地径变化趋势与之相反;幼树的冠幅、树冠面积、树冠率呈先增加后减小的趋势,并且林下与林隙、林缘的差异显著;幼树的总体分枝率、逐步分枝率、枝径比呈先增加后减小的趋势。（3）3种生境下,幼树的一级枝的枝长、直径与倾角随着树高的增加而呈减小的趋势,但3种生境的差异不显著;林下一级枝主要分布在冠层中上部,而林隙与林缘一级枝主要分布在冠层中下、中上部。（4）由林下至林缘幼树叶长、叶宽、单叶面积和比叶面积逐渐降低,而单株叶数、叶总面积、叶面积指数呈先增大后减小趋势;与其他2种生境相比林下叶片分布趋于冠层上部。（5）幼树地上部分生物量中林下主干生物量占83%,枝和叶生物量只占17%;而林隙与林缘虽然各部位生物量有所差异但比例基本一致,其中主干占66%左右,枝和叶生物量占34%左右。研究表明,林隙生境下幼树的构型优于林缘和林下生境,在今后栎林的经营中,可以通过适当间伐来增加林隙数量,为森林更新和结构的优化提供有利条件。     

Spatial patterns of tree recruitment in a relict population of Pinus uncinata: forest expansion through stratified diffusion

Aim To infer future changes in the distribution of isolated relict tree populations at the limit of a species’ geographical range, a deep understanding of the regeneration niche and the spatial pattern of tree recruitment is needed. Location A relict Pinus uncinata population located at the south‐western limit of distribution of the species in the Iberian System of north‐eastern Spain. Methods Pinus uncinata individuals were mapped within a 50 × 40‐m plot, and their size, age and reproductive status were estimated. Data on seed dispersal were obtained from a seed‐release experiment. The regeneration niche of the species was assessed based on the associations of seedling density with substrate and understorey cover. The spatial pattern of seedlings was described using point‐pattern (Ripley's K) and surface‐pattern (correlograms, Moran's I) analyses. Statistical and inverse modelling were used to characterize seedling clustering. Results Pine seedlings appeared aggregated in 6‐m patches. Inverse modelling estimated a longer mean dispersal distance (27 m), which corresponded to the size of a large cluster along the north to north‐eastward direction paralleled by an eastward trend of increasing seedling age. The two spatial scales of recruitment were related to two dispersal processes. The small‐scale clustering of seedlings was due to local seed dispersal in open areas near the edge of Calluna vulgaris mats: the regeneration niche. The long‐range expansion might be caused by less frequent medium‐distance dispersal events due to the dominant north‐westerly winds. Main conclusions To understand future range shifts of marginal tree populations, data on seed dispersal, regeneration niche and spatial pattern of recruitment at local scales should be obtained. The monitoring of understorey communities should be a priority in order to predict correctly shifts in tree species range in response to global warming.     

Regeneration of a marginal Quercus suber forest in the eastern Iberian Peninsula

Question: Small and marginal forest populations are a focus of attention because of their high biodiversity value as well as the risk of population decline and loss. In this context, we ask to what extent a small, marginal Quercus suber (Cork oak) population located in the eastern Iberian Peninsula (Valencia, Spain) has the capacity for self‐regeneration and what are the factors that determine its recruitment variability. Location: Quercus suber forest in Pinet (Valencia, Spain). Methods: We performed a spatially explicit sampling both of the recruitment and of the potential parameters that could account for the recruitment variability. Using regression techniques we model the recruitment occurrence and abundance, and then we test to what extent the model obtained is still constrained by the spatial dependence. Results: Quercus suber recruitment density ranges from 0 to 18.66 individuals/25m² (mean = 1.46, SD = 2.8), with a very skewed distribution. Recruitment is similar under Q. suber forests and under Pinus forests, but it is almost absent under shrublands. Thus the parameters that explain most of the recruitment variability in local vegetation types are: the presence and cover of shrubs (negative relationship with recruitment), the basal area of Q. suber and Pinus and the amount of bare soil (all positively related to recruitment). These parameters are strongly related to the ecological processes driving recruitment (i.e. dispersal and predation) and they remove most of the spatial dependence of recruitment. Most recruiters, however, are small, forming a seedling bank rather than growing to successfully colonize new habitats. Conclusion: The results suggest that although recruitment densities are not very high, they do not limit potential regeneration in the Pinet Q. suber forest. However, successful regeneration is not observed. If we aim to increase the Pinet Q. suber population size, land management measures need to provide appropriate conditions for both seedling establishment in shrublands (e.g. shrub clearing) and seedling growth in woodlands (e.g. Pinus logging).     

Using hierarchical sampling to understand scales of spatial variation in early coral recruitment

Ecological patterns are created by processes acting over multiple spatial and temporal scales. By combining spatially explicit sampling with variance components models, the relative importance of spatial scale to overall variability can be determined. We used a spatially structured experimental design in the Mombasa Marine National Park in Kenya to quantify variation in coral recruitment across four spatial scales (~1–1,000 m) and to generate hypotheses about processes affecting recruitment and potential sources of post-settlement mortality during early life history. For the dominant recruiting corals (Pocillopora spp.), variation in recruitment on surfaces protected from fish grazing was greatest at the largest spatial scale examined (1,000 m). We hypothesize that recruitment on protected surfaces varies mainly with larval delivery due to different lagoonal circulation and water flow between sites. Conversely, variation on surfaces exposed to fishes was greatest at the smallest spatial scale (1 m). We hypothesize that recruitment on exposed surfaces mainly reflects local differences in the scale and intensity of fish grazing, which may obscure larval delivery patterns. Spatial variation in recruitment can affect many ecological processes and factors, including growth, survival to maturity, the distribution of habitat, and variation in species interaction strengths. This study demonstrates how spatially explicit sampling, followed by variance components modeling to partition variance across scales, can help to identify potential drivers of patterns at each relevant scale.     

Predicting mechanisms across scales: amplified effects of abiotic constraints on the recruitment of yew Taxus baccata

Efforts to disentangle the mechanisms underlying large‐scale spatial patterns need to rely on multi‐scale approaches. We illustrate this key issue by analyzing the spatial consistency across scales of the effects of abiotic constraints on the regeneration of English yew Taxus baccata in Europe. We hypothesized that the recruitment rates in a given population would be strongly affected by water availability, which should result in a predictable pattern of regeneration success at regional and continental scales. Accordingly, we predicted: 1) at the regional scale water availability should be higher in sites occupied by yew populations than in random locations; 2) at the regional scale regeneration success should decrease when water availability is lower; and 3) at the continental scale, regeneration success should also decrease where water availability is lower, resulting in decreasing regeneration southwards. To test these predictions we first monitored seedling emergence and survival in two central Spanish populations over two years, and confirmed that yew recruitment is limited by water availability. Additionally, our analysis supported predictions 1 and 2: water availability strongly affected yew presence and regeneration success. At the continental scale (prediction 3), our results confirmed lower regeneration in southern European populations. Assessing the effect of climatic constraints across scales in key population parameters can help to improve large‐scale assessments of impacts of climate change on biodiversity.     

Fire disturbance and forest structure in an old‐growth Pinus ponderosa forest,southern Cascades,USA

Questions: Did fire regimes in old‐growth Pinus ponderosa forest change with Euro‐American settlement compared to the pre‐settlement period? Do tree age structures exhibit a pattern of continuous regeneration or is regeneration episodic and related to fire disturbance or fire‐free periods? Are the forests compositionally stable? Do trees have a clumped spatial pattern and are clumps even‐ or mixed‐age? How might information from this old‐growth forest inform current restoration and management practices? Location: A 235‐ha old‐growth forest in the Ishi Wilderness, southern Cascade Mountains, California. Methods: Age, size, and spatial pattern of trees were quantified in seven stands. Fire history was reconstructed using fire scar dendrochronology. The influence of fire on stand structure was assessed by comparing fire history with age, size, and spatial structure of trees and identifying and measuring trees killed by two recent fires. Results: Species composition in plots was similar but density and basal area of tree populations varied. Age structure for P. ponderosa and Quercus kelloggii showed periods of episodic recruitment that varied among plots. Fire disturbance was frequent before 1905, with a median period between fires of 12 years. Fire frequency declined after 1905 but two recent fires (1990, 1994) killed 36% and 41% of mostly smaller diameter P. ponderosa and Q. kelloggii. Clusters of similar age trees occurred at scales of 28‐1018 m² but patches were not even‐aged. Interactions between tree regeneration and fire promoted development of uneven age groups of trees. Conclusions: Fire disturbance strongly influenced density, basal area, and spatial structure of tree populations. Fire exclusion over the last 100 years has caused compositional and structural changes. Two recent fires, however, thinned stands and created gaps favorable for Q. kelloggii and P. ponderosa regeneration. The effects of infrequent 20th century fire indicate that a low fire frequency can restore and sustain structural characteristics resembling those of the pre‐fire suppression period forest.     

五台山林线过渡带华北落叶松格局过程和尺度分析

林线过渡带作为气候变化的预警区,有很重要的研究意义,林线过渡带中人工林的生存与发展对自然保护区景观生态系统影响显著。选取五台山林线内占绝对分布优势的华北落叶松为研究对象。设置50m×50m样地,随机选取5个10m×10m样方进行群落物种信息收集,对乔木的胸径和位置信息进行调查,利用点格局方法和CSR(完全空间随机模型)、HP(空间异质性过程模型)、RL(随机标签模型)对华北落叶松的活立木和枯立木的格局过程进行0—25m尺度上的分析,结果发现:活的华北落叶松平均胸径在11.54cm,死的华北落叶松平均胸径是8.27cm,这个对于30年以上华北落叶松来说胸径值偏小,其生长慢的特点是和林线这个生境特点相适应的。华北落叶松枯立木的聚块很大,在0—15m上都是聚集分布;活立木聚块小出现在0—3m、和21m上。空间异质性过程模型模拟的格局与活立木实际格局差异检验不显著,说明空间异质性可以很好解释活立木格局的成因。随机标签模型模拟结果表明现有活立木和枯立木只在21m附近出现负相关,主要是负密度制约效应是导致的华北落叶松死亡的主要原因,而且对幼苗到幼树的影响最大。同时推测灌木和华北落叶松幼苗和幼树的种间相关作用与其死亡也有一定关系。     

Size-gradient differences in the spatial patterns and processes of Pinus armandii in forest lines of Li Mountains,North Central China

Pinus armandii is one of the local dominant trees in forest lines of Li mountains. The population pattern of Pinus armandii in the forest line is greatly influenced by individual size, and individual size has effect on ecological process. Sampling plot 50 m × 50 m was established in Shunwangping Scenic spot of Li Mountains to obtain location and diameter at breast height (DBH), and spatial point pattern method was applied to explore spatial pattern and ecological process of individuals at different sizes. The results showed: (1) Individual size of Pinus armandii had a parabolic distribution, 10–15 cm DBH individuals had most aggregation scales, < 5 cm DBH individuals had least aggregation scales, and the common scale of individual aggregation is r < 10 m. (2) Homogeneous Thomas null model and Inhomogeneous Thomas null model analysis showed that seed dispersal and interaction between seed dispersal and environmental heterogeneity had significant impact on the pattern of all individuals, seed yield of Pinus armandii was the key to the development of the population, Inhomogeneous Poisson null model analysis showed that environmental heterogeneity more significantly affected the pattern of 5–10 cm DBH individuals, the 5–10 cm population was the more critical stage of the survival of Pinus armandii in the forest line. (3) Intra-specific correlation analysis showed that significant positive correlation happened between four size groups (< 5 cm, 5–10 cm, 10–15 cm, > 15 cm), individuals at 10–15 cm had wider positive correlation scales with other three groups, it might be that quantity of individuals in 10–15 cm was greatest. The size difference of individual in species population had a great influence on the pattern, the results could help to understand the significant impact factors and regeneration obstacles of Pinus armandii in the forest line at different stages.     

Large-Scale Patterns of Quercus ilex, Quercus suber, and Quercus pyrenaica Regeneration in Central-Western Spain

In Central-Western Spain, forests and woodlands composed of Quercus sp. support outstanding levels of biodiversity, but there is increasing concern about their long-term persistence due to a lack of regeneration. We hypothesize that this regenerative lack is operating on a large geographic scale; that there are differences in the abundance of regeneration between three oak species; that oak regeneration is governed mainly by forest management and structure; and that shrubs act as important physical protectors of seedlings and saplings. We analyzed whether densities of oak seedlings and saplings in several size classes were related to stand-structure, understory, and physiographic variables potentially affecting regeneration. Data collected at a regional level (1 km × 1 km grid) by the Spanish Forest Inventory were evaluated from 2,816 plots. Results revealed that regeneration failure was common for all size categories, from small seedlings to large saplings, and for the three oak species studied, especially the evergreens. Of the Quercus ilex, Q. suber, and Q. pyrenaica plots studied, 49%, 62%, and 20% were lacking any small seedlings, and 82%, 96%, and 56% did not have any large saplings, respectively. Regeneration was positively correlated with tree cover and density, especially of small and medium-sized trees, and negatively correlated with the presence of large trees, indicating that regeneration failure is mostly associated with more open, uniform, and/or aged woodlands. Regeneration densities of Q. ilex and Q. suber were positively correlated with all understory variables, suggesting that the presence of pioneer shrubs represent a major safe site for early tree recruitment, independent from specific shrub species.     

Long‐term dynamics in a planted conifer forest with spontaneous ingrowth of broad‐leaved trees

Question: What are the age structure and growth trends in a 160‐year old not‐managed Pinus sylvestris plantation with spontaneous development of Quercus robur and can recruitment of Q. robur be related to the radial growth pattern of the P. sylvestris overstorey? Location: Mattemburgh forest reserve, The Netherlands. Methods: Throughout the forest, we sampled 103 oaks and 102 pines with an increment corer. Tree ring widths were measured and cross‐dated to produce mean ring width series. With these data we determined tree ages, investigated growth trends and identified growth releases and suppressions. Results: Q. robur is uneven‐aged: some individuals recruited around 1925, but most reached coring height in the 1940s. The latter recruitment period related to a transition from stressed to released growth of the overstorey pines, growth releases of the oldest Q. robur and occurrence of P. sylvestris regeneration. No further recruitment has taken place since 1950. Conclusions: This study demonstrates that an old pine plantation can develop spontaneously into well‐structured pine forest with an understorey of oak and pine. However, understorey recruitment in these forest types is not a continuous process and in this case a single allogenic canopy disturbance triggered its establishment.