Larger Diameter At Breast Height Research Articles

Using radio frequency identification (RFID) technology to characterize nest site selection in wild Japanese tits Parus minor

Selecting a suitable nest site is critical to the survival and reproduction of birds. Prospecting allows individuals to gather information on the local quality of potential future breeding sites, which may help them make the best nest site selection decision. However, few studies have focused on the direct links between the prospecting activity of breeders and subsequent nest site selection. In this study, we investigated the prospecting pattern of Japanese tits Parus minor during the pre‐breeding period of the first breeding attempt and whether nest site characteristics influence their nest box visiting behaviour and occupied nest site. We used radio frequency identification (RFID) to track the movements of Japanese tits visiting nest boxes and compared nest site characteristics between visited and unvisited (control) nest boxes, as well as between visited and occupied nest boxes. We found that Japanese tits started visiting nest boxes approximately 20 days before breeding, visited an average of six nest boxes and eventually chose the most visited nest box for breeding activities. Japanese tits were more likely to visit nest boxes that had less canopy cover and lower shrub density but a greater total number of surrounding trees and ultimately chose breeding nest boxes with a smaller entrance inclination, in nesting trees with a larger diameter at breast height (DBH) which were surrounded by trees with a larger DBH. Our results suggest that Japanese tits visit several potential breeding sites before choosing breeding nest boxes and that nest site characteristics can influence their prospecting activity and nest site selection.

Carbon Sequestration of Above Ground Biomass Approach in the Rehabilitated Mangrove Stand at Jepara Regency, Central Java, Indonesia

Highlight Research Mangrove rehabilitation area has a better potential for carbon sequestration The more trees that grew and developed with a large DBH size the more affected the biomass, carbon content and carbon sequestration of mangroves. Among the four species studied, mucronatais characterized by highest carbon density storage Temperature and salinity affect the value of mangrove biomass, carbon content, and carbon sequestration Abstract Among its many advantages, mangroves have a function as carbon sequestration and storage. The aim of this study was to determine the differences in the ability of various rehabilitated mangrove species of carbon Sequestration of Above-Ground Biomass. This study was conducted from June 2020 to December 2021 in Kedung, Mlonggo, and Keling Subdistricts, Jepara Regency, Central Java, Indonesia. The mangrove plantation was a result of a rehabilitation programme sponsored by a society and the local government since 2009. Carbon sequestration measurement in tree biomass was estimated by a non-destructive method i.e., by measuring the Diameter at Breast Height (DBH). Statistical analysis to determine the relationship between carbon storage in several species of mangroves and the environmental factors were performed using XL stat 2022. There were 4 (four) mangrove species found i.e., Avicennia marina (Forssk) Vierh, Rhizophora apiculata (Blume), Rhizophora mucronata (Lamk), and Sonneratia alba Sm. The highest CO2 absorption (397.21 tons ha-1) was obtained both in Kedung and Mlonggo stations with R. mucronata, whereas in Keling station with R. apiculata the absorption was 54.27 tons ha-1. The results of Principal Component Analysis (PCA) showed that the number of trees and DBH had a relationship with biomass, carbon content, and carbon absorption. Diameter at Breast Height in mangrove species can be used as indicators to assess carbon sequestration in Above Ground Biomass.

Insectivorous Bats in Eastern Mediterranean Planted Pine Forests—Effects of Forest Structure on Foraging Activity, Diversity, and Implications for Management Practices

Bats are primarily forest mammals and forest structure may affect their communities through the level of vegetation clutter. Pine plantations are typically even-aged managed forests that lack structural complexity. However, an understory layer can enhance the heterogeneity of these forests, making them suitable for several animal taxa. We hypothesized that species composition, richness, and foraging activity of insectivorous bats in pine plantations vary according to forest structure, specifically with the density of the understory. We measured pine density, Diameter at Breast Height (DBH), canopy closure, and vegetation cover of 29 pine (Pinus halepensis) plantations of the Judean Lowlands, Israel, and collected acoustic data on resident bats. We found that bat species richness and total activity increased in forests with large tree DBH and dense shrubs. Cluttered-habitat species foraged preferentially in forests with large tree DBH and high pine density, while open-habitat species preferred forests with well-developed canopies and dense shrubs. Pipistrellus pipistrellus and Eptesicus serotinus foraged in mature forests with well-developed bushes and these species are endangered in Israel. We conclude that mature planted pine forests with a well-developed under-canopy are suitable foraging grounds for insectivorous bats. Management plans for planted pine forests should consider our findings to support bat populations, including rare and endangered species.

Current Status and Recent Stand Structure Dynamics in Mixed Silver Fir—European Beech Forests in Croatian Dinarides: Are There Differences between Managed and Unmanaged Forests?

The environmental, social and economic potential of Dinaric uneven-aged forests along with the complex stand dynamics influenced by different long-term management approaches and environmental factors require comprehensive forest monitoring. This study aimed to explore differences in the current status and recent past dynamics of stand structures between unmanaged and managed mixed fir-beech forests in the Croatian part of the Dinaric Alps using large-scale data from an established monitoring system. From the 74 permanent sample plots distributed within the forest type measured in 2008 and re-measured in 2019, we stratified four strata (types of management regimes): (1) forests out of regular management and tree harvest for at least 30 years, (2) managed state forests on carbonate bedrock, (3) managed state forests on non-carbonate bedrock and (4) managed private forests. In each sample plot, 34 structural attributes were computed to assess indicators of their current status and recent past dynamics of stands in the studied forests. An increasing Q shape diameter distribution with a high number of large and very large trees characterize unmanaged forests and managed forests on non-carbonate bedrock. In managed state forests and private forests, variable (rotated sigmoid) and constant (negative exponential) results were obtained, respectively. Principal component analysis (PCA) distinguished managed and unmanaged forests with decreasing harvest volume and recruitment, increasing basal area, number of very large trees, average diameter at breast height (DBH), crown defoliation of firs and basal area of died beech trees. The current structure, recent and expected stand dynamics in the unmanaged forests (accumulation of standing volume, increase of large diameter trees and large snags, large share of beech, large mean DBH) can be recognized as old-growth attributes. The differences between the studied forest types, potential of both unmanaged and state managed fir-beech forests and approaches to sustain multifunctional forest management in the Dinaric region were discussed.

Species-specific control of DBH and landscape characteristics on tree-to-tree variability of sap velocity

The substantial tree-to-tree variability of transpiration poses a major challenge to a reliable stand-scale quantification of transpiration. The diameter at breast height (DBH) and landscape characteristics have been identified as drivers of tree-to-tree variability, but it remains unclear if their control on sap velocity varies between species-specific water-use and environmental conditions. We hypothesized that their controls are specie-specific, such as the temporal dynamic of their relative importance. To test our hypotheses, we used a multi-species stand that include 37 trees equipped with sap-flow sensors from four species representing the dominant species in central Europe. We analysed the daily relative importance of DBH, landscape slope, aspect, flow accumulation, and topographical position. We found that tree-to-tree variability of sap velocity was mainly dependent on DBH for oak (twice higher relative importance than other species) and on landscape characteristics for beech (36% higher relative importance than other species) and conifers. The temporal dynamics of the relative importance of most tested drivers was found to be species-specific and linked to root-related aspects in response to hydro-meteorological conditions. During dry summer months, the daily relative importance of oak's DBH increased to almost 60% to be three times higher than the value for beech. In contrast, the relative importance of flow accumulation was always two to three times higher for beech trees than oak and conifer trees. This indicated that larger oak trees accessed deeper water sources than smaller oaks. However, the shallower root architecture of beech trees involved a higher dependence on shallow soil water because a larger DBH is seemingly not enhancing the tree's capacity to explore deeper soils. These new insights emphasize the critical importance of accounting for DBH and landscape characteristics through a species-specific and temporally dynamic correction in further approaches for upscaling of sap-flow data from individual tree to stand-scale.

Relationship of H/D and crown ratio and tree growth for Chamaecyparis obtusa and Cryptomeria japonica in Korea

This study was conducted to suggest the necessity of regulated stand density control in order to maintain the ratio of height to diameter at breast height (H/D ratio) of Hinoki cypress (Chamaecyparis obtusa) and Japanese cedar (Cryptomeria japonica) in South Korea. A total of 2,000 (1,000 each) Hinoki cypress and Japanese cedar were cut from various regions of South Korea, and their diameter at breast height (DBH), height and clear length were measured. The two species’ regional means of H/D ratio and crown ratio were then computed and compared to find the relationship with tree growth. The result of analyzing the relationship between the H/D ratio and tree growth by DBH class is as follows, 77.0% for small DBH class, 62.5% for medium DBH class, and 45.9% for large DBH class, with overall mean of 61.8%. The annual means of DBH growth were 4.6 mm, 7.4 mm, and 8.2 mm respectively for small, medium, and large DBH classes. As the DBH class went up, the H/D ratio decreased, showing a negative correlation (p < 0.0001) with the tree growth rate. However, the crown ratio showed a significant correlation with tree growth. Japanese cedar’s H/D ratios by DBH class were 100.5% for small, 74.9% for medium, and 53.6% for large, while its mean annual DBH growth were 5.1 mm, 7.6 mm, and 10.0 mm, from small to large DBH class respectively. Similar to that of Hinoki cypress, Japanese cedar’s H/D ratio showed a negative correlation with the growth rate (p < 0.0001), but no significant relationship could be established between the crown ratio and the tree growth. In both arboreal species, the correlation between the H/D ratio and growth rate is negative, and no significant correlation could be formulated between crown ratio and tree growth. In conclusion, both tree species tended to have a higher H/D ratio and a lower growth rate in small DBH class, while H/D ratio decreased and growth rate increased As DBH class got larger.

Mechanical Characteristics of the Fine Roots of Two Broadleaved Tree Species from the Temperate Caspian Hyrcanian Ecoregion

In view of the important role played by roots against shallow landslides, root tensile force was evaluated for two widespread temperate tree species within the Caspian Hyrcanian Ecoregion, i.e., Fagus orientalis L. and Carpinus betulus L. Fine roots (0.02 to 7.99 mm) were collected from five trees of each species at three different elevations (400, 950, and 1350 m a.s.l.), across three diameter at breast height (DBH) classes (small = 7.5–32.5 cm, medium = 32.6–57.5 cm, and large =57.6–82.5 cm), and at two slope positions relative to the tree stem (up- and down-slope). In the laboratory, maximum tensile force (N) required to break the root was determined for 2016 roots (56 roots per each of two species x three sites x three DBH classes x two slope positions). ANCOVA was used to test the effects of slope position, DBH, and study site on root tensile force. To obtain the power-law regression coefficients, a nonlinear least square method was used. We found that: 1) root tensile force strongly depends on root size, 2) F. orientalis roots are stronger than C. betulus ones in the large DBH class, although they are weaker in the medium and small DBH classes, 3) root mechanical resistance is higher upslope than downslope, 4) roots of the trees with larger DBH were the most resistant roots in tension in compare with roots of the medium or small DBH classes, and 5) the root tensile force for both species is notably different from one site to another site. Overall, our findings provide a fundamental contribution to the quantification of the protective effects of forests in the temperate region.

The variability of stemflow generation in a natural beech stand (Fagus orientalis Lipsky) in relation to rainfall and tree traits

AbstractStemflow (SF) has been recognised as an important process that can exert considerable effects on the hydrology, biogeochemistry, and ecology of wooded ecosystems. The aim of this study was to quantify the relationship between SF (yields and funnelling ratios, FRs) of beech (Fagus orientalis) trees and rainfall characteristics, to evaluate the effects of tree traits on SF yield and the magnitudes of FRs in differing rainfall classes. Event‐based measurements were carried out from April 2016 to November 2017 during the leafed‐out periods in a natural uneven‐aged beech stand located in the Hyrcanian forest of Iran. Tree density in the studied plot was 188 trees ha−1 with a basal area of 51 m2 ha−1. SF volume was measured in three diameter classes (10–40, 40–70, and &gt;70 cm; n = 3 per class). During the 25 rainfall events SF, SF%, and FR were 3.22 mm, 0.41%, and 1.11 on average, respectively. The linear regression analysis revealed that gross rainfall had the strongest correlation with SF yield and FR (P value &lt;.01). The linear regression with the trees structural traits indicated that canopy projected area, diameter at breast height (DBH), and mosses cover percentage, respectively, strongly influence SF yield for rainfall &lt;15 to &gt;50 mm. FR significantly decreased with increasing tree height, DBH, and mosses cover percentage (all P values &lt;.05). Smaller trees concentrated more SF than tall and large DBH trees. Pearson correlation analysis indicated tree height, canopy projected area, and MCP were positively and significantly correlated to DBH (P value &lt;.01; r ≥ .87). Therefore, SF generation in the present study is more associated with DBH. Our findings could assist managers to optimise the management strategies of deciduous forest via promotion of some large DBH trees along with small DBH trees to optimise water inputs via SF in water‐limited forest ecosystems.

Effect of spatial heterogeneity of plant communities on air PM10 and PM2.5 in an urban forest park in Wuhan, China

Understanding the associations between plant community characteristics and their effects on ambient particulate matter (PM) is a central theme of urban forest park management and development so as to maximise ecological services. The ambient PM concentrations and spatial distribution of plant communities in urban forest parks are not random, but show strong spatial patterns. We selected Ma'’anshan Mountain Forest Park in Wuhan, China, as an example of a typical park. The monitoring network consisted of 44 different plant communities at various locations that were monitored in December, April, July and October. The effects of the spatial heterogeneity of plant communities on ambient PM10 and PM2.5 were analysed using a spatial model to investigate the relationships between plant communities and levels of ambient PM. The results showed that differences in levels of ambient PM among plant communities resulted from both their composition and location. However, when spatial patterns were corrected, large seasonal variations in PM patterns were revealed due to seasonal differences in the characteristics of plants communities and pollution emissions. Significantly lower ambient PM concentrations were recorded in small-scale plant communities that were mainly distributed in the mountain areas and comprised of Pinus, Platycladus, Cunninghamia, Taxodium, Metasequoia, Quercus, Platycarya, and Cinnamomum. Correlation results revealed that six factors — diameter at breast height (DBH), leaf area index (LAI), canopy area (CA), slope (S), distance from pollution source (DPO) and distance from edge of park (DP) — had significant effects on ambient PM reduction. We found that ambient PM decline was primarily attributed to large DBH and community DPO. The effect of small-scale plant communities on ambient PM decline was the most significant in December, followed by October, April, and July. These plant community attributes are the basis of forest ecological services, and our findings indicate that the regulation of plant communities could improve urban forest services by increasing the efficiency of ambient PM concentration reduction.

Effects of pollen contamination and non-random mating on inbreeding and outbreeding depression in a seedling seed orchard of Eucalyptus urophylla

Microsatellite loci were used to assess pollen contamination and mating patterns in an Eucalyptus urophylla seedling seed orchard (SO2) along with inbreeding and outbreeding depression in a second generation progeny test (PT2) established with SO2 seeds. We measured survival, diameter at breast height (DBH), and height (H) in SO2, PT2, and two other stands (SO1, PT) located at a distance of at least 210 m from SO2. Pollen contamination was substantial (11.9%), with the largest proportion coming from the closer SO1 stand (6.1%) than PT (4.7%) and 1.1% from unknown sources. The pollen dispersal pattern was isolation by distance but reached long distances (600 m). PT2 offspring were mainly the result of outcrossing (92.6%), but mating in SO2 was not random due to self-fertilization (7.4%), mating among relatives (6.6%), correlated mating (13.7%), and high male fertility success of trees with large DBH. Thus, families are a mixture of different levels of relatedness and some inbreeding (12.7%). Inbreeding depression was variable among traits; it was higher for selfing (39.6–49.5%) than mating among relatives (11.6–20.9%) and higher for mating between full-sibs (4.4%) than half-sibs (2.2%). Outbreeding depression was higher for pollen immigration from less improved sources (33.9–41.2%). Non-random mating resulted in a coancestry (0.152) higher than expected for half-sib families and an overestimation of heritability by 17.8%. Our results indicate that isolation distances greater than 600 m are necessary to avoid pollen contamination in Eucalyptus seed orchards. Furthermore, pollen immigration results in outbreeding depression, and selfing results in higher levels of inbreeding depression than mating among related trees.

Carbon in Mature Native Forests in Australia: The Role of Direct Weighing in the Derivation of Allometric Equations

Accurate estimates of forest biomass are essential to understand the contribution of forests to climate change mitigation efforts. In this manuscript, we report on biomass determinations for 586 directly weighed trees located in three important native forest areas in Australia. The sites were paired according to management strategy; i.e., managed for periodic cycles of harvest or conservation only. The key aim of the work was to test whether non-site specific available biomass relationships are reliable, especially in the estimation of the biomass of trees with a large diameter at breast height (DBH). The above-ground carbon (AGC) estimates for largely undisturbed forests ranged from approximately 200–400 t C ha−1. Existing allometric equations were generally poor at estimating biomass for mature trees, especially those of large DBH. Direct weighing of biomass ensured a degree of certainty in the results that cannot be associated with previous studies that relied on sub-sampling, or with studies that relied on existing allometric equations. Thus, caution should be exercised when interpreting the results of previous studies that did not rely on direct weighing of the biomass in the context of decisions around optimum forest management regimens, and the contribution of mature forest stands to the global carbon balance.

Resin yield of Pinus nigra and Pinus sylvestris in the Slovenian Karst

The aim of our research was to study the impact of various environmental factors on the resin production of pines in the Slovenian Karst. Five plots were established % three in Pinus nigra (Arnold) stands and two in Pinus sylvestris (L.) stands. On each plot, the 19-20 most vigorous dominant or codominant trees with a minimum diameter at breast height (DBH) of 20 cm were selected and their resin yield analysed in 2012. Resin yield in P. nigra was considerably higher than that in P. sylvestris. The average resin yield per tree during the study period of 102 days was 1.144 kg for P. nigra and 0.612 for P. sylvestris. There were substantial differences in resin yield among individual trees in the study period: 0.336-2.487 kg for P. nigra and 0.249-1.270 kg for P. sylvestris. The resin yield in P. nigra was considerably higher for the trees with larger DBH, while this was not the case in P. sylvestris. Tree species was the most important factor in resin yield. Increased precipitation resulted in higher resin yields on most plots, whereas better site productivity positively affected resin yield on all P. nigra plots but not on P. sylvestris plots.

Modeling the diameter distribution of Larix olgensis plantation based on thinning effects.

In 1974, five permanent sample plots of Larix olgensis plantation were established in Mengjiagang forest farm in Heilongjiang Province, which included one control plot and four thinning plots with different thinning treatments (remove 3.7%-49.7% of the basal area). Diameter at breast height (DBH) for each tree (19-59 a) of the five plots was remeasured 31 times from 1974 to 2014. The three parameters Weibull function was used to describe the DBH distribution of different ages for the five plots. The dynamic changes and the effects of thinning on the diameter distribution curves and the three parameters of Weibull function were analyzed. Based on the thinning effects, the parameter prediction model (PPM) of simultaneous equations system was developed and the parameters were estimated by three-stage least squares method (3SLS) and error-in-variable method of simultaneous equations. The results showed that the diameter distribution curves with stand age changed from higher peak with narrow DBH range to lower peak with large DBH range for unthinned stand (control plot). For thinning plots, the skewness was more right-hand with higher peak, narrow DBH range, and increased asymmetry of the curves after thinning. Increasing with thinning intensity, more trees of small or middle sizes were cut and the curves of diameter distribution were obvious left-truncted higher peak with narrow DBH range than before thinning. The parameter a of the Weibull function increased with thinning intensity and the parameter b decreased. The parameter c was not influenced by lower intensity thinning, but decreased by higher thinning intensity. The fitting results for the PPM of simultaneous equations system showed that predicting models for the parameter b were best (R2>0.98) and the R2 for model of the parameter c was larger than 0.91. The method of 3SLS was as good as the error-in-variable method, and there was no significant diffe-rence. The results of validation for the two methods showed that, the precision of the three prediction models was >97%, and the fitting efficiency (EF) was >0.92. The parameter prediction mo-dels developed based on the effects of thinning performed well and could be used to predict the dynamic change of diameter distribution and to provide suitable management of L. olgensis plantation.

Nonlinear mixed-effects branch diameter and length models for natural Dahurian larch (Larix gmelini) forest in northeast China

We developed the generalized branch diameter and length models using the multi-level nonlinear mixed-effects techniques for the natural Dahurian larch ( Larix gmelini ) forest in northeast China. Dahurian larch (Larix gmelini) is the most commercially cultivated timber species in northeastern China due to its ecological prevalence and its superior wood attribute. However, its timber quality was largely driven by the crown architecture, i.e., the number, size and distribution of branches. The majority of branch-level models in the literature are focused on planted forests, which have substantially different crown architecture than that grown in natural mixed forests. Therefore, the goal of this investigation was to develop branch diameter and length models for Dahurian larch that are grown in natural mixed forests. A multi-level nonlinear mixed-effects model technique, including the fixed-effects, random-effects, variance functions and correlation structures, was employed to develop the branch growth models. The results suggested that the cumulative branch diameter and length were both increased with the increases of branch depth into the crown. Diameter at breast height (DBH) had significant positive influences on the branch size; however, tree height (HT) produced negative influences on the branch size, i.e., larger DBH and smaller HT could lead to larger branch size. Model fitting and validation results confirmed that we should avoid developing over-complex models from the perspective of application. As for the branch diameter and length models in our study, addressing the stand and tree level effects as random component were quite reliable and accurate for predicting the branch growth process of Dahurian larch in northeastern China.

不同径级国槐行道树重金属富集效能比较

PDF HTML阅读 XML下载 导出引用 引用提醒 不同径级国槐行道树重金属富集效能比较 DOI: 10.5846/stxb201403300592 作者: 作者单位: 中国林业科学研究院林业研究所,中国林业科学研究院林业研究所,中国林业科学研究院林业研究所,中国林业科学研究院林业研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家"十二五"(2011BAD38B03)科技支撑计划项目 Variation of heavy metal enrichment efficiency in roadside trees of Sophora japonica L. with different diameters at breast height Author: Affiliation: Forestry Research Institute, CAF,Forestry Research Institute, CAF,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:采用ICP-OES测定北京市台基厂大街行道树国槐各器官中7种重金属(Cd、Cr、Ni、Cu、Mn、Pb、Zn)含量,比较不同径级国槐重金属富集效能。结果表明:国槐中重金属含量因胸径级、器官、元素种类不同而存在差异。各径级国槐重金属含量大小总体趋势为Zn > Mn > Cu > Pb > Cr > Ni > Cd,各器官中树皮和根对重金属的吸收能力最强,其次是叶和枝,树干对重金属的吸收能力最弱。不同径级国槐对重金属的富集能力存在差异,表现为小径级 > 中径级 > 大径级。国槐各器官中重金属积累量大小顺序为根 > 干 > 枝 > 叶,重金属积累量随着胸径级扩大和生物量的增加而增加。综合比较不同径级国槐重金属年均积累量、单位面积富集量和单位空间富集量,小径级(20≤DBH < 30cm)国槐富集效能最高。 Abstract:The concentration of heavy metals (Cd, Cr, Cu, Mn, Ni, Pb, Zn) in roadside tree of Sophora japonica L. and their organs along Taijichang Street was measured by using the Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) to compare the heavy metal enrichment capacity between different diameter classes. The results showed that the concentration of heavy metals in different diameter classes of Sophora japonica L., the concentration of the same element in different organs, and the concentration of different elements in the same organ were all different. In general, heavy metal concentration in Sophora japonica L. followed the order of Zn > Mn > Cu > Pb > Cr > Ni > Cd. The heavy metal absorption capacity in all organs followed the order of bark > root > leaf > branch > stem. Meanwhile, the study showed that the enrichment capacity of Sophora japonica L. in diameter at breast height (DBH) of small size was stronger than those of medium and large size. Heavy metal accumulation in different organs followed the order of root > trunk > branch > leaf, which also increased in Sophora japonica L. with the increase of DBH and biomass. By comparing the accumulation per year, the bioenrichment unit area as well as the bioenrichment unit space of heavy metals with medium and large DBH, Sophora japonica L. of smaller DBH (DBH less than 30 cm or more than 20 cm) had higher enrichment efficiency. 参考文献 相似文献 引证文献

抚育间伐对蒙古栎次生林生长的影响

Forest management strategies for natural secondary forests require appropriate thinning methods that are stable,efficient,and sustainable. In the present study,we investigated the influence of thinning intensity on tree growth and forest structure. We established three different thinning regimes( light,medium,and heavy) and a no-thinning( control)treatment in young( 15 years old) and middle-aged( 35 years old) Mongolian oak( Quercus mongolica) secondary forests in Liaoning Baishilazi National Nature Reserve. Data were collected 8 years and 26 years after thinning. In the young forest,we found that light,medium,and heavy thinning significantly influenced the average diameter at breast height( DBH) of the stand and its periodical increment. After 8 years,the average stand DBHs in the light,medium,and heavy thinning plots were 2.1 cm,1.3 cm,and 2 cm larger,respectively,than that in control plot. On the contrary,thinning intensity had no significant influence on stand volume growth. After 8 years,the total increments of stand volume in trees showing anincrease in DBH of 12 cm after the light,medium,and heavy thinning treatments were 0. 97,1. 03,and 1. 21 times higher,respectively,than those of control trees. The control stand and stands subjected to each thinning treatment exhibited a left single-peak mountain shape,implying that most trees were classified in the small DBH class. In the middle-aged forest,we found that thinning significantly influenced not only the average stand DBH but also the stand volume growth and its total increment. An increase in the thinning intensity resulted in a greater increase in the average stand DBH. In addition,heavy thinning significantly influenced the periodical increment of the average stand DBH. After 26 years,the average stand DBHs in the light,medium,and heavy thinning plots were 0. 3 cm,1. 7 cm,and 5. 1 cm greater,respectively,than that of control plot. After 26 years,the total increments of stand volume in trees showing an increase in DBH of 12 cm after the light,medium,and heavy thinning treatments were 1. 97,1. 65,and 1. 63 times higher,respectively,than that of control trees. Stands subjected to the light and heavy thinning treatments exhibited a right singlepeak mountain shape,implying that most trees were classified in the large DBH class and therefore the forest structure was considered to be optimal. On the contrary,the control stand and the stand subjected to the medium thinning treatment exhibited a left single-peak mountain shape,implying that most trees were classified in the small DBH class. The results of our comprehensive analysis of the impacts of age class and thinning intensity on forest growth suggest that the most effective forest management strategy for Mongolian oak secondary forests is to conduct light,medium,and heavy thinning in young forests,but only heavy thinning in middle-aged forests. However,to achieve an increase in total volume growth,the stand density should be ≥1600 trees per hectare.

弄岗喀斯特季节性雨林枯立木多度的空间分布及影响因子

Standing dead trees are an important part of the composition of forest structure. Therefore, studying the spatial distribution of standing dead trees abundance and its impact factors has provided much needed insights to understand the mechanism of tree death and the succession of community. According to a 15-hm2 study plot investigation in northern tropical karst seasonal rain forest, Nonggang, southern China, the standing dead trees with DBH(diameter at breast height) greater than 1 cm were classified. And the spatial distribution of standing dead trees abundance and its impact factors like spatial, topographic and communities' were analyzed using zero-inflated negative binomial models. The results showed that:(1) there were 2254 standing dead trees in the plot with an average DBH of 6.21 cm. And the maximum DBH was 61.86 cm. The DBH size-class structure of standing dead trees exhibited an inverse J-shaped pattern. Dead trees with smaller DBH distributed more densely in the high elevation areas, whereas those with larger DBH had a higher density in the valley bottoms.(2) Standing dead trees with smaller DBH displayed an clumped distribution, while those with larger DBHs had a random distribution. And the abundance of standing dead trees displayed different spatial autocorrelation at different spatial scales.(3) As DBH size-class increased, the correlation between abundance and elevation, abundance and slope gradually increased, while that of abundance and convex, abundance and spatial adjacent factors gradually decreased. The correlation between abundance and spatial adjacent factors increased as unit spatial scale increased, and the correlation between abundance and convex, elevation, slope and community type factors gradually decreased as unit spatial scale increased. There were different spatial distribution of standing dead trees abundance existed as the scales changed. And the spatial, topographic factors, different communities have significant impact on these spatial patterns of standing dead trees abundance and the diameter class structure. In turn, the spatial distributions of standing dead trees have significant influence on the light resources and the distribution of woody debris, and then impact the species composition of communities.

Population structure and spatial pattern of main tree species in secondary Betula platyphylla forest in Ziwuling Mountains, China.

This study investigated a typical secondary Betula platyphylla forest in the Ziwuling Mountains, Loess Plateau, China. In the sample plot, the DBH (diameter at breast height) class structure of B. platyphylla was bimodal. Individuals with small and large DBH values were abundant. The DBH structures of Quercus wutaishanica and Pinus tabulaeformis were close to that of the logistic model, thus suggesting the increasing population of these species. B. platyphylla and Populus davidiana showed random spatial distributions at almost all scales. However, Q. wutaishanica and P. tabulaeformis were significantly clumped at small scales. B. platyphylla had a negative spatial relation with Q. wutaishanica at small spatial scales. P. tabulaeformis and Q. wutaishanica showed negative spatial correlations at small scales, but they had positive correlations at large scales. These results suggest that P. tabulaeformis and Q. wutaishanica shared habitat preferences at these scales. In the future, the secondary B. platyphylla forest in the Ziwuling Mountains in the Loess Plateau will probably change into a multi-species mixed forest (Quercus–Pinus mixed forest). Assisted restoration strategies must be employed to improve the regeneration dynamics of the forest in the long term.

Effects of site, silviculture and seedlot on wood density and estimated wood stiffness in radiata pine at mid-rotation

To understand the underlying control of patterns of important wood properties is fundamental to silvicultural control of wood quality and genetic selection. This study examines the influences of site, silviculture and seedlot on diameter growth, wood density and estimated wood stiffness in mid-rotation radiata pine (Pinus radiata D Don) stands across New Zealand. Selected treatment combinations were assessed across five sites in a 17-year-old experiment comparing silvicultural treatments and improved breeds of radiata pine. Diameter at breast height (DBH), and stress-wave velocity (an indicator of wood stiffness) and outerwood (outermost five growth rings) basic density at breast-height were assessed for ten trees from each plot in the experiment. There were large differences in DBH and wood properties between sites. Silviculture (stand density) had a stronger influence than seedlot on DBH and stress-wave velocity, while the converse applied to outerwood density. There was a positive relationship between stand density and both stress-wave velocity and outerwood density. Trees in the un-pruned 500 stems ha−1 treatment had larger DBH, lower outerwood density and lower stress-wave velocity than trees in the 400 stems ha−1 pruned treatment. This suggests that silvicultural manipulation (pruning) of green crown length is important for controlling both growth and wood properties. Results from this study support previous research which indicates that thinning, and to a lesser extent pruning, have a strong impact on DBH, stress-wave velocity and outerwood density. Increasing stand density is consistently associated with stiffer and denser outerwood.

Associations between species richness and individual densities of varying spatial scales and diameter classifications in tropical montane rainforest in Jianfengling, Hainan Island, China

Aims Our objective was to identify the degree of associations between species richness and individual densities of varying spatial scales and diameter classifications. Methods Based on the dataset from a 60 hm tropical montane rainforest plot in Jianfengling, Hainan, China, the relationship between species richness and stem density was analyzed at seven spatial scales (5 m × 5 m, 10 m × 10 m, 20 m × 20 m, 40 m × 40 m, 60 m × 60 m, 80 m × 80 m, and 100 m × 100 m) and three DBH (diameter at breast height) classifications (DBH ≥ 1.0 cm, DBH ≥ 2.5 cm, DBH ≥ 7.5 cm). Important findings The relationship between species richness and stem density varies with the spatial scales and DBH classifications. For all plants with DBH ≥ 1.0 cm, there are significantly positive correlations between species richness and stem density at the spatial scales of 5 m × 5 m, 10 m × 10 m, 20 m × 20 m and 40 m × 40 m, but not at other larger scales. The patterns are similar in the relationship between species richness and stem density after grouping all stems into the three DBH classifications, except there are weak correlations between species richness and stem density for plants with DBH ≥ 2.5 cm and DBH ≥ 7.5 cm at the scale of 60 m × 60 m. The significance levels of the relationship of species richness and stem density are similar between the DBH ≥ 2.5 cm and DBH ≥ 7.5 cm classifications, which are both higher than that of DBH ≥ 1.0 cm. It is concluded that the associations between species richness and stem density are stronger for individuals with larger DBH than those with smaller DBH. It is inferred that negative dependence and self-thinning are two possible mechanisms related to the phenomenon. 326 植物生态学报 Chinese Journal of Plant Ecology 2014, 38 (4): 325–333 www.plant-ecology.com