Comparison of 5th- and 14th-year Douglas-fir and understory vegetation responses to selective vegetation removal

The effects of early vegetation management on the survival and growth of Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] were examined 5 and 15 years after planting in the Oregon Coast Range. Our first objective was to document the effects of vegetation species competition upon key ecosystem properties. The second objective was to document the effects of vegetation removal during early Douglas-fir stand establishment upon long-term tree growth and on biomass production by vegetation components. Seven levels of manual vegetation removal were maintained for the first 5 years after planting: 0%, 25%, 50%, 75%, and 100% shrub removal; and 100% shrub removal combined with 50% or 100% herbaceous vegetation removal. Shrub and herb removal did not affect Douglas-fir survival at year five, but treatments providing less than 75% shrub removal significantly reduced Douglas-fir survival by year 15. Removing shrubs and herbs completely (100S + 100H) during the 5 years following tree planting allowed successful tree establishment, with a 366% increase in biomass accumulation per hectare for Douglas-fir in that treatment at the end of 14 years of growth. At 15 years stand age, even with shrub removal alone, a 304% gain in tree biomass per hectare was obtained compared to no vegetation removal (NVR). By stand age 15 years, any increase in the degree of understory removal beyond 75% did not contribute significantly to additional tree survival and growth. The understory vegetation on NVR treatment plots and the herbaceous vegetation on 100% shrub removal (100S) treatment plots, contained >90% and >80% of aboveground biomass N at 5 years, respectively, indicating possible competition for soil N. Soil moisture was not different among treatments at 5 years. Complete vegetation removal (100S + 100H) for 5 years resulted in a significant increase in soil bulk density (P < 0.05), a significant decrease in total soil C (P < 0.05) and no change in total soil N in the upper 15 cm of the mineral soil. By 14 years, however, only the soil bulk density remained greater (P < 0.05) on the 100S + 100H treatment. We conclude that greater tree survival and growth occurred with at least 75% shrub removal. Our results suggest that managers may have substantial flexibility in maintaining a partial understory component suitable for ecosystem productivity, canopy cover and wildlife habitat, while maintaining forests productive for timber resources.     

镇沅县思茅松天然林空间结构特征分析

以云南省镇沅县思茅松天然林为研究对象,对森林资源连续清查的固定样地进行调查,应用林分角尺度、林分混交度和林分大小比数等空间结构指标,对思茅松天然林空间分布格局、树种隔离程度和林木生长竞争等进行综合分析.结果表明,在林木空间配置上,林分平均角尺度达0.53,反映出思茅松天然林主要呈现聚集分布的空间分布格局;在思茅松天然林...     

Daily stem water deficit of Norway spruce and European beech in intra- and interspecific neighborhood under heavy drought

High-resolution measurements of stem radius variations provide information about the tree water status with changing climate conditions by swelling and shrinking due to the reduction of xylem water potential and to the exceedance of leaf transpiration over root water uptake. The aim of this study was to analyze daily stem radius variations of Norway spruce and European beech in intra- and interspecific neighborhood. The experimental plots are part of a rainfall exclusion experiment. These variations are species-specific, i.e. spruces have a higher phloem thickness and higher amplitudes during a day than beeches. The amplitudes were significantly higher at the rainfall exclusion plots, but the amplitudes of spruces decreased above 27°C with increasing drought due to reduced transpiration rates and exhausted soil water reserves. The shrinking amplitude was observed for spruces in intraspecific neighborhood from a soil volumetric water content of 0.21?m³?m^?3. In interspecific neighborhood, a shrinking amplitude for spruces could not be observed and revealed a lesser tree water deficit than in intraspecific neighborhood. Beeches showed minor differences with a higher tree water deficit in interspecific neighborhood. Consequently, stem radius variations give insights into a tree's water supply, which could help to understand changes in tree growth.     

A comprehensive framework of forest stand property–density relationships: perspectives for plant population ecology and forest management

? Context

There are many stand property–density relationships in ecology which represent emergent properties of plant populations. Examples include self-thinning, competition–density effect, constant final yield, and age-related decline in stand growth. We suggest that these relationships are different aspects of a general framework of stand property–density relationships.

? Aims

We aim to illustrate the generalities and ecological implications of stand property–density relationships, and organize them in a comprehensive framework.

? Methods

We illustrate relationships between stand property and density (1) at one point in time, (2) over time, and (3) independent of time. We review the consequences of considering different variables to characterize stand property (mean tree size, mean tree growth, stand growth, stand yield, stand leaf area).

? Results

We provide a framework that integrates the broad categories of stand property–density relationships and individual expressions of these relationships. For example, we conclude that constant final yield is a special case of the growth–growing stock relationship for life forms were yield is a reasonable approximation of growth (non-woody plants).

? Conclusion

There is support in the literature for leaf area being broadly integrative with respect to various expressions of stand property–density relationships. We show how this is and suggest implications for plant population ecology and forest management.     

北京八达岭植物群落多样性特征分析

根据34个样地的调查资料,分析了该地区森林植物群落物种多样性的特征:群落内各层物种丰富度指数的大小为草本层>灌木层>乔木层;多样性指数的大小为乔木层<灌木层和草本层。灌木层与草本层的多样性指数随林分郁闭度变化而变化,在林分郁闭度为25%的侧柏黄栌混交林中,灌木层的多样性指数和丰富度指数小于草本层;在郁闭度53%的杂木林中,灌木层和草本层的多样性指数接近;在郁闭度53%以上的各个群落内,草本层的多样性指数和丰富度指数基本上都大于灌木层。人工林中的物种多样性变化多样,明显低于天然林,林分层次单一,更新不良,缺乏灌木层和地被植物,生态系统很不稳定。     

Spatial distribution of regeneration in West-Carpathian uneven-aged silver fir forests

The objective of our study was to examine whether distribution of regeneration in uneven-aged fir (Abies alba Mill.) forests is related to the spatial pattern of trees. In 12 sample plots of size 0.45–1.00 ha (in total 8.65 ha, with stand basal areas ranging from 27.6 m² ha^–1 to 39.5 m² ha^–1), all live and dead trees above 5 cm in d_1.3 were mapped and their diameters measured. In eight plots, all live and dead fir saplings were mapped. In three plots, the number of live fir saplings and seedlings was registered on small systematically distributed circular plots. The values of an analytically developed index of stand influence were compared in patches occupied and unoccupied by live or dead fir regeneration. Contrary to preliminary assumptions, only in a few cases did saplings and trees 5–15 cm in d_1.3 appear more often in gaps and looser stand patches. Rather, in many plots, the opposite tendency was observed. The seedling density showed a weak but positive correlation with the index of influence. If the spatial pattern of regeneration reflects the spatially varying mortality of juvenile trees, then no evidence was found that stand competition was the most important factor inducing this mortality. On the contrary, on the basis of the results obtained, we can presume that the survival rate of juvenile firs was higher in patches with a relatively higher local basal area. Thus, it was hypothesised that, first, dispersion of regeneration in uneven-aged fir forests is controlled by easy-to-change edaphic factors such as humus form and acidity of the upper soil horizons, and second, that these soil features are linked with the spatial pattern of trees.     

油松林木枯损率模型研究

林木枯损率模型是树木生长与收获模拟系统中的一个重要组成部分。本文在充分研究国内外林木枯损率模型的基础上,根据北京市油松复位样地的数据,应用Logistic模型预测油松枯损率,模型自变量选择树木大小、竞争因子和林分密度等指标。研究结果显示:油松林木枯损率随径阶增加而呈U型分布,在5~15cm径阶时林木枯损率逐渐降低,之后枯损率又逐渐增加;枯损率随竞争激烈程度和林分密度的增加而增加。使用油松检验数据对建立的枯损率模型进行检验,发现该模型预测的油松枯损率与观测值之间没有显著差异。因此该模型可用于油松径阶和单木枯损率的预测。     

Quantitative analysis for interspecific relationship of larch stand mixed with ash

Lastvears.manvrescarchaboutintcr-sPecificrclationshipofmixcdstandsforIarchandasht`crcrePeatcd,mostof\`tich,hot`cvcr,isfortheplantingtypeoflinc-bclt.Thispaperanalysisash-larchrclationshipfor26agcdartificialIarchstandmixedwithcvenagcdashinnaturalreqencration.SlTEANDMEASUREMENTMETHOl)ArtincialIarchstandmcasuredlocatcdatecologicaIcxPCrimcntstationinMaocrshanMountainForcstryFarmofNortbcastForcstryUnivcrsity'(El27'34',N45"24').LarchttasplantcdonagrcatPCaccofdescrtcdfieIdinl967t"itha…     

Soil physical factors affecting the growth of sycamore (Acer pseudoplatanus L.) in a silvopastoral system on a stony upland soil in North-East Scotland

Tree growth and soil physical properties were compared on two grazed plots planted with sycamore at 5 and 10 m square spacing on an upland Scottish site. Both plots received fertilizer and stocking density of ewes and lambs was adjusted to maintain a constant sward height.Mean tree height in 1990 and height increment (1988–90) were significantly greater in the 5 m spaced plot (P<0.05). Although matric potential under the trees was generally greater than in the grassed rows between trees, mean penetration resistance (37–107 mm depth) was significantly greater (P<0.01) under the trees. Even when the soil was close to field capacity, less than 10% of penetrometer readings were < 1 MPa under the trees, in comparison to 44% in grassed areas between trees. This demonstrates that surface compaction due to preferential treading by sheep near the base of trees was sufficient to have seriously reduced tree root growth. Penetration resistance under the 5 m spaced trees was significantly less (P<0.05) than under the 10 m spaced trees. A technique for estimating the probability of root deflections by stones (in 35 mm depth intervals), Ps, from penetrometer readings was used. A significant relationship (P<0.1) was found between tree height increment and depth to Ps0.4 in the 10 m plot.     

Structure,composition and diversity of tree species in tropical moist deciduous forests of Eastern India: a case study of Nayagarh Forest Division,Odisha

Quantitative assessment of tree species diversity from sample plots in seven forest ranges of Nayagarh Forest Division in Odisha state in the Eastern Ghats of India was made during the period April, 2011 to November, 2013. A total of 120 transects(1000 m × 5 m) were laid in Nayagarh, Odogaon, Pancharida, Khandapada, Dasapalla,Mahipur, and Gania forest ranges and tree stems of at least 30 cm GBH were measured. The regeneration potential of trees was assessed from 5 m × 5 m sample plots located within the main transect. A total of 177 tree species belonging to 120 genera and 44 families were recorded from the study area. Shorea robusta, Buchanania lanzan, Lannea coromandelica, Terminalia alata and Cleistanthus collinus were the predominant tree species. The stand density varied in the range of 355.33–740.53 stems h~a)-1) while basal area ranged from 7.77 to 31.62 m~2 ha~(-1). The tree density and species richness decreased with increasing girth class. The highest number of species and maximum density was recorded in the girth class of 30–60 cm. The Shannon–Weiner and Simpson Indices with respect to trees with C30 cm GBH varied in the range of 2.07–3.79 cm and 0.03–0.37 cm respectively and the values of diversity indices are within the reported range for tropical forests of Indian sub-continent. The families, Dipterocarpaceae,Anacardiaceae, Combretaceae and Euphorbiaceae contributed to maximum species richness, stand density, and basal area. Regeneration of many tree species was observed to be poor. The present study provides baseline data for further ecological studies, forest management, and formulation of site-specific strategies for conservation of biological diversity in moist deciduous forests of Eastern India.     

杉木林下植被生物量与土壤容重关系的研究

对福建南平峡阳国有林场 2 9年生的一代杉木人工林林下植被生物量与土壤容重的关系进行了研究 ,结果表明 ,立地条件愈好 ,林下植被生长愈好 ;较低的林分密度和郁闭度 ,有利于林下植被的发育 ,尤其是有利于灌木种类的生长 ;林下植被具有降低土壤容重的作用 ,其中灌木对降低土壤容重的作用最大     

A comparison of agrisilvicultural systems with plantation forestry in the Atlantic Lowlands of Costa Rica

Survival and growth data (ages 0–5 years) are presented for two timber species (Acacia mangium, Cordia alliodora) planted in monocultures or in association with a sequence of agricultural cropsZea mays, Zingiber officinale andEugenia stipitata (a fruit shrub) in the tropical humid Caribbean lowlands of Costa Rica. Average annual height and diameter growth rates were 3.2 m and 4.0 cm (C. alliodora), 3.5 m and 3.8 cm (A. mangium).C. alliodora associated with crops gave the greatest productivity with an average total stem volume increment of 19 m³ ha^–1 yr^–1. Root rot ofA. mangium (mainlyRosellinia sp.), leading to tree mortality, was greater in pure plots compared to associated plots.A. mangium can not be recommended for similar sites because of this problem.     

Quantitative relationships between fine roots and stand characteristics

Fine roots absorb nutrients and water for photosynthesizing leaves, which in return provide them with hydrocarbon products. Knowledge of the fine root biomass (FRB) at the individual tree level and its relationships with other components related to tree growth, especially leaves aboveground, is scarce. Therefore, we reviewed the FRB of major forest-forming species using a database of 518 forest stands compiled from the literature, including 21 tree species and 16 shrub species, in order to confirm the relationships between environmental or forest stand variables and FRB at the stand and tree levels, and we further determine the relationships between fine roots belowground and leaves aboveground. Correlations between FRB and site characteristics (latitude, elevation, age, density, and basal area) appeared to be species-specific. There were hardly any significant correlations between stand FRB and latitude, elevation, stand age and stand density. Tree FRB was better correlated with tree basal area than stand FRB with stand basal area. There was a significant linear relationship between tree FRB and tree basal area. In addition, individual FRB was significantly linearly related to leaf biomass for all analyzed species. When these species were grouped into coniferous and deciduous, or all species together, there were still significant linear relationships between tree FRB and tree basal area and leaf biomass. The ratios of FRB to leaf biomass varied between and among species and even among regions for the same species. For both Picea abies and Pinus sylvestris, the ratio of FRB to leaf biomass was negatively related to the ratio of annual actual evapotranspiration to annual potential evapotranspiration, which was an indicator of water availability.     

Semi-forest coffee cultivation and the conservation of Ethiopian Afromontane rainforest fragments

Coffea arabica shrubs are indigenous to the understorey of the moist evergreen montane rainforest of Ethiopia. Semi-forest coffee is harvested from semi-wild plants in forest fragments where farmers thin the upper canopy and annually slash the undergrowth. This traditional method of coffee cultivation is a driver for preservation of indigenous forest cover, differing from other forms of agriculture and land use which tend to reduce forest cover. Because coffee farmers are primarily interested in optimizing coffee productivity, understanding how coffee yield is maximized is necessary to evaluate how, and to what extent, coffee production can be compatible with forest conservation.Abiotic variables and biotic variables of the canopy were recorded in 26 plots within 20 forest fragments managed as semi-forest coffee systems near Jimma, SW Ethiopia. In each plot, coffee shrub characteristics and coffee yield were recorded for four coffee shrubs. Cluster and indicator species analyses were used to differentiate plant communities of shade trees. A multilevel linear mixed model approach was then used to evaluate the effect of abiotic soil variables, shade tree plant community, canopy and stand variables, coffee density and coffee shrub size variables on coffee yield.Climax species of the rainforest were underrepresented in the canopy. There were three impoverished shade tree communities, which differed in tree species composition but did not exhibit significant differences in abiotic soil variables, and did not directly influence coffee yield. Coffee yield was primarily determined by coffee shrub branchiness and basal diameter. At the stand level a reduced crown closure increased coffee yield. Yield was highest for coffee shrubs in stands with crown closure less than median (49 ± 1%). All stands showed a reduced number of stems and a lower canopy compared to values reported for undisturbed moist evergreen montane rainforests.Traditional coffee cultivation is associated to low tree species diversity and simplified forest structure: few stems, low canopy height and low crown closure. Despite intensive human interference some of the climax species are still present and may escape local extinction if they are tolerated and allowed to regenerate. The restoration of healthy populations of climax species is critical to preserve the biodiversity, regeneration capacity, vitality and ecosystem functions of the Ethiopian coffee forests.     

A mixed nonlinear height–diameter model for pyrenean oak (Quercus pyrenaica Willd.)

A nonlinear mixed-effects modelling approach was used to model the individual tree height–diameter relationship in pyrenean oak (Quercus pyrenaica Willd.). A set of 24,627 pairs of height–diameter measurements were used to fit the model. These were taken at 950 Spanish National Forest Inventory plots embracing six different biogeoclimatic strata. Eleven biparametric nonlinear height–diameter equations were evaluated to find a local model, which only includes the dimensions of the tree as explanatory variables. After selecting the local model, a regional or generalized model was studied. The following stand variables were tested for inclusion in the model as fixed effects: stand density, quadratic mean diameter, arithmetic mean diameter, dominant diameter, arithmetic mean height, dominant height and basal area. Dominant height and basal area of the stand were found to produce the most satisfactory fits in the stand model. Interregional variability was studied by including strata effects as dummy categorical variables and was analysed using the non-linear extra sum of squares method and the Lakkis–Jones test. Height–diameter models were found to be similar for the six biogeoclimatic strata. Finally, a mixed nonlinear model technique was applied to fit the definitive model. By calibrating the model it is possible to predict random components of definitive model from height measurements previously taken from a subsample of trees. The different alternatives tested reveal that only two or three trees are necessary to calibrate the model.     

Process studies in aPinus radiata-pasture agroforestry system in a subhumid temperature environment. II. Analysis of dry matter yields in the third year

In this paper we analyzed the dry matter yields (DM) produced in an agroforestry trial consisting of pine trees grown over (1) Control (bare ground), (2) ryegrass/clovers (Lolium perene/Trifolium spp.), (3) ryegrass only, and (4) lucerne (Medicago sativa) during the third growing season between 1992 and 1993. In addition these pastures were grown alone in separate plots in the open. The results show that:

Seasonal variation in biomass and primary productivity of para grass (Brachiaria mutica) under a mixed tree stand and in an adjacent open area in northern India

Seasonal changes in biomass, net primary productivity and turnover of dry matter of para grass (Brachiaria mutica) under a mixed tree stand and in an adjacent open stand in northern India are presented. Both stands attained peak values of live shoot biomass in September with a higher value under mixed tree stand (665 g m^–2) than in the open stand (522 g m^–2). The net aboveground production was 590 and 527 g m^–2 yr^–1 under mixed tree stand and in the open, respectively. The belowground net primary production was also greater under mixed tree stand (100 g m^–2 yr^–1) than in the open (76 g m^–2 yr^–1). Maximum aboveground and belowground net primary productions in both stands were obtained during the rainy season. The total net primary production for para grass was about 15% higher under mixed tree stand than in the open. The turnover rates of total plant biomass were greatest in the rainy season and the least during the summer season. The system transfer functions showed that the production of para grass on both stands was aboveground-oriented, accounting for 85–87% of annual total net primary production.     

Climate-growth variability in Quercus ilex L. west Iberian open woodlands of different stand density

? We present the longest tree-ring chronology (141 y) of Quercus ilex L. (holm oak), and discuss the species climate-growth relationships and the influence of stand density on tree sensitivity to climate.

? Similarly to Quercus suber L., the most influential climatic variables upon holm oak growth were late spring and early summer precipitation, which enhanced growth, and high temperatures in the previous August and current July, which negatively affected growth.

? High density stands responded to similar climatic factors as low density stands, but their response was generally weaker. Holm oak sensitivity to climate has increased in recent decades, which might be related to increasing temperatures in the region. Sensitivity was higher in low density stands. Additionally, the effect of summer stress on growth seems to have increased during the same period, similarly to other species in the Iberian Peninsula, suggesting that trees are more vulnerable to climatic changes.

? Stand density could buffer the response to climate by smoothing climatic extremes. Nevertheless, the effect of competition might reverse this positive effect at the individual tree level. Precautions should be taken before providing management guidelines regarding the effect of climate change and stand density on holm oak.

     

Biomass and production of fine and coarse roots of trees under agrisilvicultural practices in north-east India

An understanding of the rooting pattern of tree species used in agroforestry systems is essential for the development and management of systems involving them. Seasonal variation, depth wise and lateral distribution of biomass in roots of different diameter classes and their annual production were studied using sequential core sampling. The investigations were carried out in four tree species under tree only and tree+crop situations at ICAR Research Farm, Barapani (Meghalya), India. The tree species were mandarin (Citrus reticulata), alder (Alnus nepalensis), cherry (Prunus cerasoides) and albizia (Paraserianthes falcataria). The contribution of fine roots to the total root biomass ranged from 87% in albizia to 77% in mandarin. The bulk of the fine roots (38% to 47%) in the four tree species was concentrated in the upper 10 cm soil layer, but the coarse roots were concentrated in 10–20 cm soil depth in alder (46%) and albizia (51%) and at 0–10 cm in cherry (41%) and mandarin (48%). In all the four tree species, biomass of both fine- and coarse-roots followed a unimodal growth curve by showing a gradual increase from spring (pre-rainy) season to autumn (post rainy) season. Biomass to necromass ratio varied between 2 to 3 in the four tree species. The maximum (3.2) ratio was observed during spring and the minimum (2) in the rainy season. In alder and albizia, the fine roots were distributed only up to 1 m distance from the tree trunk but in the other two species they were found at a distance up to 1.5 m from the tree trunk. The annual fine root production varied from 3.6 Mg ha^–1 to 6.2 Mg ha^–1 and total production from 4.2 to 8.4 Mg ha^–1 in albizia to mandarin, respectively. Cherry and mandarin had a large number of woody roots in the surface layers which pose physical hindrance during soil working and intercultural operations under agroforestry. But the high biomass of roots of these two species may be advantageous for sequential or spatially separated agroforestry systems. However, alder and albizia have the most desirable rooting characteristics for agroforestry systems.This revised version was published online in November 2005 with corrections to the Cover Date.     

六盘山水源林林分目标层次结构研究

为适应六盘山水源林可持续经营实践的需求,利用六盘山林业局120个森林连续清查固定样地调查资料,分析了林分郁闭度对林下灌木、草本植物生长影响的规律,建立了适用于当地的数学模型,提出了该区水源林林分的目标层次结构。结果表明:1)该区水源林林分郁闭度影响林下植被的生长,林下灌木层、草本层盖度随林分郁闭度升高而降低;2)该林区水源林林分郁闭度保持在0.5～0.8之间时能够形成明显的乔灌草层次结构,有利于实现水源林经营的生态功能和经济功能的协调;3)该区水源林林分的目标层次结构为,林分郁闭度0.5～0.8,灌木层盖度35%～46%,草本层盖度35%～46%。研究结果可为该区水源林结构调整提供依据。