Testing Binkley's hypothesis about the interaction of individual tree water use efficiency and growth efficiency with dominance patterns in open and close canopy stands

A well-recognized phenomenon during forest development is that stand level forest growth rate begins to decrease after canopy closure. Binkley [Binkley, D., 2004. A hypothesis about the interaction of tree dominance and stand production through stand development. Forest Ecology and Management 190, 265–271] proposed an interesting hypothesis relating individual contribution of trees to forest growth patterns, considering changes in dominance levels and resource use efficiency (ReUE, biomass growth per unit of resource used) of dominant vs suppressed trees. He stated that “the decline in standlevel growth near canopy closure is driven by increasing dominance of larger trees, leading to declining efficiency of resource use by smaller trees”. This decrease in ReUE of suppressed trees once canopy closes would lead to a general decline in standlevel ReUE and thus, in stand growth. This author with other colleagues found evidence according to this hypothesis, but much more research is needed to prove its generality in forests of different species and environmental conditions. The goal of this study was to test Binkley's hypothesis using information of growth patterns, water use efficiency (WUE) and growth efficiency (GE) in different stands of Pinus ponderosa in N.W. Patagonia. According to the hypothesis, we found no dominance in open stands, and some degree of dominance in closed canopy stands. However, in contrast to predictions, WUE differed between the smallest and the largest trees of each stand both with and without dominance. No differences in GE were observed between different tree size groups, and considering individual trees, the more suppressed ones were those with the highest GE. Based on our results, we proposed another hypothesis relating individual and stand ReUE: a decrease in ReUE is not determined by the establishment of dominance and subsequent decrease in suppressed trees efficiencies, but by the availability of resources for individual trees. In this regard, we postulate that differences in ReUE between trees of a stand can appear before dominance, and that these differences in ReUE lead to differences in size of the trees and later, in its social position. When trees grow, they have access to more resources, increasing at the same time, their efficiency using the resources. This efficiency is going to decrease when availability of resources decreases (for competition or environmental stress). The stand ReUE will be maintained, decreased or increased based on the balance of available resources for the individual trees, which in turn will depend on their growth rates, competitive ability and environmental site conditions.     

Spruce forest stands in a stationary state

We present stationarity criteria for forest stands,and establish embodiments using a Norwegian empirical stand development model.The natural stationary states only slightly differ from the outcome of long-term simulations previously implemented using the same empirical model.Human interference in terms of diameter-limit cutting is introduced.Consequently,stationary states differing from the natural one appear.Standing volume,growth and monetary value appear low but the financial return rate may be significant.Volume yield and financial return clearly contradict each other,the former arising from harvesting large trees,the latter from frequent removal of small trees.An exponential tree size distribution does not appear to comply with the stationarity criterion.     

Estimation of shrub biomass by airborne LiDAR data in small forest stands

The presence of shrub vegetation is very significant in Mediterranean ecosystems. However, the difficulty involved in shrub management and the lack of information about behavior of this vegetation means that these areas are often left out of spatial planning projects. Airborne LiDAR (Light Detection And Ranging) has been used successfully in forestry to estimate dendrometric and dasometric variables that allow to characterize forest structure. In contrast, little research has focused on shrub vegetation. The objective of this study was to estimate dry biomass of shrub vegetation in 83 stands of radius 0.5 m using variables derived from LiDAR data. Dominant species was Quercus coccifera, one of the most characteristic species of the Mediterranean forests. Density of LiDAR data in the analyzed stands varied from 2 points/m² to 16 points/m², being the average 8 points/m² and the standard deviation 4.5 points/m². Under these conditions, predictions of biomass were performed calculating the mean height, the maximum height and the percentile values 80th, 90th, and 95th derived from LiDAR in concentric areas whose radius varied from 0.50 m to 3.5 m from the center of the stand. The maximum R² and the minimum RMSE for dry biomass estimations were obtained when the percentile 95th of LiDAR data was calculated in an area of radius 1.5 m, being 0.48 and 1.45 kg, respectively. For this radius, it was found that for the stands (n = 39) where the DTM is calculated with high accuracy (RMSE lower than 0.20 m) and with a high density of LiDAR data (more than 8 points/m²) the R² value was 0.73. These results show the possibility of estimating shrub biomass in small areas when the density of LiDAR data is high and errors associated to the DTM are low. These results would allow us to improve the knowledge about shrub behavior avoiding the cost of field measurements and clear cutting actions.     

A hypothesis about the interaction of tree dominance and stand production through stand development

The development of forests over time involves changes in rates of growth of trees and stands, and changes in the competition and dominance between trees plays a large role in the overall development of stands. A hypothesis proposes that changes in the growth of trees and stands result from regular changes in dominance and the efficiency of resource use by dominant and non-dominant trees. Dominance is low prior to canopy closure, and efficiency of resource use is high for all trees. Increasing dominance near canopy closure reduces the efficiency of resource use by non-dominant trees, lowering overall stand growth. Later in stand development, the efficiency of resource use also declines for the largest trees, reducing the level of dominance in the stand. The dominance part of this hypothesis was examined for 150 years of stand development in two mixed-species stands in the Coast Range of Oregon. A quantitative index of dominance was minimal prior to the peak in stand growth near age 25–30 years, and then increased sharply as stand productivity declined. Dominance then declined after age 100 years as the growth rate of the 300 largest trees/ha began to decline. The dominance portion of the hypothesis was supported, and further testing may be useful.     

Modeling individual-tree growth in stands under forest conversion in East Germany

One major result of forest conversion in Saxony, East Germany, is the increasing importance of two-storied stands composed of a conifer canopy and a deciduous-tree understory. To enhance the applicability of the growth and yield simulator BWINPro under these conditions, three of its major sub-models were adapted to the regional growing conditions and to the relatively high level of diversity in spatial structure, mixture of species, and age variability typical for forests in conversion: (1) A new module for simulating single-tree juvenile growth was developed for European beech and Common oak under canopies of Norway spruce and Scots pine. Predictions in this sub-model are derived from individual height, diameter at breast height (dbh), and the influences of horizontal and vertical competition; (2) An alternative distance-dependent competition index was introduced to estimate individual basal area increment according to tree-specific growing conditions; (3) A modified logistic mortality model was parameterized for the most important Saxon species based on tree dimensions and basal area increment. Data came from permanent sample plots distributed throughout the region and from three chronosequence plot series established specifically for obtaining model input data. The new components were included into the existing structure of BWINPro. As a result of the adaption, the regional version BWINPro-S provides enhanced opportunities of planning and management for forest conversion and for multi-storied stands.     

Sapling architecture and growth in the co-occurring species Castanopsis cuspidata and Quercus glauca in a secondary forest in western Japan

This study quantitatively compared the sapling (height 62–289cm) architecture and growth of Castanopsis cuspidata and Quercus glauca, both of which are major components in the temperate zone of western Japan, under shaded light conditions in secondary forest. When the sapling architectures were compared at the same support mass (trunk + branch mass), C. cuspidata had a larger crown area but a smaller height gain than did Q. glauca owing to the allocation of more biomass to lateral branches in C. cuspidata. The above-ground relative growth rate (RGR) of C. cuspidata (0.442gg^–1 year^–1) was nearly twice that of Q. glauca (0.256gg^–1year^–1), primarily as a result of a greater total leaf area per above-ground biomass (LAR) in C. cuspidata (56cm²g^–1) as compared to Q. glauca (33cm²g^–1). Because it has a disadvantage in height gain, related to its allocation pattern of biomass, C. cuspidata realized the same height growth (RGR_H) as Q. glauca, despite the large biomass production. The great potential for photosynthesis in C. cuspidata, which results from its vigorous lateral spreading, is presumed to give it a long-term advantage over Q. glauca in the shaded forest understory. Q. glauca invests preferentially in trunk biomass, possibly giving it an advantage in sunny sites as opposed to a shaded forest understory.     

Carbon concentrations of tree components,forest floor and understorey in young Pinus sylvestris stands in north-western Turkey

Abstract

This study examines the carbon concentrations of various above-ground biomass components (stem, bark, living branch, dead branch, needle and above-ground biomass), the forest floor and understorey. The research was carried out on Scots pine (Pinus sylvestris L.) stands in north-western Turkey. Sample trees were cut, and forest floor and understorey samples were collected from the 13 sampling areas in the 31-year-old Scots pine stands. Carbon contents of these samples were determined. Carbon concentrations of all tree components were found to be higher than 50%. This value is referred to as the general carbon conversion factor (CF). The weighted mean carbon concentration was found to be 51.96%. Consequently, if the CF for a single tree is taken to be 50%, carbon storage in the above-ground parts of the tree would have been underestimated by 3.77%. Carbon concentration, which was 53.02% in needles, was reduced to 50.08% in the litter plus fermentation layer of the forest floor and to 40.08% in the humus layer owing to decomposition. In the understorey, carbon concentration was determined to be 47.64%. There was a significant difference between the carbon concentrations of the tree components, forest floor and understorey.     

Hybrid and clonal variability of nutrient content and nutrient use efficiency in Eucalyptus stands in Congo

For 20 years, there has been 42,000 ha estate of clonal Eucalyptus plantations around Pointe-Noire in Congo on sandy soils that have very low reserves of available nutrients. These plantations have been based on a natural hybrid (E. PF1). This hybrid is being replaced by E. urophylla × E. grandis (UG), a more productive hybrid developed by the breeding program of UR2PI. A study of biogeochemical cycles showed that nutrient removal by harvesting is the main nutrient output in the E. PF1 ecosystem. It is therefore important to quantify the nutrient content (NC) in both hybrids to compare corresponding nutrient removal values.

The work dealt with four UG clones and the most planted clone of E. PF1. Twelve trees per clone were sampled at the logging age (8 years) in a clonal test for UG clones and in a nearby stand for E. PF1. Tables were established to predict, from girth at breast height (C_1.30 m), the biomass and nutrient content of stemwood, bark, dead and living branches, leaves, and were applied to the inventory of the different stands to evaluate corresponding biomass, NC and nutrient use efficiency (NUE) on a per-hectare basis.

Total biomass differed between the two hybrids and among UG clones: 109 t ha⁻¹ for E. PF1 and 108–155 t ha⁻¹ for UG clones. In E. PF1 trees, total NC was globally lower for N, K, and Mg, but greater for P and Ca. In stemwood, nitrogen content was similar for both hybrids. By contrast, in UG clones, NC was much lower for P (−72%) and Ca (−40% to −55%). The same trends were observed for NUE: equivalent for both hybrids for N, but higher in UG clones for P (+72%) and Ca (+43% to +59%). A marked variability among clones was observed for K and Mg. UG clones allocated proportionally more nutrients in leaves than E. PF1.

These results show that clones should not be selected only on growth traits but also on NUE and on the concentration of nutrients in tree components removed by harvesting. It will be then possible to limit the cost of fertilising needed to maintain stand growth and soil fertility.     

Effects of silvicultural treatments and seasonal patterns on foliar nutrients in young post-fire Pinus halepensis forest stands

Tree growth and health status appear to be related to foliar nutrient contents. Foliar nutrient concentration might be the result of a complex interaction between soil nutrients and effective availability caused by climate, water and other site and treatment effects. This study examines foliar macronutrient (N, P, K, Ca, Mg) and organic C concentrations in Aleppo pine (Pinus halepensis) needles (between 5 and 18 months old), as well as time course variability (nine dates, from July 1999 to November 2001). Variability was assessed depending on quality site (two sites, Yeste and Calasparra; SE Spain) and seven silvicultural treatments including thinning, scrubbing, pruning and particular combinations of them. Foliar macronutrient concentrations for Aleppo pine in South-eastern Spain were slightly lower (N, P, K,) or higher (Mg, Ca) than the considered as adequate ranges for Aleppo pine and Pinus genera. However, our results agree well with other normal ranges reported for Aleppo pine in Spain and for other North American Pinus species such as P. elliottii, P. taeda and P. palustris. Site, treatment and date (season) affected significantly the foliar macronutrient and C concentration, although the most important was the date, likely due to the two growth periods per year that Aleppo pine has in Mediterranean sites. Silvicultural treatments affected foliar nutrient concentration, so that the concentrations of N, P and K were higher when treatments included thinning than those that did not. The contrary was true for Mg and Ca. However, treatments did not affect the time course of the concentration, i.e., seasonality was not broken due to treatments. Moreover, the effect of the treatments was markedly high along the first year after they were applied but the differences were attenuate 2 years later. Site affected the time course of N, K, Mg and C in a different way: while for N, K and C, at the end of study period, they were higher in Calasparra than in Yeste, for Mg the contrary was true. Nutrient ratios had a different behaviour regarding to single nutrient: although date was significant, we did not appreciate seasonality. In addition, some nutrient ratios were not affected by treatments (N/P, N/K, Ca/Mg,) or by site (N/Ca, K/Ca). Average foliar N concentration and Ca/Mg ratio explained significantly the mean diameter and height growth, so that higher is the foliar N concentration and lower is Ca/Mg, higher is the growth.     

Allometric equations for biomass estimations in Cameroon and pan moist tropical equations including biomass data from Africa

Moist tropical forests in Africa and elsewhere store large amounts of carbon and need accurate allometric regressions for their estimation. In Africa the absence of species-specific or mixed-species allometric equations has lead to broad use of pan moist tropical equations to estimate tree biomass. This lack of information has raised many discussions on the accuracy of these data, since equations were derived from biomass collected outside Africa.     

THE CHARACTERISTICS OF THE NUTRIENT CYCLING IN BIRCH STANDS WITH DIFFERENT AGE STAGES

SuccessionisthedynanucdeveloPInentofecosystemswhichcanbecharactetindbyenergyandndneralcyclings.Eachsuccessionstagehasitscharaceristicsofelementcycling.SomeschOlarshaveStatedbutbrieflawsofnutrienCyclinginsuccessionstagesI"3I.InthespaPer,thenutrientcyclingcharacterishcsofbirchsuccessionseriesinXiaokinganlingwerediscussed.SwrYAasAroarernoDSThestUdyareaislocatedinLiangshniNatUralReservesinthendddieofXiaox-ing'anlilg(l28"53,2o'rE,47olo'5O"N).Theclimat6belongstocontinentalmonsoonclimate,W…     

Vegetation response to strip cutting young hardwood stands in West Virginia

Three 21-year-old Appalachian hardwood stands were strip cut using three cutting widths (2.4-m, 3.7-m, and 4.9-m) and allowed to resprout. One year after strip cutting, we examined the vegetation response within the harvested strips relative to non-treated control areas, focusing on the sprouting ability of young hardwood stems and the herbaceous component for wildlife habitat. Results indicate the width of the strip cutting significantly affected the amount of biomass produced from stump sprouts (p = 0.042) and influenced species composition. Shade-intolerant species accounted for more of the biomass production within the wider cut strip widths, while shade-tolerant and shade-intermediate species were more prominent within the narrower cut strips. Cut strip width did not have a significant effect on the biomass of new seedlings germinating after the cuttings. Herbaceous vegetation was greater within the 4.9-m cut strips than in the control plots (p = 0.046); however, the amount of herbaceous biomass produced did not vary among months during the first growing season. Overall, our initial results suggest that strip cutting can provide benefits to wildlife and can possibly provide for additional biomass as the regrowth is harvested in the future.     

Effect of edge stands on the development of young Pinus sylvestris stands in southern Finland

Abstract

The quantitative effect of pine-dominated edge stands in southern Finland on the density and growth of pine saplings was addressed in the study. The cumulative effect of a mature edge stand on the development of a pine sapling stand with variable cutblock sizes was also estimated. The data were acquired from 10 study sites with a Scots pine sapling stand with a current dominant height of 1–6 m and an adjoining middle-aged to mature edge stand dominated by Scots pine. Tree level models were constructed to describe and simulate the structure and development of the sapling stands. The results indicated that dividing an average regeneration area (2 ha) into smaller cutblock units (1.0–0.5 ha) appreciably increased the edge stand effect. Total stand volume growth was 6% lower on 1 ha cutblocks, and 31% lower on 0.5 ha blocks, than on 2 ha blocks.     

国家网络森林医院中建立林木健康卡构想

为了适应林改形势,强化公共服务,完善服务功能,建议在国家网络森林医院中,针对具有林权证的用户建立林木健康卡,记录林地的基本信息、林木防治活动以及用户在网院的咨询与专家的解答等信息,实现网院"服务社会、服务林改、服务现代林业"的宗旨。本文系统地探讨了建立林木健康卡的可行性、设计原则、实现方法与使用方法。     

Growth effect of Manchurian ash in mixed stands

lntroductionThepIantingofFraxiusm8ndShurfoabeganatShangzhi,Kedong,YianandFujincountiesofHei-longjiangProvincein196o'.Ash(hainusmand-shurica)andlarch(LarisgmehnI),AshandKoreanpine(PinuskoraiensiS)mixedstandwereremainednow,whichwereartificial,orformedbyplantingAshatterpIantingpureconiferousforest,orinducedbyestablishingeffectareainnaturalashforest.TherearemanyreferencesonthegrowthofashmixedstandinChina.Butinthepast,thestudyoftherela-tionshipbetWeentheincreasinggrowthofmixedstandwithdiffe…     

Changes of carbon stocks in bamboo stands in China during 100 years

Bamboo stands are one of the most important forest types in China, covering an area of about 4.99 million hectares, and estimation of their carbon stocks is vital for China's national carbon accounting. Bamboo biomass and carbon fraction, as well as soil bulk density and soil organic matter content, data were collated from 40 publications describing conditions at 35 sites in 10 Chinese provinces where most bamboo stands are distributed. Carbon stocks and its changes in the living biomass and soil organic matter in bamboo stands in China in the past five decades were estimated based on these collated data together with the area of bamboo stands and number of bamboo culms derived from the National Forestry Inventory (NFI). Our estimates indicate that the carbon stocks in bamboo stands in China have been increasing since the 1950s with estimated values of 318.55 Tg  C (1950–1962), 427.37 Tg C (1977–1981), 463.80 Tg C (1984–1988), 493.00 Tg C (1989–1993), 548.79 Tg C (1994–1998) and 631.58 Tg C (1999–2003) accompanying the increase of bamboo stand area. Based on correlation between forest area and bamboo area, as well as the trends of forest area predicted in government strategy documents for forest development over the next five decades, the carbon stocks in bamboo stands for 2010, 2020, 2030, 2040 and 2050 are estimated to be 727.08 Tg C, 839.16 Tg C, 914.43 Tg C, 966.803 Tg C and 1017.64 Tg C, respectively.     

Evaluation of Populus deltoides clones under nursery,field and agrisilviculture system in subhumid tropics of Central India

Populus deltoides Bartr., a native of North America, is generally grown in India above latitude 28 °N. One hundred and six clones were evaluated for four years at Raipur situated at 21°12N latitude and 81°36E longitude. These were grown on vertisol soil. Based on growth and survival performance in the nursery for two successive years, nineteen clones were selected for field evaluation. The best five clones (G3, G48, 65/27, D121 and S7C1) were planted in an agrisilviculture system at a spacing of 4 × 4 m with soybean grown as an intercrop. After 4 years these clones had an increment of DBH by 66.5 to 77.5% and of height by 42.2 to 78.6% within one year when compared to that observed at 3 years of age. In rank order of growth the best five clones were 65/27 > G3 > D121 > G48 > S7C1. Total biomass varied between 20.9 to 35.8 Mg ha^–1 in different clones. Among the tree components, stemwood accounted for 52–61% of the total biomass, followed by branches (20–25%), bark (9–13%) and leaves (7–10%). No significant variation between net primary productivity and photosynthetic efficiency was found in different clones. Soybean productivity decreased as the trees aged, reaching 40.5 to 58.1% in 4-year-old trees.     

First report of Phytophthora cinnamomi in forest stands in Germany

Phytophthora cinnamomi was repeatedly isolated from the rhizosphere of recently dead sweet chestnut trees in the upper Rhine valley. Identification was genetically confirmed by RFLP and sequencing of the ITS‐region. This is the first record of P. cinnamomi on forest land in Germany. Mode of introduction of this invasive species and potential factors favouring establishment are discussed.     

Estimating carbon stock in secondary forests: Decisions and uncertainties associated with allometric biomass models

Secondary forests are a major terrestrial carbon sink and reliable estimates of their carbon stocks are pivotal for understanding the global carbon balance and initiatives to mitigate CO₂ emissions through forest management and reforestation. A common method to quantify carbon stocks in forests is the use of allometric regression models to convert forest inventory data to estimates of aboveground biomass (AGB). The use of allometric models implies decisions on the selection of extant models or the development of a local model, the predictor variables included in the selected model, and the number of trees and species for destructive biomass measurements. We assess uncertainties associated with these decisions using data from 94 secondary forest plots in central Panama and 244 harvested trees belonging to 26 locally abundant species. AGB estimates from species-specific models were used to assess relative errors of estimates from multispecies models. To reduce uncertainty in the estimation of plot AGB, including wood specific gravity (WSG) in the model was more important than the number of trees used for model fitting. However, decreasing the number of trees increased uncertainty of landscape-level AGB estimates substantially, while including WSG had limited effects on the accuracy of the landscape-level estimates. Predictions of stand and landscape AGB varied strongly among models, making model choice an important source of uncertainty. Local models provided more accurate AGB estimates than foreign models, but high variability in carbon stocks across the landscape implies that developing local models is only justified when landscape sampling is sufficiently intensive.