Planting spacing affects canopy structure,biomass production and stem roundness in poplar plantations

To improve the productivity and wood quality of poplar plantations, effects of four planting spacing on canopy characteristics, biomass production and stem roundness in poplar plantations were evaluated over 8 years. Planting spacing influenced canopy characteristics of the plantations, and further affected the understory vegetation and plantation productivity. Understory vegetation biomass and Shannon-Wiener index were negatively correlated with leaf area index, but both diversity indexes and aboveground biomass of understory vegetation were higher in stands with a wider spacing. Tree diameter growth increased with increasing planting spacing, while the increment in plantations of square configurations (5?×?5 m and 6?×?6 m) was higher than those with rectangular configurations (3?×?8 m, 4.5?×?8 m). The highest poplar biomass production was achieved in the plantation with 5?×?5 m spacing at age 8. Moreover, poplar trees showed a tendency with better stem roundness in a square configuration. The results suggest that planting spacing not only affect canopy characteristics, understory vegetation and tree growth but also wood quality, and square configurations (5?×?5 m and 6?×?6 m) could be a better option for poplar plywood timber production at similar sites.     

Impact of seedling type on early growth of poplar plantations on forest and agricultural land

Today, most poplar plantations in the temperate region are established on abandoned marginal agricultural land, but there is great potential for planting poplars on forest land as the available area is large and does not compete with food production. The objective of this study was to examine how different planting types (un-rooted cuttings, bare-rooted and containerized plants) affect the establishment and early growth of poplar plants on forest and agricultural sites. Our results suggest that on the agricultural site, survival and growth during the first two years are not influenced by plant type. However, at the forest sites, survival of rooted plants was superior compared to un-rooted cuttings. The height and biomass (stem and root) increment of bare-rooted plants was low; greater height and biomass growth was found for containerized plants. Container sizes had no effect on height growth, but leaf and stem biomasses were higher if the largest containers were used. When using the largest containers, concentrations of macronutrients (N, P) were increased compared to bare-rooted plants. Thus, these results suggest that practices for establishing poplar plantations of agricultural land include planting of un-rooted cutting, but on forest land, a plant grown in a container of 470?ml should be used. Together, this can reduce the cost of establishment, increase the available area for poplar plantations and have an impact on poplar plantation economics in Sweden.     

Juvenile growth of hybrid poplars on acidic boreal soil determined by environmental effects of soil preparation, vegetation control, and fertilization

The silviculture of hybrid poplars and other fast-growing tree species is a promising solution to reduce the pressure on natural forests while maintaining wood supplies to industries. However, hybrid poplars are very sensitive to competing vegetation and to inadequate soil conditions and fertility. Possible management tools include mechanical site preparation (MSP), vegetation control (VC), and fertilization. Experimental plantations of hybrid poplars (one clone, Populus balsamea × Populus maximowiczii) were established at eight formerly forested sites on acidic soil in the southern boreal forest of Quebec, Canada. The objective was to test the response of hybrid poplars to the interaction of several silvicultural tools, which has been rarely done. Four MSP treatments (in decreasing order of intensity: mounding, harrowing, heavy disk trenching, light disk trenching) and a control (unprepared) were all combined with four different frequencies of plant competition control by brushing (from never up to once a year). Fertilization with N or N + P was also tested in three selected MSP treatments. After five years, hybrid poplar tree growth among MSP treatments increased in the following order: unprepared < light disk trenching < heavy disk trenching < harrowing < mounding. MSP was also essential in favouring early tree survival, as illustrated by mortality rates of over 20% in unprepared plots and below 5% in all other MSP treatments. The effect of competition control on hybrid poplar growth was greatest in the less intensive MSP treatments, where competing vegetation was the most abundant. On the contrary, fertilization effect was significant only in the most intensive MSP (mounding). Moreover, neither fertilization nor VC could compensate for inadequate soil preparation. Of all the silvicultural treatments tested, mounding provided the best tree growth despite a nitrogen and carbon impoverished surface soil.     

Comparing growth and fine root distribution in monocultures and mixed plantations of hybrid poplar and spruce

Disease prevention, biodiversity, productivity improvement and ecological considerations are all factors that contribute to increasing interest in mixed plantations. The objective of this study was to evaluate early growth and productivity of two hybrid poplar clones, P. balsamifera x trichocarpa (PBT) and P. maximowiczii x balsamifera (PMB), one improved family of Norway spruce (Picea glauca (PA)) and one improved family of white spruce (Picea abies (PG)) growing under different spacings in monocultures and mixed plots. The plantations were established in 2003 in Abitibi-Témiscamingue, Quebec, Canada, in a split plot design with spacing as the whole plot factor (1 × 1 m, 3 × 3 m and 5 × 5 m) and mixture treatments as subplot factor (pure: PBT, PMB, PA and PG, and 1:1 mixture PBT:PA, PBT:PG, PMB:PA and PMB:PG). Results showed a beneficial effect of the hybrid poplar-spruce mixture on diameter growth for hybrid poplar clones, but not for the 5 × 5 m spacing because of the relatively young age of the plantations. Diameter growth of the spruces decreased in mixed plantings in the 1 × 1 m, while their height growth increased, resulting in similar aboveground biomass per tree across treatments. Because of the large size differences between spruces and poplars, aboveground biomass in the mixed plantings was generally less than that in pure poplar plots. Leaf nitrogen concentration for the two spruce families and hybrid poplar clone PMB was greater in mixed plots than in monocultures, while leaf nitrogen concentration of clone PBT was similar among mixture treatments. Because of its faster growth rate and greater soil resources demands, clone PMB was the only one showing an increase in leaf N with increased spacing between trees. Fine roots density was greater for both hybrid poplars than spruces. The vertical distribution of fine roots was insensitive to mixture treatment.     

河南省西平县杨树人工林碳贮量及其分配特征研究

基于对西平县杨树人工林植被生物量,土壤容重和碳含量的调查,估算杨树林生态系统碳贮量。研究表明:杨树林的乔木层碳密度波动在0.489~0.512g/g,杨树各器官的碳密度大小依次是树叶>树干>树枝>树根,整个植被层碳贮量大小依次是乔木层>林下植被层>凋落物层,与其各自生物量所占比例相当;土壤层的碳密度以0~20 cm的最高,往下逐渐降低;整个杨树林的碳贮量为164.29 t/hm2,乔木层碳贮量在整个植被层碳贮量中处于主导地位,占整个植被层碳贮量的97.36%。     

Habitat structure influences the spider fauna of short-rotation poplar plantations more than forest age

Plantation forests comprise an important part of the forested areas in European countries. Intensive forestry management and short-rotation cycles of plantation forests reduce habitat diversity and change the composition of invertebrate assemblages, mainly by reducing the number of habitat specialist species. Here, we analysed the effect of vegetation structure, amount of dead organic matter (DOM) and plantation age on spider functional diversity and assemblage structure in short-rotation plantations of native silver poplar in Hungary. Three stages, representing young plantations, 6- to 10-year-old stands (five stands), middle-aged plantations, aged between 23 and 26 years (five stands) and mature, 35- to 37-year-old forests at commercial maturity (five stands) were sampled. Each sample consisted of the data of ten pitfall traps. Traps were installed 5 m from each other in a 2 × 5 grid. Functional diversity was positively related to vegetation structure. High functional diversity indicates a higher number of available niches and potential resources. The abundance of moist habitat species and forest specialist species was positively correlated with DOM. Furthermore, moist habitat species were also related to vegetation structure. The most important environmental parameters affecting spiders were factors attributed to trees (litter and DOM), understory vegetation structure and, to a lesser extent, forest age. Different-aged stands may be similar in terms of species composition of their spider fauna if they comprise the same habitat structural patterns. Our study emphasises that the simple habitat structure of plantation forests has a negative effect on spider communities.     

不同立地管理措施对2代杉木1年生幼林生长影响的研究

关于现有人工林的地力衰退问题，在世界林学界范围内已得到基本一致的认同，但也有持不同意见者，有的将２代人工林的多种表现称之为“第２代效应”，包括品种改良和施肥等措施可能产生的积极影响以及常规措施导致的负面影响在内，造成认识不同的原因在于试验的方法和数据...     

Understory vegetation of boreal tree plantations: Differences in relation to previous land use and natural forests

The aim of this study was to evaluate if and how the previous land use (here: agriculture versus forest) has influenced the floristic composition now observed in the understory of jack pine plantations of Abitibi-Temiscamingue (North-Eastern Canada). Floristic inventories were conducted in jack pine plantations which had been established on forest sites after logging and on sites previously utilized for agriculture. These were compared to one another and to inventories conducted in natural forests and on agricultural sites which had not (not yet) been planted with trees (old fields). The vegetation community composition of the sites is analysed using several multivariate techniques. Results show that the flora of plantations on old agricultural fields is markedly different than that of plantations established on sites which were previously forested and that the two types of plantation are unlikely to become floristically the same before the anticipated harvest time. Comparing old and young plantations and old fields in light of natural forests sites, we show that the previous land-use is a key determinant of future compositional differences in plantations. This must be considered when we evaluate the impact of establishing plantations on sites with different land-use histories.     

鄂西南鹅掌楸天然林林分结构特征

以鄂西南鹤峰县鹅掌楸天然林为研究对象,通过对林分空间结构(角尺度、大小比、混交度)和林分非空间结构 (径级结构、树高结构、重要值)的研究与分析,直观地反映其林分结构的特征,查清该区鹅掌楸种群的发展现状,为鹅掌楸 天然林的合理保护与科学经营提供依据 。在鹅掌楸天然林集中生长的代表性地段建立 17个 20mx20m调查样地,进行 每木定位与检尺调查,应用 Excel2019、Winkelmas2.0软件对样地调查数据进行处理与分析 。结果表明:研究区鹅掌楸 天然林中共 73个树种,鹅掌楸为该群落的优势种,生长处优势地位( =0.17),种群整体呈轻微聚集分布(为 0.56),同 时该种群在林分中呈现极强度混交状态( =0.85):种群整体径级、树高分布都呈右偏正态分布,小径级林木株数很少, 种群整体呈现稳定型一衰退型 。FSI均值为 0.82,FSD 均值为 0.30,林分空间结构为接近于理想状态(41.18%)或达 到理想状态(58.82%)。鹅掌楸天然林处于演替后期,林分结构整体上较为理想,可对处于聚集分布的林木进行适当调整, 辅以 一定人为促进更新的措施,促使鹅掌楸林分结构更加合理。     

干旱和涝渍胁迫对入侵物种喜旱莲子草生长的影响

苦郎树是一种沿海防沙固堤的半红树植物，不仅在红树林群落中具有重要的生态价值，叶片提取物还有一定的医药价值。本研究通过4种光响应模型对苦郎树光响应曲线拟合，计算光合参数进行对比分析，评估最适拟合模型，并研究其光合特性。结果表明：不同模型对苦郎树光响应拟合存在差异，四种模型拟合优度均在0.996以上，苦郎树气孔导度随光合辐射增加而增加，在1800 μmol·m-2·s-1有效光合辐射下达到最大；在500 μmol·m-2·s-1有效光合辐射下水分利用效率最高，胞间二氧化碳维持在一个不变的浓度，与大部分植物的光合特性相似。非直角双曲线模型对苦郎树拟合效果最佳，如何精确拟合光饱和点还需进一步研究，应需要根据实际情况选用最适宜的光响应拟合模型，为海岸生态、防风固堤和园林绿化等工作提供理论依据。     

Towards practices favourable to plant diversity in hybrid poplar plantations

Much research effort is being devoted to developing forest management practices with limited impacts on biodiversity. While the impact of poplar Populus sp. plantations on biodiversity is relatively well-known at the landscape scale, the impact of alternative management practices at the plantation scale has received much less attention. Yet biodiversity is likely to be impacted by the choice of the poplar clone, stem density at plantation, type and duration of the understory control, and age at which the poplars are harvested. In this study, we investigated the impact of these factors on herbaceous plant communities with data from plant surveys conducted in 85 young (2–5 years) and 96 mature (11–17 years) hybrid poplar high-forest plantations in northern France. On average, ruderal or generalist plants contributed to 40.5% of the plot species richness; tall herbs (60.2%), forest (26%) and meadow plants (13.8%) contributed to the remaining 59.5% more specialised species. Soil moisture and soil nitrogen were major determinants of plant communities: wet soils were favourable to tall herbs, while meadow and forest species preferred moist soils; a significantly lower diversity of the three species groups was reported in the nutrient richer soils (in mature plantations only for forest plants). Mean species richness decreased with plantation age except for forest species. Plant communities in young plantations showed little differences in composition according to the type of understory control (chemical, mechanical or both). The development of a shrubby layer in mature plantations was restricted to the drier soils and was detrimental to both meadow plants and tall herb species. Effects of previous land use on forest and tall herb species were found only in young plantations, suggesting a rapid reset of plant communities for these two groups. This may not be the case for meadow species as the influence of previous land use was significant in mature plantations only. Finally, clone type and stem density at plantation had no significant impact on plant communities. Adjusting age at which the poplars are harvested seems the only effective way to drive plant communities in high-forest poplar plantations: delaying poplar harvest (probably beyond 15–20 years) would benefit forest plants, while advancing poplar harvest (about 10 years) would benefit tall herbs, especially in wet soil conditions.     

杉木人工林连作生物生产力的研究

在全国杉木中心产区，选择不同栽植代数（1、2、3代），不同生长发育阶段（5、10、15、20a)及不同立地（14、16、18地位指数）的杉木人工林，进行不同栽植代数杉木人工林生物生产力的比较研究。结果表明：连栽导致了不同生长发育阶段杉木人工林生产力的明显下降，随栽植代数增加，不同生长发育阶段杉木林林分生物量逐代递减，林下植被生物量呈递增趋势，其中2、3代20a生杉木林林分生物量分别比1代下降20.24%和38.09%，3代比2代下降22.38%。同时林分树干生物量所占比例下降，根系生物量所占比例增加，连栽刺激了杉木根系生长发育，并有利于林下植被恢复。     

Ecosystem carbon stocks and distribution under different land-uses in north central Alberta,Canada

Land-use and land cover strongly influence carbon (C) storage and distribution within ecosystems. We studied the effects of land-use on: (i) above- and belowground biomass C, (ii) soil organic C (SOC) in bulk soil, coarse- (250–2000 μm), medium- (53–250 μm) and fine-size fractions (<53 μm), and (iii) ¹³C and ¹⁵N abundance in plant litter, bulk soil, coarse-, and medium- and fine-size fractions in the 0–50 cm soil layer in Linaria AB, Canada between May and October of 2006. Five adjacent land-uses were sampled: (i) agriculture since 1930s, (ii) 2-year-old hybrid poplar (Populusdeltoides × Populus × petrowskyana var. Walker) plantation, (iii) 9-year-old Walker hybrid poplar plantation, (iv) grassland since 1997, and (v) an 80-year-old native aspen (Populus tremuloides Michx.) stand. Total ecosystem C stock in the native aspen stand (223 Mg C ha⁻¹) was similar to that of the 9-year-old hybrid poplar plantation (174 Mg C ha⁻¹) but was significantly greater than in the agriculture (132 Mg C ha⁻¹), 2-year-old hybrid poplar plantation (110 Mg C ha⁻¹), and grassland (121 Mg C ha⁻¹). Differences in ecosystem C stocks between the land-uses were primarily the result of different plant biomass as SOC in the 0–50 cm soil layer was unaffected by land-use change. The general trend for C stocks in soil particle-size fractions decreased in the order of: fine > medium > coarse for all land-uses, except in the native aspen stand where C was uniformly distributed among soil particle-size fractions. The C stock in the coarse-size fraction was most affected by land-use change whilst the fine fractions the least. Enrichment of the natural abundances of ¹³C and ¹⁵N across the land-uses since time of disturbance, i.e., from agriculture to 2- and then 9-year-old hybrid poplar plantations or to grassland, suggests shifts from more labile forms of C to more humified forms of C following those land-use changes.     

Experience with patterns of change in soil carbon resulting from forest plantation establishment in eastern Australia

Forest plantations are extensively established in eastern Australia for production of timber products and more recently, potentially for sequestration of carbon. Intensive management of these plantations involves clearing of existing vegetation, often using fire, ripping and/or mounding of the soil and weed control, followed by planting, use of fertilizers, and subsequent tending. The plantations are managed on a 10–30-year rotation and often have high growth rates and accumulation of carbon. However, after establishment, there are reduced inputs of carbon into the soil from prior vegetation or rapidly growing weeds, together with accelerated decomposition of soil organic matter as a result of disturbance, and this leads to a net loss of soil organic carbon. In some systems this loss of soil organic carbon is not balanced by carbon biomass sequestration until 5–10 years after establishment and on some sites, a reduction in soil organic carbon may remain until the end of the rotation. The patterns of accumulation and loss of carbon vary according to location, soil type and plantation management system. The effects of intensive forest establishment on soil organic carbon were evaluated in a number of studies in eastern Australia using time sequence and chronosequence studies and comparisons of plantation soils with those from adjacent undisturbed sites. There was a general pattern of reduced carbon in surface soil immediately after plantation establishment and with time this extended deeper into the soil profile. The actual quantities varied greatly depending on the soil type. The decline was primarily a result of losses of labile carbon and was greater when the previous land use had essentially been native vegetation or highly improved pastures as opposed to regrowth woodland, or native pasture, or degraded land. In the absence of further disturbance, soil organic carbon can accumulate to pre-establishment levels but many short rotation plantations are terminated prior to this being attained. The potential upper level of accumulation of soil carbon can be increased by alteration of the soil nutritional status using fertilizer application.     

Early stand production of hybrid poplar and white spruce in mixed and monospecific plantations in eastern Maine

Forest plantations in the northeastern United States comprise a small proportion of the total forest area. Most plantations are typically softwood dominated and managed for sawlog and pulpwood production, while high-yield hardwood plantations for bioenergy feedstocks have not been as widely investigated. The objective of this study was to compare the biomass production of planted white spruce (Picea glauca (Moench) Voss) and hybrid poplar (Populus spp.) plantations (four clones) in monoculture, and in mixture of the two on a typical reforestation site in Maine. Three years following planting, hybrid poplar height and ground line diameter growth rates began to diverge among clones, and by 6?years, the Populus nigra?×?Populus maximowiczii (NM6) clone clearly outperformed three Populus deltoides?×?Populus nigra clones (D51, DN10 and DN70) both in pure stands and in mixtures with white spruce. In mixture, we found the yield of white spruce to decline as the yield of hybrid poplar increased. Overall, yields of white spruce monocultures were comparable to those reported in eastern Canada, while the hybrid poplar biomass yields were substantially lower than those reported from studies on abandoned agricultural lands, likely due to the harsher soil conditions at our site. The dominance of rocky and poorly drained sites (like the one tested in this study) across Maine will likely limit the feasibility of widespread hybrid poplar plantations, and thus constrains their potential use as a bioenergy feedstock.     

Soil changes induced by Acacia mangium plantation establishment: Comparison with secondary forest and Imperata cylindrica grassland soils in South Sumatra,Indonesia

Acacia plantation establishment might cause soil acidification in strongly weathered soils in the wet tropics because the base cations in the soil are translocated rapidly to plant biomass during Acacia growth. We examined whether soils under an Acacia plantation were acidified, as well as the factors causing soil acidification. We compared soils from 10 stands of 8-year-old Acacia mangium plantations with soils from 10 secondary forests and eight Imperata cylindrica grasslands, which were transformed into Acacia plantations. Soil samples were collected every 5–30 cm in depth, and pH and related soil properties were analyzed. Soil pH was significantly lower in Acacia plantations and secondary forests than in Imperata grasslands at every soil depth. The difference was about 1.0 pH unit at 0–5 cm and 0.5 pH unit at 25–30 cm. A significant positive correlation between pH and base saturation at 0–20 cm depth indicated that the low pH under forest vegetation was associated with exchangeable cation status. Using analysis of covariance (ANCOVA), with clay content as the covariate, exchangeable Ca (Ex-Ca) and Mg (Ex-Mg) stocks were significantly lower in forested areas than in Imperata grasslands at any clay content which was strongly related to exchangeable cation stock. The adjusted average Ex-Ca stock calculated by ANCOVA was 249 kg ha⁻¹ in Acacia plantations, 200 kg ha⁻¹ in secondary forests, and 756 kg ha⁻¹ in Imperata grasslands at 0–30 cm. Based on a comparison of estimated nutrient stocks in biomass and soil among the vegetation types, the translocation of base cations from soil to plant biomass might cause a decrease in exchangeable cations and soil acidification in Acacia plantations.     

Site preparation,fertilization, and 10-year yields of hybrid poplar on a clearcut forest site in eastern Maine,USA

Cuttings of two similar hybrid poplar clones were planted on a drum-chopped, chip-harvested clearcut in eastern Maine. The site had never been previously cleared for agriculture. The coarse loamy glacial till soils were acid (pH < 5.0) and moist—moderately well—to somewhat poorly drained. Control, lime (L), L nitrogen (N), L phosphorus (P), LNP, and LNP potassium (K) treatments were established. Competing woody vegetation was mowed once per year for the first three years on half the area. Each mowed treatment produced significantly greater hybrid poplar biomass than the corresponding unmowed treatment. After 10 years, the mowed+LNPK treatment attained the greatest total biomass, 45 Mgha^-1, while the unmowed control attained the least, 2 Mgha^-1. On mowed plots, L produced 4 times the biomass of control: 32 vs 8 Mgha^-1. Unmowed plots with L and N produced about as much hybrid poplar biomass as the mowed control (8 Mgha^-1). Mowing and L each improved survival as well as growth.Deceased     

Structure and Function of <Emphasis Type="Italic">Populus deltoides</Emphasis> Agroforestry Systems in Eastern India: 1. <Emphasis Type="Italic">Dry matter dynamics</Emphasis>

Agroforestry systems based on poplar (Populus deltoides) are becoming popular in eastern and northern parts of India. Therefore studies on the structure and function of the systems are important. The investigations included allometric equations for above- and belowground tree components, crop and plantation floor biomass and litter fall estimation at Pusa, Bihar, India. Biomass, floor litter mass, litter fall and net primary productivity (NPP) of plantations increased with an increase in age of trees whereas, crop biomass for any specific crop interplanted with poplar decreased with the age of the plantation. The total plantation biomass increased from 12.08 to 90.59 Mg ha⁻¹ and NPP varied from 5.69 to 27.9 Mg ha⁻¹ year⁻¹. The biomass accumulation ratio ranged from 2.1 to 3.2. Total annual litter fall was in between 1.95 and 10.00 Mg ha⁻¹ year⁻¹, of which 92–94% was contributed by leaf litter. Compartmental models were developed for dry matter distribution in agroforestry systems involving young (3-year-old) and mature (9-year-old) poplar trees interplanted with various crops, the crops being grown in two rotations maize (Zea mays) – wheat (Triticum aestivum) – turmeric (Curcuma domestica) and pigeonpea (Cajanus cajan) – turmeric. This study substantiates the potential of Populus deltoides G₃ under agroforestry combinations.     

Combined surface drip irrigation and fertigation significantly increase biomass and carbon storage in a <Emphasis Type="Italic">Populus</Emphasis> × <Emphasis Type="Italic">euramericana</Emphasis> cv. Guariento plantation

Fast-growing poplar plantations are considered of great benefit to both timber production and carbon (C) sequestration, and are increasingly planted for multiple purposes worldwide. Irrigation and fertilization are common management practices in plantations in semiarid regions. However, quantitative investigation of the integrative effect of surface drip irrigation and fertigation (SDIF) on biomass and C storage in poplar plantations remains limited. In this study, we conducted a field experiment on a fast-growing poplar cultivar (Populus × euramericana cv. Guariento) plantation to compare the combination of surface drip irrigation and fertigation in growing seasons with conventional management (control; CK). Experiments repeated over 2 years showed that SDIF significantly increased biomass and C storage in both trees and soil in the plantation compared with the CK. Tree biomass C in SDIF-treated and CK stands after the first year of the experiment (age 5) was 6.20 and 4.05 t C ha^?1, respectively, and the difference further increased, i.e., 15.18 and 8.63 t C ha^?1, respectively, after the second year of the experiment (age 6). There was 53 and 76 % higher C storage in SDIF-treated trees than in the CK trees after the first and second years of the experiment, respectively. The SDIF increased the soil C concentration, especially in the surface soil at 0- to 40-cm depth. Soil organic C at a depth of 0–60 cm under the SDIF treatment was 45.42, 50.87 and 61.32 t C ha^?1 in the 1st, 2nd and 3rd years, respectively, with annual increases of 12 and 21 % between the first and second, and second and third year, respectively. The corresponding soil organic C in the CK was 43.08, 43.57 and 47.92 t C ha^?1 in the 1st, 2nd and 3rd years; the annual increases were only 1 and 10 %, respectively. The results confirmed the significant effect of the combined management on C storage in poplar plantations, thus we suggest it can be applied in forestry management, even though it generally did not change C concentrations of tree components.     

Growth dynamics and biomass accumulation of 8-year-old hybrid poplar clones in a short-rotation plantation on a clayey-sandy mining substrate with respect to plant nutrition and water budget

In 1995 a short-rotation plantation (2.5 ha) was established in the mining region Welzow-Süd in Brandenburg, Germany, on a clayey-sandy, lignite- and pyrite-free substrate in order to study the biomass potentials of fast-growing tree species (hybrid poplar clones). In this study, special emphasis was placed on yield aspects as well as on the interaction between soil and plants, especially with regard to the plant nutrition and soil–water relationships. So far, the results indicate that the cultivation of hybrid poplar clones in a short-rotation plantation is an adequate tool for establishing alternative land-use systems in the post-mining landscape as a potential source of biomass energy. Aboveground biomass production ranged from 24–49 t dry matter (DM) per hectare at age 8. In particular during this period of investigation, nitrogen nutrition of the clones decreased to below a threshold of 20 mg g^–1 DM in the year 2002. Investigations of the water budget of low- and high-yielding clones indicated that differences in the biomass accumulation seemed to be accompanied by different water-use efficiencies.