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1.
Vegetation control (VC) in forest plantations often increases growth of crop trees but can also affect biomass and nutrient partitioning to tree components. We examined above-ground biomass and macronutrients, leaf area and crown structure in 5-year old Douglas-fir (Pseudotsuga menziessi (Mirb.) Franco) growing with VC and with no vegetation control (NVC) in coastal Washington, United States of America. Trees in VC had larger stem, branch, foliage and total biomass than trees of equal stem diameter at 1.3 m above ground in NVC. The difference in component biomass between treatments was in the order: branch > foliage > stem. Trees in the VC regime did not differ in macronutrient concentration in stem, branch and foliage except for branch N which was greater in NVC than in VC. Differences in tree macronutrient stores between VC and NVC ranged from 2.2 times for Mg to 2.6 times for N and K. The relationship between stem diameter and leaf area was linear in both VC treatments. The relationship between stem diameter and foliage biomass was curvilinear for both VC treatments. Results of this study support the need for separated allometric equations to estimate biomass for young Douglas-fir growing in areas with and without VC.  相似文献   

2.
沙棘林木生长与地上部生物量动态   总被引：2，自引：0，他引：2  
依据１９９８年在半干旱黄土丘陵区安塞、吴旗的调查资料,对沙棘年生长及单株地上部生物量进行了分析。结果表明：（１）时间的三次系基式与生长的关系能较好地反映生长期内生长与时间的关系;（２）沙棘单株地上部各器官生物量占地上部生物量的分配比率顺序为：枝〉茎〉叶〉桔枝;且枝、叶、枯枝生物量与树彰有十分显著的相关关系,茎与树龄间有的相关关系;（３）可用树高、地径、树个械模型与地径、冠幅、多年生枝长结合模型估测  相似文献   

3.
对湖南省黄皮树１１个种源１年生苗木４个性状组２０个性状的遗传参数及其相关选择效率作了测定和分析。其结果表明：（１）４个性状组中，１７个性状在种源间存在显著差异，其中，生产力性状组的性状表型及遗传变异系数较大，而幼苗、复叶和地上生长性状组的表型及遗传变异较小；（２）地上生长性状间、生产力性状间及其相互间具有显著的表型相关和遗传相关，这为黄皮树地上与地下、生长与生产力性状间的相关选择提供了理论依据；（３）幼苗、生长及复叶性状组的性状遗传力较高，多在０．５以上，而生产力性状的遗传力相对较低，一般在０．４以下；（４）用苗高、柄高及地径３个性状，对苗皮质量和根总质量的间接选择效率高于直接选择。其中，用苗高选择苗皮质量和根总质量的选择效率分别提高１６．１％和６２．９％；用地径选择苗皮质量和根总质量的选择效率则分别提高２４．５％和１０３．８％。苗高和地径可作为黄皮树生产力性状苗期选择的主要指标。  相似文献   

4.
Repeated fire is key to the viability of longleaf pine (Pinus palustris Mill.) ecosystems, but its acceptance as a management tool may depend on satisfactory longleaf pine growth. This is because longleaf pine establishment often has the dual-purpose of ecosystem restoration and stemwood production. Timely recovery of scorched foliage among longleaf pine seedlings and saplings supports maximum juvenile growth. We identified two means of foliage re-establishment in the growing season after prescribed fire regardless of the season of fire application. New foliage growth after spring or fall fire was correlated with un-scorched foliage biomass and the presence of lateral branches. After prescribed fire in spring, foliage biomass recovery also appeared to benefit from the mobilization of starch. The high carbon demand of foliage recovery after fall prescribed fire was associated with interruption of seasonal starch accumulation in the stem and taproot. The implication of low starch accumulation in stem and taproot tissues during the growing season after fall prescribed fire is unknown and warrants further investigation. Our results demonstrate a positive influence of residual foliage, lateral branches, and stored starch on timely foliage recovery of young longleaf pines after fire. Together with knowledge of longleaf pine development and fuel and climate conditions at the time of prescribed fire, this information will aid prescribed fire practitioners charged with maintaining longleaf pine stands of high vigor.  相似文献   

5.
Calliandra calothyrsus has been reported to have potential for agroforestry in the humid lowlands of West and Central Africa. Provenance evaluation of the species was initiated in Yaounde, Cameroon with the objective of identifying adapted provenances with desirable traits for inclusion in evaluation of the management of various agroforestry technologies being developed for the humid lowlands of the region. Fifteen provenance seed collections from Central America and southeast Asian sources were included in the trial. Results indicate that enormous genetic variation exists between these provenances. The highest yielding provenance produced 1.8 and 2.5 times, respectively, wood and leaf biomass compared to the lowest yielding provenance. Most of the provenances evaluated flowered during the first six months after establishment while all the provenances (15) flowered by the end of the first year. However, this initial flowering did not result in productive pod development and seed setting. Two years after planting, the trees were cut at a height of 0.05 m above ground level, and more than 80% of the stumps of all the provenances re-sprouted. Leaf nitrogen content ranged between 2.25% and 2.78% of dry weight. Six provenances had above average values in at least five of the six desirable traits considered i.e.: height, growth, stem development, leaf biomass, wood biomass, leaf litter productivity and total nitrogen content of leaves; these are recommended for further testing for inclusion in appropriate technologies for soil fertility improvement. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

6.
Leaf nitrogen distribution pattern was studied four times during the growing season in a 2-year-old Salix viminalis L. and Salix dasyclados Wimm. plantation in Estonia. We measured the vertical distributions of leaf nitrogen concentration, dry mass, leaf area and light environment (as fractional transmission of diffuse irradiance, a(d)) in the canopy. The light-independent nitrogen pool was evaluated as the intercept of the leaf nitrogen concentration versus a(d) relationship, and the nondegradable nitrogen pool was evaluated as the nitrogen remaining in abscised leaves. A strong vertical gradient of mass-based leaf nitrogen concentration was detected at the beginning of the growing season, and decreased steadily during canopy development. This decline had at least three causes: (1) the amount of nitrogen in the foliage was larger at the beginning of the growing season than at the end of the growing season, probably because of pre-existing root systems; (2) with increasing leaf area index (LAI) during the growing season, the proportion of leaf nitrogen in total canopy nitrogen that could be redistributed (light-dependent nitrogen pool) decreased; and (3) the photosynthetic photon flux density gradient inside the canopy changed during the season, most probably because of changes in leaf area and leaf angle distributions. Total canopy nitrogen increased almost proportionally to LAI, whereas the light-dependent nitrogen pool had a maximum in August. Also, the proportion of the light-dependent nitrogen pool in the total canopy nitrogen decreased steadily from 65.2% in June to 17.2% in September in S. dasyclados and from 63.3 to 15.1% in S. viminalis. The degradable nitrogen pool was always bigger than the light-dependent nitrogen pool.  相似文献   

7.
为探寻科尔沁沙地东南部草地生产力自然恢复的主要限制因素,该文采用3因素2水平析因设计研究了水、氮、磷添加对沙质草地的影响。8种处理分别为添加水(W)、加氮肥(N)、加磷肥(P)、加水+氮肥(WN)、加水+磷肥(WP)、加氮肥+磷肥(NP)、加水+氮肥+磷肥(WNP)和对照(CK),每种处理6次重复,随机分配在48个4m×4m的样方中,样方之间留2m缓冲带。研究结果表明:科尔沁沙质草地生产力的恢复受氮素的限制,与水和磷无关;2005年生长季所有添加氮肥的样方,生物量和地上净初级生产力均较对照明显增加(P<0.05);禾本科根量在地下生物量中占优势。受限于地下生物量测定,目前的研究可能低估了我国北方草地的净初级生产力。  相似文献   

8.
黄连木苗期年生长节律及其生物量分配规律   总被引：2，自引：0，他引：2  
为给黄连木幼苗生产管理提供参考,在定期观测的基础上,研究黄连木苗期年生长动态、生物量积累与分配规律以及植物生长指标与生物量组分的相关性。结果表明:在整个苗期生长过程中,黄连木的苗高、地径、冠幅生长均呈现"S"型曲线,用Logistic生长方程和生长曲线能对其动态生长节律进行很好地拟合。结合实际测量值将黄连木1年生幼苗的生长过程分为4个阶段:出苗期、生长初期、速生期和生长末期。各指标速生期的生长量占其总生长量50%以上;黄连木1年生苗木的地上与地下部分生物量比例为1.78∶1.00;苗木生物量各指标中,地径与苗高、茎干质量、叶干质量显著相关,苗高与茎干质量、叶干质量显著相关,茎干质量与叶干质量极显著相关。  相似文献   

9.
To test if some leaf parameters are predictors of productivity in a range of Populus deltoides (Bartr.) Marsh. x P. nigra L. clones, we assessed leaf traits and productivity in 2-month-old rooted cuttings from 31 clones growing in 4-l pots in a greenhouse, under conditions of controlled temperature and optimal irrigation. We evaluated four groups of variables describing (1) productivity (total biomass), (2) leaf growth (total leaf number increment and total leaf area increment rate), (3) leaf structure (specific leaf area and nitrogen and carbon contents) and (4) carbon isotope discrimination (delta), which is negatively correlated with time-integrated water-use efficiency. High-yielding clones did not necessarily display high leaf growth rates, but they displayed a larger total leaf area, lower specific leaf area and lower leaf nitrogen concentration than clones with low productivity. Total leaf area was mainly controlled by maximal individual leaf area and total leaf area increment rate (r = 0.51 and 0.56, respectively). Carbon isotope discrimination did not correlate with total biomass, but it was associated with total number of leaves and total leaf area increment rate (r = 0.39 and 0.45, respectively). Therefore, leaf area and specific leaf area were better indicators of productivity than leaf growth traits. The observed independence of delta from biomass production provides opportunities for selecting poplar clones combining high productivity and high water-use efficiency.  相似文献   

10.
Sources of variation in leaf area index (LAI; m2 of projected leaf area per m2 of ground area) and its seasonal dynamics are not well known in managed Douglas-fir stands, despite the importance of leaf area in forecasting forest growth, particularly in stands impacted by insects or disease. The influence of Swiss needle cast (SNC) on coastal Douglas-fir (Pseudotsuga menziesii var. menziesii [Mirb] Franco) LAI and litterfall dynamics was quantified by destructively sampling 122 stems from 36 different permanent plots throughout north coastal Oregon, USA, and by monitoring litterfall for 3 years in 15 of these plots. LAI, total annual litterfall, and the seasonal distribution of foliage and fine woody litterfall were all influenced by stand structural attributes, physiographic features, and SNC severity. Mean LAI in this study was 5.44 ± 2.16. The relatively low LAIs were attributed primarily to the effects of SNC on foliage retention, and secondarily to its direct measurement by hierarchical foliage sampling in contrast to indirect measurement by light interception or tree allometry. For a given stand structure and SNC severity, LAI was 36% greater in the fall after current year foliage was fully developed and older aged classes had not yet senesced. Annual litterfall expressed as a proportion of LAI at the start of the growing season varied from 0.13 to 0.53 and declined with increasing initial LAI. SNC also shifted more of the annual foliage litterfall to earlier in the spring. Fine woody litterfall experienced a different seasonal shift as the peak occurred later in the year on sites with high SNC, but this only occurred on northerly aspects. Defoliation from the endemic SNC pathogen can drastically reduce LAI and change both total and seasonal foliage litterfall patterns.  相似文献   

11.
Clearcutting is a common practice for removing woody vegetation in the semiarid tropics of northeast Brazil. The prevalent belief is that clearing increases carrying capacity for livestock by increasing herbaceous vegetation, yet little empirical evidence exists to support or refute the contention. We investigated the implications to small ruminant nutrition of clearcutting in the semiarid tropics of northeast Brazil. We found that biomass of herbaceous species increased sixfold following cutting of trees, but much of this increase was in the form of poorly palatable stem. The large supply of leaf litter from woody species that was typical of uncleared areas during the dry season was replaced by persistent green foliage on coppicing trees the year following clearing. This green foliage may enhance the nutritional quality of the diets of sheep and goats foraging on cleared areas during the dry season.  相似文献   

12.
The increasing demand for forest biomass for energy generation could be partially met by growing denser stands and use of fertilizer. Before this is done at large scale, more knowledge of the effects of stand density and fertilization on aboveground allocation patterns and stem form is needed. Therefore, effects of pre-commercial thinning (PCT) to 3000 stems ha?1, an unthinned dense control (C), and PCT combined with two levels of fertilization (100 kg ha?1 of nitrogen applied either during the establishment of the field experiment (F1) or annually (F2)) were examined in 23- to 26-year-old Scots pine (Pinus sylvestris L.) stands six years after the establishment of the field experiment. In total, 114 sample trees were harvested using destructive biomass sampling. The growth allocation and stem form of trees with diameter at breast height (DBH; 1.3 m height) >5.0 cm were not affected by either the PCT or fertilization. Small trees (DBH < 5 cm) in denser, unthinned control plots had more slender stems (lower DBH/height ratios) and allocated less growth to branches and foliage than trees in PCT plots. Fertilization had little effect on the stem form and growth allocation of the smallest trees. Therefore, effects of stem density and fertilization on stem form and growth allocation to foliage were only found for small suppressed trees, and the treatments had very little influence on dominant and codominant trees.  相似文献   

13.
为进一步了解柳树优良无性系的生长特点,为无性系的合理利用提供依据,对苏柳932,799,795,797和172等5个柳树优良无性系2年生幼林的树高、胸径、材积等生长指标以及生物量和形率进行了测定分析。结果表明,苏柳5个无性系的胸径平均值为4．28cm,其中苏柳172的平均胸径最大（4．71cm）;树高平均值为6．97m,其中苏柳795平均树高最高（7．75m）。苏柳795的形率qo．5、q0．7值分别为0．68,0．44,是各无性系中形率的最高值,主干生物量占单株地上部分总生物量的比例最高（76．02％）,出材率高,是优良的用材林树种;而苏柳932的总生物量最高,为12．35kg／株,枝量、叶量占总生物量的比例最大,为42．0％,14．4％,属于防风防浪和生物能源林的造林良种。  相似文献   

14.
Above‐ground biomass has been measured on fertilized and control plots up to stand age 31 years. Each biomass fraction was estimated by two statistically coupled linear models with squared diameter at breast height as independent variable. All fractions except reproductive structures of pine and dead branches of spruce were estimated at high precision levels, R. between 0.93 and 0.99. The above‐ground biomass fractions per hectare could be precisely described by stem volume with bark. Application of the models for prognostic purposes is discussed. Annual above‐ground net biomass production in pine increased from 2.05 to 4.34 MT d.m./ha‐yr on control plots over 11 years, while plots given complete fertilizer mixture ranged from 6.75 to 9.09. Spruce stands with a nearly optimum water relationship and fertilizer programmes yielded from 9.50 to 11.86 MT d.m./ha‐yr. The combination of energy and timber production in highly productive peatland stands is discussed.  相似文献   

15.
Development of leaf chloroplast ultrastructure at five levels in a willow (Salix cv. Aquatica gigantea) canopy was followed during one growing season in the field. Changes in chloroplast ultrastructure were compared with the rate of CO(2) uptake of the same leaves. The highest rates of CO(2) uptake were recorded in young leaves exposed to full available sunlight. In these leaves, the area of the grana stacks was less than 20% of the total chloroplast area and the degree of thylakoid stacking was less than 1.5. The chloroplasts of these leaves contained large amounts of starch and small amounts of plastoglobuli. As the canopy grew and the leaves in the lower parts of the canopy became shaded, the structure of the chloroplast thylakoids gradually changed. In leaves at the two lowest levels of the canopy, the degree of stacking at the end of the growing season was close to 2 and correspondingly the rate of CO(2) uptake was low. The areas of grana stacks and plastoglobuli in these chloroplasts increased and were about 30 and 10% of the chloroplast area, respectively, by the end of the growing season. The increase in the degree of thylakoid stacking was caused by increased biosynthesis of grana lamellae, which in general were thinner than the lamellae of young leaves. The length of the stroma lamellae did not change with leaf age. Morphometric measurements showed that the structure of the chloroplasts in leaves 160 cm above ground was dynamic and responsive to environmental conditions so that photosynthetic capacity remained high for 7 weeks despite an increase in leaf shading.  相似文献   

16.
One-year-old Norway spruce (Picea abies (L.) Karst.) seedlings were grown hydroponically in a growth chamber to investigate the effects of low and high nutrient availability (LN; 0.25 mM N and HN; 2.50 mM N) on growth, biomass allocation and chemical composition of needles, stem and roots during the second growing season. Climatic conditions in the growth chamber simulated the mean growing season from May to early October in Flakaliden, northern Sweden. In the latter half of the growing season, biomass allocation changed in response to nutrient availability: increased root growth and decreased shoot growth led to higher root/shoot ratios in LN seedlings than in HN seedlings. At high nutrient availability, total biomass, especially stem biomass, increased, as did total nonstructural carbohydrate and nitrogen contents per seedling. Responses of stem chemistry to nutrient addition differed from those of adult trees of the same provenance. In HN seedlings, concentrations of alpha-cellulose, hemicellulose and lignin decreased in the secondary xylem. Our results illustrate the significance of retranslocation of stored nutrients to support new growth early in the season when root growth and nutrient uptake are still low. We conclude that nutrient availability alters allocation patterns, thereby influencing the success of 2-year-old Norway spruce seedlings at forest planting sites.  相似文献   

17.
In this study, the biomass yield and morphological traits of plants were reported from an experiment involving six genotypes of willow in northern Poland. Willow was planted using a pole cutting system, which we designated Eco-Salix, on sites that were unsuitable for food crops. The results presented here are from the first rotation of a four-year cutting cycle. In the field trial, the average willow biomass yield of oven-dry matter was 7.87 Mg ha−1 year−1. Willow plants that were planted as pole cuttings after four growing seasons reached a height of 6.64 m and a stem diameter of 50.5 mm. Clone UWM 043 produced higher yields and more favourable morphological traits when compared to registered Polish cultivars. The willow biomass yield obtained on peaty muck soil was significantly higher than from willow that was grown on heavy textured silt soil. The biomass harvested from plots planted at a density of 5,200 plants ha−1 was 14% lower than plots that had a density of 7,400 plants ha−1.  相似文献   

18.
We investigated the individual and combined effects of elevated CO2 concentration and fertilization on aboveground growth of three poplar species (Populus alba L. Clone 2AS-11, P. nigra L. Clone Jean Pourtet and P. x euramericana Clone I-214) growing in a short-rotation coppice culture for two growing seasons after coppicing. Free-air carbon dioxide enrichment (FACE) stimulated the number of shoots per stool, leaf area index measured with a fish-eye-type plant canopy analyzer (LAIoptical), and annual leaf production, but did not affect dominant shoot height or canopy productivity index. Comparison of LAIoptical with LAI estimates from litter collections and from allometric relationships showed considerable differences. The increase in biomass in response to FACE was caused by an initial stimulation of absolute and relative growth rates, which disappeared after the first growing season following coppicing. An ontogenetic decline in growth in the FACE treatment, together with strong competition inside the dense plantation, may have caused this decrease. Fertilization did not influence aboveground growth, although some FACE responses were more pronounced in fertilized trees. A species effect was observed for most parameters.  相似文献   

19.
The stand density of a forest affects the vertical distribution of foliage. Understanding the dynamics of this response is important for the study of crown structure and function, carbon-budget estimation, and forest management. We investigated the effect of tree density on the vertical distribution of foliage, branch, and stem growth, and ratio of biomass increment in aboveground tissues; by monitoring all first-order branches of five trees each from thinned and unthinned control stands of 10-year-old Chamaecyparis obtusa for four consecutive years. In the control stand, the foliage crown shifted upward with height growth but the foliage quantity of the whole crown did not increase. In addition, the vertical distribution of leaf mass shifted from lower-crown skewed to upper-crown skewed. In the thinned stand in contrast, the foliage quantity of individual crowns increased two-fold within 4 years, while the vertical distribution of leaf mass remained lower-crown skewed. The two stands had similar production rates, numbers of first-order branches per unit of tree height, and total lengths of first-order branches. However, the mortality rate of first-order branches and self-pruning within a first-order branch were significantly higher in the control stand than in the thinned stand, which resulted in a higher ratio of biomass increment in branch. Thinning induced a higher ratio of biomass increment in foliage and lower in branch. The increased foliage quantity and variation in ratio of biomass increment after thinning stimulated stem growth of residual trees. These results provide information that will be useful when considering thinning regimes and stand management.  相似文献   

20.
The distribution and quantitative recovery of fertilizer N were determined in three 29‐ to 43‐year‐old stands of Scots pine, located in western Uppland, Central Sweden. The experimental technique involved was based on the use of 15N‐labelled fertilizer materials and non‐trenched microplots of special design. The standard dose of nitrogen applied was 160 kg N ha‐1. The primary topics examined were (1) fertilizer nitrogen accumulation in trees and in the soil system as influenced by nitrogen source, nitrogen application rate, time of application during the growing season, granule size of the nitrogen material, and method of placement, (2) distribution of labelled N within the tree (different organs of the tree), and (3) redistribution of accumulated N in the tree over an observation period of two to three growing seasons. When quantified at the end of the second growing season, the labelled N accumulation in trees, concerning plots treated with calcium nitrate or ammonium nitrate, averaged 36% (SD=7). The accumulation resulting from split doses did not differ significantly from that resulting from a single‐dose application, nor did granule size of the nitrogen materials have any significant effect on accumulation. For urea source of nitrogen, the recovery figure was markedly lower, averaging 28% (SD=6). When expressed as a percentage, the accumulation in trees was not significantly different for 40 and 160 kg nitrogen application rates. In one of the experiments application timing during the growing season proved to be an important factor determining the extent of fertilizer nitrogen accumulation in trees. The figures for total recovery of labelled nitrogen in above‐ground parts of trees and in soil, when restricting measurements to the forest floor and the 0–32 cm mineral soil, ranged from 46 to 84%, with an average of 60%. The recovery was lowest for a treatment with calcium nitrate, when applied relatively late in the growing season, and highest for a split application of urea. Treatments with urea source of nitrogen were characterized by a high accumulation of immobilized N in the organic LFH layer of the soils. Recovery figures exceeded 82 % for a 40‐kg N dose of nitrogen, regardless of the nitrogen source.  相似文献   

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