杉木生长及土壤特性对土壤呼吸速率的影响

在江西大岗山生态站选择不同发育阶段杉木人工林,研究土壤呼吸速率、土壤性质和年凋落物量的变化特征以及它们之间的相互关系。结果表明:杉木人工林随林分发育过程中林龄增加,林分年凋落物量和土壤纤维素酶活性逐渐增加;蔗糖酶活性呈现出先增加后降低的变化趋势,而淀粉酶活性无明显变化规律。土壤理化性质表现为幼龄林阶段较好,中龄林最差、近熟林-过熟林又逐渐恢复的变化特征;但不同指标恢复速度不同。土壤呼吸速率从幼龄林到近熟林呈明显先降低后增加的变化规律;从近熟林到成熟林略有增加,但增加不显著;过熟林时又显著降低,达到中龄林水平。通径分析表明,不同土壤性质对土壤呼吸速率表现出不同程度的影响;在被研究的土壤性质中,年凋落物量、土壤有机碳含量和纤维素酶活性对土壤呼吸速率表现出更强烈的直接影响和间接影响作用。     

Effects of irrigation and balanced fertilization on nutrient cycling in a Douglas fir stand

The effects on growth and nutrient status of an increased availability of all major nutrients was studied in a 40 year old Douglas fir stand. The nutrient amounts were applied by daily sprinkling and were in fixed, optimal proportions to the estimated annual uptake of N. Irrigation was included to avoid drought stress. The nutrient applications were also done in combination with a lower NH₄ load, realized under a roof that was placed above the ground. According to nutritional standards nitrogen supply was optimal and was related to the moderately high atmospheric N inputs. Nutrition of P, K and in some years Ca seemed critical.In all four studied growing seasons water additions resulted in a growth increase, of 30 to 40%. Irrigation decreased needle fall. Nutrient applications increased the needle concentrations of P and K considerably, but this did not result in a growth enhancement. Fertilization also increased K and P in shedded needles. Only minor leaching losses were calculated. The recovery in trees of fertilizer K and P was maximally 15%. Input-output budgets suggested that P was strongly retained in the soil. The decrease in NH₄ load had slightly decreased N availability and soil acidification, and seemed to enhance tree growth. The use of tree growth as a parameter to evaluate the effects of an improved nutritional balance is discussed.     

The nature of inbreeding in a seed orchard of Douglas fir as shown by an efficient multilocus model

Summary The amounts of self-fertilization versus consanguineous matings (as measured by effective selfing) was estimated in a seed orchard of Douglas-fir, using progeny array data at six allozyme loci. The orchard is family structured, consisting several grafts (clones) and/or open-pollinated (o-p) progeny from each of several plus-trees. Population-wide selfing rates were found to be 7% for the o-p trees and 2% for the cloned trees. Estimates of mating system parameters for individual trees showed this difference for average outcrossing rate t (1) still largely remained when outcrossingpollen gene frequency p was not allowed to vary among trees and (2) disappeared when p was allowed to vary among trees. Under this joint t and p estimation, o-p trees showed both significant variation of t (based upon a one-way ANOVA grouped by common plus-tree) and significant regressions of p on ovule genotype (indicative of consanguineous matings); cloned trees showed neither. This higher rate of consanguineous mating for o-p trees might be explained by the larger and more variable size of o-p families in the orchard. Estimates of outcrossing rate t and outcrossingpollen gene frequency p were based upon a multilocus model which makes full use of the information in the data. The increased information it gives over observed outcross models is equivalent to adding 30–50% more loci, and it gives enough degrees of freedom to jointly estimate t and p for individual trees (individual progeny arrays) under certain conditions. In addition, inclusion of megagametophyte data nearly doubles the information about the mating system of individual trees.     

Effects of different rotations on carbon sequestration in Chinese fir plantations

Aims Under the context of global climate change, scientific management is the main way to enhance carbon sequestration of plantation forests. A reasonable rotation is one of the intensive management strategies, adjusting forest structure. The decline of productivity after continuous multigenerational cultivation is strongly related to its rotation. Therefore, it is necessary to study the effects of different rotations on carbon sequestration of Chinese fir (Cunninghamia lanceolata) plantations, which can provide a theoretical basis for their sustainable management.
Methods We set up sampling fields of Chinese fir plantations with different age sequences, and used the observation data to test the FORECAST model. We then simulated the effects of different rotations on Chinese fir plantations sequestration using FORECAST model.
Important findings The results showed that over a 150-year period, total carbon sequestration was highest under short rotation length (15-year). However the carbon persistence was poorest and the decline of carbon between each rotation was biggest, indicating an unsustainable management model. Compared with short rotation, the total carbon sequestration under normal rotation (25-year) and long rotation (50-year) was lower. However, the carbon persistence under long rotation was strongest, which was beneficial to maintaining carbon stability during each rotation. Under good site conditions (site index (SI) = 27), the shorter the rotation was, the more severely the soil fertility was consumed. In order to have persistent carbon sequestration rates in Chinese fir plantations, we suggest that rotation should be longer than 25 years. Application of FORECAST model can help quantitatively assess carbon sequestration capacity of forest plantations, which varies under different management strategies.     

不同轮伐期对杉木人工林碳固存的影响

在全球气候变化背景下, 科学的经营管理是人工林碳汇提升的主要途径。合理轮伐期从一定程度上反映了人工林集约经营的理念, 是实现森林结构调整的主要影响因素之一。杉木(Cunninghamia lanceolata)多代连栽出现立地生产力下降与轮伐期的选择密切相关, 开展不同轮伐期对杉木人工林碳固存影响的研究, 可为其可持续经营提供理论依据。通过设置不同年龄序列的杉木人工林野外观测样地, 应用野外观测数据对FORECAST模型进行验证, 在此基础上模拟不同轮伐期对其碳固存的影响。结果表明: (1)短轮伐期(15年)在150年间的总固碳量较高, 但固碳持久性较低, 每个轮伐期之间的固碳量下降幅度较大, 是一种不可持续的经营模式。(2)正常轮伐期(25年)和长轮伐期(50年)的总固碳量低于短轮伐期, 但长轮伐期固碳持久性更强, 有利于维持每个轮伐期内固碳量的稳定。(3)在好的立地条件下(立地指数(SI) = 27), 轮伐期越短对地力消耗影响越大, 为了碳固存的持久性, 建议杉木人工林的生态轮伐期选择在25年以上。(4)应用FORECAST模型可以定量地评估人工林的固碳能力, 且该固碳能力是基于不同经营管理措施下的可持续固碳能力。     

Genecology of Douglas fir in western Oregon and Washington

BACKGROUND AND AIMS: Genecological knowledge is important for understanding evolutionary processes and for managing genetic resources. Previous studies of coastal Douglas fir (Pseudotsuga menziesii var. menziesii) have been inconclusive with respect to geographical patterns of variation, due in part to limited sample intensity and geographical and climatic representation. This study describes and maps patterns of genetic variation in adaptive traits in coastal Douglas fir in western Oregon and Washington, USA. METHODS: Traits of growth, phenology and partitioning were measured in seedlings of 1338 parents from 1048 locations grown in common gardens. Relations between traits and environments of seed sources were explored using regressions and canonical correlation analysis. Maps of genetic variation as related to the environment were developed using a geographical information system (GIS). KEY RESULTS: Populations differed considerably for adaptive traits, in particular for bud phenology and emergence. Variation in bud-set, emergence and growth was strongly related to elevation and cool-season temperatures. Variation in bud-burst and partitioning to stem diameter versus height was related to latitude and summer drought. Seedlings from the east side of the Washington Cascades were considerably smaller, set bud later and burst bud earlier than populations from the west side. CONCLUSIONS: Winter temperatures and frost dates are of overriding importance to the adaptation of Douglas fir to Pacific Northwest environments. Summer drought is of less importance. Maps generated using canonical correlation analysis and GIS allow easy visualization of a complex array of traits as related to a complex array of environments. The composite traits derived from canonical correlation analysis show two different patterns of variation associated with different gradients of cool-season temperatures and summer drought. The difference in growth and phenology between the westside and eastside Washington Cascades is hypothesized to be a consequence of the presence of interior variety (P. menziessii var. glauca) on the eastside.     

Tree allometry of Douglas fir and Norway spruce on a nutrient-poor and a nutrient-rich site

Research related to the allometric relationships of tree height and projected tree crown area to diameter at breast height was conducted to look at the biological suitability and timber production potential of Douglas fir under the conditions present in central Europe. The dependence of allometric relationships on soil nutrient conditions were described in forest stands of Douglas fir and Norway spruce. The studied sites were climatically similar but differed in soil nutrient availability. A significant difference was found in the allometric relationships of Norway spruce trees from the nutrient poor and nutrient rich site. In contrast to the Norway spruce, there was no significant effect of site fertility on allometric relationships for Douglas fir suggesting that its allocation patterns were less sensitive to site nutrient conditions. Stem growth increment, which was measured weekly during two consecutive seasons for both species, was related to the weather conditions and available soil moisture. Stem growth of Douglas fir began about 2 weeks earlier than in the Norway spruce at both sites. At the nutrient rich site, most of the stem growth of both species occurred at the beginning of the season, while growth at the other site was more evenly distributed throughout the season. Data obtained in this study will be useful for modeling stem growth and analysis of water use efficiency of these two tree species.     

Effects of a single event of close inbreeding on growth and survival in steelhead

For two populations of Alaskan steelhead (Oncorhynchus mykiss) of common ancestry we evaluated effects of inbreeding in second-generation descendants of wild fish by comparing progeny of full-sibling matings to those of non-inbred controls to determine if a single event of close inbreeding has significant effects on survival and growth in captivity or the wild. In captivity, both survival and size were highly variable between inbred and control types within each line and among the five broods during five periods of freshwater culture. However, no consistent patterns of inbreeding enhancement or depression between types within lines across years were evident. In contrast, in the wild marine environment, 34 of 34 pairwise comparisons between inbred and control types in body size of returning adults after 2 or 3 years at liberty in the ocean were consistent with inbreeding depression with significant inbreeding depression varying from 2.9% for female length to 20.0% for female weight. Survival of marked juveniles (smolts) to adults in the wild marine environment was consistently and significantly lower in inbred types for both lines, for an average inbreeding depression of 78.8%. The results underscore the potential problems that can arise from using protective culture technologies, including captive broodstocks, to supplement endangered populations, and they highlight the genetic hazards that can be faced by small wild populations. This study demonstrates that high natural mortality or selection increases the amount of inbreeding depression detected in survival. Inbreeding effects on survival and growth in captivity can be poor indicators of survival and growth in a wild marine environment.     

Mapping of quantitative trait loci controlling adaptive traits in coastal Douglas fir. III. Quantitative trait loci-by-environment interactions

Quantitative trait loci (QTL) were mapped in the woody perennial Douglas fir (Pseudotsuga menziesii var. menziesii [Mirb.] Franco) for complex traits controlling the timing of growth initiation and growth cessation. QTL were estimated under controlled environmental conditions to identify QTL interactions with photoperiod, moisture stress, winter chilling, and spring temperatures. A three-generation mapping population of 460 cloned progeny was used for genetic mapping and phenotypic evaluations. An all-marker interval mapping method was used for scanning the genome for the presence of QTL and single-factor ANOVA was used for estimating QTL-by-environment interactions. A modest number of QTL were detected per trait, with individual QTL explaining up to 9.5% of the phenotypic variation. Two QTL-by-treatment interactions were found for growth initiation, whereas several QTL-by-treatment interactions were detected among growth cessation traits. This is the first report of QTL interactions with specific environmental signals in forest trees and will assist in the identification of candidate genes controlling these important adaptive traits in perennial plants.     

In vitro pollen tube growth and penetration of female gametophyte in Douglas fir (Pseudotsuga menziesii)

 Pollen tube and female gametophyte interactions in Douglas fir (Pseudotsuga menziesii) were examined in vitro. Formation of pollen tubes in Douglas fir occurred on a modified Murashige and Skoog medium in which concentrations of H₃BO₃ and Ca(NO₃)₂ were altered and supplemented with sucrose and polyethylene glycol. Addition of 100 μg/ml H₃BO₃ and 300 μg/ml Ca(NO₃)₂ resulted in optimum pollen viability. Lack of H₃BO₃ inhibited pollen tube formation. Addition of H₃BO₃ and Ca(NO₃)₂ significantly increased pollen tube formation within one week in culture. Using a medium supplemented with mannitol, viability of Douglas fir pollen can be sustained for 7 weeks in culture, about the same length of time as in vivo. However, pollen tubes are not formed. This suggests that the factors responsible for tube formation reside in the external environment of the pollen. Culture of female gametophytes to examine egg viability and longevity had not been done previously. We found that egg viability in culture is short-lived, and therefore the window to study and manipulate events of fertilization in Douglas fir is very limited. In spite of this, about 7% of the female gametophytes that were co-cultured became penetrated by pollen tubes. In vitro archegonial penetration has been repeatedly achieved, but pollen tubes also penetrated other parts of the female gametophytes. Pollen tubes also penetrated non-viable eggs. Most female gametophytes were not penetrated because of pollen tube branching and swelling, failure of tubes to orient towards the female gametophytes, or premature pollen tube death due to plasmolysis. This report outlines the first attempt towards in vitro fertilization in conifers. Received: 13 March 1997 / Revision accepted: 6 June 1997     

不同密度杉木林对林下植被和土壤微生物群落结构的影响

为揭示土壤养分和细菌群落对林下植被调控的响应机制, 调查了浙江开化3种林分密度(高密度(KH)、中密度(KM)和低密度(KL))的17年生杉木人工林林下植被和生物量, 测定土壤理化性质, 并基于16S rDNA高通量测序技术分析细菌群落结构变化。结果表明, 3种密度的杉木林下植被地上部分总生物量为0.10-2.10 t·hm^-2, 且优势植物物种差异显著。理化性质测定分析发现, 高密度与低密度林分的土壤pH、有效磷含量差异显著。相关性分析表明, 土壤pH与林下植被中草本、灌木生物量及总生物量均呈显著正相关关系, 土壤有机质含量与灌木植被生物量及林下植被总生物量呈显著正相关关系, 速效钾含量与灌木植被生物量呈显著正相关关系。土壤微生物群落结构分析可知, 3种密度杉木林地土壤中酸杆菌门、变形菌门、放线菌门和绿弯菌门为优势菌群, 总相对丰度占比超过80%。冗余分析(RDA)表明土壤pH、碱解氮、有效磷和速效钾含量是土壤细菌群落结构变化的关键影响因素。酸杆菌门的优势亚群为Gp2、Gp1、Gp3和Gp6, 占酸杆菌群的51.32%-57.38%, 且随林分密度降低, 林下植被增多, Gp1占比增大, Gp2和Gp6占比下降; Gp6相对丰度与pH呈极显著负相关关系。可见, 杉木纯林经营中适度降低林分密度有利于林下植被生长和良好细菌群落结构保持, 有利于维持杉木林地土壤肥力, 实现可持续经营。     

Impacts of a native root-rotting pathogen on successional development of old-growth Douglas fir forests

Because Pseudotsuga menziesii (Douglas fir), an early seral dominant in western Oregon forests, is particularly susceptible to the pathogenic root rot caused by the fungus Phellinus weirii, it was hypothesized that successional development in affected forests would be accelerated. The basal area of late successional tree species and common shrubs were compared inside and outside Phellinus weirii“infection centers”. Future successional impacts indirectly caused by disease presence were assessed by comparing the abundance of regenerating tree species inside and outside of these centers. Results for old-growth sites in the lower Cascades supported the initial hypothesis. The presence of Phellinus weirii at these sites appears to push changes in the late successional species basal area along the same trajectory. At the Coast Range sites, however, shrub growth was greatly enhanced rather than the growth of Tsuga heterophylla (western hemlock), the only late successional tree species at these sites. Regeneration of trees was sparse in all areas and was negatively correlated with the basal area of existing western hemlock, and not directly correlated with the presence of the pathogen. However, because the basal area of western hemlock is influenced by the presence of disease in the Cascade sites, Phellinus weirii may be an influential indirect factor in the future successional direction of the sites. This study demonstrates the potential importance of native pathogens in determining the successional status of a community, as well as the importance of such biotic agents in the physical structure of multi-strata forested communities as a whole. Received: November 1996 / Accepted: 27 March 1997     

Investigating the formation and growth of alpha-particle radiation-induced foci of altered hepatocytes: a model-based approach

The effect of alpha-particle radiation on the formation and increase in volume of preneoplastic liver lesions was investigated in an animal experiment. Mice were divided into four groups; two groups received different doses of the alpha-particle-labeled antibody (213)Bi-anti CD19 ((213)Bi-CD19), Thorotrast was administered to one group, and one group was left untreated. Hematoxylin and eosin-stained liver sections were evaluated for preneoplastic foci of altered hepatocytes 6, 12 and 17 months after treatment. The density and size distribution of focal transections were described by a mechanistic model for the formation and growth of foci of altered hepatocytes. The negative control and the (213)Bi-CD19 groups were combined to investigate the dose-response relationship for model parameters describing the formation and growth of foci of altered hepatocytes. Although (213)Bi-CD19 was given by single injection, the effect on formation of foci of altered hepatocytes lasted for the entire experiment. Likelihood-ratio tests comparing nested models showed that (213)Bi-CD19 increases the rates of both the formation and growth of foci of altered hepatocytes. Comparing the effects of Thorotrast with those of (213)Bi-CD19 revealed that Thorotrast had an effect similar to that of a low dose of (213)Bi-CD19, but the effect on focus formation was slightly smaller whereas the effect on focus growth was slightly higher for Thorotrast, in contrast to a low dose of (213)Bi-CD19.     

Effects of non-nutritive sucking on heart rate,respiration and oxygenation: a model-based signal processing approach

Several studies support the idea that the use of pacifiers can reduce the risk of Sudden Infant Death Syndrome. To investigate the effect of non-nutritive sucking (NNS), we measured heart rate, abdominal respiration, EMG and arterial oxygen saturation of 20 neonates. Also, in 10 of these neonates, changes in cerebral hemoglobin concentrations were acquired by means of near-infrared spectroscopy. Using a parametric technique to model the heart rate as a sum of exponentially damped sinusoids, two main frequency components were found in the heart rate during NNS: a frequency of approximately 0.08 Hz due to the alternation of sucking bursts and pauses, and a frequency of approximately 0.8 Hz that reflects the influence of the respiration. Our analysis shows that it is the alternation of bursts and pauses itself that causes the increased heart rate variability, and that this is not due to increased effort. This suggests that the neuronal mechanism regulating NNS also stimulates the heart rate. From our measurements, no effect of NNS on cerebral or peripheral oxygenation could be found. Furthermore, we show that our model-based signal processing technique is well suited for the analysis of non-stationary biomedical signals.     

Effect of temperature and photoperiod on diapause development in a Douglas fir seed chalcid, Megastigmus spermotrophus

Douglas fir seeds infested by diapausing larvae of a chalcid, Megastigmus spermotrophus, were transferred under different temperature and photoperiod regimes at various dates during autumn and winter. Both winter diapause and prolonged diapause were compared to the diapause patterns observed in control lots kept under natural conditions. The results showed that exposure to low temperatures in autumn and winter is required for the completion of diapause development. Median adult emergence dates and the date of transfer of larvae to 20°C were negatively correlated. The frequency of prolonged diapause of larvae transferred to 20°C decreased significantly after November. When larvae were submitted to different constant temperatures, the longer the daylength, the higher and faster the reactivation. These results suggest that chalcid larvae can perceive daylength through the seed coat. This phenomenon is probably related to the fact that most of the infested seeds falling in autumn are usually covered by a layer of leaf litter during the winter. Received: 14 June 1996 / Accepted: 24 February 1997