Simulation of the vegetation structure and function in a Malaysian tropical rain forest using the individual-based dynamic vegetation model SEIB-DGVM

An individual-based Dynamic Global Vegetation Model, the SEIB-DGVM, was adapted to a Malaysian tropical rain forest by incorporating formulas and parameters from a gap dynamics model, FORMIX3. After calibration, the model reconstructed forest structure (i.e., size structure, leaf area index, and woody biomass) and carbon fluxes (i.e., gross and net primary productivity) of a dipterocarp forest in Pasoh, Peninsular Malaysia. Sensitivity analysis demonstrated that the model was robust; forest structure and ecosystem functions moderately fluctuated due to changes in parameters and climatic environments. Sensitivity analysis also indicated that the success and decay of a dominant species group that monopolized the canopy layer greatly affected those of a less abundant, shade-intolerant group. This result indicates that even if environmental changes do not exhibit clear effects on dominant canopy species and/or whole forest structure, such changes may still substantially impact the biodiversity of subdominant species. In simulations without gap formation, woody biomass was overestimated and a shade-intolerant species group was eliminated. This finding indicates that incorporating gap formation into the individual-based model is essential for the appropriate simulation of forest biomass and biodiversity in this Malaysian tropical rain forest.     

NUTRIENT CYCLING IN THE DAHURIAN LARCH PLANTATION ECOSYSTEM

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Forest fires and vegetation during the Holocene in central Yakutia, eastern Siberia

In order to investigate the relationship between vegetation change and fire history in the Siberian boreal forest, fossil pollen and charcoal from two lakes in central Yakutia, eastern Siberia, were analyzed. The vegetation change inferred from the pollen analysis was similar to that found in previous research in the region. Open larch forest covered this region during the late Glacial and early Holocene periods. Later, during the mid-Holocene, Scots pine expanded its range. The low levels of charcoal in the lake deposits represent surface forest fires, suggesting that the present-day surface fire regime has been taking place since at least 6,500 calibrated years before the present (cal yr BP) and that stand-replacing fire has not occurred during the Holocene. Larch and Scots pine forests, which are characterized by surface fire regimes, have been predominant since the early Holocene.     

Effects of deforestation on microbial diversity in a Siberian larch(Larix sibirica) stand in Mongolia

For evaluating microbial community changes in a Siberian larch stand disturbed by forest fire or clearcutting,357 clones were randomly selected and sequenced using a culture-independent approach and 16S rRNA sequencing to characterize the bacterial composition and diversity from the different disturbed Siberian larch stands.Interestingly,the burned larch stand had an increase in the relative amounts of b-proteobacteria and Firmicutes and a decrease in Acidobacteria,while Gemmatimonadetes increased Verrucomicrobia decreased in the harvested larch stand.Microbial diversity and richness were higher in the undisturbed larch stand than the disturbed(burned or clear-cut)larch stands,and the influence of clear-cutting was more negative than that of the forest fire.This study indicates that evaluating the microbial diversity of undisturbed,burned,and clear-cutting Siberian larch stands provides information about the impact of forest disturbances on soil microbial communities,which may be helpful for understanding and evaluating soil health and devising reafforestation strategies for larch.     

诱导改造对大兴安岭低质林土壤理化性质的影响

2009年对大兴安岭地区的阔叶混交次生林及白桦萌生低质林进行不同带宽皆伐,将每条皆伐带分为3段,分别种植西伯利亚红松、落叶松和樟子松,2011年8月测定林分的土壤理化指标。结果表明:不同方式改造后土壤密度均不同程度地降低,而土壤毛管持水量、毛管孔隙度均不同程度地升高;与对照样地相比,阔叶混交次生林不同诱导改造后土壤全氮含量均升高(落叶松林升高98.26%,西伯利亚红松林升高72.70%,樟子松林升高44.91%),除落叶松林土壤全磷含量3.35g·kg-1保持不变外,西伯利亚红松林和樟子松林全磷含量均降低;与对照样地相比,白桦萌生低质林不同诱导改造后土壤全磷、全氮含量均有所降低,全磷含量降低程度表现为西伯利亚红松林降低38.90%、落叶松林降低33.15%、樟子松林降低11.78%,全氮含量降低程度表现为西伯利亚红松林降低36.02%、落叶松林降低36.75%、樟子松林降低37.68%;综合分析所有改造林,土壤有机质含量与全氮、全钾含量显著正相关(P﹤0.05);不同带宽西伯利亚红松林的土壤pH值、有机质含量、全氮含量及全钾含量变异系数最大,说明带宽对西伯利亚红松诱导林土壤理化性质有显著影响。     

不同土地利用类型下川西亚高山土壤活性有机碳研究

采用常规方法,测定、分析了川西亚高山5种不同土地利用类型的土壤活性有机碳含量,结果显示土壤有机碳含量均是上层大于下层。在0～10cm土层土壤总有机碳含量表现为灌木林地落叶松林地退耕还林地云杉林地农田;10～20cm土层土壤总有机碳含量表现为灌木林地落叶松林地云杉林地退耕还林地农田。上下层平均值来看灌木林地有机碳含量最高为79.86g.kg-1,是云杉林地的2.85倍,是落叶松林地的1.49倍,是退耕还林地的1.62倍,是农田的3.34倍,表现为灌木林地落叶松林地退耕还林地云杉林地农田。上下层土壤微生物生物量碳含量均表现为灌木林地落叶松林地退耕还林地云杉林地农田;上下层土壤水溶性有机碳含量均表现为落叶松林地灌木林地云杉林地退耕还林地农田。     

Models for predicting tree and stand development on larch plantations in Hallormsstaður,Iceland

The aim was to model the growth of Siberian larch (Larix sibirica Ledeb.) and Russian larch (Larix sukaczewii Dyl., syn. L. sibirica var. sukaczewii) plantations in Hallormsstaeur, Iceland. The field inventory was carried out in eastern Iceland in June 2006. Models were constructed for predicting dominant height, total tree height and 5-year diameter increment. Several linear and non-linear forms of models were tested in preliminary analyses to find the equations that fitted the modelled characteristics best. Due to the spatially hierarchical correlation structure of the data (stands, plots and trees), the assumption of non-correlated error terms did not hold. Therefore, a random parameter modelling approach was adopted using mixed models when the estimates obtained for the random effects were statistically significant. The variance estimates for the random effects can be further used to calibrate the models. The models generated here performed well with independent test data and were consistent with the forest growth theory. They can be used to evaluate site quality and to estimate the growth and yield of larch stands in eastern Iceland in connection with forest planning.     

不同混交比例的人工针阔带状混交林生物量变化动态

通过对20世纪80年代营造的针阔混交林生物量调查表明,红松阔叶混交林生物量比红松纯林高4.9%~21%,落叶松阔叶混交林生物量比落叶松纯林高7.6%~21.3%,红松阔叶混交林单株生物量比红松纯林高120%~148%,落叶松阔叶混交林单株生物量比落叶松纯林高108%~151%,在不同混交林型中,灌木层和草本层植物种类丰富、数量多,所以其生物量大于纯林。     

Lower forest–grassland ecotones and 20th Century livestock herbivory effects in northern Mongolia

We studied five lower forest–grassland ecotones in the Darhad Valley in northern Mongolia and investigated the effects of 20th Century grazing regimes and changes in grazing management on ecotone dynamics at a local scale. A total of 2968 Siberian larch (Larix sibirica) trees were cored and tree-age distribution was constructed to determine 20th Century tree establishment. Tree age and location within the ecotones were correlated and seedling density and their distribution were explored to describe forest–grassland ecotone shift. To examine livestock herbivory effects on ecotone shift, the number of new trees was analyzed with five different grazing regimes and changes in grazing practices during the last 80 years in the Darhad Valley.We documented some evidence of ecotone shift into the adjacent grassland. Rates and patterns of ecotone shift varied with different grazing regimes. Siberian larch tree establishment was greater at overall grazing intensities of low and high levels, which were dominated by sheep and cattle grazing. In contrast, larch establishment was lower at overall grazing intensities of low and medium levels, which were dominated by goat grazing. Twentieth Century changes in grazing practices also influenced Siberian larch regeneration. An abrupt decline in Darhad Valley larch establishment during the 20th Century coincided with locally increased grazing pressure. Furthermore, regional climate variability showed important interaction with local grazing regimes in affecting larch regeneration. A 20th Century pulse in larch establishment coincided with a time period of regionally known warmer temperatures and locally reduced grazing pressure. Our results suggest that overall grazing intensity, livestock species composition, and changes in grazing patterns are important in understanding grazing effects on Siberian larch tree encroachment.     

A process model for simulating net primary productivity (NPP) based on the interaction of water-heat process and nitrogen: a case study in Lantsang valley

Terrestrial carbon cycle and the global atmospheric CO2 budget are important foci in global climate change research. Simulating net primary productivity (NPP) of terrestrial ecosystems is important for carbon cycle research. In this study, a plant-atmosphere-soil continuum nitrogen (N) cycling model was developed and incorporated into the Boreal Ecosystem Productivity Simulator (BEPS) model. With the established database (leaf area index, land cover, daily meteorology data, vegetation and soil) at a 1 km resolution, daily maps of NPP for Lantsang valley in 2007 were produced, and the spatial-temporal patterns of NPP and mechanisms of its responses to soil N level were further explored. The total NPP and mean NPP of Lantsang valley in 2007 were 66.5 Tg C and 416 g?m-2?a-1 C, respectively. In addition, statistical analysis of NPP of different land cover types was conducted and investigated. Compared with BEPS model (without considering nitrogen effect), it was inferred that the plant carbon fixing for the upstream of Lantsang valley was also limited by soil available nitrogen besides temperature and precipitation. However, nitrogen has no evident limitation to NPP accumulation of broadleaf forest, which mainly distributed in the downstream of Lantsang valley.     

Use of a simulation model and ecosystem flux data to examine carbon-water interactions in ponderosa pine

Drought stress plays an important role in determining both the structure and function of forest ecosystems, because of the close association between the carbon (C) and hydrological cycles. We used a detailed model of the soil-plant-atmosphere continuum to investigate the links between carbon uptake and the hydrological cycle in a mature, open stand of ponderosa pine (Pinus ponderosa Dougl. ex Laws.) at the Metolius river in eastern Oregon over a 2-year period (1996-1997). The model was parameterized from local measurements of vegetation structure, soil properties and meteorology, and tested against independent measurements of ecosystem latent energy (LE) and carbon fluxes and soil water content. Although the 2 years had very different precipitation regimes, annual uptake of C and total transpiration were similar in both years, according to both direct observation and simulations. There were important differences in ratios of evaporation to transpiration, and in the patterns of water abstraction from the soil profile, depending on the frequency of summer storms. Simulations showed that, during periods of maximum water limitation in late summer, plants maintained a remarkably constant evapotranspirative flux because of deep rooting, whereas changes in rates of C accumulation were determined by interactions between atmospheric vapor pressure deficit and stomatal conductance. Sensitivity analyses with the model suggest a highly conservative allocation strategy in the vegetation, focused belowground on accessing a soil volume large enough to buffer summer droughts, and optimized to account for interannual variability in precipitation. The model suggests that increased allocation to leaf area would greatly increase productivity, but with the associated risk of greater soil water depletion and drought stress in some years. By constructing sparse canopies and deep rooting systems, these stands balance reduced productivity in the short term with risk avoidance over the long term.     

Reconciliation of research on forest carbon sequestration and water conservation

Carbon sequestration and water conservation are two of the key ecosystem services that forests provide for societal need to address environmental issues.Optimization of the dual services is the ultimate goal in forest management for mitigating global climate change and safeguarding terrestrial water balance.However,there are some tradeoffs between gain in forest productivity and ecosystem water balance.We conducted literature review based on published articles for learned knowledge on forest carbon fixation and hydrological regulations.Some knowledge gaps and research needs are identified by examining the inter-connections between forest carbon sequestration and water conservation.Past researches have helped gain basic understanding of the mechanisms and controls of forest carbon fixation and hydrological regulations as two separate issues.Tools and approaches are well established for quantifying and monitoring forest carbon and hydrological issues,operating at different spatial and temporal scales.There are knowledge gaps on how to design afforestation schemes facilitating enhanced ecosystem services in forest carbon sequestration and water conservation.For the top-down planning of afforestation in regions where water availability is anticipated to be problematic,the questions of how much and where to plant for given land availability,known environmental implications,and sustained regional development and livelihood need to be addressed.For local management considerations,the questions of what and how to plant prevail.Efforts are needed in joint studies of forest carbon sequestration and water conservation functionalities,specifically in relation to establishment and management of planted forests aiming for delivering regulatory ecosystem services in carbon sequestration,water conservation and other social values.We propose an integrated framework with dual consideration of carbon sequestration and water conservation in forest management for future research pursue.     

Modeling annual production and carbon fluxes of a large managed temperate forest using forest inventories, satellite data and field measurements

We evaluated annual productivity and carbon fluxes over the Fontainebleau forest, a large heterogeneous forest region of 17,000 ha, in terms of species composition, canopy structure, stand age, soil type and water and mineral resources. The model is a physiological process-based forest ecosystem model coupled with an allocation model and a soil model. The simulations were done stand by stand, i.e., 2992 forest management units of simulation. Some input parameters that are spatially variable and to which the model is sensitive were calculated for each stand from forest inventory attributes, a network of 8800 soil pits, satellite data and field measurements. These parameters are: (1) vegetation attributes: species, age, height, maximal leaf area index of the year, aboveground biomass and foliar nitrogen content; and (2) soil attributes: available soil water capacity, soil depth and soil carbon content. Main outputs of the simulations are wood production and carbon fluxes on a daily to yearly basis. Results showed that the forest is a carbon sink, with a net ecosystem exchange of 371 g C m(-2) year(-1). Net primary productivity is estimated at 630 g C m(-2) year(-1) over the entire forest. Reasonably good agreement was found between simulated trunk relative growth rate (2.74%) and regional production estimated from the National Forest Inventory (IFN) (2.52%), as well as between simulated and measured annual wood production at the forest scale (about 71,000 and 68,000 m(3) year(-1), respectively). Results are discussed species by species.     

Methane emissions from upland forest soils and vegetation

Most work on methane (CH(4)) emissions from natural ecosystems has focused on wetlands because they are hotspots of CH(4) production. Less attention has been directed toward upland ecosystems that cover far larger areas, but are assumed to be too dry to emit CH(4). Here we review CH(4) production and emissions in upland ecosystems, with attention to the influence of plant physiology on these processes in forests. Upland ecosystems are normally net sinks for atmospheric CH(4) because rates of CH(4) consumption exceed CH(4) production. Production of CH(4) in upland soils occurs in microsites and may be common in upland forest soils. Some forests switch from being CH(4) sinks to CH(4) sources depending on soil water content. Plant physiology influences CH(4) cycling by modifying the availability of electron donors and acceptors in forest soils. Plants are the ultimate source of organic carbon (electron donor) that microbes process into CH(4). The availability of O(2) (electron acceptor) is sensitive to changes in soil water content, and therefore, to transpiration rates. Recently, abiotic production of CH(4) from aerobic plant tissue was proposed, but has not yet been verified with independent data. If confirmed, this new source is likely to be a minor term in the global CH(4) budget, but important to quantify for purposes of greenhouse gas accounting. A variety of observations suggest that our understanding of CH(4) sources in upland systems is incomplete, particularly in tropical forests which are stronger sources then expected.     

Carbon fluxes and their response to environmental variables in a Dahurian larch forest ecosystem in northeast China

The Dahurian larch forest in northeast China is important due to its vastness and location within a transitional zone from boreal to temperate and at the southern distribution edge of the vast Siberian larch forest. The continuous carbon fluxes were measured from May 2004 to April 2005 in the Dahurian larch forest in Northeast China using an eddy covariance method. The results showed that the ecosystem released carbon in the dormant season from mid-October 2004 to April 2005, while it assimilated CO2 from the atmosphere in the growing season from May to September 2004. The net carbon sequestration reached its peak of 112 g.m^-2.month ^-1 in June 2004 （simplified expression of g （carbon）.m^-2.month^-1） and then gradually decreased. Annually, the larch forest was a carbon sink that sequestered carbon of 146 g-m^-2.a^-1 （simplified expression of g （carbon）.m^-2.a^-1） during the measurements. The photosynthetic process of the larch forest ecosystem was largely affected by the vapor pressure deficit （VPD） and temperature. Under humid conditions （VPD 〈 1.0 kPa）, the gross ecosystem production （GEP） increased with increasing temperature. But the net ecosystem production （NEP） showed almost no change with increasing temperature because the increment of GEP was counterbalanced by that of the ecosystem respiration. Under a dry environment （VPD 〉 1.0 kPa）, the GEP decreased with the increasing VPD at a rate of 3.0 μmol.m^-2.s^-1kPa -1 and the ecosystem respiration was also enhanced simultaneously due to the increase of air temperature, which was linearly correlated with the VPD. As a result, the net ecosystem carbon sequestration rapidly decreased with the increasing VPD at a rate of 5.2 μmol.m^-2.s-1.kPa^-1. Under humid conditions （VPD 〈 1.0 kPa）, both the GEP and NEP were obviously restricted by the low air temperature but were insensitive to the high temperature because the observed high temperature value comes within the category of the optimum range.     

The effects of vegetation restoration strategies and seasons on soil enzyme activities in the Karst landscapes of Yunnan,southwest China

Soil enzymes play a vital role in biogeochemical cycling and ecosystem functions. In this study, we examined the response of six soil enzymes to changes in physicochemical properties resulting from changes in season and vegetation and geological conditions. Catalase,urease, acid phosphatase, invertase, amylase, and cellulase not only promote carbon, nitrogen, and phosphorus cycling, but also participate in the decomposition of harmful substances. Thirty-six soil samples were collected from karst and non-karst areas in two different seasons and from three different types of vegetation in Yunnanprovince, southwest China. Both vegetation types and season had significant effects on soil physicochemical properties and enzyme activities. In the same plot, soil water content, electrical conductivity, organic carbon, total nitrogen, and total phosphorus increased in the rainy season, indicating enhanced microbial metabolic activity.With the exception of urease activity, the remaining five enzymes showed higher activity in the rainy season.Changes in activities between the two seasons were significant in all samples. In the same season, activity levels of soil enzymes were higher in karst areas than in non-karst areas, and higher in natural forest than in artificial forests.The transformative abilities of soil elements are higher in karst areas than in non-karst areas, and higher in natural forests than in artificial forests. Correlation analysis showed that the activities of the six enzymes correlated significantly; however, soil physical and chemical indices,such as organic matter, p H, and moisture, which are essential for enzyme activity, differed by season. Redundancy analysis also revealed that the main factors influencing enzyme activity differed between the two seasons.The results from this study provide a theoretical basis for further research on the restoration of natural ecological systems in karst landscapes.     

燕山北部华北落叶松人工林与杨桦天然次生林土壤碳密度的比较

为了了解人工造林过程对土壤碳储量的影响,对燕山西部山地常见的华北落叶松人工林和杨桦天然次生林土壤有机碳含量进行了研究。结果表明,华北落叶松人工林和杨桦天然次生林的土壤剖面平均有机碳含量分别为30.45g/kg和28.45g/kg,二者没有明显差异;2种林分的土壤有机碳含量均随着土层深度的增加而降低,下降幅度则随深度的增加逐渐减缓,表层土壤对土壤的碳存储贡献更大。总的来看,土壤有机碳含量在深层(30cm以下)相邻土层之间差异不显著,说明深层土壤中,有机碳含量变化较小。由以上结果可以得出结论,在造林措施适当、人为干扰较少的条件下,人工林同样可以维持与天然林相近的较高的土壤碳储量。     

东北过伐林区主要森林类型林分蓄积量生长模型

以吉林省汪清林业局金沟岭林场的主要森林类型为对象,基于小班调查数据,利用R ichards、Logistic、单分子、Gompertz和Korf 5种理论生长方程,建立了林分蓄积量生长模型,采用模型拟合统计量、误差及残差分布对模型进行评价和检验。结果表明:白桦林、人工混交林、天然针阔混交林用R ichards模型最好,人工落叶松林、阔叶混交林、天然针叶混交林用Logistic模型最好。研究结果为该地区森林生长预测和经营优化提供了参考和依据。     

Functional analysis of vegetation on alpine treeline ecotone in the Julian and Kamnik-Savinja Alps in Slovenia

Our study focused on the functional aspects of plant species and vegetation at the transition from larch (Larix decidua Mill.) forest to mountain pine (Pinus mugo Turra) stands on the alpine treeline ecotone. With increasing elevation, living conditions grow harsher, which is reflected in the plant species and functional trait composition of plant communities. At four different localities in the Slovenian Alps, relevés along an altitudinal gradient and according to vegetation type were made (European larch forests, larch trees-mountain pine shrubs, mountain pine shrubs), using standard Central European phytocoenological method. In the upper mountain pine belt, few differential species were found, since most species represented in mountain pine stands also occurred in the lower two vegetation belts, while there were many differential species in the lower forest belt. Species with considerable competitive ability and moderate stress tolerance dominated the upper treeline ecotone, whereas ruderality is poorly expressed. The importance of stress tolerance in plant strategies increased slightly in the mountain pine belt. Changes in the representation of some functional traits attributes were detected by vegetation belts, but complete species turnover did not occur. Changes in dominant life form involved greater cover of chamaephytes and nanophanerophytes in the upper mountain pine belt. Species with evergreen leaves dominated mountain pine stands and deciduous forest stands. The share of species with scleromorphic leaves increased in the direction of the mountain pine belt while the share of species with mesomorphic and hygromorphic leaves declined. Mountain pine stands create good conditions for the regeneration of tree species and colonisation by ecologically more demanding forest species while species of alpine grasslands withdraw on open areas. Since today’s treeline is lowered due to past human activity, an upward shift is expected. Also, considering the great importance of competition strategy, current conditions in mountain pine stands are favourable for future forest succession.