Needleleaf Trees Research Articles

The applicability of empirical vegetation indices for determining leaf chlorophyll content over different leaf and canopy structures

Retrieving leaf chlorophyll content at a range of spatio-temporal scales is central to monitoring vegetation productivity, identifying physiological stress and managing biological resources. However, estimating leaf chlorophyll over broad spatial extents using ground-based traditional methods is time and resource heavy. Satellite-derived spectral vegetation indices (VIs) are commonly used to estimate leaf chlorophyll content, however they are often developed and tested on broadleaf species. Relatively little research has assessed VIs for different leaf structures, particularly needle leaves which represent a large component of boreal forest and significant global ecosystems. This study tested the performance of 47 published VIs for estimating foliar chlorophyll content from different leaf and canopy structures (broadleaf and needle). Coniferous and deciduous sites were selected in Ontario, Canada, representing different dominant vegetation species (Picea mariana and Acer saccharum) and a variety of canopy structures. Leaf reflectance data was collected using an ASD Fieldspec Pro spectroradiometer (400–2500nm) for over 300 leaf samples. Canopy reflectance data was acquired from the medium resolution imaging spectrometer (MERIS). At the canopy level, with both leaf types combined, the DD-index showed the strongest relationship with leaf chlorophyll (R2=0.78; RMSE=3.56μg/cm2), despite differences in leaf structure. For needleleaf trees alone the relationship with the top VI was weaker (D[red], R2=0.71; RMSE=2.32μg/cm2). A sensitivity study using simulated VIs from physically-modelled leaf (PROSPECT) and canopy (4-Scale) reflectance was performed in order to further investigate these results and assess the impacts of different background types and leaf area index on the VIs’ performance. At the leaf level, the MNDVI8 index showed a strong linearity to changing chlorophyll and negligible difference to leaf structure/type. At canopy level, the best performing VIs were relatively consistent where LAI≥4, but responded strongly to differences in background at low canopy coverage (LAI=2). This research provides comprehensive assessments for the use of spectral indices in retrieval of spatially-continuous leaf chlorophyll content at the leaf (MTCI: R2=0.72; p<0.001) and canopy (DD: R2=0.78; p<0.001) level for resource management over different spatial and temporal scales.

중국 장백산의 습지성 진달래과 식물 분포와 생태적 특성

This study was conducted for clarifying distribution and characteristics of marshy Ericaceae plants on Mt. Changbai in China. The marshy Ericaceae plants in wetland of Mt. Changbai were investigated on about 1400 m altitude. This region is various developmental wetlands and vegetation mixture of needle-leaf trees and broad-leaf trees. This region also is start point of the coniferous forest zone in Mt. Changbai. As results of these researches, L. palustre var. diversipilosum and L. palustre var. decumbens populations were investigated in Larix olgensis var. amurensis community. R. lapponicum subsp. parvifolium var. parvifolium community appeared as a typical community. Environmental conditions of L. palustre var. diversipilosum and L. palustre var. decumbens populations' habitats are more soil humidity and shade condition. R. lapponicum subsp. parvifolium var. parvifolium community habitat, however, has more deposits and humidity condition. Therefore when the plants were cultivated, we should recognize the growth condition such as maintenance of humidity and control deposits. The flora of marshy Ericaceae species habitats was investigated as 28 families, 49 genera, 45 species, 14 variety, 1 forma, 1 sub-species, and total 61 taxa.

North American acetone sources determined from tall tower measurements and inverse modeling.

We apply a full year of continuous atmospheric acetone measurements from the University of Minnesota tall tower Trace Gas Observatory (KCMP tall tower; 244 m a.g.l.), with a 0.5° × 0.667° GEOS-Chem nested grid simulation to develop quantitative new constraints on seasonal acetone sources over North America. Biogenic acetone emissions in the model are computed based on the MEGANv2.1 inventory. An inverse analysis of the tall tower observations implies a 37% underestimate of emissions from broadleaf trees, shrubs, and herbaceous plants, and an offsetting 40% overestimate of emissions from needleleaf trees plus secondary production from biogenic precursors. The overall result is a small (16%) model underestimate of the total primary + secondary biogenic acetone source in North America. Our analysis shows that North American primary + secondary anthropogenic acetone sources in the model (based on the EPA NEI 2005 inventory) are accurate to within approximately 20%. An optimized GEOS-Chem simulation incorporating the above findings captures 70% of the variance (R = 0.83) in the hourly measurements at the KCMP tall tower, with minimal bias. The resulting North American acetone source is 11 Tg a-1, including both primary emissions (5.5 Tg a-1) and secondary production (5.5 Tg a-1), and with roughly equal contributions from anthropogenic and biogenic sources. The North American acetone source alone is nearly as large as the total continental volatile organic compound (VOC) source from fossil fuel combustion. Using our optimized source estimates as a baseline, we evaluate the sensitivity of atmospheric acetone and peroxyacetyl nitrate (PAN) to shifts in natural and anthropogenic acetone sources over North America. Increased biogenic acetone emissions due to surface warming are likely to provide a significant offset to any future decrease in anthropogenic acetone emissions, particularly during summer.

산림식생유형에 따른 조류 종다양성 분석

For this paper, a study targeting 9 forest patches in Dangjin to suggest for the wild birds, was conducted. The correlation between the emergence of wild birds and the forest vegetation was analyzed, and the patterns of forest vegetation for the improvement of species diversity were suggested by classifying wild birds and foraging guild by the type of forest vegetation. As for the characteristics of the wild birds emerged, more species and bigger population appeared in the vegetation type of mixed stand forest where the natural deciduous broadleaf trees and evergreen needleleaf trees coexisted in the large scale vegetation area. Thus, it was known that the advent of summer migratory birds and resident birds were affected the most by forest patches and vegetation types. As for foraging guild, the larger the forest paches the more the species and the population of the wild birds inhabiting in shrubs and bushes.

Role of vegetation change in future climate under the A1B scenario and a climate stabilisation scenario, using the HadCM3C Earth system model

Abstract. The aim of our study was to use the coupled climate-carbon cycle model HadCM3C to quantify climate impact of ecosystem changes over recent decades and under future scenarios, due to changes in both atmospheric CO2 and surface albedo. We use two future scenarios – the IPCC SRES A1B scenario, and a climate stabilisation scenario (2C20), allowing us to assess the impact of climate mitigation on results. We performed a pair of simulations under each scenario – one in which vegetation was fixed at the initial state and one in which vegetation changes dynamically in response to climate change, as determined by the interactive vegetation model within HadCM3C. In our simulations with interactive vegetation, relatively small changes in global vegetation coverage were found, mainly dominated by increases in shrub and needleleaf trees at high latitudes and losses of broadleaf trees and grasses across the Amazon. Globally this led to a loss of terrestrial carbon, mainly from the soil. Global changes in carbon storage were related to the regional losses from the Amazon and gains at high latitude. Regional differences in carbon storage between the two scenarios were largely driven by the balance between warming-enhanced decomposition and altered vegetation growth. Globally, interactive vegetation reduced albedo acting to enhance albedo changes due to climate change. This was mainly related to the darker land surface over high latitudes (due to vegetation expansion, particularly during December–January and March–May); small increases in albedo occurred over the Amazon. As a result, there was a relatively small impact of vegetation change on most global annual mean climate variables, which was generally greater under A1B than 2C20, with markedly stronger local-to-regional and seasonal impacts. Globally, vegetation change amplified future annual temperature increases by 0.24 and 0.15 K (under A1B and 2C20, respectively) and increased global precipitation, with reductions in precipitation over the Amazon and increases over high latitudes. In general, changes were stronger over land – for example, global temperature changes due to interactive vegetation of 0.43 and 0.28 K under A1B and 2C20, respectively. Regionally, the warming influence of future vegetation change in our simulations was driven by the balance between driving factors. For instance, reduced tree cover over the Amazon reduced evaporation (particularly during June–August), outweighing the cooling influence of any small albedo changes. In contrast, at high latitudes the warming impact of reduced albedo (particularly during December–February and March–May) due to increased vegetation cover appears to have offset any cooling due to small evaporation increases. Climate mitigation generally reduced the impact of vegetation change on future global and regional climate in our simulations. Our study therefore suggests that there is a need to consider both biogeochemical and biophysical effects in climate adaptation and mitigation decision making.

Continuous measurements of net CO2 exchange by vegetation and soils in a suburban landscape

In a suburban neighborhood of Minneapolis–Saint Paul, Minnesota, USA, we simultaneously measured net CO2 exchange of trees using sap flow and leaf gas exchange measurements, net CO2exchange of a turfgrass lawn using eddy covariance from a portable tower, and total surface‐atmosphere CO2 fluxes (FC) using an eddy covariance system on a tall tower. Two years of continuous measurements showed that net CO2exchange varied among vegetation types, with the largest growing‐season (Apr–Nov) net CO2 uptake on a per cover area basis from evergreen needleleaf trees (−603 g C m−2), followed by deciduous broadleaf trees (−216 g C m−2), irrigated turfgrass (−211 g C m−2), and non‐irrigated turfgrass (−115 g C m−2). Vegetation types showed seasonal patterns of CO2exchange similar to those observed in natural ecosystems. Scaled‐up net CO2 exchange from vegetation and soils (FC(VegSoil)) agreed closely with landscape FC measurements from the tall tower at times when fossil fuel emissions were at a minimum. Although FC(VegSoil) did not offset fossil fuel emissions on an annual basis, the temporal pattern of FC(VegSoil) did significantly alter the seasonality of FC. Total growing season FC(VegSoil)in recreational land‐use areas averaged −165 g C m−2 and was dominated by turfgrass CO2 exchange (representing 77% of the total), whereas FC(VegSoil) in residential areas averaged −124 g C m−2 and was dominated by trees (representing 78% of the total). Our results suggest urban vegetation types can capture much of the variability required to predict seasonal patterns and differences in FC(VegSoil) that could result from changes in land use or vegetation composition in temperate cities.

수량화 2종법을 이용한 GIS 기반의 인제지역 산사태 영향인자 분석

Gangwon-do has been suffering extensive landslide dam age, because its geography consists mainly of mountains. Analyzing the related factors is crucial for landslide prediction. We digitized the landslide and non-landslide spots on an aerial photo obtained right after a disaster in Inje, Gangwon-do. Three landslide factors-topographic, forest type, and soil factors-w ere statistically analyzed through GIS overlap analysis between topographic map, forest type map, and soil map. The analysis showed that landslides occurred mainly between the inclination of and , and needleleaf tree area is more vulnerable to a landslide. About soil properties, an area with shallow effective soil depth and parent material of acidic rock has a greater chance of landslide.

The role of vegetation feedbacks on Greenland glaciation

The role of vegetation feedbacks for the process of ice-sheet evolution could potentially be important in realistically modeling the past and future evolution of the Greenland ice-sheet. We use a fully coupled atmosphere–ocean model to assess the response of the climate when the Greenland ice-sheet is replaced with a number of fixed vegetation types (bare soil, broadleaf and needleleaf trees, C3 and C4 grasses and shrubs) in conjunction with loaded and unloaded bedrock orography. These sensitivity experiments show that albedo changes dominate the climate response during the summer months while temperature changes during winter are attributed to altitude change and changes in atmospheric circulation over Greenland. Snow-free summers occur for all fixed vegetation types, except for high altitude eastern regions for bare soil. We perform further simulations with dynamic vegetation resulting in dominant shrub coverage over central and southern Greenland with grasses supported in the north. Ice-sheet modeling shows significant regrowth of the Greenland ice-sheet can occur for a bare soil surface type, dependent on ice-sheet model parameters, while Greenland remains almost ice-free for needleleaf tree coverage. Furthermore, a realistically vegetated Greenland can only support a small amount of ice-sheet regrowth implying multi-stability of the Greenland ice-sheet under a preindustrial climate. This study highlights the importance of considering vegetation climate ice-sheet interactions, and uncertainty in ice-sheet model parameters.

Calibration of charcoal production from trees biomass for soil charcoal analyses in subalpine ecosystems

Subalpine ecosystems are mainly affected by surface fires of low to medium intensity. Charcoal production from trees is limited by the duration and the intensity of fires and, thus, by the wood combustibility. Because the combustibility properties of species differ, the functional traits that determine the wood combustibility could explain in part the taxonomic differences of charcoal abundance within the paleo-soil charcoal (pedoanthracological) assemblages. Eight subalpine broadleaf and needleleaf tree species were considered. Wood combustibility was studied by experimental burning on barked-wood samples exposed to constant heat. Two combustibility parameters are estimated (i) the rate of mass loss rate (MLR) and, (ii) the burning rate (BR). While BR describes the proportion of burned biomass per time unit assessing the potential conversion of wood biomass into charcoal, MLR reports the speed of fuel combustion that estimates the potential amount of charcoal produced. A hierarchy of species-specific potential production of charcoal by trees is developed by the use of biplot distribution of MLR and BR. Species were ranked from the worst to the best biomass for the charcoal conversion: Larix decidua, Abies alba, Pinus uncinata, Picea abies, Betula pendula, Salix caprea, Pinus cembra, Sorbus aucuparia. With thin smooth bark and dense wood, broadleaf trees are expected to produce more charcoal than needleleafs. Bark thickness and wood density explain half of combustibility variance. Thus, the production of charcoal tends to vary among species and among individuals of different diameter according to bark thickness. The amount of charcoal is a proxy of both (i) the abundance of understorey-tree (sapling) due to the high combustion susceptibility of small diameter stems (thin and smooth bark), and (ii) the abundance of woody debris on the ground produced by the canopy trees. The results are discussed in light of simulated data from Holocene soil charcoal assemblages for the western subalpine Alps. Among needleleafs, L. decidua is the least productive in terms of charcoal abundance due to its low MLR and BR values, whereas P. cembra and broadleafs should be better represented in the soil charcoal assemblages. This study provides rational elements for the quantitative calibration of soil charcoal through species-specific charcoal mass coefficients.

The Geography of Spruce Budworm in Eastern North America

Spruce budworm (Choristoneura fumiferana) is a native insect that defoliates needleleaf trees, especially balsam fir (Abies balsamea) and spruces (Picea spp.), in northern North America. Spruce budworm can defoliate millions of hectares of forest during an infestation, depressing regional economies that depend on the timber industry. Ecosystems, though, can benefit from spruce budworm because outbreaks rejuvenate the forest, maintaining optimal levels of primary production, and thereby carbon sequestration. Although many ecologists, entomologists, geographers, and resource managers have studied the effects of spruce budworm on spruce–fir forests throughout the region, no single explanation of what causes the number of insects in a forest to rise and fall is universally accepted. Spruce budworm populations can reach ‘outbreak’ levels, or densities high enough to defoliate and kill balsam fir and spruce on a landscape scale, on average every 30–40 years. We review the biology of spruce budworm, the processes that scientists follow to reconstruct spruce budworm outbreaks, the leading hypothesis to explain population dynamics and outbreak events, and the complexity of forecasting possible future trends of populations and distributions of spruce budworm. Reconstructions of past outbreaks help us understand their severity, frequency, and spatial synchrony, which might be linked in complex ways to climate, forest, and stand characteristics. Future spruce budworm dynamics are difficult to predict because the insect is part of a complex food web. In the coming decades, spruce budworm probably will survive climate change because it is adapted to a wide range of temperatures and precipitation amounts.

Impact of CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; and climate on the Last Glacial Maximum vegetation: results from the ORCHIDEE/IPSL models

Abstract. Vegetation reconstructions from pollen data for the Last Glacial Maximum (LGM), 21 ky ago, reveal lanscapes radically different from the modern ones, with, in particular, a massive regression of forested areas in both hemispheres. Two main factors have to be taken into account to explain these changes in comparison to today's potential vegetation: a generally cooler and drier climate and a lower level of atmospheric CO2. In order to assess the relative impact of climate and atmospheric CO2 changes on the global vegetation, we simulate the potential modern vegetation and the glacial vegetation with the dynamical global vegetation model ORCHIDEE, driven by outputs from the IPSL_CM4_v1 atmosphere-ocean general circulation model, under modern or glacial CO2 levels for photosynthesis. ORCHIDEE correctly reproduces the broad features of the glacial vegetation. Our modelling results support the view that the physiological effect of glacial CO2 is a key factor to explain vegetation changes during glacial times. In our simulations, the low atmospheric CO2 is the only driver of the tropical forests regression, and explains half of the response of temperate and boreal forests to glacial conditions. Our study shows that the sensitivity to CO2 changes depends on the background climate over a region, and also depends on the vegetation type, needleleaf trees being much more sensitive than broadleaf trees in our model. This difference of sensitivity leads to a dominance of broadleaf types in the remaining simulated forests, which is not supported by pollen data, but nonetheless suggests a potential impact of CO2 on the glacial vegetation assemblages. It also modifies the competitivity between the trees and makes the amplitude of the response to CO2 dependent on the initial vegetation state.

Seasonal contributions of vegetation types to suburban evapotranspiration

[1] Evapotranspiration is an important term of energy and water budgets in urban areas and is responsible for multiple ecosystem services provided by urban vegetation. The spatial heterogeneity of urban surface types with different seasonal water use patterns (e.g., trees and turfgrass lawns) complicates efforts to predict and manage urban evapotranspiration rates, necessitating a surface type, or component-based, approach. In a suburban neighborhood of Minneapolis–Saint Paul, Minnesota, United States, we simultaneously measured ecosystem evapotranspiration and its main component fluxes using eddy covariance and heat dissipation sap flux techniques to assess the relative contribution of plant functional types (evergreen needleleaf tree, deciduous broadleaf tree, cool season turfgrass) to seasonal and spatial variations in evapotranspiration. Component-based evapotranspiration estimates agreed well with measured water vapor fluxes, although the imbalance between methods varied seasonally from a 20% overestimate in spring to an 11% underestimate in summer. Turfgrasses represented the largest contribution to annual evapotranspiration in recreational and residential land use types (87% and 64%, respectively), followed by trees (10% and 31%, respectively), with the relative contribution of plant functional types dependent on their fractional cover and daily water use. Recreational areas had higher annual evapotranspiration than residential areas (467 versus 324 mm yr−1, respectively) and altered seasonal patterns of evapotranspiration due to greater turfgrass cover (74% versus 34%, respectively). Our results suggest that plant functional types capture much of the variability required to predict the seasonal patterns of evapotranspiration among cities, as well as differences in evapotranspiration that could result from changes in climate, land use, or vegetation composition.

Biological and environmental controls on tree transpiration in a suburban landscape

Tree transpiration provides a variety of ecosystem services in urban areas, including amelioration of urban heat island effects and storm water management. Tree species vary in the magnitude and seasonality of transpiration owing to differences in physiology, response to climate, and biophysical characteristics, thereby complicating efforts to manage evapotranspiration at city scales. We report sap flux measurements during the 2007 and 2008 growing seasons for dominant tree species in a suburban neighborhood of Minneapolis–Saint Paul, Minnesota, USA. Evergreen needleleaf trees had significantly higher growing season means and annual transpiration per unit canopy area (1.90 kg H2O m−2 d−1 and 307 kg H2O m−2 yr−1, respectively) than deciduous broadleaf trees (1.11 kg H2O m−2 d−1 and 153 kg H2O m−2 yr−1, respectively) because of a smaller projected canopy area (31.1 and 73.6 m2, respectively), a higher leaf area index (8.8 and 5.5 m2 m−2, respectively), and a longer growth season (8 and 4 months, respectively). Measurements also showed patterns consistent with the species' differences in xylem anatomy (conifer, ring porous, and diffuse porous). As the growing season progressed, conifer and diffuse porous genera had increased stomatal regulation to high vapor pressure deficit, while ring porous genera maintained greater and more constant stomatal regulation. These results suggest that evaporative responses to climate change in urban ecosystems will depend in part on species composition. Overall, plant functional type differences in canopy structure and growing season length were most important in explaining species' differences in midsummer and annual transpiration, offering an approach to predicting the evapotranspiration component of urban water budgets.

A clumped-foliage canopy radiative transfer model for a global dynamic terrestrial ecosystem model. I: Theory

This study develops a simple but physically based canopy radiative transfer scheme for photosynthesis, radiative fluxes and surface albedo estimates in dynamic global vegetation models (DGVMs), and particularly for the Ent Dynamic Global Terrestrial Ecosystem Model (Ent DGTEM). The Ent DGTEM can represent vegetation in mixed as opposed to homogeneous canopies. With active growth and competition, it must predict radiative transfer for dynamically changing vegetation structure, and requires computational speed for coupling with atmospheric general circulation models (GCMs). The canopy radiative transfer scheme accounts for both vertical and horizontal heterogeneity of plant canopies by combining the simple two-stream scheme with a well-described actual vertical foliage profile, an analytically derived foliage clumping factor from geometric optical theory, and, for needleleaf trees, an empirical needle-to-shoot-clumping factor. In addition, the model accounts for the effect of trunks, which is significant in bare canopies. This model provides better radiation estimates (light profiles, albedo) than the two-stream scheme currently being used in most GCMs to describe light interactions with vegetation canopies. This scheme has the same computational cost as the current typical scheme being used in GCMs, but promises to provide better canopy radiative transfer estimates for DGVMs, particularly those that model heterogeneous vegetation canopies.

Millennial-scale variability in vegetation records from the East Asian Islands: Taiwan, Japan and Sakhalin

High-resolution pollen records from Taiwan, Japan and Sakhalin document regional vegetation changes during Dansgaard-Oeschger (D-O) cycles during the last glacial. During the period from the cold phase (GS 18/19) to warm phase (D-O 19), the biome shift from temperate conifer forest to cold/cool conifer forest in Japan and from subtropical forest to temperate deciduous/conifer forest in Taiwan. The vegetation in D-O 17, cool mixed forest in central Japan, temperate deciduous broadleaf forest in western Japan and subtropical forest in Taiwan, indicates warm condition but not wet in all area. These vegetation changes lead to biome shift from MIS (Marine Isotope Stage) 4 to MIS 3. The abundance of Cryptomeria japonica and Fagus crenata in D-O 12 and D-O 8 indicates wet conditions brought by the strong summer monsoon through the Islands and high snowfall brought by the inflow of the Tsushima Warm Current into the Sea of Japan. The registration of other D-O warming events in MIS 3, although reflected by shifts in the abundance of key species, is not sufficient to produce changes in biomes. Development of cold deciduous forest in HS (Heinrich events) 1 in Sakhalin, Hokkaido and central Japan was conspicuous and was much larger than that in YD. Vegetation response in YD was small scale and within the same biome in the East Asian Islands. In D-O 1 at the termination of the last glacial, the same taxa that developed in the early Holocene, cold evergreen needleleaf trees in northern region, temperate deciduous broadleaf trees in central and western Japan, and warm-temperate evergreen trees in Taiwan, increased.

Impact of Urban Growth on Surface Climate: A Case Study in Oran, Algeria

Abstract The authors develop a land use map discriminating urban surfaces from other cover types over a semiarid region in North Africa and use it in a land surface model to assess the impact of urbanized land on surface energy, water, and carbon balances. Unlike in temperate climates where urbanization creates a marked heat island effect, this effect is not strongly marked in semiarid regions. During summer, the urban class results in an additional warming of 1.45°C during daytime and 0.81°C at night relative to that simulated for needleleaf trees under similar climate conditions. Seasonal temperatures show that urban areas are warmer than their surrounding areas during summer and slightly cooler in winter. The hydrological cycle is practically “shut down” during summer and is characterized by relatively large amounts of runoff in winter. The authors estimate the annual amount of carbon uptake to be 1.94 million metric tons with only 11.9% assimilated during the rainy season. However, if urbanization expands to reach 50% of the total area excluding forests, the annual total carbon uptake will decline by 35% and the July mean temperature would increase only 0.10°C relative to the current situation. In contrast, if urbanization expands to 50% of the total land excluding forests and croplands but all short vegetation is replaced by native broadleaf deciduous trees, the annual carbon uptake would increase by 39% and the July mean temperature would decrease by 0.9°C relative to the current configuration. These results provide guidelines for urban planners and land use managers and indicate possibilities for mitigating the urban heat.

Climate, African and Beringian subaerial continental shelves, and migration of early peoples

The impacts of rapid climate change likely influenced human behaviour during the last glacial cycle, potentially stimulating habitation of, and migration along, continental shelves exposed during periods of lowered sea level. Last glacial maximum (LGM) climate model simulation shows cooler surface air temperatures in Eastern Beringia than Western and Central Beringia. Central Beringia was slightly wetter than present day (PD), whereas Eastern and Western Beringia were drier than PD. However Eastern Beringia was wetter than either Central or Western Beringia. Increased C3 grass coverage is shown in Eastern and Western Beringia, but increased C3 grass net primary productivity (NPP) appears only in Western Beringia; needleleaf trees and many shrubs disappear, replaced by barren soil and C3 grass. Such change would have squeezed species dependant on needleleaf trees out of Western and Eastern Beringia and potentially initiated their migration to more southerly parts of East Asia where a diminishing needleleaf tree environment remained. Shrub-reliant species in Eastern and Western Beringia and C3 grass-dependant species in East Asia and Eastern Beringia would have found additional and productive habitat on the subaerial continental shelf. The LGM simulation identifies cooler LGM temperatures and increased aridity in South and particularly Central Africa, and associated large reductions in LGM broadleaf tree NPP and coverage in Africa, reduced C3 grass NPP particularly in Central Africa, decreased needleleaf tree NPP in South Africa, reduced shrub coverage in North and Central Africa, and greater barren ground coverage in Central and South Africa. Reduced productivity and shifting vegetation during the LGM may have squeezed flora, fauna, and human populations onto the potentially more productive and proximally located exposed continental shelf.

Distributional patterns of species diversity of main plant communities along altitudinal gradient in secondary forest region, Guandi Mountain, China

Fourteen plots were chosen along with the altitude of 1600–2600 m in Guandi Mountain, Shanxi Province, China to investigate all the trees in the plots, and the species diversity indexes were calculated for analyzing the effects of altitudinal gradient on plant species diversity. The results showed that the order of dominant species from low altitude to high altitude is as Quercus liaotungensis Koidz, Pinus tabulaeformis, Betula platyphylla, B. albo-sinensis, Picea wilsonii, P. Meyeri and Larix principis-rupprechtii. With altitude increasing, the average height and DBH of the arbor firstly increase and then decrease, the maximal height and DBH of the arbor present the unimodal variable trend, the maximal height of coniferous and broad-leaved trees firstly increases and then decreases, the maximal DBH of broad-leaf trees has no clear fluctuation, and the maximal DBH of the needle-leaf trees decreases gradually. Moreover, in middle altitudinal communities (the altitude of 1900–2200 m), the maximal height and DBH of the needle-leaf trees are larger than these of broad-leaf trees. Both Shannon-wiener index and Margalef index of the communities present the unimodal variable trend, with a peak in the mid-altitude. Plant species diversity in the mid-altitude (1900–2200 m) is higher than that of the low altitude (1600–1900 m) and the high altitude (2200–2600 m). In addition, the unimodal variable trend of α species diversity is clearly correlated with the altitudinal gradient. The change of plant species diversity is significantly correlated with the altitudinal gradient, and also related to the community structure, the community composition, the feature of species and the human disturbance.

Vegetation cover in a warmer world simulated using a dynamic global vegetation model for the Mid-Pliocene

In this study we employ the TRIFFID (Top-down Representation of Interactive Flora and Foliage Including Dynamics) Dynamic Global Vegetation Model (DGVM) and the Hadley Centre Atmospheric General Circulation Model version 3 (HadAM3 GCM) to investigate vegetation distributions and climate–vegetation feedbacks during the Mid-Pliocene, and examine the implications of these results for the origins of hominid bipedalism. The TRIFFID model outputs support extant palaeoenvironmental reconstructions for the Mid-Pliocene provided by the PRISM Group (Pliocene Research Interpretations and Synoptic Mapping). Compared to the pre-industrial, TRIFFID simulates a significant increase in forest cover during the Mid-Pliocene, composed of needle leaf trees in the higher latitudes of the Northern Hemisphere and broad leaf trees in other regions. Needle leaf trees extend from the Arctic Coast into the northern mid latitudes. The fractional coverage of bare soil declines in North Africa, the Arabian Peninsula, Australia and southern South America, a pattern that is consistent with PRISM's assertion of less extensive arid deserts. A significant increase in the fractional coverage of both broad leaf trees in Africa and South America in the Mid-Pliocene scenario is not indicative of a major expansion of tropical rainforests. Rather, it represents an expansion of general woodland type habitats. The principal impact of using a DGVM on the GCM predicted climatology for the Mid-Pliocene is to reduce minimum and maximum temperature extremes, thus reducing the seasonality of temperature over wide regions. The predicted Pliocene expansion in broad leaf trees in Africa is difficult to reconcile with the ‘savannah hypothesis’ for the evolution of hominid bipedalism. Rather the results lend credence to an alternative hypothesis which suggests that bipedalism evolved in wooded to forested ecosystems and was, for several million years, linked to arborealism.

An analysis of some diverse approaches to modelling terrestrial net primary productivity

We inter-compare the mathematical formulation of ten models of terrestrial net primary productivity (NPP) and their functional responses to temperature ( T), carbon dioxide (CO 2), soil water ( W) and photosynthetically active radiation (PAR). The models span a broad spectrum of complexity of approaches from the original, empirical Miami model, through β-factor, and global-average box models, to the dynamic global vegetation models (DGVMs) TRIFFID and BIOME3. Five of the models separate photosynthesis and respiration, although only three directly consider biochemistry. Equations for all the models are given in a complete, compact, standardized format. NPP responses to temperature differ markedly: β-factor models show only a tiny increase with temperature, empirical models predict a modest S-shaped response saturating above 35 °C (a surrogate for drought effects), biochemical and quasi-biochemical models show a peaked response with an optimum in the range 15–25 °C except for DEMETER (<10 °C). Qualitative differences in whether respiration exhibits a peaked or exponential response to temperature have only a modest effect on NPP. The CO 2 response of NPP is qualitatively similar in all but one model that misrepresents it. Where a water stress response of NPP is represented, it is saturating in all but the same model, where NPP declines under high soil moisture. Where represented, the PAR response of NPP is saturating, but the saturation point differs considerably. When responses to two environmental variables are combined, the second variable typically just scales the response to the first. In biochemical models, the temperature optimum of NPP increases with CO 2, and it also increases noticeably with PAR in TRIFFID and a derivative of it. Where different plant functional types (PFTs) are represented, C 4 grasses have the greatest maximum NPP at a higher optimum temperature than any C 3 PFT. Boreal, needle-leaf trees generally have the lowest NPP. Additional uncertainties in modelling respiration, stomatal conductance, light-use efficiency, and scaling to the canopy level are discussed. We suggest that a concerted effort to standardize definitions, notation, units and PFTs would add a degree of transparency that is currently lacking in NPP modelling.