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1.
Urs M. Weber 《Trees - Structure and Function》1997,11(5):277-290
Outbreaks of the larch budmoth (LBM) (Zeiraphera diniana) recur cyclically approximately every 7 to 10 years in subalpine larch-cembran pine and montane to subalpine larch-Norway
spruce forests of the relatively dry valleys of the European Alps. By dendroecologically analyzing increment cores from 570
host (European larch –Larix decidua) and non-host trees (cembran pine –Pinus cembra, Norway spruce –Picea abies) through the use of skeleton plots, at least 57 (59) outbreaks could be reconstructed in the optimum Upper Engadine Valley
(suboptimum Goms Valley), Switzerland, during the time period 1503 (1472) to 1990. The average interval between initial years
of successive outbreaks was 8.58 (8.95) years, SD 1.66 (2.13) years. Over the centuries spatial shifts of LBM activity between
the two study areas occurred, probably due to climatic changes. Clear, site-specific differences in LBM attack could only
be found in the suboptimum area where high-lying (>1800 m) and/or south-facing stands were infested most. LBM-afflicted trees
proved to be unsuitable for climate reconstructions because the impact of the persistently recurring outbreaks on tree growth
is dominant. In order to provide sufficient information for a detailed ecological interpretation of the course of an outbreak,
latewood widths and/or densities have to be analyzed in addition to the ring-widths.
Received: 11 February 1995 / Accepted: 19 July 1996 相似文献
2.
Summer temperature dependency of larch budmoth outbreaks revealed by Alpine tree-ring isotope chronologies 总被引:1,自引:0,他引:1
Anne Kress Matthias Saurer Ulf Büntgen Kerstin S. Treydte Harald Bugmann Rolf T. W. Siegwolf 《Oecologia》2009,160(2):353-365
Larch budmoth (LBM, Zeiraphera diniana Gn.) outbreaks cause discernable physical alteration of cell growth in tree rings of host subalpine larch (Larix decidua Mill.) in the European Alps. However, it is not clear if these outbreaks also impact isotopic signatures in tree-ring cellulose,
thereby masking climatic signals. We compared LBM outbreak events in stable carbon and oxygen isotope chronologies of larch
and their corresponding tree-ring widths from two high-elevation sites (1800–2200 m a.s.l.) in the Swiss Alps for the period
AD 1900–2004 against isotope data obtained from non-host spruce (Picea abies). At each site, two age classes of tree individuals (150–250 and 450–550 years old) were sampled. Inclusion of the latter
age class enabled one chronology to be extended back to AD 1650, and a comparison with long-term monthly resolved temperature
data. Within the constraints of this local study, we found that: (1) isotopic ratios in tree rings of larch provide a strong
and consistent climatic signal of temperature; (2) at all sites the isotope signatures were not disturbed by LBM outbreaks,
as shown, for example, by exceptionally high significant correlations between non-host spruce and host larch chronologies;
(3) below-average July to August temperatures and LBM defoliation events have been coupled for more than three centuries.
Dampening of Alps-wide LBM cyclicity since the 1980s and the coincidence of recently absent cool summers in the European Alps
reinforce the assumption of a strong coherence between summer temperatures and LBM defoliation events. Our results demonstrate
that stable isotopes in tree-ring cellulose of larch are an excellent climate proxy enabling the analysis of climate-driven
changes of LBM cycles in the long term. 相似文献
3.
4.
Kathrin Weidner I. Heinrich G. Helle J. Löffler B. Neuwirth G. H. Schleser H. Vos 《Trees - Structure and Function》2010,24(3):399-409
Tree-ring widths and stable carbon and oxygen isotopes of five European larch trees from Lötschental, Switzerland were investigated for the period 1900–2004. The objective was to test the suitability of each of these parameters for high-frequency climate reconstructions. This is of special interest with regard to the problem of cyclic larch budmoth (LBM) infestations of alpine larch trees. The results clearly demonstrate that tree-ring width chronologies are not suitable for high-frequency reconstructions because infestations lead to variably reduced tree-ring increments, largely suppressing climate signals. On the other hand, the stable isotope chronologies proved less affected by larch budmoth outbreaks, independent of the strength of the infestations. The correlation of the carbon isotopes with summer temperatures was especially high (r = 0.73) and with precipitation lower but nevertheless significant (r = ?0.43). Oxygen isotopes were also correlated with summer temperature (r = 0.46); however, a certain perturbation of normal oxygen isotope signatures due to LBM outbreaks was evident. Contrary to tree-ring widths, none of the LBM outbreaks caused a significant disturbance of the current year’s isotopic climate signal and, most importantly, there were no delayed effects in the following years. Thus, stable carbon isotopes in tree-ring chronologies of the European larch provide an excellent opportunity for high-frequency temperature reconstructions. 相似文献
5.
Esper J Büntgen U Frank DC Nievergelt D Liebhold A 《Proceedings. Biological sciences / The Royal Society》2007,274(1610):671-679
The long-term history of Zeiraphera diniana Gn. (the larch budmoth, LBM) outbreaks was reconstructed from tree rings of host subalpine larch in the European Alps. This record was derived from 47513 maximum latewood density measurements, and highlights the impact of contemporary climate change on ecological disturbance regimes. With over 1000 generations represented, this is the longest annually resolved record of herbivore population dynamics, and our analysis demonstrates that remarkably regular LBM fluctuations persisted over the past 1173 years with population peaks averaging every 9.3 years. These regular abundance oscillations recurred until 1981, with the absence of peak events during recent decades. Comparison with an annually resolved, millennium-long temperature reconstruction representative for the European Alps (r=0.72, correlation with instrumental data) demonstrates that regular insect population cycles continued despite major climatic changes related to warming during medieval times and cooling during the Little Ice Age. The late twentieth century absence of LBM outbreaks, however, corresponds to a period of regional warmth that is exceptional with respect to the last 1000+ years, suggesting vulnerability of an otherwise stable ecological system in a warming environment. 相似文献
6.
Knowledge about large-scale and long-term dynamics of (natural) populations is required to assess the efficiency of control
strategies, the potential for long-term persistence, and the adaptability to global changes such as habitat fragmentation
and global warming. For most natural populations, such as pest populations, large-scale and long-term surveys cannot be carried
out at a high resolution. For instance, for population dynamics characterized by irregular abundance explosions, i.e., outbreaks,
it is common to report detected outbreaks rather than measuring the population density at every location and time event. Here,
we propose a mechanical-statistical model for analyzing such outbreak occurrence data and making inference about population
dynamics. This spatio-temporal model contains the main mechanisms of the dynamics and describes the observation process. This
construction enables us to account for the discrepancy between the phenomenon scale and the sampling scale. We propose the
Bayesian method to estimate model parameters, pest densities and hidden factors, i.e., variables involved in the dynamics
but not observed. The model was specified and used to learn about the dynamics of the European pine sawfly (Neodiprion sertifer Geoffr., an insect causing major defoliation of pines in northern Europe) based on Finnish sawfly data covering the years
1961–1990. In this application, a dynamical Beverton–Holt model including a hidden regime variable was incorporated into the
model to deal with large variations in the population densities. Our results gave support to the idea that pine sawfly dynamics
should be studied as metapopulations with alternative equilibria. The results confirmed the importance of extreme minimum
winter temperatures for the occurrence of European pine sawfly outbreaks. The strong positive connection between the ratio
of lake area over total area and outbreaks was quantified for the first time. 相似文献
7.
How the Black Grouse was lost: historic reconstruction of its status and distribution in Lower Saxony (Germany) 总被引:1,自引:0,他引:1
In the Central European lowlands, the Black Grouse (Tetrao tetrix) is restricted to isolated remnant populations. Status reports have been published for some of them, but comparative analyses
of Black Grouse dynamics across larger parts of the Central European range are missing. In this paper, we used published and
unpublished historic information on local occurrences of Black Grouse in 37,000 km2 of the German federal state of Lower Saxony to reconstruct changes in the species’ distribution and abundance since the 1950s.
We calculated population trends over 52 years (1955–2006) using software trends and indices in monitoring data (TRIM). Results
showed two phases: an initial crash phase (1950s–1980s) when many local populations went extinct, and a recovery phase (1990s–2000s)
for the remnants of the initial distribution. Differences in timing and extent of the crash were related at habitat type.
Our study indicates that reconstructing population trends and distributions across larger geographic areas from historic data
may enable comparative analyses of drivers of population dynamics across sites, and thus contribute to a better understanding
of the causes of Black Grouse decline. 相似文献
8.
Joerns Fickel Heidi C. Hauffe Elena Pecchioli Ramon Soriguer Ljiljana Vapa Christian Pitra 《European Journal of Wildlife Research》2008,54(3):495-510
A substantial portion of today’s biodiversity is attributed to the climatic oscillations of the Pleistocene Ice Ages. Gradual
but dramatic climate changes were accompanied by expansion, contraction, and isolation of populations, promoting the accumulation
of genome differences and adaptations in refugial populations and resulting in allopatric differentiation in a variety of
taxa. In the present study, partial mitochondrial DNA sequences of the widely distributed European brown hare (Lepus europaeus) were analyzed to test whether the species’ present genetic structure is the result of postglacial re-colonization of Europe
from Asia Minor (clade A) and the Balkans (clade B) only, as suggested previously, or if additional refugia are likely. Analyses indicated the presence of an additional refugium
(Italy, clade I). The genealogic network of Italian hares displayed the tree-like structure expected from refugial populations, whereas central
European brown hare haplotypes revealed a clear star-phylogeny indicative of past-bottleneck population growth. This population
size expansion, which was confirmed by mismatch analysis, was estimated to have occurred ∼50–55 thousand years ago (kya).
The divergence of clade A* from the remaining matrilines is estimated at 239 kya, whereas the divergence of the ancestors of clades B* and I from A* occurred about 128 kya.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
9.
T. O. Veteli‡ A. Lahtinen‡ T. Repo P. Niemelä‡ M. Varama† 《Agricultural and Forest Entomology》2005,7(2):115-120
Abstract 1 The European pine sawfly, Neodiprion sertifer (Geoffroy) (Hymenoptera, Diprionidae), frequently defoliates Scots pine (Pinus sylvestris L.) forests in northern Europe. It overwinters as an egg. It has been proposed that the high egg mortality caused by low winter temperatures limits the occurrence of outbreaks to the southern part of Fennoscandia. 2 In this study, variation in freezing avoidance by egg supercooling between four Finnish populations (originating between latitudes 60°N and 69°N) of N. sertifer was tested by differential thermal analysis. Offspring of 20 females within each population were selected for the study. The freezing avoidance of parasitized eggs was also examined. 3 The northernmost Inari population was found to be the cold hardiest, and the southernmost (Hanko) was the least hardy population. The within‐population variation between females was greatest in the population from Inari, and the next greatest in the one from Hanko. The inland populations in Eastern Finland had the smallest within‐population variation in freezing avoidance. 4 The high variation in freezing avoidance of eggs will enable N. sertifer to adapt to the predicted climate change and to spread its distribution northwards. This may also change the risk for outbreaks in this area. Parasitized eggs froze at higher temperature than healthy eggs. This observation indicates that N. sertifer may experience reduced egg parasitism in certain winter climate conditions. 相似文献
10.
Julien Cucherousset Gordon H. Copp Michael G. Fox Erik Sterud Hein H. van Kleef Hugo Verreycken Eva Záhorská 《Biological invasions》2009,11(9):2171-2180
To evaluate the potential invasiveness of pumpkinseed Lepomis gibbosus introduced to northwestern European inland waters, growth and reproduction traits were examined in ten populations along
a trajectory spanning northwestern Europe (Norway, England, Holland, Belgium and France) and evaluated in light of published
dataset from Europe. In the 848 pumpkinseed captured, maximum age was 3–4 years, with a sex ratio near unity in all but one
population. Significant variations with increasing latitude were observed in adult growth (age 2–3 increment in total length,
TL) and mean age at maturity (A
M), with non-significant variations observed in juvenile growth (TL at age 2), sex ratio and gonado-somatic index. As observed
elsewhere in Europe, mean A
M decreased significantly with increasing TL at age 2. Using this relationship, which has been proposed elsewhere as a potential
predictive model of pumpkinseed invasiveness, eight of the ten populations could be provisionally categorized as ‘non-invasive’
(five populations), ‘transitional’ (one population) and ‘potentially invasive’ (two populations), with two populations not
categorized due to insufficient data. Based on the available knowledge on each population, the relationship between juvenile
growth and age at maturity appeared to predict reasonably the status of pumpkinseed in northwestern Europe and its applicability
to other species should be tested. 相似文献
11.
Population outbreaks of the coral-eating crown-of-thorns seastar, Acanthaster planci, continue to kill more coral on Indo-Pacific coral reefs than other disturbances, but the causes of these outbreaks have
not been resolved. In this study, we combine (1) results from laboratory experiments where larvae were reared on natural phytoplankton,
(2) large-scale and long-term field data of river floods, chlorophyll concentrations and A. planci outbreaks on the Great Barrier Reef (GBR), and (3) results from A. planci—coral population model simulations that investigated the relationship between the frequency of outbreaks and larval food
availability. The experiments show that the odds of A. planci larvae completing development increases ~8-fold with every doubling of chlorophyll concentrations up to 3 μg l−1. Field data and the population model show that river floods and regional differences in phytoplankton availability are strongly
related to spatial and temporal patterns in A. planci outbreaks on the GBR. The model also shows that, given plausible historic increases in river nutrient loads over the last
200 years, the frequency of A. planci outbreaks on the GBR has likely increased from one in 50–80 years to one every 15 years, and that current coral cover of
reefs in the central GBR may be 30–40% of its potential value. This study adds new and strong empirical support to the hypothesis
that primary A. planci outbreaks are predominantly controlled by phytoplankton availability. 相似文献
12.
Very few studies on ungulates address issues of inter-specific synchrony in population responses to environmental variation
such as climate. Depending on whether annual variation in performance of ungulate populations is driven by direct or indirect
(trophic) interactions, very different predictions regarding the pattern of inter-specific synchrony can be derived. We compared
annual autumn body mass variation in roe deer (Capreolus capreolus) and wild boar (Sus scrofa) from Poland over the period 1982–2002, and related this to variation in winter and summer climate and plant phenological
development [the Normalized Difference Vegetation Index (NDVI), derived from satellites]. Roe deer fawns (∼1.3 kg increase
from year 1982 to 2002) and yearlings both increased markedly in mass over years. There was also an increase for wild boar
mass over years (∼4.2 kg increase for piglets from 1982 to 2002). Despite our failure to link annual body mass to spring or
winter conditions or the NDVI, the body mass of roe deer and wild boar fluctuated in synchrony. As this was a field roe deer
population, and since wild boar is an omnivore, we suggest this may be linked to annual variation and trends in crop structure
(mainly rye). We urge future studies to take advantage of studying multiple species in order to gain further insight into
processes of how climate affect ungulate populations.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
13.
J. Terraube B. E. Arroyo F. Mougeot T. E. Katzner E. A. Bragin 《Journal of Ornithology》2010,151(3):713-722
The ecology and conservation status of Central Asian populations of Montagu’s Harriers Circus pygargus are poorly known. We studied the breeding biology of this species during 3 years in the Naurzum region, north-central Kazakhstan.
Most Montagu’s Harriers in the study area nested in the forest-steppe transition area, in bushy areas dominated by dogrose
Rosa canina, which was apparently the nesting vegetation type providing highest and densest nest cover in the study area. Laying occurred
from 26 April to 7 June (average 13 May, n = 49) and, although it varied significantly between years, was earlier than in western European populations of similar latitude.
Mean (±SD) clutch size was 4.44 ± 0.86 (range 2–6; n = 50), in the higher range observed for the species. There was no significant interannual variation in clutch size, despite
large variations in the abundance of small mammals in the area. Diet was mainly composed of lizards (54.2%, n = 533 identified prey in all 3 years), with small mammals (17.1%), passerine birds (14.3%) and insects (13.6%) also being
consumed. Mean brood size at the last visit was 2.55 ± 2.10 (range 0–6; n = 51). Failure rate was relatively high; the main identified cause of nest failure was predation. We compare the data obtained
in this population breeding in natural steppes with breeding parameters from the well-studied western European populations,
and discuss the implications for the conservation of this species. 相似文献
14.
Paul M. Regular Gregory J. Robertson William A. Montevecchi Fyzee Shuhood Tony Power Douglas Ballam John F. Piatt 《Polar Biology》2010,33(9):1215-1226
Seabird populations are affected by environmental and anthropogenic influences on a global scale. Many population-level responses
to climate change have been shown, yet few studies have addressed the additive and/or relative impact of environmental and
anthropogenic influences on seabird populations. Using a mixed model approach, we analyzed the trends in plot counts of common
murres (Uria aalge) from a Low Arctic colony at Cape St. Mary’s, Newfoundland, across 26 years (1980–2006). We tested for associations between
population change and various environmental and anthropogenic covariates: water temperature, winter North Atlantic Oscillation,
hunting mortality, oil pollution, by-catch in fishing gear, and visitor disturbance. The number of murres occupying central
plots decreased from 1980 to 1989 and increased from 1990 to 2006. Annual changes in the population were negatively associated
with the estimated number of murres killed in the Newfoundland murre hunt and the high numbers killed in the early 1980s likely
caused the observed population decline. The large number of gillnets set in Newfoundland waters during the 1980s, and associated
incidence of drowning through by-catch, probably also contributed to the observed decline. Though a centennially significant
cold-water perturbation in 1991 forced a regime shift in pelagic food webs, the effect of ocean climate variability on the
population was not obvious. We conclude that management efforts should focus on assessing and mitigating the effects of human-induced
influences and consider the potential additive effects of climate change. 相似文献
15.
Grant WS 《Genetica》2005,125(2-3):293-309
Genetic architectures of marine fishes are generally shallow because of the large potential for gene flow in the sea. European
anchovy, however, are unusual among small pelagic fishes in showing large differences among sub-basins and in harbouring two
mtDNA phylogroups (‘A’ & ‘B’), representing 1.1–1.85 million years of separation. Here the mtDNA RFLP dataset of Magoulas
et al. [1996, Mol. Biol. Evol. 13: 178–190] is re-examined to assess population models accounting for this subdivided population
structure and to evaluate the zoogeographical origins of the two major phylogroups. Haplotype and nucleotide diversities are
highest in the Ionian Sea and lowest in the Aegean and Black seas. However, this gradient is absent when ‘A’ and ‘B’ haplotypes
are examined separately. Neither the self-sustaining nor the basin population models adequately describe anchovy population
behaviour. Tests for neutrality, mismatch and nested clade analyses are concordant in depicting recent expansions of both
phylogroups. Unimodel mismatch distributions and haplotype coalescences dating to the last (Eemian) interglacial (‘B’) and
the Weichselian pleniglacial period (‘A’) indicate separate colonizations of the Mediterranean Basin. Phylogroup ‘A’ is unlikely
to have arisen through continuous long-term isolation in the Black Sea because of climate extremes from displaced subpolar
weather systems during the ice ages. Ancestors of both groups appear to have colonized the Mediterranean from the Atlantic
in the late Pleistocene. Hence, zoogeographic models of anchovy in the Mediterranean must also include the eastern (and possibly
southern) Atlantic. 相似文献
16.
Jonathan A. Patz Holly K. Gibbs Jonathan A. Foley Jamesine V. Rogers Kirk R. Smith 《EcoHealth》2007,4(4):397-405
Climate change, as an environmental hazard operating at the global scale, poses a unique and “involuntary exposure” to many
societies, and therefore represents possibly the largest health inequity of our time. According to statistics from the World
Health Organization (WHO), regions or populations already experiencing the most increase in diseases attributable to temperature
rise in the past 30 years ironically contain those populations least responsible for causing greenhouse gas warming of the
planet. Average global carbon emissions approximate one metric ton per year (tC/yr) per person. In 2004, United States per
capita emissions neared 6 tC/yr (with Canada and Australia not far behind), and Japan and Western European countries range
from 2 to 5 tC/yr per capita. Yet developing countries’ per capita emissions approximate 0.6 tC/yr, and more than 50 countries
are below 0.2 tC/yr (or 30-fold less than an average American). This imbalance between populations suffering from an increase
in climate-sensitive diseases versus those nations producing greenhouse gases that cause global warming can be quantified
using a “natural debt” index, which is the cumulative depleted CO2 emissions per capita. This is a better representation of the responsibility for current warming than a single year’s emissions.
By this measure, for example, the relative responsibilities of the U.S. in relation to those of India or China is nearly double
that using an index of current emissions, although it does not greatly change the relationship between India and China. Rich
countries like the U.S. have caused much more of today’s warming than poor ones, which have not been emitting at significant
levels for many years yet, no matter what current emissions indicate. Along with taking necessary measures to reduce the extent
of global warming and the associated impacts, society also needs to pursue equitable solutions that first protect the most
vulnerable population groups; be they defined by demographics, income, or location. For example, according to the WHO, 88%
of the disease burden attributable to climate change afflicts children under age 5 (obviously an innocent and “nonconsenting”
segment of the population), presenting another major axis of inequity. Not only is the health burden from climate change itself
greatest among the world’s poor, but some of the major mitigation approaches to reduce the degree of warming may produce negative
side effects disproportionately among the poor, for example, competition for land from biofuels creating pressure on food
prices. Of course, in today’s globalized world, eventually all nations will share some risk, but underserved populations will
suffer first and most strongly from climate change. Moreover, growing recognition that society faces a nonlinear and potentially
irreversible threat has deep ethical implications about humanity’s stewardship of the planet that affect both rich and poor. 相似文献
17.
Toshiyuki Sato 《Ecological Research》1992,7(1):1-7
Gametophyte populations inAthyrium brevifrons were analysed with respect to population size and surviving area (%) of individual thalli in a transplant garden at Sapporo
during 5–26 April 1983, to study the safe-microsite for gametophyte establishment in nature. Spores dispersed in August 1982
germinated and grew into thalli of various widths (<10 mm); 10.3% of the thalli matured by early October 1982. Maturation
was attained by gametophytes of width 4–7 mm. The number of gametophytes gradually decreased with increasing width. By April
1983, 20.5% of total gametophytes were mature with a mode of 5–6 mm in width. The relative number of gametophytes with surviving
area of 2–20% increased and that of 85–100% decreased in accordance with collection days delayed until after snow-melt. Surviving
area (%) on gametophyte of all widths decreased with decreasing soil moisture contents. In particular, immature gametophytes
of 2–4 mm width showed a significant correlation (P<0.01) between soil moisture content and relative number of gametophytes with 0–20% surviving area and mean surviving area
(%) of every width of thalli. The spring desiccation might be a factor that reduces or limits gametophyte populations in nature. 相似文献
18.
The potential impacts of climate change on inshore squid: biology, ecology and fisheries 总被引:2,自引:0,他引:2
Squid are important components of many marine ecosystems from the poles to the equator, serving as both important predators
and prey. Novel aspects of their growth and reproduction mean that they are likely to play an important role in the changing
oceans due to climate change. Virtually every facet of squid life-history examined thus far has revealed an incredible capacity
in this group for life-history plasticity. The extremely fast growth rates of individuals and rapid rates of turnover at the
population level mean that squid can respond quickly to environmental or ecosystem change. Their ‘life-in-the-fast-lane’ life-style
allows them to rapidly exploit ‘vacuums’ created in the ecosystem when predators or competitors are removed. In this way,
they function as ‘weeds of the sea’. Elevated temperatures accelerate the life-histories of squid, increasing their growth
rates and shortening their life-spans. At first glance, it would be logical to suggest that rising water temperatures associated
with climate change (if food supply remains adequate) would be beneficial to inshore squid populations and fisheries—growth
rates would increase, life spans would shorten and population turnover would accelerate. However, the response of inshore
squid populations to climate change is likely to be extremely complex. The size of hatchlings emerging from the eggs becomes
smaller as temperatures increase and hatchling size may have a critical influence on the size-at-age that may be achieved
as adults and subsequently, population structure. The influence of higher temperatures on the egg and adult stages may thus
be opposing forces on the life-history. The process of climate change will likely result in squids that hatch out smaller and earlier,
undergo faster growth over shorter life-spans and mature younger and at a smaller size. Individual squid will require more
food per unit body size, require more oxygen for faster metabolisms and have a reduced capacity to cope without food. It is
therefore likely that biological, physiological and behavioural changes in squid due to climate change will have far reaching
effects. 相似文献
19.
Grassland covers approximately one-third of the area of China and plays an important role in the global terrestrial carbon
(C) cycle. However, little is known about biomass C stocks and dynamics in these grasslands. During 2001–2005, we conducted
five consecutive field sampling campaigns to investigate above-and below-ground biomass for northern China’s grasslands. Using
measurements obtained from 341 sampling sites, together with a NDVI (normalized difference vegetation index) time series dataset
over 1982–2006, we examined changes in biomass C stock during the past 25 years. Our results showed that biomass C stock in
northern China’s grasslands was estimated at 557.5 Tg C (1 Tg=1012 g), with a mean density of 39.5 g C m−2 for above-ground biomass and 244.6 g C m−2 for below-ground biomass. An increasing rate of 0.2 Tg C yr−1 has been observed over the past 25 years, but grassland biomass has not experienced a significant change since the late 1980s.
Seasonal rainfall (January–July) was the dominant factor driving temporal dynamics in biomass C stock; however, the responses
of grassland biomass to climate variables differed among various grassland types. Biomass in arid grasslands (i.e., desert
steppe and typical steppe) was significantly associated with precipitation, while biomass in humid grasslands (i.e., alpine
meadow) was positively correlated with mean January-July temperatures. These results suggest that different grassland ecosystems
in China may show diverse responses to future climate changes. 相似文献
20.
Potential impacts of climate change on the distributions and diversity patterns of European mammals 总被引:2,自引:1,他引:1
Irina Levinsky Flemming Skov Jens-Christian Svenning Carsten Rahbek 《Biodiversity and Conservation》2007,16(13):3803-3816
The Intergovernmental Panel on Climate Change (IPCC) predicts an increase in global temperatures of between 1.4°C and 5.8°C
during the 21st century, as a result of elevated CO2 levels. Using bioclimatic envelope models, we evaluate the potential impact of climate change on the distributions and species
richness of 120 native terrestrial non-volant European mammals under two of IPCC’s future climatic scenarios. Assuming unlimited
and no migration, respectively, our model predicts that 1% or 5–9% of European mammals risk extinction, while 32–46% or 70–78%
may be severely threatened (lose > 30% of their current distribution) under the two scenarios. Under the no migration assumption
endemic species were predicted to be strongly negatively affected by future climatic changes, while widely distributed species
would be more mildly affected. Finally, potential mammalian species richness is predicted to become dramatically reduced in
the Mediterranean region but increase towards the northeast and for higher elevations. Bioclimatic envelope models do not
account for non-climatic factors such as land-use, biotic interactions, human interference, dispersal or history, and our
results should therefore be seen as first approximations of the potential magnitude of future climatic changes. 相似文献