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991.
西双版纳不同海拔4种雨林幼苗的光合特性和生物量 总被引:1,自引:0,他引:1
在云南西双版纳勐仑(600 m,低海拔)、菜阳河(1 100 m,中海拔)和勐宋(1 600 m,高海拔),对热带季节雨林4种主要树种绒毛番龙眼(Pometio tomentosa)、云南玉蕊(Barringtonia macrostachya)、云南肉豆蔻(Myristica yunnanensis)和小叶红光树(Knema globularia)幼苗进行移栽试验,测定幼苗的光合作用和生物量.结果表明,高海拔七的低温使幼苗处于休眠或光系统受到不可恢复的破坏,光合作用几乎停止;4种幼苗的最大净光合速率及生物量均随海拔的增加而下降;低、中海拔上4种幼苗的净光合速率日变化曲线均表现为"双峰型",低海拔的第一个峰明显高于中海拔.除小叶红光树外,其它幼苗的根生物量分数均随海拔增高而增加.海拔升高,温度降低是限制幼苗光合特性、生物量积累的主要因子,也是某些幼苗在更高海拔雨林群落中消失的潜在原因.此外,幼苗的根生物量分数随海拔上升而增加是其对极限环境温度的一种重要适应特征. 相似文献
992.
This study is an exercise to check the efficiency of the existing reserve system, and to show how systematic conservation
planning—using information available and the complementarity concept—can improve the basis for decisions and minimize costs.
We verified the performance, in number of cells and primate species representation, of the existing Atlantic Forest (Brazil)
reserve network with a quarter-degree resolution grid, with 1,884 cells. We used occurrence data of 20 endemic primate species,
and the maps of 237 existing reserves. Reserve networks were selected to represent primate species first considering no pre-existing
reserves in Atlantic Forest, and then, considering the existing reserve system, taking into account the minimum area for viable
population of the larger species (Northern muriqui Brachyteles hypoxanthus). Reserve selection was carried out using the complementarity concept implemented by a simulated annealing algorithm. Primate
species representation (at least one occurrence in the network) could be achieved with 8% of the existing reserve system (nine
cells in relation to the 120 in the existing reserve system). We found that today’s reserve system represents 89% of endemic
primate species, excluding the species Coimbra Filho’s titi monkey (Callicebus coimbrai) and Marcgraf’s capuchin (Cebus flavius). The networks selected without considering existing reserves contained nine cells. The networks selected considering existing
reserves (120 cells), had two new cells necessary to represent all the primates. This does not mean that a viable alternative
is to start from zero (i.e., nonexistent reserves). Identifying critical supplementary areas using biodiversity information
to fill the gaps and then starting “conservation in practice” in these areas should be priorities. 相似文献
993.
Most of the ambient dissolved organic carbon (DOC) is refractory to microbial degradation; bacteria can consume a minor but variable part of the DOC pool over periods of hours and days. It is important to increase our knowledge of the dynamics of the biodegradable fraction of DOC (BDOC) to understand the global carbon budget.Several methods for determining BDOC have been developed; however, the problem of most of them is the time (days/weeks) required for the colonization and/or determination.In this paper, we describe the application to seawater of a plug-flow bioreactor to measure BDOC within 3–4 h. The bioreactor was built following Søndergaard and Worm [Søndergaard, M., Worm, J., 2001. Measurement of biodegradable dissolved organic carbon (BDOC) in lake water with a bioreactor. Water Res. 35, 2505-2513.] protocols for the measurement of BDOC in lake water. We analyzed BDOC on samples collected in the Gulf of Trieste during autumn–winter and summer 2003–2004. BDOC concentrations varied from 8 to 24 μM and represented from 10.3% to 25.5% of the total DOC. To evaluate the effectiveness of this method, we compared bioreactor BDOC measurement with data obtained from batch cultures. The results indicate that BDOC in coastal seawater can be measured rapidly and reliably with this bioreactor. 相似文献
994.
Aquatic macrophytes provide essential spawning and nursery habitat for fish, valuable food source for waterfowl, migratory
birds and mammals, and contribute greatly to overall biodiversity of coastal marshes of the Laurentian Great Lakes. Two approaches
have been used to survey the plant community in coastal wetlands, and these include the grid (GR) and transect (TR) methods.
These methods have been used to identify the average species richness at different sites, but their suitability for determining
total species richness of a site has not been tested. In this paper, we compare the performance of these two established methods
with that of the Stratified method (ST), which uses the sampler’s judgment to guide them to different habitat zones within
the wetland. We used the three protocols to compare species richness of six coastal wetlands of the Great Lakes, three pristine
marshes in eastern Georgian Bay (Lake Huron) and three degraded wetlands in Lake Ontario, Canada. The greatest species richness
was associated with the ST method, irrespective of wetland quality. The ST method was also more efficient (fewer quadrats
sampled), and revealed the most number of unique (those found with only one method) and uncommon species (those found in <5%
of the quadrats). Despite these statistical differences, we found that sampling method did not significantly affect the performance
of a recently developed index of wetland quality, the Wetland Macrophyte Index. These results have important implications
for designing macrophyte surveys to track changes in biodiversity and wetland quality. 相似文献
995.
N. A. Chukwuone 《Biodiversity and Conservation》2009,18(2):339-353
Cultivation of non-wood forest products (NWFP), although a veritable means of ecosystem and biodiversity conservation and
improved natural resource management, has not been sustained in southern Nigeria (Nigeria’s major forest region) notwithstanding
the unprecedented rate of depletion of the resource in the wild. For example, efforts in the past to support cultivation of
NWFP in southern Nigeria under a USAID funded Cross River State forestry project, especially through nursery establishment
for some rural communities, was not sustained as the initiative was abandoned by the participants. Hence to promote cultivation
of NWFP, this study ascertained socioeconomic factors that influence cultivation of NWFPs. Multi stage sampling technique
was used in selection of respondents (households) from two States: Cross River and Enugu States of southern Nigeria. A sample
size of 400 households was used for the study. Probit and multinomial logistic regressions were used in estimating NWFP cultivation.
The findings show that cultivation of NWFP was positively determined by gender, farming occupation (especially of women farmers)
distance to forests where NWFP was collected, proportion of household food from NWFP, and medium wealth category. Age had
a negative effect on cultivation until the age of 46 after which the effect became positive. In addition, household size,
gender and farming occupation of household heads positively influenced cultivation of NWFP in plantations as against home
gardens while gender and farming occupation had positive effect on cultivation of some stands of NWFP as against home gardens.
Incorporating the findings of this study in future intervention project for NWFP cultivation will help sustain the initiative. 相似文献
996.
Biological legacies are organic structures and patterns remaining after a disturbance that may contribute to the complexity
of the recovering vegetation. Legacies may, in turn, reduce the impacts of human disturbances such as logging and habitat
transformation on elements of biodiversity. To examine the effects of biological legacies on biotic responses after disturbance,
we surveyed 32 sites for bryophytes in an area subject to large-scale conversion of native eucalypt forest to exotic Pinus radiata D. Don plantations in eastern Australia. We sampled bryophyte and substrate diversity (log, bare ground, upturned tree/log,
and trees) in eight sites in each of four landscape context classes: pine plantation stands, elliptical-shaped remnants, strip-shaped
remnants, and controls in a large area of contiguous, unmanaged eucalypt forest. We found a muted response by individual species
of bryophyte to landscape context. We attribute this, in part, to the presence of logs in the intensively managed pine plantation
sites. The boost in bryophyte diversity from species on logs meant that some pine sites supported similar species composition
to the continuous eucalypt forest controls. Our findings also underline the importance of local controls and structural variation,
including leaving logs and native trees in plantations, for enhancing bryophyte species richness in managed landscapes. 相似文献
997.
Species richness and density of understory plants were investigated in eight 1 ha plots, distributed one each in undisturbed
and disturbed tropical evergreen, semi-evergreen, deciduous and littoral forests of Little Andaman island, India, which falls
under one of the eight hottest hotspots of Biodiversity in the world viz. the Indo-Burma. One hundred 1 m−2 quadrats were established in each 1 ha plot, in which all the understory plants (that include herbs, undershrubs, shrubs
and herbaceous climbers) were enumerated. The total density of understory plants was 6,812 individuals (851 ha−1) and species richness was 108 species, representing 104 genera and 50 families. Across the four forest types and eight study
plots, the species richness ranged from 10 to 39 species ha−1. All the disturbed sites harbored greater number of species than their undisturbed counterparts. Herbs dominated by species
(63%) and density (4,259 individuals). The grass Eragrostis tenella (1,860 individuals; IVI 40), the invasive climber Mikania cordata (803; IVI 20) and the shrub Anaxagorea luzonensis (481; IVI 17.5) were the most abundant species. Poaceae, Asteraceae, Acanthaceae, Orchidaceae and Euphorbiaceae constituted
the species-rich families represented by 6 species each. The species-area curves attained an asymptote at 0.8 ha level except
in sites DD and DL, indicating 1 ha plot is not sufficient to capture all the understory species in disturbed forests. The
alien weeds formed about one-fourth of the species richness (31 species; 28%) and density (1,926 individuals; 28.3%) in the
study sites, indicating the extent of weed invasion and the attention required for effective conservation of the native biodiversity
of the fragile island forest ecosystem. 相似文献
998.
广西木论自然保护区铁榄群落主要乔木种群格局的分形特征 总被引:1,自引:0,他引:1
为了揭示种群空间分布特征随尺度的变化规律,探讨不同种群对空间资源的占据能力和生态适应能力及分形差异,采用计盒维数、信息维数和关联维数对木论自然保护区铁榄群落主要乔木种群格局特征进行了研究。结果表明,优势种铁榄(Sinosideroxylon pedunculatum)、东女贞(Ligustrum japonicum)、小栾树(Boniodendron minius)、稀有濒危种掌叶木(Handeliodendron bodinieri)、青檀(Pteroceltis tatarinowii)5个种群在相应的尺度具有明显的分形特征;计盒维数和信息维数大小顺序一致,均为:铁榄〉东女贞〉小栾树〉掌叶木〉青檀;在5个种群中,铁榄计盒维数为1.7763最大,接近2,对空间环境的占据能力最强,信息维数(1.7206)也最大,个体聚集强度强,在群落中处于绝对优势地位,青檀计盒维数(0.8316)和信息维数(0.8990)最小,对环境的占据利用能力弱,个体聚集程度整体较弱,在群落中处于伴生地位;在0.5~50m的尺度上,关联维数大小顺序为:铁榄(1.7314)〉东女贞(1.6688)〉小栾树(1.6050)〉青檀(0.7868),而掌叶木只有在大的尺度上才出现关联,且关联较强。3个分形维数大小的不同组合,能够全面揭示不同种群格局特征和种群在群落中所处地位的差异。 相似文献
999.
South-east Asia's tropical rainforests are experiencing the highest rate of deforestation worldwide and fire is one of the most important drivers of forest loss and subsequent carbon dioxide emissions. In this study, we analyzed all fire events in Borneo recorded by satellites over a period of 10 years. About 16.2 Mha, which corresponds to 21% of the land surface, have been affected by fire at least once and 6% more than one time. During El Niño conditions, which cause prolonged droughts in the region, the fire-affected area was on average three times larger than during normal weather conditions. Similarly, fires in forests affected 0.3 Mha in normal years and 1 Mha during El Niño years. Carbon rich peat swamp forest ecosystems were most severely affected. There is a pronounced difference in fire occurrence between different countries and provinces in Borneo although ecosystem and land use are very similar across the island. Compared with Sarawak, Sabah (Malaysia) and Brunei the relative annual fire-affected area in Kalimantan, the Indonesian part of Borneo, was on average five times larger. During El Niño conditions the fire-affected area increased only in Kalimantan and not in Brunei and the Malaysia. A similar pattern was observed in National Parks. This suggests, that El Niño related droughts are not the only cause of increased fire occurrence and do not necessarily lead to a higher number of fire events. These results improve our understanding of existing fire regimes and drivers of fire in SE Asian tropical ecosystems and may help to better protect the remaining rainforests. 相似文献
1000.
Strong links between teleconnections and ecosystem exchange found at a Pacific Northwest old-growth forest from flux tower and MODIS EVI data 总被引:1,自引:0,他引:1
SONIA WHARTON LAURA CHASMER† MATTHIAS FALK‡ KYAW THA PAW U 《Global Change Biology》2009,15(9):2187-2205
Variability in three Pacific teleconnection patterns are examined to see if net carbon exchange at a low‐elevation, old‐growth forest is affected by climatic changes associated with these periodicities. Examined are the Pacific Decadal Oscillation (PDO), Pacific/North American Oscillation (PNA) and El Niño‐Southern Oscillation (ENSO). We use 9 years of eddy covariance CO2, H2O and energy fluxes measured at the Wind River AmeriFlux site, Washington, USA and 8 years of tower‐pixel remote sensing data from the Moderate Resolution Imaging Spectroradiometer (MODIS) to address this question. We compute a new Composite Climate Index (CCI) based on the three Pacific Oscillations to divide the measurement period into positive‐ (2003 and 2005), negative‐ (1999 and 2000) and neutral‐phase climate years (2001, 2002, 2004, 2006 and 2007). The forest transitioned from an annual net carbon sink (NEP=+217 g C m?2 yr?1, 1999) to a source (NEP=?100 g C m?2 yr?1, 2003) during two dominant teleconnection patterns. Net ecosystem productivity (NEP), water use efficiency (WUE) and light use efficiency (LUE) were significantly different (P<0.01) during positive (NEP=?0.27 g C m?2 day?1, WUE=4.1 mg C g?1 H2O, LUE=0.94 g C MJ?1) and negative (NEP=+0.37 g C m?2 day?1, WUE=3.4 mg C g?1 H2O, LUE=0.83 g C MJ?1) climate phases. The CCI was linked to variability in the MODIS Enhanced Vegetation Index (EVI) but not to MODIS Fraction of absorbed Photosynthetically Active Radiation (FPAR). EVI was highest during negative climate phases (1999 and 2000) and was positively correlated with NEP and showed potential for using MODIS to estimate teleconnection‐driven anomalies in ecosystem CO2 exchange in old‐growth forests. This work suggests that any increase in the strength or frequency of ENSO coinciding with in‐phase, low frequency Pacific oscillations (PDO and PNA) will likely increase CO2 uptake variability in Pacific Northwest conifer forests. 相似文献