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91.
KENTARO TAKAGI KARIBU FUKUZAWA† NAISHEN LIANG‡ MASAZUMI KAYAMA MUTSUMI NOMURA HAJIME HOJYO SADAO SUGATA HIDEAKI SHIBATA TATSUYA FUKAZAWA§ YOSHIYUKI TAKAHASHI‡ TATSURO NAKAJI‡ HIROYUKI OGUMA‡ MASAYOSHI MANO¶ YUKIO AKIBAYASHI TAKESHI MURAYAMA TAKAYOSHI KOIKE KAICHIRO SASA YASUMI FUJINUMA‡ 《Global Change Biology》2009,15(5):1275-1288
To evaluate the effects on CO2 exchange of clearcutting a mixed forest and replacing it with a plantation, 4.5 years of continuous eddy covariance measurements of CO2 fluxes and soil respiration measurements were conducted in a conifer-broadleaf mixed forest in Hokkaido, Japan. The mixed forest was a weak carbon sink (net ecosystem exchange, −44 g C m−2 yr−1 ), and it became a large carbon source (569 g C m−2 yr−1 ) after clearcutting. However, the large emission in the harvest year rapidly decreased in the following 2 years (495 and 153 g C m−2 yr−1 , respectively) as the gross primary production (GPP) increased, while the total ecosystem respiration (RE) remained relatively stable. The rapid increase in GPP was attributed to an increase in biomass and photosynthetic activity of Sasa dwarf bamboo, an understory species. Soil respiration increased in the 3 years following clearcutting, in the first year mainly owing to the change in the gap ratio of the forest, and in the following years because of increased root respiration by the bamboo. The ratio of soil respiration to RE increased from 44% in the forest to nearly 100% after clearcutting, and aboveground parts of the vegetation contributed little to the RE although the respiration chamber measurements showed heterogeneous soil condition after clearcutting. 相似文献
92.
Free air CO2 enrichment (FACE) experiments in aggrading temperate forests and plantations have been initiated to test whether temperate
forest ecosystems act as sinks for anthropogenic emissions of CO2. These FACE experiments have demonstrated increases in net primary production and carbon (C) storage in forest vegetation
due to increased atmospheric CO2 concentrations. However, the fate of this extra biomass in the forest floor or mineral soil is less clear. After 6 years
of FACE treatment in a short-rotation poplar plantation, we observed an additional sink of 32 g C m−2 y−1 in the forest floor. Mineral soil C content increased equally under ambient and increased CO2 treatment during the 6-year experiment. However, during the first half of the experiment the increase in soil C was suppressed
under FACE due to a priming effect, that is, the additional labile C increased the mineralization of older SOM, whereas during
the second half of the experiment the increase in soil C was larger under FACE. An additional sink of 54 g C m−2 y−1 in the top 10 cm of the mineral soil was created under FACE during the second half of the experiment. Although, this FACE
effect was not significant due to a combination of soil spatial variability and the low number of replicates that are inherent
to the present generation of forest stand FACE experiments. Physical fractionation by wet sieving revealed an increase in
the C and nitrogen (N) content of macro-aggregates due to FACE. Further fractionation by density showed that FACE increased
C and N contents of the light iPOM and mineral associated intra-macro-aggregate fractions. Isolation of micro-aggregates from
macro-aggregates and subsequent fractionation by density revealed that FACE increased C and N contents of the light iPOM,
C content of the fine iPOM and C and N contents of the mineral associated intra-micro-aggregate fractions. From this we infer
that the amount of stabilized C and N increased under FACE treatment. We compared our data with published results of other
forest FACE experiments and infer that the type of vegetation and soil base saturation, as a proxy for bioturbation, are important
factors related to the size of the additional C sinks of the forest floor–soil system under FACE.
Author Contribution: MRH conceived of and designed the study, performed research, analyzed data, and wrote the paper; GES
conceived of and designed the study and performed research. 相似文献
93.
Hannes Schroeder Tamsin C. O'Connell Jane A. Evans Kristrina A. Shuler Robert E.M. Hedges 《American journal of physical anthropology》2009,139(4):547-557
The question of the ultimate origin of African slaves is one of the most perplexing in the history of trans‐Atlantic slavery. Here we present the results of a small, preliminary isotopic study that was conducted in order to determine the geographical origin of 25 enslaved Africans who were buried at the Newton plantation, Barbados, sometime between the late 17th and early 19th century. In order to gain a more nuanced understanding of the slaves' origin, we used a combination of carbon, nitrogen, oxygen, and strontium isotope analyses. Carbon and nitrogen isotope ratios were determined in bone and dentinal collagen; oxygen and strontium isotopes were measured in tooth enamel. Results suggest that the majority of individuals were born on the island, if not the estate itself. Seven individuals, however, yielded enamel oxygen and strontium ratios that are inconsistent with a Barbadian origin, which strongly suggests that we are dealing with first‐generation captives who were brought to the island with the slave trade. This idea is also supported by the fact that their carbon and nitrogen stable isotope values differ markedly between their teeth and bones. These intra‐skeletal shifts reflect major dietary changes that probably coincided with their enslavement and forced migration to Barbados. While it is impossible to determine their exact origins, the results clearly demonstrate that the slaves did not all grow up in the same part of Africa. Instead, the data seem to suggest that they originated from at least three different areas, possibly including the Gold Coast and the Senegambia. Am J Phys Anthropol, 2009. © 2009 Wiley‐Liss, Inc. 相似文献
94.
Forest floor of larch species often provides growth habitat for many kinds of understory species because of relatively sparse
structure in a larch canopy. A rich flora of forest understory species may play an essential role in maintaining fertility
of a larch stand. An attempt was made to evaluate photosynthetic nitrogen use efficiency (PNUE) of many understory and overstory
species according to their Raunkiaer lifeform. By studying 72 perennial deciduous species in a larch plantation in northeast
China, marked photosynthetic differences between phanerophytes (Ph) and other three lifeforms of chamaephytes (Ch), hemicryptophytes
(He), and cryptophytes (Cr) were found, with marginal differences found among Ch, He, and Cr. Ph species had much lower PNUE,
and much lower values of rate of nitrogen allocation to chlorophyll (Chl./N) and nitrogen allocation to carboxylation processes
(V
cmax/N) were concurrently observed in Ph compared with the other three lifeforms. Ph had much lower leaf nitrogen per unit of
projection area (N
area) and specific leaf area (SLA, cm2 g–1). At lower SLA, for Ph species the change of PNUE with SLA was small, but these changes became very large at higher SLA for
Ch, He, and Cr species. Our findings indicate that leaf morphological change is important for clarifying photosynthesis differences
among species with different lifeform. 相似文献
95.
Summary The emergence of carbon markets has provided a potential source of funding for reforestation projects. However, there is concern amongst ecologists that these markets will promote the establishment of monoculture plantations rather than more diverse restoration plantings, on the assumption that fast‐growing monocultures are likely to store more carbon than restoration plantings. We examined the validity of this assumption for three predominantly rainforest plantation types established in the moist tropical uplands of north‐east Australia: monoculture plantations of native rainforest conifers (n = 5, mean age 13 years); mixed species plantations of rainforest cabinet timber species, rainforest conifers and eucalypts (n = 5, mean age 13 years); and, environmental restoration plantings comprised mostly of a diverse range of rainforest trees (n = 10, mean age 14 years). We found that restoration plantings stored significantly more carbon in above‐ground biomass than monoculture plantations of native conifers (on average, 106 t vs 62 t carbon per ha); and tended to store more carbon than mixed species timber plantations which were intermediate in value (86 t carbon per ha). Carbon stocks were higher in restoration plantings than in monoculture and mixed species plantations for three reasons. First, and most importantly, restoration plantings were more densely stocked than monoculture and mixed species plantations. Second, there were more large diameter trees in restoration plantings than monoculture plantations. Third, the trees used in restoration plantings had a higher average wood density than the conifers used in monoculture plantations. While, on average, wood density was higher in mixed species plantations than restoration plantings, the much higher stocking rate of restoration plantings meant they stored more carbon than mixed species plantations. We conclude that restoration plantings in the moist tropics of north‐east Australia can accumulate relatively high amounts of carbon within two decades of establishment. Comparison with reference rainforest sites suggests that restoration plantings could maintain their high stocking rates (and therefore high biomass) as they develop in future decades. However, because restoration plantings are currently much more expensive to establish than monoculture plantations, restoration plantings are unlikely to be favoured by carbon markets. Novel reforestation techniques and designs are required if restoration plantings are to both provide habitat for rainforest biota and store carbon in biomass at a cost comparable to monoculture plantations. 相似文献
96.
Deforestation usually results in significant losses of soil organic carbon (SOC). The rate and factors determining the recovery of this C pool with afforestation are still poorly understood. This paper provides a review of the influence of afforestation on SOC stocks based on a meta-analysis of 33 recent publications (totaling 120 sites and 189 observations), with the aim of determining the factors responsible for the restoration of SOC following afforestation. Based on a mixed linear model, the meta-analysis indicates that the main factors that contribute to restoring SOC stocks after afforestation are: previous land use, tree species planted, soil clay content, preplanting disturbance and, to a lesser extent, climatic zone. Specifically, this meta-analysis (1) indicates that the positive impact of afforestation on SOC stocks is more pronounced in cropland soils than in pastures or natural grasslands; (2) suggests that broadleaf tree species have a greater capacity to accumulate SOC than coniferous species; (3) underscores that afforestation using pine species does not result in a net loss of the whole soil-profile carbon stocks compared with initial values (agricultural soil) when the surface organic layer is included in the accounting; (4) demonstrates that clay-rich soils (> 33%) have a greater capacity to accumulate SOC than soils with a lower clay content (< 33%); (5) indicates that minimizing preplanting disturbances may increase the rate at which SOC stocks are replenished; and (6) suggests that afforestation carried out in the boreal climate zone results in small SOC losses compared with other climate zones, probably because trees grow more slowly under these conditions, although this does not rule out gains over time after the conversion. This study also highlights the importance of the methodological approach used when developing the sampling design, especially the inclusion of the organic layer in the accounting. 相似文献
97.
西双版纳橡胶林生物量随海拔梯度的变化 总被引:8,自引:1,他引:7
对西双版纳低(550~600 m)、中(750~800 m)、高(950~1050 m)3个海拔梯度上橡胶林地上及各器官的生物量进行了测定。结果表明,海拔从低到高,地上生物量和干生物量都呈降低趋势,干生物量占地上生物量的70%以上;海拔间的地上生物量和干生物量差异显著(P<0.05)。枝和叶生物量为中海拔最高,低海拔次之,高海拔最低,二者分别占地上生物量20%和5%左右,仅高海拔和低海拔间差异显著(P<0.05)。气温的海拔间差异可能是引起生物量海拔间差异的重要原因之一。3个海拔上各器官生物量大小顺序为:干>枝>叶。橡胶林低海拔模型用于中海拔和高海拔、混合模型用于各海拔的生物量计算会导致不同程度的误差。 相似文献
98.
99.
为了了解北亚热带东部地区天然次生林转变成杉木(Cunninghamia lanceolata)人工林对土壤活性有机碳库的影响, 以浙江省富阳市庙山坞森林生态系统定位研究站杉木人工林和天然次生林为研究对象, 对达到成熟林状态的两种林分类型0-60 cm内各土层土壤活性有机碳含量进行了比较研究。结果表明: 1)天然次生林土壤总有机碳、易氧化有机碳、水溶性有机碳和轻组有机质含量均高于杉木人工林, 与人工杉木林相比, 增幅分别为19.0%-32.6%、0.8%-30.3%、3.8%-54.1%和6.3%-38.6%, 且在0-10和10-20 cm土层差异显著(p < 0.05) (水溶性有机碳仅在0-10 cm土层差异显著); 2)杉木人工林土壤水溶性有机碳与易氧化碳占总有机碳的比率均高于天然次生林; 3)两个林分土壤水溶性有机碳、易氧化碳和轻组有机质与总有机碳含量均呈现极显著相关, 且天然次生林土壤易氧化碳、轻组有机质与总有机碳的相关系数均大于杉木人工林; 4)土壤有机碳、水溶性有机碳、易氧化碳和轻组有机质与土壤养分(全氮、水解氮、速效磷、速效钾、速效钙和速效镁)的相关性均达到显著(p < 0.05)或极显著(p < 0.01)水平。 相似文献
100.
Forest transition is a process of overall forest cover from net loss to net gain over time. Forest transition especially the process after turning point from deforestation to reforestation has inspired lots of researches for its potential to improve environmental services. China has undergone forest transition since the 1980s. However, in tropical China, deforestation was still existed, while the overall forest cover increased greatly. To investigate this issue, we conducted this research by classifying overall forest into natural forest and plantation in Xishuangbanna, which has undergone forest transition and deforestation and overall forest cover increasing. We found that natural forest continues decreasing while overall forest cover increasing and plantation expansion in forest transition. The forest transition in Xishuangbanna was found to be a tree cover transition, which was mainly contributed by large plantation expansion. In Xishuangbanna, deforestation is still undergoing after its overall forest cover transition occurred in 1988. The general overall forest definition used by forest transition will not be able to recognize deforestation when natural forests are displaced by plantations because the overall forest cover remains unchanged or even increasing. We therefore recommended to classify forest types in forest transition researches. 相似文献