Based on the summed dominance ratios of species in sample plots, the first three dominant species (Litchi chinensis, Elaeocarpus sylvestris and Canarium album) of the secondary monsoon rain forest of Mt. Royal Shoe in...Based on the summed dominance ratios of species in sample plots, the first three dominant species (Litchi chinensis, Elaeocarpus sylvestris and Canarium album) of the secondary monsoon rain forest of Mt. Royal Shoe in Lianjiang City, western Guangdong, were chosen for analyzing their spatial distribution pattern with the analysis methods such as frequency models of Poisson Distribution, Two Negative Items Distribution, Neyman Distribution, aggregate indexes, Taylor exponential equation and Iwao’s equation modeling. The results showed that these three species distributed in the congregate spatial pattern. Litchi chinensis and Elaeocarpus sylvestris had the characteristic of basic congregate population and attractive characteristic between their plants. The patterns for Canarium album may change and become more evenly distributed with the increase of density. The overall species spatial pattern also depended on the conservation of the secondary monsoon rain forest besides it was affected by the species reproduction characteristics and its growing environment. The congregate spatial patterns of three dominant species showed that it is important to conserve forest urgent conservation of the forest.展开更多
CH4 and N2O fluxes from soil under a tropical seasonal rain forest in Xishuangbanna, Southwest China were measured for one year using closed static chamber technique and gas chromatography method. Three treatments wer...CH4 and N2O fluxes from soil under a tropical seasonal rain forest in Xishuangbanna, Southwest China were measured for one year using closed static chamber technique and gas chromatography method. Three treatments were set in the studied field： （A） litter-free, （B） with litter, and （C） with litter and seedling. The results showed that the soil in our study was a sink of atmospheric CH4 and source of atmospheric N2O. The observed mean CH4 fluxes from treatments A, B, and C were -50.0 ± 4.0, -35.9 ± 2.8, -31.6 ± 2.8 μgC/（m^2·h）, respectively, and calculated annual fluxes in 2003 were -4.1, -3.1, and -2.9 kgC/hm^2, respectively. The observed mean N2O fluxes from treatments A, B, and C were 30.9 ± 3.1, 28.2 ± 3.5, 50.2±3.7 μgN/（m^2·h）, respectively, and calculated annual fluxes in 2003 were 2.8, 2.6, and 3.7 kgN/hm^2, respectively. Seasonal variations in CH4 and N2O fluxes were significant among all the three treatments. The presence of litter decreased CH4 uptake during wet season （P 〈 0.05）, but not during dry season. There was a similar increase in seedlings-mediated N2O emissions during wet and dry seasons, indicating that seedlings increased N2O emission in both seasons. A strong positive relationship existed between CH4 fluxes and soil moisture for all the three treatments, and weak relationship between CH4 fluxes and soil temperature for treatment B and treatment C. The N2O fluxes correlated with soil temperature for all the three treatments.展开更多
A study was conducted to evaluate the status of soil nutrients under E. grandis plantation in comparison with that in its adjacent submontane rain forest. Twenty sequare plots, with an area of 20 m×20 m for each,...A study was conducted to evaluate the status of soil nutrients under E. grandis plantation in comparison with that in its adjacent submontane rain forest. Twenty sequare plots, with an area of 20 m×20 m for each, were established in both of E.grandis plantation and its adjacent sub-montane rain forest, independently. Soil samples were collected from each square plot, at five points （at the four comers and at the center） of each plot. The collected soil samples were mixed to make a composite and representative sample for each plot, independently. The analyses were done in a soil laboratory following appropriate methods. The analysis result indicated that there were no significance differences between E. grandis plantation and its adjacent sub-montane rain forest in the level of major soil nutrients （total N, available P, exchangeable K, Ca and Mg）, pH and total carbon of soils （p 〈 0.05）. There were significance differences between two sites of forest soils in percentage of clay particles, and exchangeable Na content. E. grandis plantation was found improving soil nutrients and total carbon as compared with that of its adjacent submontane rain forest.展开更多
The effects of canopy development, solar angle, and weather conditions on temporal variation in photosynthetic photon flux density（PPFD） at three heights within a tropical rain forest canopy in Xishuangbanna, China,...The effects of canopy development, solar angle, and weather conditions on temporal variation in photosynthetic photon flux density（PPFD） at three heights within a tropical rain forest canopy in Xishuangbanna, China, were examined. PPFD was measured every second and stored as 10-min averages from 1 December 2002 to 30 November 2003. PPFD variability was examined at three different temporal scales. Specific days in March, September, and December with clear and overcast sky conditions were selected to separate the effects of leaf area index（LAI） and solar angle on diurnal variability. On both clear and overcast days, mean daily average PPFD was significantly different between March and September at all heights, except 10 m on clear days, suggesting that LAI directly influences PPFD. In contrast, the differences in daily average PPFD among three heights between September and December were likely due to variation in solar angle. In addition, daily average PPFD at all locations were significantly lower under overcast than clear sky conditions in March, September and December. Over the year-long study, the mean daily total PPFD at 2! m, 10 m and 4 m was 2.8, 2.7 and 0.7 mol/（m^2·d）, which accounted for 9.7%, 9.4% and 2.4% of the daily PPFD above the canopy, respectively. Significant differences in mean daily total PPFD occurred at the same heights among different seasons, and diurnal, day-to-day and seasonal PPFD varied at different heights within the canopy. The possible effects of light variability on physiological and morphological responses of plants are discussed.展开更多
A pristine montane rain forest was recently discovered from Mengsong of Xishuangbanna in the southern Yunnan. It attracts botanists that many primitive plant taxa across various life forms were co-existed in the monta...A pristine montane rain forest was recently discovered from Mengsong of Xishuangbanna in the southern Yunnan. It attracts botanists that many primitive plant taxa across various life forms were co-existed in the montane rain forest. In order to know the biogeography of the montane rain forest, distribution patterns of some species of biogeographical importance from the montane forest were enumerated and their biogeographical implications were discussed with geological explanation. It was concluded that the montane rain forest in the southern Yunnan has strong affinity to montane rain forests in Sumatra or Southeast Asia in broad sense. It was tentatively suggested that Sumatra could be once connected to Myanmar and drifted away due to northward movement of continental Asia by bumping of India plate.展开更多
The effect of arbuscular mycorrhizal fungi on seedling growth across the rain forest-pasture edge has not received much attention. In a tropical rain forest in eastern Mexico, the seedlings of light demanding (Ficus i...The effect of arbuscular mycorrhizal fungi on seedling growth across the rain forest-pasture edge has not received much attention. In a tropical rain forest in eastern Mexico, the seedlings of light demanding (Ficus insipida), nonsecondary light demanding (Lonchocarpus cruentus) and shade tolerant species (Nectandra ambigens, Coccoloba hondurensis) were grown and transplanted to a forest edge with three inoculation treatments (AM fungus spores and colonized roots, spores, and no inoculum). For all species, stem height, stem diameter, total dry weight, leaf area and net assimilation rate were higher in the pasture. Stem height, stem diameter and root/shoot were higher for L. cruentus, and leaf area ratio, specific leaf area and net assimilation rate were higher for F. insipida;the lowest values of almost all variables were recorded for N. ambigens. L. cruentus and C. hondurensis with mycorrhizae had the highest values for root/shoot and net assimilation rate, respectively. The lowest values of root/shoot and net assimilation rate were observed for nonlight-demanding species in the forest. There were clear trade-offs for the pioneer species between survival and growth, and in underground biomass allocation and assimilation for nonsecondary light demanding, but there was not for the shade-tolerant species.展开更多
In order to finish the cataloging work of buttercup species in the family of Renunculaceae for the compilation of the Flora Yunnanensis, I went to the CAS Institute of Botany in Kunming City,capital of Yunnan Province...In order to finish the cataloging work of buttercup species in the family of Renunculaceae for the compilation of the Flora Yunnanensis, I went to the CAS Institute of Botany in Kunming City,capital of Yunnan Province in May 1995 to look up phyto-taxonomic specimens. At the invitation of the Institute’s director Prof. Xu Zhaifu, when the work was coming to an end, I toured the well-known botanic garden of the Institute in the township of Menglu, which nests in the picturesque district of Xishuang Banna at the southernmost tip of the subtropical territory of Yunnan. In the winter of 1958,I had visited the ever-verdant vicinity to collect floral materials. After almost 37 years, I revisited the botanic garden founded by celebrated展开更多
Biometric inventories for 25 years,from 1983 to 2005,indicated that the Jianfengling tropical mountain rain forest in Hainan,China,was either a source or a modest sink of carbon.Overall,this forest was a small carbon ...Biometric inventories for 25 years,from 1983 to 2005,indicated that the Jianfengling tropical mountain rain forest in Hainan,China,was either a source or a modest sink of carbon.Overall,this forest was a small carbon sink with an accumulation rate of(0.56±0.22) Mg C ha-1yr-1,integrated from the long-term measurement data of two plots(P9201 and P8302).These findings were similar to those for African and American rain forests((0.62±0.23) Mg C ha-1yr-1).The carbon density varied between(201.43±29.38) Mg C ha-1 and(229.16±39.2) Mg C ha-1,and averaged(214.17±32.42) Mg C ha-1 for plot P9201.Plot P8302,however,varied between(223.95±45.92) Mg C ha-1 and(254.85±48.86) Mg C ha-1,and averaged(243.35±47.64) Mg C ha-1.Quadratic relationships were found between the strength of carbon sequestration and heavy rainstorms and dry months.Precipitation and evapotranspiration are two major factors controlling carbon sequestration in the tropical mountain rain forest.展开更多
Aims Soil respiration is one of the most important components in the car-bon(c)cycle in terrestrial ecosystems.to investigate the contribution of each component of c cycle to the total soil c efflux,we quantified the ...Aims Soil respiration is one of the most important components in the car-bon(c)cycle in terrestrial ecosystems.to investigate the contribution of each component of c cycle to the total soil c efflux,we quantified the rates of litter,root,and other mineral soil respiration from 2012 to 2014 in the primary and secondary tropical mountain rain forests in Hainan Island,china.Methods the seasonal dynamics of soil(Rs),non-litter(RNL)and non-root(RNR)respiration rates were measured using an automatic chamber system(Li-8100).Litter removal and root removal treatments were used to assess the contribution of litter and roots to belowground c production.We estimated the annual c efflux of each compo-nent of soil respiration in primary and secondary forests using a temperature-based exponential model and analyzed the impact of each component in each forest type.Important Findingsthe annual total soil c efflux was significantly higher in the primary rain forest(1567±205 g c m^(−2)yr^(−1))than that in the secondary forest(1300±70 g c m^(−2)yr^(−1),P<0.05).the litter,root,and mineral soils contributed 22%(349±185 g c m^(−2)yr^(−1)),38%(589±100 g c m^(−2)yr^(−1)),and 40%(628±128 g c m^(−2)yr^(−1))to the total soil c efflux in primary rain forest,respectively.In secondary forest,these three components contributed 11%(148±35 g c m^(−2)yr^(−1)),45%(572±259 g c m^(−2)yr^(−1)),and 44%(580±226 g c m^(−2)yr^(−1)),respectively.the temperature sensitivity(Q10)of Rs(2.70±0.14)in the primary forest was significantly higher than that in the secondary forest(2.34±0.12),with the Q10 values for respiration decreasing in the order of RNR>Rs>RNL.these results show that the difference in litter respiration between primary and secondary forest caused the major difference in annual soil respiration efflux between these two forest types.In addition,the litter respiration is more sensitive to the soil temperature than the other soil respiration components.展开更多
Based on investigation of 53 gaps and 25 quadrats (15m×15m each) of non-gap closed stand in an old-growth tropical montane rain forest of Hainan Island, China, canopy disturbance regimes and gap regeneration were...Based on investigation of 53 gaps and 25 quadrats (15m×15m each) of non-gap closed stand in an old-growth tropical montane rain forest of Hainan Island, China, canopy disturbance regimes and gap regeneration were studied. Gaps were elliptical in horizontal form, the ratio of long axis /short axis was about 1.4. Percentage of expanded gaps (EG) and canopy gaps (CG) area in the landscape were 53.5% and 25.2% respectively. EG ranged from 31.4 m2 to 488.2m2 and CG/rom 14.9m2 to 354.2m2, their average sizes ...展开更多
Amongst the impacts of converting forest to agricultural activities are soil erosion and degradation of ecology service values and goods （ESVG）. The soil erosion can be seen as on-site impacts, such as the problems ...Amongst the impacts of converting forest to agricultural activities are soil erosion and degradation of ecology service values and goods （ESVG）. The soil erosion can be seen as on-site impacts, such as the problems of decreasing soil fertility and also its off-site impact such as the problems of sedimentation of the nearby rivers, whilst the degradation of ESVG are more holistie in nature, These impacts can be devastating in environmental, biological, and socio-economic manners. This paper reports the study undertaken on the impacts of agricultural development in 0.8 million ha of forest dominated landscape in Pasoh Forest Region （PFR）, Malaysia, within period of 8 years from 1995 to 2003. Three folds of impacts on agricultural development examined and analysed, are： （i） relationship of total soil loss and changes in land use pattern, （ii） mapping trends of ESVG for PFR in 1995 and 2003, and （iii） risk assessment of ESVG based on simulation of converting 339,630 ha of primary forest into mass-scale oil palm plantation. Results of this study indicated that although only minor changes of about 1464 ha （about 0.2% of PFR） of primary forest was converted to agricultural activities, it have significantly increased the total soil loss from 59 to 69 million ton/ha/yr. The mean rate of soil is loss for PFR is 0.8 mil ton/ha/yr and if translated into ESVG term, the soil loss costs about US$ 4.8mil/yr. However, majority of the soil loss within all land use classes are within range of very low-low risk categories （〈10 ton/ha/yr）. ESVG for PFR were costing US$ 179 millions in 1995, declined to US$114 millions in 2003 due to 0.2% reduction of forested land. The ESVG of converting 339,630 ha primary forest into mass plantation cost less than original forest within period of 20 years examined; the 20th year of conversion, the ESVG of plantation and to-remain as forest cost US$ 963 and US$ 575 millions, respectively. However, this difference is only marginal when full attributes of ESVG are considered.展开更多
The study of effects of acid rain in Southwestern China on forest ecosystems .has been inrestigated since 1984. The results have shown that the ecosystem of Pinus massoniana forest has been damaged severely by acid ra...The study of effects of acid rain in Southwestern China on forest ecosystems .has been inrestigated since 1984. The results have shown that the ecosystem of Pinus massoniana forest has been damaged severely by acid rain. Comparing the areas where the annual mean pH value is lower than 4.5 with that higher than 4.5, the productivity of the ecosystems decreased 50 percent. Both the percentages of the green leaves and the content of chlorophyll cut down; the acidity of soil increased a bit and the fertility showed the tendency to lower. The microbial population components in surface soil were changed and the total number of soil microbes reduced from 63.5 to 92.6 percent. Besides the direct effects of acid rain, the insect pest, especially, Blastophagus piniperdoz and Monochamus galloprovincialis, seized the opportunity to enter and reproduce in it so as to aggravate the forest dieback of P.massoniana in the areas where the annual average pH value is lower than 4.5.Additionally, the simulation study on the symptoms of main tree species in Southwestern China damaged by acid rain has obtained the results in the resistibility of 30 tree species, which provided a foundation for selecting suitable tree species to cultivate in the polluted areas.展开更多
A conceptual hydrological model that links the Xin＇anjiang hydrological model and a physically based snow energy and mass balance model, described as the XINSNOBAL model, was developed in this study for simulating ra...A conceptual hydrological model that links the Xin＇anjiang hydrological model and a physically based snow energy and mass balance model, described as the XINSNOBAL model, was developed in this study for simulating rain-on-snow events that commonly occur in the Pacific Northwest of the United States. The resultant model was applied to the Lookout Creek Watershed in the H. J. Andrews Experimental Forest in the western Cascade Mountains of Oregon, and its ability to simulate streamflow was evaluated. The simulation was conducted at 24-hour and one-hour time scales for the period of 1996 to 2005. The results indicated that runoffand peak discharge could be underestimated if snowpack accumulation and snowmelt under rain-on-snow conditions were not taken into account. The average deterministic coefficient of the hourly model in streamflow simulation in the calibration stage was 0.837, which was significantly improved over the value of 0.762 when the Xin＇anjiang model was used alone. Good simulation performance of the XINSNOBAL model in the WS 10 catchment, using the calibrated parameter of the Lookout Creek Watershed for proxy-basin testing, demonstrates that transplanting model parameters between similar watersheds can orovide a useful tool for discharge forecastin~, in un^au^ed basins.展开更多
Xishuangbanna of southern Yunnan is biogeographically located at a transitional zone from tropical southeast （SE） Asia to subtropical east Asia and is at the junction of the Indian and Burmese plates of Gondwana and...Xishuangbanna of southern Yunnan is biogeographically located at a transitional zone from tropical southeast （SE） Asia to subtropical east Asia and is at the junction of the Indian and Burmese plates of Gondwana and the Eurasian plate of Laurasia. The region, though surprisingly far from the equator and at a relatively high altitude, has a rich tropical flora and a typical tropical rain forest in the lowland areas. Based on physiognomic and ecological characteristics, floristic composition and habitats combined, the primary vegetation in Xishuangbanna can be organized into four main vegetation types： tropical rain forest, tropical seasonal moist forest, tropical montane evergreen broad-leaved forest and tropical monsoon forest. The tropical rain forest can be classified into two subtypes, i.e. a tropical seasonal rain forest in the lowlands and a tropical montane rain forest at higher elevations. The tropical seasonal rain forest has almost the same forest profile and physiognomic characteristics as equatorial lowland rain forests and is a type of truly tropical rain forest. Because of conspicuous similarity on ecological and floristic characteristics, the tropical rain forest in Xishuangbanna is a type of tropical Asian rain forest. However, since the tropical rain forest of Xishuangbanna occurs at the northern edge of tropical SE Asia, it differs from typical lowland rain forests in equatorial areas in having some deciduous trees in the canopy layer, fewer megaphanerophytes and epiphytes but more abundant lianas and more plants with microphyll. It is a type of semi-evergreen rain forest at the northern edge of the tropical zone. The tropical montane rain forest occurs at wet montane habitats and is similar to the lower montane rain forest in equatorial Asia in floristic composition and physiognomy. It is a type of lower montane rain forests within the broader category of tropical rain forests. The tropical seasonal moist forest occurs on middle and upper limestone slopes. It is similar to the tropical montane evergreen broad-leaved forest in the region in physiognomy, but differs from the latter in floristic composition. It is a vegetation type on limestone at high elevations. The monsoon forest in Xishuangbanna is a tropical deciduous forest under the influence of a strong monsoon climate and is considered to be a transitional vegetation type between a tropical rain forest and savanna in physiognomy and distribution. The tropical montane evergreen broad-leaved forest is the main montane vegetation type in the region. It is dominated largely by the families Fagaceae, Euphorbiaceae, Theaceae and Lauraceae. It differs from tropical lower montane rain forests in its lack of epiphytes and in having more abundant lianas and plants with compound leaves. It is considered to be a distinct vegetation type from the northern margin of mainland southeastern Asia, controlled by a strong seasonal climate, based on its floristic and physiognomic characteristics.展开更多
Soil respiration is a key component of the global carbon cycle, and even small changes in soil respiration rates could result in significant changes in atmospheric CO_2 levels. The conversion of tropical forests to ru...Soil respiration is a key component of the global carbon cycle, and even small changes in soil respiration rates could result in significant changes in atmospheric CO_2 levels. The conversion of tropical forests to rubber plantations in SE Asia is increasingly common, and there is a need to understand the impacts of this land-use change on soil respiration in order to revise CO_2 budget calculations. This study focused on the spatial variability of soil respiration along a slope in a natural tropical rainforest and a terraced rubber plantation in Xishuangbanna, Southwest(SW) China. In each land-use type, we inserted 105 collars for soil respiration measurements.Research was conducted over one year in Xishuangbanna during May, June, July and October 2015(wet season) and January and March 2016(dry season). The mean annual soil respiration rate was 30% higher in natural forest than in rubber plantation and mean fluxes in the wet and dry season were 15.1 and 9.5 Mg C ha^(-1) yr^(-1) in natural forest and 11.7 and 5.7 Mg C ha^(-1) yr^(-1) in rubber plantation. Using a linear mixedeffects model to assess the effect of changes in soil temperature and moisture on soil respiration, we found that soil temperature was the main driver of variation in soil respiration, explaining 48% of its seasonal variation in rubber plantation and 30% in natural forest. After including soil moisture, the model explained 70% of the variation in soil respiration in natural forest and 76% in rubber plantation. In the natural forest slope position had a significant effect on soil respiration, and soil temperature and soil moisture gradients only partly explained this correlation. In contrast, soil respiration in rubber plantation was not affected by slope position, which may be due to the terrace structure that resulted in more homogeneous environmental conditions along the slope. Further research is needed to determine whether or not these findings hold true at a landscape level.展开更多
Two years of eddy covariance measurements of above-and below-canopy carbon fluxes and static opaque chamber and gas chromatography technique measurements of soil respiration for three treatments(bare soil,soil+litterf...Two years of eddy covariance measurements of above-and below-canopy carbon fluxes and static opaque chamber and gas chromatography technique measurements of soil respiration for three treatments(bare soil,soil+litterfall,soil+litterfall+seedling)were carried out in a tropical seasonal rain forest.In addition,data of photosynthesis of dominant tree species and seedlings,leaf area index,litter production and decomposing speed,soil moisture,soil temperature and photosynthetic photon flux density within the forest were all measured concurrently.Data from January 2003 to December 2004 are used to present annual variability of carbon flux and relationships between carbon flux and impact factors.The results show that carbon flux of this forest presented unusual tendency of annual variation;above-canopy carbon fluxes were negative in the dry season(November-April)and mainly positive in the rainy season,but overall the forest is a carbon sink.Carbon flux has obviously diurnal variation in this tropical seasonal rain forest.Above-canopy carbon fluxes were negative in the daytime and absolute values were larger in the dry season than that in the rainy season,causing the forest to act as a carbon sink;at night,carbon fluxes were mainly positive,causing the forest to act as a carbon source.Dominant tree species have greater photosynthesis capability than that of seedlings,which have a great effect on above-canopy carbon flux.There was a significant correlation between above-canopy carbon flux and rate of photosynthesis of tree species.There was also a significant correlation between above-canopy carbon flux and rate of photosynthesis of seedlings;however,the below-canopy carbon flux was only significantly correlated with rate of photosynthesis of seedlings during the hot-dry season.Soil respiration of the three treatments displayed a markedly seasonal dynamic;in addition,above-canopy carbon fluxes correlated well with soil respiration,litterfall production,litterfall decomposition rate,precipitation,and soil moisture and temperature.A primary statistical result of this study showed that above-canopy carbon flux in this forest presented carbon source or sink effects in different seasons,and it is a carbon sink at the scale of a year.展开更多
With the static opaque chamber and gas chromatography technique,from January 2003 to January 2004 soil respiration was investigated in a tropical seasonal rain forest in Xishuangbanna,SW China.In this study three trea...With the static opaque chamber and gas chromatography technique,from January 2003 to January 2004 soil respiration was investigated in a tropical seasonal rain forest in Xishuangbanna,SW China.In this study three treatments were applied,each with three replicates:A(bare soil),B(soil+litter),and C(soil+litter+seedling).The results showed that soil respiration varied seasonally,low from December 2003 to February 2004,and high from June to July 2004.The annual average values of CO_(2)efflux from soil respiration differed among the treatments at 1%level,with the rank of C(14642 mgCO_(2)·m-2·h-1)>B(12807 mgCO_(2)·m-2·h-1)>A(9532 mgCO_(2)·m-2·h-1).Diurnal variation in soil respiration was not apparent due to little diurnal temperate change in Xishuangbanna.There was a parabola relationship between soil respiration and soil moisture at 1%level.Soil respiration rates were higher when soil moisture ranged from 35%to 45%.There was an exponential relationship between soil respiration and soil temperature(at a depth of 5cm in mineral soil)at 1%level.The calculated Q10 values in this study,ranging from 2.03 to 2.36,were very near to those of tropical soil reported.The CO_(2)efflux in 2003 was 5.34 kgCO_(2)·m-2·a-1 from soil plus litter plus seedling,of them 3.48 kgCO_(2)·m-2·a-1 from soil(accounting for 62.5%),1.19 kgCO_(2)·m-2·a-1 from litter(22.3%)and 0.67 kgCO_(2)·m-2·a-1 from seedling(12.5%).展开更多
In order to discuss the values and daily variation characteristics of heat storage fluxes in a tropical seasonal rain forest in Xishuangbanna,the sensible and latent heat storage flux within air column,canopy heat sto...In order to discuss the values and daily variation characteristics of heat storage fluxes in a tropical seasonal rain forest in Xishuangbanna,the sensible and latent heat storage flux within air column,canopy heat storage flux,energy storage by photosynthesis and ground heat storage above the soil heat flux plate,as well as the ratios of these heat storage fluxes to the net radiation in the cool-dry,hot-dry and rainy season were compared and analyzed based on the observation data of carbon fluxes,meteorological factors and biomass within this tropical seasonal rain forest from January 2003 to December 2004.The findings showed that heat storage terms ranged significantly in the daytime and weakly in the nighttime,and the absolute values of sensible and latent heat storage fluxes were obviously greater than other heat storage terms in all seasons.In addition,the absolute values of total heat storage fluxes reached the peak in the hot-dry season,then were higher in the rainy season,and reached the minimum in the cool-dry season.The ratios of heat storage fluxes to net radiation generally decreased with time in the daytime,moreover,the sensible and latent heat storage dominated a considerable fraction of net radiation,while other heat storage contents occupied a smaller fraction of the net radiation and the peak value was not above 3.5%.In the daytime,the ratios of the total heat storage to net radiation were greater and differences in these ratios were distinct among seasons before 12:00,and then they became lower and differences were small among seasons after 12:00.The energy closure was improved when the storage terms were considered in the energy balance,which indicated that heat storage terms should not been neglected.The energy closure of tropical seasonal rain forest was not very well due to effects of many factors.The results would help us to further understand energy transfer and mass exchange between tropical forest and atmosphere.Moreover,they would supply a research basis for studying energy closure at other places.展开更多
This paper presents the pattern and changes of fragmented forest in relation with changes of total forest cover in the state of Selangor in three decades. In this study, inventoried forest cover maps of Selangor in 19...This paper presents the pattern and changes of fragmented forest in relation with changes of total forest cover in the state of Selangor in three decades. In this study, inventoried forest cover maps of Selangor in 1971/1972, 1981/1982 and 1991/1992 produced by the Forestry Department of Peninsular Malaysia were digitized to examine the changes in area and number of fragmented forest. Results showed that in 1971/1972, 16 fragmented forests were identified in Selangor. All fragmented forests were identified as dipterocarp forest. A decade later the number of fragmented forests increased by approximately 44% (23). Of the 23 fragmented forests, two were peat swamp forests whereas the remaining were dipterocarp forests. In 1991/1992 the number of fragmented forests (12) was reduced by 47.8%. Two of the fragmented forests were identified as peat swamp forest, seven dipterocarp forest and the other three was mixed of dipterocarp forests and plantation forests. Fragmentation of both dipterocarp and peat swamp forests occurred profoundly during the period between 1971/1972 and 1981/1982, which consequently increased the number of fragmented forests compared with before the period of 1971/1972 where fragmentation happened only at dipterocarp forests. However, many fragmented forests vanished between the 1981/1982 and 1991/1992 periods.展开更多
Background:No studies have documented long-term trends in aboveground biomass(AGB)for mixed-dipterocarp forests(MDF),the dominant rain forest type in tropical wet equatorial Asia.In our study,we sought to document suc...Background:No studies have documented long-term trends in aboveground biomass(AGB)for mixed-dipterocarp forests(MDF),the dominant rain forest type in tropical wet equatorial Asia.In our study,we sought to document such trends over forty years across three sites representing lowland to lower montane elevations.Methods:To do this,we established fifty 100 m×25 m plots in 1978 across three sites sampled along an elevation gradient,identified as mature old-growth forest.We measured trees for diameter at breast height that we identified to species and tagged.We took wood samples to calculate species wood-specific gravity.We re-measured plots in 1998 and again in 2018.Results:We show standing AGB for all sites combined to be 517.52 Mg·ha^(-1)in 1978,but this declined by 17%over 40 years to 430.11 Mg·ha^(-1).No differences exist among sites in AGB primarily because of considerable within site variation;but interactions of time with site show declines across sites were not uniform,one remained about the same.Relatively few species represented a high proportion of the AGB with the top five species comprising between 34%and 65%,depending upon site and year sampled.One species,Mesua nagassarium,represented a disproportionately large amount of AGB and decline over time,particularly at the low elevation site.Conclusions:Our results are directly relevant to estimating AGB and standing carbon sequestered in MDF.Our study is the first to demonstrate varying but overall,declining trends in amounts of AGB among forests making predictions of biomass and standing carbon in MDF difficult over wide regions.展开更多
文摘Based on the summed dominance ratios of species in sample plots, the first three dominant species (Litchi chinensis, Elaeocarpus sylvestris and Canarium album) of the secondary monsoon rain forest of Mt. Royal Shoe in Lianjiang City, western Guangdong, were chosen for analyzing their spatial distribution pattern with the analysis methods such as frequency models of Poisson Distribution, Two Negative Items Distribution, Neyman Distribution, aggregate indexes, Taylor exponential equation and Iwao’s equation modeling. The results showed that these three species distributed in the congregate spatial pattern. Litchi chinensis and Elaeocarpus sylvestris had the characteristic of basic congregate population and attractive characteristic between their plants. The patterns for Canarium album may change and become more evenly distributed with the increase of density. The overall species spatial pattern also depended on the conservation of the secondary monsoon rain forest besides it was affected by the species reproduction characteristics and its growing environment. The congregate spatial patterns of three dominant species showed that it is important to conserve forest urgent conservation of the forest.
文摘CH4 and N2O fluxes from soil under a tropical seasonal rain forest in Xishuangbanna, Southwest China were measured for one year using closed static chamber technique and gas chromatography method. Three treatments were set in the studied field： （A） litter-free, （B） with litter, and （C） with litter and seedling. The results showed that the soil in our study was a sink of atmospheric CH4 and source of atmospheric N2O. The observed mean CH4 fluxes from treatments A, B, and C were -50.0 ± 4.0, -35.9 ± 2.8, -31.6 ± 2.8 μgC/（m^2·h）, respectively, and calculated annual fluxes in 2003 were -4.1, -3.1, and -2.9 kgC/hm^2, respectively. The observed mean N2O fluxes from treatments A, B, and C were 30.9 ± 3.1, 28.2 ± 3.5, 50.2±3.7 μgN/（m^2·h）, respectively, and calculated annual fluxes in 2003 were 2.8, 2.6, and 3.7 kgN/hm^2, respectively. Seasonal variations in CH4 and N2O fluxes were significant among all the three treatments. The presence of litter decreased CH4 uptake during wet season （P 〈 0.05）, but not during dry season. There was a similar increase in seedlings-mediated N2O emissions during wet and dry seasons, indicating that seedlings increased N2O emission in both seasons. A strong positive relationship existed between CH4 fluxes and soil moisture for all the three treatments, and weak relationship between CH4 fluxes and soil temperature for treatment B and treatment C. The N2O fluxes correlated with soil temperature for all the three treatments.
基金supported by the Canadian International Development Agency (CIDA)
文摘A study was conducted to evaluate the status of soil nutrients under E. grandis plantation in comparison with that in its adjacent submontane rain forest. Twenty sequare plots, with an area of 20 m×20 m for each, were established in both of E.grandis plantation and its adjacent sub-montane rain forest, independently. Soil samples were collected from each square plot, at five points （at the four comers and at the center） of each plot. The collected soil samples were mixed to make a composite and representative sample for each plot, independently. The analyses were done in a soil laboratory following appropriate methods. The analysis result indicated that there were no significance differences between E. grandis plantation and its adjacent sub-montane rain forest in the level of major soil nutrients （total N, available P, exchangeable K, Ca and Mg）, pH and total carbon of soils （p 〈 0.05）. There were significance differences between two sites of forest soils in percentage of clay particles, and exchangeable Na content. E. grandis plantation was found improving soil nutrients and total carbon as compared with that of its adjacent submontane rain forest.
文摘The effects of canopy development, solar angle, and weather conditions on temporal variation in photosynthetic photon flux density（PPFD） at three heights within a tropical rain forest canopy in Xishuangbanna, China, were examined. PPFD was measured every second and stored as 10-min averages from 1 December 2002 to 30 November 2003. PPFD variability was examined at three different temporal scales. Specific days in March, September, and December with clear and overcast sky conditions were selected to separate the effects of leaf area index（LAI） and solar angle on diurnal variability. On both clear and overcast days, mean daily average PPFD was significantly different between March and September at all heights, except 10 m on clear days, suggesting that LAI directly influences PPFD. In contrast, the differences in daily average PPFD among three heights between September and December were likely due to variation in solar angle. In addition, daily average PPFD at all locations were significantly lower under overcast than clear sky conditions in March, September and December. Over the year-long study, the mean daily total PPFD at 2! m, 10 m and 4 m was 2.8, 2.7 and 0.7 mol/（m^2·d）, which accounted for 9.7%, 9.4% and 2.4% of the daily PPFD above the canopy, respectively. Significant differences in mean daily total PPFD occurred at the same heights among different seasons, and diurnal, day-to-day and seasonal PPFD varied at different heights within the canopy. The possible effects of light variability on physiological and morphological responses of plants are discussed.
基金Under the auspices of the National Natural Science Foundation of China (No. 40271048) and Yunnan Natural Science Foundation (No. 2002C0067M)
文摘A pristine montane rain forest was recently discovered from Mengsong of Xishuangbanna in the southern Yunnan. It attracts botanists that many primitive plant taxa across various life forms were co-existed in the montane rain forest. In order to know the biogeography of the montane rain forest, distribution patterns of some species of biogeographical importance from the montane forest were enumerated and their biogeographical implications were discussed with geological explanation. It was concluded that the montane rain forest in the southern Yunnan has strong affinity to montane rain forests in Sumatra or Southeast Asia in broad sense. It was tentatively suggested that Sumatra could be once connected to Myanmar and drifted away due to northward movement of continental Asia by bumping of India plate.
基金the Programa de Apoyo a Proyectos de Investigación e Innovación Tecnológica(PAPIIT)of the Universidad Nacional Autónoma de México(UNAM Grant IN-235402)the Secretaría de Medio Ambiente y Recursos Naturales-Consejo Nacional de Ciencia y Tecnología(Grant 2002-c01-668),and the Packard Foundation.
文摘The effect of arbuscular mycorrhizal fungi on seedling growth across the rain forest-pasture edge has not received much attention. In a tropical rain forest in eastern Mexico, the seedlings of light demanding (Ficus insipida), nonsecondary light demanding (Lonchocarpus cruentus) and shade tolerant species (Nectandra ambigens, Coccoloba hondurensis) were grown and transplanted to a forest edge with three inoculation treatments (AM fungus spores and colonized roots, spores, and no inoculum). For all species, stem height, stem diameter, total dry weight, leaf area and net assimilation rate were higher in the pasture. Stem height, stem diameter and root/shoot were higher for L. cruentus, and leaf area ratio, specific leaf area and net assimilation rate were higher for F. insipida;the lowest values of almost all variables were recorded for N. ambigens. L. cruentus and C. hondurensis with mycorrhizae had the highest values for root/shoot and net assimilation rate, respectively. The lowest values of root/shoot and net assimilation rate were observed for nonlight-demanding species in the forest. There were clear trade-offs for the pioneer species between survival and growth, and in underground biomass allocation and assimilation for nonsecondary light demanding, but there was not for the shade-tolerant species.
文摘In order to finish the cataloging work of buttercup species in the family of Renunculaceae for the compilation of the Flora Yunnanensis, I went to the CAS Institute of Botany in Kunming City,capital of Yunnan Province in May 1995 to look up phyto-taxonomic specimens. At the invitation of the Institute’s director Prof. Xu Zhaifu, when the work was coming to an end, I toured the well-known botanic garden of the Institute in the township of Menglu, which nests in the picturesque district of Xishuang Banna at the southernmost tip of the subtropical territory of Yunnan. In the winter of 1958,I had visited the ever-verdant vicinity to collect floral materials. After almost 37 years, I revisited the botanic garden founded by celebrated
基金supported by the National Natural Science Foundation of China (Grant No. 40601009),the A3 Foresight Programthe Special Research Program of Research Institute for Tropical Forestry,Chinese Academy of Forestry (Grant No. 2007-1, RITFYWZX200902)+2 种基金 the Special Research Program for Public-welfare Forestry (Grant No. 200804001) the Eleventh-Five-Year Scientific Support Program of the State Forestry Administration of China (Grant Nos. 2006BAD03A07 and 2006BAD03A04)the "948" Program of State Forestry Administration of China (Grant No. 2007-4-18)
文摘Biometric inventories for 25 years,from 1983 to 2005,indicated that the Jianfengling tropical mountain rain forest in Hainan,China,was either a source or a modest sink of carbon.Overall,this forest was a small carbon sink with an accumulation rate of(0.56±0.22) Mg C ha-1yr-1,integrated from the long-term measurement data of two plots(P9201 and P8302).These findings were similar to those for African and American rain forests((0.62±0.23) Mg C ha-1yr-1).The carbon density varied between(201.43±29.38) Mg C ha-1 and(229.16±39.2) Mg C ha-1,and averaged(214.17±32.42) Mg C ha-1 for plot P9201.Plot P8302,however,varied between(223.95±45.92) Mg C ha-1 and(254.85±48.86) Mg C ha-1,and averaged(243.35±47.64) Mg C ha-1.Quadratic relationships were found between the strength of carbon sequestration and heavy rainstorms and dry months.Precipitation and evapotranspiration are two major factors controlling carbon sequestration in the tropical mountain rain forest.
基金National Natural Science Foundation of China(31321061,31330012)National Basic Research Program of China on Global Change(2014CB954001).
文摘Aims Soil respiration is one of the most important components in the car-bon(c)cycle in terrestrial ecosystems.to investigate the contribution of each component of c cycle to the total soil c efflux,we quantified the rates of litter,root,and other mineral soil respiration from 2012 to 2014 in the primary and secondary tropical mountain rain forests in Hainan Island,china.Methods the seasonal dynamics of soil(Rs),non-litter(RNL)and non-root(RNR)respiration rates were measured using an automatic chamber system(Li-8100).Litter removal and root removal treatments were used to assess the contribution of litter and roots to belowground c production.We estimated the annual c efflux of each compo-nent of soil respiration in primary and secondary forests using a temperature-based exponential model and analyzed the impact of each component in each forest type.Important Findingsthe annual total soil c efflux was significantly higher in the primary rain forest(1567±205 g c m^(−2)yr^(−1))than that in the secondary forest(1300±70 g c m^(−2)yr^(−1),P<0.05).the litter,root,and mineral soils contributed 22%(349±185 g c m^(−2)yr^(−1)),38%(589±100 g c m^(−2)yr^(−1)),and 40%(628±128 g c m^(−2)yr^(−1))to the total soil c efflux in primary rain forest,respectively.In secondary forest,these three components contributed 11%(148±35 g c m^(−2)yr^(−1)),45%(572±259 g c m^(−2)yr^(−1)),and 44%(580±226 g c m^(−2)yr^(−1)),respectively.the temperature sensitivity(Q10)of Rs(2.70±0.14)in the primary forest was significantly higher than that in the secondary forest(2.34±0.12),with the Q10 values for respiration decreasing in the order of RNR>Rs>RNL.these results show that the difference in litter respiration between primary and secondary forest caused the major difference in annual soil respiration efflux between these two forest types.In addition,the litter respiration is more sensitive to the soil temperature than the other soil respiration components.
文摘Based on investigation of 53 gaps and 25 quadrats (15m×15m each) of non-gap closed stand in an old-growth tropical montane rain forest of Hainan Island, China, canopy disturbance regimes and gap regeneration were studied. Gaps were elliptical in horizontal form, the ratio of long axis /short axis was about 1.4. Percentage of expanded gaps (EG) and canopy gaps (CG) area in the landscape were 53.5% and 25.2% respectively. EG ranged from 31.4 m2 to 488.2m2 and CG/rom 14.9m2 to 354.2m2, their average sizes ...
文摘Amongst the impacts of converting forest to agricultural activities are soil erosion and degradation of ecology service values and goods （ESVG）. The soil erosion can be seen as on-site impacts, such as the problems of decreasing soil fertility and also its off-site impact such as the problems of sedimentation of the nearby rivers, whilst the degradation of ESVG are more holistie in nature, These impacts can be devastating in environmental, biological, and socio-economic manners. This paper reports the study undertaken on the impacts of agricultural development in 0.8 million ha of forest dominated landscape in Pasoh Forest Region （PFR）, Malaysia, within period of 8 years from 1995 to 2003. Three folds of impacts on agricultural development examined and analysed, are： （i） relationship of total soil loss and changes in land use pattern, （ii） mapping trends of ESVG for PFR in 1995 and 2003, and （iii） risk assessment of ESVG based on simulation of converting 339,630 ha of primary forest into mass-scale oil palm plantation. Results of this study indicated that although only minor changes of about 1464 ha （about 0.2% of PFR） of primary forest was converted to agricultural activities, it have significantly increased the total soil loss from 59 to 69 million ton/ha/yr. The mean rate of soil is loss for PFR is 0.8 mil ton/ha/yr and if translated into ESVG term, the soil loss costs about US$ 4.8mil/yr. However, majority of the soil loss within all land use classes are within range of very low-low risk categories （〈10 ton/ha/yr）. ESVG for PFR were costing US$ 179 millions in 1995, declined to US$114 millions in 2003 due to 0.2% reduction of forested land. The ESVG of converting 339,630 ha primary forest into mass plantation cost less than original forest within period of 20 years examined; the 20th year of conversion, the ESVG of plantation and to-remain as forest cost US$ 963 and US$ 575 millions, respectively. However, this difference is only marginal when full attributes of ESVG are considered.
文摘The study of effects of acid rain in Southwestern China on forest ecosystems .has been inrestigated since 1984. The results have shown that the ecosystem of Pinus massoniana forest has been damaged severely by acid rain. Comparing the areas where the annual mean pH value is lower than 4.5 with that higher than 4.5, the productivity of the ecosystems decreased 50 percent. Both the percentages of the green leaves and the content of chlorophyll cut down; the acidity of soil increased a bit and the fertility showed the tendency to lower. The microbial population components in surface soil were changed and the total number of soil microbes reduced from 63.5 to 92.6 percent. Besides the direct effects of acid rain, the insect pest, especially, Blastophagus piniperdoz and Monochamus galloprovincialis, seized the opportunity to enter and reproduce in it so as to aggravate the forest dieback of P.massoniana in the areas where the annual average pH value is lower than 4.5.Additionally, the simulation study on the symptoms of main tree species in Southwestern China damaged by acid rain has obtained the results in the resistibility of 30 tree species, which provided a foundation for selecting suitable tree species to cultivate in the polluted areas.
基金supported by the National Natural Science Foundation of China (Grants No. 40901015 and41001011)the Major Program of the National Natural Science Foundation of China (Grants No. 51190090 and 51190091)+3 种基金the Fundamental Research Funds for the Central Universities (Grants No. B1020062 andB1020072)the Ph. D. Programs Foundation of the Ministry of Education of China (Grant No.20090094120008)the Special Fund of State Key Laboratories of China (Grants No. 2009586412 and 2009585412)the Programme of Introducing Talents of Disciplines to Universities of the Ministry of Education and State Administration of the Foreign Experts Affairs of China (the 111 Project, Grant No.B08048)
文摘A conceptual hydrological model that links the Xin＇anjiang hydrological model and a physically based snow energy and mass balance model, described as the XINSNOBAL model, was developed in this study for simulating rain-on-snow events that commonly occur in the Pacific Northwest of the United States. The resultant model was applied to the Lookout Creek Watershed in the H. J. Andrews Experimental Forest in the western Cascade Mountains of Oregon, and its ability to simulate streamflow was evaluated. The simulation was conducted at 24-hour and one-hour time scales for the period of 1996 to 2005. The results indicated that runoffand peak discharge could be underestimated if snowpack accumulation and snowmelt under rain-on-snow conditions were not taken into account. The average deterministic coefficient of the hourly model in streamflow simulation in the calibration stage was 0.837, which was significantly improved over the value of 0.762 when the Xin＇anjiang model was used alone. Good simulation performance of the XINSNOBAL model in the WS 10 catchment, using the calibrated parameter of the Lookout Creek Watershed for proxy-basin testing, demonstrates that transplanting model parameters between similar watersheds can orovide a useful tool for discharge forecastin~, in un^au^ed basins.
文摘Xishuangbanna of southern Yunnan is biogeographically located at a transitional zone from tropical southeast （SE） Asia to subtropical east Asia and is at the junction of the Indian and Burmese plates of Gondwana and the Eurasian plate of Laurasia. The region, though surprisingly far from the equator and at a relatively high altitude, has a rich tropical flora and a typical tropical rain forest in the lowland areas. Based on physiognomic and ecological characteristics, floristic composition and habitats combined, the primary vegetation in Xishuangbanna can be organized into four main vegetation types： tropical rain forest, tropical seasonal moist forest, tropical montane evergreen broad-leaved forest and tropical monsoon forest. The tropical rain forest can be classified into two subtypes, i.e. a tropical seasonal rain forest in the lowlands and a tropical montane rain forest at higher elevations. The tropical seasonal rain forest has almost the same forest profile and physiognomic characteristics as equatorial lowland rain forests and is a type of truly tropical rain forest. Because of conspicuous similarity on ecological and floristic characteristics, the tropical rain forest in Xishuangbanna is a type of tropical Asian rain forest. However, since the tropical rain forest of Xishuangbanna occurs at the northern edge of tropical SE Asia, it differs from typical lowland rain forests in equatorial areas in having some deciduous trees in the canopy layer, fewer megaphanerophytes and epiphytes but more abundant lianas and more plants with microphyll. It is a type of semi-evergreen rain forest at the northern edge of the tropical zone. The tropical montane rain forest occurs at wet montane habitats and is similar to the lower montane rain forest in equatorial Asia in floristic composition and physiognomy. It is a type of lower montane rain forests within the broader category of tropical rain forests. The tropical seasonal moist forest occurs on middle and upper limestone slopes. It is similar to the tropical montane evergreen broad-leaved forest in the region in physiognomy, but differs from the latter in floristic composition. It is a vegetation type on limestone at high elevations. The monsoon forest in Xishuangbanna is a tropical deciduous forest under the influence of a strong monsoon climate and is considered to be a transitional vegetation type between a tropical rain forest and savanna in physiognomy and distribution. The tropical montane evergreen broad-leaved forest is the main montane vegetation type in the region. It is dominated largely by the families Fagaceae, Euphorbiaceae, Theaceae and Lauraceae. It differs from tropical lower montane rain forests in its lack of epiphytes and in having more abundant lianas and plants with compound leaves. It is considered to be a distinct vegetation type from the northern margin of mainland southeastern Asia, controlled by a strong seasonal climate, based on its floristic and physiognomic characteristics.
基金the BMZ/GIZ “Green Rubber” (Project No. Project No. 13.1432.7-001.00)the CGIAR (Consultative Group for International Agricultural Research) Research Program 6: Forests, Trees and Agroforestry+2 种基金financially supported by the Federal Ministry for Economic Cooperation and Development, Germanyfunded by the National Natural Science Foundation of China (Grant No. 31450110067) the Chinese Academy of Science funded the Chinese Academy of Science funded the post-doc fellowship for Stefanie Goldberg (Grant No. 2013Y2SB0007)
文摘Soil respiration is a key component of the global carbon cycle, and even small changes in soil respiration rates could result in significant changes in atmospheric CO_2 levels. The conversion of tropical forests to rubber plantations in SE Asia is increasingly common, and there is a need to understand the impacts of this land-use change on soil respiration in order to revise CO_2 budget calculations. This study focused on the spatial variability of soil respiration along a slope in a natural tropical rainforest and a terraced rubber plantation in Xishuangbanna, Southwest(SW) China. In each land-use type, we inserted 105 collars for soil respiration measurements.Research was conducted over one year in Xishuangbanna during May, June, July and October 2015(wet season) and January and March 2016(dry season). The mean annual soil respiration rate was 30% higher in natural forest than in rubber plantation and mean fluxes in the wet and dry season were 15.1 and 9.5 Mg C ha^(-1) yr^(-1) in natural forest and 11.7 and 5.7 Mg C ha^(-1) yr^(-1) in rubber plantation. Using a linear mixedeffects model to assess the effect of changes in soil temperature and moisture on soil respiration, we found that soil temperature was the main driver of variation in soil respiration, explaining 48% of its seasonal variation in rubber plantation and 30% in natural forest. After including soil moisture, the model explained 70% of the variation in soil respiration in natural forest and 76% in rubber plantation. In the natural forest slope position had a significant effect on soil respiration, and soil temperature and soil moisture gradients only partly explained this correlation. In contrast, soil respiration in rubber plantation was not affected by slope position, which may be due to the terrace structure that resulted in more homogeneous environmental conditions along the slope. Further research is needed to determine whether or not these findings hold true at a landscape level.
基金We give thanks to Xishuangbanna Tropical Rainforest Ecosystem Station,Chinese Academy of Sciences for help on this project.We offer special thanks to Mr.Liu Mengnan,Zhou Zhihua,Cao Bizhong,Chen Defu,Lu Yun,Li Qinghua and Li Zhongfei for assistance with the fieldwork.This work was supported by the Knowledge Innovation Program of Chinese Academy of Sciences(Grant No.KZCX1-SW-01-01)the Development Program in Basic Science of China(Grant No.2002CB412501).
文摘Two years of eddy covariance measurements of above-and below-canopy carbon fluxes and static opaque chamber and gas chromatography technique measurements of soil respiration for three treatments(bare soil,soil+litterfall,soil+litterfall+seedling)were carried out in a tropical seasonal rain forest.In addition,data of photosynthesis of dominant tree species and seedlings,leaf area index,litter production and decomposing speed,soil moisture,soil temperature and photosynthetic photon flux density within the forest were all measured concurrently.Data from January 2003 to December 2004 are used to present annual variability of carbon flux and relationships between carbon flux and impact factors.The results show that carbon flux of this forest presented unusual tendency of annual variation;above-canopy carbon fluxes were negative in the dry season(November-April)and mainly positive in the rainy season,but overall the forest is a carbon sink.Carbon flux has obviously diurnal variation in this tropical seasonal rain forest.Above-canopy carbon fluxes were negative in the daytime and absolute values were larger in the dry season than that in the rainy season,causing the forest to act as a carbon sink;at night,carbon fluxes were mainly positive,causing the forest to act as a carbon source.Dominant tree species have greater photosynthesis capability than that of seedlings,which have a great effect on above-canopy carbon flux.There was a significant correlation between above-canopy carbon flux and rate of photosynthesis of tree species.There was also a significant correlation between above-canopy carbon flux and rate of photosynthesis of seedlings;however,the below-canopy carbon flux was only significantly correlated with rate of photosynthesis of seedlings during the hot-dry season.Soil respiration of the three treatments displayed a markedly seasonal dynamic;in addition,above-canopy carbon fluxes correlated well with soil respiration,litterfall production,litterfall decomposition rate,precipitation,and soil moisture and temperature.A primary statistical result of this study showed that above-canopy carbon flux in this forest presented carbon source or sink effects in different seasons,and it is a carbon sink at the scale of a year.
基金This work was supported by the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant No.KZCX1-SW-01)the Basic Science Development Program of China(Grant No.2002CB412501)the National Natural Science Foundation of China(Grant No.40173039).
文摘With the static opaque chamber and gas chromatography technique,from January 2003 to January 2004 soil respiration was investigated in a tropical seasonal rain forest in Xishuangbanna,SW China.In this study three treatments were applied,each with three replicates:A(bare soil),B(soil+litter),and C(soil+litter+seedling).The results showed that soil respiration varied seasonally,low from December 2003 to February 2004,and high from June to July 2004.The annual average values of CO_(2)efflux from soil respiration differed among the treatments at 1%level,with the rank of C(14642 mgCO_(2)·m-2·h-1)>B(12807 mgCO_(2)·m-2·h-1)>A(9532 mgCO_(2)·m-2·h-1).Diurnal variation in soil respiration was not apparent due to little diurnal temperate change in Xishuangbanna.There was a parabola relationship between soil respiration and soil moisture at 1%level.Soil respiration rates were higher when soil moisture ranged from 35%to 45%.There was an exponential relationship between soil respiration and soil temperature(at a depth of 5cm in mineral soil)at 1%level.The calculated Q10 values in this study,ranging from 2.03 to 2.36,were very near to those of tropical soil reported.The CO_(2)efflux in 2003 was 5.34 kgCO_(2)·m-2·a-1 from soil plus litter plus seedling,of them 3.48 kgCO_(2)·m-2·a-1 from soil(accounting for 62.5%),1.19 kgCO_(2)·m-2·a-1 from litter(22.3%)and 0.67 kgCO_(2)·m-2·a-1 from seedling(12.5%).
基金This research was supported by the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant No.KZCX1-SW-01-01)the National Basic Research Program of China(Grant No.2002CB412501)+1 种基金the Natural Science Foundation of Yunnan Province,China(Grant No.98C098M)We give thanks to Xishuang-banna Tropical Rainforest Ecosystem Station,the Chinese Academy of Sciences for help in this project.We offer spe-cial thanks to Associate Professor Sha Liqing for assistance with the paper.
文摘In order to discuss the values and daily variation characteristics of heat storage fluxes in a tropical seasonal rain forest in Xishuangbanna,the sensible and latent heat storage flux within air column,canopy heat storage flux,energy storage by photosynthesis and ground heat storage above the soil heat flux plate,as well as the ratios of these heat storage fluxes to the net radiation in the cool-dry,hot-dry and rainy season were compared and analyzed based on the observation data of carbon fluxes,meteorological factors and biomass within this tropical seasonal rain forest from January 2003 to December 2004.The findings showed that heat storage terms ranged significantly in the daytime and weakly in the nighttime,and the absolute values of sensible and latent heat storage fluxes were obviously greater than other heat storage terms in all seasons.In addition,the absolute values of total heat storage fluxes reached the peak in the hot-dry season,then were higher in the rainy season,and reached the minimum in the cool-dry season.The ratios of heat storage fluxes to net radiation generally decreased with time in the daytime,moreover,the sensible and latent heat storage dominated a considerable fraction of net radiation,while other heat storage contents occupied a smaller fraction of the net radiation and the peak value was not above 3.5%.In the daytime,the ratios of the total heat storage to net radiation were greater and differences in these ratios were distinct among seasons before 12:00,and then they became lower and differences were small among seasons after 12:00.The energy closure was improved when the storage terms were considered in the energy balance,which indicated that heat storage terms should not been neglected.The energy closure of tropical seasonal rain forest was not very well due to effects of many factors.The results would help us to further understand energy transfer and mass exchange between tropical forest and atmosphere.Moreover,they would supply a research basis for studying energy closure at other places.
文摘This paper presents the pattern and changes of fragmented forest in relation with changes of total forest cover in the state of Selangor in three decades. In this study, inventoried forest cover maps of Selangor in 1971/1972, 1981/1982 and 1991/1992 produced by the Forestry Department of Peninsular Malaysia were digitized to examine the changes in area and number of fragmented forest. Results showed that in 1971/1972, 16 fragmented forests were identified in Selangor. All fragmented forests were identified as dipterocarp forest. A decade later the number of fragmented forests increased by approximately 44% (23). Of the 23 fragmented forests, two were peat swamp forests whereas the remaining were dipterocarp forests. In 1991/1992 the number of fragmented forests (12) was reduced by 47.8%. Two of the fragmented forests were identified as peat swamp forest, seven dipterocarp forest and the other three was mixed of dipterocarp forests and plantation forests. Fragmentation of both dipterocarp and peat swamp forests occurred profoundly during the period between 1971/1972 and 1981/1982, which consequently increased the number of fragmented forests compared with before the period of 1971/1972 where fragmentation happened only at dipterocarp forests. However, many fragmented forests vanished between the 1981/1982 and 1991/1992 periods.
基金the National Science Foundation of Sri Lanka(RG/2016/EB/02)Uva Wellassa University(UWU/RG/2016/10)。
文摘Background:No studies have documented long-term trends in aboveground biomass(AGB)for mixed-dipterocarp forests(MDF),the dominant rain forest type in tropical wet equatorial Asia.In our study,we sought to document such trends over forty years across three sites representing lowland to lower montane elevations.Methods:To do this,we established fifty 100 m×25 m plots in 1978 across three sites sampled along an elevation gradient,identified as mature old-growth forest.We measured trees for diameter at breast height that we identified to species and tagged.We took wood samples to calculate species wood-specific gravity.We re-measured plots in 1998 and again in 2018.Results:We show standing AGB for all sites combined to be 517.52 Mg·ha^(-1)in 1978,but this declined by 17%over 40 years to 430.11 Mg·ha^(-1).No differences exist among sites in AGB primarily because of considerable within site variation;but interactions of time with site show declines across sites were not uniform,one remained about the same.Relatively few species represented a high proportion of the AGB with the top five species comprising between 34%and 65%,depending upon site and year sampled.One species,Mesua nagassarium,represented a disproportionately large amount of AGB and decline over time,particularly at the low elevation site.Conclusions:Our results are directly relevant to estimating AGB and standing carbon sequestered in MDF.Our study is the first to demonstrate varying but overall,declining trends in amounts of AGB among forests making predictions of biomass and standing carbon in MDF difficult over wide regions.
