Seasonal Rain Forest In Xishuangbanna Research Articles

Seedling dynamics differ between canopy species and understory species in a tropical seasonal rainforest, SW China

We used 11 years of census data from 450 seedling quadrats established in a 20-ha forest dynamics plot to study seedling dynamics in tree species of a tropical seasonal rainforest in Xishuangbanna, southwestern China. We found that overall seedling recruitment rate and relative growth rate were higher in the rainy season than in the dry season. Both the recruitment rate of seedlings from canopy tree species (two species) and the relative growth rate of seedlings from understory species (nine species) were higher in the rainy season than in the dry season. However, in the rainy season, the recruitment rate of seedlings was higher for canopy tree species than for understory tree species. In addition, relative growth rate of seedlings was higher in the canopy species than in understory seedlings in the dry season. We also observed that, in both rainy and dry seasons, mortality rate of seedlings was higher for canopy species than for understory species. Overall, canopy tree species appear to have evolved a flexible strategy to adapt to the seasonal changes of a monsoon climate. In contrast, understory tree species seem to have adopted a conservative strategy. Specifically, these species mainly release seedlings in the rainy season and maintain relatively stable populations with a lower mortality rate and recruitment rate in both dry and rainy seasons. Our study suggests that canopy and understory seedling populations growing in forest understory may respond to future climate change scenarios with distinct regeneration strategies.

A dataset of the litterfall recovery amount and the standing crop dynamics in the tropical seasonal rainforests of Xishuangbanna (2005–2020)

Litterfall refers to the collective organic matter generated by the aboveground parts of plants that accumulates on the surface. It is a key medium linking the ecological processes between the aboveground and the underground in terrestrial ecosystems. Litterfall recovery and the standing crop comprise the dry weight of branches, leaves, flowers and fruits, bark, moss and lichen, and so on. The annual yield of leaf litterfall can provide data support for the assessment of forest productivity, and the falling flowers and fruits are of great value to the research of forest seed rain. The proportion of each component is an important factor affecting nutrient cycling and carbon cycling in the ecosystem. The dataset collects the litterfall recovery amount and the standing crop of the tropical seasonal rainforest in Xishuangbanna during 2005–2020. The establishment and sharing of this dataset can furnish fundamental data for the in-depth examination of vegetation structure and ecosystem function under the global hydrothermal pattern changes, and serve as a foundation for advancing the study of the litterfall and tropical seasonal rain forests.

Energy Balance Closure Problem over a Tropical Seasonal Rainforest in Xishuangbanna, Southwest China: Role of Latent Heat Flux

The unresolved energy-unclosed problem in micrometeorology refers to the fact that the sum of turbulent fluxes (sensible and latent heat fluxes, Hs and LE) monitored by eddy covariance (EC) methods tends to be lower than the available energy (net radiation (Rn), soil heat flux (G), and heat storage (S)). The lack of energy balance closure (EBC) increases evapotranspiration-measurement uncertainty. Using EC data from Xishuangbanna, a Southeast Asian tropical seasonal rainforest, we analyzed the energy distribution and closure based on micrometeorological features. We found that: (1) the EBC in the rainy season exceeds that in other seasons and that the seasonal moisture content, frictional wind velocity (u*), and LE contribute to the high seasonal variability in EBC; (2) the annual closure is approximately 65%, and energy non-closure is influenced by turbulence intensity and atmospheric stability. When the atmospheric state is unstable to near neutral, u* is greatest, and EBC can reach nearly 80%. (3) energy is mainly allocated to LE, and energy non-closure leads to LE underestimation, especially in the foggy-cool and hot-dry seasons. (4) Heat storage and large time-scale flux effects on EBC were excluded. The causes of energy non-closure in the tropical calm zone need further investigation.

Intra-annual radial growth of Garuga floribunda in tropical seasonal rain forest and its response to environmental factors in Xishuangbanna, Southwest China

We examined the seasonal growth dynamics of a deciduous tree species Garuga floribunda in the tropical seasonal rain forest in Xishuangbanna and monitored the stem radial growth with both high resolution dendrometer and microcoring methods. Combining with the monitoring of non-structural carbohydrates (NSCs) in stem and environmental factors, we analyzed the eco-physiological drivers underlying the seasonal cambial activity and radial growth dynamics. The results of high reso-lution dendrometer method showed that the growth of G. floribunda began at the end of May (day of year, DOY: 149.3±7.2) and ended at the end of August (DOY: 241.0±14.7) in 2020, the annual total radial growth was 3.12 mm, and the maximum growth rate was 0.04 mm·d-1. Based on the microcoring methods, we found that xylem cell enlarging started from March 9th (69.2±6.2) and cell wall thickening ended on September 19th (DOY: 262.8±2.8). The cumulative xylem radial growth was 1.76 mm, and the maximum growth rate was 0.009 mm·d-1. The daily radial growth rate of G. floribunda was significantly and positively correlated with precipitation, relative humidity, daily minimum air temperature, soil moisture and temperature at the depth of 20 cm, and was negatively correlated with daily maximum air temperature, vapor pressure deficit, maximum wind speed, and water vapor pressure. The starch and soluble sugar contents in the sapwood of G. floribunda were relatively higher before the growing season. The starch content was lowest in the end of March, while the content of soluble sugars was lowest in middle of May. At the end of the growing season, the contents of starch and soluble sugar in G. floribunda peaked in the middle of October and the end of December, respectively.

Long-term variation characteristics of radiation in the tropical seasonal rainforest in Xishuangbanna, southwestern China

Long-term variation characteristics of radiation in the tropical seasonal rainforest in Xishuangbanna, southwestern China

Seed dormancy profiles for forest dynamics plot data: focusing on a tropical seasonal rainforest in Xishuangbanna, southwest China.

Long-term forest dynamics monitoring plots provide information on number of individual species in the plot, allowing us for the first time to construct seed dormancy profiles at the species and individual levels for a specific site. Focusing on the Xishuangbanna tropical season rainforest plot (XTRDP), we used data from nine forest dynamics plots (two for tropical, four for subtropical and three for temperate) and information on kind of seed dormancy to generate seed dormancy profiles for communities across tropical to temperate latitudes at the species and individual levels. Seed dormancy information was collected from previous publications, and some data were provided by two germplasm banks that test seed germination of wild plants in China. In XTRDP, 35% of the species and 58% of individuals have non-dormant seeds; the dominant species have non-dormant seeds. In all plots, the most common kind of dormancy among species and individuals with dormant seeds was physiological dormancy. At the species level, the profile for tropical, subtropical and temperate plots was similar to profiles for each of these vegetation regions. In all plots, except one subtropical plot, the percentage of species versus individuals with dormant seeds differed. All temperate plots had a higher percentage of individuals than species with dormant seeds, but this pattern was not consistent for tropical or subtropical plots. We show that dormancy increases with latitude at both the species and individual levels. Dormancy profiles at the individual tree level provide new insight into seed dormancy relationships within plant communities.

Size dependent associations between tree diameter growth rates and functional traits in an Asian tropical seasonal rainforest.

Many studies focus on the relationships between plant functional traits and tree growth performances. However, little is known about the ontogenetic shifts of the relationships between functional traits and tree growth. This study examined associations between stem and leaf functional traits and growth rates and their ontogenetic shifts across 20 tropical tree species in a tropical seasonal rainforest in Xishuangbanna, south-west China. For each species, physiological active branches of individual trees belonged to three size classes (i.e. small, diameter at breast height (DBH) 5-10 cm; middle, DBH 10-20 cm; big, DBH >20 cm) were sampled respectively. We measured 18 morphological and structural traits, which characterised plant hydraulic properties or leaf economic spectrum. Associations between diameter growth rates and functional traits were analysed across three size classes. Our results revealed that diameter growth rates of big-sized trees were mainly related to traits related to plant hydraulic efficiency (i.e. theoretical hydraulic conductivity (Ktheo) and leaf vein density (Dvein)), which suggests that the growth of large trees is limited mainly by their xylem water transport capacity. For middle-sized trees, growth rates were significantly related to traits representing leaf economic spectrum (i.e. specific leaf area (SLA), individual leaf mass (ILM), palisade thickness (PT) and spongy thickness (SP)). Diameter growth rates of small-sized trees were not correlated with hydraulic or leaf economic traits. Thus, the associations between tree growth rates and functional traits are size dependent. Our results suggest ontogenetic shift of functional traits which could potential contribute to different growth response to climate change.

Precipitation influences on the net primary productivity of a tropical seasonal rainforest in Southwest China: A 9-year case study

The net primary productivity (NPP) of tropical forests is a key part of the global carbon cycle. Numerous studies have estimated tropical forest NPP, yet most of them focus on how annual NPP dynamics vary over several years. Little is known about how NPP responds to long-term climatic variation at the monthly or seasonal scales. We estimated NPP at three-month intervals from 2009 to 2017 for a tropical seasonal rainforest in Xishuangbanna, Southwest China using data from >2000 dendrometer bands and litter fall traps within a 20-ha permanent forest dynamics plot. We asked which climatic factor has the greatest effect on forest NPP at the sub annual scale, and how the relationships vary with seasonality. Calculations showed that NPP ranged from 12 to 20 t ha−1 yr−1, and that forest productivity showed a slight, but insignificant increase from 2009 to 2017. NPP was significantly higher in the wet season than that in the dry season and was significantly related to precipitation only when all data were concerned. During the dry season, precipitation had a significant positive influence on NPP, but no effect during the wet season. We further identified that there was a threshold effect of precipitation on NPP. Specifically, productivity increased more rapidly when monthly precipitation below 229 mm. In summary, we conclude that periods of low rainfall strongly regulate the productivity in this tropical seasonal rainforest which could guide the management design of water use efficiency in tree based land-use system, like agroforestry ecosystems.

Impact of tropical forest conversion on soil bacterial diversity in tropical region of China

In Xishuangbanna, a China's tropical region, monoculture rubber plantations have expanded dramatically over the past two decades. However, the effect of conversion of tropical forests to rubber plantations on the soil microbial compositions and diversity remains poorly understood. This study investigated the bacterial diversity and biomass in rubber plantations, secondary tropical forest and tropical seasonal rainforest in Xishuangbanna, southwest China, based on an analyses of PCR-amplified 16S rRNA genes. Our findings revealed that soil of rubber plantation was different from secondary tropical forest and tropical seasonal rainforest in bacterial compositions at phylum, family as well as OTU (Operational Taxonomic Units) levels. The most abundant phylum in rubber plantations was Firmicutes, however, in secondary tropical forest and tropical seasonal rainforest it was Proteobacteria. In both dry season and rainy season, diversity indices of rubber plantations were significantly higher than those of secondary tropical forest and tropical seasonal rainforest, indicating that bacterial diversity increased after conversion. However, the total microbial biomass carbon (MBC) decreased after conversion. RDA results showed that soil pH and total phosphorus maybe the two most important factors controlling bacterial communities, and explained 49.2% and 38.1% of total variance of phylum compositions, respectively. Management practices, especially the application of fertilizers with phosphorous would thus probably influence the taxonomic composition and diversity of bacterial communities in this region.

Tree species diversity of a 20-ha plot in a tropical seasonal rainforest in Xishuangbanna, southwest China

We censused all free-standing trees ≥1 cm diameter at breast height (dbh) in a 20-ha plot established in a tropical seasonal rainforest in Xishuangbanna National Nature Reserve, southwest China. A total of 95,834 free-standing trees ≥1 cm dbh were recorded, and 95,498 individuals (accounting for 99.65% of the total), including 468 morphospecies in 213 genera and 70 families, were identified. Thirteen of 468 species (2.78%) had more than 1,000 individual ≥1 cm dbh, which represented 56.36% individuals of the total. On the other hand, 230 of 468 species (49.14%) had a mean density of ≤1 tree per ha, and 69 of 468 species (14.74%) were singletons in the 20-ha plot. The mean species richness, density and basal area per ha were 216.50 species, 4,791.70 stems and 42.34 m2, respectively. Pittosporopsis kerrii (20,918 stems, ≥1 cm dbh) of Icacinaceae and Parashorea chinensis (7,919 stems, ≥1 cm dbh) of Dipterocarpaceae were the two most abundant species dominating the emergent layer and treelet layer, respectively. Compared with other 50-ha plots established in other equatorial regions, tree species richness per ha and tree abundance per ha of the plot were at the moderate level.

Spatial distribution and interspecific associations of tree species in a tropical seasonal rain forest of China.

Studying the spatial pattern and interspecific associations of plant species may provide valuable insights into processes and mechanisms that maintain species coexistence. Point pattern analysis was used to analyze the spatial distribution patterns of twenty dominant tree species, their interspecific spatial associations and changes across life stages in a 20-ha permanent plot of seasonal tropical rainforest in Xishuangbanna, China, to test mechanisms maintaining species coexistence. Torus-translation tests were used to quantify positive or negative associations of the species to topographic habitats. The results showed: (1) fourteen of the twenty tree species were negatively (or positively) associated with one or two of the topographic variables, which evidences that the niche contributes to the spatial pattern of these species. (2) Most saplings of the study species showed a significantly clumped distribution at small scales (0–10 m) which was lost at larger scales (10–30 m). (3) The degree of spatial clumping deceases from saplings, to poles, to adults indicates that density-dependent mortality of the offspring is ubiquitous in species. (4) It is notable that a high number of positive small-scale interactions were found among the twenty species. For saplings, 42.6% of all combinations of species pairs showed positive associations at neighborhood scales up to five meters, but only 38.4% were negative. For poles and adults, positive associations at these distances still made up 45.5% and 29.5%, respectively. In conclusion, there is considerable evidence for the presence of positive interactions among the tree species, which suggests that species herd protection may occur in our plot. In addition, niche assembly and limited dispersal (likely) contribute to the spatial patterns of tree species in the tropical seasonal rain forest in Xishuangbanna, China.

Comparison of carbon content and carbon density of four typical zonal forest ecosystems

Based on the location observation data of the tropical seasonal rain forest in Xishuangbanna, the subtropical evergreen broadleaved forest in Dinghu Mountain, the moist evergreen broad-leaved forest in Ailao Mountain and the broad-leaved Korean pine forest in Changbai Mountain, this paper analyzed and compared the spatial distribution patterns of carbon content and carbon density in four forest ecosystems. The results showed that the carbon contents of vegetation in Ailao Mountain and Changbai Mountain were higher than those in Xishuangbanna and Dinghu Mountain, the carbon contents of different layers in four forest ecosystems were ordered from larger to little as tree, shrub and herbage. The total carbon density was 250.78 t/hm2 in Xishuangbanna, 248.72 t/hm2 in Dinghushan Mountain, 530.13 t/hm2 in Ailao Mountain and 254.67 t/hm2 in Changbai Mountain. The carbon densities of vegetation in Xishuangbanna, Dinghu Mountain and Changbai Mountain were higher than those of soil, but it was opposite in Ailao Mountain.

Structure and composition of the understory treelets in a non-dipterocarp forest of tropical Asia

Species richness, floristic composition, and structure of understory treelets were investigated in three 1-ha plots, distributed in the undisturbed tropical seasonal rain forest of Xishuangbanna, SW China. We investigated all the woody species except lianas in these plots, compared the differences of species diversity of trees and treelets in these plots and the differences of understory structure between this forest and the typical dipterocarp forests in SE Asia. We found 5089 individuals belonging to 356 species, 189 genera, and 63 families in the three plots. The five most important families were Rubiaceae, Euphorbiaceae, Lauraceae, Meliaceae, and Annonacae. The treelet layer was much more diverse than the tree layer, indicating that result based only on trees may be not an appropriate representation of the diversity status of a particular tropical forest type. The three plots were more similar when the treelet layer was considered than when tree layer was considered. In contrast with the dipterocarp forests in SE Asia, the understory of tropical seasonal rain forest was mainly composed of the trees with small and middle stature at maturity classes. These results indicate that the structure of tropical forest understory may differ not only among continents but also within continent.

Diversity and composition of understory vegetation in the tropical seasonal rain forest of Xishuangbanna, SW China

Tropical forests vegetation and community research have tended to focus on the tree component, and limited attention has been paid to understory vegetation. Species diversity and composition of the understory of tropical seasonal rain forest were inventoried in a 625 m2 area (for sapling layer) and a 100 m2 area (for herb/seedling layer) in three 1 ha plots. We found 3068 individuals belonging to 309 species, 192 genera and 89 families. The most important family as determined by the Family Importance Value (FIV) was Rubiaceae in both sapling and herb/seedling layers. In terms of Importance Value Index (IVI), the shrub Mycetia gracilis (Rubiaceae) was the most important species in the sapling layer and the pteridophyte Selaginella delicatula (Selaginellaceae) was the most ecological significant species in the herb/seedling layer. Much more vascular plant species were registered in the understory than in the tree layer totaled among the three plots. The species diversity did not differ significantly among the tree layer, sapling layer and herb/seedling layer. Given that we still know little about the understory plant community for growth forms other than trees, the results from the present study indicate that more attention should be paid to the understory vegetation during the decision-making process for biodiversity conservation in the tropical forests.

Fluxes of CH 4 and N 2O from soil under a tropical seasonal rain forest in Xishuangbanna, Southwest China

CH 4 and N 2O 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 CH 4 and source of atmospheric N 2O. The observed mean CH 4 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 N 2O 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 –4.1, –3.1, and –2.9 kgC/hm 2, respectively. The observed mean N 2O 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 CH 4 and N2O fluxes were significant among all the three treatments. The presence of litter decreased CH 4 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 CH 4 fluxes and soil moisture for all the three treatments, and weak relationship between CH 4 fluxes and soil temperature for treatment B and treatment C. The N2O fluxes correlated with soil temperature for all the three treatments.

The importance of radiation fog in the tropical seasonal rain forest of Xishuangbanna, south-west China

The tropical rain forest in Xishuangbanna, SW China has a high floristic diversity and is closely related to Malaysian rain forests in flora. This forest would not normally be established in such a climatic region as Xishuangbanna (less precipitation and lower air temperature) compared to those of the lowland moist tropics. The mean annual rainfall is 1487 mm, which is considerably lower than rain forests in other parts of the world. It is believed that the frequent occurrence of radiation fog might play an important role in the water relations of plants and in the hydrological cycle of this type of rain forest. However, the multiple hydrological and ecological effects of radiation fog are not well understood. In this paper, we describe and analyze the significance of radiation fog to this forest, and develop a hypothesis that fog plays an important role in the presence of the tropical rain forest in Xishuangbanna. Suggestions for further research on the significance of fog are offered.

Ecology of seed germination of eight non-pioneer tree species from a tropical seasonal rain forest in southwest China

We compared various aspects of the seed biology of eight non-pioneer tree species from a tropical seasonal rain forest in Xishuangbanna, SW China, that differ in time of dispersal, size and fresh seed moisture content (MC). Seeds were tested for germination under laboratory conditions after dehydration to different moisture levels and under 3.5, 10 and 30% solar irradiances in neutral-shade houses. For six species, germination was also compared in forest understory (3.5% light) and center of a forest gap (32.5% light). Under continuous dehydration over activated silica gel, 100% of seeds of four species had lost the ability to germinate after 48 h, and those of all species except Castanopsis hystrix (decreased from >90 to 30% germination) had lost the ability to germinate after 120 h. Four species did not differ in final germination percentages at the three irradiances (i.e. uniform germination). However, final germination percentages of Horsfieldia pandurifolia and Litsea pierrei var. szemaois were significantly lower in 30% than in 10 or 3.5% light, and seeds of Antiaris toxicaria and C. hystrix germinated to higher percentages in 30 and 10% than in 3.5% light. Mean time to germination (MTG) of the eight species (forest and shade house data combined) ranged from 5–5 days for Pometia tomentosa to 72–207days for L. pierrei; MTG for four species was ≤21 days. There was no obvious relationship between relative desiccation resistance and either time of dispersal, MTG or uniformity of germination at the three light levels, or between seed size and MC or MTG. However, the relationship between seed MC at maturity (25–60% fresh mass basis) and MC at 50% loss of seed viability (12.4–42.5%) was significant. Seven of the species fit Garwood’s (Ecol Monogr 53:159–181, 1983) rapid-rainy germination syndrome and one, L. pierrei, either her delayed-rainy or intermediate-dry germination syndrome. However, fresh, non-dehydrated seeds of all eight species germinated in ≤30 days at constant 30°C in light.

Interannual and seasonal variations of energy and water vapor fluxes above a tropical seasonal rain forest in Xishuangbanna, SW China

The values and variation characteristics of energy components, their relationship with net radiation and the characteristics of water balance in the forest were analyzed, based on the observation data of energy fluxes, meteorological parameters and biomass in a tropical seasonal rain forest in Xishuangbanna from January 2003 to December 2004. The results show that annual net radiation was 3516.4 MJ/(m 2 · a) and 3516.6 MJ/(m 2 · a) in 2003 and 2004, respectively, of which 46% and 44% were used in latent heat flux, and 12% and 11% were lost as sensible heat flux. Annual mean canopy surface conductance was 10.3 mm/s and 10.0 mm/s in 2003 and 2004, respectively. Moreover, canopy surface conductance was lower in dry-hot seasons than in fog-cool and rainy seasons. Canopy surface conductance correlated significantly and positively with leaf area index, but negatively with water vapor pressure deficit. In general, canopy surface conductance was not affected directly by soil water content, but highly depended on soil moisture status when soil water content was below 0.15 m 3/m 3. Annual total evapotranspiration of this forest ecosystem in dry seasons was lower than that in rainy seasons, which was considered as one of the most important reasons that tropical seasonal rain forest could survive and flourish in Xishuangbanna at limit of water and heat.

BIOMASS AND ITS ALLOCATION IN TROPICAL SEASONAL RAIN FOREST IN XISHUANGBANNA, SOUTHWEST CHINA

Aims Changes in the biomass of tropical forests play an important role in the global carbon cycle, but the biomass of these forests has been poorly quantified. A strategy for regional biomass estimation should supplement previous surveys with new data. Accurate data are necessary for reducing the uncertainty in the carbon budget of tropical regions. Methods Biomass and its allocation were estimated for the tropical seasonal rain forest in Xishuangbanna, southwest China. Regression models relating tree biomass to DBH (diameter at breast height, 1.3 m) were developed, and a power-law allometric relationship W=aDb was used to estimate the tree biomass, where W is the biomass of a tree (kg of leaves, branches, stems or roots), a and b are constants and D is the DBH (cm). Other biomass components were sampled in different quadrats in three 1 hm2 permanent research plots: shrubs (ten 25 m2 quadrats), herbs (ten 4 m2 quadrats), dead wood (the whole plot), large fallen branches (twenty-five 25 m2 quadrats) and litterfall (twenty-five 1 m2 quadrats). This method was used for estimating above- and below-ground biomass of live and dead plants (trees, seedlings, shrubs, herbs, woody lianas, epiphytes, coarse woody debris and litterfall). Important findings Total biomass for the three plots was 370.163, 550.119 and 351.442 Mg·hm -2 , with an average of (423.908±109.702) Mg·hm -2 (95% confidence interval). Living biomass made up 95.28% of the total biomass, with coarse woody debris and litterfall comprising the rest. Most living biomass (98.09%± 0.60%) (Mean±SD, n=3) of the seasonal rain forest was concentrated in the tree layer. In the allocation of total biomass, stems accounted 68.33% and roots, branches and leaves made up 18.91%, 11.07% and 1.65%, respectively. The biomass allocation among different DBH classes was concentrated in the middle and largest classes, with large trees (D70 cm) accounting for 43.67% ± 12.67%. The most important ten species, in terms of biomass, made up 63.43% of the tree layer. Leaf area index (LAI) of the tree layer for the three plots was 5.73, 7.35 and 6.08, with an average of 6.39. Estimated aboveground biomass in our study sites fell within the range of published values for tropical moist forests and was lower than that of Malaysian and Cameroon rain forests, but higher than some neotropical rain forests. In terms of total biomass, Xishuangbanna tropical seasonal rain forest is also higher than moist forest in Brazil.

Using stable isotopes to determine sources of fog drip in a tropical seasonal rain forest of Xishuangbanna, SW China

To identify the possible sources of fog drip, samples of rainfall, fog drip, throughfall, stemflow, stream water, river water, pond water and soil water were collected for 3 years (2002–2004) for stable isotopic analysis, at a tropical seasonal rain forest site in Xishuangbanna, Southwest China. We found that radiation fog is produced mainly through evaporation from pond, river, and soil, and through forest evapotranspiration. The analyses suggest that evaporation from the stream is limited. In addition, radiation fog produced during the dry season (low absolute humidity) contained more terrestrially recycled water than fog produced during the rainy season (high absolute humidity). Forest evapotranspiration appears to be the largest fraction, but a more intense sampling scheme will be needed to assign the relative contribution of the different sources of fog.