Forest In Xishuangbanna Research Articles

Soil fungi lead to stronger ‘diminishing returns’ in fine‐root length versus mass allometry towards earlier successional tropical forests

Abstract Decreasing returns in resource acquisition ability with increasing leaf mass investment is called ‘diminishing returns’, which provides important insights into plant economy. Yet, whether this is true for fine roots and how root resource acquisition strategies change with forest succession remain unclear. We investigated the scaling relationship between fine‐root length (L) and mass (M) for 215 topsoil cores from 24 plots across four successional stages in tropical forests of Xishuangbanna, southwestern China. We also assessed the relative effects of edaphic conditions, leaf functional traits, tree species diversity and soil fungal factors on L versus M scaling relationship using hierarchical variation partitioning. Our results revealed the existence of diminishing returns in root length (L vs. M scaling exponent <1), and that the exponent was higher in late‐ than early‐successional forests, corresponding to a strategy shifting from ‘do‐it‐yourself’ in the late‐successional stage to ‘outsourcing’ resource uptake by soil fungi in the early‐successional stage. Soil fungal abundance was the main driver of changes in the L versus M scaling exponent across plots (explained 58% of variances), with root endophytic fungi the strongest predictor (22.11%), followed by mycorrhizal fungi (10.41%), while other factors (leaf functional traits, edaphic nutrient conditions and tree species diversity) exerted weak effects. Our results suggest that root endophytic and mycorrhizal fungi act as key modulators of root economy changes during forest succession, but the former has received less attention previously. L versus M scaling exponent may be a better indicator for shifts in root resource acquisition strategy than the commonly used specific root length. Read the free Plain Language Summary for this article on the Journal blog.

A dataset of soil moisture in Xishuangbanna tropical seasonal rain forests (2009–2017)

As the carrier of material circulation and energy flow, soil moisture plays an important role in terrestrial forest ecosystems. Observing soil moisture is beneficial for unveiling the hydrological characteristics, water conservation capacity and ecosystem service function of forest ecosystems. The tropical rain forest is among the most biodiverse ecosystems. There are large areas of tropical rain forests in Xishuangbanna, where the tropical seasonal rain forest represents a prominent vegetation type. Conducting continuous, long-term and high-quality ecological monitoring is one of the main tasks of China Ecosystem Research Network (CERN). Soil moisture content is an important indicator in the long-term site-specific water environment observations within the terrestrial ecosystems monitored by CERN. This dataset comprises soil moisture content data collected from January 2009 to December 2017 at the Xishuangbanna Station for Tropical Rainforest Ecosystem Studies of the Chinese Academy Sciences (also known as National Forest Ecosystem Research Station at Xishuangbanna, BNF for short), with a total of 2,879 entries. The determination method used for this dataset is fixed-point continuous observation using Time Domain Reflectometry (TDR) instruments; observations were conducted at multiple, ranging from 0–10 cm, 10–20 cm, 20–30 cm, 30–40 cm, 40–50 cm, 50–70 cm, 70–90 cm and 90–110 cm. The observation frequency consists of 3 times per month, respectively at the beginning, middle and end of each month. The observations were conducted strictly according to the CERN observation and quality control protocols. The dataset is readily available for online sharing and serves as essential foundational data for conducting research on tropical forest hydrology under the global climate change and different vegetation environments.

Enhancing the dung beetle iDNA tool for mammalian biodiversity monitoring and ecological studies

AbstractMany species of dung beetles (Coleoptera: Scarabaeidae: Scarabaeinae) are coprophages and possess trophic connections with mammalian dung. Recent studies have shown that the use of genetic information from dung beetle guts (invertebrate‐derived DNA or iDNA) allows for the detection of mammals in a given habitat without intensively surveying the area. However, these studies used live or freshly killed beetles instead of preserved specimens. Here, we assessed the feasibility of extracting and sequencing iDNA from dung beetles that were collected using conventional baited pitfall traps with a mixture of propylene glycol and ethanol. We extracted iDNA from the guts of 18 dung beetles, comprising three species and three functional groups, collected from a seasonal tropical forest in Xishuangbanna, China. Eight mammalian species were detected, including rare species not previously recorded at the same location. Among the three functional groups, paracoprids (tunnelers) yielded the highest number of mammal species. Our study shows that iDNA can be successfully sequenced from preserved specimens, provided they are stored under appropriate conditions. The proposed technique offers a viable alternative to traditional cafeteria experiments for understanding dung beetle‐mammal interactions and can serve as a valuable complementary approach to current mammal survey techniques.

Correlation between soil environment and yield and quality of Sharen (Amomi Fructus) under different planting patterns

ObjectiveTo study the effects of soil environment on the growth, yield, and quality of Sharen (Amomi Fructus) under different planting patterns. MethodsSoil physical and chemical indices and enzyme activities in four periods including early flowering (March), full flowering (June), fruit ripening (September), and late fruit picking (December), were measured under three planting patterns including natural forest, greenhouse, and rubber forest in Xishuangbanna, China. The changes in soil indices during the growth periods of Sharen (Amomi Fructus) under different planting patterns were analyzed, and the differences in plant growth, yield, and quality under different planting patterns were explored. Pearson correlation analysis was used to analyze the relationship between soil indices and Sharen (Amomi Fructus) growth, yield, and quality. Principal component analysis was used to investigate the effects of soil environment under different planting patterns on Sharen (Amomi Fructus) growth, yield, and quality. ResultsThe soil moisture, available potassium content, and urease activity of the three planting patterns of Sharen (Amomi Fructus) increased initially and decreased afterwards throughout the year; pH and organic matter content showed little change in the whole year. Exchangeable manganese content and acid phosphatase activity gradually increased throughout the year. Hydrolyzed nitrogen content, exchangeable calcium content, available zinc content, protease activity, and sucrase activity decreased initially and increased afterwards throughout the year. Exchangeable magnesium content, available iron content, and catalase activity decreased annually. Total nitrogen content, total phosphorus content, and available phosphorus content fluctuated throughout the year. The total potassium content under natural forest and greenhouse planting decreased throughout the year, while the total potassium content under rubber forest showed an upward trend all year round. The organic matter content, total nitrogen content, total potassium content, available potassium content, available zinc content, urease activity, acid phosphatase activity, and catalase activity under greenhouse were significantly lower than those under natural and rubber forests (P < 0.05). Correlation analysis showed that plant growth, yield, and quality of Sharen (Amomi Fructus) were significantly correlated with soil organic matter, total nitrogen, hydrolyzed nitrogen, total phosphorus, available phosphorus, total potassium, available potassium, exchangeable manganese, exchangeable magnesium, exchangeable calcium, available zinc, urease, acid phosphatase, and invertase (P < 0.05). The results of the principal component analysis indicated that the soil environment of Sharen (Amomi Fructus) under natural forest was the best, followed by rubber forest and greenhouse. The order of its advantages and disadvantages is consistent with the growth index of Sharen (Amomi Fructus), but contrary to the yield of Sharen (Amomi Fructus), indicating that the soil environment directly affects the growth index and nutritional components of plants. ConclusionDifferent planting patterns of Sharen (Amomi Fructus) have different soil nutrient content, and the change rules in the growths period are not similar, with some differences. Soil indices have impacts on plant growth, yield, and quality of Sharen (Amomi Fructus). Soil ecological environment is positively correlated with the growth characteristics of Sharen (Amomi Fructus) plants, but has no direct correlation with yield and quality.

Estimating the gross primary productivity based on VPM correction model for Xishuangbanna tropical seasonal rainforest

ABSTRACT Due to the unique climatic characteristics and vegetation features of tropical regions, the correlation R2 of gross primary productivity (GPP) estimation in tropical regions using remote sensing models was generally lower than 0.3. Therefore, for the cloudy and rainy tropical regions, the influence brought by clouds on remote sensing images needed to be considered in GPP estimation. This paper developed a corrected vegetation photosynthesis model (VPM) for estimating GPP under cloudy conditions. It mainly corrected the two parameters, W scalar and Enhanced Vegetation Index (EVI), which were obtained from remote sensing images and were therefore greatly influenced by clouds in the model. First, the water stress factor W scalar was replaced by Evaporation Fraction (EF). Secondly, using the good correlation between near surface temperature and EVI, the conversion coefficient between near surface temperature and EVI was fitted to achieve the effective reconstruction of EVI contaminated by clouds. The correction of the two factors improved the estimation accuracy of the VPM model, and the comparison with the observed values of the GPP site in 4 years showed that the correction of EVI had a better improvement, with an increase of 0.22 in R2 compared with the pre-correction, and the correction of W scalar was increased by 0.11 in R2. To verify the proposed method, the in-situ observation data of Xishuangbanna flux site from 2007 to 2010 were used. The results showed that the proposed method effectively improved the accuracy of GPP estimation by VPM model, especially in 2007 it was strongly influenced by clouds, and the improvement was significant, with R2 increasing from 0.2 to 0.82. In general, the accuracy of GPP estimation by the proposed method had been significantly improved, with RMSE (gC·m−2·8 day−1) decreasing from 15,14.4, 18.1, 14.2 to 8.07, 6.56, 10.33, 11.44, respectively. Therefore, the proposed method can be used to estimate the GPP for tropical seasonal rain forests in Xishuangbanna.

Are fine roots ‘leaves underground' in terms of allometry? A test in a tropical forest successional series in southwest China

Fine roots have been hypothesized to be ‘leaves underground' in terms of vascular network, but this hypothesis has rarely been tested within the framework of metabolic scaling theory (MST). We measured average fine‐root (diameter &lt; 1 mm) mass (M), surface area (A), volume (V), diameter (D) and length (L) for 216 soil cores from 24 plots across four successional stages in tropical forests of Xishuangbanna (southwest China), and examined eight scaling relationships between these variables at the individual root scale. We tested whether fine‐root allometries conformed to MST's model for leaf (MSTl) or model (MSTw) for woody organs (e.g. trunk). We also assessed the relative effects of environmental factors, tree size, species composition and diversity, and stand structural factors on allometric relationships using structural equation models (SEMs). Our results showed that: 1) fine‐root scaling exponents rarely conformed to MSTl's predictions. 2) The scaling exponents between fine‐root M, A, V and D all conformed to MSTw's predictions in later successional forests, but showed greater deviation towards early successional stage. 3) The scaling exponents associated with fine‐root length differed markedly from MSTw's predictions. 4) Changes of some fine‐root scaling exponents across successional stage were mainly affected by tree size or soil fertility, and species composition affected allometry only indirectly via tree size. Our results suggested that the allometries of individual fine roots largely conform to the scaling rules governing woody organs instead of leaves, probably because leaves are nearly two‐dimensional objects while the other two are three‐dimensional. We showed that MSTwcan well predict some fine‐root allometries in later successional forests, suggesting great potential of utilizing MSTwto better estimate fine‐root biomass and productivity. However, the present MSTwstill needs to be improved for predicting the scaling relationships concerning fine‐root length, and also for better quantifying allometric exponents in earlier successional forests.

A New Tropical Species Of Lycoperdon Subgenus Morganella (Agaricales, Basidiomycota) From Yunnan Province, China

Two specimens of Lycoperdon were collected in 2012 and 2013 during surveys conducted in evergreen broadleaf forests of Xishuangbanna, Yunnan Province, China. Macro- and micro- morphological characteristics, together with analyses of combined ITS and LSU sequence data, showed that fi ve specimens represent a single new species and is thus named as Lycoperdon mengsongense. The new species is distinguished from the known taxa in Lycoperdon by its greyish white to dark grey exoperidium covered by minute and blackish grey granules, smooth to wrinkled endoperidium, non- chambered subgleba and echinate basidiospores. Comprehensive morphological descriptions, color photographs of macro- and micro- characteristics and a phylogenetic tree to show the placement of the new species are provided. In addition, the new species is compared with closely related taxa in Lycoperdon subgenus Morganella.

西双版纳地区森林变化碳效应与生态效益评估

减少发展中国家因森林砍伐与森林退化导致的碳排放和保持碳储量（REDD+），不仅能减少因森林砍伐和森林退化造成的碳排放，而且还可以带来其它生态效益，如减缓森林破碎化、保护生物多样性和增强水土保持功能等。以中国的西双版纳地区为研究区域，以毁林最严重的1976-2007年为REDD+基线，基于卫星影像，并结合植被指数，提取了研究区的土地利用变化信息。基于IPCC温室气体清单方法，计算了研究区的森林碳储量变化。在此基础上，对REDD+的碳汇效益和生态效益进行了系统综合评估。结果显示：（1）1976-2007年间天然林碳储量从占总碳储量的78.24%减少至50.52%，这是造成西双版纳地区碳储量减少的主要原因。（2）1976-2007年，天然林的斑块数量和平均最近邻距离分别增加了120.00%和25.21%，平均斑块面积下降了71.98%，说明天然林的破碎化程度加剧。从研究区整体景观格局来看，斑块数量、Shannon多样性指数和Shannon均一性指数分别增加了8.16%、51.39%和34.07%；与此同时，平均斑块面积和景观内聚力指数分别下降了26.26%和2.13%，表明研究区整体景观格局朝破碎化方向发展，这和碳排放的增加相一致。（3）该区的土壤侵蚀程度逐年加剧，并与碳储量的减少密切相关。分析表明，土壤侵蚀剧烈的区域，其平均碳排放也相对较高。1999年到2007年间，剧烈侵蚀区域的平均碳排放是轻度侵蚀区域的6倍多。这些结果说明：如果REDD+政策得以实施，不仅能减少因毁林和森林退化导致的碳排放，而且能带来高的生态效益。从这个角度出发，REDD+的本质可以认为是以"增汇"或"减排"为主导功能，同时提升生态效益的一种管理方式。;The REDD+ partnership works to promote the reduction of greenhouse gas (GHG) emissions by reducing emissions from deforestation and forest degradation in the developing countries through positive incentives and conversation of forest carbon stocks. It is regarded as an essential component of the post-2012 climate regime to stabilize GHG emissions and engage the developing countries in worldwide mitigation endeavors. If cost-efficient carbon benefits can be achieved through REDD+, increases in atmospheric CO₂ concentrations could be slowed, effectively buying much needed time for countries to move to lower emissions technologies. We chose tropical forests in Xishuangbanna of China as our study area and took the most severe deforestation from 1976 to 2007 as the baseline of REDD+. Land use information was obtained through the combination of Landsat TM images and Normalized Difference Vegetation Index masks. Forest carbon storage change in the study area was firstly calculated based on IPCC methodology. Secondly ecosystem-based benefits from REDD+ were assessed systematically. Our results showed that from 1976 to 2007, the natural forest carbon storage decreased from 78.24% to 50.52% of total carbon storage, which was the main reason for the reduction of carbon storage in Xishuangbanna. At the meantime, significant degradation of ecosystem services emerged. This was demonstrated by two important indicators:forest fragmentation and soil erosion. For example, from 1976 to 2007 the percentage change in the carbon stocks was 1.4%, accompanying with increasing 8.16% in number of patches, 51.39% in Shannon's diversity index and 34.07% in shannon's evenness index. Meanwhile, mean path area and patch cohesion index decreased by 26.26% and 2.13%, respectively. It suggested that the forest ecosystem was changing in both carbon storage and forest landscape structure. The number of patches and average nearest neighbor distance of natural forest increased by 120.00% and 25.21%, respectively, and the average patch area decreased by 71.98%, indicating the degree of exacerbated fragmentation in natural forest. In this sense, carbon emission and forest fragmentation were well integrated. Furthermore, we investigated relationship between carbon emission and soil erosion and high correlation was found. For example, carbon emissions which accounted for 45% of the total located in the high erosion area, which is 18% of the whole study area. As a result, when forests that would have been lost or degraded are retained or restored through REDD+, they deliver ‘multiple benefits’ in addition to protecting or enhancing carbon stocks. These ecosystem-based benefits may include conservation of forest biodiversity, water regulation, soil conservation, timber, forest foods and other non-timber forest products, most of which have been demonstrated or proved in this study. By securing benefits beyond carbon, REDD+ has the potential to encourage countries to realize a broader range of values.

基于树形结构的木棉叶功能性状差异性研究

PDF HTML阅读 XML下载 导出引用 引用提醒 基于树形结构的木棉叶功能性状差异性研究 DOI: 10.5846/stxb202006031431 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31860206） Variation in leaf functional traits of Bombax ceiba Linnaeus communities based on tree structure Author: Affiliation: Fund Project: The National Natural Science Foundation of China (General Program, Key Program, Major Research Plan) 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:叶功能性状不仅反应植物对资源的利用能力，还涉及植物对自身结构和环境的生存适应策略。以不同生长阶段的木棉为研究对象，于2019年12月实地测量树高、冠幅等5个主要树形因子和采样测定叶面积、比叶面积、叶干物质含量、叶片含水量等14个叶功能性状，分析其在不同生长阶段的变化规律和相互关系，探讨叶功能性状对树形结构的响应。结果表明：不同生长阶段的木棉叶功能性状之间存在差异（P<0.05），且表现出一定的相关性（P<0.05，P<0.01）；木棉叶片的面积、长度、宽度、周长、鲜重、饱和重、干重、比叶质量和干物质含量等功能性状是随生长阶段变化的主要指标。影响木棉叶片各性状的树形因子也不相同，其中叶面积主要受到冠幅的影响，叶片鲜重和饱和重主要受到枝下高的影响，叶片干重和相对含水量主要受到树高的影响，比叶面积、叶片含水量和干物质含量主要受到树高、尖削度的影响，比叶质量主要受到胸径、尖削度、树高的影响。随着木棉的生长，叶功能性状表现出受树形结构的影响而具有较强的表型可塑性，有利于其适应内外环境的变化。因此，叶功能性状之间的变化差异和相关组合，反映了不同生长阶段的木棉对树形结构的适应性调整和对资源的利用策略，在一定程度上为探索西双版纳热带雨林区的生态保护和可持续发展提供相关科学依据。 Abstract:The leaf functional traits of plants not only reflect their abilities to use resources, but also represent their adaptation strategies to structural and environmental changes. Therefore, leaf functional traits are critical indicators of biogeochemical coupling in terrestrial ecosystems. In the present study, Bombax ceiba Linnaeus at different growth stages was taken as the main research subject, five main tree shape factors (i.e., height and crown breadth) were measured, and 14 leaf functional traits were quantified, including leaf area, specific leaf area, leaf dry matter content and leaf water content. We conducted the research in Menglun Town, Mengla County, Xishuangbanna Autonomous Prefecture in December 2019. We analyzed the changing patterns and mutual relations at different growth stages, and explored the responses of leaf functional traits to tree structure based on a variety of statistical analysis methods (i.e., One-way analysis of variance and multiple linear stepwise regression analysis). The results showed that leaf functional traits of Bombax ceiba Linnaeus differed in different growth periods (from primary growth stage to tertiary growth stage)(P<0.05), although they were also correlated certainly (P<0.05,P<0.01). Principal component analysis showed that leaf area, leaf length, leaf width, leaf perimeter, leaf fresh weight, leaf saturated weight, leaf dry weight, leaf mass per area, and leaf dry matter content were the main indicators with the increasing growth stage. The pattern of leaf functional traits was affected by various tree factors, which formed the best functional combination through the functional coordination among multiple characters so that plants could well adapt to environmental changes. We found that leaf area was mainly affected by the crown breadth. The leaf fresh weight and leaf saturated weight were mainly affected by the height to crown base. The leaf dry weight and leaf relative water content were mainly affected by the height, specific leaf area, leaf water content and leaf dry matter content were mainly affected by the height and taperingness, and leaf mass per area was mainly affected by the diameter, taperingness and height. With the growth of Bombax ceiba Linnaeus, the leaf functional traits showed strongly phenotypic plasticity influenced by tree structure, which was helpful to adapt to the changes in internal and external environment. Therefore, the variation and related combinations of leaf functional traits at different periods reflect the adaptability of Bombax ceiba Linnaeus to the tree structure and resource utilization strategies, which to a certain extent also provide relevant scientific basis for the exploration of the ecological protection and sustainable development of the tropical rain forest in Xishuangbanna. 参考文献 相似文献 引证文献

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.

Framework for Accounting Reference Levels for REDD+ in Tropical Forests: Case Study from Xishuangbanna, China

The United Nations’ expanded program for Reducing Emissions from Deforestation and Forest Degradation (REDD+) aims to mobilize capital from developed countries in order to reduce emissions from these sources while enhancing the removal of greenhouse gases (GHGs) by forests. To achieve this goal, an agreement between the Parties on reference levels (RLs) is critical. RLs have profound implications for the effectiveness of the program, its cost efficiency, and the distribution of REDD+ financing among countries. In this paper, we introduce a methodological framework for setting RLs for REDD+ applications in tropical forests in Xishuangbanna, China, by coupling the Good Practice Guidance on Land Use, Land Use Change, and Forestry of the Intergovernmental Panel on Climate Change and land use scenario modeling. We used two methods to verify the accuracy for the reliability of land classification. Firstly the accuracy reached 84.43%, 85.35%, and 82.68% in 1990, 2000, and 2010, respectively, based on high spatial resolution image by building a hybrid matrix. Then especially, the 2010 Globeland30 data was used as the standard to verify the forest land accuracy and the extraction accuracy reached 86.92% and 83.66% for area and location, respectively. Based on the historical land use maps, we identified that rubber plantations are the main contributor to forest loss in the region. Furthermore, in the business-as-usual scenario for the RLs, Xishuangbanna will lose 158,535 ha (158,535 × 104 m2) of forest area in next 20 years, resulting in approximately 0.23 million t (0.23 × 109 kg) CO2e emissions per year. Our framework can potentially increase the effectiveness of the REDD+ program in Xishuangbanna by accounting for a wider range of forest-controlled GHGs.

Assessing temporal dynamics of predation and effectiveness of caterpillar visual defense using sawfly larval color and resting posture as a model.

Caterpillars (Lepidoptera and Symphyta larvae) employ diverse visual defensive tactics, and effectiveness of such tactics may be highly dynamic across time due to seasonal changes in the predator assemblages and their preferences. However, this has rarely been studied especially in tropical regions. Here we assessed temporal changes in the defensive value of caterpillar color and shape, using six types of plasticine dummy caterpillars: three colors (green, black, and white) × two shapes (curled and straight). These dummy caterpillars were deployed five times over different seasons in tropical forests of Xishuangbanna (China) and, as a comparison, twice in a temperate forest of Hirosaki (Japan). The colors and shapes of dummy caterpillars simulate visual traits of black sawfly larvae which take the curled resting posture in tropical rainforests of Xishuangbanna, apparently masquerading excrements commonly found on plants, while in Hirosaki there is no black-curled sawfly larvae and few excrements on plants. We found no significant effects of caterpillar colors or shapes on predation in Hirosaki. In contrast, black and curled caterpillars received significantly lower predation by birds in Xishuangbanna constantly across time. However, we were unable to provide evidence that the black-curled sawfly larvae are masquerading as excrements. Shapes of the dummy caterpillars also affected the predation by ants and parasitoid wasps at certain times. This is the first report on ecological function of the curled posture of sawfly larvae, and we demonstrated the importance to assess the temporal dynamics of predation and effectiveness of defensive tactics in tropical forests.

Reasons for the Survival of Tropical Forest Fragments in Xishuangbanna, Southwest China

Research Highlights: The reasons for persistence of forest fragments in human-dominated landscapes have rarely been examined, despite their importance in biodiversity and ecosystem services. We determined these reasons for forest fragments on collective land in Xishuangbanna prefecture, southwest China. Background and Objectives: Reconciling economic development with biodiversity conservation has been a major challenge in China’s small tropical land area, where local realities have often been in conflict with national policies. In Xishuangbanna, much of China’s most biodiverse forest area has been replaced by cash crops in recent decades, but numerous small forest fragments remain on collective land. Our objective was to find out why these fragments have not been cleared. Methods: We used a combination of semi-structured interviews with 600 households in 69 villages representing nine ethnic groups and information from key informants. Results: Overall, 64% of individual households retained forest fragments on the land allocated to them, and 93% of villages retained larger areas managed as a collective forest. Most (71%) interviewees said that fragments on their own land were on sites of low agricultural value and were retained as fuelwood sources. They were also often (33%) underplanted with crops and supplied other forest products. All interviewees attributed the retention of collective forests to policy restrictions on clearance, with most (96%) mentioning cultural and religious uses and many recognizing environmental benefits. Most were also used as sources of wild edible plants (61%) and other forest products. Many said these collective forests had shrunk over time, particularly in areas suitable for profitable cultivation. Conclusions: China’s new ecological redline policy will protect most larger patches of forest in Xishuangbanna, but the smaller fragments on land allocated to individual households are also of conservation value, particularly in areas with no other forest. Some form of compensation scheme is needed to encourage their continued retention.

Using landscape connectivity tools to identify conservation priorities in forested areas and potential restoration priorities in rubber plantation in Xishuangbanna, Southwest China

Maintaining connectivity is critical for fragmented habitat networks to retain native species. The tropical forest in Xishuangbanna, Southwest China, is a biodiversity hotspot for China, but is also vulnerable to deforestation due to rapid expansion of rubber plantations, thus better understanding of connectivity may be crucial to species persistence. To quantify the functional connectivity changes in the forest in Xishuangbanna from 1976 to 2014, and identify the conservation and restoration priorities for effective forest conservation and management. Using the graph theory (in Conefor sensinode 2.6), forest connectivity from 1976 to 2014 was quantified using probability of connectivity and number of components indexes. The importance of each forest patch during each period and the potential contribution of low-profit rubber plantation patches in 2014 was quantified and ranked by delta values for PC (dPC) index. Connectivity of forest in Xishuangbanna has progressively decreased over the last 40 years. The ten forest patches which had the highest dPC value remained almost the same for all five periods between 1976 and 2014, though relative importance varied. The 50 most potentially important low-profit rubber plantation patches were identified and mapped, and provide a target for effective restoration efforts to facilitate efficient use of funding to best improve conservation outcomes. Targeted and effective interventions for landscape scale conservation and management can be made based on graph theory and connectivity analysis. Restoring low-profit rubber provides a mechanism for reconnecting the forest as an effective conservation tool. Here we show the application of this approach to restore forest and most effectively increase connectivity at minimum economic cost.

A Survey of Termitomyces (Lyophyllaceae, Agaricales), Including a New Species, from a Subtropical Forest in Xishuangbanna, China

A survey of mushrooms was conducted in Xishuangbanna, Yunnan Province, China, in the rainy season (May to October) of 2012, 2013, and 2014, during which 16 specimens of Termitomyces were collected. Preliminary macro- and micro-characteristics, together with ITS sequence data, showed that four of the specimens belonged to a new species (Termitomyces fragilis), while the other 12 belonged to T. aurantiacus, T. eurrhizus, T. globules, T. microcarpus, and T. bulborhizus. In this paper, T. fragilis is introduced as a species new to science based on morphological characterization and phylogenetic analyses. Macro- and micro- morphological descriptions, color photographs and line drawings of the new species, and a phylogenetic tree to show the placement of the new species are provided. T. fragilis is then compared with other closely related taxa in the genus Termitomyces.

A SD-MaxEnt-CA model for simulating the landscape dynamic of natural ecosystem by considering socio-economic and natural impacts

Background climate and socio-economy significantly affect the landscape dynamics of natural ecosystem. And the simulated method to understand the landscape dynamics of natural ecosystems in responding to human and natural effects is increasingly important for ecosystem management. In this study, we integrated system dynamics, MaxEnt and cellular automata models (called as SD-MaxEnt-CA model) to consider climatic effects and human activities during the simulation of natural ecosystems landscape dynamics. In the integrated model, the MaxEnt process was used for the interactive coupling of the top-down SD and bottom-up CA, which improve the model’s ability to accurately acquire the weights of each layer and transition rules during the simulation with the effects of climate changes. This proposed model was applied to simulate the landscape degradation of natural forest caused by the expanding of farmland, tea gardens and rubber plantations in Xishuangbanna from 2000 to 2010, one of the world’s 34 biodiversity hotspots. By the comparison with other algorithms, the MaxEnt achieve a good performance in acquiring the weights of each layer. The spatial consistent between simulated map and actual result reached to 84.2%, indicating the promising grid-to-grid agreement. Proposed model considered the driving of climate changes and socio-economy, which improved the accuracy of simulating the landscape dynamics of natural ecosystems. The method was further used in simulating the landscape dynamics of natural forest in Xishuangbanna from 2010 to 2030 under four different climate scenarios. The variation of conversion area among different climate scenarios is consistent with their response to climate changes. The simulation results demonstrate that the proposed model is effective for the landscape simulation of natural ecosystems.

Recovery of Functional Diversity Following Shifting Cultivation in Tropical Monsoon Forests

The relationship between biodiversity and ecosystem functioning is an important issue in ecology. Plant functional traits and their diversity are key determinants of ecosystem function in changing environments. Understanding the successional dynamics of functional features in forest ecosystems is a first step to their sustainable management. In this study, we tested the changes in functional community composition with succession in tropical monsoon forests in Xishuangbanna, China. We sampled 33 plots at three successional stages—~40-year-old secondary forests, ~60-year-old secondary forests, and old growth forests—following the abandonment of the shifting cultivation land. Community-level functional traits were calculated based on measurements of nine functional traits for 135 woody plant species. The results show that the community structures and species composition of the old-growth forests were significantly different to those of the secondary stands. The species diversity, including species richness (S), the Shannon–Weaver index (H), and Pielou’s evenness (J), significantly increased during the recovery process after shifting cultivation. The seven studied leaf functional traits (deciduousness, specific leaf area, leaf dry matter content, leaf nitrogen content, leaf phosphorus content, leaf potassium content and leaf carbon content) changed from conservative to acquisitive syndromes during the recovery process, whereas wood density showed the opposite pattern, and seed mass showed no significant change, suggesting that leaf traits are more sensitive to environmental changes than wood or seed traits. The functional richness increased during the recovery process, whereas the functional evenness and divergence had the highest values in the 60-year-old secondary communities. Soil nutrients significantly influenced functional traits, but their effects on functional diversity were less obvious during the secondary succession after shifting cultivation. Our study indicates that the recovery of tropical monsoon forests is rather slow; secondary stands recover far less than the old growth stands in terms of community structure and species and functional diversity, even after about half a century of recovery, highlighting the importance of the conservation of old growth tropical monsoon forest ecosystems.

Spatial and seasonal variation in soil respiration along a slope in a rubber plantation and a natural forest in Xishuangbanna, Southwest China

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 CO2 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 CO2 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 mixed effects 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.

Nine-year seed rain dynamics in Parashorea chinensis forest in Xishuangbanna, Southwest China

Nine-year seed rain dynamics in Parashorea chinensis forest in Xishuangbanna, Southwest China

Soil respiration in sloping rubber plantations and tropical natural forests in Xishuangbanna, China

Abstract Soil respiration (SR) plays an important role in the global carbon cycle. The widespread and continued conversion of tropical forests to plantations is expected to drastically alter CO 2 production in soil, with significant consequences for atmospheric concentrations of this crucial greenhouse gas. In Southeast Asia, rubber plantations are among the most widespread monoculture tree plantations. However, knowledge of how SR differs in rubber plantations compared to natural forests is scarce. In this study, surface CO 2 fluxes and soil CO 2 concentrations (at 5 cm, 10 cm, 30 cm and 70 cm depths) were measured at regular intervals over a one-year period along slopes at three sites in paired natural tropical forests and mature rubber plantations. Annual surface soil CO 2 fluxes were 15% lower in the rubber plantations than in natural forest. This difference was due to substantially lower SR during the dry season in rubber plantations compared to natural forest. During the wet season, SR did not differ significantly between rubber plantations and natural forests. In rubber plantations, soil moisture increased from lower and middle to upper slope positions, but this did not significantly impact SR. Throughout the year, net CO 2 production per unit volume in the topsoil (2.5–7.5 cm) exceeded by 2–3 orders of magnitude net CO 2 production in the subsoil (7.5–50 cm). However, CO 2 originating from 5 cm depth and below in both land cover types could only explain up to 30% of the aboveground measured CO 2 flux, indicating that >70% of the total CO 2 respired and emitted to the atmosphere originated from the uppermost few cm of the soil. Net CO 2 production at different soil depths did not differ significantly between rubber plantations and natural forests. Our results indicate that SR characteristics in mature rubber plantation and natural forest were broadly similar, although dry season soil surface CO 2 fluxes were lower in rubber plantations. However, further information on the drivers of CO 2 production in the uppermost topsoil layers which are responsible for most CO 2 emissions is needed to understand the extent to which these results are generalisable.