Karst Forest Research Articles

Response of soil microbial community to plant composition changes in broad-leaved forests of the karst area in Mid-Subtropical China.

The rapid growth and expansion ofCryptomeria japonica (Thunb. ex L. f.) D. Don in karst area strongly affects plant composition of native deciduous broad-leaved forest, which seriously threat ecosystem function and service. Given the importance of soil microorganisms in regulating nutrients cycling and plant species coexistence, understanding soil microbial attributes and their relationships with soil and vegetation features in forests harboring different C. japonica abundance will help understanding the drivers of ecosystem function changes. Here we examined the diversity and composition of soil bacterial and fungal communities and their correlations with plant diversity as well as soil physicochemical properties in karst broad-leaved forests with different relative abundances of C. japonica (i.e., a high, moderate, low and no proportion level with a stem density of 1,487, 538, 156 and 0 plant/hm2, respectively) in Mid-Subtropical China. We found that soil pH decreased while soil water content (SWC), total nitrogen (TN), total phosphorus (TP) and total potassium (TK) tended to increase with the increase in C. japonica abundance. In contrast, soil available nitrogen (AN), available phosphorus (AP) and available potassium (AK) content declined by 26.1%∼49.3% under the high level of C. japonica abundance. A gradual decrease in relative abundance of Acidobacteria and Chloroflexi while a pronounced increase in relative abundance of Ascomycota and Basidiomycota were observed with increase of C. japonica abundance. Alternations in bacterial composition were closely related to changes in AP and AK, while the change of fungal structure was mainly related to SWC, soil organic carbon (SOC) and pH, indicating that bacterial community was sensitive to declines in soil available nutrients and fungal structure was sensitive to changes in soil physicochemical properties (i.e., pH and SWC) and organic carbon resource. Understory plants had the highest α-diversity in forest containing moderate abundance of C. japonica, which might be related to the high bacterial diversity. Our findings suggest conservation of soil bacterial and fungal taxa that are responsible for nutrients availability and carbon sequestration is of great significance for improving the resistance of natural deciduous broad-leaved forests to the rapid spread of C. japonica in karst areas. Moreover, Acidobacteria, Chloroflexi, Ascomycota and Basidiomycota are potential indicators for soil properties changes, which should be taken into consideration in karst forest managements.

Adaptation strategy of karst forests: Evidence from the community-weighted mean of plant functional traits.

Conservative survival strategy of plants growing in harsh karst habitats is observed from the view of plant functional traits, such as morphological traits and ecological stoichiometry. However, whether the plant communities in karst forests with high species turnover adopt a conservative strategy remains undetermined. This study comprehensively investigated the characteristics of functional traits of dominant plant species in four forests (i.e. Platycarya strobilacea, Quercus fabri, Quercus variabilis, and Pinus massoniana forests) in a trough‐valley karst watershed in Northern Guizhou Province, Southwestern China to explore the adaptation strategy of karst forests at the community level. At the organ and the species levels, traits differed among species, and the leaf and the bark morphological traits and root C:N:P ecological stoichiometry presented large interspecific variations. At the community level, the P. massoniana forest presented the lowest specific root length and dry matter content and tissue density of roots, branch, twig, and bark; the Q. fabri and the Q. variabilis forests displayed low specific leaf area and high dry matter content and tissue density of roots, branch, and twig; and the Platycarya strobilacea forest exhibited high specific leaf area. The P. massoniana forest was subjected to N and P colimitation, and the three other broad‐leaved forests were limited by P supply. The community‐weighted means rather than the arithmetic means of traits were preferential to represent the trait characteristics at the community level. From the view of plant functional traits at the community level, karst forests develop multiple functional traits like low specific leaf area, high dry matter content and tissue density of leaf, roots, branch, and twig, and decrease N and P investments in leaf for a conservative survival strategy to adapt to harsh habitats.

Characteristics and Drivers of Soil Organic Carbon Saturation Deficit in Karst Forests of China

Karst forests have complex and unique carbon cycle characteristics. Soil organic carbon saturation deficit (CSD) is an important indicator of soil organic carbon (SOC) sequestration potential; exploring its characteristics and driving factors is a priority theme in current research on the carbon cycles of terrestrial ecosystems. In this study, 171 topsoil samples from typical karst forests in southwest China were used as the study objects. A SOC maximum saturation capacity model was constructed using the boundary line method. The CSD is equal to the maximum saturated capacity of SOC minus the current SOC. We analyzed the CSD and its main driving factors in different regions and succession stages. The results showed that the fractions of carbon and SOC contents in the karst forests at different successional stages in descending order were as follows: climax stage > arbor stage > shrub stage > herb stage. The CSD was the highest at the herb stage in Maolan, Yuntai Mountain, and Dashahe at 83.04%, 89.99%, and 89.97%, respectively, followed by the shrub stage with 48.69%, 78.50%, and 84.95%, and the lowest at the arbor stage with 25.69%, 43.44%, and 60.49%. The main drivers of CSD in the karst forest of Maolan were litter carbon input, total nitrogen, total phosphorus, and total SOC, and were litter carbon input at Yuntai Mountain and litter carbon input and neutral phosphatase at Dashahe. The results indicate that the core driver of CSD in the karst forest is litter carbon input, and this can be adjusted in the future to regulate the carbon sequestration capacity of SOC.

Comparison of bacterial and fungal diversity and network connectivity in karst and non-karst forests in southwest China

Microbial communities contribute to sustaining the function of terrestrial ecosystems and are influenced by soil type and climate gradients. The effects of karst and non-karst soils on bacterial and fungal profiles for seven climate gradients were assessed to better understand bacterial and fungal diversity and community composition in response to soil type with changes in soil physicochemical properties under different temperatures and precipitations. Bacterial and fungal abundance, diversity, and community composition differed between karst and non-karst forests. Bacterial and fungal richness, Shannon index, and bacterial abundance in karst forests were higher than non-karst forests, but the fungal abundance was lower. Mean annual temperature was negatively correlated with bacterial diversity in the karst forest and fungal abundance in karst and non-karst forests. The community composition of bacteria and fungi differed among these two soil types. The karst forest had greater connectivity among bacterial and fungal communities than non-karst forests. The bacterial members of Acidobacteria, Proteobacteria, Actinobacteria, and fungal groups of Ascomycota and Basidiomycota were mainly connected with other taxa in the network, implying that taxa were associated with highly functional potential. The relative abundance of Actinobacteria and Ascomycota was higher in karst than in non-karst forests. Proteobacteria and Basidiomycota showed the opposite results. A random forest and multiple regression tree analyses revealed that soil properties, specifically pH, calcium, and total nitrogen, were the main factors influencing the variation in bacterial and fungal profiles between karst and non-karst forests. This study provides novel evidence that the abundant microbial taxa were kinless hubs in co-occurrence patterns. Controlling complex networks of species interactions may contribute to improving soil nutrient processes rather than microbial diversity, enhancing our understanding of developing sustainable recovery strategies in fragile ecosystems.

喀斯特森林常见树种倒木分解对土壤真菌群落组成及分布规律的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 喀斯特森林常见树种倒木分解对土壤真菌群落组成及分布规律的影响 DOI: 10.5846/stxb202101280295 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（32060266，31700385）；贵州省科技计划项目（黔科合基础[2020]1Y124）；贵州省一流学科建设项目（GNYL[2017]007） Effects of fallen woods decomposition of common tree species on soil fungal community composition and distribution in karst forest Author: Affiliation: Fund Project: 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:倒木是森林生态系统的重要组分，其分解调控着土壤的养分循环，同时也影响着土壤微生物群落结构。但目前鲜见关于倒木分解对土壤微生物群落影响方面的报道。选取贵州茂兰喀斯特常绿落叶阔叶混交林中处于轻、中和重度腐烂等级的狭叶润楠（Machilus rehderi）、枫香（Liquidambar formosana）、青冈栎（Cyclobalanopsis glauca）和圆果化香（Platycarya longipes）4种常见树种倒木为研究对象，以距倒木外围的3个不同水平距离（10cm、30cm和50cm）的土壤样品为实验材料，分析倒木树种、腐烂等级和距离对土壤真菌种类及多样性的影响。结果表明：1）喀斯特森林4种树种倒木所影响土壤真菌群落在门级分类上主要为子囊菌门、担子菌门和毛霉门，优势属有Mortierella spp.、Phlebia spp.、Pluteus spp.和Chaetomium spp.等；2）倒木的树种对土壤真菌群落相对丰度的影响有差异，圆果化香倒木下的土壤真菌丰富度Chao1指数显著高于青冈栎；3）随腐烂程度加深，4种树种倒木下的土壤真菌群落多样性呈显著增加趋势；4）土壤真菌群落丰度随着距倒木距离的增大（10-50cm）变化明显，如狭叶润楠影响的Pluteus spp.、Mortierella spp.和Ganoderma spp.，枫香的Chaetomium spp.，圆果化香的Mortierella spp.和青冈栎的Phlebia spp.和Oliveonia spp.等。本研究量化了喀斯特森林倒木所影响的土壤真菌群落组成及分布规律，在一定程度上为倒木分解与土壤微生物群落之间的作用机制的深入探索提供了科学依据。 Abstract:Fallen wood is an important component of the forest ecosystem, which plays an important role in ecological conservation, biodiversity maintenance, and forest renewal. Its decomposition regulates the nutrient cycle of the soil and often changed to changes in microbial community structure of the soil. Therefore, quantify the influence of the fallen wood on soil fungus community and distribution is very significance. However, there are few reports about the effects of decomposition of fallen wood on soil microbial community, especially in Maolan kast evergreen broad-leaved deciduous mixed forest, a rare remaining subtropical karst forest with strong original in China and even the world. In this paper, the fallen woods of four common tree species (Machilus rehderi, Liquidambar formosana, Cyclobalanopsis glauca, and Platycarya longipes) that are in mildly, moderately and severely deciduous decay levels in Maolan's evergreen and deciduous broad-leaved mixed forest in Guizhou are selected as the research object. Three different horizontal distances (10 cm, 30 cm, and 50 cm) from the outer edge of the fallen wood were used to analyze the effects of tree species, decay grade and distance on the types and abundance of soil fungi community. The results show that:1) the soil fungi affected by the fallen woods of the four tree species in the karst forest are mainly Ascomycota, Basidiomycota and Mucor in the phylum classification, and the dominant genera are Mortierella spp., Phlebia spp., Pluteus spp. and Chaetomium spp., etc; 2) Different tree species of fallen woods have different effects on the relative abundance of soil fungi communities. The soil fungi richness Chao1 index under the fallen wood of the Platycarya longipes is significantly higher than that of Cyclobalanopsis glauca; 3) With the deepening of decay, the soil fungal community diversity under the fallen wood of the four tree species showed a significant increasing trend; 4) The abundance of soil fungal communities changes significantly with the increase of the distance from the fallen wood (10- 50 cm), such as Pluteus spp., Mortierella spp. and Ganoderma spp. are affected by Machilus rehderi, Chaetomium spp. of Liquidambar formosana, Mortierella spp. of Platycarya longipes, Phlebia spp. and Oliveonia spp. of Cyclobalanopsis glauca, etc. This study quantified the soil fungal communities composition and distribution patterns affected by fallen woods in karst forests, and provided a scientific basis for further exploration of the mechanism of interaction between soil microbial communities and fallen wood decomposition to some extent. 参考文献 相似文献 引证文献

黔中北亚热带喀斯特次生林动态监测样地：物种组成与群落结构

多年来强烈的人为干扰导致我国西南喀斯特原生森林丧失殆尽并呈现植被灌丛化, 甚至石漠化现象。贵州普定县残存的片段化喀斯特次生林是黔中地区北亚热带森林植被的典型代表, 可作为监测该区域植被结构和动态的样本。在普定县天龙山建立2 hm²(200 m×100 m)森林固定样地, 对样地内胸径≥ 1 cm的所有木本植物进行了每木调查, 分析了木本植物的物种组成、区系特征、径级结构和空间分布格局。结果表明, 样地内有木本植物独立个体14, 025株, 隶属于34科55属66种。重要值最大的前3个科依次是壳斗科、胡桃科和樟科。在区系成分上, 温带区系成分占总属数的52.7%, 而热带区系成分占40.0%, 温带成分多于热带成分。稀有种有21种, 占总种数的31.82%。重要值≥ 1的物种共有13种, 贡献了88.81%的重要值, 重要值排名前三的物种分别是窄叶石栎(Lithocarpus confinis)、化香树(Platycarya strobilacea)和云南鼠刺(Itea yunnanensis)。样地内所有个体的平均胸径仅为5.12 cm, 整体径级分布呈倒“J”, 表明群落更新良好。部分优势种的空间分布表现出较明显的聚集性, 这可能与喀斯特生境的高度异质性有关。对北亚热带喀斯特次生林开展长期监测研究, 将有助于掌握亚热带喀斯特植被恢复过程中生物多样性维持和群落构建的机制。;China has the largest and widest karst regions in the world, which is mainly distributed in the subtropical mountainous regions of southwest China where a unique type of karst vegetation grows. However, the karst forests in these regions have been degraded seriously due to strongly anthropogenic disturbance over many years. Therefore, vegetation thicketization and even rocky desertification have occurred in most karst regions in southwest China. The fragmented karst secondary forest in Puding County is a typical representative of the north subtropical forest vegetation in central Guizhou Province, and can be used as a sample for monitoring the vegetation structure and dynamics in this region. In this study, a 2 hm² (200m×100m) permanent forest plot was established in Tianlongshan in Puding County. Within this plot, all woody plants with a diameter at breast height (DBH)≥1 cm were mapped and identified at species level. Based on these data, the community composition and spatial structure of the vegetation community were analyzed. Results indicated that there were 14, 025 woody plant individuals belonging to 66 species, 55 genera and 34 families. The families with high importance values (Ⅳ) are Fagaceae, Juglandaceae, Lauraceae, Saxifragaceae, Rosaceae, Betulaceae, Rhamnaceae, etc. There were more temperate elements (52.7%) than tropical elements (40.0%) found both at genus level, which showed that the flora was mainly the type of transition from tropical to temperate in the study area. Twenty-one rare species (those with individual number fewer than two in the plot) accounted for 31.82% of the species total. The distribution of rare species in Tianlongshan plot might be determined by multi-dimensional factors such as climate, topography, biogeographic processes, as well as anthropogenic disturbance. In the plot, the 13 species with Ⅳ≥1 contributed 88.81% to the Ⅳ of the community. The species with high Ⅳ are Lithocarpus confinis, Platycarya strobilacea Itea yunnanensis, Machilus cavaleriei, Carpinus pubescens, Pittosporum brevicalyx, Lindera communis, etc. The average DBH of all individuals in the plot was only 5.12 cm, and DBH size-class distribution followed a reverse J shape, indicating abundant regeneration. The spatial distribution of some dominant woody species showed obvious aggregation pattern in plot scales possibly related to high habitat heterogeneity in karst landscape. Monitoring and research on secondary forests in the north subtropical karst region will contribute to further understanding the mechanisms of biodiversity maintenance and community assembly in the process of vegetation restoration. Further studies should concentrate on the maintenance mechanisms of diversity and stability of forest community, the coupling relationships between above-ground and underground ecological processes, and the response and adaptation of vegetation to short-term disturbance events and long-term climate change in the north subtropical karst regions in southwest China.

Size-dependent and environment-mediated shifts in leaf traits of a deciduous tree species in a subtropical forest.

AimsUnderstanding the joint effects of plant development and environment on shifts of intraspecific leaf traits will advance the understandings of the causes of intraspecific trait variation. We address this question by focusing on a widespread species Clausena dunniana in a subtropical broad‐leaved forest.MethodsWe sampled 262 individuals of C. dunniana at two major topographic habitat types, the slope and hilltop, within the karst forests in Maolan Nature Reserve in southwestern China. We measured individual plant level leaf traits (i.e., specific leaf area (SLA), leaf area, leaf dry‐matter content (LDMC), and leaf thickness) that are associated with plant resource‐use strategies. We adopted a linear mixed‐effects model in which the plant size (i.e., the first principal component of plant basal diameter and plant height) and environmental factors (i.e., topographic habitat, canopy height, and rock‐bareness) were used as independent variables, to estimate their influences on the shifts of leaf traits.Key ResultsWe found that (1) plant size and the environmental factors independently drove the intraspecific leaf trait shifts of C. dunniana, of which plant size explained less variances than environmental factors. (2) With increasing plant size, C. dunniana individuals had increasingly smaller SLA but larger sized leaves. (3) The most influential environmental factor was topographic habitat; it drove the shifts of all the four traits examined. Clausena dunniana individuals on hilltops had leaf traits representing more conservative resource‐use strategies (e.g., smaller SLA, higher LDMC) than individuals on slopes. On top of that, local‐scale environmental factors further modified leaf trait shifts.ConclusionsPlant size and environment independently shaped the variations in intraspecific leaf traits of C. dunniana in the subtropical karst forest of Maolan. Compared with plant size, the environment played a more critical role in shaping intraspecific leaf trait variations, and potentially also the underlying individual‐level plant resource‐use strategies.

天坑森林植物群落叶功能性状、物种多样性和功能多样性特征

PDF HTML阅读 XML下载 导出引用 引用提醒 天坑森林植物群落叶功能性状、物种多样性和功能多样性特征 DOI: 10.5846/stxb202110273025 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（31960047）；珍稀濒危动植物生态与环境保护教育部重点实验室研究基金（ERESEP2019Z04）；广西重点研发计划项目（桂科AB21220057）；广西漓江流域景观资源保育与可持续利用重点实验室研究基金（LRCSU21Z0101） Leaf functional traits, species diversity and functional diversity of plant community in Tiankeng forests Author: Affiliation: Fund Project: 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:以天坑内部-边缘-外部森林植物群落为研究对象，通过调查植物的群落结构、叶功能性状，探究天坑内外森林植物群落叶功能性状、物种多样性和功能多样性变化特征及其内在关联，为深入了解负地形森林生态系统的功能和恢复退化喀斯特地区的植被提供一定参考。研究结果如下：（1）比叶面积（198.75 cm2/g））、叶面积（42.70 cm2）、叶磷含量（1.70 g/kg）和叶钾含量（10.27 g/kg）在天坑内部最高，叶组织密度（0.32 g/cm3）和叶干物质含量（0.41 g/g）在天坑外部最高，天坑内外森林均易受到磷限制，表明随天坑内部-边缘-外部生境变化，植物对环境的适应机制和生存策略发生了部分调整，物种的防御策略增强，生长投入策略减弱。（2） Shannon-Wiener指数（2.82）、Simpson指数（0.92）和Pielou's均匀度指数（0.87）均以天坑外部最高，功能丰富度（1.05）、功能离散度（1.88）和Rao's二次熵（4.52）以天坑内部最高，表明随天坑内部-边缘-外部生境的变化，植物功能性状的差异减少，物种分布及其功能性状分布总体上更为均匀、物种数量增多。（3）物种多样性指数之间、功能多样性指数之间存在较强的相关性，表明物种多样性指数之间、功能多样性指数之间存在不同的制约关系。（4）叶功能性状与物种多样性、功能多样性的相关性强，物种多样性和功能多样性之间相关性较弱，表明叶性状对生态学过程的变化较为敏感，叶功能性状与物种多样性之间存在较强的耦合关系。 Abstract:To explore leaf functional traits, species diversity, and functional diversity characteristics and correlation of plant community in Tiankeng forests will help to build the context of leaf traits, species diversity, and functional diversity research context, and further understand the process and functions of the ecological system in the negative terrain forest, and provide a scientific basis for restoration and reconstruction of the vegetation in degraded karst areas. This paper takes the woody plant community in three habitats (the inside of Tiankeng, the fringe of Tiankeng, and the outside of Tiankeng) of Dashiwei Tiankeng Group as the object, to study the leaf functional traits, species diversity, functional diversity characteristics and their interactions, through community investigation and leaf functional traits measurement. The results are as follows:(1) woody plant grown in the inside of Tiankeng shows the highest specific leaf area (SLA:198.75 cm2/g), leaf area (LA:42.70 cm2), leaf phosphorus content (LPC:1.70 g/kg) and leaf potassium content (LKC:10.27 g/kg), in the outer of Tiankeng presents the highest leaf tissue density (LTD:0.32 g/cm3) and leaf dry matter content (LDMC:0.41 g/g), and the growth of woody plant is limited by P in Tiankeng forests and nearby karst forests. With the variation of habitats from the inner to the outer of Tiankeng, partial adjustments are made in the adaption mechanism and survival strategy of the woody plant. A quick defense strategy on investment for the species increases, while a slow growth strategy on investment of species is weak. (2) Shannon-Wiener index (2.82), Simpson index (0.92) and Pielou's evenness index (0.87) in the outside of Tiankeng are the highest, and the functional richness index (1.05), function dispersion index (1.88) and Rao's quadratic entropy index (4.52) in the inside of Tiankeng are the highest. With the variation in the inner-edge-outer habitats of Tiankeng community, the differences in plant functional traits reduce, the range of species distribution and functional traits are steady, and the individual of species increases. (3) There is significantly correlated to each species diversity and functional diversity, indicating that there are different restrictive relationships between species diversity and functional diversity. (4) The leaf functional traits are significantly correlated with species diversity and functional diversity, and the correlation between species diversity and functional diversity is weak, indicating that leaf traits are more sensitive to variation of ecological processes and there is a strong coupling relationship between leaf functional traits and species diversity. 参考文献 相似文献 引证文献

Effects of environmental factors on quantitative characteristics of woody plant sexual system in Maolan karst forest

Effects of environmental factors on quantitative characteristics of woody plant sexual system in Maolan karst forest

Tree Biomass Estimation in Karst Forest of West Papua, Indonesia

Indonesia is estimated to have 14,5 million hectares of karst areas. The characteristic of karst vegetation is specific, one of which is the dominance of small trees. With all of the potency, their vegetation acts as a significant carbon sequester and store it in biomass. This study aims to estimate and discuss biomass estimation in the karst forest within the Nature Recreational Park of Beriat, a protected area in South Sorong, West Papua. A total of 28 plots were made in the forest using the purposive random sampling method. Tree biomass (DBH ≥10 cm) was estimated using five different allometric equations. The results showed that the biomass was estimated at ca. 264 Mg ha-1 (95 % CI: 135-454 Mg ha-1). While small trees (DBH 10 – 30 cm) only contribute 30 % of the total biomass, about 38 % of the biomass is the contribution of large trees (DBH >50 cm), where Pometia pinnata contributes ca. 39 % of the biomass at plot-level. The use of various allometric equations results in different biomass estimates and biases with deviations ranged from -14.78 % to +17.02 % compared to the reference equation. Therefore, the selection of allometric equations used must be considered carefully to reduce uncertainties in biomass estimation.

Tree Biomass Estimation in Karst Forest of West Papua, Indonesia

Indonesia is estimated to have 14,5 million hectares of karst areas. The characteristic of karst vegetation is specific, one of which is the dominance of small trees. With all of the potency, their vegetation acts as a significant carbon sequester and store it in biomass. This study aims to estimate and discuss biomass estimation in the karst forest within the Nature Recreational Park of Beriat, a protected area in South Sorong, West Papua. A total of 28 plots were made in the forest using the purposive random sampling method. Tree biomass (DBH ≥10 cm) was estimated using five different allometric equations. The results showed that the biomass was estimated at ca. 264 Mg ha-1 (95 % CI: 135-454 Mg ha-1). While small trees (DBH 10 – 30 cm) only contribute 30 % of the total biomass, about 38 % of the biomass is the contribution of large trees (DBH >50 cm), where Pometia pinnata contributes ca. 39 % of the biomass at plot-level. The use of various allometric equations results in different biomass estimates and biases with deviations ranged from -14.78 % to +17.02 % compared to the reference equation. Therefore, the selection of allometric equations used must be considered carefully to reduce uncertainties in biomass estimation.

Leaf Elemental Concentrations, Stoichiometry, and Resorption in Guam’s Coastal Karst Forests

Greater knowledge concerning the interspecific diversity of the plant leaf ionome is required to effectively understand the spatiotemporal dynamics of biogeochemistry, but Micronesia has been ignored in this literature. The objectives of this study were to quantify the leaf ionome, resorption efficiency, and stoichiometry of leaves from 25 plant species representing Guam’s coastal karst forests. Carbon and nitrogen were quantified by dry combustion, and other minerals and metals were quantified by spectrometry. Nitrogen and calcium concentrations in Guam’s green leaves exceeded the published global means, but manganese and copper concentrations were less than the global means. The remainder of the elements were within the expected ranges. Nutrient resorption rates exhibited a decreasing order of potassium > phosphorus > nitrogen > zinc > copper. The term “accretion efficiency” is introduced to describe the accumulation of an element throughout leaf aging and senescence, and calcium and iron exhibited substantial accretion efficiency in this study. Stoichiometry relations indicated that Guam’s karst forest is most limited by phosphorus and then secondarily limited by nitrogen, although several individual taxa exhibited co-limitation by potassium. Five of the species are officially listed on extinction threat lists. Of these, the Malvaceae tree Heriteria longipetiolata exhibited leaf traits depicting the most recalcitrant litter characteristics, and the Fabaceae tree Serianthes nelsonii exhibited leaf traits depicting the most labile litter characteristics. The contributions of these two tree species to spatiotemporal diversity in biogeochemistry appear to be profound, indicating species recovery efforts are of paramount importance for maintaining ecosystem function and soil heterotroph biodiversity in northern Guam.

Diazotroph and arbuscular mycorrhizal fungal diversity and community composition responses to karst and non-karst soils

Diazotrophs and arbuscular mycorrhizal fungi (AMF) are important functional microbes that provide and transport nutrients to plants. Diazotroph and AMF diversity and community composition were investigated in karst mature forests (MFs) and non-karst forests, as well as in croplands (CRs) as a reference. Diazotroph diversity and community composition significantly shifted in MFs between karst and non-karst soils, with a higher diazotroph richness and Shannon index in karst MFs than in non-karst soils. Similar levels of AMF diversity and community composition were observed between karst and non-karst CRs and MFs. According to the co-occurrence network analysis results, the pairs of correlation links within the diazotroph and AMF groups were higher in karst MFs than in non-karst MFs, whereas this interaction was lower in karst CRs than in non-karst CRs. The diazotroph genera Bradyrhizobium and Anabaena and the AMF genera Glomus and Rhizophagus were mostly correlated with other species in both karst and non-karst soils. Diazotrophs and AMF communities were mainly affected available nutrients (e.g., nitrogen and phosphorus) and environmental factors (e.g., temperature and precipitation), respectively. Soil calcium content was an important factor that affected the distributions of diazotrophs and AMF between karst and non-karst soils. Overall, our study suggested that the increased interactions between diazotrophs and AMF in karst forests, as compared with those in non-karst soil, led to the stability of the diazotrophs and AMF co-occurrence patterns for maintaining nutrients that are effectively absorbed and utilized. Thus, strengthening the cooperative relationships between diazotrophs and AMF are important and necessary in calcareous soils during natural vegetation restoration.

Shifts in Forest Species Composition and Abundance under Climate Change Scenarios in Southern Carpathian Romanian Temperate Forests

The structure and functioning of temperate forests are shifting due to changes in climate. Foreseeing the trajectory of such changes is critical to implementing adequate management practices and defining long-term strategies. This study investigated future shifts in temperate forest species composition and abundance expected to occur due to climate change. It also identified the ecological mechanisms underpinning such changes. Using an altitudinal gradient in the Romanian Carpathian temperate forests encompassing several vegetation types, we explored forest change using the Landis-II landscape model coupled with the PnET ecophysiological process model. We specifically assessed the change in biomass, forest production, species composition and natural disturbance impacts under three climate change scenarios, namely, RCP 2.6, 4.5 and 8.5. The results show that, over the short term (15 years), biomass across all forest types in the altitudinal gradient will increase, and species composition will remain unaltered. In contrast, over the medium and long terms (after 2040), changes in species composition will accelerate, with some species spreading (e.g., Abies alba Mill.) and others declining (e.g., Fagus sylvatica L.), particularly under the most extreme climate change scenario. Some forest types (e.g., Picea abies (L.) karst forests) in the Southern Carpathians will notably increase their standing biomass due to climate change, compared to other types, such as Quercus forests. Our findings suggest that climate change will alter the forest composition and species abundance, with some forests being particularly vulnerable to climate change, e.g., F. sylvatica forests. As far as productivity and forest composition changes are concerned, management practices should accommodate the new conditions in order to mitigate climate change impacts.

Soil macro‐ and mesofauna‐mediated litter decomposition in a subtropical karst forest

AbstractThis study aims to quantify the effect of different soil fauna on forest litter decomposition processes under natural conditions in the Maolan karst area of southwest China. Leaf litters of two typical evergreen species (CG, Cyclobalanopsis glauca and KS, Kmeria septentrionalis) were selected to conduct a field decomposition experiment using the mesh bags with three different apertures (5, 2, and 0.03 mm). Mass remaining and nutrient variation in the litterbags were determined for one year at 3‐month intervals. The results showed that litter decomposition rate in different mesh sizes litterbags were in the order of 5 mm >2 mm >0.03 mm. Soil macrofauna had a significant effect on litter decomposition in the two types of litter and the mixture of the two. The most considerable mesofauna effect was found in the KS litter, which is 36.5% ascribed by the lowest C/N ratio (high quality). Soil mesofauna had a more significant effect on N, which was time‐dependent. Moreover, the fauna richness and abundance were affected by the decomposition time but not limited by the litter quality. This study illustrated that soil macrofauna has a significant influence on litter decomposition. The effect of mesofauna on litter mass loss and nitrogen release are determined by litter quality in the subtropical karst forest ecosystems.Abstract in Chinese is available with online material.

Non-linear Tree Height (h-d) Model Development and Forest Resource Productivity Assessment of Diguyo Limestone Forest within Northern Sierra Madre Natural Park

Forest resource monitoring of different forest types is of great importance in sustainable forest management and climate change mitigation. Monitoring the productivity of forest resources could be achieved by modeling the basic tree parameters necessary for forest growth and yield. This study was conducted to develop a height-diameter at breast height (h-d) model necessary for tree height (h) estimation since h measurement is difficult in the field, especially in dense forests, and to estimate the forest productivity of the Diguyo limestone forest within the Northern Sierra Madre Natural Park (NSMNP). The diameter at breast height (d) and h of 124 trees were measured in seven 400-m2 plots as the basis for the model development. The h-d model was developed using different non-linear models such as the Chapman-Richards (CR), exponential (EX), Korf/Lundqvist (KL), modified logistic (ML), Schnute (SC), and Weibull (WE) models. The models were evaluated using the adjusted coefficient of determination (R2 adjusted), Akaike information criterion (AIC), Bayesian information criterion (BIC), mean absolute error (MAE), root mean square error (RMSE), percentage root mean squared error (PRMSE), and root mean squared percentage error (RMSPE). The performance of the species-specific allometric models and the generic models were compared for the biomass productivity of the limestone forest. Results showed that the CR h-d model performed best with MAE, RMSE, PRMSE, RMSPE, R2 adjusted, AIC, and BIC values of 1.47 m, 1.74 m, 19.31%, 28.71%, 0.79, 32.46, and 36.00, respectively. The highest average predicted tree biomass and carbon stock of the Diguyo limestone forest was 112.52 ± 97.65 t/ha and 50.64 ± 43.94 tC/ha, respectively, which is lower than other karst forests in Asia. The low forest resource productivity is due to the physical condition of the forest aggravated by natural and anthropogenic disturbances, thereby needing immediate attention to achieve forest sustainability.

Drivers of tree survival in an evergreen-deciduous broadleaf karst forest in southwest China

Understanding tree mortality and the underlying driving mechanisms is essential for understanding forest dynamics and tree species coexistence. Based on survival data from two censuses of a large (25-ha) fully mapped subtropical karst forest plot, the present study quantified the simultaneous effects of tree size, soil, topography, and neighborhoods on tree mortality at three levels (community, guild, and species). Our study suggested that tree size, biotic neighborhood, and abiotic factors influenced tree survival, but the relative importance of these mechanisms for tree mortality differed greatly among species guilds. Of the variables tested, tree size was the most important driver of tree survival, and had a strong negative relationship with tree mortality, while abiotic variables and neighborhood effects were of secondary importance. Regarding abiotic factors, both soil and topography affected tree survival. Abiotic factors generally influenced the survival of common trees, smaller individuals, and slow growing, shade-tolerant understory species. Regarding biotic factors, the biotic neighborhood effects may be irrelevant for tree survival under these conditions, as indicated by the results of both conspecific neighbor density and heterospecific neighbor density analyses. These results suggested that it is necessary to simultaneously consider the relative importance of intrinsic (tree size) and extrinsic (biotic and abiotic) factors on forest dynamics to better understand, conserve, and manage subtropical karst forests.

Microbial Resource Limitation in Aggregates in Karst and Non-Karst Soils

Karst is a widespread ecosystem with properties that affect the microbial activity and storage and cycling of soil organic carbon. The mechanisms underlying microbial resource availability in karst, which limit the microbial growth and activity in soil aggregates, remain largely unknown. We assessed the microbial resource limitations using exoenzymatic stoichiometry and key extracellular enzyme activities in bulk soil and aggregates in karst and non-karst forest soils. Soil organic carbon, total nitrogen, and microbial biomass carbon and nitrogen were significantly higher in bulk soil and the aggregate fractions in karst forests. However, the microbial biomass accumulation was higher in finer aggregates than in macroaggregate fractions. This may be attributed to the surface area of finer aggregates that increase the microbial C accumulation. In karst forests, the activity of extracellular enzymes β-d-glucosidase, β-N-acetylglucosaminidase, α-glucosidase, and α-d-1,4-cellobiosidase was two to three times higher in microaggregates (0.053–0.25 mm) and mineral fractions (<0.053 mm) than in macroaggregates. This coincided with the distribution of microbial biomass carbon and phosphorus in finer aggregate fractions. The microorganisms in bulk soil and aggregates in karst forests were largely co-limited by carbon and phosphorus and rarely by nitrogen and only by phosphorus in non-karst soils. The microbial phosphorus limitation in non-karst soils was alleviated in finer soil aggregates, while these fractions reflected slightly higher. microbial C limitations than bulk and other aggregates in karst forests. The patterns of microbial resource limitations in the bulk and aggregate fractions in karst ecosystems reflected the regulation of enzyme activity and soil organic carbon accumulation in finer aggregate fractions but not in other aggregates.

Stoichiometric Characteristics of Leaf Nutrients in Karst Plant Species During Natural Restoration in Maolan National Nature Reserve, Guizhou, China

ABSTRACT The cycling process of carbon (C), nitrogen (N), phosphorus (P), and potassium (K) elements plays a crucial role in ecosystem functions of karst forests. The leaf stoichiometry characteristics in four successional stages are studied in a karst area, southwest China. The N and P contents in each successional stage are generally higher in the growth phase (May–June 2016) than in the senescence phase (October–November 2015) but there are lower N: P ratios in the growth phase than in the senescence phase, showing a clear seasonal controls and coinciding with the Growth Rate Hypothesis. In the growth phase, the phytocommunity is mainly limited by the N content. In the senescence phase, all communities from the early successional stage to the mid successional stage are prone to N limitation but they are significantly affected by a combination of N, P, and K from the late successional stage to the climax successional stage and the P limitation are stronger in the climax successional stage. The specific leaf area is the most important impact factor to leaf stoichiometric characteristics at each successional stage. These results indicate that nitrogen addition in growth stage may promote vegetation restoration and karst forest ecosystem stability.

Correction to: Contrasting rhizosphere soil nutrient economy of plants associated with arbuscular mycorrhizal and ectomycorrhizal fungi in karst forests

Correction to: Contrasting rhizosphere soil nutrient economy of plants associated with arbuscular mycorrhizal and ectomycorrhizal fungi in karst forests