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.

Forest characteristics and population structure of a threatened palm tree Caryota obtusa in the karst forest ecosystem of Yunnan, China

Aims Caryota obtusa of Arecaceae is a fascinating palm tree native to southwestern China, India, Myanmar, Thailand, Laos, and Vietnam. It is an economically important and threatened species and appears as a canopy dominant in some karst areas in Yunnan. We aim to clarify the forest structure, species diversity, population status and regeneration dynamics of C. obtusa in the karst forest ecosystem of Yunnan, China. Methods We established 56 vegetation plots dominated by C. obtusa in 10 counties of southern Yunnan. As based on the plot data, we analyzed the community stratification, floristic composition, and C. obtusa’s population structure. We used questionnaires to interview local people and recorded the human activity history on C. obtusa-dominated forests. Important findings: C. obtusa palm forests were distributed on limestone mountain slopes and gullies. There were seven forest community types. The stratification of each community included arborous layer, shrub layer and understory. The communities had rich species composition. For all the plots as a whole of each community type, Shannon-Wiener diversity index of either woody or herbaceous species ranged from 2.1-3.8. The DBH-class frequency distribution of C. obtusa was a multimodal type. The regeneration was sporadic and depended on intermediate natural disturbances. In current population structure, number of C. obtusa trees with small DBHs was consisted mainly of the forest communities with no or a slight degree of human disturbances. Intensive human activities terribly hindered C. obtusa’s recruitment, followed by medium intensity of human activities.

The Relative Importance of Niche Process and Neutral Process in the Community Assembly of Subtropical Karst Forest: A Perspective on the Changes of Species Distribution Patterns at Different Scales

Background and aimsThe importance of niche processes and neutral processes to community assembly has been affirmed by most studies, although their relative importance needs to be determined in many systems. Moreover, as the spatial scale changes, the ecological processes that determine the community pattern may differ. We tested these ideas in subtropical karst forest in southwestern China in order to aid efforts of community reconstruction.MethodsTo test the importance of niche-based and neutral mechanisms we compared the fit six models to the observed SAD of the plot at three different sampling scales (10 m × 10 m, 20 m × 20 m, 50 m × 50 m). We also used spatial autocorrelation and distance-based Moran's eigenvector maps (dbMEM) combined with variation partitioning to further determine the relative contribution of the niche process and the neutral process under different sampling scales.ResultsThe neutral theoretical and statistical models fit the observed species abundance distribution curve best at each sampling scale. And variation partitioning showed that although the contribution of spatial structure was lower at larger sampling scales, it was still important, suggesting that neutral processes drive community structure at all sampling scales. In contrast, habitat filtering and interspecies competition may lead to a net weakening of the contribution of the niche process to the species abundance pattern of the community because they act in opposite directions. ConclusionsIn the restoration and reconstruction of local karst forest communities, environmental heterogeneity, inter-species relationships, and geographic spatial differences should all be considered.

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.

Seven new species and seven new records of Begonia L. (Begoniaceae) in the flora of Laos

New species of Begonia L. in the flora of Laos presented in this paper were mainly found in the course of botanical surveys made in Hin Nam No National Protected Area, Nam Phouy National Protected Area, Khammouane Karst Forest, and Phou Khao Khouay National Protected Area.Additionally, herbaria presently available in Laos (HNL, FOF, NUoL, FRC), living plants, and alcohol preserved material at Pha Tad Ke Botanical Garden and the data accessible online at BM, E, K, LE, NY, P, and PE Herbaria were critically studied. The study conducted during 2012–2019 reveals seven new species for science and seven species newly recorded for the flora of Lao PDR. Species described as new for science are: B. glabritepala (found in Khammouane Province; it is most close to B. pierrei but differs in glabrous outer tepals of staminate flowers, pistillate flowers, capsules, petioles, peduncles and pedicles), B. heterocantha (found in Sainyabuli Province; most close to B. depingiana but differs in reddish purple, glandular pubescent abaxial leaf surface, glandular pubescent pedicel, and outer tepals of pistillate flowers sparsely white glandular pubescent), B. lanxangensis (found in Vientiane Province; most close to B. paleacea but differs in elongate tubers, ovate-lanceolate, obscurely asymmetrical to symmetrical leaves, and glabrous pedicels), B. parviglandulosa (found in Vientiane Province; most close to B. martabanica but differs in smaller habit, reniform-cordate leaves and glandular indumentum on peduncle, pedicle and capsules), B. pseudobrandisiana (found in Khammouane Province; most close to B. brandisiana but differs in pistillate flowers with five elliptic-oblanceolate tepals), B. tripartifolia (found in Khammouane Province; most close to B. tricuspidata but differs in leaves palmate triangular-ovate, with deeply lobed lacerate margin, pistillate flower of five tepals, and ovary with unequal wing), and B. viriditenebris (found in Khammouane Province; most close to B. sinuata but differs in single leaf, indumentum of bristle hairs and reddish or bronzy green adaxial leaf surface, and three styles). The following species discovered and recorded for the flora of Laos at first are: B. hatacoa (known in Nepal, Bhutan, NE India, Myanmar, Thailand, and Vietnam), B. hemsleyana (China, Vietnam), B. labordei (NE India, Myanmar, S China, Vietnam), B. longifolia (tropical zone from NE India to Indonesia), B. minuscula (Vietnam), B. parvula (S China), and B. subperfoliata (Myanmar, Thailand, S Vietnam). Descriptions and line drawings are provided for all newly described species. Photographic illustrations, data on phenology, habitat, and notes on morphological variations and relations are given for all studied species.

Calcium Biogeochemical Cycle in a Typical Karst Forest: Evidence from Calcium Isotope Compositions

In order to better constrain calcium cycling in natural soil and in soil used for agriculture, we present the δ44/40Ca values measured in rainwater, groundwater, plants, soil, and bedrock samples from a representative karst forest in SW China. The δ44/40Ca values are found to differ by ≈3.0‰ in the karst forest ecosystem. The Ca isotope compositions and Ca contents of groundwater, rainwater, and bedrock suggest that the Ca of groundwater primarily originates from rainwater and bedrock. The δ44/40Ca values of plants are lower than that of soils, indicating the preferential uptake of light Ca isotopes by plants. The distribution of δ44/40Ca values in the soil profiles (increasing with soil depth) suggests that the recycling of crop-litter abundant with lighter Ca isotope has potential effects on soil Ca isotope composition. The soil Mg/Ca content ratio probably reflects the preferential plant uptake of Ca over Mg and the difference in soil maturity. Light Ca isotopes are more abundant in mature soils than nutrient-depleted soils. The relative abundance in the light Ca isotope (40Ca) is in the following order: farmland > burnt grassland > forests > grassland > shrubland. Our results further indicate that biological fractionation in a soil–plant system is a vital factor for Ca–geochemical transformations in soil surface systems.