Ecological stoichiometry of C, N, P and Si of Karst Masson pine forests: Insights for the forest management in southern China.

Ecological stoichiometry is an effective method to study the stoichiometric relations and laws of elements in biogeochemical cycle, widely used in studies on nutrient cycles, limiting elements and nutrient utilization efficiency in ecosystems. To explore C, N, P, and Si stoichiometric characteristics and reveal these nutrient cycle processes and mechanisms in the karst Masson pine forests, the typical Masson pine forests of the three different stand ages in southern China were selected as the research objects and the C, N, P, and Si stoichiometric characteristics of soil-plant-litter continuum were studied. The followed results and conclusions were obtained: 1) Content range of TOC (total organic carbon), TN (total N), TP (Total P) and TSi (total Si) of the Masson pine forests was 288.31-334.61, 0.34-6.66, 0.11-1.05, and 0.76-11.4 g·kg-1, respectively. And the ratio range of C:N, C:P, C:Si, N:P, N:Si, and P:Si was 49.95-913.57, 99.98-2872.18, 22.48-429.31, 1.85-6.33, 0.17-6.01, and 0.04-0.91, respectively. 2) The significant differences in C, N, P, and Si stoichiometric characteristics were present between different organs or different forest ages. Leaves had the highest N and P content, while roots were the best enriched organ of Si element. Si content and C:Si were obviously correlated with forest age. 3) Significant N limitation was present in the Masson pine forests. And in the young and middle-aged forests, N limitation was more obvious. 4) The litter nutrients mainly came from branches. And the litter decomposed fast, which played an important role in the nutrient return of barren karst soil. The present results not only revealed the stoichiometric characteristics and cycling processes of C, N, P, and Si elements in the Masson pine forests, but also provided important scientific bases for the artificial management of Masson pine plantations in southern China.

PhytOC sequestration characteristics and phytolith carbon sink potential of karst Masson pine forest in southern China.

Masson pine forest is an extremely important component of terrestrial ecosystems and plays a significant ecological function in forest carbon sink in China. Phytolith-occluded organic carbon (PhytOC) is the important long-term stable carbon sink mechanism in terrestrial ecosystems. To provide scientific bases for the accurate estimation of phytolith carbon sink and precise management of Masson pine forests, PhytOC sequestration and accumulation of the three typical forest ages of Masson pine in southern China karst area were studied in the present study. Although the sampling pots were still limited, PhytOC sequestration characteristics of the Masson pine forests were successfully clarified. The followed results and conclusions were obtained: 1) The range of PhytOC content, reserves, and sequestration rate of the Masson pine forests was 0.04-0.78 g·kg-1, 0.44-16.93 kg·hm-2, and 0.094-2.557 kg CO2 hm-2·a-1, respectively. 2) Among the three forest ages of Masson pine, the mature forest had the highest accumulation of PhytOC, and the middle-aged forest had the highest sequestration rate of PhytOC. Compared with biomass, vegetation productivity more positively significantly affected the PhytOC sequestration. 3) Among the three organs, leaves had the highest PhytOC content and trunks had the highest PhytOC reserves, which all took significant functions in the sequestration and accumulation of PhytOC. 4) Artificial measures to promote vegetation productivity, such as thinning, artificial tending, and low-efficiency forest transformation, will significantly increase the PhytOC sequestration and accumulation of Masson pine forests.

Phytolith occluded organic carbon in Fagopyrum (Polygonaceae) plants: Insights on the carbon sink potential of cultivated buckwheat planting.

Crop cultivation has great potential to result in a phytolith carbon sink and can play important roles in the long-term stable carbon sequestration of terrestrial ecosystems. Buckwheat, an important multigrain crop with a very long cultivation history, is widely planted around the world. The phytolith carbon sink potential of buckwheat planting is still limited in the in-depth understanding of biogeochemical carbon sequestration in croplands. In order to estimate the phytolith carbon sink potential of buckwheat planting, in the present study, six species including 17 populations of Fagopyrum plants were selected as study materials. Firstly, their phytoliths were extracted using the wet oxidation method; then, the phytolith-occluded organic carbon (PhytOC) contents were determined using the spectrophotometry method; finally, the phytolith carbon sink potential of buckwheat planting was estimated. Results showed the following: 1) The PhytOC content range of the six Fagopyrum species studied was 0.006%~0.038%, which was significantly lower than that of rice, wheat, sugarcane, and some cereal and oil crops. There were significant differences in total silicon, phytolith, and PhytOC content of Fagopyrum plants among the different species, different organs (root, stem, and leaf), and different living forms (annual, partly perennial, and completely perennial). There were significant positive relationships between PhytOC and phytolith content and between phytolith and total silicon content. 2) The average phytolith carbon sequestration rate of Fagopyrum esculentum and Fagopyrum tataricum planting was 2.62 × 10-3 and 1.17 × 10-3 t CO2 hm-2·a-1, respectively, being approximately equal to that of terrestrial shrub vegetation. 3) The global total amount of phytolith carbon sequestration of buckwheat planting reached 5,102.09 t CO2 in 2018, and the Chinese total amount of phytolith carbon sequestration of buckwheat cultivation was 624.79 t CO2 in 2020. The phytolith carbon sink of buckwheat planting had significant potential for playing obvious roles in the carbon cycle. The present results are of great significance in crop phytolith studies and provide important references for phytolith carbon sink potential estimation of farmland ecosystems.

[Effects of Land Use Change on Constitution, Stability, and C, N, P Stoichiometric Characteristics of Soil Aggregates in Southwest China Karst].

Responses of soil aggregate stability and nutrient stoichiometry to land use change are of great significance to the protection and restoration of fragile ecosystems. In order to explore the influence of the law of land use change on soil aggregate stability and C, N, and P nutrient stoichiometric characteristics in the karst ecosystem of Southwest China, a typical region of the Southwest China Karst was selected as the study area. A series of sample plots were established for the seven typical land use types, and the constitution; stability; and C, N, and P contents and stoichiometric ratios of soil aggregates were studied. The results showed that land use change significantly affected the soil aggregate stability. The soil aggregate stability of corn fields and abandoned land was relatively high, whereas that of grassland and bare land was relatively low. The soil aggregate stability generally decreased with the increase in soil layer. There were significant differences in the C, N, and P contents of soil aggregates between different land use types. The C and N contents of soil aggregates of open woodland and abandoned land were higher, the C and N contents of grassland were lower, and the P contents of soil aggregates of bare land and abandoned land were relatively higher. Land use change also significantly affected the stoichiometric ratio of soil aggregate C, N, and P. The C:N of soil aggregates of arbor forest land, open forest land, and abandoned land was relatively high, and that of grassland was the lowest. The C:P of soil aggregates of arbor woodland and open woodland was higher than that in shrub woodland and grassland. The soil aggregate N:P of arbor forest land, open forest land, and shrub forest land was higher and was significantly higher than that of bare land and abandoned land. There were significant or extremely significant correlations between the constitution and stability of soil aggregates and the stoichiometric characteristics of soil aggregate C, N, and P. Soil aggregate stability was positively correlated with the mass fraction of large soil aggregates. The mass fraction of large soil aggregates increased, and the stability of aggregates correspondingly increased, which was conducive to the maintenance and accumulation of soil C, N, and P nutrients. These results are of great significance for vegetation restoration, soil and water conservation, and land use regulation in karst ecosystems of Southwest China.

[Soil available nitrogen and phosphorus contents and the environmental impact factors across different land use types in typical karst rocky desertification area, Southwest China.] / å–€æ–¯ç‰¹çŸ³æ¼ åŒ–åœ°åŒºä¸åŒåœŸåœ°åˆ©ç”¨ç±»åž‹åœŸå£¤æ°®ç£·æœ‰æ•ˆæ€§åŠå ¶çŽ¯å¢ƒå½±å“å› å­.

In this study, we collected soil samples from four different land use types (forest land, shrub land, grassland and abandoned land) in Huajiang valley of Guizhou Province, a typical karst rocky desertification area in Southwest China. Correlation analysis and redundancy analysis were used to examine the distribution of available nitrogen (N) and available phosphorus (P) in diffe-rent soil layers from 0 to 30 cm and the relationships between soil environmental factors (soil physical indexes, organic carbon components, electrochemical properties, metal oxides and enzyme activities) and the contents of available N and available P. The results showed that the concentrations of soil total N, total P, available N, available P decreased significantly with the increases of soil depth. The concentrations of soil available N and available P in forest land and shrub land were significantly higher than those in grassland and abandoned land, which were significantly positively correlated with soil organic carbon composition, enzyme activity, surface electrochemical properties and amorphous mental oxide while significantly negatively correlated with soil silt and free metal oxides. Results of the redundancy analysis showed that the environmental factors affecting soil availa-ble N and available P of the four land use types were basically the same, with soil particulate organic carbon, total organic carbon and soil specific surface area playing a key role in driving the variations of soil available N and available P. The efficient explanation of variation to soil available N and P contents by soil particulate organic carbon might be due to the reduction of soil nutrient loss by the storage of N and P in organic matter. Except for high enzyme activity and electrochemical properties of forest land and shrub land, the higher soil available N and available P concentrations compared with grassland and abandoned land might be resulted from the inhibition of free iron and aluminum oxides information by higher soil organic carbon content and the reduced adsorption and fixation of N and P by iron and aluminum oxides.

Cluster analysis of karyotype similarity coefficients in Epimedium (Berberidaceae): insights in the systematics and evolution.

In order to evaluate the genome evolution and systematics, karyotype analysis of mitotic metaphase chromosomes in 51 taxa of Epimedium and two species of Vancouveria was conducted. The 53 taxa were clustered, based on their karyotype similarity coefficients. Results showed that the 53 taxa studied were all diploid with 12 chromosomes (2n = 2x = 12). Each taxon had one pair of satellites located on pair I of homologous chromosomes. Moreover, the karyotype types of the 53 taxa studied were all type 1A or 2A of Stebbins. It can be concluded that the karyotypes between species are indeed very similar and the genome of Epimedium was conservative in evolution. The cluster analysis of karyotype similarity coefficients could provide valuable clues for the systematics and taxonomy of Epimedium. Results of the cluster analysis strongly supported the previous taxonomic division of E. subg. Rhizophyllum and E. subg. Epimedium. The results also showed that the interspecific relationship was closely correlated with geographical distribution in E. subg. Epimedium and the taxa native to east Asia had the highest genetic diversity in Epimedium. Finally, the origin of the modern geographical distribution of Epimedium was inferred. Results of the present study have significant scientific values in further studies on resource utilisation, taxonomy and phylogeny in Epimedium.

[Effects of land use change on soil organic carbon and its components in karst rocky desertification of southwest China]. / è¥¿å—å–€æ–¯ç‰¹çŸ³æ¼ åŒ–çŽ¯å¢ƒä¸‹åœŸåœ°åˆ©ç”¨å˜åŒ–å¯¹åœŸå£¤æœ‰æœºç¢³åŠå ¶ç»„åˆ†çš„å½±å“.

Soil organic carbon (SOC) is the dynamic medium of carbon transfer and the main pathway of carbon transfer in the karst ecosystem. SOC and its components are the important parts in soil carbon cycling of karst ecosystem. However, few studies have focused on SOC and its components in the karst ecosystem. We analyzed the effects of land use change on the SOC content, SOC reserve (SOCS), water-soluble organic carbon (WSOC), easily oxidizable organic carbon (EOC), particu-late organic carbon (POC), and light fraction organic carbon (LFOC), and heavy fraction organic carbon (HFOC) and their distribution ratio, with six different land-use patterns [Zanthoxylum bungeanum forest (HJ), Hylocereus undulates forest (HL), mixed forest of Z. bungeanum and H. undulates (HHL), Sabina chinensis forest (YB), mixed forest of S. chinensis and Ligustrum luci-dum (YBN), and slope cropland (PD)] in Huajiang Canyon of Guanling County, Guizhou Pro-vince. Results showed that SOC and SOCS in YB, YBN and HJ were significantly higher than those in HL, HHL and PD. In the 0-20 cm soil layer, the concentrations of SOCS followed the order of HJ＞YB＞YBN＞PD＞HHL＞HL. Contents of WSOC, EOC, POC, LFOC and HFOC in YB, YBN, and HJ were all higher than those in the other three patterns. Significant positive correlations existed between SOC and each of its components (WSOC, EOC, POC, LFOC and HFOC), also between any two of those components. Z. bungeanum could be used as a priority economic species for the ecological rehabilitation of karst rocky desertification and mountain agriculture development in Southwest China. WSOC, EOC, POC, LFOC and HFOC could be used as indicators of soil organic carbon pool.

[Influence of Land Use Change on Litter and Soil C, N, P Stoichiometric Characteristics and Soil Enzyme Activity in Karst Ecosystem, Southwest China].

In this study, the litter and soil under four typical land use patterns of primary forest, shrub, grassland, and sloping land in Huajiang Karst Gorge in Guanling, Guizhou Province, were used to study the effects of land use change on the carbon(C), nitrogen(N), and phosphorus(P) stoichiometry characteristics of karst plant litter and soil as well as the effects on soil enzyme activities and their driving mechanism in Southwest China. The results showed significant differences in the litter-soil C, N, and P contents and soil enzyme activities among the four land use types. Compared with other regions, the litter and soil showed a pattern of high C, low N, high P and low C, low N, high P, respectively. Urease, sucrose, and amylase showed an order of primary forest > shrub forest > grassland > slope farmland, whereas alkaline phosphatase showed primary forest > shrub forest > slope farmland > grassland. The protection of primary forests should be considered in future ecological construction. The soil nutrients were significantly affected by litter C, N, P, and their ratios, although the soil enzyme activities were not significantly associated with the litter. Redundancy analysis showed that soil enzyme activity had extremely significant correlation with the soil total N (TN), water content (SWC), and C:N ratio (P<0.01) and relatively significant correlation with pH and the N:P ratio (P<0.05). The order of importance was shown to be TN > SWC > C:N > pH > N:P. The research results have significant value for the study of karst rocky desertification and karst ecosystem nutrient cycling.

Morphological, physiological, cytological and phytochemical studies in diploid and colchicine-induced tetraploid plants of Fagopyrum tataricum (L.) Gaertn.

BACKGROUND: Tartary buckwheat are very popular as an important functional food material and its cultivation is very widespread in our whole world, but there obviously lack works in the researches of genetic breeding for agricultural and medicinal utilization. The aim of this study is to obtain good germplasm resources for agricultural and medicinal use of tartary buckwheat (Fagopyrum tataricum) by inducing the tetraploid plants. RESULTS: Four cultivars of F. tataricum, that is, Qianwei 2#, Jinku 2#, Chuanqiao 1#, and Liuqiao 1# were selected to experiment. The tips of seedlings with two true leaves were treated by 0.25% (w/v) colchicine solution for 48, 72, and 96 h, respectively. The chromosome number of treated plants was determined by metaphase chromosome counting of root tip cells and PMCs (pollen mother cells) meiosis observation. Tetraploid induction successfully occurred in all three treatments with an efficiency ranging from 12.13 to 54.55%. The chromosome number of the diploid plants was 2n = 2x = 16, and that of the induced tetraploid plants was 2n = 4x = 32. The typical morphological and physiological qualities were compared between the control diploid and corresponding induced tetraploid plants. Results showed that the induced tetraploid plants had obviously larger leaves, flowers, and seeds. Moreover, the content of seed protein and flavonoid were also increased in the tetraploid plants. The pollen diameter and capsule size of diploid plants were significantly smaller than those of tetraploid plants. CONCLUSION: Fagopyrum tataricum can be effectively induced into tetraploids by colchicines. The tetraploid induction can produce valuable germplasm resources for breeding and is a practicable breeding way in F. tataricum.

A new species and a revised key of the genus Thoradonta (Orthoptera, Tetrigidae).

A new species of the genus Thoradonta (Orthoptera, Tetrigidae), Thoradonta varispina Zha & Sheng, sp. n., was found in Lengshuihe Nature Preserve, Jinsha, Guizhou, China. It is introduced with a description and photographs and compared with similar taxa. Ecology, habits, and morphological variation of the new species are discussed and illustrated. Generic characteristics of Thoradonta are updated and an updated key to all known species of Thoradonta is given.

The cytology, isozyme, HPLC fingerprint, and interspecific hybridization studies of genus epimedium (berberidaceae).

104 samples from 27 accessions belonging to 12 species of genus Epimedium were studied on the basis of cytology observation, POD (i.e., peroxide) isozyme, high performance liquid chromatography (i.e., HPLC) fingerprint, and interspecific hybridization. The cytology observation showed karyotypes of twelve species studied; all are 2A symmetry type of Stebbins standard and similar to each other, and except for karyotype of E. leptorrhizum which is 2n = 2x = 8m (2SAT) + 4sm, the rest are 2n = 2x = 6m (2SAT) + 6sm. Chromosomes C-banding of barrenwort species varies, with 15 to 22 bands, consisting of centromeric bands, intercalary bands, terminal bands, and middle satellite bands. Results of POD isozyme showed that the zymographs vary greatly and sixteen bands were detected in the eleven species, and each species has its own characteristic bands different from the others. Studies on the HPLC fingerprint showed that the HPLC fingerprint of different species has characteristic peaks, divided into two regions (retention time < 10 min and retention time > 10 min). Results of interspecific hybridization showed that crosses of any combination among seven species studied are successful and the rates of grain set vary greatly. Based on these results, the system and phylogeny of this genus were inferred.