Phylogeny of Libellulidae (Odonata: Anisoptera): comparison of molecular and morphology-based phylogenies based on wing morphology and migration.

BACKGROUND: Establishing the species limits and resolving phylogenetic relationships are primary goals of taxonomists and evolutionary biologists. At present, a controversial question is about interspecific phylogenetic information in morphological features. Are the interspecific relationships established based on genetic information consistent with the traditional classification system? To address these problems, this study analyzed the wing shape structure of 10 species of Libellulidae, explored the relationship between wing shape and dragonfly behavior and living habits, and established an interspecific morphological relationship tree based on wing shape data. By analyzing the sequences of mitochondrial COI gene and the nuclear genes 18S, 28S rRNA and ITS in 10 species of dragonflies, the interspecific relationship was established. METHOD: The wing shape information of the male forewings and hindwings was obtained by the geometric morphometrics method. The inter-species wing shape relationship was obtained by principal component analysis (PCA) in MorphoJ1.06 software. The inter-species wing shape relationship tree was obtained by cluster analysis (UPGMA) using Mesquite 3.2 software. The COI, 18S, ITS and 28S genes of 10 species dragonfly were blasted and processed by BioEdit v6 software. The Maximum Likelihood(ML) tree was established by raxmlGUI1.5b2 software. The Bayes inference (BI) tree was established by MrBayes 3.2.6 in Geneious software. RESULTS: The main difference in forewings among the 10 species of dragonfly was the apical, radial and discoidal regions dominated by the wing nodus. In contrast, the main difference among the hindwings was the apical and anal regions dominated by the wing nodus. The change in wing shape was closely related to the ability of dragonfly to migrate. The interspecific relationship based on molecular data showed that the species of Orthetrum genus branched independently of the other species. Compared to the molecular tree of 10 species, the wing shape clustering showed some phylogenetic information on the forewing shape (with large differences on the forewing shape tree vs. molecular tree), and there was no interspecific phylogenetic information of the hindwing shape tree vs. molecular tree. CONCLUSION: The dragonfly wing shape characteristics are closely related to its migration ability. Species with strong ability to migrate have the forewing shape that is longer and narrower, and have larger anal region, whereas the species that prefer short-distance hovering or standing still for a long time have forewing that are wider and shorter, and the anal region is smaller. Integrating morphological and molecular data to evaluate the relationship among dragonfly species shows there is some interspecific phylogenetic information in the forewing shape and none in the hindwing shape. The forewing and hindwing of dragonflies exhibit an inconsistent pattern of morphological changes in different species.

Reports of two peculiar pigmented new species of genus Homidia (Collembola: Entomobyridae) from Southern China, with description of subadults chaetotaxy.

Two new species with peculiar pigmentation of the genus Homidia from Guangdong Province, Southern China are described here, Homidia chroma sp. nov. and Homidia leniseta sp. nov. H. chroma is characterized by chrome pigmentation on lateral side of terga, two macrochaetae on medial abdominal segment (Abd.) III and six macrochaetae on postero-medial Abd. IV, up to 68 sensory chaetae present on Abd. IV, and five apical smooth chaetae on posterior face of ventral tube. H. leniseta is easily identified by unique colour pattern, smooth labial chaetae l2, G1-4 and H1-3, and short trichobothria on Abd. II-IV. Illustrations of adults of this two new species, chaetotaxy of the first instar larvae of H. chroma and subadults of H. leniseta are provided herein.

[Effects of soil fauna on microbial community during litter decomposition of Populus simonii and Fargesia spathacea in the subalpine forest of western Sichuan, China.] / å·è¥¿äºšé«˜å±±æ£®æž—åœŸå£¤åŠ¨ç‰©å¯¹æ¨æ ‘å’Œç®­ç«¹å‡‹è½ç‰©åˆ†è§£è¿‡ç¨‹ä¸­å¾®ç”Ÿç‰©ç¾¤è½çš„å½±å“.

To understand the relationship between soil fauna and microorganism in the detrital food chain during litter decomposition, leaf litters of poplar (Populus simonii) and fargesia (Fargesia spathacea) in a subalpine forest of western Sichuan were taken as study objects. Phospholipid fatty acid (PLFAs) biomarker method was used to determine the effects of soil fauna on the abundance, structure and diversity of microbial community during the decomposition of leaf litter of two species from April 2016 to April 2018 with in situ control experiment. The results showed that the presence of soil fauna significantly affected the microbial PLFAs content during the decomposition of both species, reducing the PLFAs content in the first 240 days and increasing the PLFAs content in the 360 to 480 days. Soil fauna participation reduced the ratio of fungi to bacteria in the decomposition of poplar litter, and increased the ratio of gram-positive bacteria (G+) to gram-negative bacteria (G-), which had the opposite effect on the ratio of fungi/bacteria and G+/G- in the decomposition of fargesia litter. Microbial diversity and evenness maintained a high level in 120th and 480th days of the decomposition, and decreased sharply in 360th and 720th days of decomposition. Soil fauna participation significantly affected microbial diversity and evenness of poplar litter, but it had no signifi-cant effect on fargesia litter. The effects of soil fauna on the changes of litter PLFAs content were different with the decomposition days and tree species. The interaction between soil fauna and microbial community during litter decomposition in subalpine forest varied with seasons and tree species.

[Effects of canopy on the redistribution of potassium and sodium ions in rainfall in Quercus acutissima and Camptotheca acuminata mixed plantation of the rainy area of western China]. / åŽè¥¿é›¨å±åŒºéº»æ Ž-å–œæ ‘äººå·¥æ··äº¤æž—æž—å† å¯¹é™é›¨ä¸­é’¾å’Œé’ ç¦»å­å†åˆ†é çš„å½±å“.

The role of canopy in redistributing rainwater K+ and Na+ at different phenological stages (leafless stage, leaf expanding stage, frondent leaf stage and senesced leaf stage) was investigated in Quercus acutissima and Camptotheca acuminata mixed plantation in Mt. Lingyan of Dujiangyan city from December 2016 to November 2017. The concentrations of K+ and Na+ were 1.87 and 1.46 mg·L-1 in the rainfall, respectively, and 5.78 and 1.39 mg·L-1 in the throughfall, respectively. The highest and lowest K+ concentrations in the rainwater were found at leaf expanding stage and frondent leaf stage, respectively. Meanwhile, higher Na+ concentration in rainwater was found at leafless stage and leaf expanding stage, and lower concentration at frondent leaf stage and senesced leaf stage. The inputs of K+ and Na+ through rainfall were 25.47 and 21.60 kg·hm-2·a-1, respectively. The leaching flux of K+ was 13.64 kg·hm-2·a-1 from canopy by rainfall, with the flux of 1.67, 6.23, 2.28 and 3.46 kg·hm-2 at the leafless stage, leaf expanding stage, frondent leaf stage and senesced leaf stage, respectively. On the contrary, the canopy intercepted 11.26 kg Na+·hm-2·a-1, with the interception rate being 32.6%, 18.0%, 44.9% and 31.5% at leafless stage, leaf expanding stage, frondent leaf stage, and senesced leaf stage, respectively. In conclusion, the redistribution of K+ and Na+ in the rainfall affected by Q. acutissima and C. acuminata mixed plantation canopy varied greatly with phenological stages. The results could provide basic data for further understanding of the cycles of K+ and Na+ in the forest ecosystem in the rainy area of western China.

[Effects of naphthalene on soil respiration, dissolved organic matter and microbial biomass in the subalpine forest of western Sichuan, China]. / 萘对川西亚高山森林土壤呼吸、可溶性有机质和微生物生物量的影响.

The effects of naphthalene on soil respiration, dissolved organic matter and microbial biomass, and its inhibition efficiency for soil fauna of subalpine forest in western Sichuan were studied by in situ control experiment. The results showed that naphthalene application significantly inhibited the individual density and group number of soil macro- and meso-/micro- arthropods, with the individual density being decreased by 76.3%-78.5% and 83.3%-84.8% respectively, and the number of groups being decreased by 48.3%-56.1% and 45.8%-58.3%, respectively. The seasonal dynamics of soil respiration rate showed single peak curves in both naphthalene treatment and control. The lowest and the highest soil respiration rates were observed in February and August, respectively. The naphthalene treatment had little effect on soil respiration. Compared with the control, naphthalene treatment significantly reduced the contents of soil dissolved carbon and dissolved nitrogen in August and October as well as microbial biomass carbon (MBC) in April and August, but increased MBC/MBN in April. The naphthalene treatment and sampling time significantly interacted to affect the MBC and MBN, but had no significant effect on individual density, the number of groups of soil fauna and DC content. In all, naphthalene as biocide could effectively inhibit the soil arthropods and had no significant effect on soil respiration, but it had varying degrees of effects on soil carbon and nitrogen components in subalpine forest of western Sichuan.

[Effects of gap and growth substrate on nitrogen and phosphorus contents of bryophytes in an alpine forest]. / 高山森林林窗和生长基质对苔藓植物氮和磷含量的影响.

Bryophyte plays an important role in nutrient enrichment and cycling in the forest ecosystems. The role of bryophyte in nitrogen (N) and phosphorus (P) cycles might be affected by forest regeneration and growth substrate. To understand the role of bryophyte in N and P cycling in the forest ecosystem, we measured the contents of N and P in the bryophytes that grew on different positions (gap center, gap edge, and closed canopy) and growth substrates (standing tree, fallen log, snag, large dead branch, stump and forest floor) in an alpine forest ecosystem. The results showed that the N content in the bryophyte on the forest floor was 3.12 mg·g-1, which was significantly lower than those on other growth substrates. Although N content in the bryophyte on the snag reached up to 17.41 mg·g-1, no significant differences of N contents in the bryophytes were observed among standing tree, fallen log, large dead branch and snag. The highest and lowest P contents was 1.09 mg·g-1 in the bryophyte on the forest floor and 0.61 mg·g-1 in the bryophytes on the snag, respectively. Furthermore, P content in the bryophyte on the forest floor was significantly higher than that on other growth substrates, but no significant differences of P contents in the bryophytes were detected among standing tree, fallen log, large dead branch and stump. The gap position significantly affected N and P contents in the bryophytes, with the N and P contents in the bryophytes on fallen log and large dead branch at gap center being significantly higher than those at the gap edge. The effects of coarse woody debris (CWD) on the N and P contents in the bryophyte depended on its types and decay classes, with their interaction having much stronger effects on N and P contents in the bryophytes. The N contents in the epiphytic bryophytes on fallen logs with V decay class were significantly higher than those with other decay classes. Similarly, the N contents in the epiphytic bryophytes on large dead branches with III decay class were significantly higher than those with other decay classes. Meanwhile, the P contents in the bryophytes on fallen logs with 2 decay class were significantly higher than those with other decay classes. Moreover, the P contents in the epiphytic bryophytes on the snags with 4 decay class were significantly higher than those with other decay classes. In conclusion, both forest gap regeneration and CWD decay process can affect the N and P contents in the bryophytes, and thereafter manipulate the nutrient cycles in the forest ecosystems.

[Diversity of soil nematode communities in the subalpine and alpine forests of western Sichuan, China.] / 川西亚高山/é«˜å±±æ£®æž—åœŸå£¤çº¿è™«å¤šæ ·æ€§.

In order to understand the diversity of soil nematodes in the subalpine/alpine forests of the eastern Qinghai-Tibet Plateau, soil nematodes in the primary forest, mixed forest and secondary forest of Abies faxoniana were extracted by elutriation and sugar-centrifugation method in July 2015, and the composition and structure characteristics of soil nematode communities were studied in the three forests at different altitudes. A total of 37950 soil nematodes were collected, which belonged to 20 families and 27 genera, and the mean density was 4217 ind·100 g-1 dry soil. Filenchus was the dominant genus in the primary forest, and Filenchus and Pararotylenchus in the mixed forest and secondary forest, respectively. The individual number of each dominant genus was significantly affected by forest type. All nematode individuals were classified into the four trophic groups of bacterivores, fungivores, plant-parasites and omnivore-predators. The fungivores were dominant in the primary and secondary forest and the bacterivores in the mixed forest. The number of soil nematode c-p (colonizer-persister) groups of c-p 1, c-p 2, c-p 3 and c-p 4 accounted for 6.1%, 51.1%, 30.0% and 12.7% of the total nematode abundance, respectively. The maturity index (MI), the total maturity index (∑MI) and the plant parasitic index (PPI) of soil nematodes decreased gradually with the increase of altitude. The nematode channel ratio in the mixed forest was higher than 0.5, but that in the primary forest and secondary forest was below 0.5. The forest type significantly affected the soil nematode maturity index and channel ratio, but the forest type, soil layer and their interaction had no significant effect on the diversity index. There were obvious diffe-rences in the composition, nutrient structure and energy flow channel of soil nematodes in the subalpine/alpine forests of western Sichuan, providing an important reference for understanding the function of soil nematodes in soil processes of this region.

[Effects of naphthalene on soil respiration, nutrients and enzyme activities in the subalpine forest of western Sichuan, China]. / è˜å¯¹å·è¥¿äºšé«˜å±±æ£®æž—åœŸå£¤å‘¼å¸ã€å »åˆ†å’Œé ¶æ´»æ€§çš„å½±å“.

As a biocide to reduce soil and litter faunal populations in field experiments, naphthalene has been widely used in the study of ecological functions of soil fauna, but the non-target effects of naphthalene bring about enormous uncertainty to its application. In order to understand whether there were non-target effects of naphthalene in subalpine forest soil, soil in the subalpine forests of west Qinghai-Tibet Plateau was taken as study object. The short-term responses of soil respiration rate, nutrient content and enzyme activity to naphthalene were studied in microcosms. The results showed that soil respiration rate was significantly suppressed by application of naphthalene within 0-10 days, and then showed a significant promotion effect. Naphthalene significantly affected the dynamics of soil NH4+-N and NO3--N contents. With application of naphthalene, the highest contents of NH4+-N and NO3--N occurred at the 3rd and 7th day, respectively. But they were observed at the 45th and 52nd day with no-naphthalene, respectively. Moreover, soil dissolved carbon content in the naphthalene microcosms showed a sharp increase and then decrease dynamic at the 3rd day, while small change was detected in the no-naphthalene microcosms. Dissolved nitrogen content in both the naphthalene and no-naphthalene microcosms showed an increase at first and then decreased subsequently during the study period. Similar dynamics were found for the soil enzyme activities in both the naphthalene and no-naphthalene microcosms. The highest activities of urease, nitrate reductase and nitrite reductase in both the naphthalene and no-naphthalene microcosms were at the 45th, 38th and 10th day, respectively. In addition, the interaction of naphthalene treatment and sampling time had significant effects on soil respiration rate, the contents of NH4+-N, NO3--N and dissolved nitrogen, but had no significant effects on soil dissolved carbon content, and the activities of invertase, nitrate reductase and nitrite reductase. In a short time, the non-target effect of naphthalene as a biocide to reduce soil fauna abundance might have an important influence on the soil nitrogen cycling in subalpine forest of western Sichuan.

[Effects of snow removal on soil labile nitrogen in a subalpine spruce forest of western Sichuan, China]. / 雪被去除对川西亚高山云杉林土壤活性氮的影响.

Warming-induced decrease in seasonal snow cover has a great potential to affect soil nitrogen cycle in alpine cold forest ecosystems. In this study, a wooden-shelter method was used to remove the snow accumulation. Soil nitrogen pools and mineralization rates in the snow removal and control plots were measured synchronously in three critical periods (early snow cover, deep snow cover and snow cover melting) in a subalpine spruce forest of western Sichuan, China. Seasonal snow cover kept soil from cold air temperature. Snow removal decreased average and minimum soil temperatures (5 cm) by 0.33 and 1.17 ℃, respectively. In addition, snow removal caused a positive effect on soil frost depth and freeze-thaw cycle. There was a significant dynamic in soil labile nitrogen pool among different periods. Snow removal on average increased NH4+-N, NO3--N and dissolved organic nitrogen (DON) contents by 38.6%, 23.5% and 57.3%, respectively, over the winter. Moreover, snow removal increased soil net nitrification and mineralization rates in the snow co-ver melting period. Overall, warming-induced decrease in snow cover could stimulate winter soil nitrogen cycle of subalpine forests.

[Effects of simulated warming on soil DOC and DON concentrations in the alpine forest of western Sichuan based on altitudinal gradient experiment.] / 利用海拔差异模拟增温对高山森林土壤溶解性有机碳和有机氮含量的影响.

In order to understand the effects of climate warming on the process of soil carbon and nitrogen in the alpine forest, intact soil columns were collected in the alpine fir forest, and dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) concentrations in both soil organic layer (OL) and mineral soil layer (ML) placed at different altitudes were measured from May 2010 to April 2011 (the first incubation period) and from May 2011 to April 2012 (the second incubation period). The results indicated that both DOC and DON concentrations in OL and ML va-ried greatly during the sampling period. The DOC concentration in soil columns at the altitudes of 3300 and 3000 m increased 6.8 and 26.6 mg·kg-1 compared with that at 3600 m, respectively. The highest DOC concentrations in soil columns at the altitudes of 3600, 3300 and 3000 m were 408.0, 317.9 and 448.2 mg·kg-1, respectively, which were all detected in LG (late growth pe-riod) during the first incubation period, while the lowest concentrations were 33.1, 32.4 and 36.5 mg·kg-1, respectively, which were all detected in MG (mid growth period) during the second incubation period. Moreover, the DON concentration in soil columns at the altitudes of 3300 and 3000 m increased 2.3 and 30.4 mg·kg-1 respectively compared with that at 3600 m. The highest DON concentrations at the altitudes of 3600 and 3300 m were 65.9 and 64.6 mg·kg-1, which were both detected in MG in the first incubation period, while the lowest concentrations were 31.9 and 37.1 mg·kg-1, both detected in ET (early thawing period) in the second incubation period. Simulated warming increased the concentrations of DOC and DON in the OL, but decreased the concentration of DOC in ML and the ratio of DOC to DON in OL and ML. The ratio of DOC to DON was significantly positively related with DOC concentration and negatively related with DON concentration in OL, whereas the ratio of DOC to DON was significantly negatively related with DOC concentration and positively with DON concentration in ML. The results indicated that climate warming would increase the concentrations of DOC and DON in soils of the high-frigid forest by changing soil tempe-rature and freeze-thaw pattern, and in turn alter the process of soil carbon and nitrogen.

[Dynamics of microbial biomass carbon and nitrogen during foliar litter decomposition under artificial forest gap in Pinus massoniana plantation.] / é©¬å°¾æ¾äººå·¥æž—æž—çª—å† å‡‹è½å¶å¾®ç”Ÿç‰©ç”Ÿç‰©é‡ç¢³å’Œæ°®çš„åŠ¨æ€å˜åŒ–.

Nowadays large areas of plantations have caused serious ecological problems such as soil degradation and biodiversity decline. Artificial tending thinning and construction of mixed forest are frequently used ways when we manage plantations. To understand the effect of this operation mode on nutrient cycle of plantation ecosystem, we detected the dynamics of microbial bio-mass carbon and nitrogen during foliar litter decomposition of Pinus massoniana and Toona ciliate in seven types of gap in different sizes (G1: 100 m2, G2: 225 m2, G3: 400 m2, G4: 625 m2, G5: 900 m2, G6: 1225 m2, G7: 1600 m2) of 42-year-old P. massoniana plantations in a hilly area of the upper Yang-tze River. The results showed that small and medium-sized forest gaps(G1-G5) were more advantageous for the increment of microbial biomass carbon and nitrogen in the process of foliar litter decomposition. Along with the foliar litter decomposition during the experiment (360 d), microbial biomass carbon (MBC), microbial biomass nitrogen (MBN) in P. massoniana foliar litter and MBN in T. ciliata foliar litter first increased and then decreased, and respectively reached the maxima 9.87, 0.22 and 0.80 g·kg-1 on the 180th d. But the peak (44.40 g·kg-1) of MBC in T. ciliata foliar litter appeared on the 90th d. Microbial biomass carbon and nitrogen in T. ciliate was significantly higher than that of P. massoniana during foliar litter decomposition. Microbial biomass carbon and nitrogen in foliar litter was not only significantly associated with average daily temperature and the water content of foliar litter, but also closely related to the change of the quality of litter. Therefore, in the thinning, forest gap size could be controlled in the range of from 100 to 900 m2 to facilitate the increase of microbial biomass carbon and nitrogen in the process of foliar litter decomposition, accelerate the decomposition of foliar litter and improve soil fertility of plantations.

[Edge effects of forest gap in Pinus massoniana plantations on the decomposition of leaf litter recalcitrant components of Cinnamomum camphora and Toona ciliata.] / 马尾松人工林林窗边缘效应对樟和红椿凋落叶难降解物质分解的影响.

The objective of the study was to evaluate the dynamics of recalcitrant components during foliar litter decomposition under edge effects of forest gap in Pinus massoniana plantations in the low hilly land, Sichuan basin. A field litterbag experiment was conducted in seven forest gaps with different sizes (100, 225, 400, 625, 900, 1225, 1600 m2) which were generated by thinning P. massoniana plantations. The degradation rate of four recalcitrant components, i.e., condensed tannins, total phenol, lignin and cellulose in foliar litter of two native species (Cinnamomum camphora and Toona ciliata) at the gap edge and under the closed canopy were measured. The results showed that the degradation rate of recalcitrant components in T. ciliata litter except for cellulose at the gap edge were significantly higher than that under the closed canopy. For C. camphora litter, only the degradation of lignin at the gap edge was higher than that under the closed canopy. After one-year decomposition, four recalcitrant components in two types of foliar litter exhibited an increment of degradation rate, and the degradation rate of condensed tannin was the fastest, followed by total phenol and cellulose, but the lignin degradation rate was the slowest. With the increase of gap size, except for cellulose, the degradation rate ofthe other three recalcitrant components of the T. ciliata at the edge of medium sized gaps (400 and 625 m2) were significantly higher than at the edge of other gaps. However, lignin in the C. camphora litter at the 625 m2 gap edge showed the greatest degradation rate. Both temperature and litter initial content were significantly correlated with litter recalcitrant component degradation. Our results suggested that medium sized gaps (400-625 m2) had a more significant edge effect on the degradation of litter recalcitrant components in the two native species in P. massoniana plantations, however, the effect also depended on species.

[Effects of altitudes on soil microbial biomass and enzyme activity in alpine-gorge regions.] / æµ·æ‹”å¯¹é«˜å±±å³¡è°·åŒºåœŸå£¤å¾®ç”Ÿç‰©ç”Ÿç‰©é‡å’Œé ¶æ´»æ€§çš„å½±å“.

In order to understand the variations of soil microbial biomass and soil enzyme activities with the change of altitude, a field incubation was conducted in dry valley, ecotone between dry valley and mountain forest, subalpine coniferous forest, alpine forest and alpine meadow from 1563 m to 3994 m of altitude in the alpine-gorge region of western Sichuan. The microbial biomass carbon and nitrogen, and the activities of invertase, urease and acid phosphorus were measured in both soil organic layer and mineral soil layer. Both the soil microbial biomass and soil enzyme activities showed the similar tendency in soil organic layer. They increased from 2158 m to 3028 m, then decreased to the lowest value at 3593 m, and thereafter increased until 3994 m in the alpine-gorge region. In contrast, the soil microbial biomass and soil enzyme activities in mineral soil layer showed the trends as, the subalpine forest at 3028 m > alpine meadow at 3994 m > montane forest ecotone at 2158 m > alpine forest at 3593 m > dry valley at 1563 m. Regardless of altitudes, soil microbial biomass and soil enzyme activities were significantly higher in soil organic layer than in mineral soil layer. The soil microbial biomass was significantly positively correlated with the activities of the measured soil enzymes. Moreover, both the soil microbial biomass and soil enzyme activities were significantly positively correlated with soil water content, organic carbon, and total nitrogen. The activity of soil invertase was significantly positively correlated with soil phosphorus content, and the soil acid phosphatase was so with soil phosphorus content and soil temperature. In brief, changes in vegetation and other environmental factors resulting from altitude change might have strong effects on soil biochemical properties in the alpine-gorge region.

[Small mammals burrow selection and habitat characteristics in an alpine forest of eastern Tibet Plateau, China.] / é’è—é«˜åŽŸä¸œç¼˜é«˜å¯’æ£®æž—å°åž‹å ½ç±»åœ°è¡¨æ´žç©´é€‰æ‹©ä¸Žç”Ÿå¢ƒç‰¹å¾.

The burrows of small mammals are one of the obvious landscapes in the forest floor, and play important roles in understanding the distribution patterns of small mammals and their ecological functions in the high-frigid regions. Therefore, the burrow selection and habitat characteristics of small mammals were investigated in an alpine forest of eastern Tibet Plateau from July to September in 2015. The results indicated that the average density of small mammals burrow was 182.8 entrances per hectare. Forest vegetation had significant effects on burrow entrances density, which showed the order of coniferous vegetation (328.6 burrow entrances per hectare) > broad-leaved and coniferous mixed vegetation (160.0 burrow entrances per hectare) > shrubbery (125.0 burrow entrances per hectare) > broad-leaved vegetation (81.5 burrow entrances per hectare) > bamboo ve-getation (66.7 burrow entrances per hectare). Mann-Whitney U Test and PCA analysis displayed that the arbor canopy, arbor height, arbor DBH, arbor density, ground-plant cover, fallen log cover, fallen log density and shrub height in the small mammals utilized habitat plots were significantly higher than those in other habitat plots (P<0.05). Compared with other factors, arbor was the primary factor in dominating the selection of small mammal burrows, showing the contribution rate with 44.8%. The following dominant factors were fallen log and shrub, with the contribution rates being 23.2% and 13.9%, respectively. In summary, there were numerous small mammal burrows in the alpine forest floor, which were primarily dominated by vegetation and fallen logs.

[Soluble nitrogen and soluble phosphorus dynamics during foliar litter decomposition in winter in alinine forest streams].

In order to understand the dynamic pattern of soluble nitrogen and soluble phosphorus in the headwater streams during the process of litter decomposition in winter, a field experiment using litterbag method was conducted in an alpine forest in Western Sichuan, China. The foliar litter of two dominant canopy trees (Sabina saltuaria, and Larix mastersiana) and two shrubs (Salix paraplesia and Rhododendron lapponicum) were selected. The litterbags were placed in a headwater stream, river, riparian zone and closed canopy, and sampled in different freezing-thawing periods of winter (pre-freezing period, freezing period and thawing period). The results indicated that the soluble nitrogen content of foliar litter showed little changes over a whole winter decomposition regardless of species. In contrast, the soluble phosphorus content displayed the order as river < stream < riparian zone < closed canopy, and showed a decrease tendency in stream, river and riparian, although little changes under closed canopy over a whole winter decomposition. Correlation analysis suggested that the dynamics of soluble phosphorus content significantly correlated to the average temperature, positive accumulated temperature, negative accumulated temperature and flow velocity during the decomposition in winter. The dynamics of soluble nitrogen content only exhibited significant correlations with positive accumulated temperature. Additionally, litter quality (species) also controlled the dynamics of soluble nitrogen and soluble phosphorus content as litter decomposition proceeded. The results implied that soluble phosphorus could be more liable to loss in streams and rivers during litter decomposition compared with soluble nitrogen, which could further provide some new ideas in understanding nitrogen and phosphorus cycling in this alpine forest.

[C, N and P stoichiometric characteristics of different root orders for three dominant tree species in subalpine forests of western Sichuan, China].

Fine root order was classified according to Pregitzer's method. This study measured carbon (C), nitrogen (N) and phosphorus (P) concentrations of the 1-5 root orders (diameter < 2 mm) in three dominant subalpine tree species (Betula albosinensis, Abies faxoniana and Picea asperata) of western Sichuan. Their stoichiometric ratios of different root orders were also calculated. The results showed that C concentration, C/N and C/P increased, but N and P concentrations decreased from the first to fifth order of fine root for all tree species. No significant changes in N/P among root orders were detected in each species. There were significant differences in C, N, P concentrations and their stoichiometric ratios among the tree species. The species-associated differences were dependent on root order. There were significant correlations between C, N, P concentrations and their stoichiometric ratios in the three tree species.

[Litter decomposition and lignocellulose enzyme activities of Actinothuidium hookeri and Cys- topteris montana in alpine timberline ecotone of western Sichuan, China].

The mass loss and lignocellulose enzyme activities of Actinothuidium hookeri residues and Cystopteris montana leaf litter in coniferous forest and timberline of western Sichuan, China were investigated. The results showed that both the mass loss rates of A. hookeri and C. Montana in timberline were higher than those in coniferous forest, while enzyme activities in timberline were lower than those in coniferous forest which was contrast with the hypothesis. The mass loss of two ground covers had significant differences in different seasons. The mass loss rate of A. hookeri in snow-covered season accounted for 69.8% and 83.0% of the whole year' s in timberline and coniferous forest, while that of C. montana in the growing season accounted for 82.6% and 83.4% of the whole year' s in timberline and coniferous forest, respectively. C. montana leaf litter decayed faster in the growing season, which was consistent with its higher cellulase activity in the growing season. The result illustrated that the enzymatic hydrolysis of cellulose and hemicellulose might be the main driving force for the early stage of litter decomposition. Multiple linear regression analysis showed that environmental factors and initial litter quality could explain 45.8%-85.1% variation of enzyme activity. The enzyme activities of A. hookeri and C. montana in the process of decomposition were mainly affected by the freeze-thaw cycle in snow-covered season.

[Seasonal release characteristics of Ca, Mg and Mn of foliar litter of six tree species in subtropical evergreen broadleaved forest].

Seasonal release dynamics of Ca, Mg and Mn during decomposition of foliar litter of Pinus massoniana, Cryptomeria fortunei, Cunninghamia lanceolata, Cinnamomum camphora, Toona ciliate, and Quercus acutissima were investigated in subtropical evergreen broad-leaved forest employing the method of litterbag. After one-year decomposition, the release rates of Ca, Mg and Mn in foliar litter of the studied tree species ranged from -13.8% to 92.3%, from 4.0% to 64.8%, and from 41.6% to 81.1%, respectively. Ca dynamics in foliar litter of P. massoniana, C. camphora exhibited the pattern of accumulating early and releasing later, while that of the other four tree species showed direct release. Similarly, the dynamics of Mg released from foliar litter of C. camphora showed the pattern of accumulating early and then releasing, while that of the other five tree species exhibited continuous release. Meanwhile, the dynamics of Mn released from foliar litter of C. fortunei and T. ciliate exhibited early accumulation, and subsequent release, while that of the other four tree species showed continuous release. The releases of Ca, Mg and Mn in foliar litter were greatly influenced by seasonal rainfall, and varied with tree species. Furthermore, the rates and amounts of Ca, Mg and Mn released from foliar litter were higher in rainy season than in dry season. In conclusion, the initial nutrient concentrations and precipitation were two key factors influencing the release dynamics of Ca, Mg and Mn during decomposition of foliar litter in the subtropical evergreen broad-leaved forest.

[Decomposition and nutrient release of root with different diameters of three subalpine dominant trees in western area of Sichuan Province, China].

In this study, a buried bag experiment was used to investigate mass loss and C, N and P release patterns of fine (≤2 mm), medium (2-5 mm) and coarse (≥ 5 mm) roots of 3 subalpine dominant trees, i. e., Betula albosinensis, Abies faxoniana and Picea asperata in the growing and non-growing seasons. In general, the remaining mass of B. albosinensis was lower than that of A. faxoniana and P. asperata. In addition, root remaining mass increased with the increase of root diameter for the same species. The mass losing rate in the non-growing season was 52.1%-64.4% of a year. The C release of B. albosinensis was the highest, but that of A. faxoniana was the lowest. Also, C release decreased with the increase of root diameter. N of A. faxoniana and P. asperata were enriched in the non-growing season but released in the growing season. However, the opposite pattern was found for B. albosinensis. During the non-growing season, the amount of N enrichment increased with the increase of root diameter. The P release of 3 species was characterized as the enrichment-release pattern. P enrichment of A. faxoniana was significantly greater than that of P. asperata and B. albosinensis. Nevertheless, no significant difference was observed between diameter sizes. In conclusion, diameter size had significant effect on root decomposition in the subalpine forests of western Sichuan, and the diameter effect was dependent on tree species and season.

[Effects of snow patches on the release of N and P during foliar litter decomposition in an alpine forest of western Sichuan China].

A field experiment using litterbags was conducted in an alpine forest of western Sichuan in order to understand the effects of snow patches on the dynamics of N and P during decomposition of six representative species foliar litter in different periods of winter. Net N immobilization during foliar litter decomposition was observed in the whole snow cover season regardless of species. In contrast, P mainly released from foliar litter in the snow cover season, with a rapid rate of P release in the snow melt stage. Thick and moderate snow patches showed higher P release rates, but lower N release rates of foliar litter. The rate of N release was negatively related to daily mean temperature regardless of species, but the rate of P release was positively related to daily mean temperature with the exception of fir needle-litter. The decrease of snow cover in the scenario of global warming could inhibit P release but promote N release from foliar litter decomposition in winter in the alpine forest.