Short-term responses of soil enzyme activities and stoichiometry to litter input in Castanopsis carlesii and Cunninghamia lanceolata plantations.

Litter input triggers the secretion of soil extracellular enzymes and facilitates the release of carbon (C), nitrogen (N), and phosphorus (P) from decomposing litter. However, how soil extracellular enzyme activities were controlled by litter input with various substrates is not fully understood. We examined the activities and stoichiometry of five enzymes including ß-1,4-glucosidase, ß-D-cellobiosidase, ß-1,4-N-acetyl-glucosaminidase, leucine aminopeptidase and acidic phosphatase (AP) with and without litter input in 10-year-old Castanopsis carlesii and Cunninghamia lanceolata plantations monthly during April to August, in October, and in December 2021 by using an in situ microcosm experiment. The results showed that: 1) There was no significant effect of short-term litter input on soil enzyme activity, stoichiometry, and vector properties in C. carlesii plantation. In contrast, short-term litter input significantly increased the AP activity by 1.7% in May and decreased the enzymatic C/N ratio by 3.8% in August, and decreased enzymatic C/P and N/P ratios by 11.7% and 10.3%, respectively, in October in C. lanceolata plantation. Meanwhile, litter input increased the soil enzymatic vector angle to 53.8° in October in C. lanceolata plantations, suggesting a significant P limitation for soil microorganisms. 2) Results from partial least squares regression analyses showed that soil dissolved organic matter and microbial biomass C and N were the primary factors in explaining the responses of soil enzymatic activity to short-term litter input in both plantations. Overall, input of low-quality (high C/N) litter stimulates the secretion of soil extracellular enzymes and accelerates litter decomposition. There is a P limitation for soil microorganisms in the study area.

[Community structure of soil fauna under different tree species in subtropical forests]. / äºšçƒ­å¸¦æ£®æž—ä¸åŒæ ‘ç§ä¸‹åœŸå£¤åŠ¨ç‰©ç¾¤è½ç»“æž„ç‰¹å¾.

Soil fauna play an important role in key functions of ecosystem such as material cycling. Litter quality and microenvironment of different tree species may regulate soil fauna community structure. In this study, we investigated soil fauna community structure, the differences of taxonomic and functional groups, and the regulatory factors under eight dominant tree species in August 2022. We captured 567 soil fauna (except for termites and ants), belonging to 3 phyla, 10 classes, 26 orders, and 99 families, with Achipteriidae, Trygoniidae, Poduridae, and Isotomidae as the dominant species. Tree species significantly affected soil fauna abundance, following an order: Michelia macclurei > Elaeocarpus decipiens > Castanopsis carlesii > Cunninghamia lanceolata > Lindera communis > Schima superba > Pinus massoniana > Liquidambar formosana. However, the richness, evenness, and diversity of soil fauna under different tree species were significantly different. Richness and diversity of M. macclurei, C. lanceolatas soil fauna were relatively high, while L. formosana, C. carlesii were relatively low. The evenness of meso-microfauna of L. formosana was the highest, which was significantly higher than that of M. macclureis and E. decipiens. The evenness of macrofauna and total soil fauna was not significantly different among the eight tree species. In addition, the abundance of omnivores and herbivores soil fauna was relatively high under M. macclurei, but relatively low under E. decipiens. The abundance of saprophages and predators soil fauna of E. decipiens, M. macclurei was higher than L. formosana, while saprophages was mainly meso-microfauna. Results of redundancy analysis showed that litter N, C:N, and K were the main factors affecting soil fauna community structure. The results indicated that the tree species with thicker litter layer and higher N and K contents may be conducive to enhancing the diversity of soil fauna community and affecting the distribution of different functional groups, thus contributing to the maintenance of forest biodiversity.

Inhibition of Structural Transformation and Surface Lattice Oxygen Activity for Excellent Stability Li-Rich Mn-Based Layered Oxides.

Li-rich Mn-based layered oxides (LLOs) are one of the most promising cathode materials, which have exceptional anionic redox activity and a capacity that surpasses 250 mA h/g. However, the change from a layered structure to a spinel structure and unstable anionic redox are accompanied by voltage attenuation, poor rate performance, and problematic capacity. The technique of stabilizing the crystal structure and reducing the surface oxygen activity is proposed in this paper. A coating layer and highly concentrated oxygen vacancies are developed on the material's surface, according to scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. In situ EIS shows that structural transformation and oxygen release are inhibited during the first charge and discharge. Optimized 3@LRMA has an average attenuation voltage of 0.55 mV per cycle (vs 1.7 mV) and a capacity retention rate of 93.4% after 200 cycles (vs 52.8%). Postmortem analysis indicates that the successful doping of Al ions into the crystal structure effectively inhibits the structural alteration of the cycling process. The addition of oxygen vacancies reduces the surface lattice's redox activity. Additionally, surface structure deterioration is successfully halted by N- and Cl-doped carbon coating. This finding highlights the significance of lowering the surface lattice oxygen activity and preventing structural alteration, and it offers a workable solution to increase the LLO stability.

[Dynamics of Ca and Mg storage of non-woody debris in a subtropical forest headwater stream during the rainy season.] / 亚热带森林降雨季节源头溪流非木质残体钙和镁储量动态特征.

Forest headwater streams are the monumental cement for relating habitats of the terrene and water. Nutri-ent dynamics of non-woody debris in stream can directly and indirectly regulate the cycle and transport of forest nutrients, for example, Ca and Mg. In the rainy season (from March to August) of 2021, we monitored the dyna-mics of Ca and Mg storage of non-woody debris in a typical headwater stream in a subtropical forest. The results showed that total Ca and Mg storage of non-woody debris per unit area of stream ranged from 178.1 to 890.5 mg·m-2 and 13.8 to 61.6 mg·m-2 during the rainy season, respectively. The Ca and Mg storages of non-woody debris per unit area of stream during the rainy season displayed a pattern of first increase and then decrease, and overall a decrease pattern. The storage varied significantly among different sites, with higher values in stream source than others. The total Ca and Mg storage of non-woody debris positively correlated with precipitation, but negatively with stream water alkalinity, temperature, and dissolved oxygen. The variation of riparian forest type (e.g., Castano-psis carlesii forests or mixed coniferous forests) and with or without tributaries did not affect the storage of Ca and Mg in stream non-woody debris. During the rainy season, total Ca and Mg storage of non-woody debris in the headwater stream from forest generally decreased over time, which was mainly controlled by the characteristics of rainfall and stream.

[Dissolved organic matter dynamics and spectral characteristics of twig litter from different Castanopsis carlesii forests in the middle subtropical region, China]. / ä¸­äºšçƒ­å¸¦ä¸åŒç±»åž‹ç±³æ§ æž—å‡‹è½æžæº¶è§£æ€§æœ‰æœºè´¨åŠ¨æ€åŠå ‰è°±å­¦ç‰¹æ€§.

To assess the dynamics and spectral characteristics of dissolved organic matter of twig litter in continuous increase stage, peak stage, and continuous decrease stage of twig litter production in different types of Castanopsis carlesii forest in middle subtropical China, a field experiment was conducted in C. carlesii natural forest, secondary forest and plantation. The results showed that litter production stage and forest type significantly affected the content and spectral characteristics of dissolved organic matter of twig litter were . Compared with the secondary forest and plantation, natural forest had higher dissolved organic carbon (DOC) content and lower special ultraviolet-visible absorption values at 254, 260 and 280 nm (SUVA254, SUVA260, SUVA280) at the continuous decrease stage of twig litter production, indicating high twig litter quality of natural forest and high cycling efficiency with dissolved organic matter in the natural forest at this stage. In contrast, the higher contents of total nitrogen (TN), total phosphorus (TP), total dissolved nitrogen (TDN), total dissolved phosphorus (TDP), and lower DOC:TDP and TDN:TDP ratios of twig litter in the plantation were observed at the peak stage of twig litter production, while no differences were detected in dissolved organic matter contents and spectral values in the secondary forest among the stages. In addition, the DOC, TDN, TDP of twig litter were negatively correlated with temperature and precipitation in the natural forests and secondary forests, but TDN and TDP of twig litter were positively correlated with temperature and precipitation in the plantations. These results suggested that the higher nutrient content at the peak stage of twig litter production in the C. carlesii plantation might lead to more efficient material cycling and that there would be a higher efficiency of material cycling for twig litter dissolved organic matter in C. carlesii natural forest at reduction stage of twig litter production.

[Nitrogen and phosphorus resorption and stoichiometric characteristics of different tree species in a mid-subtropical common-garden, China.] / ä¸­äºšçƒ­å¸¦åŒè´¨å›­ä¸åŒæ ‘ç§æ°®ç£·é‡å¸æ”¶åŠåŒ–å­¦è®¡é‡ç‰¹å¾.

To understand the nutrient use strategies of 11 tree species in a subtropical common-garden, we measured the specific leaf area, nitrogen (N) and phosphorus (P) resorption and stoichiometric characteristics of leaves in August 2019. The results showed that the specific leaf area, N and P concentrations in mature and senescent leaves of evergreen broadleaved (Lindera communis, Cinnamomum camphora, Schima superba, Castanopsis carlesii, Michelia macclurei and Elaeocarpus decipiens) and coniferous species (Cunninghamia lanceolata and Pinus massoniana) were lower than those of deciduous broadleaved species (Liquidambar formosana, Sapindus mukorossi and Liriodendron chinense). In contrast, C:N and C:P in mature leaves of evergreen broadleaved and coniferous species were significantly higher than those of deciduous broadleaved species. Except for C. carlesii, the N:P of all the species were lower than 14. Compared with other tree species, N and P resorption efficiencies of S. mukorossi were higher than 50% based on both mass and leaf area. Although P resorption efficiency of P. massoniana, C. lanceolata and C. camphora were higher than 50%, N and P resorption efficiency of M. macclurei were the lowest with only 15%-30%. In addition, specific leaf area of mature leaves was significantly positively correlated with N and P concentrations, but negatively correlated with C:N and C:P. In the common-garden, evergreen broadleaved species such as C. carlesii and L. communis, and coniferous species such as P. massoniana might belong to the slow investment species with lower specific leaf area, N and P concentrations, displaying relatively efficient in N and P resorption and utilization in comparison with other species. In contrast, deciduous broadleaved species such as S. mukoraiensis might be the fast investment species with low N and P use efficiency. Interestingly, tree species being restricted by N availability did not exhibit higher N resorption efficiency in the common-garden. Similarly, C. carlesii, the only P-restricted species here, did not exhibit higher P resorption efficiency. Our results provided scientific support for afforestation practice in the mid-subtropics.

[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 litter addition on the dynamics of soil humic substances during freeze-thaw events in a subalpine forest.] / å†»èžçŽ¯å¢ƒä¸‹äºšé«˜å±±æ£®æž—å‡‹è½å¶æ·»åŠ å¯¹åœŸå£¤è æ®–è´¨åŠ¨æ€çš„å½±å“.

During soil formation, the accumulation of humic substances such as humic acid and fulvic acid is an important way to maintain soil fertility and nutrient cycling, which is regulated by soil substrate quality, litter, and environmental factors. In a laboratory incubation experiment, we exa-mined the effects of litter addition on soil humic substances accumulation in freeze-thaw environment by controlling the freeze-thaw cycles and litter additions in soils from the typical coniferous forest, mixed forest and broadleaved forest in a subalpine forest in western Sichuan. The freeze-thaw events significantly increased the content of humic substances in the coniferous forest soils but decreased those in the mixed forest soil and broadleaved forest soil. Litter addition had no significant effect on the content of soil humic substances. Freeze-thaw events increased the content of humic acid, with the net accumulation of humic acid following the order of mixed forest > coniferous forest > broad-leaved forest. Freeze-thaw events decreased the content of fulvic acid in the three forest soils during the early stage of incubation, and the degree of fulvic acid degradation was broadleaved forest > mixed forest > coniferous forest. Litter addition had no significant effect on the content of soil humic acid and fulvic acid. With prolonged incubation, the content of humic acid and fulvic acid in the three types of forest soils all declined. These results indicated that litter had effects on soil humic substances, which were related to soil substrate quality and affected by the duration of soil freeze-thaw events in winter.

[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 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.

[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.

[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 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.

[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.

[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.

[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.

[Effects of snow pack on soil nitrogen transformation enzyme activities in a subalpine Abies faxioniana forest of western Sichuan, China].

This study characterized the dynamics of the activities of urease, nitrate reductase and nitrite reductase in both soil organic layer and mineral soil layer under three depths of snow pack (deep snowpack, moderate snowpack and shallow snowpack) over the three critical periods (snow formed period, snow stable period, and snow melt period) in the subalpine Abies faxoniana forest of western Sichuan in the winter of 2012 and 2013. Throughout the winter, soil temperature under deep snowpack increased by 46.2% and 26.2%, respectively in comparison with moderate snowpack and shallow snowpack. In general, the three nitrogen-related soil enzyme activities under shallow snowpack were 0.8 to 3.9 times of those under deep snowpack during the winter. In the beginning and thawing periods of seasonal snow pack, shallow snowpack significantly increased the activities of urease, nitrate and nitrite reductase enzyme in both soil organic layer and mineral soil layer. Although the activities of the studied enzymes in soil organic layer and mineral soil layer were observed to be higher than those under deep- and moderate snowpacks in deep winter, no significant difference was found under the three snow packs. Meanwhile, the effects of snowpack on the activities of the measured enzymes were related with season, soil layer and enzyme type. Significant variations of the activities of nitrogen-related enzymes were found in three critical periods over the winter, and the three measured soil enzymes were significantly higher in organic layer than in mineral layer. In addition, the activities of the three measured soil enzymes were closely related with temperature and moisture in soils. In conclusion, the decrease of snow pack induced by winter warming might increase the activities of soil enzymes related with nitrogen transformation and further stimulate the process of wintertime nitrogen transformation in soils of the subalpine forest.