Seasonal immunocytochemical and ultrastructural changes in the neurohypophysis of the migratory Canada goose

Immunocytochemical localization of arginine vasotocin (AVT) in the neurohypophysis of the migratory Canada goose was studied during six periods (Spring premigratory, Spring postmigratory, breeding, moulting, Fall or Autumn premigratory, and Fall postmigratory) of its annual life cycle. Ultrastructural changes in the pars nervosa, with emphasis on the axonal endings, were also examined during the above periods. In the Spring premigratory period, the staining intensity for AVT was greater in the anterior median eminence than in the pars nervosa where the density of axonal secretory granules was lower than that in the preceding period, in both sexes. During moulting females seemed to be under greater osmotic stress than males as indicated by low AVT staining intensity and secretory granule concentration in the pars nervosa. The occurrence of considerable amounts of lipofuscin bodies in the pars nervosa of both sexes during moulting was indicative of high lysosomal activity in the pituicytes. AVT release is recognized as a significant event in initiating Spring migration.     

Canada goose posterior lobe pituicytes: seasonal ultrastructural changes in relation to axonal release of neurosecretion

Changes in ultrastructure of the posterior lobe pituicytes during six phases (Spring premigratory, Spring postmigratory, breeding, moulting, Fall premigratory and Fall postmigratory) of the annual life cycle of the migratory Canada goose, were studied. Pituicyte nuclear volume in females was significantly greater than that in males during the Spring premigratory and moulting phases. In the Fall postmigratory phase, nuclear volume in males was greater than that in females. During Spring premigratory phase, the axonal endings in males contained fewer neurosecretory granules (NSG) than those in the Fall postmigratory phase. In females, however, the number of NSG was relatively more than that in males in the Spring premigratory phase but fewer in the moulting phase. Nuclear volume is correlated with pituicyte function in releasing NSG containing arginine vasotocin (AVT) from axonal endings. The significance of AVT release is discussed in relation to initiation of reproductive and migratory behaviour, and to osmotic and metabolic regulation.     

Seasonal ultrastructural changes in the pineal gland of the migratory Canada goose

Ultrastructural changes in the pineal gland were studied in relation to migration, breeding and moult. Sizes of pinealocytes and that of their nuclei were greatest in the Spring premigratory and postmigratory, and moult phases. The ratio of nuclear size to cell size was greatest for the breeding phase and lowest for the Fall premigratory and postmigratory phases. The Golgi complex was most prominent during premigratory and breeding phases. Mitochondria which were numerous in all phases except during moult, were markedly enlarged during breeding and Fall premigratory phases. Dense-core vesicles were predominant in Spring postmigratory and moult phases. In glial cells, lipoid inclusions were abundant in Spring premigratory and postmigratory, and breeding phases. Glycogen granules were abundant in Spring postmigratory, breeding and moult phases. Large vacuoles were present in Fall premigratory phase. Lamellar membraneous whorls were often present near luminal spaces during Spring premigratory and postmigratory, and breeding phases. The endothelial cells of pineal capillaries during Spring and Fall premigratory phases, contained numerous vesicles, some of which were freely dispersed in the cytoplasm while others were fused to the cell membrane, suggestive of transendothelial transport of vesicular substances.     

Isotopic (δ2Hf) evidence of “loop migration” and use of the Gulf of Maine Flyway by both western and eastern breeding populations of Blackpoll Warblers

Declining numbers of Blackpoll Warblers (Setophaga striata) have been documented at long‐term migration monitoring sites as well as in breeding areas. However, the “loop migration” of Blackpoll Warblers makes it difficult to ascribe population change at migration monitoring sites to specific breeding populations. Individuals from all populations across the breeding range of Blackpoll Warblers concentrate in fall along the Atlantic coastline of eastern North America prior to initiating a transoceanic flight to wintering areas. In spring, Blackpoll Warblers return along a different route, moving north into the southeastern United States where birds from eastern and western breeding populations then diverge during migration to reach their respective breeding areas. To monitor breeding populations outside of breeding areas and identify factors potentially affecting those populations, we must be able to identify where birds captured during migration breed and map seasonal variation in population‐specific flyways. To “map” population‐specific migration movements of Blackpoll Warblers, we used feather deuterium (δ²H_f) values and a spatially explicit model to assign molt origins of 289 Blackpoll Warblers moving through sites in the Gulf of Maine (GOM) region and at three locations further west and south (northern Great Lakes area, Pennsylvania, and Florida). The assignment method was validated with feather samples from 35 birds captured during the breeding season at Churchill, Manitoba, Canada. As predicted, the spatial pattern of movement within and between seasons reflected “loop migration.” Blackpoll Warblers captured during fall migration in the GOM region included birds from across their breeding range, whereas birds captured during the spring were exclusively from northeastern populations. During fall migration, Blackpoll Warblers captured at two sites west of the GOM were from breeding areas further northwest than those from western Canada that were captured in the GOM. Blackpoll Warblers captured in eastern Florida during spring migration were assigned exclusively to breeding areas in the northeast, suggesting that eastern and western populations diverge soon after entering the United States. Finally, most Blackpoll Warblers sampled at Manomet Bird Observatory originated from breeding populations in Alaska and western Canada that have shown a similar (70–90%) decline over the same period. Our results, therefore, not only document the “loop migration” pattern of Blackpoll Warblers, but, by mapping patterns of connectivity between breeding and non‐breeding areas, may help target conservation efforts for breeding populations of Blackpoll Warblers where most needed.     

Seasonal changes in plasma dehydro-epiandrosterone (DHEA) levels of domestic geese

Changes in plasma DHEA, testosterone (T) and 17-B-oestradiol (E2) levels were examined in domestic geese of both sexes in the fall and winter. The levels of steroid hormones were determined in blood plasma by means of radio-immunoassay (RIA). A so-called second (autumn) cycle was induced in geese via a dark-room preparation and natural keeping conditions. The plasma levels of DHEA showed a minor peak at onset of the autumn breeding and a major one prior to the more intense spring reproduction in both sexes. The seasonal curves of plasma DHEA appeared fairly similar in ganders and layers and without considerable differences between the absolute values. In ganders, plasma DHEA peaks preceded the elevations in T levels in the fall and spring alike. With layers, in turn, the autumn and spring peaks of plasma DHEA appeared after the peaks in E2 levels. With ganders, the concentration of plasma T seemed to predominate between the two androgens throughout the experimental period. With layers, in turn, the concentration of DHEA surpassed the level of plasma E2 at the time of the peak periods and other times during the study, as well. In domestic geese, DHEA is probably involved in the autumn physiological processes and the induction of reproduction during fall and early spring periods, alike.     

西藏夯错水鸟多样性及斑头雁繁殖活动区的变化

于2009年4 11月,对西藏夯错的水鸟资源状况进行了调查,旨在了解该地区水鸟资源状况的了解,并为禽流感的防控提供了科学依据。在夯错全年共记录到水鸟26种,隶属于6目10科。夯错也是斑头雁和棕头鸥重要的繁殖地。水鸟春秋季迁徙高峰期在4月份和10月份,这也是水鸟多样性较高的2个月,其主要原因是由于迁徙鸭类数量和种类的增加。卫星跟踪研究表明,在繁殖前期,斑头雁活动区面积较大,主要在夯错及其周围的湿地取食;进入繁殖中期,斑头雁的活动范围减少了许多;繁殖后期,随着幼鸟陆续出壳,父母随即带领幼鸟离开夯错,到其它湿地取食和育雏,因此此期的活动区面积较大。由于夯错面积较小,不能满足斑头雁对食物的需求,因此部分斑头雁选择其它湿地作为主要的取食地,但部分扩散到其它湿地的斑头雁在迁徙前期重新返回夯错,使得该时期斑头雁的数量有呈上升趋势。通过与青海湖水鸟资源状况的比较发现,夯错水鸟种类较少,这可能主要是由于两个湖泊所处地理区划的不同,并由此带来的气候环境的差异,以及植被条件的不同所造成的。这种差异主要是由于夯错海拔较高,紫外线很强,气候干燥,植被单一,栖息地类型多样性较低,因此水鸟的种数也相对较少一些。     

Seasonal changes in the blood composition of captive and free-living White-crowned Sparrows

Summary Seasonal changes in several blood components (cholesterol, phospholipid phosphorus, glyceride glycerol, free fatty acids, and calcium), hematocrit, and body mass were studied in captive and free-living groups of White-crowned Sparrows (Zonotrichia leucophrys gambelii) over a 2-year period. Cholesterol, phospholipid phosphorus, and glyceride glycerol levels were correlated with body mass and all of them changed in parallel during the year (Table 2 and Figs. 1–3). These lipids were elevated during premigratory and migratory periods, minimal during the summer breeding period, and reduced during periods of body molt. Concentrations of them were consistently higher in captive birds than in free-living ones. Free fatty acid levels were highly variable and not correlated with levels of other blood lipids or with body mass (Fig. 4). However, they too increased during premigratory periods. On the other hand, they were consistently higher in free-living sparrows than in captives. Plasma calcium was relatively constant at 3–5 mEq/l between July and the following March (Fig. 5). It increased during the spring, but earlier than preparations for migration by 2–3 weeks. It was also elevated in egg-laying females. The hematocrit rose during the vernal migratory period, but not during the autumnal one; was minimal in breeding birds; and declined during periods of body molt (Fig. 6). Calcium and hematocrit levels were similar in captive and free-living birds. It appears that captive populations of White-crowned Sparrows generally provide relibale information concerning changes in blood composition that are taking place concurrently in the field.This investigation was done to satisfy partially the requirements for the Ph.D. degree at Washington State University by deGraw and Kern. The project was supported by an NIH Training Grant (GM01276) from the National Institute of General Medical Sciences     

青海可鲁克湖水鸟季节动态及渔鸥活动区分析

2008-2010年,对青海可鲁克湖的水鸟季节动态进行了调查。共记录到54种34828只水鸟,隶属于6目11科,雁鸭类水鸟最多,共统计到28445只,占水鸟总数的81.7%;其次是鸥类和鸻鹬类。可鲁克湖在水鸟春秋季迁徙高峰期在4月和10月,这也是水鸟多样性较高的两个月,其主要原因是由于迁徙鸭类数量和种类的增加。卫星跟踪表明,可鲁克湖是青海湖繁殖渔鸥重要的停歇地,渔鸥在可鲁克湖的停歇天数每年也有所不同,2007年和2008年秋季较2006年停歇时间短一些,初步判断与当地的人为干扰有关。当地政府对道路进行修建,其正好位于渔鸥的活动区内,这对渔鸥的日常活动造成较大影响,迫使渔鸥提前离开可鲁克湖。春季停歇天数的不同主要与青海湖面冰融的时间有关,若青海湖由于温度较高,冰融的时间早一些,渔鸥可能提前离开可鲁克湖,前往青海湖进行繁殖活动。     

Seasonal variation in carcass composition of American Wigeon wintering in the Southern High Plains

ABSTRACT.   Studies of the dynamics of carcass components are critical to understanding survival and reproduction in waterfowl. Here, we examined the influence of sex, age, and season on the carcass composition of American Wigeon ( Anas americana ) in the Southern High Plains (SHP) of Texas during the migration and wintering periods. Wigeon ( N = 621) were collected from late fall through early spring, and carcass components (lipid, protein, and mineral) were estimated for each bird. Overall, carcass mass and lipids increased from autumn to early or midwinter and declined thereafter. However, over-winter changes in carcass reserves differed among sex and age groups. Wigeon of different sex and age groups maintained lipid and protein reserves to different degrees and used those reserves through the winter at different rates. The lack of premigratory fattening suggests that wigeon in the SHP must obtain most of the resources necessary for reproduction en route to breeding grounds, and highlights the importance of suitable stopover locations on their migratory routes. Changes in mean structural size of wigeon sampled during the nonbreeding season, in conjunction with genetic data, suggest that the wintering population in the SHP was composed of birds from several breeding populations. Our research will aid migratory bird biologists in determining how wigeon that differ in sex and age meet their over-winter resource needs, and in evaluating the responses of wigeon to habitat conservation and management efforts.     

Dichotomous strategies? The migration of Whimbrels breeding in the eastern Canadian sub‐Arctic

The conservation of migratory birds requires internationally coordinated efforts that, in turn, demand an understanding of population dynamics and connectivity throughout a species' range. Whimbrels (Numenius phaeopus) are a widespread long‐distance migratory shorebird with two disparate North American breeding populations. Monitoring efforts suggest that at least one of these populations is declining, but the level of migratory connectivity linking the two populations to specific non‐breeding sites or identifiable conservation threats remains unclear. We deployed light‐level geolocators in 2012 to track the migration of Whimbrels breeding near Churchill, Manitoba, Canada. In 2013, we recovered 11 of these geolocators, yielding complete migration tracks for nine individuals. During southbound migration, six of the nine Whimbrels stopped at two staging sites on the mid‐Atlantic seaboard of the United States for an average of 22 days, whereas three individuals made nonstop flights of ~8000 km from Churchill to South America. All individuals subsequently spent the entire non‐breeding season along the northern coasts of Brazil and Suriname. On their way north, all birds stopped at the same two staging sites used during southbound migration. Individuals staged at these sites for an average of 34 days, significantly longer than during southbound migration, and all departed within a 5‐day period to undertake nonstop flights ranging from 2600 to 3100 km to the breeding grounds. These extended spring stopovers suggest that female Whimbrels likely employ a mixed breeding strategy, drawing on both endogenous and exogenous reserves to produce their eggs. Our results also demonstrate that this breeding population exhibits a high degree of connectivity among breeding, staging, and wintering sites. As with other long‐distance migratory shorebirds, conservation efforts for this population of Whimbrels must therefore focus on a small, but widely spaced, suite of sites that support a large proportion of the population.     

达赉湖自然保护区疣鼻天鹅繁殖行为初步观察

2006年8～11月和2007年4～8月,在内蒙古达赉湖国家级自然保护区对疣鼻天鹅(Cygnus olor)的繁殖数量、繁殖行为及迁飞时间进行研究.结果显示,疣鼻天鹅通常4月初迁来,10月底迁离,居留期长达196 d左右(n=3).4月下旬开始求偶,时间一般为上午进行,没有固定求偶地点,每次求偶所需时间平均172 s(n=8).主要依靠炫耀行为来保卫和标记领域.2006与2007年的繁殖种群数量均为12只(6对),2006年育成幼鸟数分别为4、2、4、3、6、3只;2007年仅有3对繁殖成功,幼鸟数分别为4、4、5只.     

Flexibility of Continental Navigation and Migration in European Mallards

The ontogeny of continent-wide navigation mechanisms of the individual organism, despite being crucial for the understanding of animal movement and migration, is still poorly understood. Several previous studies, mainly conducted on passerines, indicate that inexperienced, juvenile birds may not generally correct for displacement during fall migration. Waterbirds such as the mallard (Anas platyrhynchos, Linnaeus 1758) are more flexible in their migration behavior than most migratory songbirds, but previous experiments with waterbirds have not yet allowed clear conclusions about their navigation abilities. Here we tested whether immature mallard ducks correct for latitudinal displacement during fall migration within Europe. During two consecutive fall migration periods, we caught immature females on a stopover site in southeast Sweden, and translocated a group of them ca. 1,000 km to southern Germany. We followed the movements of the ducks via satellite GPS-tracking and observed their migration decisions during the fall and consecutive spring migration. The control animals released in Ottenby behaved as expected from banding recoveries: they continued migration during the winter and in spring returned to the population’s breeding grounds in the Baltics and Northwest Russia. Contrary to the control animals, the translocated mallards did not continue migration and stayed at Lake Constance. In spring, three types of movement tactics could be observed: 61.5% of the ducks (16 of 26) stayed around Lake Constance, 27% (7 of 26) migrated in a northerly direction towards Sweden and 11.5% of the individuals (3 of 26) headed east for ca. 1,000 km and then north. We suggest that young female mallards flexibly adjust their migration tactics and develop a navigational map that allows them to return to their natal breeding area.     

Daily and annual variations of free fatty acid, glycerol and leptin plasma concentrations in goats (Capra hircus) under different photoperiods

The aim of the study was to differentiate the impact of lighting conditions and feeding times on the regulation of lipid metabolism of goats under different photoperiods throughout the year. Seven Finnish landrace goats were kept under artificial lighting that simulated the annual changes of photoperiod at 60 degrees N (the longest light period 18 h, the shortest 6 h). Ambient temperature and feeding regime were kept constant. Blood samples were collected six times a year at 2-h intervals for 2 days, first in light/dark (LD) conditions and then after 3 days in constant darkness (DD). Significant daily variations were detected in the concentrations of plasma free fatty acids (FFA) and glycerol throughout the year. The nocturnal decrease and morning rise of FFA levels were related to the photoperiod, while the trough levels of glycerol were associated with the concentrate meal times. In DD conditions, FFA and glycerol rhythms were unstable. A significant seasonal variation was detected in the overall FFA and glycerol levels suggesting decreased lipogenesis in winter, increased lipolysis in spring and high lipogenesis in summer and fall. There was no significant daily rhythm in serum leptin levels, nor did the profiles in LD and DD conditions differ. The leptin level was slightly lower in early fall than in the other seasons, paralleling a small decrease of body mass in the goats after the grazing season. The daily or annual variations of FFA and glycerol levels were not clearly related to leptin concentrations. The results suggest that lipid metabolism of goats is regulated by light even in constant temperature and feeding conditions; however, no significant contribution of leptin levels could be shown.     

Expression profile of BDNF-responsive genes during cerebellar granule cell development

With the aid of microarray and PCR analysis, this investigation sought expression profiles of BDNF-regulated genes in cultured mouse cerebellar granule cells and addressed their relevance to gene regulation in developing granule cells in vivo. Many of the BDNF-upregulated and downregulated genes identified were upregulated and downregulated, respectively, during cerebellar development. This developmental change was, at least partly, prevented in the TrkB receptor-deficient cerebellum. The BDNF-upregulated genes were distributed in either postmigratory or both premigratory and postmigratory granule cells at postnatal day 8 (P8) and were still present in mature granule cells at P21. In contrast, the BDNF-downregulated genes were predominantly expressed in premigratory granule cells at P8 and disappeared at P21. Furthermore, many of the BDNF-upregulated gene products are implicated in signaling cascades of N-methyl-D-aspartate receptors and MAP kinase. The results indicate that BDNF signaling plays a pivotal role in promoting gene expression in granule cell development and maturation.     

近年来乌梁素海疣鼻天鹅种群数量变化及原因分析

为查清内蒙古乌梁素海湖泊湿地疣鼻天鹅(Cygnus olor)繁殖期和秋季迁徙前期种群数量,2014至2017年采用路线统计法和样点统计法对其进行精确计数统计,结合近十余年来的文献数据和监测记录,探讨了种群数量的变化及原因。结果显示,2015至2017年春季繁殖成鸟数量依次为84只、92只、80只,基本稳定;2014至2017年,秋季种群数量依次为411只、302只、281只、153只,逐年减少;近几年适宜繁殖地和觅食地面积不断缩小、天敌偷袭、捡蛋和投毒等因素影响亚成鸟和幼鸟的生存。根据文献和保护区监测数据,1996至2004年种群数量逐年增多,与自然保护区的建立、严禁捡蛋和没收猎枪有关,而2005至2013年因干旱缺水、水域被开发利用、芦苇(Phragmites australis)和宽叶香蒲(Typhalatifolia)面积扩增、水质恶化、富营养化加重等原因种群数量下降。研究表明,近几年乌梁素海被过度开发利用,人为干扰频繁,影响疣鼻天鹅正常繁殖栖息;栖息地的科学管理和严禁捡蛋及投毒行为,对该种群的生存及增长至关重要。     

Comparative population ecology of Ephydra hians Say (Diptera: Ephydridae) at Mono Lake (California) and Abert Lake (Oregon)

The population dynamics of Ephydra hians Say final instar larvae and pupae were compared over a two year period in rocky littoral habitats of two alkaline saline lakes in the western Great Basin. Relative abundance increased from 1983 to 1984 at Mono Lake (California), during dilution from ca. 90 to 80 g 1^-1 TDS (total dissolved solids). In contrast, relative abundance decreased over the same period at Abert Lake (Oregon), accompanied by a dilution of salinity from ca. 30 to 20 g l^-1 and a marked increase in the number and abundance of other benthic macroinvertebrate species. These observations are consistent with a hypothesis that proposes biotic interactions limit E. hians abundance at low salinity, and physiological stress limits abundance at high salinity.Oviposition extends from early spring to early fall. Mixed instars present throughout this period indicates multivoltine population dynamics with overlapping generations. The standing stock biomass of final instars increases exponentially in late spring and peaks in late summer or early fall. Pupae increase in proportional representation and abundance from a spring minimum to a fall maximum. The body size of adults and pupae cycle seasonally from a spring maximum to a fall minimum, and may be related to either or both food limitation, or water temperature.     

Migration strategies of the Baltic dunlin: rapid jump migration in the autumn but slower skipping type spring migration

Migration during spring is usually faster than during autumn because of competition for breeding territories. In some cases, however, the costs and benefits associated with the environment can lead to slower spring migration, but examples are quite rare. We compared seasonal migration strategies of the endangered Baltic population of the dunlin Calidris alpina schinzii using light‐level geolocator data from 26 individuals breeding in Finland. Autumn migration was faster, with individuals showing a ‘jump’ and ‘skipping’ migration strategy characterised by fewer stationary periods, shorter total stopping time and faster flight. Spring migration was slower, with individuals using a ‘skipping’ strategy. The duration of migration was longer for early departing birds during spring but not during autumn suggesting that early spring migrants are prevented from arriving to the breeding areas or that fueling conditions are worse on the stopover sites for early arriving individuals. Dunlins showed high migratory connectivity. All individuals had one long staging at the Wadden Sea in the autumn after which half of the individuals flew 4500 km non‐stop to Banc d’Arguin, Mauritania. The other half stopped briefly on the Atlantic coast on their way to Mauritania. One bird wintered on the coast of Portugal. Nine individuals that carried geolocators for two years were site faithful to their final non‐breeding sites. Based on the strategies during the non‐breeding period we identified, Baltic dunlin may be especially vulnerable to rapid environmental changes at the staging and non‐breeding areas. Consequently, the preservation of the identified non‐breeding areas is important for their conservation.     

Annual survival and breeding dispersal of a migratory passerine,the Scissor‐tailed Flycatcher

Knowledge of survival rates is critical for advancing our understanding of the dynamics of populations and here we report apparent annual survival and breeding dispersal of Scissor‐tailed Flycatchers (Tyrannus forficatus) breeding at two sites in southwest Oklahoma (Ft. Sill and Wichita Mountain Wildlife Refuge [WMWR]). Our Cormack‐Jolly‐Seber estimate of apparent adult survival for the period from 2008 to 2105 was relatively low (0.514) compared to estimates for 36 other migratory and socially monogamous passerines breeding in North America, and was independent of sex (males: N = 151; females: N = 119), breeding status (territory holder or floater), body mass, site, year, and precipitation during the year prior to breeding. Although apparent survival did not differ between sites, dispersal (N = 66 individuals) was more common and breeding dispersal distance (BDD) was greater for Scissor‐tailed Flycatchers at Ft. Sill where anthropogenic disturbance was more frequent. BDD also increased with body mass at Ft. Sill (but not at WMWR) and, after accounting for it, BDD at Ft. Sill tended to be greater for birds that failed to breed successfully in the past year. Older birds and males had the longest BDDs at WMWR, and males exhibited a similar tendency at Ft. Sill. We contend that our estimate of apparent survival is low, not because of inherently low survivorship, but, instead, as a consequence of frequent permanent emigration from our population. We also suggest that the greater BDD of older birds (WMWR) and males (both sites) reflects a history of selection for dispersal in response to frequent habitat disturbance. Frequent habitat disturbance, in addition to the opportunity to prospect for territories both before and after breeding, probably enable the earliest spring arrivals (typically older birds and males) to often relocate between years.     

Seasonal prevalence of skin tumors from walleye (Stizostedion vitreum) from Oneida Lake, New York

A seasonal survey of skin tumor prevalence in walleyes (Stizostedion vitreum) was conducted during the ice-free period on Oneida Lake, New York in 1986. During the survey, 1,028 walleyes were collected and examined for the presence of lymphocystis disease, dermal sarcoma, discrete epidermal hyperplasia and diffuse epidermal hyperplasia. Skin growths were high in prevalence in early spring, low in prevalence during the summer, and again high in prevalence in the fall. Lymphocystis disease and dermal sarcoma were more frequently observed than either discrete or diffuse epidermal hyperplasia. Histologically, a moderate to severe inflammatory response was associated with dermal sarcoma in the early spring and late spring but not in the fall. Regardless of the time of year, varying degrees of inflammatory response were seen associated with lymphocystis disease. Samples were inadequate to assess seasonal trends in incidence of discrete and diffuse epidermal hyperplasia.     

Dry weight loss and changes in chemical composition of pine (Pinus kesiya Royle) needles and teak (Tectona grandis L.) leaves during processing in a freshwater lake

The dry weight loss and chemical changes during the process of decomposition of two types of litters viz.; pine (Pinus kesiya Royle) needles and teak (Tectona grandis L.) leaves have been studied in a small freshwater lake using plastic net (1 mm pore size) bags. The results reveal that type of litter and depth of water were the most important factors regulating the rate of decomposition. The percentage composition of cellulose and hemicellulose showed little variation and only a minor fall was noted in their values towards the end of the study period. The lignin percentage increased steadily at all the stations except the deepest station. The sugar and amino acid concentration dropped appreciably during the initial phase and stabilised during later periods. The general trend of change in nitrogen percentage was initial fall - increase - fall - stabilisation at a near original value. The rate of decomposition was faster when compared with similar studies in Canada and Europe.