scholarly journals Temporal and Spatial Variation of Aboveground Biomass of Pinus densata and Its Drivers in Shangri-La, CHINA

2021 ◽  
Vol 19 (1) ◽  
pp. 400
Author(s):  
Dongfan Xu ◽  
Jialong Zhang ◽  
Rui Bao ◽  
Yi Liao ◽  
Dongyang Han ◽  
...  
Keyword(s):  
Population Density ◽  
Aboveground Biomass ◽  
Stand Structure ◽  
High Population ◽  
Spatial And Temporal Variation ◽  
Agricultural Activity ◽  
High Population Density ◽  
Forest Protection ◽  
Pinus Densata ◽  
River Region

Understanding the drivers of forest aboveground biomass (AGB) is essential to further understanding the forest carbon cycle. In the upper Yangtze River region, where ecosystems are incredibly fragile, the driving factors that make AGB changes differ from other regions. This study aims to investigate AGB’s spatial and temporal variation of Pinus densata in Shangri-La and decompose the direct and indirect effects of spatial attribute, climate, stand structure, and agricultural activity on AGB in Shangri-La to evaluate the degree of influence of each factor on AGB change. The continuous sample plots from National Forest Inventory (NFI) and Landsat time series were used to estimate the AGB in 1987, 1992, 1997, 2002, 2007, 2012, and 2017. The structural equation model (SEM) was used to analyze the different effects of the four factors on AGB based on five scales: entire, 1987–2002, 2007–2017, low population density, and high population density. The results are as follows: (1) The AGB of Pinus densata in Shangri-La decreased from 1987 to 2017, with the total amount falling from 9.52 million tons to 7.41 million tons, and the average AGB falling from 55.49 t/ha to 40.10 t/ha. (2) At different scales, stand structure and climate were the drivers that directly affect the AGB change. In contrast, the agricultural activity had a negative direct effect on the AGB change, and spatial attribute had a relatively small indirect effect on the AGB change. (3) Analyzing the SEM results at different scales, the change of the contribution of the agricultural activity indicates that human activity is the main negative driver of AGB change in Shangri-La, especially at the high population density region. In contrast, the change of the contribution of the stand structure and climate indicates that the loss of old trees has an important influence on the AGB change. Forest resources here and other ecologically fragile areas should be gradually restored by adhering to policies, such as strengthening forest protection, improving forest stand quality, and limiting agricultural production activities.

scholarly journals Recruitment sex ratios in gray-tailed voles (Microtus canicaudus) in response to density, sex ratio, and season

2003 ◽  
Vol 81 (8) ◽  
pp. 1306-1311 ◽  
Author(s):  
Monica L Bond ◽  
Jerry O Wolff ◽  
Sven Krackow
Keyword(s):  
Population Density ◽  
Sex Ratio ◽  
Resource Competition ◽  
Sex Ratios ◽  
Female Offspring ◽  
High Population ◽  
Reproductive Value ◽  
High Population Density ◽  
Adult Sex Ratio ◽  
Sex Ratio Adjustment

We tested predictions associated with three widely used hypotheses for facultative sex-ratio adjustment of vertebrates using eight enclosed populations of gray-tailed voles, Microtus canicaudus. These were (i) the population sex ratio hypothesis, which predicts that recruitment sex ratios should oppose adult sex-ratio skews, (ii) the local resource competition hypothesis, which predicts female-biased recruitment at low adult population density and male-biased recruitment at high population density, and (iii) the first cohort advantage hypothesis, which predicts that recruitment sex ratios should be female biased in the spring and male biased in the autumn. We monitored naturally increasing population densities with approximately equal adult sex ratios through the spring and summer and manipulated adult sex ratios in the autumn and measured subsequent sex ratios of recruits. We did not observe any significant sex-ratio adjustment in response to adult sex ratio or high population density; we did detect an influence of time within the breeding season, with more female offspring observed in the spring and more male offspring observed in the autumn. Significant seasonal increases in recruitment sex ratios indicate the capacity of female gray-tailed voles to manipulate their offspring sex ratios and suggest seasonal variation in the relative reproductive value of male and female offspring to be a regular phenomenon.

Aggregations of masked shrews ( Sorex cinereus ): density-related mating behavior? / Agrégation de musaraignes masquées ( Sorex cinereus ): accouplement relatif à la densité de la population?

Mammalia ◽  
2006 ◽  
Vol 70 (1-2) ◽  
Author(s):  
Thomas J. Maier ◽  
Katherine L. Doyle
Keyword(s):  
Population Density ◽  
Mating Behavior ◽  
High Population ◽  
High Population Density ◽  
Genetic Analyses ◽  
Highly Active ◽  
Sorex Cinereus

AbstractLarge aggregations of shrews have been reported and various explanations offered for this seemingly rare behavior; however, there has been little evidence to support any particular interpretation. We observed two small aggregations of highly active vocalizing Sorex cinereus while performing wildlife surveys in forested habitats in central Massachusetts, USA. These observations, in conjunction with a review of other reports, including genetic analyses, strongly suggest that such aggregations of adult Sorex are associated with mating behavior, more readily observed during periods of high population density. Published accounts of such behavior may be rare because primarily large aggregations have been reported; however, smaller breeding aggregations may be common.

Analysis of steroid hormone levels in female mice at high population density

1998 ◽  
Vol 64 (4) ◽  
pp. 529-533 ◽  
Author(s):  
John C Chapman ◽  
John J Christian ◽  
Mary Ann Pawlikowski ◽  
Sandra D Michael
Keyword(s):  
Population Density ◽  
Steroid Hormone ◽  
High Population ◽  
High Population Density ◽  
Hormone Levels ◽  
Female Mice

Environmental Issues Regarding Space Launches over the Black Sea

2013 ◽  
Vol 330 ◽  
pp. 805-810
Author(s):  
Dragos R. Rugescu
Keyword(s):  
Population Density ◽  
Black Sea ◽  
Environmental Issues ◽  
High Population ◽  
The Black Sea ◽  
Western Coast ◽  
High Population Density ◽  
Research Activity ◽  
The West ◽  
Space Project

The Romanian NERVA space project, aimed at building and using a small rocket launcher for injecting nanosatellites into a LEO, requires the establishment of a secure launching area. The first candidate is on the western coast of the Black Sea and the candidate launching and flight corridor is the west-east vector above the sea. A series of ecological and safety challenges appear due to the high population density of the regions close to the sea-shores of the Black Sea; they must be catalogued and securely solved, before any space activity above the Black Sea begins. The main challenges of such an endeavor are analyzed henceforth and several solutions that fall within the scope of a recent research activity of the NERVA team are proposed.

Male territoriality and mating success in Nannothemis bella (Uhler) (Odonata: Libellulidae)

1986 ◽  
Vol 64 (9) ◽  
pp. 1820-1826 ◽  
Author(s):  
Rupert C. P. Lee ◽  
Patrick McGinn
Keyword(s):  
Population Density ◽  
Mating Success ◽  
Census Data ◽  
High Population ◽  
Territorial Behaviour ◽  
High Population Density ◽  
Male Population ◽  
Distinct Subpopulation ◽  
Male Territoriality ◽  
Territory Holder

Observations of territorial behaviour of male Nannothemis bella indicated that females only laid eggs on males' territories after copulating with the territory holder. Results of daily censuses of marked individuals on a study area suggested that a distinct subpopulation within the male population never retained a territory for more than 1 day on the study area. Such males tend to die or emigrate sooner than do males that hold a territory on the study area for more than 1 day at some time in their lives. Further observations of territorial behaviour showed that males holding territories for less than 1 day achieved copulations at significantly lower overall rates while on those territories than did males that retained territories for more than 1 day. We infer that all males attempt to hold territories for as long as possible, but under conditions of high population density a male must have a relatively high intrinsic "territory-holding ability" in order to hold a territory for more than 1 day. Census data indicated that males emerging late in the season were less likely to retain a territory for more than 1 day than males emerging earlier.

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