Basin-Wide Effects of Game Harvest on Vertebrate Population Densities in Amazonian Forests: Implications for Animal-Mediated Seed Dispersal

Vertebrate responses to hunting are widely variable for target and nontarget species depending on the history of hunting and productivity of any given site and the life history traits of game species. We provide a comprehensive meta-analysis of changes in population density or other abundance estimates for 30 mid-sized to large mammal, bird and reptile species in 101 hunted and nonhunted, but otherwise undisturbed, Neotropical forest sites. The data set was analyzed using both an unnested approach, based on population density estimates, and a nested approach in which pairwise comparisons of abundance metrics were restricted to geographic groups of sites sharing similar habitat and soil conditions. This resulted in 25 geographic clusters of sites within which 1811 population abundance estimates were compared across different levels of hunting pressure. Average nested changes in abundance across increasingly greater levels of hunting pressure ranged from moderately positive to highly negative. Populations of all species combined declined across greater differences in hunting pressure by up to 74.8 percent from their numeric abundance in less intensively hunted sites, but harvest-sensitive species faired far worse. Of the 30 species examined, 22 declined significantly at high levels of hunting. Body size significantly affected the direction and magnitude of abundance changes, with large-bodied species declining faster in overhunted sites. Frugivorous species showed more marked declines in abundance in heavily hunted sites than seed predators and browsers, regardless of the effects of body size. The implications of hunting for seed dispersal are discussed in terms of community dynamics in semi-defaunated tropical forests.     

落叶阔叶林反照率的时间变化与影响因素

反照率原位测量对生态系统能量收支及其遥感应用至关重要,但目前坡面地形反照率的测量方式有局限且可见光与近红外波段反照率时间变化的差异尚不清楚。本研究以东北地区帽儿山森林生态站的落叶阔叶林为例,探究入射和反射太阳辐射(SR,300～2800 nm)、光合有效辐射(PAR,400～700 nm)、近红外辐射(NIR,700～2800 nm)的反照率时间变化特征及其影响因子,同时分析了两种辐射表安装方式反照率的差异。结果表明: 晴天SR和NIR反照率日变化呈上下午不对称的U型曲线,但PAR从早到晚递增;阴天反照率均先急剧下降后趋于稳定。平行于坡面测量增大了反照率的日均值,但缓和了SR、NIR反照率日不对称的现象。从整个生长季来看,SR、NIR与PAR反照率水平测量时最大值分别为0.16、0.27和0.11,最小值分别为0.07、0.11和0.03。SR和NIR反照率季节变化均为先增大后减小(7月为峰值),PAR则相反,SR反照率主要受NIR而不是PAR控制。各波段反照率季节变化的影响因子按照贡献率排序为宽带归一化植被指数(61.7%～78.5%,可表征叶面积指数)>太阳高度角(15.4%～36.9%)>晴空指数(0.4%～36.9%)。     

Atlantic Forest topsoil nutrients can be resistant to disturbance and forest clearing

Human impacts can affect the soil properties through erosion and leaching, the ecosystem functions and, consequently, the capacity of a forest to regenerate. Here, we determine the effects of forest disturbance and succession on selected soil chemical properties using two different approaches, before‐after‐control‐impact (BACI) and space‐for‐time (SFT) substitution, and the threatened Atlantic Forest biome as model. We assessed with BACI the long‐term (37‐year) effects of clear cutting on soil properties by comparing data from two topsoil surveys (1978–2017) divided into two treatments: a preserved old growth forest (control) and an adjacent forest that was experimentally cleared with full tree removal (clear‐cut). We examined with SFT the relationship between stand age and soil properties using soil data from three old growth and 13 s growth forests ranging from 7 to 33 years. We found no significant differences between treatments for any soil property or significant changes in phosphorus, potassium, and calcium + magnesium over time. In contrast, pH increased and aluminum decreased in both areas. No relation was found between forest age and most of soil properties, with the exception of potassium which returned to old growth forest levels after 20 years of natural succession, and pH. BACI indicated that deforestation of old growth forest caused no significant effects on soil chemical properties after 37 years of regeneration. SFT demonstrated that soil properties did not change significantly during forest regeneration on formerly disturbed lands. Our findings indicate that natural nutrient‐depleted lowland forests were overall resistant to deforestation followed by passive regeneration at landscape scale. Abstract in Portuguese is available with online material.     

NEOSQUIRREL: a data set of ecological knowledge on Neotropical squirrels

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Evolution of dentition in prehistoric Ohio Valley Native Americans III. Metrics of deciduous dentition

Deciduous tooth size in Native Americans of the Ohio Valley area is fairly stable from the terminal Late Archaic (3200 BP) through the Late Prehistoric (350 BP) periods. Some fluctuation in average size did occur during this time. These fluctuations most likely reflect random changes due to gene drift. However, no difference in the pattern of interactions among the sizes of teeth (covariance structures) can be demonstrated during this period. Principal components analysis of the buccolingual and mesiodistal dimensions in the total sample indicate that the major axis of deciduous tooth size in the Ohio Valley population shows an allometric relationship, with the dimensions of the anterior teeth increasing (or decreasing) as the 1.33 power of the dimension of m1(1) and as the 2.0 power of the dimension of m2(2). Comparison of the Ohio Valley samples with other samples from the Eastern Woodlands suggests that geography may have played a minor role in structuring deciduous tooth size variation. For the most part, however, widely separated Eastern Woodlands populations appear to have been evolving independently with respect to deciduous tooth size.     

针阔混交林内白颈长尾雉栖息地利用的影响因子研究

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Modelling seedling growth rates of 18 temperate arable weed species as a function of the environment and plant traits

BACKGROUND AND AIMS: The early growth rate of seedlings in the exponential phase is an important eco- physiological trait in crop/weed competition models based on assessments of relative weed green area. An understanding of the role of various plant traits in determining early growth rate may also be useful for identifying contrasting weed strategies for establishment before canopy closure. METHODS: The response of seedling relative growth rate (RGR) to the environment was measured in outdoor sand beds in the autumn and the spring for 18 temperate annual weed species and two crops. Seedling growth was modelled using thermal time and effective day-degrees (combining the effect of temperature and radiation). The contribution of various plant traits in determining variability in RGR was investigated using regression analysis. KEY RESULTS: The effective day-degree model was more effective for describing early weed growth than thermal time. Variability in RGR measured in the autumn was largely determined by differences between the species in net assimilation rate (NAR), whereas in the spring leaf area ratio (LAR) played a larger part. There were differences between the broadleaf and grass species in the relative contribution of NAR and LAR to RGR in both seasons. RGR in the spring was negatively correlated with initial seedling size. CONCLUSIONS: The parameters derived in this study can be used to calibrate empirical models of crop yield loss based on relative weed green area to different growing seasons and assessment dates. The grass weeds, which tended to have large seeds, had a higher investment in roots in the seedling stage, potentially making them more competitive later in the season when resources become limiting.