The role of gap phase processes in the biomass dynamics of tropical forests

The responses of tropical forests to global anthropogenic disturbances remain poorly understood. Above-ground woody biomass in some tropical forest plots has increased over the past several decades, potentially reflecting a widespread response to increased resource availability, for example, due to elevated atmospheric CO2 and/or nutrient deposition. However, previous studies of biomass dynamics have not accounted for natural patterns of disturbance and gap phase regeneration, making it difficult to quantify the importance of environmental changes. Using spatially explicit census data from large (50 ha) inventory plots, we investigated the influence of gap phase processes on the biomass dynamics of four 'old-growth' tropical forests (Barro Colorado Island (BCI), Panama; Pasoh and Lambir, Malaysia; and Huai Kha Khaeng (HKK), Thailand). We show that biomass increases were gradual and concentrated in earlier-phase forest patches, while biomass losses were generally of greater magnitude but concentrated in rarer later-phase patches. We then estimate the rate of biomass change at each site independent of gap phase dynamics using reduced major axis regressions and ANCOVA tests. Above-ground woody biomass increased significantly at Pasoh (+0.72% yr(-1)) and decreased at HKK (-0.56% yr(-1)) independent of changes in gap phase but remained stable at both BCI and Lambir. We conclude that gap phase processes play an important role in the biomass dynamics of tropical forests, and that quantifying the role of gap phase processes will help improve our understanding of the factors driving changes in forest biomass as well as their place in the global carbon budget.     

The State of Federal Research Funding in Genetics as Reflected by Members of the Genetics Society of America

Scientific progress runs on the intellect, curiosity, and passion of its practitioners fueled by the research dollars of its sponsors. The concern over research funding in biology in general and genetics in particular led us to survey the membership of the Genetics Society of America for information about the federal support of genetics at the level of individual principal investigators. The results paint a mosaic of circumstances—some good, others not so good—that describes some of our present challenges with sufficient detail to suggest useful steps that could address the challenges.     

Composition and diversity of herbaceous patches in woody vegetation: The effects of grazing,soil seed bank,patch spatial properties and scale

Herbaceous plants contribute much to plant diversity in Mediterranean-type ecosystems though mostly occupying relatively small patches within the dense woody vegetation. While studying species diversity in the herbaceous patches, we hypothesized that grazing, soil seed bank, and spatial properties of the patch affect plant diversity and composition at different spatial scales. The study site was in an LTER site located in the Mediterranean region in north Israel. We determined herbaceous species composition in: (1) randomly sampled quadrats in herbaceous patches in grazed and un-grazed plots; (2) soil seed bank samples taken from the same patches and germinated under optimal greenhouse conditions; (3) quadrats in the same patches sown with a homogenous mixture of local soil samples. Using GIS methods, we determined small-scale spatial characteristics of the herbaceous patches. Alpha and beta diversities were calculated at the patch and plot scales using Shannon's entropy H. Grazing increased alpha diversity of local untreated seed bank samples but decreased alpha diversity of the artificial homogenous soil seed bank mixture at both patch and plot scales. Positive relation between alpha diversity and patch area was detected only under grazing. Grazing increased beta diversity in all three treatments at the patch scale. Grazing decreased the similarity in species composition between above-ground vegetation and soil seed bank. The results indicate that moderate cattle-grazing affects species diversity in the herbaceous patches within the dense maquis. This effect is scale-dependent, and interacts with the effects of soil seed bank and patch spatial-properties: without grazing soil seed bank plays a more important role than patch spatial properties, but under grazing the size and the accessibility of the patch are more important in the determination of herbaceous species composition.     

Modelling Direct Radiation and Canopy Gap Regimes in Tropical Forests

Spatial and temporal variation in the below‐canopy light environment of tropical forests is not well known and its measurement is technically challenging. Distributions of gap and understory areas in forests are likewise little known because of the resource requirements of forest structural censuses and a lack of consensus over how gaps should be defined. A basic model of forest structure, based on tree allometries from the 50 ha Forest Dynamics Plot on Barro Colorado Island (BCI), Panama, and a solar positioning algorithm were used to predict spatial and temporal variation in the distribution of direct light at the forest floor. Predicted duration of direct sunlight was then compared with the distribution of gap and understory areas, delimited according to four standard gap definitions, giving predictions for the correspondence between direct light regimes and forest structure. At least 36 percent of the areas of gaps of all sizes was predicted to receive < 1 h of direct sunlight per day, and the understory to receive direct sunlight for ≥ 1 h per day in up to 15 percent of its area, even when not in proximity to gaps. The predicted distribution of light changed over the course of the year with the greatest spread of light throughout the forest floor coinciding with the months when maximum daily solar elevation peaked. These predictions suggest a partial decoupling of light regimes from canopy structure, with implications for gap definitions, patch models of forest development and current understanding of tree seedling recruitment patterns.     

Comparative study on spatial patterns of the Artemisia ordosica population in the Mu Us sandy land

Artemisia ordosica is an under-shrub species, which dominates the vegetation of the Mu Us sandy land in North China. The spatial patterns of the A. ordosica population in different sandy lands were compared with the methods of Spatial Auto-correlation Analysis, Semi-variance Analysis and Nine-Term Local Quadrat Variance (9TLQV). The results show that, by contrast with the A. ordosica population in fixed sandy land, the population in semi-fixed sandy land is of stronger auto-correlation and greater spatial heterogeneity, and meanwhile it presents more intense differentiation between patches and gaps. The spatial patterns of the A. ordosica population in semi-fixed sandy land are probably governed by drifting sand caused by strong winds. Drifting sand can easily put A. ordosica shrubs to death unless they live together in form of A. ordosica patches, where the distances between shrubs are short. In semi-fixed sandy land, patches are not only the form of the A. ordosica population to survive drifting sand, but also the foundation of the A. ordosica population to develop and broaden the area. The A. ordosica population is supposed to broaden the area through edge extending out from the patches scattering in semi-fixed sandy land. The spatial patterns of the A. ordosica population in fixed sandy land are possibly affected by intra-specific competition related to high plant coverage. This study is ecologically useful to improve the practice of vegetation restoration in sandy land. When transplanting A. ordosica shrubs to bare sandy land, one had better arrange them in form of patches separated by gaps, which can promote the survival of transplanted shrubs, and also help to take advantage of A. ordosica patches to revegetate bare gaps.     

Canopy structure in a temperate old-growth evergreen forest analyzed by using aerial photographs

We used aerial photographs to create a digital elevation model of the canopy surface of a 10-ha study area in a temperate old-growth evergreen forest. A topographic map of the ground surface in a 4-ha permanent plot within the study area was also drawn from ground measurements. The difference between the two elevation values (i.e., canopy surface – ground surface) at each point in a 5-m grid was considered to be the canopy height, and a canopy height profile was constructed from these data. The canopy structure in the 4-ha plot that was estimated in this way was compared with that obtained by two ground observation methods, i.e., the canopy (vegetation) height profile method and the canopy coverage census method. Large gaps were adequately detected by the aerial photograph method, but small gaps were less often detected. Gap size distribution obtained by the aerial photograph method was similar to that observed on the ground, and was a function of gap depth. This study indicates that if a detailed topographic map can be made, the canopy height profile derived from aerial photography can be effective in analyzing the canopy structure of evergreen forests, such as tropical rain forests, over large areas.     

Propagation of local interactions create global gap structure and dynamics in a tropical rainforest

Gap dynamics in tropical forests are of interest because an understanding of them can help to predict canopy structure and biodiversity. We present a simple cellular automaton model that is capable of capturing many of the trends seen in the canopy gap pattern of a complex tropical rainforest on the Barro Colorado Island (BCI) using a single set of model parameters. We fit the global and local densities, the cluster size distributions, and two correlation functions, for gaps, gap formations, and gap closures determined from a spatial map of the forest (1983-1984). To the best of our knowledge, this is the first report that the cluster size distributions of gap formations and closures in the BCI are both power laws. An important element in the model is that when a transition from gap to non-gap (closure), or vice versa (formation), occurs, this transition is allowed to expand into adjacent cells in order to make different cluster sizes of transitions. Model results are in excellent agreement with reported field data. The propagation of local interactions is necessary in order to obtain the complex dynamics of the gap pattern. We also establish a connection between the global and local densities via the neighborhood-dependent transition rates and the effective global transition rates.     

西双版纳望天树林林窗小气候特征研究

 对西双版纳望天树林林窗小气候要素的季节变化、水平差异进行了观测研究,并对比分析了两个大小不同林窗内温度垂直分布状况、相对湿度差别。结果表明：大林窗内温度、湿度、光照的日变化均比林内大;大林窗中央光照强度为林内的10倍以上,太阳总辐射量、净辐射量为林内的5倍以上,大林窗中央的蒸发耗热量大于林内,且均占各自净辐射的较大比例(70％～80％),干季大林窗内温度、湿度日变化比雨季剧烈,大林窗内具有两个加热层(幼苗冠层、地表),小林窗仅有一个加热层(幼树冠层),且前者的加热强度大于后者,相对湿度日变化则是大林窗内较剧烈。     

黄河流域水鸟保护优先区及空缺

黄河流域为迁徙水鸟提供重要的繁殖地、越冬地和停歇地。然而,黄河流域正面临着农业开垦、城市化、水资源分布不均等一系列的生态安全问题,威胁迁徙水鸟种群及其栖息地稳定性。因此,识别黄河流域重要的水鸟栖息地分布区域,分析当前的保护现状对于开展水鸟及栖息地保护至关重要。以黄河流域为研究区,搜集整合来自国内外观鸟网站(eBird、全球生物多样性信息库(GBIF)和中国观鸟记录中心(BirdReport))、文献和水鸟调查报告中的水鸟调查数据,沿用三个国际上通用的水鸟重要栖息地识别标准,确定了黄河流域水鸟保护优先区。在此基础上,使用水鸟栖息地重要性指数确定水鸟保护优先区保护优先等级,结合国家自然保护地名录,分析水鸟保护优先区保护空缺状况。结果显示:黄河流域共有47个水鸟保护优先区,主要分布在黄河流域中游和下游,其中河南省和山东省水鸟保护优先区较多。满足水鸟保护优先区识别标准的水鸟共14种,其中,极危物种有2个,濒危物种有1个,易危物种有5个。水鸟保护优先区保护优先等级处于I、II和III类的分别有2个、8个和37个。有20个水鸟保护优先区处于保护空缺状态,占总数的42.55%,主要集中在黄河中游和下游,其中,水鸟保护优先等级处于I类或II类的地块有3个,建议将这些保护空缺地以自然保护区、保护小区或国家公园形式纳入湿地保护地体系,并加强长期监测。     

Geographic distribution,conservation effectiveness,and gaps for national key protected wild plants in China

National key protected wild plants (NKPWPs) are species with important conservation value based on genetics, ecology, culture, and/or scientific research, which are also confronted with serious threats. However, their geographical distribution patterns and conservation status remain unclear. In this study, we compiled 1032 species of NKPWPs. We measured the diversity to identify hotspots of NKPWPs based on species richness, weighted range size rarity and a complementarity-based analysis. Comparing the distribution and hotspots of NKPWPs with the coverage of Chinese nature reserves (NRs), we assessed conservation effectiveness and identified conservation gaps. The results identified 13 diversity hotspots; only 9.5% of them were covered by NRs with >30% of the grid cell area, and even 19.5% were not covered at all by NRs. Overall, 44.7% of NKPWPs were effectively protected by national NRs. Despite this success, 571 species in Yunnan, Guizhou, Sichuan, Chongqing, Guangxi, Guangdong, southern Hainan, Taiwan, and northern Xinjiang remain unprotected by NRs. The protected proportion of plants with first-level protection was lower than that of plants with second-level protection. The low overall proportion of protected hotspots indicates that the conservation outlook for NKPWPs is not optimistic. This study identifies priority conservation areas and conservation gaps and provides a scientific reference for the conservation of wild plants in China.