Eungul Lee

Positive biodiversity-productivity relationship predominant in global forests.

Global biodiversity and productivity The relationship between biodiversity and ecosystem productivity has been explored in detail in herbaceous vegetation, but patterns in forests are far less well understood. Liang et al. have amassed a global forest data set from >770,000 sample plots in 44 countries. A positive and consistent relationship can be discerned between tree diversity and ecosystem productivity at landscape, country, and ecoregion scales. On average, a 10% loss in biodiversity leads to a 3% loss in productivity. This means that the economic value of maintaining biodiversity for the sake of global forest productivity is more than fivefold greater than global conservation costs. Science, this issue p. 196 Global forest inventory records suggest that biodiversity loss would result in a decline in forest productivity worldwide. INTRODUCTION The biodiversity-productivity relationship (BPR; the effect of biodiversity on ecosystem productivity) is foundational to our understanding of the global extinction crisis and its impacts on the functioning of natural ecosystems. The BPR has been a prominent research topic within ecology in recent decades, but it is only recently that we have begun to develop a global perspective. RATIONALE Forests are the most important global repositories of terrestrial biodiversity, but deforestation, forest degradation, climate change, and other factors are threatening approximately one half of tree species worldwide. Although there have been substantial efforts to strengthen the preservation and sustainable use of forest biodiversity throughout the globe, the consequences of this diversity loss pose a major uncertainty for ongoing international forest management and conservation efforts. The forest BPR represents a critical missing link for accurate valuation of global biodiversity and successful integration of biological conservation and socioeconomic development. Until now, there have been limited tree-based diversity experiments, and the forest BPR has only been explored within regional-scale observational studies. Thus, the strength and spatial variability of this relationship remains unexplored at a global scale. RESULTS We explored the effect of tree species richness on tree volume productivity at the global scale using repeated forest inventories from 777,126 permanent sample plots in 44 countries containing more than 30 million trees from 8737 species spanning most of the global terrestrial biomes. Our findings reveal a consistent positive concave-down effect of biodiversity on forest productivity across the world, showing that a continued biodiversity loss would result in an accelerating decline in forest productivity worldwide. The BPR shows considerable geospatial variation across the world. The same percentage of biodiversity loss would lead to a greater relative (that is, percentage) productivity decline in the boreal forests of North America, Northeastern Europe, Central Siberia, East Asia, and scattered regions of South-central Africa and South-central Asia. In the Amazon, West and Southeastern Africa, Southern China, Myanmar, Nepal, and the Malay Archipelago, however, the same percentage of biodiversity loss would lead to greater absolute productivity decline. CONCLUSION Our findings highlight the negative effect of biodiversity loss on forest productivity and the potential benefits from the transition of monocultures to mixed-species stands in forestry practices. The BPR we discover across forest ecosystems worldwide corresponds well with recent theoretical advances, as well as with experimental and observational studies on forest and nonforest ecosystems. On the basis of this relationship, the ongoing species loss in forest ecosystems worldwide could substantially reduce forest productivity and thereby forest carbon absorption rate to compromise the global forest carbon sink. We further estimate that the economic value of biodiversity in maintaining commercial forest productivity alone is

Southwestern U.S. drought maps from pinyon tree‐ring carbon isotopes

166 billion to

Potential feedback of recent vegetation changes on summer rainfall in the Sahel

490 billion per year. Although representing only a small percentage of the total value of biodiversity, this value is two to six times as much as it would cost to effectively implement conservation globally. These results highlight the necessity to reassess biodiversity valuation and the potential benefits of integrating and promoting biological conservation in forest resource management and forestry practices worldwide. Global effect of tree species diversity on forest productivity. Ground-sourced data from 777,126 global forest biodiversity permanent sample plots (dark blue dots, left), which cover a substantial portion of the global forest extent (white), reveal a consistent positive and concave-down biodiversity-productivity relationship across forests worldwide (red line with pink bands representing 95% confidence interval, right). The biodiversity-productivity relationship (BPR) is foundational to our understanding of the global extinction crisis and its impacts on ecosystem functioning. Understanding BPR is critical for the accurate valuation and effective conservation of biodiversity. Using ground-sourced data from 777,126 permanent plots, spanning 44 countries and most terrestrial biomes, we reveal a globally consistent positive concave-down BPR, showing that continued biodiversity loss would result in an accelerating decline in forest productivity worldwide. The value of biodiversity in maintaining commercial forest productivity alone—US

Empirical Relationships of Sea Surface Temperature and Vegetation Activity with Summer Rainfall Variability over the Sahel

166 billion to 490 billion per year according to our estimation—is more than twice what it would cost to implement effective global conservation. This highlights the need for a worldwide reassessment of biodiversity values, forest management strategies, and conservation priorities.

Effects of Temperature on Development and Voltinism of Chaetodactylus krombeini (Acari: Chaetodactylidae): Implications for Climate Change Impacts

Tree-ring widths have long been a useful North American drought proxy [e.g., Cook et al., 1999, 2004]. A potentially rich, new tree-ring proxy associated with the trees leaf-level moisture status is stable-carbon isotope composition (δ13C = [13C/12Csample ÷ 13C/12Cstandard − 1[ × 1000), which is determined by both the rate of carbon assimilation and the rate of gas conductance through leaf stomata [Farquhar et al., 1982]. In the U.S. Southwest, where evaporation exceeds precipitation, drought may be the dominant influence on plant δ>13C [Warren et al., 2001], so measurements of tree-ring δ13C in a network of southwestern sites has allowed for spatially mapping this ecophysiological indicator back to A.D. 1600. Stomatal portals are the primary avenues of water loss and carbon gain in plants, providing carbon dioxide (CO2) for photosynthesis, which tends to discriminate against fixation of 13CO2 in favor of 12CO2. In principle, under conditions of water stress the stomata close down and the reservoir of CO2 available for continued photosynthesis is reduced, proportionally more 13CO2 is fixed, and the 13C/12C ratio of sugars eventually incorporated into tree rings increases (i.e., δ13C increases), and vice versa during moist conditions.

Societal response to monsoon variability in Medieval South India: Lessons from the past for adapting to climate change:

The Sahel region of Northern Africa is home to more than 50 million people for whom summer rainfall is a crucial water resource in terms of food security and societal stability. Using satellite-based Normalized Difference Vegetation Index (NDVI) and gridded observational precipitation records during 1982–2012, we detected a significant increase (p-value < 0.01) in both vegetation greenness and monsoon rainfall over the Sahel since the early 1980s. A significant positive association between NDVI and precipitation was observed for most of the Sahel during the boreal summer. In further efforts to examine the potential causal association behind the positive correlation, we found that summer vegetation greenness Granger-causes summer rainfall in the Sahel. Regarding the physical process behind this identified Granger causality, we inferred that significantly increasing latent heat flux and specific humidity resulted in increasing summer rainfall during the years of high NDVI in the Sahel. A significant increase in the percentage of land used for crops and pastures was a potential cause of the recent vegetation change. Our findings indicated that the positive effect of vegetation cover through agricultural activities on regional precipitation could lead to a positive feedback between the vegetation and climate in the water-limited Sahel region.

Reducing Uncertainties in Applying Remotely Sensed Land Use and Land Cover Maps in Land-Atmosphere Interaction: Identifying Change in Space and Time

AbstractRegional land surface and remote ocean variables have been considered as primary forcings altering the variability of summer rainfall over the Sahel. However, previous studies usually examined the two components separately. In this study, the authors apply statistical methods including correlation, multivariate linear regression, and Granger causality analyses to investigate the relative roles of spring–summer sea surface temperature (SST) and vegetation activity in explaining the Sahel summer rainfall variability from 1982 to 2006. The remotely sensed normalized difference vegetation index (NDVI) is used as an indicator of land surface forcing. This study shows that spring and summer SSTs over the subtropical North Atlantic have significant positive correlations with summer rainfall. The spring and summer NDVIs over the Sahel have significant negative and positive correlations, respectively, with summer rainfall. Based on the multivariate linear regression analysis, the adjusted R2 for the integr...

Continuous annual land use and land cover mapping using AVHRR GIMMS NDVI3g and MODIS MCD12Q1 datasets over China from 1982 to 2012

Temperature plays an important role in the growth and development of arthropods, and thus the current trend of climate change will alter their biology and species distribution. We used Chaetodactylus krombeini (Acari: Chaetodactylidae), a cleptoparasitic mite associated with Osmia bees (Hymenoptera: Megachilidae), as a model organism to investigate how temperature affects the development and voltinism of C. krombeini in the eastern United States. The effects of temperature on the stage-specific development of C. krombeini were determined at seven constant temperatures (16.1, 20.2, 24.1, 27.5, 30.0, 32.4 and 37.8°C). Parameters for stage-specific development, such as threshold temperatures and thermal constant, were determined by using empirical models. Results of this study showed that C. krombeini eggs developed successfully to adult at all temperatures tested except 37.8°C. The nonlinear and linear empirical models were applied to describe quantitatively the relationship between temperature and development of each C. krombeini stage. The nonlinear Lactin model estimated optimal temperatures as 31.4, 32.9, 32.6 and 32.5°C for egg, larva, nymph, and egg to adult, respectively. In the linear model, the lower threshold temperatures were estimated to be 9.9, 14.7, 13.0 and 12.4°C for egg, larva, nymph, and egg to adult, respectively. The thermal constant for each stage completion were 61.5, 28.1, 64.8 and 171.1 degree days for egg, larva, nymph, and egg to adult, respectively. Under the future climate scenarios, the number of generations (i.e., voltinism) would increase more likely by 1.5 to 2.0 times by the year of 2100 according to simulation. The findings herein firstly provided comprehensive data on thermal development of C. krombeini and implications for the management of C. krombeini populations under global warming were discussed. *Scientific Article No. 3278 of the West Virginia Agricultural and Forestry Experiment Station, Morgantown, West Virginia

Effects of irrigation and vegetation activity on early Indian summer monsoon variability

Future climate change will challenge society’s ability to adequately manage water resources, particularly in the developing world. The response of past societies to climatic variability, particularly in terms of water management, can provide useful insights into the timing and scale of response to future events. We present a regional case study from South India to illustrate the influence of climate on shaping the rise and economic prosperity of the Chola Kingdom from 850 to 1280 ce – a period approximately coinciding with the Medieval Climatic Anomaly. An investigation of instrumental and proxy climatic data sets between 500 and 2010 ce indicates that the period between ~850 and ~1300 ce, a time of frequent El Niño-like conditions, was associated with a substantial increase in North-East Indian monsoon rainfall (NEIMR), whereas South-West Indian monsoon rainfall (SWIMR) suffered substantial deficits. The spatial pattern and chronology of water harvesting infrastructure development under Chola rule indicate that these features were concentrated in the NEIMR-receiving regions of southeastern India and that their construction peaked during El Niño-dominated intervals. Overall, enhanced NEIMR conditions and adaptation strategies practiced in the Chola’s territory, combined with less favorable climatic conditions over the neighboring kingdoms, appears to have underpinned the well-documented political and economic strengths of the Chola superpower. We infer that the water management infrastructure promoted by the Chola rulers helped to buffer the consequences of climatic extremes in later history, whether droughts (e.g. the El Niño-related mega-drought of 1876–1878) or floods (because the reservoirs can contain surplus runoff). More recently, however, a preference for groundwater irrigation and other landscape changes driven by population pressure has made the region more vulnerable to the incidence of heavy NEIMR episodes, as illustrated by the severe floods of 2015. Future climate adaptation planning in South India should appreciate the merits of restoring and expanding the currently decaying legacy of Chola-style ‘no regrets’ water management infrastructures.

Simulated impacts of irrigation on the atmospheric circulation over Asia

Land use and land cover (LULC) data are a central component of most land-atmosphere interaction studies, but there are two common and highly problematic scale mismatches between LULC and climate data. First, in the spatial domain, researchers rarely consider the impact of scaling up fine-scale LULC data to match coarse-scale climate datasets. Second, in the temporal domain, climate data typically have sub-daily, daily, monthly, or annual resolution, but LULC datasets often have much coarser (e.g., decadal) resolution. We first explored the effect of three spatial scaling methods on correlations among LULC data and a land surface climatic variable, latent heat flux in China. Scaling by a fractional method preserved significant correlations among LULC data and latent heat flux at all three studied scales (0.5°, 1.0°, and 2.5°), whereas nearest-neighbor and majority-aggregation methods caused these correlations to diminish and even become statistically non-significant at coarser spatial scales (i.e., 2.5°). In the temporal domain, we identified fractional changes in croplands, forests, and grasslands in China using a recently developed and annually resolved time series of LULC maps from 1982 to 2012. Relative to common LULC change (LULCC) analyses conducted over two-time steps or several time periods, this annually resolved, 31-year time series of LULC maps enables robust interpretation of LULCC. Specifically, the annual resolution of these data enabled us to more precisely observe three key and statistically significant LULCC trends and transitions that could have consequential effects on land-atmosphere interaction: (1) decreasing grasslands to increasing croplands in the Northeast China plain and the Yellow river basin, (2) decreasing croplands to increasing forests in the Yangtze river basin, and (3) decreasing grasslands to increasing forests in Southwest China. Our study not only demonstrates the importance of using a fractional spatial rescaling method, but also illustrates the value of annually resolved LULC time series for detecting significant trends and transitions in LULCC, thus potentially facilitating a more robust use of remotely sensed data in land-atmosphere interaction studies.