Global change and species interactions in terrestrial ecosystems

vii Acknowledgements ix Authorship declaration xi Chapter I: Introduction 1 1.1 A perspective of climate change in ecological research 1 1.2 How does climate change affect us? 2 1.3 The multiple axes of real-world complexity 4 1.3.1 Biodiversity and the importance of interactions among species 4 1.3.2 Biotic complexity: from species to networks 5 1.3.3 Synergistic global environmental change drivers 7 1.4 Thesis objectives and outline 8 Chapter II: Plant-mediated and non-additive effects of two global change drivers on an insect herbivore community 12 2.1 Abstract 12 2.2 Introduction 13 2.3 Material and Methods 15 2.3.1 Study site 15 2.3.2 Experimental design 16 2.3.3 Vegetation survey 18 2.3.4 Data analysis 18 2.4 Results 20 2.4.1 Plant community response to the environmental change drivers: ....... 22

A meta-analysis of soil extracellular enzyme activities in response to global change

In recent decades, global climate change is one of the main concerns around the world. Land use change and the high demand for fossil fuel have caused severe consequences of climate change, such as elevated greenhouse gases, warming, and altering precipitation pattern. These combined factors have substantial impacts on ecosystem processes, especially carbon and nitrogen cycles in terrestrial ecosystems. Since the 1970s, a series of field manipulative experiments had been set up to stimulate the influences of monofactorial and/or multifactorial climate changes, improving our understanding of ecosystem response and feedback to global change. In this review, we summarized the development history of global change experiments, and discussed the main issues of using field manipulative experiments in simulating global change. The application of multifactorial experiments, such as CO2 enrichment, warming, precipitation and nitrogen deposition, were highlighted in the research of soil microbial ecology. Moreover, the response and feedback of soil biota as well as the biogeochemical processes that they mediated were further addressed. We also proposed the prospects of their application in global change research to explore the impact of global change on terrestrial ecosystems.

Global change may be considered to encompass recent (post-1960s) changes in land use and climate, and largely human-induced impacts in atmospheric chemistry (especially inorganic nutrients such as nitrogen compounds and carbon dioxide) and biotic interactions, such as invasions by alien species. The relative importance according to the severity and extent of impact of each of these factors, or drivers of global change on alpine biodiversity has been estimated to follow the order of: land use ≈ climate change > nitrogen deposition > carbon dioxide enrichment > biotic interactions (Walker et al. 2001a). We consider the three most important of these. Climate change is the focus of this chapter, together with briefly discussing the potential impacts of nitrogen deposition; land use is dealt with in the following chapter. We start with an outline of past climate changes and their perceived changes in the extent and quality of alpine habitats and vegetation. This is followed by characterizing climatic drivers and enlisting climate change scenarios and observed changes attributed to climate warming. Considerations are given to factors that couple or decouple climate and plant growth at the landscape scale. Finally, the reader is directed to the chapter on land use and conservation.

Environmental changes alter the diversity and structure of communities. By shifting the range of species traits that will be successful under new conditions, environmental drivers can also dramatically impact ecosystem functioning and resilience. Above and belowground communities jointly regulate whole-ecosystem processes and responses to change, yet they are frequently studied separately. To determine whether these communities respond similarly to environmental changes, we measured taxonomic and trait-based responses of plant and soil microbial communities to four years of experimental warming and nitrogen deposition in a temperate grassland. Plant diversity responded strongly to N addition, whereas soil microbial communities responded primarily to warming, likely via an associated decrease in soil moisture. These above and belowground changes were associated with selection for more resource-conservative plant and microbe growth strategies, which reduced community functional diversity. Functional characteristics of plant and soil microbial communities were weakly correlated (P = 0.07) under control conditions, but not when above or belowground communities were altered by either global change driver. These results highlight the potential for global change drivers operating simultaneously to have asynchronous impacts on above and belowground components of ecosystems. Assessment of a single ecosystem component may therefore greatly underestimate the whole-system impact of global environmental changes.

Ecosystem coupling: A unifying framework to understand the functioning and recovery of ecosystems

SummaryDuring the last centuries, humans have transformed global ecosystems. With their temporal dimension, herbaria provide the otherwise scarce long‐term data crucial for tracking ecological and evolutionary changes over this period of intense global change. The sheer size of herbaria, together with their increasing digitization and the possibility of sequencing DNA from the preserved plant material, makes them invaluable resources for understanding ecological and evolutionary species’ responses to global environmental change. Following the chronology of global change, we highlight how herbaria can inform about long‐term effects on plants of at least four of the main drivers of global change: pollution, habitat change, climate change and invasive species. We summarize how herbarium specimens so far have been used in global change research, discuss future opportunities and challenges posed by the nature of these data, and advocate for an intensified use of these ‘windows into the past’ for global change research and beyond.

Emerging Microbes & Infections (2017) 6, e34; doi:10.1038/emi.2017.45; published online 10 May 2017

Tropical ecosystems face escalating global change. These shifts can disrupt tropical forests' carbon (C) balance and impact root dynamics. Since roots perform essential functions such as resource acquisition and tissue protection, root responses can inform about the strategies and vulnerabilities of ecosystems facing present and future global changes. However, root trait dynamics are poorly understood, especially in tropical ecosystems. We analyzed existing research on tropical root responses to key global change drivers: warming, drought, flooding, cyclones, nitrogen (N) deposition, elevated (e) CO2, and fires. Based on tree species- and community-level literature, we obtained 266 root trait observations from 93 studies across 24 tropical countries. We found differences in the proportion of root responsiveness to global change among different global change drivers but not among root categories. In particular, we observed that tropical root systems responded to warming and eCO2 by increasing root biomass in species-scale studies. Drought increased the root: shoot ratio with no change in root biomass, indicating a decline in aboveground biomass. Despite N deposition being the most studied global change driver, it had some of the most variable effects on root characteristics, with few predictable responses. Episodic disturbances such as cyclones, fires, and flooding consistently resulted in a change in root trait expressions, with cyclones and fires increasing root production, potentially due to shifts in plant community and nutrient inputs, while flooding changed plant regulatory metabolisms due to low oxygen conditions. The data available to date clearly show that tropical forest root characteristics and dynamics are responding to global change, although in ways that are not always predictable. This synthesis indicates the need for replicated studies across root characteristics at species and community scales under different global change factors.

The policy relevance of global environmental change research

Click to increase image sizeClick to decrease image size Notes 1. Intergovernmental Panel on Climate Change, Climate Change 2001: Impacts, Adaptation, and Vulnerability Technical Summary, A Report of Working Group II of the Intergovernmental Panel on Climate Change (Cambridge: Cambridge University Press, 2001). 2. Exposure, in the context of global change, was defined in 2008 by R. M. Leichenko and K. L. O'Brien (in Environmental Change and Globalization: Double Exposures [Oxford: Oxford University Press]) as "prone or sensitive to change." Sensitivity leads to vulnerability, that is, the "negative outcomes from stresses and shocks." This conceptualization of global change in terms of context, response, and outcome explicitly considers social and environmental outcomes. 3. B. Smit and J. Wandel, "Adaptation, Adaptive Capacity and Vulnerability," Global Environmental Change 16 (2006): 282–292. 4. W. N. Adger and P. M. Kelly, "Social Vulnerability to Climate Change and the Architecture of Entitlements," Mitigation and Adaptation Strategies for Global Change 4 (1999): 253–266. 5. Arid (including hyperarid) areas receive less than 250 mm of preciptation per year; semiarid areas receive 250 to 500 mm. C. F. Hutchinson, R. G. Varady, and S. Drake, "Old and New: Changing Paradigms in Arid Lands Water Management," in G. Schneier-Madanes and M. F. Courel, eds., Water and Sustainability in Arid Regions (Dordrecht, the Netherlands: Springer, 2009), pp. 311–332. We use "arid" to include semiarid, in that both imply water-short conditions. 6. The Water Center for Arid and Semi-Arid Zones in Latin America and the Caribbean (http://www.cazalac.org/eng/mision_eng.php, accessed on 19 January 2012) notes that aridity characterizes some 4.5 million sq km from Mexico to South America, where decisionmakers lack appropriate knowledge on water management and preservation. 7. World Economic Forum Water Initiative, Water Security: The Water-Food-Energy-Climate Nexus (Washington, DC: Island Press, 2011). 9. "Humans shoulder at least half the blame," according to Diana Liverman's reading of the 2007 Intergovernmental Panel on Climate Change report, "From Uncertain to Unequivocal," in Environment 49, no. 8 (2007): 28–32. 9. H. Eakin and M. C. Lemos, "Institutions and Change: The Challenge of Building Adaptive Capacity in Latin America," Global Environmental Change 20 (2010): 1–3. 10. Ongoing support is provided by the Inter-American Institute for Global Change Research (http://www.iai.int). 11. See related article: W. Laird-Benner and H. Ingram, "Sonoran Desert Network Weavers," Environment 53, no. 1 (2011): 6–16. 12. B. J. Morehouse, D. Ferguson, G. Owen, A. Browning-Aiken, P. Wong-Gonzales, N. Pineda, and R. G. Varady," Science and Socio-Ecological Sustainability: Examples From the Arizona-Sonora Border," Environmental Science and Policy 11, no. 3 (2008): 272–284. 13. G. Saliba and K. L. Jacobs, "Saving the San Pedro River: Science, Collaboration, and Water Sustainability in Arizona," Environment 50, no. 6(2008): 30–32. See also R. G. Varady, M. A. Moote, and R. Merideth, "Water Allocation Options for the Upper San Pedro Basin: Assessing the Social and Institutional Landscape," Natural Resources Journal 40, no. 2 (2000): 223–235. 14. R. G. Varady and E. Ward, "Transboundary Conservation in Context: What Drives Environmental Change?," in L. Lopez-Hoffman, E. McGovern, R. G. Varady, and K. W. Flessa, eds., Conservation of Shared Environments: Learning From the United States and Mexico (Tucson: University of Arizona Press, 2009), pp. 9–22. A. K. Gerlak and M. Wilder, "Exploring the Textured Landscape of Water Insecurity and the Human Right to Water," Environment 54, no. 2 (2012): (in press). 15. C. Pahl-Wostl, "The Implications of Complexity For Integrated Resources Management," Environmental Modelling & Software 22 (2007): 561–569. 16. R. E. Saunier and R. A. Meganck, Dictionary and Introduction to Global Environmental Governance (London: Earthscan, 2007). 17. C. A. Scott, S. Dall'erba, and R. Díaz, "Groundwater Rights in Mexican Agriculture: Spatial Distribution and Social and Economic Determinants," Professional Geographer 62, no. 1 (2010): 1–15. 18. H. A. Loaiciga, "Climate Change and Ground Water," Annals of the Association of American Geographers 93, no. 1 (2003): 30–41. 19. "Virtual water" is embedded or hidden water, as in irrigation to grow crops. The concept was developed by J. A. Allan in 1993. See Allan, J. A. "Virtual water - the water, food and trade nexus: useful concept or misleading metaphor?" Water International, 28 (2003): 4-11. 20. M. Wilder, C. A. Scott, N. Pineda Pablos, R. G. Varady, G. M. Garfin, and J. McEvoy, "Adapting Across Boundaries: Climate Change, Social Learning, and Resilience in the U.S.–Mexico Border Region," Annals of the Association of American Geographers 100, no. 4 (2010): 917–928. 21. C. A. Scott and M. J. Pasqualetti, "Energy and Water Resources Scarcity: Critical Infrastructure for Growth and Economic Development in Arizona and Sonora," Natural Resources Journal 50, no. 3 (2010): 645–682. 22. C. J. Bauer, "Dams and Markets: Rivers and Electric Power in Chile," Natural Resources Journal 49 (2009): 583–651. 23. F. J. Meza, D. S. Wilks, L. Gurovich, and N. Bambach, "Impacts of Climate Change on Irrigated Agriculture in the Maipo Basin, Chile: Reliability of Water Rights and Changes in the Demand for Irrigation," Journal of Water Resources Planning and Management (in press). 24. The critical need to "reconnect science and policy" is highlighted in a recent report by the United Nations Environment Programme (UNEP, 21 Issues for the 21st Century: Results of the UNEP Foresight Process on Emerging Environmental Issues, Alcamo, J., Leonard, S.A. (Eds.). United Nations Environment Programme (UNEP), Nairobi, Kenya, 56pp., 2012). Based on an extensive survey of scientists, decisionmakers, and other stakeholders, the report calls for "a new look at… how the science-society-policy interface can be improved." In addition, it addresses numerous key issues that the dialogue process presented in this article also focuses on, including freshwater, climate change, food, biodiversity, land, and energy. 25. These science-policy interactions have been generously funded by the Inter-American Institute for Global Change Research, U.S. National Oceanic and Atmospheric Administration (NOAA), National Science Foundation, U.S. Geological Survey, Dialogue on Water and Climate (The Netherlands), and Morris K. and Stewart L. Udall Foundation. In Mexico the workshops were supported by the national water commission (CONAGUA), the Univesity of Sonora, El Colegio de Sonora, the national water research institute (IMTA), the national meteorological service (SMN), the Sonoran state water agency, and local governments. 26. Dialogues have been held in Hermosillo (2006, 2008, 2010), Guaymas (2006), Cuernavaca (2009), Mexico City (2005, 2006), Puerto Peñasco (2009), Tucson (2009, 2010), and Cabos (2011). Findings were promulgated at the World Water Forums (2003, 2006, and 2009), Hydrology for the Environment, Life and Policy meetings (Tucson 1999, 2008; Kalmar [Sweden] 2002; Dundee [Scotland] 2001, 2004; Guayaquil [Ecuador] 2005; Panama 2011), Internationally Shared Aquifer Resources Management Program (Paris 2010), and other fora. 27. See F. J. Meza, "Variability of Reference Evapotranspiration and Water Demands. Association to ENSO in the Maipo River Basin, Chile," Global and Planetary Change 47 (2005): 212–220; Meza et al. (in press), note 23, above. See also: http://cambioglobal.uc.cl/index.php?option=com_content&view=article&id=81&Itemid=62&lang=en 28. See http://www.planestrategico.mendoza.gob.ar. 29. R. G. Varady and A. Browning-Aiken, "The Birth of a Mexican Watershed Council in the San Pedro Basin in Sonora," in C. Fuentes-Flores and S. Peña-Medina, eds., Planeación y Cooperación Transfronteriza en la Frontera México-Estados Unidos (Transboundary Planning and Cooperation in the U.S.-Mexico Border Region) (Ciudad Juárez, Mexico: El Colegio de la Frontera Norte & Universidad Autónoma de Ciudad Juárez, Ambiente y Desarrollo, 2005), pp. 165–183. 30. U.S. Public Law 109-448, the United States–Mexico Transboundary Aquifer Assessment Act, was approved in late 2006 and authorized up to $50 million; to date, $2 million has been appropriated. The intent is to provide scientific information useful to policymakers and water managers. 31. R. G. Varady, R. Salmón Castillo, and S. Eden, "Key Issues, Institutions, and Strategies for Managing Transboundary Water Resources in the Arizona–Mexico Border Region," in S. B. Megdal, R. G. Varady, and S. Eden, eds. Shared Borders, Shared Waters: Israeli-Palestinian and Colorado River Basin Water Challenges (Delft, The Netherlands: UNESCO-IHE Press in collaboration with Taylor & Francis, in press); C. A. Scott, S. Megdal, L. A. Oroz, J. Callegary, and P. Vandervoet, "Climate Change and Population Growth Impacts on the Transboundary Santa Cruz Aquifer," Climate Research 51 (2012):159-170, doi: 10.3354/cr01061. 51: 159–170, doi: 10.3354/cr01061 32. G. Young, H. Zavala, J. Wandel, B. Smit, S. Salas, E. Jimenez, M. Fiebig, R. Espinoza, H. Diaz, and J. Cepeda, "Vulnerability and Adaptation in a Dryland Community of the Elqui Valley, Chile," Climatic Change 98 (2010): 245–276, doi: 10.1007/s10584-009-9665-4; E. Montaña, "Central Andean Foothill Farmers Facing Global Environmental Change," IHDP Update 2 (2008): 36–39. See http://www.ihdp.unu.edu/file/get/7724. 33. Young et al. (2010), note 32, above. 34. G. Schneier-Madanes and M. F. Courel, "Introduction," in G. Schneier-Madanes and M. F. 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Coordination of plant functional traits under nitrogen deposition with phosphorus addition in a desert steppe ecosystem.

Rapid deforestation is a major sustainability challenge, partly as the loss of carbon sinks exacerbates global climate change. In Cambodia, more than 13% of the total land area has been contracted out to foreign and domestic agribusinesses in the form of economic land concessions, causing rapid large-scale land use change and deforestation. Additionally, the distant drivers of local and global environmental change often remain invisible. Here, we identify hotspots of carbon loss between 1987–2017 using the dynamic global vegetation model LPJ-GUESS and by comparing past and present land use and land cover. We also link global consumption and production patterns to their environmental effects in Cambodia by mapping the countries to which land-use embedded carbon are exported. We find that natural forests have decreased from 54%–21% between 1987 and 2017, mainly for the expansion of farmland and orchards, translating into 300 million tons of carbon lost, with loss rates over twice as high within economic land concessions. China is the largest importer of embedded carbon, mainly for rubber and sugarcane from Chinese agribusinesses. Cambodian investors have also negatively affected carbon pools through export-oriented products like rubber. The combined understanding of environmental change and trade flows makes it possible to identify distant drivers of deforestation, which is important for crafting more environmentally and socially responsible policies on national and transnational scales.

Responses of individual leaves to short-term changes in CO2 partial pressure have been relatively well studied. Whole-plant and plant community responses to elevated CO2 are less well understood and scaling up from leaves to canopies will be complicated if feedbacks at the small scale differ from feedbacks at the large scale. Mathematical models of leaf, canopy, and ecosystem processes are important tools in the study of effects on plants and ecosystems of global environmental change, and in particular increasing atmospheric CO2, and might be used to scale from leaves to canopies. Models are also important in assessing effects of the biosphere on the atmosphere. Presently, multilayer and big leaf models of canopy photosynthesis and energy exchange exist. Big leaf models - which are advocated here as being applicable to the evaluation of impacts of 'global change' on the biosphere - simplify much of the underlying leaf-level physics, physiology, and biochemistry, yet can retain the important features of plant-environment interactions with respect to leaf CO2 exchange processes and are able to make useful, quantitative predictions of canopy and community responses to environmental change. The basis of some big leaf models of photosynthesis, including a new model described herein, is that photosynthetic capacity and activity are scaled vertically within a canopy (by plants themselves) to match approximately the vertical profile of PPFD. The new big leaf model combines physically based models of leaf and canopy level transport processes with a biochemically based model of CO2 assimilation. Predictions made by the model are consistent with canopy CO2 exchange measurements, although a need exists for further testing of this and other canopy physiology models with independent measurements of canopy mass and energy exchange at the time scale of 1 h or less.

Global concern with environmental degradation today cuts across political and economic boundaries and east-west and north-south relations. Delicate Indian ecosystems such as mountains, deserts, and coastal and river systems pass across boundaries. However we lack broad understanding and an environmental data base to monitor and forecast the dimensions and dynamics of ecosystem functioning and global change in order to manage and conserve the geosphere and biosphere. Global change study serves as a basis for devising mechanisms to integrate physical and social aspects of the environment. The major causes of global environmental changes are various anthropogenic activities, not only those of present but also the integrated past activities. However, the interaction between man and environment systems has not been understood sufficiently. The previous programmes of monitoring on-going global environmental changes have paid little attention to socio-economic dimensions of anthropogenic activities which have induced various types of serious environmental changes. Land-use forms a major element of terrestrial systems. The emerging Remote Sensing and Geographic Information System techniques help in providing land use, environmental and natural resources information and data to support decision-making processes in India (Singh, 1995).