Life Sciences Commons^™

Experimental Evidence Of Bark Beetle Adaptation To A Fungal Symbiont, Bracewell R. Ryan, Diana Six

Ecosystem and Conservation Sciences Faculty Publications

The importance of symbiotic microbes to insects cannot be overstated; however, we have a poor understanding of the evolutionary processes that shape most insect–microbe interactions. Many bark beetle (Coleoptera: Curculionidae, Scolytinae) species are involved in what have been described as obligate mutualisms with symbiotic fungi. Beetles benefit through supplementing their nutrient- poor diet with fungi and the fungi benefit through gaining transportation to resources. However, only a few beetle–fungal symbioses have been experimentally manipulated to test whether the relationship is obligate. Furthermore, none have tested for adaptation of beetles to their specific symbionts, one of the requirements for coevolution. We …

A Fatty Acid Based Bayesian Approach For Inferring Diet In Aquatic Consumers, Aaron W. E. Galloway, Michael T. Brett, Gordon W. Holtgrieve, Eric J. Ward, Ashley P. Ballantyne, Carolyn W. Burns, Martin J. Kainz, Doerthe C. Muller-Navarra, Jonas Persson, Joseph L. Ravet, Ursula Strandberg, Sami J. Taipale, Gunnel Alhgren

Ecosystem and Conservation Sciences Faculty Publications

We modified the stable isotope mixing model MixSIR to infer primary producer contributions to consumer diets based on their fatty acid composition. To parameterize the algorithm, we generated a ‘consumer-resource library’ of FA signatures of Daphnia fed different algal diets, using 34 feeding trials representing diverse phytoplankton lineages. This library corresponds to the resource or producer file in classic Bayesian mixing models such as MixSIR or SIAR. Because this library is based on the FA profiles of zooplankton consuming known diets, and not the FA profiles of algae directly, trophic modification of consumer lipids is directly accounted for. To test …

Suitable Days For Plant Growth Disappear Under Projected Climate Change: Potential Human And Biotic Vulnerability, Camilo Mora, Iain R. Caldwell, Jamie M. Caldwell, Micah R. Fisher, Brandon M. Genco, Steven W. Running

Ecosystem and Conservation Sciences Faculty Publications

Ongoing climate change can alter conditions for plant growth, in turn affecting ecological and social systems. While there have been considerable advances in understanding the physical aspects of climate change, comprehensive analyses integrating climate, biological, and social sciences are less common. Here we use climate projections under alternative mitigation scenarios to show how changes in environmental variables that limit plant growth could impact ecosystems and people. We show that although the global mean number of days above freezing will increase by up to 7% by 2100 under “business as usual” (representative concentration pathway [RCP] 8.5), suitable growing days will actually …

Topographic Controls On Soil Nitrogen Availability In A Lowland Tropical Forest, Samantha R. Weintraub, Philip G. Taylor, Stephen Porder, Cory C. Cleveland, Gregory P. Asner, Alan R. Townsend

Ecosystem and Conservation Sciences Faculty Publications

Geomorphic position often correlates with nutrient cycling across landscapes. In tropical forests, topography is known to influence phosphorus (P) availability, but its effect on nitrogen (N) cycling has received less exploration, especially in lowland forests where widespread N richness is frequently assumed. Here, we report significant effects of topographic slope and landscape position on multiple aspects of the N cycle across a highly dissected lowland tropical forest on the Osa Peninsula, Costa Rica. A suite of N cycle metrics measured along a topographic sequence revealed a distinct gradient in N availability. Values of soil d15N, inorganic N pools, net nitrification …

A Comparison Of Plot-Based Satellite And Earth System Model Estimates Of Tropical Forest Net Primary Production, Cory C. Cleveland, Philip Taylor, K. Dana Chadwick, Kyla Dahlin, Christopher E. Doughty, Yadvinder Malhi, W. Kolby Smith, Benjamin W. Sullivan, William R. Wider, Alan R. Townsend

Ecosystem and Conservation Sciences Faculty Publications

Net primary production (NPP) by plants represents the largest annual flux of carbon dioxide (CO₂) from the atmosphere to the terrestrial biosphere, playing a critical role in the global carbon (C) cycle and the Earth’s climate. Rates of NPP in tropical forests are thought to be among the highest on Earth, but debates about the magnitude, patterns, and controls of NPP in the tropics highlight uncertainty in our understanding of how tropical forests may respond to environmental change. Here, we compared tropical NPP estimates generated using three common approaches: (1) field-based methods scaled from plot-level measurements of plant …

Nutrient Addition Dramatically Accelerates Microbial Community Succession, Joseph E. Knelman, Steven K. Schmidt, Ryan C. Lynch, John L. Darcy, Sarah C. Castle, Cory C. Cleveland, Diana R. Nemergut

Ecosystem and Conservation Sciences Faculty Publications

The ecological mechanisms driving community succession are widely debated, particularly for microorganisms. While successional soil microbial communities are known to undergo predictable changes in structure concomitant with shifts in a variety of edaphic properties, the causal mechanisms underlying these patterns are poorly understood. Thus, to specifically isolate how nutrients – important drivers of plant succession – affect soil microbial succession, we established a full factorial nitrogen (N) and phosphorus (P) fertilization plot experiment in recently deglaciated (~3 years since exposure), unvegetated soils of the Puca Glacier forefield in Southeastern Peru. We evaluated soil properties and examined bacterial community composition in …

Modeling And Monitoring Terrestrial Primary Production In A Changing Global Environment: Toward A Multiscale Synthesis Of Observation And Simulation, Shufen Pan, Hanqin Tian, Shree R. S. Dangal, Zhiyun Ouyang, Bo Tao, Wei Ren, Chaoqun Lu, Steven W. Running

Ecosystem and Conservation Sciences Faculty Publications

There is a critical need to monitor and predict terrestrial primary production, the key indicator of ecosystem functioning, in a changing global environment. Here we provide a brief review of three major approaches to monitoring and predicting terrestrial primary production: (1) ground-based field measurements, (2) satellite-based observations, and (3) process-based ecosystem modelling. Much uncertainty exists in the multi-approach estimations of terrestrial gross primary production (GPP) and net primary production (NPP). To improve the capacity of model simulation and prediction, it is essential to evaluate ecosystem models against ground and satellite-based measurements and observations. As a case, we have shown the …

Ecological Processes Dominate The 13C Land Disequilibrium In A Rocky Mountain Subalpine Forest, D. R. Bowling, Ashley P. Ballantyne, J. B. Miller, S. P. Burns, T. J. Conway, O. Menzer, B. B. Stephens, B. H. Vaughn

Ecosystem and Conservation Sciences Faculty Publications

Fossil fuel combustion has increased atmospheric CO₂ by ≈ 115 µmol mol⁻¹ since 1750 and decreased its carbon isotope composition (δ¹³C) by 1.7–2‰ (the ¹³C Suess effect). Because carbon is stored in the terrestrial biosphere for decades and longer, the δ¹³C of CO₂released by terrestrial ecosystems is expected to differ from the δ¹³C of CO₂ assimilated by land plants during photosynthesis. This isotopic difference between land-atmosphere respiration (δ_R) and photosynthetic assimilation (δ_A) fluxes gives rise to the ¹³C land disequilibrium …

Exposure Of U.S. National Parks To Land Use And Climate Change 1900-2100, Andrew J. Hansen, Cory Davis, Jessica Haas, David M. Theobald, John E. Gross, William B. Monahan, Tom Olliff, Steven W. Running

Ecosystem and Conservation Sciences Faculty Publications

Many protected areas may not be adequately safeguarding biodiversity from human activities on surrounding lands and global change. The magnitude of such change agents and the sensitivity of ecosystems to these agents vary among protected areas. Thus, there is a need to assess vulnerability across networks of protected areas to determine those most at risk and to lay the basis for developing effective adaptation strategies. We conducted an assessment of exposure of U.S. National Parks to climate and land use change and consequences for vegetation communities. We first defined park protected-area centered ecosystems (PACEs) based on ecological principles. We then …

Comparison Of Gross Primary Productivity Derived From Gimms Ndvi3g, Gimms, And Modis In Southeast Asia, Junbang Wang, Jingwei Dong, Jiyuan Liu, Mei Huang, Guicai Li, Steven W. Running, William Kolby Smith, Warwick Harris, Nobuko Saigusa, Hiroaki Kondo, Yunfen Liu, Takashi Hirano, Xiangming Xiao

Ecosystem and Conservation Sciences Faculty Publications

Gross primary production (GPP) plays an important role in the net ecosystem exchange of CO2 between the atmosphere and terrestrial ecosystems. It is particularly important to monitor GPP in Southeast Asia because of increasing rates of tropical forest degradation and deforestation in the region in recent decades. The newly available, improved, third generation Normalized Difference Vegetation Index (NDVI3g) from the Global Inventory Modelling and Mapping Studies (GIMMS) group provides a long temporal dataset, from July 1981 to December 2011, for terrestrial carbon cycle and climate response research. However, GIMMS NDVI3g-based GPP estimates are not yet available. We applied the GLOPEM-CEVSA …

Assessing Nutrient Limitation In Complex Forested Ecosystems : Alternatives To Large-Scale Fertilization Experiments, Benjamin W. Sullivan, Silvia Alvarez-Clare, Sarah C. Castle, Stephen Porder, Sasha C. Reed, Laura Schreeg, Cory C. Cleveland, Alan R. Townsend

Ecosystem and Conservation Sciences Faculty Publications

Quantifying nutrient limitation of primary productivity is a fundamental task of terrestrial ecosystem ecology, but in a high carbon dioxide environment it is even more critical that we understand potential nutrient constraints on plant growth. Ecologists often manipulate nutrients with fertilizer to assess nutrient limitation, yet for a variety of reasons, nutrient fertilization experiments are either impractical or incapable of resolving ecosystem responses to some global changes. The challenges of conducting large, in situ fertilization experiments are magnified in forests, especially the high-diversity forests common throughout the lowland tropics. A number of methods, including fertilization experiments, could be seen as …

Snowshoe Hares Display Limited Phenotypic Plasticity To Mismatch In Seasonal Camouflage, Marketa Zimova, L. Scott Mills, Paul M. Lukacs, Michael S. Mitchell

Ecosystem and Conservation Sciences Faculty Publications

As duration of snow cover decreases owing to climate change, species undergoing seasonal colour moults can become colour mismatched with their background. The immediate adaptive solution to this mismatch is phenotypic plasticity, either in phenology of seasonal colour moults or in behaviours that reduce mismatch or its consequences. We observed nearly 200 snowshoe hares across a wide range of snow conditions and two study sites in Montana, USA, and found minimal plasticity in response to mismatch between coat colour and background. We found that moult phenology varied between study sites, likely due to differences in photoperiod and climate, but was …

Agricultural Conversion Without External Water And Nutrient Inputs Reduces Terrestrial Vegetation Productivity, William Kolby Smith, Cory C. Cleveland, Sasha C. Reed, Steven W. Running

Ecosystem and Conservation Sciences Faculty Publications

Driven by global population and standard of living increases, humanity co-opts a growing share of the planet's natural resources resulting in many well-known environmental trade-offs. In this study, we explored the impact of agriculture on a resource fundamental to life on Earth: terrestrial vegetation growth (net primary production; NPP). We demonstrate that agricultural conversion has reduced terrestrial NPP by ~7.0%. Increases in NPP due to agricultural conversion were observed only in areas receiving external inputs (i.e., irrigation and/or fertilization). NPP reductions were found for ~88% of agricultural lands, with the largest reductions observed in areas formerly occupied by tropical forests …

Management For Mountain Pine Beetle Outbreak Suppression: Does Relevant Science Support Current Policy?, Diana Six, Eric Biber, Elisabeth Long

Ecosystem and Conservation Sciences Faculty Publications

While the use of timber harvests is generally accepted as an effective approach to controlling bark beetles during outbreaks, in reality there has been a dearth of monitoring to assess outcomes, and failures are often not reported. Additionally, few studies have focused on how these treatments affect forest structure and function over the long term, or our forests’ ability to adapt to climate change. Despite this, there is a widespread belief in the policy arena that timber harvesting is an effective and necessary tool to address beetle infestations. That belief has led to numerous proposals for, and enactment of, significant …

Nitrogen Cycling Responses To Mountain Pine Beetle Disturbance In A High Elevation Whitebark Pine Ecosystem, Megan P. Keville, Sasha C. Reed, Cory C. Cleveland

Ecosystem and Conservation Sciences Faculty Publications

Ecological disturbances can significantly affect biogeochemical cycles in terrestrial ecosystems, but the biogeochemical consequences of the extensive mountain pine beetle outbreak in high elevation whitebark pine (WbP) (Pinus albicaulis) ecosystems of western North America have not been previously investigated. Mountain pine beetle attack has driven widespread WbP mortality, which could drive shifts in both the pools and fluxes of nitrogen (N) within these ecosystems. Because N availability can limit forest regrowth, understanding how beetle-induced mortality affects N cycling in WbP stands may be critical to understanding the trajectory of ecosystem recovery. Thus, we measured above- and belowground N …

New Species Of Gondwanamyces From Dying Euphorbia Trees In South Africa, Johannes Alwyn Van Der Linde, Diana Six, Michael J. Wingfield, Jolanda Roux

Ecosystem and Conservation Sciences Faculty Publications

Gondwanamyces and its Custingophora anamorphs were first described from Protea infructescences in South Africa. Subsequently these unusual fungi were also found on Cecropia in Central America. During an investigation into the decline and death of native Euphorbia trees in South Africa, several fungal isolates resembling the anamorph state of Gondwanamyces were obtained from diseased tissues. In this study these isolates are identified based on morphology and comparisons of DNA sequences. Two previously unknown Gondwanamyces species were identified, both were associated with damage caused by beetles (Cossonus sp.). Inoculation studies showed that the new species of Gondwanamyces are pathogenic on Euphorbia …

Satellite Finds Highest Land Skin Temperatures On Earth, David J. Mildrexler, Maosheng Zhao, Steven W. Running

Ecosystem and Conservation Sciences Faculty Publications

The location of the hottest spot on Earth has undoubtedly been an interesting curiosity for centuries. Even with the advent of the instrumental temperature record around the year 1850, the location of the hottest spot on Earth has continued to be the subject of debate and controversy. In 1913, the weather station at Furnace Creek in Death Valley National Park, California, measured an air temperature of 56.7°C (134.1°F) and claimed the title of “hottest place on Earth.” Nine years later in El Azizia, Libya, an air temperature of 57.8°C (136°F) was recorded on land owned by an Italian farmer and …

An Ecosystem-Scale Model For The Spread Of A Host-Specific Forest Pathogen In The Greater Yellowstone Ecosystem, Jaclyn A. Hatala, Michael C. Dietze, Robert L. Crabtree, Katherine Kendall, Diana Six, Paul R. Moorcroft

Ecosystem and Conservation Sciences Faculty Publications

The introduction of nonnative pathogens is altering the scale, magnitude, and persistence of forest disturbance regimes in the western United States. In the high-altitude whitebark pine (Pinus albicaulis) forests of the Greater Yellowstone Ecosystem (GYE), white pine blister rust (Cronartium ribicola) is an introduced fungal pathogen that is now the principal cause of tree mortality in many locations. Although blister rust eradication has failed in the past, there is nonetheless substantial interest in monitoring the disease and its rate of progression in order to predict the future impact of forest disturbances within this critical ecosystem.

This …

Experimental Drought In A Tropical Rain Forest Increases Soil Carbon Dioxide Losses To The Atmosphere, Cory C. Cleveland, William R. Wieder, Sasha C. Reed, Alan R. Townsend

Ecosystem and Conservation Sciences Faculty Publications

Climate models predict precipitation changes for much of the humid tropics, yet few studies have investigated the potential consequences of drought on soil carbon (C) cycling in this important biome. In wet tropical forests, drought could stimulate soil respiration via overall reductions in soil anoxia, but previous research suggests that litter decomposition is positively correlated with high rainfall fluxes that move large quantities of dissolved organic matter (DOM) from the litter layer to the soil surface. Thus, reduced rainfall could also limit C delivery to the soil surface, reducing respiration rates. We conducted a throughfall manipulation experiment to investigate how …

Linking Environmental Nutrient Enrichment And Disease Emergence In Humans And Wildlife, Pieter T. J. Johnson, Alan R. Townsend, Cory C. Cleveland, Patricia M. Glibert, Robert W. Howarth, Valerie J. Mckenzie, Eliska Rejmankova, Mary H. Ward

Ecosystem and Conservation Sciences Faculty Publications

Worldwide increases in human and wildlife diseases have challenged ecologists to understand how large-scale environmental changes affect host–parasite interactions. One of the most profound changes to Earth's ecosystems is the alteration of global nutrient cycles, including those of phosphorus (P) and especially nitrogen (N). Along with the obvious direct benefits of nutrient application for food production, anthropogenic inputs of N and P can indirectly affect the abundance of infectious and noninfectious pathogens. The mechanisms underpinning observed correlations, however, and how such patterns vary with disease type, have long remained conjectural. Here, we highlight recent experimental advances to critically evaluate the …

Controls Over Leaf Litter Decomposition In Wet Tropical Forests, William R. Wieder, Cory C. Cleveland, Alan R. Townsend

Ecosystem and Conservation Sciences Faculty Publications

Tropical forests play a substantial role in the global carbon (C) cycle and are projected to experience significant changes in climate, highlighting the importance of understanding the factors that control organic matter decomposition in this biome. In the tropics, high temperature and rainfall lead to some of the highest rates of litter decomposition on earth, and given the near-optimal abiotic conditions, litter quality likely exerts disproportionate control over litter decomposition. Yet interactions between litter quality and abiotic variables, most notably precipitation, remain poorly resolved, especially for the wetter end of the tropical forest biome. We assessed the importance of variation …

Assemblage Of Hymenoptera Arriving At Logs Colonized By Ips Pini (Coleoptera: Curculionidae: Scolytinae) And Its Microbial Symbionts In Western Montana, Celia K. Boone, Diana Six, Steven J. Krauth, Kenneth F. Raffa

Ecosystem and Conservation Sciences Faculty Publications

Colonization of a tree by bark beetles and their symbionts creates a new habitat for a diverse assemblage of arthropods, including competing herbivores, xylophages, fungivores, saprophages, predators, and parasitoids. Understanding these assemblages is important for evaluating nontarget effects of various management tactics and for subsequently evaluating how changes in climate, the presence of invasive species, and altered forestry practices and land-use tenure may affect biodiversity. We characterized the assemblage of hymenopterans attracted to logs of ponderosa pine (Pinus ponderosa C. Lawson (Pinaceae)) colonized by the bark beetle Ips pini (Say) and its microbial symbionts. In one experiment, the composition and …

Transport Of Fungal Symbionts By Mountain Pine Beetles, K. P. Bleiker, S. E. Potter, C. R. Lauzon, Diana Six

Ecosystem and Conservation Sciences Faculty Publications

The perpetuation of symbiotic associations between bark beetles (Coleoptera: Curculionidae: Scolytinae) and ophiostomatoid fungi requires the consistent transport of fungi by successive beetle generations to new host trees. We used scanning electron microscopy and culture methods to investigate fungal transport by the mountain pine beetle (MPB), Dendroctonus ponderosae Hopkins. MPB transports its two main fungal associates, Grosmannia clavigera (Robinson-Jeffrey and Davidson) Zipfel, de Beer and Wingfield and Ophiostoma montium (Rumbold) von Arx, in sac-like mycangia on the maxillary cardines as well as on the exoskeleton. Although spores of both species of fungi were observed on MPB exoskeletons, often in pits, …

Tree Species Control Rates Of Free-Living Nitrogen Fixation In A Tropical Rain Forest, Sasha C. Reed, Cory C. Cleveland, Alan R. Townsend

Ecosystem and Conservation Sciences Faculty Publications

Tropical rain forests represent some of the most diverse ecosystems on earth, yet mechanistic links between tree species identity and ecosystem function in these forests remains poorly understood. Here, using free-living nitrogen (N) fixation as a model, we explore the idea that interspecies variation in canopy nutrient concentrations may drive significant local-scale variation in biogeochemical processes. Biological N fixation is the largest “natural” source of newly available N to terrestrial ecosystems, and estimates suggest the highest such inputs occur in tropical ecosystems. While patterns of and controls over N fixation in these systems remain poorly known, the data we do …

Detection Of Host Habitat By Parasitoids Using Cues Associated With Mycangial Fungi Of The Mountain Pine Beetle, Dendroctonus Ponderosae, A. S, Adams, Diana Six

Ecosystem and Conservation Sciences Faculty Publications

Cues used by parasitoids to detect habitat of the mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae), were investigated by observing parasitoid attraction to logs infested with D. ponderosae, logs inoculated with one or both of the symbiotic fungi of D. ponderosae (Grosmannia clavigera (Rob.-Jeffr. & R.W. Davidson) Zipfel, Z.W. de Beer & M.J. Wingf. (Ophiostomataceae) and Ophiostoma montium (Rumbold) Arx (Ophiostomataceae)), logs containing no beetles or fungi, or empty screen cylinders. Captures of Heydenia unica Cook and Davis (Hymenoptera: Pteromalidae) and Rhopalicus pulchripennis (Crawford) (Hymenoptera: Pteromalidae) on logs with both G. clavigera and O. montium were greater than those …

Biogeochemical Consequences Of Rapid Microbial Turnover And Seasonal Succession In Soil, S. K. Schmidt, E. K. Costello, D. R. Nemergut, Cory C. Cleveland, S. C. Reed, M. N. Weintraub, A. F. Meyer, A. M. Martin

Ecosystem and Conservation Sciences Faculty Publications

Soil microbial communities have the metabolic and genetic capability to adapt to changing environmental conditions on very short time scales. In this paper we combine biogeochemical and molecular approaches to reveal this potential, showing that microbial biomass can turn over on time scales of days to months in soil, resulting in a succession of microbial communities over the course of a year. This new understanding of the year-round turnover and succession of microbial communities allows us for the first time to propose a temporally explicit N cycle that provides mechanistic hypotheses to explain both the loss and retention of dissolved …

Controls Over Foliar N:P Ratios In Tropical Rain Forests, Alan R. Townsend, Cory C. Cleveland, Gregory P. Asner, Mercedes M. C. Bustamante

Ecosystem and Conservation Sciences Faculty Publications

Correlations between foliar nutrient concentrations and soil nutrient availability have been found in multiple ecosystems. These relationships have led to the use of foliar nutrients as an index of nutrient status and to the prediction of broadscale patterns in ecosystem processes. More recently, a growing interest in ecological stoichiometry has fueled multiple analyses of foliar nitrogen : phosphorus (N:P) ratios within and across ecosystems. These studies have observed that N:P values are generally elevated in tropical forests when compared to higher latitude ecosystems, adding weight to a common belief that tropical forests are generally N rich and P poor. However, …

A New Satellite-Based Methodology For Continental-Scale Disturbance Detection, David J. Mildrexler, Maosheng Zhao, Faith Ann Heinsch, Steven W. Running

Ecosystem and Conservation Sciences Faculty Publications

The timing, location, and magnitude of major disturbance events are currently major uncertainties in the global carbon cycle. Accurate information on the location, spatial extent, and duration of disturbance at the continental scale is needed to evaluate the ecosystem impacts of land cover changes due to wildfire, insect epidemics, flooding, climate change, and human-triggered land use. This paper describes an algorithm developed to serve as an automated, economical, systematic disturbance detection index for global application using Moderate Resolution Imaging Spectroradiometer (MODIS)/Aqua Land Surface Temperature (LST) and Terra/MODIS Enhanced Vegetation Index (EVI) data from 2003 to 2004. The algorithm is based …

Sensitivity Of Pan-Arctic Terrestrial Net Primary Productivity Simulations To Daily Surface Meterology From Ncep-Ncar And Era-40 Reanalyses, Ke Zhang, John S. Kimball, Maosheng Zhao, Walter C. Oechel, John Cassano, Steven W. Running

Ecosystem and Conservation Sciences Faculty Publications

We applied a terrestrial net primary production (NPP) model driven by satellite remote sensing observations of vegetation properties and daily surface meteorology from the 45-year ECMWF Re-Analysis (ERA-40) and the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP-NCAR) reanalysis (NNR) to assess NPP spatial and temporal variability for the pan-Arctic basin and Alaska from 1982 to 2000. Sensitivity analysis of the production efficiency model (PEM) to uncertainties in surface meteorological inputs indicate that ERA-40 solar radiation and NNR solar radiation and surface temperatures are the primary sources of PEM-based NPP uncertainty for the region. Considerable positive bias in …

Nutrient Regulation Of Organic Matter Decomposition In A Tropical Rain Forest, Cory C. Cleveland, Sasha C. Reed, Alan R. Townsend

Ecosystem and Conservation Sciences Faculty Publications

errestrial biosphere–atmosphere CO₂ exchange is dominated by tropical forests, so understanding how nutrient availability affects carbon (C) decomposition in these ecosystems is central to predicting the global C cycle's response to environmental change. In tropical rain forests, phosphorus (P) limitation of primary production and decomposition is believed to be widespread, but direct evidence is rare. We assessed the effects of nitrogen (N) and P fertilization on litter-layer organic matter decomposition in two neighboring tropical rain forests in southwest Costa Rica that are similar in most ways, but that differ in soil P availability. The sites contain 100–200 tree species …