The expansion of woody riparian vegetation,and subsequent stream restoration,influences the metabolism of prairie streams

1. Tallgrass prairies and their streams are highly endangered ecosystems, and many remaining streams are threatened by the encroachment of woody riparian vegetation. An increase in riparian vegetation converts the naturally open‐canopy prairie streams to closed‐canopy systems. The effects of a change in canopy cover on stream metabolism are unknown. 2. Our goal was to determine the effects of canopy cover on prairie stream metabolism during a 4‐year period in Kings Creek, KS, U.S.A. Metabolic rates from forested reaches were compared to rates in naturally open‐canopy reaches and restoration reaches, the latter having closed canopies in 2006 and 2007 and open canopies in 2008 and 2009. Whole‐stream metabolism was estimated using the two‐station diurnal method. Chlorophyll a concentrations and mass of filamentous algae were measured after riparian removal to assess potential differences in algal biomass between reaches with open or closed canopies. 3. Metabolic rates were spatially and temporally variable even though the sites were on very similar streams or adjacent to each other within streams. Before riparian vegetation removal, whole‐stream community respiration (CR) and net ecosystem production were greater with greater canopy cover. In the vegetation removal reaches, gross primary production was slightly greater after removal. 4. Chlorophyll a concentrations were marginally significantly greater in open (naturally open and removal reaches) than in closed canopy and differed significantly between seasons. Filamentous algal biomass was greater in open than in closed‐canopy reaches. 5. Overall, the restoration allowed recovery of some features of open‐canopy prairie streams. Woody expansion apparently increases CR and moves prairie stream metabolism towards a more net heterotrophic state. An increase in canopy cover decreases benthic chlorophyll, decreases dominance of filamentous algae and potentially alters resources available to the stream food web. The results of this study provide insights for land managers and conservationists interested in preserving prairie streams in their native open‐canopy state.     

Watershed Land Use and Seasonal Variation Constrain the Influence of Riparian Canopy Cover on Stream Ecosystem Metabolism

Ecosystem metabolism is an important determinant of trophic structure, nutrient cycling, and other critical ecosystem processes in streams. Whereas watershed- and local-scale controls on stream metabolism have been independently investigated, little is known about how controls exerted at different scales interact to determine stream metabolic rates, particularly in urban streams and across seasons. To address this knowledge gap, we measured ecosystem metabolism in four urban and four reference streams in northern Kentucky, USA, with paired closed and open riparian canopies, during each of the four seasons. Gross primary production (GPP), ecosystem respiration, and net ecosystem production (NEP) were all best predicted by models with season as a main effect, but interactions between season, canopy, and watershed varied for each response. Urban streams exhibited higher GPP during most seasons, likely due to elevated nutrient loads. Open canopy reaches in both urban and forested streams, supported higher rates of GPP than the closed canopy which reaches during the summer and fall, when the overhead vegetation shaded the closed reaches. The effect of canopy cover on GPP was similar among urban and forested streams. The combination of watershed and local-scale controls resulted in urban streams that alternated between net heterotrophy (NEP <0) and net autotrophy (NEP >0) at the reach-scale during seasons with dense canopy cover. This finding has management relevance because net production can lead to accumulation of algal biomass and associated issues like nighttime hypoxia. Our study suggests that although watershed urbanization fundamentally alters ecosystem function, the preservation and restoration of canopied riparian zones can provide an important management tool at the local scale, with the strongest impacts on stream metabolism during summer.     

Growth, production and bioenergetics of brown trout in upland streams with contrasting riparian vegetation

1. A series of laboratory-based equations on trout growth and bioenergetics developed by J.M. Elliott were applied to data collected for brown trout ( Salmo trutta L.) under field conditions in Co. Mayo, Western Ireland. Fish were collected by electrofishing eight upland streams with contrasting riparian vegetation; grassland, open canopy and closed canopy deciduous.
2. Stream temperatures, one of the main influencing factors on fish growth and energetics, did not differ significantly between riparian types.
3. Observed growth rates were lower than the predicted maximum growth rates and were not influenced by riparian vegetation type. Growth ranged between 0.66% day⁻¹ for 0 + trout to 0.08% day⁻¹ for 2 + trout.
4. Production estimates showed no clear difference between riparian vegetation types over the growing season.
5. Fish densities and biomass tended to be greater in closed canopy streams particularly in summer.
6. Actual ration sizes calculated for trout were similar to the ration required for maintenance metabolism and were only 45–63% of the maximum potential rations. Although there was an ontogenetic increase in ration size with increasing fish age, the proportion of ration available for growth (i.e. the difference between actual and maintenance rations) did not differ between age classes but was greatest in summer. 1+ and 2+ trout show greatest ration available for growth in grassland streams.
7. Trout growth did not differ between riparian vegetation types but did vary seasonally with greatest attainment in summer. Growth was limited in the present study possibly due to combined effects of reduced prey available to fish and low stream temperatures reducing metabolic requirements. In such food limited systems, terrestrial invertebrate energy subsidies could have significant benefits to brown trout growth, production and bioenergetics.     

Non-native earthworms in riparian soils increase nitrogen flux into adjacent aquatic ecosystems

Riparian zones are an important transition between terrestrial and aquatic ecosystems, and they function in nutrient cycling and removal. Non-native earthworms invading earthworm-free areas of North America can affect nutrient cycling in upland soils and have the potential to affect it in riparian soils. We examined how the presence of earthworms can affect riparian nutrient cycling and nutrient delivery to streams. Two mesocosm experiments were conducted to determine how (1) the biomass of earthworms and (2) earthworm species can affect nutrient flux from riparian zones to nearby streams and how this flux can affect streamwater nutrients and periphyton growth. In separate experiments, riparian soil cores were amended with one of four mixed earthworm biomasses (0, 4, 10, or 23 g m(-2) ash-free dry mass) or with one of three earthworm species (Aporrectodea caliginosa, Lumbricus terrestris, L. rubellus) or no earthworm species. Riparian soil cores were coupled to artificial streams, and over a 36-day period, we measured nutrient leaching rates, in-stream nutrient concentrations, and periphyton growth. Ammonium leaching increased with increasing biomass and was greatest from the A. caliginosa treatments. Nitrate leaching increased through time and increased at a greater rate with higher biomass and from cores containing A. caliginosa. We suggest that the overall response of increased nitrate leaching [90% of total nitrogen (N)] was due to a combination of ammonium excretion and burrowing by earthworms, which increased nitrification rates. During both experiments, periphyton biomass increased through time but did not differ across treatments despite high in-stream inorganic N. Through time, in-stream phosphorus (P) concentration declined to <5 microg l(-1), and periphyton growth was likely P-limited. We conclude that activities of non-native earthworms (particularly A. caliginosa) can alter biogeochemical cycling in riparian zones, potentially reducing the N-buffering capacity of riparian zones and altering stoichiometric relationships in adjacent aquatic ecosystems.     

Changes in avian species composition following surface mining and reclamation along a riparian forest corridor in southern Indiana

Data on the response of bird communities to surface mining and habitat modification are limited, with virtually no data examining the effects of mining on bird communities in and along riparian forest corridors. Bird community composition was examined using line transects from 1994 to 2000 at eight sites within and along a riparian forest corridor in southwestern Indiana that was impacted by an adjacent surface mining operation. Three habitats were sampled: closed canopy, riparian forest with no open water; fragmented canopy, riparian forest with flood plain oxbows; and reclaimed mined land with constructed ponds. Despite shifts in species composition, overall bird species richness, measured as the mean number of bird species recorded/transect route, did not differ among habitats and remained unchanged across years. More species were recorded solely on mined land than in either closed forest or forested oxbow habitats. Mined land provided stopover habitat for shorebirds and waterfowl not recorded in other habitats, and supported an assemblage of grassland-associated bird species weakly represented in the area prior to mining. A variety of wood warblers and other migrants were recorded in the forest corridor throughout the survey period, suggesting that, although surface mining reduced the width of the forest corridor, the corridor was still important habitat for movement of forest-dependent birds and non-resident bird species in migration. We suggest that surface mining and reclamation practices can be implemented near riparian forest and still provide for a diverse assemblage of bird species. These data indicate that even narrow (0.4 km wide) riparian corridors are potentially valuable in a landscape context as stopover habitats and routes of dispersal and movement of forest-dependent and migratory bird species.     

Forest canopy cover determines invertebrate diversity and ecosystem process rates in depositional zones of headwater streams

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Distribution of ecosystem C and N within contrasting vegetation types in a semiarid rangeland in the Great Basin,USA

Semiarid sagebrush ecosystems are being transformed by wildfire, rangeland improvement techniques, and exotic plant invasions, but the effects on ecosystem C and N dynamics are poorly understood. We compared ecosystem C and N pools to 1 m depth among historically grazed Wyoming big sagebrush, introduced perennial crested wheatgrass, and invasive annual cheatgrass communities, to examine whether the quantity and quality of plant inputs to soil differs among vegetation types. Natural abundance δ¹⁵N isotope ratios were used to examine differences in ecosystem N balance. Sagebrush-dominated sites had greater C and N storage in plant biomass compared to perennial or annual grass systems, but this was predominantly due to woody biomass accumulation. Plant C and N inputs to soil were greatest for cheatgrass compared to sagebrush and crested wheatgrass systems, largely because of slower root turnover in perennial plants. The organic matter quality of roots and leaf litter (as C:N ratios) was similar among vegetation types, but lignin:N ratios were greater for sagebrush than grasses. While cheatgrass invasion has been predicted to result in net C loss and ecosystem degradation, we observed that surface soil organic C and N pools were greater in cheatgrass and crested wheatgrass than sagebrush-dominated sites. Greater biomass turnover in cheatgrass and crested wheatgrass versus sagebrush stands may result in faster rates of soil C and N cycling, with redistribution of actively cycled N towards the soil surface. Plant biomass and surface soil δ¹⁵N ratios were enriched in cheatgrass and crested wheatgrass relative to sagebrush-dominated sites. Source pools of plant available N could become ¹⁵N enriched if faster soil N cycling rates lead to greater N trace gas losses. In the absence of wildfire, if cheatgrass invasion does lead to degradation of ecosystem function, this may be due to faster nutrient cycling and greater nutrient losses, rather than reduced organic matter inputs.     

A Synthesis of Climate and Vegetation Cover Effects on Biogeochemical Cycling in Shrub-Dominated Drylands

Semi-arid and arid ecosystems dominated by shrubs (“dry shrublands”) are an important component of the global C cycle, but impacts of climate change and elevated atmospheric CO₂ on biogeochemical cycling in these ecosystems have not been synthetically assessed. This study synthesizes data from manipulative studies and from studies contrasting ecosystem processes in different vegetation microsites (that is, shrub or herbaceous canopy versus intercanopy microsites), to assess how changes in climate and atmospheric CO₂ affect biogeochemical cycles by altering plant and microbial physiology and ecosystem structure. Further, we explore how ecosystem structure impacts on biogeochemical cycles differ across a climate gradient. We found that: (1) our ability to project ecological responses to changes in climate and atmospheric CO₂ is limited by a dearth of manipulative studies, and by a lack of measurements in those studies that can explain biogeochemical changes, (2) changes in ecosystem structure will impact biogeochemical cycling, with decreasing pools and fluxes of C and N if vegetation canopy microsites were to decline, and (3) differences in biogeochemical cycling between microsites are predictable with a simple aridity index (MAP/MAT), where the relative difference in pools and fluxes of C and N between vegetation canopy and intercanopy microsites is positively correlated with aridity. We conclude that if climate change alters ecosystem structure, it will strongly impact biogeochemical cycles, with increasing aridity leading to greater heterogeneity in biogeochemical cycling among microsites. Additional long-term manipulative experiments situated across dry shrublands are required to better predict climate change impacts on biogeochemical cycling in deserts.     

Ecological Values of Shallow-Water Habitats: Implications for the Restoration of Disturbed Ecosystems

A presumed value of shallow-habitat enhanced pelagic productivity derives from the principle that in nutrient-rich aquatic systems phytoplankton growth rate is controlled by light availability, which varies inversely with habitat depth. We measured a set of biological indicators across the gradient of habitat depth within the Sacramento–San Joaquin River Delta (California) to test the hypothesis that plankton biomass, production, and pelagic energy flow also vary systematically with habitat depth. Results showed that phytoplankton biomass and production were only weakly related to phytoplankton growth rates whereas other processes (transport, consumption) were important controls. Distribution of the invasive clam Corbicula fluminea was patchy, and heavily colonized habitats all supported low phytoplankton biomass and production and functioned as food sinks. Surplus primary production in shallow, uncolonized habitats provided potential subsidies to neighboring recipient habitats. Zooplankton in deeper habitats, where grazing exceeded phytoplankton production, were likely supported by significant fluxes of phytoplankton biomass from connected donor habitats. Our results provide three important lessons for ecosystem science: (a) in the absence of process measurements, derived indices provide valuable information to improve our mechanistic understanding of ecosystem function and to benefit adaptive management strategies; (b) the benefits of some ecosystem functions are displaced by water movements, so the value of individual habitat types can only be revealed through a regional perspective that includes connectedness among habitats; and (c) invasive species can act as overriding controls of habitat function, adding to the uncertainty of management outcomes.     

Plastic allometry in young sugar maple (Acer saccharum): adaptive responses to light availability

Age, height, number of shoot endings, neighbor density, and overhead cover from local neighbors were recorded for over 1, 400 young sugar maple trees under 200 cm tall and growing in open vs. closed (shaded) habitats from two sites. Up to about age 5 yr, seedlings increase in height but rarely branch. Once branching starts, there begins a general decrease with age in the number of centimeters of height added for every new shoot ending that is produced. The pattern of this allometric relationship, however, is plastic—in the closed habitats, this switch to increased branching relative to height growth is delayed compared with trees from the open habitats. Within the closed habitats, branching is also delayed for trees having dense cover from local neighboring understory vegetation compared with trees that are not overtopped by understory vegetation. The oldest and tallest unbranched seedlings were recorded from the closed habitats. Seedlings displaying the first branch, however, were younger in the open habitats than in the closed habitats, and at one site they were shorter in the open habitat than in the closed habitat. These results suggest that the allometric relationship between height and degree of branching can display adaptive plasticity depending on light availability: As competition for light decreases (with greater light availability), there is an increasing premium on lateral growth (branching) to maximize light interception. Conversely, as competition for light increases (under decreasing light availability), there is an increasing premium on vertical growth (through strong and persistent apical dominance) to minimize the chances of being overtopped by neighbors.     

Notes on habitat relationships of ungulates in Yankari Game Reserve, Nigeria

Yankari Game Reserve in northeastern Nigeria consists largely of savanna woodland with trees on the better soils growing to 15 m and with spreading crowns. On shallow and stony soils the tree height is generally less and the canopy is discontinuous. The Gaji River riparian zone supports a wide variety of vegetation types ranging from evergreen, closed canopy forest to sedge meadows and patches of open grassland.
Elephant ( Loxodonta africana ) range backwards and forwards along the riparian strip, feeding on perennial grasses and a variety of browse material and utilizing closed canopy forest patches for shade cover. The major movement patterns of other important herbivore species are perpendicular to the riparian strip. Areas used intensively are: waterbuck ( Kobus defassa )–open savanna woodland immediately behind the riparian strip: Western hartebeest ( Alcelaphus buselaphus major )– open grassy habitat in relatively poor woodland at middle distances from the river; Roan antelope ( Hippotragus equinus )–patches of well-developed and infrequently burned woodland, often at major distances from the river. Buffalo ( Syncerus caffer brachyceros ) during the dry season ranged between the riparian grassland areas and the more open sections of nearby savanna woodland, but travelled out to distant sections of the reserve after rainwater pools had formed.
A major problem in management was the development of a burning policy that would maintain an appropriate balance between perennial and annual grasses and the shade providing trees.     

The relative importance of shading and nutrients on algal production in subtropical streams

1. We used artificial substrata in forested and open streams in South-East Queensland, Australia, to determine the relative importance of shading from riparian vegetation and of nutrients on periphyton growth, and whether nitrogen and/or phosphorus limited algal productivity.
2. Nutrient-diffusing substrata consisting of agar enriched with N, P and N + P, and controls without nutrients, were deployed in duplicate at 15 sites in headwater streams with riparian canopy cover ranging from 0 to 88%.
3. Shading was the over-riding factor controlling periphyton biomass accrual on the artificial substrata, with nutrients playing a relatively minor role. Microscopic examination of periphyton scrapings taken after 7 weeks revealed that diatoms dominated on the artificial substrata in shaded streams, whereas filamentous green algae dominated the algal assemblage in the more open canopy streams.
4. Whilst nutrients had little effect on the accrual of algal biomass compared with riparian shading, there was evidence that nitrogen, and not phosphorus, stimulated periphyton production in streams with sufficient light.     

Experimental shading alters leaf litter breakdown in streams of contrasting riparian canopy cover

1. Headwater stream ecosystems are primarily heterotrophic, with allochthonous organic matter being the dominant energy. However, sunlight indirectly influences ecosystem structure and functioning, affecting microbial and invertebrate consumers and, ultimately, leaf litter breakdown. We tested the effects of artificial shading on litter breakdown rates in an open‐canopy stream (high ambient light) and a closed‐canopy stream (low ambient light). We further examined the responses of invertebrate shredders and aquatic hyphomycetes to shading to disentangle the underlying effects of light availability on litter breakdown. 2. Litter breakdown was substantially slower for both fast‐decomposing (alder, Alnus glutinosa) and slow‐decomposing (beech, Fagus sylvatica) leaf litters in artificially shaded stream reaches relative to control (no artificial shading) reaches, regardless of stream type (open or closed canopy). 3. Shredder densities were higher on A. glutinosa than on F. sylvatica litter, and shading had a greater effect on reducing shredder densities associated with A. glutinosa than those associated with F. sylvatica litter in both stream types. Fungal biomass was also negatively affected by shading. Results suggest that the effects of light availability on litter breakdown rates are mediated by resource quality and consumer density. 4. Results from feeding experiments, where A. glutinosa litter incubated under ambient light or artificial shade was offered to the shredder Gammarus fossarum, suggest that experimental shading and riparian canopy openness influenced litter palatability interactively. Rates of litter consumption by G. fossarum were decreased by experimental shading in the open‐canopy stream only. 5. The results suggest that even small variations in light availability in streams can mediate substantial within‐stream heterogeneity in litter breakdown. This study provides further evidence that changes in riparian vegetation, and thus light availability, influence organic matter processing in heterotrophic stream ecosystems through multiple trophic levels.     

Habitat selection of riparian birds at restoration sites along the Trinity River,California

Riparian habitats in the western United States are imperiled, yet they support the highest bird diversity in arid regions, making them a conservation priority. Riparian restoration efforts can be enhanced by information on species response to variation in habitat features. We examined the habitat selection of four riparian birds known as management indicators at restoration and reference sites along the Trinity River, California. We compared vegetation structure and composition at nest sites, territories, and random points to quantify used versus available habitat from 2012 to 2015. Vegetation in focal species' territories differed between site types, and from available habitat, indicating nonrandom site choice. Birds selected aspects of more structurally complex habitats, such as greater canopy cover, canopy height, and tree species richness. Yellow‐breasted Chats preferred greater shrub cover, and Yellow Warblers preferred greater cover by non‐native Himalayan blackberry. Territory preferences on restoration sites were often a subset of those on reference sites. One exception was canopy height, which was taller on restoration site territories than random points for all species, suggesting that birds preferentially used patches of remnant habitat. Few variables were significant in nest site selection. Restoration plantings along the Trinity River were only 3–10 years old during this study, and have not developed many of the characteristics of mature riparian habitat preferred by birds, but may improve in habitat value over time. Understanding habitat selection is especially important in recently human‐modified environments, where indirect cues used to assess habitat quality may become disassociated from actual habitat quality, potentially creating ecological traps.     

Roles of dominant understory Sasa bamboo in carbon and nitrogen dynamics following canopy tree removal in a cool‐temperate forest in northern Japan

To clarify the role of dense understory vegetation in the stand structure, and in carbon (C) and nitrogen (N) dynamics of forest ecosystems with various conditions of overstory trees, we: (i) quantified the above‐ and below‐ground biomasses of understory dwarf bamboo (Sasa senanensis) at the old canopy‐gap area and the closed‐canopy area and compared the stand‐level biomasses of S. senanensis with that of overstory trees; (ii) determined the N leaching, soil respiration rates, fine‐root dynamics, plant area index (PAI) of S. senanensis, and soil temperature and moisture at the tree‐cut patches (cut) and the intact closed‐canopy patches (control). The biomass of S. senanensis in the canopy‐gap area was twice that at the closed‐canopy area. It equated to 12% of total biomass above ground but 41% below ground in the stand. The concentrations of NO₃^? and NH₄⁺ in the soil solution and soil respiration rates did not significantly change between cut and control plots, indicating that gap creation did not affect the C or N dynamics in the soil. Root‐length density and PAI of S. senanensis were significantly greater at the cut plots, suggesting the promotion of S. senanensis growth following tree cutting. The levels of soil temperature and soil moisture were not changed following tree cutting. These results show that S. senanensis is a key component species in this cool‐temperate forest ecosystem and plays significant roles in mitigating the loss of N and C from the soil following tree cutting by increasing its leaf and root biomass and stabilizing the soil environment.     

Relationship Between Avifaunal Occupancy and Riparian Vegetation in the Central Great Basin (Nevada, U.S.A.)

In western North America, riparian vegetation is being lost in response to changes in land use and climate. We examined the relationship between obligate riparian species of songbirds and environmental and riparian habitat factors in three mountain ranges in the central Great Basin (Nevada, U.S.A.). We estimated patterns of occupancy, colonization, and local extinction for three species detected during the breeding seasons of 2001–2006: MacGillivray's Warbler ( Oporornis tolmiei ), Broad-tailed Hummingbird ( Selasphorus platycercus ), and Song Sparrow ( Melospiza melodia ). We used model selection and multimodel inference to identify functional relationships between the occupancy of each species and multiple habitat variables, including the structure and composition of riparian vegetation. Among all years and species, we observed considerable variation in estimates of detection probability. For MacGillivray's Warbler, annual occupancy rates were relatively constant. Occupancy rates for Broad-tailed Hummingbird and Song Sparrow increased during the first 3–4 years of our study and then decreased. Each species experienced its highest rate of local extinction during 2005. Different components of riparian vegetation were good predictors of occupancy, colonization, and local extinction for each species. Typically, elevation and latitude also were strong predictors. Establishing functional relationships between avifauna and vegetation is essential to predicting how land-cover change may affect the occupancy of riparian areas and other habitats for birds. The conservation of breeding birds in riparian areas in the central Great Basin is more likely to succeed if the quality of their understory habitat as well as the canopy is maintained and restored.     

Tradeoffs and scaling of functional traits in Sphagnum as drivers of carbon cycling in peatlands

Growth and decomposition of Sphagnum controls turnover of a large global store of soil organic carbon. We investigated variation in morphological and physiological traits of Sphagnum shoots, and related this variation to canopy variables relevant to peatland carbon cycling. We sampled Sphagnum along a bog plateau‐swamp forest gradient and measured a suite of shoot traits and canopy variables. Major axes of variation were identified using principal component analysis and correlated with canopy variables such as growth, biomass and decomposition. We also examined scaling of shoot traits with one another and with canopy variables. Two distinct tradeoffs in shoot traits emerged. From dry to wet habitats, individual metabolic rates and capitulum size increased while numerical density decreased, leading to faster growth and elongation on an individual basis. From treed to open habitats, photosynthetic efficiency decreased and photosynthetic biomass increased, driving faster growth on an area basis and slower litter mass loss. The tradeoffs identified have important implications for peatlands undergoing climate‐related changes in water and light availability. Sphagnum trait comparisons, combined with scaling analyses, offer a promising approach to understanding and predicting the effects of environmental change on peatland carbon cycling.     

Nitrogen processing by grazers in a headwater stream: riparian connections

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Benthic invertebrate community structure is influenced by forest succession after clearcut logging in southeastern Alaska

To assess the effects of timber harvesting on headwater streams in upland forests, benthic community structure was contrasted among four dominant forest management types (old growth, red alder-dominated young growth, conifer-dominated young growth, clearcut) and instream habitats (woody debris, cobble, gravel) in southeastern Alaska. Benthos in streams of previously harvested areas resulted in increased richness, densities and biomass relative to old growth types, particularly in young growth stands with a red alder-dominated riparian canopy. Woody debris and gravel habitats supported a combination of higher densities and biomass of invertebrates than cobble habitats. In addition, woody debris also supported a richer and more diverse invertebrate fauna than either cobble or gravel substrates. Maintaining both a woody debris source and a red alder component in regenerating riparian forests following timber harvesting should support greater invertebrate densities and diversity following clearcutting.     

Effects of open-top passive warming chambers on soil respiration in the semi-arid steppe to taiga forest transition zone in Northern Mongolia

The response of soil respiration to warming has been poorly studied in regions at higher latitude with low precipitation. We manipulated air temperature, soil temperature and soil moisture using passive, open-top chambers (OTCs) in three different ecosystem settings in close proximity (boreal forest, riparian area, and semi-arid steppe) to investigate how environmental factors would affect soil respiration in these different ecosystems, anticipating that soil respiration would increase in response to the chamber treatment. The results indicated that OTCs significantly increased air and soil temperature in areas with open canopy and short-statured vegetation (i.e., steppe areas) but not in forest. OTCs also affected soil moisture, but the direction of change depended on the ecosystem, and the magnitude of change was highly variable. Generally, OTCs did not affect soil respiration in steppe and riparian areas. Although soil respiration was slightly greater in OTCs placed in the forest, the difference was not statistically significant. Analyses of relationships between soil respiration and environmental variables suggested that different factors controlled soil respiration in the different ecosystems. Competing effects analysis using a model selection approach and regression analyses (e.g., Q₁₀) demonstrated that soil respiration in the forest was more sensitive to warming, while soil respiration in the steppe was more sensitive to soil moisture. The differing responses and controlling factors among these neighboring forest, riparian and steppe ecosystems in Northern Mongolia highlight the importance of taking into account potential biome shifts in C cycling modeling to generate more accurate predictions of landscape-scale responses to anticipated climate change.