The effects of water- and nitrogen-induced stresses on plant community structure in a semiarid grassland

Lauenroth, William K.; Dodd, J. L.; Sims, Phillip L.

doi:10.1007/bf00349810

Cited by 230 publications

(163 citation statements)

References 14 publications

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“…Losses in species richness were mainly due to decreases in perennial forbs while no significant changes occurred in annuals, shrubs and semi-shrubs, or annual forbs in our steppe (Song et al, 2011). This is in accordance with Lauenroth et al (1978) who found that changes in community structure occurred mainly in several dominant groups. Different species responses to N addition may also be related to species functional traits such as root depth, N use efficiency, and mycorrhizal colonization which are associated with strategies for species adaptation to variable nutrient conditions (Ren et al, 2011).…”

Section: Plantsupporting

confidence: 93%

Nitrogen enrichment enhances the dominance of grasses over forbs in a temperate steppe ecosystem

et al. 2011

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Abstract. Chinese grasslands are extensive natural ecosystems that comprise 40 % of the total land area of the country and are sensitive to N deposition. A field experiment with six N rates (0, 30, 60, 120, 240, and 480 kg N ha −1 yr −1 ) was conducted at Duolun, Inner Mongolia, during 2005 and 2010 to identify some effects of N addition on a temperate steppe ecosystem. The dominant plant species in the plots were divided into two categories, grasses and forbs, on the basis of species life forms. Enhanced N deposition, even as little as 30 kg N ha −1 yr −1 above ambient N deposition (16 kg N ha −1 yr −1 ), led to a decline in species richness. The cover of grasses increased with N addition rate but their species richness showed a weak change across N treatments. Both species richness and cover of forbs declined strongly with increasing N deposition as shown by linear regression analysis (p < 0.05). Increasing N deposition elevated aboveground production of grasses but lowered aboveground biomass of forbs. Plant N concentration, plant δ 15 N and soil mineral N increased with N addition, showing positive relationships between plant δ 15 N and N concentration, soil mineral N and/or applied N rate. The cessation of N application in the 480 kg N ha −1 yr −1 treatment in 2009 and 2010 led to a slight recovery of the forb species richness relative to total cover and aboveground biomass, coinciding with reduced plant N concentration and soil mineral N. The results show N deposition-induced changes in soil N transformations and plant N assimilation that are closely related to changes in species composition and biomass accumulation in this temperate steppe ecosystem.

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Section: Plantsupporting

confidence: 93%

Nitrogen enrichment enhances the dominance of grasses over forbs in a temperate steppe ecosystem

et al. 2011

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“…Control, water, nitrogen, and water-plus-nitrogen treatments were initiated in 1971 (Lauenroth et al 1978, Dodd andLauenroth 1979). The experimental design consisted of two replications of factorial combinations of water and nitrogen, with each treatmentreplicate extending over a 1-ha area, and the treatments applied from 1971 to 1975.…”

Section: Methodsmentioning

confidence: 99%

“…Treatments were terminated in 1975, after 5 yr, and vegetation was sampled through 1977 (Lauenroth et al 1978, Dodd andLauenroth 1979). Sampling was resumed in 1982 by sampling 10 permanent plots on each of five transects in each of the treatment-replicates (4 treatments X 2 locations X 50 plots).…”

Section: Methodsmentioning

confidence: 99%

Inertia in Plant Community Structure: State Changes After Cessation of Nutrient‐Enrichment Stress

Milchunas¹,

Lauenroth²

1995

Ecological Applications

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240

167

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Abstract. Water, nitrogen, and water-plus-nitrogen at levels beyond the range normally experienced by shortgrass steppe communities were applied from 1971through1975, plant populations were sampled through 1977, and the results of the experiment were published. Upon revisiting the plots in 1982, we found it apparent that large changes had occurred since 1977. Sampling was re-established in 1982 to follow trajectories of recovery. Our purposes in this paper are to examine how conclusions from this study changed through time, and discuss implications of these changes for monitoring potentially stressed ecosystems.Although productivities increased, dissimilarities in plant species composition at the end of the 5 yr of nutrient treatments were not significantly different from controls. Two years after cessation of the treatments exotic "weed" species were increasing in waterplus-nitrogen treated communities, and community dissimilarities were diverging in water and water-plus-nitrogen treated communities. Seven years after cessation of treatments all communities were significantly different from controls. Exotics were more than ten times more abundant in water-plus-nitrogen and nitrogen treated communities than they had been 2 yr post-treatment. A consistent trend in recovery of all treated communities was evident over the next 5 yr. However, the trend towards recovery reversed over the next four consecutive years in the previously water-plus-nitrogen and water treated communities. The four-to-five year cycles in species composition and abundance of exotics towards, and then away from, conditions in undisturbed control communities were not related to weather, but large accumulations of litter suggested biotic regulation.Inertia of existing plant populations, or the tendency to continue to occupy a site when conditions become unfavorable, can mask both future deterioration in ecosystem condition and unstable behavior resulting from environmental stressors. Time lags in initial response means that an ecosystem can pass a threshold leading to transitions to alternate states before it is evident in structural characteristics such as species composition. Global climate change and sulfur and nitrogen oxide pollutants also have the potential to act as enrichment-stressors with initial time lags and/or positive effects and cumulative, subsequent negative effects, rather than as disturbance forces with immediate negative impacts. Sociopolitical systems, however, often require change in biological variables or negative impacts before acting to ameliorate environmental problems. The manner in which conclusions changed at various periods in time, and the potential for time lags in responses of species populations, raises questions about which variables are most useful for detection of stress and how long studies must last to be useful.

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“…Nitrogen (N) and water availability both directly control the functioning of arid ecosystems (Lauenroth et al 1978, Yahdjian et al 2011). In addition, water and N availability interact with each other so that water availability affects the N cycle; and N availability affects the water cycle.…”

Section: Introductionmentioning

confidence: 99%

Water controls on nitrogen transformations and stocks in an arid ecosystem

Reichmann¹,

Sala²,

Peters³

2013

Ecosphere

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Abstract. Following water, nitrogen (N) is the most frequent limiting factor to aboveground net primary production in arid ecosystems. Increased water availability can stimulate both plant nitrogen uptake and microbial nitrogen mineralization, but may also stimulate losses from the ecosystem. Here, we assess the effect of water availability on nitrogen stocks and transformations in an arid ecosystem. We conducted a field experiment with five levels of precipitation input (À80%, À50%, ambient, þ50%, þ80%) and two levels of N fertilization (ambient or 10 gÁm À2 Áyr À1 NH 4 NO 3 ) in a desert grassland of the Chihuahuan Desert. We measured in situ net N mineralization, plant N uptake, foliar N, N leaching under grass-rooting zone, and soil N availability during two years. Our results showed that increased water availability did not affect net N mineralization, but there was higher plant N uptake than with drought. Soil inorganic N pools were 2-4 times lower with increased water availability compared to drought conditions. N leaching below grass-rooting zone was higher in dry than wet conditions because of higher available N. Increased water availability differentially affected N species significantly reducing the NO 3 :NH 4 ratio. The accumulation of inorganic N during drought was the result of a decoupling between microbial and plant activity, and suggests that the cycling of N is more open in dry years than in wet years.

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The effects of water- and nitrogen-induced stresses on plant community structure in a semiarid grassland

Cited by 230 publications

References 14 publications

Nitrogen enrichment enhances the dominance of grasses over forbs in a temperate steppe ecosystem

Nitrogen enrichment enhances the dominance of grasses over forbs in a temperate steppe ecosystem

Inertia in Plant Community Structure: State Changes After Cessation of Nutrient‐Enrichment Stress

Water controls on nitrogen transformations and stocks in an arid ecosystem

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