As above, not so below: Long‐term dynamics of net primary production across a dryland transition zone

Brown, Renée F; Collins, Scott L.

doi:10.1111/gcb.16744

Cited by 3 publications

(1 citation statement)

References 135 publications

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“…Similarly, Keller et al (2023) reported no correlation for the responses of above-ground and root production to N addition with a rate of 10 g N m −2 year −1 across nine North American grasslands. A recent study in Chihuahuan Desert shrubland also found that the relationship between ANPP and BNPP was weak and that BNPP was unaffected by chronic N enrichment (Brown & Collins, 2023), indicating that BNPP would be controlled by a different set of drivers than ANPP. Globally, ANPP but not BNPP is sensitive to climate variations (Sun et al, 2021), resulting in different response patterns between ANPP and BNPP along climatic gradients.…”

Section: Discussionmentioning

confidence: 98%

Different nitrogen saturation thresholds for above‐, below‐, and total net primary productivity in a temperate steppe

Yang

Zhang²,

Luo

et al. 2023

Global Change Biology

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Identifying the thresholds for the positive responses of total net primary productivity (NPP) to nitrogen (N) enrichment is an essential prerequisite for predicting the benefits of N deposition on ecosystem carbon sequestration. However, the responses of below‐ground NPP (BNPP) to N enrichment are unknown in many ecosystems, which limits our ability to understand the carbon cycling under the scenario of increasing N availability. We examined the changes in above‐ground NPP (ANPP), BNPP, and NPP of a temperate meadow steppe across a wide‐ranging N addition gradient (0, 2, 5, 10, 20, and 50 g N m−2 year−1) during 5 years. Both ANPP and NPP increased nonlinearly with N addition rates. The N saturation threshold for ANPP (TA) and NPP (TN) was at the rate of 13.11 and 6.70 g N m−2 year−1, respectively. BNPP decreased with increasing N addition when N addition rates ˃5 g N m−2 year−1, resulting in much lower TN than TA. Soil N enrichment played a key role in driving the negative impacts of high N addition rates on BNPP, and consequently on the earlier occurrence of N saturation threshold for NPP. Our results highlight the negative effects of soil N enrichment on NPP in natural grasslands super‐saturated with N. Furthermore, by considering ANPP and BNPP simultaneously, our results indicate that previous findings from above‐ground might have over‐estimated the positive effects of N deposition on primary productivity.

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Section: Discussionmentioning

confidence: 98%

Different nitrogen saturation thresholds for above‐, below‐, and total net primary productivity in a temperate steppe

Yang

Zhang²,

Luo

et al. 2023

Global Change Biology

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Sensitivity of root production to long‐term aridity under environmental perturbations in Chihuahuan Desert ecosystems

Vojdani,

Baur,

Rudgers

et al. 2024

Journal of Ecology

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Root production influences carbon and nutrient cycles and subsidizes soil biodiversity. However, the long‐term dynamics and drivers of belowground production are poorly understood for most ecosystems. In drylands, fire, eutrophication, and precipitation regimes could affect not only root production but also how roots track interannual variability in climate. We manipulated the intra‐annual precipitation regime, soil nitrogen, and fire in four common Chihuahuan Desert ecosystem types (three grasslands and one shrubland) in New Mexico, USA, where the 100‐year record indicates both long‐term drying and increasing interannual variability in aridity. First, we evaluated how root production tracked aridity over 10–17 years using climate sensitivity functions, which quantify long‐term, nonlinear relationships between biological processes and climate. Next, we determined the degree to which perturbations by fire, nitrogen addition or intra‐annual rainfall altered the sensitivity of root production to both mean and interannual variability in aridity. All ecosystems had nonlinear climate sensitivities that predicted declines in production with increases in the interannual variance of aridity. However, root production was the most sensitive to aridity in Chihuahuan Desert shrubland, with reduced production under drier and more variable aridity. Among the perturbations, only fire altered the sensitivity of root production to aridity. Root production was more than twice as sensitive to declines with aridity following prescribed fire than in unburned conditions. Neither the intra‐annual seasonal rainfall regime nor chronic nitrogen fertilization altered the sensitivity of roots to aridity. Synthesis. Our results yield new insight into how dryland plant roots respond to climate change. Our comparison of dryland ecosystems of the northern Chihuahuan Desert predicted that root production in shrublands would be more sensitive to future climates that are drier and more variable than root production in dry grasslands. Field manipulations revealed that fire could amplify the climate sensitivity of dry grassland root production, but in contrast, the climate sensitivity of root production was largely resistant to changes in the seasonal rainfall regime or increased soil fertilization.

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Long-term fertilization increases soil but not plant or microbial N in a Chihuahuan Desert grassland

Mendoza-Martinez,

Collins,

McLaren

2024

Biogeosciences

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Abstract. Although the negative consequences of increased nitrogen (N) supply for plant communities and soil chemistry are well known, most studies have focused on mesic grasslands, and the fate of added N in arid and semi-arid ecosystems remains unclear. To study the impacts of long-term increased N deposition on ecosystem N pools, we sampled a 26-year-long fertilization (10 g N m−2 yr−1) experiment in the northern Chihuahuan Desert at the Sevilleta National Wildlife Refuge (SNWR) in New Mexico. To determine the fate of the added N, we measured multiple soil, microbial, and plant N pools in shallow soils at three time points across the 2020 growing season. We found small but significant increases with fertilization in soil-available NO3--N and NH4+-N, yet the soil microbial and plant communities do not appear to be taking advantage of the increased N availability, with no changes in biomass or N content in either community. However, there were increases in total soil N with fertilization, suggesting increases in microbial or plant N earlier in the experiment. Ultimately, the majority of the N added in this multi-decadal experiment was not found in the shallow soil or the microbial or plant community and is likely to have been lost from the ecosystem entirely.

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As above, not so below: Long‐term dynamics of net primary production across a dryland transition zone

Cited by 3 publications

References 135 publications

Different nitrogen saturation thresholds for above‐, below‐, and total net primary productivity in a temperate steppe

Different nitrogen saturation thresholds for above‐, below‐, and total net primary productivity in a temperate steppe

Sensitivity of root production to long‐term aridity under environmental perturbations in Chihuahuan Desert ecosystems

Long-term fertilization increases soil but not plant or microbial N in a Chihuahuan Desert grassland

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