10.5061/DRYAD.T76HDR81T
Song, Jian
0000-0001-9957-6533
Hebei University
Xia, Jianyang
East China Normal University
Hui, Dafeng
Tennessee State University
Zheng, Mengmei
Henan Normal University
Wang, Jing
Hebei University
Ru, Jingyi
Hebei University
Wang, Haidao
Hebei University
Zhang, Qingshan
Hebei University
Yang, Chao
Hebei University
Wan, Shiqiang
Hebei University
Responses of soil temperature, moisture, and respiration to five-year
warming and nitrogen addition in a semi-arid grassland
Dryad
dataset
2021
Global change ecology
National Natural Science Foundation of China
https://ror.org/01h0zpd94
31830012
2021-08-08T00:00:00Z
2021-08-08T00:00:00Z
en
81325 bytes
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CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
How climate warming interacts with atmospheric nitrogen (N) deposition to
affect carbon (C) release from soils remains largely elusive, posing a
major challenge in projecting climate change‒terrestrial C feedback. As
part of a five-year (2006–2010) field manipulative experiment, this study
was designed to examine the effects of 24-hour continuous warming and N
addition on soil respiration and explore the underlying mechanisms in a
semi-arid grassland on the Mongolian Plateau, China. Across the five years
and all plots, soil respiration was not changed under the continuous
warming, but was decreased by 3.7% under the N addition. The suppression
of soil respiration by N addition in the third year and later could be
mainly due to the reductions in the forb-to-grass biomass ratios.
Moreover, there were interactive effects between continuous warming and N
addition on soil respiration. Continuous warming increased soil
respiration by 5.8% in the ambient N plots, but reduced it by 6.3% in the
enriched N plots. Soil respiration was unaffected by N addition in the
ambient temperature plots yet decreased by 9.4% in the elevated
temperature plots. Changes of soil moisture and the proportion of legume
biomass in the community might be primarily responsible for the
non-additive effects of continuous warming and N addition on soil
respiration. This study provides empirical evidence for the positive
climate warming‒soil C feedback in the ambient N condition. However, N
deposition reverses the positive warming‒soil C feedback into a negative
feedback, leading to decreased C loss from soils under a warming climate.
Incorporating our findings into C-cycling models could reduce the
uncertainties of model projections for land C sink and global C cycling
under multifactorial global change scenarios.
2.1. Study site The study site is located in a semi-arid grassland in
Duolun County (42°02ʹ N, 116°17ʹ E, 1324 m a.s.l.), Inner Mongolia, China.
Long-term (1953–2019) mean annual temperature and precipitation are 2.4°C
and 382 mm, respectively (China Meteorological Data Sharing Service
System). The sandy soil is classified as chestnut soils (Chinese
classification) and Xeric Haplocalcids according to the US soil taxonomy
classification system (Soil Survey Staff, 1999). Plant community at the
study site is dominated by perennial species such as Agropyron cristatum,
Artemisia frigida, Artemisia pubescens, Lespedeza davurica, and Stipa
krylovii (Zheng et al., 2021). 2.2. Experimental design and manipulations
A randomized complete block design was used in this experiment with four
treatments including a control (C; no warming and without N addition),
24-hour continuous warming (W), N addition (N), and continuous warming
plus N addition (WN). There were six replicates (block) for each treatment
(see also Xia et al., 2009). Twenty-four 3-m × 4-m plots were arranged in
4 × 6 matrix, with a 3-m buffer zone between any two adjacent plots. The
continuous warmed plots were heated continuously using MSR–2420 infrared
radiators (Kalglo Electronics Inc., Bethlehem, PA, USA) suspended 2.25 m
above the ground from 23 April to 15 November in 2006 and from 15 March to
15 November during 2007–2010. In the unwarmed plots, one ‘dummy’ heater
with the same shape and size as infrared radiators was suspended 2.25 m
high to mimic the shading effects of infrared radiators. The level of N
addition was set at 10 g N m-2 year-1 as ecosystem responses to N
enrichment in this area could reach the saturation point at a rate of 10.5
g N application m-2 year-1 (Bai et al., 2010). NH4NO3 was applied in the
enriched N plots once on 19 July in each of the five experimental years
from 2006 to 2010. 2.3. Soil microclimate and plant biomass measurements
In each growing season from May to October, soil temperature (°C) at 10-cm
depth was measured three times per month using a portable temperature
probe (LI-8100-201) attached to a LI-8100 Soil CO2 Flux System (Li-Cor
Inc., Lincoln, Nebraska, USA). Soil volumetric water content (% V/V) at
10-cm depth was measured weekly with a Diviner-2000 Portable Soil Moisture
Probe (Sentek Pty Ltd, Balmain, Australia). Both the measurements of soil
temperature and moisture were conducted adjacent to collars used for soil
respiration measurements on clear and sunny days between 09:00 and 12:00
a.m. (local time). 2.4. Soil respiration measurements Two 5-cm tall
polyvinyl chloride collars (10 cm in diameter) were permanently inserted 3
cm into the soil at two opposite corners of each plot. A CO2 flux chamber
attached to the LI-8100 Soil CO2 Flux System was put on each collar for 90
secs to measure soil respiration, and then moved to the next collar. To
eliminate influences of plant respiration, the aboveground parts of living
plants inside collars were cut at least one day prior to the measurement.
The aboveground cut materials were left inside the collars. Soil
respiration was measured three times per month on clear and sunny days
between 09:00 and 12:00 a.m. (local time).