The Linkage of Soil CO2 Emissions in a Moso Bamboo (Phyllostachysedulis (Carriere) J. Houzeau) Plantation with Aboveground and Belowground Stoichiometry

Understanding the effects of soil stoichiometry and nutrient resorption on soil CO2 emissions is critical for predicting forest ecosystem nutritional demands and limitations tooptimal forest growth. In this study, we examined the effects of above- and belowground stoichiometry on soil CO2 emissions and their mediating effect on soil respiration in subtropical moso bamboo (Phyllostachys edulis) plantations. Our results showed that the soil respiration rate did not differ significantly among four bamboo stands. Nitrogen (N) and phosphorous (P) concentrations were higher in bamboo leaves than litter, whereas the C:N and C:P ratios showed the opposite trend. Significant positive correlations of soil cumulative CO2 emission with litter C:P (p = 0.012) and N:P (p = 0.041) ratios indicated that litter stoichiometry was a better predictor of soil respiration than aboveground stoichiometry. Cumulative soil CO2 emissions were significantly negatively correlated with soil microbe C:N (p = 0.021) and C:N (p = 0.036) ratios, and with soil respiratory quotients (p < 0.001). These results suggest that litter and soil stoichiometry are reliable indicators of the soil respiration rate. This study provides important information about the effects of ecosystem stoichiometry and soil microbial biomass on soil CO2 emissions and highlights them editing role of soil nutritional demands and limitations in the association between soil respiration rates and aboveground plant tissues.

Soil Respiration May Overestimate or Underestimate in Forest Ecosystems

The inappropriate selection of measurement points and measurement times in an ecosystem may easily lead to the underestimation or overestimation of soil respiration due to spatial and temporal heterogeneity. To assess the law of spatial and temporal heterogeneity and more accurately determine the soil respiration rate, we measured the soil respiration rate of a forest in the plant growing season from 2011 to 2013 on Changbai Mountain in 8 directions and 7 distances from each tree trunk. Neglecting the direction of the measuring point may overestimate or underestimate the soil respiration rate by 29.81% and 26.09%, respectively; neglecting the distance may overestimate or underestimate the soil respiration rate by 41.36% and 20.28%, respectively; and ignoring the measurement time may overestimate and underestimate the soil respiration rate by 41.71% and 57.64%, respectively. In addition, choosing a measurement point in the eastern direction at a 1.8 m distance and conducting the measurement in September may relatively accurately reflect the soil respiration rate of the ecosystem. These findings can deepen our understanding of soil respiration rate heterogeneity and may provide new ideas for improving the measurement method of soil respiration.

Effects of Micropore Group Spacing and Irrigation Amount on Soil Respiration and Yield of Tomato with Microsprinkler Irrigation under Plastic Film in Greenhouse

Microsprinkler irrigation under a plastic film in the greenhouse (MSPF) is a water-saving way which adopts the porous discharge form of a pipe under the plastic film. The effects of different micropore group spacings (L1:30 cm, L2: 50 cm) and irrigation amounts [I1: 0.7 Epan; I2: 1.0 Epan; and I3: 1.2 Epan (Epan is the diameter of 20 cm standard pan evaporation, mm)] of the MSPF on the soil respiration and yield of tomato were studied. A completely randomized trial design was used, and drip irrigation under plastic film (CK1) and microsprinkler irrigation (CK2) were also used as controls. The results showed that under the same irrigation amount, the soil respiration rate, tomato yield, and water use efficiency (WUE) of MSPF in spring and autumn are 8.09% and 6.74%, 19.39% and 4.54%, and 10.03% and 2.32% higher than those of CK1, respectively; they are significantly increased by 31.02% and 20.46%, 49.22% and 38.38%, and 58.05% and 34.66% compared with those of CK2, respectively, indicating that MSPF increased the amount of CO2 emission, but tomato yield and WUE were effectively improved, and a dynamic balance was reached among them. Compared with the 50 cm micropore group spacing, the spring and autumn tomato yields and WUE under the 30 cm micropore group spacing were significantly increased by 16.00% and 13.01% and 20.85% and 14.25%, respectively, and the micropore group spacing had no significant effect on the soil respiration rate in both root and nonroot zones. When the I increased from 0.7 Epan to 1.2 Epan, the soil respiration rate and yield in the root and nonroot zones of the spring and autumn tomatoes increased at first and then decreased, and the WUE showed a decreasing trend. The relationship of soil respiration rate between the nonroot and root zones obeys a logarithmic function, and the soil respiration rate in the nonroot zone has a quadratic curve relationship with the yield of tomato. This study can provide data support for the development of water-saving irrigation and yield increase of facility agricultural tomato and the analysis of the soil carbon cycling mechanism.

Soil Respiration Variation under the Canopy of Dominant Tree Species across different seasons in Temperate Forest

Soil respiration is defined as the production of carbon dioxide when soil organisms are active. It is an important process in the ecosystem and has direct influence on climate change. Therefore understanding it under different vegetation types is an essential goal in soil science. The major sources which effect the soil respiration rate are plant roots, the rhizosphere, microbes and soil fauna and these sources are control by various factors like temperature, moisture, nutreint content and oxygen in the soil. Soil respiration rate is important for understanding soil biological activity, nutrient cycling, soil microbial biomass, soil organic matter and its decomposition.Therefore soil respiration was studied under the canopy of ten dominant tree species of temperate forest. Our study determined that highest soil respiration was under the canopy of Eunonymous pendulus (EP) i.e. 20.01 μmolm−2 s−1 and across season it was high during the rains.

Soil respiration in seven types of temperate forests exhibits similar temperature sensitivity

Purpose The aim of the study was to compare the temperature sensitivity of soil respiration rate in two soil horizons of seven types of temperate forests. Materials and methods Soil samples were collected in O and A horizons in seven types of temperate forests, each one represented by five independent stands distributed throughout Poland. Soil respiration rates were measured at standard moisture in five temperatures (4 °C, 10 °C, 16 °C, 22 °C and 28 °C), and the first-order Q10 values were calculated for each stand. General linear models (GLM) were fitted for respiration rate and for Q10 values separately using selected soil physical-chemical properties: C:N ratio, dissolved organic carbon (DOC) content and soil pH. Results and discussion The soil respiration rate increased with temperature was the highest in O horizon of fresh mixed forest dominated by hornbeam and increased with C:N ratio, DOC content and soil pH (model p < 0.0001). In turn, model for Q10 was not significant meaning none of tested variables affected soil temperature sensitivity (p = 0.2886). Conclusions Despite studied forest types exhibit substantial distinctness in many soil properties including respiration rate, they showed similar susceptibility to temperature increase (roughly to climate warming).