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Soil respiration in tropical forests is a major source of atmospheric CO2. The ability to partition soil respiration into its individual components is becoming increasingly important to predict the effects of disturbance on CO2 efflux from the soil as the responses of heterotrophic and autotrophic respiration to change are likely to differ. However, current field methods to partition respiration suffer from various methodological artefacts; root-rhizosphere respiration is particularly difficult to estimate. We used trenched subplots to estimate root-rhizosphere respiration in large-scale litter addition (L+), litter removal (L−) and control (CT) plots in a lowland tropical semi-evergreen forest in Panama. We took a new approach to trenching by making measurements immediately before-and-after trenching and comparing them to biweekly measurements made over one year. Root-rhizosphere respiration was estimated to be 38%, 17% and 27% in the CT, L+, and L− plots, respectively, from the measurements taken immediately before and one day after trenching in May-June 2007. Biweekly measurements over the following year provided no estimates of root-rhizosphere respiration for the first seven months due to decomposition of decaying roots. We were also unable to estimate root-rhizosphere respiration during the dry season due to differences in soil water content between trenched and untrenched soil. However, biweekly measurements taken during the early rainy season one year after trenching (May-June 2008) provided estimates of root-rhizosphere respiration of 39%, 24% and 36% in the CT, L+, and L− plots, respectively, which are very similar to those obtained during the first day after trenching. We suggest that measurements taken immediately before and one day after root excision are a viable method for a rapid estimation of root-rhizosphere respiration without the methodological artefacts usually associated with trenching experiments. 相似文献
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Tamon?YamashitaEmail author Nobuhiko?Kasuya Sen?Nishimura Hiroshi?Takeda 《Journal of Forest Research》2004,9(4):333-340
The effects of root exclusion and planted tree species on soil nitrogen (N) dynamics were examined at two plantations, one
planted with Japanese cedar and the other with Japanese cypress. We set up ten 1 × 1 × 0.2-m-deep trenched sites and ten untrenched
control sites at each plantation. We measured the pool size and leaching of inorganic N at each site for 2 years and the net
N mineralization 1 and 2 years after trenching. Despite similar soil conditions, the cedar plantation showed higher net N
mineralization than the cypress plantation. Stopped tree uptake of N was expected to cause an increased pool size and leaching
of inorganic N at the trenched sites. Nevertheless, we found no significant increase in those variables at both plantations.
The trenched cypress sites showed no decrease in the net N mineralization during the 2 years after trenching. However, the
net nitrification at the trenched cypress sites increased remarkably at the deeper horizons in comparison with that at the
control sites. Enhanced nitrification might result from improved ammonium availability through root exclusion. Net N mineralization
at the trenched cedar sites decreased more than 60% compared with that at the control sites 2 years after trenching. Higher
nitrification potential at the cedar plantation and enhanced nitrification potential at the trenched cypress sites never resulted
in increased leaching of N, due to added fine root litter which acted as an immobilization agent for excess N, thus preventing
N loss. 相似文献
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Effects of trenching on soil processes and properties in a New Mexico mixed-conifer forest 总被引:6,自引:0,他引:6
Summary Trenching was used to reduce root activity in treeless plots in a New Mexico mixed-conifer forest to examine the effects of plant roots on soil processes. Trenching led to increases in moisture content (104%), inorganic N concentration (115%), and mass loss from cellulose (196%). In laboratory incubations, trenched soils collected in the 1st and 2nd year after trenching evolved 52% and 115% more CO2, respectively, than control soils. Amending incubated trenched and control soils with moisture and inorganic N indicated that increased soil moisture content in trenched plots could explain the increased microbial activity. Trenching also had statistically significant but inconsistent effects on net N mineralization in incubated soils. The greatest effect of trenching was to increase net N mineralization under favorable temperature and moisture conditions. Irrigation of field plots increased both CO2 evolution and net N mineralization. Overall, these data are consistent with the hypothesis that plant roots reduced microbial activity by moisture uptake during the time of the study. 相似文献
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Impacts of understory species removal and/or addition on soil respiration in a mixed forest plantation with native species in southern China 总被引:1,自引:0,他引:1
Xiaoling Wang Jie Zhao Jianping Wu Hua ChenYongbiao Lin Lixia ZhouShenglei Fu 《Forest Ecology and Management》2011,261(6):1053-1060
Although the removal or addition of understory vegetation has been an important forest management practice in forest plantations, the effects of this management practice on soil respiration are unclear. The overall objective of this study was to measure and model soil respiration and its components in a mixed forest plantation with native species in south China and to assess the effects of understory species management on soil respiration and on the contribution of root respiration (Rr) to total soil respiration (Rs). An experiment was conducted in a plantation containing a mixture of 30 native tree species and in which understory plants had been removed or replaced by Cassia alata Linn. The four treatments were the control (Control), C. alata addition (CA), understory removal (UR) and understory removal with C. alata addition (UR + CA). Trenched subplots were used to quantify Rr by comparing Rs outside the 1-m2 trenched subplots (plants and roots present) and inside the trenched subplots (plants and roots absent) in each treatment. Annual soil respiration were modeled using the values measured for Rs, soil temperature and soil moisture. Our results indicate that understory removal reduced Rs rate and soil moisture but increased soil temperature. Regression models revealed that soil temperature was the main factor and soil moisture was secondary. Understory manipulations and trenching increased the temperature sensitivity of Rs. Annual Rs for the Control, CA, UR and UR + CA treatments averaged 594, 718, 557 and 608 g C m−2 yr−1, respectively. UR decreased annual Rs by 6%, but CA increased Rs by about 21%. Our results also indicate that management of understory species increased the contribution of Rr to Rs. 相似文献
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Subtropical plantations are large carbon sinks: Evidence from two monoculture plantations in South China 总被引:2,自引:0,他引:2
Dima ChenChenlu Zhang Jianping WuLixia Zhou Yongbiao LinShenglei Fu 《Agricultural and Forest Meteorology》2011,151(9):1214-1225
Quantifying the net carbon (C) storage of forest plantations is required to assess their potential to offset fossil fuel emissions. In this study, a biometric approach was used to estimate net ecosystem productivity (NEP) for two monoculture plantations in South China: Acacia crassicarpa and Eucalyptus urophylla. This approach was based on stand-level net primary productivity (NPP, based on direct biometric inventory) and heterotrophic respiration (Rh). In comparisons of Rh determination based on trenching vs. tree girdling, both trenching and tree girdling changed soil temperature and soil moisture relative to undisturbed control plots, and we assess the effects of corrections for disturbances of soil moisture and soil moisture on the estimation of soil CO2 efflux partitioning. Soil microbial biomass and dissolved organic carbon were significantly lower in trenched plots than in tree girdled plots for both plantations. Annual soil CO2 flux in trenched plots (Rh-t) was significantly lower than in tree-girdled plots (Rh-g) in both plantations. The estimates of Rh-t and Rh-g, expressed as a percentage of total soil respiration, were 58 ± 4% and 74 ± 6%, respectively, for A. crassicarpa, and 64 ± 3% and 78 ± 5%, respectively, for E. urophylla. By the end of experiment, the difference in soil CO2 efflux between the trenched plots and tree-girdled plots had become small for both plantations. Annual Rh (mean of the annual Rh-t and Rh-g) and net primary production (NPP) were 470 ± 25 and 800 ± 118 g C m−2 yr−1, respectively, for A. crassicarpa, and 420 ± 35 and 2380 ± 187 g C m−2 yr−2, respectively, for E. urophylla. The two plantations in the developmental stage were large carbon sinks: NEP was 330 ± 76 C m−2 yr−1 for A. crassicarpa and 1960 ± 178 g C m−2 yr−1 for E. urophylla. 相似文献
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We examined the effects of root and litter exclusion on the rate of soil CO2 efflux and microbial biomass at a soil depth of 25 cm in a secondary forest (dominated by Tabebuia heterophylla) and a pine (Pinus caribaea) plantation in the Luquillo Experimental Forest in Puerto Rico. The experimental plots were initially established in 1990, when root, forest floor mass and new litterfall were excluded for 7 y since then. Soil respiration was significantly reduced in the litter and root exclusion plots in both the secondary forest and the pine plantation compared with the control. Root exclusion had a greater effect on soil CO2 efflux than the litter exclusion in the plantation, whereas a reversed pattern was observed in the secondary forest. The reduction of microbial biomass in the root exclusion plot was greater in the secondary forest (59%) than in the plantation (31%), while there was no difference of the reduction in the litter exclusion plots between these forests. Our results suggest that above-ground input and roots (root litter and exudates) differentially affect soil CO2 efflux under different vegetation types. 相似文献
8.
XiaoGuo Wang Bo Zhu YanQiang Wang XunHua Zheng 《European Journal of Forest Research》2008,127(4):285-291
The contribution of root respiration to total soil respiration is one of the most interesting, important, and methodologically
complicated problems in the study of the carbon budget in soils. A trenching method and a root biomass regression method were
used to determine the contribution of root respiration to total soil respiration in a subtropical forest ecosystem. The average
root respiration contributions were 37.15% with the range of 13.04–51.23% by trenching method and 31.80% with the range of
10.64–56.10% by root biomass regression method from August 2005 to July 2006. In growing season, the contributions of root
respiration were 47.25 and 43.53% estimated by trenching method and root biomass regression method, respectively. There was
no significant difference between the monthly attributions of root respiration to soil respiration estimated by two methods.
Our results showed that trenching and root biomass regression methods were both suitable to estimate the root respiration
in this forest. 相似文献
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皖南地区小麦高产栽培技术的探讨 总被引:11,自引:0,他引:11
分析了皖南地区小麦的发展情况与存在的问题,并结合多年的试验示范和大田生产实践,提出小麦免耕机开沟直播高产栽培技术,详细阐述了其主要技术措施,以期指导大田生产实践。 相似文献
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