Land use conversion and fertilization have been widely reported to be important managements affecting the exchanges of greenhouse gases between soil and atmosphere. For comprehensive assessment of methane (CH 4 ) and nitrous oxide (N 2 O) fluxes from hilly red soil induced by land use conversion and fertilization, a 14-month continuous field measurement was conducted on the newly converted citrus orchard plots with fertilization (OF) and without fertilization (ONF) and the conventional paddy plots with fertilization (PF) and without fertilization (PNF). Our results showed that land use conversion from paddy to orchard reduced the CH 4 fluxes at the expense of increasing the N 2 O fluxes. Furthermore, fertilization significantly decreased the CH 4 fluxes from paddy soils in the second stage after conversion, but it failed to affect the CH 4 fluxes from orchard soils, whereas fertilizer applied to orchard and paddy increased soil N 2 O emissions by 68 and 113.9 %, respectively. Thus, cumulative CH 4 emissions from the OF were 100 % lower, and N 2 O emissions were 421 % higher than those from the PF. Although cumulative N 2 O emissions were stimulated in the newly converted orchard, the strong reduction of CH 4 led to lower global warming potentials (GWPs) as compared to the paddy. Besides, fertilization in orchard increased GWPs but decreased GWPs of paddy soils. In addition, measurement of soil moisture, temperature, dissolved carbon contents (DOCs), and ammonia (NH 4 + -N) and nitrate (NO 3 − -N) contents indicated a significant variation in soil properties and contributed to variations in soil CH 4 and N 2 O fluxes. Results of this study suggest that land use conversion from paddy to orchard would benefit for reconciling greenhouse gas mitigation and citrus orchard cultivation would be a better agricultural system in the hilly red soils in terms of greenhouse gas emission. Moreover, selected fertilizer rate applied to paddy would lead to lower GWPs of CH 4 and N 2 O. Nevertheless, more field measurements from newly converted orchard are highly needed to gain an insight into national and global accounting of CH 4 and N 2 O emissions.
Antibiotic pollution has become one of the most challenging
environmental
issues in aquatic ecosystems, with adverse effects on planktonic organisms
that occupy the base of the aquatic food chain. However, research
regarding this topic has not been systematically reviewed, especially
in terms of community-level responses. In this review, we provide
an overview of current antibiotic pollution in aquatic environments
worldwide. Then, we summarize recent studies concerning the responses
of planktonic communities to antibiotics, ranging from individual-
to community-level responses. Studies have shown that extremely high
concentrations of antibiotics can directly harm the growth and survival
of plankton; however, such concentrations are rarely found in natural
freshwater. It is more likely that environmentally relevant concentrations
of antibiotics will affect the physiological, morphological, and behavioral
characteristics of planktonic organisms; influence interspecific interactions
among plankton species via asymmetrical responses in species traits;
and thus alter the structure and function of the entire planktonic
ecosystem. This review highlights the importance of community analysis
in revealing antibiotic toxicity. We also encourage the establishment
of the causal relationships between impacts at multiple scales in
the future for predicting the community-level consequences of antibiotics
based on the currently available individual-level evidence.
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