Impacts of Climate Variability and Human Activities on the Changes of Runoff and Sediment Load in a Catchment of the Loess Plateau, China

The objectives of this study are to investigate the changes of runoff and sediment load and their potential influencing factors in the Huangfuchuan catchment. The Mann-Kendall test and accumulative anomaly methods were, respectively, applied to examine the changing trends and abrupt changes. Both annual runoff and sediment load demonstrated significant reduction (p<0.05) with decreasing rates of −3.2 × 106 m3/a and −1.09 Mt/a, respectively. The abrupt changes were detected in 1979 and 1996 for the runoff and sediment load. All the runoff and sediment indices (runoff, sediment load, runoff coefficient, and sediment concentration) exhibited remarkable reduction (p<0.01). The climate variability contributed 24.4% and 25.1% during 1980–1996 and 1997–2010 to annual runoff decrease, respectively, and human activities accounted for the remaining 75.6% and 74.9%. In contrast, changes in precipitation accounted for 43.5% and 20.2% of sediment load reduction during 1980–1996 and 1997–2010, whereas the human activities contributed 56.5% and 79.8%, respectively. The relative contributions from climate variability and human activities to runoff and sediment load changes at annual scale were different from that at flood season scale. Results suggested the dominant role of soil and water conservations in the variation of runoff and sediment load in the catchment

Neuropeptide F regulates courtship in Drosophila through a male-specific neuronal circuit.

Male courtship is provoked by perception of a potential mate. In addition, the likelihood and intensity of courtship are influenced by recent mating experience, which affects sexual drive. Using Drosophila melanogaster, we found that the homolog of mammalian neuropeptide Y, neuropeptide F (NPF), and a cluster of male-specific NPF (NPFM) neurons, regulate courtship through affecting courtship drive. Disrupting NPF signaling produces sexually hyperactive males, which are resistant to sexual satiation, and whose courtship is triggered by sub-optimal stimuli. We found that NPFM neurons make synaptic connections with P1 neurons, which comprise the courtship decision center. Activation of P1 neurons elevates NPFM neuronal activity, which then act through NPF receptor neurons to suppress male courtship, and maintain the proper level of male courtship drive

Differential regulation of the Drosophila sleep homeostat by circadian and arousal inputs.

One output arm of the sleep homeostat in Drosophila appears to be a group of neurons with projections to the dorsal fan-shaped body (dFB neurons) of the central complex in the brain. However, neurons that regulate the sleep homeostat remain poorly understood. Using neurogenetic approaches combined with Ca2+ imaging, we characterized synaptic connections between dFB neurons and distinct sets of upstream sleep-regulatory neurons. One group of the sleep-promoting upstream neurons is a set of circadian pacemaker neurons that activates dFB neurons via direct glutaminergic excitatory synaptic connections. Opposing this population, a group of arousal-promoting neurons downregulates dFB axonal output with dopamine. Co-activating these two inputs leads to frequent shifts between sleep and wake states. We also show that dFB neurons release the neurotransmitter GABA and inhibit octopaminergic arousal neurons. We propose that dFB neurons integrate synaptic inputs from distinct sets of upstream sleep-promoting circadian clock neurons, and arousal neurons