秸秆覆盖对红壤旱地间作生态系统小气候的影响

田间试验研究秸秆覆盖对红壤旱地间作生态系统小气候的影响结果表明,红壤旱地实施秸秆覆盖后湍流交换热通量增大、潜热交换热通量和土壤热通量变小,且使秸秆全覆盖和半覆盖处理近地面温度和土壤湿度增高、土壤温度和近地面湿度降低,秸秆覆盖具有蓄水保墒和低温效应。

小麦-玉米间作生态系统能流参数研究

采用田间调查与室内测定相结合的方法,以小麦-玉米间作生态系统为例,较系统地研究了初级生产者(农作物、杂草)、次级生产者(害虫、天敌)和分解者(微生物、原生动物和腐生动物)的能流参数值结果表明,该生态系统能流具有初级生产力和能量转化效率高,通过食物链递减率大,各营养层内每生产单位能量所需的能量相对较少,上一营养层对下一营养层能量利用程度逐渐增大等特征。

红壤旱地的间作生态系统小气候特征分析

通过对不同生态系统小气候观测,结果表明:与玉米单作系统相比,玉米间作生态系统在受光结构、通风、湿度、温度方面存在明显差异,其可以通过生物种群的多层次立体配置、空间立体利用来改善生态系统空间生态位。

Spatial and Temporal Changes of Wetlands on the Qinghai-Tibetan Plateau from the 1970s to 2010s

Wetlands on the Qinghai-Tibetan Plateau （QTP） perform a dazzling array of vital ecological functions and are one of the most fragile ecosystems in the world. Timely and accurate information describing wetland resources and their changes over time is becoming more important in their protection and conservation. By using remote sensing data, this study intended to investigate spatial distribution and temporal variations of wetlands on the QTP at different watershed scales from 1970s to 2010s. Results show that wetlands on the QTP have undergone widespread degradation from 1970s to 2010s, with nearly 6.4% of their area being lost. Areas of freshwater marsh, salt marsh and wet meadow declined by 46.6%, 53.9% and 15.6%, respectively, while lake area increased by 14.6%. The most extensive losses of natural wet/ands have occurred in endorheic basins, such as in the Kunlun-Altun-Qilian Drainage Basin and Qiangtang Basin, which shrank by 44.5% and 33.1%, respectively. A pronounced increase in temperature tends to facilitate the evaporation process and reduce water availability for wetlands, One-third of the wetlands on the QTP are under threat of being submerged due to lakes rising in recent years. More research is needed to gain insight into the interaction mechanisms behind observed variations and potential impacts from further warming in the future.

Energy Balance of Irrigated Intercropping Field in the Middle Reaches of Heihe River Basin

Based on the experiments conducted in an irrigated intercropping field in Zhangye Oasis in the middle reaches of Heihe River basin in 2004, the characteristics of radiation budget are analyzed. Furthermore, energy balance is cal- culated by using Bowen-Ratio Energy Balance (BREB) method. The results show that the ratio of the absorbed radiation to the incoming short radiation in intercropping crop canopy-soil system is increasing with growing stages, from 0.81 in the initial growing stage (IGS) to 0.86 in the late growing stage (LGS). The net radiation, which is smaller in IGS, in- creases rapidly in the first period of the middle growing stage (MGS) and reaches the maximum value in the second period of MGS. It then somewhat decreases in LGS. The ratio of net radiation to total radiation has a similar trend with the net radiation. In the whole growing stages, latent heat flux, which takes up 70% or so of the net radiation, is the dominant item in energy balance. Sensible heat flux shares 20% of the net radiation and soil heat flux has a percentage of 10%. The characteristics of heat balance vary distinctly in different growing stages. In IGS, the ratios of latent heat flux, sensible heat flux and soil heat flux to net radiation are 44.5%, 23.8% and 31.7% respectively. In MGS, with the in- creasing of latent heat flux and the decreasing of sensible heat flux and soil heat flux, the ratios turn into 84.4%, 6.3% and 9.3%. In LGS, the soil heat flux maintains 0W/m2 or so, and latent heat flux and sensible heat flux take up 61.4% and 38.6% respectively. The energy balance also shows an obvious daily variation characteristic.

The Effectiveness of Coccinellids as Natural Enemies of Aphids in Maize, Beans and Cowpeas Intercrop

A field study was conducted in Busia district of Kenya to elucidate the dynamics of ladybirds in mixed stands of maize, beans and cowpeas to determine their efficacy as sole control measures for Aphids. Maize, beans and cowpeas were intercropped using conventional husbandry practices and the general Coccinellid quantified as follows： Colonies of four Coccinellids, starved for 12 hours to enhance feeding on Aphids were assessed. The effects of weather on the abundance of Coccinellids were also investigated and involved collection of meteorological data from the Busia District Agricultural Office （BDAO） and from Busia Farmers Training Centre （BFTC） and relating them to the abundance and predation values. The predator population was most abundant in the mixed stands of maize and beans （2.33 predators/30 Aphids） as compared to their occurrence in pure stands of cowpeas （0.85 predators/30 Aphids）. The genus Cheilomenes spp. was the most ubiquitous predator with a mean of 4.00 individuals/30 Aphids while Hippodamia variegata was the least abundant predator species with a mean of 0.92 individuals/30 Aphids in all the agro-ecosystems. The larvae of Hippodamia variegata were the most bio-efficient, consuming 32.44 Aphids while their adults were the least bio-efficient, consuming 4.22 individuals for a period of 12 hours. The Coccinellids consumed more Aphids at higher aphid densities （24.05 Aphids） than at lower aphid densities （9.44 Aphids） over the same period of time. Rainfall and relative humidity had significant （F = 3.675; P 〈 0.05） effects on the abundance of Coccinellids. Temperature had significant （F = 3.58; P 〈 0.05） effect on the abundance of Coccinellids though at a lower level. Rainfall （r = -0.162） and relative humidity （r = - 0.084） were both inversely correlated with the abundance of Coccinellids. On the other hand, temperature was positively correlated （r = 0.159） with the prevalence of Coccinellids indicating that warmer and drier conditions favoured their multiplication.

Spatial and Temporal Analysis of Carbon Sequestrations in the Conterminous United States

This study develops geospatial analysis of terrestrial carbon exchange for the conterminous United State and estimates large-scale NEP （net ecosystem production） dynamic from 2008 to 2013. We apply land-use and land-cover data in order to coherently include cropland, forest, wetland and other ecologically active landscapes in the mapping. Our results show a distribution of high harvest carbon release in the Corn Belt states, in addition to hot spots around the US in areas like Southern California and Arizona. Harvest carbon is low in areas in the southern United States, and central/southern Appalachian Mountains. We identify NEP changes for coupled agricultural, forest and other high-carbon-uptake ecosystems systems, conversions to and from crop, and land in frequent conversion among forest, wetland, pasture and rangeland. Findings from this study will provide important information to support and promote the co-production of science and decision-making.