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Ammonia (NH3) emissions have become a serious environmental pollution problem, and livestock production is an important source of NH3 emissions, especially pig farming. The origin of NH3 release is the hydrolysis of urea in urine that is catalyzed by urease present in feces. This research determined the urease activity in fresh feces by Michaelis–Menten kinetics and then compared the process of urea hydrolysis and ammonia production in fresh slurry. For feces, the kinetic parameters Vmax and K’m were calculated by determining the concentration of ammonium in initial 5 minutes in closed vessels, and the resulting Vmax and K’m were 26.9 ± 1.2 mmol·[urea]·kg−1·min−1 and 99.7 ± 3.5 mmol·[urea]·l−1, respectively. In fresh slurry, the rate of urea hydrolysis determined directly was higher than the ammonium formation rate in the early stage (0–8 h) and was accompanied by a rapid rise in pH. In addition, we further explored the effects of temperature, pH, and mixing rate on urease activity within different periods (0–5 min, 5 min–2 h and 2 h–8 h). Our observations show that the optimal urease activity occurred at 35 °C, pH 6.71, and 821.83 rpm of stirring, indicating that microbial species and communities associated with urease production are affected by environmental conditions.

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In order to reverse the global trend of biodiversity loss, the concept of ecosystem services has been widely applied to make policymakers and the general public realize that conserving biodiversity possesses both intrinsic and utilitarian values. However, to achieve this goal, it is necessary to first have a clear understanding of the relationships between biodiversity and ecosystem services (BES). To advance our understanding of this issue, we first reviewed the major progress in current BES studies, with an emphasis on three biodiversity dimensions (i.e., taxonomic diversity, functional diversity, and ecosystem diversity). Based on the findings, we then propose three research topics as future directions: (1) More direct and explicit studies on the effects of different dimensions of biodiversity on various ecosystem service types; (2) developing a biodiversity-based understanding of the formation of ecosystem services; (3) creation of science-based ecosystem management plans and policies that can maximize synergies between biodiversity conservation and ecosystem service enhancement. By conducting such research, we will be able to not only further understand the complex relationships between biodiversity and ecosystem services but also better promote the concept of ecosystem services for more successful biodiversity conservation in the future.

Since the beginning of the 21st century, the net primary productivity (NPP) of grassland in the Three-Rivers Headwaters (TRH) region has changed significantly. In this study, NPP was assessed by the Carnegie-Ames-Stanford approach (CASA) model in TRH from 2000 to 2019. The abrupt changes of NPP and meteorological factors were analyzed by cumulative departure, MK test, and Pettitt test. The contributions of meteorological and human factors to changes in grassland NPP were quantitatively assessed using the scenario simulation method. The obtained results showed that: (1) From 2000 to 2019, the NPP of grasslands increased from 135.72 to 141.16 gC/m−2a−1. However, the overall growth trend was not significant, and the proportion of significant growth was only 31.45%; (2) An abrupt increase in meteorological factors occurred around 2005, while an abrupt increase in NPP occurred around 2008, which showed that 2008 was the year when human factors, such as ecological projects and policies, began to show a significant impact on the growth of NPP; and (3) The contribution of human factors to the abrupt increase in NPP was significantly greater than the contribution of meteorological factors. The contribution of human factors exceeded 70% in 93.68% of the studied area, reaching 98% in general, while the contribution of meteorological factors was less than 2%. Among them, the human contributions to the Yangtze River Source, the Yellow River Source, and the Lancang River Source all exceeded 95%. The negative effects of meteorological factors on the growth of NPP in the abovementioned three regions were as high as 47.35%, 48.66%, and 36.91%, respectively. Human factors have contributed greatly to the increase in NPP in most of the source areas of the Yellow River, the eastern part of Tanggulashan County, the southeastern part of Zhiduo County, and the western part of Zaduo County at the source of the Yangtze River.