Effects of Climate Change and Fencing on Forage Nutrition Quality of Alpine Grasslands in the Northern Tibet

Abstract

How climate change and fencing will affect forage nutrition quality of alpine grasslands is still unknown in the Northern Tibet. Here, we reported the effects of climate change and fencing on forage nutrition quality (i.e., CP: crude protein, ADF: acid detergent fiber, NDF: neutral detergent fiber, Ash: crude ash, EE: ether extract and DTS: dissolvable total sugar) in alpine grasslands across the Northern Tibet based on a transect survey dataset from 2018. Over the whole survey transect, fencing reduced the NDF content by 5.15% and the EE content by 15.79%, but did not affect forage nutrition quality (R2 = 0.04, p = 0.389). Air temperature and precipitation explained 24% and 8% of variation in the CP content under the fencing conditions, respectively. Precipitation explained 22% of variation in the NDF content under the fencing conditions. The CP content decreased and increased exponentially with increasing air temperature under the fencing and grazing conditions, respectively. The NDF content showed logarithmic and negative relationships with precipitation under the fencing and grazing conditions (−8.45 vs. −6.68lnNDF). The response of the CP content to fencing showed negative relationships with temperature and the response of AGB to fencing, but showed a positive relationship with precipitation. The CP and DTS contents showed negative relationships with AGB under the fencing and grazing conditions. In contrast, the ADF content showed a positive relationship with AGB. The response of AGB, SR and community composition to fencing explained 11%, 56% and 35% of variation in the response of forage nutrition quality to fencing, respectively. Therefore, climate change may not always have adverse effects on forage nutrition quality, whereas fencing may not always have favorable effects on forage nutrition quality. Fencing and climate change can have an interactive effect on forage nutrition quality. Fencing can alter the temperature and precipitation sensitivities of forage nutrition quality. In colder and wetter regions, the forage nutrition quality may be more responsive to fencing. There may be a trade-off between forage nutrition quality and quantity. Compared to the change in AGB caused by fencing, the changes in species α-diversity and community composition caused by fencing can have greater effects on the response of forage nutrition quality to fencing. Local climate conditions and the trade-offs between forage nutrition quality and biomass should be considered when evaluating the effects of fencing on the restoration of degraded grassland plants.

Influences of human activity and climate change on growing-season soil moisture in the Qinghai–Tibet grasslands from 2000 to 2020

“…We hypothesized that climate change caused soil wetting over the whole TP grasslands. Based on previous studies (Sun et al, 2023;Zhang et al, 2023), we hypothesized that human activities may alter the sensitivities of SM to climate change.…”