The hypothetical degradation trajectory in ‘Overgrazing leads to soil
cracking that later triggers the severe degradation of alpine meadows on
the Tibetan Plateau’ was not precisely right
Wenjing Li1,2
1CAS Key Laboratory of Adaptation and Evolution of
Plateau Biota, Northwest Institute of Plateau Biology, Chinese Academy
of Sciences, Xining, Qinghai 810008, PR China
2Scientific Research and Popularization base of
Qinghai-Tibet Plateau Biology, Qinghai Provincial Key Laboratory of
Animal Ecological Genomics, Xining, Qinghai 810008, PR China
Correspondence
Li, CAS Key Laboratory of Adaptation and Evolution of Plateau Biota,
Northwest Institute of Plateau Biology, Chinese Academy of Sciences,
Xining, Qinghai 810008, PR China. E-mail address: lwenjing125@126.com
Dear Editor:
During reading the paper recently (Niu et al., 2019), I found that the
hypothetical degradation trajectory was not of precisely validity.
According to their data, they hypothesized a degradation trajectory of
an alpine rangeland based on the cracking phenomenon induced by
overgrazing. The first three stages and the last two were isolated in
their hypothesis, and can be found in the figure legend in Figure 9 of
their paper (Niu et al., 2019). The main result of this paper is that
cracks were found in grassland under the conditions of overgrazing (Niu
et al., 2019). The cracks became larger in cold season, became smaller
in the plant growth season, and were a process of circulation of bigger
and smaller (Niu et al., 2019). And if it just so, there was not a lot
of bare patches in the grassland. But in the last two stages of their
hypothesis, they put the figures of the habitat of the plateau pika
(Ochotona curzoniae ) with bare patches of different area. There
was no plateau pika in their study site (Niu et al., 2019), and the
overgrazing and disturbance of plateau pika were two independent
factors, so they can not get the conclusion of the crack induced by
overgrazing later triggers the severe degradation of alpine meadows on
the Tibetan Plateau.
Digging for food behavior of plateau pika was ignored by the former
researches, and was not published in any journal before, and now is
available in a preprint paper of Researchgate (Li et al., 2020). The
pika used its two forelegs together when digging on the ground, and pits
of different size was left both on the primary grassland and former bare
grounds (Li et al., 2020). Ignored digging of plateau pika is the
primary reason for the occurrence and enlargement of bare patches in
alpine meadow ecosystem. And the occurrence and enlargement of bare
patches by digging of plateau pika is an irreversible progress, and is
different with the cracking become smaller in plant growth season of
this study.
The soft layer soil with low water content on the surface of alpine
meadow was the precondition of digging for food behavior of plateau pika
in the long period of cold season. Diggings were more than 40% of the
entire observation time in the cold season(Li et al., 2020). Soil with
low water content on the surface of alpine meadow is the reason why the
cracks became large in the cold season (Niu et al., 2019). After the
soil cracking, the surface area increased, and the soil water content in
this surface soil declined, and the crack became large. In the warm
season, the soil water content increased, and the crack became small.
Although overgrazing and digging of plateau pikas are related to each
other in alpine meadows, but affect the ecological progresses in
different ways, so it is more necessary to carry out relatively
independent research. The degradation of alpine meadows is a complex
process in which different factors act in different ways and with
different intensities. It is not appropriate to try to have a general
theory about the grassland degradation in alpine meadow ecosystem.
This study (Niu et al., 2019) and our study (Li et al., 2020) focus on
the ecological processes in long-term cold season of alpine meadow
ecosystem, which is being the most under-researched period. The greater
significance of this two study is to attract more attention to the
window period (cold season) in the Tibetan Plateau and other areas.
Yours Li Wenjing
CAS Key Laboratory of Adaptation and Evolution of Plateau Biota,
Northwest Institute of Plateau Biology, Chinese Academy of Sciences,
Xining, Qinghai 810008, PR China
ACKNOWLEDGMENTS
This paper was financially supported by the Applied Basic Research
Programs of Qinghai Province (2017-ZJ-714), and CAS ”Light of West
China” Program.
REFERENCES
Niu Y., Zhu H., Yang S., Ma S., Zhou J., Chu B., Hua R. & Hua L. (2019)
Overgrazing leads to soil cracking that later triggers the severe
degradation of alpine meadows on the Tibetan Plateau. Land Degradation
& Development, 30, 1243–1257 . https://doi.org/10.1002/ldr.3312
Li W.J., Zhang H., Wang Y.S., Hu YP (2020) Ignored digging of plateau
pika is the primary reason for the occurrence and enlargement of bare
patches in alpine meadow ecosystem. DOI:10.13140/RG.2.2.32428.28809
Preprint in Researchgate:
https://www.researchgate.net/publication/344576622