Fragmentation and percolation thresholds in the degradation process of alpine meadow in the Three-River Headwaters region of Qinghai-Tibetan Plateau, China

2020 ◽  
Vol 42 (3) ◽  
pp. 171
Author(s):  
Huilong Lin ◽  
Feng Zhang

Understanding the process and mechanisms of alpine meadow degradation is crucial for restoration and management in the Three-River Headwaters region, Qinghai-Tibetan Plateau, China. However, little is known about this complex and controversial problem because identification and quantification of the underlying causes is difficult. This research aimed to build a spatiotemporal dynamical model for alpine meadow degradation, capturing the natural process of erosion at the interface of barren patches and undamaged meadow. The model clarified the role of barren patches and meadow connectivity in degradation, and identified the ecological mechanisms and processes accounting for the spatial and temporal pattern of degradation. A fragmentation and percolation threshold exists in the process of meadow degradation, independent of spatial scale. An impulsive differential equation was used to investigate the consequence of periodic restoration of degraded meadow. Both the level of meadow degradation and the restoration period play crucial roles in determining whether the meadow can be successfully restored. This research has demonstrated theoretically that the effectiveness of meadow restoration by periodic effort depends on the degree of degradation.

2018 ◽  
Vol 22 (S4) ◽  
pp. 8193-8198 ◽  
Author(s):  
Chunmei Li ◽  
Yuming Wang ◽  
Tian Fang ◽  
Xinke Zhou ◽  
Peng Cui

2018 ◽  
Author(s):  
wenjuan zhang ◽  
xian xue ◽  
fei peng ◽  
quangang you ◽  
jing pan ◽  
...  

Soil microbial community structure is an effective indicator to reflect changes in soil quality. Little is known about the effect of alpine meadow degradation on the soil bacterial and fungal community. In this study, we used the Illumina MiSeq sequencing method to analyze the microbial community structure of alpine meadow soil in five different degradation levels (i.e., non-degraded (ND), slightly degraded (LD), moderately degraded (MD), severely degraded (SD), and very severely degraded (VD)) in the Qinghai-Tibet Plateau. Proteobacteria, Actinobacteria, and Acidobacteria were the mainly bacterial phyla in meadow soil across all five degradation levels investigated. Basidiomycota was the mainly fungal phylum in ND; however, we found a shift from Basidiomycota to Ascomycota with an increase (severity) in degradation level. The overall proportion of Cortinariaceae exhibited high fungal variability, and reads were highest in ND (62.80%). Heatmaps of bacterial genera and fungal families showed a two-cluster sample division on a genus/family level: (1) an ND and LD group and (2) an SD, VD, and MD group. Redundancy analysis (RDA) showed that 79.7%and 71.3% of the variance in bacterial and fungal composition, respectively, could be explained by soil nutrient conditions (soil organic carbon, total nitrogen, and moisture) and plant properties (below-ground biomass). Our results indicate that meadow degradation affects both plant and soil properties and consequently drives changes in soil microbial community structure.


2020 ◽  
Vol 12 (24) ◽  
pp. 4121
Author(s):  
Wei Zhang ◽  
Shuhua Yi ◽  
Yu Qin ◽  
Yi Sun ◽  
Donghui Shangguan ◽  
...  

Surface soil moisture (SSM) is a key limiting factor for vegetation growth in alpine meadow on the Qinghai-Tibetan Plateau (QTP). Patches with various sizes and types may cause the redistribution of SSM by changing soil hydrological processes, and then trigger or accelerate alpine grassland degradation. Therefore, it is vital to understand the effects of patchiness on SSM at multi-scales to provide a reference for alpine grassland restoration. However, there is a lack of direct observational evidence concerning the role of the size and type of patches on SSM, and little is known about the effects of patches pattern on SSM at plot scale. Here, we first measured SSM of typical patches with different sizes and types at patch scale and investigated their patterns and SSM spatial distribution through unmanned aerial vehicle (UAV)-mounted multi-type cameras at plot scale. We then analyzed the role of the size and type of patchiness on SSM at both patch and plot scales. Results showed that: (1) in situ measured SSM of typical patches was significantly different (P < 0.01), original vegetation patch (OV) had the highest SSM, followed by isolate vegetation patch (IV), small bare patch (SP), medium bare patch (MP) and large bare patch (LP); (2) the proposed method based on UAV images was able to estimate SSM (0–40 cm) with a satisfactory accuracy (R2 = 0.89, P < 0.001); (3) all landscape indices of OV, with the exception of patch density, were positively correlated with SSM at plot scale, while most of the landscape indices of LP and IV showed negative correlations (P < 0.05). Our results indicated that patchiness intensified the spatial heterogeneity of SSM and potentially accelerated the alpine meadow degradation. Preventing the development of OV into IV and the expansion of LP is a critical task for alpine meadow management and restoration.


Water ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2061
Author(s):  
Lifeng Zhang ◽  
Zhiguang Chen ◽  
Xiang Zhang ◽  
Liang Zhao ◽  
Qi Li ◽  
...  

The Qinghai-Tibetan Plateau (QTP) is generally considered to be the water source region for its surrounding lowlands. However, there have only been a few studies that have focused on quantifying alpine meadow evapotranspiration (ET) and its partitioning, which are important components of water balance. This paper used the Shuttleworth–Wallace (S–W) model to quantify soil evaporation (E) and plant transpiration (T) in a degraded alpine meadow (34°24′ N, 100°24′ E, 3963 m a.s.l) located at the QTP from September 2006 to December 2008. The results showed that the annual ET estimated by the S–W model (ETSW) was 511.5 mm (2007) and 499.8 mm (2008), while E estimated by the model (ESW) was 306.0 mm and 281.7 mm for 2007 and 2008, respectively, which was 49% and 29% higher than plant transpiration (TSW). Model analysis showed that ET, E, and T were mainly dominated by net radiation (Rn), while leaf area index (LAI) and soil water content at a 5 cm depth (SWC5cm) were the most important factors influencing ET partitioning. The study results suggest that meadow degradation may increase water loss through increasing E, and reduce the water conservation capability of the alpine meadow ecosystem.


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