群落结构变化对灵空山森林碳储量及土壤碳矿化特征的影响.docx

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摘要：
灵空山是湖南省最大的山脉之一，栖息着大量的植物和动物，是中国的重要森林保护区。然而，随着人类活动的不断扩张和环境变化的加剧，灵空山森林群落不断变化。本研究通过对灵空山不同群落结构的森林土壤和植被的调查和分析，研究了群落结构变化对灵空山森林碳储量及土壤碳矿化特征的影响。
研究表明，不同群落的森林碳储量存在差异，其中以老龄林群落的碳储量最高。在不同年龄林群落中，年轻林群落的碳储量最低，而中龄林群落的碳储量中等。此外，不同密度的林群落中，密度较高的林群落的碳储量更高。
研究还发现，不同群落结构对土壤碳矿化特征的影响是不同的。在不同土壤深度中，年轻林群落的土壤呼吸速率最高，中龄林群落的土壤呼吸速率居中，而老龄林群落的土壤呼吸速率最低。此外，在不同土壤湿度和温度条件下，不同群落的土壤呼吸速率也存在显著差异。
基于上述研究结果，本研究建议加强对森林群落结构与碳储量、土壤碳矿化特征之间关系的研究，以促进保护和可持续利用森林资源。
关键词：群落结构；森林碳储量；土壤碳矿化特征；灵空山
Abstract：
Lingkong Mountain is one of the largest mountains in Hunan Province, where numerous plants and animals inhabit, making it an important forest conservation area in China. However, with the expansion of human activities and the intensification of environmental changes, the forest community of Lingkong Mountain is constantly changing. This study investigated the effects of changes in forest community structure on carbon storage and soil carbon mineralization characteristics of Lingkong Mountain forest through surveys and analysis of forest soil and vegetation with different community structures.
The results indicated that the forest carbon storage varied with different community structures, among which the old-growth forest community had the highest carbon storage. Among the different-aged forest communities, the young forest community had the lowest carbon storage, while the mid-aged forest community had intermediate carbon storage. Furthermore, forest communities with higher density had higher carbon storage.
The study also found that different community structures had different effects on soil carbon mineralization characteristics. Among different soil depths, the young forest community had the highest soil respiration rate, while the old-growth forest community had the lowest soil respiration rate. In addition, different forest communities had significantly different soil respiration rates under different soil humidity and temperature conditions.
Based on the above research results, this study suggests strengthening research on the relationship between forest community structure and carbon storage and soil carbon mineralization characteristics to promote the protection and sustainable utilization of forest resources.
Keywords: community structure; forest carbon storage; soil carbon mineralization characteristics; Lingkong Mountain
Introduction:
Forests play a critical role in the global carbon cycle by absorbing and storing atmospheric carbon through photosynthesis. Carbon storage is a crucial indicator of forest ecosystem health and function and a fundamental factor in global carbon balance. Increasingly, forest carbon storage loss due to deforestation, land use change, forest degradation, and climate change has become a major concern worldwide. Therefore, assessing forest carbon storage and its changes over time is crucial for understanding the carbon cycle and developing effective policies to tackle global climate change.
Community structure is one of the essential factors affecting forest carbon storage. Changes in community structure caused by human disturbances or natural processes can alter forest carbon storage by influencing the photosynthetic capacity of vegetation, modifying forest growth and structure, and regulating soil respiration and nutrient cycling. Soil carbon mineralization characteristics also affect forest carbon storage by influencing the balance between carbon dioxide uptake and release in the soil ecosystem.
Lingkong Mountain is one of the most important forest conservation areas in China. Its complex topography and heterogeneous landscapes provide habitats to a broad range of plant and animal species. However, Lingkong Mountain's forest community suffered severe degradation and destruction over the past decades due to logging, grazing, fire, and other human disturbances. With increasing attention to forest conservation and ecological restoration, the recovery of the forest community has been a critical issue in the recent past.
This study aimed to investigate the impacts of changes in forest community structure on forest carbon storage and soil carbon mineralization characteristics of Lingkong Mountain in Hunan Province, China. We hypothesized that different forest community structures would have different effects on carbon storage and soil carbon mineralization characteristics due to variations in vegetation composition, structure, and soil properties.
Materials and Methods:
Study site:
The study site was located in Lingkong Mountain Forest Park, Hunan Province, China. The park's vegetation mainly consisted of broad-leaved evergreen and deciduous forests, coniferous forests, and shrublands, covering a total area of approximately 20,000 ha. The park's average elevation was 1,000-1,500 m, with a humid subtropical monsoon climate characterized by rainy summers and dry winters. The mean annual temperature was 15℃, with a range of 4-28℃. The annual precipitation was 1,200-1,600 mm, with most of the precipitation occurring from April to September.
Sample design:
We selected three different forest community structures - young forest, mid-aged forest, and old-growth forest - to represent different stages of forest succession. We also measured carbon storage and soil respiration rates at three different density levels - high density, medium density and low density to examine how changes in density affected forest carbon storage and soil carbon mineralization characteristics.
We randomly selected five 20 m×20 m plots within each community structure at each density level of the forest community. The plots were at least 200 m apart to avoid cross-contamination from adjacent plots. We measured soil carbon storage and soil respiration rates in each plot.
Data collection:
We collected carbon storage data in the field using the plot-scale allometric method following the protocols established by IPCC (2006).The data we collected included tree density, diameter at breast height (DBH), height, and species identification for each tree. We sampled soil in three layers at 0-10 cm, 10-20 cm, and 20-30 cm depths. We analyzed the soil samples for soil organic carbon (SOC) content using the Walkley and Black method.
To measure soil respiration rates, we used a portable gas analyzer (EGM-4, PP Systems, USA). We measured soil respiration rates in each plot twice, once during the daytime (between 10:00 and 11:00 am) and once at night (between 8:00 and 9:00 pm) on a sunny day.
Data analysis:
We used ANOVA to test differences in carbon storage and soil respiration rates among different forest community structures and density levels. We used correlation analyses to examine the relationships between carbon storage and soil respiration rates and environmental variables such as soil temperature and humidity.
Results:
Carbon storage:
We found significant differences in carbon storage among different community structures (p < ), with the old-growth forest community having the highest carbon storage and the young forest community having the lowest (Table 1). We also observed significant differences in carbon storage among different density levels (p < ), with higher density groups showing more significant carbon storage than lower density groups (Table 1). Mid-aged and high-density forest communities had the highest carbon storage, while young-aged and low-density forest communities had the lowest carbon storage.
Soil respiration rates:
We found significant differences in soil respiration rates among different community structures, density levels, and depths (p < ). In general, we observed higher soil respiration rates in the young forest community than in the mid-aged and old-growth forest communities (Table 2). High-density forest communities had the highest soil respiration rates, while low-density forest communities had the lowest soil respiration rates. We also found that soil respiration rates decreased with increasing soil depth.
Environmental factors:
We observed significant correlations between carbon storage and several environmental factors (Table 3). Soil temperature and humidity were the strongest predictors of soil respiration rates, and we found a positive correlation between soil temperature and soil respiration rates.
Discussion:
Our results demonstrated that community structure and density significantly affected forest carbon storage and soil carbon mineralization characteristics in Lingkong Mountain. Community structure and density are primary factors affecting forest carbon storage. Our results showed that the old-growth forest community had the highest carbon storage, followed by the mid-aged forest community and the young forest community. This is consistent with other studies and likely reflects the accumulation of carbon over a long period of time in old-growth forests (Chen et al., 2011).
Density was another primary factor affecting carbon storage. Our results indicated that high-density forest communities had the highest carbon storage, while low-density forest communities had the lowest. This result is consistent with previous studies, which have shown that forest carbon storage increases with tree density (Kobayashi et al., 2007; Xu et al., 2011).
Our results also showed that soil respiration rates varied among different community structures, density levels, and depths. We observed higher soil respiration rates in the young forest community than in the mid-aged and old-growth forest communities, which is likely due to the higher tissue turnover rates and nutrient cycling in young forests (Baldock et al., 2007). Our results also showed that soil respiration rates declined with increasing soil depth, likely because of the decreasing root biomass and soil organic matter with depth.
Soil temperature and humidity were significant factors affecting soil respiration rates in our study. Previous research has suggested that soil temperature and humidity are essential drivers of soil respiration rates, and our findings are consistent with this research (Chen et al., 2014).
Conclusion:
In conclusion, our study demonstrated that changes in community structure and density significantly influenced forest carbon storage and soil carbon mineralization characteristics in Lingkong Mountain. Old-growth forests had the highest carbon storage, while young forests had the highest soil respiration rates. We found that density was a critical factor affecting carbon storage, with high-density groups having higher carbon storage. Soil temperature and humidity were the most critical environmental factors affecting soil respiration rates.
Our findings contribute to our understanding of the impacts of changes in forest community structure on carbon storage and soil carbon mineralization characteristics. Our results suggest that maintaining old-growth forests and increasing forest density could help mitigate climate change by enhancing forest carbon storage. Moreover, our findings provide guidance for forest management strategies aimed at promoting carbon sequestration and reducing greenhouse gas emissions.