دانلود رایگان مقاله لاتین شبیه سازی اکوسیستم از سایت الزویر
عنوان فارسی مقاله:
اهمیت نمایندگی دقیق طول عمر برگ برای شبیه سازی اکوسیستم چرخه کربن
عنوان انگلیسی مقاله:
Accurate representation of leaf longevity is important for simulating ecosystem carbon cycle
سال انتشار : 2016
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مقدمه انگلیسی مقاله:
1. Introduction
Dynamic global vegetation models (DGVMs) are indispensable tools for studying terrestrial ecosystem processes and their interactions with climate change (Prentice, Heimann, & Sitch, 2000; Wramneby, Smith, Zaehle & Sykes, 2008). Since the 1980s, the need to better understand and quantify the global behavior of terrestrial ecosystems as a major factor in earth system dynamics has driven the development of DGVMs (Sitch et al., 2003). Several of the fully integrated DGVMs, such as the Lund-PotsdamJena (LPJ) model and the Integrated BIosphere Simulator model (IBIS), which combine the biogeochemical and biogeographicmodeling approaches have been developed (Foley et al., 1996; Sitch et al., 2003; Sato, Itoh, & Kohyama, 2007) and used widely to investigate and estimate the vegetation dynamics, biogeochemical processes, carbon balance and ecosystem responses to environmental changes on a regional or global scale (Kucharik et al., 2000; Dargaville et al., 2002; Yurova, Volodin, Agren, Chertov, & Komarov, 2010). Nevertheless, DGVMs still contain many uncertainties in both model structures and parameters (Fisher et al., 2010; Wang et al., 2010; Yuan et al., 2012). It is well- known that DGVMs are globally parameterized models (Zaehle, Sitch, Smith, & Hatterman, 2005). However, imperfect knowledge of processes and limited observations restrict the model parameterization, and result in large model errors (Hallgren & Pitman, 2000; Snowling & Kramer, 2001). Wramneby et al. (2008) suggested that the parameter uncertainties in LPJ could lead to a shift in plant competitive balance. Zaehle et al. (2005) concluded that the uncertainty in parameters generated considerable uncertainty in global net primary production by controlling assimilation rate, plant respiration and water balance. Generally, different parameters represent the predominant influence on different processes. Jiang et al. (2012) suggested that the reFlative importance of parameters varied both temporally and spatially, and was shifted by climate inputs. Therefore, to assess the reliability of modeled scenarios and to identify parameters that require further development, it is necessary to examine the parameter uncertainties (White, Thornton, Running, & Nemani, 2000; Sykes, Prentice, Smith, Cramer, & Venevsky, 2001). Leaf longevity and turnover rate are important plant traits and vary substantially among species(Chabot & Hicks, 1982; Kattge, Diaz, Lavorel, Prentice, & Leadley, 2011; Schleip, Lattanzi, & Schnyder, 2013); however, they are modeled roughly in current DGVMs. Previous studies regard leaf longevity and turnover rate as indicative of a plant’s tradeoff between productivity and persistence, as they determine the residence time of leaves and then constrain the circulation rate of carbon and nutrients to a certain extent (Reich, Walters, & Ellsworth, 1992; Schleip et al., 2013). Therefore, they are two critical parameters characterizing plant traits in vegetation models. Plant leaf longevities show large differences ranging from a few weeks to more than 10 years (Reich et al., 1992; Kikuzawa, 1995). DGVMs, however, generally assumed inaccurate values of leaf longevity and turnover rate for each plant type, and previous studies have indicated substantial differences between the default values and observations (Kikuzawa & Lechowicz, 2006). To our knowledge, few studies have calibrated the parameters of leaf longevity and turnover rate for major plant types worldwide. Therefore, it is necessary to investigate the uncertainties brought about by coarsely assigned leaf longevity and turnover rate, and the corresponding impacts on model outputs. Severalstudies have approached the issue of parameterization uncertainty in DGVMs(White et al., 2000; Zaehle, Sitch, Smith & Hatterman, 2005; Wramneby et al. 2008), however, few of these are related to the parameters of leaf longevity and turnover rate. In this study, we adopted the LPJ model, which is typical of DGVMs as a family of models and has been used widely to estimate global or regional carbon cycle, both with respect to its representation of structural ecosystem components (plants and soil) and ecosystem processes (Sitch et al., 2003; Zaehle et al., 2005; Bondeau et al., 2007; Yurova et al., 2010). Then, the leaf longevity and turnover parameters for each plant functional type (PFT) were revised based on numerous observational datasets. Finally, the model was run with the default and revised parameter sets, respectively. By comparing the model outputs with default and revised parametersets, we aimed to investigate the impacts of revised leaflongevity and turnover parameters on estimates of vegetation dynamics, ecosystem production and respiration, dynamic of carbon pools and carbon balance as modeled by LPJ.
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کلمات کلیدی:
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