The role of protected areas in land use/land cover change and the carbon cycle in the conterminous United States

Protected areas (PAs) cover about 22% of the conterminous United States. Understanding their role on historical land use and land cover change (LULCC) and on the carbon cycle is essential to provide guidance for environmental policies. In this study, we compiled historical LULCC and PAs data to explore these interactions within the terrestrial ecosystem model (TEM). We found that intensive LULCC occurred in the conterminous United States from 1700 to 2005. More than 3 million km² of forest, grassland and shrublands were converted into agricultural lands, which caused 10,607 Tg C release from land ecosystems to atmosphere. PAs had experienced little LULCC as they were generally established in the 20th century after most of the agricultural expansion had occurred. PAs initially acted as a carbon source due to land use legacies, but their accumulated carbon budget switched to a carbon sink in the 1960s, sequestering an estimated 1,642 Tg C over 1700–2005, or 13.4% of carbon losses in non‐PAs. We also find that PAs maintain larger carbon stocks and continue sequestering carbon in recent years (2001–2005), but at a lower rate due to increased heterotrophic respiration as well as lower productivity associated to aging ecosystems. It is essential to continue efforts to maintain resilient, biodiverse ecosystems and avoid large‐scale disturbances that would release large amounts of carbon in PAs.     

Distinct controls over the temporal dynamics of soil carbon fractions after land use change

Soil organic carbon (SOC), the largest terrestrial carbon pool, plays a significant role in soil‐related ecosystem services such as climate regulation, soil fertility and agricultural production. However, its fate under land use change is difficult to predict. A major issue is that SOC comprised of numerous organic compounds with potentially distinct and poorly understood turnover properties. Here we use spatiotemporal measurements of the particulate (POC), mineral‐associated (MOC) and charred SOC (COC) fractions from 176 trials involving changes in land use to assess their underlying controls. We find that the initial pool sizes of each of the three fractions consistently and dominantly control their temporal dynamics after changes in land use (i.e. the baseline effects). The effects of climate, soil physicochemical properties and plant residues, however, are fraction‐ and time‐dependent. Climate and soil properties show similar importance for controlling the dynamics of MOC and COC, while plant residue inputs (in term of their quantity and quality) are much less important. For POC, plant residues and management practices (e.g. the frequency of pasture in crop‐pasture rotation systems) are substantially more important, overriding the influence of climate. These results demonstrate the pivotal role of measuring SOC composition and considering fraction‐specific stabilization and destabilization processes for effective SOC management and reliable SOC predictions.     

Effects of land use change and management on the European cropland carbon balance

We model the carbon balance of European croplands between 1901 and 2000 in response to land use and management changes. The process‐based ORCHIDEE‐STICS model is applied here in a spatially explicit framework. We reconstructed land cover changes, together with an idealized history of agro‐technology. These management parameters include the treatment of straw and stubble residues, application of mineral fertilizers, improvement of cultivar species and tillage. The model is integrated for wheat and maize during the period 1901–2000 forced by climate each 1/2‐hour, and by atmospheric CO₂, land cover change and agro‐technology each year. Several tests are performed to identify the most sensitive agro‐technological parameters that control the net biome productivity (NBP) in the 1990s, with NBP equaling for croplands the soil C balance. The current NBP is a small sink of 0.16 t C ha^?1 yr^?1. The value of NBP per unit area reflects past and current management, and to a minor extent the shrinking areas of arable land consecutive to abandonment during the 20th Century. The uncertainty associated with NBP is large, with a 1‐sigma error of 0.18 t C ha^?1 yr^?1 obtained from a qualitative, but comprehensive budget of various error terms. The NBP uncertainty is dominated by unknown historical agro‐technology changes (47%) and model structure (27%), with error in climate forcing playing a minor role. A major improvement to the framework would consist in using a larger number of representative crops. The uncertainty of historical land‐use change derived from three different reconstructions, has a surprisingly small effect on NBP (0.01 t C ha^?1 yr^?1) because cropland area remained stable during the past 20 years in all the tested land use forcing datasets. Regional cross‐validation of modeled NBP against soil C inventory measurements shows that our results are consistent with observations, within the uncertainties of both inventories and model. Our estimation of cropland NBP is however likely to be biased towards a sink, given that inventory data from different regions consistently indicate a small source whereas we model a small sink.     

碳税政策对农业土地利用变化及其碳排放的影响

农业生态系统具有碳源和碳汇的双重特征,其在减缓气候变化中的重要性已得到国际社会的广泛认可。相较于技术手段的创新,碳税、补贴等经济手段被认为是较为简单、可行、易出台的碳排放减缓政策。采用气候变化综合评估模型-GOPer-GC模型,构建国际碳税情景,模拟分析了2008年至2050年碳税政策的实施对全球各区域农业土地覆被及土地利用变化碳排放的影响。模拟结果表明,情景2和情景3中全球农业土地利用变化累计碳排放分别达到49.6 GtC和23.1 GtC,明显低于基准情景的累计排放量51.9 GtC。这说明,实施碳税政策后,相较于将碳税收入用作一般性财政收入,将碳税收入补贴至农业部门在一定程度上减缓农业碳排放。此外,林业部门获取更多的碳税补贴时,多数区域农业土地利用变化碳排放规模大幅减少,主因是耕地变为林地、草地变为林地面积的增加。情景3中,中国的碳汇量较其他情景显著增加,主要来自耕地变为林地、草地变为林地,累计碳汇量分别达到1.7和3.7 GtC。因此,对于中国、美国、印度等大部分区域来说,碳税收入更多地补贴至林业部门有利于在整体上减缓农业碳排放,而欧盟、日本、东亚、马来西亚、印度尼西亚、俄罗斯、东欧地区,碳税收入平均补贴至种植业、畜牧业和林业反而具有相对更好的减排效果。     

Intertwined effects of climate and land use change on environmental dynamics and carbon accumulation in a mangrove‐fringed coastal lagoon in Java,Indonesia

The identification and quantification of natural carbon (C) sinks is critical to global climate change mitigation efforts. Tropical coastal wetlands are considered important in this context, yet knowledge of their dynamics and quantitative data are still scarce. In order to quantify the C accumulation rate and understand how it is influenced by land use and climate change, a palaeoecological study was conducted in the mangrove‐fringed Segara Anakan Lagoon (SAL) in Java, Indonesia. A sediment core was age‐dated and analyzed for its pollen and spore, elemental and biogeochemical compositions. The results indicate that environmental dynamics in the SAL and its C accumulation over the past 400 years were controlled mainly by climate oscillations and anthropogenic activities. The interaction of these two factors changed the lagoon's sediment supply and salinity, which consequently altered the organic matter composition and deposition in the lagoon. Four phases with varying climates were identified. While autochthonous mangrove C was a significant contributor to carbon accumulation in SAL sediments throughout all four phases, varying admixtures of terrestrial C from the hinterland also contributed, with natural mixed forest C predominating in the early phases and agriculture soil C predominating in the later phases. In this context, climate‐related precipitation changes are an overarching control, as surface water transport through rivers serves as the “delivery agent” for the outcomes of the anthropogenic impact in the catchment area into the lagoon. Amongst mangrove‐dominated ecosystems globally, the SAL is one of the most effective C sinks due to high mangrove carbon input in combination with a high allochthonous carbon input from anthropogenically enhanced sediment from the hinterland and increased preservation. Given the substantial C sequestration capacity of the SAL and other mangrove‐fringed coastal lagoons, conservation and restoration of these ecosystems is vitally important for climate change mitigation.     

1980-2010年北京市农用地碳储量对土地利用变化的响应

分析北京市农用地碳储量对土地利用变化的响应,对快速城市化和工业化区域及全国农用地低碳利用调控具有重要意义。利用1980年第二次土壤普查数据与2010年测土配方施肥项目成果土壤数据核算北京市农用地表层土壤碳储量,利用生物量遥感信息（NDVI）模型反演林地、草地植被碳储量,对北京市土地利用变化造成的农用地碳储量变化进行研究,结果表明：1）1980-2010年,北京市农用地碳储量由75.29 Tg-C增至81.13Tg-C,增加5.83 Tg-C,其中,土壤碳储量减少7.51 Tg-C,植被碳储量增加13.34 Tg-C;2）30年间,北京市农用地面积减少14.11×10⁴ hm²,其中,耕地流失最为显著,主要去向为建设用地和林地,林地面积略有增加;3）北京市用地类型保持不变的农用地土壤碳储量减少297.63×10⁴ t,植被碳储量增加1095.21×10⁴ t,共计增加797.58×10⁴ t,其中,用地类型保持不变的耕地、林地碳储量增加,草地碳储量减少;4）30年间,土地利用类型转化使北京市农用地土壤碳储量减少75.71×10⁴ t,植被碳储量增加212.49×10⁴ t,共计增加136.78×10⁴ t,其他用地类型转为林地使碳储量增加,有利于碳汇的形成,林地转出为其他用地类型均会造成一定碳排放;5）平原造林、退耕还林等工程有利于增加北京市农用地固碳量。未来北京市可通过控制农用地面积减少量,优化农用地内部结构,降低用地类型间的转换频率以提高农用地碳储量。研究可为其他区域及全国在快速城市化工业化过程中提升农用地碳储量提供一定参考。     

土地利用变化对土壤有机碳的影响研究进展

土壤有机碳是陆地碳库的重要组成部分,也是当前全球碳循环和全球变化研究的热点。土地利用/覆被变化及土地管理变化通过影响土壤有机碳的储量和分布,进而影响温室气体排放和陆地生态系统的碳通量。研究土地利用变化影响下的土壤有机碳储量及其动态变化规律,有助于加深理解全球气候变化与土地利用变化之间的关系。在阅读国内外有关文献的基础上,分别从土地利用及其管理方式变化的角度,概括了土地利用变化对土壤有机碳的影响过程与机理;针对当前研究的两大类方法,即实验方法和模型方法,分类详细介绍了它们各自的特点以及存在的一些问题。在此基础上,提出今后土地利用变化对土壤有机碳影响研究的发展趋势。     

Forecasting the combined effects of future climate and land use change on the suitable habitat of Davidia involucrata Baill

Accurately predicting the future distribution of species is crucial for understanding how species will response to global environmental change and for evaluating the effectiveness of current protected areas (PAs). Here, we assessed the effect of climate and land use change on the projected suitable habitats of Davidia involucrata Baill under different future scenarios using the following two types of models: (a) only climate covariates (climate SDMs) and (b) climate and land use covariates (full SDMs). We found that full SDMs perform significantly better than climate SDMs in terms of both AUC (p < .001) and TSS (p < .001) and also projected more suitable habitat than climate SDMs both in the whole study area and in its current suitable range, although D. involucrate is predicted to loss at least 26.96% of its suitable area under all future scenarios. Similarly, we found that these range contractions projected by climate SDMs would negate the effectiveness of current PAs to a greater extent relative to full SDMs. These results suggest that although D. involucrate is extremely vulnerability to future climate change, conservation intervention to manage habitat may be an effective option to offset some of the negative effects of a changing climate on D. involucrate and can improve the effectiveness of current PAs. Overall, this study highlights the necessity of integrating climate and land use change to project the future distribution of species.     

The pace of past climate change vs. potential bird distributions and land use in the United States

Climate change may drastically alter patterns of species distributions and richness, but predicting future species patterns in occurrence is challenging. Significant shifts in distributions have already been observed, and understanding these recent changes can improve our understanding of potential future changes. We assessed how past climate change affected potential breeding distributions for landbird species in the conterminous United States. We quantified the bioclimatic velocity of potential breeding distributions, that is, the pace and direction of change for each species’ suitable climate space over the past 60 years. We found that potential breeding distributions for landbirds have shifted substantially with an average velocity of 1.27 km yr^?1, about double the pace of prior distribution shift estimates across terrestrial systems globally (0.61 km yr^?1). The direction of shifts was not uniform. The majority of species’ distributions shifted west, northwest, and north. Multidirectional shifts suggest that changes in climate conditions beyond mean temperature were influencing distributional changes. Indeed, precipitation variables that were proxies for extreme conditions were important variables across all models. There were winners and losers in terms of the area of distributions; many species experienced contractions along west and east distribution edges, and expansions along northern distribution edges. Changes were also reflected in the potential species richness, with some regions potentially gaining species (Midwest, East) and other areas potentially losing species (Southwest). However, the degree to which changes in potential breeding distributions are manifested in actual species richness depends on landcover. Areas that have become increasingly suitable for breeding birds due to changing climate are often those attractive to humans for agriculture and development. This suggests that many areas might have supported more breeding bird species had the landscape not been altered. Our study illustrates that climate change is not only a future threat, but something birds are already experiencing.     

Land use change and the global carbon cycle: the role of tropical soils

Millions of hectares of tropical forest are cleared annually for agriculture, pasture, shifting cultivation and timber. One result of these changes in land use is the release of CO₂ from the cleared vegetation and soils. Although there is uncertainty as to the size of this release, it appears to be a major source of atmospheric CO₂, second only to the release from the combustion of fossil fuels. This study estimates the release of CO₂ from tropical soils using a computer model that simulates land use change in the tropics and data on (1) the carbon content of forest soils before clearing; (2) the changes in the carbon content under the various types of land use; and (3) the area of forest converted to each use. It appears that the clearing and use of tropical soils affects their carbon content to a depth of about 40 cm. Soils of tropical closed forests contain approximately 6.7 kg C · m^-2; soils of tropical open forests contain approximately 5.2 kg C · m^-2 to this depth. The cultivation of tropical soils reduces their carbon content by 40% 5 yr after clearing; the use of these soils for pasture reduces it by about 20%. Logging in tropical forests appears to have little effect on soil carbon. The carbon content of soils used by shifting cultivators returns to the level found under primary forest about 35 yr after abandonment. The estimated net release of carbon from tropical soils due to land use change was 0.11–0.26 × 10¹⁵ g in 1980.     

Effects of 21st‐century climate,land use,and disturbances on ecosystem carbon balance in California

Terrestrial ecosystems are an important sink for atmospheric carbon dioxide (CO₂), sequestering ~30% of annual anthropogenic emissions and slowing the rise of atmospheric CO₂. However, the future direction and magnitude of the land sink is highly uncertain. We examined how historical and projected changes in climate, land use, and ecosystem disturbances affect the carbon balance of terrestrial ecosystems in California over the period 2001–2100. We modeled 32 unique scenarios, spanning 4 land use and 2 radiative forcing scenarios as simulated by four global climate models. Between 2001 and 2015, carbon storage in California's terrestrial ecosystems declined by ?188.4 Tg C, with a mean annual flux ranging from a source of ?89.8 Tg C/year to a sink of 60.1 Tg C/year. The large variability in the magnitude of the state's carbon source/sink was primarily attributable to interannual variability in weather and climate, which affected the rate of carbon uptake in vegetation and the rate of ecosystem respiration. Under nearly all future scenarios, carbon storage in terrestrial ecosystems was projected to decline, with an average loss of ?9.4% (?432.3 Tg C) by the year 2100 from current stocks. However, uncertainty in the magnitude of carbon loss was high, with individual scenario projections ranging from ?916.2 to 121.2 Tg C and was largely driven by differences in future climate conditions projected by climate models. Moving from a high to a low radiative forcing scenario reduced net ecosystem carbon loss by 21% and when combined with reductions in land‐use change (i.e., moving from a high to a low land‐use scenario), net carbon losses were reduced by 55% on average. However, reconciling large uncertainties associated with the effect of increasing atmospheric CO₂ is needed to better constrain models used to establish baseline conditions from which ecosystem‐based climate mitigation strategies can be evaluated.     

Land use change and carbon cycle in arid and semi-arid lands of East and Central Asia

Dramatic changes in land use have occurred in arid and semi-arid landsof Asia during the 20th century. Grassland conversion into croplands and ecosystem degradation is widespread due to the high growth rate of human population and political reforms of pastoral systems. Rangeland degradation made many parts of this region vulnerable to environmental and political changes. The collapse of the livestock sector in some states of central Asia, expansion of livestock inChina and intensive degradation of grasslands in China are examples of the responses of pastoral systems to these changes over the past decades. Carbon dynamics in this region is highly variable in space and time. Land use/cover changes with widespread reduction of forest and grasslands increased carbon emission from the region.     

Defining the importance of including transient ecosystem responses to simulate C‐cycle dynamics in a global change model

The ability of plant species to migrate is one of the critical issues in assessing accurately the future response of the terrestrial biosphere to climate change. This ability is confined by both natural and human‐induced changes in land cover. In this paper we present land‐cover and Carbon (C) cycle models designed to simulate the biospheric consequences of different types of land‐cover changes. These models, imbedded in the larger integrated assessment model IMAGE 2, were used to demonstrate the importance of considering spatial aspects for global C‐cycle modelling. A gradual‐migration, an unlimited‐migration and a no‐migration case were compared to show the range of possible consequences. Major differences between these cases were simulated for land‐cover patterns and the carbon budget. A large geographical variation in the biospheric response was also simulated. The strongest response was simulated in high‐latitude regions, especially for the migration cases in which land‐cover changes were permitted. In low‐latitudes regions the differences between the migration cases were smaller, mainly due to the effects of land‐use changes. The geographical variation among, and the different responses, the migration cases clearly demonstrate how essential it is to assess biospheric responses to climate change and land use simultaneously. Moreover, it also shows the urgent need for enhanced understanding of spatial and temporal dynamics of the biospheric responses.     

福州市森林碳储量定量估算及其对土地利用变化的响应

基于RS与GIS技术,以遥感影像数据、土地利用数据、森林资源二类调查数据为主要数据源,采用逐步回归法建立森林蓄积量定量估测模型。根据"蓄积量-生物量-碳储量"推算方法,对福州市森林植被碳储量和碳密度进行估算。建立福州市土地利用转移矩阵,分析2000—2010年土地利用变化影响下的福州市森林碳储量变化特征。结果表明:(1)根据不同的森林类型,即常绿阔叶林、常绿针叶林、针阔混交林分别建立的多元线性回归模型修正决定系数分别为0.599、0.679、0.694,通过模型适用性检验和精度验证。(2)2000年、2010年福州市森林植被碳储量总量分别为12.499Tg、12.642Tg,植被碳密度分别为18.694、18.708 t/hm~2,森林植被碳储量增加了1.430×10~5t。(3)福州市闽清县、永泰县、闽侯县的森林植被碳密度常年保持较高水平,并呈现出增长趋势;罗源县、长乐市、连江县森林植被碳密度较低,并呈现下降趋势。(4)2000—2010年,灌木和耕地是主要土地利用类型转出者,森林和建设用地是主要土地利用类型转入者。森林主要由灌木和耕地转化,主要向建设用地、耕地进行转化。由于土地利用变化,10年间福州市总碳储量减少了1.711×10~4t,其中土壤碳储量减少2.230×10~3t,植被碳储量减少1.489×10~4t。     

Effects of species composition, land surface cover, CO2 concentration and climate on isoprene emissions from European forests.

Emissions of isoprene from terrestrial vegetation are known to affect atmospheric chemical properties, like its oxidation capacity or the concentration of tropospheric ozone. The latter is of concern, since besides being a potent greenhouse gas, O(3) is toxic for humans, animals, and plants even at relatively low concentrations. Isoprene-emitting forests in the vicinity of NO(x) pollution sources (like cities) can contribute considerably to O(3) formation, and to the peak concentrations observed during hot summer weather. The biogenic contribution to O(3) concentrations is generally thought to increase in a future, warmer climate--pushing values beyond health thresholds possibly even more frequently and over larger areas--given that emissions of isoprene are highly temperature-dependent but also because of the CO(2) fertilisation of forest productivity and leaf growth. Most projections of future emissions, however, do not include the possible CO(2)-inhibition of leaf isoprene metabolism. We explore the regional distribution of emissions from European woody vegetation, using a mechanistic isoprene-dynamic vegetation model framework. We investigate the interactive effects of climate and CO(2) concentration on forest productivity, species composition, and isoprene emissions for the periods 1981-2000 and 2081-2100. Our projection of future emissions includes a direct CO(2)-isoprene inhibition. Across the model domain, we show that this direct effect has the potential to offset the stimulation of emissions that could be expected from warmer temperatures and from the increased productivity and leaf area of emitting vegetation. Changes in forest species composition that may result from climate change can play a substantial additional role in a region's future emissions. Changes in forest area or area planted in woody biofuels in general are not noticeable in the overall European forest isoprene budget, but--as was the case for changes in species composition--may substantially affect future projections in some regions of the continent.     

Global response of terrestrial ecosystem structure and function to CO2 and climate change: results from six dynamic global vegetation models

The possible responses of ecosystem processes to rising atmospheric CO₂ concentration and climate change are illustrated using six dynamic global vegetation models that explicitly represent the interactions of ecosystem carbon and water exchanges with vegetation dynamics. The models are driven by the IPCC IS92a scenario of rising CO₂ ( Wigley et al. 1991 ), and by climate changes resulting from effective CO₂ concentrations corresponding to IS92a, simulated by the coupled ocean atmosphere model HadCM2‐SUL. Simulations with changing CO₂ alone show a widely distributed terrestrial carbon sink of 1.4–3.8 Pg C y^?1 during the 1990s, rising to 3.7–8.6 Pg C y^?1 a century later. Simulations including climate change show a reduced sink both today (0.6–3.0 Pg C y^?1) and a century later (0.3–6.6 Pg C y^?1) as a result of the impacts of climate change on NEP of tropical and southern hemisphere ecosystems. In all models, the rate of increase of NEP begins to level off around 2030 as a consequence of the ‘diminishing return’ of physiological CO₂ effects at high CO₂ concentrations. Four out of the six models show a further, climate‐induced decline in NEP resulting from increased heterotrophic respiration and declining tropical NPP after 2050. Changes in vegetation structure influence the magnitude and spatial pattern of the carbon sink and, in combination with changing climate, also freshwater availability (runoff). It is shown that these changes, once set in motion, would continue to evolve for at least a century even if atmospheric CO₂ concentration and climate could be instantaneously stabilized. The results should be considered illustrative in the sense that the choice of CO₂ concentration scenario was arbitrary and only one climate model scenario was used. However, the results serve to indicate a range of possible biospheric responses to CO₂ and climate change. They reveal major uncertainties about the response of NEP to climate change resulting, primarily, from differences in the way that modelled global NPP responds to a changing climate. The simulations illustrate, however, that the magnitude of possible biospheric influences on the carbon balance requires that this factor is taken into account for future scenarios of atmospheric CO₂ and climate change.     

Land use change and carbon cycle in arid and semi-arid lands of East and Central Asia

Dramatic changes in land use have occurred in arid and semi-arid lands of Asia duringthe 20th century. Grassland conversion into croplands and ecosystem degradation is widespreaddue to the high growth rate of human population and political reforms of pastoral systems. Rangeland degradation made many parts of this region vulnerable to environmental and political changes. The collapse of the livestock sector in some states of central Asia, expansion of livestockin China and intensive degradation of grasslands in China are examples of the responses of pastoral systems to these changes over the past decades. Carbon dynamics in this region is highly variable in space and time. Land use/cover changes with widespread reduction of forest and grasslands increased carbon emission from the region.     

CO2 emissions from land‐use change affected more by nitrogen cycle,than by the choice of land‐cover data

The high uncertainty in land‐based CO₂ fluxes estimates is thought to be mainly due to uncertainty in not only quantifying historical changes among forests, croplands, and grassland, but also due to different processes included in calculation methods. Inclusion of a nitrogen (N) cycle in models is fairly recent and strongly affects carbon (C) fluxes. In this study, for the first time, we use a model with C and N dynamics with three distinct historical reconstructions of land‐use and land‐use change (LULUC) to quantify LULUC emissions and uncertainty that includes the integrated effects of not only climate and CO₂ but also N. The modeled global average emissions including N dynamics for the 1980s, 1990s, and 2000–2005 were 1.8 ± 0.2, 1.7 ± 0.2, and 1.4 ± 0.2 GtC yr^?1, respectively, (mean and range across LULUC data sets). The emissions from tropics were 0.8 ± 0.2, 0.8 ± 0.2, and 0.7 ± 0.3 GtC yr^?1, and the non tropics were 1.1 ± 0.5, 0.9 ± 0.2, and 0.7 ± 0.1 GtC yr^?1. Compared to previous studies that did not include N dynamics, modeled net LULUC emissions were higher, particularly in the non tropics. In the model, N limitation reduces regrowth rates of vegetation in temperate areas resulting in higher net emissions. Our results indicate that exclusion of N dynamics leads to an underestimation of LULUC emissions by around 70% in the non tropics, 10% in the tropics, and 40% globally in the 1990s. The differences due to inclusion/exclusion of the N cycle of 0.1 GtC yr^?1 in the tropics, 0.6 GtC yr^?1 in the non tropics, and 0.7 GtC yr^?1 globally (mean across land‐cover data sets) in the 1990s were greater than differences due to the land‐cover data in the non tropics and globally (0.2 GtC yr^?1). While land‐cover information is improving with satellite and inventory data, this study indicates the importance of accounting for different processes, in particular the N cycle.