A modified framework for the regional assessment of climate and human impacts on net primary productivity

Abstract

a b s t r a c tImproving models that depict the components of net primary production (NPP) in ecosystems will help us to better understand how climate change and human activities affect the biosphere. In this study, NPP gap was introduced into the present human appropriation of net primary production (HANPP) framework. We introduced NPP gap in this study as potential NPP (NPP pot ) minus the sum of ecosystem NPP (NPP eco ) and HANPP, which relates to the ability of models to depict NPP components. Using the Lhasa River region of the Tibetan Plateau, we examined temporal and spatial variations in the components of NPP over a 10-year period. Results showed that NPP pot , HANPP and NPP eco increased from 2000 to 2010, but at different rates and with different spatial patterns. NPP gap each year ranged from −9.2% to 13.1% for each site and on average composed 1.2% of the total NPP pot . NPP gap was significantly correlated with precipitation, plant biodiversity, plant height and soil properties. NPP gap increased if either of the previous 2 years had been wet years with relative high precipitation. An increase in the richness of palatable species would lead to a larger NPP gap through more compensatory growth. The large fluctuation level of NPP gap reflected the higher stability of vegetation productivity, which is caused by higher plant heights and soil maximum water capacity. This study showed the potential of the HANPP framework in regional assessment of climate and human impacts on net primary productivity. The use of the NPP gap measure reflects the gap in our knowledge and our ability to accurately estimate the components of NPP.

Identifying the Relative Contributions of Climate and Grazing to Both Direction and Magnitude of Alpine Grassland Productivity Dynamics from 1993 to 2011 on the Northern Tibetan Plateau

“…Therefore, the proportion of grassland productivity consumed by livestock should be included in remote-sensing based models for simulating grassland productivity, to represent the actual grassland productivity that has really been influenced by both climate change and human activities. Pan et al [21] proposed a modified framework for assessing the climate and human impacts on grassland productivity on the Tibetan Plateau, in which the proportion of productivity appropriated by human society was estimated from current-year livestock inventories and meat production with specific transform coefficients for yak and sheep, respectively. Thus, the difference between potential and actual productivity, stimulated by theoretical (mechanism) models and by remote-sensing models, respectively, can be used not only to indicate the relative contribution of natural and anthropogenic factors, but also to reasonably direct the livestock regulation under differential climate change scenarios.…”

“…The method of comparing trends between NPP P and NPP A has been widely adopted in identifying the direction of natural and human influences, and in assessing the magnitude of various divers on long-term vegetation trends [8,20,21,31,32]. In each dataset, the temporal trend across the entire study period of 19 years was calculated with Equation (8).…”

“…NPP livestock and NPP meat were estimated following the approach of Pan et al [21]. NPP livestock was estimated from the daily forage intake per standardized sheep unit, about 1.8 kg dry matter per day [27].…”

“…This is because NPP A includes the plant's regrowth after grazing in the same season. In a recent study, Pan et al [21] proposed a modified framework for assessing the relative impacts of climate and grazing on vegetation productivity at local small villages, and reported a method for estimating the actually consumed productivity by livestock (NPP ac ). At a coarser spatial scale, the field investigations generally cost more time and money, while remote sensing provides a more economical and effective data source for assessing historical vegetation dynamics.…”

Decreasing Net Primary Productivity in Response to Urbanization in Liaoning Province, China

“…The majority of previous research has focused on the NPP of different land use types with little analysis of the impacts of land use conversion on NPP loss in the urbanization process. A number of papers have come out recently focused on quantitative assessment and influencing factors of the Human Appropriation of Net Primary Production (HANPP) [29][30][31][32].…”