Shouzhang Peng

Estimating realized and potential carbon storage benefits from reforestation and afforestation under climate change: a case study of the Qinghai spruce forests in the Qilian Mountains, northwestern China

Greenhouse gas emission has been scientifically shown to be the primary cause of observed global climate change. The reduction of greenhouse gas levels in the atmosphere deserves international attention. Aside from strategies to reduce emissions, increasing carbon (C) storage by forests has become an alternative method to lower carbon dioxide (CO2) levels. The present study assesses the potential of C storage to decrease gas emission by restoring cleared and disturbed spruce (picea) forests in the Qilian Mountains, northwestern China. We first introduced and tested a new method for live aboveground biomass (AGB) estimation. We then used the method to define the relationship of AGB with topographic wetness index (TWI) and precipitation seasonality for total AGB estimation and quantification of the realized C storage in the live AGB of existing spruce forests. The same strategies were adopted to estimate the total AGB and the related potential C storage in the projected potential spruce forest distribution. A species distribution model was used, and the results showed that the AGB of the Qinghai spruce forests ranged between 2.30 and 4.96 Mg per plot (0.021 ha), i.e., 110 Mg ha-1 to 236 Mg ha-1). Actual total AGB was measured at 33 Tg, and C storage was 17.3 Tg in existing spruce forests. Potential total AGB and potential C storage were greater if the cleared and the potential C storage was ~50 Tg.

Modeling stem volume growth of Qinghai spruce (Picea crassifolia Kom.) in Qilian Mountains of Northwest China

Qinghai spruce (Picea crassifolia Kom.), the dominant species in Qilian Mountains of Northwest China, has an important role in ecological service function, especially in carbon sequestration. The current work simulated stem volume growth of Qinghai spruce at individual and stand levels using a widespread bio-geochemical cycle (BIOME-BGC) model and considering the crown projection area (CPA). CPA was introduced because photosynthesis was only carried out on the vegetation canopy. The results showed that: (1) the CPA-simulated stem volume of individual Qinghai spruce in the three sites fitted well with the observed stem volume; (2) the introduction of CPA corrected the over-predicted stem volume for relatively younger stands and the under-predicted stem volume for relatively older stands in BIOME-BGC; and (3) meteorological factors may be crucial parameters that influence the model accuracy, aside from CPA. Therefore, CPA should be considered in correcting the carbon simulated by BIOME-BGC, and the meteorological data should be improved to obtain high-accuracy BIOME-BGC outputs.

Mapping Daily Temperature and Precipitation in the Qilian Mountains of Northwest China

Daily meteorological data are the critical inputs for distributed hydrological and ecological models. This study modified mountain microclimate simulation model (MTCLIM) with the data from 19 weather stations, and compared and validated two methods (the MTCLIM and the modified MTCLIM) in the Qilian Mountains of Northwest China to estimate daily temperature (i.e., maximum temperature, minimum temperature) and precipitation at six weather stations from 1 January 2000 to 31 December 2009. The algorithm of temperature in modified MTCLIM was improved by constructing the daily linear regression relationship between temperature and elevation, aspect and location information. There are two steps to modify the MTCLIM to predict daily precipitation: firstly, the linear regression relationship was built between annual average precipitation and elevation, location, and vegetation index; secondly, the distance weight for measuring the contribution of each weather station on target point was improved by average wind direction during the rainy season. Several regression analysis and goodness-of-fit indices (i.e., Pearson’s correlation coefficient, coefficient of determination, mean absolute error, root-mean-square error and modeling efficiency) were used to validate these estimated values. The result showed that the modified MTCLIM had a better performance than the MTCLIM. Therefore, the modified MTCLIM was used to map daily meteorological data in the study area from 2000 to 2009. These results were validated using weather stations with short time data and the predicted accuracy was acceptable. The meteorological data mapped could become inputs for distributed hydrological and ecological models applied in the Qilian Mountains.

The canopy rainfall interception in actual and potential distribution of Qinghai spruce (Picea crassifolia) forest

Abstract Interception is one of the most underestimated processes in hydrological cycle in arid and semiarid regions. In Qilian Mountains of northwestern arid and semiarid China, the Qinghai spruce (Picea crassifolia) forest plays an important role in the hydrological cycle of the inland Heihe River basin. The historical disturbance of Qinghai spruce forest has resulted in various ecological problems. In order to realize the sustainable development of Heihe River basin, the Chinese government implemented restoration practices for Qinghai spruce in the past three decades. In this study, we estimated the rainfall interception in the actual and potential distribution of Qinghai spruce forest. Some of the important findings include: (1) The interception ratio of rainfall events ranged from 11-51% with a mean value of 27.02%; (2) Totally, 147 Mt of rainfall is intercepted by canopy of actual Qinghai spruce forest, in the projected potential distribution of the forest, totally 407 Mt of rainfall will be intercepted.