The use of harvested wood products (HWPs) influences the carbon flux. China is both the major producer and trader of HWP, so estimating the carbon stock change of China’s HWP is important to help curb climate change. Accurate reporting and accounting of carbon flows in the HWP pool is needed to meet greenhouse gas monitoring and climate change mitigation objectives under the United Nations Framework Convention on Climate Change (UNFCCC) and the Paris Agreement. This study applied production approach (PA) to estimate the carbon stock change of China’s HWP from 1900 to 2016. During the estimating period, the carbon stock of HWP in use and deposed at solid waste disposal sites (SWDS) were 649.2 Teragrams Carbon (TgC) (346.8 TgC in wood-based panels, 216.7 TgC in sawnwood and 85.7 TgC in paper & paperboard) and 72.6 TgC, respectively. The carbon amount of annual domestic harvest HWP varied between 87.6 and 118.7 TgC. However, the imported carbon inflow increased significantly after the 1990s and reached 47.6 TgC in 2016, accounting for 46% of the domestic harvest of that year. China has great mitigation potential from HWP and use of this resource should be considered in future strategies to address climate change.

Background: As a key agricultural region in China, Heilongjiang Province has experienced significant carbon emissions over the past few decades. To understand the underlying factors and future trends in these emissions, a comprehensive analysis was conducted from 1993 to 2030. Methods: The agricultural carbon emissions from 1993 to 2020 were estimated using the emission factor method. To analyze the influencing factors and future trends of these emissions, the study employed the Logarithmic Mean Divisia Index (LMDI) and integrated it with the Stochastic Impacts by Regression on Population, Affluence, and Technology (STIRPAT) model. Results: Results showed that (1) the agricultural carbon emissions in Heilongjiang were primarily driven by rice cultivation, followed by fertilizer production and irrigation electricity. (2) The economic and labor structure effects were the main driving factors of agricultural carbon emissions, while the population, demographic, and intensity effects were the main inhibitors. (3) Agricultural carbon emissions in Heilongjiang Province peaked in 2016 with 69.6 Mt CO₂-eq and could subsequently decline by −3.92% to −4.52% between 2020 and 2030 in different scenario simulations. In the future, Heilongjiang Province should prioritize the reduction of agricultural carbon emissions from rice production. Adjusting the planting structure, managing the layout of rice paddies, and promoting the cultivation of dry rice varieties would significantly contribute to mitigating agricultural carbon emissions.

Nitrogen (N) pulse is a frequent event in agroecosystems caused by fertilization. Understanding the responses of nitrogen metabolisms in native crops and invasive weeds to N pulses is essential in investigating the invasive mechanism of invasive weeds. A pot experiment was carried out to study the impacts of N pulse and the interspecific competition on nitrogen metabolism of an invasive weed (Amaranthus retroflexus) and a native crop (Glycine max); the plants were applied with an equal amount of N in three N pulse treatments, i.e., sole-summit treatment (SS) with N only applied on the seeding date, double-summit treatment (DS) with twice N applied (the fertilizer was applied on both the seeding date and the flowering date), and no-summit treatment (NS) in which N was applied evenly during the experiment. The results showed that A. retroflexus increased the nitrate reductase (NR) activity more than G. max (except for the roots) in the early growing stage, and increased the glutamine synthetase (GS) and glutamate dehydrogenase (GDH) activities in stem more than G. max in SS and DS treatments during the last two growing stages, however, the advantages were far weaker in the NS treatment. Interspecific competition had negative effects on the nitrogen metabolism of the two species among most of the sample times, and the effects of interspecific competition exerted a tissue-specific influence on nitrogen metabolism in the two species. A. retroflexus switched to reproductive growth earlier in SS treatment than in the DS and NS treatments when it was grown in mixed planting, and its height was the lowest in the NS treatment, so the competitive ability of A. retroflexus was higher in the SS and DS treatments than in the NS treatment, while SS treatment was the common application method of N fertilizer in the G. max farmland in China. Thus, the results of this study suggest that, if the farmer changed the N fertilizer application mode to a constant multiple fertilization mode, the competitive capacity of A. retroflexus will be reduced.