## 1 Introduction  
Agricultural land accounts for one-third of global land area but contributes about 31% of greenhouse emissions produced by anthropogenic activities [1]. The potential of a cropland ecosystem to act as a carbon sink or source depends on the balance between carbon captured by plants through photosynthesis and carbon lost through microbial and plant respiration. Orchard ecosystems, like other agricultural ecosystems, release carbon via respiration and fix carbon through photosynthesis. Compared to annual crops, orchards have a greater carbon sink potential over a 15-20-year period of carbon sequestration [2]. The annual carbon accumulation can be significantly enhanced by regulating orchard management strategies [3]. Therefore, understanding the variation patterns of -orchard ecosystem carbon fluxes and their responses to environmental changes is crucial for assessing orchard carbon sink function and optimizing horticultural management [4; 5; 6; 7]. The eddy covariance (EC) technique has been widely recognized as a reliable and extensively adopted method for measuring carbon fluxes in situ across various terrestrial ecosystems [8; 9; 10; 11; 12; 13]. In agricultural systems, the EC technique has been employed to investigate how biotic and abiotic factors influence carbon exchange [14; 15; 16; 17; 18; 19; 20; 21]. [PERSON] et al. (2020) revealed that elevated temperatures not only increased daily net ecosystem exchange (NEE) but also accelerated apple tree sprouting [15]. In northeast China, NEE in an apple orchard showed negative correlations with net radiation, soil temperature (T\({}_{\text{s}}\)), air temperature (T\({}_{\text{a}}\)), and vapor pressure deficit (VPD) [22]. Similarly, in citrus orchards, diurnal NEE was strongly influenced by the interplay of photosynthetically active radiation (PAR) and T\({}_{\text{a}}\)[23]. Gross primary productivity (GPP) and ecosystem respiration (R\({}_{\text{e}}\)) were sensitive to T\({}_{\text{a}}\), with their responses further influenced by crop phenology and VPD [24]. Under nearly saturated light conditions, the impact of VPD on GPP was greater than that of soil water content (SWC) and T\({}_{\text{a}}\)[25]. Water availability remained a critical determinant, as highlighted by [PERSON] et al. (2022), who reported that humidity significantly affected carbon fluxes, particularly during dry periods [26]. R\({}_{\text{e}}\) is widely acknowledged as primarily temperature-driven in water-sufficient regions [27; 28; 29]. Orchard ecosystems, unlike unmanaged natural systems, are shaped by human interventions such as irrigation, pruning, and fertilization, which alter soil moisture, surface radiation dynamics, and local microclimatic conditions. Moreover, diverse underlying surface conditions suggest variations in the carbon balance [30], yet the complex interactions among these variables remain unclear. Kiwifruit is a valuable cash crop widely cultivated worldwide [31; 32], and its planted area has been increasing in China over the past decades due to its high commercial value [33]. The kiwifruit cultivation area in southwest China has exceeded 60,000 ha, accounting for one-third of the total national planting area. The intensification of climate change, such as rising CCO\({}_{2}\) and T\({}_{\text{a}}\), will alter the transport of matter and energy at the land-atmosphere interface. How the climate variables affect orchard ecosystem carbon flux variations remains unclear, though it is important for understanding the regional carbon flux dynamics and orchard production management. In this study, we measured carbon fluxes and meteorological variables in two consecutive growing seasons using an EC system in a kiwifruit orchard located in a seasonal-dry region in southwest China.