# The Effects of Fertilization on the Growth and Physiological Characteristics of _Ginkgo biloba_ L.
## 1 Introduction  
Nutrient limitations develop when a stand's potential nutrient use cannot be met by the soil nutrient supply [1]. Improving stand nutrient supply through fertilization is a viable silvicultural option [2]. As an intervention strategy, large-scale application of fertilizers to forests has been implemented to accelerate growth of existing stands and shorten rotation times to overcome future projected timber shortfalls [3]. It is well established that fertilization, in particular nitrogen (N) and phosphate (P) applications, on nutrient limited sites increases tree productivity by increasing photosynthesis in the short term [4, 5] and leaf area over the long term [6]. N is a vital constituent in proteins, nucleic acids, chlorophylls, and many secondary metabolites of plants [7]; therefore, it plays an essential role in the enzymatic activities of photosynthetic processes [8]. P plays a central role in almost all aspects of plant metabolism and is one of the nutrients that most commonly limits growth [9]. Potassium (K) is one of important nutrient elements and plays a major role in growth, modifying abundant enzyme activations and controlling cell osmoregulation [10]. Gross primary production (GPP) was also greatly increased by K fertilization as a result of lower stomatal and mesophyllresistance to CO\({}_{2}\) diffusion and higher photosynthetic capacity in the leaves [11; 12]. In addition, potassium can also alleviate the harmful effects of abiotic stress [13; 14; 15]. The advantage of using chemical fertilizers is that nutrients are soluble and immediately available to the plants; therefore, the effect is usually direct and fast. Several studies have reported an increase in growing efficiency and higher enzymatic activities following fertilization [16; 17]. Many studies have found that growing efficiency is largely unaffected by nutrient additions [18; 19]. Different plants do not have the same nutrient demand and specific fertility targets [20]. The fast-growing broad-leaved tree _Populus alba_\(\times\)_P. glandulosa_ is more sensitive to increasing N availability [21], while the slow-growing _P. popularis_ is more sensitive to decreasing N availability [22]. Among confers, the fast-growing spruce families show more plasticity in biomass allocation than do the slowly growing ones under different nitrogen supplies [23], and the fast growing species _Pinus radiata_ allocates more to the aboveground biomass under N and P fertilization [24]. _Ginkgo_ is commonly referred to as Gongsun Tree or Duck Foot Tree, is one of the most ancient gymosperms in the world, and is native to the temperate forests of China [25]. _Ginkgo_ is an eco-economic tree species which is valuable for food, health care, medicine, timber, landscape, ecological protection, and scientific research. The great environmental adaptability and beauty of _Ginkgo_ have made the tree a favorite species for planting as an ornamental tree throughout the world [26]. Its widespread use has been facilitated by its tolerance of air pollution and soil compaction. _Ginkgo_ has a long history in leaf and nut production. However, it is still in the initial stage for timber cultivation in China. _Ginkgo_ wood has also been highly valued for making furniture and handicraft articles, and _Ginkgo_ wood is also an ideal material for making musical instruments [27]. Nowadays, _Ginkgo_ wood is only used for carving and chopping blocks. The compression of _Ginkgo_ wood was found to be stiffer than that of the other species [28]. [PERSON] et al. (2004) consequently concluded that there has been an evolutionary trend towards much more flexible compression wood [29]. [PERSON] et al. (2009) reported higher lignin content in _Ginkgo_ than in conifers [30]. _Ginkgo_ wood was once used for pillars and rafters in the palaces and temples in ancient China. _Ginkgo_ also has an anti-dust function, purifying the environment.